The role of collagen abnormalities in ultrasound and densitometry assessment: In vivo evidence

There is little information concerning how the mutation of collagen affects bone mineralization and the assessment of bone properties. To estimate the se influences, we performed ultrasonic assessments of the calcaneus and bon e mineral density (BMD) measurements of the hip and lumbar spine. Females w ith diseases related to the mutation of collagen [Ehlers-Danlos syndrome (E DS) type III and systemic sclerosis (SSc)] participated in this study. We c ompared the broadband ultrasound attenuation (BUA and UBI-4), the average t ransit rime through the heel (TTH), and a multiple factor index (UBI-4T) wi th control subjects matched on age, race, and menstrual status. Both groups of patients had BMD of the spine (L2-L4) within the normal range for their age and sex (for EDS: n = 23, 1.14 +/- 0.14 g/cm(2) and z-score = 0.37; fo r SSc: n = 15, 0.98 +/- 0.15 g/cm(2) and z-score = 0.20). EDS and SSc subje cts had lower BMD of the femoral neck (FN) compared with controls (for EDS: 0.91 +/- 0.13 g.cm(2), z-score = -0.41, P = 0.025; for SSc 0.67 +/- 0.13 g /cm(2) z-score = 0.92, P = 0.006). Subjects with EDS and SSc also had lower BUA values (P = 0.051-0.001) compared with controls. After adjusting for b ody weight, height, and the level of physical activity, the difference in F N BMD between EDS or SSc and controls became marginal (EDS: P = 0.072; SSc: P = 0.086). However, the significant difference for BUA between subjects a nd controls remained for EDS (P = 0.008), and disappeared for SSc (0.70) af ter adjusting for weight, height, level of physical activity, and BMD. Thes e results suggest that the abnormalities of collagen may impact on bone mas s measurements differently depending on skeletal sire, modality of the asse ssment, and the source and nature of collagen defects. To determine whether collagen properties influence QUS, proper models in vivo and in vitro shou ld be used.