Innovations and future research directions on hip preservation management options for osteonecrosis of the femoral head

Abstract

Osteonecrosis of the femoral head remains a major cause of hip pain and disability in young and middle-aged adults and contributes substantially to total hip arthroplasty utilization in this population. Although hip-preserving strategies have expanded markedly, management remains heterogeneous and a universally accepted, stage-stratified algorithm is lacking. This minireview synthesizes contemporary hip-preservation options and highlights recent innovations and research directions within an Association Research Circulation Osseous-informed (multi-agent reinforcement learning) framework. Nonoperative and pharmacologic adjuncts may be used in pre-collapse disease, primarily for symptom control and as adjuncts to surgical preservation. Core decompression remains the foundational pre-collapse procedure, with technique variants, enabling technologies (robotic or arthroscopic assistance), and biologic augmentation-most commonly bone marrow aspirate concentrate-aimed at improving repair, while outcomes remain influenced by lesion characteristics and variability in biologic processing and delivery. When mechanical failure risk is prominent, structural reconstruction or internal support implants may be considered in selected patients. Overall, advances in biologically augmented decompression, structural support constructs, and emerging translational approaches (including acellular biologics, scaffold strategies, and imaging analytics) underscore a rapidly evolving field. Future progress will depend on multicenter, stage-stratified comparative studies with standardized lesion characterization, reproducible reporting of biologic preparation and dose, and harmonized clinical and imaging endpoints.

Key Words: Hip preservation; Avascular necrosis; Femoral head necrosis; Hip replacement; Hip preservation surgery; Femoral head avascular necrosis; Hip osteoarthritis

Core Tip: The past decade has brought substantial advances in hip preservation for Osteonecrosis of the femoral head, particularly through biologically augmented core decompression and innovative implants. Yet high-quality randomized evidence remains sparse, especially for comparative effectiveness across strategies and for long-term survivorship. There is an urgent need for multicenter, stage-stratified trials with standardized outcome measures to refine algorithms that truly balance joint preservation against timely total hip arthroplasty.

INTRODUCTION

Osteonecrosis of the femoral head (ONFH), also termed avascular necrosis (AVN), is a clinically significant cause of hip pain and disability in young and middle-aged adults and contributes meaningfully to the demand for total hip arthroplasty (THA) in this population[1-4]. Because many affected patients are in highly active decades of life, there is sustained interest in strategies that preserve the native hip, with the aim of delaying femoral head collapse and the subsequent progression to secondary osteoarthritis[1,5]. Despite expansion of the hip-preservation literature, therapeutic decision-making remains challenged by heterogeneity in staging, lesion characteristics, and reported outcomes, and a universally accepted, stage-stratified algorithm has not been established[2,5].

In the post-coronavirus disease 2019 (COVID-19) era, ONFH has been increasingly discussed in selected cohorts, particularly in association with corticosteroid exposure during COVID-19 management[6]. In addition, COVID-19 infection itself has been proposed as a potential contributor to osteonecrosis risk beyond corticosteroid exposure, reinforcing the importance of diagnostic vigilance and careful attribution of etiologic factors in contemporary practice[7].

ONFH is characterized by compromised perfusion of the femoral head, leading to osteocyte death and progressive weakening of subchondral bone. If untreated or unresponsive to therapy, this process may culminate in subchondral fracture and collapse, with accelerated degenerative changes and worsening function[1,3]. Given the strong relationship between structural integrity and prognosis, management is inherently stage-dependent and early-stage ONFH (pre-collapse) continues to be the critical window for joint preservation. Clinical practice and research therefore rely on imaging-based staging systems that integrate radiographic and magnetic resonance imaging findings, including the widely used Ficat and Arlet classification; Association Research Circulation Osseous (ARCO) staging is also commonly applied in contemporary studies[1,5].

Treatment options span nonoperative measures and adjunctive pharmacologic or biophysical approaches, as well as multiple hip-preserving surgical procedures[1,3]. Early-stage (pre-collapse) disease represents the principal therapeutic window for joint preservation, and publication trends indicate sustained growth in research focused on hip-preserving strategies, including core decompression (CD), osteotomy, bone grafting, and biologic augmentation[2,5]. Accordingly, this review synthesizes contemporary hip-preserving surgical options, with emphasis on newer strategies and translational directions that may refine patient selection, expand indications, or improve clinical outcomes. The following sections synthesize stage-dependent hip-preserving strategies with emphasis on recent innovations and an ARCO-informed treatment framework.

