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Lumbar fusion

164 citationsUpdated Sep 2026

Overview

Lumbar fusion is indicated for persistent, disabling pain that remains unrelieved by non-surgical treatment, requiring careful patient selection to ensure appropriate candidacy [13]. For degenerative lumbar spondylolisthesis, individual patient factors must guide the selection of the specific surgical strategy [18]. Spinal fusion for non-specific low back pain lacks robust evidence and should only be performed as part of a randomised controlled trial [6]. Preoperative hemoglobin level thresholds can assist surgeons in counseling patients on their specific postoperative risk profile for single-level lumbar fusion [3].

Posterior decompression with instrumented fusion is the most common surgical treatment for degenerative lumbar spondylolisthesis [18]. Among adult patients with isthmic spondylolisthesis undergoing single-level lumbar fusion, 81.5% had posterior surgery while 7.9% had combined anterior-posterior surgery [19]. Anterior approaches are increasingly used due to proven efficacy and low morbidity, provided the technique and vascular risks are well mastered [26]. Lateral lumbar interbody fusion at L4-L5 has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with appropriate indications using a standardized surgical technique [70]. Oblique lumbar interbody fusion and transforaminal lumbar interbody fusion have comparable fusion rates, complication rates, and lumbar pain improvements [9].

One- and two-level lumbar fusion procedures demonstrated high durability with an overall revision surgery rate of 15% [4]. Approximately one-third of adverse events after posterior lumbar fusion were diagnosed 31 to 90 days after surgery [1]. In a study of workers' compensation subjects, the reoperation rate was 27% for surgical patients, and 36% of lumbar fusion subjects had complications [20]. No completely reliable method of spine fusion has been developed, with success rates varying widely and often overestimated by roentgenographic methods [7]. Greater use of fusion-based procedures for lumbar spinal disorders is observed in the private sector irrespective of the clinical condition [12]. A meta-analysis summarized evidence regarding risk factors for symptomatic adjacent segment disease following lumbar fusion [11].

Anatomy & Pathophysiology

Lumbar Spine Anatomy

The lumbar vertebral bodies are large, with a transverse diameter exceeding the anterior-posterior diameter [98]. Pedicles arise from the superior aspect of the vertebral bodies and project more horizontally than thoracic pedicles [98]. While L1 pedicles are minimally medially angled, the orientation becomes increasingly medial down the lumbar spine, particularly at L5 [98]. A study of 2905 pedicle measurements from T1 to L5 found that pedicles were widest at L5 and narrowest at T5 in the horizontal plane, with the largest pedicle angle in the horizontal plane occurring at L5 [97]. In the sagittal plane, the widest pedicles were at T11 and the narrowest at T1 [97]. Pedicles angle caudal at L5 and cephalad at L3-T1 [97]. The depth to the anterior cortex is significantly longer along the pedicle axis than along a line parallel to the midline of the vertebral body at all levels except T12 and L1 [97].

The sagittal orientation of lumbar facet joints allows flexion and extension while providing resistance to axial rotation and translation [98]. Each spinal segment consists of three joints: the intervertebral disk and two facet joints [50]. The human spine possesses 23 intervertebral disks that separate the vertebrae and provide flexibility [101]. Intervertebral disks account for about 20% to 30% of the length of the spine and increase in size from the cervical to the lumbar regions [101]. The nucleus pulposus consists mainly of a high concentration of proteoglycans and water surrounded by a loose type II collagen network [101]. The annulus fibrosus has a low proteoglycan and water content and a high concentration of type I collagens organized into concentric lamellae [101]. The annulus fibrosus possesses 20 to 25 lamellae rich in collagen fibrils arranged in a parallel fashion [101]. In each adjacent lamella of the annulus fibrosus, collagen fibrils are fashioned in the opposite direction to create an alternating pattern between the lamellae [101].

The content of water and proteoglycan concentration within the disk increases when progressing from the annulus fibrosus to the nucleus pulposus [101]. Conversely, the content of collagen within the disk decreases from the outer annulus to the nucleus [101]. With increasing age, the proteoglycan and water content of the nucleus decrease [101]. The collagen content of the nucleus is highest in cervical disks and lowest in lumbar disks [101]. The proteoglycan content of the disk shows an opposite trend to collagen content when evaluating spinal levels [101].

The central canal is defined as the space posterior to the posterior longitudinal ligament, anterior to the ligamentum flavum and laminae, and bordered laterally by the medial border of the superior articular process [50]. The lateral recess is defined by the superior articular facet posteriorly, the thecal sac medially, the pedicle laterally, and the posterolateral vertebral body anteriorly [50]. The intervertebral foramen is bordered superiorly and inferiorly by the adjacent level pedicles, posteriorly by the facet joint and lateral extensions of the ligamentum flavum, and anteriorly by the adjacent vertebral bodies and disk [50]. Normal foraminal height is 20 to 30 mm [50]. Normal superior width of the intervertebral foramen is 8 to 10 mm [50].

In the thoracic and lumbar spine, the named nerve root exits below the named pedicle [95]. Discs are formally named for the vertebral bodies between which they lie [95]. Lateral recess pathology, such as lateral recess stenosis or posterolateral disc herniation, typically involves the next nerve root exiting caudal to that disc [95]. An L4-5 posterolateral disc herniation is expected to cause L5 nerve root symptoms [95]. The dorsal root ganglion lies within the outer confines of the intervertebral foramen [95]. The orientation of nerve roots in the dural sac follows a pattern where the most cephalad roots lie lateral and the most caudad lie centrally [95]. Motor roots are ventral to sensory roots at all levels [95]. The arachnoid mater holds the nerve roots in their specific positions [95].

Pathophysiology of Degeneration and Stenosis

Lumbar spondylosis is due to a degenerative cascade associated with intervertebral disk degeneration [96]. Intervertebral disk degeneration is a multifactorial process characterized by altered biomechanics of loading, an imbalance of extracellular matrix synthesis and degradation, increased secretion of proinflammatory cytokines, and increased apoptosis and senescence in nucleus pulposus cells [96]. Mechanical progression and disk space narrowing lead to adjacent level pedicle approximation with narrowing of the superior-inferior dimensions of the intervertebral foraminal canal [96]. Laxity of associated ligaments and vertebral column translates into altered loading mechanics and an altered pressure relationship on vertebral bone and joint surfaces [96]. Altered loading mechanics and pressure relationships influence osteophyte formation and facet joint hypertrophy [96]. Altered biomechanics lead to further degenerative changes and osteophyte formation [96].

Lumbar central and foraminal stenosis can result from degenerative changes, leading to symptomatic nerve compression and radiculopathy [96]. Lumbar spinal stenosis is the final stage of a cascade of events initiated by disk degeneration [50]. As disk height decreases, the loading characteristics of the facets are altered [50]. Facet joint capsules become incompetent, leading to capsular, ligamentum flavum, and facet hypertrophy [50]. The ligamentum flavum becomes less pliable with age [50]. When the spine is in extension, the spinal canal diameter diminishes resulting in buckling of the shortened, hypertrophied ligamentum flavum [50]. In flexion, there is a relative increase in the spinal canal diameter [50].

Degeneration of the disc occurs with disc narrowing and subsequent ligamentous redundancy, which compromises the spinal canal area [94]. Instability may ensue from disc degeneration and ligamentous redundancy [94]. Relative hypermobility precipitates the formation of facet overgrowth and ligamentous hypertrophy [94]. The ligamentum flavum may be markedly thickened into the lateral recess where it attaches to the facet capsule, causing nerve root compression [94]. Central spinal stenosis denotes involvement of the area between the facet joints occupied by the dura and its contents [94]. Stenosis in the central region is usually caused by protrusion of a disc, bulging anulus, osteophyte formation, or buckled or thickened ligamentum flavum [94]. Symptomatic central spinal stenosis results in neurogenic claudication with generalized leg pain [94]. Compression in the lateral canal region results in radiculopathy [94].

The lateral recess begins at the medial border of the superior articular process and extends to the medial border of the pedicle [94]. Facet arthritis most frequently causes stenosis in the lateral recess zone [94]. Vertebral body spurring and disc or anulus pathology also cause stenosis in the lateral recess zone [94]. The foraminal region lies ventral to the pars [94]. The dorsal root ganglion and ventral motor root occupy 30% of the foraminal space [94]. Causes of stenosis in the foraminal region include pars fracture with proliferative fibrocartilage or a lateral disc herniation [94]. Thickening of the ligamentum flavum can extend into the foramen and be associated with a spur from the undersurface of the pars [94]. This association is especially present if foraminal height is less than 15 mm and posterior intervertebral disc height is less than 4 mm [94]. The exit zone is identified as the area lateral to the facet joint [94]. The nerve root in the exit zone can be compressed by a "far lateral" disc, spondylolisthesis and associated subluxation, or facet arthritis [94].

The most common type of spinal stenosis is caused by degenerative arthritis of the spine [94]. Acquired forms of spinal stenosis are most commonly localized to the facet joints and ligamentum flavum [94]. The L4-5 level is the most commonly involved in acquired spinal stenosis, followed by L5-S1 and L3-4 [94]. Disc herniation and spondylolisthesis may exacerbate the narrowing of the spinal canal further [94]. The incidence of lumbar spinal stenosis is 1.7% to 8.0% in the general population [50]. The incidence of lumbar spinal stenosis increases in the fifth decade of life [50]. Lumbar spinal stenosis is the most common diagnosis requiring spine surgery in patients older than 65 years [50].

Most authors support a multifactorial etiology of low back pain and leg pain associated with lumbar spinal stenosis [50]. Mechanical compression, nutritive insufficiency, heredity, structural decompression, individual pain perception, and chemical insult likely play a role in lumbar spinal stenosis symptoms [50]. The natural history of spinal stenosis is typically favorable, with approximately 15% deteriorating clinically [50]. Improvement occurs in 30% to 50% of patients with spinal stenosis [50].

The degenerative process has been divided into three separate stages: dysfunction, instability, and stabilization [156]. The dysfunction stage is seen in individuals 15 to 45 years old and is characterized by circumferential and radial tears in the disc annulus and localized synovitis of the facet joints [156]. The instability stage is found in 35- to 70-year-old individuals and is characterized by internal disruption of the disc, progressive disc resorption, and degeneration of the facet joints with capsular laxity, subluxation, and joint erosion [156]. The stabilization stage is present in individuals older than 60 years and is characterized by the progressive development of hypertrophic bone around the disc and facet joints leading to segmental stiffening or frank ankylosis [156]. Disc herniation is considered a complication of disc degeneration in the dysfunction and instability stages [156]. Spinal stenosis from degenerative arthritis is a complication of bony overgrowth compromising neural tissue in the late instability and early stabilization stages [156]. The natural history of degenerative disc disease is one of recurrent episodes of pain followed by periods of significant or complete relief [156].

