Abstract
In the USA, 34.9% of adults are currently obese (BMI > 30). Growth in total knee arthroplasty (TKA) is outpacing growth in total hip arthroplasty (THA) largely due to a differential utilization of TKA in overweight patients in the USA. In a recent study, 54.5% of patients reporting to arthroplasty clinics in the USA were obese. From 2006–2010, 61.2% of primary unilateral TKA patients in the USA ACS-NSQIP database were obese. Arthroplasty surgeons are directly affected by the obesity epidemic and need to understand how to safely offer a range of peri-operative care for these patients in order to insure good clinical outcomes.
Pre-operative care for the obese patient involves nutritional counseling, weight loss methods, consideration for bariatric surgery, physical therapy, metabolic workup, and diagnosis and management of frequent comorbid conditions (OSA, DM2, HTN, HLD). Obese patients must also be counseled on their increased risk of complications following TKA.
In the operating room, several steps can be taken to insure success when performing TKA on obese patients. We recommend performing TKA without the use of a tourniquet in order to prevent fat necrosis and increased pain. The incision is made in 90 degrees of knee flexion, atypically midline proximally and curved distally to the midpoint between the tubercle and the medial edge of the tibia. Care is used to minimise the creation of dead space, and the approach to the knee is an extensile medial parapatellar incision. Closure is in multiple layers. The use of negative pressure dressing following surgery can minimise the early wound drainage that is frequently seen after TKA in obese patients.
Post-operative care of the obese patient following TKA involves several unique considerations. Chronic pain and obesity are frequent comorbid conditions and post-operative pain control regimens need to be tailored. Although the physical therapy regimen does not differ in obese patients, obese patients are more likely to be discharged to a rehabilitation facility.
Obese patients have a higher rate of all complications compared to healthy weight. All infection and deep infection increased in obese patients in large meta-analysis. Patients with BMI > 35 are 6.7 times more likely to develop infection after TKA. Patients with BMI > 40 have a 3.35 times higher rate of revision for deep infection than those with BMI < 35. The odds ratio for major complications increases dramatically beyond BMI > 45.
Although there are a few studies that have demonstrated worse clinical outcome in obese patients following TKA, most studies show no difference in clinical outcomes at short- or long-term follow-up. The arthroplasty surgeon must optimise the obese patient prior to surgery, use intra-operative techniques to maximise success, and anticipate potential problems in the post-operative course in order to achieve success with TKA in obese patients.
