ObjectiveTo explore the clinical efficacy and safety of ultrasound-guided intra-articular injection of platelet-rich plasma (PRP) in the treatment of avascular necrosis of the femoral head.MethodsWe retrospectively collected and analyzed the clinical characteristics, imaging data, and clinical outcomes of patients with femoral head necrosis who received ultrasound-guided intra-articular PRP injection in the Department of Rehabilitation Medicine of Sun Yat-sen Memorial Hospital, Sun Yat-sen University between June 2019 and June 2020. All the patients received 4 injections at one-week intervals. The Visual Analogue Scale (VAS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and Harris Hip Joint Function Scale (HHS) were evaluated before treatment and 1 month, 3 months, and 6 months after the first injections. Adverse events were recorded. The normally distributed data were presented as mean±standard deviation, and analyzed by one-way repeated measures analysis of variance; the non-normally distributed data were presented as median (lower quartile, upper quartile), and analyzed by Friedman test.ResultsA total of 29 patients were included. According to the Association Research Circulation Osseous classification standard, 2 patients were classified as stageⅠ, 11 as stageⅡ, 11 as stage Ⅲ, and 5 as stage Ⅳ. Before treatment and 1 month, 3 months, and 6 months after treatment, the VAS scores were 7.0 (5.5, 8.0), 4.0 (3.0, 5.0), 3.0 (2.0, 3.0), and 3.0 (2.0, 5.0), respectively, the WOMAC scores were 39.27±11.70, 28.34±8.08, 22.82±6.09, and 24.13±7.55, respectively, and the HHS were 46.0 (40.0, 64.0), 71.0 (57.5, 75.0), 78.0 (68.0, 80.5), and 78.0 (64.0, 80.0), respectively. The time effects in VAS (χ2=65.423, P<0.001), WOMAC (F=46.710, P<0.001), and HHS (χ2=66.347, P<0.001) were all statistically significant. There were significant differences in each index between the values 1 month, 3 months, and 6 months after treatment and those before treatment respectively, and there was also a significant difference in each index between the value 1 month after treatment and that 3 months after treatment (P<0.05). There was no significant difference in any indicator between the value 6 months after treatment and that 3 months after treatment (P>0.05). Significant difference was shown between the value 6 months after treatment and that 1 month after treatment in WOMAC (P=0.016), but not in VAS or HHS (P>0.05). No obvious adverse event was reported during the follow-up period.ConclusionsUltrasound-guided intra-articular PRP injection can effectively alleviate the pain and improve the hip joint function of patients with femoral head necrosis for at least 6 months. However, randomized controlled studies with a larger sample size and longer-term follow-up are needed in the future to confirm the efficacy and safety of PRP injection in femoral head necrosis.