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Is more lordosis associated with improved outcomes in cervical laminectomy and fusion when baseline alignment is lordotic?
Accepted Manuscript Title: Is more lordosis associated with improved outcomes in cervical laminectomy and fusion when baseline alignment is lordotic? Author: John A. Sielatycki, Sheyan Armaghani, Arnold J. Silverberg, Matthew J. McGirt, Clinton J. Devin, Kevin R. O'Neill PII: DOI: Reference:
S1529-9430(16)30037-7 http://dx.doi.org/doi: 10.1016/j.spinee.2016.04.009 SPINEE 57009
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
29-10-2015 25-2-2016 7-4-2016
Please cite this article as: John A. Sielatycki, Sheyan Armaghani, Arnold J. Silverberg, Matthew J. McGirt, Clinton J. Devin, Kevin R. O'Neill, Is more lordosis associated with improved outcomes in cervical laminectomy and fusion when baseline alignment is lordotic?, The Spine Journal (2016), http://dx.doi.org/doi: 10.1016/j.spinee.2016.04.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Is More Lordosis Associated with Improved Outcomes in Cervical Laminectomy and Fusion when Baseline Alignment is Lordotic? John A. Sielatycki, M.D., Sheyan Armaghani, M.D., Arnold Silverberg, B.S., Matthew J. McGirt, M.D., Clinton J. Devin, M.D., Kevin O’Neill, M.D., M.S. John A. Sielatycki, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville TN, [email protected] Sheyan Armaghani, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN [email protected] Arnold J. Silverberg, B.S. Vanderbilt University School of Medicine, Nashville, TN, [email protected] Matthew J. McGirt, M.D., Carolina Neurosurgery & Spine Associates, Charlotte, NC, [email protected] Clinton J. Devin, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, [email protected] Kevin R. O’Neill, M.D., M.S. Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, [email protected] Corresponding Author: John A. Sielatycki, M.D. Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Medical Center East – South Tower, Suite 4200 Nashville, TN 37232 Phone: (435) 770-7098 Fax: (615) 875-1079 Email: [email protected] Funding: No external funding sources were utilized for this project. Background Context: In cervical spondylotic myelopathy (CSM), cervical sagittal alignment (CSA) is associated with disease severity. Increased kyphosis and C2-7 sagittal vertical axis (SVA) correlate with worse myelopathy and poor outcomes. However, when alignment is lordotic it is unknown whether these associations persist. Purpose: To investigate associations between CSA parameters and patient-reported outcomes (PROs) following posterior decompression and fusion for CSM when baseline lordosis is maintained. 1 Page 1 of 15
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Study Design/Setting: Analysis of a prospective surgical cohort at a single academic institution.
36
the spinal cord from degenerative changes is one of the most common causes of spinal cord
37
dysfunction in the world.1,2 CSM leads to progressive neurologic deficits, hence there is little
38
role for nonsurgical management.3 Clinical improvements following surgery have been
39
demonstrated using both anterior and posterior approaches,4 with cervical sagittal alignment
40
(CSA) often cited as a primary factor in surgical approach planning.5-7 Further, CSA has been
41
demonstrated to correlate both with baseline disease severity8,9 as well as postoperative
Patient Sample: Adult patients undergoing primary cervical laminectomy and fusion for CSM over a 3-year period. Outcome Measures: PROs included EuroQol-5D (EQ-5D), Short-Form-12 (SF-12) physical component (PCS) and mental component scales (MCS), Neck Disability Index (NDI), and modified Japanese Orthopaedic Association (mJOA) scores. Radiographic CSA parameters measured included C1-2 Cobb, C2-7 Cobb, C1-7 Cobb, C2-7 SVA, C1-7 SVA, and T1 Slope. Methods: PROs were recorded at baseline and at 3- and 12-months postoperatively. CSA parameters were measured on standing radiographs in the neutral position at baseline and 3months. Wilcoxon rank test was used to test for changes in PROs and CSA parameters, and Pearson correlation coefficients were calculated for CSA parameters and PROs preoperatively and at 12 months. No external sources of funding were utilized for this work. Results: There were 45 patients included with an average age of 63 years who underwent posterior decompression and fusion of 3.7±1.3 levels. Significant improvements were found in all PROs except SF-12 MCS (p=0.06). Small but statistically significant changes were found in C27 Cobb (mean change: +3.6 degrees; p=0.03) and C2-7 SVA (mean change: +3mm; p=0.01). At baseline, only C2-C7 SVA associated with worse SF-12 PCS scores (r = -0.34, p = 0.02). Postoperatively, there were no associations found between PROs and any CSA parameters. Similarly, no CSA parameters were associated with changes in PROs. Conclusions: While creating more lordosis and decreasing SVA are associated with improved myelopathy and outcomes in patients with kyphosis, our study did not find such associations in patients with lordosis undergoing posterior laminectomy and fusion for CSM. This suggests that any amount of lordosis may be sufficient. Keywords: Cervical myelopathy; cervical sagittal alignment; patient reported outcomes; posterior; sagittal alignment INTRODUCTION Cervical spondylotic myelopathy (CSM) caused by repetitive, dynamic compression of
2 Page 2 of 15
Cervical Sagittal Alignment and Outcomes 1
outcomes.10,11 Recent studies have shown that when baseline kyphosis is present, increased
2
sagittal vertical axis (SVA) and more kyphosis are associated with worse myelopathy and poor
3
outcomes.8,10 Other studies have shown discrepancies in the associations between CSA
4
parameters and outcomes based on the overall cervical alignment (lordotic vs. kyphotic)8,9 and
5
surgical approach (anterior vs. posterior).10 Therefore, focusing on a more homogenous patient
6
population with CSM may allow for a better understanding of the potential correlations
7
between CSA and outcomes.
8 9
Studies have discovered a seemingly paradoxical relationship between overall sagittal alignment and the associations found between CSM disease severity and CSA parameters.
10
Mohanty et al. did not find an association between CSA and severity of myelopathy, function,
11
or disability in patients with maintained lordosis.8 However, when kyphosis was present,
12
increasing SVA was associated with qualitative MRI parameters and myelopathy severity.
13
Similarly, Smith et al. demonstrated paradoxically opposite correlations between MRI
14
parameters and disease severity based on whether overall cervical alignment was lordotic or
15
kyphotic.9 Animal and human cadaveric models have also shown that kyphosis can result in
16
decreased perfusion, increased intramedullary cord pressure, and increased neuronal loss.12-14
17
Considering these results, patients with lordosis versus kyphosis should likely be considered
18
independently when evaluating potential associations between CSA parameters and outcomes.
19
Recent studies have also demonstrated associations between CSA and outcomes
20
following surgery for CSM. Tang et al looked at a heterogeneous group of patients undergoing
21
posterior cervical fusion, and found correlations between postoperative SVA and patient
22
outcomes.11 However, only a minority of these patients had myelopathy and there were no
23
baseline radiographic or patient outcomes, making interpretation of these results problematic.
24
Roguski et al. found increased postoperative SVA to be associated with worse patient outcomes
25
and myelopathy in those undergoing either anterior or posterior surgery.10 Interestingly, they
26
also found postoperative SVA to be an independent predictor of outcomes in those undergoing
27
posterior surgery, but not in those who had anterior surgery. Thus, surgical approach may also
28
impact associations found between CSA parameters and outcomes.
3 Page 3 of 15
Cervical Sagittal Alignment and Outcomes 1
The purpose of the present study was to investigate the possible association between
2
CSA parameters and patient reported outcomes following posterior decompression and fusion
3
in the treatment of CSM for patients with maintained cervical lordosis. Based on the results of
4
the aforementioned studies, we hypothesized that greater lordosis and lower SVA would be
5
associated with less patient disability and myelopathy severity both at baseline and
6
postoperatively.
