Physiologic effects of long-term immobilization of the equine distal limb

An ex vivo biomechanical comparison of two suture materials and two pattern combinations for equine superficial digital flexor tendon tenorrhaphy

OBJECTIVE

To compare biomechanical characteristics of three-loop pulley (3LP) pattern versus Bunnell technique (BT) using polydioxanone (PDS) suture; to determine the influence of polyester tape (PT) versus PDS on the BT for equine superficial digital flexor tendon (SDFT) tenorrhaphy; to compare BT with PT versus 3LP with PDS.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Forty equine forelimb SDFT.

METHODS

Two experiments were performed: (1) 10 SDFT pairs were repaired with 3LP or BT using PDS; (2) 10 SDFT pairs were repaired with PDS or PT using BT. Load at failure, mode of failure, load at 2 mm gap, and gap at failure were obtained using a material testing machine.

RESULTS

In experiment 1, 3LP + PDS₁ had higher loads at failure (p < .001) and at 2 mm gap (p < .001), and smaller gap at failure than BT + PDS₁ (p = .024). In experiment 2, BT + PT₂ had higher loads at failure (p < .001) and at 2 mm gap (p = .001), and larger gap at failure (p = .004) than the BT + PDS₂ . 3LP + PDS₁ and BT + PT₂ mostly failed by suture/implant pull-through while BT + PDS failed by suture breakage. BT + PT₂ had greater load (p = .035) and gap at failure (p < .001) than 3LP + PDS_1, with no difference in load at 2 mm gap (p = .14).

CONCLUSION

The use of BT may be justified over 3LP if combined with PT. However, the larger size of the PT required stab incisions in the tendon for placement and was subjectively more difficult to place than PDS.

CLINICAL SIGNIFICANCE

The BT + PT, although the strongest among the tested repairs, would only be able to withstand 12%-24% of the load encountered by the SDFT at walk.