Triple Arthrodesis Treatment & Management

As with most cases, nonsurgical measures should be exhausted before considering surgical intervention. This is especially true when planning a salvage procedure like a triple arthrodesis. Conservative treatment consists of physical therapy, strapping and tapping, nonsteroidal anti-inflammatory drugs (NSAIDs), steroid injections, and bracing.

Most triple arthrodesis procedures are performed by removing all of the cartilage from the three joints and fusing them with bone-to-bone contact. Positional corrections can usually be achieved by rotating the foot along the natural contours of the joint surfaces prior to fusion. In cases of severe deformity, however, wedges of bone may need to be removed from or added to the joints to achieve the desired correction.^{[2, 3, 4, 5, 6, 7, 8, 9, 10]}

The patient is placed supine on the operating table and either general or spinal anesthesia is administered. A popliteal block should be considered to help with postoperative pain control. A proximal thigh tourniquet is applied, and a bump is placed under the ipsilateral hip. This positioning internally rotates the foot and allows easier access for the lateral incision and the ipsilateral iliac crest should autogenous bone graft be needed.

A lateral incision is made from just inferior to the distal tip of the lateral malleolus to the base of the fourth metatarsal (see images below). The STJ, CC joint, and the lateral portion of the TN joint are thereby exposed. Care is taken to avoid branches of the sural and superficial peroneal nerves running just inferior and superior to the incision. This approach follows a plane between both nerves, but small branches may enter the area and should be avoided if possible.

The deep fascia is visualized through the entire course of the incision, and the EDB muscle belly is identified. An L -shaped incision is made through the deep fascia traveling along the course of the EDB insertion and then distally across the CC joint (see first image below). This releases the insertion of the EDB, allows access to the CC joint, and gives exposure to the sinus tarsi and the Hoke tonsil. The EDB muscle belly is flapped distally, starting at its proximal lateral margin, giving excellent exposure to the CC joint and allowing eventual exposure to the lateral TN joint. The Hoke tonsil is next evacuated by carefully following the contours of the calcaneus with a No. 15 blade beginning at the anterior process (see second image below).

Care should be taken to identify and protect the peroneal tendons. All of the contents of the sinus tarsi should be removed, including the interosseous ligament, to gain exposure to the anterior portion of the STJ.

A laminar spreader is placed into the sinus tarsi and used to open the STJ, vertically separating the talus from the calcaneus. Transection of the calcaneofibular (CF) ligament may become necessary in cases in which the joint remains tight and adequate exposure is not achieved. Articular cartilage is removed from the anterior, middle, and posterior facets by scraping with a curette or stripping with an osteotome. The remaining subchondral bone is then fenestrated using a 0.062 K-wire, small drill bit, or power bur. This allows vascular ingrowth through the subchondral plate and excellent bone preparation for fusion. Another method for penetrating the subchondral bone is to use a small osteotome or gouge to shingle the articular surface.

Attention is next directed to the CC joint where the cartilage is denuded, leaving only subchondral bone. The surfaces are fenestrated in the fashion described above. Care should be taken to leave as much bone as possible at this joint, especially in valgus deformities, because lateral column length is important for correction. The lateral border of the TN joint can be reached after the CC joint is prepared by dissecting directly medially. A capsulotomy is performed and the laminar spreader is once again used to separate the articular surfaces. Any cartilage that can be removed through this incision should be before starting the medial approach.

A medial incision is made beginning just anterior to the distal tip of the medial malleolus extending dorsomedially toward the naviculocuneiform joint (see images below). It lies between the anterior and posterior tibial tendons. The saphenous vein and nerve are typically located slightly dorsal to the incision and should be carefully retracted away during the dissection. A capsulotomy of the TN joint is performed in line with the skin incision, and periosteal flaps are created to expose the articular surface. A laminar spreader is inserted for exposure, and the cartilage is removed. The articular surface of the navicular is usually deeply concave making cartilage excision difficult. Care must be taken to ensure the entire surface is properly denuded in order to avoid healing problems. Osteophytes and a large medial tubercle on the navicular can be removed, if present.

