In a triple arthrodesis , the subtalar, talonavicular (TN), and calcaneocuboid (CC) joints are included in the surgical fusion. A trend emerging over the past few years has been to try to preserve as much movement as possible in the remaining joint(s) of the hindfoot yet to create a functional plantigrade foot. Although a more limited hindfoot procedure such as a TN-subtalar arthrodesis or a subtalar-CC arthrodesis can be performed, such procedures may not reliably correct deformity. We try not to overuse the triple arthrodesis in the setting of the flexible flatfoot because osteotomy combined with tendon transfer usually is sufficient for correction of flexible deformity and generally can be expected to maintain joint motion. On the other hand, because a triple arthrodesis is so reliable a procedure, the indications for a flatfoot reconstruction should not be extended for semi-rigid deformity in order to specifically avoid an arthrodesis, because motion is not always preserved in these cases. When arthritis of the tarsometatarsal or naviculocuneiform joints is present and a triple arthrodesis needs to be performed, there is obviously a considerable amount of stress on the intervening open joint, which may ultimately require arthrodesis. Nonetheless, what we refer to as an “extended hindfoot arthrodesis” must at times be performed.
Key Wordstriple, arthrodesis, hindfoot, talonavicular, subtalar, arthritis
Overview and Approach
In a triple arthrodesis, the subtalar, talonavicular (TN), and calcaneocuboid (CC) joints are included in the surgical fusion. A trend emerging over the past few years has been to try to preserve as much movement as possible in the remaining joint(s) of the hindfoot yet also create a functional plantigrade foot. Although a more limited hindfoot procedure such as a TN-subtalar arthrodesis or a subtalar-CC arthrodesis can be performed, such procedures may not reliably correct deformity. Nonetheless, as discussed further on, these more limited approaches have a lot of merit if performed in the right patient and with careful technique.
The triple arthrodesis is an extremely reliable procedure for correction of hindfoot deformity and treatment of associated arthritis. Although the approach to the procedure may have evolved or even changed technically, over the decades this has remained a standard method for correction of severe deformity regardless of the etiology. A triple arthrodesis is performed if a simpler hindfoot arthrodesis will not be sufficient; indications include a severe flexible flatfoot deformity, a rigid flatfoot deformity, posttraumatic arthritis, severe tarsal coalition associated with arthritis or uncorrectable deformity of the subtalar and transverse tarsal joint, congenital and neuromuscular deformity, and inflammatory arthritis. We try not to overuse the triple arthrodesis in the setting of the flexible flatfoot because osteotomy combined with tendon transfer is usually sufficient for correction of flexible deformity and generally can be expected to maintain joint motion. On the other hand, because a triple arthrodesis is so reliable a procedure, the indications for a flatfoot reconstruction should not be extended for semirigid deformity to specifically avoid an arthrodesis, because motion is not always preserved in these cases. When arthritis of the tarsometatarsal or naviculocuneiform joints is present and a triple arthrodesis needs to be performed, there is obviously a considerable amount of stress on the intervening open joint, which may ultimately require arthrodesis. Nonetheless, what we refer to as an “extended hindfoot arthrodesis” must at times be performed.
Posttraumatic arthritis generally follows a talus or calcaneus fracture, but for most patients with arthritis and deformity secondary to a calcaneus fracture, a subtalar rather than a triple arthrodesis is the procedure of choice. A triple arthrodesis is usually the preferred procedure after a talar neck fracture with malunion, particularly when a varus malunion associated with arthritis is present ( Fig. 30.1 ). In the presence of a middle facet tarsal coalition, a subtalar arthrodesis is sufficient, and a triple arthrodesis is preferred only in the setting of arthritis or deformity, which is typically associated with a naviculocuneiform coalition, and when the coalition is not resectable. In patients with inflammatory arthritis, caution is indicated in selecting an isolated TN fusion, even when this is the only involved hindfoot joint. An isolated TN arthrodesis is associated with a higher incidence of nonunion, and once this occurs, correction is far more difficult because of bone loss and erosion, even with a triple arthrodesis.
