Summary

Class 1 obesity does not affect radiographic, clinical, or patient-reported outcomes following MPFL-reconstruction.

Abstract

Introduction

Dislocations of the kneecap may cause significant pain and disability, with recurrent dislocations often requiring surgical reconstruction. Medial patellofemoral ligament reconstruction (MPFL-R) has been developed to achieve stability in such knees. Body mass index (BMI) is a known risk factor for a variety of conditions, yet there exists a lack of data regarding the influence of BMI on radiographic, clinical, and patient-reported outcomes (PROs) following MPFL-R. The purpose of this study was to evaluate the outcomes from obese and non-obese patients undergoing MPFL-R without tibial tubercle osteotomy (TTO). We hypothesized that patients with a BMI = 30 would exhibit worsened outcomes across all variables.

Methods

A billing query identified all patients from one academic medical center who were twelve to eighty-five years-old and had undergone MPFL-R over an 8.5-year period. Records were reviewed for demographic, physical exam, radiographic, surgical, and clinical outcomes data. PROs included the Norwich Patellar Instability (NPI) grade, Marx activity rating, and Knee Injury and Osteoarthritis Outcome Score (KOOS). Descriptive statistics, Chi-squared analysis, and linear regressions were performed to assess the effects of BMI as a categorical and continuous variable.

Results

A total of 161 MPFL-Rs without TTO were included. Of this cohort, 115 were BMI < 30 and 46 were BMI = 30. Clinical follow up was 66.2 and 54.4 weeks among the non-obese and obese cohorts, respectively (p=0.07). Functional outcomes (time in brace, time to weight bearing, return to sport) and postop complications (deep vein thrombosis, infection, pain, repeat dislocation/instability) were similar between both cohorts (p>0.50). When comparing between BMI of 30, PROs were all similar (p>0.10). Linear regression fit BMI and NPI with r2= 0.0622, p=0.0137; and BMI and Marx with r2= 0.0525, p=0.0239. When comparing cohorts with a BMI cutoff of 35, NPI and Marx were significantly worse in the obese cohort (p=0.0184 and p=0.0108, respectively).

Conclusion

To our knowledge, this is the largest study to date to assess the effects of BMI following MPFL-R. Among our cohort, BMI = 30 was not associated with worsened outcomes, yet BMI = 35 may be associated with worsened PROs. Surgeons may consider MPFL-R and more invasive procedures such as TTO among obese patients without fear of worsened outcomes. Future outcomes studies among morbidly obese patients may be warranted.