Trochleoplasty combined with MPFL reconstruction is associated with a postoperative reduction in the measured Caton–Deschamps index

Introduction To investigate changes in MRI-measured Caton–Deschamps index (CDI) at mid- to long-term follow-up following groove-deepening trochleoplasty (TP) combined with medial patellofemoral ligament reconstruction (MPFLR) and to compare these changes between single-bundle quadriceps tendon graft (QTG) and double-bundle hamstring tendon graft (HTG) reconstruction. Materials and methods Seventeen patients who had undergone TP with concomitant MPFLR were analyzed retrospectively. Patellar height was assessed preoperatively and postoperatively on sagittal magnetic resonance images by three independent observers using the CDI. Preoperative and postoperative CDI values were compared using a paired t -test. CDI changes were compared between single-bundle QTG ( n = 9) and double-bundle HTG ( n = 8) reconstruction using an independent-samples t -test. Interobserver reliability was assessed using the intraclass correlation coefficient (ICC). Results The mean CDI decreased significantly from 1.06 ± 0.13 preoperatively to 0.95 ± 0.15 postoperatively (Δ = −0.10 ± 0.07; P < 0.001). Significant postoperative reductions in CDI were observed in both subgroups (QTG: P = 0.002; HTG: P = 0.004), with no significant difference in CDI change between the groups ( P = 0.77). Interobserver reliability was good for single measurements and excellent for measurements averaged across the three observers. Conclusions Combined trochleoplasty and MPFL reconstruction was associated with a significant postoperative reduction in MRI-measured CDI at mid- to long-term follow-up, with an average decrease of − 0.10. Whether this finding reflects true anatomical patellar distalization cannot be determined from the present study.