ObjectiveOsteonecrosis of the femoral head (ONFH) is a disabling and intractable orthopedic disease largely affecting young and middle-aged groups. Current standard of treatment relies on the collapse of femoral head as a predictor for prognosis. However, a wide range of variability in repair potentials is observed in patients with femoral head collapse. Therefore, the present study aimed to evaluate the accuracy of femoral head collapse as a predictor and to propose the necrotic lesion boundary as a novel yet reliable measure for ONFH prognosis.MethodsA retrospective cross-sectional study was conducted at the First Affiliated Hospital of Guangzhou University of Chinese Medicine, 203 hips with ONFH from 134 patients were included. The occurrences and progression of femoral head collapse were recorded. Necrosis lesion boundary was quantified and classified for each case based on anteroposterior view intact ratio (APIR) and the frog-leg view intact ratio (FLIR) as independent variables. Dependent variables were defined as progressive collapse or terminal collapse for Association Research Circulation Osseous (ARCO) stage II and III respectively. Logistic regression analysis, Receiver Operating Characteristic (ROC) curve and Kaplan-Meier (K-M) survival analysis was performed and results were interpreted.ResultsOut of the 106 hips in ARCO stage II, 31 hips collapsed with further progression, while 75 hips had no collapse or collapse with repair of the necrotic areas. Out of the 97 hips in ARCO stage IIIA, the collapse continued to progress in 58 hips while the necrotic areas were repaired in 39 hips. Logistic regression analysis demonstrated that both APIR and FLIR, were independent risk factors. Further ROC curve analysis indicated that the cutoff values of APIR and FLIR could be considered as indications for evaluating the prognosis of ONFH. Contrary to the traditional view of poor prognosis after femoral head collapse, K-M survival analysis demonstrated a high value of APIR and FLIR for ONFH prognosis.ConclusionThe present study found that the occurrence of collapse is an oversimplified predictor for ONFH prognosis. The collapse of the femoral head in ONFH does not predict a poor prognosis. The necrosis lesion boundary has a high value in predicting ONFH prognosis and informing clinical treatment strategies.

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Objective:Osteonecrosis of the femoral head (ONFH) is a common and difficult disease. The effect of cystic area on femoral head mechanics in patients with ONFH is unknown. The purpose of this study was to investigate the effect of cystic areas of osteonecrosis of the femoral head on stress distribution and disease progression in the femoral head.Methods:A total of 85 patients (106 hips) diagnosed with ARCO stage II non-traumatic and non-surgical treatment of ONFH from February 2017 to November 2018 were retrospectively analyzed. All patients were followed up for an average of more than 2 years. According to whether the femoral head collapsed during the follow-up, they were divided into collapse group and non-collapse group. The age, gender, etiology, height, weight, BMI, JIC classification, presence of cystic areas and diameter of cystic areas were compared between the two groups. In addition, five spherical cystic areas of different diameters of 0, 5, 10, 15, and 20 mm were constructed to simulate the hip joint load of a person during standing by finite element methods, and the maximum stress, mean stress, and maximum stress values in the necrotic area of the femoral head without cystic areas and in the area 1 mm around the cystic areas with different diameters were observed and analyzed.Results:All 85 patients (106 hips) completed the follow-up, with an average age of 37.4 ± 8.12 years. The mean follow-up time was 2.8 ± 0.6 years. Forty-five patients (57 hips) with ONFH who had femoral head collapse were included in the collapse group, and the remaining 40 patients (49 hips) were included in the non-collapse group. There was significant difference in JIC classification between the two groups (P < 0.05), most of which were C2 type in the collapse group and B type in the non-collapse group. 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 von Mises stress value and mean von Mises stress value around the cortical bone, necrotic area and around the cystic area of the femoral head increased with the increase of the cystic diameter. Furthermore, linear regression analysis showed a linear positive correlation between the maximum stress, mean stress in the necrotic area in the femoral head, and the maximum stress value in the 1 mm area around the cystic area and the diameter of the cystic area.Conclusion:The maximum stress and average stress of necrotic area can be increased in cystic area, and the increase of stress in cystic area is more obvious. 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 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.