FUSIONS OF THE FOOT AND ANKLE IN PATIENTS WITH RHEUMATOID ARTHRITIS
April 19th, 1996
Steven B. Weinfeld, MD: Lew C. Schon, MD;
and Mark S. Myerson, MD
Abstract
Rheumatoid arthritis commonly affects the foot and ankle, and those patients for whom nonoperative methodologies fail require surgical intervention. The most commonly affected area is the forefoot, followed by the hindfoot, midfoot, and ankle. In the forefoot, first metatarsophalangeal fusion, along with resection of the lesser metatarsal heads, is an effective means for correcting deformity and alleviating pain. Some authors recommend isolated talonavicular fusion for hindfoot arthritis. However, our experience indicates that the addition of calcaneocuboid fusion or triple arthrodesis allows a more durable foot with higher fusion rates. Midfoot arthritis with or without deformity can be corrected with fusion and corrective osteotomy as needed. Ankle arthrodesis is often necessary due to advanced disease or secondary to increased stress from previous arthrodeses. In general, we recommend fusion utilizing screw compression techniques with local bone graft. The application of these methods has produced a high fusion rate, minimal complications, and a plantigrade, shoeable foot.
Overview
Rheumatoid arthritis can affect multiple joints, including those in the lower extremities. Foot pain is the presenting complaint in approximately 16% of all patients with rheumatoid arthritis and begins in or around the ankle in 4% of these cases (1). Patients with long-standing disease will often have foot and ankle symptoms typically parallelling those in the hand and wrist. As in the upper extremity, conservative treatment with oral medications, physical therapy, braces, steroids, and injections is the mainstay of care. Shoe style changes, pedorthic shoe modifications, and ambulatory aids such as platform walkers are often beneficial.
Despite these measures, some patients continue to deteriorate and surgery must be considered. Historically, arthroplasty of the hip and knee have met with considerable success; however, in the foot and ankle, arthrodesis continues to be the most frequently indicated method of surgical correction and stabilization. Arthrodesis should be considered for patients with intractable pain, severe deformity, ulceration, and decreasing ability to ambulate. The following discussion will include indications for arthrodesis of the forefoot, midfoot, hindfoot, and ankle, as well as our preferred surgical approaches and technical tips. We will also discuss our postoperative protocol and briefly review some complications.
One of the perioperative concerns in a patient undergoing fusion for rheumatoid arthritis is steroid management. Patients who are taking more than 5 mg of prednisone per day have suppression of their endogenous adrenal corticosteroids, and will require perioperative steroid boluses when major procedures are performed. This would routinely include a hydrocortisone dose of 100 mg immediately preoperatively, two doses postoperatively, and then a return to their normal oral prednisone dose. All nonsteroidal medication should be stopped, preferably within 7 days before surgery, to ensure normal platelet function. Patients on Methotrexate, Plaquenil, and Gold may continue this treatment, although this is controversial as some surgeons have reported an increased incidence of wound complications in such patients.
Other perioperative concerns include the use of prophylactic antibiotics, blood loss, and the choice of anesthetic. The administration of prophylactic antibiotics minimizes the risk of infection and routinely consists of a first-generation cephalosporin intravenously in the operating room. We do not routinely use a tourniquet, but blood loss during surgery can be decreased by placing the patient in the Trendelenburg position. If preoperative chronic anemia is severe and substantial blood loss is expected, the tourniquet may be used. In our experience, most of the arthrodesis procedures, even those of the hindfoot and ankle, can be performed under a local anesthetic block with or without intravenous sedation. This is fortunate since patients with rheumatoid arthritis often have some degree of cervical spine arthritis, with or without instability, that could cause difficulty with intubation. If general anesthesia with intubation is anticipated, lateral flexion-extension cervical spine radiographs are mandatory.
Adequate postoperative analgesia is crucial to early mobilization and recovery. Most patients on preoperative oral steroids do not require high doses of narcotic medications, but those who are not should expect to experience pain consistent with the magnitude of the reconstruction.
