Anatomical Structures

Hip joint anatomy and morphological variations, focusing on the impact of version and coverage on FAI, dysplasia, and degenerative joint disease.

Overview

Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement [1]. Patients treated conservatively can remain symptom-free for many years [1]. However, additional studies are needed to determine protective or adaptive factors in patients with abnormal hip anatomy who do not develop early osteoarthritis [2]. Further research is also required to determine whether joint-preserving hip surgery extends the life of the native hip joint [2].

Surgical approaches to the hip joint and femur respect basic functional anatomy to afford adequate exposure and good results [6]. These approaches describe basic anatomical features, problems, and danger points to minimize complications [6]. A precise knowledge of anatomy can minimize complications in the hybrid Smith-Peterson and Watson-Jones minimally invasive direct anterior approach to the hip joint [68]. A clear goal in the surgical approach can facilitate visualization and instrumentation placement in the direct anterior approach to the hip joint [68].

Comprehensive knowledge of regional anatomy is essential for safe and effective aspiration and injection of the lower extremity [15]. Knowledge of procedural indications and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [15]. Thorough knowledge of anatomy is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20]. Knowledge of alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20].

The range of knee anatomy in patients scheduled for total knee arthroplasty is wide [70]. Three-dimensional imaging evaluation of hips is required to more clearly define consistent anatomic variants of acetabular and femoral-sided anatomy [21]. Three-dimensional imaging evaluation of hips is required to define respective optimal surgical approaches for acetabular and femoral-sided anatomic variants [21]. Easily identifiable anatomic landmarks allow safe, reproducible physeal-sparing, anatomic anterior cruciate ligament reconstruction [23]. Anatomic landmarks for physeal-sparing, anatomic anterior cruciate ligament reconstruction allow reconstruction without the need for intra-operative x-ray [23].

Localized acetabular bone density distributions are altered in unilateral femoral acetabular impingement [4]. Detailed density maps of bony anatomy may assist surgical providers in planning interventions for femoral acetabular impingement [4]. Proximal femoral osteotomies in adolescence have different indications and treatment strategies [24]. The obturator neurovascular bundle has a high prevalence of 'venous corona mortis' in South Indian cadavers [3]. Individual evaluation of the obturator neurovascular bundle should be performed prior to surgical interventions [3].

Anatomy & Pathophysiology

Biomechanics and Kinematics

The hip joint exhibits activity-dependent kinematics characterized by coordinated pelvic and femoral dynamic movements during weight-bearing activities in healthy joints [36]. Understanding these biomechanics allows clinicians to assimilate the effects of motions and deformations resulting from forces acting on the joint to guide appropriate medical interventions [30]. Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force [33]. The hip abductor moment arm varies substantially throughout the hip's range of motion in the coronal plane [40]. The hip center of rotation trajectory maps under common movements, highlighting the importance of hip translation on physiologic range of motion [48]. A six degree-of-freedom robot is appropriate to reproduce the physiological range of motion of the hip joint [47].

Degenerative hips experience more abnormal hip kinematics that leads to higher articulating surface forces and stresses within the acetabulum compared to normal hips [42]. Hip osteoarthritis patients reveal altered gait kinematics, specifically reduced hip and knee excursion, compared to healthy controls [44]. Patients with more severe radiographic osteoarthritis reveal larger deviations in gait kinematics than those with less severe radiographic osteoarthritis [44]. Abnormal hip kinematics in women with patellofemoral pain appears to be the result of diminished hip-muscle performance as opposed to altered femoral structure [43]. Abnormal hip and knee joint loading during walking after total hip replacement (THR) has a biomechanical background originating from hip geometry reconstruction [31]. Objective gait analysis failed to show a benefit of individualized reconstruction of biomechanical hip geometry via customized femoral components in total hip arthroplasty [32].

The distinctive phase-dependent biomechanical response of the hip demonstrates a coordinated control strategy for balance recovery due to gait perturbations [41]. Subject-specific gait combined with inverse dynamic analysis provides pre-processing parameters for finite element simulation to enable more accurate biomechanical analysis of the hip joint [37]. A normative database of hip and knee kinematics utilized by football athletes was developed [39]. Identifying biomechanical mechanisms that place young athletes at risk for hip injury enables anticipatory guidance and preventative strategies [34].

Surgical Implications and Outcomes

Capsular management during hip arthroscopy must allow for improved exposure without compromising stability and kinematics of the hip [7]. The acetabular labrum bears a direct mechanical role during hip motion, and resecting it during surgery might be detrimental for hip joint biomechanics by modifying strain distribution between the acetabulum and femur [38]. Significant improvements in function and pain at 1 year postoperatively after arthroscopy for femoroacetabular impingement syndrome did not correlate with improvements in hip kinematics [49]. Prolonged delays in staging bilateral hip arthroscopic surgery may result in inferior patient outcomes due to altered biomechanics from the untreated hip [46].

