Three-dimensional distribution of cystic lesions in osteonecrosis of the femoral head

Panoramic heat map for spatial distribution of necrotic lesions

Aims

In this study, we aimed to visualize the spatial distribution characteristics of femoral head necrosis using a novel measurement method.

Methods

We retrospectively collected CT imaging data of 108 hips with non-traumatic osteonecrosis of the femoral head from 76 consecutive patients (mean age 34.3 years (SD 8.1), 56.58% male (n = 43)) in two clinical centres. The femoral head was divided into 288 standard units (based on the orientation of units within the femoral head, designated as N[Superior], S[Inferior], E[Anterior], and W[Posterior]) using a new measurement system called the longitude and latitude division system (LLDS). A computer-aided design (CAD) measurement tool was also developed to visualize the measurement of the spatial location of necrotic lesions in CT images. Two orthopaedic surgeons independently performed measurements, and the results were used to draw 2D and 3D heat maps of spatial distribution of necrotic lesions in the femoral head, and for statistical analysis.

Results

The results showed that the LLDS has high inter-rater reliability. As illustrated by the heat map, the distribution of Japanese Investigation Committee (JIC) classification type C necrotic lesions exhibited clustering characteristics, with the lesions being concentrated in the northern and eastern regions, forming a hot zone (90% probability) centred on the N4-N6E2, N3-N6E units of outer ring blocks. Statistical results showed that the distribution difference between type C2 and type C1 was most significant in the E1 and E2 units and, combined with the heat map, indicated that the spatial distribution differences at N3-N6E1 and N1-N3E2 units are crucial in understanding type C1 and C2 necrotic lesions.

Conclusion

The LLDS can be used to accurately measure the spatial location of necrotic lesions and display their distribution characteristics.

Sclerosis rim volume ratio and Japanese Investigation Committee classification as predictive factors for femoral head collapse progression after non-vascularized fibular grafting in osteonecrosis patients

OBJECTIVE

The purpose of this retrospective cohort study was to determine the relationship between sclerosis rim volume ratio (SVR) and the progression of femoral head collapse after non-vascularized fibular grafting (NVFG) surgery in patients with osteonecrosis of the femoral head (ONFH), investigating risk factors associated with femoral head collapse progression and establishing a predictive model to enhance clinical decision-making.

METHODS

ONFH patients who underwent NVFG between January 2008 and December 2021 were analyzed retrospectively to assess the risk of post-operative collapse progression (collapse >2 mm). A logistic regression model was used to evaluate the independent risk factors associated with collapse progression, including age, sex, etiology, affected side, Japanese Investigation Committee classification (JIC), and the sclerosis rim volume ratio (SVR). SVR values was collected from three weight-bearing columns, namely SVR1, SVR2, and SVR3, respectively.

RESULTS

57 patients with 64 hips who had undergone NVFG and were followed up for at least one year were included. During the follow-up, collapse＞2 mm occurred in 30 hips (46.88%). Multivariable analysis revealed that JIC (p =0.037) and SVR1 (p = 0.04) were independent risk factors for collapse progression after NVFG. The results of the receiver operating characteristic (ROC) analysis indicated that the aforementioned indices provided a satisfactory prediction of early femoral head collapse progression in ONFH patients after NVFG. The regression model using the above two indicators as a composite index showed satisfactory performance in predicting early postoperative femoral head collapse progression, with an area under the curve (AUC) of 84.6%.

CONCLUSIONS

SVR is significant predictor of post-operative collapse progression following NVFG, and the composite index provides an optimal predictive value for femoral head collapse progression after surgery.

The Effect of the Hip Flexion Angle in Osteonecrosis of the Femoral Head Based on China-Japan Friendship Hospital Classification - A Finite Element Study

OBJECTIVE

The alteration in the mechanical environment of the necrotic area is the primary cause of the collapse observed in osteonecrosis of the femoral head (ONFH). This study aims to evaluate the biomechanical implications of the China-Japan Friendship Hospital (CJFH) classification system and hip flexion angles on the necrotic area in ONFH using finite element analysis (FEA). The goal is to provide valuable guidance for hip preservation treatments and serve as a reference for clinical diagnosis and therapeutic interventions.

