Association of Baseline Femoral Trochlear T2* Mapping with Clinical Response to Platelet-Rich Plasma in...

Background: Platelet-rich plasma (PRP) is utilised in the treatment of patellofemoral chondropathy, although clinical responses remain variable. This retrospective exploratory study assessed whether baseline quantitative T2* mapping of femoral cartilage was associated with clinical improvement following PRP administration. Methods: In this retrospective observational study conducted within routine clinical practice, patients with patellofemoral chondropathy received three ultrasound-guided intra-articular PRP injections administered weekly according to an institutional protocol. Baseline and 9-month T2*-mapping MRI scans and clinical questionnaires were collected as part of standard follow-up. The main imaging variable was the worst-region femoral trochlear T2* value, evaluated as a candidate prognostic biomarker. Clinical outcomes included the Visual Analogue Scale (VAS, 0-10) and Kujala (0-100) scores, with responders defined by minimum clinically important difference (MCID) thresholds (ΔVAS ≥ 1.5; ΔKujala ≥ 8). Results: Thirty-two knees from 22 patients completed follow-up, including 10 bilateral cases (19 right knees, 13 left knees). Both VAS and Kujala scores improved significantly at 9 months (p < 0.001 for both). Baseline femoral trochlear worst-region T2* values were inversely correlated with pain and functional improvement (ΔVAS: rho = -0.51, p = 0.003; ΔKujala: rho = -0.36, p = 0.042). Baseline patellar T2* values were not associated with clinical change (ΔVAS: rho = -0.18, p = 0.32; ΔKujala: rho = -0.12, p = 0.51). Sensitivity analyses using baseline mean femoral T2* values did not show significant associations with ΔVAS or ΔKujala. Interobserver reproducibility for the worst-region T2* metric was limited, particularly for the femoral compartment (femur ICC 0.37; patella ICC 0.47), which limits immediate clinical applicability. Mean regional longitudinal ΔT2* changes did not exceed the 14% QIBA MDC95 threshold. Conclusions: In this small retrospective cohort, baseline femoral trochlear worst-region T2* values were associated with clinical improvement after PRP. These preliminary hypothesis-generating findings should be interpreted with caution and require validation in larger controlled cohorts with standardised and reproducible segmentation workflows.