Abstract: Objectives Osteonecrosis of the femoral head is a disease without effective treatment, and features a high disability rate and a high hip joint replacement rate. This study aims to observe the clinical effect and safety of local implantation of mesenchymal stem cells guided by ultrasound on femoral head necrosis, and explore an effective treatment method for the disease. Methods A total of 29 hip joints of 21 patients （14 males and 7 females） with osteonecrosis of the femoral head and undergoing treatment using umbilical mesenchymal stem cells were selected from January 2017 through September 2019 in the Affiliated Hospital of Xuzhou Medical University. According to the Association Research Circulation Osseous （ARCO） system, 17 hips were classified as stage II, and 12 hips as stage III. Umbilical mesenchymal stem cells （1×10⁷） were implanted intra-articularly under ultrasonic localization. VAS score was used to evaluate pain changes before and at 3, 6, and 12 months after transplantation, Harris score was used to evaluate hip function at 3, 6, and 12 months after transplantation, and imaging results were measured in low-signal area at the maximum level of necrotic area on MRI T1 images before and at 12 months after transplantation. Statistical analysis was performed by SPSS 26.0. Results Postoperative pain was improved： VAS scores at postoperative 3 months （5.29±1.59）, 6 months （3.76±1.22）, and 12 months （2.10±0.70） were lower than that before transplantation （6.86±1.31, P<0.05）. Clinical symptoms were alleviated： 19 cases （90.4%） showed reduced pain of the affected side; 17 cases （80.9%） had improved gait or extended walking distance; 14 cases （66.6%） showed greater range of motion. Harris scores at postoperative 3 months （74.62±9.70）, 6 months （76.90±8.21）, and 12 months （77.48±7.54） were higher than that before transplantation （62.76±10.08, P<0.05）. The necrotic area was （187.27±11.01） mm² at postoperative 12 months, which was significantly reduced compared with （236.31±23.43） mm² before transplantation （P<0.05）. There were 3 patients with aggravation of short-term joint pain on the affected side after transplantation, which was alleviated after non-steroidal anti-inflammatory drug treatment. No adverse reactions such as fever, gastrointestinal reactions, or local infections occurred. Conclusion Local implantation of mesenchymal stem cells can alleviate clinical symptoms, improve joint function, and delay or reverse the imaging progress of patients with early and middle-stage osteonecrosis of the femoral head, which is expected to be a new treatment for femoral head necrosis.

Key words: Mesenchymal stem cells, Osteonecrosis of the femoral head, Local transplantation, Necrosis area, Joint function