METHODS

Hip tomography CT scan data from a healthy volunteer was used to create a 3D model of the left hip. The model was preprocessed and imported into Solidworks 2018, based on the CJFH classification. Material parameters and boundary conditions were applied to each fractal model in ANSYS 21.0. Von Mises stresses were calculated, and maximum deformation values were obtained to evaluate the biomechanical effects of the load on the necrotic area and post-necrotic femur, as well as assess each fractal model's collapse risk.

RESULTS

(1) At the same hip flexion angle, maximum deformation followed this order: M Type < C Type < L Type. The L3 type necrotic area experienced the most significant deformation at 0, 60, and 110° angles (1.121, 1.7913, and 1.8239 mm respectively). (2) Under the same CJFH classification, maximum deformation values increased with hip flexion angle (0 < 60 < 110°), suggesting a higher risk of collapse at larger angles. (3) Von Mises stress results showed that the maximum stress was not located in the necrotic area but near the inner and outer edge of the femoral neck, indicating decreased stiffness and strength of the subchondral bone after osteonecrosis.

CONCLUSION

The study found that femoral head collapse risk was higher when the necrotic area was located in the lateral column under the same stress load and flexion angle. Mechanical properties of the necrotic area changed, resulting in decreased bone strength and stiffness. Large-angle hip flexion is more likely to cause excessive deformation of the necrotic area; thus, ONFH patients should reduce or avoid large-angle hip flexion during weight-bearing training in rehabilitation activities.

Lateral classification system predicts the collapse of JIC type C1 nontraumatic osteonecrosis of the femoral head: a retrospective study

PURPOSES

The aim of this study was to construct a lateral classification system for nontraumatic osteonecrosis of femoral head (NONFH) through three-dimensional reconstruction of the necrotic area to assist in evaluating the prognosis of patients with JIC type C1.

METHODS

Retrospective analysis of patients with JIC type C1 NONFH from January 2018 to December 2020. All patients were followed up for more than 3.5 years. The patients were divided into collapse group and non-collapse group according to whether the femoral head collapsed during the follow-up.Lateral classification system for femoral head necrosis is constructed through three-dimensional reconstruction of the necrotic area.Comparison of lateral classification system,midsagittal necrosis angle(MNA)and general data between the two groups.Furthermore, ROC curve analysis and survival analysis were performed.

RESULTS

318 patients were included in this study.There was a significant difference between the two groups in the lateral classification system (P < 0.05). In addition, the MNA in the collapsed group was significantly greater than that in the non-collapse group(P < 0.05). As revealed by the results of ROC analysis, the cutoff point of MNA was 104.5° (P < 0.05).According to the survivorship analysis, the mean survival time of the hips of patients with MNA less than 104.5°was greater than that of patients with MNA over 104.5° (P < 0.05). The survival rates of 3.5 years femoral head were 45.8%, 33.7%, 14.8%, 93.0%, and 100% for lateral classification system 1, 2, 3, 4, and 5, respectively.

CONCLUSION

Necrosis involving the anterior aspect of the femoral head is an important risk factor for collapse. The Lateral classification system can effectively predict the femoral head collapse in JIC C1 type NONFH patients, supplementing the deficiency of JIC classification in evaluating the front of the femoral head.

Subchondral Bone Plate Classification: A New and More Sensitive Approach for Predicting the Prognosis of Osteonecrosis of the Femoral Head

BACKGROUND

This study explores the impact of subchondral bone plate necrosis on the development of the osteonecrosis of femoral head (ONFH) and its joint collapse.

METHODS

This retrospective study included 76 ONFH patients (89 consecutive hips) with Association for Research on Osseous Circulation stage II who received conservative treatment without surgical intervention. The mean follow-up time was 15.60 ± 12.29 months. ONFH was divided into 2 types (I and II): Type I with a necrotic lesion involving subchondral bone plate and Type II with a necrotic lesion not involving subchondral bone plate. The radiological evaluations were based on plain x-rays. The data were analyzed using SPSS 26.0 statistical software.

