American Academy of Orthopaedic Surgeons Annual Meeting

American Academy of Orthopaedic Surgeons Annual Meeting

Issue: June 2011
June 01, 2011
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Age, gender and surgeon volume found to affect long-term THR revision rates

Issue: June 2011
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Long-term risk of revision following primary total hip replacement was found to be higher among men, patients younger than 75 years old and patients operated on by a low-volume surgeon, according to a study presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.

Jeffrey N. Katz, MD, and his team conducted a study to estimate the 12-year revision risk following primary total hip replacement (THR) in the Medicare population. The investigators paid specific attention to whether the risk differed according to patient demographic factors, and investigated further into the influence of hospital and surgeon volume on the risk of revision.

Medicare population

Katz and his group performed an observational cohort study using Medicare claims for 51,347 patients age 65 years or older who underwent primary elective THR between July 1995 and June 1996 for hip osteoarthritis, Katz said. He reported a primary outcome of a revision of the hip replacement identified in claims through ICD9 codes for revision. These patients were followed in claims through 2008.

Jeffrey N. Katz, MD
Jeffrey N. Katz

Two methods of analysis were performed: a Cox proportional hazards model and Kaplan-Meier analysis. The dependent variable in the Cox model was time to revision in 12 years of follow-up. Independent variables included age, gender, poverty status, comorbidity and annual hospital or surgeon volume of THR in the Medicare population.

Revision and mortality

Men were found to have an adjusted hazard ratio of 1.23 compared with women, indicating a 20% higher risk of revision compared with women. Similarly, patients aged 65 to 75 years had a 47% greater risk of revision than patients older than 75 years, and patients whose THRs performed by a low-volume surgeon were also at a higher risk of revision, Katz reported.

According to the Kaplan-Meier analysis, 94% of women older than 75 years and 86% of men aged 65 to 75 years were revision-free at 12 years. Additionally, Katz explained that the 12-year mortality risk exceeded the 12-year revision risk.

Among those older than 75 years at the time of surgery, the 12-year mortality was 58% and revision rate was 6%. For patients aged 65 to 75 years, the 12-year mortality was 31% and the revision rate was 9%.

Katz noted a few limitations of his study, such as ICD9 coding not distinguishing between right and left hip replacements or revisions. He estimated up to 30% of the revisions may have been performed only on the contralateral side. Further, he noted, revision is “an ambiguous proxy” for failure of a THR.

“In summary, revision risk is higher for younger patients, for males and for those operated upon by low-volume surgeons,” Katz said. “The volume effect occurs in the first 18 months and not thereafter. These data suggest the innovations to increase prosthesis longevity should be targeted at younger patients.” – by Robert Press

Reference:
  • Katz JN, Wright EA, Nti AA, et al. Predictors of 12-year revision rate following primary THR in the U.S. Medicare population. Paper #184. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.

  • Jeffrey N. Katz, MD, can be reached at Brigham and Women’s Hospital, 75 Francis St., Boston, MA 02115; (617) 732-5500; email: jnkatz@partners.org
  • Disclosure: The study was funded by the National Institutes of Health.