Histomorphometric analysis of a calcaneal stress fracture: a possible complication of fluoride therapy for osteoporosis

Pain and swelling of the large joints of the lower limbs occur in about 33% of patients receiving sodium fluoride, calcium, and vitamin D therapy. In a previous study we described radiographic and scintigraphic features suggesting that these symptoms are due to juxtaarticular stress fractures. We now report the histologic features of one such lesion in a calcaneum of a patient receiving fluoride, calcium, and 1 alpha-vitamin D therapy for postmenopausal osteoporosis. Bone biopsy after tetracycline double labeling showed a trabecular fissure fracture and large intratrabecular resorption cavities surrounded by microcallus. Comparison of the static and dynamic histomorphometric parameters in the calcaneum with those in the simultaneously taken iliac bone biopsy showed a marked regional acceleratory phenomenon in the calcaneum that we ascribe to the microfractures. It cannot be said with certainty whether the microfractures resulted from the osteoporosis, the vitamin D, or the sodium fluoride therapy.