Factors Accounting for Variation in the Biomechanical Properties of Flexor Tendon Repairs

The consistency and reliability of six-strand and four-strand flexor tendon repairs: a comparative porcine cadaveric study

The aim of this study was to compare the consistency and reliability of the six-strand Gan modification of the Lim-Tsai flexor tendon repair with the four-strand Adelaide repair, both with 3-0 sutures and with eight to ten runs of simple 5-0 running peripheral suture as well as the influence of the surgeons' level of experience on the strength of the repair in a cadaveric animal setup. Thirty-nine surgeons repaired 78 porcine flexor digitorum profundus tendons with either the Adelaide technique (39 tendons) or the modified Lim-Tsai technique (39 tendons). Each repaired tendon was tested in a material testing machine under a single cycle load-to-failure test. The forces were recorded when the gap between the two tendon stumps reached 1 and 2 mm and when irreversible elongation or total rupture occurred. We found no significant differences in gap formation force and yielding strength of the tendons between the two methods. The surgeon's previous experience in tendon repairs did not improve the consistency, reliability or tensile strength of the repairs. We conclude that if a strong peripheral suture is added, the modified Lim-Tsai repair has the same technical reliability and consistency as the Adelaide repair in term of ultimate loading strength in this test setup.

Biomechanical Analysis of Zone 2 Flexor Tendon Repair With a Coupler Device Versus Locking Cruciate Core Suture

PURPOSE

To compare flexor tendon repair strength and speed between a tendon coupler and a standard-core suture in a cadaver model.

METHODS

In 5 matched-pair fresh cadaver hands, we cut the flexor digitorum profundus tendon of each finger in zone 2 and assigned 20 tendons to both the coupler and the suture groups. Coupler repair was with low-profile stainless steel staple plates in each tendon stump, bridged by polyethylene thread. Suture repair was performed using an 8-strand locking-cruciate technique with 4-0 looped, multifilament, polyamide suture. One surgeon with the Subspecialty Certificate in Surgery of the Hand performed all repairs. Via a load generator, each flexor digitorum profundus was loaded at 5 to 10 N and cycled through flexion just short of tip-to-palm and full extension at 0.2 Hz for 2,000 cycles to simulate 6 weeks of rehabilitation. We recorded repair gapping at predetermined cycle intervals. Our primary outcome was repair gapping at 2,000 cycles. Tendons that had not catastrophically failed by 2,000 cycles were loaded to failure on a servohydraulic frame at 1 mm/s.

RESULTS

Tendon repair gapping was similar between coupled and sutured tendons at 2,000 cycles. Tendons repaired with the coupler had higher residual load to failure than sutured tendons. Mean coupler repair time was 4 times faster than suture repair.

CONCLUSIONS

Zone 2 flexor repair with a coupler withstood simulated early active motion in fresh cadavers. Residual load to failure and repair speed were better with the coupler.

CLINICAL RELEVANCE

This tendon coupler may eventually be an option for strong, reproducible, rapid flexor tendon repair.