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59. The Effect of Sagittal Alignment on Posterior Fixation at the Cervicothoracic Junction
30S
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S
(PRA 6 L4 VES) was always 45 ; L4 VES was approximately neutral (range: 16 to -24 ); T12 VES was always positive (4 to 37 ); PI was approximately 55 (range 31 to 80 ) and PRA was better correlated with the lordosis measurements (r5-.72) compared to PI (r5-.52). In the volunteers, intra- and inter-observer reliabilities were very high for both PRA and PI measurements (r .95 for all). When applied clinically in the patients, intra- and inter-observer reliabilities were better for PRA vs. those for PI (r5.93 and .89 vs. r5.79 and .68, respectively). Measurement of PRA was 50% faster than PI. CONCLUSIONS: PRA and VES can determine minimum lordosis requirements, which are dependent on individual pelvic morphology, without having to identify the entire sacral endplate. This methodology, based on the PR technique, can be both efficiently and reliably applied in the clinical setting of any spinal practice. When fixing the lordosis by surgical fusion, minimum requirements should be met. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
slip (0.4860.47% vs. 0.6861.78%, p52.39) or angular motion (0.8260.50 degrees vs. 0.5360.32 degrees, p50.23). CONCLUSIONS: Increasing sagittal alignment, or kyphosis, at the cervicothoracic junction is related to several factors such as normal variation in upper thoracic spine alignment and the relative changes in posture that occur with natural aging. As our population ages, issues of fixation and sagittal alignment in cervicothoracic trauma become an important consideration. This data suggests that C7-T1 single level posterior fixation of a two column cervicothoracic junction injury, using a pedicle screw-rod construct may be sufficient to resist significant angular motion and translation at that level. While our study applies only to the immediate stability of the spine after injury and fixation, our data suggest that our fixation model provides a stable environment for the formation of bony fusion. Further studies are necessary to study long term implications of sagittal alignment on posterior cervicothoracic fixation. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
doi: 10.1016/j.spinee.2009.08.071
doi: 10.1016/j.spinee.2009.08.072
59. The Effect of Sagittal Alignment on Posterior Fixation at the Cervicothoracic Junction Thomas Sylvester, MD1, Alexander Ghanayem, MD1, Susan Renner, PhD2, Leonard Voronov, MD, PhD2, Braden McIntosh2, Gerard Carandang2, Robert Havey, MS2, Dongkeun Lee2, Anastasios Dimitriadis, MD2, Avinash Patwardhan, PhD2; 1Loyola University Chicago, Maywood, IL, USA; 2Hines VA Hospital, Hines, IL, USA
60. Impact of Degenerative Changes of Soft Tissue Structures on Motion at Diseased and Adjacent Levels in Lumbar Spondylolisthesis as Assessed with Kinetic MRI Scott Daffner, MD1, Kent Sheridan2, Min Ho Kong, MD2, Jeffrey Wang, MD3; 1West Virginia University, Morgantown, WV, USA; 2University of California, Los Angeles, Los Angeles, CA, USA; 3University of California, Los Angeles, Santa Monica, CA, USA
BACKGROUND CONTEXT: Traumatic injuries at the cervicothoracic junction are common injuries with reported incidences as high as 9% in spinal cord injured patients. Fixation at this level is challenged by the anatomical transition from the flexible, lordotic cervical spine to the rigid, kyphotic thoracic spine. Much data has been published regarding the adequacy of varying lengths of anterior, posterior and combined fusion constructs. However, there has been no data regarding the influence of sagittal alignment on posterior cervicothoracic stabilization. PURPOSE: The purpose of this study is to characterize the effect of sagittal alignment on a posterior fusion for a two column cervicothoracic junction injury. STUDY DESIGN/SETTING: Biomechanical Laboratory Study. PATIENT SAMPLE: Cadaveric specimens. OUTCOME MEASURES: N/A. METHODS: Eight fresh-frozen cadaveric spine specimens (levels C5-T1, age 49.8þ/8.4 years) were cleaned of soft tissue, leaving the ligamentous structures intact. Each specimen was radiographed to rule out obvious deformity or malignancy. Pedicle screws were placed bilaterally at C7 and T1. Follower load guides were secured to C6 and C7. C5 and T1 were secured proximally and distally in PMMA. The intact specimen was compressed to 150 N using the follower load technique. The load path at C7-T1 was then varied in the anterior-posterior plane to simulate a change in kyphotic sagittal alignment at the C7-T1 disc space from the follower load alignment (0 degrees) to a relative kyphotic alignment (40 degrees). This procedure was then repeated for each specimen with a C7-T1 posterior two column injury with and without posterior fixation in place. C7-T1 segmental angular and translational motion was measured using both optoelectronic instrumentation and digital fluoroscopy. Comparisons (t-test) were then made between the follower load alignment and the increased kyphotic alignment. RESULTS: Analysis of the eight tested specimens demonstrated that increased kyphosis at the C7-T1 disc space significantly increased C7-T1 anterior slip from 0.8760.85% to 2.0461.91% (p50.03) and angular motion from 0.2060.52 degrees to 1.3861.08 degrees (p50.03) in the posterior two-column injury model. Increased kyphosis also significantly increased C7-T1 angular motion in the intact spine from 0.5060.35 degrees to 2.3661.56 degrees (p50.03). Increased kyphosis with posterior fixation for the two-column injury did not significantly affect the C7-T1 anterior
