title: Comparison of hinged and contoured rods for occipitocervical arthrodesis in adults: A clinical study.
abstract: BACKGROUND
  A rigid construct that employs an occipital plate and upper cervical screws and rods is the current standard treatment for craniovertebral junction (CVJ) instability. A rod is contoured to accommodate the occipitocervical angle. Fatigue failure has been associated these acute bends. Hinged rod systems have been developed to obviate intraoperative rod contouring.
  
  
  OBJECTIVE
  The aim of this study is to determine the safety and efficacy of the hinged rod system in occipitocervical fusion.
  
  
  METHODS
  This study retrospectively evaluated 39 patients who underwent occipitocervical arthrodesis. Twenty patients were treated with hinged rods versus 19 with contoured rods. Clinical and radiographic data were compared and analyzed.
  
  
  RESULTS
  Preoperative and postoperative Nurick and Frankel scores were similar between both groups. The use of allograft, autograft or bone morphogenetic protein was similar in both groups. The average number of levels fused was 4.1 (±2.4) and 3.4 (±2) for hinged and contoured rods, respectively. The operative time, estimated blood loss, and length of stay were similar between both groups. The occiput to C2 angle was similarly maintained in both groups and all patients demonstrated no movement across the CVJ on flexion-extension X-rays during their last follow-up. The average follow-up for the hinged and contoured rod groups was 12.2 months and 15.9 months, respectively.
  
  
  CONCLUSIONS
  Hinged rods provide a safe and effective alternative to contoured rods during occipitocervical arthrodesis.
authors.affiliation: Department of Neurological Surgery, The University of Iowa, Carver School of Medicine, Iowa City, IA 52242, USA.
authors.forename: Kingsley O
authors.initials: KO
authors.lastname: Abode-Iyamah
authors.affiliation: Department of Neurological Surgery, The University of Iowa, Carver School of Medicine, Iowa City, IA 52242, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Dlouhy
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Lopez
authors.affiliation: Department of Neurological Surgery, The University of Iowa, Carver School of Medicine, Iowa City, IA 52242, USA.
authors.forename: Arnold H
authors.initials: AH
authors.lastname: Menezes
authors.affiliation: Department of Neurological Surgery, The University of Iowa, Carver School of Medicine, Iowa City, IA 52242, USA.
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Hitchon
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Nader S
authors.initials: NS
authors.lastname: Dahdaleh
keywords: Craniovertebral; fusion; hinged; instrumentation; occipitocervical; occiput; rod