Modified tibial nails for treating distal tibia fractures.

OBJECTIVE: To determine the biomechanical consequences of cutting one centimeter off the tip of a tibial nail when treating distal tibia fractures with intramedullary nails.

DESIGN: Randomized laboratory investigation using matched pairs of cadaveric tibias with osteotomies made to resemble distal tibia fractures extending to four and five centimeters from the tibiotalar joints.

INTERVENTION: The smaller (four-centimeter) distal tibias were stabilized using ten-millimeter diameter tibial nails that had been modified by removing the distal one centimeter of the nail. The five-centimeter distal tibias were stabilized with standard ten-millimeter diameter tibial nails. Each tibia was tested in elastic compression, rotation, and compression-bending on a servohydraulic materials testing machine.

MAIN OUTCOME MEASUREMENTS: Stiffness was calculated for each type of loading to compare stability of the modified nail construct to that of the standard nail construct.

RESULTS: Four-centimeter distal tibia fragments stabilized with modified nails have comparable stiffness in compression and in torsion to five-centimeter distal tibia fragments stabilized with standard tibial nails. The stiffness in compression-bending was surprisingly low in both groups and differed by only 3.7 percent.

CONCLUSIONS: Removal of one centimeter from the tip of a tibial nail allows placement of two distal interlocking screws in tibial fractures located four centimeters from the tibiotalar joint. The fixation strength achieved is comparable to that of standard intramedullary nailing of tibial fractures located five centimeters from the tibiotalar joint using two distal interlocking screws. Fixation strength with these distal fractures, however, is not strong enough to resist moderate compression-bending loads. Thus, patients with distal tibia fractures treated with intramedullary nailing must follow weight-bearing restrictions until significant fracture healing occurs to prevent coronal plane malalignment of the fracture.