Genetic factors are more important than mechanical stresses in the development of disc herniations [22]. Internal disc derangement is a pathologic condition resulting in axial spine pain with no or minimal deformation of spinal alignment or disc contour [22]. Internal disc derangement is distinguished from measurable instability associated with fractures, traumatic ligamentous disruptions, degenerative listhesis, or scoliosis [22]. There are no defined criteria for internal disc derangement [22]. The diagnosis of internal disc derangement requires a compilation of findings consistent with the condition and elimination of other diagnostic possibilities [22]. Patients with internal disc derangement are usually relatively young, in the third to sixth decades of life [22]. Pain in internal disc derangement is usually chronic with symptoms present for several years [22]. Pain in internal disc derangement is axial primarily, often with buttock and posterior thigh pain [22]. Pain distal to the knee indicates either different or coexistent pathology in patients with internal disc derangement [22]. Positions and activities that increase intradiscal symptoms, such as sitting or flexion, exacerbate internal disc derangement symptoms [22]. Recumbency, especially in the fetal position, often decreases internal disc derangement pain [22].

Examination for internal disc derangement reveals no weakness or reflex changes if it is the only diagnosis [22]. Lumbar range of motion is mildly limited, especially in flexion, in patients with internal disc derangement [22]. Straight-leg raising typically causes back and buttock pain but no pain distal to the knee in internal disc derangement [22]. There is no spasm in the paraspinal musculature in internal disc derangement [22]. Extension usually gives some temporary relief in internal disc derangement [22]. Radiographs for internal disc derangement are negative for instability but may show disc space narrowing or other stigmata of spondylosis [37]. MRI typically reveals decreased signal intensity in the disc space on T2-weighted imaging in internal disc derangement [37]. MRI findings for internal disc derangement may include an annular tear or high intensity zone [37].

Discography is a controversial study designed as a preoperative study to correlate MRI findings with a clinically significant pain generator [37]. For a discography result to be considered reliably positive, the procedure should elicit pain after injection similar to that usually described by the patient [37]. The discography study should involve at least one minimally painful, nonconcordant level [37]. The discography study should be performed at multiple levels to include all abnormal levels and one or more normal levels as identified on MRI [37]. Evidence suggests that annular tears created by the needle during discography may accelerate the rate of symptomatic disc degeneration [37].

The causes of Modic changes are still unclear, but endplate microfracture is considered an important biomechanical factor for their occurrence [8]. A hypothesis for Modic change development is that inflammatory factors and metabolites after disc damage directly permeate into the endplates and vertebral body through microfracture gaps in the endplates [8]. Barzouhi et al. reported that 50.6% of patients who had undergone surgery developed new Modic changes in the first year after lumbar discectomy [8]. Most new Modic changes after lumbar discectomy progressed from no Modic changes to Modic type 1 [8]. Vital et al. found that in 17 patients with Modic type 1 at baseline, 13 cases progressed to Modic type 2 and 4 converted to normal bone marrow signal at the 6-month follow-up after posterior osteosynthesis [8]. Ohtori et al. reported that of 21 patients with Modic type 1, 10 remained with Modic type 1, 9 exhibited conversion to Modic type 2, and 2 changed to no Modic changes [8]. Ohtori et al. reported that of 12 patients with Modic type 2, 10 remained with Modic type 2 and 2 converted to no Modic changes [8]. Studies on the development of new Modic changes after lumbar fusion are lacking [8].

The sinuvertebral nerve is a small filamentous nerve that originates from the ventral ramus and progresses medially over the posterior aspect of the disc and vertebral bodies [95]. The sinuvertebral nerve innervates the posterior disc, vertebral bodies, and posterior longitudinal ligament [95]. The dorsal ramus courses dorsally, piercing the intertransverse ligament near the pars interarticularis [95]. The medial branch of the dorsal ramus innervates the facet joint at that level and the adjacent levels above and below [95]. Disc innervation is through afferent axons with cell bodies within the dorsal root ganglion [95]. Animal studies revealed two paths between the annulus and the dorsal root ganglion: one from the sinuvertebral nerve and another along the paravertebral sympathetic trunk [95]. In animal models, the lateral annulus was innervated by fibers coursing from the index level and two additional superior levels through the sinuvertebral nerves [95]. The lateral annulus also received innervation through the sympathetic trunk by the dorsal root ganglion from three levels even more superior than the sinuvertebral innervations [95]. Contralateral dorsal root ganglion involvement occurs through both sinuvertebral and sympathetic pathways [95]. Similar nonsegmental, multilevel innervation patterns have been reported for the ventral disc surface [95]. Innervations of the disc from the vertebral endplate have been shown [95]. Intraosseous nerves follow the osseous vasculature [95]. Endplate innervation is through the sinuvertebral nerve and the basivertebral nerve [95]. The basivertebral nerve enters the foramen, and its nerve fibers enter the vertebral margin with the vessels [95]. The density of endplate innervation is similar to that seen in the outer annulus [95].

Spondylolisthesis Pathophysiology

Most patients with isthmic spondylolisthesis present with low-grade deformities less than a 50% slip [155]. 90% to 95% of isthmic spondylolisthesis cases involve the L5-S1 level [155].

Classification

Spondylolisthesis Grading

Meyerding: This classification divides spondylolisthesis slip into five grades based on the percentage of vertebral translation: Grade I (0 to 25%), Grade II (25 to 50%), Grade III (50 to 75%), Grade IV (75 to 100%), and Grade V (greater than 100%) [244].

Spinal Deformity Study Group: The Spinal Deformity Study Group Classification of Lumbosacral Spondylolisthesis lacks robust clinical outcome studies to support its recommendations [204]. Observers demonstrated disagreement in applying this classification, particularly when classifying low-grade spondylolisthesis [204].

French Classification: The French classification of lumbar degenerative spondylolisthesis demonstrated intraobserver reliability K values ranging from 0.721 to 0.835 across four graders [227].

CARDS: The CARDS classification of lumbar degenerative spondylolisthesis demonstrated comparable demographics for gender, age, and BMI across different types [227]. Preoperative VAS (back) scores for CARDS Type D were higher than for other types [227].

Other Considerations: A new classification system that incorporates spinopelvic balance in the radiographic assessment may aid orthopaedic surgeons in identifying patients who would benefit from partial reduction and fusion [164].

Fusion Quality Assessment

Bridwell: Bridwell’s grading criteria define Grade I as fused with remodelling and trabeculae present, Grade II as graft intact but not fully remodelled with no lucency, Grade III as graft intact with potential lucency at the top and bottom, and Grade IV as fusion absent with collapse or resorption of the graft [208]. In the assessment of fusion using Bridwell’s criteria, grades I and II are considered radiographic signs of successful fusion, while grades III and IV are considered unsuccessful [208].

Lenke et al.: The Lenke et al. grading scale for posterolateral fusion defines Grade A as definitely solid with big trabeculated bilateral fusion masses, Grade B as possibly solid with unilateral large and contralateral small fusion masses, Grade C as probably not solid with small thin masses and probable unilateral pseudarthrosis, and Grade D as definitely not solid with graft resorption or obvious bilateral pseudarthrosis [240]. In the Lenke et al. grading scale, Grades A and B are considered fused, while Grades C and D are considered not fused [240].

Micro-CT: A micro-CT based grading system for fusion quality defines Grade I as complete fusion, Grade II as partial fusion, Grade III as unipolar pseudarthrosis, and Grade IV as bipolar pseudarthrosis or complete absorption of the bone graft [243].

Complication and Degeneration Classification

Modified Clavien–Dindo: The modified Clavien–Dindo classification (MCDC) scheme contains five types of complications: Type I (normal recovery without treatment), Type II (pharmacologic treatment needed), Type III (invasive intervention under general anesthesia needed), Type IV (intensive care unit admission needed), and Type V (death) [208].

Adjacent Segment Degeneration: Adjacent segment degeneration (ASDeg) is diagnosed when imaging demonstrates one or more of the following at the adjacent segment not present preoperatively: anterolisthesis or retrolisthesis > 4 mm, range of motion > 10°, loss of disc height > 10%, osteophyte formation > 3 mm, or spinal stenosis caused by facet joint hypertrophy, compression fracture, or degenerative scoliosis [208]. Symptomatic adjacent segment degeneration requiring reoperation is diagnosed as adjacent segment disease (ASDis) [208].

Hardware Loosening: Pedicle screw or cage loosening is defined as a radiolucency of ≥ 1 mm around the screw or the cage [208].

Kulowski: Kulowski’s classification evaluates the degree of end-plate destruction in infectious spondylitis: Grade I (only disk space narrowing), Grade II (bony destruction limited only in the end-plate), Grade III (vertebral body destruction of less than 50% of vertebral height), and Grade IV (vertebral body destruction over 50% of vertebral height) [78].

Other Considerations: A proposed classification system for cage retropulsion in degenerative lumbar disease suggests that early revision may yield better outcomes [230].

Fusion Level Definitions

Single-Level: Single-Level fusion is defined as fusion at one motion segment [81].

Double-Level: Double-Level fusion is defined as fusion involving two motion segments [81].

Multi-Level: Multi-Level fusion is defined as fusion involving three or more motion segments [81].

Clinical Presentation

Indications and Patient Selection

Careful patient selection for lumbosacral fusion is essential, requiring persistent, disabling pain unrelieved by non-surgical treatment [13]. The evidence for spinal fusion in non-specific low back pain is poor; spinal fusion should only be performed as part of a randomised controlled trial [6]. Surgical interventions for discogenic back pain are controversial and should be avoided whenever possible, with conservative measures exhausted before consideration of surgery [37, 38]. Currently, there is no good surgical option available that reliably reduces symptoms of discogenic back pain [37, 38]. Total disc arthroplasty is a surgical option for patients with degenerative disc disease at a single level (L4–L5 or L5–S1) with the absence of spondylolisthesis and no relief from 6 months of nonoperative therapy [37, 38].

