|Beitragstitel||Three-dimensional accuracy of high tibial osteotomy using two generations of CT-based patient-specific guides|
INTRODUCTION: High tibial osteotomy (HTO) is a useful treatment option in early osteoarthritis due to the possibility of joint preservation. However, planning and realization of planning are challenging. Patient-specific instrumentation (PSI) has previously been established in joint replacement and is now more and more introduced in osteotomies. The goal of this study is to assess the 3D-accuracy of HTO using an initial and a revised generation of CT based PSI.
METHODS: All patients who underwent PSI-HTO between 03/14-08/16 were retrospectively included. Data were collected on mechanical axis, posterior tibial slope (pTS), joint line convergence angle, lateral proximal femoral angle, lateral distal femoral angle, medial proximal tibial angle, lateral distal tibial angle, and intersection point between mechanical axis and tibia plateau.
Based on CT-scans, 3D differences between preoperative planning and postoperative implementation were calculated by two raters for the following parameters: frontal tibial axis, tibial rotation, tibial slope, and rotation angle. The differences between two generations of PSI were evaluated.
RESULTS: A total of 35 patients (45.1±8.5 years) were included. Beside age and deformity, there was no significant difference between the two generations. All corresponding parameter changed significantly. The mean varus preoperatively (7.3°±3.8°) was changed by 9.2°±3.7° (p<0.001), the pTS changed by 1.4°±2.9° (p=0.009).
Average 3D differences were calculated as 1.7°±2.5° for 3D axis, 0.3°±2.6° for 3D tibial rotation, 0.3°±2.2° for 3D tibial slope, and 4.4°±2.5° for 3D rotation angle. The ICC showed “almost perfect” agreement for 3D rotation angle (0.832), “substantial” agreement for 3D axis (0.626), and “moderate” agreement for 3D tibial rotation (0.573) and 3D tibial slope (0.450).
CONCLUSIONS: The utilization of patient-specific guides results in a significant and reproducible correction of mechanical axis in the setting of HTO. Only a minimal divergence in tibial slope occured while divergence of tibial axis excels average anatomical side differences. The correction of angles with the novel generation of PSI showed similar results and accuracy compared to first-generation guides but less outliers.