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Avascular necrosis of the femoral head

116 citationsUpdated Sep 2026

Overview

Osteonecrosis of the femoral head is a disabling pathology affecting a young population and represents the most important cause of total hip arthroplasty in this demographic [5]. The prognosis for patients can be significantly improved with early diagnosis and timely intervention [2]. However, nearly 80% of patients present with late-stage disease, indicating a narrow window of opportunity for hip preservation surgery before femoral head collapse [14]. Joint-preserving procedures should be attempted in early-stage lesions to save the femoral head [23]. Small, asymptomatic, medially-placed lesions of non-traumatic osteonecrosis may be treated with observation alone [7], whereas larger lesions carry a 25% to 50% risk of progression [7]. Necrosis involving the anterior aspect of the femoral head is an important risk factor for collapse in JIC type C1 nontraumatic osteonecrosis [6].

In the pediatric population, avascular necrosis is the most common and most devastating complication associated with hip fractures [12]. It is the principal cause of poor results in children’s hip fractures, resulting in poor outcomes in up to 60% of cases [12]. Treatment of avascular necrosis after pediatric hip fractures has been relatively unsuccessful, and some investigators have suggested that treatment does not affect the natural history [12]. The management of pediatric osteonecrosis is complicated by a limited body of evidence and a lack of consensus on prevention or treatment of femoral head collapse [16].

Patients with nontraumatic osteonecrosis of the femoral head have a higher incidence and risk of major adverse cardiovascular and cerebrovascular events than the general population, with a greater than 1.3-fold risk [30]. Outcomes of total hip arthroplasty in the setting of osteonecrosis are excellent [23]. A previous joint-preserving procedure for osteonecrosis poses technical challenges for subsequent total hip reconstruction and might have a detrimental effect on the short-term clinical outcome [31]. Avascular necrosis of the femoral head is relatively uncommon in type 1 dislocations reduced within 6 hours [10]. Symptomatic avascular necrosis can develop 8 years post-injury despite no evidence at 3 years, implying a need for extended follow-up [10].

Anatomy & Pathophysiology

Vascular Anatomy

The primary blood supply to the adult femoral head derives from cervical arteries originating from the extracapsular ring at the base of the femoral neck [101]. This ring is formed by contributions from the medial femoral circumflex artery (MFCA) posteriorly and the lateral femoral circumflex artery (LFCA) anteriorly [101]. The superior and posterior vessels, derived primarily from the MFCA, constitute the dominant blood supply to the femoral head [101]. The MFCA supplies the inferior retinacular branch, which runs along the ligament of Weitbrecht to supply the inferior medial portion of the femoral head [101]. A minor contribution arises from the foveal artery, a branch of the obturator artery located within the ligamentum teres [101]. In approximately 75% of hips, the foveal artery makes a significant contribution to the epiphyseal portion of the femoral head vasculature [101].

In newborns, the main source of femoral head blood supply is derived from vessels arising from the medial and lateral circumflex femoral arteries [97]. In 79% of cases, these circumflex arteries are branches of the profunda femoris, while in 20% of patients, one or both arise from the femoral artery [97]. At about 3 years of age, the lateral circumflex artery regresses, and branches of the medial circumflex femoral artery become the main blood supply of the femoral epiphysis and proximal femoral physeal plate [97]. The deep branch of the medial femoral circumflex artery is the most important source of femoral head blood supply [97]. This deep branch gives off the inferior retinacular artery, which runs toward the femoral head in the ligament of Weitbrecht [97]. The main terminal branch of the deep MFCA, often referred to as the superior retinacular artery, divides into two to four terminal branches [97]. These terminal vessels course within fibrous extensions of the capsule wall known as the retinacula of Weitbrecht posterosuperiorly on the femoral neck [97]. They perforate the bone at a distance 2 to 4 mm lateral to the bone–cartilage junction of the head [97]. The lateral group of retinacular vessels is the largest contributor to femoral head blood supply [97]. A cadaveric MRI study estimated the contribution of the MFCA to femoral head perfusion at 82% and that of the LFCA at 18% [97].

The subchondral regions of bone are particularly prone to osteonecrosis due to the microarchitecture of blood vessels at these locations [79]. There are no collateral vessels for the arterioles in the subchondral region, which are isolated from the rest of the circulation by a cartilage boundary [79]. In children with slipped capital femoral epiphysis (SCFE), the blood supply to the capital epiphysis is primarily by vessels arising from the lateral epiphyseal system entering the epiphysis at its outer posterior margin [131]. The ligamentum teres supplies the epiphysis in children, and in late adolescence, metaphyseal vessels that pierce the physis reappear [131].

Pathogenic Mechanisms

Osteonecrosis of the femoral head is defined as an end condition resulting from many possible pathogenic pathways [42]. Proposed mechanisms include ischemia from various mechanisms, direct cellular toxicity, and alteration of differentiation of mesenchymal stem cells [42]. Ischemic mechanisms include vascular disruption, vascular compression or constriction, and intravascular occlusion [134]. Vascular disruption can result from femoral head fracture, hip dislocation, or surgery [134]. Vascular compression or constriction can be caused by increased intraosseous pressure from marrow fatty infiltration, corticosteroids, alcohol, or vasoconstriction of arteries perfusing the femoral head [134]. Intravascular occlusion mechanisms include thrombosis (associated with thrombophilia, low protein C and S, activated protein C resistance, factor V mutation, high homocysteine, eNOS polymorphisms), hypofibrinolysis (high PAI activity, PAI-1 polymorphisms, high lipoprotein(a)), embolization (fat, air), and sickle cell occlusion [134]. Direct cellular toxicity can result from pharmacologic agents, irradiation, or oxidative stress [134]. Altered differentiation of mesenchymal stem cells is a proposed mechanism associated with corticosteroids and alcohol [134].

The basic mechanism of osteonecrosis involves impaired circulation to a specific area that ultimately becomes necrotic [11]. No single pathophysiologic mechanism has been identified as the definitive etiology for the development of osteonecrosis of the femoral head [11]. Most etiologic factors in atraumatic osteonecrosis are related to underlying pathologic conditions that alter blood flow, leading to cellular necrosis and ultimately to collapse of the femoral head [3]. Direct damage to osteocytes may occur via toxin production, while indirect damage may result from disorders in fat metabolism or hypoxia [3]. Approximately 10% to 20% of osteonecrosis cases have no clearly identifiable risk factor and are classified as idiopathic [3]. The edema associated with cell death and the normal reparative process causes further damage by increasing local compartmental pressure and decreasing vascular ingress [79]. Repeated mechanical insult without the inherent healing mechanism of live bone results in propagated stress fractures and eventual femoral head collapse [79]. Femoral head collapse generally results in an anterolateral wedge-shaped area of necrosis with normal cartilage overlying the defect [79]. Large defects in the femoral head do not heal spontaneously [79]. Osteonecrosis of the femoral head is characterized by microfractures of the subchondral bone and subsequent collapse of the femoral head [157]. The failure of bone formation by osteoblasts to match bone resorption by osteoclasts is the main mechanism of avascular necrosis [178]. A reduced head–neck offset in patients with nontraumatic osteonecrosis may act as a mechanical co-factor in developing osteonecrosis [37]. Necrosis involving the anterior aspect of the femoral head is an important risk factor for collapse [6]. Osteoarthritis in hips with osteonecrosis can be caused by elevated contact stress [184].

