title: A Comparison of Implants Used in Double Door Laminoplasty : Allogeneic Bone Spacer versus Hydroxyapatite Spacer.
abstract: OBJECTIVE
  The aim of this study was to compare the clinical and radiological outcomes associated with the use of hydroxyapatite (HA) spacer and allogeneic bone (AB) spacer in laminoplasty.
  
  
  METHODS
  From January 2006 to July 2014, 79 patients with cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament underwent cervical laminoplasty. The radiologic parameters were obtained from plain radiography and three-dimensional computed tomography. All images were taken before and after surgery. Cervical lordosis, spinal canal dimension, fusion between lamina and spacer, and resorption of spacer were checked. Clinical outcomes were assessed using visual analog scale and Japanese Orthopedic Association.
  
  
  RESULTS
  Double-door laminoplasty was performed on 280 levels : 182 in the HA group and 98 in the AB group. The mean follow-up was 23.1 months (range : 4-69 months). Similar fusion rates were found in these groups (p=0.3). The resorption rate between lamina and spacer was lower in the HA group (p<0.001). During the immediate postoperative period, the canal dimension of both groups increased compared with the results in the preoperative period. However, the canal dimension of the AB group decreased over time compared with that of the HA group (p<0.001).
  
  
  CONCLUSIONS
  Double-door laminoplasty improved the clinical outcomes of both groups. However, the spinal canal dimension in the AB group showed a greater degree of reduction than in the HA group at the final postoperative follow-up. Therefore, we suggest that surgeons consider the use of larger-sized AB spacers in double-door laminoplasties.
authors.affiliation: Department of Neurosurgery, Keimyung University, School of Medicine, Dongsan Medical Center, Daegu, Korea.
authors.forename: Dong Yoon
authors.initials: DY
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Keimyung University, School of Medicine, Dongsan Medical Center, Daegu, Korea.
authors.forename: Chang Kyu
authors.initials: CK
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Keimyung University, School of Medicine, Dongsan Medical Center, Daegu, Korea.
authors.forename: In-Soo
authors.initials: IS
authors.lastname: Kim
keywords: Allograft; Cervical myelopathy; Hydroxyapatites; Ossification of posterior longitudinal ligament; Spinal fusion