小转子下骨折

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Anatomy & Pathophysiology¶

Bony Anatomy¶

• The subtrochanteric region of the femur extends from the inferior aspect of the lesser trochanter to the junction of the proximal and middle thirds of the femoral shaft [30].
• The distal border of the subtrochanteric region is more specifically described as a point 5 cm distal to the inferior border of the lesser trochanter [30].
• The hemipelvis comprises three bones, the ilium, ischium, and pubis, which unite at the triradiate cartilage within the concave acetabulum [8].
• The acetabulum comprises an articular crescent-moon–shaped lunate surface and a nonarticular central fossa that serves as the attachment point for the ligamentum teres [8].
• The femoral head forms two-thirds of a sphere, with a small depression at its center from which the ligamentum teres extends to connect to the acetabular notch [8].
• The neck-shaft angle of the femur averages 125° [8].
• Normal version, defined as the head-neck angle in the frontal plane, averages 15 to 20° [8].
• At the junction of the femoral neck and shaft are the greater and lesser trochanters, which are connected by the intertrochanteric line anteriorly and the intertrochanteric crest posteriorly [8].
• The acetabulum is normally anteverted 15 degrees and obliquely oriented in the coronal plane 45 degrees caudally [14].
• The posterosuperior articular surface of the acetabulum is thickened to accommodate weight bearing [14].
• The inferior surface of the acetabulum contains the acetabular (cotyloid) notch, which is bound by the transverse acetabular ligament [14].
• The femoral neck is normally anteverted approximately 14 degrees in relation to femoral condyles, with a range of 1–40 degrees [14].
• The femoral neck-shaft angle averages 127 degrees, beginning at 141 degrees in the fetus [14].
• The mean femoral neck-shaft angle in the adult is 130° ± 7° [18].
• The mean anteversion of the femoral neck is 10° ± 7° [18].
• The two prime trabecular groups of the proximal femur are the principal tensile group and the principal compressive group [18].
• Secondary compressive and tensile trabecular groups also exist in the proximal femur [18].
• The weakest area in the femoral neck is located in the Ward triangle [18].
• The calcar femorale is a medial area of dense trabecular bone that transfers stress from the femoral shaft to the inferior portion of the femoral neck [18].

Ligaments and Capsule¶

• The hip is surrounded by a dense fibrous capsule extending from the periphery of the acetabulum to the intertrochanteric line of the femoral neck [8].
• The hip capsule attaches anteriorly and posteriorly along the periphery of the acetabulum outside the labrum [9].
• Inferiorly, the hip capsule is attached to the acetabular labrum [9].
• The capsule is attached to the femur anteriorly along the intertrochanteric crest [9].
• On the posterior side, the capsule attaches only partially, such that the basicervical region of the femoral neck and the intertrochanteric region of the femur are not intracapsular [9].
• The iliofemoral ligament is also known as the Y ligament of Bigelow; it originates at the AIIS and inserts at the intertrochanteric line [9].
• The iliofemoral ligament becomes taut in full extension, preventing anterior dislocation and hyperextension of the hip [9].
• The pubofemoral ligament attaches to the inferior and medial part of the capsule [9].
• The ischiofemoral ligament reinforces the posterior capsule and provides a check to internal rotation of the hip [9].
• The twisted orientation of the hip ligaments provides a screw mechanism for the hip in full extension [9].
• The ligamentum teres originates in the cotyloid fossa and attaches on the fovea of the femoral head [9].
• The sacrospinous and sacrotuberous ligaments create the boundaries of the greater and lesser sciatic foramina [9].
• The sacrospinous ligament creates the upper border of the lesser sciatic foramen and the lower border of the greater sciatic foramen [9].
• The sacrotuberous ligament creates the inferior border of the lesser sciatic foramen [9].
• The piriformis muscle and the sciatic nerve exit from the greater sciatic foramen [9].
• The short external rotator muscles exit from the lesser sciatic foramen [9].
• The iliofemoral ligament is the thickest and strongest of the three main ligaments supporting the hip [8].
• The medial portion of the iliofemoral ligament connects the anterior inferior iliac spine to the anterior intertrochanteric line [8].
• The lateral portion of the iliofemoral ligament originates slightly superior to the medial arm and attaches to the anterior greater trochanter [8].
• The iliofemoral ligament functions to limit external rotation [8].
• In isolation, the lateral arm of the iliofemoral ligament limits extension of the joint [8].
• The ischiofemoral ligament extends from the ischial margin of the acetabulum to the greater trochanter of the femur [8].
• The ischiofemoral ligament provides support posteriorly and restricts internal rotation motion [8].
• The pubofemoral ligament extends from the obturator crest of the pubic bone to the femoral neck and acts to limit abduction of the joint [8].
• Deep fibers from all three hip ligaments merge to form the zona orbicularis, which circumvents the femoral neck [8].

