Reduced loading due to spinal-cord injury at birth results in “slender” bones: a case study |
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Authors: | L M Giangregorio N McCartney |
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Institution: | (1) Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON, N2L 3G1, Canada;(2) Department of Kinesiology, McMaster University, Hamilton, ON, Canada;(3) Spinal Cord Rehabilitation Program, Toronto Rehabilitation Institute, Toronto, ON, Canada |
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Abstract: | Introduction The present case study compared bone density, bone geometry and muscle cross-sectional area (CSA) in a male who sustained
spinal-cord injury (SCI) at birth (from here called SCI-B) with two matched controls without SCI, and also with four individuals
with SCI of similar level and injury completeness but sustained at age 15 or greater.
Methods All subjects with SCI were at least 3 years post-injury and had experienced motor incomplete lesions at the cervical level.
Computed tomography was used to measure volumetric bone density, indices of bone strength CSA and maximum, minimum and polar
area moments of inertia (I
max, I
min, I
pol)] and muscle CSA at the tibia (66% of tibia length, measured proximally from the distal end).
Results Lower leg muscle CSA of SCI-B was 63±6% of values in non-SCI controls, and 72±12% of values in other males with SCI. In SCI-B,
bone CSA was roughly half (52±4%) that of non-SCI controls and 73±16% of bone CSA values in other males with SCI. The magnitudes
of the area moment of inertia variables (I
max, I
min, and I
pol) in SCI-B were ~25% of control values. Further, the moment of inertia variables in SCI-B were 27–54% of values obtained in
other males with SCI, indicating that experiencing SCI in the early stages of life has a remarkable impact on bone shape.
Interestingly, tibia bone density did not appear to be affected; the average difference in bone density between SCI-B and
non-SCI controls was −1.2±0.7%. The bone densities of other males with SCI were 4–19% lower than in SCI-B.
Conclusions Muscle atrophy and bone loss are commonly reported consequences of SCI. This case reveals that important changes in bone geometry
occur after SCI, and that mechanical loading during growth plays a vital role in the development of bone size and shape. |
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Keywords: | Bone density Bone size Growth Mechanical loading Spinal cord injury |
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