NONOPERATIVE AND PHARMACOLOGIC ADJUNCTS

Nonoperative measures and pharmacologic adjuncts are primarily considered in pre-collapse ONFH as supportive strategies for symptom control and as adjuncts to hip-preserving surgery. Although activity modification, protected weight bearing, biophysical modalities, and selected pharmacologic agents have been explored, the evidence base remains heterogeneous with variable staging, protocols, and outcome definitions. These approaches should therefore be framed as adjunctive rather than reliably disease-modifying for patients at meaningful risk of collapse[1,3,5].

KEY HIP-PRESERVING SURGICAL STRATEGIES

Hip-preserving surgery for ONFH is most appropriately considered before femoral head collapse, with procedure selection guided by stage, lesion size/location, and patient factors[1,3,5]. Contemporary preservation can be framed by three operative objectives: (1) Decompression of the necrotic segment; (2) Biologic augmentation to enhance repair; and (3) Mechanical/structural support of the subchondral plate to reduce collapse risk[1,5].

CD remains the reference intervention for pre-collapse disease[1,3,5]. Classical CD commonly uses a single large-bore tract (8-10 mm) directed into the necrotic area under fluoroscopic guidance[8]. An alternative is multiple small-diameter drillings (classically about 3 mm Steinmann pin), intended to create several channels with less removal of supportive bone stock[8,9]. Across reviews, CD demonstrates its most consistent effectiveness in early-stage, pre-collapse ONFH, with less predictable results as lesion burden increases or subchondral integrity becomes compromised[1,5,10].

Technical adjuncts aim to improve accuracy and address concomitant pathology. Robot-assisted CD has been evaluated as a precision-enabling technology; meta-analytic evidence supports feasibility and comparative clinical assessment vs freehand techniques, without implying that robotics alters the underlying biologic mechanism of decompression[11]. Arthroscopic-assisted CD has been proposed to permit intra-articular assessment and treatment alongside decompression; a meta-analysis reports feasibility and safety, but the evidence base remains heterogeneous, and arthroscopy is best presented as a selective adjunct rather than routine practice[12].

Biologic augmentation of CD is the dominant innovation in early-stage joint preservation. Bone marrow aspirate concentrate (BMAC) is most frequently reported; syntheses support improvement in symptoms with variable effects on radiographic progression and conversion to THA, and outcomes likely depend on lesion characteristics and substantial non-standardization of aspirate processing, delivered dose, and delivery technique[9,10]. Other orthobiologic approaches, including platelet-rich plasma), are frequently discussed in the broader sports-medicine and soft-tissue literature; however, evidence from non-ONFH indications (e.g., ligament repair) should be treated as contextual rather than confirmatory for ONFH and should not be used to infer ONFH efficacy in the absence of ONFH-specific comparative data[13-19].

When mechanical failure risk is prominent, structural reconstruction or internal support may be considered. Surgical hip dislocation (SHD) with fenestration/debridement and impaction bone grafting allows direct treatment of necrotic bone and restoration of subchondral support; reported outcomes are stage-sensitive and depend on adherence to protected weight-bearing protocols[13]. Not all substitutes provide durable structural benefit: A 5-year follow-up of an injectable synthetic graft combined with CD reported high failure rates in advanced patterns, underscoring the importance of material behaviour and remodelling[14]. Dedicated support devices such as AVN cage combined with CD have shown encouraging short-term outcomes in carefully selected early-stage, non-collapsed lesions, with worse results associated with larger necrotic burden or more advanced disease[15]. Where finite element analyses are cited for implants or constructs, they must be described as mechanistic (stress redistribution) and not conflated with clinical survivorship[16].

For “borderline” early post-collapse disease (ARCO stage III), patient-specific partial femoral head replacement has been proposed to restore local head contour via targeted segment resection and implant insertion through a femoral-neck tunnel. Early clinical series suggest short-term improvement in pain and function, but interpretation is limited by small cohorts and short follow-up[17]. Biomechanical simulations suggest favourable stress/displacement profiles but remain theoretical and often incompletely model cartilage contact mechanics[16]. Critically, replacement of the femoral head (PRFH) introduces a prosthesis–native cartilage interface, and the potential for altered contact pressures and acetabular cartilage wear should be stated as an unresolved failure mechanism requiring longer-term, comparative evaluation[16,17].

