Ankle Replacement Survivorship: Do You Believe Me, or Your Own Lyin’ Eyes?

What’s the Claim?

This two-fer showcases what we can get out of two different study designs: The single-center, single-implant expert series, and the national arthroplasty registry report. An expert-surgeon case series from South Korea with “minimum 10-year follow-up” (scare quotes to remind us to return to those missing before the 10-year interval) using the HINTEGRA implant claimed 93.5% survivorship at 10 years free from revision of the metal components, and 75.2% survivorship when they counted polyethylene exchanges as revisions. Outcomes scores in that series stayed about the same long term, but the data distribution widened, suggesting that some patients are living with devices that are doing poorly rather than revising them. A study drawing data from the UK National Joint Registry (augmented with National Health Service data because ankle arthroplasty revisions somehow are underreported in the UK NJR) found the 10-year survivorship statistic to be lower, at 86.2%. Data in that study come from all surgeons in the UK who do ankle replacements, and a wide variety of implants (including one that never made it outside of developer series across the pond here in the US because of unacceptably high revision rates).

How’s It Stack Up?

The HINTEGRA series is comparable to other reports using that device, and as is commonly the case, where there were differences among series, they mainly had to do with how “revision” was defined — numbers look better if one limits the definition to revision of the metal components, and worse (or much worse) if one counts poly exchanges (or any secondary procedure, which may occur in some 25% of patients after ankle replacement). The key fact to know when comparing the UK registry paper to others is that unlike most national hip and knee arthroplasty registries, which capture all or nearly all revisions, the UK registry is still finding its way with ankle replacements, and so it’s good the authors backstopped the registry with NHS data. They found that the registry missed about one-third of the revisions that were performed.  

What’s Our Take?

Back to the country music cliché in the headline: We can’t always believe “our own lyin’ eyes” when it comes to survivorship. But despite the registry paper including a mixed bag of implants (with some underperformers), that is the paper to rely on here. The HINTEGRA series excluded missing patients, which generates rosier estimates, and about 20% were missing. Rosy estimates, indeed. Beyond that, many patient outcomes scores deteriorated to the point where they likely would no longer consider the procedure a “success” but have not (yet) had revision, perhaps because of poor health or advanced age. So for the purposes of sharing real-world realistic survivorship estimates before surgery with your patients, use the numbers from the UK registry report — we never really know if our implant is about to be the next recall, and registries are more reflective of real-world practice than are single-surgeon expert series. Quote this: Between 91% and 96% of fixed-bearing implants will survive 5 years, and about 85% may get 10 years. But remember: These are full-on revisions. Another 25% of patients will have a reoperation for some other reason (lysis, gutter osteophytes, or some other cause) over that span of time.

Sources

Jennison T, Ukoumunne O, Lamb S, Sharpe I, Goldberg AJ. How Long Do Ankle Arthroplasties Last? Bone Joint J. 2023;105-B:301-306.

Yoon YK, Park KH, Park JH, Lee W, Han SH, Lee JW. Long-Term Clinical Outcomes and Implant Survivorship of 151 Total Ankle Arthroplasties Using the HINTEGRA Prosthesis: A Minimum 10-Year Follow-up. J Bone Joint Surg Am. 2022;104:1483-1491.