Outcomes of the conservative hip preservation treatment in patients with osteonecrosis of the femoral head: With 4-year follow-up

Abstract

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a prevalent clinical condition, and as the affected population becomes younger and more widespread, an increasing number of patients prefer to retain their own hip joints. In comparison to joint replacement and hip-preserving surgeries, conservative hip preservation treatment is gaining more recognition from both clinicians and patients.

AIM

To observe the clinical efficacy and influencing factors of conservative hip preservation treatment for patients with ONFH.

METHODS

A total of 73 patients (119 hips) were included, and patients were grouped based on Association Research Circulation Osseous (ARCO) stage, Japanese Investigation Committee (JIC) classification, lesion size, and collapse degree. The clinical efficacy of conservative hip preservation treatment was evaluated from two aspects: Radiological progression and clinical functional scores [Harris Hip Score, Western Ontario and McMaster Universities Arthritis Index (WOMAC), international Hip Outcome Tool 12 (iHOT-12), and visual analogue scale (VAS)]. Analyzing the success rate of conservative hip preservation based on conversion to total hip arthroplasty or hip preservation surgery.

RESULTS

In this retrospective cohort study, we retrospectively analyzed 73 patients (119 hips) with an average follow-up time of 53.58 ± 26.80 (18-129) months. The overall success rate of hip preservation is 90.76%. The success rates of hip preservation in ARCO I-II, IIIa, and IIIb were 97.67%, 91.53%, and 70.59%, respectively (P < 0.05). The success rates of hip preservation for JIC A-B, C1, and C2 were 93.37%, 92.59%, and 77.78%, respectively (P < 0.05). The success rates of hip preservation with collapse degree ≤ 2 mm and > 2 mm were 94.12% and 70.59%, respectively (P < 0.05). There was no significant difference in the success rate of hip preservation between different lesion sizes. In terms of clinical function, the Harris Hip Score, WOMAC, iHOT-12, and VAS scores at the last follow-up were significantly better than before treatment (P < 0.05). The VAS scores of ARCO IIIa and IIIb were significantly worse than those of ARCO I and II (P < 0.05). The iHOT-12, WOMAC, and VAS scores were significantly better with the lesion size < 15% (P < 0.05). In terms of radiological results, there was significant progress in ARCO staging and collapse degree after conservative hip preservation treatment, but there was no significant difference in JIC classification and lesion size.

CONCLUSION

Conservative hip preservation treatment can effectively treat ONFH, prevent the progression of the necrosis, and significantly improve the clinical function of patients. The radiological staging and lesion size at the initial visit may help determine the prognosis of conservative hip preservation treatment.

Key Words: Hip preservation treatment; Conservative; Osteonecrosis of the femoral head; Survival with collapse; Nonsurgical

Core Tip: The clinical efficacy of conservative hip preservation treatment has always been a vague concept. This study reviewed 119 hips with an average follow-up time of 4 years (including the longest 10 years), and demonstrated through radiological findings and clinical functional scores that conservative hip preservation treatment can achieve certain long-term good therapeutic effects. It may contribute to enhancing hip joint function and postponing the need for arthroplasty.

INTRODUCTION

Osteonecrosis of the femoral head (ONFH) is a potentially disabling disease[1]. If treatment is not promptly initiated, 80% of cases will result in femoral head collapse, eventually leading to total hip arthroplasty (THA)[2]. Approximately 75% of THA can last 15 to 20 years, and only 50% can last 25 years[3]. However, younger patients are often prone to prosthetic loosening and may even require revision after THA due to their high activity and functional requirements. Therefore, selecting the appropriate treatment option for hip preservation in young patients is essential. Hip preservation therapy aims to halt the progress of necrosis, prevent collapse, and maintain the spherical shape of the femoral head and the fit of the acetabulum, thereby improving limb function and delaying or even avoiding THA[4,5]. The efficacy of hip preservation surgery remains controversial. Some studies have reported positive outcomes in patients under 50 years of age with ONFH without significant collapse[4,6-9]. However, other procedures, such as simple core decompression or tantalum rods, do not always yield satisfactory results[5,10]. Conservative hip preservation can effectively alleviate clinical symptoms, improve the range of motion, and promote the repair of osteonecrosis in patients with ONFH[11,12]. Patients with early-stage ONFH without collapse are often recommended non-surgical therapy[13]. Although conservative hip preservation was previously believed to have a limited scope, our clinical experience shows that it can also be effective for patients in the early stage following collapse. This study aimed to evaluate the clinical efficacy of conservative hip preservation for patients with ONFH. The clinical manifestations and radiological changes of patients before and after treatment were compared. In addition, the factors potentially affecting the clinical outcome were analyzed.