Although hip preservation is the focus of this chapter, a concise acknowledgment is warranted that some patients progress despite preservation attempts and may ultimately require THA; in such cases, rigorous preoperative planning is essential, particularly in complex anatomy[20].

INNOVATIONS AND FUTURE RESEARCH DIRECTIONS

Several developments may refine hip preservation for ONFH, but most remain preclinical or early clinical and should be presented as translational trajectories rather than established standards of care[21].

A near-term priority is strengthening the biologic, mechanical construct created by surgery. Beyond cell-based augmentation (e.g., BMAC), acellular biologics, particularly extracellular vesicles/exosomes, are being investigated as mediators of osteogenesis, angiogenesis, and immune regulation relevant to ONFH. Current syntheses emphasize biologic plausibility but also highlight translational barriers (standardized sourcing/characterization, potency assays, dose–response, delivery/retention, and safety), and the need to evaluate clinically meaningful endpoints [collapse-free survival, MRI-based structural outcomes, and validated patient reported outcome measures (PROMs)][22-25]. In addition, peptide-based acellular strategies investigated in bone regeneration (e.g., amelogenin-derived peptides) are conceptually relevant, but currently remain translational and are not supported by ONFH-specific clinical evidence[18]. In parallel, scaffold-assisted and composite reconstruction after decompression aims to combine biologic repair support with subchondral mechanics; animal and pilot human studies support feasibility, but comparative human durability remains insufficiently defined[26,27]. Relatedly, 3D printing and patient-specific instrumentation may improve targeting precision and enable individualized constructs, yet the evidence base remains uneven and should be interpreted cautiously until validated in stage-stratified comparative cohorts[28,29] (Table 1).

Table 1 Stage-stratified (association research circulation osseous-informed) treatment framework for osteonecrosis of the femoral head.

Stage/risk group	Preferred treatment pathway	Key considerations
ARCO I–II (pre-collapse)	Core decompression (single large-bore vs multiple small-diameter) ± BMAC	Best-evidence window for preservation; outcomes vary with lesion size/location and non-standardized biologic processing/dose[1,3,5,8-10]
High-risk pre-collapse (large/lateral lesions; threatened subchondral integrity)	Add mechanical support: SHD + impaction grafting or selected implants (e.g., AVN cage)	Stage/lesion burden and rehabilitation strongly influence survivorship; avoid equating finite element analyses with clinical outcomes[13-16]
ARCO III (“borderline” early post-collapse)	Selected investigational preservation (e.g., PRFH) vs early transition planning	Evidence is early; cartilage–implant interface and acetabular wear remain unresolved risks[16,17]
Advanced ARCO III-IV/secondary arthritis	THA	Define a transition point; emphasize preoperative planning in complex anatomy[20]

BMAC: Bone marrow aspirate concentrate; AVN: Avascular necrosis; SHD: Surgical hip dislocation; THA: Total hip arthroplasty; PRFH: Replacement of the femoral head; ARCO: Association Research Circulation Osseous.

A second innovation axis is risk stratification. Imaging analytics (radiomics/deep learning) have been proposed to predict collapse and may ultimately improve treatment allocation; however, these tools require external validation and demonstration of incremental value beyond established staging and lesion quantification before routine clinical deployment[30].

For “borderline” early post-collapse disease (ARCO stage III), patient-specific partial femoral head replacement represents a distinct innovation aimed at restoring local head contour through targeted segment resection and implantation. Early clinical series report short-term functional improvement, but remain limited by small cohorts and short follow-up, while finite element analyses provide mechanistic hypotheses rather than survivorship evidence[16,17]. Importantly, PRFH introduces a prosthesis-native cartilage interface, and the risk of altered contact mechanics and acetabular cartilage wear should be stated explicitly as a key unresolved failure mechanism requiring longer-term, comparative evaluation[16,17].

