Severity of Preoperative HbA1c and Predicting Postoperative Complications in Spine Surgery

Background: Diabetes mellitus (DM) is associated with a greater incidence of perioperative complications. The measurement of hemoglobin A1c (HbA1c) has not been routinely used in the preoperative assessment for spine surgeries.

Methods: In the present single-institution, prospective study, HbA1c testing was included in the preoperative laboratory examination of patients undergoing spinal surgery from 2016 through 2018. The HbA1c levels were categorized using the American Diabetes Association guidelines as normal (HbA1c <5.7%), pre-DM (HbA1c 5.7%-6.4%), and diabetes (HbA1c >6.5%). Those with a HbA1c of ≥8% were separated as having poorly controlled DM for analysis. Perioperative complication and comorbidity data were collected to assess for associations with DM using logistic regression models. Odds ratios (ORs) and 95% confidence intervals were computed.

Results: A total of 440 patients (238 men, mean age, 56.43 ± 13.28 years; mean body mass index, 30.80 ± 6.65 kg/m²) met the study criteria. The HbA1c was <5.7% in 206 patients (46.8%), 5.7%-6.4% in 148 (33.6%), 6.5%-7.9% in 64 (14.5%), and ≥8.0% in 23 patients (5.22%). Bivariate logistic modeling showed that patients with poorly controlled DM had a higher risk of complications (OR, 2.92) than did the patients with DM (OR, 2.13). Malignancy (OR, 2.62) and hypertension (OR, 1.86) were also significant risk factors for complications. However, smoking (OR, 0.83) was not significant. Poorly controlled DM remained associated with complications in multivariable logistic regression modeling (OR, 2.72).

Conclusions: Poorly control DM defined by the preoperative HbA1c was significantly associated with postoperative complications. Smoking, however, was not so associated. Preoperative HbA1c can be used to assess the risk of postoperative spine surgery complications.