Analysis of the efficacy of autologous adipose-derived stromal vascular fraction and calcium phosphate bone cement combined with core decompression in patients with femoral head necrosis: a retrospective study

Abstract

Background

Osteonecrosis of the femoral head (ONFH) is a progressive disorder characterized by impaired perfusion, inflammation, neural dysregulation, and structural failure of the femoral head. While core decompression (CD) is commonly used for joint preservation, its effectiveness remains limited, particularly in the absence of adequate structural support and biological modulation. Adipose-derived stromal vascular fraction (SVF) has emerged as a potential biological adjunct due to its angiogenic, immunomodulatory, and regenerative properties. This study aimed to evaluate the clinical outcomes of combining autologous SVF and calcium phosphate cement (CPC) with CD in patients with ONFH.

Methods

We retrospectively analyzed 148 patients (219 hips) with ONFH treated between 2009 and 2022. Eighty-five hips underwent CD alone (CD group), and 134 hips received SVF combined with CPC and CD (SVF + CPC + CD group). Radiographic progression and conversion to total hip arthroplasty (THA) were assessed according to the Association Research Circulation Osseous (ARCO) staging system. Hip survival was evaluated using Kaplan–Meier analysis, and multivariable Cox proportional hazards regression was performed to identify factors associated with conversion to THA. Clinical outcomes were assessed using the Harris Hip Score (HHS), visual analogue scale (VAS), and the 36-Item Short Form Health Survey (SF-36).

Results

The SVF + CPC + CD group demonstrated significantly lower radiographic progression (33.6% vs. 55.3%, P < 0.001) and THA conversion rates (20.1% vs. 35.3%, P = 0.013) compared with the CD group. Kaplan–Meier analysis showed superior THA-free survival in the SVF + CPC + CD group. In multivariable Cox regression analysis, treatment with SVF + CPC + CD was independently associated with a reduced risk of conversion to THA, whereas higher ARCO stage was associated with increased failure risk. Smoking status showed a borderline association with THA conversion. At final follow-up, patients treated with SVF + CPC + CD reported lower pain scores, improved hip function, and better outcomes in selected quality-of-life domains compared with CD alone (all P < 0.05).

Conclusion

In this retrospective cohort, combining core decompression with structural augmentation and biological modulation using SVF and CPC was associated with improved mid-term radiographic and clinical outcomes compared with CD alone. These findings suggest that an integrated mechanical–biological strategy may offer advantages for hip preservation in selected patients with ONFH; however, prospective randomized studies with longer follow-up are required to confirm efficacy and define optimal indications.

Introduction

Osteonecrosis of the femoral head (ONFH) is a progressive and debilitating disorder characterized by compromised blood supply, bone cell death, and eventual structural collapse of the femoral head [1]. Clinically, ONFH leads to chronic hip pain, functional limitation, and a high likelihood of conversion to total hip arthroplasty (THA), particularly in young and middle-aged adults [2]. Despite advances in surgical techniques, preserving the native hip joint before collapse remains a major clinical challenge [3, 4].

Traditionally, the pathogenesis of ONFH has been viewed primarily through a mechanical and vascular lens, emphasizing ischemia, increased intraosseous pressure, and impaired structural integrity [5, 6]. However, accumulating evidence suggests that ONFH is not solely a disorder of blood flow or biomechanics, but rather a complex, multisystem process involving inflammation, angiogenic failure, and neurovascular dysregulation [7]. Bone is now recognized as a highly innervated and neuroactive organ, in which neural signaling plays a critical role in bone remodeling, pain perception, and tissue repair [8].

Experimental and clinical studies have demonstrated that neuropeptides such as substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP), and neuropeptide Y (NPY) are actively involved in bone metabolism and nociception [9, 10]. In hormone-related bone loss models, including ovariectomized osteoporosis models, alterations in these neuropeptides occur in parallel with bone degeneration and inflammatory activation [10]. These neurogenic changes not only contribute to pain sensitization but also influence osteogenesis, angiogenesis, and immune regulation [11]. Such findings suggest that neural and inflammatory signaling pathways may represent important, yet underappreciated, contributors to the progression of ONFH and the persistence of symptoms.

