Collagen metabolite excretion as a predictor of bone- and skin-related complications in spinal cord injury.

Immediately after the trauma, spinal cord injury patients have an increased rate of collagen synthesis and an even greater increase of collagen degradation. Collagen lost from bone is implicated in the etiology of osteoporosis and heterotopic ossification, and collagen lost from skin might lead to a propensity to develop pressure ulcers. The urinary excretion of two collagen metabolites has been monitored and their fluctuation related to the onset of skin or bone complications in these patients. One metabolite, glucosyl-galactosyl hydroxylysine, is more abundant in skin collagen; the other, galactosyl hydroxylysine, is more abundant in bone collagen. The excretion of both metabolites increases after injury, reaching a peak between three and six months after injury, and declines gradually, reaching control values about a year after injury. If a skin pressure ulcer develops, the urinary excretion of the diglycoside remains elevated instead of gradually decreasing. Similarly, if osteoporosis or heterotopic ossification is diagnosed, the monoglycoside excretion does not return to control values until the bone turnover stabilizes. Monitoring of the urinary excretion of both glycosides might prove helpful in prompting early examination to establish the presence of emerging skin and bone complications. Thus, aggressive preventive therapy could be given sooner.