Hallux Interphalangeal Joint Arthrodesis
Arthrodesis of the hallux interphalangeal (IP) joint is performed for hyperextension of the toe at the IP joint, with or without a plantar nodule. Hyperextension leading to instability most often is associated with limited motion of the hallux metatarsophalangeal joint. This deformity may also occur after a Keller procedure, with cocking up of the toe, or after sesamoidectomy. Arthritis of the IP joint with persistent pain is another indication for arthrodesis. This arthrodesis can be combined with an extensor hallucis longus transfer for the treatment of a hallux varus or claw hallux deformity. The true Jones procedure with IP fusion and extensor hallucis longus transfer to the metatarsal head is rarely performed in rheumatoid patients, as flexible cavus foot deformities are not seen.
The recommended position of IP arthrodesis is neutral to 5o of plantarflexion. If an ulcer or plantar callus is present, 5 to 10o of plantarflexion is recommended (8).
The surgical approach is through a dorsal L-shaped incision over the IP joint of the hallux. The transverse limb of the incision is distal and parallel to the joint surface. The longitudinal limb courses along the medial or lateral border of the proximal phalanx. The dissection is taken sharply to the extensor tendon, which is incised transversely to allow adequate repair. The joint surfaces are denuded of remaining cartilage and sclerotic bone by making flush bone cuts using the microsagittal saw. A 3.5-mm drill is then passed from the IP joint distally to the end of the distal phalanx, and a stab incision is made at the tip of the hallux. This drill hole should be widened slightly to permit gliding of the 4.0-mm cancellous screw. A 2.5-mm drill is then passed retrograde across the IP joint into the proximal phalanx. A partially or fully threaded 4.0-mm cancellous bone screw is then placed across the fusion site with axial compression, while inserting the screw to prevent rotation (Fig. 1). A K-wire may be necessary in addition to the screw to provide rotational stability. The extensor tendon is then repaired and the wounds are closed. Bone grafting is not usually necessary.
Postoperatively, the patient's foot is placed in a wooden shoe. The patient is full weight-bearing as tolerated. Full weight-bearing in a regular shoe can be resumed at approximately 6 weeks, depending on bone healing.
Complications of the procedure include nonunion of the arthrodesis site due to poor bone quality or malalignment of the joint surfaces. One particular problem that can occur is hyperextension at the IP joint with a malunion or nonunion, which may result in a painful callus underneath the IP joint of the great toe. Hyperflexion can also occur but is uncommon. These can be treated either with trimming of the bony prominences or revising the fusion.
Arthrodesis of the First Metatarsophalangeal Joint
Arthrodesis of the first metatarsophalangeal (MTP) joint is performed for painful MTP arthritis, hallux rigidus, a severe hallux valgus deformity, osteonecrosis of the first metatarsal head, or instability, or as a salvage for a failed implant arthroplasty or Keller procedure (2). In a rheumatoid patient with dislocation of the lesser MTP joints, the first MTP fusion is combined with a resection of the second through the fifth metatarsal heads (6).
Two techniques are used for forefoot reconstructions. The standard dorsal approach is used for mild to moderate deformities; the less frequently used plantar approach is reserved for severe deformities. Generally, 1 of every 15 cases is appropriate for the plantar approach.
The indications for the plantar approach include severe dislocation of the MTP joints where the proximal phalanges are bayonetted at the level of the metatarsal neck or shaft. When this situation occurs in conjunction with large plantar nodules, a plantar technique would be more expeditious. This technique involves making a transverse incision, excising the thickened skin, calluses, bursa, and nodules down to the metatarsal heads. Care is taken to protect the neurovascular bundles that lie dorsal to their normal location in between the metatarsal heads. Metatarsal heads are then resected using a microsaggital saw. The proximal phalanges should then be delivered into the wound plantarly. This is not possible until release of the extensor tendons is performed through small dorsal incisions. Adequate bone is removed from the metatarsals, until there is a gap between the proximal phalanx and the metatarsal. Hemiresection of the proximal phalanx, as described by Clayton (4), is rarely required. After all heads have been resected, the toes are pinned by running the pins anterograde and leaving the wires protruding from the tips of the toes. All the toes should be pinned first, before they are reduced and pinned sequentially to the metatarsals. It is difficult to assure the alignment of the pins in the metatarsal shafts. This can be done under direct vision for the first one or two toes with some retraction, but occasionally needs to be done by feel or confirmed radiographically. The wound is then closed with 3-0 nylon suture. The first MTP joint is then fused in the normal fashion, except that it is often necessary to excise the sesamoids in these cases.