From a therapeutic perspective, core decompression (CD) remains one of the most commonly employed joint-preserving procedures for early-stage ONFH [12]. By reducing intraosseous pressure and improving local perfusion, CD aims to slow disease progression [13]. Nevertheless, CD alone has shown inconsistent outcomes, particularly in patients with extensive necrosis or compromised bone quality, where insufficient mechanical support and delayed biological repair may predispose to femoral head collapse [14].

To address these limitations, various adjunctive strategies have been explored [15].Calcium phosphate bone cement (CPC) provides immediate structural augmentation and may help restore subchondral support following decompression [16, 17]. However, mechanical stabilization alone does not directly address the hostile biological microenvironment of necrotic bone, which is characterized by inflammation, hypoxia, impaired angiogenesis, and altered neurogenic signaling [18, 19]. Consequently, interest has increasingly shifted toward biological approaches that can modulate the local microenvironment and promote tissue regeneration.

Adipose-derived stromal vascular fraction (SVF) represents a heterogeneous cell population containing mesenchymal stromal cells, endothelial progenitor cells, immune-regulatory cells, and a rich array of paracrine factors [20–23]. Unlike culture-expanded cell products, SVF can be obtained rapidly without in vitro expansion, offering practical advantages for clinical application [20, 24]. Compared with bone marrow–derived cell concentrates, SVF provides a higher cell yield with less donor-site morbidity and a cellular composition particularly suited to angiogenic and immune-modulatory functions [25]. In the context of ONFH, where inflammation, vascular insufficiency, and neurovascular dysfunction coexist, SVF may plausibly exert therapeutic effects by enhancing angiogenesis, modulating inflammatory and immune responses, and indirectly influencing neurogenic signaling within bone [26].

Taken together, these considerations support a treatment paradigm that integrates mechanical decompression, structural augmentation, and biological modulation. Rather than viewing ONFH as a purely mechanical failure, such an approach acknowledges the interplay between vascular, inflammatory, neural, and structural factors in disease progression and symptom generation [27]. However, clinical evidence evaluating this integrated strategy remains limited [28].

Therefore, the purpose of this study was to investigate the clinical efficacy of autologous SVF combined with CPC and core decompression in patients with ONFH. We hypothesized that this combined mechanical–biological approach would result in improved radiographic outcomes, reduced conversion to THA, and better pain and functional outcomes compared with core decompression alone.

Materials and methods

Ethics statements

This study is a retrospective study that has been approved by the Medical Ethics Committee of the General Hospital of the People's Liberation Army of China, with approval number 2023KY088-KS001. The experiment adheres to the principles set forth in the Declaration of Helsinki, and all participants were formally informed of the purpose and content of the research and signed an informed consent form.

Patient selection

A total of 148 patients with ONFH (219 hips) who received hip preservation treatment at the General Hospital of the People's Liberation Army from November 2009 to April 2022 were included. Preoperative routine imaging examinations were performed, including standard anteroposterior and lateral X-ray examinations, bilateral hip CT scans, and bilateral hip MRI scans, and staging was conducted according to the 2019 ARCO staging criteria [29].Exclusion criteria were as follows: (1) follow-up duration of less than 36 months; (2) presence of severe systemic diseases or psychiatric disorders that precluded surgery or reliable follow-up, as determined by the treating physician; (3) history of prior hip-preserving procedures on the affected hip, including but not limited to vascularized or non-vascularized bone grafting, osteotomies, or other joint-preserving surgeries; and (4) inability or unwillingness to tolerate surgery or comply with postoperative follow-up.

Importantly, patients who underwent total hip arthroplasty (THA) within 36 months after surgery were not excluded. Conversion to THA was defined as a study endpoint and was included in the outcome analysis as treatment failure.Given the potential impact of autoimmune diseases on the pathogenesis and progression of osteonecrosis of the femoral head, we further classified steroid-related etiologies according to the underlying primary diseases. The distribution of these autoimmune diseases and their corresponding ARCO stages were compared between the two treatment groups to assess baseline balance.

