Predictors of early failure of the cannulated screw system in patients, 65 years and older, with non-displaced femoral neck fractures

Background: Hip fractures represent the most common injury and the main cause of morbidity and mortality among patients 65 years and older. About 20% of all femoral neck fractures (FNFs) are non-displaced or valgus impacted, for which internal fixation with the cannulated screws system (CSS) is indicated. Aims: The aim of this study was to identify predictors of early failure of CSS. Methods: Patients with non-displaced FNFs (Garden type I and II) treated operatively using the CSS were enrolled. Their characteristics, Pauwels angle, and posterior tilt were assessed and related with outcomes. The primary outcome was fixation failure within 6 months. Results: 259 patients were included with a mean age of 81.44 years. Most patients were female with ASA 3. The majority of fractures were classified as Garden I and Pauwels I. On average, Pauwels angle was 27°, while posterior tilt was 12°. A linear correlation between Pauwels angle and posterior tilt was found; the failure rate was 9.7%. Using the adjusted Cox competing risk regression analysis, posterior tilt was found to be independently associated with failure rate (sub-distribution hazard ratio or SHR 1.14 [95% CI 1.05–1.24], p = 0.0020). A posterior tilt greater than 18° resulted predictive of failure. The 1-year mortality rate was 12%. Conclusions: Non-displaced Garden type II fractures, Pauwels type II or III fractures, and a posterior tilt greater than 18° represent radiographic predictors of CSS early failure in the elderly. Level of evidence: Level IV, retrospective cohort study.