21 Naviculocuneiform Fusion to Treat Midfoot Arthritis and Deformity Abstract Naviculocuneiform (NC) fusion is not a new concept and was first described in the literature in the early 20th century. However, over the years, it has played second fiddle to various other procedures as the workhorse for flatfoot deformity correction due to its perceived unreliability. In recent years, foot and ankle surgeons are reevaluating the role of NC fusions in the treatment of deformity correction and symptomatic arthritis. A better appreciation of NC collapse in a certain subgroup of patients with planovalgus feet where the apex of the deformity lies in the NC joint has highlighted the role of deformity correction through the NC fusion. Biomechanically, fusion of the NC joint is the most effective procedure to correct the forefoot varus in a planovalgus deformity. This medializes the joint reaction force in the ankle and restores more normal ankle joint mechanics while preserving motion at the ankle and Chopart’s joints. Recent literature suggests that NC fusion is a safe and reliable procedure. Fusion rates have been shown to be upward of 95% when performed for the correct indication and with good surgical technique. Complication rates are similar to that of other joint fusions in the foot. Our experience is in keeping with that of the literature and we recommend NC fusion as an option for pes planovalgus deformity correction and symptomatic arthritis of the medial column. It may be performed in isolation or in conjunction with other soft-tissue and bony procedures. Keywords: naviculocuneiform, fusion, planovalgus • Flat foot deformity. Naviculocuneiform (NC) fusion within our practice is most commonly used to derotate the forefoot in flatfoot correction. In symptomatic flatfoot deformity such as in posterior tibial tendon dysfunction, the joint reaction force in the ankle joint is laterally placed. This needs to be corrected. There are three components to the deformity that causes the lateral load. The hindfoot may be in valgus and this may occur through the subtalar joint, through the ankle, or be supramalleolar in origin. The larger mechanical component of the lateral load arises in the forefoot. This is because the forefoot makes for a larger lever arm at the ankle. There are two components to the forefoot malposition in flatfoot. The forefoot may be externally rotated on the hindfoot. This places a valgus load on the ankle. The second forefoot deformity, which may laterally load the ankle, is forefoot varus on the hindfoot. • Posttraumatic arthritis. The midfoot can be involved in crush injuries and trauma. These include navicular crush or impaction injuries, navicular cuneiform dislocations, and variants of the Lisfranc fracture–dislocation pattern. Traumatic injuries resulting in medial column dissociation with significant osteochondral injuries and gross instability will benefit from primary in situ or corrective fusion. • Post–tumor resection. Following excision of a tumor, the NC joint may need to be fused. • Inflammatory arthritis. Patients with rheumatoid arthritis may have degenerative change at this level, with or without a flatfoot deformity. • Correction of forefoot deformity in ankle joint replacement. In patients with forefoot varus who are undergoing an ankle joint replacement, an NC fusion may be required to correct the forefoot deformity to ensure that the medial side of the ankle (the medial malleolus and deltoid ligament) is not overloaded (Fig. 21.1). • Muller–Weiss disease. Muller–Weiss disease is an avascular collapse of the navicular. Typically, the collapse can involve the TN and navicular cuneiform joints. The navicular cuneiform joint may need to be fused in conjunction with the TN and possible triple arthrodesis. • The patient is observed walking and standing. The forefoot external rotation will be manifest by the “too many toes” sign when the patient is observed from behind. The forefoot varus will be visible when the patient sits and the hindfoot is corrected to a neutral position. The forefoot position is assessed by determining the degree of forefoot varus on the long axis of the tibia. This may reach 40 to 50 degrees. • Assessment of the tibialis posterior tendon is important especially in the setting of medial-sided symptoms. Clinical tenderness and weakness on resisted eversion is suggestive of some element of inflammation or dysfunction. Clinical assessment of the TN, NC, and first tarsometatarsal (TMT) joints may point to degenerative or inflammatory arthritis as the underlying etiology. • Standing anteroposterior (AP) and lateral radiographs of the ankle and foot are required to assess the deformity. • Lateral views will show if the apex of the collapse of the flat foot is at the NC joint or at the TMT joints. Fig. 21.1 Preand post-op radiographs of pes planus reconstruction through naviculocuneiform (NC) fusion in conjunction with total ankle replacement to correct the forefoot position and offload the NC joint. • The AP view will show if the translation is at the TN joint. • If needed, three-dimensional imaging may be required. This will almost certainly be required if arthritis is present. The imaging will allow the midfoot to be more clearly seen than on plain radiographs. AP and lateral views of the ankle will also be needed to rule out injury to the deltoid ligament (Fig. 21.2). • Custom rigid orthotic inserts. • Rigid soled shoes (full-length carbon fiber or steel