Morbid Obesity: A Significant Risk Factor for Failure of Two-Stage Revision Total Knee Arthroplasty for Infection

BACKGROUND: Obese patients have a higher risk of complications following primary total knee arthroplasty, including periprosthetic joint infection. However, there is a paucity of data concerning the efficacy of two-stage revision arthroplasty in obese patients. METHODS: We performed a two-to-one matched cohort study to compare the outcomes of thirty-seven morbidly obese patients (those with a body mass index of ≥ 40 kg/m(2)) who underwent two-stage revision total knee arthroplasty for periprosthetic joint infection following primary total knee arthroplasty with the outcomes of seventy-four non-obese patients (those with a body mass index of <30 kg/m(2)). Groups were matched by sex, age, and date of reimplantation. Outcomes included subsequent revision, reinfection, reoperation, and Knee Society pain and function scores. The minimum follow-up time was five years. RESULTS: Morbidly obese patients had a significantly increased risk for revision surgery (32% compared with 11%; p < 0.01), reinfection (22% compared with 4%; p < 0.01), and reoperation (51% compared with 16%; p < 0.01). Implant survival rates were 80% for the morbidly obese group and 97% for the non-obese group at five years and 55% for the morbidly obese group and 82% for the non-obese group at ten years. Knee Society pain scores improved significantly following surgery in both groups; the mean scores (and standard deviation) were 50 ± 5 points for the morbidly obese group and 55 ± 2 points for the non-obese group (p = 0.06) preoperatively, 74 ± 5 points for the morbidly obese group and 89 ± 2 points for the non-obese group (p < 0.0001) at two years, 72 ± 6 points for the morbidly obese group and 88 ± 3 points for the non-obese group (p < 0.0001) at five years, and 56 ± 9 points for the morbidly obese group and 84 ± 3 points for the non-obese group (p = 0.01) at ten years. CONCLUSIONS: Morbid obesity significantly increased the risk of subsequent revision, reoperation, and reinfection following two-stage revision total knee arthroplasty for infection. In addition, these patients had worse pain relief and overall function at intermediate-term clinical follow-up. Although two-stage revision should remain a standard treatment for chronic periprosthetic joint infection in morbidly obese patients, increased failure rates and poorer outcomes should be anticipated.