Over the years, we have been performing more hindfoot arthrodesis procedures through a single medial incision. Initially, we identified correction of a severe fixed valgus deformity as the specific indication for use of this approach, to limit the risk of lateral wound complications occurring as the hindfoot position is corrected to neutral (when using a lateral incision). This rationale still holds; nevertheless, we have been very pleased with the ability to correct deformity and associated arthritis from a single medial incision. Although the medial approach to triple arthrodesis is discussed in more detail further on, the concept of use of a single incision to perform a hindfoot correction is important. As might be expected, the inclusion of the CC joint in the fusion in performing a triple arthrodesis from the medial approach is difficult. In our own experience, both anatomic observations and outcomes in clinical series have demonstrated that the CC joint can be exposed and included in the arthrodesis with this approach. Nonetheless, as supported by results with our frequent use of the medial approach to correct deformity, it is apparent that the CC joint does not always need to be included in the arthrodesis ( Fig. 30.2 ). In performing the more limited arthrodesis (subtalar and TN), however, it is important to recognize the potential for inferior subluxation of the cuboid relative to the calcaneus. This subluxation will produce a fixed rotation of the transverse tarsal joint, causing pain under the cuboid and the base of the fifth metatarsal. A good example of this potential problem is presented in Fig. 30.3 : after a limited arthrodesis was performed using a medial approach, intraoperative fluoroscopy revealed that the CC joint was inferiorly subluxated, demonstrated by pushing up from below the cuboid to correct the subluxation, and could be corrected only by including the CC joint in the arthrodesis. There are probably fewer indications for a limited lateral arthrodesis, such as a subtalar and CC arthrodesis, but when the correction can be obtained, it is well worth trying to leave the TN joint untouched.
The Lateral Incision
The incision is made from the tip of the fibula extending distally down over the sinus tarsi toward the CC joint ( Fig. 30.4 and ). On the inferior surface of the incision, the peroneal tendon sheath is identified, and the terminal branch of the sural nerve must be looked for more distally in the incision. Both the peroneal tendons and the sural nerve are retracted inferiorly, and the incision can be deepened down on the periosteum directly over the calcaneus. The incision is extended distally toward the CC joint and then further toward the base of the fourth metatarsal. In the terminal aspect of the incision, care must be taken to ensure that no branches of either the sural or lateral cutaneous branch of the superficial peroneal nerve are present. The retinaculum of the undersurface of the peroneal tendon sheath is stripped and elevated off the lateral wall of the calcaneus. We prefer to save the contents of the sinus tarsi, because in the event of a wound dehiscence, sufficient tissue may be present for covering the peroneal tendons. The soft tissues are elevated sharply off the floor of the sinus tarsi until the anterior aspect of the posterior facet of the subtalar joint is visualized.
The incision is deepened directly onto the periosteum along the CC joint, and a large periosteal elevator is used to strip the lateral aspect of the calcaneus and then the cuboid. The peroneal retinaculum is retracted inferiorly, and a knife blade is inserted directly into the CC joint and then manipulated dorsally to cut the cervical ligament. The knife blade is swept vertically through the CC joint and then rotated dorsally across the bifurcate ligament and directly into the posterior facet with one maneuver. The cuboid bone should now be freely mobile, and the articular surface of the entire joint is denuded with a 2-cm flexible chisel, as well as with a rongeur and curette. Removal of more than 2 mm of bone and cartilage on either side of the joint is unnecessary. An important point here is that regardless of the type of deformity, a lateral bone wedge is not removed, and the position of the hindfoot is corrected with translation and rotation, not with resection of bone wedges. A laminar spreader is inserted into the CC articulation to check that all of the cartilage has been removed. Care must be taken to ensure that a minimal amount of bone is resected, to minimize any shortening of the lateral column. A saw may be used to remove the subchondral bone and the remaining cartilage simultaneously. Although this technique is highly efficient, the risk of heat necrosis and excessive shortening must be considered. We prefer not to use a tourniquet when using this technique to minimize heat necrosis and risk of nonunion and do not advocate this maneuver in the setting of a flatfoot given the shortening that will occur.