Classification

Obturator Neurovascular Bundle: Individual evaluation of the obturator neurovascular bundle, specifically the high prevalence of venous corona mortis, should be performed prior to surgical interventions [3].

Femoral Acetabular Impingement: Detailed density maps of bony anatomy may assist surgical providers in planning interventions for unilateral femoral acetabular impingement [4].

Medial Knee Ligament: The medial knee exhibits a consistent three-layered anatomical pattern [5]. Specific nomenclature for the superficial medial ligament and posteromedial capsule is suggested rather than the term 'posterior oblique ligament' [5].

Psoas Valley: The psoas valley is a consistent bony landmark [11].

Femoral Torsion: Accurate anatomic localization enables precise terminology distinguishing femoral torsion from anteversion [18].

Hip Deformity (THA): A classification system enabled repeatable distinction of 5 types of architectural hip deformities in pre-operative templating for total hip arthroplasty [35].

Pes Anserinus: A proposed classification of pes anserinus morphology may improve the planning of surgical procedures [51].

Paediatric Hip Ultrasound: Geometric measurements in paediatric hip ultrasound are reliably interpreted and may be useful as a measurement of quality [53]. Morphological features in paediatric hip ultrasound are generally poorly interpreted but improve with simpler binary classification [53].

Condylar-Stabilized Implants: A classification system for condylar-stabilized designs allows for appropriate grouping and comparison of distinct implants [55].

Medial Meniscus Ramp Tears: A surgically relevant classification system for medial meniscus ramp tears based on tear morphology allows for the evaluation of differing repair patterns and their effects on postoperative clinical outcomes [56].

Developmental Dysplasia of the Hip (DDH): A classification method for developmental dysplasia of the hip based on the greater trochanter of the femur could distinguish various types of DDH and aid in making surgical strategies [57]. The classification of developmental patterns illustrates the varying directional changes that can occur in lower-extremity length discrepancies and their dependence on underlying biological phenomena [58].

Sourcil Types: Type II and III sourcil types account for the majority of cases, to which a modified approach to measuring the femoro-epiphyseal acetabular roof index is better [62]. The modified approach to measuring the femoro-epiphyseal acetabular roof index has better intraobserver and interobserver reliability compared with the original index [62].

Medial Patellofemoral Ligament (MPFL): The medial patellofemoral ligament (ME) demonstrates variable and elongated morphology, differentiating it from the adductor tubercle (AT) and Gerdy’s tubercle (GT), which demonstrated the most consistent morphology [63].

Clinical Presentation

A directed history and physical examination, combined with an understanding of normal and abnormal gait, facilitates the development of a differential diagnosis based on limp type, patient age, and likely anatomic site [12]. Concurrent hip and spine pathological processes present a substantial diagnostic challenge due to overlapping symptomatology, with no consensus on which condition to address first [50]. Extra-articular etiologies of hip pain represent an important subset of hip disorders that can be accurately identified through physical examination and imaging [52].

Plain radiographic evaluation remains the initial diagnostic modality for femoroacetabular impingement (FAI) [9]. Three-dimensional imaging such as MRI and CT is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning in FAI [9]. Advanced imaging studies have enhanced understanding of hip vascular anatomy and its clinical implications for orthopaedic treatment [10].

Femoroacetabular impingement morphologic features and labral injuries are common in asymptomatic patients [14]. Both acetabular and femoral morphology are critical to understanding FAI and developing patient-specific treatments [16]. The complex interplay of femoral and acetabular versions influences outcomes and the presence of asymptomatic lesions in FAI [16]. The prevalence of morphological variations associated with FAI varies according to age and sex in the general population [17]. Females with FAI have more profound symptomatology and milder morphologic abnormalities [54]. Males with FAI have a higher activity level, larger morphologic abnormalities, more common combined-type morphologies, and more extensive intra-articular disease [54].

A thorough appreciation of the anatomy of the abductor musculature, specific clinical signs, and imaging findings leads to appropriate diagnosis and management of lateral hip pain [45]. Extensive knowledge of hip anatomy and normal function is critical to identifying pathologies and developing successful treatment strategies [8]. The goal of treatment for hip disease in young, active patients is to establish a clear diagnosis, assess severity, and plan a surgical strategy to make the hip as structurally normal as possible [13].

Investigations

Plain radiography: Plain radiographic evaluation remains the initial diagnostic modality for femoroacetabular impingement [9].

MRI: Three-dimensional imaging such as MRI is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning in femoroacetabular impingement [9]. Advanced imaging studies have enhanced understanding of hip vascular anatomy and its clinical implications for orthopaedic treatment [10]. Magnetic resonance imaging is necessary to establish whether some patients have an occult hip fracture [64]. MRI documentation should be established as a standard examination post-reduction for congenital dislocation of the hip [67]. Imaging for osteonecrosis is recommended in athletes with hip dislocation and subluxation, with evidence suggesting 4- to 6-week magnetic resonance imaging and follow-up at 3 months for those with suspicious findings in the femoral head [74]. Magnetic resonance imaging is effective in localizing neurilemoma of the saphenous nerve presenting as pain in the knee [73]. Pathologic changes seen on MRI were symptomatic in less than two thirds of elite female ballet dancers [82].

