Pathologic Fractures and Stress Fractures: A Review of Pathogenesis and Assessment

Abstract

Pathologic fractures are classically defined as fractures resulting from physiologic forces applied to abnormal bone (Biewener et al, 1983). This definition, however, is too all-embracing considering the wide variation in both physiologic forces and abnormal bone. The most common pathologic fractures are those seen in osteoporosis regardless of origin. The Singh index was an early attempt to predict impending fractures of then proximal femur in both postmenopausal and senile osteoporosis (singh et al, 1970). Normal distribution of forces across the hip joint leads to a standard pattern of trabecular bone. (fig. 1). A significant alteration in these forces, either in time or in load, will result in a reproducible pattern of bone loss in the proximal femur. Singh attempted to determine at what point fracture was inevitable. Predicting similar fragility points in other anatomic sites has been less successful, and is a continued clinical problem particularly when dealing with disuse osteoporosis. Early reports (McBroom and Hayes; Ruegsegger et al, 1984) suggest that quantitative computerized tomography may help solve of this dilemma.