Biomechanical testing of a shape memory alloy suture in a meniscal suture model

The purpose of this study was to evaluate the biomechanical results of meniscal repair in vitro by a nitinol suture and compare them with Ethibond (Ethicon, Somerville, NJ) and nylon.

The 6 testing groups consisted of nitinol, Ethibond, and nylon sutures (No. 2-0 and No. 3-0). Sixty bovine menisci with a vertical longitudinal tear were repaired with 1 horizontal mattress suture and were fully immersed into a water bath, adjusted to a tensile testing machine. All specimens were subjected to tensile testing, and force/displacement curves were obtained. Load to 5-mm gap, load to failure, tensile strength, stiffness, and mode of failure for each suture group were recorded. Statistical analysis included analysis of variance with Bonferroni correction for the post hoc multiple comparisons.

Nylon sutures achieved the lowest scores in all measurements. Nitinol achieved better scores, but not significantly better scores, than Ethibond in load to 5-mm gap and stiffness. The No. 2-0 and No. 3-0 nitinol suture repair showed the highest mean tensile strength and load to failure, with significant differences, being 36% and 45% stronger, respectively, than Ethibond. Modes of failure included pulling through the inner segment of meniscus and rupture of the suture at the knot.

This study shows the superior load-to-failure and tensile strength characteristics of nitinol. However, in terms of stiffness and gap resistance force, the results were equivalent to those of Ethibond. Nitinol is an interesting and promising suture.

Nitinol can be elongated and become soft and flexible for proper suturing at low temperature. At body temperature, it can contract to its original length, providing stronger knots. This may result in more efficient primary stability of meniscal repair, minimizing the chances of loosening during healing and allowing earlier rehabilitation.