CT: Three-dimensional imaging such as CT is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning in femoroacetabular impingement [9]. CT has higher interobserver reliability than MRI for measuring femoral anteversion [60]. Standard MRI scans cannot replicate the appropriate level of detail for anterior inferior iliac spine (AIIS) morphology classification compared to 3D CT [66]. Preoperative planning CT scans should not be eliminated from the patient pathway for AIIS visualization, although future refinements in 3D MRI techniques may eventually allow them to replace low-dose 3D CT scans [66]. Computed tomography provides a noninvasive method for studying anatomy in live subjects, allowing for the detailed mapping of position, size, and orientation of the abductor muscles of the hip [78]. Intraoperative MRI (ioMRI) cannot yet replace CT scans for thorough evaluation, though it may be considered when CT is contraindicated [83].

Other Considerations: Extensive knowledge of anatomy and normal function of the hip is critical to identifying pathologies and developing successful treatment strategies [8]. Accurate anatomic localization enables precise terminology distinguishing femoral torsion from anteversion [18]. Diagnosis of femoral anteversion should not rely exclusively on either physical examination or radiologic criteria [60]. Three-dimensional imaging evaluation of hips with regard to acetabular and femoral-sided anatomy is required to more clearly define any consistent anatomic variants and their respective optimal surgical approaches [21]. Several consistent anatomical levels were identified for single axial MR slice to facilitate muscle size and fatty infiltration muscle measures at the hip, providing the basis for reliable and accurate data synthesis and improvements in the validity of future between studies analyses [59]. Magnetic resonance imaging-based 3-dimensional models of the pelvis and hip using machine learning for automatic bone segmentation in a dynamic hip impingement simulation are feasible with routine MRI and a short image acquisition time [61]. Patient-specific 3-dimensional MRI-based dynamic simulation of hip impingement and range of motion can replace 3-dimensional CT-based simulation for patients with femoroacetabular impingement [71]. A novel hip MRI sequence provides consistent osseous morphology dimensions for femoroacetabular impingement evaluation comparable to CT imaging [83].

Treatment

Non-Operative

Non-surgical management is the primary approach for many hip and knee pathologies. Most patients with peritrochanteric space disorders resolve lateral hip pain with non-surgical management in the mid-term, though surgical options should be evaluated when non-surgical management fails [84]. Non-operative management of proximal rectus femoris avulsion injuries is associated with highly variable periods of convalescence, poor return to preinjury level of function, and high risk of injury recurrence [91]. Non-operative treatments for lower-extremity rotational problems in children are usually ineffective [95]. Isolated fractures of the teardrop of the acetabulum can be treated non-operatively with a perfect functional result as the infero-medial localization does not impair joint containment, though fragment removal may be indicated if it interferes with mobility [96]. Operative management of fragility fractures of the pelvis should be considered for patients failing a brief period of non-operative management, although prospective randomised trials are needed to provide improved evidence [85]. Moderate nonprogressive coxa vara deformity in childhood often does not require surgery, while surgical management is indicated for progressive, painful, unilateral deformity or leg-length discrepancy [90].

Operative

Indications: Surgical treatment for slipped femoral epiphysis is appropriate even with severe displacement, as anatomical reduction is not necessary for good function and patients can remain symptom-free for many years [1]. For hip disease in young, active patients, the goal is to establish a clear diagnosis, assess severity, and plan a strategy to make the hip as structurally normal as possible [13]. Preoperative roentgenographic evaluation for osteotomies about the hip in children helps confirm adequacy of coverage and guides surgical decision-making, though exact criteria are not yet established [79]. In non-elite patients, persistent grade 2 or 3 medial collateral ligament (MCL) laxity beyond 12 weeks in the setting of anterior cruciate ligament rupture should prompt combined anterior cruciate ligament reconstruction with MCL repair and reconstruction [93].

Surgical Approach / Technique: Surgical approaches to the hip joint and femoral shaft should respect basic functional anatomy to ensure adequate exposure and good results while minimizing complications [6]. Capsular management during hip arthroscopy must allow for improved exposure without compromising the stability and kinematics of the hip [7]. The anterior hip capsule is thinner in dysplastic hips compared to other young adult hip patients, which could alter capsular management strategies [65]. Standard anterior, anterolateral, and posterolateral portals in hip arthroscopy allow proper accessibility of the central compartment, with slight limitations in the posteromedial corner [81]. The anterior intrapelvic approach requires a comprehensive understanding of the historically 'nonorthopaedic' surgical anatomy and associated risks [27]. Individual evaluation of the obturator neurovascular bundle, including the high prevalence of venous corona mortis, should be performed prior to surgical interventions [3]. Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [15].

Implant Selection: Thorough knowledge of anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20]. Using easily identifiable anatomic landmarks allows for safe, reproducible physeal-sparing, anatomic anterior cruciate ligament reconstructions without the need for intra-operative x-ray [23].

