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Changes of tibia bone properties after spinal cord injury: effects of early intervention
E D de Bruin1, P Frey-Rindova, R E Herzog
1Department of Material Sciences, Laboratory for Biomechanics ETH, Zurich, Switzerland.
Objective:
To evaluate the effectiveness of an early intervention program for attenuating bone mineral density loss after acute spinal cord injury (SCI) and to estimate the usefulness of a multimodality approach in diagnosing osteoporosis in SCI.
Design:
A single-case, experimental, multiple-baseline design.
Setting:
An SCI center in a university hospital.
Methods:
Early loading intervention with weight-bearing by standing and treadmill walking.
Patients:
Nineteen patients with acute SCI.
Outcome Measures:
(1) Bone density by peripheral computed tomography and (2) flexural wave propagation velocity with a biomechanical testing method.
Results:
Analysis of the bone density data revealed a marked decrease of trabecular bone in the nonintervention subjects, whereas early mobilized subjects showed no or insignificant loss of trabecular bone. A significant change was observed in 3 of 10 subjects for maximal and minimal area moment of inertia. Measurements in 19 subjects 5 weeks postinjury revealed a significant correlation between the calculated bending stiffness of the tibia and the maximal and minimal area moment of inertia, respectively.
Conclusion:
A controlled, single-case, experimental design can contribute to an efficient tracing of the natural history of bone mineral density and can provide relevant information concerning the efficacy of early loading intervention in SCI. The combination of bone density and structural analysis could, in the long term, provide improved fracture risk prediction in patients with SCI and a refined understanding of the bone remodeling processes during initial immobilization after injury.