Influence of Hydroxyapatite Coating for the Prevention of Bone Mineral Density Loss and Bone Metabolism after Total Hip Arthroplasty: Assessment Using 18F-Fluoride Positron Emission Tomography and Dual-Energy X-Ray Absorptiometry by Randomized Controlled Trial.

BACKGROUND: Hydroxyapatite- (HA-) coated implants tend to achieve good osteoinductivity and stable clinical results; however, the influence of the coating on the prevention of bone mineral density (BMD) loss around the implant is unclear. The purpose of this randomized controlled trial was to evaluate the effectiveness of HA-coated implants for preventing BMD loss and to determine the status of bone remodeling after total hip arthroplasty (THA), making comparisons with non-HA-coated implants. METHODS: A total of 52 patients who underwent primary THA were randomly allocated to HA and non-HA groups. BMD was measured by dual-energy X-ray absorptiometry (DEXA) at 1 week postoperation to form a baseline measurement, and then 24 weeks and 48 weeks after surgery. The relative change in BMD was evaluated for regions of interest (ROIs) based on the Gruen zone classifications. 18F-fluoride positron emission tomography (PET) was performed at 24 weeks postsurgery, and the maximum standardized uptake values (SUVmax) were evaluated in the proximal (HA-coated) and distal (non-HA-coated) areas in both groups. RESULTS: There were significant differences in BMD loss in ROIs 3 and 6 (p = 0.03), while no significant difference was observed in ROI 7 at either 24 or 48 weeks postsurgery. There was no significant correlation between PET uptake and BMD (24 or 48 weeks) in either group. CONCLUSION: The influence of a HA coating in terms of BMD preservation is limited. No significant correlation was found between BMD and SUVmax measured by PET, either with or without the use of a HA coating.

Plasma accumulation of fondaparinux 2.5 mg in patients after total hip arthroplasty.

Fondaparinux (FPX), a selective inhibitor of factor Xa, is widely used for the prophylaxis of venous thromboembolism (VTE) after total joint arthroplasty. However, the association between plasma FPX concentration and adverse events and the occurrence of VTE has not been clarified thus far. We aimed to prospectively evaluate these associations by measuring anti-Xa activity of FPX in patients undergoing total hip arthroplasty (THA) and investigate whether factors such as age, body weight, and renal function influence the anti-Xa levels. We enrolled 85 patients who underwent primary THA. All patients received subcutaneous FPX (2.5 mg/day for 14 days) after surgery. Anti-Xa activity was measured on postoperative days 1, 3, 7, and 14. To assess VTE, multidetector row computed tomography was performed in all patients at 1 week after surgery. The median levels of anti-Xa activity increased as follows (medians with 95 % confidence interval): 0.00 (0.00-0.01) mg/L, 0.13 (0.11-0.14) mg/L, 0.19 (0.17-0.20) mg/L, and 0.24 (0.22-0.25) mg/L on postoperative days 1, 3, 7, and 14, respectively. The plasma accumulation of FPX was more likely in patients with renal impairment than in those with normal renal function. In contrast, a poor correlation was observed between the plasma levels of anti-Xa activity and age or body weight. No differences were observed in the anti-Xa activity in patients with and without postoperative VTE or bleeding. Substantial increase in the levels of anti-Xa activity was observed, especially in patients with renal impairment, after subcutaneous administration of FPX 2.5 mg after THA.