Change in limb length after high tibial osteotomy using computer-assisted surgery: a comparative study of closed- and open-wedge osteotomies.
Closed- and 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 ± 10.7 mm, respectively, versus 6.2 ± 2.6 and 7.8 ± 2.9 mm 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 increased slightly after open-wedge HTO. 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."
In a closed wedge osteomy, a piece of the bone is removed and medal plates or pins are used to pin the bone together. In open-wedge osteomy, the surgeon cuts open a wedge and puts in a bone graft to hold the wedge open. Now unlike limb lengthening surgery the bone is not fractured completely. The force of growth in the bone graft must be such to cause expansion of the bone to a slightly longer length. The bone must after all grow into and within the bone graft. All the mechanical reactions required to do this may produce force that causes overall bone expansion.
Unlike limb lengthening surgery where the bone is held out at a longer length, the only stimulation to increase length is the force of bone growing in and around the wedge itself. Thus a force inside the bone like LSJL induced growth plates may be able to cause expansion in the bone increasing length. There is no cut like with open-wedge osteomy but there is already a wedge that exists called the epiphyseal bone marrow. LSJL induced chondrogenesis or even osteogenesis may produce that wedge within the epiphyseal bone marrow. An osteogenic wedge though may only produce the millimeters of height gain reported in this study. A chondrogenic wedge may produce more height gain.