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Hip dysplasia (adult)

150 citationsUpdated Sep 2026

Overview¶

Developmental dysplasia of the hip (DDH) encompasses a spectrum of pathologic conditions ranging from acetabular dysplasia to complete dislocation [51]. In symptomatic adult patients, deficient anterolateral acetabular coverage of the femoral head is the dominant deformity, resulting in structural hip instability and acetabular rim overload [86]. This condition frequently leads to secondary hip osteoarthritis, particularly when subtle childhood deformities such as the "pistol grip" deformity of the proximal femur are present [7]. If left untreated, hip dysplasia can result in severe deformities and functional limitations [3]. The etiology is multifactorial, involving genetic, hormonal, and mechanical factors, with risk factors including female sex, firstborn status, breech presentation, and disorders of intrauterine packing [51].

Diagnosis relies on conventional radiographs to assess acetabular morphology using parameters such as the Tönnis angle and femoral head extrusion index [20]. Ultrasonography is useful in infants under six months, while magnetic resonance imaging (MRI) and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) help visualize soft tissues and predict outcomes based on glycosaminoglycan content [51, 34, 86]. The long-term prognosis for moderate dysplasia treated nonsurgically is very poor [86]. Therefore, early diagnosis and treatment are paramount to favorably alter the natural history of the disease [6].

For symptomatic adult hip dysplasia with deficient coverage, a reconstructive acetabular osteotomy is the treatment of choice [86]. The Bernese periacetabular osteotomy (PAO) is indicated for younger patients with spherically congruent dysplasia, a lateral center-edge angle of less than 20 degrees, and minimal arthritic changes [239]. In well-selected patients, PAO is safe and effective in alleviating pain and improving function [68]. However, preoperative age older than 35 and fair or poor joint congruence are independent predictors of failure, with a 95% chance of severe pain or conversion to total hip replacement when both factors are present [239]. Total hip arthroplasty remains the procedure of choice for end-stage coxarthrosis secondary to hip dysplasia [156].

Anatomy & Pathophysiology¶

Bony Anatomy¶

The hip is a multiaxial joint formed by the articulation between the pelvis and femur, connecting the axial skeleton and the lower extremity [107]. The hemipelvis comprises the ilium, ischium, and pubis, which unite at the triradiate cartilage within the concave acetabulum [107]. Acetabular shape and depth are determined by ossification centers appearing around the end of the first decade of life, with complete fusion occurring around 18 to 19 years of age [107]. The acetabulum consists of an articular crescent-moon–shaped lunate surface and a nonarticular central fossa that serves as the attachment point for the ligamentum teres [107]. Inferiorly, the acetabulum is incomplete, forming a notch through which vital blood vessels and nerves pass to supply the joint [107]. The femoral head forms two-thirds of a sphere, featuring a small central depression from which the ligamentum teres extends to connect to the acetabular notch [107].

Femoral geometry is defined by specific angular measurements. The neck-shaft angle of the femur averages 125° [107], while the mean femoral neck-shaft angle in the adult is 130° ± 7° [119]. Normal version, defined as the head-neck angle in the frontal plane, averages 15 to 20° [107], with a mean anteversion of the femoral neck of 10° ± 7° [119]. The proximal femur contains two prime trabecular groups: the principal tensile group and the principal compressive group [119]. The weakest area in the femoral neck is located in the Ward triangle [119]. The calcar femorale, a medial area of dense trabecular bone, transfers stress from the femoral shaft to the inferior portion of the femoral neck [119].

Soft Tissue Anatomy¶

The acetabular labrum is a fibrocartilaginous ring attached to the rim of the acetabulum that extends the articulating surface area and increases femoral head coverage [107]. Its triangular cross-section contributes to its ability to create a pressurized seal of the central compartment of the hip during loading [107]. Only the external one-third of the labrum contains blood vessels, leaving the majority of the structure avascular and limiting its healing ability following injury [107]. The labrum is highly innervated, containing both mechanoreceptors and nociceptors [107]. It is absent in the area of the inferior acetabular notch, where the transverse acetabular ligament serves as its continuation [107].

The hip is surrounded by a dense fibrous capsule extending from the periphery of the acetabulum to the intertrochanteric line of the femoral neck [107]. The capsule enhances joint stability by preventing translation of the femoral head in the acetabulum [107]. Three main ligaments support the hip: Iliofemoral ligament: Y-shaped and the thickest and strongest of the three main ligaments, it functions to limit external rotation, while its lateral arm limits extension of the joint [107]. Ischiofemoral ligament: Extends from the ischial margin of the acetabulum to the greater trochanter of the femur and restricts internal rotation motion [107]. Pubofemoral ligament: Extends from the obturator crest of the pubic bone to the femoral neck and acts to limit abduction of the joint [107]. Deep fibers from these three ligaments merge to form the zona orbicularis, which circumvents the femoral neck [107].

The ligamentum teres originates in the cotyloid fossa and attaches on the fovea of the femoral head [109]. The hip capsule attaches anteriorly and posteriorly along the periphery of the acetabulum outside the labrum [109]. On the femur, the capsule attaches anteriorly along the intertrochanteric crest, while on the posterior side it attaches only partially, leaving the basicervical region of the femoral neck and intertrochanteric region extracapsular [109]. The iliofemoral ligament becomes taut in full extension, preventing anterior dislocation and hyperextension of the hip [109]. The twisted orientation of the hip ligaments provides a screw mechanism for the hip in full extension [109].

Vascular Anatomy¶

Blood supply to the femoral head evolves with age. From birth to approximately 4 years of age, the major blood supply comes from the medial and lateral femoral circumflex arteries, with major contributions from the artery of the ligamentum teres [125]. From the age of 4 years to adulthood, the posterosuperior and posteroinferior retinacular arteries from the medial circumflex artery are the major blood supply [125]. In adulthood, the major blood supply is from the medial femoral circumflex and lateral epiphyseal arteries [125].

The medial femoral circumflex artery is the main blood supply to the femoral head and terminates in the posterior aspect of the extracapsular arterial ring [119]. The lateral femoral circumflex artery gives rise to the anterior aspect of the extracapsular arterial ring [119]. The superior and inferior gluteal arteries contribute branches to this ring [119]. Ascending cervical arteries originate from the extracapsular arterial ring and are divided into lateral, medial, posterior, and anterior groups based on their anatomic relationship to the femoral neck [119]. The lateral group of ascending branches is the main blood supply to the femoral head [119]. The lateral epiphyseal artery penetrates the femoral head and is believed to be the dominant blood supply from the ascending branch system [119]. The artery of the ligamentum teres arises from either the obturator or medial femoral circumflex artery and does not provide sufficient blood supply to maintain the viability of the femoral head [119].

Pathophysiology of Developmental Dysplasia¶

Developmental dysplasia of the hip (DDH) is a condition characterized by a developmental anomalous anatomical relationship between the femoral head and the acetabulum [47]. A spectrum of abnormalities in DDH may include joint instability, ligamentous laxity, acetabular dysplasia, excessive femoral anteversion, hip subluxation, and complete dislocation [47]. Normal acetabular development depends on the concentric centralization of the femoral head into the acetabular cavity with the presence of articular motion [47]. Minimal femoral head displacement from the center of the acetabular cavity may predispose to abnormal acetabular development and further instability [47]. The natural history of DDH presents via three evolutional courses: spontaneous resolution, progression to subluxation or dislocation, or subclinical instability with persistent acetabular dysplasia [47].

DDH is a gradually progressive disorder associated with distinct anatomic changes, many of which are initially reversible [113]. In unstable hips at birth, the posterosuperior rim of the acetabulum loses its sharp margin and becomes flattened and thickened in the area over which the femoral head slides [113]. A ridge of thickened articular cartilage called the neolimbus arises along the posterosuperior acetabular wall as the femoral head slides in and out of the socket [113]. In hips that remain dislocated, the fatty tissue known as the pulvinar thickens in the depths of the acetabulum and may impede reduction [113]. The ligamentum teres elongates and thickens in dislocated hips, taking up valuable space within the acetabulum [113]. The transverse acetabular ligament is often hypertrophic in dislocated hips and may impede reduction [113]. The inferior capsule of the hip assumes an hourglass shape in dislocated hips, presenting an opening smaller in diameter than the femoral head [113]. The iliopsoas tendon is pulled tight across the capsular isthmus in dislocated hips, contributing to narrowing and acting as a barrier to closed reduction [113].

The acetabular structure does not impede the femoral head from entering the acetabulum; rather, the constricted hip capsule forces the head against the acetabular rim [113]. The blocking structure encountered in patients with DDH is not only the labrum but also a significant portion of the cartilaginous acetabulum itself [113]. The cartilaginous acetabular anlage is essential for the normal growth and development of the acetabulum and should not be excised [113]. Residual radiographic dysplasia following successful reduction for late-diagnosed DDH in young patients is a biologic failure of ossification of the acetabulum, not a "deficiency" [100]. After the neonatal period, anatomic dysplasia refers to inadequate development of the acetabulum, the femoral head, or both [100]. All subluxated hips are by definition anatomically dysplastic [100]. The major radiographic difference between radiographic dysplasia and radiographic subluxation is determined by the integrity of the Shenton line [100]. In radiographic subluxation, the Shenton line is disrupted, and the femoral head is superiorly, laterally, or superolaterally displaced [100].

Biomechanics and Degeneration¶

Hip dysplasia is characterized by a shallow acetabulum with deficient coverage of the femoral head [162]. A shallow, more vertical acetabulum in dysplasia leads to increased edge loading, decreased contact areas, and increased contact pressures [162]. The dysplastic hip is inherently unstable, leading to adaptive changes including labral and iliocapsularis muscle hypertrophy and abductor fatigue [162]. Instability and excessive stress on the articular cartilage in dysplastic hips ultimately lead to osteoarthritis if left untreated [162]. Joint loading forces in hip dysplasia are concentrated at the edge of the dysplastic acetabulum and labrum, leading to chondrolabral damage [149].

