Summary
The tibial length and the lower limb length after opening wedge HTO were compared to that after closing wedge HTO, respectively and the amount of change in lower limb length was greater in opening wedge.
Abstract
Introduction
High tibial osteotomy(HTO) is a common surgical procedure for medial compartment osteoarthritis of the knee. The two major operative methods, which are opening wedge and closing wedge HTO, are universally performed. HTO produces valgus limb alignment, and this change can affect leg length.
The aim of this study was to assess changes in tibial length and leg length after opening wedge and closing wedge HTO using the 3D software of preoperative planning.
Methods
In this study, 24 knees from 21 patients with osteoarthritis of the knee who underwent computed tomography(CT) examination from hip to ankle joint were included. For the preoperative assessment, digital imaging and communications in medicine data obtained from CT was used and applied to a 3D picture software program(ZedView,LEXI,Tokyo,Japan). Then, using the ZedHTO program (LEXI,Tokyo,Japan) under ZedView, a 3D model of the lower extremity bones was created. We performed 3D visualization and preoperative planning of opening wedge and closing wedge HTO with ZedHTO. The correction of lower lim alignment was defined as the mechanical axis, which ran from femoral head center to tibial prafond center, reached 62.5% of the width of the tibial plateau from the medial side.
The tibial length and leg length before and after planning of HTO were measured. The tibial length was defined as the distance from the center of the tibial plateau to the center of the tibial plafond and the leg length was defined as the distance from the center of the femoral head to the center of the tibial plafond.
The tibial length and the leg length after opening wedge HTO were compared to that after closing wedge HTO, respectively. In addition, we evaluated the association of the change in the tibial length and the leg length after opening wedge and closing wedge HTO to the correction angle.
Results
In opening wedge HTO, the mean postoperative tibial length(312.2±23.9mm)and leg length (700.8±50.1mm) did not differ from the mean preoperative tibial length(308.7±23.3mm)and leg length(694.7±50.0mm)(p=0.69,0.65,respectively).
In closing wedge HTO, the mean postoperative tibial length(303.0±23.5mm)and leg length(691.9±50.6mm)did not differ from the mean preoperative tibial length(308.7±23.3mm)and leg length(694.7±50.0mm)(p=0.20,0.42,respectively).
The mean tibial length changes were +3.5±2.3mm in opening wedge HTO and -5.7±4.4mm in closing wedge HTO. The mean leg length changes were +6.1±4.7mm in opening wedge HTO and -2.8±2.4mm in closing wedge HTO. There were significant difference between the changes in tibial length and leg length in opening wedge HTO and those in closing wedge HTO(p<0.05). The amount of the change in leg length in opening wedge HTO was greater than that in closing wedge HTO, especially when a large correction angle was required. The mean correction angle was 12.6±5.1 degrees for opening wedge HTO and 12.7±5.2 degrees for closing wedge HTO. There was a positive correlation between the correction angle and the change in tibial length and leg length in opening wedge HTO(correlation coefficient:0.78,0.95,respectively). There was a negative correlation in closing wedge HTO(correlation coefficient:-0.85,-0.42,respectively).
Conclusion
The changes in tibial length and leg length were not statistically significant for either opening wedge or closing wedge HTO. However, the amount of change in leg length was greater in opening wedge HTO than closing wedge HTO.
The tibial lengthening due to the opening wedge added with lengthening due to valgus realignment resulted in a large amount of the change in leg length in opening wedge HTO. In contrast, tibial shortening due to removing osteotomy site in the closing wedge offset by lengthening from valgus realignment.
We consider that it is necessary to be careful about leg lengthening in opening wedge HTO, when a large correction angle is required.