Achilles tendon torsion has no effect on percutaneous triple-cut tenotomy results

Achilles tendon lengthening is an important part of the operative management of numerous foot and ankle disorders. The most commonly used percutaneous technique involves three hemitenotomies: medial, lateral, and medial. The discovery that Achilles tendon fibers may undergo external torsion created concern that improper consideration of this feature could result in fiber division insufficient to allow adequate percutaneous lengthening. Varying degrees of torsion have been reported since it was originally described. We hypothesized that torsion of the Achilles tendon does not decrease the effectiveness of a percutaneous lengthening procedure. This hypothesis was tested by comparing the medial-lateral-medial tenotomy pattern to a lateral-medial-lateral pattern. If tendon torsion affects fiber division, then asymmetrical tenotomy patterns should yield different results.

Mechanical testing was performed using 22 human fresh tissue lower extremities. Specimens were divided into two groups (11 in each group): "MLM" which underwent testing using a medial-lateral-medial pattern and "LML" which underwent a lateral-medial-lateral pattern. Dorsiflexion load was applied evenly across the forefoot and measured with a force transducer. Dorsiflexion measurements were made from reproducible reference marks. After testing, specimens were dissected to examine tenotomy gap widths and other tissue effects.

All specimens lengthened successfully. None of the following parameters were statistically different: pre-tenotomy or post-tenotomy dorsiflexion, force to lengthen, total tissue lengthening, and individual gap widths. In no specimen was there complete disruption of the Achilles tendon, and in 18 of 22 specimens (81.8%) the paratenon sleeve was intact except for the tenotomy puncture. In one LML specimen, the sural nerve was partially cut at the distal tenotomy site.

Regardless of pattern, percutaneous triple-cut Achilles tendon lengthening was effective in achieving additional dorsiflexion at roughly one-third degree per millimeter of tissue lengthening. The pattern of the Achilles tendon lengthening used and, by inference, Achilles tendon torsion had no effect on achievable dorsiflexion. One explanation is that both patterns cut all tendon fibers at least once. We concluded that a properly designed triple-cut tenotomy would be successful regardless of Achilles torsion. Percutaneous Achilles tendon lengthening also appears to be a safe procedure if care is taken to avoid the sural nerve.