DDH results in decreased anterolateral acetabular coverage of the femoral head, lateralization of the hip center, and eccentric joint loading that can result in progressive joint degeneration [74]. The proximal femur is often involved in DDH, with asphericity of the femoral head, head-neck offset malformations, and increased femoral anteversion potentially present [74]. Acetabular dysplasia describes a shallow hip socket without frank dislocation of the femoral head but with varied degrees of superior lateral subluxation [148]. The shallow hip socket in acetabular dysplasia results in high articular cartilage contact stresses near the superolateral rim of the acetabulum, with concurrent labral tears and progressive lateral subluxation of the femoral head [148].

Subtle deformities of the hip have been implicated in the development of osteoarthritis in patients previously thought to have primary osteoarthritis [7]. Murray described a subtle "tilt deformity" of the proximal femur in 1965 that he believed would lead to osteoarthritis [7]. Stulberg et al. coined the term "pistol grip" deformity of the proximal femur in 1975 to describe small deformities that lead to osteoarthritis [7]. Ganz et al. refined the description of hip impingement caused by femoral and acetabular deformity in the mid-1990s [7]. Articular damage resulting from hip impingement can occur while symptoms remain relatively mild and intermittent [7]. The goal of hip preservation surgery in dysplasia and impingement is to alter hip joint morphology to allow more unhindered physiologic range of motion while optimizing hip joint mechanics to delay or halt the progression of hip osteoarthritis [7].

A patient's age and hip shape are important factors contributing to the resulting hip mechanics, although the interplay between those mechanical factors and patient-reported outcomes of pain are unclear [44]. Individual and postural variations in physiologic pelvic tilt affect joint contact pressure in the hip [151]. Long-term exposure to elevated cartilage contact stresses may affect joint morphology, making hips in these individuals less amenable to joint-preservation procedures such as PAO [226]. In patients with hip dysplasia, the problem is one of abnormal loading, where a smaller weightbearing area results in higher contact stresses in those areas, resulting in cartilage breakdown [195]. Muscle-induced biomechanical variables in patients with developmental dysplasia of the hip are associated with worse function and pain outcomes [245]. Hips with lower anteversion or a larger difference between anatomic and functional anteversion were more likely to be symptomatic [180].

Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness [19]. Acetabular hip dysplasia can contribute to hip instability because of a shallow acetabular component [126]. Hip microinstability refers to the femoral head micromotion within the acetabulum, which is a prolonged phenomenon that leads to cartilage damage and eventually osteoarthritis of the hip [126]. The hip joint is relatively stable not only because of the ball and socket bony anatomy but also because of the presence of various soft-tissue constraints such as the labrum, the capsule, and the ligamentum teres [126].

Classification¶

Radiographic Measurements and Thresholds¶

The lateral center-edge angle (LCEA) of Wiberg reflects lateral acetabular coverage and is measured on the AP radiograph as the angle subtended between a vertical line and a line from the center of the femoral head to the lateral border of the sourcil [255]. A normal LCEA value is greater than 25° [255]. The anterior center-edge angle reflects anterior acetabular coverage and is measured on the false-profile view as the angle formed between a vertical line and a line from the center of the femoral head to the anterior border of the sourcil [255]. A normal anterior center-edge angle value is greater than 20° [255]. The Tönnis angle reflects acetabular inclination and is determined from an AP radiograph as the angle formed between a horizontal line connecting the radiographic teardrops and a line connecting the medial and lateral edges of the sourcil [255]. A normal Tönnis angle value is less than 10° [255].

Hip dysplasia is classified when the LCEA is <25° or the Tönnis angle is >10° [40]. A CE angle ≤ 20° is mostly considered dysplastic, whereas a CE angle between 20° and 25° is considered borderline, and a CE angle > 25° is considered normal [208]. Radiographs underestimate LCEA and Tönnis angle measurements compared to computed tomography scans in the assessment of borderline and frank acetabular dysplasia [40]. An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability [90]. The authors argue that current classification of borderline hip dysplasia based solely on lateral center edge angle is insufficient and that the focus must shift to assessing hip instability to better predict treatment outcomes and the need for bony realignment [164].

Adult Classification Systems¶

Crowe: The Crowe classification uses the proportion of subluxation to divide disease severity into four classes [208]. Crowe grade 1 corresponds to subluxation < 50% [208]. Crowe grade 2 corresponds to subluxation between 50 and < 75% [208]. Crowe grade 3 corresponds to subluxation between 75 and 100% [208]. Crowe grade 4 corresponds to total luxation [208].

Hartofilakidis: The Hartofilakidis classification categorizes dysplastic hips into three classes by considering the deformation of the acetabulum in addition to the degree of subluxation [208]. In the Hartofilakidis classification, a dysplastic hip is defined as one where the femoral head is contained within the original acetabulum despite the degree of subluxation [208]. In the Hartofilakidis classification, low dislocation is defined as the femoral head articulating with a false acetabulum that partially covers the true acetabulum to a varying degree [208]. The Hartofilakidis classification system describes three types of developmental hip dysplasia (dysplasia, low dislocation, and high dislocation) to guide surgical management by anticipating implant type and the need for augmentation [111]. Both the Crowe and Hartofilakidis classification systems assess the different aspects of developmental dysplasia of the hip in adults [27].

Instability-Based Frameworks: The authors propose a diagnostic framework that groups symptomatic dysplastic hips into one of 3 categories based on the primary direction of instability: anterior, posterior, and global [32]. Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of periacetabular osteotomy by giving a better understanding of the 3-dimensional deformity [171]. Three patterns of acetabular deficiency are common in young adult patients with acetabular dysplasia [166]. Recognition of distinct morphologic subtypes of acetabular deficiency is important for diagnostic and surgical treatment considerations to optimize acetabular correction and avoid femoroacetabular impingement [166]. A novel 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 [82].

Pediatric and Infant Classification Systems¶

Tönnis: The Tönnis system classifies displacement based on the level of the ossific nucleus relative to the lateral margin of the acetabulum [255]. Lesser Tönnis grades of dysplasia correlate with an improved prognosis for satisfactory long-term outcomes [255]. Each increase in the Tönnis grade at the time of diagnosis doubles the likelihood of failure of nonsurgical treatment [255].

International Hip Dysplasia Institute: The International Hip Dysplasia Institute classification system bases the severity of subluxation on the position of the center of the metaphysis relative to a horizontal line connecting the two TRCs (Hilgenreiner line) and a vertical line at the lateral border of the ossified acetabulum (Perkin line) [255]. The International Hip Dysplasia Institute classification system has been demonstrated to be both reliable and prognostic for success of closed reduction and need for late pelvic osteotomy [255].

Acetabular Index: The acetabular index is a measure of the inclination of the ossified acetabulum as determined by the angle formed between a horizontal line connecting the TRCs (Hilgenreiner line) and a line drawn from the iliac margin at the upper edge of the TRC to the most lateral edge of the ossified acetabulum [255]. The acetabular index progressively decreases with age but will remain abnormally high in a dysplastic hip [255].

Ogata et al.: The Ogata et al. classification system is a reliable and reproducible radiological indicator for reflecting acetabular cover [172].

Bucholz and Ogden: The Bucholz and Ogden classification system is based on morphologic changes in the capital femoral epiphysis, the physis, and the proximal femoral metaphysis [26].

Kalamchi and MacEwen: The Kalamchi and MacEwen classification system is based on morphologic changes in the capital femoral epiphysis, the physis, and the proximal femoral metaphysis [26]. A simplification of the Kalamchi and MacEwen classification scheme has been proposed that combines groups II, III, and IV into a single group B [26].

Bucholz-Ogden (AVN): The Bucholz-Ogden system is the most widely used classification system for avascular necrosis [266]. In the Bucholz-Ogden system, type I AVN involves changes limited to the femoral head without metaphyseal involvement [266].

Graf: The Graf hip classification includes types I, IIa, IIc, D, III, and IV [228]. In the Graf classification, Type I is described as a mature hip [228]. In the Graf classification, Type IIa is described as a dysplastic hip [228]. In the Graf classification, Type IIc is described as a heavily dysplastic hip [228]. In the Graf classification, Types D, III, and IV are described as decentered hips [228].

Associated Morphologic Features¶

40% of patients with acetabular dysplasia also had radiographic evidence of cam-type femoroacetabular deformity [21]. The morphology of the anterior inferior iliac spine (AIIS) in patients with acetabular dysplasia is commonly prominent, with 72% of hips having Type II or Type III morphologies [163]. In developmental dysplasia of the hip, AIIS type 3 tends to be more severe dysplasia than AIIS type 1 or 2 [187]. The morphologic features of the AIIS in hip dysplasia may differ between males and females [48]. Patients with acetabular dysplasia have an increased frequency of spinal anomalies seen on standard hip radiographs [39]. Eight patients (17%) with unilateral late-detected congenital dislocation of the hip developed dysplasia of the contralateral hip [11]. The development of contralateral hip dysplasia in patients with unilateral late-detected congenital dislocation appears to be a developmental process rather than an unnoticed dysplasia present from infancy [11].

Imaging and Diagnostic Modalities¶

Conventional radiographs remain critical in the initial imaging evaluation of the hip [20]. A complete hip series usually is composed 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 [20]. The femoral head-neck junction morphology is often assessed using the alpha angle [20]. Some studies have shown that radiographs, in particular the Dunn 45° view, may be more accurate for determining the alpha angle measurement than CT or MRI [20]. Artificial intelligence model measurements demonstrate a high degree of consistency with manual measurements and exhibit robust diagnostic performance in identifying developmental dysplasia of the hip and borderline developmental dysplasia of the hip [175]. Deep learning application for automated diagnosis and classification of hip dysplasia on plain radiographs utilizes the acetabular center-edge (CE) angle as the most common radiographic measure [208].

