Surgical approach influences periprosthetic femoral bone density

Our hypothesis was that the bone mineral density of the proximal femur is altered significantly by surgical approach. The change in long-term periprosthetic bone mineral density in relation to the alteration of the musculature after the anterolateral (Group A) and transgluteal approaches (Group B) has been compared. There were 35 hips (30 patients) in Group A and 47 hips (37 patients) in Group B. No significant differences were seen between groups with respect to age, gender, diaphyseal bone mineral density distribution, or average stem size in a Wilcoxon-Mann-Whitney test. Measurement of bone mineral density in femoral Gruen zones revealed a significant bone loss in Group B compared with Group A in the multivariate analysis, which was confirmed by univariate post hoc tests in Zones I, II, VI, and VII (multiple significance according to Bonferroni-Holm's procedure). The functional outcome, however, showed no significant differences between the two groups postoperatively. A potential reason for the bone mineral density shift might have been a redistribution of the musculoskeletal loading across the hip after a transgluteal, compared with an anterolateral, surgical approach. A difference in the muscular damage caused by the two surgical approaches seems to have a significant influence on the long-term bone loss.