Mechanical strength of repairs of the rotator cuff

TLDR

The authors compared nine tendon‑grasping techniques on 159 sheep infraspinatus tendons and evaluated anchorage methods on osteoporotic bone specimens. Testing these techniques revealed that non‑absorbable braided polyester and absorbable polyglactin/polyglycolic acid sutures had the best strength, simple stitches performed poorly, a Mason‑Allen modification raised ultimate tensile strength to 359 N, and a 2 mm plate‑like augmentation increased failure load to 329 N, demonstrating that repair strength can be greatly improved with better materials, refined suture technique, and bone augmentation.

Abstract

We have studied the mechanical properties of several current techniques of tendon-to-bone suture employed in rotator-cuff repair. Non-absorbable braided polyester and absorbable polyglactin and polyglycolic acid sutures best combined ultimate tensile strength and stiffness. Polyglyconate and polydioxanone sutures failed only at high loads, but elongated considerably under moderate loads. We then compared the mechanical properties of nine different techniques of tendon grasping, using 159 normal infraspinatus tendons from sheep. The most commonly used simple stitch was mechanically poor: repairs with two or four such stitches failed at 184 N and 208 N respectively. A new modification of the Mason-Allen suture technique improved the ultimate tensile strength to 359 N for two stitches. Finally, we studied the mechanical properties of several methods of anchorage to bone using typically osteoporotic specimens. Single and even double transosseous sutures and suture anchor fixation both failed at low tensile loads (about 140 N). The use of a 2 mm thick, plate-like augmentation device improved the failure strength to 329 N. The mechanical properties of many current repair techniques are poor and can be greatly improved by using good materials, an improved tendon-grasping suture, and augmentation at the bone attachment.