Medial patellofemoral ligament (MPFL) reconstruction improves radiographic measures of patella alta in children.

BACKGROUND

Patellofemoral instability has previously been associated with patella alta. The purpose of this study was to evaluate adolescents undergoing MPFL reconstruction for standardized indices of patellar height on pre- and post-operative radiographs to determine if these radiographic parameters change after MPFL reconstruction.

METHODS

Twenty-seven children (mean age 14.9years old) who underwent MPFL reconstruction without a distal realignment procedure were evaluated pre- and post-operatively for Insall-Salvati Ratio, Modified Insall-Salvati Ratio, and Caton-Deschamps Index by three blinded raters. Intrarater reliability and interrater reliability were calculated for each index, and means of each were compared pre- and post-operatively to determine if MPFL reconstruction was associated with improved patellar height.

RESULTS

All three indices of patellar height indicated that there was patella alta present in this cohort preoperatively. Furthermore, all three measures were significantly improved postoperatively (paired t-tests, P<0.001 for all) to within normal childhood ranges. Interrater reliability was excellent for both the Insall-Salvati Ratio (ICC=0.89) and Caton-Deschamps Index (ICC=0.78), and adequate for the Modified Insall-Salvati Ratio (ICC=0.57); intrarater reliability was excellent for all three (ICCs: 0.91, 0.82, 0.80 respectively).

CONCLUSIONS

MPFL reconstruction in children using hamstring autograft was associated with consistently improved patellar height indices to within normal childhood ranges. This associated improvement of patellar height as measured on a lateral radiograph may subsequently improve patellofemoral mechanics by drawing the patella deeper and more medially into the trochlear groove.

LEVEL OF EVIDENCE

Level 4.