Total Ankle Arthroplasty: An Emerging Paradigm for End-Stage Ankle Arthritis

July 5, 2018

Alan Y. Yan, MD
Assistant Professor, Department of Orthopaedic Surgery
MaCalus V. Hogan, MD
Assistant Professor; Vice Chairman of Education; Residency Program Director; Director, Foot and Angle Injury Research (FAIR) Group, Department of Orthopaedic Surgery

End-stage ankle arthritis is a debilitating condition that is paramount to the level of physical disability to hip arthritis, end-stage renal disease, and congestive heart failure.^1,2 While different from arthritis in knees and hips, end-stage ankle arthritis is mostly related to trauma (70 percent) and less so to primary degenerative arthritis (7 percent), and other causes such as rheumatoid arthritis (12 percent).³ For many years, ankle arthrodesis has been the accepted standard of surgical management for end-stage ankle arthritis. Ankle arthrodesis is a straightforward procedure that suits almost all types of end-stage ankle arthritis. Clinical evidence from levels I to IV studies have shown that there is reliable pain relief derived from the procedure.⁴

However, recent decades of development of total ankle arthroplasty (TAA) offer a new and attractive alternative option with similar pain relief. Besides pain relief, TAA also provides increased mobility and more physiological functioning. Furthermore, when patients present with arthritic periarticular joint disease in the midfoot and hindfoot, TAA is a better option in avoiding the transfer of more motion and thus further worsening of conditions in the already degenerative joints. 

Indications and Contraindications
Understanding the indications and contraindications of TAA is vital for a successful clinical result. A good soft tissue condition, and adequate vascular perfusion, is essential for a safe and successful total ankle procedure. Similar to total knee and hip arthroplasty, an ideal candidate is likely a middle- to older-age patient with reasonable bone stock and alignment of the ankle and foot, and no significant medical comorbidities. Furthermore, a bilateral ankle end-stage arthritis and previous extensive foot fusion patient may benefit from TAA more than from an arthrodesis, because the latter may further restrict the motion of foot/ankleand gait function.⁵

Similar to other total joint replacement surgeries, the following groups of individuals are not typically considered candidates for the procedure:
-Younger patients who perform heavy labor or have higher activity-demand levels
-Patients with severe bone loss or poor bone quality
-A history of infection or necrosis
-Charcot joints
-Severe laxity of soft tissues

However, available studies do not show a significant increase in complication rates in patients with higher body mass index (BMI) or patients who are diabetic.⁶ Higher risks for failure did occur in reports with patients who are smokers or have rheumatoid arthritis.⁷ Diabetic patients are, however, highly likely to develop neuropathy and loss of protective mechanisms for the implants in the future. 

Outcomes and Complications
TAA has gained popularity in recent years with continuous improvements in implant design and instrumentation advancement. Mid- and long-term data on the newer generations of implants are showing better outcomes, catching up to current outcomes in total hip and knee arthroplasty. However, the demanding technical skills needed with TAA and the surgeon's experience required to properly use these implants and instruments are reflected in the complication rates.⁸

Variability in many reports on survival and failure rates exists due to the different implants used in different countries and different registries. The Cochrane review showed an overall survival of 89 percent in 10 years, along with an annual failure rate of 1.2 percent in 7,942 TAAs globally.9 In several multicenter studies, survivorship rates showed to be 96 percent at five years, and 90 percent at 10 years.¹⁰

Clinical outcome studies from Saltzman, et al. in 200911 showed a significant higher function score in total ankle groups with STAR prosthesis compared to ankle arthrodesis, while the pain score at one year was similar. However, a prospective study from Canada12 reported in 2014 showed that complication rates in TAA compared to ankle arthrodesis were doubled, while no differences in function scores were seen. 

When patients opt to maintain their ankle mobility, the option of TAA over ankle arthrodesis has offered the possibility of significantly higher arc of motion (Pedowitz et al., 2016), and also better pain relief and patient-reported outcomes.¹³ Current literature also demonstrates significant improvement in gait compared to preoperative function.¹⁴

Followed by the high success rates of total knee and hip arthroplasty, total ankle replacement (TAR) surgery was inspired and first introduced in the United States in the 1970s with the goal to preserve motion in the ankle. However, early first-generation device design was not successful, harboring many complications. Its clinical use was largely discouraged given the reliability of ankle arthrodesis in reducing ankle pain.¹⁵ Most first-generation TAR designs were two-component prostheses that used cement fixation on both the talar and tibial sides and was restrictive. Learning from the main failure reasons of the first-generation of TAR led to the development of the second and third generation ankle prostheses with either fixed two- component or mobile-bearing three-component designs, allowing for more anatomical congruency, conservational bone cuts, and the elimination of bone cement. Later designs in component surface with new biologic interfaces and with special coatings for better osseous integration were also investigated and developed as another way to ensure the primary prosthesis fixation.¹⁶ 

Other features of newer designs, such as increased surface area of metallic components, decrease local contact pressure and thus prolong the survival rate of the implants. An increasing number of reports on positive clinical results, high patient satisfaction, and acceptable survivorship of prosthesis components presented at national and international meetings and published in the orthopaedic literature has led to the consideration that ankle fusion may not be the only reasonable treatment option for patients with severe ankle osteoarthritis. 

It is important to understand that not all cases of ankle arthritis are amenable to total ankle replacement. TAR surgery is technically demanding, with a steep learning curve. Reported intraoperative complications of the surgery include medial or lateral malleolar fracture, nerve injury of the peroneal nerve (more common), or a devastating tibial nerve injury and tendon lacerations.¹⁷

Consulting patients for proper indications is important for the success of total ankle surgery. The decision for ankle replacement versus arthrodesis should be made on a case-by-case basis. There is currently no consensus or definitive clinical guideline. 

Conclusion
Total ankle arthroplasty is no longer considered experimental but is an established option for certain patients group with end-stage ankle arthritis. Likewise, with the past decades of continuous effort in the improvement and development of implants and instrumentation and techniques, ankle fusion is no longer the Ògold standardÓ treatment for all patients with severe end-stage ankle osteoarthritis. 

References
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