Patients eligible for lumbar spinal fusion surgery in clinical trials are typically aged 18–64 years with pain and disability due to degenerative diseases or spondylolisthesis grade 1 or 2 [54]. Inclusion criteria for lumbar interbody fusion trials often require persistence of clinical symptoms despite conservative treatment for more than 3 months [111]. Inclusion criteria for posterior lumbar interbody fusion trials include persistent or recurrent low back or leg pain lasting at least 6 months resulting in a significant reduction of quality of life [113]. Patients with sleep apnoea who undergo posterior lumbar fusion pose significant challenges to clinicians [151].

History and Physical Examination

The approach to the active patient with low back pain begins with a thorough history and physical examination to establish a timeline and identify the nature, duration, onset, and characterization of symptoms [176]. Red flag signs such as fevers, chills, weight loss, history of cancer, immunosuppression, or intravenous drug abuse should prompt consideration of infection or malignancy [176]. Reports of clumsiness, gait instability, bowel, bladder, or sexual dysfunction should prompt assessment for causes of spinal cord dysfunction such as cervical or thoracic myelopathy [176].

Diskogenic pain related to disk degeneration or herniation may be worse in flexion, while sitting, or with prolonged axial loading and is often described in a diffuse, bandlike distribution [176]. Facet-mediated pain related to facet arthrosis or spondylolysis may be worse in extension and is often activity related and well localized [176]. A thorough examination should include observing the patient walk to assess coordination, strength, and symmetry of motion [176]. Palpation of the back should assess for points of maximal tenderness such as the facets, paraspinal musculature, or sacroiliac joints [176]. Assessing the range of motion of the hips can help rule out referred pain due to hip arthrosis [176].

Provocative tests such as straight leg raise, contralateral straight leg raise, or femoral nerve stretch test can be performed to corroborate physical examination or imaging findings [176]. For detecting lumbar disk herniation, the straight leg raise is more sensitive but less specific than the contralateral straight leg raise in patients with single leg radicular pain [176]. The presence of three or more Waddell signs should prompt evaluation for other etiologies such as depression, hypochondriasis, or secondary gain issues [176]. The presence of three or more Waddell signs is associated with higher pain scores and poorer treatment outcomes overall [176].

Other pathologies that can mimic or overlap the signs and symptoms of degenerative spondylolisthesis include vascular claudication, degenerative hip arthritis, and peripheral neuropathy [174]. If history and physical examination findings are inconsistent with degenerative spondylolisthesis, evaluation for vascular claudication, degenerative hip arthritis, and peripheral neuropathy should be considered [174]. At a minimum, hip range of motion and irritability should be evaluated as well as peripheral pulses in the feet and proprioception [174].

Diagnostic Imaging

Standing lateral and posteroanterior scoliosis radiographs should be obtained to adequately assess the patient's global balance and pelvic parameters [30]. These radiographs should include the skull and both proximal femoral heads so the hip axis can be determined [30]. A high-resolution CT scan is obtained to evaluate pedicle morphology, adequacy of the L5 transverse process, sacral morphology, facet arthritis at adjacent levels, and bony foraminal dimensions when more thorough anatomic evaluation is needed [30]. If the patient has significant radicular symptoms, an MRI is usually obtained to determine the specific location and etiology of the nerve root symptoms [30]. The health of the adjacent disc levels can be assessed on MRI, which will influence how many levels may need to be fused and the method of fusion [30]. Provocative discography is not found to be reliable by some authors for evaluating adjacent levels [30]. A pars injection with a small volume of long-acting local anesthetic is helpful as a diagnostic tool when evaluating patients with extensive degenerative changes at multiple levels in addition to isthmic spondylolisthesis [30].

Standing lateral, seated or standing flexion/extension laterals, and anteroposterior radiographs are imperative because 15% of deformities spontaneously reduce on supine imaging such as an MRI [174]. Instability is considered to be present when 4 mm of translation or 10 degrees of sagittal rotation greater than the adjacent level is identified [174]. Upright flexion-extension lateral views may reveal translational motion, indicating a more unstable motion segment [174]. The Ferguson anteroposterior view shows any significant degenerative changes in the lumbosacral joint and allows a better view of the transverse processes of L5 [174]. Hypoplastic transverse processes should prompt consideration for interbody fusion because of the paucity of bony substrate for fusion [174].

MRI is generally satisfactory for advanced neuroimaging, but patients with pacemakers or cardiac stents may require lumbar myelography and post-myelogram high-resolution CT scans [174]. Post-myelogram CT scans do not show pathology as well in the mid and lateral foramen because the subarachnoid space is not present out to the dorsal root ganglion [174]. Intraforaminal stenosis is relatively common, affecting the L4 nerve root, which is compressed against the inferior aspect of the L4 pedicle by annulus from a pseudohermiation due to the spondylolisthesis [174]. The presence of a facet joint effusion more than 2 mm in width is highly suggestive of instability at that level [174]. A 42% probability of dynamic instability exists for each 1 mm of facet joint effusion [174].

Radiographs are negative for instability but may show disc space narrowing or other stigmata of spondylosis in discogenic back pain [37, 38]. MRI typically reveals decreased signal intensity in the disc space on T2-weighted imaging (dark disc), with or without annular tear or HIZ in discogenic back pain [37, 38]. For a discography result to be considered reliably positive, the procedure should elicit pain after injection similar to that usually described by the patient (concordant pain) [37, 38]. Bone SPECT/CT was useful to identify the specific cause of pain in elderly patients with lumbar degenerative disease and to provide appropriate treatment, avoiding the unnecessary use of invasive spinal fusion surgery [65].

Preoperative Risk Factors and Comorbidities

Preoperative hemoglobin levels are associated with the risk of major complications and surgical site infections after single level lumbar fusion [3]. These hemoglobin thresholds can assist surgeons in counseling patients on their specific postoperative risk profile [3]. Higher BMI, larger facet joint angle, and wider sagittal and coronal diameters are prognostic factors that influence outcomes after lumbar fusion surgery [34]. Poor bone quality is associated with pseudarthrosis and poor clinical outcomes in single-level instrumented lumbar arthrodesis using local autologous bone graft [66]. There was an association between radiographic fusion status and clinical outcomes in patients with poor bone quality [66].

For posterior lumbar fusion, easily obtained patient ASA and age have overall similar or better discriminative abilities for perioperative adverse outcomes than numerically tabulated indices that have multiple inputs [67]. Knowledge of risk factors for new-onset cardiac arrhythmias may improve appropriate selection of an outpatient surgical center or orthopaedic specialty hospital versus an inpatient hospital for lumbar fusions [61]. Thorough understanding of clinical aging indices is essential when managing degenerative spine diseases, particularly in the selection of effective treatment approaches [40].

Natural History and Disease Progression

The natural history of discogenic back pain is one of recurrent episodes of pain followed by periods of symptomatic or complete relief [163]. More than half of patients who seek treatment for low back pain recover in 1 week, and 90% recover within 1 to 3 months [37, 38]. The natural history of developmental spondylolisthesis is different from that of acquired spondylolisthesis because of a lytic defect in an otherwise normal pars [69]. Degenerative spondylolisthesis is different from both developmental and acquired spondylolisthesis [69]. The association of spondylolysis and spondylolisthesis with clinically relevant low back pain is not clear [69].

Approximately 26% of those with isthmic spondylolisthesis have a first-degree relative who also had an isthmic spondylolisthesis [69]. The risk of progression to higher grades in spondylolytic spondylolisthesis is very small, and no children with a unilateral lytic defect had a slip that progressed [69]. Clinically there was no difference between the general population and those with a grade I or II slip regarding the development of back pain [69]. Most children (approximately 90%) with a lytic defect have been found to have spina bifida occulta, suggesting a dysplastic etiology [69]. The incidence of lytic defects increases with age, from 4.4% at age 6 to 6.0% in adults [69].

Females, those with higher grade slips (>50%) at the time of diagnosis, and those diagnosed before adolescent growth have a greater probability of progression in spondylolytic spondylolisthesis [69]. Facet tropism was identified as a risk factor for isthmic spondylolisthesis in males [69]. Developmental spondylolisthesis with dysplasia is more likely to progress than the spondylolytic type [69]. Dysplasia of the anterior sacrum correlates best with progression in the dysplastic group [69]. At 18-year follow-up, 36% of patients with Meyerding types III and IV spondylolisthesis treated nonoperatively were asymptomatic [69].

Degenerative spondylolisthesis usually occurs at the L4-L5 level, primarily affects females over the age of 50, and is more frequent in people of African descent [69]. Slip progression has been found to occur in about 30% of patients with degenerative spondylolisthesis, but there usually is only mild progression [69]. If neurologic symptoms are present, operative treatment is superior to nonoperative treatment for degenerative spondylolisthesis [69]. 76% of patients with degenerative spondylolisthesis without neurologic symptoms remained stable over long-term follow-up (10 to 18 years) [69]. The slip angle has been found to have some predictive value for slip progression when it is larger than 30 degrees [69]. The lumbosacral angle has been found to have some predictive value for progression when it is larger than 10 degrees [69]. Pelvic incidence is a constant anatomic pelvic variable specific to each individual and strongly determines sacral slope, pelvic tilt, and lumbar lordosis [69]. A value of 60 degrees for L5 incidence was a threshold to define spinopelvic balance versus unbalance in high-grade developmental spondylolisthesis [69].

Postoperative Presentation and Complications

The possibility of pseudarthrosis after spinal arthrodesis should be remembered from the time the operation is proposed until the fusion mass is solid [182]. The reported pseudarthrosis rate ranges from 9% to 30% [182]. Some authors have correlated higher pseudarthrosis rates with a greater number of levels fused, but multiple studies have reported single-level pseudarthrosis rates as high as 30% [182]. It has been estimated that 50% of patients with pseudarthrosis have no symptoms [182]. Persistent pain after spinal fusion with no other identifiable cause is presumed to be caused by pseudarthrosis when this condition is present [182].

Discretely localized pain and tenderness over the fusion area are helpful in making a diagnosis of pseudarthrosis [182]. Progression of the deformity or disease is a helpful finding in making a diagnosis of pseudarthrosis [182]. Localized motion in the fusion mass, as found in biplane bending radiographs, is a helpful finding in making a diagnosis of pseudarthrosis [182]. Motion in the fusion mass found on exploration is a helpful finding in making a diagnosis of pseudarthrosis [182]. The amount of motion on flexion-extension radiographs that is consistent with solid fusion is controversial, ranging from no motion to 5 degrees of motion [182]. When rigid instrumentation has been used, lack of motion does not necessarily indicate solid fusion [182]. The presence of broken spinal implants implies pseudarthrosis [182].

