Speed of sound in bone at the tibia: is it related to lower limb bone mineral density in spinal-cord-injured individuals?

Abstract

Study design: A cross-sectional study evaluating BMD at the hip and tibia, and SOS at the radius and mid-tibia in individuals with spinal cord injury (SCI) and a subgroup of non-SCI individuals. Objectives: To investigate the speed of sound (SOS) in bone in relation to bone mineral density (BMD). Setting: Kinesiology Department, McMaster University, Ontario, Canada. Methods: In 14 individuals with SCI and 10 non-SCI individuals, proximal femur and tibia BMD were measured using dual energy X-ray absorptiometry, and radius and tibia SOS were measured with an ultrasonometer. T-scores were calculated using healthy reference databases. Inter-relationships between measurement techniques were determined using Pearson's correlation coefficients. P-values less than 0.05 were considered statistically significant. Results: The average ages of the SCI and non-SCI groups were 3379 and 2776 years, respectively. Lesion level ranged from C4 to T12 and average time postinjury was 12 years, with a range of 1.6-25 years. Using the WHO criteria for osteoporosis, nine of 14 SCI subjects were osteoporotic at the hip, with the remainder in the osteopenic range. Tibia SOS T-scores were in the osteoporotic range for one subject with SCI, and two were in the osteopenic range. Among non-SCI individuals, one male had a tibia SOS T-score of À1.4, all others were within the normal range. Hip BMD and tibia SOS were significantly correlated (r ¼ 0.46, Po0.01). Hip BMD and tibia BMD were more strongly correlated (r ¼ 0.80, Po0.0005). Tibia BMD was not significantly correlated with SOS at the tibia (r ¼ 0.35, P ¼ 0.09). Radius SOS T-scores were positive and not significantly correlated with any lower limb variable. Conclusion: Lower-limb bone mass is reduced in spinal cord-injured individuals, but SOS at the mid-tibia is not. It remains to be determined whether ultrasound measurements can predict fracture in the SCI population.

Associations of Bone Mineral Density and Lead Levels in Blood, Tibia, and Patella in Urban-Dwelling Women

“…However, BMD was measured at the lumbar spine (L1–L4), which consists of more than 66% trabecular bone (Einhorn 1992; Riggs et al 1982; World Health Organization 1994), whereas lead in bone was measured in both tibia and patella. Tibia is approximately 99% cortical bone (Giangregorio and Webber 2004), and patella is approximately 99% trabecular bone (Hughes et al 1998). These large differences in bone type by the three sites of the measurements thus complicate interpretation of the associations.…”

Bone Loss and Muscle Atrophy in Spinal Cord Injury: Epidemiology, Fracture Prediction, and Rehabilitation Strategies

“…However, one study demonstrated that SOS measurements at mid-tibia were not different in individuals with SCI compared with a reference population (46). The time course of change in BUA and SOS varied at each site; changes in ultrasound variables at the calcaneus leveled off 6 to 12 months postinjury, whereas tibia SOS decreased linearly with time postinjury, perhaps reflecting the type of bone represented at each site (ie, trabecular vs cortical) (29).…”

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“…Ng and Sundram (1998) reported that quantitative ultrasound provides bone speed of sound (SOS) results which can contribute additional information on bone contents and microarchitectures as well as BMD. The speed of sound of bone, which is an alternative to DXA for osteoporosis screening, can be measured by quantitative ultrasound through bone at the phalanx, radius, tibia and metatarsal (Njeh et al, 2001;Giangregorio & Webber, 2004).…”