Autologous protein solution injections in end-stage hip and knee osteoarthritis: comparison of rates of conversion to arthroplasty

Purpose: This study evaluated the efficacy of autologous protein solution (APS) injections in patients with end-stage osteoarthritis of the hip (HOA) or knee (KOA). Given the limited evidence for APS in HOA, the focus was on comparing the rates of conversion to arthroplasty between the two joints after APS therapy. Therefore, the primary aim of this study was to compare conversion rates to arthroplasty, while the secondary aim was to evaluate response rates based on short-term patient-reported outcomes. Additionally, given the anticipated differences in patient backgrounds between KOA and HOA groups, a supplementary analysis was conducted using propensity score matching (PSM). Methods: Patients with Kellgren–Lawrence grade 4 HOA or KOA who received APS injections at a single institution between 2018 and 2023 were retrospectively reviewed. PSM was used to adjust for age, sex, body mass index, and follow-up duration. Arthroplasty-free survival was assessed using the Kaplan–Meier method. Clinical efficacy was evaluated with the OMERACT-OARSI criteria, using the Knee Injury and Osteoarthritis Outcome Score for KOA and the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire for HOA. Results: Of 704 cases treated, 16 hips and 183 knees met the inclusion criteria; 15 hips and 15 knees were matched for analysis. Kaplan–Meier curve analysis revealed a significantly higher 2 year rate of conversion to arthroplasty for HOA (75.0% vs. 36.6%; p < 0.0001). However, there was no significant difference in the 6 month OMERACT-OARSI response rate (HOA 54.2%, KOA 40.0%; p = 0.38). Conclusion: APS provided short-term symptom relief in both HOA and KOA but failed to delay arthroplasty in most HOA cases. Anatomical and biomechanical factors may influence long-term efficacy.