Ankle replacement

Why replace ankles?

The impact of severe ankle arthritis on an individual’s quality of life is significant, both physically and emotionally, and its effects are reported to be as severe as those caused by end-stage hip arthritis.¹ Ankle arthritis is most commonly post-traumatic, either as a result of a fracture or repeated ligamentous injury.² Thus, unusually for arthritis, it typically presents in young patients with high functional demands. Ankle arthrodesis has long been considered the ‘gold standard’ for treatment of end-stage ankle arthritis. A solid well-aligned fusion offers good pain control and improved mobility without the need for future revision surgery. It has therefore traditionally been seen as the ideal ‘one-off’ procedure. However, fusion does have its limitations. Loss of ankle movement permanently disturbs normal gait which affects the kinematics of the subtalar, knee and midfoot joints. Coester et al³ has shown that at a mean of 22 years post-fusion, the majority of ankle fusion patients had functionally limiting arthritic changes in the ipsilateral foot. The early pain control provided by arthrodesis may not always be the solution to a long-term pain-free foot, as is often thought. This limitation, coupled with the success of arthroplasty in other weight-bearing joints, makes ankle replacement an attractive alternative.

Development of ankle replacements

Themistocles Gluck attempted the first hip replacement in 1891 using an ivory femoral head replacement for tuberculosis. Ankle joint replacements were developed much later; a case report in 2002 of the 40-year follow-up of a talar replacement indicates that attempts to replace the ankle were being made as early as 1962.⁴ Nevertheless, it was not until the 1970s that interest in ankle replacement gained momentum. Lord and Marotte are credited with the first series of total ankle replacements. Their replacement consisted of the femoral stem from a hip arthroplasty implanted in the tibia and an acetabular cup cemented into the calcaneum, following a talectomy.

A number of early implants were developed including the St George, Imperial College Hospital London, Irvine, Mayo, New Jersey and Richard Smith prostheses. In general they were variations of a two-component design, predominantly with a polyethylene tibial component and a metal talar component. All were cemented. It became apparent that there were high complication and failure rates limiting these early designs.^5–7 Almost 50% of Lord and Marotte’s implants failed by ten years; a similar rate was seen in other early designs.⁸ Failure was mainly due to loosening, massive osteolysis, subsidence and pain. The reliance on cement fixation required significant tibial resection. This meant that the tibial component was seated in less supportive metaphyseal cancellous bone, which was prone to failure and subsidence under compressive loads. The limitation of the constrained two-component designs results in transmission of large forces to the cement prosthesis interface, leading to early loosening. Revision of these failed arthroplasties to fusion was made more difficult by the loss of bone stock resulting from the primary procedure. The high failure rates associated with salvaging the failed ankle replacement led to the stalling of interest in ankle replacements, and the first generation implants were abandoned. In 1985 Bolton-Maggs stated, “[T]he overall results and the long-term outlook of ankle arthroplasty is so poor as to warrant offering only ankle arthrodesis as the surgical treatment of disabling ankle arthritis”.⁹

With the subsequent development of uncemented fixation for hip and knee arthroplasties, several groups utilised the new surface technologies associated with uncemented hips to develop uncemented ankle replacement through the 1980s. By the 1990s there was a resurgence of interest, with the availability of second-generation models: the Buechel-Pappas, Scandinavian Total Ankle Replacement (STAR) and Agility ankle replacements.

The Agility was the first second-generation replacement to be developed by Frank Alvine in 1984. It is a semi-constrained design consisting of a cobalt chrome talus and a titanium tibial component with a fixed polyethylene bearing. As well as sagittal movements, some axial rotation and medial to lateral translation can occur as the talus is smaller than the tibial cup-shaped articulation. The Agility requires fusion of the tibiofibular syndesmosis (Fig. 1). It is still in use today, mainly in the USA where up until 2006 it was the only FDA- (Food and Drug Association) approved ankle prosthesis.