#524 Assessment of Neuroforaminal and Canal Dimensions During Cervical Kinematics
Poster Presented by: R. Havey
R. Havey (1)
T. Potluri (1)
L. Voronov (2)
P. Tsitsopoulos (2)
F. Phillips (3)
M. Zindrick (2)
J. Goodsitt (1)
G. Carandang (1)
A. Patwardhan (2)
(1) Edward Hines VA Hospital, Hines, IL, USA
(2) Loyola University Chicago, Maywood, IL, USA
(3) Rush University Medical Center, Chicago, IL, USA
Introduction: Nerve root compression is a key factor in symptomatic progression of degenerative disc disease. Degenerative changes of the cervical spine in the form of bone spurs and disc space narrowing secondary to DDD affect both the area available for the nerve roots as well as the space available for the spinal cord. The area is greatly affected by the posture of the spine. Traditional techniques to evaluate the foraminal dimension have used direct measurement by caliper and blunt probe and measurement using CT scans in static postures. The goal of this study was to assess the neural foramen and canal dimension of intact cervical spine specimens undergoing flexion-extension range of motion testing.
Methods: Nine cadaveric spines (C3-T1) (46±9.1years) were instrumented with five radiopaque markers per vertebral body. A 3-dimensional (3-D) specimen-specific anatomical model was reconstructed using fine-slice (0.63mm) axial CT scans. During kinematic testing a digital link was made between the radiopaque markers in the CT reconstruction and the 3-D motion measurement system. The 3-D motion of each vertebra was tracked optoelectronically as the specimen was subjected to moments in FE. The 3-D vertebral motion data was used to drive the CT anatomical model. As a result, motion of any anatomical landmark could be assessed in response to loads applied during flexibility testing. Angular motion, canal area as well as the foraminal area of the C5-C6 motion segment were calculated.Canal area was calculated by tracing the C5 posterior inferior endplate edge and neutral arch and the C6 posterior superior endplate edge and neutral arch. These points were projected onto a plane defined by the C6 superior endplate and the canal area was calculated in this plane.To calculate the foraminal area the isthmus of the C5-C6 neural foramen was traced on the neutral posture of the specimen resulting in a non planar semi-circle of points which were projected onto a plane oriented at 45 degrees from the sagittal plane of C6. Foraminal isthmus area was calculated throughout the flexion-extension motion.The foraminal and canal areas were processed to obtain the percent change relative to the neutral posture. Linear regression analysis was performed on percent change in canal and foraminal areas vs change in C5-C6 angular motion from neutral posture.
Results: The canal and foraminal areas for all specimens increased in flexion and decreased in extension. Regression analysis showed a significant correlation between percent change in canal area and change in angular motion (R2 =0.89, p< 0.05) as well as percent change in foraminal area and change in angular motion (R2=0.87, p< 0.05). The canal and foraminal areas changed by 1.5% and 1.0% respectively per degree of angular motion.
Conclusions: The increase in foraminal and canal space in flexion as demonstrated in this study is consistent with the treatment modalities used in manipulation and physical therapies to relieve radicular symptoms associated with foraminal and canal stenosis. The specimen specific model used in this experiment allowed evaluation of these areas over the full flexion-extension range of motion. Although not presented in this analysis, the model allows similar assessment in other modes of motion and at all cervical levels.