Progression of a Fracture Site Impaction as a Prognostic Indicator of Impacted Femoral Neck Fracture Treated with Multiple Pinning

BACKGROUND We evaluated the clinical and radiologic results of impacted femoral neck fractures treated with multiple pinning and determined the influence of the progression of impaction at the fracture site on clinical outcome. METHODS There were 34 patients with a mean age of 65.5 years. The mean follow-up period was 3.4 years. Progression of fracture site impaction was measured using an articulo-trochanteric distance index and the percentage decrease in the articulo-trochanteric distance index between follow-up intervals. The failure of treatment was clarified as non-union and avascular necrosis. Other characteristics of the patients, including mean waiting time for surgery, preoperative Singh index score, and body mass index, were also measured to evaluate the influence on the clinical outcome of surgery. RESULTS There were 6 fractures which were not treated successfully (3 non-union, 8.8% and 3 avascular necrosis, 8.8%). The mean percentage decrease of the articulo-trochanteric distance index within the first 6 weeks after surgery was 4.5% in the successful group and 25.1% in the failure group (p < 0.001). There was also a significant mean percentage decrease in the articulo-trochanteric distance index between 6 weeks and 3 months (p < 0.001). CONCLUSIONS Primary stabilization with Knowles pins for impacted femoral neck fractures had a reasonable clinical outcome with low morbidity. Despite a significant difference of a mean percentage decrease in the articulo-trochanteric distance index between the successful group and the failure group, we could not verify it as a risk factor for failure of treatment because the odds ratio was not statistically significant.