Effect of body mass index on functional outcomes following arthroplasty procedures

To evaluate the body mass index (BMI) change in arthroplasty patients and its impact on the patients' functional results.

Between October 2010 and May 2013, 606 patients who were operated due to gonarthrosis, coxarthrosis, aseptic loosening of the total knee and hip prosthesis were evaluated prospectively. Patients were operated by three surgeons in three medical centers. Patients who were between 30-90 years of age and who were underwent total knee arthroplasty, total hip arthroplasty, revision knee arthroplasty, or revision hip arthroplasty were included in the study. We excluded the patients who cannot tolerate our standard postoperative rehabilitation program. Additionally, patients who had systemic inflammatory diseases, diabetes mellitus, or endochrinopathies were excluded from the study. The remaining 513 patients comprised our study group. Preoperative functional joint scores, height, weight and BMI of all patients were recorded. We used the Knee Society Score (KSS) for knee and Harris Hip Score (HHS) for hip patients. Postoperative functional scores were measured at 1(st), 6(th) and 12(th) months and recorded separately at outpatient visits.

The mean age of the patients was 64.7 (range: 30-90) years (207 males/306 females) and the mean follow-up duration was 14.3 (range: 12-26) mo. We found that arthroplasty patients had weight gain and had an increase in BMI at the postoperative 1(st), 6(th) and 12(th) months. The mean BMI of the patients was 27.7 preoperatively, 27.8 at the postoperative 1(st) month, 28.1 at the 6(th) month and 28.6 at the 12(th) month (P < 0.01). At the last visit, the mean postoperative HHS of the hip arthroplasty patients was 82.2 ± 7.12 (preoperatively, 52.3; 1(st) month, 78.2; 6(th) month, 81.1; 12(th) month, 82.2), and the mean KSS of the knee arthroplasty patients was 79.3 ± 4.31 (preoperatively, 35.8; 1(st) month, 75.2; 6(th) month, 79.1; 12(th) month, 79.3). Worse functional results were noted in the patients who had a BMI increase, however, this correlation was statistically significant only at the postoperative 6(th) month (P = 0.03).

To prevent the negative functional effects of this weight gain during the postoperative period, arthroplasty patients should be advised for weight control and risky patients should consult with a dietician.