Background: The purpose of this study was to evaluate the hypothesis that medial patellofemoral ligament (MPFL) reconstruction for patellar instability decreases patellar height.
Methods: Preoperative and postoperative lateral knee radiographs of 38 adolescents who underwent MPFL reconstruction between 2005 and 2011 were reviewed. The Insall-Salvati index, Blackburne-Peel index, Caton-Deschamps index, and plateau-patella angle were measured on all radiographs to identify differences in patellar height. These patellar height indices were also measured on lateral knee radiographs of 25 adolescents (control group) who were treated conservatively for osteochondritis dissecans of the knee. The 2 groups were compared to account for patellar height changes secondary to growth and ossification. Intrarater reliability was measured for all patellar height indices at 1-month interval.
Results: Preoperatively, patients who underwent MPFL reconstruction had significantly greater patellar height on all indices compared with the control group before and after controlling for age and sex. The patients who underwent MPFL reconstruction showed a significantly greater decrease in patellar height on the Blackburne-Peel or Caton-Deschamps indices over time compared with the control group such that postoperatively there was no difference between groups in these patellar height indices. Furthermore, the change in patellar height indices after MPFL reconstruction did not differ between patients with less than or more than 1-year follow-up. All indices demonstrated good to excellent intrarater reliability.
Conclusions: The present study showed a decrease in patellar height in the postoperative period in patients after MPFL reconstruction for patellar instability. Further investigation is necessary to determine the long-term effects of MPFL reconstruction on patellar height.
Level of evidence: Level III--therapeutic, case series.