0.5-to 1-Fold Intervertebral Distraction Is a Protective Factor for Adjacent Segment Degeneration in Single-level Anterior Cervical Discectomy and Fusion

Study Design.Retrospective analysis.Objective.This study aimed to compare the clinical and radiological outcomes of different degrees of distraction in anterior cervical discectomy and fusion (ACDF) and evaluate the risk factors for adjacent segment degeneration (ASD).Summary of Background Data.ASD is a common complication following ACDF. Inadequate distraction of the intervertebral space during surgery is associated with ASD; however, there is still an ongoing debate regarding what degree of distraction is appropriate.Methods.This retrospective study enrolled 130 patients who underwent single-level ACDF for cervical degenerative disc disease and were followed up at least 2 years. The patients were divided into the following three groups according to the degree of distraction (<= 0.5, 0.5-1, >= 1): insufficient distraction group (ID group), appropriate distraction group (AD group), and excessive distraction group (ED group). The clinical outcomes and radiological parameters were evaluated before and after operation and at the last follow-up. Risk factors for ASD were identified through logistic regression analysis.Results.A significant difference was found in the Visual Analog Scale values between the AD group and ED group at the final follow-up. Moreover, the highest upper segmental disc height (DH), highest lower segmental DH, and lowest incidence of ASD were found in the AD group among the three groups at last follow up. Logistic regression analysis revealed that segmental kyphosis (odds ratio=2.821, P=0.020) was a risk factor for the occurrence of ASD and 0.5- to 1-fold distraction (odds ratio=0.350, P=0.025) was a protective factor.Conclusion.Good clinical and radiological outcomes were achieved in ACDF with 0.5- to 1-fold distraction. Segmental kyphosis is a risk factor for ASD in ACDF, whereas 0.5- to 1-fold distraction is a protective factor of ASD.Level of Evidence: 4