Femorale und tibiale Transplantatfixation der vorderen Kreuzbandplastik mit der neuartigen bioresorbierbaren Interferenzschraube Milagro®

Abstract

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. It is the aim of this study to examine the clinical results as well as the in vivo degradation and biocompatibility of the new Milagro® interference screw. The Milagro® interference screw is composed of 30% ß-TCP (TriCalcium phosphate) and 70 % PLGA (Poly-lactic-co-glycolic acid). Between June 2005 and October 2006, 35 patients underwent arthroscopic graft fixation with Milagro® screws in our hospital. Arthroscopic anterior cruciate ligament (ACL) reconstruction was performed using only the semitendinosus tendon in 15 patients. The remaining 20 patients underwent Arthroscopic ACL reconstruction in which the semitendinosus tendon in combination with the gracilis tendon was used. Twelve randomly selected patients out of the total 35 underwent MRT-examinations after three, six, and twelve months after surgery. During these examinations, the volume loss of the screws and the tunnel enlargement were determined. Moreover, the patients were checked for osteolysis and the extent of postoperative screw replacement by bone tissue was also evaluated. After twelve months the Tegner, Lysholm, Marshall, and the IKDC score was determined for all 35 patients, as well as the visual analog scale pain and function and the anterior translation with the KT-1000 arthrometer. Additionally, it was examined if there were differences in the clinical results in ACL reconstruction using only the semitendinosus tendon (ST) versus using the semitendinosus tendon in combination with the gracilis tendon (STG). After one year the average Lysholm Score for the overall patient collective was 93.4 (+/- 5.4) points, the average Marshall Score was 46.6 (+/-2.5) points. The stability test with the KT-1000 arthrometer showed average side-to-side difference of 1.61 mm (+/- 1.1) at a force of 67N, 1.94 mm (+/- 1.1) at a force of 89N, and 2.19 mm (+/- 1.3) at the maximal manual drawer. Judging from the Lysholm and Tegner Scores, the visual analog scale pain and function as well as from objective knee laxity test with the KT-1000 Arthrometer, there were no significant differences in ST patients compared to STG patients.ST patients had an average Marshall Score of 47.7 (+/- 2.1) points, while STG patients had an average Marshall Score of 45.8 (+/- 2.5). Patients whose transplant was composed only of the semitendinosus tendon showed a significantly better Marshall Score. The average volume loss in the tibial screws was 8.1% (+/- 7.9%) after six months and 82.5% (+/-17.2%) after twelve months. In the femoral screws, the volume loss was 2.5% (+/- 2.1%) after three months, 31.3% (+/- 21.6%) after six months, and 92.0% (+/- 6.0%) after twelve months. The osteolysis rate was at a low 5%. The drill ducts which were situated close to the joints showed an average increase in diameter of 85.2% (+/- 72.6%) after twelve months. The femoral increase was 78.7% (+/- 50.9%). The present study shows that the resorbing Milagro®-screw is partially replaced by bone tissue. MRI examinations could prove the replacement of the resorbable Milagro® screw by bone tissue which lead to a volume reduction of the drill ducts. The resorption characteristics of the Milagro®-screws are ideally suited to the healing process of the cruciate ligament: In the first six months after ACL replacement the screws are hardly resorbed at all, but this phase is followed by a rapid decrease in volume. Their easy detection in conventional x-ray images is another advantage of the MilagroÒ-screws.