A laminar spreader is inserted into the sinus tarsi, and when it is placed on stretch, the interosseous ligament is easily visualized and cut to gain access to the posterior aspect of the subtalar joint and the middle facet. A 1-cm flexible chisel or osteotome is used to denude the articular surface of the posterior facet. As with the CC joint, minimal bone is removed. The use of curette directed from posterior to anterior is effective at removing any loose or remaining cartilage. Irrigation is used to clear out debris to accurately visualize any remaining articular cartilage to ensure a thorough joint preparation is performed. The posterior facet must be debrided down to bleeding healthy subchondral bone ( Fig. 30.5 ). Care is taken with the debridement of the posteromedial corner of the joint, where the flexor hallucis longus tendon is at risk for injury from the chisel. Finally, the more medial aspect of the subtalar joint and the middle facet must be completely denuded, including the undersurface of the talus and the dorsal surface of the middle facet. Before the medial incision is made, the space between the navicular and the cuboid is debrided with a rongeur. This debridement adds another segment and bone surface to the fusion mass and converts the triple arthrodesis to a “quadruple arthrodesis” ( Fig. 30.6 ). The TN joint is clearly the most difficult of the three joints to visualize and to debride adequately. With either a varus or valgus deformity, the TN joint is only partly visible, but it must be distracted to permit visualization in its entirety. It may be tempting to approach the TN joint from the lateral incision, but only one-third of the joint is visible from this incision, perhaps more if the hindfoot is fixed in varus. Of note, however, the TN joint is the one joint that will end up in nonunion if the joint debridement is not performed carefully. The medial incision is made medial to the anterior tibial tendon, extending from the ankle toward the medial cuneiform bone ( Fig. 30.7 ). The extensor retinaculum is incised, and the anterior tibial tendon is retracted laterally, exposing the deep subcutaneous tissue. Partially cutting into the extensor retinaculum and the medial edge of the anterior tibial tendon more distally may be necessary at times, because the tendon blends into the fibers of the retinaculum.
After the dissection, a retractor is inserted to pull aside the anterior tibial tendon and the medial soft tissues. The periosteum along the navicular bone is stripped, and then the TN joint is fully exposed with a curved periosteal elevator. Inserting an elevator directly into the joint to fully expose the head of the talus, followed by further stripping of the soft tissue dorsally and laterally, is useful. When a severe valgus deformity is corrected, pushing the midfoot into varus and then loosening the tension of the medial TN joint are helpful. We then cut around the medial joint from the outside in, through the remnant of the posterior tibial tendon and spring ligament into the TN joint. This step makes opening and distraction of the joint far easier. A smooth laminar spreader ( Fig. 30.8A ) or rongeur is inserted into the joint and then exchanged for a toothed laminar spreader to facilitate distraction of the joint. This, however, may crush the joint surface and is not our preferred method of joint exposure, which is to use a pin distractor or by using pins inserted through a laminar spreader through which distraction can be applied (see Fig. 30.8B ). The entire joint is denuded of cartilage using a 1-cm flexible chisel. An important consideration with the navicular is that because this bone can be hard, it can fragment if not debrided gently. The same contour must be maintained with debridement of the talar head while a small flexible chisel is used. Presence of osteopenia increases the risk of injury with use of the laminar spreader, which may crush into the talus. At the completion of the joint debridement, surfaces should appose well, with maintenance of the overall joint contour. If bone is resected from either joint surface, the medial column of the foot will be shortened, followed by a varus malunion.
Once the joints have been adequately visualized and their surfaces debrided, the final preparation is accomplished with a 2.0- or 2.5-mm drill bit to thoroughly perforate each bone surface. This aspect of the procedure is particularly important when the bone is sclerotic, which is often the case with the navicular. A Kirschner wire (K-wire) is associated with increased heat generation relative to a drill and this is not preferred for joint preparation.
Reduction of Deformity and Fixation
The reduction maneuver of the hindfoot relative to the forefoot is critical ( ). For most deformities, the hinge point is the TN joint; therefore this is the joint that we reduce and fix first. The foot is rotated around the axis of the TN joint, and as the forefoot is adducted, the first metatarsal is plantarflexed to correct the forefoot relative to the hindfoot ( Fig. 30.9 ). This maneuver is unsuccessful only when the subtalar joint is rigid and the calcaneus is laterally translated, in which case we fix the subtalar joint first. In the latter instance, then the TN joint may not line up perfectly, although clinically the forefoot alignment may appear to be corrected. For some very severe deformities that feature gross posterior subluxation of the subtalar joint, it is helpful to address this problem first by inserting a laminar spreader between the anterior process of the calcaneus and the lateral process of the talus ( Fig. 30.10 ). This maneuver forces the calcaneus forward, reducing the subtalar subluxation.