Thin-cut CT scans appear to be more reliable than radiographs in evaluating fusion [182]. A prospective study comparing imaging findings to intraoperative findings showed that CT most closely agreed with intraoperative findings compared with plain radiographs and MRI [182]. The expense of MRI and its susceptibility to metallic artifact from instrumentation remain disadvantages to its routine use in the assessment of spinal fusion [182]. Exploration is the only way to be absolutely certain that a fusion mass is completely solid [182].

Failure to recognize the pathologic condition causing the patient's original symptoms remains a leading cause of failed fusion procedures [32]. Intraoperative problems, such as dural injury and internal fixator complications, are known causes of persistent pain after lumbar spinal fusion [32]. Psychosocial issues can make a satisfactory functional outcome unlikely, with these patients never achieving the desired relief of symptoms or return to full function [32]. Failures may occur when a posterolateral fusion has been used to treat diskogenic causes of back pain and the patient's continued symptoms are the result of elasticity of the fusion mass such that the disk continues to be loaded and produce pain [32]. Other possible causes of persistent pain after lumbar fusion include disorders in adjacent motion segments, such as spinal stenosis and acquired instability [32]. Indolent infection after lumbar interbody fusion is an under-recognized cause of pseudarthrosis [29].

Patients undergoing isolated decompression for lumbar facet cysts undergo subsequent lumbar fusion at a 5-year rate of 6.79% [146]. The rate of lumbar fusion in the cauda equina syndrome cohort was 3.6% after 1 year, 6.7% after 3 years, and 7.8% after 5 years [42]. This rate of lumbar fusion in the cauda equina syndrome cohort was significantly higher than the lumbar spinal stenosis control group at all time points [42]. Pre-existing L5-S1 degeneration does not affect clinical and radiographical outcomes after isolated L4-5 fusion [33]. No differences were found in 90-day aggregated postoperative adverse events and 5-year lumbar revision surgery rates between instrumented and noninstrumented posterolateral approaches for lumbar degenerative spondylolisthesis [5]. Both oblique lumbar interbody fusion and transforaminal lumbar interbody fusion have comparable fusion rates, complication rates, and lumbar pain improvements [9]. Results demonstrate significant improvements in clinical outcomes and pain reduction after lumbar spinal fusion with a PEEK-based dynamic instrumentation device, topping off at 2 years after surgery [21].

Investigations

Plain radiography: Standing lateral and posteroanterior scoliosis radiographs are required to assess global balance and pelvic parameters for operative planning [30]. In patients with prior total hip arthroplasty scheduled for lumbar fusion, obtaining flexed-seated radiographs preoperatively may help communicate potential risks of postoperative dislocation [267].

MRI: MRI is the standard for advanced spinal imaging, superior to CT for identifying infections, tumors, and degenerative changes within discs [105]. It is also superior to CT for directly imaging neural structures and the nerve root in the foramen [105]. MRI is usually obtained to determine the specific location and etiology of nerve root symptoms in patients with significant radicular symptoms [30]. However, MRI evidence of lumbar disc degeneration was found in 35% of patients aged 20 to 39 years and in 100% of patients older than 50 years [105]. Abnormal MRI findings did not correlate with low back pain in professional beach volleyball players, indicating MRIs must be interpreted with caution [268]. Consequently, MRI findings must be correlated with the clinical impression, as abnormal anatomy may be asymptomatic [105]. The most meaningful clinical information from MRI is obtained by posing specific questions regarding neural compression, instability, and deformity derived from history and physical examination [105]. On MRI, Modic changes, particularly Type 2, are common radiological findings in lumbar spine imaging, most frequently occurring at L4/L5 and L5/S1 levels [257]. Additionally, the volume of multifidus muscles was markedly decreased after posterior lumbar fusion, as apparent in MRI [241].

CT: CT is the diagnostic imaging modality of choice for injuries involving the thoracic, lumbar, or sacral regions of the spine [118]. In thoracic and lumbar trauma, additional evaluation with MRI is typically not necessary, although there are circumstances where it is appropriate [118]. High-resolution CT scans are used to evaluate pedicle morphology, adequacy of the L5 transverse process, sacral morphology, facet arthritis, and bony foraminal dimensions [30]. CT may help diagnose endplate sclerosis in patients with type 2 Modic change and inform the choice of the best site for spinal fusion [265].

Myelography: Myelography is indicated when MRI cannot be obtained, when there is suspicion of an intraspinal lesion, or when spinal instrumentation causes artifact [121]. It is valuable in evaluating previously operated spines and in patients with marked bony degenerative change that may be underestimated on MRI [121].

Nuclear Medicine: Bone SPECT/CT is useful to identify the specific cause of pain in elderly patients with lumbar degenerative disease [65]. This modality can help avoid the unnecessary use of invasive spinal fusion surgery by identifying the primary cause of pain [65]. 18F-fluoride PET/CT bone metabolism of the operated intervertebral disc space at six weeks had the highest diagnostic accuracy for predicting fusion status at one year [255].

Other Considerations: Provocative discography has not been found to be reliable for evaluating adjacent levels in patients with isthmic spondylolisthesis [30]. Pars injection with a small volume of long-acting local anesthetic is helpful as a diagnostic tool when evaluating patients with extensive degenerative changes at multiple levels [30]. Twenty-nine percent of patients developed radiologic adjacent segment degeneration two years after lumbar fusion for degenerative spondylolisthesis [261]. Preoperative spinopelvic assessment is recommended for all patients undergoing total hip arthroplasty, as only a minority of those with limited lumbar flexion have an instrumented fusion [76]. Preoperative hemoglobin level thresholds can assist surgeons in counseling patients on their specific postoperative risk profile for major complications and surgical site infections [3]. The evidence for spinal fusion in non-specific low back pain is poor, and spinal fusion should only be performed as part of a randomised controlled trial [6].

Treatment

Non-Operative

Nonsurgical management remains the standard of care for lumbar degenerative disk disease [85]. For discogenic back pain, surgery should be avoided whenever possible, and conservative measures must be exhausted before any consideration is given to surgical intervention [37]. Spinal fusion should only be performed as part of a randomised controlled trial for non-specific low back pain, and lumbar disc replacement should not be performed for this condition [6].

Operative

Indications: Lumbar decompression remains the benchmark for patients with lumbar spinal stenosis, with no benefit to routinely performing fusion [39]. Surgical treatment of lumbar stenosis is successful in 80% to 85% of cases, defined as significant pain relief with a return to activities of daily living [56]. However, in a retrospective review 4 years after lumbar decompression, "successful outcomes" (defined as relief of pain and no reoperation) were found in only 57% of cases [56]. Factors associated with unsuccessful outcomes include multiple comorbidities, single-level decompressions, a 5% annual incidence of degeneration at levels adjacent to the decompression, and predominating low back pain [56]. Arthrodesis is at present the best surgical treatment for the persistently painful degenerative back, though it increases morbidity and mortality rates and carries a risk of non-union [45]. Currently no good surgical option is available that reliably reduces symptoms of discogenic back pain [37]. Total disc arthroplasty is a surgical option for patients with degenerative disc disease at a single level (L4–L5 or L5–S1) in the lumbar spine with the absence of spondylolisthesis and no relief from 6 months of nonoperative therapy [37]. Additional studies are required to elucidate which patients with degenerative spondylolisthesis can undergo a decompression only, which require a fusion, and which can benefit from interbody fusion [39]. Operative treatment of lumbar stenosis and degenerative spondylolisthesis offered a significant benefit over nonoperative treatment in patients at least eighty years of age [219].

Surgical Approach / Technique: The best technique for a particular patient remains controversial, and the decision should be based on the pathologic entity being treated, expected applicable biomechanics and healing potential of different constructs, and the surgeon’s experience [124]. Posterior decompression with instrumented fusion is the most common surgical treatment for degenerative lumbar spondylolisthesis, though individual patient factors must guide the selection of the specific strategy [18]. No differences were found in 90-day aggregated postoperative adverse events and 5-year lumbar revision surgery rates between noninstrumented and instrumented posterolateral approaches for lumbar degenerative spondylolisthesis, suggesting that instrumentation can be safely performed and that both approaches had similarly durable results [5].

The classic PLIF technique is performed through a wide laminotomy, with resection of the ligamentum flavum and partial or complete removal of the cranial lamina [80]. In PLIF, the lower one third of the inferior facet and the medial two thirds of the superior facets are resected to expose the pedicle of the vertebra as far laterally as possible [80]. The traversing nerve root and dural sac are retracted medially during PLIF, with special attention given to identifying and protecting the true axilla of the upper nerve root to prevent neurologic damage from undue tension [80]. ULIF is an effective minimally invasive lumbar fusion surgical technique [102]. The biportal endoscopic transforaminal lumbar interbody fusion technique with a large cage is a straightforward, safe, and minimally invasive method for inserting large cages in the treatment of lumbar instability [109]. LLIF involving the L4-5 disc level has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with the appropriate indications and using a standardized surgical technique [70]. Posterior lateral lumbar fusion surgery which preserves partial facet joint unilaterally during neural decompression can offer greater benefits to patients with degenerative lumbar spinal stenosis presenting bilateral lower limb symptoms under strict adherence to surgical indications [71].

Direct lateral or far lateral approaches to the interbody space in the lumbar spine are especially useful for degenerative scoliosis, allowing for complete disc resection with a bony bed for fusion, excellent correction of coronal deformities, and very good indirect decompression of foraminal stenosis [149]. The overlap between adjacent neurovascular structures and the vertebral body endplate gradually increases from L1-2 to L4-5, resulting in a very narrow safe zone at L4-5 for the minimally invasive lateral approach [145]. The lumbar plexus is at the greatest risk of injury at the L4-5 level during the minimally invasive lateral approach [145]. Nayar et al. found that the lateral approach was associated with a significantly lower rate of reoperation than the posterior approach at 30 days and at 2 years [145]. Mini-open oblique lumbar interbody fusion (OLIF) is a safe approach for accessing the L2 down to L5, but another approach is advised for the L5-S1 due to the danger of injuring the iliac vessels [193]. The minimally invasive lateral trans-psoas approach to the lumbar spine poses a risk of injuring the neural structures of the lumbar plexus as they course through the psoas [193]. The approach to L5-S1 via the minimally invasive lateral trans-psoas route is extremely difficult because of the presence of the iliac crest and the iliolumbar vein [193]. In a hybrid lumbar interbody fusion sequence, ALIF is performed first to open the L5-S1 gap, especially in patients with high iliac, to facilitate the L4–5 segment surgery [220]. ALIF has proven effective for revision lumbar fusion surgery, yielding positive clinical and radiographic results [14]. ALIF is the preferred strategy for L5-S1 arthrodesis at the bottom of a long construct in minimally invasive surgery treatment of adult spinal deformity [225]. Circumferential fusion is recommended by several authors to regain stability at the lumbosacral junction in lumbosacral dislocation [46]. SA-LLIF can provide immediate stability and good results for lumbar degenerative diseases with a standalone anchored cage without posterior internal fixation [214]. Posterior fixation can further improve the segmental alignment of lumbar degenerative spondylolisthesis with oblique lumbar interbody fusion [210]. Transsacral fixation/fusion may allow for safe lumbosacral fusion without iliac fixation in the setting of long-segment constructs in carefully selected patients [167]. When patients with L4–S1 lumbar degenerative disease with osteoporosis undergo lumbosacral fusion and fixation, the use of S1 pedicle screws with PMMA augmentation has better stability and less screw loosening [202]. Pedicle screw insertion into infected vertebrae during minimally invasive posterior fixation reduces the operative time and range of fixation without increasing the occurrence of unplanned reoperations due to surgical site infection or implant failure [82].

