Relationships among tibial ultrasound velocity and bone mineral density of the tibia and hip

Abstract

MINERAL DENSITY OF THE TIBIA AND HIP M. Bouxsein, B. Colin, Beth Israel Hospital and Harvard Medical School, Orthopedic Biomedmnics Laboratory, Boston, MA The measurement of ultrasound velocity (SOS) in the cortical bone of the tibia is currently being investigated as a potential diagnostic tool for asteoporosis. This technique is of interest as it may reveal information about skeletal status without the use of ionizing radiation. However, it is not known whell~er massunng ultrasound transmission along the cortical bone at the mid-tibia will here the ability to predict fracture risk at other sites. The objective of this study was to assess the relationships among tibial SOS, tibial bone mineral density (BMD), and femoral BMD in human cadaverio specimens. In addition we daterminad the coefficient of variation (CV, %) end standardized CV (sCV, Miller el EJ, Ostcop Int, 3:31-35,1993) for tri~icate tibial SOS measurements. We obtained 20 in~ct legs from the local anatomic gifts program. The donom included 11 women and 9 men with 8 mean age of 82 years (range 62-98 yrs). The specimens were obtained fresh, stored frozen, End thawed before testing. We assessed tibtal SOS (m/s) using the Mydad SoundS(an 2000 system. For each specimen, scans were performed three limes with rspositioning. BMD (g/cm 2) of the mid-tibia End proximal femur were messed using DXA. Tibial BMD was very strongly correlated to femoral net;k, trechanteric, and total femoral BMD (r-0.81 0.85, p<0.01, Figure). Tibial SOS was strongly correlated with tibial BMD (r-0.72, p<0.01, Figure) and moderately correlatedwith femoral BMD (r=0.46-O.51, IO<0.05). The mean CV for triplicsts measurements of tibiE SOS was 0.62%. The sCV, defined as the mean SD divided by the sample range (taken to be the 5-95% range), was 2.9%. In condasion, we found slreng correlations between SOS and mid-tibial BMD, and between mid-tibial BMD and femoral BMD. Thus, tibial ultrasound measurements may be useful for assessing bone status to predict future hip fracture dsk. Tibial SOS explained only about 50% of the vEdation in tidal BMD. This may be because ultrasound reflects aspects of bone status that ~e, in part, independent of BMD, but that may be related to fracture risk.