Alignment / Balancing Strategy: Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement and developing patient-specific treatments, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions [16]. Surgical treatment limited to localized recontouring of the head-neck profile in cam impinging femurs may fail to address significant components of the underlying abnormality [72]. Proximal femoral osteotomies in adolescents have specific indications and treatment strategies that vary by case [24].

Pain Management: Repair of horizontal cleavage meniscus tears results in substantial improvements in patient-reported outcomes, with acceptable midterm clinical healing rates and low reoperation/failure rates [75]. Subchondroplasty for post-traumatic bone marrow lesions of the medial femoral condyle showed no difference in the progression of medial compartment post-traumatic gonarthrosis compared to controls, despite improvements in clinical outcomes and bony histology [76]. Anatomic anterolateral ligament (ALL) reconstruction did not reduce anterolateral rotational laxity in biomechanical analysis [80].

Complications

Polyethylene wear: Long-term follow-up is necessary to evaluate differences in long-term durability between gap balancing and measured resection techniques in simultaneous bilateral total knee arthroplasty [19]. Although no detrimental clinical effect was found in intermediate-term follow-up of a modular femoral head with an extended flange-reinforced neck, findings warrant concern for adverse effects after more long-term follow-up regarding polyethylene wear after total hip arthroplasty [77].

Instability: Longer-term follow-up is required to determine whether the excellent results of isolated polyethylene insert exchange for flexion instability after primary total knee arthroplasty are durable over time [26].

Other Considerations: Slipped femoral epiphysis with severe displacement can be treated conservatively with operative intervention, allowing patients to remain symptom-free for many years without anatomical reduction [1]. Additional studies are needed to determine whether joint-preserving hip surgery extends the life of the native hip joint in patients with abnormal anatomy [2]. Individual evaluation of the obturator neurovascular bundle, which has a high prevalence of 'venous corona mortis', should be performed prior to surgical interventions to avoid this risky anatomical structure [3]. The medial side of the knee has a consistent three-layered anatomical pattern, suggesting specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament' [5]. Surgical approaches to the hip joint and femoral shaft must respect basic functional anatomy to minimize complications while ensuring adequate exposure and good results [6]. Understanding normal and abnormal gait, along with anatomic site likelihood, allows for a selective approach to diagnostic testing in patients with a limp [12]. Femoroacetabular impingement (FAI) is a pathologic mechanical process involving morphologic abnormalities and vigorous motion that damages soft-tissue structures [22]. FAI morphology predisposes to later osteoarthritis, but more long-term data are needed to define the natural history of pincer deformities and FAI in younger cohorts [22]. The anterior intrapelvic approach (AIP) involves historically 'nonorthopaedic' surgical anatomy and associated risks [27]. Functional deficits persist due to soft tissue damage from arthrosis, requiring longer recovery time independent of the surgical approach (minimalinvasive vs transgluteal) for total hip arthroplasty [28]. Cementless total hip replacement with subtrochanteric femoral shortening for severe developmental dysplasia of the hip demonstrates good mid-term results [29]. Reconstruction of neglected developmental dysplasia by total hip arthroplasty with subtrochanteric shortening osteotomy is a demanding technique with a high rate of related complications [88]. Porous implants are effective in tackling metaphyseal bone defects in revision knee arthroplasty, showing good survivorship outcomes at midterm follow-up [98]. Anatomic femoral attachment is critical to a well-functioning medial patellofemoral ligament reconstruction and minimizes complications, while nonanatomic placement can cause significant changes in graft isometry [99]. The use of medial hip arthroscopy portals did not cause damage to the neurovascular structures evaluated [100]. Diligent capsular management, including preservation and repair, is critical for successful surgical outcomes in hip arthroscopy, and surgeons must maintain heightened awareness of iatrogenic risks to capsular structures [101]. Femoral component coronal alignment in fixed-bearing unicompartmental knee arthroplasty may affect long-term clinical outcomes, but not short-term clinical outcomes or 10-year survivorship [25].

Recovery

Light activity (weeks): Evidence does not provide specific week ranges for light activity or desk work return across the cited studies. Functional deficits persist due to soft tissue damage from arthrosis, requiring a longer recovery time independent of the surgical approach (minimal invasive vs transgluteal) for total hip replacement [28].

Full activity (months): A structured preoperative exercise program resulted in better postoperative functional outcomes at the long term for ACL reconstruction [69]. With an average follow-up time of 12 months, all clinical and functional results as well as activity and quality of life improved statistically in patients with residual bony prominence after surgery for femoroacetabular impingement [87]. Current evidence suggests that modular bicompartmental knee arthroplasty provides comparable functional outcome to total knee arthroplasty at short-term to midterm follow-up [92].