Treatment allocation was not randomized in this retrospective study. The choice between core decompression alone and SVF combined with CPC and CD was primarily influenced by the treatment era, evolving surgical techniques, availability of SVF processing, and shared decision-making between surgeons and patients. Earlier in the study period, core decompression alone was more commonly performed, whereas the combined SVF + CPC + CD strategy was increasingly adopted in later years as surgical experience and institutional resources developed.

Treatment allocation was not determined solely by ARCO stage. Patients across different ARCO stages, including stage IIIB and IV, were included in both groups when hip preservation was considered clinically reasonable and total hip arthroplasty was deferred due to patient preference, age, or functional demands.

Among the 148 included patients, 71 patients presented with bilateral osteonecrosis of the femoral head, accounting for a total of 219 hips analyzed. In all bilateral cases, the same surgical procedure was applied to both hips. Treatment allocation was therefore consistent at the patient level.

ARCO staging was assessed separately for each hip and was symmetrical in some patients and asymmetrical in others. Consequently, treatment decisions were based on overall clinical judgment rather than strict symmetry of ARCO staging.

Surgical procedures

Control group: Treatment with simple core decompression only.

SVF + CPC + CD group:

SVF extraction and preparation:

A 0.3 cm incision is made in the patient's abdomen, and approximately 300 ml of swelling solution (500 ml of saline + 1 mg of norepinephrine + 5 ml of 2% lidocaine hydrochloride) is injected into the subcutaneous fat layer. After 5 min, about 50 ml of autologous fat tissue is extracted using a liposuction needle. Centrifuge at 900 rpm for 1 min to extract the upper layer of adipose tissue after centrifugation, and digest with collagenase (Roche, concentration of 5 mg/ml, total volume of 1 ml) at 37℃ for 30 min. During the digestion process, shake intermittently to ensure complete digestion of the fat. After digestion is complete, centrifuge again at 1500 rpm for 10 min. Remove the upper oily layer and most of the lower blood, leaving a small amount of blood and undigested fat for later use. Then centrifuge again at 1500 rpm for 10 min to remove the supernatant. To ensure sufficient SVF cells remain in the femoral head, resuspend the bottom layer of SVF cells in 1–2 ml of undigested fat and a small amount of blood to prepare a cell suspension of approximately 3–5 × 10^8/ml for later use (Fig. 1).

Fig. 1.

Cell suspension made from SVF cells, undigested fat, and a small amount of blood

Use the G-arm X-ray machine for fluoroscopic localization, drill two 2.5 mm guide pins into the necrotic area of the femoral head from the lateral aspect of the affected femur (Fig. 2A), introduce the bone graft sleeve, scrape away some necrotic bone, and repeatedly rinse the necrotic area with saline until the rinse fluid becomes clear (Fig. 2B).Inject 5 ml of processed SVF into the necrotic area along the bone grafting sleeve and implant CPC into the ONFH area. X-ray fluoroscopy shows satisfactory support in the necrotic area. Withdraw the bone grafting sleeve (Fig. 2C), and after confirming no metallic foreign bodies remain through another X-ray fluoroscopy, rinse the wound with saline, disinfect the wound edges with alcohol, and perform full-thickness suturing of the skin (Figs. 3 and 4).

Fig. 2.

A Drill two 2.5 mm guide pins into the necrotic area on the lateral side of the proximal femur on the affected side. B Import the bone grafting sleeve, scrape away some necrotic bone, and repeatedly rinse the necrotic area with saline until the rinsing fluid becomes clear. C Inject 5 ml of processed SVF into the necrotic area along the bone graft sleeve and implant CPC into the ONFH area. X-ray fluoroscopy shows satisfactory support in the necrotic area, and withdraw the bone graft sleeve

Fig. 3.

A case of post-operative follow-up for 3 years of ONFH hip, from left to right, are pre-operative, 3 days post-operative, 1 year, 2 years, and 3 years X-ray images

Fig. 4.

