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.

We compared the short term follow-up clinical and radiological results after PCL substituting (PS) Medial Pivot Knee and Nexgen^® LPS total knee arthroplasty (TKA).

Seventy knees in 48 patients after TKA with PS ADVANCE^® Medial Pivot Knee (Group I) and sixty seven knees in 45 patients after TKA with Nexgen^® LPS (Group II) were evaluated retrospectively from March 2004 to May 2006. The mean follow up period was 31 months (range: 24–43 months) in group I and 32 month (range: 24–46 months) in group II. All the knees were operated by one surgeon. The evaluations included the preoperative and postoperative range of motion (ROM), Knee society score (KSS), tibiofemoral angle, and postoperative complications.

In group I, ROM increased from preoperative mean flexion contracture of 6.3° and further flexion of 116° to postoperative mean flexion contracture 1.9° and further flexion 121°, KS knee score increased from 46 to 87, KS function score increased from 37 to 83, and tibiofemoral angle changed from preoperative varus 4.0° to postoperative valgus 5.5°. In group II, ROM increased from preoperative mean flexion contracture of 13° and further flexion of 118° to postoperative mean flexion contracture 0.9° and further flexion 123°, KS knee score increased from 50 to 87, KS function score increased from 48 to 83, and tibiofemoral angle changed from preoperative varus 4.1° to postoperative valgus 5.3°. The complications were two periprosthetic patellar fracture and one failure of tibial component in group I, and one early failure of femoral component and one arthrofibrosis in group II. There was no statistical difference in radiological and clinical results between the two groups.

Minimum 2-year follow-up result of PS Medial Pivot Knee TKA was comparable to that of Nexgen^® LPS TKA and longer term follow-up would be necessary.

We evaluated the minimum 3 year follow-up clinical and radiological results after Nexgen^® LPS-flex total knee arthroplasty (TKA).

Two hundred eighteen knees in 166 patients, who could be followed up more than 3 years after Nexgen^® LPS-flex TKA from October 2001 to February 2005, were evaluated retrospectively. The average age was 64.2 years. Twenty-two patients were male and 144 patients were female. The mean follow-up period was 51 months (range 36–73 months). The evaluations included the preoperative and postoperative range of motion (ROM), Knee Society (KS) Score, tibiofemoral angle and postoperative complications.

The ROM increased from preoperative mean flexion contracture of 8.7° and further flexion of 117.3° to postoperative mean flexion contracture of 1.8° and further flexion of 131.3°. The KS knee score and function score improved from 52 and 38 before surgery to 87 and 82 after surgery, respectively. The tibiofemoral angle changed from preoperative varus 5.7° to postoperative valgus 5.4°. The complications were 30 knees (13.8%, 27 patients) of early loosening of the femoral component on X-ray, 2 instabilities, 2 periprosthetic fractures and 1 failure of extensor mechanism. Early loosening (30 knees) was found at mean 24 months after operation. Among these cases, 23 knees were able to squat, 5 knees to flex over 130°, 1 knee upto 115° and 1 knee upto 95°. Seven knees (3.2%, 6 patients) were revised at mean 49 months after index operation.

The results after Nexgen^® LPS-flex TKA were satisfactory in terms of ROM, but relatively high incidence of early loosening of the femoral components occurred, which might be associated with passive-maximal flexion activity, such as squatting or kneeling.

Introduction: Osteonecrosis of the femoral head occurs in young patients. The preservation of the hip joint is vitally important because hip replacement arthroplasty is associated with high rates of failure in young and active patients. Curved intertrochanteric varus osteotomy is one of several joint preserving procedures used to treat these patients.

Methods: Between June 2003 and June 2006, 46 patients (49 hips) who had osteonecrosis of the femoral head were treated with curved intertrochanteric varus osteotomy. There were 23 men and 23 women who had a mean age at the time of osteotomy was 33 years (range, 17 to 51 years). The osteotomy was fixed with a 120 degree compression hip screw in the first 34 hips and with a 95 degree dynamic condylar screw in the remaining 15 hips. Clinical evaluation was performed using the scoring system of Merle d’Aubigne et al. Radiological failure of the operation was defined as further collapse of the femoral head by more than 2 mm or progressive narrowing of the joint space compared with the immediate postoperative radiograph.

Results: The mean duration of follow-up was 22 months (range, 12 to 48 months). One patient (one hip) required a total hip arthroplasty due to loss of fixation and penetration of the lag screw into the joint space. In two patients (two hips), the plate fractured at 3 and 4 months after the operation, which was changed to a new plate. Thus, 48 of the 49 hips survived at a mean follow-up 22 months. In these 48 hips, the mean Merle d’Aubigne hip score was 17.2 points at latest evaluation and there was no instance of radiologic failure.

Discussion: Curved intertrochanteric varus osteotomy is a satisfactory joint preserving method to treat osteonecrosis of the femoral head.

The role of femoral and acetabular version in correction of dysplasia of the hip has been undereported. Between June 1995 and September 2000, a Bernese periacetabu-lar osteotomy (BPO) was performed in 25 patients (26 hips) by the senior author with an average follow-up of 3.7 years (range 2-5 years). The mean age of the patients (24 female, 1 male) at the time of surgery was 29.4 years (range, 11.5 to 45 years). Only patients with a primary diagnosis of acetabular dysplasia were included in this series.

The average Harris hip score increased from 55.1 (range 34–75) preoperatively to 92.9 (range 72–100) at the latest follow up (p< 0.0001). The mean pre-operative Merle d’Aubign score increased from 13.5 (range 10–15) to 17 (range 15–18) at the latest follow up. The mean lateral centre edge angle of Wiberg increased from 13.10 (range 00–200) pre-operatively to 52.60 (range 200-740) at latest follow-up (p< 0.0001). The anterior centre edge angle averaged 10.90 (range 4-170) pre-operatively and improved to 490 (range 210–760) at latest follow-up (p< 0.0001). The Mckibbin instability index is the sum of femoral and acetabular version (normal range 200–500). There were 6 hips with low instability index and 11 hips with high instability index pre-operatively. At the latest follow-up there were only 2 hips with low instability index and there were no patients with a high instability index. Our clinical results showed fi fteen patients with excellent results, eight good results and one fair and one poor results. Thus, overall good to excellent results were obtained in 92% of our patients. It is therefore possible that we had higher success rate in our series than that reported in other series because of the correction of version of the hip in addition to the coronal and sagittal defi ciency of the hip.