Key points

Triple arthrodesis for adult acquired flatfoot is typically indicated in stage III and stage IV deformities.1–4 These patients often have end-stage arthritis and significant deformity that is nonreducible. The authors also consider triple arthrodesis when there has been a failed joint-sparing procedure or a failed arthrodesis of an isolated tritarsal joint to address stage II adult acquired flatfoot. The goals of surgery include resolution of symptoms, realignment, and sound arthrodesis.

Acceptable outcomes following triple arthrodesis in stage III adult acquired flatfoot are based on the surgeon’s ability to obtain a plantigrade foot that will support the ankle in optimal alignment. Therefore, realignment becomes the most important factor relative to good results. A well-aligned triple arthrodesis will result in normal physiologic contact pressures throughout the ankle, and prevent medial soft-tissue attenuation and ensuing degenerative changes. A triple arthrodesis with residual valgus deformity predisposes the ankle to attenuation of medial soft-tissue constraints and subsequent valgus deformity in addition to degenerative joint disease.

Preoperative imaging should include weight-bearing radiographs of the foot and ankle, hindfoot alignment/long-leg calcaneal axial radiographs, and advanced imaging. Weight-bearing radiographs of the ankle are necessary to evaluate the presence of valgus deformity and degenerative changes. Long-leg calcaneal axial and hindfoot alignment views provide information regarding frontal alignment. The authors sometimes consider magnetic resonance imaging (MRI) to evaluate the ankle arthritis that might be equivocal on standard radiographs. In addition, when the foot deformity is somewhat severe and the ankle is congruent on an anteroposterior (AP) radiograph, an MRI is obtained to evaluate the deltoid ligament. In such situations whereby the deltoid ligament is attenuated on MRI, the authors will consider as adjunct procedures a medial displacement osteotomy to offload the deltoid ligament, and deltoid repair.

Several ancillary procedures are necessary to obtain a plantigrade foot. Posterior muscle group lengthening, in the form of either an Achilles tendon lengthening or gastrocnemius recession, is invariably required in stage III adult acquired flatfoot. The authors use gastrocnemius recession in most cases. However, following realignment of a severe deformity, an Achilles tendon lengthening may be necessary to obtain adequate length and restore sagittal plane position.

Medial displacement osteotomy of the calcaneus has been mentioned previously as an adjunct procedure to address ankle valgus or medial soft-tissue attenuation (Fig. 1). Resnick and colleagues⁵ have shown that a triple arthrodesis in combination with a medial displacement osteotomy of the calcaneus will reduce deltoid ligament forces by 56%. Song and colleagues⁶ have also suggested that medializing the calcaneus following triple arthrodesis protects the deltoid complex.

The authors will consider medial column stabilization, in the form of either naviculocuneiform arthrodesis or first tarsometatarsal arthrodesis, when medial column instability is identified following triple arthrodesis for stage III adult acquired flatfoot (Fig. 2). Insufficiency of the medial column can result in a functional varus. Failure to address medial column instability can result in a lateral column overload when patients begin weight bearing, with subsequent fifth metatarsal base bursitis or fifth metatarsal head callosities.

Harvesting of regional bone graft and/or bone marrow aspirate is a part of virtually every triple arthrodesis. Cancellous bone is often harvested from the calcaneus using 6- to 8-mm trephines through small lateral incisions (Fig. 3). Bone marrow aspirate is obtained from the calcaneus before tourniquet inflation. The cancellous bone is packed into arthrodesis sites. The extra-articular areas along the undersurface of the talus and the dorsal surface of the calcaneus are decorticated. The bone marrow aspirate is mixed with bioactive glass and is then packed into this extra-articular area.

Transfer of peroneus brevis to peroneus longus tendon is performed when the deformity is severe (Fig. 4). Severe contracture of the peroneus brevis tendon can sometimes make it difficult to obtain complete realignment. As an alternative, the authors sometimes transect both tendons.

Triple arthrodesis is usually performed under general anesthesia; however, these procedures may also be performed with spinal anesthesia depending on the patient’s comorbidities and overall medical status. The patient is positioned supine with a bump placed under the ipsilateral hip to internally rotate the foot and ankle. The patient’s heel should be located just distal to the end of the operating room table to allow access to the posterior calcaneus for delivery of fixation and to permit easier manipulation of the extremity during intraoperative imaging. The extremity is elevated on several stacks of towels or a bump to facilitate use of retractors and to enhance imaging during the procedure. The authors typically use a thigh tourniquet, which is released after osteosynthesis has been achieved.

Triple arthrodesis is typically performed through a combination of medial and lateral incisions. The lateral incision extends from the tip of the lateral malleolus and courses distally to the fourth metatarsal base (Fig. 5). This incision is dorsal to the peroneal tendons and sural nerve. Care is taken to maintain hemostasis with cauterization or ligation of the venous structures within this area. A sponge lightly moistened with saline may be used for planal dissection down to the fascia. The peroneal tendons are then mobilized with Metzenbaum scissors and retracted inferiorly (Fig. 6). Dissection is then carried down to the level of deep fascia and the extensor digitorum brevis muscle belly. An inverted T-shaped incision is performed with the base of the incision along the inferior aspect of the muscle belly, extending proximally along the lateral capsule of the talocalcaneal joint. The vertical arm of the incision is within the sinus tarsi. A second vertical incision is then placed parallel within the sinus tarsi, and the contents of the sinus tarsi are thoroughly evacuated (Fig. 7). This action enhances visualization and access to the subtalar joint (STJ). Dissection is then carried proximally along the lateral talocalcaneal joint, where the calcaneofibular ligament is incised to facilitate access to the STJ (Fig. 8). The lateral talocalcaneal ligaments and calcaneofibular ligament are often contracted in long-standing adult acquired flatfoot. Releasing these periarticular structures will enhance mobilization of the STJ, and therefore permit easier access and realignment.

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