The role of ankle arthroplasty in treating end-stage ankle arthritis
Management of patients with symptomatic ankle arthritis is challenging, particularly in regards to the clinical decision to treat by arthrodesis or arthroplasty. Use of total ankle arthroplasty for debilitating end-stage ankle arthritis is expanding as implant design and technique have steadily improved over the past 20 years. Interest in arthroplasty has also been renewed by concerns that arthrodesis, the traditional treatment modality, may contribute to progression of arthritis in adjacent joints due to transmission of increased stress.
However, long-term effectiveness data on modern ankle arthroplasty are not yet available for several reasons. One is the lack of uniform outcome measures to apply to clinical results. Another is the variation in mobile-bearing and fixed-bearing prostheses.
Generalizations are therefore difficult to make. But recent prospective controlled trials, meta-analyses and experience suggest that when the latest prostheses, instrumentation and techniques are employed, total ankle arthroplasty can offer equivalent pain relief — and perhaps even better function due to increased range of motion — than ankle arthrodesis.
Patient selection, education
Patient selection and education, along with physician expertise and experience from a high-volume foot and ankle practice, remain cornerstones of consistent success with arthroplasty in terms of functional outcomes and revision-free implant survival. "The importance of carefully considering and fitting the selection criteria for ankle replacement to each patient individually cannot be overstated," explains Norman S. Turner III, M.D., an orthopedic surgeon at Mayo Clinic in Minnesota. "It is the key to achieving the best possible outcomes with total ankle arthroplasty." He adds that patients tend to equate ankle replacement with hip and knee replacements — with little appreciation for the fact that ankles have unique physiological and mechanical attributes that complicate arthroplasty.
As a result, one of the first tasks of the consulting foot and ankle surgeon often is to explain the unique character of the ankle joint to patients. Notes Richard J. Claridge, M.D., an orthopedic foot and ankle specialist at Mayo Clinic in Arizona, "A range of treatment options exist, and we consider them all for our ankle patients — but there are patients who come in asking for arthroplasty right away, assuming it will solve all their problems. While we understand their desires, it's very important to choose the treatment that best suits their needs."
Adds their colleague, Joseph L. Whalen, M.D., Ph.D., of Mayo Clinic in Florida, "Ankle replacement is not for everyone. We select patients in whom it is most likely to succeed, which certainly influences our outcomes as consistently among the best. Educating a patient about total ankle replacement including the risks, benefits and current outcomes is important."
The treatment continuum
The most common causes of ankle arthritis are trauma and abnormal mechanics that produce pain, inflammation, impaired mobility and ankle instability. Nonoperative treatment modalities include:
- Physical therapy and anti-inflammatory medications
- Modifying footwear
- Behavior changes such as switching to low-impact activities or sports
- Weight loss in the case of obese patients
- Joint injections
When pain remains debilitating, and conservative measures have failed to treat end-stage ankle arthritis, surgical options include:
- Arthroscopic or open debridement of chondral defects
- Impinging and loose bodies
- Ankle arthrodesis through a variety of techniques
- Plate and screw styles and arrangements
First developed more than 40 years ago, ankle arthroplasty has improved as it has evolved, particularly in terms of refinements in hardware design and fabrication, instrumentation, implant positioning technique, and reconstructive benefits to the hind foot.
Indications and contraindications
No standard clinical indications have been formulated. In general, primary indications for total ankle arthroplasty are degenerative, post-traumatic and rheumatoid arthritis. Experienced specialists tend to consider arthroplasty for patients with:
- Advanced, debilitating ankle arthritis
- Joint surfaces destroyed by trauma, scarring or deformity
- Pain and impairment so severe that daily life tasks are interrupted
Arthroplasty is contraindicated for patients with recent infections and serious comorbidities such as:
- Vascular impairment
- Severe joint laxity
- Compromised soft-tissue envelope
- A neuropathic joint disease (avascular necrosis of the talus)
- Severe deformities of the ankle
Evaluation and rehabilitation
Evaluation starts with a thorough medical and orthopedic evaluation of the patient. This includes gait analysis and weight-bearing X-ray, and possibly computerized tomography (CT) scan, magnetic resonance imaging (MRI) and bone scan. Obtaining a complete understanding of lifestyle factors and medical history is also important because it can impact the implant durability and performance and patient likelihood to comply with a rehabilitation program.
The postoperative rehabilitation of ankle arthroplasty patients is a period of nonweight bearing and cast immobilization for several weeks. If the soft tissue structures have been balanced during the surgery and the intraoperative range of motion was satisfactory, physical therapy is usually not required to achieve range of motion. Patients at six weeks following surgery can usually start bearing weight and progress to normal activities over the following month.