Use of Radiostereometric Analysis (RSA) Following Spinal Fusion Versus the DYNESYS Stabilization System
Condition: Spinal Fusion; Orthopedic Procedures
Study type: Observational

Summary: 
      Twelve subjects will be sought for this study. Six subjects will receive the DYNESYS system
      and six subjects will receive a posterior lumbar interbody fusion (PLIF) with the Silhouette
      device. All subjects will already be participating in the DYNESYS multi-center study (under
      IRB #4884) and will have been randomized to either group. Five tantalum beads will be
      inserted into each vertebra associated with the DYNESYS or fusion surgery. Subjects will be
      followed in conjunction with the multi-center follow-up schedule and will have RSA exams at
      the following time points after surgery: 3, 6, 12, 18, and 24 months. Standing neutral,
      flexion, extension, and lateral bending films will be collected at each time point and the
      amount of motion in each direction of the "marked" vertebrae will be measured. The time
      points have been selected based on their clinical relevance for comparison against the
      standard of care, which is the fusion procedure. Depending on the initial tension of the
      annular fibers, it is possible the DYNESYS will exhibit more motion with time. The time
      points are important to track the potential changes.
    

Detailed description: 
      The amount of motion of the vertebrae following spinal surgery is important in determining
      the success of a procedure. Assessment of spinal motion has been, and continues to be, a
      difficult clinical problem. Errors of up to 10 degrees for simple measurements of flexion,
      extension, and side bending have been recorded using conventional radiographs. It has
      therefore been difficult to accurately measure changes in spinal motion using conventional
      radiographs.

      Radiostereometric Analysis, or RSA, is an accurate in vivo measurement technique using two
      simultaneous radiographs for examining spinal motion. The measurement accuracy offered by
      this technique far exceeds the manual techniques currently used. In addition to improved
      accuracy, it provides more information on spinal motion in comparison to conventional
      radiographs. Utilization of the RSA technology at the IHP and the United States is in its
      infancy. The investigators have placed much effort over the past 1-2 years to put the
      necessary dedicated resources and personnel in place. This has been a collaborative effort
      between the Department of Orthopedic Surgery and the Imaging Core at IHP. Preliminary work on
      the accuracy, reliability, and surgical planning for use of RSA has been completed and
      presented at national conferences.

      The purpose of this study is to assess the amount of motion in the lumbar spine in patients
      with a dynamic stabilization system, DYNESYS. Currently the DYNESYS is under investigation as
      part of a multi-center clinical trial (IRB # 4884). The DYNESYS system is designed to allow
      for some motion in the spine while providing the necessary stability to the spinal segment.
      The amount and degree of this motion is currently unknown. By using tantalum bead markers
      placed in the spine at the time of the surgery, RSA analysis can determine the amount of
      motion the DYNESYS system provides. Normal spinal motion of the lower spine is approximately
      18 and 12 degrees for flexion/extension and lateral bending, respectively. Lumbar interbody
      fusion, which is the current standard surgical procedure, results in 5 degrees or less of
      spinal motion. Since the DYNESYS provides dynamic stabilization, it is estimated that there
      will be a 20% loss of motion with the DYNESYS in comparison to normal motion. Two questions
      will be examined in this study: 1) what is the amount of flexion/extension and lateral
      bending motion that occurs in the spine with a dynamic stabilization system in relation to a
      lumbar interbody fusion procedure? and 2) will the amount of motion change during the time
      frame of the study?

      This study will involve 12 patients (6 with DYNESYS and 6 with posterior lumbar interbody
      fusion, PLIF) here at SUNY Upstate Medical University. Any subject who is part of the DYNESYS
      multi-center clinical trial (IRB # 4884) will be approached to participate in this RSA study.
      The subjects will already have been randomly assigned to the fusion group or the DYNESYS
      group. The RSA study is a single center, non-randomized design. All 12 subjects will have
      10-15 tantalum markers placed in their spine at the time of their DYNESYS or fusion surgery.
      After surgery, subjects will have the special x-rays taken and the RSA analysis will be
      completed. Subjects will be seen at the following time points after surgery: 3, 6, 12, 18,
      and 24 months.
    

Intervention name(s): Radiostereometric Analysis beads inserted during surgery
Intervention type(s): Procedure
Time perspective: Prospective
Keywords: spinal motion; tantalum beads; DYNESYS Stabilization system; spinal fusion; Radiostereometric Analysis following spinal fusion; Radiostereometric Analysis following surgery with DYNESYS Stabilization System