A dorsal approach is indicated when the MTP dislocation is not severe, with the proximal phalanx positioned distal to the metatarsal neck. In this case, small, soft plantar bursal sacs, or rheumatoid nodules may be present. An incision is made between the second and third toes distally and is extended for 4 to 5 cm proximally between the second and third metatarsal shafts. A second parallel incision of the same length is made between the fourth and fifth toes. Sharp dissection is carried out through the subcutaneous tissue, avoiding excessive subcutaneous dissection, until the plane of the extensor tendons is reached. Once this is reached, the extensor tendon is identified and transected as far proximally as possible.
The tendons are then pulled distally, and dissection is performed plantarly along the course of the tendon leading to the MTP joint. Once the base of the proximal phalanx is identified, a capsulotomy and synovectomy is performed. Frequently the collateral ligaments have been destroyed by inflammation and dislocation and have been replaced by fibrous tissue. A small, thin, gouge is inserted between the metatarsal head and the base of the proximal phalanx. Using this tool, the toe is levered distally, releasing the metatarsal from its plantar tissues, which are often contracted and adherent to the head. Two Hohman retractors are placed along the neck of the metatarsal, leaving the gouge between the toe and the metatarsal head, and an oblique cut is made, going from dorsal distal to plantar proximal with a microsagittal saw. The entire metatarsal head (including the condyles) is removed by using a gouge going through the osteotomy site, or using a bone cutter as an elevator to lever the metatarsal head out of the wound. It is difficult to obtain purchase on the metatarsal head with a towel clamp or a Kocher clamp, as the metatarsal head usually fragments. A screw modified to function as a cork screw may facilitate removal of the metatarsal head. This is similar to the technique of femoral head removal when doing a hip replacement for a neck fracture.
After completing the second metatarsal head resection, the same exposure technique is used for the third MTP joint. When the cut of the third metatarsal head is performed, the cascade of the metatarsals should be recreated so that the third metatarsal is shorter than the length of the second metatarsal. Through the incision between the fourth and fifth metatarsals, the metatarsal heads are removed, again making sure that the cascade is preserved by cutting each metatarsal shorter than the one medial to it. The surgeon should attempt to palpate the defect when the metatarsal head has been removed to ensure that there are no bony or cartilaginous fragments that remain in the depth of the wound. These may be a source of persistent pain after this procedure.
Once all the metatarsal heads have been resected, pins are inserted in anterograde fashion, down the base of the proximal phalanx, through the tip of the toe, and then retrograde into the metatarsal shaft. In osteoporotic bone, the pins may not gain good purchase in the proximal metaphyseal bone. Therefore, the pins should then be driven into the cuneiform as well as the cuboid to prevent loosening of the fixation. Before placing the pins across the MTP joint space, the extensor tendons are placed plantar to the metatarsal shaft and interposed between the base of the proximal phalanx and distal metatarsal. The wire skewers the tendon to preserve its position. The toe should be held in slight distraction relative to the metatarsal shaft to permit some formation of scar tissue between the bones.
The MTP fusion may be done through a dorsal or a medial incision, depending on previous surgeries. The medial incision is made midline and carried down to bone, avoiding the dorsal medial or plantar medial cutaneous nerves. Subcapsular dissection is performed around the metatarsal head medially, dorsally, and plantarly, and around the entire base of the proximal phalanx. If the degree of lesser MTP dislocation is severe, requiring marked shortening of the lesser metatarsal shafts, then the sesamoids should be removed to prevent pain under the first metatarsal head. The base of the proximal phalanx is cut by holding the toe and using the microsaggital saw to create a resection of the base of the proximal phalanx in the subchondral bone that is perpendicular to the long axis of the hallux. This sliver of bone should remove about 3 mm at the periphery, but 1 to 2 mm at the base of the concavity of the proximal phalanx.
