ABSTRACT
BACKGROUND: Hip fracture caused by fall is a common injury of the elderly. The risk of sustaining a contralateral hip fracture has been reported to be 5-10%. Aging society heightens the need of efficient prevention tools. To be able to cope with this demand, understanding of biomechanics of hip fractures are mandatory. Previous studies suggest that geometry of the proximal femur could play an important role for fracture probability and fracture type. Thus, analysis of hip geometry could play an important role in the prediction and prevention of bilateral hip fractures. Aim of this study was to elucidate the influence of caput collum diaphyseal angle on the fracture type of proximal femur. MATERIAL AND METHODS: In a retrospective analysis, data of patients with an acute hip fracture who underwent surgical treatment within five years were included. Data was separated into two groups: (I) intra capsular femur fracture (femoral neck fractures) and (II) extra capsular femur fracture (inter- and subtrochanteric femur fractures). Occurrence of a bilateral fracture, age, gender, weight, height and caput collum diaphyseal angle (standardized measurement of the opposite joint on preoperative digital x-rays) of each group were further analyzed. RESULTS: Data of 448 patients were included ((I): 250 vs. (II): 198 patients). Group (I) showed a significant higher mean caput collum diaphyseal angle of 133.9 ± 7.0° (mean ± standard deviation) compared to group (II) with 127.6 ± 6.1° (F (1, 451) = 106.5, p = 0.00). In group (I) 0 patients had a caput collum diaphyseal angle <120° (varus), 214 patients (86%) 120°-140° and 35 patients (14%) angle>140° (valgus). In contrast, in group (II) 21 patients (10%) had a caput collum diaphyseal angle <120° (varus), 175 patients (86%) 120°-140° and 7 patients (4%) >140° (valgus). 52 patients had a bilateral hip fracture. 36 patients (69%) sustained a bilateral hip fracture of the same fracture type. CONCLUSION: Patients with an intra capsular proximal femur fracture showed a significantly higher caput collum diaphyseal angle compared to patients with an extra capsular proximal femur fracture. Moreover, intra capsular femur fractures are correlated with an indifferent (120-140°) or valgus (>140°) femoral neck configuration. Extra capsular femur fractures correlate with an indifferent (120-140°) or varian femoral neck configuration (<120°). The results support the assumption that the caput collum diaphyseal angle has an influence on fracture type of the proximal femur. This could possibly be a predictor for the fracture type of the contralateral hip (second fracture). Based on this, present data may benefit prosthetists in developing new and more efficient hip protectors. LEVEL OF EVIDENCE: Level III. Retrospective comparative study.