Diabetic and nondiabetic foot ulcerations are independently associated with spinal infection

Spinal infections are associated with substantial morbidity, disability, and health care costs. Diabetes mellitus is a recognized risk factor; however, the contribution of foot ulceration itself, independent of diabetic status, to spinal infection risk has not been adequately explored.

To evaluate whether diabetic foot ulcer (DFU) and nondiabetic foot ulcer (NDFU) are independently associated with subsequent spinal infection and to determine whether ulceration confers risk beyond diabetes alone.

Retrospective matched cohort study using a nationwide administrative claims database (PearlDiver) with 2-year follow-up.

Adults with foot ulceration were stratified into DFU and NDFU cohorts. Separately, patients with diabetes were stratified into those with DFU and those without foot ulcers (D-NFU). After 1:1 matching, 514,370 patients with foot ulcers and 660,796 patients with diabetes were included.

Self-report measures were not available. Physiologic measures included development of spinal infection within 2 years, defined as spinal osteomyelitis, discitis, spinal epidural abscess, or vertebral infection identified using diagnostic codes. Functional measures were not available.

Cohorts were matched on age, sex, Elixhauser Comorbidity Index, body mass index, tobacco use, chronic kidney disease, immunologic disorders, socioeconomic indicators, and diabetes type when applicable. Multivariable logistic regression was performed to evaluate independent associations.

Among patients with diabetes, DFU was associated with increased odds of spinal infection compared with D-NFU (OR 2.55; 95% CI 2.41-2.70), including spinal osteomyelitis (OR 3.29; 95% CI 3.06-3.53). Among patients with foot ulcers, NDFU was associated with higher rates of spinal infection compared with DFU (1.22% vs 0.95%; OR 1.28; 95% CI 1.22-1.35) and remained independently associated on multivariable analysis (OR 1.24; 95% CI 1.17-1.31).

Foot ulceration was independently associated with increased odds of subsequent spinal infection regardless of diabetic status. Among patients with diabetes, the presence of a foot ulcer was associated with more than twofold higher odds of spinal infection, while diabetes was not associated with further increased odds once ulceration is present. Incorporating foot ulcer status into clinical risk stratification may facilitate suspicion of spinal infection in high-risk patients.