[Total knee arthroplasty with the Beznoska S.V.L. implant: short-term results].

PURPOSE OF THE STUDY: To present and evaluate short-term clinical results of total knee arthroplasty using the Beznoska S. V. L. implant and to compare them with the results of other authors.

MATERIAL: In the period from April 1997 to October 2002, 197 total knee replacements with a S. V. L. implant were carried out of these, 164 implants were evaluated in 146 patients. This group comprised 116 women (78 %) and 48 men (22 %), with an average age of 73.6 years (range, 63 to 83) at the time of surgery. The patients were evaluated on average at 4.3 years (range, 1.5 to 6.5) after surgery. Indications for replacement were primary knee arthritis in 151, rheumatoid arthritis in nine, secondary post-traumatic arthritis in two and conditions following tibial osteotomy in two cases.

METHODS: The results were evaluated using the Knee Society Clinical Rating System which consists of three parts: Knee Score (100 points), Knee Function Score (100 points) and Categorical Score (allocating patients to three groups according to function deficiencies of other joints). X-ray images were examined for implant position, the presence of radiolucent lines and patellar position, and assessed on the basis of the Knee Society Total Knee Arthroplasty Roentgenographic and Scoring System.

RESULTS: No or mild pain in the treated joint was reported by 90.2 % of the patients. Severe pain was not recorded at all. The average maximal range of flexion increased from 94 degrees preoperatively to 104 degrees post-operatively. The range of motion more than 90 degrees and that of more than 100 degrees were recorded in 96 % and 76.8 % of the operated-on knees, respectively. An anteroposterior mild instability of 5 to 10 mm was objectively found in nine knees (5.5 %) a medial laxity of 6 to 9 degrees was detected in 36 knees (22 %) and that of 10 to 15 degrees only in one patient. Severe instability was not recorded. The leg axis achieved after surgery was on average 6.4 degrees valgus, compared to 5.5 degrees varus before surgery. The total Knee Score was 85.1 points (range, 53 to 100), with excellent or good outcomes in 151 knee replacements (92 %). Six patients (4.6 %) reported failure to walk a distance of more than 500 m on an even terrain, six (4.6 %) could not manage the stairs and five (3 %) required a permanent use of two crutches or a walking frame. The average function score, which also included the effect of concomitant diseases of other joints, was 64.9 points (range, 40 to 100), with excellent or very good outcomes being achieved in 64 implants (39 %). On X-ray examination of implant position in anteroposterior projection, the average valgus angle of the femoral component was 94.8 degrees (range, 92 to 100) and the tibial angle was 90.3 degrees (range, 85 to 94). In lateral projection the flexion angle of the femoral component was 2.5 degrees (-1 to 6) and the average dorsal tilt of the tibia was 3 degrees. Distinct radiolucent lines up to 1 mm in width were seen in the femoral component in 10 (6 %) cases and in the tibial component in 27 (16.5 %) cases, this occurred in zones 1, 2 or 4. Wider lines of 2 mm were present in both components in 6 (3 %) cases. Radiolucent lines were recorded in 43 (26 %) implants. The patella examined in axial projection was correctly centered in 140 (85 %) total knee replacements. Eleven patients reported femoropatellar problems and, in three of them, patella replacement was subsequently performed. No aseptic loosening occurred and one deep infection (0.6 %) was treated by a two-stage reimplantation.

DISCUSSION: Excellent to very good outcomes, with an average Knee Score of 85.1 points, were achieved in 92 % of the implants. The total outcome characterized by an average Functional Score of 64.9 points was related to a higher average age of our patients and a high proportion of patients with diseases of other joints, which interfered with overall mobility and self-sufficiency. The results of implant position evaluation, based on X-ray examination, showed good values, which testifies to the use of an appropriate surgical technique and accuracy of the instrumentation applied. The occurrence of radiolucent lines was low, as was the number of complications. Our results are comparable with those reported in the literature.

CONCLUSIONS: Our short-term evaluation shows that the S. V. L. implant is fully useful for total knee replacement in patients of higher age categories.