7 8
METHODS
9
Patients
10
With institutional review board approval, all adult patients who underwent posterior
11
cervical laminectomy and instrumented fusion for cervical spondylotic myelopathy from 2010
12
to 2013 at a single academic institution were retrospectively reviewed. All patients were
13
enrolled in an outcomes registry at baseline. The diagnosis of myelopathy was made based on
14
physical exam findings in combination with cervical spinal cord compression demonstrated on
15
MRI or CT myelogram. No cases of trauma, tumor, or infection were included. Patients were
16
excluded if they 1) did not have standing cervical radiographs at baseline and at 3 months
17
postoperatively; 2) did not complete patient-reported outcome (PRO) measures at 12 months
18
postoperatively; or 3) had previous cervical spine surgery; or 4) had cervical kyphosis. Cervical
19
kyphosis was defined as a C1-C7 Cobb angle greater than zero degrees.
20 21 22 23 24
Surgical Treatment All patients reviewed underwent posterior cervical central laminectomy with lateral
25
mass screw and rod instrumentation. The operations were performed by 4 separate spine
26
surgeons at our institution, each with at least 5 years of post-graduate experience in spine
27
surgery. Patients were in the prone position in all cases with a Mayfield head holder (Integra
28
LifeSciences, Plainsboro, NJ) utilized, taking care to position the head with the external auditory
29
canal in line with the shoulders. Laminoforamenotomies were performed at the surgeons’ 4 Page 4 of 15
Cervical Sagittal Alignment and Outcomes 1
discretion for the purpose of decompression or for palpating the pedicle for screw placement at
2
C7. Care was taken to preserve at least 50% of the facets during decompression. No
3
facetectomies or osteotomies were performed in this patient cohort.
4 5 6
Alignment Parameters
7
Standing radiographs of the cervical spine in the neutral position were obtained at
8
baseline and at a minimum of 3 months following surgery. The following parameters were
9
measured utilizing the image-viewing software (Impax, Agfa Healthcare, Belgium) at each time
10
point: C1-C2 Cobb, C2-C7 Cobb, C1-7 Cobb, C1-C7 SVA, C2-C7 SVA, and T1 slope.
11
Measurements were made according to previously described methods12,15-18 by two
12
independent investigators; one a 4th-year orthopaedic resident, the other a 4th-year medical
13
student. If there was disagreement between investigators, a repeat measurement taken by the
14
resident was utilized. If clear measurements could not be made due to image quality, that
15
patient was not included. Figure 1 illustrates measured alignment parameters on a standing
16
lateral radiograph.
17 18 19
Patient Reported Outcomes PROs were collected by telephone interview or in person at baseline and at 3- and 12-
20
months postoperatively. The Short-Form-12 (SF-12) and EuroQol-5D (EQ-5D) general health
21
questionnaires were utilized.19-23 The Neck Disability Index (NDI) was utilized to assess neck-
22
related disability.24 Myelopathy severity was scored utilizing the modified Japanese
23
Orthopaedic Association Scale (mJOAS).25
24 25 26 27 28 29
Statistical Analysis Statistical analysis was performed using SPSS v.22 (IBM Corp, Armonk, NY). Wilcoxon signed rank test was utilized to assess changes in CSA parameters and PRO measures following 5 Page 5 of 15
Cervical Sagittal Alignment and Outcomes 1
surgery between baseline and 1-year postoperatively. Pearson correlational coefficients were
2
calculated to assess associations between CSA parameters and PRO measures. Correlations
3
were evaluated between baseline values as well as postoperative values. Additionally, we
4
evaluated correlations between changes in PROs and postoperative CSA parameters. Pearson
5
correlation coefficients were also calculated to determine correlation between postoperative
6
alignment and changes in PROs. Results were considered statistically significant at p<0.05.
7
Preliminary data showed that NDI at 12 months post-operatively was 15.2 ± 9.7. In a
8
power analysis assuming no improvement from baseline in the study group, a sample size of 25
9
would give 80% power to detect a difference in NDI related to change in sagittal alignment.
10
However, most patients in this setting may have improved NDI with decompression alone
11
regardless of alignment. Thus, when we assume improvement from baseline to be 50% of the
12
improvement in controls, a sample size of 72 would give 80% power to detect the impact of
13
alignment.
14 15 16
RESULTS A total of 163 patient records were available for review; of these, 45 patients met the
17
inclusion criteria and had both baseline and post-operative standing radiographs (Table 1). The
18
mean number of laminectomy levels was 3.9, and mean number of motion segments fused was
19
3.7. Overall 90-day complications occurred in 5 (11.1%) patients. Two patients developed
20
urinary tract infections, 2 had superficial wound infections treated with antibiotics, and one
21
patient required re-operation in the setting of worsening myelopathy and inadequate
22
decompression at the caudal adjacent level.
23 24 25
Alignment Parameters Comparison of preoperative to postoperative radiographs revealed small but statistically
26
significant changes noted in C1-2 Cobb, C2-7 Cobb, C1-7 SVA, and C2-7 SVA (Table 2).
27
Interestingly, C2-7 Cobb revealed a straightening of the subaxial cervical spine postoperatively
28
with an associated slight increase in SVA and an increase in C1-2 lordosis.
29 6 Page 6 of 15
Cervical Sagittal Alignment and Outcomes 1 2
Patient Reported Outcomes Baseline and 12-month PROs were available for all 45 patients included in the study. All
3
PROs were found to have statistically significant improvements from baseline to 12-months
4
except improvement in the SF-12 MCS (p=0.06, Table 3).
5 6
Associations between Cervical Alignment and Outcomes
7
At baseline, C2-C7 SVA and C1-C7 SVA were found to correlate with worse general
8
physical health (SF-12 PCS). No statistically significant correlation was found between any of the
9
other CSA parameters and PROs at baseline (Table 4). At 1-year postoperatively, none of the
10
CSA parameters were found to correlate with any of the PROs (Table 5). Finally, postoperative
11
CSA parameters were not found to be associated with changes in PROs from baseline (Table 6).
12 13
DISCUSSION
14
There is an increasing interest in the impact of sagittal alignment in patients with
15
cervical spondylotic myelopathy. CSA has been associated with disease severity8,9,12 and
16
pathophysiology12,15, often directs the surgical approach4,6, and may have an effect on patient
17
outcomes.10,11 Previous studies have demonstrated variable associations between CSA
18
parameters and outcomes, based on whether the overall alignment was lordotic or kyphotic8
19
and whether surgery was performed from an anterior or posterior approach.10 In this study, we
20
evaluated patients with maintained baseline lordosis who underwent posterior decompression
21
and fusion. This therefore represents a more homogenous group than previous studies. While
22
we demonstrated an association at baseline between SVA and SF-12 PCS, no other correlations
23
between CSA parameters and patient outcomes or myelopathy severity were found either pre-
24
or postoperatively. This highlights the need for further studies in characterizing the potential
25
relationships between CSA parameters, disease severity, and surgical outcomes in the
26
treatment of CSM.
27
In contrast to the report by Smith et al, we were unable to find a correlation between
28
myelopathy severity at baseline and SVA. However, an important difference between these
29
studies is their inclusion of patients with kyphosis, representing 30% of patients evaluated. The 7 Page 7 of 15
Cervical Sagittal Alignment and Outcomes 1
overall association between mJOA and SVA may have been predominantly driven by these
2
patients with kyphotic alignment. Indeed, in this same study, they discovered a seemingly
3
paradoxical relationship between quantitative MRI measurements and mJOA scores –
4
dependent upon the alignment being lordodic versus kyphotic. This would seemingly be
5
supported by the study of Mohanty et al, who also found no correlation between myelopathy
6
severity and CSA measurements in patients with maintained lordosis. In Mohanty’s work,
7
higher SVA was even associated with lower cord signal intensity on MRI. However, in patients
8
with kyphosis, increasing SVA was associated with higher cord intensity signal, more severe
9
myelopathy scores, and increased disability.
