Methods: We performed a retrospective case-control study of patients who had had an orthopaedic spinal operation performed at a university-affiliated tertiary-care hospital from 1998 to 2002.

• 研究方法：我们采用回顾性病例对照研究对一所医科大学附属的三级医院1998年至2002年的骨科脊柱手术病例进行了分析。