A case of ONFH hip with a 2-year postoperative follow-up, from left to right, showing preoperative, 3 days postoperative, 1 year, and 2 year CT images. Figures A-E are coronal CT images of the left hip at different levels after three-dimensional reconstruction

Clinical and imaging assessment

Follow-up once every 4 months in the first year after surgery, once every 6 months in the second year, and once every 12 months after two years. During follow-up, the hip function score [30] (Harris hip score, HHS), visual analogue scale [31] (VAS), and quality of life score [32] (36-Item Short Form Health Survey, SF-36) are used, along with pelvic anteroposterior X-rays and hip CT and MRI examinations to assess the recovery of hip function. Based on the ARCO staging, we define any progression of one stage or more for each hip as having radiological progression. For patients undergoing THA, we calculate the hip replacement rate, with the preoperative assessment serving as the last follow-up.

Statistical analysis

Statistical analysis was completed using IBM SPSS 25.0 and independently verified by the second researcher. Categorical data were expressed as numbers and percentages, while continuous data were presented as means and standard deviations. Continuous data following a normal distribution were analyzed using independent samples t-test, and categorical data were analyzed using chi-square test.Kaplan–Meier survival curves were used to show the proportion of hips that did not undergo THA at different time points in each treatment group, and Log-Rank test was used for difference analysis. Cox multivariate regression model was used to explore the influencing factors of the survival process. All hypothesis tests were two-tailed, and P < 0.05 was considered statistically significant.All survival and regression analyses were performed at the hip level.

Results

Baseline characteristics of the population

A total of 232 patients were initially screened. In the CD group, 108 patients were enrolled, of whom 53 were excluded due to loss to follow-up. In the SVF + CPC + CD group, 124 patients were enrolled, of whom 31 were excluded for the same reason. Ultimately, 148 patients (219 hips) were included in the final analysis, with a mean follow-up duration of approximately 40 months.

Baseline demographic and clinical characteristics are summarized in Table 1. No statistically significant differences were observed between the two groups with respect to age, sex, body mass index, disease duration, smoking status, limping, hip involvement, ARCO stage distribution, physical examination findings (Patrick sign, Thomas test, Trendelenburg test, log roll test), or hip flexion angle (all P > 0.05).

Table 1.

Baseline demographic and clinical characteristics of hips

	CD (n = 85 hips)	SVF + CPC + CD group (n = 134 hips)	χ2/t value	P value
Age (years)	39.3 ± 9.3	36.6 ± 12.2	−1.328	0.078
Male/Female	68/17	118/16	2.640	0.104
BMI (kg/m2)	24.6 ± 3.5	24.6 ± 3.2	−0.774	0.882
Follow-up time (month)	40.0 ± 14.2	41.4 ± 9.4	−0.221	0.825
Hip involved			2.013	0.156
Unilateral (n)	25	52
Bilateral (n)	30	41
Total number	85	134
Etiology			—	0.022
Idiopathic	32(37.6)	61(38.8)
Alcohol	29(34.1)	37(27.6)
Steroid	24(28.2)	26(19.4)
Traumatic	0(0)	10(14.2)
ARCO Stage			4.936	0.294
Stage I	8(9.8)	6(4.5)
Stage Ⅱ	40(47.1)	62(46.3)
Stage ⅢA	31(36.5)	51(38.1)
Stage ⅢB	4(4.7)	10(7.5)
Stage Ⅳ	2(2.4)	5(3.7)
Patrick sign	67(78.8)	112(83.6)	0.789	0.374
Tomas test	30(35.3)	43(32.1)	0.240	0.624
Trendelenburg test	12(14.1)	24(17.9)	0.545	0.461
Log roll test	28(32.9)	33(24.6)	1.789	0.181
Hip flexion angle	102.1 ± 16.4	100.9 ± 13.9	−0.610	0.543

Abbreviations: BMI Body mass index, ARCO Association Research Circulation Osseous

^aValues are presented as mean ± standard deviation or number (percentage)

^bContinuous variables were compared using the independent samples t-test

^cCategorical variables were compared using the Chi-square test or Fisher’s exact test, as appropriate.For etiology, Fisher’s exact test was applied due to small cell counts

^dt values represent differences between groups calculated as SVF + CPC + CD group minus CD

The distribution of etiological factors differed significantly between the two groups (P = 0.022). Among patients with steroid-induced ONFH, autoimmune-related diseases were present in both groups with comparable distributions, and no baseline imbalance was observed. The observed difference in etiology likely reflects temporal variation and evolving clinical practice during the prolonged enrollment period rather than intentional etiological selection.