The Wiltse and Spencer approach for in situ posterolateral instrumented fusion involves making a midline skin incision at the L5-S1 level and fascial incisions 3 cm off the midline at the interval between the multifidus and longissimus muscles [159]. In the Wiltse and Spencer approach, S1 screw holes are prepared for a bicortical technique for enhanced screw purchase by penetrating the sacral cortex medially at the promontory just caudal to the endplate [159]. The patient is mobilized without a brace beginning the morning after surgery in the Wiltse and Spencer approach, and patients are generally independent with activity and can be discharged the second or third postoperative day [159]. The technique of bilateral posterolateral fusion combined with a Hibbs fusion is an improvement in the evolution of the best technique for fusion of the lumbosacral spine [51].

Implant Selection: Both PEEK rods and titanium rods are effective fixation materials in lumbar fusion surgery [153]. The biomechanical benefit of a stand-alone two-part fusion cage can be justified [59]. A new assembled lumbar interbody fusion cage provides more advantageous endplate stress distribution, peak von Mises stress, and cage stress compared to the assembled state [75]. Biodegradable rods may present more favourable clinical outcomes for lumbar fusion by providing sufficient initial stability while gradually transferring loading to adjacent segments as rigidity decreases over time [192]. The results demonstrate a fusion rate similar to that of metallic implant systems with the use of a carbon-fiber PEEK pedicle screw and a TLIF cage system [184]. After total en bloc spondylectomy, the posterior long-segment fixation combined with the anterior 3D printed prosthesis could maintain postoperative spinal stability, but adding artificial pedicle fixation increased the stability of the fixation system and reduced the risk of prosthesis subsidence and instrumentation failure [224]. The polymer enhanced AS-ELARIS® pedicle screw system using ultrasonically liquefied polylactide has biocompatibility, biodegradability, safe removal, and ease of handling, making it a valuable addition to spinal fixation strategies [218]. Among patients who achieved successful posterior lumbar internal fixation, whether or not to remove the fixation instruments should be evaluated carefully [185].

Adjuncts: Computer-navigation and robotic devices can be helpful in the placement of pedicle screws, but are typically reserved for placement across a fusion mass that has lost all anatomic landmarks or in severe deformities where anatomy is difficult to identify [149]. Image guidance and robotics can facilitate instrumentation placement and correction while reducing radiation exposure to the surgeon and patient in less-invasive decompression and fusion procedures [149].

Other Considerations: Elderly patients undergoing minimally invasive transforaminal lumbar interbody fusion had comparable rates of perioperative complications and similar improvements in pain, function, and quality of life as younger counterparts when clinical and surgical heterogeneity were minimized [252]. Greater use of fusion-based procedures for lumbar spinal disorders was found in the private sector, irrespective of the clinical condition [12]. In direct comparison with anterior interbody fusion, total disc arthroplasty showed equivalent clinical results and no catastrophic failures at 2-year follow-up [37]. Significant concerns regarding total disc arthroplasty include long-term results, design issues, cost, and the safety of revision procedures [37]. Non-operative treatment for stable thoracolumbar burst fractures and uninstrumented fusion for low-grade lytic spondylolisthesis demonstrate established clinical proficiency with excellent long-term outcomes and lower complication rates compared to instrumented approaches [216].

Outcomes and Efficacy: In Spinal Stenosis with Degenerative Spondylolisthesis, Decompression Surgery Alone Was Noninferior to Decompression Surgery with Instrumented Fusion for Reducing Impairment at 2 Years [58]. Decompression alone demonstrates non-inferiority in terms of efficacy for treating low back pain due to degenerative spondylolisthesis compared to fusion, with additional benefits in operation time and blood loss [183]. Both the Topping-off technique and lumbar fusion surgery achieved satisfactory clinical outcomes in treating lumbar degenerative diseases [107]. Postoperative lower back pain was significantly diminished at follow-up visits in patients undergoing pedicle screw fixation and posterior fusion for lumbar degenerative diseases [259]. Thirty-six out of 38 patients had complete relief from pain and discomfort along with radiographic fusion after anterior lumbar fusion in Pott's disease [41]. All patients demonstrated a resolution of symptoms after placement of an anterior lumbar interbody cage, without intraoperative complications, and a subsequent antibiotic regimen for indolent infection after lumbar interbody fusion [29]. The early results of lumbar spine fusion and pedicle fixation with C-D screws for lumbar iatrogenic instability are most encouraging, showing relief of symptoms, solid fusion of the spine, and maintenance of the lumbar curve with no major complications [10]. Successful treatment of complete spondylolisthesis in an infant consisted in spine fusion from the third lumbar vertebra to the sacrum [15].

Complications and Adverse Events: Approximately one-third of adverse events after posterior lumbar fusion were diagnosed 31 to 90 days after surgery, highlighting the importance of looking past the 30-day mark for adverse event characterization [1]. Perioperative neurologic injury is among the most serious complications of spinal surgery, with a reported rate of zero to 7% during instrumented PLIF and TLIF [35]. At one institution, the complication rate for neurologic injury was higher with PLIF than with TLIF (7.8% and 2%, respectively) [35]. Lower rates of neurologic injury have been reported with open TLIF than with minimally invasive procedures [35]. In both TLIF and PLIF, the nerve roots must be retracted to gain access to the posterior disk space, and traction can substantially reduce nerve root blood flow, causing ischemic nerve root injury [35]. Radicular pain is the most commonly reported postoperative symptom of neurologic injury after TLIF or PLIF [35]. Postoperative weakness or numbness is reported less often than radicular pain, which indicates either a lower incidence or lesser patient concern [35]. Lumbar fusion surgery should be performed meticulously to minimize the incidence of intraoperative incidental durotomy [117]. The complication rate for patients undergoing adult spinal deformity surgery is high, and patients should be counseled on their risk for short- and long-term complications and need for potential revision surgery [39]. Patients with cystic fibrosis undergoing posterior lumbar fusion are at an increased odds of perioperative complications [74].

Complications, primarily related to nerve root injury or irritation, have been reported in 22% of patients after a minimally invasive direct lateral anterior lumbar fusion and extreme lateral interbody fusion [141]. Knowledge of “safe zones” for the minimally invasive direct lateral approach and familiarity with the dilating retractor systems are essential for avoiding complications [141]. Reported complications of combined transpsoas extreme lateral interbody fusion and posterior pedicle screw instrumentation have included intraoperative bowel injury, motor radiculopathy, and postoperative thigh paresthesias or dysesthesias [149]. The rate of major complications after a far lateral approach in one study was 12% [149].

Cage migration occurred in 48% of cases and cage subsidence in 44% of cases among patients with infected lumbar interbody cages [78]. The mean elapsed time to the diagnosis of cage infection from the previous primary surgery was 72.1 days (range, 27–170 days) [78]. The most common infected cage level was L4–L5 (52%), followed by L5–S1 (19%) and L3–L4 (15%) [78]. Smoking is associated with increased blood loss and transfusion use after lumbar spinal surgery [23]. The effects of lumbar fusion on the development of Modic changes are limited in evidence, with studies lacking on the development of new Modic changes after lumbar fusion [8]. Lumbar discectomy positively accelerates the development of Modic changes, with 50.6% of patients developing new Modic changes in the first year after surgery [8].

Perioperative Management and Risk Factors: Lumbar fusion surgery was associated with a higher rate of hip prosthesis dislocation and higher risk of revision surgery following total hip arthroplasty [43]. Lumbar fusion of more than two segments is a predictor of more posterior sagittal pelvic tilt changes in individuals receiving total hip arthroplasty, but fusion of L5S1 is not [47]. Preoperative spinopelvic assessment is recommended for all patients undergoing total hip arthroplasty, as only a minority of those with limited lumbar flexion have an instrumented fusion and may otherwise be overlooked [76]. For posterior lumbar fusion, easily obtained patient ASA and age have overall similar or better discriminative abilities for perioperative adverse outcomes than numerically

Complications

General Adverse Events and Reoperation: The overall revision surgery rate for one- and two-level lumbar fusion procedures is 15% [4]. In workers' compensation cohorts, the reoperation rate reaches 27% for surgical patients, with 36% of lumbar fusion subjects experiencing complications [20]. Reoperation incidence is higher in lumbar fusion patients than in those undergoing cervical fusion for degenerative spinal diseases [128]. Surgical site infection is the most common reason for early reoperation, while adjacent segment disease drives late operations [283]. Despite an increasing comorbidity burden from 2010 to 2022, the overall incidence of adverse events has not increased [278]. Surgeons must account for substantial unmeasured blood loss during these procedures [291].

Neurologic Injury: Perioperative neurologic injury occurs in 0% to 7% of instrumented PLIF and TLIF cases [35]. One institution reported higher rates with PLIF (7.8%) than TLIF (2%) [35]. Traction on nerve roots during these procedures can substantially reduce blood flow, causing ischemic injury [35]. Symptoms include radicular pain, paresthesias, numbness, and weakness, with radicular pain being the most common postoperative symptom [35]. Iatrogenic injury may lead to temporary or permanent impairment [35]. No effective surgical options exist for managing these postoperative neurologic complications [35]. A single serious adverse event of postoperative radiculopathy was definitely related to bone graft extrusion in a cellular bone allograft trial [136].

