Related Experiment Videos
Immobilization osteoporosis in paraplegia
1Department of Medicine, Endocrinology & Metabolism, University of California, Irvine.
The Journal of the American Paraplegia Society
|July 1, 1992
Summary
Immobilization osteoporosis in paraplegics results from reduced bone stress, impacting piezoelectric forces and leading to bone loss primarily from decreased formation. Early remobilization is key, with electrical fields and medications under investigation.
Area of Science:
- Orthopedics
- Physiology
- Biophysics
Background:
- Osteoporosis in paraplegics, known as immobilization or disuse osteoporosis, stems from reduced mechanical loading on bones.
- Bone integrity is influenced by piezoelectric forces generated during mechanical stress, a phenomenon potentially linked to collagen and fluid flow within bone.
Purpose of the Study:
- To review the pathophysiology of immobilization osteoporosis in paraplegics.
- To discuss the role of piezoelectric forces in bone integrity and their loss in paraplegia.
- To examine the biochemical and endocrine changes associated with immobilization.
Main Methods:
- Review of existing literature on bone physiology, immobilization, and osteoporosis.
- Discussion of piezoelectricity in bone, including mechanisms of electrical potential generation.
- Analysis of biochemical markers (serum calcium, PTH, vitamin D) and urinary/stool excretion (hydroxyproline, calcium).
Main Results:
- Diminished bone forces in paraplegia alter bone remodeling, detectable via histomorphic and histoenzymatic methods.
- Immobilization leads to increased serum calcium, decreased parathyroid hormone (PTH), and reduced dihydroxy-vitamin D synthesis.
- Increased urinary hydroxyproline and calcium excretion, alongside elevated stool calcium, are observed.
Conclusions:
- Bone loss in immobilization osteoporosis is mainly due to decreased bone formation rather than accelerated resorption.
- Fracture susceptibility increases, particularly in long bones, following immobilization.
- Early remobilization is the primary treatment, with electrical fields and pharmacological agents (bisphosphonates, calcitonin, growth hormone) being explored.