Biomechanical evaluation of a proximal tibial opening-wedge osteotomy plate

This biomechanical study evaluated the static response of a new opening-wedge osteotomy plate to compression and torsion loads in a human cadaver model. This plate incorporates a metal block that distracts the medial tibial cortices to ensure precise correction and prevent bone collapse. The 15-mm plate was inserted into 23 fresh cadaver specimens using a standard surgical technique. Axial loading of 13 specimens (compression) and external rotation loading of 10 specimens (torsion) was performed using a servohydraulic-testing machine. Compression loading resulted in failure at a mean of 1810 N due to bone collapse, fracture, or translation. Torsional loading resulted in failure at a mean of 10 Nm due to fracture of the lateral tibial cortex in all specimens. The ratio of the experimental failure load to the calculated estimate of the knee joint forces during gait were 1.07 in axial compression and 0.925 in torsion. This opening-wedge osteotomy plate construct appears marginally strong enough to withstand the estimated axial load on the proximal tibia during gait. Estimated torsional load on the knee during level walking slightly exceeds the failure load prior to osteotomy healing. This information can be used to guide further experimental protocols for static and dynamic testing of this device to determine the appropriate rehabilitation guidelines following opening-wedge proximal tibial osteotomy.