Higher UTI Risk After Spinal Fusion in Patients With Certain Comorbidities

Patients with diabetes, obesity, rheumatoid arthritis, and/or coronary artery disease had an increased risk of urinary tract infections (UTIs) following spinal fusion for deformities, with the highest risk observed in those whose procedures involved more than 12 levels fused, a study found.¹

Authors of the study published in the International Journal of Spine Surgery study noted that while past studies have addressed risk factors and complications affecting spinal deformity procedure outcomes, they often focus on a specific type of spinal deformity, such as scoliosis, or particular postoperative complications, like UTIs.

The researchers noted that UTIs account for 23% of infections in the intensive care unit and 12.9% of health care-associated infections. They also significantly affect morbidity, mortality, sepsis, and cost of care.²

However, postoperative UTI is understudied for fusion procedures, particularly spinal deformity procedures.¹ Consequently, the researchers conducted a study to identify risk factors and the incidence of postoperative UTIs in patients undergoing fusion for spinal deformities.

This study investigated the incidence of postoperative urinary tract infections (UTIs) in patients undergoing spinal fusion for deformities, finding that patients with more than 12 levels fused had the highest UTI rates. | Image Credit: valiantsin - stock.adobe.com

To do so, they used patient data from the PearlDiver Database, spanning 2010 to 2019; PearlDiver is a national insurance database, consisting of Medicare and multiple private insurance agencies.³ Patients within the database who received spinal fusion for deformities were identified using The International Classification of Diseases, 9^th Edition (ICD-9), ICD, 10^th Edition (ICD-10), and/or Current Procedural Terminology (CPT) codes.¹

Based on the CPT codes, the researchers categorized patients by fusion technique, either anterior or posterior. Each category was then split into 3 subgroups based on the number of levels fused. The anterior fusion category was divided into subgroups for those with 2 to 3 levels fused, 4 to 7 levels fused, and more than 7 levels fused. Conversely, the posterior fusion category included subgroups for patients with fewer than 7 levels fused, 7 to 12 levels fused, and more than 12 levels fused. The researchers noted that the subgroups were matched to account for differences in age and gender.

Next, the researchers identified patients in each level group who contracted a UTI within 1 week, 1 month, 2 months, and 3 months post-surgery using ICD-9 and ICD-10 codes. Patients who contracted a UTI within 1 month were then analyzed for the presence of various risk factors during the 1 year before surgery. More specifically, the researchers used ICD-9 and ICD-10 codes to identify obesity, diabetes, rheumatoid arthritis, and coronary artery disease. Patients in each group with any of these risk factors were compared with those without any risk factors.

The researchers identified 11,827 patients who underwent spinal fusion for deformities, including 1442 anterior and 10,385 posterior procedures. Due to low sample sizes across the 3 fusion level groups for the anterior procedures, these patients were excluded from the analysis. Instead, the researchers focused on the posterior group.

After matching for age and gender, each posterior level subgroup consisted of 1787 patients. The highest UTI incidence occurred in the 15 to 19-year age range, with the majority of patients being women (73.4%). After 1 week post-surgery, the incidence of UTIs was 1.2% for patients with less than 7 levels fused, 1.1% for those with 7 to 12 levels fused, and 0.7% for those with more than 12 levels fused.

The researchers found no significant difference in UTI incidence between the 3 subgroups at 1 week or 1 month post-surgery. However, patients with more than 12 levels fused had a significantly higher UTI incidence than those with 7 to 12 levels fused, both at 2 months (3.6% vs 2.2%; P = .04) and 3 months (3.9% vs 2.7%; P = .04).

At 3 months, the UTI rate between the fewer than 7 and 7 to 12 levels fused groups were similar, with rates of 3.6% and 2.9%, respectively (P = .15). The UTI rate was statistically higher in the group with more than 12 levels fused, with a rate of 3.9% (P < .04).

Overall, the greatest increase in UTI incidence occurred within the first 7 days post-surgery for the fewer than 7 and 7 to 12 levels fused groups. Among patients with more than 12 levels fused, the highest increase in UTI incidence occurred between 1 week and 1 month post-surgery.

Across all subgroups, patients with any risk factors had significantly higher rates of UTIs at 1, 2, and 3 months. The largest risk differences were observed at 1 month for those with fewer than 7 levels fused, at 3 months for those with 7 to 12 levels, and at 2 months for more than 12 levels.

Patients who underwent fewer than 7 levels fused were 2.73 times more likely to contract a UTI if they had a risk factor (P = .01). Similarly, those with a risk factor who underwent 7 to 12 levels fused or more than 12 levels fused were 2 times (P = .01) and 2.8 times (P < .001) more likely to contract a UTI, respectively.

The largest difference in UTI incidence between patients with and without risk factors occurred at 3 months in the fewer than 7 levels (5.5% vs 2.4%; OR, 2.4; P = .004), 7 to 12 levels (3.8% vs 2.0%; OR, 2.0; P = .01), and more than 12 levels (6.4% vs 2.8%; OR, 2.4; P = .002) fused groups.

The researchers acknowledged their study’s limitations, including that their small sample size required them to pool all risk factors together. Also, other associated comorbidities and complications may not have been accounted for. Despite their limitations, they expressed confidence in their findings.

“This is the first study to analyze and compare UTI incidence following fusion for spinal deformity,” the authors concluded.

References

1. Shelby H, Shelby T, Fresquez Z, Wang JC, Hah R. Risk factors for postoperative urinary tract infection in patients undergoing arthrodesis for spinal deformity of different levels. Int J Spine Surg. doi:10.14444/8724
2. Schuller K, Probst J, Hardin J, Bennett K, Martin A. Initial impact of Medicare's nonpayment policy on catheter-associated urinary tract infections by hospital characteristics. Health Policy. 2014;115(2-3):165-171. doi:10.1016/j.healthpol.2013.11.013
3. About PearlDiver services. PearlDiver. Published 2025. Accessed March 4, 2025. https://pearldiverinc.com/about-us/