Strength Characteristics and Failure Modes of Locking‐Loop and Three‐Loop Pulley Suture Patterns in Equine Tendons

Abstract

Size 3–0 polydioxanone was used as a single strand, single braid (3 strands), or double braid (6 strands) to create six suture material‐pattern combinations for equine tenorrhaphy: single‐strand locking loop, single‐braid locking loop, double‐braid locking loop, single‐strand three‐loop pulley, single‐braid three‐loop pulley, and double‐braid three‐loop pulley. Maximum load to failure for the single‐strand locking loop (46.1 ± 2.9 newtons [N]) was less than for all other sutures (range, 103–155 N). The load required to form a 2 mm gap between tendon ends was greater for the single‐braid three‐loop pulley (66.7 ± 6.9 N) and double‐braid three‐loop pulley (85.4 ± 17.7 N) than any other sutures. The load required to produce a 10 mm gap was least for the single‐strand locking loop (34.3 ± 3.9 N) and greatest for the double‐braid three‐loop pulley (131.5 ± 27.5 N). Gap between tendon ends at maximum load was greater for the single‐braid (18.1 ± 0.9 mm) and double‐braid (19.2 ± 2.2 mm) locking loops than for any other sutures. Suture material broke in 53% of the locking‐loop tests but in only 17% of the three‐loop pulley tests. Tendon matrix disruption accounted for 43% of the locking‐loop failures and 77% of the three‐loop pulley failures. The three‐loop pulley pattern provided more support, less tendon distraction, and less tendon matrix constriction and distortion than the locking‐loop pattern. However, considering previously reported in vivo loads, these results suggest that none of these sutures can maintain tendon apposition under normal loading conditions in a living horse. Under these test conditions the limiting factor was tendon matrix for the double‐braid locking loop, single‐braid three‐loop pulley, and double‐braid three‐loop pulley. Suture material failure predominated in the single‐strand locking loop, single‐braid locking loop, and single‐strand three‐loop pulley.