Biomechanical Comparison of Nonlocked Minimally Invasive and Locked Open Achilles Tendon Simulated Rupture Repairs

Open repair of Achilles tendon ruptures is associated with a risk of infection and other wound complications. Although percutaneous repairs reduce these complications, they may increase the risk of nerve injury. This study was designed to determine whether a percutaneous nonlocking repair can approach the gapping resistance offered by a standard open repair under conditions approximating typical postoperative physiotherapy.

Ten pairs of cadavers Achilles tendons were transected in situ 5 cm above the insertion. One tendon from each pair was repaired using an open 4-strand Krackow locking loop, and the contralateral tendon was repaired with the Achillon system using the same suture material. Displacement transducers were attached to the medial, lateral, anterior, and posterior aspects of the tendon, spanning the repair. Each tendon underwent 1000 tensile loading cycles to 86.5 N, simulating passive ankle range-of-motion physiotherapy. Gapping was documented on the 1st, 50th, 100th, 500th, and 1000th cycles. The ultimate tensile strength of each repaired tendon was then measured by distracting until gross failure occurred.

Gapping of the percutaneous repairs exceeded that of conventional open repairs on the first, 500th, and 1000th load cycles. All 10 conventionally repaired tendons withstood 1000 load cycles without gross failure, but 4 of 10 percutaneous minimally invasive repairs failed, one on the 9th load cycle and the others between the 100th and 500th cycles. On average, tendons repaired with the open technique withstood 66% greater tensile load in failure testing than those repaired with the percutaneous technique.

Open Krackow Achilles tendon repairs may better withstand more aggressive postoperative physiotherapy than nonlocked percutaneous repairs.

The study suggests that surgeons should consider locking suture approaches to avoid loss of repair integrity with early motion.