Generally, a closed-wedge HTO tends to shorten the tibial length, while an open-wedge HTO tends to lengthen it. Overall limb length changes were evaluated after closed- and open-wedge high tibial osteotomies (HTOs) using computer-assisted surgery. The hypothesis was that the overall limb length of the corrected extremity does not change much after closed-wedge HTO because the effect of extremity realignment on limb length counterbalances the effect of tibial shortening caused by the metaphyseal bone loss of the proximal tibia. After an open-wedge HTO, the overall limb length would increase within a certain range.

A total of 78 closed- and 30 open-wedge HTOs were performed. The changes in limb length were evaluated on a navigation system and radiographs. The correction angle was defined as the difference between the pre- and postoperative mechanical axis on the navigation system. The change in limb length with respect to the correction angle was analyzed.

Following the closed-wedge HTOs, the mean changes in limb length based on the navigation system and radiographs were −1.3±1.9 and −1.3±10.7mm, respectively, versus 6.2±2.6 and 7.8±2.9mm after the open-wedge HTOs. The mean correction angle was 11.6±3.2° for closed-wedge HTOs and 11.5±1.9° for open-wedge HTOs. The correction angle did not affect the change in limb length after closed-wedge HTO, while the larger the correction angle required, the greater the increase in limb length after open-wedge HTO.

The change in limb length was negligible after closed-wedge HTO, while the limb length was slightly increased in every knee after open-wedge HTO. The greater the correction angle required in the open-wedge HTO, the greater limb length increased. The possibility of limb lengthening must be considered carefully when determining whom to perform open-wedge HTO on, especially when a large correction angle is required.