A Good Tip-Apex Distance Does Not Make Up For a Poor Reduction in Intertrochanteric Hip Fractures Treated with an Cephalomedullary Nail: The Utility of the Neck-Shaft Angle in Preventing Fixation Failure

Abstract

Purpose: Determine if any fracture characteristics or radiographic parameters were predictive of fixation failure [FF] within 1 year following cephalomedullary nailing for intertrochanteric fractures. Methods: A consecutive series of intertrochanteric hip fracture patients (AO/OTA 31A) treated with a cephalomedullary nail were reviewed. Pre-fixation (neck-shaft angle [NSA], distance from ischial tuberosities to greater and lesser trochanters, integrity of lesser trochanter, and fracture angulation) and post-fixation (post-fixation NSA, posteromedial cortex continuity, lag screw position, tip to apex distance [TAD], and post-fixation angulation and translation) radiographic parameters were measured by blinded independent reviewers. The FF and non-FF groups were statistically compared. Logistic regression was performed to determine radiographic parameter correlates of FF. Results: Of 1249 patients, 23 (1.8%) developed FF within 1 year. The FF patients were younger than their non-FF counterparts (77.2 years vs 81.0 years, p=0.048), however there were no other demographic differences. The FF cohort did not differ in frequency of TAD over 25 mm (4.3% vs 9.6%, p=0.624) and had decreased mean TAD (13.6mm vs 16.3mm, p=0.021) relative to the non-FF cohort. The FF cohort had a higher rate of a post-fixation coronal plane NSA more than 10° different from the contralateral side (delta NSA>10°, 34.8% vs 13.7%, p=0.011) with the majority fixed in relative varus. For every 1° increase in varus compared to the contralateral side the odds of FF increased 7% (OR=1.065, 95%CI[1.005–1.130], p=0.034) on univariate analysis. On univariate logistic regression, patients with an absolute post-fixation NSA of 10° or more of varus compared to contralateral were significantly more likely to have a FF (OR=3.139, 95%CI[1.067–8.332], p=0.026). Conclusion: Despite an acceptable TAD, post-fixation NSA in relative varus as compared to the contralateral side was significantly associated with failure in intertrochanteric hip fractures fixed with a cephalomedullary nail. Level of evidence: Prognostic Level III.