Biomechanical comparisons of four-strand tendon repairs with double-stranded sutures: effects of different locks and suture geometry.

Multi-strand repairs are often used in flexor tendon surgery. We evaluated the strength of four four-strand tendon repairs with different locks and suture geometry. Forty-eight pig flexor tendons were repaired with the following methods: a cross-lock four-strand repair; a U-shaped repair with circle-locks; a modified Kessler repair with Pennington locks (with longitudinal sutures located more centrally; and another modified Kessler (with longitudinal sutures located more laterally). The tendons were loaded to complete failure of the repairs. The two Kessler repairs showed a 35% lower 2 mm gap force, and 15% lower ultimate strength compared with the other two repairs; the differences were of statistical significance. The failure pattern was breakage of sutures in almost all tendons. These four-strand repairs differed in gapping and ultimate strengths. The Kessler-type repairs with different geometry in the longitudinal sutures produced identical strengths. The Kessler-type repairs with Pennington locks were weaker than the two repairs with either cross-locks or circle-locks.