The indications for a triple arthrodesis can be segregated into the same categories:

Typically, patients have more than one indication for surgery (e.g., both instability and pain). Arthrodesis should be reserved for instances in which all conservative measures have failed. In cases involving hindfoot deformity or instability, consideration should be given to motion-sparing procedures, such as tendon transfers or osteotomies or limited hindfoot arthrodeses, before deciding on a triple arthrodesis. If only one of the three joints is the source of clinical symptoms, that specific joint usually should be fused rather than doing a triple arthrodesis. However, if two of the hindfoot joints are symptomatic, fusing all three joints often is preferable because the functional consequences of fusing two joints are about the same as fusing three, whereas fusing only two carries a higher risk of clinically significant nonunion.

A contraindication is a patient with inadequate vascular supply to the foot; appropriate evaluation and vascular specialist referral may be indicated. Advanced patient age is not a contraindication for surgery, nor is the presence of diabetes mellitus, although it has implications for the postoperative regimen.

The history and examination are useful in providing clues to the diagnosis and to indicate the specific concerns that need to be treated. A routine foot and ankle physical examination should be undertaken. Observing the patient’s gait can reveal the functional derangements potentially causing symptoms. The patient should be observed for signs of an antalgic gait. The inability to perform a single-leg heel rise is a reliable test for posterior tibial tendon dysfunction. Observing the patient
in a standing position anteriorly and posteriorly generally demonstrates the deformity (Fig. 24.1). A cavus foot should raise suspicion about an underlying neuromuscular cause, such as Charcot-Marie-Tooth disease or a spinal lesion.

Whether the foot is plantigrade, meaning that it contacts the floor in a physiological manner, should be determined. The non-weight-bearing examination focuses on the measurement of ankle and hindfoot range of motion and stability. It is useful to determine painful joint motions, numbness, swelling, and the presence of callosities in the medial or lateral forefoot associated with malalignment and deformities such as claw toes. Muscle strength testing, sensation assessment, and palpation of pulses should be part of the examination.

The varus hindfoot seen in a cavus foot is usually associated with a compensatory valgus forefoot deformity and an adducted forefoot (Fig. 24.2). In the more common pes planus from posterior tibial dysfunction, the hindfoot is in valgus, and the forefoot has a compensatory varus-abducted deformity. Generally, these compensatory deformities occur through the Chopart joint and can be
corrected with the triple arthrodesis without the need for additional surgery in the anterior foot. There may also be a secondary Achilles tendon contracture due to the valgus, laterally deviated calcaneus which places the Achilles tendon in a shortened position. This can be ascertained by the Silfverskiöld test, in which ankle dorsiflexion is significantly limited when the knee is extended. In a rigid valgus hindfoot, with the talus locked in a plantarflexed position, this contracture sometimes cannot be definitively determined preoperatively, but restricted dorsiflexion of the ankle should be ascertained intraoperatively using the Silfverskiöld test. Inadequate dorsiflexion due to tendon contracture may require a partial gastroc lengthening or, rarely, a formal tendo-Achilles lengthening. This should be discussed preoperatively with the patient.

All patients should have weight-bearing radiographs of their feet and ankles: anteroposterior foot, lateral foot, and anteroposterior ankle views. In the flatfoot, the anteroposterior (Fig. 24.3A) and lateral talocalcaneal angles (Fig. 24.3B) diverge, whereas in the cavus foot, these angles tend to be parallel or converge. The ankle radiographs are necessary, as they can reveal calcaneofibular impingement (which is not unusual) and significant arthritis (Fig. 24.4). Failure to appreciate these preoperatively can lead to an unhappy outcome because of persistent ankle complaints. The weight-bearing ankle radiographs also provide insight into the overall alignment of the lower extremity.

Although the usual goal for a triple arthrodesis is a plantigrade foot, the optimal position of the foot has to be determined with respect to the entire lower extremity. In those cases in which proximal deformity will also be corrected (e.g., total knee arthroplasty, tibial osteotomy), the interaction of the proximal realignment on ultimate plantigrade position must be anticipated to prevent the foot from being placed into too much valgus or varus by the triple arthrodesis. Computed tomography, radioisotope bone scanning, and magnetic resonance imaging usually are unnecessary for preoperative assessment. Selective joint injections with a long-acting local anesthetic (e.g., mepivacaine [Carbocaine], bupivacaine [Marcaine]) are occasionally useful diagnostically to help determine the most symptomatic joints.

Autograft bone graft, which may not be needed, can be obtained from the iliac crest or proximal tibia, or demineralized bone graft allograft (250- to 400-μm particles) can be used (9). The latter has the advantage of avoidance of an additional, sometimes painful, incision with attendant blood loss, and it carries no risk of viral infection transmission. The union rates for grafting technique are equivalent.

The goals and limitations of surgery should be discussed with the patient. Patients’ expectations must be realistic, or they are likely to be unsatisfied with the result.

Every effort should be made to use sharp dissection and to gently handle the soft tissues. The approach is made with a minimum of blunt dissection and avoidance of raising subcutaneous skin flaps. The closure should be performed carefully. The use of 5-0 chromic sutures for skin closure has been found to yield excellent cosmetic results. While a Surgairtome (or equivalent) with a 5-mm-long shaft, pineapple-shaped cutting burr can be used for the debridement of cartilage and subchondral bone, the possibility of thermal necrosis is avoided by using a light touch with the burr. Alternatively, one can choose to use sharp osteotomes (straight and curved), curettes, and rongeurs to debride the joint surfaces. The tourniquet can be placed on the upper calf with adequate soft roll padding to protect the common peroneal nerve as it wraps around the proximal fibular head. This allows use of lower cuff pressures, typically 250 mm Hg, and results in less ischemic tissue compared with the use of thigh tourniquets. In addition to the usual surgical skin preparation and draping, it is generally easiest to drape the surgical field using a stockinette and an extremity drape that is reversed so that the long end of the drape is unfolded cephalad. The stockinette can be opened distally and rolled proximally, and the toes and forefoot can be covered using a surgical glove or iodine adhesive plastic. This reduces the potential for contamination of the surgical field from debris adjacent to the toenails. The exposed skin is covered with an iodine adhesive plastic to reduce skin contamination of the wound. Preoperative antibiotics are administered.