Plastic deformation of sutures creates an irreversible extension during load. To test our hypothesis that such plastic deformation causes gap formation after tendon repair, we determined the plasticity of five different suture materials commonly used in tendon surgery. Prolene, Polydioxanone (PDS), Ethibond, Vicryl, and FiberWire sutures were biomechanically tested to determine their offset yield strength, initial extension, creep, relaxed elongation, peak-to-peak displacement, stiffness, and maximum tensile strength under static, constant, and cyclic loading. In addition, 35 porcine hindlimb tendons were used to evaluate gap formation and the biomechanical behavior of the suture materials after tendon repair. Prolene had a low offset yield strength and high initial extensions at 30, 60, and 90N combined with relatively large creep, relaxed elongation, and peak-to-peak displacement. Aside from the low maximum tensile strength and stiffness, these parameters indicate an early plastic deformation during loading. The material properties of PDS were generally better for suturing than those of Prolene, but no difference was found in offset yield strength or initial extension. In contrast to the monofilament materials Prolene and PDS, the braided Ethibond, Vicryl, and FiberWire materials showed significantly less plastic deformation. The lowest amount of plastic deformation was found in the FiberWire and the results for Ethibond and Vicryl were equal. Gap formation occurred at the lowest tension force in the Prolene group, but only FiberWire required a significantly larger tension force to produce gapping at the repair site, indicating a higher resistance to gap formation. The results of this study show that plastic deformation occurs at a lower tension force in the monofilament sutures Prolene and PDS than in the braided materials Ethibond, Vicryl, and FiberWire. After tendon repair, FiberWire likely prevents gap formation, whereas Prolene induces gapping through low-tension plastic deformation. Therefore, plastic deformation should be considered when selecting suture materials for tendon repair surgery.
Keywords: Achilles; Gap; Patella; Quadriceps; Repair; Suture; Tendon.
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