Miner Ross, MD, MPH, Sudarshan Iyer, Kenneth R. Gundle, MD, Donald A. Ross, MD

Int J Spine Surg published online 20 July 2021
doi: 10.14444/8104

Summary by Kyle Plusch, BA

Diabetes has a well-known negative impact on surgical outcomes, and the prevalence of diabetes has increased significantly in recent years, including in patients undergoing spine surgery.^1-3 The specific effect of diabetes on elective spine surgery patients is less documented than in patients undergoing joint surgery and peripheral nerve surgery.^4-6

The objective of this study was to determine if pre-operative obesity and glycemic control (approximated with BMI and Hemoglobin A1c, respectively) increase the risk of post-surgical wound infection in spinal surgery. The study population consisted of 174,520 VA patients undergoing elective spinal surgery between 2007 and 2016 from the national VA database, determined by CPT codes. Surgeries for trauma, neoplasm, or infection were excluded, as well as BMI >50 or <15. Patient demographics, surgery information, height/weight within 3 months prior to surgery, and HbA1c within 3 months prior to surgery were recorded. The primary outcome was the presence of an infectious complication based on ICD codes within 6 months of the procedure.

28% of patients received a pre-op HbA1c test; the presence of pre-op testing was an independent risk factor for infectious complication, regardless of the test result (6.0% infection with test vs 3.9% infection without test, p<0.0001). In a separate model, the HbA1c value was a significant predictor of infection with an odds ratio of 1.042 for each 1% increase in test result. Similar analyses for BMI and age showed significant odds ratios of 1.027 for each 1kg/m² increase in BMI, and 1.009 for each 1 year increase in age.

The authors concluded that HbA1c value, BMI, and age all significantly contribute to the risk of wound infection after elective spine surgery in a large, nationwide VA patient population. The association of HbA1c testing with infection, regardless of result, was likely because pre-op diabetes testing was performed only when the patient had a history or strong likelihood of diabetes. This study establishes a dose-response relationship between BMI, HbA1c, and the odds of infection, and is supported by the large sample size. The retrospective nature of the study brings potential limitations such as unidentified confounders and improper ICD/CPT coding. Additionally, the study population is overwhelmingly male and Caucasian, potentially limiting the generalizability of the findings.

References:

1. Centers for Disease Control and Prevention. 2017. National diabetes statistics report. https://www.cdc.gov/ diabetes/data/statistics/statistics-report.html. Accessed November 1, 2019.
2. Guzman JZ, Iatridis JC, Skovrlj B, et al. Outcomes and complications of diabetes mellitus on patients undergoing degenerative lumbar spine surgery. Spine (Phila Pa 1976). 2014;39(19):1596–1604.
3. Yong PH, Weinberg L, Torkamani N, et al. The presence of diabetes and higher HbA1c are independently associated with adverse outcomes after surgery. Diabetes Care. 2018;41(6):1172–1179.
4. Fang A, Hu SS, Endres N, Bradford DS. Risk factors for infection after spinal surgery. Spine (Phila Pa 1976). 2005;30(12):1460–1465.
5. Cancienne JM, Deasey MJ, Kew ME, Werner BC. The association of perioperative glycemic control with adverse outcomes within 6 months after arthroscopic rotator cuff repair. Arthroscopy. 2019;35(6):1771–1778.
6. Cunningham DJ, Baumgartner RE, Federer AE, Richard MJ, Mithani SK. Elevated preoperative hemoglobin A1c associated with increased wound complications in diabetic patients undergoing primary, open carpal tunnel release. Plast Reconstr Surg. 2019;144(4):632e–638e.