Abstract
INTRODUCTION: Although total knee arthroplasty (TKA) effectively improves knee pain and functional decline due to knee osteoarthritis, hip fractures are more likely to occur in the first year after surgery. Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) decreases in the first year after TKA, but it is not clear whether BMD measured by quantitative ultrasound (QUS) also shows a decrease. This study aimed to evaluate the change in QUS parameters before and 1 year after TKA and to investigate the association of QUS parameters with quadriceps strength and function 1 year after TKA. METHODS: This prospective cohort study included 30 patients scheduled for their unilateral TKA. We assessed BMD using QUS before and 1 year after surgery. Quadriceps strength was assessed using a hand-held dynamometer, and function was assessed using a self-reported questionnaire. A linear mixed model estimated the mean difference in QUS parameters before and 1 year after TKA. A general linear model was also used to examine the association of QUS parameters with quadriceps strength and self-reported function at 1 year after surgery. RESULTS: We found no significant decrease in the QUS parameters on either the surgical or non-surgical side at 1 year postoperatively compared to preoperatively. The QUS parameters were not associated with quadriceps strength or self-reported function on either the surgical or non-surgical side at 1 year postoperatively. CONCLUSIONS: QUS alone may not be sufficient to detect changes in BMD from before surgery to 1 year after TKA. Clinicians should evaluate BMD preoperatively to identify patients at high risk for hip fractures and develop a program to prevent postoperative hip fractures. LEVEL OF EVIDENCE: Level 3, Cohort study.