shank). • Rocker-bottom soled shoes. • Ankle foot orthosis. • Combined orthotic and double upright brace. • Inadequate circulation. • Active infection at the surgical site. • Poor local soft-tissue envelope. • Severe osteoporosis preventing adequate fixation and healing of fusion. • Reconstruction of the medial longitudinal arch. • Rigid stabilization of the navicular cuneiform joints. • Rebalancing of the foot tripod creating a plantigrade foot. • Ability to resect arthritis from the NC joint. • Restabilization of the medial arch. • Only sacrifices noncrucial anatomically stable joints. • Exposure of the appropriate joint: • Joint preparation: • Reduction and alignment of the joint to recreate normal foot anatomy and stable plantar grade foot for ambulation. • Rigid compressive fixation of the joint to maximize fusion. A popliteal block is administered. The patient is positioned on the table with the foot toward the bottom of the table. The ipsilateral hip is bumped up so that the foot points directly vertical. The concomitant lateral column lengthening in many of these patients will require the lateral foot to be exposed. A thigh tourniquet is preferable. The foot is approached through a dorsal incision centered over the NC joint. The tibialis anterior tendon is mobilized medially. The neurovascular bundle is typically mobilized laterally, but the lateral aspect of the NC joint may be accessed via a soft-tissue window lateral to the neurovascular bundle if necessary. The NC joint is identified and exposed via sharp subperiosteal dissection (Fig. 21.3). Fig. 21.2 Preoperative anteroposterior and lateral standing radiographs of a patient with a planovalgus foot. Care is taken to ensure that the correct joint is exposed. There is a possibility that the TN joint is exposed inadvertently. The TN joint can be identified by palpation because it will be proximal to the tuberosity of the navicular as opposed to distal. The plane of motion of both joints is different with the TN joint moving in a transverse plane and the NC joint, if any motion exists, will be in a dorsiflexion plantar flexion direction. The intercuneiform joint between the medial and intermediate cuneiforms can also be inadvertently dissected. This should be avoided given that it may compromise the blood supply of the medial cuneiform, particularly if the NC joint and TMT joints are fused. Finally, the TMT joints should not be exposed inadvertently. The anatomy of these is quite different and the surgeon should be aware of the difference. If there is any doubt, then the C-arm can be used to confirm the level of the fusion. The NC joint is then prepared using a combination of a curved osteotome and curettes to remove all cartilage till subchondral bone is visible. The subchondral plate is then perforated with a 1.6-mm K-wire (Kirschner wire). The cuneiform is then plantarflexed and compressed on the navicular to achieve correction of the deformity. The plantar cartilage can be hard to remove with the open technique. The joint can be better visualized once all three joints have been exposed and released. A small curette (OOO) can be placed between the medial cuneiform and the navicular. This will open the joint and can be used to carefully release the plantar capsule. The curette can be used to keep the joint open, while a 5-mm curved osteotome is used to remove the cartilage (Fig. 21.4). Care should also be taken to remove all cartilage from all three joints. The lateral side of the lateral joint can be challenging to reach. All cartilage is then removed using a pituitary rongeur. The cartilage fragments can release factors preventing neovascularization and migration of osteoblasts. Cartilage therefore works against the factors released by the bone graft or bone graft substitute. Once debrided, the joint is held reduced. Correction of the NC joint is often required, and usually into plantar flexion. Temporary fixation is achieved with a 1.6-mm K-wire.
21.1 Indications and Pathology
The hindfoot position can be corrected by a medializing calcaneal osteotomy, a subtalar fusion, or a lateral column lengthening. The lateral or externally rotated position of the forefoot can be corrected by a lateral column lengthening or a talonavicular (TN) fusion. Both procedures may leave the forefoot in varus, and the TN fusion may cause stiffness that can be avoided. The NC fusion is the most powerful and effective fusion to correct the forefoot varus in a flat foot deformity. It will medialize the joint reaction force in the ankle and restore more normal ankle joint mechanics.
In addition, there is a group of patients with symptomatic flatfoot deformity where the apex of the deformity is centered at the NC joint. This is readily apparent on the lateral weight-bearing radiographs of the foot. In such cases, correction of the deformity at the NC joint is indicated.
21.1.1 Clinical Evaluation
21.1.2 Radiographic Evaluation
21.1.3 Nonoperative Options
21.1.4 Contraindications
21.2 Goals of Surgical Procedure
21.3 Advantages of Surgical Procedure
21.4 Key Principles
Anatomic deformity can make the NC joint easy to miss and cause inadvertent arthrotomy of the TN or TMT joints.
Removal of any remaining arthritic cartilage.
Removal of sclerotic subchondral or necrotic bone to ensure adequate bleeding surfaces for fusion.
21.5 Operative Technique
21.5.1 Open Technique
Positioning
Exposure
Reduction of the Joint
Musculoskeletal Key
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