Once this perpendicular cut has been performed, the toe is positioned in proper alignment. Generally, we strive for 10 to 15o of valgus and 10 to 15o of dorsiflexion, depending on the patient's shoewear needs and the level of the metatarsal head resections. With the toe held in proper position, a resection of the metatarsal head is made 0 to 15o off the perpendicular to the shaft of this metatarsal, parallel to the proximal phalanx cut. This then serves to line the toe up in the proper amount of dorsiflexion and valgus. The toe is then pinned with K-wires and, with the arthrodesis site closed, the alignment is checked clinically and fluoroscopically. The dorsiflexion of the big toe may be determined by placing a flat metal plate underneath the forefoot. In a typical situation where the patient will be wearing low heeled or flat shoes, a heel lift of approximately 1/4 inch is anticipated. This is simulated during surgery by taking a 1/4-inch block of metal and placing it under the heel between the foot and flat metal plate. If the distal phalanx of the toe just touches the plate, then this is the correct position for the hallux. It is important to note that the surgeon may be fooled by the amount of dorsiflexion or plantarflexion of the IP joint of the hallux. It is important that the toe should just touch with the IP joint in about 3 to 4o of flexion. If the patient has voiced a desire to wear a higher heeled shoe, such as a 1/2-inch heel, then a 1/2-inch block is placed underneath the heel, and the measurement is made, again achieving a toe tip that just touches the plate.
Fixation is achieved by placing a screw from the plantar aspect of the metatarsal head in the sulcus between the medial and lateral plantar condyles and distally down the shaft of the proximal phalanx. Although a cannulated screw may be used, we prefer using a 3.5-mm drill in the metatarsal head and then the 2.5-mm drill down the shaft of the proximal phalanx. Usually a 40-mm long, 4.0-mm diameter AO partially threaded cancellous screw is used (Synthes, Paoli, PA). Another screw is then placed in the dorsal medial aspect of the metatarsal head, heading to the base of the proximal phalanx, in a slightly oblique fashion. The head of the screw should be countersunk in the bone if possible. At times, countersinking the screw will compromise fixation. In these cases, it is preferable to leave the screw prominent and remove it subsequently. It is not uncommon to have the great toe fixed slightly dorsal and valgus relative to the plantarflexed toes, which are pinned along the line of the metatarsals. The skin is closed with nylon suture, and a compression dressing is applied.
Postoperatively, the patient is allowed to walk on the heel and lateral aspect of the foot. At 1 week, the dressing is changed; at 2 to 3 weeks, the sutures are removed; and at approximately 6 weeks, the pins are removed. This procedure is performed in the office. Between postoperative weeks 6 and 12, the patient is allowed to progressively increase weight-bearing on the forefoot, depending on healing of the fusion site. Recovery may be 3 months, but complete resolution of aches, pains, and swelling may require a full year.
Failures may occur due to malunion or nonunion of the MTP joint or to pain in the IP joint with clawing of the hallux or rubbing at the tip of the hallux or at the top of the IP joint. Failure may also occur due to bony overgrowth at the end of the metatarsal resection sites. Patients may also have recurrent clawing of the toes, which requires proximal IP joint resection, or a painful IP joint from hyperextension or from prominence of the head of the proximal phalanx distally at the IP joint. The patient may note a lack of push off power or a floppiness of the lesser toes, which can be disturbing; however, if they are prepared for it, they are usually very happy to trade severe metatarsalgia for weakness or floppiness of the toes.
Tarsometatarsal Arthrodesis
Rheumatoid arthritis may involve isolated or multiple joints in the midfoot, although the midfoot is involved less frequently than the forefoot and hindfoot. The instability can be multiplanar in addition to articular destruction from the arthritic process. It is important to determine whether the medial or lateral columns are involved, or the entire midfoot, before any attempted arthrodesis. When there is arthritis and pain without deformity, an in situ fusion can be performed; however, if deformity is present, the arthrodesis must include a correction of the deformity. A first metatarsocuneiform fusion may also be performed when stabilizing a severe hallux valgus deformity (9).
