Association of ABO blood group with fracture pattern and mortality in hip fracture patients

The mechanism of falling has been proposed as the exclusive explanation for hip fracture pattern. Evidence exists that other genetic factors also influence proximal femoral fracture configuration. The ABO blood group serotype has been associated with other pathologies but any role in hip fracture has yet to be definitively characterised.

Our National Hip Fracture Database was interrogated over a four-year period. All patients had their blood group retrieved, and this was compared with hip fracture pattern and mortality rates. Confounding factors were accounted for using logistic regression and the Cox proportional hazards model.

A total of 2,987 consecutive patients presented to our institution. Those with blood group A were significantly more likely to sustain intracapsular fractures than 'non-A' individuals (p=0.009). The blood group distribution of patients with intracapsular fractures was identical to that of the national population of England. However, blood group A was less common in patients with intertrochanteric fractures than in the general population (p=0.0002). Even after correction for age and sex, blood group A was associated with a decrease in the odds of suffering an intertrochanteric fracture to 80% (p=0.002). Blood group A had inferior survivorship correcting for age, sex and hip fracture pattern (hazard ratio: 1.14, p=0.035). This may be due to associated increased prevalence of co-morbid disease in this cohort.

Blood group is an independent predictor of hip fracture pattern, with group A patients more likely to sustain an intracapsular fracture and non-A individuals more likely to sustain an intertrochanteric fracture. The determinants of fracture pattern are likely to be related to complex interactions at a molecular level based on genetic susceptibility. The mechanism of fall may not be the only aetiological determinant of proximal femoral fracture configuration.