Muscular Anatomy¶

• The primary hip flexor muscles are the iliopsoas, rectus femoris, and sartorius muscles [16].
• The iliopsoas muscle has a large origin along the iliac crest, the iliac fossa, the sacra ala, the iliolumbar ligaments, and the sacroiliac ligaments [16].
• The iliopsoas muscle also has origins along the bodies of the T12 through L4 thoracic lumbar vertebra, the transverse process of the first through fifth lumber vertebra, and the intervertebral disks [16].
• The rectus femoris crosses the hip joint and the knee joint [16].
• The straight head of the rectus femoris originates from the AIIS, whereas the reflected head originates from the supra-acetabular tubercle at the superior-anterior edge of the acetabulum [16].
• The sartorius muscle originates on the ASIS, crosses the hip and knee joints, and inserts on the medial aspect of the tibia and the pes anserine complex [16].
• The tensor fasciae latae muscle originates laterally on the anterolateral edge of the iliac crest [16].
• The action of the tensor fasciae latae is to flex, abduct, and rotate the hip [16].
• Other flexors of the hip include the pectineus, adductor longus, adductor brevis, magnus, and gracilis muscles [16].
• The gluteus maximus and hamstring muscles are the most important hip joint extensors [16].
• The gluteus maximus originates from the sacrum, the coccyx, and the sacrotuberous ligaments [16].
• The hamstring muscles originate on the ischial tuberosity [16].
• The abductors of the hip are predominantly the gluteus medius and minimus muscles [16].
• The gluteus medius has three different components: anterior, middle, and posterior [16].
• The gluteus medius and minimus muscles function together to maintain and abduct the femur during the stance phase of gait [16].
• The adductor muscles of the hip include the adductor brevis, the adductor longus, the adductors magnus, the pectineus, and the gracilis [16].
• The external rotators of the hip include the obturator internus and externus, superior and inferior gemelli, quadratus femoris, and piriformis muscles [16].
• The obturator internus muscle originates from the inner component of the obturator foramen and emerges through the lesser sciatic foramen [16].
• The piriformis muscle originates from the greater sciatic foramen and inserts onto the greater trochanter [16].
• The superior gluteal nerve and artery exit the pelvis above the piriformis muscle [16].
• The pudendal nerve, the internal pudendal artery, the nerve to the obturator internus, the posterior femoral cutaneous nerve, the sciatic nerve, the inferior gluteal nerve, the inferior gluteal artery, and the nerve to the quadratus femoris all exit the pelvis below the piriformis [16].
• In 10% of cases, the common peroneal component of the sciatic nerve can pass through the division in the piriformis [16].
• Most often, the sciatic nerve passes below the piriformis and is situated on top of the short external rotators [16].
• The most consistent internal rotators of the hip joint are the gluteus medius and tensor fascia latae muscles [16].

