Total knee replacement in the morbidly obese: a literature review

The 'obesity epidemic' is expected to result in an increased incidence of knee osteoarthritis and hence total knee replacements (TKRs). Reviews have demonstrated the conflicting results of TKR for all obese (body mass index (BMI) >30). The aim of this literature review was to specifically evaluate outcomes of TKR in patients with morbid obesity (MO; BMI >40).

A systematic review of medical databases (PubMed, Medline, Cochrane Library, ScienceDirect) by use of keywords from January 1990 to September 2009 was undertaken.

Clinical and functional Knee Society Scores (KSS) improve after TKR for patients with MO. The post-operative functional KSS was, in general, less than in controls. Radiographic analysis was inconclusive because of small study populations and short duration of follow-up. All studies reporting complications noted a greater prevalence in MO patients (10-30%). Of concern was the significantly higher prevalence of deep prosthetic infection (3-9-times that of controls). The morbidly obese also had a significantly higher incidence of wound complications. TKR did not result in weight loss for MO patients, and therefore has no benefit on weight-related medical conditions. Bariatric surgery in MO under 65 years of age has been shown to be a cost-effective and clinically effective method of weight reduction. This surgery also results in significant improvement in weight-related medical conditions, the KSS and knee pain.

Given the increase in complications for MO patients after TKR, these patients should be advised to lose weight before surgery and, if suitable, would probably benefit from bariatric surgery.