RESULTS

The collapse rate in Type I ONFH was significantly higher than that in Type II ONFH (P < 0.001). The survival time of hips with Type I ONFH was significantly shorter than those with Type II ONFH and with the endpoint of the femoral head collapse (P < 0.001). The collapse rate of Type I in the new classification (80.95%) was higher compared with that of the China-Japan Friendship Hospital (CJFH) classification (63.64%), and the difference was statistically significant (χ2 = 1.776, P = 0.024).

CONCLUSION

Subchondral bone plate necrosis is an important factor that affects ONFH collapse and prognosis. Current classification using subchondral bone plate necrosis is more sensitive for predicting collapse compared with the CJFH classification. Effective treatments should be taken to prevent collapse if ONFH necrotic lesions involve the subchondral bone plate.

PDGF-BB prevents destructive repair and promotes reparative osteogenesis of steroid-associated osteonecrosis of the femoral head in rabbits

Destructive repair characterized by inadequate angiogenesis and osteogenesis is the main pathological progression in steroid-associated osteonecrosis of the femoral head (SONFH). Platelet-derived growth factor-BB (PDGF-BB) is an "angiogenesis and osteogenesis coupling" factor that has been used for the treatment of bone defects in clinic. This study was designed to analyze the ability of PDGF-BB for preventing destructive repair and promoting reparative osteogenesis in SONFH. Steroid-associated osteonecrosis (SAON) was induced and triggered destructive repair of the femoral head by repeated lipopolysaccharide (LPS) and methylprednisolone (MPS) injections in rabbits. At 2, 4, and 6 weeks after induction, recombinant human PDGF-BB, neutralizing PDGF-BB antibody, or saline was intramedullary injected into the proximal femora. At week 6 after SAON induction, the proximal femora were dissected for bone architecture and histological analysis. C3H10T1/2 cells and HUVECs were used for further mechanistic investigation. After PDGF-BB treatment, type H vessels and leptin receptor-positive (LepR+) mesenchymal stem cells (MSCs) increased in the affected femoral head, and more osteoblastic osteogenesis along the bone surfaces but scattered adipocytes in bone marrow tissue than that in the SAON group. PDGF-BB treatment prevented destructive repair progression and led to 50-70 % of osteonecrotic femoral heads undergoing reparative osteogenesis. In particular, we found that PDGF-BB could mediate MSC self-renewal and maintain their osteogenic potency by activating PDGFR/Akt/GSK3β/CERB signaling in the presence of steroids. Moreover, PDGF-BB also stabled the newly formed vascular tubes by recruiting MSCs for improving intraosseous vascular integration. PDGF-BB may be a candidate for the promotion of reparative osteogenesis in SONFH.

CT and MRI findings beyond the subchondral bone in osteonecrosis of the femoral head to distinguish between ARCO stages 2 and 3A

OBJECTIVES

To determine the diagnostic values of deep changes beyond the subchondral bone in osteonecrosis of the femoral head (ONFH) to distinguish between Association Research Circulation Osseous (ARCO) stages 2 and 3A.

METHODS

This retrospective study included 124 hips with ONFH of stages 2 (n = 49; 23 females; mean age, 50.7 years) and 3A (n = 75; 20 females; mean age, 53.2 years) from May 2017 to August 2022, who underwent CT (n = 124) and MRI (n = 85). Deep changes beyond subchondral bone were analyzed on CT (bone resorption area and cystic change) and on MRI (bone marrow edema [BME] and joint effusion). Diagnostic performance and multivariate analysis were evaluated for detecting stage 3A.

RESULTS

Stage 3A showed more frequent bone resorption area (72.0% vs. 4.1%), cystic change (52.0% vs. 0.0%), BME (93.5% vs. 43.6%), and joint effusion (76.0% vs. 24.5%) than stage 2 (p < 0.001, all). Bone resorption area and cystic change showed low sensitivities (52.0~72.0%) but high specificities (96.0~100.0%), while BME and joint effusion showed high sensitivities (76.0~93.0%) but low specificities (56.0~76.0%) for stage 3A. Predictors were in the order of bone resorption area, cystic change, and joint effusion (odds ratio: 32.952, 26.281, 9.603, respectively), and combined bone resorption area and cystic change had the best predictive value (AUC, 0.900) for stage 3A.