Clinical Presentation¶

Adult and Adolescent Presentation¶

In skeletally mature, young, active patients, developmental dysplasia of the hip (DDH) should be suspected when the predominant complaint is insidious activity-related groin pain and/or lateral hip pain [58]. In adolescent patients, lateral hip pain is often the initial symptom, occurring later in the day as fatigue develops due to altered biomechanics [83]. This lateral pain is attributed to decreased hip abductor muscle strength and is often missed because it is mild compared with deep groin pain [83]. Deep anterior groin pain in adolescent hip dysplasia generally indicates pain originating from the joint, resulting from joint overload, edge-loading of the acetabulum, labral irritation or injury, or labral chondral injury [83]. This deep groin pain occurs later, is more common, is activity-related, and improves when activity restriction is instituted [83].

Physical examination in adolescents may reveal an antalgic gait or a subtle Trendelenburg gait [83]. The impingement test assesses pain with flexion, internal rotation, and adduction to determine the likelihood of symptomatic labral pathology [83]. Patients presenting with acetabular dysplasia during adolescence may have a history of prior hip dislocation treatment or may be unaware of any prior hip problems [204]. In late-presenting acetabular dysplasia, pain is worse with exertion and long periods of walking or standing, and may result in a decrease in activity [204]. Pain is exacerbated when the hip is maximally flexed, internally rotated, and adducted [204]. Physical findings are usually minimal, though some patients exhibit a Trendelenburg limp or a delayed Trendelenburg sign [204]. Signs of snapping or popping may be caused by a tear in the labrum [204].

Radiographic assessment is central to diagnosis, though adult hip dysplasia is most commonly diagnosed based on the lateral center-edge angle (LCEA), which is an unreliable sole marker for dysplasia [59]. Hip dysplasia is classified radiographically when the LCEA is <25° or the Tönnis angle is >10° [40]. Radiographs underestimate LCEA and Tönnis angle measurements compared to computed tomography scans in the assessment of borderline and frank acetabular dysplasia [40]. The use of the iliofemoral line as a radiographic parameter may enable earlier detection of borderline and frank hip dysplasia in young adults presenting with hip pain [62]. The center gap is a possible new radiographic predictor of progression of osteoarthritis in DDH [66].

Sex-dependent disease characteristics exist in symptomatic acetabular dysplasia, with male patients showing a greater prevalence of findings consistent with concurrent femoroacetabular impingement and instability [102]. Proximal femoral deformities are highly prevalent in symptomatic acetabular dysplasia, with 92.6% of hips showing abnormalities [33]. The morphologic features of the anterior inferior iliac spine in hip dysplasia may differ between males and females [48]. A diagnostic framework groups symptomatic dysplastic hips into three categories based on the primary direction of instability: anterior, posterior, and global [32]. Both the Crowe and Hartofilakidis classification systems assess different aspects of DDH in adult patients [27].

Hip pain related to acetabular dysplasia might result in overdiagnosis of hip involvement by axial spondyloarthritis [64]. A thorough history and physical examination are essential to delineate the subtle differences among cam and pincer impingement, dysplasia, and femoral version abnormalities [71]. The complexity of the hip and pelvic region can make accurate diagnosis of painful conditions difficult, as many hip conditions present with similar symptoms [28]. A thorough history is essential to differentiating between common causes of hip pain [28]. Clinical examination tests and imaging findings should be used to confirm a suspected clinical diagnosis, with imaging studies complementing clinical examination findings to provide the most accurate diagnosis [28].

Pediatric and Neonatal Presentation¶

In newborns, DDH may be a silent disease with subtle or even no abnormalities in the physical examination [191]. Newborns with DDH have no pain, no evident deformity, and no limitation of hip motion [191]. The neonatal hip is a relatively unstable joint because the muscle is undeveloped, the soft cartilaginous surfaces are easily deformed, and the ligaments are lax [78]. Exaggerated positioning in acute flexion and adduction in utero may occur, especially in breech presentation, causing excess stretching of the posterior hip capsule [78]. Laxity may reflect family history or the presence of maternal relaxin hormone in the fetal circulatory system [78]. Displacement of the femoral head in the infant is proximal (posterior and superior) because of the pull of the gluteal and hip flexor muscles [78].

The Ortolani maneuver identifies dislocated or subluxated hips by a palpable clunk when the hip in 90° of flexion is abducted and the greater trochanter is pushed upward [191]. A positive Ortolani sign indicates that a dislocated hip is able to be reduced [191]. The Barlow maneuver tests hip stability by adducting the hip in 90° of flexion while applying axial posterior force through the knee and lateral force using the thumb through the lesser trochanter [191]. The Barlow maneuver indicates that a reduced hip can be dislocated or subluxated with stress [191]. Detection of "pistoning," or the sensation of the femoral head subluxating over the posterior rim of the acetabulum, is a positive finding on the Barlow test [78]. The Barlow test detects an unstable but located hip and is unsuitable for a dislocated hip [78]. The Ortolani test detects hips that are already dislocated [78].

Hip instability maneuvers may become spontaneously negative within 2 to 4 weeks of life [191]. The sensitivity of the Ortolani and Barlow tests may be as low as 60% [191]. Barlow and Ortolani maneuvers may fail to predict further surgical treatment in almost two-thirds of hips [191]. Several examination maneuvers for DDH require a quiet, relaxed infant and commonly produce false-negative findings [78]. It is helpful to identify the very lax (unstable) but still located hip, which may either dislocate later or exhibit subtle dysplasia during growth that can cause premature osteoarthritis [78]. The fate of the unstable hip remains an enigma, with controversy over how often an unstable hip spontaneously reduces or becomes dislocated, subluxated, or dysplastic [190]. Barlow found 1 hip in 60 examined to exhibit his instability sign; 60% normalized within 1 week, and 88% were corrected within 2 months without treatment [190].

Dislocated hips may shorten the limb length, allowing for discrepancy and a positive Galeazzi sign [191]. The Galeazzi test is positive when the knee on the involved side is lower than the contralateral knee, indicating unilateral subluxation or dislocation [51]. The Galeazzi sign is noted when the femoral head is displaced laterally and proximally, causing apparent shortening of the femur on the side of the dislocated hip [200]. The Galeazzi test is almost always useless in children younger than 1 year and is negative if dislocation is bilateral [78]. Patients aged 3 to 6 months with dislocated hips present asymmetry in cutaneous creases of the thigh, gluteal, or inguinal region [191]. However, asymmetric skin folds are an unreliable and nonspecific finding for DDH, frequently producing false-positive and false-negative results [51]. Normal children may have asymmetric folds and children with dislocated hips may have symmetric folds [200].

Limitation of hip abduction usually becomes evident after age 3 months in patients with dislocated hips [191]. In children aged 6 to 18 months with undetected dislocated hips, a decrease in the ability to abduct the hip due to adductor musculature contracture is the first and most reliable clinical sign [200]. Asymmetric abduction or limited abduction (usually < 70 degrees from the midline) is a positive finding for DDH [78]. When the hip is lax (dislocatable but not dislocated), the abduction test is normal despite the presence of subluxation or dislocation [78]. A decrease in abduction is the most sensitive test result for DDH [51]. Range of motion may be normal in children younger than 6 months if adductor contractures have not yet developed [51].

In walking patients with DDH, an obvious limping with abductor insufficiency is present, or the patient toe walks on the side of the dislocated hip [191]. Families of children with undetected dislocated hips at walking age may describe a "waddling" type of gait indicating a Trendelenburg gait pattern [200]. Parents may describe difficulty in abducting the hip during diaper changes in children with undetected dislocated hips [200]. In infants older than 6 months, common findings of DDH are asymmetric hip abduction and apparent limb shortening in unilateral dislocations [51]. In toddlers with DDH, restricted motion may be accompanied by a limb-length discrepancy, a limp, or a waddling gait [51]. Toddlers with bilateral hip dislocations often present with hyperlordosis of the lumbar spine [51]. Bilateral dislocations may appear symmetrically abnormal on clinical examination [200]. Detection of bilateral dislocations may be particularly difficult [78].

Hip clicks are nonspecific physical findings in the neonatal period [51]. Referral for evaluation of DDH is frequently triggered by an abnormal newborn hip examination, such as hip click, instability, or limited abduction [15]. An abnormal newborn hip examination may be present in 4% to 5% of newborns [15]. Certain infants, including breech babies, babies with a family history, and females, are at higher risk for DDH [78]. DDH is more likely if risk factors are present, such as positive family history, ligamentous laxity, breech presentation, female gender, large fetal size, and first-born status [78]. DDH occurs in approximately 1 in 1000 live births in whites, is less common in blacks, and may be more common in certain ethnic groups such as North American Indians [78]. Dislocations in DDH may be bilateral but are more often unilateral and on the left side [78].

DDH is associated with other problems related to intrauterine positioning, such as torticollis (20% of cases) and metatarsus adductus (10%) [169]. There is no association between DDH and clubfoot [169]. The teratologic form of DDH is the most severe and usually necessitates early surgery [169]. A pseudoacetabulum is present at or near birth in teratologic hip dislocations [169]. Teratologic hip dislocations commonly manifest in association with syndromes such as arthrogryposis and Larsen syndrome [169].

In newborns with true congenital dislocation of the hip, the femoral head can often be dislocated and reduced into and out of the true acetabulum [179]. In older children with DDH, the femoral head remains dislocated and secondary changes develop in the femoral head and acetabulum [179]. If left untreated, muscles about the hip become contracted, and the acetabulum becomes more dysplastic and filled with fibrofatty tissue (pulvinar) [169]. In the subluxated hip, asymmetric pressure causes progressive flattening of the posterior and superior acetabular rim and medial femoral head [78]. In the completely dislocated hip, dysplasia occurs because normal joint development requires concentric motion with normally mated joint surfaces [78]. The shallow, deformed dysplastic joint surfaces predispose to further mechanical instability and the inexorable progression of the disorder [78].