Follow-up outcomes

At final follow-up, imaging progression occurred in 55.3% (47/85) of hips in the CD group and 33.6% (45/134) in the SVF + CPC + CD group, representing a statistically significant difference (P < 0.001). Conversion to total hip arthroplasty occurred in 35.3% (30/85) of hips in the CD group and 20.1% (27/134) in the SVF + CPC + CD group, which was also significantly different between groups (P = 0.013). Both imaging progression and THA rates were lower in the SVF + CPC + CD group (Table 2).

Table 2.

Imaging progress rate and THA rate

Group	Number of hip joints	Number of progress	Number of THA	Progress rate	THA rate
CD	85	47	30	55.3%	35.3%
SVF + CPC + CD group	134	45	27	33.6%	20.1%
P value				0.001	0.013

^aCategorical variables were compared using the Chi-square test or Fisher’s exact test, as appropriate

Outcomes were further analyzed according to preoperative ARCO stage. Across most stages, both imaging progression and THA rates were lower in the SVF + CPC + CD group compared with the CD group. In ARCO stage IV, the THA rate in the SVF + CPC + CD group was higher than that in the CD group; however, this finding should be interpreted with caution due to the limited number of stage IV cases in the CD group (Table 3).

Table 3.

Progression rates of different stages of ARCO imaging and THA rates

CD group	Number of hips	Number of progress	Number of THA	Progress rate	THA rate
Stage I	10	2	1	20%	10%
Stage Ⅱ	40	17	9	42.5%	22.5%
Stage ⅢA	29	22	16	75.9%	55.2%
Stage ⅢB	4	4	3	100%	75%
Stage Ⅳ	2	2	1	100%	50%
SVF + CPC + CD group	Number of hips	Number of progress	Number of THA	Progress rate	THA rate
Stage I	6	0	0	0%	0%
Stage Ⅱ	62	13	4	21.0%	6.5%
Stage ⅢA	51	22	15	43.1%	29.4%
Stage ⅢB	10	7	5	70%	50%
Stage Ⅳ	5	3	3	60%	60%

For Kaplan–Meier survival analysis, ARCO stage IIIB and IV were combined due to small sample sizes

^aCategorical variables were compared using the Fisher’s exact test due to small sample sizes in some subgroups

Kaplan–Meier survival analysis stratified by ARCO stage demonstrated consistently higher THA-free survival in the SVF + CPC + CD group compared with the CD group in ARCO stage I, II, and IIIA (Fig. 5A–C). In advanced-stage disease (ARCO IIIB/IV), the combined-treatment group showed a trend toward improved hip survival; however, this comparison was underpowered due to limited sample size (Fig. 5D).

Fig. 5.

Kaplan–Meier curves for THA-free survival stratified by ARCO stage. A Stage I; B Stage II; C Stage IIIA; D Advanced stage IIIB/IV

Overall hip survival analysis using conversion to total hip arthroplasty as the endpoint further confirmed superior THA-free survival in the SVF + CPC + CD group compared with the CD group (log-rank test, P = 0.006) (Fig. 6).

Fig. 6.

Cumulative proportion of patients not accepting THA treatment during follow-up

Multivariable Cox proportional hazards regression analysis was performed to identify independent predictors of conversion to total hip arthroplasty. The model included demographic variables (age and sex), body mass index, disease duration, smoking status, limping, hip involvement, etiology, ARCO stage, physical examination findings (Patrick sign, Thomas test, Trendelenburg test, log roll test), hip flexion angle, and treatment group.