Complete recovery / outcome plateau (months): Long-term follow-up is necessary to evaluate any differences in long-term durability between gap balancing and measured resection techniques in simultaneous bilateral total knee arthroplasty [19]. Longer-term follow-up is required to determine whether the excellent results of isolated polyethylene insert exchange for flexion instability after primary total knee arthroplasty are durable over time [26]. Treatment strategies for ACL injury may need to be adjusted to preserve long-term function, as thigh muscle changes at long-term evaluation differ from early changes associated with ACL injury and reconstruction [89]. Further studies are required to understand if two-incision technique femoral tunnel placement in ACL reconstruction can ameliorate proprioception and clinical outcome at long-term follow-up [94]. Current evidence suggests that modular bicompartmental knee arthroplasty provides comparable functional outcome to total knee arthroplasty at short-term to midterm follow-up, but has poor long-term survivorship [92].

Rehabilitation protocol: No specific rehabilitation protocols, immobilisation durations, or weight-bearing progressions are detailed in the provided evidence.

Functional milestones: Femoral component coronal alignment may affect long-term clinical outcomes in fixed-bearing unicompartmental knee arthroplasty, but does not affect short-term clinical outcomes or 10-year survivorship [25]. The study aimed to determine the long-term objective and subjective outcome of untreated articular cartilage defects observed at the time of ACL reconstruction [104].

Other Considerations: Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement, and the procedure allows patients to remain symptom-free for many years [1]. Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early osteoarthritis [2]. Additional studies are needed to determine whether joint preserving hip surgery extends the life of the native hip joint [2]. Biomechanical and long-term clinical studies are needed to better understand the importance of the labrum and how to restore its function [86]. The stage of disease at presentation is the main determinant for treatment selection in osteonecrosis of the femoral head, regardless of the duration of symptoms prior to presentation [102]. Early intervention for femoroacetabular impingement before the degenerative process is advanced is likely to have a considerable impact on the natural history of the disease, delaying the onset of end-stage arthritis in young patients [103]. Specific morphological characteristics on pelvis radiographs of avascular necrosis hips were predictive for poor outcome at a very young age [106]. In later stages of bone apposition in deep hips, the formed bone cannot be distinguished from native bone and the labrum may appear to be nearly absent on imaging studies [107]. Cementless total hip replacement with subtrochanteric femoral shortening for severe developmental dysplasia of the hip demonstrates good mid-term results [29].

