Voor et al. (2012) - Bone loss following SCI in a Rat model

Summary of Vorr et al. (2012) - Bone loss following SCI in a Rat model

Intro/justification Study follows the time course of bone loss in the proximal tibia of rats across several weeks following a T9 contusion SCI of varying severity. Bone loss quantified using mCT Hypothesis - bone loss worse in the more severely injured animals, and hindlimb weight bearing would help prevent bone loss.

Method Overview SCI model - T9 Contusion (of varying severity) ( energies of mild - 6.25 (n=6), moderate - 12.5 (n=7), moderately-severe - 25 (n=7) and severe -50 g-cm (n =6). Injury severity confirmed by weekly BBB testing (hindlimb function) and and at termination by histological analysis (white matter). Rats - 6-7 weeks old female Sprague-Dawley (200-225g) (n=26) mCT (ACTIS of right proximal tibia carried out at 0, (2 or 3), 8 weeks post- in vivo µCT of proximal tibia was carried out at 0-weeks before injury for half the animals. (establish baseline). Mechanical indentation testing was done to measure compressive strength of trab. bone structure after sacrifice. Histology carries out after sacrifice.

Results - locomotion function all rats exhibited significant improvements in hindlimb function over 2-3 weeks post-injury. BBB scores plateaued after 3 weeks. locomoter (BBB) scores of rats correlated well (r^2= 0.898) with the %age of spared white matter at injury epicenter @ 8 weeks.

results - Trab. microarch. All 4 injury groups lossed > 25% of cancellous BV within 3-weeks compared to pre-injury baseline (p only severely injured group loss a significant amount of bone @ 3 weeks*. the same is ture at 8-weeks**.

Results - Cortical microarch. Cortical bone results were similar. mildly and moderately loss ~ 11% of cortical bone @ 2-weeks., while they were recovering plantar hindlimb stepping. (cBV/TV = 0.58) severly injured group experienced greater cortical bone loss. (32%), resulting in significantly lower bone vol. fraction (cBV/TV = 0.43).

Discussion 1st study to follow and compare the time course of bone loss following SCIs of varying severity. Instead of a linear proportionality between injury severity, there appears to be a distinct threshold