10
Considering our results along with these studies, it seems clear that associations
11
between CSA and myelopathy severity differ based on whether the spine has maintained
12
lordosis or has developed kyphosis. There are studies that have demonstrated possible
13
explanations for this finding. Both animal and human cadaveric studies have been done that
14
demonstrate that kyphosis results in decreased perfusion, increased intramedullary cord
15
pressure, and increased neuronal loss.12-14 Therefore, we would advocate that future studies
16
dichotomize patients based on their overall alignment being kyphotic or lordotic.
17
In perhaps the most similar study to ours, Roguski et al. evaluated pre- and post-
18
operative radiographs of 49 surgical patients undergoing either anterior or posterior surgery for
19
CSM.10 Patients with more than 5 degrees of kyphosis were excluded. Postoperative SVA was
20
found to be associated with postoperative SF-36 PCS and mJOA scores and changes in SF-36 PCS
21
and NDI scores. In the subset of patients undergoing posterior surgery (n=28) the association
22
with SF-36 PCS was maintained, while in those undergoing anterior surgery it was not. This
23
appears to contrast with the results of our study, as we did not find any correlations with
24
postoperative CSA parameters. It is possible that the inclusion of anterior surgeries in their
25
study precludes direct comparison with our study. Further, we did not include patients with any
26
amount of kyphosis, and the mean amount of lordosis in our study at baseline (14 degrees) was
27
greater than their study (7.5 degrees). Finally, our study involved a population with significantly
28
greater comorbidities, which may have masked quality of life outcome measure changes. While
29
their study excluded patients with ASA of 3 or greater, 86% of our cohort had an ASA of at least 8 Page 8 of 15
Cervical Sagittal Alignment and Outcomes 1
3. The findings of our study suggest that sagittal alignment correction may not be necessary in
2
the treatment of CSM for patients with maintained cervical lordosis.
3
Our study is not without limitations. One potential limitation of this study is the follow
4
up duration of 12 months. However, several reports have shown that maximal improvement in
5
myelopathy following surgical decompression for CSM occurs by 6 months post-operatively.26,27
6
Another limitation of this study was the use of 3-month rather than 1-year post-operative
7
radiographs. Radiographs were not commonly obtained at the 1-year follow-up visit, making
8
the number available at this time point too low to utilize. Another limitation was the lack of
9
global sagittal alignment assessments, including coronal balance, which would potentially also
10
contribute to outcomes. This is an important area for future research, however full-length spine
11
radiographs were not commonly obtained for most cervical spine operations. Finally, as this
12
study included 45 patients it is underpowered to detect a more subtle effect of alignment on
13
PROs. The sample size of 45 gives us 80% power to detect the effect of alignment if alignment is
14
assumed to contribute to at least 50% or more of the improvement in NDI. Thus the findings of
15
this study suggest that increased lordosis may not contribute to greater than 50% of the
16
improvement in NDI in this cohort; however we cannot determine the impact alignment may
17
have below this threshold. Larger studies are warranted to explore the impact of increased
18
cervical lordosis in more depth. No external sources of funding were utilized for this
19
investigation.
20 21 22 23
CONCLUSION In a study of patients with maintained cervical lordosis who underwent posterior
24
decompression and fusion in the treatment of cervical myelopathy, we found no correlations
25
between cervical sagittal alignment parameters and postoperative outcomes. Neither baseline
26
nor postoperative myelopathy severity was associated with either the amount of lordosis or
27
SVA. This suggests, in contrast to previous reports, that surgical improvement of SVA may not
28
improve outcomes – provided that cervical lordosis is maintained. While creating more lordosis
29
and decreasing SVA are associated with improved myelopathy and outcomes in patients with 9 Page 9 of 15
Cervical Sagittal Alignment and Outcomes 1
kyphosis, our study did not find such associations in patients with lordosis. This suggests that
2
any amount of lordosis is sufficient, and that more is not necessarily better. Further studies are
3
certainly needed to further assess and characterize associations between CSA and outcomes in
4
CSM surgery.
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
REFERENCES 1. 2.
3.
4.
5.
6. 7.
8.
9.
10.
11.
Young WF. Cervical spondylotic myelopathy: a common cause of spinal cord dysfunction in older persons. American family physician. 2000;62(5):1064-1070, 1073. Karadimas SK, Erwin WM, Ely CG, Dettori JR, Fehlings MG. Pathophysiology and natural history of cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S21-36. Fehlings MG, Wilson JR, Yoon ST, Rhee JM, Shamji MF, Lawrence BD. Symptomatic progression of cervical myelopathy and the role of nonsurgical management: a consensus statement. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S19-20. Fehlings MG, Gray R. Importance of sagittal balance in determining the outcome of anterior versus posterior surgery for cervical spondylotic myelopathy. J Neurosurg Spine. 2009;11(5):518-519; discussion 519-520. Uchida K, Nakajima H, Sato R, et al. Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid alignment: outcome after anterior or posterior decompression. J Neurosurg Spine. 2009;11(5):521-528. Emery SE. Cervical spondylotic myelopathy: diagnosis and treatment. J Am Acad Orthop Surg. 2001;9(6):376-388. Bapat MR, Chaudhary K, Sharma A, Laheri V. Surgical approach to cervical spondylotic myelopathy on the basis of radiological patterns of compression: prospective analysis of 129 cases. Eur Spine J. 2008;17(12):1651-1663. Mohanty C, Massicotte EM, Fehlings MG, Shamji MF. Association of preoperative cervical spine alignment with spinal cord magnetic resonance imaging hyperintensity and myelopathy severity: analysis of a series of 124 cases. Spine (Phila Pa 1976). 2015;40(1):11-16. Smith JS, Lafage V, Ryan DJ, et al. Association of myelopathy scores with cervical sagittal balance and normalized spinal cord volume: analysis of 56 preoperative cases from the AOSpine North America Myelopathy study. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S161-170. Roguski M, Benzel EC, Curran JN, et al. Postoperative cervical sagittal imbalance negatively affects outcomes after surgery for cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2014;39(25):2070-2077. Tang JA, Scheer JK, Smith JS, et al. The impact of standing regional cervical sagittal alignment on outcomes in posterior cervical fusion surgery. Neurosurgery. 2012;71(3):662-669; discussion 669. 10 Page 10 of 15
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
12. 13.
14.
15.
16.
17.
18.
19. 20. 21.
22. 23.
24. 25.
26.
Scheer JK, Tang JA, Smith JS, et al. Cervical spine alignment, sagittal deformity, and clinical implications: a review. J Neurosurg Spine. 2013;19(2):141-159. Shimizu K, Nakamura M, Nishikawa Y, Hijikata S, Chiba K, Toyama Y. Spinal kyphosis causes demyelination and neuronal loss in the spinal cord: a new model of kyphotic deformity using juvenile Japanese small game fowls. Spine (Phila Pa 1976). 2005;30(21):2388-2392. Takenouchi T, Setoguchi T, Yone K, Komiya S. Expression of apoptosis signal-regulating kinase 1 in mouse spinal cord under chronic mechanical compression: possible involvement of the stress-activated mitogen-activated protein kinase pathways in spinal cord cell apoptosis. Spine (Phila Pa 1976). 2008;33(18):1943-1950. Ames CP, Blondel B, Scheer JK, et al. Cervical radiographical alignment: comprehensive assessment techniques and potential importance in cervical myelopathy. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S149-160. Harrison DE, Harrison DD, Cailliet R, Troyanovich SJ, Janik TJ, Holland B. Cobb method or Harrison posterior tangent method: which to choose for lateral cervical radiographic analysis. Spine (Phila Pa 1976). 2000;25(16):2072-2078. Polly DW, Jr., Kilkelly FX, McHale KA, Asplund LM, Mulligan M, Chang AS. Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability. Spine (Phila Pa 1976). 1996;21(13):1530-1535; discussion 1535-1536. Singer KP, Jones TJ, Breidahl PD. A comparison of radiographic and computer-assisted measurements of thoracic and thoracolumbar sagittal curvature. Skeletal Radiol. 1990;19(1):21-26. Ware J, Jr., Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Medical care. 1996;34(3):220-233. Nemeth G. Health related quality of life outcome instruments. Eur Spine J. 2006;15 Suppl 1:S44-51. Godil SS, Parker SL, Zuckerman SL, Mendenhall SK, Glassman SD, McGirt MJ. Accurately measuring the quality and effectiveness of lumbar surgery in registry efforts: determining the most valid and responsive instruments. Spine J. 2014. EuroQol--a new facility for the measurement of health-related quality of life. Health policy (Amsterdam, Netherlands). 1990;16(3):199-208. Luo X, George ML, Kakouras I, et al. Reliability, validity, and responsiveness of the short form 12-item survey (SF-12) in patients with back pain. Spine (Phila Pa 1976). 2003;28(15):1739-1745. Vernon H. The Neck Disability Index: state-of-the-art, 1991-2008. J Manipulative Physiol Ther. 2008;31(7):491-502. Benzel EC, Lancon J, Kesterson L, Hadden T. Cervical laminectomy and dentate ligament section for cervical spondylotic myelopathy. Journal of spinal disorders. 1991;4(3):286295. Acharya S, Srivastava A, Virmani S, Tandon R. Resolution of physical signs and recovery in severe cervical spondylotic myelopathy after cervical laminoplasty. Spine (Phila Pa 1976). 2010;35(21):E1083-1087.
