Does hip morphology correlate with proximal femoral fracture type?

Purpose: To determine if boney morphology influences the anatomic location of hip fractures in elderly patients. Methods: All patients with hip fractures between 2008 and 2012 who had hip radiographs taken prior to the fracture were reviewed. Fractures were classified as intracapsular or extracapsular and hip morphology was measured on the pre-fracture x-rays. Hip morphology was determined by alpha angle, lateral central edge angle, acetabular index, neck-shaft angle, hip axis length, femoral neck diameter, Tönnis classification for hip osteoarthritis (OA) and the presence of a crossover sign. Results: 148 subjects (78.4% female, age 83.5 years) with proximal femur fractures were included. 44 patients (29.7%) had intracapsular fractures and 104 (70.3%) had extracapsular fractures. 48% of patients had previous hip fractures on the contralateral side and 74.6% had the same type of fracture bilaterally. The rates of bilateral intracapsular and extracapsular fractures were similar (33.7% vs. 40.9% respectively, p = 0.39). Extracapsular fractures had a statically significant higher neck-shaft angle, a shorter hip axis length, a narrower femoral neck diameter and a higher grade of Tönnis classification of OA (p = 0.04, 0.046, 0.03, 0.02 respectively). Acetabular coverage and the proximal femoral head-neck junction, which were evaluated by lateral centre-edge angle (LCEA), acetabular index and the presence of a crossover sign, did not correlate with fracture type. The alpha angle > 40° had a statistically significant higher likelihood for extracapsular fractures (p = 0.013). Conclusions: Acetabular coverage and proximal femoral head-neck junction morphology, were found to partially correlate with the location of hip fractures and do not fully elucidate fracture type susceptibility.