April 2013

Replacement revisited: Positive outcomes include younger patients

In the moment: Ankle

By Jordana Bieze Foster

Total ankle replacement (TAR) is growing in popularity, as an increasing number of studies suggest that the procedure’s outcomes rival those of ankle fusion—perhaps even in patients previously thought to be poor candidates for TAR.

Interest in TAR, or total ankle arthroplasty, was apparent in March at the American Academy of Orthopaedic Surgeons (AAOS), where more than half of a two-hour session was devoted to studies on the subject. In an analysis of billing codes for more than 11 million orthopedic procedures presented during that session, researchers from the University of California, Los Angeles, found that between 2004 and 2009, TAR rates increased from .42 to .65 cases per 10,000 patients while ankle fusion rates remained unchanged.

In 137 patients followed for two years after ankle surgery, researchers from the University of Washington in Seattle found that the 44 patients who underwent arthrodesis and the 93 patients who underwent TAR had similar, statistically significant improvements on the Musculoskeletal Functional Assessment, the Short Form 36, total step count, and step count frequency. Revision surgery was performed in 7% of fusion patients and 12.9% of TAR patients.

“We can’t say that arthroplasty is going to replace arthrodesis as the gold standard, but it does produce equal results,” said Paul H. Kim, MD, a resident in the department of orthopaedics and sports medicine at the University of Washington (UW), who presented his group’s findings at the AAOS meeting.

The mid-term results of a Canadian multicenter investigation follow a similar pattern. First presented last summer at the annual meeting of the American Orthopaedic Foot & Ankle Society with 4.5 years of follow up (see “Fusion vs replacement”), the mid-term results were updated at the AAOS meeting with an average follow up of five years. In the 339-patient mid-term analysis, both the TAR and fusion groups demonstrated significant improvement on the Ankle Osteoarthritis Scale, but the improvement in the TAR group was significantly greater than in the fusion group. The between-group significant difference disappeared, however, after adjustment for baseline differences; patients in the fusion group were significantly younger, were more likely to have diabetes, and were more likely to smoke than those in the TAR group.

“Mid-term outcomes were equivalent when treatment was tailored to patient presentation,” said Alastair S.E. Younger, MD, a clinical associate professor in the division of lower extremity reconstruction at the University of British Columbia in Vancouver, who presented the findings at the AAOS meeting.

The fusion groups in both the UW and Canadian studies were significantly younger than the TAR groups, reflecting the popular perception that TAR is contraindicated in patients younger than 54 years. This belief is based on the findings of a study published in the June 2004 issue of the Journal of Bone & Joint Surgery, in which five-year ankle prosthesis survival rate was significantly longer in patients older than 54 years than in younger patients.

But ankle prosthesis technology has evolved considerably since that study was conducted, and newer implants require much less bone removal and are therefore less likely to fail, according to Ricardo Rodrigues-Pinto, MD, an orthopedic surgeon at the Centro Hospitalar do Porto in Oporto, Portugal.

At the AAOS meeting, Rod­rigues-Pinto presented the results of a study in which 43 TAR patients younger than 50 years had significantly greater range of motion and ankle function at follow up (between two and five years) than 72 patients older than 50 years. Improvements from baseline were also significantly greater in the younger group; implant survivorship was similar between groups.

“The lesson here is not to go home and do total ankle replacement in all young patients. We are doing it in some selected patients,” Rodrigues-Pinto said. “Studies will require longer follow up to determine if the guidelines should be revised for younger patients.”

Sources:

Terrell R, Montgomery S, Pannell W, et al. Comparison of trends in ankle arthrodesis and total ankle replacement in the United States. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

Kim PH, Coleman NW, Benich MR, et al. Prospective comparison of ankle arthroplasty and arthrodesis. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

Younger ASE, Daniels TR, Glazebrook M, et al. Multicenter study comparing total ankle arthroplasty and ankle arthrodesis: Mid-term results. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

Spirt AA, Assal M, Hansen ST Jr. Complications and failure after total ankle arthroplasty. J Bone Joint Surg Am 2004;86(6):1172-1178.

Rodrigues-Pinto R, Geada JMM, Oliva XM, Amado P. Total ankle replacement in patients under the age of 50. Should this still be contraindicated? Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

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