Hip axis length in an Italian osteoporotic population

Models proposed so far for the pathogenesis of osteoporosis often do not ta ke into account the factors underlying the different incidences of hip frac ture in different populations. To address this issue, we identified 34 fema le patients with hip fracture (HF) and 16 women with at least four vertebra l fractures (VF) in a population-based retrospective study. Each participan t had a bone mineral density (BMD) measurement of the lumbar spine and hip using a Hologic QDR-2000 scantier, in single beam mode for the latter site. Hip axis length (HAL) was determined automatically (precision 1.5%). HAL d erived from 149 normal subjects (age range 19-75 years) was 10.3+/-0.5 cm. BMD values found at the femoral neck were almost similar, but differed sign ificantly at the spine between the two groups. Mean values of femur HAL in HF patients (10.55+/-0.5 cm) were significantly higher compared with VF pat ients (9.85+/-0.54 cm; p<0.001). Interestingly, both mean values differed s ignificantly from the mean for normal subjects. Our results demonstrate tha t patients with multiple vertebral fractures have significantly lower verte bral BMD values but similar femoral neck values compared with patients who fracture at the hip; furthermore, hip axis length was more than 1 SD higher in these latter patients compared with that of VF patients. These results suggest that the size and shape of the hip can explain part of the observed aetiologic differences between these two types of osteoporotic fractures.