11 Page 11 of 15
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27.
Furlan JC, Kalsi-Ryan S, Kailaya-Vasan A, Massicotte EM, Fehlings MG. Functional and clinical outcomes following surgical treatment in patients with cervical spondylotic myelopathy: a prospective study of 81 cases. J Neurosurg Spine. 2011;14(3):348-355.
6 7 8
FIGURE LEGEND
9 10 11 12
Figure 1: Representative standing lateral radiograph illustrating the cervical sagittal alignment parameters utilized in this study.
13
Table 1: Baseline Demographics and Clinical Characteristics Number of Patients Age Gender Male Female Smoker ASA¹ 1 2 3 4 BMI² Primary Cause of Myelopathy Congenital Stenosis Ventral disc herniation OPLL Spondylolisthesis Surgical Data Mean Operative Time in Minutes Mean EBL³ in Milliliters Mean motion segments fused
14 15
45 63
±
10.5
28 17 11
(62%) (38%) (24%)
0 6 37 2 27.7
(13%) (82%) (4%) 4.8
±
32 4 3 6 170 321 3.7
(71%) (8%) (6%) (13%) ± ± ±
46 222 1.3
* Values given as mean ± standard deviation, or as total (percentage%). ¹American Society of Anesthesiologist classification 12 Page 12 of 15
Cervical Sagittal Alignment and Outcomes 1
²Body Mass Index
2 3
Table 2: Alignment change from baseline to 1-year post-op Pre-Operative -25.8 -14.0 2.9 4.5 -39.8 28.2
C1-C2 Cobb° C2-C7 Cobb° C2-C7 SVA (cm) C1-C7 SVA (cm) Cerv Lordosis°† T1 Slope° 4 *standard deviation 5 † C1-2 Cobb + C2-7 Cobb
± ± ± ± ± ±
std dev* 6.5 9.7 1.5 1.8 10.9 10.2
min -4.9 0.0 0 0.8 -16 7
max -41 -44 5.8 8.7 -72 50
Post-Operative -27.1 -11.3 3.3 5.0 -38.4 27.9
± ± ± ± ± ±
std dev* 6.5 7.6 1.5 1.8 8.7 8.1
min -6.7 0.0 0.0 1.1 -16 6
max p-value -41 0.03 -44 0.01 7.1 0.01 9.5 0.01 -64 0.09 40 0.43
6 7
Table 3: Health-Related Quality of Life outcomes results Pre-Operative
Post-Operative
0.54 ± 0.24
0.71 ± 0.19
<0.001
NDI²
21.57 ± 10.57
13.93 ± 9.77
<0.001
mJOAS³
10.62 ± 3.37
12.20 ± 3.22
<0.001
SF-12 PCS†
26.7 ± 10.3
34.63 ± 13.61
0.01
SF-12 MCS‡
47.96 ± 12.18
49.76 ± 12.29
0.06
EQ-5D¹ score
8 9 10 11 12 13 14
p-value
*Values reported as mean ± standard deviation ¹ EuroQol-5D ²Neck Disability Index ³Modified Japanese Orthopaedic Association score †Short-Form 12 Physical Composite Scale ‡Short-Form 12 Mental Composite Scale
13 Page 13 of 15
Cervical Sagittal Alignment and Outcomes 1
Table 4: Correlation between pre-operative outcomes and pre-operative alignment C1-C2 Cobb
EQ-5D NDI
SF-12 PCS SF-12 MCS
C2-7 SVA C1-C7 SVA
0.08
-0.20
-0.22
0.11
-0.30
Sig.*
0.68
0.58
0.17
0.13
0.47
0.08
-0.07
-0.16
0.17
0.18
-0.18
0.32
Sig.
0.63
0.30
0.25
0.24
0.23
0.06
Pearson Correlation
0.03
0.25
-0.25
-0.23
0.23
-0.31
Sig.
0.88
0.18
0.17
0.21
0.21
0.19
Pearson Correlation
0.06
0.01
-0.34
-0.33
0.04
-0.16
Sig.
0.71
0.97
0.02
0.03
0.80
0.36
-0.11
0.18
0.09
0.07
0.09
-0.05
0.46
0.25
0.55
0.62
0.54
0.80
Pearson Correlation
2 3
†Bolded values indicate statistically significant correlation. *Significance, two-tailed.
4
Table 5: Correlation between 1 year outcomes and post-operative alignment
NDI
T1 Slope
0.06
Sig.
EQ-5D
Cervical Lordosis
Pearson Correlation Pearson Correlation
mJOAS
C2-C7 Cobb
C1-C2 Cobb
C2-C7 Cobb
-0.12
0.15
-0.17
-0.15
0.10
-0.16
Sig.*
0.32
0.22
0.15
0.21
0.41
0.28
Pearson Correlation
0.10
-0.13
0.16
0.15
-0.08
0.23
Sig.
0.40
0.29
0.18
0.20
0.50
0.12
Pearson Correlation
C2-7 SVA C1-C7 SVA Cervical Lordosis
T1 Slope
14 Page 14 of 15
Cervical Sagittal Alignment and Outcomes
mJOAS
Pearson Correlation Sig.
SF-12 PCS
Pearson Correlation Sig.
SF-12 MCS Pearson Correlation 1 2 3
Sig. *Significance (Two-Tailed)
0.09
0.08
0.09
-0.03
0.03
0.18
0.49
0.55
0.51
0.82
0.84
-0.10
0.16
-0.20
-0.20
0.10
-0.19
0.42
0.20
0.10
0.11
0.40
0.19
-0.14
0.21
0.03
0.07
0.10
-0.17
0.25
0.08
0.82
0.57
0.41
0.24
Table 6: Correlation between post-operative alignment and 1-year change in outcome scores
EQ-5D
SF-12 PCS
NDI
mJOAs 4 5
-0.17
C1-C2 Cobb
C2-C7 Cobb
C2-C7 SVA
C1-C7 SVA
Cervical Lordosis
T1 Slope
Pearson Correlation
0.01
0.01
0.00
0.07
0.00
0.01
sig.*
0.42
0.56
0.56
0.54
0.96
0.92
Pearson Correlation
0.00
0.01
0.02
0.14
0.00
0.05
sig.
0.72
0.52
0.29
0.26
0.74
0.75
Pearson Correlation
0.00
0.00
0.03
0.20
0.01
0.02
sig.
