Introduction: Adjacent segment disease (ASD) is hypothesized to occur due to increased biomechanical pressure placed on segments near an adjacent spinal fusion. However, the precise etiology remains obscure, and a clear understanding of risk factors for the development of ASD does not exist.
Methods: A retrospective review was performed for all patients surgically treated with their first lumbar arthrodesis at one institution between January 2008 and December 2011. All patients requiring a corrective surgery at an adjacent level to the original fusion by January 2014 were considered as having developed ASD. The ASD group was compared to the non-ASD patients who had a lumbar arthrodesis over the same time period examined. Demographic, medical and surgical factors were analyzed along with radiographic measurements of pelvic incidence, sacral slope, pelvic tilt, horizontal angle of the L3-L4 interverterbral space, lumbar lordosis and Cobb angle for the arthrodesis. Multivariable logistic regression was used to model the probability developing ASD on the basis of one or more predictors.
Results: A total of 174 patients fit the inclusion criteria, including 17 patients with adjacent segment disease. Patients who developed adjacent segment disease were more likely to be using antidepressants preoperatively (p=.003), have a diagnosis of scoliosis (p=.006), have a previous decompression (p=.003), not have L2 or L3 involved in the fusion (p<0.0001 and p=0.0008, respectively), have L5 involved within the fusion (p=0.0003), not have a decompression one level above the fusion (p=0.02) and have a lower sacral slope angle (p=0.05).
Conclusions: This study is the first to evaluate demographic, medical, and surgical factors to define predisposing characteristics for the development of ASD. This prediction formula may allow for better patient selection to prepare patients that have an increased probability of developing this complication.
Patient Care: By defining predisposing characteristics of adjacent segment disease following lumbar fusion, spine surgeons may select patients for lumbar fusion and prepare patients that have an increased probability of developing ASD.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of determining predisposing characteristics of adjacent segment disease following lumbar fusion, 2) Discuss, in small groups, risk factors associated with developing adjacent segment disease, 3) Identify the likelihood of a patient developing adjacent segment disease following a lumbar fusion.