Biomechanical Comparison of Suture Caliber and Number of Passes in Epitendinous Repair

The epitendinous suture is a critical part of flexor tendon repair. In addition to smoothing the repair site, it augments repair strength and increases gap resistance. This study aimed to determine whether increasing the number of passes or increasing suture caliber would improve the strength (primary outcome), 2 mm gap resistance, or stiffness of a simple running epitendinous suture.

A total of 30 flexor pollicis longus (FPL), flexor digitorum profundus (FDP), and flexor digitorum superficialis (FDS) tendons were harvested from three cadavers, and transverse tendon lacerations were produced. Tendons were repaired with only an epitendinous suture (no core suture) in three groups: 6-0 Prolene with six passes, 5-0 Prolene with six passes, or 5-0 Prolene with six passes. Epitendinous repair strength was tested using a materials testing machine.

The use of eight passes had significantly greater ultimate tensile strength than six passes (21 +/- 7 N vs 14 +/- 5 N). Although 5-0 suture had a higher average ultimate tensile strength than 6-0 suture, this difference was not statistically significant (14 N +/- 5 vs 10 N +/- 3). Failure mode for all groups was most often suture tear-through.

A simple epitendinous suture using eight passes provides almost 50% more epitendinous repair strength and greater 2 mm gap resistance than six passes when using 5-0 Prolene.

When performing a simple running epitendinous repair to augment a core flexor tendon repair, the surgeon should consider the additional strength and gap resistance provided by eight passes compared to six.