The Effect of Epitendinous-First Repair of Flexor Digitorum Profundus in Zone II on Gapping and Load-To-Failure in a Cadaveric Simulated Active Motion Model.

Purpose: Surgeons routinely use epitendinous suturing to augment zone II flexor digitorum profundus (FDP) repairs. We sought to determine whether completing epitendinous suturing first, with proposed improved repair alignment and core-suture tensioning, facilitates durability for cyclic and load-to-failure testing in a cadaver model.

Methods: In fresh, matched-pair human cadaver hands, we sharply cut all FDPs transversely in zone II. A single surgeon repaired each FDP with a running-locking epitendinous technique using 6-0 polypropylene suture and locking cruciate 8-strand core technique with 4-0 looped multi-strand polyethylene/braided polyester suture. For each matched pair, the surgeon completed the epitendinous repair first in one FDP (n = 12) and for the other FDP they completed the core repair first (n = 12). Using a computer-controlled system attached to the finger flexors and extensors, we simulated active range of motion from full extension to 5 mm short of tip-to-palm flexion at 0.2 Hz for 2,000 cycles, replicating a 6-week protocol. We measured repair gapping at predetermined cycle timepoints. We explanted FDPs with repairs that had not failed by 2,000 cycles and loaded them to repair failure on a materials testing machine at 1 mm/s. We defined failure as gapping >2 mm throughout the study. Our primary outcome was residual repair load-to-failure after cyclic testing.

Results: One core-first repair failed during cyclic testing. Gapping during cyclic testing and residual median loads-to-failure between epitendinous-first and core-first repairs were similar (98 N vs 91 N, respectively). Median repair times were also similar between groups (15.3 min vs 13.4 min, respectively).

Conclusions: For transverse Zone II FDP lacerations, the order of epitendinous and core-suture placement does not appear to substantially affect repair residual strength after cyclic loading.

Clinical Relevance: Regarding repair durability for clean, transverse zone II FDP lacerations, surgeons can place epitendinous and core sutures in their preferred sequence.