Biomechanical studies of 3 different 6-strand flexor tendon repair techniques

We investigated the gap formation and ultimate strength, energy to failure, and patterns of failure of tendon repairs with the modified Savage, Lim, and Tang methods. Fifty-four fresh-frozen flexor digitorum profundus tendons were assigned to 3 groups and repaired with one of the previously mentioned methods. Nine tendons from each group were pulled to failure in a tensile testing machine when they were subjected to a linear load. The 2-mm gap formation force of the tendons was 37.4 N for the modified Savage, 44.5 N for the Tang, and 40.2 N for the Lim method. Ultimate strength was 57.8 N for the modified Savage, 60.2 N for the Tang, and 51.3 N for the Lim method. Statistically, the gap formation force was significantly higher in the Tang method than in the modified Savage and the Lim methods. Ultimate strength of the modified Savage and Tang methods was similar and significantly higher than that of the Lim method. The rest of the tendons were subjected to angular tension by placement of the tendons against a pulley. The tests show that resistance of the modified Savage and Tang methods to angular tension was significantly greater than that of the Lim method. The results indicate that the resistance to failure and failure modes of the repairs vary according to number of locking junctions with the tendon, location, and orientation of the sutures regardless of an equal number of strands across the repair site. We conclude that the modified Savage and Tang methods have greater tensile strength than the Lim method and may more effectively resist linear and angular tension generated by postoperative tendon motion.