Tibiotalocalcaneal fusion with talar cage for hindfoot reconstruction

Tibiotalocalcaneal (TTC) fusion is a salvage procedure for patients with substantial ankle and subtalar arthritis or severe malalignment of the ankle-hindfoot complex. In many cases, this procedure is the only option available to provide patients with a stable, painless, plantigrade foot for ambulation. General indications for TTC include severe symptomatic hindfoot and ankle deformity or combined ankle and hindfoot arthritis for which nonsurgical management has failed. What makes this treatment modality even more challenging is the often-associated bone loss, especially in cases of neuropathic arthropathy or Charcot arthropathy. As the indications for TTC fusion expand, the number of procedures performed continues to rise.

Specific conditions for which such fusion is commonly indicated include inflammatory arthropathies; congenital deformity; neuropathic arthritides secondary to diabetes mellitus or inherited polyneuropathies; failed total ankle arthroplasty; severe pes planovalgus deformity; fracture malunion and nonunion; and bone loss and collapse secondary to trauma, tumor, osteonecrosis, Charcot arthropathy, or infection.

Patient factors that have been shown to affect outcomes of TTC fusion include medical comorbidities such as diabetes mellitus, previous ulcerations, peripheral vascular disease, renal disease, immunosuppression, chronic steroid use, rheumatologic disease, malnutrition, and smoking. In addition, a history of surgical intervention, particularly with postoperative complications (e.g., deep infection, problems with wound healing), may affect postoperative outcomes. In several studies of TTC arthrodesis, 20% to 40% of patients had a history of diabetes mellitus or smoking, resulting in poorer than average outcomes in these patients. ^,

The ankle joint is a ginglymus (hinge) joint involving the tibia, talus, and fibula. The talar dome is biconcave with a central talar sulcus. Viewed axially, the joint is trapezoidal and wider anteriorly than posteriorly. The talus is the only tarsal bone without muscular or ligamentous insertions.

The syndesmosis is the tibiofibular articulation composed of the tibial incisura fibularis and its corresponding fibular facet. It has three ligamentous structures that are variably responsible for its support: the anterior inferior tibiofibular ligament, the interosseous ligament, and the posterior tibiofibular ligament.

The subtalar joint has three facets: posterior, middle, and anterior. The posterior facet is the largest, the middle facet rests on the sustentaculum of the calcaneus and is located medially. The anterior facet is often continuous with the talonavicular joint.

The transverse tarsal joint (Chopart joint) is composed of the talonavicular and calcaneocuboid joints and acts in concert with the subtalar joint to control foot flexibility during gait. The talonavicular joint is supported by the spring ligament complex, which has two separate components: the superior medial calcaneonavicular ligament and the inferior calcaneonavicular ligament. The calcaneocuboid joint is saddle-shaped. It is supported plantarly by the inferior calcaneocuboid ligaments (superficial and deep) and superiorly by the lateral limb of the bifurcate ligament.

The ankle joint’s primary motion is dorsiflexion and plantarflexion. With the foot fixed, dorsiflexion is accompanied by internal tibial rotation and plantar flexion is accompanied by external tibial rotation. The bimalleolar axis runs obliquely at 82 degrees ± 4 degrees in the coronal plane and defines the main motion of the ankle. The talus is wider anteriorly than posteriorly, and the contact area of the dome of the talus increases and moves anteriorly with dorsiflexion. Increased load transmission in the malleoli also occurs with dorsiflexion. The fibula transmits approximately 10% to 15% of the axial load. The tibiofibular syndesmosis allows rotation and proximal and distal migration of the fibula with the tibia but little motion in the sagittal or coronal planes.

The subtalar and Chopart joint act through a series of coupled motions to create inversion and eversion of the hindfoot and to lock and unlock the midfoot. Inversion of the subtalar joint locks the transverse tarsal joint; eversion unlocks the joint. The joints are parallel during heel strike when the calcaneus is in eversion, allowing the midfoot to be flexible for shock absorption as the foot accepts the body’s weight. The joint axes are deviated as the subtalar joint moves to inversion (e.g., during push-off), making the foot inflexible so that it provides a rigid lever arm for push-off.