CONCLUSIONS

Among deep changes, bone resorption area and cystic changes were highly specific and BME and joint effusion were highly sensitive for stage 3A. Combined bone resorption area and cystic change had the best predictive value for predicting ARCO stage 3A.

KEY POINTS

• The exact classification between ARCO stage 2 and 3A is essential but it is sometimes difficult to distinguish between ARCO stage 2 and 3A only by subchondral fracture, especially early post-collapse stage with preservation of femoral head contour. • The predictors of stage 3A were in the order of bone resorption area, cystic change, and joint effusion and combined bone resorption area and cystic change had the best predictive value for predicting stage 3A. • Analysis of deep changes beyond the subchondral bone may make it easier to distinguish between ARCO stage 2 and 3A.

High-energy focused extracorporeal shock wave prevents the occurrence of glucocorticoid-induced osteonecrosis of the femoral head: A prospective randomized controlled trial

Background

Studies have shown that high-energy focused extracorporeal shock wave therapy (HF-ESWT) has a certain therapeutic effect on glucocorticoid-induced osteonecrosis of the femoral head (ONFH). This study aimed to observe the efficacy and safety of HF-ESWT as a precautionary measure to reduce the probability of glucocorticoid-induced ONFH.

Methods

A prospective randomized controlled trial was designed to evaluate whether HF-ESWT (Group A) can significantly prevent the incidence of glucocorticoid-induced ONFH relative to a control group without shockwave intervention (Group B). MRI was used to assess whether all participants experienced ONFH at 3, 6, and 12 months after the intervention. Continuous scoring was used to evaluate the intervention results: the 10-cm visual analog scale (VAS) was used to evaluate pain, and the hip Harris score (HHS) was used to evaluate the function of the hip joint. Any adverse events were recorded.

Results

153 patients (89 females and 64 males) who had been allocated to group A (75 patients) or Group B (78 patients) were included in the final analysis. The patients were 45.0 ​± ​13.0 years old. There were significant differences between the two groups in MRI diagnosis of ONFH patients (2 cases in Group A, 9 cases in Group B; p ​= ​0.034). Significant differences between groups were found in bilateral hip function measured using the HHS at 6 months (Left p ​= ​0.026; Right p ​= ​0.033) and 12 months (Left p ​= ​0.018; Right p ​= ​0.038). However, there was no difference in the functional results measured at 3 months and the VAS at any points.

Conclusions

This study confirms that HF-ESWT can be successfully used to reduce the probability of glucocorticoid-induced ONFH. Pain and hip dysfunction are common clinical manifestations when ONFH is unavoidable. Therefore, HF-ESWT can be recommended for the prevention and intervention of ONFH high-risk populations receiving high-dose glucocorticoid therapy.

The Translational potential of this article

The effective prevention of HF-ESWT on ONFH after high-dose glucocorticoid application demonstrated its transformation potential as a preventive method in the clinical prevention of glucocorticoid-induced ONFH.

Effect of femoral head necrosis cystic area on femoral head collapse and stress distribution in femoral head: A clinical and finite element study

The purpose of this study was to investigate the effect of cystic areas of osteonecrosis of the femoral head (ONFH) on stress distribution and disease progression in the femoral head. A total of 85 patients (106 hips) diagnosed with Association Research Circulation Osseous stage II non-traumatic and non-surgical treatment were retrospectively analyzed. The presence of cystic areas and diameter of cystic areas were compared between the two groups. In addition, five spherical cystic areas of different diameters were constructed and the maximum stress was observed. There was a difference between the two groups in whether cystic areas appeared in the femoral head, with 49.1% in the collapse group showing cystic areas, which was significantly higher than that in the non-collapse group (18.4%) (P < 0.05). In addition, the diameter of the cystic areas was significantly larger in the collapsed group than in the non-collapsed group (P < 0.05). The maximum and mean von Mises stress value around the necrotic area and around the cystic area of the femoral head increased with the increase of the cystic diameter. Stress concentration areas can be generated around the cystic areas. The presence and increased diameter of the cystic areas accelerates the collapse of the ONFH femoral head.