In the past, we routinely used cannulated screws for fixation of the arthrodesis of each of the joints, and for the most part we still prefer screws for fixation. We currently use one 6.5- or 7.0-mm cannulated screw for the subtalar joint and one or two 4.5- to 5.5-mm screws for the CC and TN joints. The specific screw diameter is dependent on which implant company is preferred. We have noted, however, that it is difficult to obtain good placement of screws across the TN joint. One screw is easy to insert from the plantar medial aspect of the navicular, but the available space is not always sufficient for a second screw, and even use of two screws inserted from the medial aspect of the joint does not provide adequate fixation of the dorsal joint surface ( Fig. 30.11 ). The fixation of the TN joint may then be quite inadequate, because the joint is compressed predominantly medially, which may be associated with a delayed union or even nonunion of the joint fusion ( Fig. 30.12 ). If we are not satisfied with the fixation in the TN joint after placement of one or more screws, we supplement this with a nitinol compression staple or dorsal two-hole locking compression plate ( Fig. 30.13 ). The use of nitinol compression staples for the Chopart joint can be considered in the setting of a triple arthrodesis as an alternative to screw fixation ( Fig. 30.14 ). If isolated staple fixation is considered, two staples should be placed across each joint to ensure rigid fixation and improve angular stability.
We generally begin with the TN joint fixation for patients with primarily an abduction deformity. One or two guide pins are inserted into the TN joint, the first from the inferior medial tuberosity and the second from a slightly more dorsal location, immediately adjacent to the anterior tibial tendon. The head of the second, more dorsal screw will be close to the naviculocuneiform joint. The heads of all screws must be well buried flush with the margin of the bone and not protrude into the naviculocuneiform joint. As noted, this configuration of screw fixation will provide fixation and compression of the medial aspect of the TN joint only. To improve the surface area that is compressed, use of a dorsolateral screw in parallel to the medial screw or a dorsolateral staple/plate is advocated. The use of a screw from the navicular to the calcaneus will improve torsional rigidity; however, the clinical superiority of this screw has not been defined. We only use this screw from the navicular into the calcaneus when the anatomy of the joint is difficult for other methods of fixation.
A few alternatives are available for insertion of the subtalar joint screw. The traditional method is to introduce a guide pin from the undersurface of the calcaneus, but off the weight-bearing surface of the heel. The problem with this method is that pin placement is not always accurate and the screw is frequently not exactly in the body of the talus. Another method is to insert the guide pin from the top of the talus just anterior to the ankle joint and then direct the guide pin all the way out the back of the heel. This maneuver permits determination of the exact starting position of the guide pin in the center of the talus. The pin is pulled out of the heel until the length in the body of the talus is correct, and then the screw is introduced from the heel up into the talus. The use of a headless screw may be considered to avoid late hardware irritation and the need for removal. Given the low profile (buried under the tuberosity) of a headless screw, the screw may be placed from the weight-bearing aspect of the calcaneus, which allows for the screw trajectory to be angulated more vertical, facilitating placement into the center of the talar body. In general, when a triple arthrodesis is performed, only one screw is placed across the subtalar joint, given the increased rigidity to the subtalar joint imparted by the TN fusion.
The CC joint is fixed last, using a posterior-to-anterior approach. The lateral aspect of the CC joint is flat, and screw insertion will not be easy unless the surface of the calcaneus is prepared by making a notch with a chisel 1 cm proximal to the articular surface ( Fig. 30.15 ). This step is important in obtaining a solid fusion, and the lateral aspect of the foot must be elevated across the CC joint. Although the TN and subtalar joints are already fixed, some lateral mobility will still be present, and if the cuboid bone drops down, weight bearing will be painful as a result of a malunion. It is therefore imperative to elevate the inferior aspect of the cuboid, to create a plantigrade lateral weight-bearing surface. The guide pin for a 5.5-mm screw is inserted across the notched surface into the CC joint, followed by a 35-mm partially threaded screw. If the joint surface is very flat and a screw cannot be easily inserted, then use of a small locking compression plate is ideal (Orthohelix, Akron, United States) ( Fig. 30.16 ). The use of a compression nitinol staple may be considered for the CC joint as well.
