Deep perioperative infection risk after THA was greater with higher HbA1c levels

HbA1c values correlate with the risk of infection, but it is a poor predictor of who will develop an infection.

Patients with diabetes who underwent total hip arthroplasty had an increased risk of deep perioperative infection that required surgical intervention as their perioperative hemoglobin A1c levels increased, based on results presented at the American Association of Hip and Knee Surgeons Annual Meeting.

“In patients with diabetes, a perioperative hemoglobin A1c value does correlate with the risk of infection following total hip arthroplasty,” James A. Browne, MD, associate professor of orthopedic surgery and division head of adult reconstruction at the University of Virginia, told Orthopedics Today.

Infection risk analyzed

Using a national administrative database, Browne and his colleagues stratified 7,736 patients with diabetes who underwent total hip arthroplasty (THA) between 2007 and 2015 into mutually exclusive groups with hemoglobin A1c (HbA1c) values in increments of 0.5 mg/dL. They were most interested in deep periprosthetic joint infection (PJI) within 1 year of surgery as an outcome, Browne noted.

Results showed at 1 year postoperatively, patients with low HbA1c levels at or below 5.49 mg/dL had an incidence of PJI that was as low as 0.7% vs. 5.9% for patients with HbA1c levels of 11.5 or greater. This difference was statistically significant (P<.0001).

“When we developed our [receiver operating characteristic] ROC curve, we found the inflection point is around 7.0 [mg/dL] to 7.5 mg/dL,” Browne said in his presentation.

He noted statistically significant differences in the PJI rate when patients were divided into two groups: patients with a HbA1c level below 7.5 mg/dL and patients with a HbA1c level above 7.5 mg/dL. The investigators found the patients with a HbA1c level below 7.5 mg/dL had a PJI rate of 1% vs. 2.4% in patients with a HbA1c level above 7.5 mg/dL.

Based on the multivariate regression analysis, which was done to control for the patients’ demographics and comorbidities, “this [difference] remained significant with an odds ratio of 2.6; again, with the cut off being 7.5 [mg/dL],” Browne said at the meeting.

Predicting infection risk

Although a patient’s HbA1c correlated with the risk of infection after THA, Browne told Orthopedics Today that was a poor predictor of who would go on to develop an infection.

“As we look at patients who have diabetes, the A1c is an important way to risk stratify patients,” Browne said. “Patients with a higher A1c value do have a higher risk for periprosthetic joint infection. However, taken by itself the A1c value is a poor way to predict who will develop an infection and is not a good way to screen out or exclude patients for hip replacement,” he told Orthopedics Today.

He also noted further research is needed on whether lowering HbA1c levels prior to surgery will improve the chances of a patient not developing an infection.

Browne said he still refers patients with poorly controlled diabetes and an elevated HbA1c to their medical doctor or endocrinologist to try to get that value down before surgery. Whether that improves the patient’s chance of not developing a PJI remains uncertain. – by Casey Tingle

Reference:

Cancienne JM, et al. Paper #54. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 10-13, 2016; Dallas.

For more information:

James A. Browne, MD, can be reached at 545 Ray C. Hunt Dr., Charlottesville, VA 22908; email: jab8hd@hscmail.mcc.virginia.edu.

Disclosure: Browne reports no relevant financial disclosures.