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Research Papers

Contact Pressure in the Facet Joint During Sagittal Bending of the Cadaveric Cervical Spine

[+] Author and Article Information
Nicolas V. Jaumard

Dept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104njaumard@mail.med.upenn.eduDept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104; Dept. of Bioengineering,  University of Pennsylvania, 210 S. 33rd Street, Room 240 Skirkanich Hall, Philadelphia, PA 19104njaumard@mail.med.upenn.eduDept. of Bioengineering,  University of Pennsylvania, 210 S. 33rd Street, Room 240 Skirkanich Hall, Philadelphia, PA 19104njaumard@mail.med.upenn.eduDept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104njaumard@mail.med.upenn.edu

Joel A. Bauman, Christine L. Weisshaar, Benjamin B. Guarino, William C. Welch

Dept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104Dept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104; Dept. of Bioengineering,  University of Pennsylvania, 210 S. 33rd Street, Room 240 Skirkanich Hall, Philadelphia, PA 19104Dept. of Bioengineering,  University of Pennsylvania, 210 S. 33rd Street, Room 240 Skirkanich Hall, Philadelphia, PA 19104Dept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104

Beth A. Winkelstein1

Dept. of Neurosurgery,  University of Pennsylvania, HUP-3 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104; Dept. of Bioengineering,  University of Pennsylvania, 210 S. 33rd Street, Room 240 Skirkanich Hall, Philadelphia, PA 19104 e-mail: winkelst@seas.upenn.edu

1

Corresponding author.

J Biomech Eng 133(7), 071004 (Jul 13, 2011) (9 pages) doi:10.1115/1.4004409 History: Received December 22, 2010; Revised June 02, 2011; Posted June 13, 2011; Published July 13, 2011; Online July 13, 2011

The facet joint contributes to the normal biomechanical function of the spine by transmitting loads and limiting motions via articular contact. However, little is known about the contact pressure response for this joint. Such information can provide a quantitative measure of the facet joint’s local environment. The objective of this study was to measure facet pressure during physiologic bending in the cervical spine, using a joint capsule-sparing technique. Flexion and extension bending moments were applied to six human cadaveric cervical spines. Global motions (C2-T1) were defined using infra-red cameras to track markers on each vertebra. Contact pressure in the C5-C6 facet was also measured using a tip-mounted pressure transducer inserted into the joint space through a hole in the postero-inferior region of the C5 lateral mass. Facet contact pressure increased by 67.6 ± 26.9 kPa under a 2.4 Nm extension moment and decreased by 10.3 ± 9.7 kPa under a 2.7 Nm flexion moment. The mean rotation of the overall cervical specimen motion segments was 9.6 ± 0.8° and was 1.6 ± 0.7° for the C5-C6 joint, respectively, for extension. The change in pressure during extension was linearly related to both the change in moment (51.4 ± 42.6 kPa/Nm) and the change in C5-C6 angle (18.0 ± 108.9 kPa/deg). Contact pressure in the inferior region of the cervical facet joint increases during extension as the articular surfaces come in contact, and decreases in flexion as the joint opens, similar to reports in the lumbar spine despite the difference in facet orientation in those spinal regions. Joint contact pressure is linearly related to both sagittal moment and spinal rotation. Cartilage degeneration and the presence of meniscoids may account for the variation in the pressure profiles measured during physiologic sagittal bending. This study shows that cervical facet contact pressure can be directly measured with minimal disruption to the joint and is the first to provide local pressure values for the cervical joint in a cadaveric model.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 5

Pressure-moment responses from the isolated extension tests, showing generally linear relationships for all specimens as defined by the ΔP/ΔM slopes labeled on the graph

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Figure 4

Global angle-moment responses from the applied isolated flexion and extension tests showing linear relationships for both loading scenarios and all specimens. The linear relationship was defined by the flexibility slopes (Δθg /ΔMy) labeled f on the graphs.

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Figure 3

Example of moment-angle curves measured during the sagittal bending test and the isolated flexion and extension tests for Specimen #4. The ROMs of the neutral position and of the isolated tests are also shown.

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Figure 2

(a) Reconstruction in PEAK software of the tracking markers of a representative specimen (Specimen #1) in its initial position (bold segments) and under applied extension (light segments). The markers for each segment, as well as the C2 and T1 potting cups, are also labeled. (b) Time history trace of the corresponding applied extension moment and the associated pressure changes developed in the facet joint during loading. The rate of loading is defined by the ΔM/t slope of the moment trace during the loading phase between the onset and maximum moments.

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Figure 1

(a) Representative fluoroscopic image of a cadaveric specimen (Specimen #1) showing the pressure probe inserted in the C5-C6 left facet joint. (b) Photograph of the test setup showing a cadaveric specimen (Specimen #6) with the pressure probe in the left C5-C6 facet joint, positioned on top of the six-axis load cell. Reflective markers are affixed to the C4-C7 vertebrae and the C2 and T1 cups for motion tracking by the infra-red cameras. The bar serving as a moment arm is attached to the top of the C2 cup and is connected to the cable and pulley system with the specimen oriented for the application of isolated extension.

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