The foot is next manipulated into the corrected position and bone on bone contact at each joint is confirmed. Larger deformities may require wedges to be removed for optimal correction. Small gaps in joints can be filled with bone graft to help ensure solid union. Once satisfied that the foot will reduce properly, it is temporarily fixated. The STJ should be placed in about 4° of valgus relative to the ground. It is extremely important to not leave the hindfoot in varus, as this will most certainly lead to postoperative complications. A helpful thought to keep in mind during this procedure is "thou shall not varus!" The forefoot is then aligned plantigrade to the floor.

Fixation techniques vary and often depend on surgeon preference. The STJ should be fixated with a cannulated 6.5 or larger screw and can be placed from the posterior plantar portion of the calcaneus into the body of the talus or from the neck of the talus into the body of the calcaneus (see images below). Care should be taken not to disrupt nutrient arteries entering the neck of the talus if the latter approach is used.

Newer headless screws are useful with this technique as there is less chance of impingement on the Tibia during dorsiflexion of the ankle joint. This can also be a time saver because the area is very accessible after the TN joint has been exposed. A secondary point of fixation is used if there is concern for rotational instability. The TN and CC joints can be fixed with either staples or screws. If staples are used, at least 2 are placed in each joint, directed at 90° angles to each other. The advent of compression staples and locking compression plates has greatly enhanced this technique and should be considered over antiquated standard staples.

The technique preferred by the authors is to use two or three 4.0-4.5 cannulated screws placed parallel to each other in the TN and CC joints and to use a single 7.0-7.3 cannulated screw in the STJ, as seen in the last image above. This technique works very well and spares time because the guide pins are used as temporary fixation. Once in place, the corrected position is verified using fluoroscopy, and the screws are easily placed over the guide pins. Headless screws should be considered at the surgeon’s discretion. Two- or 4-hole locking compression-style plates have also been used at the CC and TN joints, providing excellent stability, compression, and time savings.

Hardware placement is verified using fluoroscopy, and residual gaps in joints, including the sinus tarsi, are filled with bone graft. The surgical sites are closed in layers with care taken to repair the CF ligament and insertion of the EDB. A lateral drain should be used to help prevent hematoma formation, especially when large portions of bone are resected. If a preoperative block was not performed, an ankle block with 0.5% plain Marcaine is performed to help decrease postoperative pain. Finally, a Jones-style compression dressing is applied with a posterior splint prior to deflation of the tourniquet.

Patients are usually kept overnight in the hospital for observation, pain control, and IV antibiotics. Anticoagulation therapy is started if deemed necessary. After discharge, patients are instructed to spend at least the first 3 days with their foot elevated above their heart in order to control edema and pain. The patients are seen within 1 week for a dressing change, and a short leg cast is applied if the edema is controlled. Sutures are removed after 2 weeks, and the patient is placed back into a non – weight-bearing (NWB) cast. The authors have also used external electric stimulation from the first day postoperatively on higher-risk patients with good success, and the benefits of this have been shown in recent studies.^[11]

The patient remains NWB for 6-8 weeks and is then reevaluated. At that time, the patient is allowed to bear weight in a removable walker boot if no complications have arisen and trabeculation is noted on radiographs. Additional films are obtained at approximately 12 weeks and evaluated for consolidation. If stable fusion is observed, the patient is taken out of the cast boot and allowed to progress to normal shoes. The patient should undergo physical therapy for continued ROM and strength training.

Delayed union, especially at the TN joint, is not uncommon and may require further immobilization and NWB.

For patient education resources, see the Foot, Ankle, Knee, and Hip Center and Arthritis Center, as well as Rheumatoid Arthritis.

Because of the complex nature of the procedure and the various disease states being treated, complications after triple arthrodesis are relatively common. Those most frequently encountered are as follows:

Nonunion

As with any type of arthrodesis procedure, nonunion is a potential complication. In the case of the triple arthrodesis, the TN joint is the most common site, with most literature reporting a rate of 5-10%. This is probably related to poor preparation of the joint surfaces, which are difficult to expose, especially if only a single lateral incision is used. Adding a second medial incision provides much better access to the joint and allows for a more aggressive capsule release as well as easier distraction and better exposure for complete cartilage removal. A cadaveric study by Bono showed that only 38% of the cartilage from the TN joint was successfully removed using a lateral incision alone.^[7]

Degenerative joint disease

A properly functioning foot goes through a multitude of movements with each phase of the gait cycle. A high degree of these movements takes place at the ST, TN, and CC joints. Most foot pronation and supination occurs around these joints. Once these joints are fused, a large amount of stress is transferred to the joints immediately proximal and distal. Midfoot DJD can develop with time. An important intraoperative consideration is foot position. Excessive varus or valgus alignment of the rearfoot or forefoot can accelerate the onset of DJD.