After adjustment for all covariates, treatment group remained an independent predictor of hip survival. Patients treated with SVF combined with CPC and core decompression exhibited a significantly lower risk of conversion to THA compared with those treated with core decompression alone (HR = 0.42, 95% CI 0.23–0.74, P = 0.003).

ARCO stage was also independently associated with THA risk. Compared with ARCO stage I, ARCO stage IIIA was associated with a significantly increased risk of conversion to THA (HR = 8.33, 95% CI 1.14–61.0, P = 0.009). Although higher hazard ratios were observed for ARCO stage IIIB and IV, these associations did not reach statistical significance, likely due to limited sample size.

Etiology was not independently associated with conversion to THA after adjustment for disease stage, treatment group, and other clinical variables (all P > 0.05). Among other covariates, smoking status and positive Patrick sign showed borderline associations with THA risk, whereas age, sex, body mass index, disease duration, hip involvement, and other physical examination findings were not independently predictive of conversion to THA (Table 4).

Table 4.

Multivariable Cox proportional hazards regression for conversion to THA

Variable	Reference category	HR	95.0% CI	P value
Treatment group	CD	0.42	0.23–0.74	0.003
Age	—	1.03	0.99–1.05	0.133
Sex	Female	1.29	0.53–3.17	0.579
BMI (kg/m2)	—	1.05	0.95–1.15	0.346
Disease course (months)	—	1.02	1.00–1.04	0.073
Smoking	No	1.84	0.93–3.65	0.082
Limping	No	1.39	0.75–2.57	0.291
Hip involvement	Unilateral	1.33	0.71–2.48	0.378
Etiology	(reference: Idiopathic)
├─ Alcohol		1.31	0.72–2.42	0.368
├─ Steroid		1.52	0.74–3.12	0.126
└─ Trauma		1.39	0.74–4.55	0.184
ARCO Stage	(reference:Stage I)
├─ Stage II		1.97	0.28–13.5	0.511
├─ Stage IIIA		8.33	1.14–61.0	0.009
├─ Stage IIIB		2.46	0.50–12.0	0.131
└─ Stage IV		4.22	0.87–20.5	0.071
Patrick sign	No	2.61	0.99–6.85	0.052
Tomas test	No	1.16	0.65–2.06	0.955
Trendelenburg test	No	0.91	0.38–2.15	0.840
Log roll test	No	1.93	0.84–4.41	0.184
Hip flexion angle	—	1.01	0.98–1.03	0.630

Variables were analyzed using a multivariate Cox proportional hazards regression model

Etiology was included as a categorical covariate with idiopathic osteonecrosis as the reference group

^aHR Hazard ratio, CI Confidence interval

Functional outcomes

Functional outcomes were assessed using VAS, HHS, and SF-36 scores. At final follow-up, the SVF + CPC + CD group demonstrated significantly lower VAS scores and higher HHS scores compared with the CD group (both P < 0.001).

In addition, the SVF + CPC + CD group showed significantly better outcomes in several SF-36 domains, including bodily pain, general health, role-emotional functioning, and health change (all P < 0.05) (Table 5).

Table 5.

Preoperative and postoperative functional outcomes

	CD group	SVF + CPC + CD group	χ2/t value	P value
Preoperative VAS	3.9 ± 1.1	4.2 ± 1.5	1.305	0.193
Last follow-up VAS	2.4 ± 2.3	1.3 ± 1.5	−3.998	0.001
Preoperative HHS	67.2 ± 11.3	65.9 ± 13.6	−0.744	0.458
Last follow-up HHS	67.4 ± 17.6	75.8 ± 17.8	3.396	0.001
Last follow-up SF-36
Physical function	55.8 ± 13.5	51.8 ± 15.2	−1.963	0.051
Role-physical	26.2 ± 22.1	31.2 ± 24.0	1.541	0.125
Bodily pain	67.1 ± 13.0	72.5 ± 14.9	2.745	0.007
General health	57.5 ± 14.5	65.4 ± 11.0	4.569	0.001
Vitality	64.9 ± 10.1	66.4 ± 11.5	0.974	0.331
Social function	65.5 ± 14.9	67.8 ± 13.4	0.997	0.229
Role-emotion	40.8 ± 31.4	51.7 ± 30.2	2.575	0.011
Mental health	58.6 ± 12.3	60.97 ± 12.9	1.355	0.177
Health change	47.4 ± 33.6	63.1 ± 33.0	3.472	0.001

