Calcaneus Malunion with Subtalar Fusion (Bone Block Arthrodesis)

Figure 18.1

Standing clinical picture of a patient showing broadened right heel positioned in more valgus than left heel

Radiological Evaluation

Weight-bearing ankle and foot series X-rays were taken. The lateral film demonstrated shortening of the calcaneus, subtalar arthritis, and posterior exostosis from malunited calcaneus. The talus was dorsiflexed in the ankle mortise (Fig. 18.2). Comparative axial views were taken to judge the amount of heel shortening, broadening, and positioning of the heel. The heel was positioned in more valgus than the opposite side (Fig. 18.3).

Figure 18.2

The lateral radiograph of the right heel showing subtalar arthritis (orange arrow) and posterior exostosis (yellow arrow). Note that talus is also dorsiflexed in the ankle mortise (black lines)

Figure 18.3

Comparative axial views of both the heels showing broadening (orange lines) and shortening (yellow lines) of the right heel with a valgus position (black lines)

Treatment

Surgery was planned after preoperative medical clearance. At surgery it was planned to perform a subtalar fusion with distraction bone grafting to treat the subtalar arthritis as well as the widening and shortening of the heel. The ipsilateral iliac crest was selected for tricortical bone graft harvesting. Bone graft placement was planned in such a manner to increase the height of posterior subtalar joint to address the talar dorsiflexion. The correction of the valgus heel was accomplished by carrying out generous soft-tissue releases and strategical shaping and placing of the bone graft. The lateral and posterior exostectomy was also planned together with these surgical procedures. The logic was to target all the pain-generating elements of the calcaneus malunion. The valgus positioning of heel was thought to get corrected by the generous release. If not able, a calcaneal osteotomy would be required.

Surgical Tact

Position

The patient was placed in a lateral decubitus position with affected lower limb facing up. Alternatively, a directly posterior approach can be used, with the patient in a prone position. The right limb was slightly flexed at the knee to bring the heel to the corner of the radiolucent table. A thigh tourniquet was applied and the ipsilateral iliac crest was also prepared (Fig. 18.4). An image intensifier was positioned diagonally in such a manner that an AP projection would show the lateral image of the calcaneus and a lateral projection would show an axial image of the calcaneus assisted by dorsiflexion of the foot (Fig. 18.5).

Figure 18.4

The patient position at surgery. The patient lies in a lateral decubitus position with affected limb up towards the ceiling. The ipsilateral iliac crest is also prepared

Figure 18.5

Positions of operative personnel at surgery. Surgeon stands at heel end of affected foot while assistant stands at the toe end with diagonally positioned image intensifier

Approach

A lateral extensile approach based on the lateral plantar artery was used (Fig. 18.6). The peroneals, calcaneo-fibular ligament, and sural nerve were lifted within the flap. The flap was handled gently with blunt skin hooks and the flap lifting was assisted with sharp dissection. The flap was retracted with two bent k-wires, one wire each in the anterior and posterior talus (Fig. 18.7). The flap was kept moist with the use of a wet gauze. This approach gave an access to the subtalar joint as well as the posterior exostosis. This approach would also allow for a medial calcaneal slide osteotomy, if at all it was needed.

Figure 18.6

The lateral extensile approach

Figure 18.7

Positioning of two k-wires for retraction of the flap

Exostectomy

Exposure with extension of the proximal limb and retraction of the Achilles allowed for complete visualization of the lateral as well as posterior exostosis (Fig. 18.8). The lateral wall exostosis was resected flush with the lateral talar wall. With the heel in plantarflexion, the tendoachilles was retracted posteriorly and all prominent bone in front of it was excised taking care of not entering into the posterior subtalar joint (Fig. 18.9). Fluoroscopic imaging was used to verify the adequacy of this bone removal. The excised bone was preserved for utilization as bone graft in the subtalar distraction arthrodesis.

Figure 18.8

Demonstration of the lateral wall exostosis (white arrow) and posterior wall exostosis (yellow circle)

Figure 18.9

Excision and removal of posterior exostosis

Fusion and Fixation

Meticulous preparation of the subtalar joint articulating surfaces must be performed. The articular cartilage is denuded up to bleeding subchondral bone with curettes, osteotomes, or a saw. Infrequently, a burr is used, but care is taken to irrigate the burr to avoid any thermal necrosis of the bone. Visualization of the flexor hallucis longus marks the completion of joint preparation medially. This was followed by drilling of the subchondral bone and feathering of the articular margins to increase the bleeding bone surface area. Once the joint is prepared and mobilized, a laminar spreader in the joint, or a pin distraction, can help in distracting the joint and restoring the talar declination angle. An image is checked with the distracted lamina spreader to get a precise idea about restoration of heel height. After release of soft tissues, the subtalar joint and the heel could easily be manipulated out of gross valgus to neutral obviating the need for a medial slide calcaneal osteotomy. The graft size was measured. An adequately sized iliac crest bone graft was harvested and crafted to fit in the space created. The bone graft was positioned in the subtalar joint in such a manner that the posterior heel height could be restored, the hindfoot could be put out of valgus, and the talar declination angle could be improved. Additional cancellous graft from the iliac crest and from the excised bone was packed into the fusion site. At this stage, soft tissue-retracting k-wires were removed and flap closure assessment was done.

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