The Role of Structural Deterioration and Biomechanical Changes of the Necrotic Lesion in Collapse Mechanism of Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a crippling disease which is due to a lack of effective therapeutic measures. Its natural progression is rapid, the internal bone structure of the femoral head changes dramatically, and the subsequent fractures and collapse cause severe hip pain and loss of hip function. Femoral head collapse is a critical turning point in the development of ONFH and is related to the prognosis of patients. Early prevention and intervention help to preserve the hip joint and delay femoral head collapse. However, the mechanism of collapse still needs to be further studied because it is affected by different complex factors. This review discusses the underlying causes of femoral head collapse from two aspects: structural degradation and regional changes of biomechanical properties in the necrotic femoral head.

Combining frog-leg lateral view may serve as a more sensitive X-ray position in monitoring collapse in osteonecrosis of the femoral head

Load-bearing capacity of the bone structures of anterolateral weight-bearing area plays an important role in the progressive collapse in osteonecrosis of the femoral head (ONFH). The purpose of this study is to assess the efficacy of combined evaluation of anteroposterior (AP) and frog-leg lateral (FLL) view in diagnosing collapse. Between December 2016 and August 2018, a total of 478 hips from 372 patients with ONFH (268 male, 104 female; mean age 37.9 ± 11.4 years) were retrospectively evaluated. All patients received standard AP and FLL views of hip joints. Japanese Investigation Committee (JIC) classification system was used to classify necrotic lesion in AP view. Anterior necrotic lesion was evaluated by FLL view. All patients with pre-collapse ONFH underwent non-operative hip-preserving therapy. The collapse rates were calculated and compared with Kaplan–Meier survival analysis with radiological collapse as endpoints. Forty-four (44/478, 9.2%) hips were classified as type A, 65 (65/478, 13.6%) as type B, 232 (232/478, 48.5%) as type C1 and 137 (137/478, 28.7%) as type C2. Three hundred cases (300/478, 62.5%) were collapsed at the initial time point. Two hundred and twenty six (226/300, 75.3%) hips and 298 (298/300, 99.3%) hips collapse were identified with AP view and FLL view, respectively. An average follow-up of 37.0 ± 32.0 months was conducted to evaluate the occurrence of collapse in 178 pre-collapse hips. Collapses occurred in 89 hips (50.0%). Seventy-seven (77/89, 86.5%) hips were determined with AP view alone and 85 (85/89, 95.5%) hips were determined with the combination of AP and FLL views. The collapse rates at five years were reported as 0% and 0%, 16.2% and 24.3%, 58.3% and 68.1% and 100% and 100% according to AP view alone or combination of AP and FLL views for types A, B, C1 and C2, respectively. The collapse can be diagnosed more accurately by combination of AP and FLL views. Besides, JIC type A and type B ONFH can be treated with conservative hip preservation, but pre-collapse type C2 ONFH should be treated with joint-preserving surgery. Type C1 needs further study to determine which subtype has potential risk of collapse.

The Therapeutic Effect of Huo Xue Tong Luo Capsules in Association Research Circulation Osseous (ARCO) Stage II Osteonecrosis of the Femoral Head: A Clinical Study With an Average Follow-up Period of 7.95 Years

Background: Huo Xue Tong Luo (HXTL) capsules are an oral preparation that could relieve pain and ameliorate osteonecrosis in patients with asymptomatic osteonecrosis of femoral head (ONFH). We wanted to verify whether it could be a treatment option for ARCO stage II ONFH.

Methods: A total of 44 patients (66 hips) with ARCO stage II ONFH were recruited from June 1996 to October 2013 (clinical trial registry number: ChiCTR-RPC-15006,290). HXTL capsules were given under a specific protocol, and the endpoint was set as femoral head collapse. The clinical indicators [including visual analog scale (VAS) and Harris Hip Score (HHS)] and radiological indicators [including Tonnis classification, ARCO stage, Japanese Investigation Committee (JIC) classification, lateral preserved angle (LPA), anterior preserved angle (APA), and combined preserved angle (CPA)] before and after treatment were compared. Kaplan–Meier survival analysis and Cox regression analysis were used to identify the risk factors associated with femoral head collapse.

