Biomechanical Analysis of a Novel Flexor Tendon Coupler Versus Suture Repair
Chetan Shawn Irwin, M.D.; Brent Parks, MSc; Kenneth R Means Jr, MD; The Curtis National Hand Center, Baltimore, MD
Variation in surgeons' flexor tendon repair technical ability may influence rupture rate and postoperative rehabilitation. A device to standardize expeditious flexor tendon repair could be beneficial. We sought to compare a novel flexor tendon-coupling device to a conventional core-suture technique with regard to repair strength and speed.
MATERIALS & METHODS
Five matched-pair fresh never-frozen human cadaver hands had the FDP of each finger cut between A2 and A4 pulleys in zone 2 (20 tendons in each of the 2 groups). Coupler repair was performed using a device comprised of low-profile stainless steel staple plates in each tendon stump bridged by a continuous spool of polyethylene thread. CoNextions Medical(Salt Lake City, UT) donated the couplers. Suture repair was performed using 4-0 looped Supramid in a locking-cruciate fashion for an 8-strand core repair. One CAQ-hand surgeon performed all repairs; time to complete each repair was recorded. We assessed durability of the repairs in each group by recording repair gapping during a simulation of 6 weeks of active range of motion. The simulation was performed with a custom computer-controlled device with each flexor tendon loaded at 5-10N to recreate a minimal estimated force transmitted across a repair site during early rehabilitation. Each flexor tendon was cycled at a rate of 0.2Hz for 2000 cycles. Failure was defined as repair gapping greater than 2mm or catastrophic failure. Each repair that had not failed during cyclic loading was explanted and loaded to failure on a servohydraulic load frame(MTS Systems, Eden Prairie, MN) at a rate of 1 mm/s.
There was no significant difference in repair gapping between coupled and sutured tendons at 2000 cycles(mean gap 1.35mm vs 0.86mm, SD 1.29 vs 0.7, p=0.19). There were no catastrophic failures in either group. Coupled tendons had significantly higher residual load-to-failure than sutured tendons(mean failure load 77N vs 54N, SD 14 vs 15, p<0.0007). Tendon-coupler repair was four times faster than core-suture repair with an average repair time of 1:21 min vs 5:32 min(SD 48 sec vs 35 sec, p<0.00006).
Flexor tendon repair in zone 2 with a novel coupler device was able to withstand simulated early active flexion in a manner similar to a conventional core suture repair in this fresh-cadaver study. Tendon repair speed and residual load-to-failure were significantly improved with the coupler device. Tendon repair with this device merits further biomechanical, biologic, and possible eventual clinical study.
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