title: Bone resorption during the first year after implantation of a single-segment dynamic interspinous stabilization device and its risk factors.
abstract: BACKGROUND
  Dynamic interspinous stabilization devices generally provide satisfactory results, but can result in recurrent lumbar disc herniation, spinous process fracture, or bone resorption of the spinous process. The purpose of this study was to investigate if the Wallis dynamic stabilization device is associated with bone resorption.
  
  
  METHODS
  Patients who underwent single-segment posterior lumbar decompression and implantation of a Wallis dynamic interspinous stabilization device at the L4/5 level between January 1, 2009 and October 1, 2011 were included. Bone resorption rate, Oswestry Disability Index (ODI), Japanese Orthopedic Association (JOA) score, and visual analogue scale (VAS) pain score were measured. Patient baseline and 1-year follow-up data were collected and analyzed. The bone resorption rate of the L4 and L5 spinous processes was calculated.
  
  
  RESULTS
  Twenty four males and 20 females with a mean age of 42.7 ± 14.7 years were included. Twenty nine patients had significant bone resorption (bone resorption rate > 20%) and 15 had no bone resorption (bone resorption rate ≤ 20%) at 1 year after surgery. Lumbar lordosis ≥ 50° was associated with a lower bone resorption than lumbar lordosis < 50° and increasing BMI was associated with increased bone resorption. There were no significant differences between the bone resorption and no bone resorption groups in the improvement rate of VAS pain score, ODI, and JOA score at 1 year after surgery.
  
  
  CONCLUSIONS
  Significant bone resorption occurs within 1 year after implantation of the Wallis device in more than 50% of patients. However, it does not affect short-term functional results.
authors.affiliation: Department of Spinal Surgery, Peking University People's Hospital, 11 Xizhimen South Street, West District, Beijing, China. kevinwang27@163.com.
authors.forename: Kaifeng
authors.initials: K
authors.lastname: Wang
authors.affiliation: Department of Spinal Surgery, Peking University People's Hospital, 11 Xizhimen South Street, West District, Beijing, China. zhuzhenqi2000@vip.sina.com.
authors.forename: Zhenqi
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Department of Spinal Surgery, Peking University People's Hospital, 11 Xizhimen South Street, West District, Beijing, China. wangbo@pkuph.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Spinal Surgery, Peking University People's Hospital, 11 Xizhimen South Street, West District, Beijing, China. judewayne@sina.com.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Spinal Surgery, Peking University People's Hospital, 11 Xizhimen South Street, West District, Beijing, China. Liu_haiying@263.net.
authors.forename: Haiying
authors.initials: H
authors.lastname: Liu
mesh_terms: D000328:Adult; D001862:Bone Resorption / Q000000981:diagnostic imaging* / Q000209:etiology; D019299:Decompression, Surgical / Q000009:adverse effects* / Q000639:trends; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects* / Q000639:trends; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects* / Q000639:trends; D013997:Time Factors