Comparative biomechanical analysis of a new circumferential flexor tendon repair and a modified Kessler repair.

We present the technical details and the results of a biomechanical analysis of a new type of circumferential flexor tendon repair, designed with the more stringent requirements of zone II injuries in mind. Apart from good initial strength we aimed for a design with little bulk at the repair site and good control of the tendon edges. The new repair is achieved using a single, continuous, inverting and locking suture of the periphery of the tendon. The repair was compared with a Kessler core suture of 4/0 polydioxanone, with Tajima and Strickland modifications, to which has been added a simple running circumferential suture (6/0 polypropylene), the repair currently used in our unit. Fresh human cadaver flexor tendons were divided and repaired by one of the two techniques (n = 12 for each technique), using 5/0 polypropylene for the new circumferential suture. A third group of tendons (n = 8) were divided and repaired with a 5/0 multifilament steel circumferential suture. The repaired tendons were tested at longitudinal stress to failure. The first two groups of tendons were tested at two crosshead speeds. Overall, crosshead speed had no effect on ultimate tensile strength (P = 0.5). The 5/0 polypropylene circumferential repair (median 32.29 N) was significantly stronger than the Kessler repair (median 24.03 N) (P = 0.046). The circumferential repair was significantly stronger with steel (median 56.04 N) than with polypropylene (median 32.29 N) (P = 0.007). The size of the repair site, resistance to gap formation and the patterns of failure were analysed on video recordings.