Impact of the fat mass index on early functional recovery after total knee arthroplasty / 中华骨科杂志

ABSTRACT

Objective:To investigate the effect of fat mass index (FMI) on early recovery after total knee arthroplasty (TKA).Methods:Patients who underwent primary unilateral TKA in Xi'an Honghui Hospital from July 2020 to July 2021 were retrospectively analyzed. The preoperative body composition was measured by dual energy X-ray absorptiometry and the FMI was calculated. Patients were divided into normal group (male 3.0-6.0 kg/m 2; female 5.0-9.0 kg/m 2), overweight group (male 6.1-9.0 kg/m 2; female 9.1-13.0 kg/m 2), and obese group (male >9 kg/m 2; female >13 kg/m 2) according to level of FMI, and the operation time, blood loss, and incidence of postoperative complications were collected. Multifactorial analysis of the effect of FMI on early recovery after TKA was performed using a generalized linear model. Draw the receiver operating characteristics (ROC) curve of BMI and FMI on the predicted effect of postoperative Western Ontario and McMaster Universities (WOMAC) osteoarthritis index scores and Knee Society Score (KSS) to compare the effect of FMI with BMI on early recovery after TKA. Results:A total of 100 patients were included in the study, 24 males and 76 females, aged 65.0±8.2 years (range, 42-81 years). There were 15 cases in normal group, 55 cases in overweight group and 30 cases in obese group. All patients successfully completed the operation and were followed up for 3.15±0.72 months (range, 2.8-3.2 months). The WOMAC scores of the obese group at 2 weeks, 1 and 2 months postoperative were 34.57±3.68, 22.03±2.79, and 15.77±2.96, which were greater than those of the normal group (28.73 ±2.58, 19.07±2.71, 12.27±3.10), as well as the overweight group (30.05±4.09, 19.33±2.42, 14.84±2.42), with statistically significant differences ( P<0.05). The KSS scores of the obese group at postoperative 1 and 2 months were 68.83±5.52 and 81.17±4.49, which were lower than those of the normal group (77.33±5.63, 87.33±4.17), as well as the overweight group (72.64±5.43, 83.73 ±5.02), with statistically significant differences ( P<0.05). The WOMAC score, KSS score, and postoperative complications at 2 months postoperatively were selected as outcome indicators to plot the ROC curve, and the ROC curve for the WOMAC score at 2 months postoperatively showed an area under the curve corresponding to FMI of 0.744 (95% CI 0.54, 0.82), which was greater than that of BMI [0.624 (95% CI 0.51, 0.74)], and the difference was statistically significant ( Z=2.19, P=0.021). The ROC curve for the KSS score at 2 months postoperatively showed an area under the curve corresponding to FMI of 0.718 (95% CI 0.62, 0.82), which was greater than that of BMI [0.612 (95% CI 0.52, 0.74)], with a statistically significant difference ( Z=2.58, P=0.016). The ROC curve for postoperative complications showed an area under the curve of 0.639 (95% CI 0.41, 0.88) for FMI and 0.605 (95% CI 0.37, 0.84) for BMI, with no statistically significant difference ( Z=0.48, P=0.632). Conclusion:The greater the FMI the poorer the early functional recovery after initial TKA, and FMI is more valuable than BMI in predicting the early functional recovery.