American Academy of Orthopaedic Surgeons Annual Meeting

American Academy of Orthopaedic Surgeons Annual Meeting

Issue: July 2011
July 01, 2011
2 min read

Study links dementia with increased mortality and obesity with infection after THA

Issue: July 2011
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Obesity, preoperative anemia and diabetes are among the risk factors associated with an increase of periprosthetic joint infection in Medicare patients who undergo total hip arthroplasty, according to a recently presented study.

Kevin J. Bozic, MD, MBA, presented his team’s findings at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.

Bozic noted that risk factors such as psychoses, renal disease and dementia were also found in his team’s study to be associated with an increased postoperative mortality risk among Medicare patients who underwent total hip arthroplasty (THA).

“Despite a number of classification systems available to stratify patients by risk preoperatively … none have been validated for hip and knee arthroplasty patients, and therefore patient-specific risk factors in the elderly population are poorly understood,” Bozic said. “The purpose of this study was to identify baseline patient co-morbidities associated with an increased risk of prosthetic joint infection and postoperative mortality in Medicare patients.”

Kevin J. Bozic, MD, MBA
Kevin J. Bozic

More than 40,000 cases

To calculate the relative risk of prosthetic joint infection (PJI) and mortality as baseline medical co-morbidities, Bozic and his team used the Medicare 5% sample and reviewed 40,919 primary THAs performed between 1998 and 2007. Cox regression was used to gauge the impact of 30 comorbidities on mortality and PJI. Controls were put in place for age, gender, race, census region, public assistance and other baseline co-morbidities.

“It was important that we defined the presence of the comorbidity as being present during the 1-year period prior to [THA], so these were not comorbidities that were identified for the first time during the inpatient hospitalization from the index procedure,” Bozic said.

The team also constructed adjusted hazard ratios for each condition, using Wald’s X2 statistic to rank degrees of association for co-morbidities with postoperative death or PJI.

Mental health

Bozic’s team found rheumatologic disease, obesity, coagulopathy, preoperative anemia, diabetes and cardiac arrhythmia to be the most significant independent PJI risk factors. Bozic noted that congestive heart failure, metastatic cancer, psychoses, renal disease and dementia were “most significant risk factors for 90-day postoperative mortality.”

“The importance here is that both psychoses and dementia were identified as risk factors for mortality, and this is important,” Bozic said. “Consider the mental health — and the stability of mental health — of your patients before considering elective surgery.”

“I think this information’s important for clinical decision-making and for risk-stratifying patients, particularly when we get to public reporting of total joint arthroplasty outcomes,” he concluded. “These conditions should be optimized by primary care physicians and surgeons prior to considering elective surgery.” – by Robert Press

  • Bozic KJ, Lau E, Ong K, et al. Risk factors for PJI & Postoperative Mortality following THA in Medicare patients. Paper #480. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego.
  • Kevin J. Bozic, MD, MBA, can be reached at University of California, San Francisco, 500 Parnassus, MU-320 W, San Francisco, CA 94143; 415-476-3320; email:
  • Disclosure: Bozic has no relevant financial disclosures.