[Varus supracondylar osteotomy of the femur -- long-term results].

PURPOSE OF THE STUDY

Varus supracondylar osteotomy of the femur is the surgical procedure indicated in young patients with symptomatic unicompartmental gonarthrosis associated with a valgus knee deformity. The aim of the study was to evaluate long-term results and to draw attention to the most frequent mistakes in the indication and surgical technique.

MATERIAL

In the period from 1985 to 1995, 35 knees in 33 patients were treated by varus supracondylar osteotomy of the femur in the Department of Orthopedics, Teaching Hospital, Faculty of Medicine, Palacký University in Olomouc. The technique of medial closing wedge osteotomy of the distal femur held with a 90 degrees plate was used. For post-operative immobilization, a brace was applied in most of the patients.

METHODS

The information recorded was as follows: age, type of arthritis, follow-up period, preoperative tibio-femoral angle, postoperative tibio-femoral angle, range of motion before and after surgery, post-operative Knee Society scores, complications, number of osteotomies converted to total knee arthroplasty, and time between osteotomy and knee prosthesis implantation. The survival of osteotomy was evaluated by the Kaplan-Meier analysis for censored data. The change in parameters obtained before and after surgery was assessed by the one-sample t-test and non-parametric Wilcoxon test.

RESULTS

All 35 knees were evaluated. The average Knee Society score at follow-up was 77 points (range, 61-95), the average functional knee score was 78 points (range, 61-95). The average range of motion increased from the pre-operative 112 degrees (range, 75-130 degrees ) to post-operative 115 degrees (range, 90-135). This difference was statistically significant (p = 0.032; t-test for paired samples; Wilcoxon test). The average follow-up was 14.7 years (range, 10-20 years). The most frequent complications were progression of medial compartment arthritis (8 knees), loss of correction (6 knees) and arthrofibrosis (5 knees). Osteosynthesis failed in two knees and, in two, superficial wound infection was recorded. Due to failure of osteotomy, six patients (17 %) subsequently underwent total knee replacement. The osteotomy survival rate was 95% at 18 years (CI, 16-19 years).

DISCUSSION

The results of this study are based on long-term observation and can be compared with the studies by Mironneau et al. or Finkelstein et al. These and other authors have achieved better results in terms of score values, which can be explained by the following five factors: the follow-up in their studies was significantly shorter than in our study. At our department knee arthroplasty became a routine surgical technique as late as the early 1990s, and even after that some tendency continued to indicate bi- and tri-compartmental osteoarthritis for osteotomy. Also we operated on patients who were overweight and on those who were older than recommended for this procedure.

CONCLUSIONS

The prerequisite for successful varus supracondylar osteotomy of the femur in unicompartmental gonarthrosis is that the patient is active, younger than 62 years and is not overweight. Early diagnosis followed by osteotomy, which prevents further progression of the disease, is also important. The detailed pre-operative planning and exact performance of the procedure are fundamental conditions. In the post-operative period it is necessary to observe the relevant regimen including rehabilitation therapy. When these conditions are fulfilled, osteotomy can markedly postpone the necessity of total knee arthroplasty.