Pseudarthrosis and Fusion Failure: A systematic review identified 17 risk factors for pseudarthrosis, emphasizing age, smoking status, and the number of fusion levels as significant predictors [290]. Fusion rates are 90% in painful degenerative disease, 93% in spondylolisthesis, and 65% in preoperative pseudarthrosis [296]. Indolent infection is an under-recognized cause of pseudarthrosis after lumbar interbody fusion [29]. Adding interbody fusion to posterolateral fusion increases the risk for additional surgery without improving patient-reported outcomes [284]. Anterior spinal fusion carries the highest reoperation rate, while posterior procedures show lower rates that do not differ significantly; adding interbody fusion to posterior spinal fusion does not improve outcomes [293].

Infection: Patients on chronic preoperative steroid therapy face increased risks of multiple perioperative complications, particularly surgical site complications and venous thromboembolic events, following elective PLF [269]. For single-level posterior lumbar fusion, cefazolin alone yields similar 90-day adverse outcome and 2-year revision rates compared to cefazolin combined with gentamicin or tobramycin [299]. In minimally invasive posterior fixation for thoracolumbar pyogenic spondylitis, pedicle screw insertion into infected vertebrae reduces operative time and fixation range without increasing unplanned reoperations due to surgical site infection or implant failure [82]. Delayed infection after posterior instrumentation and fusion for adolescent idiopathic scoliosis occurs in 1% to 10% of cases [168]. Risk factors for delayed infection include significant past medical history, blood transfusion, and the absence of a deep drain [168].

Adjacent Segment Disease: Arthroplasty demonstrates reduced revision rates for adjacent segment disease compared to fusion [44]. The incidence of adjacent segment disease in patients after spine surgeries for cancer metastases does not differ between study groups [292].

Implant and Hardware Complications: Lumbar-pedicle fixation devices are classified as class III medical devices by the FDA, indicating they are investigational or experimental, have not been proved safe and effective, and may pose a risk to patients [72]. Low bone mineral density and large correction of both main and fractional curves predict distal pedicle screw loosening after posterior corrective surgery for degenerative lumbar scoliosis [285]. Posterolateral fusion acts as a protective factor against distal pedicle screw loosening in this context [285]. Asymptomatic cage migration occurred in two cases after percutaneous endoscopic transforaminal lumbar interbody fusion, requiring no further operation [249]. Symptomatic cage migration requiring conventional secondary reoperation occurred in 13 cases after a mean delay of eight months following percutaneous endoscopic transforaminal lumbar interbody fusion [249]. Screw migration of the posterior construct occurred in one case of L1/2 fusion after percutaneous endoscopic transforaminal lumbar interbody fusion [249]. The overall subsidence rate was 12.6% in a comparative study of ALIF, OLIF, and TLIF, with TLIF showing a significantly higher rate (16.1%) than ALIF (7.1%) and OLIF (9.8%) [132]. Primary complications of posterior surgery and instrumentation for adolescent idiopathic scoliosis include infection, pseudarthrosis, neurologic deficit, and implant-related problems such as prominence, discomfort, and implant failure [168].

Vascular and Medical Complications: Patients with osteoporosis undergoing 2- to 3-level lumbar fusion for degenerative disc disease experience higher rates of medical and surgical complications, as well as revision surgeries, at 2-year follow-up [272]. Combined intravenous and topical tranexamic acid effectively reduces total blood loss and transfusion rates in patients over 60 undergoing 2-level lumbar fusion without increasing DVT or PE incidence [258]. Identifying modifiable risk factors for underlying liver disease allows preoperative optimization to decrease the incidence and severity of complications after posterior lumbar fusion [274]. Preoperative hemoglobin level thresholds assist surgeons in counseling patients on their specific postoperative risk profile for major complications and surgical site infections after single-level lumbar fusion [3].

Impact on Other Procedures: Patients with a history of lumbar fusion have significantly greater rates of revision hip arthroscopy and conversion to total hip arthroplasty compared to those without previous fusion [83]. Patients undergoing lumbar fusion and subsequent total hip arthroplasty face significantly higher risks of dislocation and revision than a matched cohort undergoing only total hip arthroplasty [84]. Lumbosacral spinal fusions prior to total hip arthroplasty increase the risk of dislocation within the first six months, with fusions involving the sacrum and multiple lumbar levels notably increasing risk compared to controls [89]. Prior lumbar spine fusion increases the risk of post-operative dislocation and the need for revision surgery for instability after total hip arthroplasty [282]. Lumbar fusion before total hip arthroplasty is an independent risk factor for dislocation leading to increased risk of revision total hip arthroplasty [260]. Patients with prior total hip arthroplasty undergoing long fusion to the pelvis experience longer length of stay, more surgical complications, and a lower rate of spinal revisions compared to those fused to the sacrum [286]. Patients with prior total hip arthroplasty undergoing multilevel thoracolumbar fusions experience more dislocations, higher spinal revision rates, less frequent discharge home, longer hospital length of stay, and higher 90-day readmission rates [288].

Learning Curve and Technique-Specific Risks: The overall complication rate for minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) is 20% in systematic reviews of learning curve studies [207]. The cumulative complication rate reaches 33% in the initial 10 cases performed by the learning surgeon for MIS TLIF [207]. The MIS TLIF learning curve for operative time is approximately 20 cases, with mean decreases in operative time of 33% and 50% over the initial 20 cases [207]. PLIF is associated with a significantly higher overall complication rate and longer operative time compared to TLIF [300]. The incidence of neurologic deficit following surgery for adolescent idiopathic scoliosis is below 1% [168]. Neurologic deficit incidence is regarded to be higher with combined anterior/posterior surgery and when osteotomies are performed, and is generally thought to be of vascular origin [168]. Laminoplasty shows lower complication rates than fusion [44]. Major surgical complications occurred in 11.6% of patients, and 11.6% experienced major medical complications in a study of high-dose rhBMP-2 for adults [289]. Posterolateral lumbar fusion with BMP-2 in veterans yields high fusion rates and favorable complication profiles [68].

Recovery

Adverse Events and Complications: In a cohort of workers' compensation subjects, 36% of lumbar fusion patients experienced complications [20]. The reoperation rate in this same cohort was 27% for surgical patients [20].

Functional Recovery and Rehabilitation: Early initiation of a postoperative rehabilitation program based on strength training principles is safe 3 weeks after lumbar spine fusion [119]. This early strength training approach enables earlier functional recovery compared to standard rehabilitation protocols [119]. Objective activity trackers indicate that lumbar surgery results in a decrease in activity amount 1 month just after surgery [196]. Activity levels demonstrate gradual postoperative recovery within 3 months after lumbar surgery [196]. Rehabilitation provides benefits for patient recovery after spine surgery [209]. Prompt postoperative mobilization does not prevent fusion when a posterolateral technique is used [212]. An enhanced recovery after surgery (ERAS) protocol has been described for elderly patients undergoing short-level lumbar fusion surgery [64]. Patients with metabolic syndrome require appropriate management and rehabilitation to achieve optimal outcomes based on longitudinal recovery patterns [162].

Long-term Outcomes and Durability: No differences were found in 90-day aggregated postoperative adverse events between instrumented and noninstrumented posterolateral lumbar fusions for lumbar degenerative spondylolisthesis [5]. Similarly, no differences were found in 5-year lumbar revision surgery rates between these two groups [5]. At mid-term follow-up, posterior lumbar interbody fusion (PLIF) and oblique lateral interbody fusion (OLIF) provided sustained improvement in pain and function for lumbar spinal stenosis [273]. Clinical outcomes and pain reduction after lumbar spinal fusion with a PEEK-based dynamic instrumentation device top out at 2 years after surgery [21]. Short-term studies demonstrate similar clinical improvements for both disk replacements and fusion procedures at up to 2-year follow-up [231].

Specific Populations and Scenarios: Surgical management of selected lumbar spine conditions can produce excellent outcomes in athletes of all sports [276]. Lumbar spine surgery can facilitate the return of military pilots to their profession after treatment for symptomatic lumbar disc herniation and lumbar isthmic spondylolisthesis [217]. Pre-existing L5-S1 degeneration does not affect clinical and radiographical outcomes after isolated L4-5 fusion for spondylolisthesis [33]. Sociodemographic differences can guide patient counseling and recommendations to improve surgical outcomes for patients after lumbar spine surgery [235].

