Biomimetic Approach to Designing Adhesive Hydrogels: From Chemistry to Application

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.

The purpose of this study was to examine the failure mode of supraspinatus tendon repairs with and without human dermal allograft augmentation.

The purpose of this study was to determine the load to failure strengths and modes of failure of various commercially available tendon augmentation xenografts and allografts. Experimental laboratory study. GraftJacket (Wright Medical Technology, Arlington, TN), CuffPatch (Arthrotek, Warsaw, IN), Restore (Depuy, Warsaw, IN), Permacol (Tissue Science Laboratories, Covington, GA; licensed to Zimmer, Warsaw, IN), and TissueMend (TEI Biosciences, Boston, MA; licensed to Stryker Howmedica Osteonics, Kalamazoo, MI) measuring 2 x 5 cm were hydrated according to manufacturers guidelines, a horizontal mattress stitch 5-mm wide was placed 5 mm from the narrow edge of the graft. Tensile loads to failure were applied on the suture while an Instron machine held the graft material and mean loads to failure of the suture graft construct were obtained and modes of graft failure noted. The mean loads to failure were obtained: GraftJacket thin (157 N), GraftJacket MaxForce (182 N), GraftJacket Extreme (229 N), CuffPatch (32 N), Restore (38 N), Permacol (128 N), and TissueMend (70 to 76 N). Failure occurred principally by suture pull-through in all specimens and patterns tended to vary by implant type. CuffPatch and TissueMend tended to fail by isthmus pullout, whereas Restore and Graft jacket failed by end pullout. The tissues were statistically stratified into four groups depending on the material. Human skin (GraftJacket) was the strongest followed by porcine skin (Permacol) and bovine skin (TissueMend). Both in turn were stronger than the porcine small intestine submucosa (Restore and CuffPatch) (P < 0.001). Suture retention can be reliably tested with a narrow range of standard error utilizing this testing methodology. Skin has higher loads to failure than intestine submucosa. Failure modes differed significantly among the implant types, suggesting that suturing methods for each implant should be considered independently before use. These data cannot be interpreted to suggest that one graft material is clinically superior to another. Rather, each has different properties that the surgeon should recognize when considering their use. These grafts have been used as augmentations and substitutions in tendon repairs and as a material for interpositional arthroplasty. These data show that the successful use of these materials requires adequate separation of the fixation sutures and provides an understanding of how each material will fail if subjected to excessive loading during the rehabilitation period.