Background: The strength of a supraspinatus tendon repair depends on many factors. One factor, the distance from the
suture-bite to the lateral edge of the repaired tendon, has never been biomechanically evaluated.

Objective: The more medial suture depth to the repaired supraspinatus tendon could obtained the better pull-out strength compared to the lateral suture-depth distance.

Materials and Methods: Six paired human supraspinatus tendons were harvested and were randomly assigned to be repaired with Fiberwire® No. 2 at different suture depths (distance from the lateral tendon edge to the suture bite). Biomechanics properties were tested and modes of failure were noted.

Results: All characteristics of the tendon specimens were normal. Load to failure was found to be proportional to the suture depth by 19.65 N/mm displacement. A suture depth of 15 mm had the
highest load to failure at 275.1+10.5 N (p-value <0.01). The mode of failure in two of the six 15 mm specimens was suture breakage; the remaining four specimens failed at the suture- tendon interface.

Conclusion: A suture bite located 15 mm from the lateral tendon edge provides the best possible biomechanical properties with the lowest failure rate. The most common mode of failure is pull-out
at the suture-tendon interface.

Keywords: Supraspinatus tendon repair, Suture depth, Pull-out strength, Mode of failure