ACD Study

Induction and Maintenance of
Lordosis in MultiLevel ACDF Using
Allograft
Saad Khairi, MD
Jennifer Murphy
Robert S. Pashman, MDPurpose
• Is lordosis induced
by multilevel
cortical allograft
ACDF placed on
intact endplates
maintained at 2
year follow-up?
• With this
technique, does
graft-endplate
fusion correlate
with clinical
result?Lordosis Maintained by
DistractionAllograft under compressionMethods
• Retrospective
series
– 40 patients
– 89 levels
• Single surgeon
• Standardized
technique
– Right neck
approach
Distribution of Cases
Two level 32
Three level 6
Four level 2
Distribution of Cases
80%
15%
5%
two level three level four levelDemographics
• 19 Males / 21 Females
• 24 Month Average
follow-up
– Range 10-44 months
Follow up distribution
0
10
20
30
40
50
60
70
80
1 7 13 19 25 31 37 43 49 55 61 67 73
Level #
Months of Follow upIndications
• Radiculopathy
• Myeloradiculopathy
• None for axial neck painIndications -2Technique Details
• X-ray localization • Caspar pin Technique Details-2
• Maximum distraction
– Intervertebral spreader
Bony end
plates
preservedTechnique Details-3
• Oversize graft
• Cornerstone brand
– Fibular pre-milled
allograft
• Average size 8mm
(range 7-10mm)
• Packed with local boneTechnique – 5Technique -4
• Codman plateInduction and Maintenance of Lordosis
• Grafting on intact
endplates
• Oversize grafts &
distraction
• Î compression on graftThree LevelOdom’s Criteria
• Excellent
– All preoperative symptoms relieved; abnormal findings improved
• Good
– Minimal persistence of preoperative symptoms; abnormal findings
unchanged or improved
• Fair
– Definite relief of some preoperative symptoms; other symptoms
unchanged or slightly improved
ƒ Poor
ƒ Symptoms and signs unchanged or exacerbated
Odom GL, Finnery W, Woodhall B, Cervical Disk Lesions, JAMA
Vol.66 (1):pp23-28Radiograhic Pseudarthrosis
1. Absence of bridging, osseous, trabecular bone from
the vertebral bodies to the graft
2. Motion on dynamic radiographs
3. the presence of a lucent line at the graft–vertebral
body junctionLucencyResults
Clinical
• All patients had
‘excellent’ or good
outcomes as defined by
Odom’s criteria
Radiographic
• Lordosis improved an
average of 14.3 degrees
(range 5-35 degrees)
• 35 of 40 (87%) fused by
radiographic criteriaComplications
• Posterior cervical pain ceased on POD#3 on average
• Mild transient dysphagia & hoarseness which
resolved by POD#7
• One patient (2.5%) had dysphagia lasting 2 monthsComplications -2
• One patient (2.5%) had Horner’s syndrome ipsilateral
to the approach
– resolved at 3 months post-op
• No hardware removal
• No infections
• No same level revisionsWhy?Junctional Problems After FusionAdjacent Segment at Risk
• Fusion produces stress riser (ergo the enthusiasm for
artificial discs)
• Hypolordosis increases shear across the adjacent disc
space
• Hypolordotic alignment increased flexion-extension
at the adjacent segmentAdjacent Segment (Lumbar)
• Hypolordosis produces
increased posterior
element loading in
adjacent segments
(compensatory
hyperlordosis)
The Biomechanical Effect of Postoperative
Hypolordosis in Instrumented Lumbar
Fusion on Instrumented and Adjacent
Spinal Segments
Umehara, SPINE Volume 25, Number 13, pp
1617–1624Correlation between sagittal plane changes and
adjacent segment degeneration following lumbar
spine fusion
– Kumar MN. Et al European Spine Journal. 10(4):314-9,
2001 Aug.
• 83 patients followed for 5 years following lumbar
fusion
• spondylolytic spondylolisthesis and degenerative
scoliosis were not included
• Those with a normal c7 plumb line and normal sacral
inclination had a significantly decreased incidence of
adjacent level degenerationComparison of axial and flexural stresses in
lordosis and three buckled configurations of the
cervical spine
• Harrison DE, et al, Clinical Biomechanics. 16(4):276-84, 2001 May
• Mathematical modeling of cervical vertebral shear
stress in lordosis vs. kyphosis
• In lordosis, stresses at the anterior and posterior body
are balanced and minimal
• In Kyposis, the anterior body experiences tension
opposite the normal compression vector Î
osteophytesÆ degenerationBiomechanical Studies
• Stresses from C5 to T1 are reversed when the spine is
not in lordosis
– Harrison DE – J Manipulative Physiol Ther – 01-
JUL-2002; 25(6): 391-401
• Intra-discal pressure was significantly increased
especially in flexion at c4/5 and c6/7 after plating at
c5/6
– Eck JC – Spine – 15-Nov-2002; 27(22): 2431-4 Clinical Adjacent Level Disease
• 42 patients with myelopathy 9.8 year follow-up
• 50% (21) had adjacent level degenerative change
• 8 of the 21 had neurologic compromise secondary to
the degeneration
• 77% of those with kyphosis had adjacent level
degeneration (significant difference)
– Katsuura A Eur Spine J – 01-AUG-2001; 10(4):
320-4Radiculopathy and myelopathy at segments adjacent to
the site of a previous anterior cervical arthrodesis
– Hilibrand AS. Carlson GD. Palumbo MA. Jones PK. Bohlman HH.. Journal of Bone &
Joint Surgery – American Volume. 81(4):519-28, 1999 Apr
• Symptomatic adjacent segment 2.9% annual
incidence of degeneration
• Survivorship modeling suggests 25.6% new disease
in ten years
• No comment on the relationship of lordosis and
symptomatic adjacent segment degenerationClinical Implications
• Most current series do not emphasize Induction and
Maintenance Lordosis
Exception
• Non-plated single level ACDF lordosis decreased by
4.2° while it was maintained in the plated group
Troyanovich, Journal of Spinal Disorders &
Techniques. 15(1):69-74, February 2002Discussion
• Is lordosis necessary
– Wang, Spine 2000, Vol.25, pp41-45Increased Fusion Rates With Cervical Plating for Three
Level Anterior Cervical Discectomy
and Fusion
• Wang, et al SPINE Volume 26, Number 6, pp 643–647
• The average amount of kyphotic deformity of the
fused segment was 0.4° (range, 0–2°) for patients
with cervical plates,
• The actual significance of preserving the normal
contour of the cervical spine is not known. A
kyphotic posture of the cervical spine may lead to the
development of adjacent segment degeneration.
However, a longer follow-up period is needed to
confirm a relationship.Figure 2. A, Immediate postoperative radiograph of a two-level anterior cervical discectomy and
fusion without plate fixation, showing initial preservation of anatomic alignment. B, The same
patient after the development of a pseudarthrosis at the lower fusion level. Note the collapse of the
graft and the resultant kyphotic deformity at the level of the nonunion. C, Radiograph taken after
posterior fusion, demonstrating healing of the pseudarthrosis. Note the residual collapse and
kyphosis even after successful fusion.
From: Wang: Spine, Volume 25(1).January 1, 2000.41Induction of Lordosis
6
o
12
oRoom to Improve
• Retrospective
• Relatively short follow up
• CT scan to better assess fusionConclusions
1. Multiple level ACDF does not require autograft if
supplemented with instrumentation
2. End plates do not need to be removed
3. It is our opinion that the recreation of physiologic
sagittal plane alignment will lessen adjacent level
degeneration