Site-specific bone measurements in patients with ankle fracture.

Ankle fracture is one of the most common fractures in adults, particularly postmenopausal women. Few studies have examined the bone mineral density (BMD) and ultrasound properties of bone close to the site of fracture in patients with ankle fracture. The aim of this study was to evaluate these measurements in women with ankle fractures compared with controls. We studied 31 healthy post-menopausal women ages 50-79 years (mean age 63.2+/-3.3 years) from a population-based group and 31 postmenopausal women ages 52-76 years (mean age 61.2+/-2.2 years) with an ankle fracture. Distal tibia and fibula BMD were measured by dual-energy X-ray absorptiometry using the Hologic QDR 1000/W densitometer. In addition to total distal and tibia BMD, three subregions were automatically selected: ultradistal, middle and one-quarter regions. Speed of sound (SOS) and broadband ultrasound attenuation (BUA) of the calcaneus were measured using the Lunar Achilles+ (LA+) and CUBA Clinical (CC). In addition to SOS and BUA, LA+ Stiffness Index (SI) was also measured. The nondominant limb was measured in the population group and the contralateral limb in the ankle group. Differences between the groups were determined using t-tests. The ankle fracture group was heavier than the control group by an average of 10 kg. BMD measurements were therefore adjusted for weight. There were no significant differences between the ankle fracture and control groups in lumbar spine BMD, total or regional ankle BMD or calcaneal BUA. However, calcaneal SOS was decreased in the ankle fracture group when measured on the LA+ and CC by 50 m/s (-2.0 SD units, p<0.001) and 19 m/s (-0.5 SD units, p<0.01) respectively. LA+ SI was decreased in the ankle fracture group by 14 units (-1.1 SD units, p<0.001). In conclusion, ankle fracture is not a typical osteoporotic fracture. However, there may be structural changes in the bone (unrelated to bone density) which result in increased fragility and susceptibility to fracture.