ARCHITECTURE OF THE FEMORAL MEDULLARY CANAL AND WORKING LENGTH FOR INTRAMEDULLARY NAILING - BIOMECHANIC INDICATIONS FOR DYNAMIC NAILING

We classified human femoral intramedullary architecture into 3 types. The cortex in the first type is thick and the medullary canal narrow w ith an even and smooth translation towards the metaphysis. In the seco nd type, the cortex is thin and the canal wider, also evenly distribut ed along the entire length, while in the third type the canal narrows just distal to the subtrochanteric region and similarly a few centimet ers distally. Some medullary canals of the second type do not allow dy namic nailing, while canals of the third type presents some difficulti es for unreamed nails. Most medullary canals belong to the first and s econd type and only few belong to type three. We performed comparative experimental loading in 11 pairs of cadaveric fractured femoral fixed with static and dynamic nailing. Dynamic nailing was found to behave as safely as static ones in the presence of a sound femoral shaft cent ral and peripheral to the fracture with a length twice the diameter of the femur at the fracture level. This could be checked intraoperative ly with gentle rotation under image intensifier. In a clinical series, dynamic nailing was performed in about one quarter of the patients wi th femoral shaft fractures (18 of 72 patients) with excellent results.