MATERIALS AND METHODS

Inclusion and exclusion criteria

A retrospective cohort study was conducted based on the hospital’s clinical medical records and radiological data. The study was approved by the ethics committee (No. PJ-KY-20220512-004). The diagnosis and evaluation were based on history, physical examination, radiological data, and limb function score. The inclusion criteria were as follows: (1) 18-70 years; (2) Diagnosis of ONFH; (3) No cerebrovascular or nervous system diseases; (4) Conservative hip preservation treatment; and (5) Follow-up time ≥ 12 months. The exclusion criteria were: (1) Patients who had previously undergone any hip preservation surgery; (2) Those who still needed to receive long-term steroid hormones due to other diseases; and (3) Incomplete or missing follow-up data. Patients with cerebrovascular disease may have impaired limb function, and continuous use of hormones may accelerate the progression of osteonecrosis. Conservative hip preservation treatment includes oral Chinese medicine, protective weight-bearing, physical therapy, and functional exercise.

Clinical and radiological evaluation

Patient characteristics, including age and pathogenic factors, were extracted for analysis. The outcomes were recorded at the initial and final visits, including the Harris Hip Score (HHS), international Hip Outcome Tool 12 (iHOT-12) score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and visual analogue scale (VAS). X-rays, including anteroposterior and frog views, were collected and analyzed to determine the Association Research Circulation Osseous (ARCO) staging system of ONFH staging, the Japanese Investigation Committee (JIC) classification, lesion size, and collapse degree. The clinical and radiological evaluations were independently performed by two investigators, one week apart. Patients who underwent hip preservation surgery or THA after conservative hip preservation treatment were also recorded. As of the time of writing, hip joints in this cohort that do not require arthroplasty and do not have severe clinical symptoms that need to undergo hip preservation surgery were defined as hip preservation success.

Statistical analysis

The Kolmogorov-Smirnov test was used to test the normality of the measurement data. Variables conforming to a normal distribution were expressed as mean ± SD, whereas non-normally distributed variables were expressed as medians and quartiles [median (quartile 3, quartile 1)]. The Kappa coefficient of agreement was used to test for intra- and inter-observer agreement[14]. The Fisher’s exact test or McNemar test was used to compare differences in the overall distribution of ARCO staging, JIC classification, lesion size, and collapse degree before and after treatment. Paired t-tests were carried out to compare the pre- and post-treatment differences in iHOT-12, HHS, VAS, and WOMAC scores if they were normally distributed, and the Wilcoxon test if they showed a skewed distribution. In addition, subgroup analysis was performed according to ARCO staging, JIC staging, degree of collapse, and lesion size at the initial visit. The VAS, HHS, WOMAC, and iHOT-12 results were compared among different subgroups by using an independent samples t-test, Kruskal-Wallis H-test, Mann-Whitney U-test, and one-way analysis of variance. In this study, P < 0.05 was considered statistically significant. The software SPSS 25.0 (SPSS Inc., Chicago, IL, United States) was used for data analysis.

RESULTS

A total of 73 patients (119 hips) with ONFH were included in the study according to the inclusion criteria. All the patients were treated with conservative hip preservation treatment at the First and Third Affiliated Hospital of Guangzhou University of Chinese Medicine between June 2012 and February 2023. There were 45 males and 28 females with a mean age of 39.10 ± 11.22 (21-67) years and a mean body mass index of 23.00 ± 3.48 kg/m². The average follow-up time was 53.58 ± 26.80 (18-129) months. The etiology of ONFH included trauma, steroids, alcohol, and idiopathic factors. The patients were classified before treatment according to the ARCO stage, JIC classification, lesion size, and collapse degree (Table 1). Seven patients eventually underwent THA, and four received hip preservation surgery due to exacerbation.

