[Effect of surgical technique on meniscus transplants. A histological, animal experiment study]

After transplantation, a meniscus undergoes alterations in mechanical loading, which causes changes in its histological structure. We studied the degenerative effects on meniscus and tibial cartilage resulting from variations in the congruity or the isometric fixation of medial meniscus transplants. In three groups of five sheep each, the menisci were transplanted in three different ways, using the same operative approach. The menisci were evaluated 24 weeks after operation. In group 1, the meniscus was totally detached from its base at the capsule and refixed without changes in the congruity or isometry. This group provided the basic data. In group 2, the contralateral medial meniscus was turned upside down and transplanted. The reattachment was performed according to isometric conditions. With this technique the congruity of the tibial and femoral surface was modified. In group 3, the medial meniscus was reimplanted by choosing defined non-isometric fixation points for the anterior and posterior meniscal ligaments without changing the position of the corpus. For evaluation, the morphological alterations of meniscus and tibial cartilage were assessed by the Jackson score. The more distinct changes of the meniscus were assessed histologically by three criteria: surface cells, surface fibers and changes in the meniscus center. The highest degree of degenerative changes occurred in group 3 (score 4.5); however, considerable changes were also found in group 2 (score 3.5). Incongruous or non-isometric placement of a meniscal graft will lead to degeneration and failure of the graft.