Tibiotalocalcaneal arthrodesis aims to recreate physiologic ankle and hindfoot alignment with a plantigrade foot position (the foot is at a 90-degree angle to the long axis of the tibia) and about 5 to 7 degrees of hindfoot valgus.^{3, 10}

In general, rotation of the foot relative to the longitudinal axis of the tibia in the coronal plane is congruent with the anterior tibia—that is, the second ray of the foot is usually in line with the anteromedial crest of the tibia.

Hindfoot position influences forefoot position. With longstanding ankle and hindfoot deformity, forefoot pronation, supination, adduction, and abduction may be affected. Proper positioning of a tibiotalocalcaneal arthrodesis must take forefoot position into account. Ideally, in stance phase, the foot has near-equal pressure distribution under the heel and first and fifth metatarsal heads.¹¹

Severe ankle and hindfoot deformities and pathologic processes result in disabling pathomechanics and, when left untreated, often confine patients to cumbersome brace use, limited ambulation with assistive devices, or a wheelchair.⁷

Tibiotalocalcaneal arthrodesis is a major reconstructive process usually applied to otherwise disabling conditions.^{5, 6}

The patient being considered for tibiotalocalcaneal arthrodesis with a medullary nail presents with a myriad of orthopaedic pathology affecting gait, weight bearing, and ability to earn a living.

This patient may present with limited mobility, an equinus posture associated with genu recurvatum, and transverse plane deformity ranging from severe varus and instability of the hindfoot through profound valgus and ulceration over the medial structures (FIG 1).^{6, 9}

The neuromuscular or neuropathic patient may present with ulceration, intrinsic muscle loss, and multiple fractures in various stages of healing.⁶

The posttraumatic patient often has a compromised soft tissue envelope, previously placed hardware, and already medullary canal sclerosis that must be considered in preoperative planning (FIG 2).⁷ Evaluation must include gait and weight-bearing posture, assessment of the soft tissue envelope, and a thorough neuromuscular examination.

We routinely obtain three weight-bearing radiographs of the ankle and foot. As many of these patients have deformity, we often obtain additional long-cassette radiographs of the ankle or even mechanical axis views of the lower leg from the hip to the foot.

Posttraumatic and osteoarthritis

Radiographs may reveal joint space narrowing, osteophyte formation, and subchondral sclerosis and cysts, all characteristic of osteoarthritis. Posttraumatic deformity and retained hardware may be identified and must be considered in preoperative planning (FIG 3).^{7, 8, 9}

Rheumatoid arthritis and other inflammatory arthritides

Neuropathic arthrosis or Charcot neuroarthropathy

Plain tomography or computed tomography (CT) may further define deformity, arthritis, bone loss, and prior malunion or nonunion (FIG 4).

Magnetic resonance imaging (MRI) may complement CT by evaluating for fluid in and around the joints, bone marrow
edema, talar vascularity, infection, and periarticular tendon and ligament pathology (FIG 5).

Technetium 99 bone scans may be useful in the evaluation of osteonecrosis after talus fracture, arthritic involvement of one or several joints, stress fracture, or neoplasm.

Indium-labeled white blood cell scans can be helpful in the diagnosis of osteomyelitis or septic arthritis.

Selective (diagnostic) injection of local anesthetic may help locate the exact anatomic source of the patient’s pain.

Tibiotalar arthritis may be associated with a stiff, painful subtalar joint that has a relatively normal radiographic appearance.

The injection of 5 to 10 mL of 1% lidocaine into the subtalar joint can clarify whether the pain may not be isolated to the ankle but in fact be generated in both the ankle and subtalar joints.

This has important implications when considering isolated tibiotalar versus tibiotalocalcaneal arthrodesis. We do not routinely incorporate the subtalar joint into the arthrodesis when performing an ankle arthrodesis. In select cases of endstage ankle arthritis associated with severe deformity and talar bone loss, we consider including an otherwise normal asymptomatic subtalar joint in the fusion mass achieved for tibiotalocalcaneal fusion. Alternatively, an injection carefully placed in the peroneal tenosynovial sheath may prove that pain may be related to the tendons rather than the joint.

Although often challenging for the patient with deformity, we recommend bracing for the patient with prohibitive medical illness or a dysvascular extremity, particularly for
the patient with a nonfixed, passively correctible deformity. A custom-molded polypropylene ankle-foot orthosis (AFO) or a supramalleolar AFO with Velcro closures may be considered as an alternative to tibiotalocalcaneal arthrodesis in poor surgical candidates (FIG 6).⁶

For the neuropathic patient in whom bracing can achieve a relatively plantigrade posture for the hindfoot and ankle, we prescribe a double metal upright AFO attached to an Oxford shoe that includes Plastazote liners (total contact inserts).