Table 1 Patient demographic characteristics.

Demographics	Value
Gender (male/female)	45/28
Age (years)	39.10 ± 11.22 (21-67)
BMI (kg/m2)	23.00 ± 3.48
Follow up time (month)	53.58 ± 26.80 (18-129)
THA (hips)	7
Hip preservation surgery (hips)	4
Etiology (hips)
Steroid	59
Alcohol	22
Trauma	13
Idiopathic	25
ARCO stage (hips)
Stage I	2
Stage II	41
Stage IIIa	59
Stage IIIb	17
JIC classification (hips)
Type A	12
Type B	26
Type C1	54
Type C2	27
Lesion size (hips)
< 15%	26
15%-30%	37
> 30%	56
Collapse degree (hips)
≤ 2 mm	102
> 2 mm	17

BMI: Body mass index; THA: Total hip arthroplasty; ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Consistency coefficients

High intra- and inter-observer consistency coefficients were observed at the initial visit and the final follow-up regarding the ARCO stage, JIC classification, lesion size, and collapse degree (P < 0.05, Tables 2 and 3).

Table 2 Kappa consistency coefficients for radiological data assessment at the initial visit.

Items	Intra-observer kappa		Inter-observer
	Observer 1	Observer 2	Kappa	P value
AROC stage	0.431	0.590	0.403	< 0.001
JIC classification	0.706	0.771	0.796	< 0.001
Lesion size	0.813	0.802	0.656	< 0.001
Collapse degree	0.627	0.804	0.525	< 0.001

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Table 3 Kappa consistency coefficients for radiological data at the final follow-up.

Items	Intra-observer kappa		Inter-observer
	Observer 1	Observer 2	Kappa	P value
AROC stage	0.942	0.454	0.504	< 0.001
JIC classification	0.928	0.374	0.348	< 0.001
Lesion size	0.959	0.492	0.430	< 0.001
Collapse degree	0.895	0.638	0.666	< 0.001

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Clinical results

The median HHS, iHOT-12, WOMAC, and VAS scores before conservative hip preservation treatment were 61.00, 72.00, 90.00, and 7.00, respectively. At the final follow-up, the median scores were 75.00, 102.00, 45.00, and 3.00, respectively (Table 4). The HHS and iHOT-12 scores at the final follow-up were significantly higher than before treatment (P < 0.05), while the VAS and WOMAC scores were significantly lower than the pre-treatment scores (P < 0.05).

Table 4 Results of Harris Hip Score, international Hip Outcome Tool 12, visual analogue scale, and Western Ontario and McMaster Universities Arthritis Index before treatment and at the last follow-up.

Items	Pre-treatment	Post-treatment	Z	P value
HHS	61.00 (77.00, 51.00)	75.00 (93.00, 67.00)	-9.389	< 0.001
iHOT-12	72.00 (80.00, 63.00)	102.00 (110.00, 94.00)	-9.472	< 0.001
WOMAC	90.00 (99.00, 75.00)	45.00 (63.00, 29.00)	-9.472	< 0.001
VAS	7.00 (7.00, 6.00)	3.00 (4.00, 2.00)	-9.326	< 0.001

HHS: Harris Hip Score; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Radiological findings

The final follow-up results included 2 hips in ARCO I stage, 31 hips in ARCO II, 34 hips in ARCO IIIa, 39 hips in ARCO IIIb, and 13 hips in ARCO IV; 15 hips in JIC A, 21 hips in JIC B, 51 hips in JIC C1, and 32 hips in JIC C2; 28 hips with a lesion size < 15%, 30 hips with a lesion size 15%-30%, and 61 hips with a lesion size > 30%; 67 hips had a collapse degree ≤ 2 mm, and 52 hips had a collapse degree > 2 mm (Table 5). The ARCO staging and collapse degree distribution in patients after conservative treatment showed significant changes from those before treatment (P < 0.05).

