No benefit in biomarkers assessing muscle damage for minimally invasive anterior over SPAIRE approach in hemiarthroplasty : a subgroup analysis with 100 patients from a randomized controlled trial.

Aims: Muscle damage and inflammation after hemiarthroplasty (HA) for femoral neck fracture (FNF) could affect time to mobilization. Early mobilization is key in enhanced recovery and fast-track care systems. We have compared muscle damage and inflammation using creatine kinase (CK) and CRP as biomarkers in FNF patients operated on with the direct anterior (DA) and the sparing piriformis and obturator internus, repairing externus (SPAIRE) approach. Methods: From January 2022, 158 eligible patients with a dislocated FNF were included in a randomized controlled trial comparing the approaches (n = 158). Hypothesis and planned statistical tests were pre-specified in this sub-group analysis and 100 patients were tested for CK, CRP, and haemoglobin (Hb) levels during hospital admission. Results: Mean difference in CK between groups was, on postoperative day one, 45 u/l (95% CI -22 to 151, p = 0.290) and day two, 66 U/l (95% CI -42 to 185, p = 0.19). Mean difference in CRP was 3 mg/l (95% CI -23 to 19, p = 0.933) and Hb, 0.3 g/dl (95% CI -0.2 to 0.5, p = 0.388) on day two postoperatively. No correlation was found between CK/CRP and Timed Up and Go test and Harris Hip Score. Conclusion: There were no differences in CK and CRP changes between the groups on day one and two after surgery. No correlation was found between CK and clinical outcomes in FNF patients operated with SPAIRE and the DA approach.