Elsevier

The Journal of Hand Surgery

Volume 45, Issue 9, September 2020, Pages 878.e1-878.e6
The Journal of Hand Surgery

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

https://doi.org/10.1016/j.jhsa.2020.02.015Get rights and content

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.

Section snippets

Materials and Methods

We used 5 matched-pair fresh, never-frozen, human cadaver hands. We exposed the flexor sheath of all fingers via a midline volar longitudinal incision from the distal palmar fingertip to the level of the A1 pulley. A rectangular portion of the sheath was excised from the distal A2 pulley edge to the proximal A4 pulley edge. The flexor digitorum profundus (FDP) tendon of each finger was then cut with a scalpel. The location for each cut was standardized with a metal ruler to lie halfway between

Results

All data passed normality and equal variances testing. Coupled and sutured tendons performed similarly for our primary outcome of repair gapping at 2,000 cycles with no clinically relevant mean differences noted (mean gap, 1.27 ± 1.17 mm [SD] vs 0.92 ± 0.67 mm [SD]) respectively. Given the novelty of the coupler device, and lack of previously published or pilot data comparing it with conventional suture repair, post hoc power analysis was performed after initial testing. Post hoc power

Discussion

Given the technical difficulty of consistently achieving a robust flexor tendon repair that enables early motion rehabilitation, the development of a coupler device designed to standardize strong, expeditious repair is intriguing. The recent work of Linnanmäki et al1 highlights an often-overlooked source of variability in hand surgery: technical ability. Differences in surgeon performance introduced the greatest variability in flexor tendon repair load resistance in their biomechanical study.

Acknowledgments

CoNextions Medical (Salt Lake City, UT) donated the coupler repair devices for this study. The company had no control or input for the study design, execution, or manuscript preparation.

This study was funded by The Raymond M. Curtis Research Foundation, The Curtis National Hand Center, Baltimore, MD.

No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.

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