Efficacy and safety of stem cell therapy for the early-stage osteonecrosis of femoral head: a systematic review and meta-analysis of randomized controlled trials

Background Osteonecrosis of femoral head (ONFH) is a seriously degenerative disease with no effective therapies to slow its progression. Several studies have reported short-term efficacy of stem cells on early-stage ONFH. However, its long-term effect was still unclear especially on progression events. This study was performed to evaluate the long-term efficacy and safety of stem cells and analyze its optimal age group and cell number. Methods Our review was registered on PROSPERO (http://www.crd.york.ac.uk/PROSPERO), registration number CRD42020136094. Following PRISMA guideline, we searched 8 electronic databases on January 5, 2020, and rigorous random controlled trials (RCTs) utilizing stem cell therapy on early-stage ONFH were included. Quality and bias were analyzed. Pooled analysis was performed to assess difference between various outcomes. Results A total of 13 RCTs (619 patients with 855 hips) were included. The application of stem cells significantly delayed collapse of femoral head(I2, 70%; RR, 0.54; 95% CI, 0.33 to 0.89; P < .00001) and total hip replacement (THR) (I2, 68%; RR, 0.55; 95% CI, 0.34 to 0.90; P = .02) in the long term. It effectively decreased the events of collapse of femoral head (≥ 60 months) (I2, 0%; RR, 0.37; 95% CI, 0.28 to 0.49; P < .00001) and THR (> 36 months) (I2, 0%; RR, 0.32; 95% CI, 0.23 to 0.44; P < .00001). There existed a beneficial effect for patients under 40 (Collapse of femoral head: I2, 56%; RR, 0.41; 95% CI, 0.23 to 0.76; P = .004) (THR: I2, 0%; RR, 0.31; 95% CI, 0.23 to 0.42; P < .00001). In addition, quantity of stem cells at 108 magnitude had better effects on disease progression events (I2, 0%; RR, 0.34; 95%CI, 0.16 to 0.74; P = .007). Besides, there were no significant differences on adverse events between the stem cell group and control group (I2, 0%; RR, 0.82; 95% CI, 0.39 to 1.73; P = .60). Conclusion Our findings build solid evidence that stem cell therapy could be expected to have a long-term effect on preventing early-stage ONFH patients from progression events, such as collapse of femoral head and total hip replacement. Furthermore, patients under 40 may be an ideal age group and the optimal cell number could be at 108 magnitude for this therapy. Further studies including strict RCTs are required to evaluate a clear effect of stem cells on ideal patient profile and the procedures of implantation.