Pathologic fractures in a patient with renal osteodystrophy. Failure of early detection on bone scans

A case of false-negative Tc-99m MDP bone scintigrams, taken at one and two weeks for pathologic fractures in a patient with metabolic bone disease and a super-scan appearance, is described. The patient had renal osteodystrophy, and postparathyroidectomy hypocalcemia. Postoperative seizures caused multiple pathologic fractures. Initial scans were negative for focal tracer localization in the presence of a continued super-scan appearance. After months of calcium and vitamin D replacement therapy, fracture sites became positive on Tc-99m MDP imaging. The observations in this case lend credence to the hypothesis of Tc-99m MDP binding by immature collagen in the production of a super scan in metabolic bone disease, as well as that of Tc-99m MDP chemisorption to calcium hydroxyapatite crystal in fracture healing. In addition, aluminum toxicity, common in chronic renal osteodystrophy, may have played a role in the delayed fracture healing.