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

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.

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.

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).

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.

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