Risk factors for deep surgical site infection following posterior instrumented fusion for degenerative diseases in the thoracic and/or lumbar spine: a multicenter, observational cohort study of 2913 consecutive cases.

Purpose Surgical site infection (SSI) is one of the most devastating complications following spinal instrumented fusion surgeries because it may lead to a significant increase in morbidity, mortality, and poor clinical outcomes. Identifying the risk factors for SSI can help in developing strategies to reduce its occurrence. However, data on the risk factors for SSI in degenerative diseases are limited. This study aimed to identify risk factors for deep SSI following posterior instrumented fusion for degenerative diseases in the thoracic and/or lumbar spine in adult patients. Methods This was a multicenter, observational cohort study conducted at 10 study hospitals between July 2010 and June 2015. The subjects were consecutive adult patients who underwent posterior instrumented fusion surgery for degenerative diseases in the thoracic and/or lumbar spine and developed SSI. Detailed patient-specific and procedure-specific potential risk variables were prospectively recorded using a standardized data collection chart and retrospectively reviewed. Results Of the 2913 enrolled patients, 35 developed postoperative deep SSI (1.2%). Multivariable regression analysis identified three independent risk factors: male sex (P = 0.002) and American Society of Anesthesiologists (ASA) score of ≥ 3 (P = 0.003) as patient-specific risk factors, and operation including the thoracic spine (P = 0.018) as a procedure-specific risk factor. Conclusion Thoracic spinal surgery, an ASA score of ≥ 3, and male sex were risk factors for deep SSI after routine thoracolumbar instrumented fusion surgeries for degenerative diseases. Awareness of these risk factors can enable surgeons to develop a more appropriate management plan and provide better patient counseling.