Result: Twenty-six males and 18 females with an average age of 38.3 ± 2.8 were followed for an average of 7.95 years. Forty-six of the 66 (69.7%) hips had no progression in pain or collapse, and patients exhibited a higher HHS (p < 0.05) after therapy. Twenty of the 66 (30.3%) hips progressed in Tonnis classification and ARCO stage, but only one of the 66 (1.5%) hips required total hip arthroplasty (THA). The Kaplan–Meier survivorship curve suggested that the survival rates were 96.97% at 5 years, 69.15% at 10 years, and 40.33% at 15 years. Patients with type A necrotic lesions on anteroposterior (AP) and frog-leg lateral (FLL) radiographs revealed 100% survival rates. Multivariate Cox regression analysis revealed that patients with an LPA ≤ 60.9 exhibited a 3.87 times higher risk of collapse of the femoral head [95% confidence interval (CI), 1.241–5.673] than did those patients with an LPA>60.9.

Conclusion: HXTL capsules could be a treatment option for ARCO stage II ONFH, resulting in improved hip function and delayed progression to femoral head collapse, especially when the anterior and lateral portions of the femoral head were not affected. However, an LPA of less than 60.9° may be a risk factor for collapse of the femoral head.

Clinical Trial Registration:http://www.chictr.org.cn/showproj.aspx?proj=10829, identifier ChiCTR-OPC-15007030

General recommendation for assessment and management on the risk of glucocorticoid-induced osteonecrosis in patients with COVID-19

BACKGROUND/OBJECTIVE

Coronavirus disease 2019 (COVID-19) is a disaster in human medical history and glucocorticoids remain the most promising therapy. Osteonecrosis is a disease caused by reduced intraosseous blood flow to bones in the joints, which will rapidly induce joint destruction. Approximately one-third patients with severe acute respiratory syndrome (SARS) who received high cumulative doses and long treatment durations of glucocorticoids occurred osteonecrosis. Considering the similarity of SARS and COVID-19 on their pathogen, clinical characteristics, and therapeutic strategies, it is particularly desirable to investigate whether osteonecrosis will become a common sequela among convalescent COVID-19 patients.

METHODS

This multi-strategy study was designed by integrating different research methods, such as meta-analysis, systematic review, and cross-sectional investigations to address above study objectives. At first, two meta-analyses were performed on the osteonecrosis incidence among SARS patients and the clinical data of glucocorticoid exposure among COVID-19 patients. Then, a systematic review of low-dosage glucocorticoid associated osteonecrosis and a cross-sectional investigation of glucocorticoid exposure of COVID-19 patients in Wuhan city of China were also conducted. Moreover, the pathogenesis, diagnosis, prevention, and treatment options for osteonecrosis patients with COVID-19 infection were further presented and discussed.

RESULTS

Our meta-analysis showed that 32% of SARS patients had developed osteonecrosis after receiving glucocorticoid treatment with high dose, and our system review supported that low level glucocorticoid exposure might also lead to the occurrence of osteonecrosis. Similarly, 40% of COVID-19 patients had undergone glucocorticoid treatment according to our meta-analysis. The cross-sectional investigation in Wuhan city of China found that the average of cumulative glucocorticoid exposure level was 504 ​mg calculated by the dosage of methylprednisolone. Notably, a confirmed osteonecrosis case was identified from 1406 patients with COVID-19 during our cross-sectional investigation, implying that preventive management of osteonecrosis should be better started with regular clinical follow-up observation.

CONCLUSION

Growing evidence of the glucocorticoid therapy for COVID-19 patients prompts us to establish risk-classification-based early screening and to introduce early prevention protocol of its associated osteonecrosis that will be of clinical significance in favor of improved prognosis of this disease.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

To establish risk-classification-based early screening and to introduce early prevention protocol of glucocorticoid-induced osteonecrosis will be of clinical significance in favor of improved prognosis of COVID-19.

Three-Dimensional Distribution of Bone-Resorption Lesions in Osteonecrosis of the Femoral Head Based on the Three-Pillar Classification

Objective

To investigate three‐dimensional distribution of bone‐resorptive lesions based on the three‐pillar classification and its effect on the disease progression of osteonecrosis of the femoral head (ONFH).