Table 5 Overall distribution of clinical scores in patients pre-treatment and at the last follow-up.

Items	Pre-treatment	Post-treatment	χ2	P value
ARCO stage (hips)
Stage I	2	2	31.966	< 0.0011
Stage II	41	31
Stage IIIa	59	34
Stage IIIb	17	39
Stage IV	0	13
JIC classification (hips)
Type A	12	15	7.071	0.070
Type B	26	21
Type C1	54	51
Type C2	27	32
Lesion size (hips)
< 15%	26	28	5.485	0.140
15%-30%	37	30
> 30%	56	61
Collapse degree (hips)
≤ 2 mm	102	67	25.002	< 0.001
> 2 mm	17	52

¹Indicates Fisher’s exact test.

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Success rate of hip preservation

The overall success rate of hip preservation in this study was 90.76%. The hip preservation success rates in ARCO I-II, IIIa, and IIIb patients were 97.67%, 91.53%, and 70.59%, respectively (P < 0.05). The success rates of hip preservation in JIC A-B, C1, and C2 patients were 93.37%, 92.59%, and 77.78%, respectively (P < 0.05). The success rates of hip preservation for lesion size < 15%, 15%-30%, and > 30% patients were 88.46%, 89.19%, and 92.86%, respectively. The success rates of hip preservation for collapse degree ≤ 2 mm and > 2 mm were 94.12% and 70.59%, respectively (P < 0.05), as shown in Table 6.

Table 6 Success rate of hip preservation.

Items	Number of hips	Conversion to THA	Conversion to HPS	Success rate	χ2	P value
ARCO stage (hips)
Stage I, II	43	1	0	97.67%	8.736	0.011
Stage IIIa	59	2	3	91.53%
Stage IIIb	17	4	1	70.59%
JIC classification (hips)
Type A, B	38	0	1	97.37%	6.521	0.031
Type C1	54	2	2	92.59%
Type C2	27	5	1	77.78%
Lesion size (hips)
< 15%	26	2	1	88.46%	0.798	0.771
15%-30%	37	2	2	89.19%
> 30%	56	3	1	92.86%
Collapse degree (hips)
≤ 2 mm	102	3	3	94.12%	9.616	0.009
> 2 mm	17	4	1	70.59%

THA: Total hip arthroplasty; HPS: Hip preservation surgery; ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Clinical outcomes at the last follow-up based on ARCO staging

The median HHS, iHOT-12, WOMAC, and VAS scores for ARCO I and II patients were 81.00, 106.00, 43.00, and 3.00, respectively. In contrast, the median HHS, iHOT-12, WOMAC, and VAS scores for ARCO IIIa and IIIb patients were 75.00, 101.00, 46.00, and 3.00, respectively (Table 7). Among them, the VAS score results of ARCO IIIa and IIIb patients were significantly poorer than those of ARCO I and II patients (P < 0.05).

Table 7 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on Association Research Circulation Osseous stages.

Items	ARCO I, II	ARCO IIIa, b	Z	P value
Harris	81.00 (93.00, 67.00)	75.00 (86.50, 66.25)	-1.133	0.257
iHOT-12	106.00 (114.00, 96.00)	101.00 (109.50, 91.00)	-1.877	0.060
WOMAC	43.00 (62.00, 20.00)	46.00 (63.00, 33.00)	-1.822	0.069
VAS	3.00 (3.00, 0.00)	3.00 (6.00, 3.00)	-2.286	0.007

ARCO: Association Research Circulation Osseous; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Clinical outcomes at the last follow-up based on JIC classification

After conservative hip preservation treatment, the mean HHS, iHOT-12, WOMAC, and VAS scores for JIC A and B patients were 75.50, 104.00, 44.47, and 3.00, respectively, while the mean scores for JIC C1 patients were 75.00, 101.00, 49.07, and 3.00, respectively. Moreover, the JIC C2 patients showed mean scores of 77.00, 98.00, 47.22, and 3.00, respectively (Table 8). These results demonstrated no statistically significant differences in clinical evaluation scores between patients of different JIC classifications (P > 0.05).

