Background:

Previous research has shown that diabetes mellitus (DM) is associated with postoperative complications, including surgical site infections (SSIs). However, evidence for the association between diabetes control and postoperative complications in patients with DM is mixed. Prior studies relied on a single metric for defining uncontrolled DM, which does not account for glycemic variability, and it is unknown whether a more comprehensive assessment of diabetes control is associated with postoperative complications.

Questions/purposes:

(1) Is there a difference in the incidence of SSI after lumbar spine fusion in patients with uncontrolled DM, defined with a comprehensive assessment of glycemic control, compared with patients with controlled DM? (2) Is there a difference in the incidence of other select postoperative complications after lumbar spine fusion in patients with uncontrolled DM compared with patients with controlled DM? (3) Is there a difference in total reimbursements between these groups?

Methods:

We used the PearlDiver Patient Records Database, a national administrative claims database that provides access to the full continuum of perioperative care. We included 46,490 patients with DM undergoing posterior lumbar fusion with instrumentation. Patients were required to be continuously enrolled in the database for at least 1 year before and 90 days after the index procedure. Patients were divided into uncontrolled and controlled DM cohorts, as defined by ICD-9 diagnostic codes. These are based on a comprehensive assessment of glycemic control, including consideration of patient self-monitoring of blood glucose levels, hemoglobin A1c, and the presence/severity of diabetes-related comorbidities. The cohorts differed only by age, insurance type, and Elixhauser comorbidity score. The primary outcome was the incidence of SSI, divided into superficial and deep, within 90 days postoperatively. Secondary complications included the incidence of cerebrovascular events, acute kidney injury, pulmonary embolism, pneumonia, urinary tract infection, blood transfusion, and total reimbursements. These are the sum of reimbursements occurring within 90 days of surgery, which capture the total professional and facility cost burden to the health payer (such as the insurer). We constructed multivariable logistic regression models to adjust for the effects of age, insurance type, and comorbidities.

Results:

After adjusting for potentially confounding variables including age, insurance type, and comorbidities, we found that patients with uncontrolled DM had an odds ratio for deep SSI of 1.52 (95% confidence interval 1.16 to 1.95; p = 0.002). Similarly, patients with uncontrolled DM had adjusted odds ratios of 1.25 (95% CI 1.01 to 1.53; p = 0.03) for cerebrovascular events, 1.36 (95% CI 1.18 to 1.57; p < 0.001) for acute kidney injury, 1.55 (95% CI 1.16 to 2.04; p = 0.002) for pulmonary embolism, 1.30 (95% CI 1.08 to 1.54; p = 0.004) for pneumonia, 1.33 (95% CI 1.19 to 1.49; p < 0.001) for urinary tract infection, and 1.27 (95% CI 1.04 to 1.53; p = 0.02) for perioperative transfusion. Patients with uncontrolled DM had higher median 90-day total reimbursements than patients with controlled DM: USD 27,915 (interquartile range 5472 to 63,400) versus USD 10,263 (IQR 4101 to 49,748; p < 0.001).

Conclusion:

Our findings encourage surgeons to take a full diabetic history beyond the HbA1c value, including any self-monitoring of glucose measurements, time in acceptable range for continuous glucose monitors, and/or consideration of the presence/severity of diabetes-related complications before lumbar spine fusion, as HbA1c does not fully capture glycemic control or variability. We emphasize that uncontrolled DM is a clinical, rather than laboratory, diagnosis. Comprehensive diabetes histories should be incorporated into existing preoperative diabetes care pathways and elective surgery could be deferred to improve glycemic control. Future development of an index measure incorporating multidimensional measures of diabetes control (such as continuous or self-glucose monitoring, diabetes-related comorbidities) is warranted.

Level of evidence:

Level III, therapeutic study.