2004 OITE Question 188

Question

An orthopaedic surgeon is performing an antegrade nailing of a midshaft femoral fracture. During nail insertion, the proximal fragment comminutes. No previous fracture lines are visible on the initial radiographs or fluoroscopy. What is the most likely cause of this complication?

1. A too anterior starting point in the piriformis fossa

2. A too lateral starting point in the trochanter

3. Reaming only 1mm over the proximal nail diameter

4. Use of a rigid closed section nail

5. Not enough adduction of the affected limb

Figures

Answer (click for answer)

Complications of nailing femoral diaphyseal fractures include fracture instability, proximal nail migration, malrotation, delayed union, and occasionally femoral bursting during insertion of the nail. Femoral bursting can lead to fracture instability and shortening. Johnson et al evaluated the effect of starting hole position, fracture component length, reamed diameter, and nail type on the potential for femoral bursting and fracture instability in JOT 1987. The most significant factor in the proximal femoral component was found to be starting position of the hole. Anterior displacement by more than 6mm from the neutral axis of the medullary canal consistently caused high hoop stresses at the level of the fracture, which resulted in bursting of the proximal femoral component by lifting off the anterior cortex. Hoop stresses at the level of the fracture were less sensitive to lateral or medial placement of the starting hole. Fracutre stability and bursting were affected by the type of nail used, but to a lesser degree relative to starting point positioning.

Reference: Johnson KD, Tencer AF, Sherman MC: Biomechanical factors affecting fracture stability and femoral bursting in closed intramedullary nailing of femoral shaft fractures, with illustrative case presentations. J Orthop Trauma 1987;1:1-11.