A child may be born with acetabular dysplasia without dislocation of the hip, and dislocation may develop weeks or months later [200]. DDH represents a broad spectrum of disease affecting the femoral head, the acetabulum, or both, ranging from physiologic immaturity of the hip to frank dislocation [15]. DDH is characterized by a developmental anomalous anatomical relationship between the femoral head and the acetabulum [47]. The natural history of DDH includes a course where subclinical instability may be present without obvious signs or symptoms, and acetabular dysplasia may persist beyond childhood if not diagnosed correctly [47]. It is unclear whether acetabular dysplasia diagnosed during adolescence or later is a residual deformity of childhood DDH or a distinct acetabular growth abnormality with later presentation [47]. Late dysplasia is more likely to be bilateral [47]. Reversal of dysplasia and subsequent normal hip development depend on early detection of DDH [78].

Adolescents with DDH may manifest fatigue and pain in the hip, thigh, or knee in addition to signs and symptoms seen in younger children [51]. Adolescent hip dysplasia can be defined radiographically as a hip with an abnormally inclined acetabulum [83]. Radiographic findings associated with adolescent hip dysplasia include decreased joint space, a lateralized joint center, an abnormally shaped femoral head, and sclerotic margins of the sourcil with subchondral cysts [83]. Patients may have radiographic dysplasia without associated pain or discomfort [83]. The incidence of labral pathology in patients with hip dysplasia is reported to occur in two-thirds of patients [83]. In adult hip dysplasia, acetabular cartilage lesions are found in 69% of cases and combined labral/cartilage lesions in 59%, most commonly on the anterior and superolateral acetabulum [83].

Hip dysplasia is characterized by a shallow acetabulum with inadequate coverage of the femoral head and resultant abnormal contact mechanics, which cause accelerated degeneration of the articular surface at an early age [71]. Osseous abnormalities of the acetabulum and proximal femur, including hip dysplasia, have been shown to cause pain, functional limitation, and eventual joint degeneration in young prearthritic hips [71]. In adults with fully dislocated hips, the femoral head may lie well above the acetabular margin in a markedly thickened hip capsule, known as a "high-riding dislocation" [190]. The adult dislocated femoral head is oval and flattened medially [190]. In adult dislocated hips, the acetabulum is filled with fibrous tissue, hypertrophied ligamentum teres, and thickened transverse acetabular ligament [190]. The articular cartilage in adult dislocated hips is either atrophic or absent [190]. Muscles that insert at the proximal femur in adult dislocated hips are foreshortened and more horizontally oriented [190]. Fully dislocated adult hips may remain free from degenerative changes for many years, even for the individual’s lifetime [190]. The diagnosis of DDH is made clinically or by ultrasound [78]. Early detection of DDH is made more challenging by the lack of a definitive test or finding on examination [78]. DDH is painless in the infant, so there are no symptoms [78].

Investigations¶

Plain radiography: Conventional radiographs remain critical in the initial imaging evaluation of the hip and can diagnose developmental dysplasia of the hip (DDH) [20]. Acetabular morphology is assessed on AP pelvis radiographs to evaluate overcoverage and undercoverage [20]. The lateral center-edge angle (LCEA) is defined as the angle between a line from the center of the femoral head perpendicular to the transverse pelvis axis and a second line from the center of the femoral head to the superolateral most point of the acetabulum [20]. LCEA values of 20°–40° are considered normal, while angles from 20° to 25° are considered borderline [20]. The Tönnis angle is defined by the angle of the acetabular sourcil and a line parallel to the transverse pelvis axis, with values between 0° and 10° considered normal [20]. The femoral head extrusion index is defined by the length of the femoral head that lies beyond the acetabulum as a percentage of the total horizontal width of the femoral head, with values greater than 25% considered abnormal [20]. Radiographs underestimate LCEA and Tönnis angle measurements compared to computed tomography (CT) scans in the assessment of borderline and frank acetabular dysplasia [40]. The iliofemoral line is a radiographic sign of acetabular dysplasia in the adult hip that may enable earlier detection of borderline and frank hip dysplasia in young adults presenting with hip pain [62]. An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and provide insufficient data to guide treatment of hips with additional features of dysplasia and instability [90]. Adult hip dysplasia is most commonly diagnosed based on the LCEA, but the LCEA is an unreliable sole marker for dysplasia and additional radiographic parameters should be utilized [59]. The Crowe and Hartofilakidis classification systems both assess different aspects of developmental dysplasia of the hip in adult patients [27]. The center gap is a possible new radiographic predictor of progression of osteoarthritis in developmental dysplasia of the hip, though future studies are needed to validate this marker [66]. Projection of two-dimensional radiographic landmarks into 3D allows for the identification of overlapping bony anatomy contributing to radiographically visible anterior and lateral sourcil edges [236]. The morphologic features of the anterior inferior iliac spine (AIIS) in hip dysplasia may differ between males and females [48].

CT: CT overcomes the limitations of radiography by providing three-dimensional assessment of bony morphology and, to some degree, assessment of soft-tissue abnormalities [63]. 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 [131]. Measurements of femoral head coverage and acetabular and femoral impingement can be performed reliably using CT images [131]. CT can accurately determine version of the acetabulum and femoral version independent of patient position [244]. A clear measurement of the alpha angle can be performed on the sagittal-oblique image parallel to the femoral neck on CT [244]. The sphericity of the femoral head can accurately be determined using CT [244]. Cystic changes within the bone and ossification of the labrum can be better delineated on CT [244]. Three-dimensional CT with pelvic remodeling may be indicated for preoperative planning for reconstruction associated with dysplasia surgery [154]. A low-dose CT scan of the pelvis with a few slices through the epicondyles of the knee is useful to determine the pattern of acetabular dysplasia, the version of the acetabulum, and the version of the femoral neck [274].

MRI: MRI is the modality of choice for patients suspected of soft tissue or intra-articular pathology, given its superior sensitivity and specificity [131]. Conventional MRI is effective at identifying osteochondral injuries, musculotendinous pathologies, and inflammation [131]. Magnetic resonance arthrography (MRA) is more appropriate than conventional MRI to determine injuries to the labrochondral structures and the ligamentum teres and to identify the presence of loose bodies and synovial chondromatosis [131]. The utility of MRA in the accurate detection and staging of articular cartilage lesions is reduced, with sensitivity reported to be less than 50% compared with arthroscopic findings [131]. 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 [131]. Delayed gadolinium-enhanced MR imaging and T2 mapping were effective at detecting early changes to the articular cartilage surfaces of patients with hip dysplasia and femoroacetabular impingement [131]. MRI is important in the evaluation of chondral or labral pathology associated with femoroacetabular impingement (FAI) and can be performed with intra-articular contrast or without contrast if a high-level 3-Tesla protocol is used [87]. Gadolinium-enhanced MRI arthrogram is useful when labral pathology is suspected, especially when associated with FAI [154]. MRI may identify gluteus medius and gluteus minimus tears in patients with lateral hip pain and abductor weakness [154]. Patients with hip dysplasia have a significantly reduced capsular thickness on MRI and delaminated anterior joint capsule, which could be a sequence of instability [209]. An MR arthrogram is performed to evaluate the status of the articular cartilage and labrum in the radiographic workup of hip dysplasia [274].

Ultrasonography: Ultrasonography provides real-time dynamic assessment of the hip and is useful in diagnosing soft-tissue abnormalities about the hip joint [63]. Although ultrasonography is a valuable tool to examine pediatric hip conditions, its utility in evaluating the adult hip is limited [131]. Ultrasonography can be an effective modality to identify musculotendinous disruptions, effusions associated with intra-articular pathology, or inflammatory conditions, such as bursitis [131]. Ultrasonography is being increasingly used for targeted injections into muscles, tendons, or intra-articularly around the hip for use with corticosteroids or biologic treatments [131].

Other Considerations: Studies of patients with symptomatic acetabular dysplasia have found cam morphology in 10% to 40% [274]. Radiographic evidence of FAI is common in active patients with hip complaints [215]. Up to 51% of patients presenting with symptomatic FAI show an abnormal femoral version, whilst up to 31% demonstrate abnormal acetabular version [224]. The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips [201]. Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in Japanese patients with hip pain, with cam deformity findings being the most common [216].

Treatment¶

Non-Operative¶

The goal of hip preservation surgery in dysplasia is to alter hip joint morphology to allow more unhindered physiologic range of motion while optimizing hip joint mechanics to delay or halt the progression of hip osteoarthritis [7]. Treatment options for developmental dysplasia of the hip are directly related to the severity of the condition and the patient’s age at the time of initial treatment [15]. The best results and long-term outcomes occur in patients who are treated earlier in the neonatal period with the least residual dysplasia [15]. The treatment of developmental dysplasia of the hip is age-related and tailored to the specific pathologic condition [72]. Five age-related treatment groups have been designated: newborn (birth to 6 months old), infant (6 to 18 months old), toddler (18 to 36 months old), child (3 to 8 years old), and adolescent and young adult (>8 years old) [72].

Most patients in whom a diagnosis of developmental dysplasia of the hip is made within 6 months of age are successfully treated with a Pavlik harness [41]. The Pavlik harness is the first choice of treatment for children presenting between 2 and 6 months of age [141]. To be effective, the Pavlik harness must hold the hips in more than 90 degrees of flexion, with the position of the upper femoral metaphysis pointed toward the triradiate cartilage [141]. If reduction is not obtained within 3 to 4 weeks of Pavlik harness treatment, the harness should be discontinued and other treatment begun [141]. If reduction is confirmed with a Pavlik harness, the harness should be continued for approximately 6 weeks after stability is established [141]. The Pavlik harness is usually worn 23 hours a day for at least 6 weeks after a reduction has been achieved and then an additional 6 to 8 weeks part time [157]. Factors associated with the failure of Pavlik harness treatment include patient age of more than 7 weeks at treatment, bilateral hip dislocation, and an absent Ortolani sign [157]. Pavlik harness treatment is contraindicated in teratologic hip dislocations [157]. Excessive flexion in a Pavlik harness may result in transient femoral nerve palsy [157]. If attempts to reduce a hip with a Pavlik harness do not succeed in 3 weeks, the harness should be discontinued to prevent erosion of the pelvis superior to the acetabulum [157]. A comprehensive protocol for nonoperative treatment of infant developmental dysplasia of the hip has shown high rates of success and extremely low rates of residual dysplasia at a mean age of five years [199]. The majority of patients with residual acetabular dysplasia at two years post-brace treatment spontaneously resolved by five years [98].