Traumatic Etiology and Vascular Injury

AVN is the most common and most devastating complication associated with hip fractures in children [12]. AVN of the femoral head in children is thought to result from disruption or compromise of the blood supply at the time of initial trauma or from the tamponade effect of hip hemarthrosis [12]. Fracture displacement is the most important risk factor for AVN following hip fractures in children [12]. The presence of a type I or II fracture and a fracture in an older child (>12 years) are risk factors for AVN [12]. In adults, the primary blood supply to the femoral head derives from cervical arteries originating from the extracapsular ring [101]. The position of the hip when dislocated can kink the vessels supplying the head, making collateral circulation important [101]. Injection studies in cadaveric hips after forceful dislocation and relocation demonstrated filling defects at the junction of the external iliac and common femoral arteries and at the circumflex vessels [101]. Changes in extraosseous blood supply due to dislocation did not cause a consistent change in intraosseous supply to the head, presumably due to collateral circulation [101].

AVN is predominantly present after posterior hip dislocation and correlates with the time to reduction [153]. If the hip is reduced within 6 hours of dislocation, AVN rates are reported as 0% to 10% [153]. Reduction after 12 hours increases the risk of AVN by 5.6 times [153]. The cause of avascular injury in hip dislocation is multifactorial, involving damage to cervical vessels and ligamentum teres contributions at the time of injury, and secondary ischemic insult while dislocated [153]. Studies in rabbits demonstrated that cervical vessels are not normally disrupted by dislocation but do not provide adequate circulation due to spasm of larger vessels or the cervical vessels themselves [153]. Early reduction restored the vascular supply to the femoral head better than late reduction, in some cases almost to the level of the contralateral hip [153]. The majority of AVN following hip dislocation is secondary to initial ischemia of the femoral head rather than torn vessels [153]. Osteonecrosis following femoral head fractures occurs in up to 23% of patients, depending on injury, dislocation, and time to relocation [63]. Osteonecrosis is most common following Pipkin III fractures [63]. Delayed reduction of a hip dislocation or fracture-dislocation increases the risk of osteonecrosis and long-term sequelae [59].

In children with SCFE, the lateral epiphyseal arteriolar system may be damaged by tearing of the periosteum during acute displacement, forcible reduction attempts, or intraarticular surgery [131]. Intraarticular tamponade by traumatic effusion associated with acute displacement could theoretically cause loss of blood supply indirectly, although this mechanism has not been substantiated [131]. Multiple pins in the superior posterior quadrant of the femoral head may pose a risk of injury to the intraepiphyseal blood supply, producing segmental AVN [131].

Natural History and Progression

Osteonecrosis of the femoral head is a progressive disease that generally affects patients in the third through fifth decades of life [42]. When symptomatic, osteonecrosis typically leads to collapse of the femoral head and eventual deterioration of the hip joint [42]. The prognosis of patients with osteonecrosis can be significantly improved with early diagnosis and timely intervention [2]. Most cases of osteonecrosis are diagnosed in an advanced stage of disease, when minimally invasive surgical procedures are no longer helpful [3]. Patients in the advanced stage of the disease must undergo total hip replacement at a young age, which carries a poor long-term prognosis [3]. In untreated patients, the femoral head is completely collapsed in 80% of cases [157].

Radiographic evidence of AVN can be seen as early as 2 months after injury in children, and is generally present within 1 year of injury [12]. The median time to presentation of AVN symptoms after hip fracture in children is 7.8 months [12]. Radiographs may demonstrate osteopenia of the femoral head, followed later by sclerosis, fragmentation, and often collapse and deformity [12]. In SCFE, the affected epiphysis first fails to become osteopenic because the absence of blood supply prevents normal resorption of bone from disuse [131]. This abnormality in SCFE is evident as early as a few weeks after onset of the slip, and almost all cases are evident within 1 year after slip [131]. Resorption of the necrotic bone with collapse of the affected portion of the epiphysis usually follows early radiographic changes in SCFE [131]. Two patterns of distribution are typically seen in SCFE-related AVN: total head necrosis and partial (or segmental) necrosis [131].

In LCPD, the fourth radiographic stage is the healed stage, during which no additional changes are noted in the density of the femoral head [47]. The shape of the femoral head may continue to evolve after healing, and only at the completion of skeletal growth is its permanent contour established [47]. If the disease has disrupted growth of the capital physis, gradual relative overgrowth of the greater trochanter may occur [47]. The more severe the disease, the longer the duration of each stage, particularly the reossification stage [47]. In LCPD, epiphyseal and physeal cartilage involvement is a pathologic feature of vascular disruption of the growing epiphysis [144]. Cell death in the deep layer of the epiphyseal cartilage following ischemia is followed by degenerative changes in the cartilage matrix [144]. The viable, superficial region of the epiphyseal cartilage highly expresses hypoxia inducible factor-1, a master regulator of cell response to hypoxia [144]. Vascular endothelial growth factor (VEGF) and other proteins such as interleukin-6 are released in response to hypoxic stress in the viable superficial region of the epiphyseal cartilage [144]. Necrotic bone stimulates proinflammatory responses in macrophages through the activation of Toll-like receptor 4 [150]. In a large animal model of ischemic osteonecrosis, radiolucent areas appeared in the infarcted epiphyses before the development of femoral head deformity [144]. Histologic assessment of these radiolucent areas showed revascularization with increased presence of osteoclasts and active bone resorption not accompanied by new bone formation [144]. The necrotic bone was replaced by fibrovascular granulation tissue, compromising the mechanical properties of the epiphysis [144].

In Bucholz-Ogden type IV AVN, primary ischemia occurs medially, producing early closure of the medial portion of the physis with resultant growth into a varus deformity [83]. Closure of the lateral portion of the capital femoral growth plate during adolescence may be a manifestation of AVN, leading to progressive valgus tilting of the femoral head [148]. When the tip of the greater trochanter reaches the level of the femoral head, abductor muscle tension is altered, and the patient will usually develop an abductor limp [148]. The effectiveness of abductor muscles is decreased as the lever arm (femoral neck) shortens and the direction of pull becomes steeper [148].

Classification

Ficat: The modified Ficat classification for osteonecrosis of the femoral head lacks acceptable interobserver reliability and intraobserver reproducibility, rendering it unsuitable as a basis for treatment protocols or outcome determinations [116]. Commonly used classification systems for osteonecrosis of the femoral head generally lack intraobserver and interobserver reliability and fail to fully incorporate advances in biology, biomechanics, and imaging [85].

ARCO: The 2021 Association Research Circulation Osseous (ARCO) classification is a highly reliable and valid method compared to previous classifications and is recommended by ARCO as a unified classification for early-stage osteonecrosis of the femoral head [53]. By utilizing MRI, the 2021 ARCO classification system serves as a reliable and valid tool for predicting the occurrence of collapse in patients with early-stage osteonecrosis of the femoral head [159]. A staging system was developed to revise the 1994 ARCO classification for osteonecrosis of the femoral head by an expert panel-based Delphi survey [130].

CJFH: The China-Japan Friendship Hospital (CJFH) classification system is a simple and direct evaluation model for osteonecrosis of the femoral head with substantial inter- and intraobserver reliability [163].

BRB: The newly proposed BRB classification provides a systematic approach to assessing necrotic lesion severity in traumatic osteonecrosis of the femoral head and demonstrates significant correlation with femoral head collapse risk [128].

Matrix Model: The matrix model, which combines ARCO staging, Japanese Investigation Committee (JIC) classification, and necrotic area, demonstrated strong predictive ability for femoral head collapse, with higher scores correlating to higher collapse rates [139].

Stulberg: The Stulberg classification classifies the radiographic appearance of hips at skeletal maturity into five groups based on femoral head shape and acetabular fit [20]. * Group I: Completely normal femoral head shape [20]. * Group II: Spherical femoral head (same concentric circle on AP and frog-leg lateral radiographs), with possible coxa magna, short neck, or steep acetabulum [20]. * Group III: Femoral head that is more elliptical and deviates from a circle by more than 2 mm [20]. * Group IV: Flattened femoral head, defined as a flattened area greater than 1 cm in the weight-bearing area [20]. * Group V: Collapse of the femoral head without change in acetabular contour [20].

