In conventional high tibial osteotomy it is difficult to obtain the ideal correction angle consistently and there is high variability of postoperative alignment. We assessed the reliability, accuracy and variability of closed wedge high tibial osteotomy using computer-assisted surgery compared to the conventional technique. Fifty closed wedge HTO procedures were performed and analysed between July 2005 and July 2006, using the CT-free navigation system(Vector Vision^® version 1.1, Brain-LAB, Heimstetten, Germany) for medial compartment osteoarthritis of the knee and fifty knee operations using conventional closed-wedge HTO, performed between 1994 and 2006, were retrospectively reviewed as a control group. The mean age was 59.4 years for the navigation group and 60.7 years for the conventional group. In the navigation group, the mean mechanical axis (MA) before osteotomy was varus 8.2°, and the mean MA after the fixation was valgus 3.6°. On the radiographs, the mean preoperative MA was varus 7.3°, and the mean postoperative MA was valgus 2.1°. In the conventional group, the mean MA was varus 10.6° preoperatively and valgus 0.1° postoperatively via the radiograph. The mean preoperative posterior slope angle (PSA) was 11.0°, which decreased to 9.0° in the navigation group. The mean preoperative PSA was 10.4°, which decreased to 6.4° in the conventional group(p = 0.000). There was a positive correlation between measured data taken under navigation and by radiographs(r > 0.3, P < 0.05). The mean correction angle was significantly more accurate in the navigation group(p < 0.002). The variability of the correction was significantly lower in the navigation group (2.3° versus 3.7°, p = 0.012), and the distribution of MA was also narrower in the navigated group.

We concluded that navigation provides reliable real-time intraoperative information and may increase accuracy, and improve the precision of closed-wedge HTO.

In the anatomical studies for Caucasian, it has been reported that the center of plateau tends to be located central or lateral from the tibial canal axis. However, in the three dimensional analysis of author, the center of plateau was located on average 4.4 mm medial from the point of tibial canal axis passing through the plateau. The purpose of this study is to examine the placement of the tibial component in relation to the anatomical axis of the tibia in total knee arthroplasties for Korean patients and to identify this mismatch affecting the measurement of postoperative mechanical axis.

Measurements were performed on the pre- and postoperative radiographs of 60 osteoarthritic knees with varus deformity replaced between October 2005 and May 2008 using PFC. The inclusion criteria was the cases with the accurate coronal alignment of component, in which α angle ranged from 94 to 96° and β angle ranged from 89 to 91°. The mean age was 66.6 years (range, 54 to 79), and the body mass index was 27.0 kg/m2 (range, 20.7 to 37.7). Radiological measurements were performed using an orthoreontgenogram. Preoperatively, 30 patients with varus deformity lesser than vaurs 10° were classified to group A and 30 patients greater than vaurs 10° were classified to group B. Post-operatively, the distance between the midline of the tibial stem and anatomical axis (medial offset) was measured at the level of tibial resection. These distances were compared between the group A and B. The postoperative mechanical axes were compared between the group A and B. The intra- and inter-observer reliabilities were assessed. In this study, intraclass correlation coefficient values of all measurements were greater than 0.8.

The mean preoperative mechanical axes were varus 7.4±2.3° in group A and varus 16.9±4.0° in group B (p=0.000). The mean medial offsets were 2.5±1.9mm (range, −3.6 to 5.9) in group A and 3.9±2.7mm (range, −1.1 to 10.2) in group B (p=0.021). The tibial stems were located medial to anatomical axis in 22 knees (73.3%) of group A and 26 knees (86.7%) of group B. The mean postoperative mechanical axis were varus 1.3± 1.2° (range, varus 3.6 to valugs 1.6°) in group A and varus 2.5± 2.0° (range, varus 5.9 to valugs 2.1°) in group B (p=0.004).

In this study of TKA, the tibial component in relation to anatomical axis tends to be located medial. The postoperative mechanical axis remained more varus in spite of the accurate coronal alignment of the component as the preoperative varus deformity was more severe. This study suggests that the radiographic measurement of postoperative mechanical axis using a line passing the component center has the limitation.