0.71
0.64
0.14
0.09
0.54
0.91
Pearson Correlation
0.00
0.01
0.01
0.12
0.01
0.82
0.92
0.49
0.50
0.45
0.59
0.38
sig. *Significance (Two-Tailed)
15 Page 15 of 15
S1529-9430(16)30037-7 http://dx.doi.org/doi: 10.1016/j.spinee.2016.04.009 SPINEE 57009
To appear in:
The Spine Journal
Received date: Revised date: Accepted date:
29-10-2015 25-2-2016 7-4-2016
Please cite this article as: John A. Sielatycki, Sheyan Armaghani, Arnold J. Silverberg, Matthew J. McGirt, Clinton J. Devin, Kevin R. O'Neill, Is more lordosis associated with improved outcomes in cervical laminectomy and fusion when baseline alignment is lordotic?, The Spine Journal (2016), http://dx.doi.org/doi: 10.1016/j.spinee.2016.04.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Is More Lordosis Associated with Improved Outcomes in Cervical Laminectomy and Fusion when Baseline Alignment is Lordotic? John A. Sielatycki, M.D., Sheyan Armaghani, M.D., Arnold Silverberg, B.S., Matthew J. McGirt, M.D., Clinton J. Devin, M.D., Kevin O’Neill, M.D., M.S. John A. Sielatycki, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville TN, [email protected] Sheyan Armaghani, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN [email protected] Arnold J. Silverberg, B.S. Vanderbilt University School of Medicine, Nashville, TN, [email protected] Matthew J. McGirt, M.D., Carolina Neurosurgery & Spine Associates, Charlotte, NC, [email protected] Clinton J. Devin, M.D., Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, [email protected] Kevin R. O’Neill, M.D., M.S. Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, [email protected] Corresponding Author: John A. Sielatycki, M.D. Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Medical Center East – South Tower, Suite 4200 Nashville, TN 37232 Phone: (435) 770-7098 Fax: (615) 875-1079 Email: [email protected] Funding: No external funding sources were utilized for this project. Background Context: In cervical spondylotic myelopathy (CSM), cervical sagittal alignment (CSA) is associated with disease severity. Increased kyphosis and C2-7 sagittal vertical axis (SVA) correlate with worse myelopathy and poor outcomes. However, when alignment is lordotic it is unknown whether these associations persist. Purpose: To investigate associations between CSA parameters and patient-reported outcomes (PROs) following posterior decompression and fusion for CSM when baseline lordosis is maintained. 1 Page 1 of 15
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Study Design/Setting: Analysis of a prospective surgical cohort at a single academic institution.
36
the spinal cord from degenerative changes is one of the most common causes of spinal cord
37
dysfunction in the world.1,2 CSM leads to progressive neurologic deficits, hence there is little
38
role for nonsurgical management.3 Clinical improvements following surgery have been
39
demonstrated using both anterior and posterior approaches,4 with cervical sagittal alignment
40
(CSA) often cited as a primary factor in surgical approach planning.5-7 Further, CSA has been
41
demonstrated to correlate both with baseline disease severity8,9 as well as postoperative
Patient Sample: Adult patients undergoing primary cervical laminectomy and fusion for CSM over a 3-year period. Outcome Measures: PROs included EuroQol-5D (EQ-5D), Short-Form-12 (SF-12) physical component (PCS) and mental component scales (MCS), Neck Disability Index (NDI), and modified Japanese Orthopaedic Association (mJOA) scores. Radiographic CSA parameters measured included C1-2 Cobb, C2-7 Cobb, C1-7 Cobb, C2-7 SVA, C1-7 SVA, and T1 Slope. Methods: PROs were recorded at baseline and at 3- and 12-months postoperatively. CSA parameters were measured on standing radiographs in the neutral position at baseline and 3months. Wilcoxon rank test was used to test for changes in PROs and CSA parameters, and Pearson correlation coefficients were calculated for CSA parameters and PROs preoperatively and at 12 months. No external sources of funding were utilized for this work. Results: There were 45 patients included with an average age of 63 years who underwent posterior decompression and fusion of 3.7±1.3 levels. Significant improvements were found in all PROs except SF-12 MCS (p=0.06). Small but statistically significant changes were found in C27 Cobb (mean change: +3.6 degrees; p=0.03) and C2-7 SVA (mean change: +3mm; p=0.01). At baseline, only C2-C7 SVA associated with worse SF-12 PCS scores (r = -0.34, p = 0.02). Postoperatively, there were no associations found between PROs and any CSA parameters. Similarly, no CSA parameters were associated with changes in PROs. Conclusions: While creating more lordosis and decreasing SVA are associated with improved myelopathy and outcomes in patients with kyphosis, our study did not find such associations in patients with lordosis undergoing posterior laminectomy and fusion for CSM. This suggests that any amount of lordosis may be sufficient. Keywords: Cervical myelopathy; cervical sagittal alignment; patient reported outcomes; posterior; sagittal alignment INTRODUCTION Cervical spondylotic myelopathy (CSM) caused by repetitive, dynamic compression of
2 Page 2 of 15
Cervical Sagittal Alignment and Outcomes 1
outcomes.10,11 Recent studies have shown that when baseline kyphosis is present, increased
2
sagittal vertical axis (SVA) and more kyphosis are associated with worse myelopathy and poor
3
outcomes.8,10 Other studies have shown discrepancies in the associations between CSA
4
parameters and outcomes based on the overall cervical alignment (lordotic vs. kyphotic)8,9 and
5
surgical approach (anterior vs. posterior).10 Therefore, focusing on a more homogenous patient
6
population with CSM may allow for a better understanding of the potential correlations
7
between CSA and outcomes.
8 9
Studies have discovered a seemingly paradoxical relationship between overall sagittal alignment and the associations found between CSM disease severity and CSA parameters.
10
Mohanty et al. did not find an association between CSA and severity of myelopathy, function,
11
or disability in patients with maintained lordosis.8 However, when kyphosis was present,
12
increasing SVA was associated with qualitative MRI parameters and myelopathy severity.
13
Similarly, Smith et al. demonstrated paradoxically opposite correlations between MRI
14
parameters and disease severity based on whether overall cervical alignment was lordotic or
15
kyphotic.9 Animal and human cadaveric models have also shown that kyphosis can result in
16
decreased perfusion, increased intramedullary cord pressure, and increased neuronal loss.12-14
17
Considering these results, patients with lordosis versus kyphosis should likely be considered
18
independently when evaluating potential associations between CSA parameters and outcomes.
19
Recent studies have also demonstrated associations between CSA and outcomes
20
following surgery for CSM. Tang et al looked at a heterogeneous group of patients undergoing
21
posterior cervical fusion, and found correlations between postoperative SVA and patient
22
outcomes.11 However, only a minority of these patients had myelopathy and there were no
23
baseline radiographic or patient outcomes, making interpretation of these results problematic.
24
Roguski et al. found increased postoperative SVA to be associated with worse patient outcomes
25
and myelopathy in those undergoing either anterior or posterior surgery.10 Interestingly, they
26
also found postoperative SVA to be an independent predictor of outcomes in those undergoing
27
posterior surgery, but not in those who had anterior surgery. Thus, surgical approach may also
28
impact associations found between CSA parameters and outcomes.
3 Page 3 of 15
Cervical Sagittal Alignment and Outcomes 1
The purpose of the present study was to investigate the possible association between
2
CSA parameters and patient reported outcomes following posterior decompression and fusion
3
in the treatment of CSM for patients with maintained cervical lordosis. Based on the results of
4
the aforementioned studies, we hypothesized that greater lordosis and lower SVA would be
5
associated with less patient disability and myelopathy severity both at baseline and
6
postoperatively.