Neurovascular Anatomy¶

• The medial femoral circumflex artery is the main blood supply to the femoral head [18].
• The medial femoral circumflex artery terminates in the posterior aspect of the extracapsular arterial ring [18].
• The lateral femoral circumflex artery gives rise to the anterior aspect of the arterial ring [18].
• The superior and inferior gluteal arteries also contribute branches to the extracapsular arterial ring [18].
• The ascending cervical arteries originate from the extracapsular arterial ring and are divided into four distinct groups based on their anatomic relationship to the femoral neck: lateral, medial, posterior, and anterior [18].
• The lateral group of ascending branches is the main blood supply to the femoral head [18].
• The ascending branches give off multiple perforator vessels to the femoral neck and terminate in the subsynovial arterial ring located at the margin of the articular surface of the femoral head [18].
• The lateral epiphyseal artery penetrates the femoral head and is believed to be the dominant blood supply to the femoral head from this system [18].
• Fractures that disrupt the ascending blood flow to the lateral epiphyseal vessel have an increased risk of osteonecrosis [18].
• The artery of the ligamentum teres arises from either the obturator or medial femoral circumflex artery [18].
• The artery of the ligamentum teres does not provide sufficient blood supply to maintain the viability of the femoral head [18].
• From birth to approximately 4 years of age, the major blood supply to the femoral head comes from the medial and lateral femoral circumflex arteries, with major contributions from the artery of the ligamentum teres [21].
• From the age of 4 years to adulthood, the posterosuperior and posteroinferior retinacular arteries (from the medial circumflex artery) are the major blood supply to the femoral head [21].
• In adulthood, the major blood supply to the femoral head is from the medial femoral circumflex and lateral epiphyseal arteries [21].
• The common femoral artery arises from the external iliac artery as it passes underneath the inguinal ligament [21].
• The common femoral artery passes anterior and medial to the hip capsule [21].
• The common femoral vein is a continuation of the external iliac vein [21].
• The common femoral vessels are the most commonly reported extrapelvic vascular structures that are injured during total hip arthroplasty [21].
• The most common mechanism for injury to the common femoral vessels is errant retractor placement anterior to the acetabulum [21].
• The profundus or deep femoral artery arises from the lateral aspect of the common femoral artery approximately 3.5 cm below the inguinal ligament [21].
• The profundus femoral artery travels between the pectineus and adductor longus muscles [21].
• The lateral circumflex artery arises from the lateral side of the proximal profundus femoris artery [21].
• The medial circumflex artery most commonly comes from the posteromedial profundus femoris artery but may also come directly from the femoral artery [21].
• The medial circumflex artery traverses between the pectineus and psoas muscles and appears at the upper border of the quadratus femoris [21].
• The superior gluteal vessels are branches of the posterior division of the internal iliac artery [21].
• The superior gluteal vessels are closest to the hip as they exit from the sciatic notch [21].
• Superior gluteal artery injury can occur with the placement of screws in the region of the sciatic notch [21].
• The inferior gluteal vessels and internal vessels are branches of the anterior division of the internal iliac artery [21].
• The inferior gluteal vessels and internal vessels exit the pelvis between the piriformis and coccygeus muscles [21].
• The inferior gluteal vessels can be injured by screws in the posterior column that are at least 5 mm past the bony margin [21].

Pathophysiology of Subtrochanteric Fractures¶

• Subtrochanteric femoral fractures have a bimodal distribution of incidence [30].
• High-energy subtrochanteric fractures typically occur in younger patients [30].
• Low-energy subtrochanteric fractures occur in older patients and are associated with dementia and obesity [30].
• The incidence of subtrochanteric femoral fractures among older patients is increasing [30].
• The incidence of atypical subtrochanteric femoral fractures secondary to long-term diphosphonate use or other metabolic abnormalities is increasing [30].
• Strong deforming muscular forces act on the proximal femur, affecting the alignment of both fracture segments in subtrochanteric fractures [30].
• The proximal segment of a subtrochanteric fracture is flexed by the pull of the iliopsoas [30].
• The proximal segment of a subtrochanteric fracture is abducted by the gluteus medius and minimus [30].
• The proximal segment of a subtrochanteric fracture is externally rotated by the short external rotators [30].
• The distal segment of a subtrochanteric fracture is shortened and medialized by the pull of the adductors [30].
• The widening of the intramedullary canal as it approaches the proximal metaphysis must be considered when using an intramedullary implant for subtrochanteric fractures [30].
• Subtrochanteric fractures involve cortical bone that heals more slowly than the adjacent metaphyseal bone of the intertrochanteric region [30].
• Compressive stresses in the proximal femur peak at the medial cortex 1 to 2 inches distal to the lesser trochanter [30].
• Compressive stresses in the femur are greatest in the medial cortex of the subtrochanteric region below the lesser trochanter, where they can exceed 1,200 lb per square inch [30].
• Significant fracture displacement in subtrochanteric fractures occurs secondary to the pull of the iliopsoas, gluteus medius, and short external rotators on the proximal fracture segment [34].
• The proximal segment of a subtrochanteric fracture is pulled into a position of flexion, abduction, and external rotation relative to the distal segment [34].
• The unopposed pull of the adductors on the distal segment of a subtrochanteric fracture often leads to femoral shortening [34].
• The subtrochanteric portion of the femur contends with the highest compressive and tensile forces in the human skeleton [34].
• Comminution of the medial cortex in subtrochanteric fractures increases the demand of the fixation construct, surpassing loads of 1,200 lbs per square inch in a 200-lb person [34].
• Varus malreduction leads to an increased mechanical stress on the fixation construct by altering the weight-bearing force vector through the proximal segment [34].
• Varus malreduction contributes to higher compressive forces on the medial cortex [34].
• The appropriate relationship between the tip of the greater trochanter and femoral head can be appreciated on the unaffected side, as viewed on an AP pelvis radiograph, and should be restored to prevent a varus malreduction [34].