BACKGROUND CONTEXT: Pathologic changes associated with the development of degenerative lumbar spondylolisthesis include degeneration of the intervertebral disc, facet joint arthrosis, ligamentum flavum hypertrophy, interspinous ligament degeneration, and paraspinal muscle fatty atrophy. Prior studies of lumbar kinematics in this condition have relied almost exclusively on plain radiographic assessment of motion or cadaveric experiments. Kinetic MRI (kMRI) allows accurate measurement of spinal segmental motion while also permitting assessment of associated soft tissue structures. To date, no studies have reported the in vivo role of these soft tissue structures in segmental motion in lumbar spondylolisthesis. PURPOSE: To assess segmental motion at spondylolisthetic and adjacent levels based on the degree of degenerative changes of associated soft tissue structures. STUDY DESIGN/SETTING: In vivo imaging study of human lumbar spinal kinematics. PATIENT SAMPLE: 113 patients with single-level Grade 1-2 degenerative spondylolisthesis at L3-4, L4-5, or L5-S1 and 307 patients with symptomatic back or leg pain but no spondylolisthesis. OUTCOME MEASURES: Angular and translational segmental motion at diseased and adjacent segments. METHODS: All patients underwent weightbearing kMRI of the lumbar spine in neutral, 30 of flexion, and 20 of extension. Mid-sagittal T2 W images were evaluated. Digital imaging software determined values of translational motion (TM) and angular motion (AM) through the range of motion. An experienced spine surgeon graded the degree of disc degeneration (DDD), facet degeneration (FD), ligamentum flavum hypertrophy (LF), interspinous ligament degeneration (IS), and paraspinal muscle fatty atrophy (PSM) based on previously described scoring systems. Motion values at the diseased and adjacent segments were compared to degenerative change grades at the diseased level as well as to control values obtained for patients with degenerative changes at corresponding levels who did not have spondylolisthesis. RESULTS: As DDD grade increased, TM at diseased levels increased whereas TM at adjacent levels decreased. AM slightly increased initially then decreased at diseased levels, whereas adjacent levels showed a steady decrease in AM. As FD increased, TM slightly increased at diseased and adjacent levels; AM steadily decreased. With LF hypertrophy, TM increased and AM remained stable with L3-4 and L4-5 spondylolisthesis,
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S
(PRA 6 L4 VES) was always 45 ; L4 VES was approximately neutral (range: 16 to -24 ); T12 VES was always positive (4 to 37 ); PI was approximately 55 (range 31 to 80 ) and PRA was better correlated with the lordosis measurements (r5-.72) compared to PI (r5-.52). In the volunteers, intra- and inter-observer reliabilities were very high for both PRA and PI measurements (r .95 for all). When applied clinically in the patients, intra- and inter-observer reliabilities were better for PRA vs. those for PI (r5.93 and .89 vs. r5.79 and .68, respectively). Measurement of PRA was 50% faster than PI. CONCLUSIONS: PRA and VES can determine minimum lordosis requirements, which are dependent on individual pelvic morphology, without having to identify the entire sacral endplate. This methodology, based on the PR technique, can be both efficiently and reliably applied in the clinical setting of any spinal practice. When fixing the lordosis by surgical fusion, minimum requirements should be met. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
slip (0.4860.47% vs. 0.6861.78%, p52.39) or angular motion (0.8260.50 degrees vs. 0.5360.32 degrees, p50.23). CONCLUSIONS: Increasing sagittal alignment, or kyphosis, at the cervicothoracic junction is related to several factors such as normal variation in upper thoracic spine alignment and the relative changes in posture that occur with natural aging. As our population ages, issues of fixation and sagittal alignment in cervicothoracic trauma become an important consideration. This data suggests that C7-T1 single level posterior fixation of a two column cervicothoracic junction injury, using a pedicle screw-rod construct may be sufficient to resist significant angular motion and translation at that level. While our study applies only to the immediate stability of the spine after injury and fixation, our data suggest that our fixation model provides a stable environment for the formation of bony fusion. Further studies are necessary to study long term implications of sagittal alignment on posterior cervicothoracic fixation. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
doi: 10.1016/j.spinee.2009.08.071
doi: 10.1016/j.spinee.2009.08.072
59. The Effect of Sagittal Alignment on Posterior Fixation at the Cervicothoracic Junction Thomas Sylvester, MD1, Alexander Ghanayem, MD1, Susan Renner, PhD2, Leonard Voronov, MD, PhD2, Braden McIntosh2, Gerard Carandang2, Robert Havey, MS2, Dongkeun Lee2, Anastasios Dimitriadis, MD2, Avinash Patwardhan, PhD2; 1Loyola University Chicago, Maywood, IL, USA; 2Hines VA Hospital, Hines, IL, USA
