Page 50 - WNS 2022 Program Book-Final version

Scientific Session VI
Closed cervical traction using a motorized robot: a biomechanical proof
of concept
Marcus D Mazur,MD University of Utah, Salt Lake City, Utah

Introduction: Closed cervical traction is commonly used to reduce subaxial
cervical spine dislocation injuries and to distract the intervertebral space dur-
ing cervical spine surgery. However, the standard weight-and-pulley cervical
traction with cranial tongs relies on cumbersome and imprecise technology
without any safeguard to prevent over- traction or weights being pulled/
released inadvertently.
Objective: To overcome the limitations of current traction methods, our goal
is to demonstrate that robotic cervical traction can apply closed cervical trac-
tion more safely and efficiently than manual weight-and-pulley traction in ex-
tension spring and cadaveric models.

Methods: A prototype robotic traction device was designed and manufactured
with the following objectives: real-time tensile force measurement, ± 1lb (5 N)
force application accuracy, locking/non back -driveable linear actuators with
actuator position sensing, maximum force capability of 200 lbs (900 N), up to
20 degrees of flexion/extension manipulation, device weight < 25 lbs (111
N), and compatibility with Gardner-Wells tongs or Mayfield head clamp. The
device was tested using both an extension spring model and an intact fresh
cadaver specimen to assess applied force and desired force over time as well
as radiographic changes in the cervical spine as traction force increased. The
cadaver was tested in manual traction and then robotic traction in 10 lbs (50
N) increments up to 80 lbs (400 N) to compare methods.
Results: The prototype device met or exceeded all objectives. In extension
spring testing, the device was able to reach prescribed forces of 111 N and
355 lbs accurately and maintain a desired weight. In cadaveric testing, radio-
graphic outcomes were equivalent between the prototype and manual weight-
and-pulley traction at 80 lbs (355 N) (disc space measurements within ±10%
for all levels), and the device was able to reach the desired weight amount
within ±1 lb (5 N) of accuracy at each weight interval.
Conclusion: This preliminary work demonstrates that motorized robotic cervi-
cal traction can safely and effectively apply controlled traction forces that are
more precise than weight-and-pulley traction. Further cadaveric studies on
efficacy of reducing facet dislocation injuries are warranted.

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