EFFECT OF LACERATION AND SAUCERISATION ON TENDON FRICTION COEFFICIENT AT THE A2 PULLEY INTERFACE: IN VITRO STUDY ON TURKEY TENDON

Abstract

Treatment of a partial laceration in zone two of a flexor tendon remains controversial. The intact part of the tendon can sustain forces of normal un-resisted motion, and repaired partially treated tendons can actually be weaker than un-repaired ones. Trimming these lacerations has been shown to be beneficial in partially lacerated tendons with triggering or entrapment.

The purpose of this study is to observe the behaviour of a partially lacerated and subsequently trimmed tendon under strain, and measure their friction coefficient at different flexion angle and load. Ten long flexor tendons from long digit of turkey foot, along with the equivalent of A2 pulley were used. All experiments were carried out for intact, lacerated (50%) and trimmed tendon at 10, 30, 50 and 70 degrees of flexion and two load settings of 200 and 400g.

The friction forces were measured by the difference between the two load transducers and the friction coefficient was measured using this formula, μ = Ln[(F2/F1)]/Ø.

Friction coefficient (μ), Tension forces (F2 and F1), arc of tendon and pulley contact (Ø).

Results: Friction coefficient increased significantly by three folds (0.3) after laceration compare with intact tendon (0.12) at both loads. This was reduced significantly after trimming the tendon but the friction coefficient was still approximately twice the value of the intact tendon (0.2).

Triggering was noticed in all tendon lacerations. Triggering was reduced after trimming in 10 and 30 degrees of flexion but increased markedly at 50 and 70 degrees of flexion associated with tendon fragmentation at the trimmed area.

Trimming partially lacerated flexor tendons will reduce the gliding resistance of the tendon through the pulley but this can lead to further fragmentation and triggering at higher flexion degrees and loads.