Comparison of monoplanar versus biplanar medial opening-wedge high tibial osteotomy techniques for preventing lateral cortex fracture

The purpose of this study was to investigate the mechanical strength of both monoplanar and biplanar medial opening-wedge high tibial osteotomy (MOWHTO) procedures and assess the risk of lateral cortex disruption for both techniques. Twelve synthetic tibia models with cortical shells were used as test models. Saw cuts for monoplanar MOWHTO and biplanar MOWHTO were generated on the test models in equal numbers (n = 6 for both groups). Wedge opening load and wedge gap distance were evaluated via compressive tests. The mean gap distance just before the lateral cortex fracture in the monoplanar group was 14.7 +/- 2.9 mm, which was significantly narrower than that in the biplanar group of 19.1 +/- 2.0 mm (p = 0.015). The mean load just before the occurrence of lateral cortex fracture of 32.4 +/- 3.2 N in the monoplanar osteotomy group was significantly lower than that in the biplanar osteotomy group of 111.8 +/- 9.3 N (p = 0.009). Performing a MOWHTO via the biplanar rather than the monoplanar technique allows larger-sized wedges to be opened with less risk of lateral cortical fracture. Thus, larger gaps can be opened and higher angle corrections can be achieved using the biplanar osteotomy procedure. From a clinical viewpoint, the biplanar osteotomy technique reduced the risk of lateral cortical hinge fracture during MOWHTO.