Published 4/1/2017
Terry Stanton

Study: HbA1c Risk Threshold for Infection Identified for Diabetes Patients Undergoing Shoulder Replacement

A study, presented at the AAOS Annual Meeting in San Diego, reported, that, in patients with diabetes mellitus undergoing shoulder arthroplasty, the risk of deep postoperative infection rises with increasing hemoglobin A1c (HbA1c) levels. The data also suggested a perioperative HbA1c greater than 8.0 mg/dL might serve as a threshold for a significantly increased risks of postoperative infection.

Although diabetes has been strongly associated with an increased risk of postoperative wound complications and deep postoperative infection after total hip arthroplasty (THA) and total knee arthroplasty (TKA), it has not been routinely associated with higher rates of infection after shoulder arthroplasty, said Brian C. Werner, MD, of the University of Virginia, who presented the study. The likely explanation is that lower infection rates and lower numbers of shoulder arthroplasty procedures challenge investigators to achieve adequate statistical power to investigate any association. The study reviewed outcomes for 2,257 patients with diabetes and with a perioperative HbA1c recorded in the PearlDiver Patient Records Database who underwent shoulder reconstruction, including anatomic total shoulder arthroplasty, reverse total shoulder arthroplasty, and shoulder hemiarthroplasty. Patients with a history of prior or concomitant diagnoses of periprosthetic infection were excluded from the analysis. These patients were identified from an overall group of 18,729 patients who underwent shoulder arthroplasty. Patients then grouped into 13 groups based on 1 mg/dL increments of their HbA1c level , A low group started with patients with a level between 0.00 and 5.9 mg/dL. The highest group included those with a level of 10.0 mg/dL or greater. For patients with multiple HbA1c levels recorded, the level taken closest to the date of surgery was chosen. Using ICD-9 codes, the investigators identified patients who had (1) a diagnosis of a superficial wound complication within 6 months postoperatively and (2) a deep infection requiring surgical intervention within 1 year postoperatively. Deep infection requiring surgical intervention was identified through codes for an open or arthroscopic procedure performed for a diagnosis of postoperative infection, periprosthetic infection, or septic shoulder/abscess. Patients who underwent subsequent revision shoulder arthroplasty for an infectious indication as above were also considered to have surgical deep infections. The overall rate of superficial wound complications among the 18,729 patients was 1.1 percent (208) within 6 months; the overall rate of deep infection requiring surgical intervention within 1 year was 0.5 percent (103). After controlling for patient demographics and other comorbidities, patients with diabetes mellitus had significantly higher rates of wound complications (1.4 percent vs. 0.9 percent, P = 0.028) and deep infection requiring surgery (0.7 percent vs. 0.4 percent, P = 0.001) after shoulder arthroplasty compared to patients without diabetes. The wound complication rate increased significantly as perioperative HbA1c level increased (P = 0.0008). A plot of the rate of postoperative deep infection requiring surgical intervention within 1 year following shoulder arthroplasty as a function of perioperative HbA1c showed that the rate of deep infection increased significantly as perioperative HbA1c level increased (P = 0.002). A threshold suggested
Statistical analysis revealed that, after controlling for demographics and additional comorbidities, patients with HbA1c levels above the 8.0 mg/dL threshold had a significantly higher risk of wound complications (P < 0.0001) and deep postoperative infection requiring surgical intervention (P = 0.007) compared to patients below that threshold. Describing the clinical implications of the study, Dr. Werner said, “Although the overall risk of infection following shoulder arthroplasty is low, the consequences and morbidity of this complication are devastating to the patient and represent a substantial financial burden to the healthcare system. The risk of wound complications and deep postoperative infection requiring surgical intervention following shoulder arthroplasty in patients with diabetes mellitus increases as the perioperative HbA1c increases. A perioperative HbA1c level above 8.0 mg/dL could serve as a threshold for a significantly increased risk of deep postoperative infection following shoulder arthroplasty. It is important to note, however, that even in patients with high A1c levels, the absolute risk of infection still remains low (less than 2 percent). Although we do not recommend using strict cutoffs based on this data, it is reasonable to screen patients with diabetes for hemoglobin A1c preoperatively if they are planning shoulder arthroplasty to assess whether optimization of their blood glucose control could potentially lower postoperative wound complication or infection rates.” Dr. Werner's coauthors of “Not All Patients with Diabetes Have the Same Risks: The Association of Perioperative Glycemic Control with Deep Postoperative Infection Following Shoulder Arthroplasty in Patients with Diabetes,” are Jourdan M. Cancienne, MD; Dustin Richter, MD; Stephen F. Brockmeier, MD; and James A. Browne, MD. The authors' disclosures as submitted to the Orthopaedic Disclosure Program can be found in the Final Program; the most current disclosure information may be accessed electronically at www.aaos.org/disclosure Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org