HbA_1c Levels May Help Predict Post-Arthroplasty Complications

SAN FRANCISCO — Complications after total knee or hip arthroplasty in patients with diabetes were significantly more common in those with higher hemoglobin A_1c levels, a retrospective study of 119 patients found.

The overall rate of medical and surgical complications was more than 50% in patients with a hemoglobin A_1c (HbA_1c) level greater than 7%, and less than 40% in those with an HbA_1c level below 7%, researchers reported.

American Diabetes Association recommendations set a treatment goal of an HbA_1c level below 7%.

“Patients with significantly elevated HbA_1c levels should have their glycemic control better optimized prior to undergoing total hip [or knee] arthroplasty, as well as in the perioperative period,” Dr. Yossef C. Blum said during a poster session at the annual meeting of the American Academy of Orthopaedic Surgeons.

In a review of inpatient and outpatient charts of total knee or hip arthroplasty performed by a single surgeon at one institution from 2000 to 2007, Dr. Blum, of Montefiore Medical Center, New York, and his associates found 199 patients whose HbA_1c level had been measured in the year before surgery or within 3 months after the surgery. Those with conditions other than diabetes that led to an immunosuppressed state, such as HIV or rheumatoid arthritis, were excluded.

Patients did not have to have a diagnosis of diabetes to be included—just an HbA_1c measurement—because up to a third of people with diabetes do not have a formal diagnosis, they reported.

In all, 73% of the patients underwent total knee arthroplasty and 27% had total hip arthroplasty. Their mean age was 68 years. The cohort was 76% men, 34% white, 34% black, 23% Hispanic, and 9% other races or ethnicities. Their mean body mass index was 34 kg/m

A multivariate analysis looking for associations between HbA_1c levels and outcomes within 3 months of the surgery showed that higher HbA_1c levels were significantly associated with a higher risk for any complications, and surgical site and wound complications after surgery.

Only four surgical site infections occurred—too few to demonstrate a specific association between HbA_1c levels and wound infection—but “it is notable that three of four infections occurred in patients with an HbA_1c [level] above 7.5%,” Dr. Blum said, adding that although too few complications occurred to show a significant association with HbA_1c levels, an association might be seen in a larger study.

The current study found no association between HbA_1c level and the risk of non-surgical-site infections, urinary retention, or discharge after surgery to an inpatient facility. Overall, 43% of the patients developed medical or surgical complications.

“Future studies with [more] patients may help determine a cut-off HbA_1c level above which total hip [or knee] arthroplasty can be considered too high risk,” Dr. Blum said.

A 2003 review by other investigators of 290 diabetes patients who underwent noncardiac surgeries found that those with an HbA_1C level above 7% had a statistically significant increased risk for postoperative complications. But there have been few studies to date on the results of total knee arthroplasty in diabetes patients, and even fewer studies on the results of total hip arthroplasty in diabetes patients, he noted.

Some reports suggest a risk of 1%–7% for deep infection in diabetes patients after total knee arthroplasty, and overall wound complication rates of 1%–12%. A 1983 study of outcomes after total hip arthroplasty in diabetes patients reported superficial infections in 10% of the patients and deep infections in 7%.