7 8
METHODS
9
Patients
10
With institutional review board approval, all adult patients who underwent posterior
11
cervical laminectomy and instrumented fusion for cervical spondylotic myelopathy from 2010
12
to 2013 at a single academic institution were retrospectively reviewed. All patients were
13
enrolled in an outcomes registry at baseline. The diagnosis of myelopathy was made based on
14
physical exam findings in combination with cervical spinal cord compression demonstrated on
15
MRI or CT myelogram. No cases of trauma, tumor, or infection were included. Patients were
16
excluded if they 1) did not have standing cervical radiographs at baseline and at 3 months
17
postoperatively; 2) did not complete patient-reported outcome (PRO) measures at 12 months
18
postoperatively; or 3) had previous cervical spine surgery; or 4) had cervical kyphosis. Cervical
19
kyphosis was defined as a C1-C7 Cobb angle greater than zero degrees.
20 21 22 23 24
Surgical Treatment All patients reviewed underwent posterior cervical central laminectomy with lateral
25
mass screw and rod instrumentation. The operations were performed by 4 separate spine
26
surgeons at our institution, each with at least 5 years of post-graduate experience in spine
27
surgery. Patients were in the prone position in all cases with a Mayfield head holder (Integra
28
LifeSciences, Plainsboro, NJ) utilized, taking care to position the head with the external auditory
29
canal in line with the shoulders. Laminoforamenotomies were performed at the surgeons’ 4 Page 4 of 15
Cervical Sagittal Alignment and Outcomes 1
discretion for the purpose of decompression or for palpating the pedicle for screw placement at
2
C7. Care was taken to preserve at least 50% of the facets during decompression. No
3
facetectomies or osteotomies were performed in this patient cohort.
4 5 6
Alignment Parameters
7
Standing radiographs of the cervical spine in the neutral position were obtained at
8
baseline and at a minimum of 3 months following surgery. The following parameters were
9
measured utilizing the image-viewing software (Impax, Agfa Healthcare, Belgium) at each time
10
point: C1-C2 Cobb, C2-C7 Cobb, C1-7 Cobb, C1-C7 SVA, C2-C7 SVA, and T1 slope.
11
Measurements were made according to previously described methods12,15-18 by two
12
independent investigators; one a 4th-year orthopaedic resident, the other a 4th-year medical
13
student. If there was disagreement between investigators, a repeat measurement taken by the
14
resident was utilized. If clear measurements could not be made due to image quality, that
15
patient was not included. Figure 1 illustrates measured alignment parameters on a standing
16
lateral radiograph.
17 18 19
Patient Reported Outcomes PROs were collected by telephone interview or in person at baseline and at 3- and 12-
20
months postoperatively. The Short-Form-12 (SF-12) and EuroQol-5D (EQ-5D) general health
21
questionnaires were utilized.19-23 The Neck Disability Index (NDI) was utilized to assess neck-
22
related disability.24 Myelopathy severity was scored utilizing the modified Japanese
23
Orthopaedic Association Scale (mJOAS).25
24 25 26 27 28 29
Statistical Analysis Statistical analysis was performed using SPSS v.22 (IBM Corp, Armonk, NY). Wilcoxon signed rank test was utilized to assess changes in CSA parameters and PRO measures following 5 Page 5 of 15
Cervical Sagittal Alignment and Outcomes 1
surgery between baseline and 1-year postoperatively. Pearson correlational coefficients were
2
calculated to assess associations between CSA parameters and PRO measures. Correlations
3
were evaluated between baseline values as well as postoperative values. Additionally, we
4
evaluated correlations between changes in PROs and postoperative CSA parameters. Pearson
5
correlation coefficients were also calculated to determine correlation between postoperative
6
alignment and changes in PROs. Results were considered statistically significant at p<0.05.
7
Preliminary data showed that NDI at 12 months post-operatively was 15.2 ± 9.7. In a
8
power analysis assuming no improvement from baseline in the study group, a sample size of 25
9
would give 80% power to detect a difference in NDI related to change in sagittal alignment.
10
However, most patients in this setting may have improved NDI with decompression alone
11
regardless of alignment. Thus, when we assume improvement from baseline to be 50% of the
12
improvement in controls, a sample size of 72 would give 80% power to detect the impact of
13
alignment.
14 15 16
RESULTS A total of 163 patient records were available for review; of these, 45 patients met the
17
inclusion criteria and had both baseline and post-operative standing radiographs (Table 1). The
18
mean number of laminectomy levels was 3.9, and mean number of motion segments fused was
19
3.7. Overall 90-day complications occurred in 5 (11.1%) patients. Two patients developed
20
urinary tract infections, 2 had superficial wound infections treated with antibiotics, and one
21
patient required re-operation in the setting of worsening myelopathy and inadequate
22
decompression at the caudal adjacent level.
23 24 25
Alignment Parameters Comparison of preoperative to postoperative radiographs revealed small but statistically
26
significant changes noted in C1-2 Cobb, C2-7 Cobb, C1-7 SVA, and C2-7 SVA (Table 2).
27
Interestingly, C2-7 Cobb revealed a straightening of the subaxial cervical spine postoperatively
28
with an associated slight increase in SVA and an increase in C1-2 lordosis.
29 6 Page 6 of 15
Cervical Sagittal Alignment and Outcomes 1 2
Patient Reported Outcomes Baseline and 12-month PROs were available for all 45 patients included in the study. All
3
PROs were found to have statistically significant improvements from baseline to 12-months
4
except improvement in the SF-12 MCS (p=0.06, Table 3).
5 6
Associations between Cervical Alignment and Outcomes
7
At baseline, C2-C7 SVA and C1-C7 SVA were found to correlate with worse general
8
physical health (SF-12 PCS). No statistically significant correlation was found between any of the
9
other CSA parameters and PROs at baseline (Table 4). At 1-year postoperatively, none of the
10
CSA parameters were found to correlate with any of the PROs (Table 5). Finally, postoperative
11
CSA parameters were not found to be associated with changes in PROs from baseline (Table 6).
12 13
DISCUSSION
14
There is an increasing interest in the impact of sagittal alignment in patients with
15
cervical spondylotic myelopathy. CSA has been associated with disease severity8,9,12 and
16
pathophysiology12,15, often directs the surgical approach4,6, and may have an effect on patient
17
outcomes.10,11 Previous studies have demonstrated variable associations between CSA
18
parameters and outcomes, based on whether the overall alignment was lordotic or kyphotic8
19
and whether surgery was performed from an anterior or posterior approach.10 In this study, we
20
evaluated patients with maintained baseline lordosis who underwent posterior decompression
21
and fusion. This therefore represents a more homogenous group than previous studies. While
22
we demonstrated an association at baseline between SVA and SF-12 PCS, no other correlations
23
between CSA parameters and patient outcomes or myelopathy severity were found either pre-
24
or postoperatively. This highlights the need for further studies in characterizing the potential
25
relationships between CSA parameters, disease severity, and surgical outcomes in the
26
treatment of CSM.
27
In contrast to the report by Smith et al, we were unable to find a correlation between
28
myelopathy severity at baseline and SVA. However, an important difference between these
29
studies is their inclusion of patients with kyphosis, representing 30% of patients evaluated. The 7 Page 7 of 15
Cervical Sagittal Alignment and Outcomes 1
overall association between mJOA and SVA may have been predominantly driven by these
2
patients with kyphotic alignment. Indeed, in this same study, they discovered a seemingly
3
paradoxical relationship between quantitative MRI measurements and mJOA scores –
4
dependent upon the alignment being lordodic versus kyphotic. This would seemingly be
5
supported by the study of Mohanty et al, who also found no correlation between myelopathy
6
severity and CSA measurements in patients with maintained lordosis. In Mohanty’s work,
7
higher SVA was even associated with lower cord signal intensity on MRI. However, in patients
8
with kyphosis, increasing SVA was associated with higher cord intensity signal, more severe
9
myelopathy scores, and increased disability.
10
Considering our results along with these studies, it seems clear that associations
11
between CSA and myelopathy severity differ based on whether the spine has maintained
12
lordosis or has developed kyphosis. There are studies that have demonstrated possible
13
explanations for this finding. Both animal and human cadaveric studies have been done that
14
demonstrate that kyphosis results in decreased perfusion, increased intramedullary cord
15
pressure, and increased neuronal loss.12-14 Therefore, we would advocate that future studies
16
dichotomize patients based on their overall alignment being kyphotic or lordotic.
