[Initial experience with implantation of the cemented Beznoska/S.V.L. total knee joint endoprosthesis].

PURPOSE OF THE STUDY

The authors present the results of their first trial of a new, Beznoska/S. V. L. type, knee prosthesis in order to introduce it to a broad orthopedic public.

MATERIAL

Clinical and radiological evaluation was carried out on 34 knee prostheses implanted in 31 patients between September 1997 and October 1999. The average patient age at the time of surgery was 71.3 years and the average interval between surgery and assessment was 22.4 months (range 6 to 31 months). All patients underwent implantation due to primary or secondary gonarthosis. A brief description of the implant and the instrumentation and used surgical technique is provided.

METHODS

Clinical outcomes were evaluated according to the "Knee-Society Clinical Rating System" by John N. Insall. The system classifies both knee joint parameters and knee function. X-ray films were assessed on the basis of the "Knee-Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System" by Frederic C. Ewald. In standardized X-ray projections, this allowed us to evaluate the implant position as well as radiolucent lines.

RESULTS

On stability evaluation, we found anteroposterior instability up to 5 mm in 85% of the implants and mediolateral instability up to 9 degrees in 97% of them. A maximum flexion of 90 degrees to 120 degrees was achieved in 91% of the implants. The final outcome in terms of knee score was on average 80.3 points (range, 40 to 97 points), which was a very good result. Evaluation by function score showed that only 17% of the patients were not able to walk farther than 500 meters. Although 82% of them had to hold on a railing when going upstairs, all were able of stair ascent and descent; 13% had to use a walking stick permanently. The average function score was 68.4 points (range, 30 to 100), which was a good outcome. Radiograms in anteroposterior projection, assessed according to Ewald, showed the average femoral flexion angle (alpha) to be 95.2 degrees, the average tibial angle (beta) to be 89 degrees and the total valgus angle (omega) to be 3.2 degrees. In lateral projection, the femoral flexion angle (gamma) was on average 2.5 degrees and the average tibial angle (delta) was 86.7 degrees. An optimal position of the patella was achieved in 27 implants. Five radiolucent lines, up to 1 mm, were found in zone 1 of the femoral component and further lines were observed in zones 1, 2 and 4 of the tibial component.

DISCUSSION

When assessing the results by the knee and function scores, it had to be taken into consideration that the average age of the patients was 71.3 years. At this age, walking without a stick, or stair ascent or descent without the use of a railing can hardly be expected. The average result of 68.4 points achieved can, therefore, be considered a very satisfactory outcome. The values shown by X-ray examination were close to the normal condition. The patients were also asked for their subjective opinion of the effect of arthroplasty; 97% of them regarded the effect as good or very good, only one patient reported no benefit.

CONCLUSIONS

The results of the first trial of the use of a cemented prosthesis, type Beznoska/S. V. L., in total knee arthroplasty are presented, together with practical recommendations. Although the patient sample was small and the follow-up period short, the results are promising and suggest excellent prospects for this implant.