title: Paraspinal muscle, facet joint, and disc problems: risk factors for adjacent segment degeneration after lumbar fusion.
abstract: Adjacent segment degeneration (ASD) is one of the major complications after lumbar fusion. Several studies have evaluated the risk factors of ASD. Although the paraspinal muscles play an important role in spine stability, no study has assessed the relationship between paraspinal muscle atrophy and the incidence of ASD after lumbar fusion.
  
  
  
  In the present study, we aimed to verify the known risk factors of ASD, such as body mass index (BMI), preoperative adjacent facet joint degeneration, and disc degeneration, and to assess the relationship between paraspinal muscle atrophy and ASD.
  
  
  
  This is a retrospective 1:1 pair analysis matched by age, sex, fusion level, and follow-up period.
  
  
  
  To calculate the appropriate sample size for the study, we performed a pre-study analysis of the paraspinal muscle cross-sectional area (CSA), and estimated that at least 35 cases would be needed for each group. Among the 510 patients who underwent posterior lumbar fusion for degenerative lumbar disease between January 2009 and October 2009, a total of 50 patients with ASD after surgery were selected. Another group of 50 matched patients with degenerative lumbar disease without ASD after spinal fusion were selected as the control group. Each patient in the ASD group was matched with a control patient according to age, sex, fusion level, and follow-up period.
  
  
  
  Radiographic measurements and demographic data were reviewed.
  
  
  
  The risk factors considered were higher BMI, preoperative adjacent segment disc and facet degeneration, and preoperative paraspinal muscle atrophy and fatty degeneration. The radiographic data were compared between the ASD and control groups to determine the predictive factors of ASD after posterior lumbar fusion by using logistic regression analysis. The study was not externally funded. The authors have no conflict of interest to declare.
  
  
  
  Multivariate logistic regression analysis indicated that higher BMI (odds ratio [OR]: 1.353, p=.008), preoperative facet degeneration on computed tomography examination (OR: 3.075, p=.011), disc degeneration on magnetic resonance imaging (MRI) (OR: 2.783, p=.003), fatty degeneration (OR: 1.080, p=.044), and a smaller relative CSA of the paraspinal muscle preoperatively (OR: 0.083, p=.003) were significant factors for predicting the development of ASD.
  
  
  
  The occurrence of radiological ASD is most likely multifactorial, and is associated with a higher BMI, preexisting facet and disc degeneration on preoperative examination, and a smaller preoperative relative CSA of the paraspinal muscle on MRI.
authors.affiliation: Department of Neurosurgery, Gospel Hospital, Kosin University College of Medicine, 262 Gamcheon-ro, Seo-gu, Busan, 49267, Republic of Korea.
authors.forename: Jong Yeol
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Dal Sung
authors.initials: DS
authors.lastname: Ryu
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Ho Kyu
authors.initials: HK
authors.lastname: Paik
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Sang Soak
authors.initials: SS
authors.lastname: Ahn
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Moo Sung
authors.initials: MS
authors.lastname: Kang
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Kyung Hyun
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Jeong Yoon
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Dong Kyu
authors.initials: DK
authors.lastname: Chin
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Keun Su
authors.initials: KS
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea.
authors.forename: Yong Eun
authors.initials: YE
authors.lastname: Cho
authors.affiliation: Department of Neurosurgery, Gangnam Severance Hospital, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-gu, Seoul, 135-720, Republic of Korea. Electronic address: KUHSU@yuhs.ac.
authors.forename: Sung Uk
authors.initials: SU
authors.lastname: Kuh
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D015994:Incidence; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000453:epidemiology / Q000209:etiology*; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging*; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology*; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects*; D014057:Tomography, X-Ray Computed / Q000009:adverse effects; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging*
keywords: Adjacent segment degeneration; Lumbar spinal fusion; Paraspinal muscle atrophy; Posterior lumbar interbody fusion; Risk factors; Spine surgery