THE CLUSTER PHENOMENON IN PATIENTS WHO HAVE MULTIPLE VERTEBRAL COMPRESSION FRACTURES

Little is known about the natural history of patients who have multipl e compression fractures. During an eight-year period, eight patients w ho suffered relentless nonmechanical back pain after an initial compre ssion fracture were evaluated. Radiographs and radionuclide bone scans were obtained in all eight patients and showed the temporal clusterin g of at least five spontaneous thoracic or lumbar vertebral compressio n fractures within a period of eight months. The patient database duri ng this eight-year period included 21 patients with a similar number o f fractures but without the phenomenon of temporal clustering. Age and gender distribution, premorbid activity levels, presence of secondary causes of osteopenia, dietary history, and vertebral bone density mea surements were similar in both groups. Five of the eight patients with cluster fractures were on chronic glucocorticoid therapy for treatmen t of an underlying illness. All five patients experienced an exacerbat ion of their chronic illness that required an increase in the dose of their steroid medication within three months preceding the onset of th e cluster fractures. No patient in the noncluster fracture control gro up experienced a similar exacerbation of an underlying illness or requ ired a similar boost in their steroid medication. The temporal cluster ing of numerous fractures (cluster phenomenon) is a cause of transient severe disability in patients who have profound osteopenia, and may b e precipitated by exacerbation of an intercurrent illness or by an ass ociated obligate increase in glucocorticoid medication in a patient wi th preexisting severe osteopenia.