title: Adjacent segment disease after instrumented fusion for adult lumbar spondylolisthesis: Incidence and risk factors.
abstract: OBJECTIVE
  A potential long-term complication of lumbar fusion is the development of adjacent segment disease (ASD), which may necessitate second surgery and adversely affect outcomes. The objective of this is to determine the incidence of ASD following instrumented fusion in adult patients with lumbar spondylolisthesis and to identify the risk factors for this complication.
  
  
  METHODS
  We retrospectively assessed adult patients who had undergone decompression and instrumented fusion for lumbar spondylolisthesis between January 2006 and December 2012. The incidence of ASD was analyzed. Potential risk factors included the patient-related factors, surgery-related factors, and radiographic variables such as sagittal alignment, preexisting disc degeneration and spinal stenosis at the adjacent segment.
  
  
  RESULTS
  A total of 154 patients (mean age, 58.4 years) were included. Mean duration of follow-up was 28.6 months. Eighteen patients (11.7%) underwent a reoperation for ASD; 15 patients had reoperation at cranial ASD and 3 at caudal ASD. The simultaneous decompression at adjacent segment (p=0.002) and preexisting spinal stenosis at cranial adjacent segment (p=0.01) were identified as risk factors for ASD. The occurrence of ASD was not affected by patient-related factors, the types, grades and levels of spondylolisthesis, surgical approach, fusion procedures, levels of fusion, number of levels fused, types of bone graft, use of bone morphogenetic proteins, sagittal alignment, preexisting adjacent disc degeneration and preexisting spinal stenosis at caudal adjacent segments.
  
  
  CONCLUSIONS
  Our findings suggest the overall incidence of ASD is 11.7% in adult patients with lumbar spondylolisthesis after decompression and instrumented fusion at a mean follow-up of 28.6 months, the simultaneous decompression at the adjacent segment and preexisting spinal stenosis at cranial adjacent segment are risk factors for ASD.
authors.affiliation: Department of Spinal Surgery, Nanfang Hospital, Southern Medical University, 1838 North Guangzhou Avenue, Guangzhou, 510515, China. Electronic address: zhongzm@smu.edu.cn.
authors.forename: Zhao-Ming
authors.initials: ZM
authors.lastname: Zhong
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
authors.forename: Vedat
authors.initials: V
authors.lastname: Deviren
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
authors.forename: Bobby
authors.initials: B
authors.lastname: Tay
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
authors.forename: Shane
authors.initials: S
authors.lastname: Burch
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
authors.forename: Sigurd H
authors.initials: SH
authors.lastname: Berven
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D019299:Decompression, Surgical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D055959:Intervertebral Disc Degeneration / Q000150:complications / Q000601:surgery; D008159:Lumbar Vertebrae; D008161:Lumbosacral Region / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology*; D012086:Reoperation / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects*; D013130:Spinal Stenosis / Q000150:complications / Q000601:surgery; D013168:Spondylolisthesis / Q000473:pathology* / Q000601:surgery*; D055815:Young Adult
keywords: Adjacent segment disease; Fusion; Incidence; Lumbar spondylolisthesis; Risk factor