We hypothesized that navigation can help provide a well-balanced knee, through real-time feedback of alignment accuracies and gap sizes in flexion and extension. The purpose of this study was to evaluate in vivo stabilities of mediolateral laxity in full extension and anteroposterior laxities in 90° of flexion after navigation-assisted total knee arthroplasty, and to determine the nature of the correlations between these and range of motion (ROM).

Forty-two total knee arthroplasties performed using a navigation system with a minimum two-year follow-up were included. The following were measured at final follow-ups; mediolateral laxities at extension and anteroposterior laxities at 90 degrees of flexion (using stress radiographs and a Telos arthrometer), modified HSS scores (excluding laxity and range of motion), and range of motion (ROM).

At final follow-up the mean modified HSS score was 82% of total points and mean postoperative ROM was 128.1 ± 10.4°. Mean medial laxity was 3.5 ± 1.4°, mean lateral laxity 4.4 ± 2.2°, and mean anteroposterior laxity 7.1 ± 4.1 mm. We found no significant correlation between mediolateral laxity and postoperative ROM. However, a significant correlation was found between postoperative ROM and anteroposterior laxity.

In the present study, the use of a navigation system in total knee arthroplasty was found to improve in vivo stability and produce promising short-term clinical results.

Summary: Using a navigation system in total knee arthroplasty, we obtained good in vivo stability and found the positive correlation between the range of motion and anteroposterior laxity

Introduction: The aim of this study was to report the clinical and radiographic results of a modified transtrochanteric rotational osteotomy (MTRO) for osteonecrosis of the femoral head.

Materials and Methods: A MTRO was performed in 43 hips with osteonecrosis. The mean age was 34 years (range, 20 to 51 years). According to the classification system of the Association Research Circulation Osseous, 17 hips were stage 2 and 26 stage 3. We performed simple MTRO in 15 cases, combination of MTRO and simple bone grafting in 3 cases, and a combination of MTRO and muscle pedicle bone grafting in 25 cases.

Results: At a mean 37 months after surgery, there was further collapse of the femoral head in 3 hips. All these lesions were in the lateral location, and 2 were large lesions. One of these 3 hips was converted to a total hip arthroplasty. The overall survival rate was 93 percent. Among the surviving 40 cases, excellent results were obtained in 26 hips, good results in 11, and fair results in 3 hips.

Conclusion: A MTRO is an effective method for delaying the progression of collapse in the treatment of osteonecrosis of the femoral head in selected cases.

Introduction: The results of transtrochanteric rotational osteotomies for osteonecrosis of the femoral head were reviewed.

Materials and Methods: The results of 26 transtrochanteric osteotomy in 24 patients with Ficat stage II or stage III osteonecrosis of the femoral head performed between April 1994 and June 2001 were evaluated. Osteotomy was primarily conducted on patients younger than 50 years of age when the necrotic lesion was at least 30% of the whole femoral head and was located at the superior aspect. Twenty-three hips in 22 patients were available for clinical and radiological follow-up at 59 months (range, 24–109 months). The average age of the patients at the time of the index procedure was 35 years (range, 23–51 years). The results were considered successful if there was no radiologic failure (progression to necrosis, further collapse) or clinical failure (the need for total hip arthroplasty).

Results: Eighteen (78%) hips had a successful result. Two hips showed progressive varus deformity and were treated by valgus osteotomy. One hip survived and one hip underwent a Girdlestone operation followed by total hip arthroplasty to treat an associated deep infection. Four other hips were also subsequently treated with total hip arthropalsty because of head collapse with severe varus deformity or neck fracture in three hips and infection after osteotomy in one hip.

Discussion: Our results suggest that transtrochanteric osteotomy is a dependable procedure in the treatment of a large lesion even in the later stages of osteonecrosis of the femoral head, which is especially true for patients under the age of 50 years.