[Effect of surgical technique on meniscus transplants. A histological, animal experiment study]. / Der Einfluss der Operationstechnik auf Meniskustransplantate. Eine histologische, tierexperimentelle Studie.

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.

[Meniscus replacement using incongruent transplants--an experimental study]. / Der Meniskusersatz mit inkongruenten Transplantaten--eine experimentelle Untersuchung.

The effect of incongruous medial meniscal grafts on the articular surface was studied. We compared the cartilage degeneration in 4 Groups of 25 sheep knees. The histological changes were graded according to the score of Mankin, the morphological alterations by the score of Jackson. In Group 1 no surgery was performed. In group 2, 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 3, the contralateral medial meniscus was used as a transplant by reversing it. The reattachment was done according to isometric conditions. With this technique only the congruity of the tibial and femoral surface was modified. In group 4, the medial meniscus was completely removed. The results of group 1 (Mankin grade 0.58; Jackson grade 0.00) and group 2 (grade 0.50 and 0.47) showed no difference. The highest degree of degenerative changes occurred in the meniscectomized knees (group 4, grade 4.47 and 1.73), however considerable changes were also found in the knees with an incongruous meniscal graft (group 3, grade 3.37 and 1.27). The results suggest that incongruous grafts will lead to degeneration of the articular surface but still have a chondroprotective effect.