CHARACTERISTICS OF CALCANEAL BONE INFARCTION - AN MR-IMAGING INVESTIGATION

Objective. Bone infarction (BI) of the calcaneus is an uncommon entity which has received little mention in the recent literature. In this p aper, we review the MR images of six calcanei with BI, which demonstra te a pattern of presentation that may explain the etiology of BI at th is unusual location. Design. A retrospective review was performed of t he transcribed reports of the foot or ankle MR examinations at our ins titution. MR images of ex.aminations with any marrow signal abnormalit y were reviewed for presence of BI and its distribution. Patients. Bas ed on MRI criteria, four patients had calcaneal BI(none biopsy proven) ; they ranged in age from 37 to 51 years old. Two patients were diagno sed with systemic lupus erythematosus, one with fibrositis, and anothe r with polymyositis. All were treated with corticosteroids. Results. S ix calcanei (in four patients) contained a region of calcaneal BI. In five of the six, the lesions were entirely or predominantly located in the posterior half of the calcaneus. Conclusion. Two theories are pro posed which may explain why BI predominantly occurs in the posterior h alf of the calcaneus. First, the convergence of the recurrent intraoss eous calcaneal vessels may occasionally produce the equivalent of a si ngle dominant vessel that is more prone to vascular accidents. Secondl y, the region between the recurrent and the epiphyseal vessels may act as a watershed zone, increasing its susceptibility to ischemia.