Ultrasound analyses of the calcaneus predict relative risk of the presence of at least one vertebral fracture and reflect different physical qualities of bone in different regions of the skeleton

Abstract

Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were determined together with bone mineral density (BMD) of the lumbar spine and of the proximal right hip (QDR 2000, Hologic) in 1252 females (mean age 56 +/- 11). We then calculated the predictive power of BUA and SOS for at least one vertebral fracture and correlation-coefficients of BMD of the spine and hip as well as BUA and SOS in different age groups (SPSS PC + Vers. 2.2. for IBM PC software). The overall prevalence of at least one vertebral fracture was 10.14% (127 out of 1252 patients). The relative risk for the presence of at least one vertebral fracture was 2.7 for BMD spine below 0.7 g Calcium/cm2 (69 out of 249 patients), 1.8 for BMD hip below 0.7 g Calcium/cm2 (106 out of 589 patients), 1.9 for SOS calcaneus below 1500 m/s (99 out of 499 patients) and 1.7 for BUA calcaneus below 110 dB/MHz (103 out of 605 patients). The relative risk for the presence of at least one vertebral fracture increases significantly (p < 0.01). In the age group < 50 the coefficients of correlation were 0.4655 between BMD spine and BUA calcaneus, 0.5259 between BMD spine and SOS calcaneus, 0.4327 between BMD hip and BUA, 0.2760 between BMD hip and SOS. In the age group > 70 the coefficients of correlation were 0.3699 between BMD spine and BUA, 0.3481 between BMD spine and SOS, 0.5946 between BMD hip and BUA, 0.5138 between BMD hip and SOS, respectively. All coefficients of correlation were highly statistically significant (p < 0.001). We conclude that BUA and SOS predict relative risk of the presence of at least one vertebral fracture as well as BMD spine and BMD hip. With increasing age BUA and SOS appear to be an independent predictor, not being inevitably correlated to BMD but possibly reflecting different qualities of bone at different sites of the skeleton.