The purpose of this study is to identify the optimum entry point
for retrograde femoral nailing, defined as that point which will provide adequate fracture
alignment while minimizing soft-tissue and articular cartilage injury.
Main Outcome Measure
Anatomic relationships and fracture
Eleven cadaveric femori with attached knee joints underwent retrograde femoral nailing with a Synthes femoral nail (Synthes, Paoli, PA, U.S.A.). After placement of the nail, the specimens underwent an osteotomy 3 inches proximal to the articular surface. Multiple entry points were tested to determine fracture
alignment and extent of articular cartilage injury. Medial–lateral and anterior–posterior displacements, in addition to any soft-tissue or articular surface trauma, were recorded for these various points of entry.
An entry point
of 1.2 cm anterior to the femoral origin of the posterior cruciate ligament resulted in the least anterior–posterior displacement of the femoral shaft following fracture
. In the coronal plane, an entry point
at the midpoint of the intercondylar sulcus was identified as minimizing the displacement following fracture
. This ideal position allows for proper seating of the nail within the intercondylar sulcus, resulting in minimal damage to the articular cartilage and posterior cruciate ligament and minimal disruption of the patella femoral joint.
Retrograde femoral nailing should be used cautiously in select patients, when conventional antegrade nailing cannot be used, due to the unavoidable injury to the knee articular surface associated with this technique. The optimum entry point
of 1.2 cm anterior to the femoral posterior cruciate ligament origin and centered in the intercondylar sulcus provides the optimal balance of fracture
reduction and knee joint sparing. It may be difficult to target this site with a percutaneous technique and may require direct visualization of the intercondylar sulcus for ideal nail placement.