Morbid obesity in total hip arthroplasty: What does it mean?

Obesity affects 34% of the U.S. population, and the number of obese patients undergoing elective total hip arthroplasty (THA) is increasing each year. The objective of this study is to summarize the current scientific findings regarding the outcomes of THA in the morbidly obese (BMI > 40 kg/m²) patients. Specifically, our goal is to identify the incidence of complications and the influence on clinical and functional outcome measures in morbidly obese patients undergoing elective primary THA. A systematic review was performed identifying all of the studies from the PubMed, Medline, EBSCO and Cochrane Library databases that reported outcomes of primary THA in morbidly obese [body mass index (BMI) ≥ 40 kg/m²] patients. We identified 13 articles that met inclusion criteria for systematic review. These studies included 15,906 primary THAs in morbidly obese patients. Morbidly obese patients underwent THA at a significantly younger age compared to the non-morbidly obese cohort (63 years versus 70 years) comparator group. Eleven of the 13 studies reported complication rates in morbidly obese versus non-obese patient cohorts. Eight of the 11 studies reported increased complication rates in morbidly obese patients. Of the 13 studies, 9 had documented outcome scores in morbidly obese patients. All studies concluded that morbidly obese patients had the poorest overall preoperative and postoperative functional scores. Seven of the studies also documented the net gain in functional scores after THA between the morbidly obese and the non-morbidly obese groups. No difference was found between the groups. Morbidly obese patients undergo primary THA at a significantly younger age than non-obese patients. Furthermore, morbidly obese patients have a higher perioperative complication rate. Overall outcome measures are worse in the pre operative and the post operative phase in the short- and the medium-term follow-up time intervals. However, morbidly obese patients have similar functional gains as non-morbidly obese patients following THA.