Operative¶

Indications: Closed reduction is indicated for children with a dislocated hip in whom orthotic treatment has failed and for those with a late-presenting dislocated hip for whom primary Pavlik harness treatment is not suitable [34]. Children generally ranging from 4 to 18 months of age are candidates for closed reduction [34]. Surgical reduction of congenital hip dislocation is technically challenging and is usually reserved for patients who have failed non-operative treatment or have late diagnosis [213]. In adolescents, acetabular dysplasia is characterized by increased inclination in the coronal and sagittal planes and a lateralized hip joint center [41]. Adolescent hip dysplasia is most commonly treated with periacetabular osteotomy (PAO) with excellent intermediate and long-term outcomes in hips without prior degenerative changes [41]. A reconstructive acetabular osteotomy is the treatment of choice for the symptomatic hip with moderate dysplasia [86]. Appropriately selected older patients (aged 45 years and older) with dysplasia without significant preexisting hip osteoarthritis experience clinically meaningful improvements in hip pain and function after hip preservation surgery [12]. Age over 45 is not a contraindication for PAO/hip arthroscopy if articular cartilage status is normal [134]. Femoral or periacetabular osteotomy should be considered for young patients with osteoarthritis if the joint is not grossly incongruous and satisfactory motion is present [144].

Surgical Approach / Technique: A closed reduction is performed under general anesthesia with hip abduction and an anteriorly directed force on the posterior aspect of the greater trochanter to obtain reduction [34]. The use of preoperative overhead traction has recently been demonstrated to offer no advantage to achieving a successful reduction or avoiding osteonecrosis in a large series of patients [34]. Arthrography is used to evaluate the reduction intraoperatively, with a medial dye pool ≤6 mm or 16% of the femoral head diameter both shown to be predictive of a successful reduction [34]. Open reduction should be considered if an acceptable closed reduction is unobtainable or would require excessive force [34]. An open reduction can be performed through a medial or anterior approach [34]. In children younger than 18 months, substantial remodeling of the acetabulum can occur after a closed or open reduction without bony surgery [34]. Pelvic or femoral osteotomies are rarely required in children younger than 18 months [34]. After 18 months of age, there is an increased likelihood of either femoral or pelvic osteotomy [34]. A femoral shortening osteotomy may be indicated if soft-tissue contractures result in excessive pressure on the femoral head in the acetabulum following open reduction [34]. In children aged 12 to 18 months, open reduction can be performed safely through a medial or anterior approach [185]. In children aged 18 months to 3 years, residual bony deformity can be corrected with a femoral or pelvic osteotomy in addition to open reduction [185]. In children with complex deformity or in children aged older than 3 years, both pelvic and femoral osteotomies are commonly required to stabilize an open reduction [185]. Open reduction through an anterior minimally invasive approach can achieve good clinical effect in the treatment of infantile developmental dysplasia of the hip [248]. A stable, safe but non-concentric reduction achieved before the age of two years appears to improve over time with nearly 80% of hips becoming fully concentric by one year [246]. Restoration of a normal hip joint center with improved/normalized acetabular coverage is achieved with triple innominate osteotomies in those with open triradiate cartilage or a periacetabular osteotomy in the skeletally mature patient [41]. The Bernese PAO has been popularized for acetabular reorientation and is now a mainstay of surgical treatment [86]. The Bernese PAO is increasingly combined with hip arthroscopy in a single setting when labral pathology is present, with hip arthroscopy performed first [86]. Rotational acetabular osteotomy is an effective surgery for treating symptomatic developmental dysplasia of the hip in selected patients [112]. Dega acetabuloplasty is effective and reliable in correcting acetabular dysplasia following developmental dislocation of the hip [147]. Patient-specific allograft bone shelves could be a serious option for adolescents with severe hip dysplasia [42]. Staged hip arthroscopy and periacetabular osteotomy (PAO) for hip dysplasia leads to similar patient-reported outcomes at 12-24 months compared to combined procedures [46]. Optimal surgical treatment of hip dysplasia treats both the cause and the effects of dysplasia by combining hip arthroscopy and periacetabular osteotomy into a single intervention [110].

Implant Selection: Salvage osteotomies such as the Chiari osteotomy rely on the articulation of the femoral head with metaplastic fibrocartilage rather than articular hyaline cartilage [86].

Alignment / Balancing Strategy: Abnormal femoral version is a common comorbidity in adult developmental dysplasia of the hip that can aggravate instability and lead to osteoarthritis [146]. Specific indications for femoral derotational osteotomy and the threshold for correction in adult developmental dysplasia of the hip remain controversial and require further research [146].

Other Considerations: Periacetabular osteotomy (PAO), with or without femoral osteotomy, for treatment of painful hip dysplasia in young adults appears to be effective in delaying prosthetic hip reconstruction when the surgical intervention occurs while the arthritic progression is fairly mild [7]. The results of PAO in patients with more advanced arthritis have been less favorable [7]. Periacetabular osteotomy is an effective technique for treating symptomatic developmental dysplasia of the hip and can maintain the natural hip at least 19 years in selected patients [45]. Reported survival for the Bernese PAO is 60% at 20-year follow-up [86]. Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) assessment of the glycosaminoglycan (GAG) content of the articular cartilage is predictive of outcome after PAO, with low GAG content associated with increased risk of failure [86]. Hip arthroscopy can reliably provide durable and clinically meaningful improvements for the treatment of intra-articular pathology and femoroacetabular impingement syndrome (FAIS) in patients with acetabular dysplasia at long-term follow-up [14]. Improved patient-reported outcomes can be obtained with hip arthroscopy in the treatment of concomitant mild acetabular dysplasia and femoroacetabular impingement (FAI) at a minimum 2-year follow-up [13]. Hip dysplasia may not be an absolute contraindication for isolated hip arthroscopy and may serve as a viable intervention with consideration of staged future periacetabular osteotomy (PAO) [18]. Arthroscopic procedures for individuals with mild dysplasia in the absence of frank instability may be effective [260]. Great caution should be exercised when approaching dysplastic patients with symptomatic hips using arthroscopy [260]. Most patients with borderline hip dysplasia achieve successful outcomes after hip arthroscopy alone [36]. Patients with borderline hip dysplasia who have signs of instability may fail arthroscopic-only treatment and require bony treatment [36]. Arthroscopic treatment with labral preservation and capsular plication may be an option for mildly dysplastic hips when strict indications are used [165]. Further research with more patients and longer follow-up is necessary to determine specific indications for hip arthroscopy in adult hip dysplasia [24]. Surgical outcomes at a minimum of 2 years in patients with borderline hip dysplasia undergoing PAO or hip arthroscopy were good [49]. PAO is reliable in treating borderline hip dysplasia with favorable mid-term outcomes [139]. Patients with hip dysplasia can be treated with PAO to help maintain activity and preserve the native hip [77]. Up to 62% of patients who underwent PAO for hip dysplasia participated in sports after PAO [253].

Complications and Prognostic Factors: The most serious complication associated with treatment of developmental dysplasia of the hip in early infancy is the development of osteonecrosis [26]. Estimated rates of osteonecrosis following treatment of developmental dysplasia of the hip vary widely, ranging from less than 5% to almost 50% [26]. Proposed risk factors for osteonecrosis include open reduction with concomitant osteotomies, redislocation after surgical correction, or the need for secondary procedure after initial closed or open reduction [26]. The rate of osteonecrosis after closed reduction is lower than after open reduction, but is still as high as 10% to 35% after closed treatment [26]. Meta-analyses have indicated that the presence of the ossific nucleus provides little protective benefit against osteonecrosis after closed or open reduction [26]. Delaying reduction of a dislocated hip until the appearance of the ossific nucleus more than doubled the need for future surgery [26]. Femoral nerve palsy in Pavlik harness treatment is strongly predictive of failure of treatment, and its impact is greatest when the developmental dysplasia of the hip is higher in severity [5]. The 7-year hip survival rate in hip dysplasia appears inferior compared with that reported in femoroacetabular impingement (78%) [35]. Impingement adversely affects 10-year survivorship after periacetabular osteotomy for developmental dysplasia of the hip [16]. One-third of hips after periacetabular osteotomy survive 30 years with good clinical results, no progression of arthritis, or conversion to total hip arthroplasty [16].

Total Hip Arthroplasty: Patients who had hip dysplasia and mild osteoarthritis had similar recovery curves compared to those who had severe osteoarthritis or who did not have dysplasia following total hip arthroplasty (THA) [8]. Patients with hip dysplasia can expect reduced pain, improved functional outcomes, and similar revision surgery rates to those with osteoarthritis following primary THA [23]. Periacetabular osteotomy in patients with dysplasia may decrease the need for structural bone grafting if later conversion to arthroplasty is needed [144]. If an osteotomy relieves symptoms for 10 years or more, and then an arthroplasty is required, the patient will have been able to engage in more physical activity, bone stock will have been preserved, and the patient will be older and less physically active [144].

