Validation of a histologic scoring system for the examination of quality of tendon graft to bone tunnel healing in anterior cruciate ligament reconstruction.

Objective: To develop and validate a histologic scoring system for the assessment of tendon graft to bone tunnel healing in anterior cruciate ligament (ACL) reconstruction.

Methods: The scoring system, tendon-bone tunnel healing (TBTH) score, comprised 5 items on graft status,fiber type and interface connectivity, evaluated on either a 5- or 6-point scale. Two observers were trained to use the scoring system, examining 15 blinded histologic slides from an ongoing study. Afterward, an independent validation dataset consisting of 89 blinded histologic slides from the same study of different time points, tunnel positions and bone tunnels were scored for validity and reliability. Interrater and intrarater reliabilities were calculated. The sum was validated by the time-dependent change of healing.

Results: Both the intrarater and interrater reliabilities of the scoring system were high, with weighted K of 0.90-0.99 (all p < 0.001) and 0.84-0.94 (all p < 0.001), respectively, for different items. The sum of score increased significantly with time at different segments of both tunnels (all p < 0.05), consistent with the process of tunnel healing.

Conclusions: TBTH score is a reliable, valid measure for evaluating the histologic outcome of tendon graft to bone tunnel healing in ACL reconstruction.