Objective: In people with spinal cord injury (SCI), active-resisted stance using electrical stimulation of the quadriceps delivered a therapeutic stress to the femur (∼150% of body weight) and attenuated bone mineral density (BMD) decline. In standard densitometry protocols, BMD is averaged over the entire bone cross-section. An asymmetric adaptation to mechanical load may be masked by non-responding regions. The purpose of this study was to test a novel method to assess regional BMD of the femur in individuals with SCI. We hypothesize that there will be regional bone-sparing changes as a result of active-resisted stance.
Design: Mixed cross-sectional and longitudinal.
Setting: Research laboratory.
Participants: Twelve individuals with SCI and twelve non-SCI controls.
Intervention: Individuals with SCI experienced active-resisted stance or passive stance for up to 3 years.
Outcome measures: Peripheral quantitative computed tomography images from were partitioned so that femur anatomic quadrants could be separately analyzed.
Results: Over 1.5 years, the slope of BMD decline over time was slower at all quadrants for the active-resisted stance limbs. At >2 years of training, BMD was significantly higher for the active-resisted stance group than for the passive stance group (P = 0.007). BMD was preferentially spared in the posterior quadrants of the femur with active-resisted stance.
Conclusions: A regional measurement technique revealed asymmetric femur BMD changes between passive stance and active-resisted stance. Future studies are now underway to better understand other regional changes in BMD after SCI.