Segmental malalignment with the Bryan Cervical Disc prosthesis--does it occur?

J Spinal Disord Tech. 2007 Feb;20(1):1-6. doi: 10.1097/01.bsd.0000211262.13250.f8.


The early clinical results with the Bryan Cervical Disc prosthesis are encouraging but 2 recent small published series have noted postoperative radiologic kyphosis of the functional spinal unit (FSU) of 4 and 6 degrees. The current study was undertaken to accurately assess the extent of any sagittal deformity after the use of this prosthesis in a substantial, multisurgeon case series. The neutral, erect x-rays of 67 consecutive patients (88 disc levels) operated by one of 3 surgeons, were examined using manual and digital image analysis techniques for FSU sagittal angulation (lordosis), prosthesis shell angulation, segmental olisthesis, and overall cervical alignment. Measurement accuracy was confirmed using interobserver and intraobserver studies. There was a median loss of 2 degrees in FSU lordosis when compared with preoperative imaging (P<0.0001, range: 8-degree loss to 5-degree gain). A median 2 degrees of prosthesis shell kyphosis also occurred (range: 15-degree kyphosis to 12-degree lordosis) but shell angulation correlated weakly with the change in FSU lordosis (rs=0.37, P=0.001). There was a significant difference in the median loss of FSU lordosis between surgeon 1 and surgeons 2 and 3 (3.5 degrees vs. 2 degrees, P=0.005). Median olisthesis of the prosthesis shells was -0.1 mm (range: +1.5 to -2.5 mm). Median postoperative overall cervical lordosis reduced by 4 degrees (P<0.004). A small loss in median FSU lordosis was observed after insertion of the Bryan disc. The observed changes were generally small but varied among both the patients and the surgeons, suggesting that variables may exist which contribute to postoperative sagittal alignment. These are the subject of an accompanying study.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biomechanical Phenomena
  • Cervical Vertebrae / pathology
  • Cervical Vertebrae / physiopathology
  • Cervical Vertebrae / surgery*
  • Decompression, Surgical / adverse effects
  • Decompression, Surgical / instrumentation
  • Decompression, Surgical / methods
  • Diskectomy / adverse effects
  • Diskectomy / instrumentation
  • Diskectomy / methods
  • Female
  • Humans
  • Intervertebral Disc / pathology
  • Intervertebral Disc / physiopathology
  • Intervertebral Disc / surgery
  • Intervertebral Disc Displacement / surgery*
  • Kyphosis / etiology*
  • Kyphosis / pathology
  • Kyphosis / physiopathology
  • Male
  • Middle Aged
  • Neck Pain / etiology
  • Neck Pain / physiopathology
  • Polyurethanes
  • Postoperative Complications / etiology
  • Postoperative Complications / pathology
  • Postoperative Complications / physiopathology
  • Prostheses and Implants / adverse effects*
  • Prostheses and Implants / standards
  • Prostheses and Implants / statistics & numerical data*
  • Range of Motion, Articular / physiology
  • Spinal Fusion / adverse effects*
  • Spinal Fusion / instrumentation*
  • Spinal Fusion / methods
  • Titanium
  • Treatment Outcome


  • Polyurethanes
  • Titanium