Abbreviations: VAS Visual analog scale, HHS Harris hip score, SF-36 36-Item Short Form Health Survey

^aContinuous variables are presented as mean ± standard deviation

^bBetween-group comparisons were performed using the independent samples t-test

Safety and complications

No instances of pulmonary embolism, fat embolism syndrome, or symptomatic vascular occlusion were observed following SVF harvesting, processing, or intra-osseous implantation in either group.

Postoperative hip joint infections occurred in three hips in the CD group and six hips in the SVF + CPC + CD group. All infections were localized surgical-site infections and were successfully managed with standard treatment, including antibiotic therapy and local wound care. No patient developed systemic infection, sepsis, or required revision surgery related to infection.

No complications related to abdominal adipose tissue harvesting were observed. Specifically, no cases of abdominal infection, hematoma, seroma, or delayed wound healing occurred. Apart from the hip joint infections described above, no other procedure-related complications were recorded.

Discussion

The present study demonstrates that core decompression augmented with stromal vascular fraction and calcium phosphate cement is associated with improved hip survival and a lower risk of conversion to total hip arthroplasty compared with core decompression alone. These findings suggest that combining biological modulation with mechanical support may provide additive benefits for hip preservation in patients with osteonecrosis of the femoral head.

The rationale for this combined strategy extends beyond structural decompression [33].Osteonecrosis of the femoral head is characterized by a complex pathological microenvironment involving ischemia, inflammation, impaired angiogenesis, and altered neurovascular signaling [34]. Stromal vascular fraction represents a heterogeneous cell population containing mesenchymal stromal cells, endothelial progenitor cells, and immune-regulatory components, which may collectively promote angiogenesis and tissue repair primarily through paracrine mechanisms [35]. In this context, SVF may help modulate the inflammatory and hypoxic milieu of necrotic bone, complementing the mechanical benefits of decompression and structural augmentation [36].

Pain relief and functional improvement observed in the SVF + CPC + CD group may reflect not only delayed structural collapse but also modulation of local inflammatory and neurogenic signaling pathways [37, 38]. Experimental and clinical evidence suggests that neuropeptides and neurovascular interactions play a role in bone degeneration and repair [9]. Therefore, biological adjuncts such as SVF may contribute to symptomatic improvement by influencing both tissue regeneration and pain-related pathways, linking radiographic preservation with patient-reported outcomes [39, 40].These mechanistic considerations remain hypothesis-generating and require further experimental validation.

Disease stage remained a critical determinant of treatment outcome [41, 42]. In the present study, patients with ARCO stage IIIA exhibited a significantly higher risk of conversion to total hip arthroplasty compared with those at stage I, even after adjustment for treatment group and other clinical variables. Although trends toward improved hip survival were observed in advanced stages (ARCO IIIB and IV) in the combined-treatment group, these subgroup analyses were limited by small sample sizes. Accordingly, while augmented decompression may offer a potential delay in disease progression for select advanced-stage patients, total hip arthroplasty remains the standard of care for symptomatic ARCO stage IIIB and IV disease, and the present findings should not be interpreted as evidence to broadly expand hip preservation indications in these stages [43].

Etiology was included as a covariate in multivariable analysis but was not independently associated with conversion to total hip arthroplasty after adjustment for disease stage, treatment group, and other clinical factors. This finding suggests that, within the limitations of the current cohort, disease severity at presentation and treatment strategy appear to exert a greater influence on outcomes than etiology alone.

Nevertheless, the biological heterogeneity underlying different etiological mechanisms warrants further investigation in larger, prospectively designed studies.