Table 8 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on Japanese Investigation Committee classification.

Items	JIC A, B	JIC C1	JIC C2	F/H	P value
Harris	75.50 (93.00, 65.00)	75.00 (93.00, 63.00)	77.00 (95.00, 67.00)	0.714	0.7001
iHOT-12	104.00 (112.00, 96.00)	101.00 (108.50, 93.75)	98.00 (110.00, 92.00)	2.077	0.3541
WOMAC	44.47 ± 24.55	49.07 ± 23.37	47.22 ± 22.95	0.422	0.657
VAS	3.00 (4.00, 0.75)	3.00 (4.00, 3.00)	3.00 (6.00, 2.00)	1.047	0.5921

¹Indicates Kruskal-Wallis H test.

JIC: Japanese Investigation Committee; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Clinical outcomes at the last follow-up based on lesion size

After conservative hip preservation treatment, the median HHS, iHOT-12, WOMAC, and VAS scores in the lesion size < 15% group were 82.50, 111.00, 30.00, and 2.00, respectively, whereas the lesion size 15%-30% group showed median clinical scores of 77.00, 104.00, 45.00, and 3.00, respectively. In addition, the median clinical scores of the lesion size > 30% group were 72.00, 98.00, 46.00, and 3.00, respectively (Table 9). These results revealed significantly better iHOT-12, WOMAC, and VAS scores in the < 15% group compared to the other two groups (P < 0.05).

Table 9 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on lesion size.

Items	< 15%	15%-30%	> 30%	H	P value
Harris	82.50 (93.00, 67.00)	77.00 (93.00, 68.00)	72.00 (85.00, 60.25)	3.638	0.162
iHOT-12	111.00 (120.00, 98.00)	104.00 (110.00, 93.50)	98.00 (106.00, 91.25)	12.344	0.0021
WOMAC	30.00 (53.50, 18.00)	45.00 (61.50, 28.50)	46.00 (66.00, 36.00)	6.456	0.0401
VAS	2.00 (3.00, 0.00)	3.00 (4.50, 2.50)	3.00 (5.50, 3.00)	8.872	0.0121

¹Refers to a two-by-two comparison, where the results of the two-by-two comparison between the necrosis range > 30% group and the < 15% group were P (international Hip Outcome Tool 12) = 0.002, P (Western Ontario and McMaster Universities Arthritis Index) = 0.035, and P (visual analogue scale) = 0.009.

iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Clinical outcomes at the last follow-up based on the collapse degree

After conservative hip preservation treatment, the mean HHS, iHOT-12, WOMAC, and VAS scores in the collapse ≤ 2 mm group were 79.41, 99.82, 48.71, and 3.00, respectively, while the mean scores of the collapse > 2 mm group were 84.29, 107.24, 38.06, and 3.00, respectively (Table 10). Among them, the iHOT-12 results of the collapse > 2 mm group were significantly higher than those of the collapse ≤ 2 mm group (P < 0.05).

Table 10 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on collapse degree.

Items	≤ 2 mm	> 2 mm	t/Z	P value
Harris	75.00 (93.00, 65.25)	82.00 (93.00, 71.50)	-1.096	0.2731
iHOT-12	99.82 ± 13.41	107.24 ± 10.24	-2.172	0.032
WOMAC	38.06 (64.75, 30.50)	38.06 ± 19.03	-1.592	0.1111
VAS	3.00 (4.00, 2.00)	3.00 (3.00, 0.00)	-1.267	0.2051

¹Refers to the Mann-Whitney U test.

iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

DISCUSSION

The treatment of ONFH aims to preserve the femoral head and extend the lifespan of the hip[15]. The most common methods of hip preservation in Western medicine are medullary core decompression and bone grafting[16], but these minimally invasive procedures have a collapse rate of up to 50% within two years of the surgery[17]. Conservative hip preservation treatment is not widely accepted, but the results of this study have shown that femoral head necrosis can effectively be treated, with a success rate of up to 90%. The study’s clinical evaluation results indicate that conservative hip preservation treatment can effectively reduce pain, improve limb function, and enhance a patient’s quality of life, which is consistent with findings reported in previous studies[18]. The conservative hip preservation plan adopted in this study is a series of non-invasive treatment methods that can achieve good clinical efficacy while avoiding a series of potential risks caused by surgical procedures. It not only reduces patients’ pain but also helps them save costs.

