Biomechanic comparison of the Teno Fix tendon repair device with the cruciate and modified Kessler techniques

To compare the mechanical behavior of a novel internal tendon repair device with commonly used 2-strand and 4-strand repair techniques for zone II flexor tendon lacerations.

Thirty cadaveric flexor digitorum profundus tendons were randomized to 1 of 3 core sutures: (1) cruciate locked 4-strand technique, (2) modified Kessler 2-strand core suture technique, or (3) Teno Fix multifilament wire tendon repair device. Each repair was tested in the load control setting on a Instron controller coupled to an MTS materials testing machine load frame by using an incremental cyclic linear loading protocol. A differential variable reluctance transducer was used to record displacement across the repair site. Cyclic force (n-cycles) to 1-mm gap and repair failure was recorded using serial digital photography.

There was no significant difference in differential variable reluctance transducer displacement between the cruciate, modified Kessler, and Teno Fix repairs. The cruciate repair had greater resistance to visual 1-mm repair-site gap formation and repair-site failure when compared with the Kessler and Teno Fix repairs. No significant difference was found between the modified Kessler repair and the Teno Fix repair. In all specimens, the epitenon suture failed before the core suture. Repair failure occurred by suture rupture in the 7 cruciate specimens that failed, with evidence of gap formation before failure. Seven of 10 modified Kessler repairs failed by suture rupture. All of the Teno Fix repairs failed by pullout of the metal anchor.

The Teno Fix repair system did not confer a mechanical advantage over the locked cruciate or modified Kessler suture techniques for zone II lacerations in cadaveric flexor tendons during cyclic loading in a linear testing model. This information may help to define safe boundaries for postoperative rehabilitation when using this internal tendon repair device.