Bone Abstracts

Introduction: The authors experienced a ipsilateral femoral stress fracture after total knee arthroplasty (TKR). Decreased bone mineral density (BMD) after TKR have been proposed as cause. However, reports regarding changes of BMD in the proximal hip after TKR have been rare. Therefore, first, we studied the question of whether TKR can effect change of proximal hip BMD? Second, if so, does TKR have different effects on BMD of the operative and non-operative sides?

Materials and methods: Forty-eight patients scheduled to undergo unilateral TKA because of primary knee OA were included in this study, conducted at a medical center, between October 2006 and October 2009. In these 48 patients, 96 hips were evaluated. Measurement of BMD was performed preoperatively and 1 month, 3 months, 6 months, and 1 year after unilateral TKA.

Results: BMD of both femoral neck areas was significantly lower than preoperative BMD at 1 month and 3 months after TKA. BMD of both trochanter areas was significantly lower than preoperative BMD at 1 month and 3 months after TKA. However, no statistical differences of changes in BMD of femur neck and trochanter were observed between the operative and non-operative sides at each measurement time.

Conclusion: Total knee arthroplasty was found to affect both proximal femurs during the early period after TKR. However, it does not affect the ipsilateral side and contralateral side differently. Therefore, we thought that a temporary decrease in BMD after TKR was not the direct cause of ipsilateral femoral stress fracture.