A previous study indicated that, in patients maintained by hemodialysis, clinically and roentgenographically apparent bone disease appeared almost exclusively when the dialystate calcium concentration was less than 5.7 mg per 100 ml. In the present study, bone biopsy specimens from the iliac crest were studied at the beginning and end of 2 to 9 months’ treatment using dialysate with low calcium concentrations (< 5.7 mg. per 100 ml.) in 7 patients. Two patients in each group were exposed to dialysate high in fluoride. Bone resorption was increased in all but 1 patient at the beginning of treatment. At the end of treatment, it had increased more in 5 of the 7 exposed to low-calcium dialysate and decreased significantly in all exposed to high-calcium dialysate. Except for 1 in each group, bone formation was below normal in all patients and did not appear to change between the first and second biopsies. All 4 patients exposed to high-fluoride dialysate showed excessive osteoid formation with little change during the 3 to 9 month interval. Single biopsies from 5 additional patients who had been maintained by dialysis for 13 months or longer also were studied to assess any effect of long-term treatment with high-fluoride dialysate. Osteoid formation was 9 times greater in those exposed to high-fluoride dialysate (50 uM) than in those exposed to lower concentrations (5 uM).
Increased osteoid is typically found in fluorosis, hence, ascribing our findings to an F effect seems reasonable. There are several possible reasons for F causing increased osteoid. In vivo, excessive F can result in increased bone production and failure of mineralization… It may be noteworthy that 4 of the 5 patients with the most disabling symptoms of bone pain, muscle weakness, wasting and multiple spontaneous fractures were exposed to high-F dialysate. This would suggest that prolonged exposure to F can contribute to the bone disease seen in long-term hemodialysis… The use of F-free dialysate decreases the risk of severe morphologic osteomalacia.