Ankle and Hindfoot Fusions

Craig S. Radnay, MD, MPH

Dr. Radnay or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of OrthoDevelopment and Wright Medical Technology; serves as a paid consultant to OrthoDevelopment and Wright Medical Technology; and serves as a board member, owner, officer, or committee member of the American Orthopaedic Foot and Ankle Society.

Introduction

Arthritis is second only to cardiovascular disease in producing chronic disability that directly impacts the quality of life. Arthritis is also the leading cause for decreased work performance in the United States. The ankle and hindfoot joints are exposed to enormous joint reactive forces during gait and activity, 3 to 4 times more than that experienced in the hip and knee, with a smaller contact area and higher peak contact stresses. Fortunately, activity-limiting ankle arthritis is less common than degenerative disease of other major weight-bearing joints.

Ankle arthritis is most commonly posttraumatic, following a fracture of the ankle. For this reason, ankle and hindfoot arthritis patients tend to be younger than their hip/knee counterparts. Other causes for ankle and hindfoot arthritis include chronic joint instability, rheumatoid or inflammatory arthritis, neuropathy, postsepsis, and osteonecrosis with talar collapse.

While there have been numerous recent design advances in screw and plate technology, a successful outcome for an ankle or hindfoot fusion procedure still relies on the same concepts: appropriate preparation of the joint surfaces and rigid multiplanar internal fixation. Once the joint is successfully fused, after 3 to 4 months, functional rehabilitation will continue to help patients adjust to lack of motion at the fused joint. Most patients will be satisfied with their pain relief and surrounding joints may accommodate to allow resumption of most regular activities.

While a hip or knee fusion is poorly tolerated, patients with an ankle fusion generally do well. This is largely because adjacent joints (subtalar and talonavicular) provide compensatory motion in plantarflexion (PF) and dorsiflexion (DF). Conversely, patients with stiff hindfoot joints may be not as good candidates for fusion.

When considering surgery for someone with ankle arthritis, the patient should have failed nonoperative management, including shoewear and activity modification, physical therapy, exercise, weight loss, pain medications, and bracing. Total ankle replacement may be an alternative surgical option for some patients. Risks of complications are higher for ankle replacement, although some patients may see better function. Certainly, patients who are not as good candidates for ankle fusion (those with hindfoot stiffness) may be the best candidates for ankle replacement. Patients with advanced arthritis of the hindfoot (subtalar or calcaneocuboid joints) may benefit from arthrodesis/fusion of these joints. Most hindfoot arthritis is posttraumatic as well, although some fusions are performed for deformity, as in an advanced flatfoot deformity. Rare patients will have arthritis of both ankle and hindfoot, in which case combined fusions of multiple joints may be necessary. Patients with such “pantalar” fusions tend to have not as good results, with much more stiffness and less ability to compensate.

Selective arthrodesis is employed to achieve as much pain relief and stability with deformity correction as possible while preserving as many joints as possible. Pantalar arthrodesis is now limited as a salvage procedure for extreme posttraumatic pathology across multiple joints or for advanced Charcot reconstruction. The pain relief, restoration of alignment, improved soft-tissue status, and return to ambulation achieved in these cases, however, still justifies the use of this technique.

Contraindications to ankle or hindfoot fusions include active infection, especially with an open or arthroscopic approach. Relative contraindications include history of infection in the joint, advanced arthritis, and/or fusions at surrounding joints.

Surgical Approach

Ankle Arthrodesis

Ankle arthrodesis is often performed in a supine position through a direct anterior approach, utilizing the interval between the tibialis anterior and extensor hallucis longus tendons. Alternately, a lateral approach can be made, with an incision over the fibula. The fibula is cut and rotated externally, and the ankle joint is entered from the lateral side. With either approach, the tibiotalar joint is exposed, and any loose bodies and prominent osteophytes are carefully removed. The joint
is distracted with the use of laminar spreaders or pin distraction clamps, and the remaining articular cartilage is sharply débrided with the use of sharp periosteal elevators. Setting the ankle in the correct position for fusion is essential. This should also be planned out preoperatively, considering the entire lower leg, ankle, and foot. The tibiotalar joint should be in neutral DF/PF, 5° of external rotation and 5° of valgus. The anterior aspect of the talar dome should be positioned at the anterior border of the tibial plafond. Any deformity is corrected at this time; supplemental bone graft is utilized as needed for defects, although not routinely. With a rigid foot, a few degrees of ankle DF may be preferred. The position of the knee and the bow of the tibia should also be examined prior to surgical stabilization. For example, with quadriceps weakness, the arthrodesis should be positioned with the foot in 10° of equinus, which can help stabilize the knee joint. An equinus foot will force the knee into hyperextension, which is helpful if the quadriceps is weak.

