title: Long-term radiographic outcomes of a central hook-rod construct for osteotomy closure: minimum 5-year follow-up.
abstract: METHODS
  Retrospective study.
  
  
  OBJECTIVE
  To evaluate long-term effectiveness of central hook-rod constructs for posterior spinal osteotomy closure.
  
  
  BACKGROUND
  During osteotomy site closure various techniques are used, including patient positioning, rod cantilevering, extending fixation points, and compressing through pedicle fixation points. All add premature stress on fixation points and may lead to loosening/eventual fixation failure. To avoid this, we often use a central compression hook-rod construct for osteotomy closure.
  
  
  METHODS
  Fifty-six consecutive patients with fixed sagittal imbalance were treated with multilevel posterior column osteotomies (N = 19), pedicle subtraction osteotomy (N = 31), or vertebral column resection (N = 6). All 56 patients had undergone osteotomy closure using central compression hook-rod constructs and were analyzed at a follow-up of 5 years or more. Compression hooks were inserted into the fusion mass or lamina above/below the osteotomy and centrally attached to a short rod connected to pedicle screw-based rods via a cross-link. Diagnoses included sagittal imbalance associated with scoliosis (N = 39), degenerative sagittal imbalance (N = 14), ankylosing spondylitis (N = 2), and Scheuermann's kyphosis (N = 1). There were 55 revision cases and 1 primary. Radiographic/clinical analysis was performed to evaluate the efficacy/complications of this technique.
  
  
  RESULTS
  Overall lumbar lordosis increased an average of 31.7° and local lordosis through the osteotomy site increased an average of 29.3°. Sagittal balance improved by an average of 92 mm. In all cases, osteotomy closures were performed without screw loosening or loss of correction intraoperatively. At a follow-up of 5 years or more, no failures of the hook-rod construct were seen, but there were 3 patients with partial implant failure; however, no symptomatic pseudarthroses at the osteotomy sites occurred. Seven patients developed pseudarthrosis below the central hook-rod construct.
  
  
  CONCLUSIONS
  A central hook-rod construct is safe, controlled, and effective for applying compressive forces to close various spinal osteotomies without fixation failure or pseudarthrosis at the osteotomy site noted at a follow-up of 5 or more years. It adds fixation strength to the overall construct avoiding undue stress on pedicle screws.
  
  
  METHODS
  3.
authors.affiliation: *Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO; and †Department of Neurosurgery, Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Republic of Korea; ‡Spine Center, Department of Orthopaedic Surgery, Hallym University Sacred Heart Hospital, Hallym University School of Medicine, Anyang, Gyeonggi-do, Republic of Korea.
authors.forename: Seung-Jae
authors.initials: SJ
authors.lastname: Hyun
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Yong Chan
authors.initials: YC
authors.lastname: Kim
authors.forename: Linda A
authors.initials: LA
authors.lastname: Koester
authors.forename: Kathy M
authors.initials: KM
authors.lastname: Blanke
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001858:Bone Nails; D001863:Bone Screws; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D016268:Internal Fixators; D008141:Lordosis / Q000453:epidemiology / Q000517:prevention & control; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008875:Middle Aged; D010027:Osteotomy / Q000295:instrumentation* / Q000379:methods*; D056888:Patient Positioning; D004856:Postural Balance; D011859:Radiography; D012189:Retrospective Studies; D012544:Scheuermann Disease / Q000000981:diagnostic imaging / Q000601:surgery*; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging / Q000601:surgery*; D013314:Stress, Mechanical; D016896:Treatment Outcome; D055815:Young Adult