Foot & Ankle

Radiographic severity important in predicting outcomes in total ankle arthroplasty

It is widely known and accepted that in total knee arthroplasty, the best predictor of post-operative outcome is pre-operative function. However, this is not a concept that has ported across to the world of ankle arthroplasty. Reasoning that patient selection for total ankle arthroplasty is key to achieving the best outcomes, researchers in Newcastle upon Tyne (UK) set out to investigate the impact that the pre-operative radiographic arthritis grade may have on post-operative functional results in total ankle arthroplasty (TAA).⁷ The research team focused on a large series of 178 ankle replacements in 170 patients. They undertook a retrospective review of their pre-operative radiographs and prospectively collated clinical outcome data (Foot and Ankle Outcome Score [FAOS; pain, function, and stiffness], MOS 36-item and Short-Form Health Survey [SF-36] scores). The patients were subdivided by the pre-operative Kellgren-Lawrence scores assessed on pre-operative weight-bearing films. There were few differences in patient demographic data; perhaps most interestingly, pre-operative FAOS scores were similar across all three groups with no statistically significant differences observed. However, the improvements in both domain-specific and general outcome scores differed dramatically between the groups. As perhaps might be expected, those patients with severe or end-stage arthritis had the greatest post-operative satisfaction rates (achieving > 90% at two years in severe arthritis), whereas in the mild to moderate group rates were as low as 50%. This paper informs decision making in an area where technologies continue to evolve and the relative indications for arthroplasty are not yet clear.

Osteolysis around the ankle: a ballooning problem?

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There are definitely some differences in the osteolytic reaction between patients, but there are also some differences between joints and implants, suggesting that perhaps the final common pathway for bone loss is likely to be through a single, unified route. In common with the pattern of ballooning osteolysis seen on the tibial plafond following osteochondral defects, wear debris around ankle arthroplasties can result in a very similar pattern of osteolysis. A research team in Magdeburg (Germany) have investigated the outcomes of 71 patients, all undergoing revision surgery for failed ankle replacements.⁸ Those with ballooning osteolytic cysts were compared with a primary group of ankle arthroplasties and some revisions without the characteristic balloon lysis. The research team undertook a fairly thorough basic science analysis of the explanted tissue including histomorphometric, immunohistochemical, and elemental analysis. Those patients with ballooning osteolysis showed characteristic changes including higher levels of lymphocytic expression and perivascular expression of CD3+, CD11c+, CD20+, and CD68+ cells. The study team also established that there were much higher odds of balloon osteolysis in those patients with a high calcium concentration in the periprosthetic tissue. Putting it all together, the study team propose that perhaps the pattern of tissue expression and very high calcium concentrations implicate the hydroxyapatite coating in the development of balloon osteolysis.