A recent study depicted that in KOA patients after total knee arthroplasty TKA, BMD is an effective predictor for postoperative pain alleviation. When the patient's BMD T-level < 3.0 SD, the poor pain relief should be fully taken into consideration. Antiosteoporosis drugs should be continually administered to these patients.

A retrospective observational single-center study was conducted between October 2016 to March 2018 to investigate the risk factors for poor postoperative pain relief and assess the predictive significance of BMD in postoperative pain relief in 156 KOA patients after TKA. To estimate the pain intensity in individuals within one year after TKA, a visual analogue scale (VAS) was utilized.

With a one year of follow-up, the participants were grouped into either good pain relief group (the improvement of VAS > 3) or poor pain relief group (the improvement of VAS < 3). BMD and other clinical characteristics were also accurately collected.

To determine the predictive significance of BMD, the receiver operating characteristic curve (ROC curve) and logistic regression analysis were utilized. To comparatively evaluate the difference of postoperative pain between high and low BMD group, the subgroup analysis was utilized.

Overall, 34 (21.8%) patients were found to have poor pain relief after TKA. According to logistic regression analysis, BMD, age, preoperative hospital for special surgery (HSS) scores, postoperative posterior slope angles (PSA), and preoperative VAS score were the risk factors of poor pain relief.

Using BMD as a predictor, the optimum cut-off value of poor pain relief was T-level= -3.0 SD in the ROC curve, where sensitivity and specificity were 73.5% and 83.7%, respectively as shown in the following figure:

Based on this cut-off value, a better pain alleviation was witnessed in the high BMD group compared with low BMD group from the sixth month after TKA in the subgroup analysis as depicted in the following figure:

Thus, in KOA patients after TKA, BMD can effectively predict postoperative pain relief.