17
In perhaps the most similar study to ours, Roguski et al. evaluated pre- and post-
18
operative radiographs of 49 surgical patients undergoing either anterior or posterior surgery for
19
CSM.10 Patients with more than 5 degrees of kyphosis were excluded. Postoperative SVA was
20
found to be associated with postoperative SF-36 PCS and mJOA scores and changes in SF-36 PCS
21
and NDI scores. In the subset of patients undergoing posterior surgery (n=28) the association
22
with SF-36 PCS was maintained, while in those undergoing anterior surgery it was not. This
23
appears to contrast with the results of our study, as we did not find any correlations with
24
postoperative CSA parameters. It is possible that the inclusion of anterior surgeries in their
25
study precludes direct comparison with our study. Further, we did not include patients with any
26
amount of kyphosis, and the mean amount of lordosis in our study at baseline (14 degrees) was
27
greater than their study (7.5 degrees). Finally, our study involved a population with significantly
28
greater comorbidities, which may have masked quality of life outcome measure changes. While
29
their study excluded patients with ASA of 3 or greater, 86% of our cohort had an ASA of at least 8 Page 8 of 15
Cervical Sagittal Alignment and Outcomes 1
3. The findings of our study suggest that sagittal alignment correction may not be necessary in
2
the treatment of CSM for patients with maintained cervical lordosis.
3
Our study is not without limitations. One potential limitation of this study is the follow
4
up duration of 12 months. However, several reports have shown that maximal improvement in
5
myelopathy following surgical decompression for CSM occurs by 6 months post-operatively.26,27
6
Another limitation of this study was the use of 3-month rather than 1-year post-operative
7
radiographs. Radiographs were not commonly obtained at the 1-year follow-up visit, making
8
the number available at this time point too low to utilize. Another limitation was the lack of
9
global sagittal alignment assessments, including coronal balance, which would potentially also
10
contribute to outcomes. This is an important area for future research, however full-length spine
11
radiographs were not commonly obtained for most cervical spine operations. Finally, as this
12
study included 45 patients it is underpowered to detect a more subtle effect of alignment on
13
PROs. The sample size of 45 gives us 80% power to detect the effect of alignment if alignment is
14
assumed to contribute to at least 50% or more of the improvement in NDI. Thus the findings of
15
this study suggest that increased lordosis may not contribute to greater than 50% of the
16
improvement in NDI in this cohort; however we cannot determine the impact alignment may
17
have below this threshold. Larger studies are warranted to explore the impact of increased
18
cervical lordosis in more depth. No external sources of funding were utilized for this
19
investigation.
20 21 22 23
CONCLUSION In a study of patients with maintained cervical lordosis who underwent posterior
24
decompression and fusion in the treatment of cervical myelopathy, we found no correlations
25
between cervical sagittal alignment parameters and postoperative outcomes. Neither baseline
26
nor postoperative myelopathy severity was associated with either the amount of lordosis or
27
SVA. This suggests, in contrast to previous reports, that surgical improvement of SVA may not
28
improve outcomes – provided that cervical lordosis is maintained. While creating more lordosis
29
and decreasing SVA are associated with improved myelopathy and outcomes in patients with 9 Page 9 of 15
Cervical Sagittal Alignment and Outcomes 1
kyphosis, our study did not find such associations in patients with lordosis. This suggests that
2
any amount of lordosis is sufficient, and that more is not necessarily better. Further studies are
3
certainly needed to further assess and characterize associations between CSA and outcomes in
4
CSM surgery.
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
REFERENCES 1. 2.
3.
4.
5.
6. 7.
8.
9.
10.
11.
Young WF. Cervical spondylotic myelopathy: a common cause of spinal cord dysfunction in older persons. American family physician. 2000;62(5):1064-1070, 1073. Karadimas SK, Erwin WM, Ely CG, Dettori JR, Fehlings MG. Pathophysiology and natural history of cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S21-36. Fehlings MG, Wilson JR, Yoon ST, Rhee JM, Shamji MF, Lawrence BD. Symptomatic progression of cervical myelopathy and the role of nonsurgical management: a consensus statement. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S19-20. Fehlings MG, Gray R. Importance of sagittal balance in determining the outcome of anterior versus posterior surgery for cervical spondylotic myelopathy. J Neurosurg Spine. 2009;11(5):518-519; discussion 519-520. Uchida K, Nakajima H, Sato R, et al. Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid alignment: outcome after anterior or posterior decompression. J Neurosurg Spine. 2009;11(5):521-528. Emery SE. Cervical spondylotic myelopathy: diagnosis and treatment. J Am Acad Orthop Surg. 2001;9(6):376-388. Bapat MR, Chaudhary K, Sharma A, Laheri V. Surgical approach to cervical spondylotic myelopathy on the basis of radiological patterns of compression: prospective analysis of 129 cases. Eur Spine J. 2008;17(12):1651-1663. Mohanty C, Massicotte EM, Fehlings MG, Shamji MF. Association of preoperative cervical spine alignment with spinal cord magnetic resonance imaging hyperintensity and myelopathy severity: analysis of a series of 124 cases. Spine (Phila Pa 1976). 2015;40(1):11-16. Smith JS, Lafage V, Ryan DJ, et al. Association of myelopathy scores with cervical sagittal balance and normalized spinal cord volume: analysis of 56 preoperative cases from the AOSpine North America Myelopathy study. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S161-170. Roguski M, Benzel EC, Curran JN, et al. Postoperative cervical sagittal imbalance negatively affects outcomes after surgery for cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2014;39(25):2070-2077. Tang JA, Scheer JK, Smith JS, et al. The impact of standing regional cervical sagittal alignment on outcomes in posterior cervical fusion surgery. Neurosurgery. 2012;71(3):662-669; discussion 669. 10 Page 10 of 15
Cervical Sagittal Alignment and Outcomes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
12. 13.
14.
15.
16.
17.
18.
19. 20. 21.
22. 23.
24. 25.
26.
Scheer JK, Tang JA, Smith JS, et al. Cervical spine alignment, sagittal deformity, and clinical implications: a review. J Neurosurg Spine. 2013;19(2):141-159. Shimizu K, Nakamura M, Nishikawa Y, Hijikata S, Chiba K, Toyama Y. Spinal kyphosis causes demyelination and neuronal loss in the spinal cord: a new model of kyphotic deformity using juvenile Japanese small game fowls. Spine (Phila Pa 1976). 2005;30(21):2388-2392. Takenouchi T, Setoguchi T, Yone K, Komiya S. Expression of apoptosis signal-regulating kinase 1 in mouse spinal cord under chronic mechanical compression: possible involvement of the stress-activated mitogen-activated protein kinase pathways in spinal cord cell apoptosis. Spine (Phila Pa 1976). 2008;33(18):1943-1950. Ames CP, Blondel B, Scheer JK, et al. Cervical radiographical alignment: comprehensive assessment techniques and potential importance in cervical myelopathy. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S149-160. Harrison DE, Harrison DD, Cailliet R, Troyanovich SJ, Janik TJ, Holland B. Cobb method or Harrison posterior tangent method: which to choose for lateral cervical radiographic analysis. Spine (Phila Pa 1976). 2000;25(16):2072-2078. Polly DW, Jr., Kilkelly FX, McHale KA, Asplund LM, Mulligan M, Chang AS. Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability. Spine (Phila Pa 1976). 1996;21(13):1530-1535; discussion 1535-1536. Singer KP, Jones TJ, Breidahl PD. A comparison of radiographic and computer-assisted measurements of thoracic and thoracolumbar sagittal curvature. Skeletal Radiol. 1990;19(1):21-26. Ware J, Jr., Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Medical care. 1996;34(3):220-233. Nemeth G. Health related quality of life outcome instruments. Eur Spine J. 2006;15 Suppl 1:S44-51. Godil SS, Parker SL, Zuckerman SL, Mendenhall SK, Glassman SD, McGirt MJ. Accurately measuring the quality and effectiveness of lumbar surgery in registry efforts: determining the most valid and responsive instruments. Spine J. 2014. EuroQol--a new facility for the measurement of health-related quality of life. Health policy (Amsterdam, Netherlands). 1990;16(3):199-208. Luo X, George ML, Kakouras I, et al. Reliability, validity, and responsiveness of the short form 12-item survey (SF-12) in patients with back pain. Spine (Phila Pa 1976). 2003;28(15):1739-1745. Vernon H. The Neck Disability Index: state-of-the-art, 1991-2008. J Manipulative Physiol Ther. 2008;31(7):491-502. Benzel EC, Lancon J, Kesterson L, Hadden T. Cervical laminectomy and dentate ligament section for cervical spondylotic myelopathy. Journal of spinal disorders. 1991;4(3):286295. Acharya S, Srivastava A, Virmani S, Tandon R. Resolution of physical signs and recovery in severe cervical spondylotic myelopathy after cervical laminoplasty. Spine (Phila Pa 1976). 2010;35(21):E1083-1087.
