Obesity as a Risk Factor for Failure following a Modified Brostrom Procedure

CATEGORY: Ankle; Hindfoot INTRODUCTION/PURPOSE: The modified Brostrom procedure has been widely accepted as the operative treatment of choice for treating lateral ankle instability in patients that have failed nonoperative management. However, the predisposing risk factors for failure of operative treatment, which has important implications for patient selection, is unknown. Foot and ankle surgeons often raise body mass index (BMI) as a particular concern due to the increased pressure and strain that is applied to the repair with standing and walking in the setting of an elevated BMI. The purpose of this study was to investigate the effect of patient BMI at the time of surgical intervention on preoperative and long-term postoperative functional outcomes, as well as complication and reoperation rates. METHODS: A retrospective single institutional study of 160 modified Brostrom procedures, average age 43.8 years, was performed with a minimum of 2-year follow-up. An electronic query based on Current Procedural Terminology codes was initially performed followed by a manual review of the operative report. Patients with any concurrent osteotomy, arthrodesis, or arthroplasty procedures were excluded. Pre- and postoperative Foot and Ankle Ability Measure (FAAM) ADL and Sports survey responses along with Visual Analog Scale for Pain (0-100) patient reports were recorded. Comorbidities and relevant demographic information were manually obtained. Patients were split into two groups based on their preoperative BMI: those patients with BMI <30 and those >=30 (considered obese). Treatment success was defined as achieving the previously established minimal clinically important difference (MCID) FAAM-ADL increase of >=8 and/or FAAM-Sport increase of >=9 from the preoperative to postoperative period. RESULTS: Of 97 patients with BMI <30, 22 (22.7%) did not demonstrate a self-reported MCID in the FAAM-ADL score, and 20 (20.6%) did not demonstrate positive MCID in the FAAM-Sport score. For the 63 patients with BMI >=30, 13 (20.6%) failed to reach FAAM-ADL MCID, while 12 (19%) failed to reach FAAM-Sport MCID. BMI was not shown to be significant in terms of clinical improvement following surgery, as both groups improved significantly on average from preoperative period to follow-up with 125/160 (78.1%) achieving MCID in FAAM-ADL and 128/160 (80%) achieving MCID in FAAM-Sport. However, patients with BMI <30 had significantly higher average preoperative FAAM-ADL scores than those >=30 (66.7 vs 51.2; p=0.003) and higher average postoperative ADL scores that approached significance (92.9 vs 84.5; p=0.075). CONCLUSION: The modified Brostrom procedure has been previously shown to effectively improve stability and function of the ankle with relatively high rates of success, and such findings are supported by this study. In addition, this study demonstrates that patient BMI is not a prohibitive factor in limiting clinical success in the postoperative period. The procedure was generally effective for both groups of patients. However, data suggests that the condition of lateral ankle instability may simply be more debilitating for those patients with obese BMI, and that these patients should have lower expectations in terms of their absolute recovery of function.