A dorsal longitudinal incision is made over the joint that requires fusion. If two joints, adjacent to each other require fusion, such as the first and second metatarsocuneiform joints, an incision is made dorsally between the two. In the case of the incision between the first and second metatarsals, care must be taken to avoid the neurovascular bundle, which is in this location. Sharp dissection is carried out down to the bone. Subperiosteal and subcapsular dissection is then carried out sharply, exposing the affected joints. Next, using a chisel or a microsaggital saw, cartilage and subchondral bone is removed. It is important to ensure that enough cartilage is taken plantarly to avoid dorsiflexion at the fusion site and dorsal malunion. The surfaces are then drilled multiple times with K-wires; sometimes a chisel is used to gently feather the fusion site to promote healing. Next, a 4.0- or 4.5-mm cannulated screw system is used. First, the guidepin is drilled across the fusion site from the metatarsals to the cuneiform. After the length of the screw is determined based on the positioning of the pin, the screw is inserted. The tissues are reopposed with vicryl suture and the skin is closed with nylon suture.
A compression dressing is applied, followed by a splint or a postoperative shoe. If just one or two medial joints are fused, the patient may ambulate on the heel and outer aspect of the foot. If the entire medial column is fused (first, second, and third metatarsocuneiform joints), then it may be advisable to keep the patient non-weight-bearing for 2 weeks, followed by progressive weight-bearing in a boot brace beginning 6 weeks postoperatively. Full weight-bearing is allowed on the fused joints by 3 months, assuming that arthrodesis has been achieved.
If the foot is markedly collapsed, or if there is a rocker-bottom foot deformity, as is sometimes the case in patients with Lupus and neuropathy, it may be worthwhile to achieve correction through a medial approach to the foot and excise a small plantarly based wedge, with its apex at the dorsal aspect of the metatarsocuneiform joints. Achilles tendon lengthening may be required when correcting a rocker-bottom deformity in a patient with an equinus contracture of the hindfoot. This technique is detailed elsewhere in this issue (see "Plantar Exposure for Midfoot Rocker-Bottom Deformities"). With this method, the surgeon uses a plantar plate, or medial and plantar plates, for fixation.
Some patients with a severe hallux valgus and wide intramedullary angle, even those with some arthritic changes of the first MTP joint, may benefit from an isolated first metatarsocuneiform fusion, performed in conjunction with lesser toe corrections as indicated (Fig. 2). It is often tempting, when looking at a foot preoperatively with a very wide forefoot region and pronounced bunion, to recommend a first MTP fusion, especially given arthritic findings on the radiographs. Clinically, this is a flat foot. These hallux MTP joints are often asymptomatic and will benefit from realignment and preservation of the joints. In these cases, the instability of the first metatarsocuneiform joint is addressed with a fusion, thereby reconstituting the arch, reducing the intermetatarsal angle, and bringing the metatarsal head in line with the great toe. Arthrodesis of the medial column of the midfoot usually is well tolerated because of the small amount of motion at the first, second, and third tarsometatarsal joints. However, if the mobile fourth and fifth rays are fused, functional loss is increased substantially.
Complications include nonunion or malunion of the fusion site. The symptomatic nonunion can be treated with a local or iliac crest bone graft and additional internal fixation. Other complications that can occur are malalignment of the joints, as well as a neuroma of the dorsal aspect of the foot at the incision site. Skin slough is always a possibility when carrying out extended fusions through a dorsal incision, especially in rheumatoid patients. Meticulous handling of the skin edges from the time of surgery to postoperative immobilization may help minimize this problem. Skin grafting or flap coverage may be necessary for an extensive loss of tissue.
Hindfoot Arthrodesis
Rheumatoid involvement of the hindfoot joints (the talonavicular joint, calcaneocuboid, and subtalar joints) is common. It is often necessary to perform an arthrodesis for severe arthrosis or deformity of one or all the joints of the hindfoot. Although isolated talonavicular fusion has been advocated (5), in our experience, it can be difficult to obtain an isolated fusion of the talonavicular joint. In most cases, we combine it with at least a calcaneocuboid fusion to increase the fusion rate with little added morbidity. Technically, the talonavicular joint is a difficult joint in which to obtain anatomic fusion, as care must be taken not to shorten the medial column of the foot. With fusion of both the talonavicular and calcaneocuboid joints, nearly all subtalar motion is eliminated. Subtalar arthrodesis also results in loss of inversion and eversion of the hindfoot, which can give patients a problem with ambulation on uneven terrain. Generally, however, this procedure is well tolerated.