Figure 55.1 A, B, Anteroposterior and lateral radiographs of ankle fusion with anterior neutralization plate.

In rare cases, persistent equinus deformity may be corrected with a percutaneous Achilles lengthening or gastrocnemius recession. In general, both equinus and calcaneus positioning should be minimized to prevent a back-knee thrust or excessive heel strike, respectively. In addition, rigid-foot deformity might necessitate slight overcorrection at the ankle or additional selective osteotomy or arthrodesis to create a plantigrade foot.

As an alternative to lag screws, a plate can be placed anteriorly or laterally. (Figure 55.1, A and B). An anterior plate neutralizes the PF, DF, and torsion moments across the joint, increasing rigidity and decreasing micromotion at the ankle fusion interface in the sagittal, coronal, and axial planes. Alternative approaches may be considered in special situations, such as ankles with soft-tissue concerns or a revision procedure. A lateral transfibular approach can be utilized, with the fibula preserved with internal fixation at the conclusion to provide greater stability and options for potential future surgical procedures. A posterior midline approach could also be utilized in a complex posttraumatic or revision situation from the prone position.

Arthroscopic Ankle Arthrodesis

Arthroscopic ankle arthrodesis has gained increasing popularity, with reports of shorter hospital stays, shorter time to solid fusion, equivalent to improved union rates, and earlier functional improvement when compared with open arthrodesis. Arthritic ankles with minimal deformity are excellent candidates for this procedure. With increasing experience with ankle arthroscopy and improved instrumentation, this technique can also be utilized for more complex deformities. The minimal soft-tissue disruption via an arthroscopic approach may also reduce the degree of permanent functional impairment of the joints and soft tissues adjacent to the fusion site. Arthroscopic fusion can extend surgical indications to patients with a compromised soft-tissue envelope or vasculopathy, which might otherwise be a relative contraindication to an open procedure. Patients with global inflammatory, postseptic, or hemophilic arthritis are also good candidates. Contraindications to the arthroscopic technique include the same as those for an open approach, as well as significant focal bone loss and deformity, and extremely stiff, immobile ankles, which preclude arthroscopy.

Figure 55.2 Photograph of set-up for arthroscopic ankle arthrodesis.

The arthroscopic procedure is performed utilizing standard anteromedial and anterolateral portals (Figure 55.2). Removal of the articular cartilage is achieved with the use of an aggressive soft-tissue resector and the hard chondral bone is cleared down to softer, bleeding subchondral bone with the use of a high-speed burr. The fusion is stabilized, in appropriate alignment, with 2 or 3 large fragment compression screws, as described for the open technique. Pin and screw placement is verified utilizing multiplanar fluoroscopy.

Hindfoot Fusions

Hindfoot fusion approaches are specific to the pathology. The subtalar and calcaneocuboid joints can be easily accessed through either a lateral Ollier incision or via a longitudinal incision extending from distal to the fibular tip in line with the fourth metatarsal. The talonavicular joint can be approached through a medial incision utilizing the plane between the anterior and posterior tibial tendons.

Rigid internal fixation utilizing large fragment screws and/or plates is confirmed with multiplanar fluoroscopy (Figure 55.3). For an isolated subtalar joint fusion, the prepared joint should be positioned in slight valgus (5°) alignment, with the calcaneus positioned underneath the talus. Residual forefoot varus should be eliminated. Bone graft is utilized in revision procedures, and as needed in primary cases.

Figure 55.3 A, B, Multiplanar radiographs following triple hindfoot (subtalar, talonavicular, calcaneocuboid) arthrodesis.

Extended ankle and hindfoot fusion cases are approached from either a direct anterior or extensile lateral exposure. The anterior approach usually requires an additional small lateral subtalar incision. The extended fusions via the extensile
lateral approach is performed with an incision along the fibula curving anteriorly in line with the fourth metatarsal, with an additional medial window at the tibiotalar joint. The fibula is osteotomized above the level of the ankle joint to expose the ankle and subtalar joints; the fibula is débrided of soft tissue, decorticated, and fused to the lateral tibia at the end of the case. Alternatively, the fibula can be removed, morselized, and used as autograft across the articular surfaces. The tibiotalocalcaneal joint is then stabilized with either an intramedullary nail placed in compression in retrograde fashion, or with anterior and/or posterior plating (Figure 55.4, A and B).

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