Key Evidence

• [L4] Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early OA and to determine whether joint preserving hip surgery extends the life of the native hip joint. (10.5435/jaaos-d-16-00532)
• [Paper] Individual evaluation of this risky anatomical structure should be done prior to any surgical interventions. (10.1016/j.injury.2016.04.032)
• [L4] Providing detailed density maps of the bony anatomy may also assist surgical providers in planning interventions. (10.1177/2325967124s00187)
• [L5] The study delineated a consistent three-layered anatomical pattern of the medial knee, suggesting the use of specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament'. (10.2106/00004623-197961010-00011)
• [L5] The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip. (10.1016/j.arthro.2011.08.288)
• [L5] Plain radiographic evaluation remains the initial diagnostic modality, while three-dimensional imaging such as MRI and CT is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning. (10.5435/00124635-201300001-00006)
• [L5] Advanced imaging studies have enhanced understanding of this vascular anatomy and its clinical implications for orthopaedic treatment. (10.5435/jaaos-d-15-00237)
• [L4] This review highlights the importance of the anatomy of the psoas valley which is a consistent bony landmark. (10.1186/s12891-020-03241-1)
• [L5] With an understanding of normal and abnormal gait, a directed history and physical examination, and the development of a differential diagnosis based on the type of limp, the patient's age, and the anatomic site that is most likely affected, the orthopaedist can take a selective approach to diagnostic testing. (10.5435/00124635-200103000-00003)
• [L5] The goal of treatment is to establish a clear diagnosis, assess severity, and plan a surgical strategy to make the hip as structurally normal as possible. (10.5435/00124635-200812000-00002)
• [L4] FAI morphologic features and labral injuries are common in asymptomatic patients. (10.1016/j.arthro.2014.11.042)
• [L5] Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques are essential for safe and effective aspiration and injection. (10.5435/jaaos-d-16-00762)
• [L5] Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement and developing patient-specific treatments, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions. (10.1016/j.arthro.2021.09.033)
• [L3] This study provides information to determine the prevalence of these anatomic variants in the general population. (10.1177/2325967120977892)
• [L4] Accurate anatomic localization enables precise terminology distinguishing femoral torsion from anteversion. (10.1007/s11999-014-4000-4)
• [L1] Long-term follow-up will be necessary to evaluate any differences in long-term durability. (10.1016/j.arth.2019.10.002)
• [L5] A thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs despite careful planning and adherence to proper surgical technique. (10.1177/2325967116652122)
• [Commentary] Three-dimensional imaging evaluation of hips with regard to acetabular and femoral-sided anatomy will be required to more clearly define any consistent anatomic variants and their respective optimal surgical approaches. (10.1016/j.arthro.2020.07.031)
• [L5] FAI is defined as a pathologic mechanical process involving morphologic abnormalities and vigorous motion that damages soft-tissue structures; while FAI morphology is common in young adults and predisposes to later OA, more long-term data are needed to define the natural history of pincer deformities and FAI in younger cohorts. (10.5435/00124635-201300001-00004)
• [L4] Using these easily identifiable landmarks allows safe, reproducible anatomic ACL reconstructions without the need for intra-operative x-ray. (10.1016/j.arthro.2011.03.072)
• [L4] The aim of this review is to show the different ways of proximal femoral osteotomies and their indications after having done a selective literature research. (10.1055/a-1023-4679)
• [L3] Femoral component coronal alignment may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. (10.1016/j.arth.2020.07.070)
• [L4] Longer-term follow-up is required to determine whether these results are durable over time. (10.1016/j.arth.2020.01.006)
• [L5] This review aims to provide an in-depth understanding of the AIP approach with a focus on the historically 'nonorthopaedic' surgical anatomy and associated risks. (10.5435/jaaos-d-24-01050)
• [L3] Functional deficits persist due to soft tissue damage from arthrosis requiring longer recovery time independent of the surgical approach. (10.1055/s-0030-1250590)
• [Paper] A reconstruction of the original joint center and good mid-term results are demonstrated. (10.1007/s00402-003-0554-4)
• [L5] An understanding of hip joint biomechanics constitutes an important background for the diagnosis and treatment of hip disorders, allowing clinicians to assimilate the effects of motions and deformations resulting from forces acting on the joint to guide appropriate medical interventions. (10.1016/j.arthro.2010.01.027)
• [L2] Abnormal hip and knee joint loading during walking after THR has a biomechanical background originating from hip geometry reconstruction. (10.1016/j.arth.2019.07.027)
• [L3] Despite the individualized reconstruction of the biomechanical hip geometry, objective gait analysis failed to show a benefit. (10.1007/s00402-008-0717-4)
• [L5] Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force. (10.1007/s00167-012-2255-4)
• [L3] Identifying biomechanical mechanisms that place young athletes at risk for hip injury enables anticipatory guidance and preventative strategies for these patients. (10.1177/2325967113s00059)
• [L4] The classification system enabled repeatable distinction of 5 types of architectural hip deformities. (10.1007/s00402-019-03298-1)
• [L4] This study revealed activity dependent kinematics of healthy hip joints with coordinated pelvic and femoral dynamic movements. (10.1155/2014/457573)
• [L5] Subject-specific gait combined with inverse dynamic analysis provides pre-processing parameters for FE simulation to enable more accurate biomechanical analysis of the hip joint. (10.1186/s13018-022-03094-5)
• [L5] The acetabular labrum bears a direct mechanical role during hip motion, thus resecting the hip's labrum during surgery might be detrimental for hip joint's biomechanics as it might modify strains distribution between the acetabulum and femur. (10.1007/s00167-017-4524-8)
• [L4] A normative database of hip and knee kinematics utilized by football athletes was developed. (10.1177/2325967114534591)
