Preoperative posterior tilt of at least 20° increased the risk of fixation failure in Garden-I and -II femoral neck fractures

Background and purpose — It has been suggested that preopera- tive posterior tilt of the femoral head may increase the risk of fi xa- tion failure in Garden-I and -II femoral neck fractures. To inves- tigate this association, we studied a cohort of 322 such patients. Patients and methods — Patients treated with internal fi xation between 2005 and 2012 were retrospectively identifi ed using hos- pital records and the digital image bank. 2 raters measured the preoperative posterior tilt angle and categorized it into 3 groups: < 10°, 10–20°, and  20°. The inter-rater reliability (IRR) was determined. Patients were observed until September 2013 (with a minimum follow-up of 18 months) or until failure of fi xation necessitating salvage arthroplasty. The risk of fi xation failure was assessed using competing-risk regression analysis, adjusting for time to surgery. Results — Patients with a posterior tilt of  20° had a higher risk of fi xation failure: 19% (8/43) as compared to 11% (14/127) in the 10–20° category and 6% (9/152) in the < 10° category (p = 0.03). Posterior tilt of  20° increased the risk of fi xation failure, with an adjusted hazard ratio of 3.4 (95% CI: 1.3–8.9; p = 0.01). The interclass correlation coeffi cient for angular measurements of posterior tilt was 0.90 (95% CI: 0.87–0.92), and the IRR for the categorization of posterior tilt into 3 groups was 0.76 (95% CI: 0.69–0.81). Interpretation — Preoperative posterior tilt of  20° in Gar- den-I and -II femoral neck fractures increased the risk of fi xa- tion failure necessitating salvage arthroplasty. The reliability of the methods that we used to measure posterior tilt ranged from good to excellent.