SPAIRE approach shows equivalent changes in bone mineral density as a conventional approach in femoral neck fracture patients : a sub-group analysis of 49 patients from a randomized controlled trial.

Aims: The incidence of periprosthetic fractures is increasing and, in 2023, was the main reason for revision arthroplasty in Norway. Some studies indicate that the surgical approach affects periprosthetic bone density and possibly could influence fracture risk. The SPAIRE (sparing piriformis and obturator internus, repairing externus) approach is gaining popularity. As a relatively novel surgical approach, we designed a randomized controlled trial (RCT) comparing the SPAIRE and direct anterior (DA) approaches in femoral neck fracture (FNF) patients operated with hemiarthroplasty, and hypothesized equal changes in periprosthetic bone mineral density (BMD).

Methods: From January 2022, eligible patients with a dislocated FNF were included in a RCT comparing the approaches (n = 158). Hypothesis and planned statistical tests were prespecified in this sub-group analysis, and 49 patients were examined by dual energy x-ray absorptiometry and followed for one year.

Results: Both groups displayed a reduction in BMD from baseline to final follow-up. Mean BMD was -1.8% (95% CI -3 to 0.6) at three months and -0.5% (95% CI -1.2 to 0.2) at 12 months. In the SPAIRE group, total BMD decreased by 1.2% (95% CI -2.7 to 0.3) compared with 2.3% (95% CI -4.3 to -0.4) in the DA group at three months. At 12 months, total BMD increased by 0.2% (95% CI -0.9 to 1.2) in the SPAIRE group compared with a reduction of 1.2 (95% CI -2.3 to -0.1) in the DA group. Non-significant changes in Gruen zones 1 to 6 were found at three and 12 months. There was bone loss in Gruen zone 7 at 12 months in favour of the SPAIRE approach.

Conclusion: There were substantially insignificant differences in periprosthetic BMD changes between the groups at baseline, three, and 12 months. The results indicate that SPAIRE and DA approaches affect periprosthetic BMD equally, and the approaches do not seem to have an unequal periprosthetic fracture risk.