Groups III and IV are termed "congruous incongruity" because the contour of the acetabulum matches that of the femoral head, whereas Group V is termed "incongruous incongruity" [20]. The Stulberg classification correlates with the development of arthritic changes in the hip joints at an average follow-up of 40 years [20]. Patients with Stulberg Group I and II hips had a good long-term prognosis, whereas those with Group III, IV, and V had evidence of arthritic changes [20].

Lateral Pillar: The lateral pillar classification system is based on radiographic changes in the lateral portion of the femoral head when it enters the fragmentation stage, as seen on the AP view [87]. * Group A: Minimal density change in the lateral pillar and no loss of height [87]. * Group B: Lucency in the lateral segment and loss of height up to, but not exceeding, 50% of the original height of that segment [87]. * B/C Border: Intermediate changes where the lateral pillar may be a very narrow band of ossification 2 to 3 mm wide with height maintained at more than 50% of the original height [87]. * Group C: Collapse of the lateral pillar to less than half its original height [87].

A strong correlation exists between the lateral pillar classification and subsequent outcome, with Group A hips faring the best and Group C faring the worst [87]. The lateral pillar classification system has been reported to have greater interobserver reliability and to be a better predictor of final outcome compared with the Catterall classification system [87]. The Catterall and lateral pillar classification systems are best applied during the middle stage of fragmentation, as earlier application has been shown to lead to inaccurate assignment [87].

Pipkin: The Pipkin classification describes femoral head fractures associated with posterior dislocations [18]. * Type I: Fracture line inferior to the fovea [18]. * Type II: Fracture fragment that includes the fovea [18]. * Type III: Associated with a femoral neck fracture [18]. * Type IV: Involves any pattern of femoral head fracture and an acetabular fracture [18].

Garden: The Garden classification is commonly used to describe displacement in intracapsular hip fractures [18]. * Stage I: Incomplete impacted fracture, typically valgus [18]. * Stage II: Complete but undisplaced fracture [18]. * Stage III: Complete fracture with moderate displacement [18]. * Stage IV: Severely displaced fracture [18].

Other Considerations: Assessment of preserved angles on plain radiographs is a simple method to quantify the extent of lateral and anterior necrosis of the femoral head [24]. The location of the necrotic lesion exerts a greater impact on femoral head collapse compared with the size of the lesion [41].

Clinical Presentation

General Demographics and Epidemiology

Osteonecrosis of the femoral head typically affects patients in their late 30s and early 40s [3]. In the United States, new cases number between 10,000 and 20,000 per year [3]. The estimated mean annual prevalence from 2002 to 2006 was 14,103 cases, corresponding to 28.91 cases per 100,000 persons [45].

Symptomatology and Diagnosis

Nearly 80% of patients present with late-stage disease, indicating a narrow window of opportunity for hip preservation surgery before femoral head collapse [14]. Key clinical practice guidelines require accurately staging osteonecrosis and determining when pain may be due to the condition [35]. Small, asymptomatic, medially-placed lesions may be treated with observation alone [7]. In contrast, larger lesions carry a 25% to 50% risk of progression [7].

Pediatric Presentation (Legg-Calvé-Perthes Disease)

Legg-Calvé-Perthes disease onset occurs between 2 and 12 years of age, with a peak between 6 and 8 years [82]. Boys are four times more likely to be affected than girls, and approximately 10% of patients have bilateral disease [82]. On presentation, children usually exhibit a limp, and some complain of pain in the hip, thigh, or knee [82]. Primary physical examination findings include limited range of motion of the affected hip, particularly in abduction and internal rotation, and slight atrophy of the femoral muscles [82]. Most children experience moderate symptoms and endure 12 to 18 months of difficulty, followed by resolution of symptoms and a return to normal physical activities [71].

The age of the patient at onset is the most consistently reported factor affecting the course of the disease [71]. Children younger than 4 years are often asymptomatic and have no deformation of the femoral head [71]. Conversely, patients with onset after the age of 12 years have the worst prognosis [71]. In the healed stage, patients may experience occasional limp, locking, popping, or impingement symptoms [71]. Hip pain appearing late in adolescence after a period of asymptomatic time can indicate the presence of an osteochondrotic lesion in the femoral head [88]. Similarly, complaints of locking, catching, or crepitation in the hip can indicate the presence of an osteochondrotic lesion [88].

Pediatric Presentation (Post-Traumatic AVN)

Symptoms of avascular necrosis following pediatric hip fractures may occur early, with complaints of groin pain [12]. The median time to presentation is 7.8 months [12]. Radiographic evidence can be seen as early as 2 months after injury and is generally present within 1 year of injury [12]. However, symptomatic avascular necrosis of the femoral head can develop 8 years post-injury despite no evidence at 3 years [10].

Radiographic and Imaging Findings

In avascular necrosis following pediatric hip fractures, radiographs may demonstrate osteopenia of the femoral head, followed later by sclerosis, fragmentation, and often collapse and deformity [12]. MRI is the most sensitive test to confirm the diagnosis and defines the extent of femoral head and neck involvement [12]. Radioisotope scanning shows decreased uptake in the femoral head or neck [12].

In Legg-Calvé-Perthes disease, radiographic changes vary by stage: * Increased density stage: Increased density of the femoral head, with or without subchondral fracture [71]. * Fragmentation stage: Fragmentation and resorption of the femoral head, which may lateralize and flatten [71]. * Reossification stage: The femoral head gradually reossifies and flattening of the head may improve [71]. * Healed stage: The shape of the femoral head may vary from completely normal to extremely flat and aspherical [47].

MRI is an accurate imaging modality for the early diagnosis of Legg-Calvé-Perthes disease and for visualizing the configuration of the femoral head and acetabulum [49]. Noncontrast MRI relies on signal changes from fat degradation in the necrotic epiphysis to detect avascular necrosis [49]. Gadolinium-enhanced subtraction MRI is more effective than noncontrast MRI in delineating epiphyseal necrosis early in the disease process [49]. Accurate evaluation of the posterior boundary of the necrotic lesion using the oblique axial plane is necessary for predicting the prognosis of the femoral head [70].

Prognostic Factors and Natural History

In nontraumatic osteonecrosis, collapse of the femoral head starts in the lateral column due to ischemia [29]. Preserving blood supply to the lateral column improves prognosis and delays collapse [29]. A reduced head–neck offset may act as a mechanical co-factor in developing osteonecrosis [37]. Collapse progression on the symptomatic side is a poor prognostic factor for the natural history of contralateral osteonecrosis [26].

In Legg-Calvé-Perthes disease, healing duration and outcomes correlate with severity groups: * Group A: Hips healed in 37 months with a 100% good or excellent outcome [71]. * Group B: Hips healed in 50 months with a 79% good or excellent outcome [71]. * Group C: Hips healed in 67 months with a 29% good or excellent outcome [71].

Long-term prognosis is stratified by Stulberg classification. Patients with Stulberg group I and II hips had a good long-term prognosis [20]. Patients with Stulberg group III, IV, and V hips had evidence of arthritic changes in the hip joints at an average follow-up of 40 years [20]. In Stulberg group IV hips, the range of motion changes to match the cylindrical shape of the femoral head, resulting in an almost normal range of flexion and extension [20]. Additionally, the hip rotates externally whenever the joint is flexed and resumes a neutral position with extension [20].