Investigations¶

Radiography¶

• Conventional radiographs remain critical in the initial imaging evaluation of the hip and can be used to diagnose fractures [2].
• A complete hip series usually consists of an anterior-posterior (AP) pelvis, a centered AP hip, a lateral view (frog-leg, cross-table, Dunn 45° or 90°), and a false-profile (Lequesne) view [2].
• Radiographs remain integral to the assessment of fractures and can be supplemented with CT to further investigate suspected occult fractures, define fracture morphology, and assist in preoperative planning [2].
• Standard AP radiographs of the hip and pelvis are obtained to examine bony architecture, check for evidence of joint space narrowing or changes to bone quality, and quantify femoral head coverage [25].
• The Dunn view and frog leg view are appropriate to measure the alpha angle to determine the presence of impingement [25].
• Radiographs can serially assess hardware positioning and evaluate symptomatic hardware related to open reduction and internal fixation and total hip arthroplasty [2].

Computed Tomography¶

• CT overcomes the limitations of radiography by providing three-dimensional assessment of bony morphology and, to some degree, assessment of soft-tissue abnormalities [10].
• CT is helpful in fracture evaluation, particularly in the setting of negative radiographs, or for further defining fracture morphology in patients requiring surgical reduction [10].
• CT scans are effective for examining cortical and cancellous bone and can be used to create three-dimensional reconstructions of the hip for use in surgical planning [25].
• Measurements of femoral head coverage and acetabular and femoral impingement can be performed reliably using CT images [25].
• The multiplanar and 3D capabilities of CT make it an invaluable tool for assessing bone morphology, but at higher cost and radiation dose [28].
• 3D volume renderings are useful to aid in preoperative planning in FAI and subspine impingement [28].

Magnetic Resonance Imaging¶

• MRI is the modality of choice for patients suspected of soft tissue or intra-articular pathology, given its superior sensitivity and specificity [25].
• Conventional MRI is effective at identifying osteochondral injuries, musculotendinous pathologies, and inflammation [25].
• Magnetic resonance arthrography (MRA) is more appropriate to determine injuries to the labrochondral structures and the ligamentum teres and identify the presence of loose bodies and synovial chondromatosis [25].
• In the accurate detection and staging of articular cartilage lesions, the utility of MRA is reduced, with sensitivity reported to be less than 50% compared with arthroscopic findings [25].
• Recent advances in MRI imaging techniques, such as delayed gadolinium-enhanced MR imaging and T2* mapping, allow for a more in-depth analysis of the structure of articular cartilage [25].
• MRI is useful for the assessment of DDH and FAI, as well as for extra-articular pathologies, stress injuries of bone, and hip arthroplasties [28].
• Noncontrast MRI at 3T is generally adequate for diagnosing intra-articular pathology [28].
• If 3T imaging is unavailable, MRA can be considered at 1.5T for increased diagnostic accuracy [28].
• MRI is helpful in identifying femoral neck stress fracture in athletes and predicting patients that may require surgical intervention [28].
• MRI is helpful in assessing complications of conventional and resurfacing hip arthroplasties, particularly those with metal-on-metal bearing systems [28].
• Major MRI findings that help predict histologic ALVAL scores include synovial thickening, synovitis, synovial volume, abductor disruption, and soft-tissue edema [28].
• MRI or magnetic resonance arthrography provides information regarding the integrity of the acetabular labrum and articular cartilage [3].
• The anatomy of the proximal femur as well as the version of the acetabulum and femur may be assessed using MRI or magnetic resonance arthrography [3].
• Sensitivity to acetabular rim chondral lesions is limited when using MRI or magnetic resonance arthrography [3].
• For nondisplaced stress fractures, MRI or bone scan is used to rule out occult fracture, with MRI being more sensitive if the injury is less than 24 hours old [22].

Ultrasonography¶

• Ultrasonography provides real-time dynamic assessment of the hip and is useful in diagnosing soft-tissue abnormalities about the hip joint [10].
• Ultrasonography is particularly useful in providing real-time guidance during diagnostic and therapeutic procedures [10].
• Although ultrasonography is a valuable tool to examine pediatric hip conditions, its utility in evaluating the adult hip is limited [25].
• Ultrasonography can be an effective modality to identify musculotendinous disruptions, effusions associated with intra-articular pathology, or inflammatory conditions, such as bursitis [25].
• Ultrasonography is increasingly used for targeted injections into muscles, tendons, or intra-articularly around the hip for use with corticosteroids or biologic treatments [25].
• Ultrasonography allows bedside evaluation of the hip and can be used to guide interventions in the office setting [28].
• Ultrasonography cannot image inside bone because bone cortex reflects almost all sound waves [29].
• Internal joint structures are not well visualized using ultrasonography unless they are in a superficial location [29].
• Image quality and interpretation of ultrasonography depend on the experience of the ultrasonography technician and the radiologist [29].

