Abstract
Anterior tibial tendon (ATT) ruptures tend to occur in older persons as a consequence of degeneration and friction underneath the extensor retinaculum, although traumatic ruptures can occur and commonly involve the insertion. The rupture is followed by a variable degree of retraction of the tendon. A small stump of tendon is usually left distally under the retinaculum, and the proximal stump retracts between 2 and 10 cm. The options for correction include an end-to-end repair, transfer of the extensor hallucis longus tendon, a tendon graft interposition, and a V-Y lengthening advancement of the proximal ATT. The decision regarding which of these is performed depends on the strength of the limb, the presence of an equinus contracture, and the presence of any accessory claw toe deformities as a result of the rupture of the ATT or additional foot deformities. Most importantly, it is the quality of the anterior tibial muscle that will determine the outcome for many of these cases that are diagnosed late. Indeed, it is not often that a patient will present early enough that a simple end-to-end repair or reattachment of the tendon can be easily performed. The most common presentation complaint is that of a painless mass along the anterior ankle or mild foot drop.
Key Words
anterior tibial tendon, pseudotumor, allograft, EHL, foot drop, painless mass, rupture
Indications
In general, anterior tibial tendon (ATT) ruptures occur in older persons as a consequence of degeneration and friction underneath the extensor retinaculum, although traumatic ruptures can occur and commonly involve the insertion. The rupture is followed by a variable degree of retraction of the tendon. A small stump of tendon is usually left distally under the retinaculum, and the proximal stump retracts between 2 and 10 cm. The options for correction include an end-to-end repair, transfer of the extensor hallucis longus (EHL) tendon, a tendon graft interposition, and a V-Y lengthening advancement of the proximal ATT. The decision regarding which of these is performed depends on the strength of the limb, the presence of an equinus contracture, and the presence of any accessory claw toe deformities as a result of the rupture of the ATT or additional foot deformities. Most importantly, it is the quality of the anterior tibial muscle that will determine the outcome for many of these cases that are diagnosed late. Indeed, it is not often that a patient will present early enough that a simple end-to-end repair or reattachment of the tendon can be easily performed. The most common presentation complaint is that of a painless mass along the anterior ankle or mild foot drop ( Figs. 22.1 and 22.2 ).
Occasionally we obtain a magnetic resonance imaging (MRI) of the ankle to document the extent of the rupture and retraction. However, it is more important with chronic ruptures to obtain an MRI of the leg. If fatty infiltration or muscle atrophy is present, then a repair or graft will not likely work, and one has to rely on a tendon transfer, either the EHL or the EHL and the extensor digitorum longus (EDL) combined. Even with early prompt diagnosis, degeneration of the tendon is usually present, with fraying of the tendon ends and retraction, and augmentation or supplementation of the tendon repair will be necessary. Assessment of an equinus contracture whether isolated gastrocnemius or Achilles is required for every patient and an appropriate lengthening should be performed at the time of reconstruction. Given the degeneration of the tendon in most cases that are atraumatic, a gastroc recession is performed if the patient does not have at least 10 degrees of dorsiflexion. Although historically the use of a rigid ankle foot orthosis was considered appropriate, the surgical results have proven to be superior in all age groups, and therefore, unless medically contraindicated, reconstruction is advocated.
Approach to an Insertional Rupture
In the setting of an insertional rupture, if the tendon exhibits minimal retraction, ideally it should be reattached to the medial cuneiform. The course of the ATT is marked out, noting the proximal extent of the retraction. The incision is taken down to the sheath of the ATT, leaving a portion intact to minimize the risk of bowstringing. The proximal stump is then identified and secured with a locking whipstitch of No. 0 nonabsorbable suture. Distally, the medial cuneiform is identified and two secure anchors are placed directed 90 degrees to the medial aspect of the cuneiform to maximize pullout. The use of a 3.5-mm anchor (metallic or biocomposite) or a 1.6-mm all-suture anchor is effective. We recommend using a 3.5-mm anchor inserted perpendicular to the medial cuneiform. The tendon is secured to the bone with the foot held in dorsiflexion to ensure appropriate native tension has been restored. In the setting of a bony avulsion, without a medial cortex to secure the anchors, the use of a suture button device secured on the lateral aspect of the medial cuneiform via a medial to laterally directed drill hole can be used to provide a static point of fixation. Further fixation to the remaining soft tissue with 0 absorbable suture is used to complete the fixation ( Fig. 22.3 ).
A very reasonable alternative is to insert the tendon into the navicular. This repair is very effective in cases in which retraction of the tendon is minimal but not enough length is available to reattach it distally into the cuneiform. With this technique, a 2-cm incision is made over the dorsum of the midfoot to retrieve the stump of the ATT. A puncture is then made over the navicular to insert a suture anchor, which is done under fluoroscopic guidance to ensure correct positioning of the anchor. The sutures at the tip of the stump of the tendon are then passed subcutaneously out of the puncture incision used for the anchor. The sutures from the anchor are then passed subcutaneously into the longitudinal incision, with needles attached, and through the tendon. The tension on the tendon is maximized by simultaneously pulling the sutures on the stump out distally through the puncture incision ( Fig. 22.4 ).
If fixed clawing of the hallux is present as a result of accessory use of the EHL and EDL tendons, then an arthrodesis of the hallux interphalangeal joint is ideal, and the EHL tendon can be used to augment the repair ( Fig. 22.5 ). A tendon graft works well in this instance, but it should be supplemented possibly with an EHL tenodesis to strengthen the repair. Positioning the foot in at least 10 degrees of dorsiflexion at the completion of the repair regardless of the technique is important.
