A retrospective cohort analysis of the effects of renin-angiotensin system inhibitors on spinal fusion in ACDF patients

BACKGROUND CONTEXT: Recently, preclinical and clinical studies suggest an association between renin-angiotensin system (RAS) blockers and bone healing, particularly in the context of osteoporotic bone fractures. PURPOSE: To determine the correlation between the use of RAS inhibitors and fusion outcomes and neurologic status in anterior cervical discectomy and fusion (ACDF) surgery. STUDY DESIGN: Retrospective observational study. PATIENT SAMPLE: Patients who underwent ACDF for degenerative disorders. OUTCOME MEASURES: Spinal fusion status and neurologic function (modified Japanese Orthopedic Association [mJOA] and Nurick grading scales). METHODS: A retrospective chart review was performed, including 200 patients who underwent ACDF for degenerative disorders with 1-year minimum follow-up. Demographic data, comorbidities, antihypertensive medication, neurologic examination, and fusion status were collected. Spinal fusion was assessed via plain cervical x-ray, resorting to dynamic radiographs and/or computer tomography (CT) in cases of uncertainty. Preoperative mJOA and Nurick scores and recovery rates were calculated to determine neurologic status. RESULTS: Of the 200 patients (42.5% females, 57.5% males, median age of 53.7 years), 82 hypertensive patients were identified. Seventy-seven (93.9%) were taking antihypertensive medication as follows: 36.4% angiotensin-II receptor blockers (ARBs), 35.1% angiotensin-converting enzyme inhibitors (ACEIs), and the remaining patients were taking other medication. In the analysis of fusion rates, patients treated with ARBs exhibited a higher fusion rate, while those treated with ACEIs displayed a lower fusion rate compared to untreated nonhypertensive patients (p =.04 and.02, respectively). The difference in fusion rates between ARBs and ACEIs was also significant, with the former displaying higher rates (p <.001). Smoking exhibited a negative correlation with spinal fusion (p <.001). In the multivariate analysis, ARBs remained an independent factor for successful fusion (p =.02), while smoking remained a risk factor for failed fusion (p =.002). In the neurologic examination, ACEIs, hypertension status, and older age correlated with lower modified Japanese Orthopedic Association (mJOA) recovery rates (p =.001, <.001, and <.001, respectively) in the univariate analysis. CONCLUSIONS: In ACDF patients, we observed that ARBs were associated with higher fusion rates. Conversely, ACEIs and smoking were related to failed fusion. Prospective case-control studies are needed to confirm these RAS inhibitors effects on spinal fusion.