With regard to safety, no cases of pulmonary embolism, fat embolism syndrome, or symptomatic vascular occlusion were observed following SVF harvesting, processing, or intra-osseous implantation. Postoperative infection represented the main complication in both groups, occurring at the hip joint in a small number of cases. Importantly, no infections were observed at the abdominal donor site, and all hip infections were localized and successfully managed with standard treatment. The slightly higher number of infections in the combined-treatment group may be related to increased procedural complexity rather than the biological properties of SVF itself. Overall, these findings suggest that SVF harvesting and implantation can be performed safely when standardized techniques and appropriate precautions are applied.

Several limitations of this study should be acknowledged. The retrospective design introduces the potential for selection bias, and treatment allocation was influenced by treatment era and clinical decision-making rather than randomization. The absence of a core decompression plus calcium phosphate cement–only control group limits the ability to isolate the specific contribution of SVF relative to mechanical augmentation alone. In addition, subgroup analyses in advanced ARCO stages were underpowered, and rare adverse events cannot be fully excluded. Finally, although follow-up was sufficient to assess mid-term outcomes, longer-term results are needed to determine the durability of hip preservation.

The findings of this study are consistent with the concept that integrating biological augmentation with mechanical decompression may enhance hip preservation outcomes in osteonecrosis of the femoral head, particularly in early and intermediate stages. Prospective, randomized studies are warranted to further define optimal indications, clarify the independent contribution of biological adjuncts, and establish long-term safety and efficacy.

Conclusion

In conclusion, this study suggests that combining core decompression with calcium phosphate cement and autologous stromal vascular fraction may improve mid-term hip preservation and symptom control in patients with osteonecrosis of the femoral head. Rather than acting through mechanical support alone, this integrated approach may influence the local biological microenvironment by potentially addressing inflammation, impaired angiogenesis, and neurovascular dysfunction that contribute to disease progression and pain generation.

While the combined strategy appears promising, particularly in early and intermediate stages, total hip arthroplasty remains the gold standard for symptomatic advanced-stage disease. Accordingly, the present findings should be interpreted as evidence supporting a multimodal, biologically informed treatment concept rather than definitive proof of superiority. Further prospective, randomized, and mechanistic studies are required to validate these observations and to clarify the long-term role of biological adjuncts in hip-preserving treatment paradigms.

Abbreviations

ADSVF

Adipose-derived stromal vascular fraction

ARCO

Association research circulation osseous

BMI

Body mass index

CD

Core decompression

CI

Confidence interval

CPC

Calcium phosphate cement

HHS

Harris hip score

HR

Hazard ratio

KM

Kaplan–Meier

ONFH

Osteonecrosis of the femoral head

RA

Rheumatoid arthritis

SF-36

36-Item short form health survey

SLE

Systemic lupus erythematosus

SVF

Stromal vascular fraction

THA

Total hip arthroplasty

VAS

Visual analogue scale

Authors’ contributions

Junming Zhang and Tingjie Zhao contributed equally to this work. Junming Zhang and Jiang Peng conceived and designed the study. Tingjie Zhao and Yanbin Wu performed the data collection and statistical analysis. Yazhou Li, Zexian Liu, Tao Qian, Zhaodi Mi, and Biao Ma participated in patient enrollment, surgical procedures, and clinical follow-up. Yun Bai, Ying He, Jiazhou Wu, Jialiang You, Liang Zuo, and Endong Luo assisted with data interpretation and manuscript preparation. Dawei Zhang and Jiang Peng supervised the study and critically revised the manuscript for important intellectual content. All authors read and approved the final manuscript.

Funding

This work was funded by National Key Research and Development Program (2024YFA1108600);

Natural Science Foundation of Beijing (ID:L242042).

Data availability

The datasets generated and/or analyzed during the current study are not publicly available due to limitations of ethical approval involving the patient data and anonymity but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Medical Ethics Committee of the General Hospital of the People's Liberation Army of China.e (Approval No: 2023KY088-KS001,approval date: 18 July 2023). The experiment adheres to the principles set forth in the Declaration of Helsinki, and all participants were formally informed of the purpose and content of the research and signed an informed consent form.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.