David I. Pedowitz

Abstract

The Scandinavian Total Ankle Replacement (STAR) system is a mobile bearing total ankle replacement designed to achieve physiologic ankle motion and minimize stresses at the bone–implant interface. It is the only implant approved by the Food and Drug Administration (FDA) for use in the United States without cement and therefore relies on bony ingrowth into its porous surfaces. Long-term results suggest that the STAR is reliable in achieving pain relief and good function for the treatment of end-stage tibiotalar arthritis.

Keywords: total ankle replacement, arthroplasty, tibiotalar arthritis, posttraumatic arthritis

48.1 Indications and Pathology

• End-stage degenerative, posttraumatic, or inflammatory tibiotalar arthritis.

48.1.1 Clinical Evaluation

• Tenderness over tibiotalar joint line.

• Patients should have pain with weight-bearing activity.

• May present with or without significant ankle, midfoot, or hindfoot deformity.

• May have some decreased sagittal arc of motion at ankle joint.

48.1.2 Radiographic Evaluation

• Plain weight-bearing X-rays of the foot and ankle looking for the following:

Tibiotalar congruence.

Intra versus extra-articular deformity at the ankle.

Hindfoot deformity and how, if at all, it effects ankle joint.

Bone loss.

Collapse or signs of avascular necrosis (AVN) of the talus.

Location of preexisting hardware as it affects placement of implant and impacts the need for removal at the time of arthroplasty.

Anterior or posterior subluxation of the talus.

Adjacent segment (subtalar and talonavicular) arthritic change.

• Magnetic resonance imaging (MRI):

Used in the setting of suspected AVN of the talus that may be a contraindication for arthroplasty.

• Computed tomography (CT) scan:

Used to assess bone stock when cysts or osteochondral lesions can be seen with plain radiography.

Used to assess talar morphology in the setting of collapse or prior fracture that may affect choice of talus implant or helping to anticipate the need for bone grafting.

48.1.3 Nonoperative Options

• Brace immobilization.

• Activity modification.

• Rocker-bottom sole and cushioned heel to shoe; orthotic inserts.

• Medications: cortisone injection, hyaluronic acid injections, anti-inflammatory medications.

48.1.4 Contraindications

• Insufficient bone stock to support the implant, particularly on the talar side.

• Extensive AVN of the talus. The authors’ recommendation is that arthroplasty should be highly cautioned when greater than 30% of talar AVN exists.

• Severe neuropathy.

• Active infection.

• Prior infection remains a relative contraindication and ankle replacement may be performed under select circumstances in which latent infection can largely be ruled out.

• Psychiatric or psychosocial conditions that may make a patient unable to follow the postoperative protocol.

• Smoking remains relative contraindication. The authors do not perform total ankle arthroplasty in smokers.

• Uncontrolled diabetes with an HgA1c greater than 6.5 brings with it an unusually high complication rate and those patients who have an elevated HbA1c should be cautioned about elective surgery.

• BMI (body mass index) greater than 40. This has been shown to lead to an increased rate of complications in hip and knee arthroplasty. To date, no hard recommendations have been set forth for the ankle. Some surgeons use this as a relative contraindication.

48.2 Goals of Surgical Procedure

• Painand brace-free ambulation.

• Plantigrade, balanced ankle with correction of any coronal plane deformity.

• Functional range of motion of the tibiotalar joint.

• Protection of the adjacent joints from increased biomechanical stress and potential degeneration.

48.3 Advantages of Surgical Procedure