Subtalar arthrodesis, the most common fusion in the hindfoot, is usually performed in association with other hindfoot fusions. Many techniques have been described for this type of fusion, including intraarticular, extraarticular, and bone block interposition techniques (1,7,12). Internal fixation has also been used, employing screws, staples, or K-wires.
For the triple arthrodesis technique, a lateral incision is made, beginning at the tip of the fibula, extending over the sinus tarsi and the anterior process of the calcaneus, ending up over the cuboid. Plantar sharp dissection is carried out with minimal subcutaneous undermining, down to the bone. Subcapsular and subperiosteal dissection is carried out dorsally into the sinus tarsi, exposing the posterior and medial facets of the subtalar joint. Insertion of a lamina spreader facilitates access to the posterior facet. At the calcaneocuboid joint, dorsal and plantar dissection is carried out as well. The second incision is then made just medial to the tibialis anterior tendon over the talonavicular joint. Plantar sharp dissection is carried down to the talonavicular joint. Subperiosteal dissection is carried out, exposing the joint. Next, cartilaginous surfaces are removed down to bleeding subchondral bone in the talonavicular, talocalcaneal, and calcaneocuboid joints.
Then the hindfoot is reduced with slight valgus of the heel and plantigrade position of the forefoot. It is important not to correct the hindfoot excessively into neutral, which could cause the talonavicular joint to supinate. It is helpful to manually hold the corrected heel position and work the transverse tarsal position until a balance is achieved between the hindfoot position and the forefoot position.
Once the slight valgus position of the heel and plantigrade metatarsals are produced, a guidepin from the cannulated screw set is inserted medially, just distal to the naviculum into the talus to hold the joint. A second guidepin is inserted from the posterior tuberosity of the calcaneus into the body of the talus, just proximal to the neck. The calcaneocuboid joint is stabilized last with a guidepin beginning 1 to 1.5 cm proximal to the anterior process of the calcaneus with the hand held as close to the heel and lateral ankle as possible. The pin should be virtually sitting on top of, or just under, the tip of the fibula when it is properly angled to cross the calcaneocuboid joint. It sometimes is helpful to make a trough in the calcaneus at the point of insertion of the pin where the screw can sit and gain purchase; this will prevent splitting the bone. Finally, the position is checked fluoroscopically and proper length screws are inserted in the usual fashion (Fig 3). Deep tissues are closed with absorbable sutures, and skin is closed with nylon suture.
Patients are non-weight-bearing for 4 to 6 weeks, using a splint for 2 weeks, and a boot brace for the subsequent 3 months. Progressive weight-bearing is generally begun at 6 weeks after surgery, progressing 20 pounds every 5 to 7 days until full weight-bearing is achieved by 3 months.
Complications include nonunion, which can be treated with in situ-type bone grafting, and malalignment, which can be treated with calcaneal osteotomy or midfoot osteotomy to correct excessive supination.
Triple arthrodesis has been shown to increase stresses at adjacent joints and to result in an increased incidence of arthritis at these joints (12). Some of the complications seen with triple arthrodesis include ankle instability and rocker-bottom deformities of the fourth and fifth cuboid joint and/or naviculocuneiform joint.
Ankle Arthrodesis
Ankle arthrosis is extremely common in patients with rheumatoid arthritis and may be seen primarily or after hindfoot arthrodesis. Many techniques of arthrodesis have been proposed, including intra- and extraarticular techniques, open or arthroscopic techniques, and internal or external fixation (10). Generally, if there is mild to moderate deformity, a minimal incision technique or arthroscopic method may be used. Severe deformity, however, requires an open technique. Internal fixation devices include cannulated screws, K-wires, intramedullary rods, and plates with screws. External fixation modalities include a ring fixator with a tension wire technique, a uniplanar half-pin frame, or a hybrid-type fixator combining ring and half-pin components. The recommended position for ankle arthrodesis is neutral dorsiflexion, 5 to 10o of external rotation and 0 to 5o of valgus (3).
