BIOMECHANICAL ANALYSIS OF NONREAMED TIBIAL INTRAMEDULLARY NAILING AFTER SIMULATED TRANSVERSE FRACTURE AND FIBULECTOMY

A tibial shaft fracture model was created to study the effects of an i ntramedullary nail and partial fibulectomy on fracture loading. Cadave ric lower extremities were instrumented with strain gages and subjecte d to biomechanical testing. A nonreamed nail was inserted into each ti bia using only the proximal locking screws. Each specimen was tested u nder six conditions: intact tibia; intact tibia with nail; fractured t ibia with nail removed and fibula intact; fractured tibia with nail an d fibula intact; fractured tibia with nail and partial fibulectomy; an d fractured tibia with partial fibulectomy and nail removed. In the in tact tibia the anterior cortices were in relative tension compared wit h the posterior cortex. After transverse fracture this relative tensio n was increased. Inserting the nail after fracture significantly incre ased anteromedial and anterolateral compressive strains and decreased posterior strains. Performing a partial fibulectomy in the fractured t ibia with a nail had no significant effect on the strain patterns: The se results confirm the relative anterior tension present in the intact tibia and demonstrate an increase in this anterior tension following transverse fracture. Performing a partial fibulectomy or inserting an intramedullary nail increased anterior compressive loading. This loadi ng alteration may be responsible for the clinical success seen using t hese treatment methods.