A novel noninvasive approach to measure facet joint pressure in the cervical spine was investigated using a tip-mounted transducer that can be inserted through a hole in the bony lateral mass. This technique is advantageous because it does not require resection of the joint capsule, but there are potential issues regarding its applicability that are addressed.
The objective was to evaluate the effect of a tip-mounted pressure probe's position and orientation on contact pressure measurements in biomechanical experiments.
Measurements of direct contact pressure in the facet joint of cadaveric spines have been obtained via pressure-sensitive films. However, that method requires the resection of the facet capsule, which can alter the overall joint's mechanical behavior and can affect the measured contact pressures.
Influence of position and orientation on probe measurements was evaluated in companion surrogate and cadaveric investigations. The probe was placed in the facet of an anatomic vertebral C4/5 surrogate undergoing sagittal bending moments. Pressure-sensitive paper was used to map contact regions in the joint of the surrogate and cadaveric cervical segments (n = 3) during extension. The probe also underwent uniaxial compression in cadaveric facets to evaluate the effect of orientation relative to the contact surface on the probe signal.
Although experimental and theoretical pressure profiles followed the same trends, measured maximum pressures were half of the theoretical ones. In the orientation study, maximum pressures were not different for probe orientations of 0° and 5°, but no signal was recorded at orientations greater than 15°.
This approach to measure pressure was selected to provide a minimally-invasive method to quantify facet joint pressures during clinically relevant applications. Both the position and orientation of the probe are critical factors in monitoring local pressure profiles in this mobile synovial joint.
Facet joint pressure was measured using a capsule-sparing technique with a tip-mounted probe that was evaluated in cadaveric and surrogate cervical spinal motion segments. Position, orientation, and design of the probe influence pressure signal accuracy. Design modifications and imaging technique can help overcome the issues associated with using this technique.
* Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA.
† Bioengineering, University of Pennsylvania, Philadelphia, PA.
Address correspondence and reprint requests to Beth A. Winkelstein, PhD, Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, 210 S. 33rd St, Room 240, Skirkanich Hall, Philadelphia, PA; E-mail: firstname.lastname@example.org
Acknowledgement date: January 28, 2010. Revision date: May 3, 2010. Acceptance date: June 17, 2010.
The manuscript submitted does not contain information about medical device(s)/drug(s).
Corporate/Industry, Institutional, and Foundation funds were received in support of this work.
Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.