Commentary & Perspective by
Charles L. Saltzman, MD*,
Department of Orthopaedics, University of Iowa, Iowa City, Iowa
Revised July 2, 2004
This well-documented, retrospective study is one of the largest single cohort series of total ankle replacements reported to date1. The patients had a relatively high rate of secondary operations and complications. At first glance, the findings appear worrisome and suggest again that total ankle replacement is a procedure plagued by difficulties. However, I believe that this report suggests that the proverbial glass is half full rather than half empty.
Spirt et al.'s results stand in stark contrast to our independent review of the first 100 ankle arthroplasties performed with use of the Agility (DePuy, Warsaw, Indiana) ankle prosthesis2. At an average 4.8 years follow-up, we found that four of the eighty-six ankles in living patients had been revised. One patient had a resection of the implant with subsequent arthrodesis. One patient had a fractured tibial component, but the patient was not symptomatic and had no additional treatment. Delayed union of the syndesmosis (twenty-eight ankles) and nonunion of the syndesmosis (nine ankles) were associated with the development of lysis around the tibial component, although at the time of our study this was not a major factor impacting the need for revision.
How do we account for these differences between the report of Spirt et al. and our previous report? Which set of results is most generalizable to other surgeons and patients? I think the answers lie somewhere between the two reported series, as each clinical practice has unique biases.
In the current report from Spirt et al., patients selected to undergo total ankle replacement included those with severe deformities, instability, neurological imbalances, multiple previous surgeries and even previous solid ankle arthrodeses. Thus, a choice was made to push the limits of standard treatments in an attempt to improve the function of patients with complex causes for ankle pain. The higher rates of failure and reoperations must be interpreted in this context.
Hansen's underlying strategy for the selection of patients and procedures differs from that reported previously for total ankle arthroplasty3. His philosophy, as embodied in his book, is to restore foot and ankle function by adhering to the fundamental principles of surgical reconstruction. In that spirit, at the time of ankle replacement, his aims are to address all of the features that may contribute to foot or ankle dysfunction. For example, in the current report, nearly all patients underwent lengthening of the gastrocsoleus complex and more than half of the patients received complex, multilevel osseous and soft-tissue reconstructions. In addition to differences in surgical techniques, the patient population and the setting (a nonteaching versus a teaching hospital) differed between these two reports.
In our report2 of the early experience with the Agility ankle prosthesis, patients underwent only one procedure—total ankle replacement. None had issues relating to Workers' Compensation, and only one was involved in litigation. None had undergone a previous ankle fusion. In contrast to the patients in the study by Spirt et al., most did not have previous trauma to the ankle. In our report, the average age at the time of total ankle replacement was a decade older than that of Spirt's group (sixty-three versus fifty-three years). One hundred ankle replacements were performed over a 9.5-year period, a rate of approximately ten replacements per year. Thus, in our series, only patients who were considered by the inventor/surgeon to be optimal candidates for ankle replacement underwent the procedure.
The current report suggests that age at time of ankle replacement has the largest impact on implant longevity. With component revision as an endpoint, in the group that was less than or equal to 54 years of age, the likelihood of having retained the original implant at five years was 0.74 (95% confidence interval: 0.60 to 0.91), whereas in the group that was >54 years of age, the likelihood of having retained the original implant at forty-seven months was 0.89 (95% confidence interval: 0.80 to 0.99). Thus, just one extra decade of life will decrease the chance of reoperation by 19% and the chance of implant failure by 35%. This is important information. These numbers are consistent with the survivorship analysis of the two study cohorts at five years.
Pending further study, we can draw some clinically relevant conclusions from these two papers. First, total ankle replacements fare better in older people. Second, low-demand patients with simple or isolated problems appear to be the most optimal candidates for this procedure. Patients whose ankles were previously fused and those with severe trauma have a higher rate of early reoperation. Third, the rate of wound complication is acceptable. Fourth, the rates of component loosening suggest that better instrumentation and better interface materials or designs are needed. Surgeons must have a detailed understanding of the implant design and the surgical requirements to optimize the stability and ingrowth of the prosthesis.
As implant design and instrumentation continues to improve, I expect that many of the implant loosening/osseous overgrowth problems will diminish dramatically. This article provides important information that begins to define the limits of use of the Agility ankle replacement. Only with careful clinical reports like this one will we be able to make advancements in this area of research and improve our ability to identify optimal patients for total ankle replacement.
*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.
1. Spirt AA, Assal M, Hansen ST Jr. Complications and failure after total ankle arthroplasty, J Bone Joint Surg Am. 2004;86:1172-8.
2. Pyevich MT, Saltzman CL, Callaghan JJ, Alvine FG. Total ankle arthroplasty: a unique design. J Bone Joint Surg Am. 1998;80:1410-20.
3. Hansen ST Jr. Functional reconstruction of the foot and ankle. Philadelphia: Lippincott Williams and Wilkins; 2000. p 415-7.