Anterior Tibial Tendon Transfer

Adrienne Socci

Haemish Crawford

The transfer of the anterior tibial tendon is a useful tool for managing any pediatric foot condition in which there is a supination deformity with an imbalance in the inversion and eversion strength. This imbalance can be neurologic (e.g., cerebral palsy, Charcot-Marie-Tooth disease, and stroke) or posttraumatic (e.g., a nerve injury); however, the most common occurrence of muscular imbalance is in the residual or relapsed clubfoot. Studies have shown that clubfoot relapse can occur in up to 50% of the cases regardless of initial treatment. This usually occurs before the age of five and can be a sign of residual deformity incompletely corrected or true relapse caused by the same original etiology (1, 2, 3). In residual or relapsed clubfoot deformity, the navicular can still be medially displaced on the talus. This mechanically repositions the pull of the tibialis anterior tendon, which then acts more as a supinator and invertor rather than as a dorsiflexor. This deformity is noticed primarily in the swing phase of gait when the tibialis anterior concentrically fires and is seen to supinate and invert the forefoot, which leads to weight bearing on the lateral aspect of the foot.

In addition to medial displacement of the tendon insertion causing muscle imbalance, supination can also be caused by relative weakness of the peroneal muscles. The peroneal muscles are further weakened by the mechanical disadvantage of the medial displacement of the forefoot. Unaddressed, this muscle imbalance and dynamic deformity can lead on to fixed supination deformity of the forefoot, with a bowed lateral border of the foot, lateral weight bearing, and varus and equinus deformities of the hindfoot. Early tibialis anterior tendon transfer, combined with pre- and postoperative casting, can rebalance the foot and correct deformity, prevent progression, and avoid the need for intra-articular procedures. Tibialis anterior transfer may decrease the need for more invasive intraarticular releases if the foot develops fixed deformities.

The anterior tibial transfer was originally described by Garceau in 1940 for the treatment of residual clubfoot deformity (4). Most subsequent publications have also reported on the use of this transfer in the treatment of clubfoot with residual supination and adductus deformity. The transfer has been performed either alone or in combination with other soft-tissue releases or osteotomies (2, 4, 5, 6, 7, 8). The tendon is best transferred into the third (or lateral) cuneiform to prevent overcorrection although some authors have inserted it into the cuboid, fifth metatarsal, or peroneus tertius.

The split anterior tibial tendon transfer (SPLATT) has also been widely used to rebalance the foot. This transfer has been used more commonly in patients with cerebral palsy or other neurologic conditions where the tendon has spasticity and overcorrection with a full transfer is a concern to the surgeon. The lateral half of the tendon is usually inserted into the cuboid or peroneus tertius in a SPLATT. In cerebral palsy patients, a fractional lengthening of tibialis posterior is often performed at the same time. The SPLATT can also be used in residual clubfoot deformity and Kuo et al. published comparative results with a SPLATT and a full anterior tibial transfer in their series of residual functional clubfoot deformity (9).

INDICATIONS AND CONTRAINDICATIONS

The anterior tibial transfer is indicated when there is a full correction of all the foot deformities and the foot is flexible. The muscular imbalance is the overpull of the anterior tibialis compared to the peroneal muscles resulting in a dynamic supination deformity. If there is any fixed deformity, this
must also be addressed at the time of surgery. Preoperative casting helps in correcting the forefoot abduction and supination before the transfer.

SURGICAL PROCEDURES

Full Anterior Tibial Tendon Transfer

Before proceeding with the full or split anterior tibial transfer, any fixed deformity must be corrected. In the young child, this can usually be achieved by two or three Ponseti casts prior to surgery. These above-knee casts can be applied for 2 weeks’ duration each. A careful assessment must be made of the hindfoot equinus before proceeding with the tendon transfer. If the hindfoot does not dorsiflex greater than 10 degrees after the preoperative casting, a concurrent lengthening of the tendo Achillis needs to be performed at the same time as the tendon transfer. This is usually a percutaneous or small open procedure that can be carried out in the same supine position as for the tendon transfer outlined below. If a more severe equinus contracture persists, consideration needs to be given to a more formal posterior ankle joint and subtalar release and delaying the tendon transfer until adequate dorsiflexion and mobility is achieved. Performing an extensive posterior release and tendon transfer in the same sitting can lead to a stiff hindfoot due to the length of immobilization.

The child is placed supine under general anesthesia, with a tourniquet of appropriate size and pressure on the thigh. A 4-cm dorsomedial incision is made overlying the tibialis anterior tendon, and the tendon sheath is incised (Fig. 27-1). The tendon is released fully from its insertion on the first metatarsal and medial cuneiform, as distally as possible. Dorsal retraction of the tendon with a smooth hook can help with the distal exposure (Fig. 27-2). Care must be taken to peel the tendon off the capsule and ligaments of the medial cuneiform— first metatarsal joint (Fig. 27-3). Avoid dissecting too far distally and damaging the first metatarsal growth plate. The tendon is secured with a Bunnell-type suture using 1-0 Vicryl (Fig. 27-4). The suture should begin and finish by being passed through the end of the tendon to prevent “bunching” when it is passed through the third cuneiform. The tendon sheath must be sufficiently opened proximally to allow for later passage to the lateral aspect of the foot. Not releasing the tendon sheath sufficiently may result in the tendon being tethered distally when transferred laterally. Care must be taken not to release the extensor retinaculum. Releasing this will result in bowstringing of the transfer and reduced power.

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