Actual concept of osteoporosis in paraplegia.

The osteoporosis which appears in paraplegics below the neurological lesion has been studied in 100 patients with the following parameters: quantitative X-rays, urinary hydroxyproline excretion, kinetic study of calcium metabolism by 45Ca, serum phosphorus and calcium, parathormone and calcitonin radio-immunoassay, quantitative histology, density fractionation of bone and amino-acid composition of fractionated bone analysis. All our results show that the important bone resorption occurring very early in the paraplegia is immediately followed by an increase of the bone repair. This osteoporosis below the neurological lesion in paraplegia represents an unbalance between the synthesis and the resorption of bone which possesses a large degree of activity. Furthermore, we demonstrated that the collagen of this bone is underhydroxylated. Following the quantitative X-rays and intraosseous phlebography results we have considered the aetiopathogenesis of this osteoporosis. It seems that vascular modifications due to the lesion of the autonomic nervous system play an important role and furthermore we believe that immobilisation represents only a minor factor in the aetiology of this osteoporosis.