Abstract
The posteromedial fragment in tibial plateau fractures is considered unstable and
requires specific fixation. However, if not loaded by the femur, it may remain stable
and not require additional fixation. Our purpose was to determine the size of the
posteromedial fragment that would remain unloaded by the femoral-tibial contact area,
as a function of fracture line orientation and knee flexion angle. Seven human cadaveric
knees with intact capsule and ligaments were mounted in a mechanical rig and flexed
from 0 to 30, 90, 105, and 120 degrees of flexion. The fiducial points and articular
surfaces were digitized, and 3-dimensional software models of the knees at each flexion
angle were created. The femoral-tibial contact areas were determined using the software
under high- and low-load conditions. Posteromedial fragments of various sizes and
fracture line orientations relative to the posterior femoral condylar axis (PFCA)
were modeled, and their locations relative to contact areas were determined. The size
of unloaded fragments decreased with increased flexion angle. Fragments occupying
60% of the medial plateau were loaded at all angles, but fragments with 30% of the
plateau became loaded at 90 degrees under high load and 120 degrees under low load.
Fracture line orientations of 0 to 20 degrees external rotation relative to PFCA allowed
for the largest fragments to remain unloaded. The size of posteromedial tibial plateau
fracture fragment that remains unloaded by the femur varies with knee flexion angle
and fracture line orientation. This may have implications for the management of posteromedial
tibial plateau fractures.
Keywords
tibial plateau fracture - Posteromedial fragment - Contact area - fracture stability
