Fusion of the tibiotalar joint is an accepted technique used to treat patients with pain and disability caused by disorders that result in destruction of the normal articular cartilage of the joint. Fusion of the ankle joint is used to achieve joint stability, decrease pain, or arrest disease progression. Numerous techniques to achieve fusion have been advocated over the past decades, including anterior arthrodesis using a sliding tibial graft, compression arthrodesis utilizing external fixator, and flat cut osteotomies of the talus and tibia with removal or partial excision of the fibula. 1–3 Each of the procedures has been associated with a significant incidence of complications including nonunion, delayed union, malunion, skin necrosis, and infection. A simplified method of in situ ankle fusion using an open anterolateral approach to the joint with retention of the normal bony contours of the talus and tibia has been described. 4 Using this technique with internal fixation using crossed transmalleolar screws, a high rate of fusion with a very low incidence of complications was reported. This technique has been replicated using arthroscopic surgical techniques, and high fusion rates with low complication rates have also been reported so that minimally invasive surgery can usually be performed on an outpatient basis.
The indications for arthroscopic ankle arthrodesis are the same as for open ankle arthrodesis. The most common indication is pain that is unresponsive to nonoperative treatment or other forms of surgical treatment such as joint debridement (including debridement of osteophytes, removal of loose bodies, synovectomy, and chondroplasty). The most common indications include articular cartilage destruction from degenerative arthritis, posttraumatic degenerative arthritis, and rheumatoid arthritis. Less common indications include joint destruction resulting from hemophilic arthritis, infection, or crystalline induced arthritis. Failed treatment of osteochondritis dissecans using debridement techniques or osteochondral grafting techniques occasionally results in the need for arthrodesis of the joint.
Contraindications to arthroscopic ankle fusion include active infection or significant deformity. The arthroscopic technique cannot be relied upon to correct deformity exceeding approximately 5–10 degrees of valgus/varus or equinus. Patients with significant bone loss, malrotation, or failed previous fusion are also not candidates for arthroscopic ankle fusion. Patients with reflex sympathetic dystrophy are poor candidates for arthrodesis using open or arthroscopic techniques, as are patients with Charcot joints from neuropathic destruction. 5
A thorough orthopaedic history and physical examination must be performed on any patient when ankle fusion is contemplated. The etiology of the joint destructive process must be appreciated and the treating physician must be certain that all reasonable nonoperative or more conservative operative techniques have been attempted before considering ankle arthrodesis. The surgeon must be careful to exclude other causes of hindfoot pain such as a subtalar degenerative process. The alignment of the ankle must be evaluated to be certain that the joint can be manipulated into an adequate position for ankle fusion without the need for corrective osteotomy. A position of neutral dorsiflexion is desirable, but up to 5–10 degrees of equinus is generally acceptable. Slight hindfoot valgus of approximately 5 degrees is preferred, and hindfoot varus should be assiduously avoided.
Radiographs should be carefully evaluated to determine if there are osteophytes that require excision, whether there are any loose bodies present, and whether there is any hardware from previous surgery that will affect the ability to place fixation screws. (Fig. 1) Routine anteroposterior, lateral, and mortise views are obtained. Other studies such as computed tomography, magnetic resonance imaging, and bone scanning are usually not required I preoperative planning except as necessary to rule out other diagnoses which may effect treatment.
The surgical procedure is performed under general or spinal anesthesia in either an outpatient surgery center or hospital setting. The operative extremity is placed into a position of hip and knee flexion with the leg supported by a well-padded leg holder. (Fig. 2) This position allows the foot to assume a plantigrade position, allows complete skin preparation and draping from the toes to the knee, and allows free intraoperative ankle motion. A noninvasive ankle distractor consisting of a sterile commercially available strap around the heel and midfoot, a sterile clamp and bar attached to the Clark siderail of the operating table, and a sterile Velcro strap, which attaches the strap and bar with which tension is adjusted, is applied (Fig. 3).
Routine anteromedial, anterolateral, and posterolateral portals are created at the start of the case. All portals are created in such a way as to minimize the risk of injury to superficial sensory nerves. The skin is incised, exercising care that the tip of the scalpel penetrates only through the dermis and not into the subcutaneous tissue, which is then bluntly dissected down to the level of the joint capsule using a fine hemostat clamp. The capsule is then penetrated with an arthroscopic cannula loaded with a blunt trochar. The ankle joint capsule is thin, and a sharp cannula is not required to enter the joint.
The anteromedial portal is made at the level of the joint adjacent to the medial border of the anterior tibial tendon and the anterolateral portal is placed lateral to the peroneus tertius tendon (Fig. 4). The posterolateral portal is placed under direct visualization with the entry point at the lateral margin of the Achilles tendon approximately 1–2 cm distal to the anterior portals (Fig. 5). This more distal position allows the cannula to be directed into the joint beneath the posterior tibiofibular ligament accommodating the posterior talar convexity.
