In an arthritic condition, for example, very little decision-making is necessary. If the subtalar and calcaneocuboid joints are painfree and without apparent arthrosis, then the single joint fusion can be done as a stand-alone procedure. If there is any appreciable ankle equinus, then a posterior muscle lengthening procedure should be considered.

In other foot pathologies, such as the adult acquired flatfoot, however, decision making is more complex. When choosing a talonavicular joint fusion for a completely flexible flatfoot, often it can be done as a single procedure in the foot. However, assessing for equinus is paramount, and it is critical to assess whether the forefoot can be completely reduced of any varus deformity. Careful inspection of the medial column is needed in the preoperative decision-making process. If there is significant breakdown of the more distal joints, the naviculocuneiform joint, and/or the tarsometatarsal joint, then despite having a realigned rearfoot from the talonavicular joint fusion, there still may be instability and further breakdown on the medial column, which can ultimately lead to failure of the surgery. If the equinus is not addressed, then there will be increased strain and load to the medial column.

The lower extremity is scrubbed, prepped, and draped in the usual sterile fashion. This procedure can be performed with or without a tourniquet according to the surgeon’s preference. If a posterior lengthening procedure is to be performed, it should be done prior to the fusion. The anatomic landmarks should be identified, including the medial malleolus, tibialis anterior tendon, and the navicular tuberosity. The incision placement should be midway between the medial malleolus and the tibialis anterior tendon and should start at the ankle joint and be carried distally to the naviculocuneiform joint (Fig. 60.1). The critical part of the soft tissue dissection is handling the medial marginal vein, which will always be encountered.

Once the skin incision is made, the superficial veins in the superficial fascia should be cauterized with an electrocautery device. The deeper layer of the subcutaneous tissue contains the medial marginal vein (great saphenous). Once the medial marginal vein is isolated, the tributaries running medial and lateral are clamped, cut, and hand tied. If possible, the medial tributaries are ligated to allow for dorsal retraction of the vein. Once the vein is retracted, a sponge is used to bluntly clear away any residual subcutaneous tissue.

The bony landmarks, the tibia, talus, and navicular tuberosity are identified by palpating with forceps. A scalpel is then used to open the talonavicular joint with an incision in line with the skin incision. The capsule is loosely attached to the talar neck, but firmly attached to the navicular. Obtaining adequate exposure of the talonavicular joint can be easily accomplished if the dorsal talonavicular ligaments and the posterior tibial tendon/spring ligament tissues on the inferior aspect of the navicular tuberosity are released. The easiest way to get good dorsal exposure is to take a Freer elevator or Key elevator and pass it over the dorsal neck of the talus where the tissue is loosely attached. The elevator is pried upward, which exposes the tight attachment of dorsal capsule and ligaments. A scalpel can then
be used to hug the bone and dissect away tight dorsal tissues to allow for adequate exposure. The large dorsal flap of tissue will include the neurovascular structures and tendons. You should be able to palpate the entire talar neck and dorsal navicular bone with the index finger. The joint is easily visualized, and the dorsal talonavicular ligaments can be released if necessary. Any existing dorsal exostosis can be removed at this time.