Investigations

MRI: Magnetic resonance imaging is the most sensitive test for confirming avascular necrosis and defining the extent of femoral head and neck involvement [12]. MRI demonstrated accuracy in all hips with histological proof of osteonecrosis and in those with medullary changes without necrotic bone [118]. A systematic review and meta-analysis evaluated the diagnostic accuracy of MRI in early osteonecrosis of the femoral head [60]. In comparative studies, MRI proved more accurate for early diagnosis than conventional imaging, with diagnostic accuracy of 97% to 99% compared with 88% to 93% for radiography and 88% to 91% for scintigraphy [49]. Gadolinium-enhanced subtraction MRI is more effective than noncontrast MRI in delineating epiphyseal necrosis early in the disease process [49]. Noncontrast MRI relies on signal changes from fat degradation in the necrotic epiphysis to detect AVN, though false-negative results have been reported in few isolated cases manifesting very early [49]. In a study of nine patients in the early stage of Perthes disease, the extent of epiphyseal involvement was clearly visualized on MRI 3 to 8 months after the first symptoms [49].

Quantitative assessment of femoral head perfusion using perfusion MRI obtained at the initial or early fragmentation stage can predict lateral pillar involvement and the radiographic outcome at the 2-year follow-up [49]. Diffusion and contrast-enhanced MRI in the early stages of LCPD predict the risk of later development of femoral head deformity [49]. Increased apparent diffusion coefficient in the metaphysis and decreased significant enhancement in the central epiphysis are significant prognostic indicators of subsequent femoral head deformation [49]. Perfusion MRI provides quantitative information about hip synovitis by depicting synovial membrane hyperemia and thickening [49]. Subtraction MRI allows recognition of early reperfusion patterns, and contrast-enhanced MRI better delineated revascularization patterns in the femoral head than scintigraphy [49]. Biplanar MRI is as effective as arthrography in evaluating femoral head sphericity and containment [49]. Although MRI is essential for detecting pre-radiographic stage ONFH, less than half of preradiographic ONFH cases progress to stage 2 or higher [142].

Plain radiography: Standard anteroposterior and lateral radiographs were made when patients were first seen and at three to six month intervals throughout the study [61]. All radiographs were staged using the modified criteria of Ficat [61]. Hips with ONFH had a higher risk of disease progression with far more anterior necrotic lesions (type III) in the FL radiographs [147]. Accurate evaluation of the posterior boundary of the necrotic lesion using the oblique axial plane is necessary for predicting the prognosis of the femoral head and considering indications for anterior rotational osteotomy [70]. Radiographic evidence of AVN can be seen as early as 2 months after injury; such evidence is generally present within 1 year of injury [12]. The median time to presentation of AVN symptoms is 7.8 months [12]. In most patients, osteonecrosis is commonly seen by 1 year following injury [59]. The fourth radiographic stage is the healed stage, during which no additional changes are noted in the density of the femoral head [47]. The shape of the femoral head may continue to evolve, and only at the completion of skeletal growth is its permanent contour established [47].

CT: CT scan should be obtained to evaluate for loose bodies because it is more sensitive than plain radiographs [57]. A 2018 systematic review found CT scan was 87% sensitive for detecting intra-articular fragments [57]. The CT scan is more sensitive in detecting small intra-articular fragments, femoral head fractures, femoral head impaction injuries, acetabular fractures, and joint incongruity [122]. A difference as small as 0.5 mm in the distance from the anterior, articular surface to the femoral head has been reported to indicate a subluxation of the hip [122].

Bone scan: SPECT/CT was useful in evaluating the perfusion status of the femoral head, showing high accuracy in predicting the occurrence of avascular necrosis [143]. Bone scintigraphy performed within three weeks after the operation can predict a satisfactory outcome of rotation of the femoral head, whereas conventional radiographs were not associated with the final result [168]. Radioisotope scanning shows decreased uptake in the femoral head or neck (or both) and is useful in a hip that has stainless steel internal fixation [12]. Studies evaluating single photon emission computed tomography and MRI following hip dislocation were unable to correlate findings with the risk for osteonecrosis [57].

Other Considerations: Positron emission tomography/computed tomography (PET/CT) at 6 weeks could detect recovery of vascularity and could predict the risk of a vascular necrosis [102]. Dynamic MRI–positive enhancement integral color mapping (PEICM) preoperatively estimated femoral head perfusion by classifying it as normal, decreased, or completely absent [102]. The nonunion rate was zero in the normal perfusion group, 6.7% in the reduced perfusion group, and 50% in the absent perfusion group when using dynamic MRI-PEICM [102].

The Stulberg classification system classifies the radiographic appearance of hips at skeletal maturity into five groups based on the femoral head shape and acetabular fit [20]. In Stulberg group I hips, the shape of the femoral head is completely normal [20]. In Stulberg group II hips, a spherical femoral head is present, but coxa magna, short neck, or steep acetabulum may also be present [20]. In Stulberg group III hips, the femoral head is more elliptical and deviates from a circle by more than 2 mm [20]. In Stulberg group IV hips, the femoral head is flattened, with a flattened area greater than 1 cm in the weight-bearing area [20]. In Stulberg group V hips, there is collapse of the femoral head but the acetabular contour does not change [20]. The Stulberg classification system was found to correlate with the development of arthritic changes in the hip joints at an average follow-up of 40 years [20]. The study demonstrates varying levels of reliability and diagnostic precision among different classification systems for femoral head avascular necrosis [32]. Key recommendations of international evidence-based clinical practice guidelines require accurately staging ONFH and determining when pain may be due to ONFH [35]. Preserving blood supply to the lateral column improves prognosis and delays collapse [29]. Small, asymptomatic, medially-placed lesions may be treated with observation alone while larger lesions have a 25% to 50% risk of progression [7]. Volumetric measurements should be universally included in the assessment of patients with osteonecrosis of the femoral head [154].

Type I AVN is characterized by severe diffuse necrosis totally involving the femoral head and the proximal fragment of the femoral neck, resulting from interruption of the lateral epiphyseal and metaphyseal vessels [12]. Type I AVN accounts for more than 50% of cases and has the worst prognosis [12]. Type II AVN is characterized by more localized necrotic changes, often in the anterosuperior aspect of the femoral head, with little collapse, usually caused by interruption of the lateral epiphyseal vessels before entrance into the epiphysis [12]. Type II AVN is seen in approximately 25% of cases and has a better prognosis than does type I AVN [12]. Type III AVN is characterized by sclerosis from the fracture line of the femoral neck to the physis, with sparing of the femoral head [12]. Type III AVN accounts for 25% of cases of AVN and has the best results [12]. AVN after PFNF showed a tendency toward extensive necrotic lesions, presumably resulting in a rapid progression of femoral head collapse [22]. Symptomatic AVN can develop 8 years post-injury despite no evidence at 3 years [10]. Osteonecrosis occurs in up to 23% of patients with femoral head fractures, depending on the injury, dislocation, and time to relocation and definitive treatment [63]. Hips reduced after 6 hours were five times more likely to develop femoral head osteonecrosis compared to those reduced within 6 hours [76]. There was no association between grade of dislocation and rates of osteonecrosis in a meta-analysis of five retrospective cohort studies [76]. Hips that were dislocated longer than 6 hours were less likely to be successfully reduced in the emergency department with primary conscious sedation [76].

Arthrography clearly shows the configuration of the femoral head and its relation to the acetabulum [135]. Arthrographic studies have shown that the apparent widening in the joint space results from thickening of the articular cartilage [135]. Arthrography can provide reliable information regarding containment of the femoral head within the acetabulum [135]. The major advantage of arthrography is that the examiner can assess the congruity of the hip in many different positions [135]. Arthrography is most often used in the assessment of loss of hip containment and hinge abduction of the hip [135].