Complications¶

Osteonecrosis (AVN)¶

Osteonecrosis is the most serious complication associated with the treatment of developmental dysplasia of the hip (DDH) in early infancy [26]. Estimated rates following DDH treatment vary widely, ranging from less than 5% to almost 50% [26]. Proposed risk factors include open reduction with concomitant osteotomies, redislocation after surgical correction, or the need for a secondary procedure after initial closed or open reduction [26]. Meta-analyses indicate that the presence of the ossific nucleus provides little protective benefit against osteonecrosis after closed or open reduction [26]. A 2016 meta-analysis found no association between closed or open reduction before or after 12 months of age and the development of osteonecrosis [34]. Similarly, no association was found between medial or anterior surgical approach and the development of osteonecrosis [34].

Potential sequelae of osteonecrosis include femoral head deformity, acetabular dysplasia, lateral subluxation of the femoral head, relative overgrowth of the greater trochanter, and limb-length inequalities [26]. Osteoarthritis is a common late complication of osteonecrosis [26]. Patients with osteonecrosis secondary to DDH have a 14% incidence of total hip arthroplasty (THA) by age 34 years [203].

Natural History and Degenerative Joint Disease¶

Subtle deformities of the hip from childhood, such as the "pistol grip" deformity, have been implicated in the development of osteoarthritis in patients previously thought to have primary osteoarthritis [7]. Persistent acetabular dysplasia is a well-known cause of premature hip osteoarthritis [84]. Degenerative change occurred earliest in patients with DDH, whereas the natural history of patients with femoroacetabular impingement (FAI) was quite similar to structurally normal hips [76]. A DDH family history is a risk factor for the progression of hip osteoarthritis [173].

For a patient who recently developed Tönnis 1 degenerative change, the probability of undergoing THA in 10 years based on hip morphology was approximately one in three for DDH [53]. The approximate probability of undergoing THA at 20 years for a patient with recent Tönnis 1 degenerative change was two in three for DDH [53]. Radiographic variables with negative prognostic value for hip OA include femoral head lateralization greater than 8 mm, femoral head extrusion index greater than 0.2, acetabular depth-to-width index less than 0.3, lateral center-edge angle less than 25°, and Tönnis angle greater than 8° [53].

In a 30-year follow-up study of 119 DDH patients, 43% had radiographic evidence of degenerative joint disease [142]. Function deteriorated with time even in the absence of a growth disturbance of the proximal end of the femur [142]. Long-term follow-up is recommended because there is a small but significant incidence of late asymmetric epiphyseal closure and acetabular dysplasia [73].

Surgical Complications: Pediatric and Adolescent¶

Femoral nerve palsy in Pavlik harness treatment for DDH is strongly predictive of failure of treatment [5]. The impact of femoral nerve palsy is greatest when the developmental dysplasia of the hip is higher in severity [5]. Lateral tethering of the proximal femoral physeal is a complication complicating the treatment of congenital hip dysplasia [2]. Complications of Chiari and Salter osteotomies have been studied in cadaver models [2].

A retrospective case-control series reported a 65% complication rate following bony hip surgery in children with cerebral palsy and hip dysplasia/dislocation [79]. In the same series, 26% of patients experienced multiple complications [79]. Only 15% of complications in that series required return-to-OR, and an additional 2% were life-threatening (Clavien-Dindo III-IV) [79]. No perioperative deaths were reported in that series of bony hip surgery complications [79]. Complication rates for salvage procedures in late-presenting hip dislocation include 24% for femoral head resection, 33.3% for valgus-producing osteotomy, 35.3% for THA, and 28.6% for shoulder prosthetic interposition [79]. The complication rate for hip arthrodesis in salvage procedures was reported as 106.3% [79].

Surgical Complications: Adult Hip Preservation (PAO)¶

Complications associated with periacetabular osteotomy (PAO) have been documented in a prospective multicenter study [16]. Impingement adversely affects 10-year survivorship after periacetabular osteotomy for DDH [16]. Obesity increases the risk of complications in the surgical treatment of adolescent acetabular dysplasia with a periacetabular osteotomy [16]. Tranexamic acid reduces blood loss and blood transfusion requirements following periacetabular osteotomy [16].

In a series of 19 hips with symptomatic dysplasia in 14 Charcot-Marie-Tooth (CMT) patients, Bernese periacetabular osteotomy complications included osteonecrosis of the femoral head, transient complete bilateral peroneal nerve palsy, inferior rami fractures, and heterotopic ossification [206]. Complications were much more frequent in patients with CMT (33%) than in those with developmental dysplasia of the hip (13%) undergoing Bernese periacetabular osteotomy [206]. Seven patients in the CMT series showed signs of radiographic progression of osteoarthritis after PAO [206].

Surgical Complications: Hip Arthroscopy¶

Mild dysplastic features and female sex are associated with failure of hip arthroscopy [10]. Isolated hip arthroscopy is being increasingly utilized in patients with acetabular dysplasia, raising concern regarding failure rates [10]. Borderline hip dysplasia is not associated with a significant difference in hip survivorship or patient-reported outcomes following primary hip arthroscopy for femoroacetabular impingement syndrome [178].

Surgical Complications: Total Hip Arthroplasty (THA)¶

Primary or conversion THA performed for developmental dysplasia can add significant complexity to the surgical procedure and risk of complications [181]. Patients undergoing conversion THA faced approximately 20% greater direct costs compared with a matched group of patients undergoing primary THA [181]. Patients undergoing conversion THA faced significantly greater surgical times, estimated blood loss, length of stay, intraoperative complications, and postoperative complications [181]. Femoral and acetabular complications in complex THA may be decreased with the use of modern implants specifically designed for complex scenarios, such as dual mobility acetabular implants or versatile conical femoral implants [181].

Patients who had hip dysplasia and mild osteoarthritis had similar recovery curves compared to those who had severe osteoarthritis or who did not have dysplasia following THA [8]. Rotational acetabular osteotomy (RAO) does not lead to higher revision rates, compromised hip health scores, or shortened survivorship in eventual THA for DDH [174]. Femoral osteotomy and shortening at the subtrochanteric level predictably allows a stable reduction in patients with high developmental dysplasia of the hip and does not lead to any reduction in long-term survival [95]. Cemented sockets with roof graft have high survivorship in severe acetabular dysplasia at a mean follow-up of more than 10 years [96].

Other Considerations¶

Contralateral hip dysplasia appears to be a developmental process rather than an unnoticed dysplasia present from infancy [11]. Hip dysplasia has been reported in 6% to 8% of patients with Charcot-Marie-Tooth (CMT) disease [206]. Acetabular dysplasia, hip subluxation, acetabular anteversion, coxa valga, and hip osteoarthritis were more severe in patients with CMT than in those with developmental dysplasia [206]. Foot deformity is a risk factor for developmental dysplasia of the hip [196].

Recovery¶

The provided evidence base for adult hip dysplasia focuses on long-term survivorship, natural history, and surgical outcomes rather than short-term postoperative rehabilitation timelines. Consequently, specific data regarding the duration of light activity, full activity return, or complete recovery plateaus in weeks or months are absent from this dataset. Similarly, no evidence is provided regarding specific rehabilitation protocols, immobilisation durations, weight-bearing progressions, or functional milestone trajectories (e.g., WOMAC scores) during the immediate postoperative period. The following sections detail the long-term prognostic data and surgical outcomes available in the evidence.

Hip Preservation Surgery (PAO)¶

Periacetabular osteotomy (PAO) is an effective technique for treating symptomatic developmental dysplasia of the hip and can maintain the natural hip at least 19 years in selected patients [45]. The 10-year survivorship of the native hip after PAO is approximately 86% [81], while the 20-year survivorship is approximately 60% [81]. Twenty-year results from the originating surgical center in Berne showed hip preservation in 60% of hips at 20-year follow-up [99]. At thirty years postoperatively, 29% of hips undergoing PAO for hip dysplasia can be preserved [55]. Conversely, more than 70% of hips undergoing PAO for hip dysplasia will develop progressive osteoarthritis, pain, and/or undergo total hip arthroplasty (THA) by 30 years postoperatively [55]. Factors identified as likely to negatively impact the result of PAO for dysplasia include advancing age, moderate preoperative arthritis, labral pathologic processes, postoperative impingement, and fair or poor congruence of the joint [99]. The absence of differences in early postoperative patient-reported outcomes across multiple age ranges emphasizes that PAO in the setting of symptomatic acetabular dysplasia can be successful regardless of patient age alone [69].

Hip Arthroscopy¶

Patients with borderline hip dysplasia undergoing primary hip arthroscopy demonstrated significant improvement in patient-reported outcomes at midterm and long-term follow-up [92]. Further research with more patients and longer follow-up is necessary in order to determine specific indications, if any, for hip arthroscopy in adult hip dysplasia [24]. Greater long-term follow-up is necessary to assess the efficacy of hip arthroscopic surgery in altering the natural history and progressive degenerative changes associated with femoroacetabular impingement (FAI) [275].

Total Hip Arthroplasty (THA)¶

Patients who had hip dysplasia and mild osteoarthritis (OA) had similar recovery curves compared to those who had severe OA or who did not have dysplasia [8]. Hybrid total hip arthroplasty in Chinese developmental dysplasia of hip patients has favorable results at midterm follow-up, even though their lifestyle includes more deep flexion of the hip [88]. High survivorship of cemented sockets with roof graft in severe acetabular dysplasia was found at a mean follow-up of more than 10 years [96].

Natural History and Prognosis¶

Degenerative change occurred earliest in patients with developmental dysplasia of the hip (DDH), whereas the natural history of patients with femoroacetabular impingement (FAI) was quite similar to structurally normal hips [76]. For a patient who recently developed Tönnis 1 degenerative change, the probability of undergoing THA in 10 years based on hip morphology was approximately one in three for dysplasia of the hip (DDH) [53]. The approximate probability at 20 years for a patient with recent Tönnis 1 degenerative change to undergo THA was two in three for DDH [53]. Several radiographic variables were found to have negative prognostic value including femoral head lateralization greater than 8 mm, femoral head extrusion index greater than 0.2, acetabular depth-to-width index less than 0.3, lateral center-edge angle less than 25°, and Tönnis angle greater than 8° [53]. The RAO cohort with a median follow-up period of 14 years demonstrated good survival rates in patients at the preosteoarthritis stage and in patients at the initial stage of DDH [182]. Successful management of late presenting hip dislocation is judged by outcomes well beyond skeletal maturity into adulthood [37]. Eight patients (17%) developed dysplasia of the contralateral hip, which appears to be a developmental process rather than an unnoticed dysplasia present from infancy [11].

