Strength analysis and comparison of the Teno Fix Tendon Repair System with the two-strand modified Kessler repair in the Achilles tendon.

BACKGROUND: Various options exist for repair of Achilles tendon ruptures, yet a method that consistently provides sufficient gap resistance to allow early mobilization remains elusive. This study compares the mechanical performance of a modified Kessler repair with that of the Teno Fix Tendon Repair System (Ortheon Medical, LLC) in matched pairs of cadaver Achilles tendons.

METHODS: The two-strand modified Kessler repair was selected as the control construct on the basis of literature review and physician interviews which identified it among the many options as a popular method for repair of acutely ruptured Achilles tendons. Test specimens were harvested from matched pairs of cadaver ankles. The tendons were transected 3.5 cm proximal to the calcaneal insertion and repaired with either the two-strand modified Kessler suture construct or the Teno Fix Tendon Repair System. Assignment to the modified Kessler or Teno Fix group was done randomly for the first member of each pair. All test and control repairs were performed by the same author to reduce variability. Evaluation of the repairs consisted of tensile strength testing and measurement of the gap formation and peak stresses.

RESULTS: Gap and peak stress for the two-strand modified Kessler repair were 0.30 +/- 0.15 N/mm2 and 1.03 +/- 0.51 N/mm2, respectively. For the Teno Fix repairs the mean gap and peak stress values were 0.80 +/- 0.46 N/mm2 and 1.19 +/- 0.12 N/mm2, respectively. The mean gap formation stress was significantly higher in the Teno Fix repairs than in the control repairs (p < .0005). There was no significant difference in peak strength between the repairs (p < .10).

CONCLUSIONS: The Teno Fix repair was superior to the modified Kessler repair. In the Teno Fix repairs, the gap formation stress was 67% of the peak tensile stress. In comparison, in the modified Kessler repairs, the gap formation stress was 29% of the peak stress. This can be correlated to the elastic property of the modified Kessler suture and the initial tightening of the suture around the tendon fibers. The Teno Fix system is nonelastic and is fully tensioned during installation. This lends to a more gap resistant repair.