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Cervical Sagittal Alignment and Outcomes 1 2 3 4 5
27.
Furlan JC, Kalsi-Ryan S, Kailaya-Vasan A, Massicotte EM, Fehlings MG. Functional and clinical outcomes following surgical treatment in patients with cervical spondylotic myelopathy: a prospective study of 81 cases. J Neurosurg Spine. 2011;14(3):348-355.
6 7 8
FIGURE LEGEND
9 10 11 12
Figure 1: Representative standing lateral radiograph illustrating the cervical sagittal alignment parameters utilized in this study.
13
Table 1: Baseline Demographics and Clinical Characteristics Number of Patients Age Gender Male Female Smoker ASA¹ 1 2 3 4 BMI² Primary Cause of Myelopathy Congenital Stenosis Ventral disc herniation OPLL Spondylolisthesis Surgical Data Mean Operative Time in Minutes Mean EBL³ in Milliliters Mean motion segments fused
14 15
45 63
±
10.5
28 17 11
(62%) (38%) (24%)
0 6 37 2 27.7
(13%) (82%) (4%) 4.8
±
32 4 3 6 170 321 3.7
(71%) (8%) (6%) (13%) ± ± ±
46 222 1.3
* Values given as mean ± standard deviation, or as total (percentage%). ¹American Society of Anesthesiologist classification 12 Page 12 of 15
Cervical Sagittal Alignment and Outcomes 1
²Body Mass Index
2 3
Table 2: Alignment change from baseline to 1-year post-op Pre-Operative -25.8 -14.0 2.9 4.5 -39.8 28.2
C1-C2 Cobb° C2-C7 Cobb° C2-C7 SVA (cm) C1-C7 SVA (cm) Cerv Lordosis°† T1 Slope° 4 *standard deviation 5 † C1-2 Cobb + C2-7 Cobb
± ± ± ± ± ±
std dev* 6.5 9.7 1.5 1.8 10.9 10.2
min -4.9 0.0 0 0.8 -16 7
max -41 -44 5.8 8.7 -72 50
Post-Operative -27.1 -11.3 3.3 5.0 -38.4 27.9
± ± ± ± ± ±
std dev* 6.5 7.6 1.5 1.8 8.7 8.1
min -6.7 0.0 0.0 1.1 -16 6
max p-value -41 0.03 -44 0.01 7.1 0.01 9.5 0.01 -64 0.09 40 0.43
6 7
Table 3: Health-Related Quality of Life outcomes results Pre-Operative
Post-Operative
0.54 ± 0.24
0.71 ± 0.19
<0.001
NDI²
21.57 ± 10.57
13.93 ± 9.77
<0.001
mJOAS³
10.62 ± 3.37
12.20 ± 3.22
<0.001
SF-12 PCS†
26.7 ± 10.3
34.63 ± 13.61
0.01
SF-12 MCS‡
47.96 ± 12.18
49.76 ± 12.29
0.06
EQ-5D¹ score
8 9 10 11 12 13 14
p-value
*Values reported as mean ± standard deviation ¹ EuroQol-5D ²Neck Disability Index ³Modified Japanese Orthopaedic Association score †Short-Form 12 Physical Composite Scale ‡Short-Form 12 Mental Composite Scale
13 Page 13 of 15
Cervical Sagittal Alignment and Outcomes 1
Table 4: Correlation between pre-operative outcomes and pre-operative alignment C1-C2 Cobb
EQ-5D NDI
SF-12 PCS SF-12 MCS
C2-7 SVA C1-C7 SVA
0.08
-0.20
-0.22
0.11
-0.30
Sig.*
0.68
0.58
0.17
0.13
0.47
0.08
-0.07
-0.16
0.17
0.18
-0.18
0.32
Sig.
0.63
0.30
0.25
0.24
0.23
0.06
Pearson Correlation
0.03
0.25
-0.25
-0.23
0.23
-0.31
Sig.
0.88
0.18
0.17
0.21
0.21
0.19
Pearson Correlation
0.06
0.01
-0.34
-0.33
0.04
-0.16
Sig.
0.71
0.97
0.02
0.03
0.80
0.36
-0.11
0.18
0.09
0.07
0.09
-0.05
0.46
0.25
0.55
0.62
0.54
0.80
Pearson Correlation
2 3
†Bolded values indicate statistically significant correlation. *Significance, two-tailed.
4
Table 5: Correlation between 1 year outcomes and post-operative alignment
NDI
T1 Slope
0.06
Sig.
EQ-5D
Cervical Lordosis
Pearson Correlation Pearson Correlation
mJOAS
C2-C7 Cobb
C1-C2 Cobb
C2-C7 Cobb
-0.12
0.15
-0.17
-0.15
0.10
-0.16
Sig.*
0.32
0.22
0.15
0.21
0.41
0.28
Pearson Correlation
0.10
-0.13
0.16
0.15
-0.08
0.23
Sig.
0.40
0.29
0.18
0.20
0.50
0.12
Pearson Correlation
C2-7 SVA C1-C7 SVA Cervical Lordosis
T1 Slope
14 Page 14 of 15
Cervical Sagittal Alignment and Outcomes
mJOAS
Pearson Correlation Sig.
SF-12 PCS
Pearson Correlation Sig.
SF-12 MCS Pearson Correlation 1 2 3
Sig. *Significance (Two-Tailed)
0.09
0.08
0.09
-0.03
0.03
0.18
0.49
0.55
0.51
0.82
0.84
-0.10
0.16
-0.20
-0.20
0.10
-0.19
0.42
0.20
0.10
0.11
0.40
0.19
-0.14
0.21
0.03
0.07
0.10
-0.17
0.25
0.08
0.82
0.57
0.41
0.24
Table 6: Correlation between post-operative alignment and 1-year change in outcome scores
EQ-5D
SF-12 PCS
NDI
mJOAs 4 5
-0.17
C1-C2 Cobb
C2-C7 Cobb
C2-C7 SVA
C1-C7 SVA
Cervical Lordosis
T1 Slope
Pearson Correlation
0.01
0.01
0.00
0.07
0.00
0.01
sig.*
0.42
0.56
0.56
0.54
0.96
0.92
Pearson Correlation
0.00
0.01
0.02
0.14
0.00
0.05
sig.
0.72
0.52
0.29
0.26
0.74
0.75
Pearson Correlation
0.00
0.00
0.03
0.20
0.01
0.02
sig.
0.71
0.64
0.14
0.09
0.54
0.91
Pearson Correlation
0.00
0.01
0.01
0.12
0.01
0.82
0.92
0.49
0.50
0.45
0.59
0.38
sig. *Significance (Two-Tailed)
15 Page 15 of 15