Femoral neck bone mineral density levels unaffected following hip resurfacing

Cordingley R, et al. J Bone Joint Surg (Br). 2010;92(12):1648-1653.

There was no significant deterioration of superolateral femoral neck bone mineral density in 423 patients that Australian investigators studied by comparing bone mineral density levels in their hips that underwent resurfacing arthroplasty to their unoperated contralateral hips.

Investigators based this conclusion on bone mineral density (BMD) studies repeated over 2 postoperative years.

Rebecca L. Cordingley, PhD, and colleagues at the University of Technology in Sydney recruited patients for their prospective consecutive case control study who were not osteoporotic based on preoperative bilateral femoral BMD (mean age 54 years). All patients underwent hip resurfacing done by the same surgeon with the Birmingham hip resurfacing system (Smith & Nephew Inc.) between January 2000 and September 2004.

The study’s primary endpoint was whether BMD was affected by the procedure with a secondary endpoint of whether activity levels changed in any patients. Investigators separated patients by age and gender to determine any differences in results based on those demographic factors.

T-scores were used to determine the quality of bone for each patient.

No patients experienced a femoral neck fracture during the study period or had infections or other conditions that might affect their reaching either endpoint, according to the abstract.

Based on dual energy X-ray absorptiometry BMD tests done on both hips preoperatively and at 6, 12 and 24 months postoperatively, median BMD values did not differ statistically between the resurfaced and unoperated hips at any follow-up time period, Cordingley and colleagues noted in the study results.

Only women aged 65 years and younger showed a different trend: investigators found a slight correlation between BMD in the resurfaced and unresurfaced hips only through 1 year postoperatively, which “suggests that the level of correlation for a specific subgroup could be because of, or coupled with, some other characteristic within the subgroup,” the researchers wrote.

Clinically significant changes occurred in activity based on SF-36 physical function scores, which Cordingley and her colleagues concluded was due to a general improvement in health related to better correlation between bilateral femoral BMD.