60. Impact of Degenerative Changes of Soft Tissue Structures on Motion at Diseased and Adjacent Levels in Lumbar Spondylolisthesis as Assessed with Kinetic MRI Scott Daffner, MD1, Kent Sheridan2, Min Ho Kong, MD2, Jeffrey Wang, MD3; 1West Virginia University, Morgantown, WV, USA; 2University of California, Los Angeles, Los Angeles, CA, USA; 3University of California, Los Angeles, Santa Monica, CA, USA
BACKGROUND CONTEXT: Traumatic injuries at the cervicothoracic junction are common injuries with reported incidences as high as 9% in spinal cord injured patients. Fixation at this level is challenged by the anatomical transition from the flexible, lordotic cervical spine to the rigid, kyphotic thoracic spine. Much data has been published regarding the adequacy of varying lengths of anterior, posterior and combined fusion constructs. However, there has been no data regarding the influence of sagittal alignment on posterior cervicothoracic stabilization. PURPOSE: The purpose of this study is to characterize the effect of sagittal alignment on a posterior fusion for a two column cervicothoracic junction injury. STUDY DESIGN/SETTING: Biomechanical Laboratory Study. PATIENT SAMPLE: Cadaveric specimens. OUTCOME MEASURES: N/A. METHODS: Eight fresh-frozen cadaveric spine specimens (levels C5-T1, age 49.8þ/8.4 years) were cleaned of soft tissue, leaving the ligamentous structures intact. Each specimen was radiographed to rule out obvious deformity or malignancy. Pedicle screws were placed bilaterally at C7 and T1. Follower load guides were secured to C6 and C7. C5 and T1 were secured proximally and distally in PMMA. The intact specimen was compressed to 150 N using the follower load technique. The load path at C7-T1 was then varied in the anterior-posterior plane to simulate a change in kyphotic sagittal alignment at the C7-T1 disc space from the follower load alignment (0 degrees) to a relative kyphotic alignment (40 degrees). This procedure was then repeated for each specimen with a C7-T1 posterior two column injury with and without posterior fixation in place. C7-T1 segmental angular and translational motion was measured using both optoelectronic instrumentation and digital fluoroscopy. Comparisons (t-test) were then made between the follower load alignment and the increased kyphotic alignment. RESULTS: Analysis of the eight tested specimens demonstrated that increased kyphosis at the C7-T1 disc space significantly increased C7-T1 anterior slip from 0.8760.85% to 2.0461.91% (p50.03) and angular motion from 0.2060.52 degrees to 1.3861.08 degrees (p50.03) in the posterior two-column injury model. Increased kyphosis also significantly increased C7-T1 angular motion in the intact spine from 0.5060.35 degrees to 2.3661.56 degrees (p50.03). Increased kyphosis with posterior fixation for the two-column injury did not significantly affect the C7-T1 anterior
BACKGROUND CONTEXT: Pathologic changes associated with the development of degenerative lumbar spondylolisthesis include degeneration of the intervertebral disc, facet joint arthrosis, ligamentum flavum hypertrophy, interspinous ligament degeneration, and paraspinal muscle fatty atrophy. Prior studies of lumbar kinematics in this condition have relied almost exclusively on plain radiographic assessment of motion or cadaveric experiments. Kinetic MRI (kMRI) allows accurate measurement of spinal segmental motion while also permitting assessment of associated soft tissue structures. To date, no studies have reported the in vivo role of these soft tissue structures in segmental motion in lumbar spondylolisthesis. PURPOSE: To assess segmental motion at spondylolisthetic and adjacent levels based on the degree of degenerative changes of associated soft tissue structures. STUDY DESIGN/SETTING: In vivo imaging study of human lumbar spinal kinematics. PATIENT SAMPLE: 113 patients with single-level Grade 1-2 degenerative spondylolisthesis at L3-4, L4-5, or L5-S1 and 307 patients with symptomatic back or leg pain but no spondylolisthesis. OUTCOME MEASURES: Angular and translational segmental motion at diseased and adjacent segments. METHODS: All patients underwent weightbearing kMRI of the lumbar spine in neutral, 30 of flexion, and 20 of extension. Mid-sagittal T2 W images were evaluated. Digital imaging software determined values of translational motion (TM) and angular motion (AM) through the range of motion. An experienced spine surgeon graded the degree of disc degeneration (DDD), facet degeneration (FD), ligamentum flavum hypertrophy (LF), interspinous ligament degeneration (IS), and paraspinal muscle fatty atrophy (PSM) based on previously described scoring systems. Motion values at the diseased and adjacent segments were compared to degenerative change grades at the diseased level as well as to control values obtained for patients with degenerative changes at corresponding levels who did not have spondylolisthesis. RESULTS: As DDD grade increased, TM at diseased levels increased whereas TM at adjacent levels decreased. AM slightly increased initially then decreased at diseased levels, whereas adjacent levels showed a steady decrease in AM. As FD increased, TM slightly increased at diseased and adjacent levels; AM steadily decreased. With LF hypertrophy, TM increased and AM remained stable with L3-4 and L4-5 spondylolisthesis,