Rate of adverse events following THA improved during 2002 to 2007

Medicare data reveal that older age, obesity and early procedures are risk factors for adverse events.

Issue: May 2010

The annual rate of adverse events after total hip arthroplasty trended downward from 2002 to 2007, with a rate of 9.1% in 2002 and 3% in 2007, according to data from the Medicare Patient Safety Monitoring System.

James I. Huddleston III, MD,of the Department of Orthopaedic Surgery at Stanford University Medical Center, Stanford, Calif., presented data on adverse events among 1,809 Medicare patients at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons in New Orleans.

“[The incremental improvement in adverse event rates] may be due to a change in a small number of individual adverse events — the implementation of standard operating procedures, and it may also be due to the fact that the length of stay has decreased,” he said.

Random sampling

The patient population came from an original group of approximately 180,000 Medicare patients, a subset of patients from the Hospital Payment Monitoring Program. The Centers for Medicare & Medicaid Services randomly select the sample of patients for the monitoring program each month from approximately 1 million hospital discharges around the country.

Of the 1,809 patients, 105 experienced at least one adverse event, with a total of 136 events. The overall rate of adverse events while hospitalized was 5.8%. Annual rates of adverse events were 9.1% in 2002, 8.2% in 2003, 4.9% in 2004, 4.1% in 2005, 3.5% in 2006, and 3.0% in 2007. The researchers found that older age, obesity and earlier year of surgery were risk factors for these events.

An evaluation of unadjusted Medicare claims data revealed that the length of stay decreased for patients with and without adverse events during the course of the study. Experiencing any adverse event was associated with an increased length of stay but not with an increased risk for mortality within 30 days of the procedure, Huddleston said. After 30 days, the mortality rate was 0.6%. Thirty-day readmission rates were 12.4% for patients with adverse events and 6.4% for those without adverse events.

Dislocation

Huddleston and colleagues also found that the dislocation rate reduced compared with data from a similar Medicare cohort in Mahomed and colleagues’ report in 1995: 3.1% vs. 1.5%.

“It may be affected by the fact that our data collection period is only 30 days compared with Mahomed et al,” Huddleston said. “Also, the increase in the usage of large femoral heads is probably affecting it as well.”

Huddleston and colleagues also found a 0.6% rate of venous thromboembolism, down from the 0.9% rate of pulmonary embolism that Mahomed’s group found in 1995. They also found a higher readmission rate than that in 1995. “The mortality rate is unchanged compared to 1995 [data], though the study may be underpowered to detect a difference,” Huddleston told Orthopedics Today.

They are currently analyzing the data set to investigate whether there is a correlation between reduced length of stay and readmission, he said, which may provide for improvement in patient safety and cost reduction,” Huddleston said.

He further added that based on these data, “patients aged 75 years or older and obese patients should be advised preoperatively that they may be at increased risk for experiencing adverse events postoperatively. Programs that optimize high-risk patients preoperatively may improve patient safety in the future.” — by Tina DiMarcantonio

References:

Huddleston JI III, Wang Y, Herndon JH, et al. Epidemiology of adverse events after total hip arthroplasty in Medicare beneficiaries from 2002-2007. Paper 118. Presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons. March 9-13, 2010. New Orleans.

Mahomed NN, Barrett JA, Katz JN, et al. Rates and outcomes of primary and revision total hip replacement in the United States Medicare population. J Bone Joint Surg (Am). 2003;85(1):27-32.

James I. Huddleston III, MD, can be reached at the Stanford Medicine Outpatient Center, Orthopedic Surgery — North Campus, 450 Broadway St., Pavilion C, 4th Floor MC 6342, Redwood City, CA 94063; 650-721-7661.

Epidemiology of adverse events after total hip arthroplasty in Medicare beneficiaries from 2002-2007 was directly funded by a grant from the Agency for Health Care Research and Quality.