The surgical technique begins with anteromedial and anterolateral longitudinal incisions made just over the anteromedial and anterolateral joint spaces, at the junction of the malleoli and the talus. Sharp dissection is carried out down to the bone. The joint is opened up and a lamina spreader is inserted through one of the incisions, distracting the ankle joint. With distraction achieved through either incision, it is possible to insert a high-speed burr to remove any residual cartilage and subchondral bone. The lamina spreader is switched from side to side, permitting thorough joint debridement. Curettes and chisels are also useful to remove the cartilage. Next, the joint is thoroughly lavaged.
Debridement is continued down to bleeding bone, with removal of as little bone as possible; the slurry of subchondral bone is retained in the joint. The bony surfaces should be bleeding and easily opposed. If they cannot be opposed, it is usually because of the inferior aspect of the medial malleolar- talar articulation or the inferior aspect of the fibula and lateral talar articulation. These areas should then be inspected and debrided. Once adequate position has been achieved, a guidepin is placed with the ankle held in neutral position, most specifically by holding the heel in the proper amount of ankle dorsiflexion. The guidepin is inserted from the medial aspect of the medial malleolus into the talus. A second guidepin is inserted from the fibula into the talus. A final pin is placed from just lateral to the Achilles tendon posteriorly, into the posterior aspect of the tibia 2.5 cm proximal to the joint, down into the neck of the talus. Fluoroscopy is used to ensure proper placement of pins in both the lateral and the anteroposterior ankle radiographs, and the screws are inserted after drilling (Fig. 4).
To avoid putting the talus into too much equinus during the fusion, it is important to allow for slight dorsiflexion of the entire foot when holding the ankle in its proper neutral position because approximately 5 to 10o of dorsiflexion occurs in the transverse tarsal and midfoot joint complexes after ankle fusion. If the foot is held in neutral position during fixation, further dorsiflexion is often unobtainable at the transverse tarsal and midfoot joints. It is also sometimes desirable to remove a portion of the anterior aspect of the fibula and insert this portion in the lateral talofibular gutter. With the exception of local bone graft, autogenous bone grafting is not used routinely in a primary ankle arthrodesis.
Postoperatively, the patient is kept non-weight-bearing for 4 to 6 weeks and uses a "U" splint and a posterior splint for 2 weeks followed by a brace for an additional 2 weeks. After 4 to 6 weeks, the patient begins progressive weight-bearing, preferably in a cast, although a removable walker-type boot may be used.
The most common complication seen with ankle arthrodesis is nonunion, which can be treated with repeat rigid compression and fixation, along with bone grafting. Malunion may require corrective osteotomy.
Pantalar Fusion
Pantalar arthrodesis includes fusion of the ankle, subtalar, talonavicular, and calcaneocuboid joints. Indications for this type of fusion include extensive rheumatoid involvement of the entire hindfoot, as a salvage procedure for failed ankle replacement arthroplasty, or for infection (11). It is also useful for a patient with previous ankle or hindfoot fusion who develops degenerative disease at neighboring joints due to increased stresses.
We use a transfibular approach, thereby allowing the fibula to be harvested as bone graft. A lateral incision is made over the fibula extending distally to the calcaneocuboid joint, and sharp dissection is carried out down to the bone. Subperiosteal dissection is carried out over the fibula and, within that flap, the capsule of the ankle joint is opened and dissection is carried out over the anterior distal tibia. The calcaneocuboid joint is exposed subperiosteally. Using a microsaggital saw, the fibula is cut 2 to 4 cm proximal to the talotibial articulation and then removed, thereby exposing the ankle and subtalar joints. Alternatively, an acetabular reamer may be used to morselize the fibula for bone graft.
