Preoperative planning is essential to achieve a good outcome after surgery. It should start with a thorough history and clinical examination. Assessment of the hindfoot alignment while weight bearing, heel position, pattern of foot callosity, testing of muscle strength and gastrocnemius tightness can help confirm underlying pathology. Weight bearing radiographs are mandatory to assess bony alignment and joint arthrosis. CT scans may offer further three-dimensional information in the presence of complex deformities.

The ideal position of the hindfoot should be plantigrade (foot at 90° to the leg) with 0–5° of valgus of the heel and external rotation to match the contralateral uninjured side [19]. Excessive dorsiflexion will cause heel pain and ulceration while plantarflexion will result in metatarsalgia and genu recurvatum. Valgus and varus malalignment will result in collateral ligament strain at the knee and forefoot pronation and supination respectively if the midfoot joints are stiff and unable to compensate. Translating the talus as far posteriorly as possible reduces the lever arm acting on the forefoot, decreasing the pressure through the midfoot. In the frontal plane, the anatomic axis of the tibia falls just medial to the midpoint of the body of the talus while in the sagittal plane, the anatomic axis of the tibia should intersect the lateral talar process [20]. As much as is feasible, the target of reconstruction of the hindfoot should be to restore this anatomic alignment.

The procedure may be done under general, spinal or regional anaesthesia (sciatic and femoral nerve blocks). The patient is positioned supine with a sandbag under the ipsilateral buttock to keep the foot in neutral position. The entire lower leg is prepared and draped, keeping the knee exposed to aid in realignment of the limb and also to facilitate the harvest of bone graft from the proximal tibia if necessary.

If open hindfoot fusion is to be undertaken, the lateral approach between the sural and superficial peroneal nerve, along the distal fibula and then curving anteriorly, extending to the sinus tarsi and towards the base of the fourth metatarsal base may be used. Excision of the distal fibula allows exposure of the ankle joint and the subtalar joint may be exposed through the distal limb of the incision and sinus tarsi. Alternately, the ankle and subtalar joints may be accessed through an anterolateral approach, preserving the fibula as a buttress of support. The articular surfaces of the ankle and subtalar joints are resected until the foot can be placed in a plantigrade position, at 90° to the leg. Percutaneous Z lengthening of the Achilles tendon and other soft tissue releases are undertaken as necessary to get the foot into a plantigrade position.

Our preferred approach is to prepare the ankle and subtalar joints arthroscopically. We have previously reported our results from arthroscopic ankle fusion and hindfoot arthrodesis [1, 21, 22]. Unless the severity of the deformity necessitates the use of an open approach, arthroscopic arthrodesis has the advantage of earlier healing due to avoidance of periosteal stripping, less pain and consequently, quicker rehabilitation. In the presence of skin compromised by previous scarring or vascular disease, it reduces the significant risk of wound breakdown and infection. The ankle is arthroscoped with the leg in traction, after distension of the joint with normal saline, through standard anteromedial and anterolateral portals. The joint is routinely prepared using soft tissue abraders and bony burrs. Following this, the traction is removed and a sandbag placed under the ipsilateral buttock to allow arthroscopy of the subtalar joint through the sinus tarsi. The subtalar joint is thereafter prepared in similar fashion using standard soft tissue resectors and bony burrs. Enough bone is resected to allow correction of the hindfoot malalignment. Percutaneous tendoachilles lengthening is performed if there is any evidence of tightness.

Once the joints are prepared, a 2 cm longitudinal incision is made in the plantar heel pad just lateral to the midline and a blunt haemostat is used to dissect down to the calcaneus. While the hindfoot is held by an assistant in the optimum position for arthrodesis, a guide wire is inserted under fluoroscopic control through the calcaneus and talus, into the distal tibia. The tibia is entered at the junction of lateral third and medial two thirds, which corresponds to the medullary canal of the tibia. A hand reamer is used to prepare the calcaneal entry point and the talus. Once the tibial entry point is reached, a flexible cannulated reamer can be used to prepare the tibial canal. We ream to 1 mm above the size of the nail to be used, as is standard recommendation for most femoral and tibial nailing systems. If the access is good and the medullary canal relatively wide, especially in the elderly, it is not always necessary to ream above the level of the tibial metaphysis. The nail is introduced under fluoroscopic control, centered in the body of the calcaneus and the distal tibia. Locking screws are inserted into the calcaneus and talus distally and compression obtained before two proximal locking screws are inserted into the nail in the tibia. We use a short, curved nail which reduces the risk of lateral plantar nerve injury and ensures good purchase in the body of the calcaneus without risking blowout fractures of the medial wall (Fig. 28.2a–d). This avoids the need to medialise the medial malleolus with its attendant risks of soft tissue stripping, delayed union and infection. The shorter nail reduces the risk of stress fractures proximally.

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