Pediatric and Adolescent Outcomes¶

Early diagnosis and treatment of developmental dysplasia of the hip is of paramount importance to favorably alter the natural history of the disease, with early treatment using a Pavlik harness generally safe and effective in patients younger than 6 months [6]. A retrospective study of closed reductions with mean 30-year follow-up reported good or excellent functional outcomes in 90% of patients, but residual radiographic dysplasia in over half of the patients [192]. A retrospective study of patients undergoing open reduction and innominate osteotomy with mean 43-year follow-up reported hip survivorship of 99% at 30 years, but only 54% by 45 years after initial treatment [192]. Rates of secondary surgery for residual dysplasia following closed reduction were reported between 35% and 58% in two recent retrospective studies [192]. Additionally, 19% of patients who underwent open reduction required secondary surgery [192]. Clinical results at follow-up for the Dial Osteotomy in the treatment of high-grade acetabular dysplasia were 73% satisfactory and 27% unsatisfactory, with 13% of hips failing between 10–20 years [282].

Key Evidence¶

[L4] Hip dysplasia is best treated before 5 years of age, and surgery should not be performed unnecessarily. [1] (10.1016/j.otsr.2021.103172)
[L5] If left untreated, hip dysplasia can result in severe deformities and functional limitations. [3] (10.5435/jaaosglobal-d-23-00291)
[L3] This complication is strongly predictive of failure of treatment, and its impact is greatest when the developmental dysplasia of the hip is higher in severity. [5] (10.2106/jbjs.j.01210)
[L3] Patients who had hip dysplasia and mild OA had similar recovery curves compared to those who had severe OA or who did not have dysplasia. [8] (10.1016/j.arth.2024.04.060)
[L5] When confronted with a controversial topic and treatments for hip dysplasia we need more consistent definitions of hip dysplasia, and then study our outcomes of these treatments in the short, mid, and long term before we adopt them as reliable treatment options. [9] (10.1016/j.arthro.2017.10.021)
[L3] Mild dysplastic features and female sex are associated with failure of hip arthroscopy, raising concern that isolated hip arthroscopy is being increasingly utilized in patients with acetabular dysplasia. [10] (10.1177/2325967117s00230)
[L3] Eight patients (17%) developed dysplasia of the contralateral hip, which appears to be a developmental process rather than an unnoticed dysplasia present from infancy. [11] (10.1302/0301-620x.96b9.33768)
[L3] Our findings show that appropriately selected older patients with dysplasia without significant preexisting hip osteoarthritis experience clinically meaningful improvements in hip pain and function after hip preservation surgery. [12] (10.1016/j.arthro.2024.10.039)
[L4] This systematic review indicates that improved patient-reported outcomes can be obtained with hip arthroscopy in the treatment of concomitant mild acetabular dysplasia and FAI at a minimum 2-year follow-up. [13] (10.1016/j.arthro.2019.11.122)
[L4] Hip arthroscopy can reliably provide durable and clinically meaningful improvements for the treatment of intra-articular pathology and FAIS in patients with acetabular dysplasia at long-term follow-up. [14] (10.1177/03635465261429491)
[L4] These findings suggest that hip dysplasia may not be an absolute contraindication for isolated hip arthroscopy and may serve as a viable intervention with consideration of staged future periacetabular osteotomy (PAO). [18] (10.1177/03635465231197177)
[L5] Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness. [19] (10.1016/j.arthro.2024.07.012)
[L3] 40% of patients with acetabular dysplasia also had radiographic evidence of cam-type femoroacetabular deformity. [21] (10.1186/s13018-014-0093-4)
[L3] Patients with hip dysplasia can expect reduced pain, improved functional outcomes, and similar revision surgery rates to those with osteoarthritis following primary THA. [23] (10.5435/jaaos-d-24-01315)
[L5] Further research with more patients and longer follow-up is necessary in order to determine specific indications, if any, for hip arthroscopy in adult hip dysplasia. [24] (10.1016/j.arthro.2015.12.020)
[L4] Both classification systems assess the different aspects of developmental dysplasia of the hip in adults. [27] (10.1007/s00402-012-1600-x)
[L5] The authors propose a diagnostic framework that groups symptomatic dysplastic hips into one of 3 categories based on the primary direction of instability: anterior, posterior, and global, to aid clinicians in developing a differential diagnosis and planning appropriate surgical management. [32] (10.1016/j.arth.2017.02.067)
[L2] Proximal femoral deformities are highly prevalent in symptomatic acetabular dysplasia, with 92.6% of hips showing abnormalities. [33] (10.1007/s11999-008-0481-3)
[L3] Overall, the 7-year hip survival rate in hip dysplasia appears inferior compared with that reported in femoroacetabular impingement (78%). [35] (10.1177/0363546517713176)
[L5] Most patients with borderline hip dysplasia achieve successful outcomes after hip arthroscopy alone, but those with signs of instability may fail and require bony treatment; future studies must identify characteristics that predict failure of an arthroscopic-only approach. [36] (10.1016/j.arthro.2022.10.005)
[L4] Successful management of late presenting hip dislocation is judged by outcomes well beyond skeletal maturity into adulthood. [37] (10.1302/0301-620x.97b6.35395)
[L3] Patients with acetabular dysplasia have an increased frequency of spinal anomalies seen on standard hip radiographs. [39] (10.1302/0301-620x.103b8.bjj-2020-2481.r1)
[L4] [40] (10.1016/j.arthro.2024.10.038)
[L5] The excellent and predictable functional and radiologic outcomes suggest that patient-specific allograft bone shelves could be a serious option for adolescents with severe hip dysplasia. [42] (10.5435/jaaosglobal-d-24-00382)
[L4] PAO with concomitant hip arthroscopy for symptomatic hip dysplasia resulted in significant improvements in functional outcomes, with a high percentage of patients achieving important clinical thresholds. [43] (10.1177/03635465251391182)
[L5] A patient's age and hip shape are important factors contributing to the resulting hip mechanics, although the interplay between those mechanical factors and patient-reported outcomes of pain are unclear. [44] (10.1097/corr.0000000000000621)
[L3] Periacetabular osteotomy is an effective technique for treating symptomatic developmental dysplasia of the hip and can maintain the natural hip at least 19 years in selected patients. [45] (10.1007/s11999-008-0242-3)
[L3] Staged hip arthroscopy and PAO for hip dysplasia leads to similar PROs at 12-24 months compared to combined procedures. [46] (10.1016/j.arthro.2023.02.017)
[L4] The morphologic features of AIIS in hip dysplasia may differ between males and females. [48] (10.1016/j.arth.2016.02.018)
[L3] Surgical outcomes at minimum of 2 years in patients with borderline hip dysplasia in selected patients undergoing PAO or hip arthroscopy were good. [49] (10.1177/2325967120s00209)
[L1] Longer follow-up will be required to determine if hip arthroscopy provides added value to a PAO for symptomatic hip dysplasia. [54] (10.1016/j.arth.2024.05.035)
[L3] Thirty years postoperatively, 29% of hips undergoing PAO for hip dysplasia can be preserved, but more than 70% will develop progressive osteoarthritis, pain, and/or undergo THA. [55] (10.1007/s11999-016-5169-5)
[L4] The diagnosis of developmental dysplasia of the hip should be suspected and investigated when a skeletally mature, young, active patient has a predominant complaint of insidious activity-related groin pain and/or lateral hip pain. [58] (10.2106/jbjs.j.01735)
[L5] Adult hip dysplasia is most commonly diagnosed based on the LCEA; however, the LCEA is an unreliable sole marker for dysplasia, and additional radiographic parameters should be utilized. [59] (10.1177/0363546519881411)
[L2] The use of this radiographic parameter as an additional tool may enable the earlier detection of borderline and frank hip dysplasia in young adults presenting with hip pain. [62] (10.1177/0363546517708983)
[L3] Hip pain related to acetabular dysplasia might result in overdiagnosis of hip involvement by axial spondyloarthritis. [64] (10.1186/s12891-022-05575-4)
[L5] The center gap is a possible new radiographic predictor of progression of osteoarthritis in developmental dysplasia of the hip, but future studies are needed to validate this marker in larger, more diverse patient populations. [66] (10.1097/corr.0000000000000501)
[L5] In well-selected patients, this reconstructive osteotomy should be considered safe and effective in alleviating pain and improving hip function in patients with symptomatic acetabular dysplasia. [68] (10.1016/j.arth.2017.02.015)
[L2] The absence of differences in early postoperative patient-reported outcomes across multiple age ranges emphasizes that PAO in the setting of symptomatic acetabular dysplasia can be successful regardless of patient age alone. [69] (10.1016/j.arth.2021.05.029)
[L3] Degenerative change occurred earliest in patients with DDH, whereas the natural history of patients with FAI was quite similar to structurally normal hips. [76] (10.1007/s11999-016-4815-2)
[L4] Patients with hip dysplasia can be treated with PAO to help maintain activity and preserve the native hip. [77] (10.1177/03635465251334770)
[L3] The 10- and 20-year survivorship of the native hip after PAO is approximately 86% and 60%, respectively, in this cohort. [81] (10.5435/jaaos-d-17-00810)
[L3] The greater trochanter classification system based on the anatomy and biomechanics could distinguish various types of DDH and aid in making surgical strategies. [82] (10.1016/j.arth.2025.08.013)
[L5] [84] (10.5435/00124635-199909000-00005)
[L4] The majority (71%) of active patients with hip dysplasia return to presurgical or higher activity levels after open hip preservation surgery with the periacetabular osteotomy. [85] (10.1177/0363546514535906)
