Histologic stages of healing correlate with restoration of tensile strength in a model of experimental tendon repair.

Much current research is focused on biologic enhancement of the tendon repair process. To evaluate the different methods, which include a variety of gene therapy and tissue engineering techniques, histological and biomechanical testing is often employed. Both modalities offer information on the progress and quality of repair; however, they have been historically considered as two separate entities. Histological evaluation is a less costly undertaking; however, there is no validated scoring scale to compare the results of different studies or even the results within a given study. Biomechanical testing can provide validated outcome measures; however, it is associated with increased cost and is more labor intensive. We hypothesized that a properly developed, objective histological scoring system would provide a validated outcome measure to compare histological results and correlate with biomechanics. In an Achilles tendon model, we have developed a histological scoring scale to assess tendon repair. The system grades collagen orientation, angiogenesis, and cartilage induction. In this study, histology scores were plotted against biomechanical testing results of healing tendons which indicated that a strong linear correlation exists between the histological properties of repaired tendons and their biomechanical characteristics. Concordantly, this study provides a pragmatic and financially feasible means of evaluating repair while accounting for both the histology and biomechanical properties observed in surgically repaired, healing tendon.