Treatment

General Principles and Prognosis

Joint-preserving procedures are indicated for precollapse disease, with multiple studies demonstrating successful outcomes at mid-term and long-term follow-up [11]. While total hip arthroplasty yields excellent results in the setting of osteonecrosis [23], joint-preserving strategies should be attempted in early-stage lesions to salvage the femoral head [23]. Management of osteonecrosis in young patients remains complicated by a limited evidence base and a lack of consensus regarding the prevention or treatment of femoral head collapse [16]. International evidence-based clinical practice guidelines mandate accurate staging of osteonecrosis and determination of whether pain is attributable to the condition [35]. Care for adults with osteonecrosis of the femoral head varies among American orthopaedic surgeons specializing in hip and knee surgery [27].

Non-Operative

Small, asymptomatic, medially-placed lesions may be managed with observation alone [7]. In children with Gaucher disease experiencing symptomatic bone crisis, recommended management includes bed rest and analgesics followed by non-weight-bearing on the involved limb, as no known treatment effectively prevents femoral head deformity [137]. For children with avascular necrosis following hip fractures, treatment should commence at symptom onset and entail partial or non-weight bearing until painful symptoms resolve [12]. In Legg-Calvé-Perthes disease, symptomatic treatment is preferred for patients with onset on or before the sixth birthday in the initial stage [172], and for those with onset after the eighth birthday in the fragmentation stage who present with lateral pillar group A [172].

Operative

Indications: Core decompression augmented with autologous bone marrow aspiration concentrate is recommended for early stages of avascular necrosis, specifically Ficat stages 0 through II [4]. Core decompression combined with concentrated autologous bone marrow containing mononuclear cells may be the treatment of choice for stages I–II nontraumatic osteonecrosis [13]. Implantation of autologous bone-marrow mononuclear cells appears safe and effective for early stages of osteonecrosis [121]. Free vascularized fibular grafting is indicated for small osteonecrosis involving less than 300 degrees of the femoral head without preoperative collapse, corresponding to Steinberg's stages I and II [36]. Vascularized pedicle bone-grafting is sometimes indicated for early-stage avascular necrosis before femoral head collapse [138]. Femoral head-preserving surgery is not recommended for patients with type 3 osteonecrosis according to the 2021 ARCO classification [64]. For children with Legg-Calvé-Perthes disease, surgical treatment is considered for those with onset after the eighth birthday who present at the initial stage with >50% head involvement on perfusion MRI [172]. Multiple epiphyseal drilling or core decompression is recommended for children with onset after the eleventh birthday if the head has not collapsed [172]. In the fragmentation stage, surgical treatment is recommended for children with onset after the eighth birthday presenting with lateral pillar groups B and B/C border [172].

Surgical Approach / Technique: Arthroscopic management of avascular necrosis is viable and offers significant advantages [15]. The success of arthroscopic core decompression depends on the amount of necrotic tissue remaining in the femoral head after the procedure [125]. Core decompression with multiple small-size holes is an effective method for treating early-stage avascular necrosis, particularly in patients with pathological changes in the hip joint [141]. Combining core decompression with biotechnology could result in a novel long-lasting hip-preserving treatment option, provided therapeutic principles are correctly mastered and methods are specifically oriented to different stages [21]. A vascularized pedicle iliac bone graft is considered promising for joint preservation [136]. Intertrochanteric curved varus osteotomy for idiopathic osteonecrosis was successful when indicated for cases with an intact load-bearing area of more than 40% [73]. For children with Legg-Calvé-Perthes disease in the healing or healed stage, late measures include femoral valgus osteotomy for established head and acetabular flattening, adducted hip, or short leg gait [172]. Surgical hip dislocation with possible trochanteric advancement, relative femoral neck lengthening, and osteochondroplasty is used for impingement and labral disorders in the healing or healed stage [172]. Hip arthroscopy with removal of osteochondrotic fragment is a preferred treatment approach for children presenting with mechanical symptoms [172].

Implant Selection: Cementless total hip arthroplasty in patients with osteonecrosis of the femoral head has satisfactory midterm clinical and radiographic outcomes [46]. Femoral head necrosis following renal transplantation and extension of the necrotic area into the femoral neck are contraindications for the thrust plate prosthesis [65].

Other Considerations: The combination of bone marrow-derived cell therapy with core decompression may be better for pain relief, function, and joint survival than core decompression alone, though evidence remains limited and heterogeneous [111]. Patients with postcollapse, predegenerative osteonecrosis appear to benefit from free vascularized fibular grafting, with good overall joint survival and significant improvement in the Harris hip score [28]. Unilateral free vascularized fibula is effective for the treatment of bilateral osteonecrosis [140]. Patients with preoperative stage V osteonecrosis or corticosteroid use had worse outcomes after vascularized fibular grafting if they had a previous core decompression [145]. Impaction bone allograft and fibular grafting report favourable medium-term results [19]. One in five patients require conversion to arthroplasty after non-vascularized bone grafts [80]. Vascularized fibular grafting provides a good outcome at medium-term follow-up in adolescent patients with partial avascular necrosis after slipped capital femoral epiphysis [43]. When avascular necrosis is evident before any collapse of the articular surface in children, the use of a revascularization procedure such as a vascularized fibular graft may be considered [81]. If metallic implants in the epiphysis have secondarily encroached on the articular cartilage due to collapse of the capital epiphysis, the implant should be removed, partially withdrawn, or replaced so that the residual epiphysis remains stabilized to the femoral neck without further compromise of the articular surface [81]. If a child experiences little pain despite radiographic deformity and the hip is in a poor functional position, an intertrochanteric osteotomy may be performed to reposition the limb in a more functional arc of motion and prevent impingement [81]. Trochanteric epiphysiodesis should be performed when major avascular necrosis is recognized and the ossific nucleus of the greater trochanter is present, being most effective if performed when the child is approximately 5 years old [83]. Trochanteric advancement may be considered when an objectionable abductor limp results from trochanteric overgrowth, specifically when the greater trochanter has reached the level of the top of the femoral head, there is a congruous and concentric reduction of the hip, a Trendelenburg sign can be elicited, and the child is older than 8 years [83].

Joint Replacement: Studies of total joint arthroplasty, once femoral head collapse is present, have described excellent outcomes at greater than ten years of follow-up [11]. The results of hemiresurfacing and total resurfacing arthroplasty have been suboptimal, and these procedures have restricted indications in patients with osteonecrosis [11]. Management of Ficat stage III and IV osteonecrosis remains controversial; the choice of option depends on patient age, the cause of osteonecrosis, the extent of femoral head involvement, and the condition of the acetabular articular cartilage [75]. Total hip arthroplasty was a safe, effective treatment for young osteonecrosis patients, with demonstrated efficacy over 120 months [55]. For children with avascular necrosis, debilitating pain with progressive radiographic changes may be treated with joint arthroplasty (total or partial) or hip fusion [81]. Total joint arthroplasty offers the advantages of pain relief and maintenance of motion [81]. Hip arthrodesis is a traditional salvage procedure that relieves pain, allows most activities, and places stresses on the knee and lumbar spine [81].

Prognostic Factors and Risk: Collapse of the femoral head in nontraumatic osteonecrosis starts in the lateral column due to ischemia; preserving blood supply to the lateral column improves prognosis and delays collapse [29]. A reduced head–neck offset may act as a mechanical (co-)factor in developing osteonecrosis [37]. Patients with nontraumatic osteonecrosis had a higher incidence and risk of major adverse cardiovascular and cerebrovascular events than the general population, with a greater than 1.3-fold risk [30]. In the context of electrical stimulation management, hips with small lesions fared significantly better than those with intermediate and large lesions [114]. Having a femoral head with a greater than 15% necrotic area influenced the likelihood of progression [114]. All femoral heads that went on to have roentgenographic progression had predominantly lateral involvement [114]. Corticosteroid use as an aetiology may have influenced response to electrical stimulation therapy [114]. Idiopathic lesions may be more sensitive to electrical stimulation therapy [114]. Patients who have had alcohol and steroid use as disease aetiologies may have had poorer outcomes with electrical stimulation therapy, although the difference was not statistically significant [114].

