High periprosthetic bone mineral density measured in immediate postoperative period may not guarantee less periprosthetic bone loss in the proximal femur after cementless total hip arthroplasty - A retrospective study.

BACKGROUND: Total hip arthroplasty is the most common orthopaedic procedure for the end-stage hip diseases. Periprosthetic bone loss is closely related to the increased risk of implant loosening and periprosthetic fractures, but the predictive value of periprosthetic bone mineral density (BMD) measured immediately after surgery has not yet been investigated. METHODS: From April 2015 to October 2017, 64 patients with femoral neck fracture, hip osteoarthritis, femoral head necrosis, or developmental dysplasia of the hip underwent unilateral total hip arthroplasty. Demographic data, bone mineral density of the hip and spine, periprosthetic BMD of 7 Gruen zones, and radiographic parameters measured preoperatively, 1 week, 3 months, and 12 months after surgery were collected. A p value < 0.05 was considered to be statistically significant. RESULTS: Significant decreases of the periprosthetic BMD were found in Gruen zone 1 (- 8.0%; p < 0.05), Gruen zone 2 (- 6.3%; p < 0.05), Gruen zone 7 (- 8.6%; p < 0.05), and total Gruen zone (- 4.7%; p < 0.05) in the first postoperative year, compared with the values measured 1 week after surgery. The relationship between the preoperative BMD of the hip/spine and the BMD of Gruen zone 1 and Gruen zone 7 measured 1 week after surgery did not reach statistical significance. The multiple linear regression analysis illustrated that the bone loss in Gruen zone 7 at the end of the follow-up period was negatively affected (ß = - 0.703) by the BMD of Gruen zone 7 measured 1 week after surgery, with a R2 of 0.486 (p < 0.05). Similar results were also found in Gruen zone 1 (ß = - 0.448, R2 = 0.186; p < 0.05). CONCLUSION: There were marked decreases in periprosthetic BMD of the proximal femur in the first postoperative year. The predictive values of preoperative BMD of hip and spine on periprosthetic bone loss after THA were limited. Higher periprosthetic BMD measured in immediate postoperative period may not guarantee less periprosthetic bone loss in the proximal femur after cementless THA.