[L3] Hybrid total hip arthroplasty in Chinese developmental dysplasia of hip patients has favorable results at midterm follow-up, even though their lifestyle includes more deep flexion of the hip. [88] (10.1016/j.arth.2009.07.002)
[L3] An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability. [90] (10.1177/0363546518810731)
[L4] Patients with borderline hip dysplasia undergoing primary hip arthroscopy demonstrated significant improvement in PROs at midterm and long-term follow-up. [92] (10.1016/j.arthro.2022.12.030)
[L2] Our data suggest femoral osteotomy and shortening at the subtrochanteric level predictably allows a stable reduction in patients with high developmental dysplasia of the hip and does not lead to any reduction in longterm survival. [95] (10.1007/s11999-009-1218-7)
[L4] In contrast to reported series and the common use of cementless cups in patients with developmental dysplasia of the hip, we found high survivorship of cemented sockets with roof graft in severe acetabular dysplasia at a mean followup of more than 10 years. [96] (10.1007/s11999-012-2346-z)
[L3] The majority of patients with residual acetabular dysplasia at two years post-brace treatment spontaneously resolved by five years. [98] (10.1302/0301-620x.106b7.bjj-2023-1169.r1)
[L5] [100] (10.2106/jbjs.23.00697)
[L3] There are sex-dependent, disease characteristic differences in patients with symptomatic acetabular dysplasia, with male patients showing a greater prevalence of findings consistent with concurrent FAI and instability. [102] (10.1007/s11999-015-4155-7)
[L5] Optimal surgical treatment of hip dysplasia treats both the cause and the effects of dysplasia by combining hip arthroscopy and periacetabular osteotomy into a single intervention. [110] (10.1016/j.arthro.2023.07.046)
[L5] The Hartofilakidis classification system describes three types of developmental hip dysplasia (dysplasia, low dislocation, and high dislocation) to guide surgical management by anticipating implant type and the need for augmentation. [111] (10.1097/corr.0000000000000802)
[L3] Rotational acetabular osteotomy is an effective surgery for treating symptomatic developmental dysplasia of the hip in selected patients. [112] (10.1007/s00402-017-2636-8)
[L5] Age over 45 is not a contraindication for PAO/hip arthroscopy if articular cartilage status is normal. [134] (10.1016/j.arthro.2024.11.074)
[L4] PAO is reliable in treating borderline hip dysplasia with favourable mid-term outcomes. [139] (10.1302/0301-620x.105b7.bjj-2022-1058.r2)
[L5] [142] (10.5435/00124635-200111000-00005)
[L4] Abnormal femoral version is a common comorbidity in adult developmental dysplasia of the hip that can aggravate instability and lead to osteoarthritis, yet specific indications for femoral derotational osteotomy and the threshold for correction remain controversial and require further research. [146] (10.1530/eor-23-0145)
[L4] Dega acetabuloplasty is effective and reliable in correcting acetabular dysplasia following developmental dislocation of the hip. [147] (10.1016/j.otsr.2013.12.015)
[L5] Individual and postural variations in physiologic pelvic tilt affect joint contact pressure in the hip. [151] (10.1097/corr.0000000000001737)
[L5] Total hip arthroplasty is the procedure of choice for most patients with symptomatic end-stage coxarthrosis secondary to hip dysplasia, demonstrating a high rate of pain relief and functional improvement. [156] (10.5435/00124635-200209000-00005)
[L4] The morphology of the AIIS in patients with acetabular dysplasia is commonly prominent, with 72% of hips having Type II or Type III morphologies. [163] (10.1097/corr.0000000000001547)
[L5] The authors argue that current classification of borderline hip dysplasia based solely on lateral center edge angle is insufficient and that the focus must shift to assessing hip instability to better predict treatment outcomes and the need for bony realignment. [164] (10.1016/j.arthro.2023.10.023)
[L5] They suggest that while open treatment remains the gold standard, arthroscopic treatment with labral preservation and capsular plication may be an option for mildly dysplastic hips when strict indications are used. [165] (10.1177/0363546519825641)
[L4] Recognition of these distinct morphologic subtypes is important for diagnostic and surgical treatment considerations to optimize acetabular correction and avoid femoroacetabular impingement. [166] (10.1007/s11999-016-5150-3)
[L3] Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of PAO by giving a better understanding of the 3-dimensional deformity. [171] (10.1177/0363546521992108)
[Paper] The Ogata et al. classification system is a reliable and reproducible radiological indicator for reflecting acetabular cover. [172] (10.1007/s00402-001-0376-1)
[L3] A DDH family history is a risk factor for the progression of hip OA. [173] (10.1016/j.arth.2023.08.026)
[L3] Our midterm results demonstrated that RAO does not lead to higher revision rates, compromised HHSs, or shortened survivorship in eventual THA for DDH. [174] (10.1007/s00402-015-2154-5)
[L4] The artificial intelligence model measurements demonstrate a high degree of consistency with manual measurements and exhibit robust diagnostic performance in identifying developmental dysplasia of the hip and borderline developmental dysplasia of the hip. [175] (10.1186/s12891-024-08035-3)
[L3] Borderline hip dysplasia is not associated with a significant difference in hip survivorship or patient-reported outcomes following primary hip arthroscopy for femoroacetabular impingement syndrome. [178] (10.1016/j.arthro.2023.09.003)
[L3] Hips with lower anteversion or a larger difference between anatomic and functional anteversion were more likely to be symptomatic. [180] (10.1097/corr.0000000000002768)
[L3] The RAO cohort with a median follow-up period of 14 years demonstrated good survival rates in patients at the preosteoarthritis stage and in patients at the initial stage of DDH. [182] (10.1016/j.arth.2025.06.021)
[L5] [185] (10.5435/jaaos-d-15-00154)
[L3] In DDH, AIIS type 3 tends to be more severe dysplasia than AIIS type 1 or 2. [187] (10.1016/j.jisako.2023.03.068)
[L5] [195] (10.1097/corr.0000000000000364)
[L3] The study confirms that foot deformity is a risk factor for developmental dysplasia of the hip. [196] (10.1302/0301-620x.102b11.bjj-2020-0290.r3)
[L3] Our comprehensive protocol for nonoperative treatment of infant DDH has shown high rates of success and extremely low rates of residual dysplasia at a mean age of five years. [199] (10.1302/0301-620x.105b8.bjj-2023-0149.r1)
[L3] The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips. [201] (10.1302/0301-620x.98b9.37267)
[L3] We identified a 14% incidence of THA by age 34 years in patients with osteonecrosis secondary to DDH. [203] (10.1186/s12891-024-07517-8)
[L4] [208] (10.1186/s12891-024-07244-0)
[L3] Patients with hip dysplasia have a significantly reduced capsular thickness on MRI and delaminated anterior joint capsule, which could be a sequence of instability. [209] (10.1007/s00167-022-07022-2)
[L5] Surgical reduction of congenital hip dislocation is technically challenging and is usually reserved for patients who have failed non-operative treatment or have late diagnosis. [213] (10.1016/j.otsr.2017.04.021)
[L2] Radiographic evidence of FAI is common in active patients with hip complaints. [215] (10.1007/s11999-010-1233-8)
[L4] Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in these Japanese patients with hip pain, with cam deformity findings being the most common. [216] (10.1302/0301-620x.96b2.32680)
[L2] Up to 51% of patients presenting with symptomatic FAI show an abnormal femoral version, whilst up to 31% demonstrate abnormal acetabular version. [224] (10.1007/s00167-021-06643-3)
[L5] Long-term exposure to elevated cartilage contact stresses may affect joint morphology, making hips in these individuals less amenable to joint-preservation procedures such as PAO. [226] (10.1097/corr.0000000000000715)
[Paper] [228] (10.1055/a-0924-5491)
[L4] Projection of two-dimensional radiographic landmarks contributing to the diagnosis of structural hip deformity into 3D allowed for the identification of the overlapping bony anatomy contributing to radiographically visible anterior and lateral sourcil edges. [236] (10.1097/corr.0000000000003268)
[L5] This CORR Insights article is a commentary on a study by Wu et al. and does not present original data; it highlights that muscle-induced biomechanical variables in patients with developmental dysplasia of the hip (DDH) were associated with worse function and pain outcomes, suggesting these variables can better predict prognosis than bony anatomy alone. [245] (10.1097/corr.0000000000002787)
[L3] A stable, safe but non-concentric reduction achieved before the age of two years appears to improve over time with nearly 80% of hips becoming fully concentric by one year. [246] (10.1302/0301-620x.102b5.bjj-2019-1496.r1)
[L4] Open reduction through anterior minimally invasive approach can achieve good clinical effect in the treatment of infantile developmental dysplasia of the hip. [248] (10.1186/s12891-023-06582-9)
[L2] Up to 62% of patients who underwent PAO for hip dysplasia participated in sports after PAO. [253] (10.1177/03635465251385258)
[L4] Arthroscopic procedures for individuals with mild dysplasia in the absence of frank instability may be effective; however, great caution should be exercised when approaching dysplastic patients with symptomatic hips. [260] (10.1016/j.arth.2017.02.022)
[L5] While favorable short-term and midterm clinical outcomes have been reported after arthroscopic treatment of prearthritic hip lesions, greater long-term follow-up is necessary to assess the efficacy of hip arthroscopic surgery in altering the natural history and progressive degenerative changes associated with FAI. [275] (10.1177/0363546513476281)
[L4] Clinical results at followup were 73% satisfactory and 27% unsatisfactory, with 13% of hips failing between 10–20 years. [282] (10.1097/01.blo.0000153992.17554.67)

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