Complications

Natural History and Progression

Osteonecrosis of the femoral head is a progressive disease that typically leads to collapse of the femoral head and eventual deterioration of the hip joint [42]. Large defects in the necrotic area do not heal spontaneously [79]. More than one-third of patients with symptomatic osteonecrosis of the femoral head experienced accelerated collapse within 1 year [56]. In pediatric populations, AVN following femoral neck fracture showed a tendency toward extensive necrotic lesions, presumably resulting in a rapid progression of femoral head collapse [22]. Osteonecrosis of the femoral head, particularly involving the lateral head-neck junction, was confirmed as a major risk factor for spontaneous femoral neck fracture [174]. This is the first report of pathological fractures of the bilateral femoral neck caused by femoral head necrosis, conforming to the histological characteristics of rapidly destructive hip disease [40].

Post-Traumatic Complications

Historically, the incidence of AVN has been reported to be 100%, 50%, 25%, and 15% for types I, II, III, and IV fractures, respectively, with an overall incidence of 43% [12]. In a more recent literature review, the incidence of AVN was lower: 38%, 28%, 18%, and 5% for types I, II, III, and IV fractures, respectively and an overall rate of 29% [12]. Fracture displacement is the most important risk factor for AVN after hip fractures in children [12]. The presence of a type I or II fracture is a risk factor for AVN after hip fractures in children [12]. A fracture in an older child (>12 years) is a risk factor for AVN after hip fractures in children [12]. Type I AVN results from interruption of the lateral epiphyseal and metaphyseal vessels and accounts for more than 50% of cases [12]. Type I AVN has the worst prognosis among the patterns of AVN after hip fractures in children [12]. In general, AVN after hip fractures in children results in poor outcomes in up to 60% of cases [12].

Complications following a femoral head fracture include OA in approximately 50% [18]. Complications following a femoral head fracture include osteonecrosis in approximately 20% [18]. Complications following a femoral head fracture include sciatic nerve palsy [18]. Complications following a femoral head fracture include fracture malreduction [18]. Complications following a femoral head fracture include non-union [18]. Complications following a femoral head fracture include heterotopic ossification [18]. The report documents the danger of developing avascular necrosis of the femoral head after intramedullary fixation of a femoral fracture in an adolescent [44]. Avascular necrosis was more common in the sliding hip screw group than in the cancellous screws group (9% vs. 5%) for low-energy hip fractures [77]. The incidence of AVN was 17.2% in the closed reduction group and 17.7% in the open reduction group for displaced intracapsular fractures in patients under the age of 50 years [77].

Surgical and Treatment-Related Complications

A previous joint-preserving procedure for osteonecrosis of the femoral head poses technical challenges for subsequent total hip reconstruction [31]. A previous joint-preserving procedure for osteonecrosis of the femoral head might have a detrimental effect on the short-term clinical outcome [31]. Salvage THA is associated with more complications than primary THA for intracapsular neck of femur fractures [77]. Salvage THA has a significantly higher rate of dislocation, infection, and periprosthetic fracture compared to primary THA [77]. The surgery could not restore normal hip anatomy, and arthritis progressed with time despite subjective success in 90% of patients without failure [69]. The procedure is effective for early atraumatic avascular necrosis, though failure may occur if risk factors persist or if the graft does not extend completely into the lesion [92]. The prognosis of the femoral head did not improve significantly in the long term for core decompression with β-tri-calcium phosphate grafts in combination with platelet-rich plasma [39].

Systemic and Associated Conditions

Occasionally, pain in the hip that begins during pregnancy is caused by osteonecrosis of the femoral head [179].

Recovery

Prognosis and Natural History: The natural history of avascular necrosis is influenced by multiple factors, though acetabular coverage was not as strong an associated factor as expected [56]. Collapse of the femoral head and the contralateral condition of osteonecrosis strongly affect patients' activities of daily life [162]. In pediatric femoral neck fracture, avascular necrosis showed a tendency toward extensive necrotic lesions, presumably resulting in a rapid progression of femoral head collapse [22]. Symptomatic avascular necrosis can develop 8 years post-injury despite no evidence at 3 years, implying a need for extended follow-up [10].

Joint-Preserving Procedures: Platelet-rich plasma use after core decompression provides significant pain relief, better midterm functional outcome, retards progression, and enhances survivorship free from reoperation for hip arthroplasty and femoral head collapse in early stages of avascular necrosis than core decompression alone [89]. However, the prognosis of the femoral head did not improve significantly in the long term with core decompression with β-tri-calcium phosphate grafts in combination with platelet-rich plasma [39]. In patients with precollapse osteonecrosis of the femoral head, core decompression combined with allograft-bone threaded cage or mineralized collagen threaded scaffold demonstrated comparable long-term survivorship and functional outcomes [177]. The efficacy of core decompression combined with allograft-bone threaded cage or mineralized collagen threaded scaffold diminished in advanced stages [177]. Structural bone-grafting is effective for early atraumatic avascular necrosis, though failure may occur if risk factors persist or if the graft does not extend completely into the lesion [92]. Eighteen of 21 hips (86%) were clinically successful at latest followup with nonvascularized bone grafting for osteonecrosis of the femoral head [93]. VFITO provides a good outcome at medium-term follow-up in adolescent patients with partial avascular necrosis of the femoral head after slipped capital femoral epiphysis [43]. Valgus intertrochanteric osteotomy can improve the long-term function of the hip joint in adolescents with avascular necrosis of the femoral head after a femoral neck fracture, but cannot restore completely the original shape and structure of the femoral head [155]. Hormonal osteonecrosis of the femur, extent of necrosis, type C1 and type C2 in the Japanese Society for the Study of Femoral Osteonecrosis staging, and distance of the tip of the tantalum rod from the center of necrosis are risk factors for postoperative femoral head collapse in patients with Ficat I, II, and III stages [90]. A nomogram could divide precollapse nontraumatic osteonecrosis of the femoral head patients into prognosis groups and performed well in internal validation [51].

Total Hip Arthroplasty: Reports since 1993 have suggested improved survivorship of total hip arthroplasty reconstructions for the treatment of osteonecrosis of the hip [176].

Pediatric and Special Populations: In children less than one year old, premanipulation traction of twenty-one days or more substantially reduces the incidence of avascular necrosis [204]. Cases submitted to early reduction and internal fixation had a reduced incidence in severity of avascular necrosis compared with those in whom operation was delayed [200].

