Back for More? Assessment of Time to Subsequent Cervical Surgery Following Lumbar Fusion: Understanding Shared Risk Factors for Spine Surgery

Introduction: Cervical spine fusion surgery is not uncommon following remote lumbar surgery. The underlying relationship and common risk factors are well characterized. Understanding the risk factors leading to cervical surgery in patients who underwent lumbar surgery is necessary in informing patient selection.

Methods: There were 6,444 patients who received lumbar fusion between 10/2009-10/2015 at a single tertiary care institution (median follow-up: 11 years (IQR = 8–13 years)) who were 1:3 propensity-matched over 24 characteristics (including degenerative spine disease) to patients from internal medicine clinics who during the same period (n = 2,361,959) who had not received lumbar fusion. Time to subsequent diagnosis of cervical disease and subsequent surgery was assessed through several multivariable Cox proportional hazard models accounting for the competing risks of time to outcome (e.g. diagnosis or surgery) and death.

Results: After propensity matching, lumbar fusion patients had almost 3 times the risk of cervical fusion, compared to control patients. In the non-cervical fusion cohort, older age, higher BMI, former or current smoker, degenerative spine disease, diabetes, and rheumatoid arthritis were linked with an increased risk of future cervical fusion. Diabetes and shoulder arthritis were associated with greater risk of cervical fusion while older age was associated with lower risk in patients who received a lumbar fusion. Preoperative patient-reported outcomes (PROs) were not significantly associated with the likelihood of cervical fusion; however, improved postoperative EuroQoL 5-Dimensions Index and Pain Disability Questionnaire total score were associated with decreased risk of cervical fusion.

Conclusion : This was the first study assessing the risk of cervical surgery following lumbar spine surgery using a large propensity-matched sample and found patients undergoing lumbar spine fusion had significantly increased risk of future cervical spine fusion. The success of lumbar fusion surgery measured by PROs was associated with a decreased risk of future cervical fusion surgery, while classical patient characteristics were not. This implies that additional factors may mediate this increased risk and should be further investigated.