The influence of nonanatomical insertion and incongruence of meniscal transplants on the articular cartilage in an ovine model

Background: Adequate size matching and anatomically correct positioning must be recognized as essential factors influencing the outcome of meniscal transplantation. Hypothesis: Nonanatomical insertion and incongruence of meniscal transplants has an influence on the development of degenerative changes. Study Design: Controlled laboratory study. Methods: Ten female sheep were used for this animal study. Both knees (N = 20) were divided into 3 groups, subjected to either meniscectomy (group I; n = 10), to a medial meniscal autograft transplantation with a nonanatomical insertion of the anterior and posterior horn (group II; n = 5), or a meniscal autograft transplantation from the opposite knee as an incongruent meniscal autograft (group III; n = 5). After 6 months, radiographic (Fairbank's criteria), macroscopic (Jackson score), and histological evaluation by light microscopy (Mankin score) and scanning electron microscopy of the articular cartilage was performed. Results: All applied evaluation methods demonstrated that nonanatomical insertion of meniscal transplants resulted in the highest amount of degenerative cartilage changes. The histological assessment even revealed a significantly enlarged cartilage damage for the non-anatomic-positioned meniscal transplants in relation to the meniscectomized knees. Furthermore, the incongruent meniscal transplants demonstrated a significantly better cartilage situation than nonanatomically inserted meniscal transplants. Conclusion: The histological evaluation demonstrated clearly that a nonanatomically inserted meniscal transplant leads to degenerative cartilage changes that are worse than that after meniscectomy. Clinical Relevance: Precise anatomic positioning is mandatory for the potential chondroprotective effect of meniscal transplants.