A thorough joint examination is performed with the arthroscope placed into each portal, and then the debridement procedure is initiated (Fig. 6). The ubiquitous anterior tibial osteophyte should be debrided using a motorized abrader, pituitary rongeur, or osteotome. Doing so will allow easier entry into the joint with arthroscopic instruments and will allow better reduction and coaptation of the joint surfaces at the conclusion of the case. Depending upon the etiology and degree of joint destruction, a variable amount of articular cartilage may remain. Motorized shavers are used to systematically debride any remaining articular cartilage over the talar dome, tibial plafond, and both the medial and lateral gutters. A selection of straight and angled curettes is used to remove any articular cartilage remaining after motorized shaver debridement. Instruments can be placed into the joint from the posterolateral portal to debride areas of the posterior talar dome and tibial plafond that cannot be reached from the anterior portals.
A round motorized abrader is then introduced to debride the eburnated subchondral bone down to viable, bleeding bone. Care must be exercised to maintain the normal bony contours of the talus and tibia. After bone abrasion the inflow pressure may be reduced to evaluate bleeding from the surfaces of the talus and tibia. If areas are found to be devoid of bleeding, then the abrader is used to further remove bone from these areas (Fig. 7).
Fixation screws can be placed in a crossed, transmalleolar configuration introducing one from the medial malleolus and one from the lateral malleolus, or two medial screws may be placed, one into the talar body and one into the talar neck. Partially threaded cannulated cancellous screws of at least 6.5 mm diameter are used. The guide pins can be placed under arthroscopic guidance to the certain that they enter the joint in a position to engage the talar dome.
After the adequacy of guide pin position is confirmed arthroscopically, the pins are pulled back to just beneath the surface of the bone. The arthroscopic instrumentation is removed from the joint and the leg is removed from the leg holder so that the lower extremity can be placed flat on the table. The fluoroscope is used to confirm that an adequate joint reduction can be obtained using anteroposterior and lateral views. Then, with a surgical assistant holding the ankle in the desired position of fusion, the guide pins are advanced into the talus. If crossed screws are to be used, the medial pin is drilled first. Then, the appropriate length screw is placed and tightened. Joint compression can be achieved with this medial screw. Adequate screw position is confirmed using anteroposterior, lateral, and oblique views to ensure that all screw threads are within the talus and that there has been no penetration of the subtalar joint by the screw tip (Fig. 8). Then the lateral screw is placed in a similar fashion. If two medial screws are used, both guide pins can be advanced and both screws placed. The adequacy of the final hardware position is assessed once again using the image intensifier. Simple sutures are placed to close the portals, and then a bulky compressive dressing with a posterior plaster splint is placed.
The patient uses crutches and remains nonweight bearing until the wounds are checked and sutures are removed at 7–10 days postoperative. At that point a removable walking boot is applied and the patient is allowed to gradually resume weight bearing as tolerated. Radiographs are monitored at monthly intervals until radiographic union, usually at 8–12 weeks postoperative.
When bony union is achieved, the patient transitions to a regular shoe, which may be fitted with a rocker bottom to facilitate ambulation. (Fig. 9)
The most common complication of ankle arthrodesis is nonunion or pseudarthrosis. Studies have suggested a union rate of 85–90% with the arthroscopic technique. 6–10 Other complications relating to arthroscopic ankle surgery include nerve injury at the portal sites causing diminished sensation or painful neuroma, sinus tract formation, or infection. These complications are rare. In one study comparing 17 patients undergoing open ankle arthrodesis to 19 patients undergoing arthroscopic arthrodesis, there were 16% nonunions in the arthroscopic group, one of which occurred in a patient with avascular necrosis of the talus. There were no other complications in the arthroscopic group. 10
FUTURE OF THE TECHNIQUE
Arthroscopic ankle fusion has been shown to be an effective technique for achieving tibiotalar arthrodesis with a low complication rate, low time to fusion, and good patient acceptance. The procedure must be applied to patients with minimal deformity and is not applicable for patients where angular or rotational malalignment must be corrected.
1. Charnley J. Compression arthrodesis
of the ankle
and shoulder. J Bone Joint Surg 1951; 33B:180.
2. Johnson FW, Boseker EH. Arthrodesis
of the ankle
. Arc Surg 1968; 97:766.
3. Campbell CJ, Rinehart WT, Kalenak A. Arthrodesis
of the ankle
: deep autogenous graft with maximum cancellous bone appositioin. J Bone Joint Surg 1974; 56A:63.
4. Morgan CD, Henke JA, Bailey RW, et al. Long-term results of tibiotalar arthrodesis
. J Bone Joint Surg 1985; 67A:546.
5. Glick JM, Ferkel RD. Arthroscopic ankle arthrodesis
. In Ferkel RD, ed. Arthroscopic Surgery
: The Foot and Ankle
. Philadelphia: Lippincott-Raven;1996:215–229.
6. Morgan CD. Arthroscopic tibiotalar arthrodesis
. Jefferson Orthop J 1987; 16:50.
7. Myerson MS, Allon SM. Arthroscopic ankle arthrodesis
. Contemp Orthop 1989; 19:21.
8. Myerson MS, Quill G. Ankle arthrodesis
-a comparison of an arthroscopic and an open method of treatment. Clin Orthop 1991; 268:84.
9. Ogilvie-Harris DJ, Lieberman I, et al. Arthroscopically assisted arthrodesis
for osteoarthrotic ankles. J Bone Joint Surg
10. O'Brien TS, Hart TS, Shereff MJ, et al. Open versus arthroscopic ankle arthrodesis
: A comparative study. Foot Ankle
Int 1999; 20:368.