Once fixation has been completed, the stability of the ankle should be checked, particularly with those procedures that are performed for a severe valgus deformity. As a result of the chronic valgus impingement between the calcaneus and the fibula, there is frequently erosion of the calcaneofibular ligament leading to ankle instability. In the case illustrated in Fig. 30.17 , gross instability was noted after screw fixation, and repair was accomplished with a modified Chrisman-Snook procedure.
There are types of deformity that are more amenable to an alternative approach to the standard triple arthrodesis outlined previously. In particular, where there is a cavus or equinus deformity with the apex at the navicular, a modified triple described as a “beak” arthrodesis can be performed where the navicular is slid into a slot cut in the talar head. The dorsal and proximal articular surfaces of the navicular are cut sharply with a small saw, and a reciprocal cut is made in the head of the talus to receive the navicular. This then allows the cavus deformity to be corrected into a more neutral planar position in the sagittal plane ( Fig. 30.18 ).
Two incisions are ideal for complete visualization of all three joints.
A single medial incision approach to the triple arthrodesis is useful to correct fixed hindfoot valgus deformity or when a modified triple arthrodesis with fusion of the talonavicular (TN) and subtalar joints is performed.
The “fourth joint” of a triple arthrodesis is the recess between the navicular and the cuboid. This is the so-called “quadruple arthrodesis.”
Minimal bone should be resected, and wedges of bone should not be removed, because the resulting defect will lead to shortening of the foot and possibly malunion. Correction of deformity is obtained by translation and rotation, not by resection of wedges of bone.
Rigid internal fixation is preferable, and we have found that cannulated screws are very useful to maintain and hold reduction. As an alternative to screws, small locking plates or nitinol compression staples are very useful to maintain the alignment of the TN and calcaneocuboid (CC) joints and may be used in conjunction with a screw if desired.
There are really no hindfoot deformities that cannot be readily corrected with a triple arthrodesis. Even with gross dislocation of the hindfoot and severe subtalar deformity, this can be corrected. For these severe deformities, we recommend that a computed tomography scan is obtained to better appreciate the location of the subtalar joint, particularly where there is a peritalar dislocation. It is, however, essential that an x-ray of the ankle is obtained both pre- and postoperatively ( Fig. 30.19 ). One must only be aware of the ankle joint in these cases, since the triple will place an increased load on the tibiotalar joint, which may fail with deformity and arthritis sooner than expected ( Fig. 30.20 ).
We have not found it necessary to use bone graft in many cases because of the creation of good bleeding cancellous bone surfaces, which are always well apposed. However, with the recent literature advocating graft augmentation for arthrodesis of the ankle and hindfoot, we now routinely use autograft or allograft within the fusion sites. Bone graft is essential in cases of severe deformity with a nonunion consequent to a previously attempted triple arthrodesis when a void exists after the debridement and realignment.
The reduction maneuver before insertion of the cannulated guide pins is important, and the hinge of the TN joint is the key to correct alignment. If a severe fixed valgus deformity of the subtalar joint is present, then we fix this joint first, followed by the TN joint, which then has to be more forcibly adducted and plantarflexed. This will result in a lateral radiograph where the navicular is plantarly translated relative to the talus. Although this radiographically appears abnormal, it is required to create a plantigrade foot in deformity cases when the subtalar joint is fixed first.
Severe abduction of the forefoot with marked subluxation of the TN joint may require a structural bone graft with lengthening of the CC joint for correction ( Fig. 30.21 ). It is not easy to predict which patients will benefit from a lengthening of the lateral column during a triple, for example with a bone block inserted into the CC joint. Even in those cases where the abduction is severe, one is at times able to swing the midfoot around by very slightly removing more bone from the head of the talus. The latter is easy to see and anticipate in Fig. 30.21 , where severe abduction was present. However, in Fig. 30.22 , there was no abduction present, only deformity that is visible on the lateral foot with inferior subluxation of the talus and severe hindfoot valgus. In this case, following the TN and subtalar joint fixation, there was a large gap present at the CC joint, and a graft was inserted.