Analysis of Risk Factors of Adjacent Segment Disease with Lumbar and Lumbosacral Arthrodesis for the Degenerative Lumbar Spinal Disorders

Purpose: The objective of this study is to confirm the effects of risk factors on Adjacent Segment Disease (ASD). Materials and Methods: The subjects of this study were 793 patients who had degenerative lumbar spine disease and were followed-up for an average period of 7.2 years from January of 1999 to September of 2010 after undergoing spinal fusion. To confirm the risk factors, a study on patient factors, surgical factors and radiologic factors was performed. Results: Of 793 patients, 69 patients (group A, 8.7%) underwent a secondary surgical treatment due to ASD. Age of patient, sex, bone mineral density, history of smoking and occupation were not statistically significant. Preoperative body mass index (BMI) (≥25 kg/m 2 ) and postoperative increase of BMI were the patient’s factor in ASD (p=0.02, p＜0.001). Regarding surgical factors, multilevel fusion (more than 3 levels) was higher risk in prevalence of ASD than short level fusion (p=0.01). Degeneration of intervertebral disc (p=0.01) and facet joints (p=0.02), and segmental instability (p=0.001) were also associated with the prevalence of ASD in radiologic factors. Conclusion: To prevent the occurrence of ASD after lumbosacral fusion, selection of the proper level of fusion preoperatively and modifying the life style with body weight control and reduction of hypermobility after fusion surgery are essential.