CHAPTER 19 Complex Ankle, Subtalar, and Triple Fusions
Arthroscopy allows surgeons to perform foot and ankle procedures that would otherwise be contraindicated because of the risks of an open approach. Although early in their development and more time-consuming than their open counterparts, combined arthroscopic subtalar and ankle fusion and arthroscopic triple arthrodesis have increasing roles to play in treating complex conditions in patients who are not candidates for an open procedure.
Arthroscopic ankle arthrodesis can be extended to include cases with some bone deformity or extensive osteophyte formation if the surgeon is patient and experienced with simpler cases.1 These cases should be performed after the surgeon has achieved proficiency with arthroscopic ankle and subtalar fusion. When the soft tissue envelope is compromised, the additional time required for the more complex operation may be justified by the prevention of soft tissue complications.
NORMAL AND PATHOLOGIC ANATOMY
Anatomic considerations are addressed in Chapter 17. Talonavicular arthritis with deformity or subtalar arthritis is a clear indication for triple arthrodesis. Isolated talonavicular arthritis may be amenable to isolated talonavicular fusion. However, an isolated talonavicular fusion is more likely to progress to a nonunion because there may be motion across the joint despite two screws being used for fixation. Because no significant gain in motion is achieved with an isolated talonavicular fusion compared with a full triple arthrodesis, a triple arthrodesis may be preferable because a larger fusion mass is obtained and better stabilization performed.
Usually, these procedures are performed open. However, for patients with bleeding problems (e.g., hemophilia), poor wound healing, or preexisting scar, a less invasive procedure may be preferable. For patients with anticipated wound-healing problems who are not candidates for an open procedure, an arthroscopic fusion is an ideal alternative.
History and Physical Examination
Location of Pain
To allow the patient to correctly identify the area of discomfort, both feet and ankles should be exposed during the physical examination. Patients with isolated ankle arthritis present with pain localized anteriorly in the ankle between the malleoli. Swelling may occur in the same area, and the pain is localized above and between the tips of the malleoli.
Talonavicular joint pain is localized anterior to the ankle and malleoli and down toward the tuberosity of the navicular. Swelling occurs anterior to the ankle and onto the dorsum of the foot. Because the superior joint margin of the talonavicular joint is only 1 to 2 cm in front of the anterior margin of the ankle joint, talonavicular arthritis can be confused with ankle arthritis.
Subtalar joint pain is localized in the sinus tarsi inferior to the lateral malleolus. Medially, pain is localized directly inferior to the medial malleolus.
Degree of Disability
Patients should be assessed for their degree of disability. Their walking tolerance and standing tolerance are good indicators of disability. They might have had to stop work because of the hindfoot pain. Sports might have been permanently discontinued or restricted due to pain or instability. Before treatment, the degree of disability should be outlined to determine success of intervention.
Patients with hemophilia should be followed closely by the hematologist if surgery is contemplated. Their ability to be anticoagulated before and after surgery should be assessed.
Patients with rheumatoid arthritis should be optimized with regard to medical treatment. Other joint involvement should be assessed and the degree of associated disability known. Only in exceptional circumstances should the foot or ankle undergo fusion if another joint is more symptomatic.
Extra-articular manifestations of rheumatoid arthritis include iritis, cardiomyopathy, conduction delays, respiratory disease, and skin breakdown. A systemic evaluation is required.
Both extremities should be exposed to the knee. While standing, alignment of the hindfoot and forefoot is assessed from behind and in front of the patient.
Gait is observed, concentrating on stance and swing phases. Pain is associated with a reduced stance phase on the painful side and failure to toe-off. On inspection, the location and size of scars, calluses, and ulcers are recorded.
Palpation is used to determine the area of maximum tenderness. In ankle arthritis, this is localized on the anterior and posterior joint margins between the malleoli. For the subtalar joint, the pain is under the fibula, toward the sinus tarsi, behind and inferior to the ankle, and under the medial malleolus. For the talonavicular joint, tenderness is localized medially behind and above the navicular tubercle and just anterior to the ankle joint.
Assessing range-of-motion deficits may assist in determining the painful joints. To isolate the ankle, the examiner should move the talus on the tibia and palpate the joint margin at the same time. For the subtalar joint, the calcaneus is moved on the talus, and for the talonavicular joint, the navicular is moved on the talus. Absolute motion is difficult to measure, but pain and loss of motion (i.e., normal, mild, moderate, or severe restriction) is more instructive than the actual degree of motion.
