Abstracts: Abstracts of Platform and Poster Presentations for the 2006 Combined Sections Meeting: Platform Presentations
To determine the bone mineral density (BMD) of the hip and the knee in children with spinal cord injury (SCI) and to compare the BMD of the hip to published data for children with typical development.
Number of Subjects:
Nine boys and five girls (ages 5 to 13 years, mean age 9.1 ± 2.5 years) with spastic motor complete SCI (neurological levels C7 to T10) and no history of lower extremity fractures underwent BMD testing of the left hip, distal femur, and proximal tibia via dual energy X-ray absorptiometry (DEXA) as part of a prospective study of the effects of a lower extremity functional electrical stimulation training program in children with SCI. Subjects were 5.1 ± 2.1 years (1 to 8 years) post injury when tested.
The baseline BMD values from the intervention study were analyzed for each subject. BMD at the hip was compared to age and sex matched published normative values obtained using DEXA (Zanchetta et al., Bone, 1995;16(4 Suppl):393S-399S) and Z-scores were calculated. Normative values were not available for the machine on which the testing was performed. There are no published normative values available for comparison for BMD at the distal femur and proximal tibia.
All subjects had decreased BMD as compared to age and sex-matched norms. At the hip, BMD averaged 0.44 ± 0.17 g/cm2 at the femoral neck (Z = −1.88 ± 0.97), 0.41 ± 0.19 g/cm2 at the trochanter (Z = −1.82 ± 1.55), and 0.44 ± 0.17 g/cm2 at Wards triangle (Z = −1.88 ± 0.81).
At the knee, BMD averaged 0.35 ± 0.10 at the distal femur and 0.36 ± 0.08 at the proximal tibia.
These pediatric subjects with SCI showed reduced BMD at the hip as compared to their peers. While norms are not available at the knee, the BMD values in this area were comparable to the values for BMD at the hip, with both showing a marked decrease thus suggesting an increased fracture risk in both of these areas. Techniques such as magnetic resonance imaging and quantitative computerized tomography may provide more in-depth information regarding the specific components of bone affected.
As individuals with SCI spend most of the day in a seated position, they may be at less risk of fracture than the non-disabled population due to decreased weight bearing on these joints. However, children with SCI may be more at risk than adults with SCI due to their higher activity level, lack of understanding of protecting their lower extremities, and a desire for upright mobility. In addition, it is unknown as to what BMD threshold constitutes an increased risk for fractures in these children due to activity or how age at injury and length of time since injury impact BMD in a growing child. Protection strategies should be taught early to children with SCI and interventions need to be developed to improve BMD in this population to prevent fractures that may lead to deformity in the presence of growth.