Stress distribution in the supraspinatus tendon after tendon repair - Suture anchors versus transosseous suture fixation

Background: The stress concentration at the site of supraspinatus tendon repair, either by suture anchor fixation or by transosseous suture fixation, has not been fully clarified. Hypothesis: Suture anchor fixation showed higher stress concentrations in the tendon than did transosseous suture fixation. Study Design: Controlled laboratory study. Methods: Three finite element models were developed based on a previously published model of normal supraspinatus tendon (0 degrees abduction). Single-row fixation, double-row fixation, and transosseous suture fixation were simulated. A tensile force was applied to the proximal end of the supraspinatus tendon to simulate its contraction force. Results: In the single-row model, the stress appeared from the site of the anchor and extended into the proximal tendon. The highest stress concentration was observed on the bursal surface of the tendon. The double-row model showed a similar pattern to the single-row model except that the stress concentration was observed only around the medial anchor. In the transosseous model, the stress appeared from the attachment site to a bony trough, which extended proximally into the tendon substance. No significant stress concentration was observed inside the tendon. Conclusion: Both single-row and double-row fixations showed higher stress concentration inside the tendon than did transosseous suture fixation. Clinical Relevance: A high stress concentration might be a cause of the rerupture often observed after arthroscopic cuff repair using suture anchors.