489 - Factors Affecting Large Developed Anterior Subsidence after Standalone...

#489 Factors Affecting Large Developed Anterior Subsidence after Standalone Cage Assisted Anterior Cervical Fusion and Changes of Cervical Sagittal Alignment

Cervical Therapies and Outcomes

Poster Presented by: J. Jang

Author(s):

J.-W. Jang (1)
J.-K. Lee (1)
S.-H. Kim (1)

(1) Chonnam National University Hospital, Neurosurgery, Hak Dong, Dong-gu, Gwang-ju, Korea, Republic of

Abstract

Objective: Anterior cervical discectomy and fusion (ACDF) using stand-alone synthetic PEEK (polyetheretherketone) cage is an effective and safe for one-level degenerative cervical disease. However, recent studies have shown that cage subsidence is a major complication of ACDF using stand-alone cages regardless of the composite materials. That complication can eventually result in narrowing of the foramen, nerve root compression, cervical instability and adjacent segment degeneration due to the loss of lordosis. Especially, anterior subsidence of fusion site may result in severe kyphotic deformity. The purpose of this study is to evaluate the risk factors of large anterior subsidence after ACDF using a stand-alone cage and the changes of overall cervical alignment by performing a radiological analysis.

Methods: This study included eighty patients, who underwent anterior cervical fusion using stand-alone PEEK cage and DBM (demineralized bone matrix) in single level degenerative cervical disease between January 2006 and December 2010. Radiographs were obtained before surgery, immediately after surgery, and at final follow-up for accessing the restoration of spinal column. For the radiologic parameters, anterior height (AH) and posterior height (PH) of fusion segment, segmental angle (SA) of fusion level, and overall C2-C7 angle (cervical sagittal angle, CSA) were assessed in plain lateral thoracolumbar radiograph. Anterior subsidence was calculated by the difference between postoperative and last follow-up AH and posterior subsidence was calculated by the difference between postoperative and last follow-up PH. In simple postoperative lateral radiograph, the percent of cage length to antero-posterior (AP) body length was measured. Cage height, location and species were also assessed. For patient's pain and functional assessment, visual analogue scale (VAS) and Japanese orthopedic association (JOA) score were measured.

Results: The average follow up period was 26.7 months. The patients were divided into two groups; group A was composed by 29 patients who anterior subsidence was more than 1mm compared to posterior subsidence and group B was composed by opposite cases. There were no significant differences of age, sex, operative level, and cage height between two groups. However, patients with large anterior subsidence had a positive correlation with posterior located cage, or lordotic cage (p < 0.05). Percent of cage length to antero-posterior body length was also associated with large anterior subsidence (p < 0.05). In sagittal alignment, SA was significantly decreased in group A at the last follow-up (p < 0.05). However, there was no significant difference of CSA between two groups at the last follow-up period. In clinical outcomes, there were no significant differences of VAS and JOA between two groups.

Conclusions: Despite some subsidence, ACDF using stand-alone PEEK cage with DBM is a safe and reliable surgical treatment option in single-level degenerative cervical disease. However, anterior subsidence was largely developed compared to posterior subsidence in cases with posterior located cage, lordotic cage, or low percent of cage length to AP body length. Although CSA was not significantly different between two groups, however, large developed anterior subsidence was associated with kyphotic changes of fusion segment at the last follow-up.