The size of the necrotic lesion provides a visual method of assessing the repair situation within the femoral head. This study revealed no significant difference in the distribution of the lesion size before and after treatment, with some cases even showing some reduction, indicating that conservative hip preservation treatment can effectively treat ONFH and promote necrosis repair. In this study, a Chinese herbal compound preparation, Sheng Mai Cheng Gu tablets, and Huo Xue Tong Luo capsules were used. Studies have shown that the Huo Xue Tong Luo capsule can effectively promote the osteogenic differentiation of bone marrow mesenchymal stem cells[19]. The most important ingredient in Sheng Mai Cheng Gu tablets, Cajanus cajan leaf, contains flavonoids and astragalus compounds as its main components[20]. A study by Zhang et al[21] demonstrated that flavonoids can regulate the self-repair and differentiation potential of bone marrow mesenchymal stems and can effectively promote osteogenic differentiation and bone repair.

After necrosis, the bone trabecular structure is altered. Bone trabeculae become thinner, and the bone quality is reduced, which increases the risk of microfractures under continuous stress. Subsequently, fractures occur in the subchondral bone plate, and the articular surface of the femoral head collapses[22]. Klumpp and Trevisan[23] reported that protective weight-bearing could reduce the local stress on the femoral head and contribute to the repair of ONFH. He[24] stated that the presence of pain often indicates microfractures within the femoral head. Crutches and other auxiliary supports can be used to reduce the force on the affected limb and avoid continuous micro-movement of the broken bone trabeculae, thereby reducing pain in the affected limb.

The collapse degree, lesion size, and classification have an impact on the final success rate and clinical outcomes of conservative hip preservation. In the results of this study, the success rate of hip preservation in ARCO stage I and II patients was 97.67%, and the success rate in stage IIIa patients was 91.53%, both significantly higher than that of ARCO stage IIIb patients. In terms of clinical outcomes, the four scoring scales measured in this study showed better results in the ARCO stage I and II groups compared to the ARCO stage III group, but only the iHOT-12 and VAS scores showed statistically significant differences. Meanwhile, the success rate of hip preservation for patients with a collapse degree of ≤ 2 mm was 94.12%, which was significantly higher than that of patients with a collapse degree > 2 mm. However, at the last follow-up, patients with a collapse degree > 2 mm had better results in all four scoring scales than those with a collapse degree ≤ 2 mm, with a significant difference in the iHOT-12 score. The ARCO staging of ONFH not only reflects the collapse of the femoral head but also reflects the stage of the condition. Patients in ARCO stage IIIa often experience shorter periods of hip joint pain and have higher psychological expectations for the effectiveness of conservative hip preservation, especially in relieving pain. The median VAS score for ARCO IIIa and IIIb patients and the median for patients with collapse > 2 mm were both 3.00, and the interquartile range between the two was also 3.00, but the interquartile range of ARCO IIIa and IIIb patients was higher than that of patients with collapse > 2 mm. These results indicated that under the same degree of dispersion, ARCO IIIa patients were more sensitive to pain. In contrast, ARCO stage IIIb patients with a degree of collapse greater than 2 mm often experience pain for an extended period of time, affecting their daily activities and even walking gait. Most of these patients have a preliminary understanding and awareness of their illness, and their treatment demands are more focused on rescuing hip joint function. Therefore, they have a higher acceptance of residual occasional pain after conservative hip-conserving treatment. Upon improvement of the hip joint function, patients can return to daily life and work, thereby reducing the economic, familial, and psychological burden of the disease. These factors might explain the good clinical evaluation of ARCO IIIb patients with a collapse degree greater than 2 mm, especially the significantly higher iHOT-12 score, which is closely related to the patient’s psychological state.

