Histological scoring systems for tissue-engineered, ex vivo and degenerative meniscus

PURPOSE: Because its function is strictly related to the quality of meniscal tissue, one of the most important outcome measures for the evaluation of meniscal repair effectiveness is the assessment of histological features. Data on the validation and application of the histological scoring systems in research settings and specific fields of meniscal disorders are lacking. The available histological scoring systems to assess meniscal tissue were systematically evaluated. METHODS: Histological scoring systems for the analysis of degenerative meniscal changes, ex vivo and tissue-engineered meniscal repair were reviewed. Furthermore, the validity and applicability of the scoring systems were assessed. RESULTS: The Copenhaver classification and Mankin score have been modified to classify the degeneration of collagen bundles in the meniscal structure. The Pauli score seems to be a comprehensive and simple scoring system for the evaluation of both macroscopic and histologic meniscal changes related to ageing and osteoarthritic degeneration. The Zhang score may be used for ex vivo gene therapy in meniscus healing. The Ishida score seems to be the most adequate for the evaluation of tissue-engineered meniscal repair. CONCLUSION: Although several histological scoring systems are available to assess meniscal structure, only few of them have been validated for specific application in research settings. Validated scores are required to provide a standardized data collection to allow the comparison of results of different research groups. Further experimental and clinical studies are needed to find a comprehensive and validated histological scoring system in the field of meniscus repair. LEVEL OF EVIDENCE: Systematic review of Level III studies, Level III.