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.

The minimal invasive total knee arthroplasty has demonstrated shorter hospital stays, less postoperative blood loss, and less pain associated with these techniques but concerns are raised about inaccurate implant alignment due to limited visibility. The combination of computer assisted arthroplasty and MIS could aid in the improvement of the accuracy of implantation.

This prospective randomized study presents the initial results of the first 25 cases of two different imageless computer-assisted arthroplasty, the Orthopilot(B. Braun-Aesculap, Tuttlingen, Germany) and the Ci navigation system(DePuy, Munich, Germany). The same surgeon performed all TKA procedures using the minimidvastus approach. Coronal and sagittal alignments of the femoral and tibial components were determined using postoperative full length radiographs.

Comparison of the 2 groups demonstrated no difference in postoperative limb alignment, femoral and tibial coronal alignment, and sagittal tibial alignment. The sagittal alignment between the 2 groups showed different results. The Orthopilot group showed a tendency toward flexion of the femoral components, and the Ci navigation group showed a tendency toward extension of the femoral components. The tourniquet time was longer by an average of 16minutes in the Ci navigation group. One complication of femoral fracture through the pin site occurred in the Orthopilot group. Combined CAS and MIS has he advantage in improving the accuracy of component alignment but caution is needed for improving sagittal femoral component alignment.

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.

We assessed the reliability, accuracy and variability of closed-wedge high tibial osteotomy (HTO) using computer-assisted surgery compared to the conventional technique. A total of 50 closed-wedge HTO procedures were performed using the navigation system, and compared with 50 HTOs that had been performed with the conventional technique. In the navigation group, the mean mechanical axis prior to osteotomy was varus 8.2°, and the mean mechanical axis following fixation was valgus 3.6°. On the radiographs the mean pre-operative mechanical axis was varus 7.3°, and the mean post-operative mechanical axis was valgus 2.1°. There was a positive correlation between the 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° vs 3.7°, p = 0,012). We conclude that navigation provides reliable real-time intra-operative information, may increase accuracy, and improves the precision of a closed-wedge HTO.

Between July 1986 and August 1996, we performed 32 total knee arthroplasties (TKA) on 32 patients with partially or completely ankylosed knees secondary to infection. Their mean age at surgery was 40 years (20 to 63) and the mean follow-up was ten years (5 to 13). The mean post-operative range of movement was 75.3° (30 to 115) in those with complete and 98.7° (60 to 130) in those with partial ankylosis. The mean Hospital for Special Surgery knee score increased from 57 to 86 points post-operatively. There were complications in four knees (12.5%), which included superficial infection (one), deep infection (one), supracondylar femoral fracture (one) and transient palsy of the common peroneal nerve (one). Although TKA in the ankylosed knee is technically demanding and has a considerable rate of complications, reasonable restoration of function can be obtained by careful selection of patients, meticulous surgical technique, and aggressive rehabilitation.