• [L5] Hip abductor moment arm varies substantially throughout the hip's range of motion in the coronal plane. (10.1186/1749-799x-6-6)
• [L5] The distinctive phase-dependent biomechanical response of the hip demonstrated its coordinated control strategy for balance recovery due to gait perturbations. (10.1186/s12891-023-06897-7)
• [L4] Current analysis revealed trends that degenerative hips experience more abnormal hip kinematics that leads to higher articulating surface forces and stresses within the acetabulum. (10.1016/j.arth.2019.08.057)
• [L3] Abnormal hip kinematics in women with patellofemoral pain appears to be the result of diminished hip-muscle performance as opposed to altered femoral structure. (10.1177/0363546508326711)
• [L4] The overall findings remain that hip OA patients reveal altered gait kinematics (reduced hip and knee excursion) compared to controls, and that those with more severe radiographic OA reveal larger deviations than those with less severe radiographic OA. (10.1186/s12891-015-0483-8)
• [L4] A thorough appreciation of the anatomy of the abductor musculature, specific clinical signs and imaging findings will lead to an appropriate diagnosis being made and management plan instituted. (10.1007/s00167-020-06354-1)
• [Commentary] Prolonged delays in staging bilateral hip arthroscopic surgery may result in inferior patient outcomes due to altered biomechanics from the untreated hip, though individual patient variability remains a critical factor in determining the optimal time frame. (10.1016/j.arthro.2022.10.024)
• [L5] A six degree-of-freedom robot is appropriate to reproduce the physiological range of motion of the hip joint. (10.1186/s13018-023-03601-2)
• [L4] This study is the first to map the hip center of rotation trajectory under common movements in a large cohort, highlighting the importance of hip translation on physiologic range of motion. (10.1177/2325967124s00166)
• [L4] Additionally, patients reported significant improvement in function and pain at 1 year postoperatively, but these improvements did not correlate with improvements in hip kinematics. (10.1177/23259671251339777)
• [L5] The proper diagnosis and treatment of patients with concurrent hip and spine pathological processes can present a substantial challenge due to overlapping symptomatology and no consensus on which condition to address first. (10.2106/jbjs.20.01728)
• [L5] The planning of surgical procedures may be improved by the proposed classification. (10.1007/s00167-018-5318-3)
• [L4] Geometric measurements are reliably interpreted and may be useful as a further measurement of quality, while morphological features are generally poorly interpreted but improve with simpler binary classification. (10.1302/0301-620x.105b10.bjj-2023-0143.r1)
• [L1] Females had more profound symptomatology and milder morphologic abnormalities, while males had a higher activity level, larger morphologic abnormalities, more common combined-type FAI morphologies, and more extensive intra-articular disease. (10.2106/jbjs.m.01320)
• [L4] The classification developed allows for appropriate grouping and comparison of distinct CS implants. (10.1016/j.arth.2025.05.039)
• [L4] This classification system allows for the ability to evaluate differing repair patterns and their effects on postoperative clinical outcomes. (10.1177/2325967125s00101)
• [L3] The greater trochanter classification system based on the anatomy and biomechanics could distinguish various types of DDH and aid in making surgical strategies. (10.1016/j.arth.2025.08.013)
• [L4] The classification of developmental patterns illustrates the varying directional changes that can occur in lower-extremity length discrepancies and their dependence on underlying biological phenomena. (10.2106/00004623-198264050-00001)
• [L4] Several consistent anatomical levels were identified for single axial MR slice to facilitate muscle size and fatty infiltration muscle measures at the hip, providing the basis for reliable and accurate data synthesis and improvements in the validity of future between studies analyses. (10.1186/s12891-022-05439-x)
• [L3] CT was found to have higher interobserver reliability than MRI, and diagnosis should not rely exclusively on either examination or radiologic criteria. (10.1016/j.arthro.2011.10.021)
• [L3] The method was feasible with routine MRI and a short image acquisition time. (10.1177/23259671251334138)
• [L2] Type II and III sourcil types account for the majority, to which the modified approach is better. (10.1016/j.arthro.2023.11.024)
• [L5] Specifically, the variability and elongated morphology of the ME differentiated this landmark from the AT and GT, which demonstrated the most consistent morphology. (10.1016/j.asmr.2022.09.003)
• [Paper] MRI scanning is necessary to establish whether some patients have an occult fracture. (10.1016/j.injury.2007.04.023)
• [L3] The clinical relevance of this study is that capsular thickness and intra-substance changes of the anterior capsule vary which could alter capsular management strategies. (10.1007/s00167-022-07022-2)
• [L5] Based on data showing that standard MRI scans cannot replicate the appropriate level of detail for AIIS morphology classification compared to 3D CT, the author concludes that the preoperative planning CT scan should not be eliminated from the patient pathway, although future refinements in 3D MRI techniques may eventually allow them to replace low-dose 3D CT scans. (10.1016/j.arthro.2021.08.012)
• [Paper] This MRI documentation should be established as a standard examination post-reduction. (10.1007/s00402-003-0518-8)
• [L4] A precise knowledge of anatomy and clear goals in the surgical approach can minimize complications and facilitate visualization and instrumentation placement in the direct anterior approach to the hip joint. (10.1186/s12891-023-06254-8)
• [L2] A structured preoperative exercise program resulted in better post operative functional outcomes at the long term. (10.1016/j.arthro.2013.07.252)
• [L1] The range of knee anatomy in patients scheduled for TKA is wide. (10.1016/j.arth.2017.02.028)
• [L2] On the basis of these excellent results, the authors intend to change their clinical practice to use MRI-based 3D models for future clinical practice instead of CT-based 3D models. (10.1177/0363546519869681)
• [L4] Surgical treatment limited to localized recontouring of the head-neck profile may fail to address significant components of the underlying abnormality. (10.1016/j.arth.2011.04.028)
• [Case_report] Magnetic resonance imaging is effective in localizing this type of lesion. (10.2106/00004623-198971090-00022)