General Principles¶

• Findings from imaging studies should complement clinical examination findings to provide the most accurate diagnosis [1].
• A thorough history is essential to differentiating between common causes of hip pain, and clinical examination tests and imaging findings should be used to confirm a suspected clinical diagnosis [1].
• Many imaging modalities and techniques are available to evaluate pathologies within and about the hip, including soft-tissue structures, the acetabular labrum, articular cartilage, and osseous structures [28].

Treatment¶

Non-Operative¶

• Nonoperative treatment of subtrochanteric femur fractures is indicated when the patient refuses surgical consent [36].
• Nonoperative treatment of subtrochanteric femur fractures is indicated when the patient is a medically unacceptable surgical candidate [36].
• Nonoperative treatment of subtrochanteric femur fractures is indicated for nonambulatory patients [36].
• Nonoperative treatment of subtrochanteric femur fractures is indicated for hemi- and quadriplegic patients [36].
• Operative treatment is recommended in all instances of subtrochanteric femur fractures unless surgical consent is refused or the patient is deemed an unfit surgical candidate secondary to a prohibitive medical comorbidity [36].
• The indications for nonoperative treatment of subtrochanteric femur fractures are extremely limited due to the deformity created, the instability of the fracture pattern, and poor outcomes associated with this treatment modality [36].
• Operative fixation in nonambulatory or hemi- and quadriplegic patients may decrease rates of pulmonary complications [36].
• Operative fixation in nonambulatory or hemi- and quadriplegic patients may decrease rates of decubitus ulcers [36].
• Operative fixation in nonambulatory or hemi- and quadriplegic patients allows for easier hygiene and patient transport with a stable long bone [36].

General Principles¶

• Subtrochanteric femur fractures are generally defined as those fractures occurring within 5 cm of the distal extent of the lesser trochanter [33].
• Subtrochanteric femur fractures represent an unstable injury [33].
• The characteristic deformity of a subtrochanteric femur fracture involves a flexed, abducted, and externally rotated proximal segment [33].
• The flexion, abduction, and external rotation of the proximal segment in subtrochanteric femur fractures are secondary to the pull of the iliopsoas, gluteus medius, and short external rotators, respectively [33].
• The distal segment of a subtrochanteric femur fracture is often shortened and adducted via the unopposed pull of the adductor magnus and longus [33].
• The subtrochanteric region of the femur experiences mechanical forces several multiples of the patient's weight [33].
• Various fixation options, including intramedullary nails (IMN) and extramedullary devices, are available for the treatment of subtrochanteric femur fractures [33].
• The surgeon must ensure that the reduction of a subtrochanteric femur fracture is maintained throughout the healing process [33].

References¶

[1] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Summary.

[2] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Radiography.

[3] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Hip > I. Femoroacetabular Impingement.

[8] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Osseous and Ligamentous Anatomy.

[9] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > IV. Hip Capsule and Ligaments.

[10] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Introduction.

[14] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > LOWER EXTREMITY.

[16] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > V. Hip Joint Muscles.

[18] Aaos Comprehensive Orthopaedic Review 3. Fractures of the Hip > I. General Considerations.

[21] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > VI. Neurovascular Structures Surrounding the Hip.

[22] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > YOUNG ADULT PROXIMAL FEMUR INJURIES.

[25] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Imaging.

[28] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Summary.

[29] Aaos Comprehensive Orthopaedic Review 3. Musculoskeletal Imaging* > IV. Ultrasonography.

[30] Orthopaedic Knowledge Update Trauma. Subtrochanteric Femoral Fractures > Introduction.

[33] Rockwood And Green S Fractures In Adults. 51: Hip Dislocations and Femoral Head Fractures > Introduction to Subtrochanteric Femur Fractures.

[34] Rockwood And Green S Fractures In Adults. 51: Hip Dislocations and Femoral Head Fractures > Pathoanatomy and Applied Anatomy Relating to Subtrochanteric Femur Fractures.

[36] Rockwood And Green S Fractures In Adults. 51: Hip Dislocations and Femoral Head Fractures > Subtrochanteric Femur Fracture Treatment Options.