The Effect of Body Mass Index on Outcomes of Isolated Medial Patellofemoral Ligament Reconstruction

The effect of body mass index (BMI) on complication risk, recurrent instability risk, and patient-reported outcomes (PROs) after surgical intervention for recurrent patellar instability is unclear.

The purpose was to evaluate the differences in complications, recurrence, and PROs in obese and nonobese patients undergoing isolated medial patellofemoral ligament reconstruction (MPFLR). It was hypothesized that obesity is associated with increased complication risk, increased risk of recurrent patellar instability, and poorer PROs after MPFLR.

Cohort study; Level of evidence, 3.

A retrospective review identified all patients who underwent isolated MPFLR over an 8.5-year period at an academic medical center. Records were reviewed for demographic, physical examination, radiographic, surgical, and clinical outcome data. Patients were contacted to collect PROs, including the Norwich Patellar Instability score, Marx activity scale score, and Knee injury and Osteoarthritis Outcome Score (KOOS). Patients were stratified by BMI (<30 and ≥30 kg/m² for primary analysis and then by ≥35 kg/m² for secondary analysis) and complications and outcomes were compared. Regression analysis was then performed to evaluate the effects of increased BMI on PROs.

The records of 107 patients were analyzed in this investigation. Complication rates were similar across groups. Patients with a BMI ≥35 kg/m² demonstrated a lower Marx activity scale score compared with those with a BMI <30 kg/m² (P = .039). Regression analysis demonstrated no association between BMI and PROs adjusting for age, sex, and articular cartilage damage.

No significant differences in complications or repeat dislocation risk after isolated MPFLR were noted based on BMI ≥30 or <30 kg/m². Patients with a BMI ≥35 kg/m² demonstrated lower activity level, but no other differences in PROs compared with patients with a BMI <30 kg/m².