A new anatomic classification of capital fragments in femoral neck fractures with the epiphyseal scar as a guide.

Seventy femoral neck fractures were examined clinically, radiologically, and histologically to ascertain whether the shape of the capital fragment, irrespective of the nature or age of the fracture, could be a determinant of the biologic condition within the head. Three types of excised capital fragments were defined according to the anatomic location of the fracture surface, with particular reference to the epiphyseal scar. Type I fragments, in which the fracture surface lies along the epiphyseal scar, showed complete capital necrosis, whereas Types II and III fragments, with the fracture surface in the subepiphyseal and subcapital zones, respectively, were found to be histologically viable. Moreover, Type III specimens tended to be more abundant in biologic response than Type II specimens. Thus, the biologic condition of the capital fragment is closely related to its shape. Since the type of capital fragment is, in most cases, judged correctly on the preoperative roentgenogram, this classification can be a helpful clue to the choice of treatment. From the biologic point of view, osteosynthesis should be limited to fractures with Type III capital fragments. The authors also hypothesize that the fractured femoral head, if untreated, may decrease in size and, therefore, in vascularity during the postfracture course.