Key Evidence

• [L4] The prognosis of patients with osteonecrosis of the femoral head can be significantly improved with early diagnosis and timely intervention. [2] (10.1302/2058-5241.4.180073)
• [L5] [3] (10.5435/00124635-199907000-00005)
• [Paper] The authors recommend this procedure for early stages of avascular necrosis (Ficat stages 0 through II) of the femoral head. [4] (10.1016/j.eats.2016.02.009)
• [L5] Osteonecrosis of the femoral head is a disabling pathology affecting a young population and is the most important cause of total hip arthroplasty in this group. [5] (10.1302/2058-5241.4.180036)
• [L3] Necrosis involving the anterior aspect of the femoral head is an important risk factor for collapse. [6] (10.1186/s12891-023-06890-0)
• [L2] The review provides an up-to-date, evidence-based guide to the management, both non-operative and operative, of non-traumatic osteonecrosis of the femoral head, emphasizing that small, asymptomatic, medially-placed lesions may be treated with observation alone while larger lesions have a 25% to 50% risk of progression. [7] (10.1302/0301-620x.99b10.bjj-2017-0233.r2)
• [L5] Avascular necrosis of the femoral head is relatively uncommon in type 1 dislocations reduced within 6 hours, but this case demonstrates symptomatic AVN developing 8 years post-injury despite no evidence at 3 years, implying a need for extended follow-up and reconsideration of medico-legal reporting timing. [10] (10.1016/j.injury.2006.11.004)
• [L5] [11] (10.2106/jbjs.o.00071)
• [L4] It may be the treatment of choice particularly in stages I–II nontraumatic osteonecrosis of the femoral head. [13] (10.1007/s00402-009-0939-0)
• [L3] Nearly 80% of the patients presented with late-stage ONFH, indicating a narrow window of opportunity for hip preservation surgery before femoral head collapse. [14] (10.1016/j.arth.2020.04.092)
• [L4] Arthroscopic management of avascular necrosis of the femoral head is viable and has significant advantages. [15] (10.1007/s00167-011-1587-9)
• [Paper] The management of pediatric ONFH is complicated by a limited body of evidence and a lack of consensus on prevention or treatment of femoral head collapse. [16] (10.2106/jbjs.rvw.25.00046)
• [L3] The study reports favourable medium-term results of impaction bone allograft and fibular grafting for osteonecrosis of the femoral head. [19] (10.1302/0301-620x.102b7.bjj-2019-1101.r2)
• [L2] Combining core decompression with biotechnology could result in a novel long-lasting hip-preserving treatment option, but only by correctly mastering therapeutic principles and adopting proper methods specifically oriented to different stages can the best therapeutic effect be achieved. [21] (10.1302/2058-5241.2.150006)
• [L4] AVN after PFNF showed a tendency toward extensive necrotic lesions, presumably resulting in a rapid progression of femoral head collapse. [22] (10.1186/s13018-020-02037-2)
• [L4] Joint-preserving procedures should be attempted in early-stage lesions to save the femoral head, while outcomes of total hip arthroplasty in the setting of osteonecrosis are excellent. [23] (10.2106/jbjs.19.01271)
• [L3] Assessment of preserved angles on plain radiographs is a simple method to quantify the extent of lateral and anterior necrosis of the femoral head. [24] (10.2106/jbjs.20.00507)
• [L3] Collapse progression on the symptomatic side is a poor prognostic factor for the natural history of contralateral osteonecrosis of the femoral head. [26] (10.1016/j.arth.2021.08.005)
• [L5] The care of adults with osteonecrosis of the femoral head varies among American orthopaedic surgeons specializing in hip and knee surgery. [27] (10.2106/jbjs.f.00302)
• [L4] Patients with postcollapse, predegenerative osteonecrosis of the femoral head appear to benefit from free vascularized fibular grafting, with good overall survival of the joint and significant improvement in the Harris hip score. [28] (10.2106/00004623-200306000-00001)
• [L4] Collapse of the femoral head in nontraumatic osteonecrosis starts in the lateral column due to ischemia; preserving blood supply to the lateral column improves prognosis and delays collapse. [29] (10.2106/jbjs.20.00490)
• [L2] Patients with nontraumatic osteonecrosis of the femoral head had a higher incidence and risk of major adverse cardiovascular and cerebrovascular events than the general population, with a greater than 1.3-fold risk. [30] (10.1007/s11999.0000000000000161)
• [L3] A previous joint-preserving procedure for osteonecrosis of the femoral head poses technical challenges for subsequent total hip reconstruction and might have a detrimental effect on the short-term clinical outcome. [31] (10.1016/j.arth.2007.05.026)
• [L3] The study demonstrates varying levels of reliability and diagnostic precision among different classification systems for femoral head avascular necrosis. [32] (10.1186/s12891-025-08398-1)
• [L1] Key recommendations of these guidelines require accurately staging ONFH and determining when pain may be due to ONFH. [35] (10.2106/jbjs.25.01616)
• [L4] Small osteonecrosis (less than 300 degrees of the femoral head) without preoperative collapse (Steinberg's stages I and II) is the major indication for free vascularized fibular grafting. [36] (10.1186/1471-2474-8-78)
• [L3] A reduced head–neck offset in patients with nontraumatic osteonecrosis of the femoral head may act as a mechanical (co-)factor in developing osteonecrosis of the femoral head. [37] (10.1007/s00402-013-1771-0)
• [L3] However, the prognosis of the femoral head did not improve significantly in the long term. [39] (10.1186/s12891-022-06120-z)
• [Case_report] This is the first report of pathological fractures of the bilateral femoral neck caused by femoral head necrosis, conforming to the histological characteristics of rapidly destructive hip disease. [40] (10.1186/s12891-023-06992-9)
• [L5] The location of the necrotic lesion exerts a greater impact on femoral head collapse compared with the size of the lesion. [41] (10.1186/s13018-025-05453-4)
• [L4] VFITO provides a good outcome at medium-term follow-up in adolescent patients with partial avascular necrosis of the femoral head after slipped capital femoral epiphysis. [43] (10.1007/s00402-010-1161-9)
• [Case_report] The report documents the danger of developing avascular necrosis of the femoral head after intramedullary fixation of a femoral fracture in an adolescent. [44] (10.2106/00004623-199411000-00014)
• [L3] The estimated mean annual prevalence of osteonecrosis of the femoral head from 2002 to 2006 was 14,103 cases, corresponding to 28.91 cases per 100,000 persons. [45] (10.1016/j.arth.2009.05.022)
• [L3] Cementless total hip arthroplasty in patients with osteonecrosis of the femoral head has satisfactory midterm clinical and radiographic outcomes, but the long-term effect should be further studied. [46] (10.1016/j.arth.2006.12.098)
• [L5] Thus, the long-term effect of core decompression in the treatment of steroid-induced femoral head osteonecrosis is not satisfactory. [48] (10.1186/1471-2474-13-142)
• [L3] The nomogram could divide precollapse nontraumatic osteonecrosis of the femoral head patients into prognosis groups and performed well in internal validation. [51] (10.1186/s13018-021-02664-3)
• [L3] The novel 2021 ARCO classification is a highly reliable and valid method compared to previous classifications and is recommended by ARCO as a unified classification for early-stage osteonecrosis of the femoral head. [53] (10.1016/j.arth.2022.02.009)
• [L3] THA was a safe, effective treatment for young ONFH patients, with demonstrated efficacy over 120 months. [55] (10.1016/j.arth.2025.05.106)
• [L5] More than one-third of patients with symptomatic osteonecrosis of the femoral head experienced accelerated collapse within 1 year, and acetabular coverage was not as strong an associated factor in the natural history of the disease as expected. [56] (10.1097/corr.0000000000002501)
• [L1] This review provides a systematic review and meta-analysis to evaluate the diagnostic accuracy of MRI in early osteonecrosis of the femoral head. [60] (10.1186/s13018-018-0836-8)
• [L3] [61] (10.2106/00004623-198971050-00003)
• [L4] We do not recommend femoral head-preserving surgery for patients with type 3 ONFH. [64] (10.1186/s12891-023-06587-4)
• [Paper] Femoral head necrosis following renal transplantation and extension of the necrotic area into the femoral neck are contraindications for TPP. [65] (10.1007/s00402-002-0422-7)
• [L3] Despite subjective success in 90% of patients without failure, the surgery could not restore normal hip anatomy, and arthritis progressed with time. [69] (10.1097/01.blo.0000071756.07450.76)