Finally, preservation-focused algorithms should explicitly recognize that a subset of patients will progress and require arthroplasty. In the context of modern THA, the “innovation” is not to broaden arthroplasty discussion in a preservation review, but to ensure an evidence-based transition point and emphasize that outcomes in complex anatomy benefit from meticulous preoperative planning (templating, component positioning strategy, and reconstruction planning)[20]. Methodologically, the field would benefit most from standardized reporting (stage, lesion size/location, biologic dose/processing, delivery technique, rehabilitation protocol) and harmonized endpoints (collapse, THA conversion, imaging progression, PROMs), enabling robust stage-stratified comparisons and clinically deployable algorithms[1,5,10,21].

TOWARDS AN UPDATED TREATMENT FRAMEWORK

An updated ONFH framework should be stage-based and incorporate lesion size/location to match the dominant determinants of collapse and survivorship. The central principle remains early intervention prior to collapse, while explicitly distinguishing clinically supported strategies from approaches supported mainly by mechanistic rationale or early series[1,3,5]. Given ongoing heterogeneity in staging, lesion quantification, biologic preparation/dose, technique, and endpoints, standardized reporting is essential to enable meaningful comparisons and algorithm refinement[5,9,10].

Pre-collaose (ARCO I–II)

CD is the foundational procedure; technique (single large-bore vs multiple small-diameter drillings) should prioritize accurate lesion targeting with minimal iatrogenic weakening[1,3,5,8]. Biologic augmentation, most commonly BMAC, may be added to improve the reparative milieu, but outcomes vary with non-standardized processing/dose, delivery method, and lesion characteristics; these variables should be reported explicitly[9,10]. Robot guidance may be used as a precision adjunct, and arthroscopy should be reserved for selected cases with suspected intra-articular pathology rather than routine use[11,12]. Table 1 summarizes this ARCO-informed, lesion-risk–stratified framework.

High-risk pre-collapse (large/lateral lesions; threatened subchondral integrity)

When mechanical failure risk is high despite absence of radiographic collapse, CD ± biologics may be insufficient and strategies that provide subchondral support should be considered. Options include structural reconstruction (SHD with fenestration/debridement and impaction grafting) and selected internal support implants (e.g., AVN cage), recognizing strong dependence on stage/lesion burden and rehabilitation[13,15]. Evidence from injectable synthetic substitutes cautions that some fillers lack durable mechanical benefit, particularly in advanced patterns[14]. Finite element analyses should be presented as mechanistic hypotheses and not as evidence of clinical superiority[16].

Early post-collapse (“borderline” ARCO III)

After collapse, preservation is less predictable because congruency and load transfer are compromised[1,3,5]. Patient-specific partial femoral head replacement has been proposed to restore local head contour; early clinical results are promising but limited by small cohorts and short follow-up, while finite element analyses do not establish survivorship[16,17]. The prosthesis–native cartilage interface and potential acetabular wear should be stated as key unresolved failure mechanisms requiring longer-term comparative evaluation[16,17].

Late collapse/secondary arthritis (advanced ARCO III–IV)

When structural failure and/or degenerative change is established, the framework should define a clear transition to THA rather than repeated low-yield preservation attempts[1,3,5]. Although arthroplasty technique is outside the scope of a preservation review, in complex anatomy, outcomes may be optimized by meticulous preoperative planning[20].

Future studies should be stage-stratified and standardize reporting of lesion size/location, biologic characterization and dose, delivery technique, and rehabilitation protocol, using harmonized endpoints (collapse, THA conversion, imaging progression, validated PROMs)[5,9,10]. Emerging enabling technologies (extracellular vesicles/exosomes, scaffold constructs, 3D printing/patient-specific guides, imaging analytics) should be evaluated within such pathways and not presented as established care[21-30].

CONCLUSION

Hip preservation in ONFH is most reliable before collapse: CD remains foundational, with improved but variable outcomes when combined with BMAC and lesion-based patient selection[1,3,5,9,10]. Structural support procedures and implants may be considered for high-risk pre-collapse lesions, but durability is stage- and lesion-dependent and not all substitutes perform well long term[13-15]. For ARCO III disease, PRFH is promising yet investigational; long-term survivorship and risks related to the cartilage–implant interface and potential acetabular wear require comparative follow-up[16,17]. Advanced collapse/arthritis warrants timely transition to THA, where careful preoperative planning remains important in complex anatomy[20]. Future progress hinges on standardized, stage-stratified studies with harmonized endpoints and transparent reporting of lesion metrics, biologic dose/processing, technique, and rehabilitation; emerging technologies should be integrated only after validation[5,9,10,21-30].