In fact, due to the lack of a control group in this study, although scoring scales such as iHot-12 and WOMAC are sufficient to cover all aspects of patients’ clinical symptoms and joint function, and to some extent can intuitively reflect the current disease situation of patients, the conclusion of good clinical efficacy still needs more rigorous evaluation due to subject adaptation or sensitivity of clinical scoring standards. Notably, although no significant difference in the distribution of necrosis extent was observed before and after conservative hip preservation treatment, patients with different necrosis extents exhibited significantly different results of iHOT-12, WOMAC, and VAS at the last follow-up. The differences in HHS followed the same trend as the other three evaluations, despite not showing statistically significant changes. A smaller lesion size was associated with higher clinical results, fewer symptoms, and better function. These findings are consistent with those of previous studies[25]. An assessment of the lesion size at the patient’s initial visit may help determine the prognosis of conservative hip preservation for ONFH.

The collapse of the femoral head can seriously affect the daily activities of patients and reduce the quality of life[26]. The results of this study suggest that although conservative hip preservation cannot completely prevent the collapse of the femoral head and stop the progression of necrosis, the treatment can still improve clinical outcomes and quality of life, and achieve “survival with collapse”. “Survival with collapse” refers to the state of patients with collapsed femoral head necrosis, which cannot be completely corrected through hip preservation therapy, but with minimal pain and acceptable hip function over the long term[27]. Conservative hip preservation intervention may not show significant improvement in imaging assessments such as staging, degree of collapse, and area of necrosis. Moreover, some patients might be qualified for THA based on their imaging changes, but 70%-90% of patients may not require joint replacement or hip preservation surgery, considering their clinical symptoms and subjective feelings. This kind of clinical presentation does not match the severity of the imaging change, which is one of the characteristics of “survival with collapse” (Figures 1, 2, 3 and 4).

Figure 1 A 38-year-old woman presented at the hospital with left hip pain lasting for 3 months. She had a history of treatment with glucocorticoids for systemic lupus erythematosus. Based on the initial X-ray and magnetic resonance imaging, she was diagnosed with steroid-induced osteonecrosis of the femoral head. Conservative hip-preserving treatment was administered. A and B: X-Ray: The density within the left femoral head is uneven, with a clearly visible sclerotic zone. The joint alignment remains normal, and there are no significant changes in the joint space; C and D: Magnetic resonance imaging: No obvious collapse of the femoral head is observed. The left femoral head exhibits patchy and linear signal abnormalities, with low signal intensity on T1W1 and slightly high and low signal intensity on T2W2.

Figure 2 Left hip joint anterior-posterior X-ray. A: Left hip pain for 3 months (initial visit); B: At 16 months; C: At 3.5 years; D: At 5 years; E: At 6.5 years; F: At 10 years.

Figure 3 Left hip joint frog-position X-ray. A: Left hip pain for 3 months (initial visit); B: At 16 months; C: At 3.5 years; D: At 5 years; E: At 6.5 years; F: At 10 years.

Figure 4  At the last follow-up, the patient’s left hip joint function had good flexion and extension, with limited abduction but no significant pain.

CONCLUSION

Conservative hip preservation combines dynamic and static methods, effectively reducing hip joint pain, improving limb function, enhancing the quality of life, maintaining hip joint stability, and promoting the repair of femoral head necrosis. This non-invasive and affordable method helps patients achieve “survival with collapse”. Nevertheless, the limitations of the current study should be acknowledged. Firstly, this is a retrospective cohort study with a small sample size and no control group, which may have involved selection bias. Secondly, the course of conservative hip preservation varies among individuals, including medication duration and crutch usage, which are often adjusted based on patient feedback. Most patients can walk without crutches within six months of conservative hip preservation treatment. Although the longest follow-up time for our patients was 10 years, the shortest was only 12 months, which may be a shorter average follow-up. Finally, some patients did not strictly adhere to protective weight-bearing, which may have affected the progression of the collapse and necrosis stage. Further research will be conducted to analyze the risk factors for the clinical efficacy of conservative hip preservation. In conclusion, conservative hip preservation remains a viable treatment option for ONFH patients with significant collapse, significant necrosis, and involvement of the lateral column.