Key Evidence

• [L3] Approximately one-third of adverse events after posterior lumbar fusion were diagnosed 31 to 90 days after surgery, highlighting the importance of looking past the 30-day mark for adverse event characterization. [1] (10.5435/jaaos-d-21-01121)
• [L3] It should be considered by surgeons before realizing a lumbar fusion. [2] (10.1016/j.otsr.2013.09.003)
• [L3] These thresholds are a unique addition to the single-level lumbar fusion literature and can assist surgeons in counseling patients on their specific postoperative risk profile. [3] (10.5435/jaaosglobal-d-24-00074)
• [L3] One- and two-level lumbar fusion procedures demonstrated high durability with an overall revision surgery rate of 15%. [4] (10.5435/jaaosglobal-d-25-00424)
• [L4] No differences were found in 90-day aggregated postoperative adverse events and 5-year lumbar revision surgery rates, suggesting that instrumentation can be safely performed and that both approaches had similarly durable results. [5] (10.5435/jaaosglobal-d-25-00192)
• [L5] The evidence for spinal fusion or disc replacement in non-specific low back pain is poor; spinal fusion should only be performed as part of a randomised controlled trial, and lumbar disc replacement should not be performed. [6] (10.1302/0301-620x.99b8.bjj-2017-0199.r1)
• [L4] No completely reliable method of spine fusion has been developed, with success rates varying widely and often overestimated by roentgenographic methods. [7] (10.2106/00004623-196850010-00017)
• [L3] [8] (10.1186/s13018-022-02971-3)
• [L1] Both methods have comparable fusion rates, complication rates, and lumbar pain improvements. [9] (10.3389/fsurg.2024.1374134)
• [L4] The early results are most encouraging, showing relief of symptoms, solid fusion of the spine, and maintenance of the lumbar curve with no major complications. [10] (10.1007/bf00393719)
• [L1] This meta-analysis addressed the limitations of prior reviews and summarized evidence with regard to risk factors for ASD following lumbar fusion. [11] (10.2106/jbjs.20.00408)
• [L2] We found greater use of fusion-based procedures for lumbar spinal disorders, irrespective of the clinical condition, in the private sector. [12] (10.1097/corr.0000000000003487)
• [L4] ALIF has proven effective for revision lumbar fusion surgery, yielding positive clinical and radiographic results. [14] (10.1186/s13018-023-03972-6)
• [L4] Posterior decompression with instrumented fusion is the most common surgical treatment, though individual patient factors must guide the selection of the specific strategy. [18] (10.1302/2058-5241.3.170050)
• [L3] Among adult patients with IS undergoing single-level lumbar fusion, 81.5% had posterior surgery while 7.9% had combined AP surgery. [19] (10.5435/jaaos-d-25-00610)
• [L3] The reoperation rate was 27% for surgical patients, and 36% of lumbar fusion subjects had complications. [20] (10.1097/brs.0b013e3181ccc220)
• [L4] Results demonstrate significant improvements in clinical outcomes and pain reduction after lumbar spinal fusion with topping off at 2 years after surgery. [21] (10.1186/s13018-018-0905-z)
• [Paper] Anterior approaches to the lumbar spine are increasingly used due to proven efficacy and low morbidity, provided the technique and vascular risks are well mastered. [26] (10.1016/j.otsr.2019.05.024)
• [L4] All patients demonstrated a resolution of symptoms after placement of an anterior lumbar interbody cage, without intraoperative complications, and a subsequent antibiotic regimen. [29] (10.5435/jaaosglobal-d-21-00259)
• [L4] [32] (10.5435/00124635-199705000-00004)
• [L3] Pre-existing L5-S1 degeneration does not affect clinical and radiographical outcomes after isolated L4-5 fusion. [33] (10.1186/s13018-015-0186-8)
• [L3] It also identifies several prognostic factors that influence outcomes after lumbar fusion surgery, including higher BMI, larger FJA, and wider sagittal and coronal diameters. [34] (10.1186/s13018-025-05835-8)
• [L5] [35] (10.5435/jaaos-20-05-283)
• [L3] Thorough understanding of these characteristics is essential when managing degenerative spine diseases, particularly in the selection of effective treatment approaches for the increasingly aging society in the future. [40] (10.1186/s12891-025-09185-8)
• [L4] Thirty-six out of 38 patients had complete relief from pain and discomfort along with radiographic fusion. [41] (10.1097/blo.0b013e318067bcd9)
• [L3] The rate of lumbar fusion in the CES cohort was 3.6% after 1 year, 6.7% after 3 years, and 7.8% after 5 years, significantly higher than the LSS control group at all time points. [42] (10.5435/jaaosglobal-d-22-00153)
• [L3] Lumbar fusion surgery was associated with higher rate of hip prosthesis dislocation and higher risk of revision surgery. [43] (10.1302/0301-620x.102b8.bjj-2019-1037.r1)
• [L4] Each method offers distinctive advantages and limitations, with laminoplasty showing lower complication rates than fusion and arthroplasty showing reduced revision rates for adjacent segment disease. [44] (10.5435/jaaos-d-22-00956)
• [L5] Arthrodesis is at present the best surgical treatment for the persistently painful degenerative back, though it increases morbidity and mortality rates and carries a risk of non-union. [45] (10.2106/00004623-196345070-00016)
• [L4] Circumferential fusion is recommended by several authors to regain stability at the lumbosacral junction. [46] (10.1016/j.injury.2009.06.008)
• [L3] Lumbar fusion of more than two segments is a predictor of more posterior sagittal pelvic tilt changes, but fusion of L5S1 is not. [47] (10.1186/s42836-019-0014-4)
• [L2] [54] (10.1186/1471-2474-15-62)
• [L5] [56] (10.5435/00124635-199907000-00004)
• [L1] [58] (10.2106/jbjs.22.00307)
• [L5] The biomechanical benefit of a stand-alone two-part fusion cage can be justified. [59] (10.1186/1471-2474-9-88)
• [L3] Knowledge of these risk factors may improve appropriate selection of an outpatient surgical center or orthopaedic specialty hospital versus an inpatient hospital for lumbar fusions. [61] (10.5435/jaaos-d-22-00884)
• [L3] The general clinical efficacy is equivalent to titanium rod fusion surgery, presenting an alternative treatment for individuals with mild and moderate lumbar degenerative disease. [62] (10.1186/s12891-023-06329-6)
• [L3] This report describes the first enhanced recovery after surgery protocol used in elderly patients after short-level lumbar fusion surgery. [64] (10.1186/s13018-020-01814-3)
• [L4] Bone SPECT/CT was useful to identify the specific cause of pain in elderly patients with lumbar degenerative disease and to provide appropriate treatment, avoiding the unnecessary use of invasive spinal fusion surgery. [65] (10.1186/s13018-019-1236-4)
• [L3] However, there was an association between radiographic fusion status and clinical outcomes. [66] (10.5435/jaaos-d-23-01124)
• [L3] For posterior lumbar fusion, easily obtained patient ASA and age have overall similar or better discriminative abilities for perioperative adverse outcomes than numerically tabulated indices that have multiple inputs and are harder to implement in clinical practice. [67] (10.1016/j.spinee.2017.05.028)
• [L4] Posterolateral lumbar fusion with BMP-2 in veterans yields high fusion rates and favorable complication profiles and should be considered in multimorbid hosts. [68] (10.5435/jaaosglobal-d-23-00122)
• [L3] LLIF involving the L4-5 disc level has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with the appropriate indications and using a standardized surgical technique. [70] (10.1302/0301-620x.106b1.bjj-2023-0693.r2)
• [L3] Under strict adherence to surgical indications, posterior lateral lumbar fusion surgery which preserves partial facet joint unilaterally during neural decompression can offer greater benefits to patients. [71] (10.1186/s13018-024-05020-3)
• [L5] [72] (10.5435/00124635-199509000-00002)
• [L3] These findings are pertinent in the perioperative risk assessment, patient/family recommendations, and surgical preparations for patients with cystic fibrosis being considered for posterior lumbar fusion. [74] (10.5435/jaaosglobal-d-24-00304)
• [L5] The new cage provides more advantageous endplate stress distribution, peak von Mises stress, and cage stress compared to the assembled state. [75] (10.1007/s00402-010-1055-x)
• [L3] We recommend preoperative spinopelvic assessment of all patients undergoing THA, as only a minority of those with limited lumbar flexion have an instrumented fusion and may otherwise be overlooked. [76] (10.1016/j.arth.2020.01.031)
• [L3] [78] (10.1186/s13018-021-02535-x)
• [L5] [80] (10.5435/00124635-200803000-00004)
• [L1] [81] (10.1186/s13018-026-06778-4)
• [L3] PS insertion into infected vertebrae during minimally invasive posterior fixation reduces the operative time and range of fixation without increasing the occurrence of unplanned reoperations due to SSI or implant failure. [82] (10.1186/s12891-024-07565-0)
• [L3] Patients with a history of lumbar fusion had significantly greater rates of revision hip arthroscopy and conversion to THA compared with patients without previous fusion. [83] (10.1016/j.arthro.2024.08.026)
• [L3] Patients undergoing lumbar fusion and subsequent THA have significantly higher risks of dislocation and revision of their hip arthroplasty than a matched cohort of patients with similar hip and spine pathology but only undergoing THA. [84] (10.1016/j.arth.2016.11.029)
• [L5] Nonsurgical management is the standard of care for lumbar degenerative disk disease, while spondylolysis is typically managed nonsurgically with successful outcomes, though surgery may be required for return to sports. [85] (10.5435/jaaos-d-16-00135)
• [L3] Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months, with fusions involving the sacrum and multiple lumbar levels notably increasing the risk compared to controls. [89] (10.1302/0301-620x.101b2.bjj-2018-0754.r1)
• [L3] ULIF is an effective minimally invasive lumbar fusion surgical technique. [102] (10.1186/s13018-024-04674-3)
• [L3] Both the Topping-off technique and lumbar fusion surgery achieved satisfactory clinical outcomes in treating lumbar degenerative diseases. [107] (10.1186/s12891-025-09316-1)
• [L4] The technique is a straightforward, safe, and minimally invasive method for inserting large cages in the treatment of lumbar instability. [109] (10.1186/s13018-024-05018-x)
• [L3] [111] (10.1186/s13018-022-03249-4)
• [L2] [113] (10.1186/s12891-016-1237-y)
• [L3] Lumbar fusion surgery should be performed meticulously to minimize the incidence of intraoperative incidental durotomy. [117] (10.1186/s13018-025-05792-2)
• [L1] The study showed that early initiation of a postoperative rehabilitation program based on principles of strength training is safe, 3 weeks after lumbar spine fusion, and enable earlier functional recovery than standard rehabilitation protocol. [119] (10.1186/s13018-018-0853-7)
• [L2] The incidence of reoperation was higher in the patients who underwent lumbar fusion surgery than those who underwent cervical fusion surgery for degenerative spinal diseases. [128] (10.1186/s12891-021-04491-3)
• [L3] [132] (10.1186/s13018-023-03652-5)
• [L2] [136] (10.1186/s12891-023-06996-5)
• [L3] Patients undergoing isolated decompression for lumbar facet cysts undergo subsequent lumbar fusion at a 5-year rate of 6.79%. [146] (10.5435/jaaos-d-23-00765)
• [L3] Patients with sleep apnoea who undergo posterior lumbar fusion pose significant challenges to clinicians. [151] (10.1302/0301-620x.96b2.31842)
• [L1] Both PEEK rods and titanium rods are effective fixation materials in lumbar fusion surgery. [153] (10.1186/s13018-023-03817-2)