Wound healing problems

Many of these patients are elderly or debilitated from an underlying disease process that requires chronic steroid therapy. These issues can lead to delayed wound healing most commonly seen as a mild dehiscence at the edges of the incision. Excessive postoperative edema can also delay healing. A rare situation that can cause large amounts of skin slough is placing the lateral tissues on stretch after reducing a large valgus deformity. This is a good indication for an isolated TN-STJ arthrodesis through a medial approach if there are no arthritic changes seen at the CC joint.^[5] An important point that must also be appreciated is the relatively small amount of subcutaneous and fatty tissue in the foot. Dissection should be meticulous, with delicate handling of tissues, and healthy full-thickness skin flaps need to be maintained..

Nerve injury

The placement of both the lateral and medial incisions are close to underlying nerves. The lateral incision lies between the sural and the superficial peroneal nerves. Small branches from each may be transected during the procedure. The intermediate dorsal cutaneous nerve, which is an extension of the superficial peroneal, is located very close to the distal portion of this incision. Variations of these nerves do exist and can cross the path of the standard lateral incision so careful dissection is warranted. The medial incision is located in proximity to the saphenous nerve as well as the medial dorsal cutaneous nerve at the distal margin of the wound.

Entrapments within surgical scar tissue can take place in the postoperative period; however, painful neuromas rarely occur. When they do happen, standard conservative measures with appropriate medications, injections, and physical therapy should be used. If these measures fail, surgical neurolysis or proximal neurectomy with implantation into muscle is performed.

Avascular necrosis

This is a rare complication but has been reported.^[8] The predominant bone affected is the talus. The main reason for this is disruption of the blood supply while accessing the STJ, resecting a large portion of the talar head to increase correction of deformity, or excessive dissection of the talar neck while placing a screw from the talus down into the calcaneus.

Lateral instability

Lateral instability occurs for 2 main reasons. The first is malposition of the rearfoot in varus leading to excessive lateral stress on the ankle joint postoperatively. The other is inherent within the procedure. The CF ligament must often be transected for adequate exposure to the STJ. If the ligament does not heal properly, lateral ankle instability can result.

Stiff foot

Stiff foot is not so much a complication of the procedure as it is a result of the procedure. The motions of pronation and supination around the STJ allow the foot to adapt over uneven terrain. When the STJ is pronated, the entire foot becomes flexible. Conversely, when the STJ is supinated, the entire foot becomes rigid. These motions are normal and allow for shock absorption and conformation to surface terrain when pronated and propulsion when supinated. Once the three joints are fused, the foot becomes stiff and loses flexibility. This should be explained to the patient before surgery as something to expect postoperatively. Ankle motion is also affected. One report showed a 13% decrease in dorsiflexion and a 16% decrease in plantarflexion.^[9]

Outcomes are typically good with high union rates of the subtalar and CC joints. The TN joint has the highest incidence of nonunion; however, this decreases with better understanding of the procedure and stable fixation. Degenerative changes at the unfused distal and proximal joints are still a long-term complication, but this is true with any fusion procedure. A study examining 400 triple arthrodesis procedures found less than perfect results in 24.5% of patients.

Up to 10 months are required for the patient to become pain free. Return to high-impact activity is not a given. Lower-impact activities like walking, cycling, and swimming should be obtainable goals postoperatively.

The future and controversy for this procedure pertain to using external fixation devices. Proponents would argue it to be a stable fixation method that allows the patients to ambulate with partial to full weight bearing on the operative side. Others would argue that the risk of pin-tract infections is high and could be disastrous to the procedure's outcome. A study looked at 87 patients using a ring-style external fixation device. A 97% fusion at 6-8 weeks, with 36% developing superficial pin-site infections, was reported.^[10]

Orthobiologics are taking an increased roll in augmenting these procedures. Autologous bone grafting is still the product of choice when filling voids; however, it is associated with a certain degree of morbidity. Allograft bone and other orthobiologic materials are safe and effective alternatives that reduce risks to the patient.