Cervical double-door laminoplasty with a hydroxy-apatite spacer : time-course of radiographic findings and clinical outcomes over 30 months

Abstract

Objective: Various kinds of cervical laminoplasty have been attempted on patients with long segment cervical stenosis. The purpose of this study was to evaluate the time-course of radiologic findings and clinical outcomes during a 30-month follow-up following three- or four-level double-door laminoplasty using a hydroxyl-apatite (HA) spacer.Methods: We followed 29 patients (male to female ratio 24:5; mean age 52.2; 105 total laminoplasty levels) who had undergone double-door cervical laminoplasty from 2004 to 2007. Preoperative diagnoses included 21 cases of OPLL and eight cases of degenerative spondylosis. Patients were divided into three groups in order to estimate time-coursed radiologic alterations and clinical outcomes according to the follow-up periods: early (12-<18 months), middle (18-30 months), and late (>30 months). All cervical laminoplasty was performed using HA spacers. Neutral and flexion-extension cervical lateral radiographs and CT scans were taken at the final follow-up. Stability of HA spacers, C2-7 range of motion (ROM) and kyphosis were evaluated. Bone fusion status between the HA spacer and laminae were estimated using a five-point classification from A to E. Types C, D and E were considered to be successful HA-laminae fusion. Bone fusion on the bilateral gutters was also evaluated. Nurick grade and JOA score were determined to evaluate neurological improvement preoperatively and at the final follow-up. A visual analogue scale (VAS, 0-10) was used to measure post-operative neck pain and radiating pain in all patients.Results: The numbers of patients in the early, middle, and late groups were 9, 11 and 9, respectively. The successful HA-laminae fusion rate was 24%, 42% and 69% in early, middle and late groups, respectively. Bilateral gutter fusion was 95% in the early group and 100% in both the middle and late groups. Of the 105 levels, only two showed unstable HA position on flexion-extension lateral films. ROM of C2-C7 was significantly decreased after surgery: 10, 11 and 13 degrees of reduction compared to preoperative ROM were observed in the early, middle and late groups, respectively. Kyphotic change was slightly increased after surgery, although the change was not significant. Nurick grade, JOA score and VAS of radiating pain were significantly improved after surgery, but there were no differences between the three groups. The VAS for neck pain improved in the group with severe preoperative neck pain but worsened in the group with mild neck pain. There was no direct clinical correlation between HA-laminae fusion rate and clinical improvement.Conclusions: We believe that double-door laminoplasty using an HA spacer is a very safe and effective method for improving neurological status. This method resulted in a decrease in cervical ROM and a constant but acceptable degree of neck pain after surgery. HA-laminae fusion progressed very slowly; however, HA spacers showed stable positions and improved clinical outcomes regardless of fusion status. The stability of HA-laminae seems to be maintained by early successful bone fusion at the bilateral gutters.