• [L3] This study evaluated the longitudinal trajectory of functional outcomes in patients with MetS undergoing lumbar fusion surgery, providing precise information on recovery patterns and emphasizing the importance of appropriate management and rehabilitation for both patients and physicians to achieve optimal outcomes. [162] (10.1186/s13018-025-06003-8)
• [L5] A new classification system that incorporates spinopelvic balance in the radiographic assessment may aid orthopaedic surgeons in identifying patients who would benefit from partial reduction and fusion. [164] (10.5435/jaaos-20-04-194)
• [L4] Transsacral fixation/fusion may allow for safe lumbosacral fusion without iliac fixation in the setting of long-segment constructs in carefully selected patients. [167] (10.1007/s11999-013-3335-6)
• [L1] Decompression alone demonstrates non-inferiority in terms of efficacy for treating low back pain due to DS compared to fusion, with additional benefits in operation time and blood loss. [183] (10.1186/s13018-025-06550-0)
• [L4] The results demonstrate a fusion rate similar to that of metallic implant systems with the use of a CF-PEEK pedicle screw and a TLIF cage system. [184] (10.1186/s12891-025-08457-7)
• [L3] Among patients who achieved successful posterior lumbar internal fixation, whether or not to remove the fixation instruments should be evaluated carefully. [185] (10.1186/s13018-022-03031-6)
• [L5] Biodegradable rods may present more favourable clinical outcomes for lumbar fusion by providing sufficient initial stability while gradually transferring loading to adjacent segments as rigidity decreases over time. [192] (10.1371/journal.pone.0188034)
• [L4] [193] (10.1016/j.otsr.2016.11.016)
• [L2] The objective activity tracker demonstrated that lumbar surgery results in the amount of activity decreasing 1 month just after surgery followed by gradual postoperative recovery within 3 months. [196] (10.1186/s12891-020-3102-2)
• [L3] When patients with L4–1 LDD with osteoporosis undergo lumbosacral fusion and fixation, the use of S1 pedicle screws with PMMA augmentation has better stability and less screw loosening. [202] (10.1186/s13018-024-05281-y)
• [L5] Although the Spinal Deformity Study Group Classification seems promising, there is a lack of robust clinical outcome studies to support its recommendations, and observers showed disagreement especially in classifying low-grade spondylolisthesis. [204] (10.1097/corr.0000000000001005)
• [L1] [207] (10.1007/s11999-014-3495-z)
• [L3] [208] (10.1186/s13018-023-04507-9)
• [L4] Rehabilitation has benefits on the recovery of patients after spine surgery, but further investigation is needed to achieve a standardized rehabilitation approach. [209] (10.1530/eor-23-0015)
• [L4] [210] (10.1186/s12891-021-04086-y)
• [L4] SA-LLIF can provide immediate stability and good results for lumbar degenerative diseases with a standalone anchored cage without posterior internal fixation. [214] (10.1186/s12891-023-06974-x)
• [L5] Non-operative treatment for stable thoracolumbar burst fractures and uninstrumented fusion for low-grade lytic spondylolisthesis demonstrate established clinical proficiency with excellent long-term outcomes and lower complication rates compared to instrumented approaches. [216] (10.1302/0301-620x.98b1.37508)
• [L4] Lumbar spine surgery can successfully alleviate the physical constraints associated with spinal conditions, facilitating the return of military pilots to their demanding profession. [217] (10.1186/s12891-024-07175-w)
• [L5] Its biocompatibility, biodegradability, safe removal, and ease of handling make it a valuable addition to spinal fixation strategies. [218] (10.1186/s13018-026-06773-9)
• [L2] Operative treatment of lumbar stenosis and degenerative spondylolisthesis offered a significant benefit over nonoperative treatment in patients at least eighty years of age. [219] (10.2106/jbjs.n.00313)
• [L4] [220] (10.1186/s12891-022-06079-x)
• [L5] After TES, the posterior long-segment fixation combined with the anterior 3D printed prosthesis could maintain postoperative spinal stability, but adding artificial pedicle fixation increased the stability of the fixation system and reduced the risk of prosthesis subsidence and instrumentation failure. [224] (10.1186/s13018-021-02354-0)
• [L3] ALIF is the preferred strategy for L5-S1 arthrodesis at a bottom of a long construct. [225] (10.5435/jaaosglobal-d-18-00067)
• [L4] [227] (10.1186/s12891-019-2753-3)
• [L4] The study proposes a practical classification system with preliminary feasibility in surgical approach selection for cage retropulsion, suggesting that early revision may yield better outcomes. [230] (10.1186/s12891-026-09616-0)
• [L5] Short-term studies demonstrate similar clinical improvements for both disk replacements and fusion procedures at up to 2-year follow-up. [231] (10.5435/00124635-200612000-00002)
• [L4] The finding of this study can help guide patient counseling and recommendations that aim to target health system–related issues to improve surgical outcomes for patients after lumbar spine surgery. [235] (10.5435/jaaosglobal-d-25-00238)
• [L4] [240] (10.1186/s12891-021-04584-z)
• [L3] After posterior lumbar fusion, the volume of the multifidus muscles was markedly decreased, and the degree of decrease was apparent in the MRI. [241] (10.1186/s12891-020-3104-0)
• [L5] [243] (10.3390/biomedicines9070733)
• [L4] [244] (10.1186/s12891-021-04811-7)
• [Paper] [249] (10.1007/s00264-013-1905-6)
• [L2] When clinical and surgical heterogeneity were minimized, elderly patients undergoing minimally invasive transforaminal lumbar interbody fusion not only had comparable rates of perioperative complications but also experienced similar improvements in pain, function, and quality of life. [252] (10.1097/corr.0000000000001054)
• [L2] Overall bone metabolism of the operated intervertebral disc space at six weeks had the highest diagnostic accuracy for predicting the fusion status at one year. [255] (10.1186/s13018-025-05814-z)
• [L4] Modic changes, particularly Type 2, are common radiological findings in lumbar spine imaging, most frequently occurring at L4/L5 and L5/S1 levels. [257] (10.1186/s12891-025-09182-x)
• [L1] The combined use of TXA effectively reduced the total blood loss and blood transfusion rate in patients aged over 60 scheduled for a 2-level lumbar fusion, without increasing the incidence of DVT and PE formation. [258] (10.1186/s13018-020-01758-8)
• [L3] Postoperative lower back pain was significantly diminished at follow-up visits. [259] (10.1186/s12891-016-0927-9)
• [L3] Results of this study demonstrate that lumbar fusion before THA is an independent risk factor for dislocation leading to increased risk of revision THA. [260] (10.1016/j.arth.2017.10.041)
• [L4] Twenty-nine percent of patients developed radiologic adjacent segment degeneration, with a surgical revision rate of 10%. [261] (10.1016/j.otsr.2016.03.012)
• [L3] CT may help diagnose endplate sclerosis in patients with type 2 change and inform the choice of the best site for spinal fusion. [265] (10.1186/s12891-021-04461-9)
• [L2] Obtaining flexed-seated radiographs preoperatively in patients with prior THA scheduled for lumbar fusion may be helpful to communicate potential risks of postoperative dislocation and support shared decision-making. [267] (10.1097/corr.0000000000003883)
• [L3] Abnormal MRI findings did not correlate with low back pain, thus MRIs have to be interpreted with caution. [268] (10.1177/2325967114528862)
• [L3] Patients on chronic preoperative steroid therapy are at increased risk of multiple perioperative complications following elective PLF, particularly surgical site complications and venous thromboembolic events. [269] (10.1177/2192568218775960)
• [L3] Patients with osteoporosis undergoing 2- to 3-level lumbar fusion for DDD experienced a higher rate of medical and surgical complications, as well as revision surgeries, at the 2-year follow-up. [272] (10.5435/jaaos-d-21-01258)
• [L3] At mid-term follow-up, PLIF and OLIF provided sustained improvement in pain and function. [273] (10.1186/s13018-026-06818-z)
• [L2] The identification of modifiable risk factors would allow them to be addressed and optimized preoperatively to decrease the incidence and severity of complications and improve patient outcomes after PLF. [274] (10.1016/j.wneu.2019.01.160)
• [L4] Surgical management of selected lumbar spine conditions can produce excellent outcomes in athletes of all sports, with microdiscectomy for lumbar disc herniation leading to favorable return to play rates and direct pars repair leading to high return to play rates. [276] (10.1016/j.csm.2016.05.006)
• [L4] Despite an increasing comorbidity burden of patients undergoing posterior lumbar fusion from 2010 to 2022, the incidence of adverse events overall did not increase. [278] (10.5435/jaaosglobal-d-25-00379)
• [L3] Patients with prior lumbar spine fusion are at increased risk of post-operative dislocation and more often require revision surgery for instability. [282] (10.1007/s00264-018-3955-2)
• [L3] The most common reasons for early reoperation and late operation were surgical site infection and adjacent segment diseases, respectively. [283] (10.1186/s13018-022-03273-4)
• [L3] The addition of interbody fusion to posterolateral fusion was associated with a higher risk for additional surgery and showed no advantages in patient-reported outcome. [284] (10.1302/0301-620x.101b12.bjj-2019-0427.r1)
• [L3] Low bone mineral density, large correction of both main curve and fractional curve are predictive factors for loosening, while posterolateral fusion is a protective factor. [285] (10.1186/s12891-025-08519-w)
• [L3] Patients with prior THA undergoing long fusion to the pelvis experienced longer length of stay, more surgical complications, and a lower rate of spinal revisions compared to those fused to the sacrum. [286] (10.5435/jaaos-d-22-00897)
• [L3] Patients with prior THA undergoing multilevel fusions experienced more dislocations, higher spinal revision rates, less frequent discharge home, longer hospital length of stay, and higher 90-day readmission rates. [288] (10.5435/jaaos-d-24-00606)
• [L4] Major surgical complications occurred in 11.6% of patients, and 11.6% experienced major medical complications. [289] (10.2106/jbjs.l.01730)
• [L1] The study identified 17 risk factors for pseudarthrosis after lumbar fusion surgery, emphasizing age, smoking status, and the number of fusion levels as significant predictors. [290] (10.1186/s12891-024-07531-w)
• [L3] There is often a substantial unmeasured blood loss in lumbar fusion surgeries. [291] (10.1016/j.otsr.2017.01.011)
• [L3] The incidence of ASD in patients after spine surgeries due to cancer metastases does not differ between the study groups. [292] (10.1186/s13018-017-0574-3)
• [L3] Patients undergoing anterior spinal fusion (ASF) had the highest reoperation rate, while posterior procedures had lower rates that did not differ significantly, and adding an interbody fusion to PSF did not improve outcomes. [293] (10.2106/jbjs.23.01242)
• [L4] The rate of fusion was 90 per cent in patients with painful degenerative disease, 93 per cent in those with spondylolisthesis, and 65 per cent in those with preoperative pseudarthrosis. [296] (10.2106/00004623-199173080-00006)
• [L3] For single-level posterior lumbar fusion, cefazolin alone versus cefazolin and gentamicin/tobramycin did not differ in rates of 90-day adverse outcomes or 2-year revisions. [299] (10.5435/jaaosglobal-d-24-00082)
• [L1] PLIF is associated with a significantly higher overall complication rate and longer operative time compared to TLIF. [300] (10.1186/1471-2474-15-367)

See Also

• Low back pain
• Lumbar spinal stenosis
• Lumbar discectomy
• Degenerative spondylolisthesis
• Cauda equina syndrome
• Lumbar decompression
• Adult spinal deformity
• Adolescent idiopathic scoliosis
• Lumbar disc herniation

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