Methods

A total of 194 femoral head CT images from 117 patients diagnosed with ARCO stage II and III ONFH were retrospectively reviewed from April 2014 to February 2019. Three‐dimensional structures of the femoral head and the bone‐resorptive lesions were reconstructed. Using the three‐pillar classification and coronal plane of the femoral head, we divided each femoral head into six regions to observe the location characteristics of bone‐resorption lesions, and explore the destruction of different areas of the femoral head by the bone‐resorptive lesions. Then the hips were divided into two groups based on whether they contained bone‐resorption lesions and compared the difference of stage II and stage III between the two groups.

Results

The regional distribution revealed 39 (27.27%), 55 (38.46%), six (4.20%), 23 (16.08%), 17 (11.89%) and three (2.10%) bone‐resorptive lesions in regions I, II, III, IV, V and VI respectively. The lateral pillar, AL (I + IV), contained 44.76% of the lesions, central pillar, C (II + V), 48.95%, and medial pillar, M (III + VI), 6.29%. Moreover, there were 81.82% bone‐resorption lesions in anterolateral pillar, AL (I + II + IV), and 18.18% in posteromedial pillar, PM (III + V + VI). In all ONFH hips, the lateral pillar of 81(88.04%) femoral heads were affected, the central pillar of 84 (91.30%) femoral heads were affected, and the medical pillar of 29 (31.52%) femoral heads were affected. The ratio of ARCO stage III in the group with bone‐resorption lesions was significantly higher than that of the group without bone‐resorption lesions (76.09% vs 30.39%, P < 0.001).

Conclusions

This study demonstrated that the bone‐resorption lesions are mainly distributed in the lateral and central pillar of the femoral head, and the two pillars of the femoral head are usually involved by bone‐resorption lesions. Furthermore, the ratio of ARCO stage III in the group with bone‐resorption lesions was significantly higher than that of the group without bone‐resorption lesions, suggesting that the bone‐resorption lesions might accelerate the progression of ONFH.

Prediction of the progression of femoral head collapse in ARCO stage 2-3A osteonecrosis based on the initial bone resorption lesion

OBJECTIVES

To predict the progression of femoral head collapse in Association Research Circulation Osseous (ARCO) Stage 2-3A osteonecrosis based on the initial bone resorption lesion.

METHODS

A retrospective analysis of the location, attenuation, and maximum area in coronal position (MAC) of the initial bone resorption lesion in ARCO Stage 2 and 3A was conducted in 85 cases of osteonecrosis of the femoral head (ONFH). The cases were divided into rapid and slow progression groups according to whether femoral head collapse at follow-up was greater than 2 mm. The characteristics of the bone resorption lesion between the two groups were compared by analysis of variance. Receiver operating characteristic curve was used to analyze the MAC, regions of A2, and C1 of bone resorption lesion in predicting collapse progression.

RESULTS

The MAC of initial bone resorption lesion in rapid progression group (117.8 ± 72.1 mm²) was significantly larger than slow (53.1 ± 39.5 mm²) (p < 0.001). Regions of A2 and C1 involved were significantly higher in rapid than slow progression group. The area under the receiver operating characteristic curve of MAC, regions of A2 and C1 of bone resorption lesion to predict collapse progression were 0.81, 0.72 and 0.62 respectively. A threshold MAC of 49 mm² had sensitivity of 86.1% and specificity of 61.9% to predict collapse progression.

CONCLUSIONS

The MAC of initial bone resorption lesion in ARCO Stage 2-3A ONFH can predict the progression of femoral head collapse. If it is greater than 49 mm² and located in regions of A2 and C1, the possibility of rapid progression is high, active monitoring and intervention should be recommended.

ADVANCES IN KNOWLEDGE

This study is the first to find that the maximum area in coronal position of initial bone resorption lesion in ARCO Stage 2 or 3A can predict progression of the femoral head collapse with a threshold of 49 mm². If the maximum area is larger than 49 mm² and located in the anterolateral or lateral column of the femoral head, the possibility of rapid collapse progression is high, therefore, monitoring should be strengthened and active intervention should be considered.