In femoral locked nailing, the distal locking screws is vulnerable to mechanical failure. The stress on these screws is substantially affected by fitness of the nail in the medullary canal. In this study a closed form mathematical model based on elastic column-beam theory is developed to investigate how the nail-cortical contact which is simulated by a linear elastic foundation affects the stress of the distal locking screws. The model is comprised of a construct of a fractured femur with an intramedullay locked nail loaded by an eccentric vertical load. The stress of the locking screw is analysed as a function of the depth of the locking screw in the distal fragment under two situations: with or without nail-cortical contact in the distal fragment. In situation with nail-cortical contact, the screw stress is decreased as the length of nail-cortical contact and the depth of the screw in the distal fragment increases, but this stress contrarily increased when the nail is inserted beyond a certa

Background: Reconstruction nail had developed since 1985. General indications reviewed from literatures are 1. Ipsilateral femoral neck-shaft fracture (nondisplaced), 2. Russell-Type IB subtrochanteric fracturtes (intact piriformis fossa, fractured less trochanter). Many authors did not recommend that application of reconstruction nail in displaced ipsilateral femoral neck-shaft fractures. The reason is that unpredictable femoral neck-shaft reduction and over-distraction of shaft fracture. We developed one new method for overcoming such technical puzzle to achieve one-step reduction for displaced ipsilateral femoral neck-shaft fractures.

Material: There are 24 consecutive cases were treated by reconstruction nail by the same operator in Chi-Mei Foundation Hospital from February, 1999 to June, 2000. Five of them were diagnosed as displaced ipsilateral femoral neck-shaft fractures and treating new surgical technique in reconstruction nailing. Initial radiographic assessment revealed displaced neck fracture can be classified as Garden III, the fracture morphology is vertical (Pauwell III). Average age of these five patients is 37.6 y/o. The sex distribution is M:F=3:2

Method: Provisional proximal fixation of femur is mandatory. First, we use two 5.0mm drillpit transfixed trochanter region after assure of femoral anteversion. Second, release of traction and distal locking for reduction and fixation of shaft fracture part. Third, remove application handle and use Internal rotation or other remote maneuver for restoration of neck-shaft angle. Finally, complete drilling through neck and sequent proximal cephalomedullary locking was performed by free-hand method.

Result: Initial reduction result was acceptable. There was no significant coxa-varus or coxa-brevis. Two of them had removed of implants and clinical result was satisfied. No avascular necrosis was noted in our following up.

Discussion: How to treat displaced ipsilateral femoral neck-shaft fractures in one-step was obstacle in our orthopedic practice. Abandonment of reconstruction nail just due to technique demanding purpose is very pity. We developed such technique to make patient with displaced ipsilateral femoral neck-shaft fractures treat by closed and one-step method and gained more satisfaction.