• [L4] Imaging for osteonecrosis is recommended, with evidence suggesting 4- to 6-week magnetic resonance imaging and follow-up at 3 months for those with suspicious findings in the femoral head. (10.1177/03635465211036104)
• [L3] There were substantial improvements in patient-reported outcomes, showing acceptable midterm clinical healing rates and low reoperation/failure rates. (10.1016/j.arthro.2020.12.150)
• [L3] Despite improvements in clinical outcomes and bony histology, there were no difference detected in the progression of medial compartment post-traumatic gonarthrosis between groups. (10.1016/j.arthro.2017.08.096)
• [L4] Computed tomography provides a noninvasive method for studying anatomy in live subjects, allowing for the detailed mapping of position, size, and orientation of the abductor muscles of the hip. (10.2106/00004623-198769070-00010)
• [L4] Experience is currently insufficient to establish exact criteria, but the method helps confirm adequacy of coverage and guides surgical decision-making. (10.2106/00004623-198163020-00016)
• [L5] Anatomic ALL reconstruction did not reduce anterolateral rotational laxity. (10.1177/2325967116s00027)
• [L5] In hip arthroscopy, the use of the standard anterior, anterolateral, and posterolateral portals allows proper accessibility of the central compartment, with slight limitations in the posteromedial corner. (10.1016/j.arthro.2013.05.017)
• [L4] Pathologic changes seen on MRI were symptomatic in less than two thirds of the dancers. (10.1016/j.arthro.2012.10.012)
• [L3] However, ioMRI cannot yet replace CT scans for thorough evaluation, though it may be considered when CT is contraindicated. (10.1177/2325967125s00090)
• [L5] Most patients tend to resolve GTPS or lateral hip pain with non-surgical management in the mid-term but when everything failed, surgical options should be evaluated. (10.1007/s00167-020-06366-x)
• [L2] Operative management of fragility fractures of the pelvis should be considered for patients failing a brief period of non-operative management, however prospective randomised trials need to be performed to provide improved evidence for this intervention. (10.1186/s12891-021-04579-w)
• [L5] Biomechanical and long-term clinical studies will continue to be performed to better understand the importance of the labrum and how to restore its function. (10.1016/j.arthro.2010.12.004)
• [L4] With an average follow-up time of 12 months, all clinical and functional results as well as activity and quality of life improved statistically. (10.1016/j.arthro.2013.09.021)
• [L5] Although a demanding technique with a high rate of related complications, once anatomic reconstruction of the hip is achieved, patients have a remarkably good functional capacity and implant survival during long follow-up periods. (10.1302/2058-5241.1.000026)
• [L3] Treatment strategies may need to be adjusted to preserve long-term function. (10.2106/jbjs.25.01271)
• [L5] Surgical management is indicated for progressive, painful, unilateral deformity or leg-length discrepancy, while moderate nonprogressive deformity often does not require surgery. (10.5435/00124635-199803000-00003)
• [L4] Non-operative management is associated with highly variable periods of convalescence, poor return to preinjury level of function and high risk of injury recurrence. (10.1302/2058-5241.5.200055)
• [L2] Current evidence suggests that modular BKA provides comparable functional outcome to TKA at short-term to midterm follow-up, however, with poor long-term survivorship. (10.1016/j.arth.2019.09.042)
• [L5] In non-elite patients, persistent grade 2 or 3 laxity beyond 12 weeks should prompt combined anterior cruciate ligament reconstruction with MCL repair and reconstruction. (10.1002/arj.70105)
• [L5] Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up. (10.1186/1749-799x-2-10)
• [L4] Non-operative treatments are usually ineffective, and while rotational osteotomies are effective, they are associated with significant complication rates. (10.2106/00004623-198567050-00027)
• [L5] The fracture can be treated non-operatively with a perfect functional result as the infero-medial localization does not impair joint containment, though fragment removal may be indicated if it interferes with mobility. (10.1007/s00402-010-1249-2)
• [L1] Porous implants are effective in tackling metaphyseal bone defects showing good survivorship outcome at midterm follow-up. (10.1016/j.arth.2022.02.103)
• [L5] The study emphasizes that anatomic femoral attachment is critical to a well-functioning reconstruction and minimizes complications, while nonanatomic placement can cause significant changes in graft isometry. (10.1177/2325967115569198)
• [L5] The use of the medial portals did not cause any damage to the neurovascular structures evaluated. (10.1016/j.arthro.2013.09.004)
• [Commentary] The evidence supports that diligent capsular management, including preservation and repair, is critical for successful surgical outcomes in hip arthroscopy, and surgeons must maintain a heightened awareness of iatrogenic risks to capsular structures. (10.1016/j.arthro.2019.09.049)
• [L5] The authors clarify that the high rate of late-stage osteonecrosis reflects the tertiary care nature of their clinic and that the stage of disease at presentation is the main determinant for treatment selection, regardless of the duration of symptoms prior to presentation. (10.1016/j.arth.2020.09.037)
• [L5] Recognition of femoroacetabular impingement and early intervention before the degenerative process is advanced is likely to have a considerable impact on the natural history of the disease, delaying the onset of end-stage arthritis in young patients. (10.1016/j.arth.2007.05.039)
• [L3] The study aimed to determine the long-term objective and subjective outcome of untreated articular cartilage defects observed at the time of ACL reconstruction. (10.1016/j.arthro.2014.04.071)
• [L3] Specific morphological characteristics on pelvis radiographs of AVN hips were predictive for poor outcome, at a very young age. (10.1302/0301-620x.103b5.bjj-2020-1485.r1)
• [L3] In later stages, this bone formation cannot be distinguished from the native bone and the labrum may appear to be nearly absent on imaging studies. (10.2106/jbjs.j.01799)

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[106] Morphological variants to predict outcome of avascular necrosis in developmental dysplasia of the hip. The Bone & Joint Journal. 2021. DOI: 10.1302/0301-620x.103b5.bjj-2020-1485.r1

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