A 4-cm incision is then made over the anteromedial aspect of ankle joint just medial to the tibialis anterior tendon. The medial incision over the ankle joint is carried distally over the talonavicular joint, and subcapsular dissection is carried out, exposing this joint. This incision is used to permit debridement of the cartilage in the medial malleolar-talar articulation, as well as the medial ankle joint. Cartilage and subchondral bone is removed from all joint surfaces. Care is taken to remove minimal bone from the posterior facet to prevent excessive valgus positioning of the heel.
Once all joint surfaces have been debrided, the subtalar joint is reduced, followed by reduction of the transverse tarsal joints. Pin fixation is used, similar to the triple arthrodesis at this time. Finally, the ankle is held in proper position, and alignment is determined before fixation, in a manner similar to the ankle fusion technique with the following exception. Instead of using the screw from the posterior aspect of the tibia, down into the body and neck of the talus, two screws are often inserted from the calcaneus through the talus and into the anterior distal aspect of the tibia. The screw from the medial malleolus used for the ankle fusion is modified so that this screw begins at the posteromedial aspect of the tibia and extends down into the body of the calcaneus (Fig. 5). Once the final screws have been inserted, deep tissue is closed with absorbable sutures, and the skin is closed with nylon.
It is important to realize that, when correcting a severe valgus deformity into a more neutral position, soft tissue may be difficult to close. It is sometimes necessary to transpose the peroneus brevis muscle anteriorly to permit a deep closure if the skin cannot be opposed, although the wound can often be closed after tension has been applied to the skin for a short while. While performing the reapproximation to relieve any tension on the skin, it is often helpful to have an assistant compressing the skin edges together.
Conversion of a triple to a pantalar fusion is complex. The forefoot remains plantigrade and, although the hindfoot usually appears to be in severe valgus, the major deformity often occurs at the ankle. If the ankle is fused in this position, the forefoot remains plantigrade, but shoewear is difficult. It is necessary to correct the valgus in the ankle but this cannot be achieved by a varus wedge cut in the ankle, since doing so would fix the forefoot in supination. We recommend correcting the valgus partially and improving the alignment by translating the talus medially. The valgus may be partly corrected and the alignment improved by translating the talus medially under the tibia.
The weight-bearing schedule and postoperative course is similar to that for ankle and subtalar fusion. It is also possible with the rheumatoid ankle to perform a modified pantalar whereby the calcaneus is fused to the talus and tibia and the talonavicular and calcaneocuboid joints are left undisturbed (Fig. 1).
Complications of this procedure include malunion, nonunion, and stress fractures of bones adjacent to the fusion mass secondary to increased shear stresses in these areas after arthrodesis (Fig. 6). Malunion and nonunion can be treated with corrective osteotomies, bone grafting, and external fixation devices to allow compression of nonunion sites.
Conclusion/Summary
Patients with rheumatoid arthritis often require arthrodesis of the foot and ankle to alleviate pain and correct progressive deformities. When planning surgical correction, it is important to consider the overall limb alignment, the location of the deformity, deformities elsewhere in the limb, and the patient's overall medical condition, as these factors may affect the timing of surgery and the choice of operative modality. Since these patients often have poor bone quality, which may necessitate creative surgical approaches, it is useful to have several methods of fixation in one's armamentarium. Delicate handling of the fragile soft tissues in these patients is also critical to successful outcome. Until replacement arthroplasty techniques are improved, arthrodesis remains the cornerstone of treatment for a patient with rheumatoid arthritis whose pain or progressive deformity is refractory to nonoperative measures.
References
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Figure Legends
Fig. 1. Hallux IP joint arthrodesis.
Fig. 2. Preoperative (A) and postoperative (B) radiographs of first metatarsocuneiform arthrodesis in a rheumatoid patient with severe hallux valgus.
Fig. 3. Lateral (A) and anteroposterior (B) radiographs of triple arthrodesis in a rheumatoid patient.
Fig. 4. Anteroposterior (A) and lateral (B) radiographs of ankle arthrodesis in a rheumatoid patient.
Fig. 5. Pantalar arthrodesis in a rheumatoid patient.
Fig. 6. Pantalar arthrodesis with supramalleolar fracture salvaged with intramedullary nail. A, lateral view. B, anteroposterior view. C, anteroposterior view after nailing. D, lateral view after nailing.
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