Special tests include a single-leg heel raise to determine the integrity of the tibialis posterior tendon and the foot’s ability to act as a lever arm. Pulses and sensation should be assessed and recorded.
Standing anteroposterior and lateral views of the ankle and foot should be obtained if the patient has hindfoot arthritis. For ankle arthritis, the status of the talonavicular joint should be determined on an anteroposterior view of the foot. An ankle fusion may increase the load on a compromised joint and lead to symptoms. Similarly, the condition of the ankle joint should be determined if a triple arthrodesis is considered.
If the plain radiographs do not clearly identify the status of these joints, helical computed tomography (CT) is the appropriate imaging technique to better define the anatomy of the hindfoot. Occasionally, magnetic resonance imaging (MRI) can be performed, but it tends to be oversensitive for this assessment. Single photon emission computed tomography (SPECT) can assist in defining the precise location of bone turnover in patients with undiagnosed pain.
Differential local anesthetic blocks are beneficial. However, care should be taken in their interpretation, because there may be flow between joints that confuses the result.
Indications and Contraindications
Combined arthroscopic ankle and subtalar fusion is indicated for the patient with combined symptomatic ankle and subtalar arthritis with a risk of soft tissue complications. These patients may have post-traumatic arthritis with extensive soft tissue damage, hemophiliac arthropathy of the ankle and subtalar joints, or rheumatoid arthritis with a history of poor wound healing. Patients with scleroderma are also at risk for wound healing problems, and they may benefit from an arthroscopic approach. Patients with psoriatic arthritis with plaques around the ankle are at risk for wound complications and can benefit from an arthroscopic procedure.
Patients with arthritis of the talonavicular joint in isolation or with other hindfoot involvement may benefit from an arthroscopic talonavicular or arthroscopic triple arthrodesis. The indications for patients at risk for wound healing complications are the same as outlined previously.
Many patients have contraindications for these procedures. Major bone defects require grafting or osteotomies, and an arthroscopic procedure is not possible. Patients with avascular necrosis require bone resection of an amount that cannot be performed through the arthroscope. Patients with Charcot arthropathy have a combination of bone defect and avascular necrosis that requires resection beyond the capabilities of arthroscopy.
Nonoperative treatment of ankle and hindfoot arthritis involves activity modification, bracing and orthotics, analgesia, or a combination of these methods. Activity modification may include the use of a cane and avoiding activities that cause discomfort.
Braces beneficial in hindfoot arthritis should reduce the range of motion of the affected joint. Some may be designed to also off load the limb. An off-the-shelf ankle-stabilizing brace is a cost-effective start. If this fails, a custom brace, ankle-foot orthotic, or Richie Brace may assist in reducing motion and correcting any associated deformity. Orthotics can correct the foot shape and reduce impingement or eccentric loading. The orthotic can be combined with a brace (e.g., Richie Brace).
Complex Arthroscopic Ankle Fusion
When there is erosion of the medial or lateral side of the joint, a standard arthroscopic fusion can be performed and augmented by correction of the deformity by sculpting of the prominent side of the joint with a burr to allow correction of the varus or valgus plane deformity. Removal of some of the tip of the medial or lateral malleolus may be required to allow joint compression. The edge of the bone deformity often is located within the joint and can indicate where to start applying the burr to reduce the deformity. The degree of bone removal can be estimated using intraoperative fluoroscopy.
After correction is achieved in the varus and valgus plane, the talus can be corrected using a Kirschner wire or drill from the lateral or medial malleolus. Any defect left gapping on one side can be filled with bone graft or bone graft substitute. A screw is first placed through the malleolus to the talus to hold the correction, and the opposite side of the ankle is compressed with two or three compression screws.
Extensive Osteophyte Formation
In cases with extensive osteophyte formation, the joint may be difficult to instrument with an arthroscope. This situation usually requires an open procedure, but in cases in which the soft tissue complications may merit arthroscopic fusion, it can be performed. However access to the joint may take some time and patience.
Osteophytes can be identified for removal by fluoroscopy before arthroscopy (Fig. 19-1