• [L3] Accurate evaluation of the posterior boundary of the necrotic lesion using the oblique axial plane is necessary for predicting the prognosis of the femoral head and considering indications for anterior rotational osteotomy. [70] (10.2106/jbjs.20.00493)
• [L4] The results of CVO for idiopathic osteonecrosis of the femoral head were successful if the procedure was indicated for cases with an intact load-bearing area of more than 40%. [73] (10.1007/s00402-013-1919-y)
• [L5] Management of Ficat stage III and IV osteonecrosis of the hip remains controversial; the choice of option depends on patient age, the cause of osteonecrosis, the extent of femoral head involvement, and the condition of the acetabular articular cartilage. [75] (10.5435/00124635-200403000-00005)
• [L4] [79] (10.5435/00124635-199801000-00005)
• [L1] One in five patients require conversion to arthroplasty after non-vascularized bone grafts in patients with osteonecrosis of the femoral head. [80] (10.1186/s13018-023-03544-8)
• [L5] There remains plenty of room for improvement in the classification of ONFH, as commonly used classification systems lack intraobserver and interobserver reliability and do not fully incorporate advances in biology, biomechanics, and imaging. [85] (10.1097/01.blo.0000533640.75452.45)
• [L1] PRP use after CD provides significant pain relief, better midterm functional outcome, retards the progression, and enhances the survivorship free from reoperation for hip arthroplasty and femoral head collapse in early stages of avascular necrosis of hip than CD alone. [89] (10.1016/j.arth.2020.07.010)
• [L3] Hormonal osteonecrosis of the femur, extent of necrosis, type C1 and type C2 in the Japanese Society for the Study of Femoral Osteonecrosis staging, and distance of the tip of the tantalum rod from the center of necrosis are risk factors for postoperative femoral head collapse in patients with Ficat I, II, and III stages of aseptic necrosis of the femoral head. [90] (10.5435/jaaos-d-22-00198)
• [L4] The procedure is effective for early atraumatic avascular necrosis, though failure may occur if risk factors persist or if the graft does not extend completely into the lesion. [92] (10.2106/00004623-199173090-00011)
• [L4] Eighteen of 21 hips (86%) were clinically successful at latest followup. [93] (10.1097/01.blo.0000096826.67494.38)
• [L1] The combination of bone marrow-derived cell therapy with core decompression may be better for pain relief, function, and survival of joints for osteonecrosis of the femoral head than core decompression alone but remains limited and heterogeneous. [111] (10.1002/arj.70449)
• [L4] [114] (10.1186/s12891-017-1663-5)
• [L4] The modified Ficat classification for osteonecrosis of the femoral head does not have acceptable interobserver reliability and intraobserver reproducibility on which to base treatment protocols and determinations of outcome. [116] (10.2106/00004623-199611000-00010)
• [L3] Magnetic resonance imaging was accurate in all hips with histological proof of osteonecrosis and in those with medullary changes without necrotic bone. [118] (10.2106/00004623-198971050-00002)
• [L2] Implantation of autologous bone-marrow mononuclear cells appears to be a safe and effective treatment for early stages of osteonecrosis of the femoral head. [121] (10.2106/jbjs.d.02662)
• [L3] The success of ACD depends on the amount of necrotic tissue remaining in the femoral head after the procedure. [125] (10.1007/s00402-015-2287-6)
• [L3] The newly proposed BRB classification provides a systematic approach to assessing necrotic lesion severity in TONFH and demonstrates significant correlation with femoral head collapse risk. [128] (10.1016/j.arth.2025.06.030)
• [L5] A staging system has been developed to revise the 1994 ARCO classification for ONFH by an expert panel-based Delphi survey. [130] (10.1016/j.arth.2019.11.029)
• [L4] A vascularized pedicle iliac bone graft to treat avascular necrosis of the femoral head is considered promising for joint preservation. [136] (10.1007/s004020100263)
• [L4] The authors recommend symptomatic management with bed rest and analgesics followed by non-weight-bearing on the involved limb during the symptomatic stage of bone crisis, as no known treatment effectively prevents femoral head deformity. [137] (10.2106/00004623-199601000-00003)
• [L4] Vascularized PBG is sometimes indicated for ANFH in an early stage before collapse of the femoral head. [138] (10.1007/bf00390047)
• [L3] The matrix model, which combines ARCO staging, JIC classification, and necrotic area, demonstrated strong predictive ability for femoral head collapse, with higher scores correlating to higher collapse rates. [139] (10.1186/s13018-024-04587-1)
• [L4] Unilateral free vascularized fibula is effective for the treatment of bilateral osteonecrosis of the femoral head. [140] (10.1016/j.arth.2012.09.002)
• [L4] The core decompression with multiple small-size holes is an effective method for treating early-stage avascular necrosis of the femoral head, particularly in those with pathological changes in the hip joint. [141] (10.1186/s42836-023-00181-8)
• [L3] Although MRI is essential for detecting pre-radiographic stage ONFH, less than half of preradiographic ONFH cases progress to stage 2 or higher. [142] (10.1016/j.arth.2025.05.089)
• [L2] SPECT/CT was useful in evaluating the perfusion status of the femoral head, showing high accuracy in predicting the occurrence of avascular necrosis. [143] (10.1186/s12891-020-03538-1)
• [L3] However, patients with preoperative stage V osteonecrosis or corticosteroid use had worse outcomes after vascularized fibular grafting if they had a previous core decompression of the femoral head. [145] (10.1016/j.arth.2006.12.042)
• [L4] Hips with ONFH had higher risk of disease progression with far more anterior necrotic lesions (type III) in the FL radiographs. [147] (10.1002/jor.24825)
• [L4] Volumetric measurements should be universally included in the assessment of patients with osteonecrosis of the femoral head. [154] (10.1016/j.arth.2019.05.039)
• [L4] VITO can improve the long-term function of the hip joint in adolescents with ANFH after a femoral neck fracture, but cannot restore completely the original shape and structure of the femoral head. [155] (10.1186/s12891-023-06598-1)
• [L4] [157] (10.3389/fgene.2022.1037190)
• [L3] The 2021 ARCO classification system, by using MRI, is a reliable and valid tool for predicting the occurrence of collapse in patients who have early-stage ONFH. [159] (10.1016/j.arth.2025.05.071)
• [Paper] Collapse of the femoral head and the contralateral condition of ONFH strongly affect patients' activities of daily life. [162] (10.1007/s00264-018-3867-1)
• [L4] The CJFH classification system is a simple and direct evaluation model for ONFH with substantial inter- and intraobserver reliability. [163] (10.2106/jbjs.20.00051)
• [L3] Bone scintigraphy performed within three weeks after the operation can predict a satisfactory outcome of rotation of the femoral head, whereas conventional radiographs were not associated with the final result. [168] (10.2106/00004623-200010000-00008)
• [L3] Osteonecrosis of the femoral head, particularly involving the lateral head-neck junction, was confirmed as a major risk factor for spontaneous femoral neck fracture. [174] (10.1186/s12891-023-07058-6)
• [L3] Previously, THA was believed to have poor survivorship and clinical results for the treatment of osteonecrosis of the hip, but reports since 1993 have suggested improved survivorship of these reconstructions. [176] (10.1007/s11999-013-3220-3)
• [L3] In patients with precollapse ONFH, CD combined with ATC or MCTS demonstrated comparable long-term survivorship and functional outcomes, though both their efficacy diminished in advanced stages. [177] (10.1016/j.arth.2025.05.003)
• [L5] [178] (10.1016/j.eats.2024.103233)
• [L4] Occasionally, pain in the hip that begins during pregnancy is caused by osteonecrosis of the femoral head. [179] (10.2106/00004623-199906000-00006)
• [L5] Osteoarthritis in hips with osteonecrosis can be caused by elevated contact stress. [184] (10.1097/01.blo.0000203472.88926.c8)
• [L2] This study shows that those cases which were submitted to early reduction and internal fixation had a reduced incidence in severity of avascular necrosis compared with those in whom operation was delayed. [200] (10.1016/0020-1383(85)90162-7)
• [L4] In children less than one year old, premanipulation traction of twenty-one days or more substantially reduces the incidence of avascular necrosis. [204] (10.2106/00004623-197759030-00002)

See Also

• Total hip replacement
• Hip arthroscopy

References

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