Accepted Manuscript Progression of coronal Cobb angle after short segment lumbar inter-body fusion in patients with degenerative lumbar stenosis Nam Lee, MD, Seong Yi, MD, PhD, Dong Ah Shin, MD, PhD, Keung Nyun Kim, MD, PhD, Do Heum Yoon, MD, PhD, Yoon Ha, MD, PhD PII:
S1878-8750(16)00139-X
DOI:
10.1016/j.wneu.2016.01.051
Reference:
WNEU 3655
To appear in:
World Neurosurgery
Received Date: 17 September 2015 Revised Date:
11 January 2016
Accepted Date: 13 January 2016
Please cite this article as: Lee N, Yi S, Shin DA, Kim KN, Yoon DH, Ha Y, Progression of coronal Cobb angle after short segment lumbar inter-body fusion in patients with degenerative lumbar stenosis, World Neurosurgery (2016), doi: 10.1016/j.wneu.2016.01.051. 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.
ACCEPTED MANUSCRIPT
Progression of coronal Cobb angle after short segment lumbar inter-body fusion in patients with degenerative lumbar stenosis
RI PT
Risk factor analysis of progression of scoliosis after lumbar fusion
Department of Neurosurgery, Spine and Spinal Cord Institute,
AC C
EP
TE D
M AN U
Yonsei University College of Medicine, Seoul, Korea
SC
Nam Lee, MD; Seong Yi, MD, PhD; Dong Ah Shin, MD, PhD; Keung Nyun Kim, MD, PhD; Do Heum Yoon, MD, PhD; Yoon Ha, MD, PhD
Correspondence to: Yoon Ha Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Severance Hospital, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea, tel: 82-2-2228-2165, fax: 82-2-393-9979, e-mail: [email protected]
1
ACCEPTED MANUSCRIPT Abstract Objectives: The progression of scoliosis after fusion surgery is a poor prognostic factor of long-term outcomes in patients with degenerative lumbar stenosis (DLS). We aimed to investigate changes in
RI PT
coronal alignment and to identify risk factors related to progression of scoliosis after fusion
Methods: 540 patients with symptomatic DLS treated by short segment lumbar fusion surgery.
SC
Among them, 50 patients had coronal Cobb angles greater than 10° at final follow-up. Sixteen patients had increases greater than 5° (progression, P group), and 34 patients less than 5° (non-
M AN U
progression, NP group). Radiological parameters that may affect the progression of scoliosis were compared.
Results: The mean progression of the Cobb angle was 7.92° in the P group, and 1.25° in the NP group.
TE D
The P group had significantly longer follow-up periods and lower preoperative Cobb angle. The apical vertebra (AV) of the major curve was more frequently thoracic in the P group. Progression of the Cobb angle was correlated with follow-up period, preoperative Cobb angle and location of AV.
EP
Multivariate regression analysis showed that progression of the Cobb angle was significantly associated with a lower preoperative Cobb angle, and both facet degeneration of the upper
AC C
instrumented vertebra at the fusion site and vertebral spur formation on the concave side also appeared to be associated with progression of the Cobb angle.
Conclusion: The global magnitude of progression of the Cobb angle after short segment lumbar fusion surgery in patients with DLS is similar to the natural curve progression of adult degenerative scoliosis. 2
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
Key Words: degenerative lumbar stenosis, lumbar fusion surgery, progression of the Cobb angle
3
ACCEPTED MANUSCRIPT Introduction Degenerative lumbar stenosis (DLS) is a common disease in the elderly. Short segment lumbar decompression and fusion surgery is a major treatment option for patients with DLS and instability,
RI PT
with excellent clinical outcomes (4, 19). Increasing prevalence of adult degenerative scoliosis (ADS) is of concern as society ages, due to associations between ADS and the development of DLS (15). Therefore, when clinicians advise surgical treatment for DLS, risk of scoliosis progression after fusion surgery should be assessed preoperatively. Risk factors that may affect the progression of curvature
SC
after surgery (selective decompression only) in patients with mild lumbar degenerative scoliosis have been reported, such as spur formation on the concave side of the curve (3). However, these studies did
M AN U
not provide the ADS is defined by any curvature of the spine more than 10° not confined to only lumbar region (11). Short segment decompression and fusion is the most common surgical procedure used to treat DLS. Compared to laminectomy alone, short segment fusion surgery results in wider decompression and restoration of coronal and sagittal alignment (17). However, the normal
TE D
progression of the Cobb angle after short segment lumbar fusion surgery is not clearly understood. Therefore, in this study, we investigated the progression of the coronal Cobb angle at thoracolumbar region after short segment lumbar fusion surgery and identified risk factors associated with curve
EP
progression in patients with DLS.
AC C
Materials and Methods
Institutional review board approval (1-2013-0070) was obtained before initiating this study. Five hundred and forty patients with symptomatic DLS and instability were underwent fusion surgery of either one or two levels of the lumbar spine at our institute between January 2010 and December 2012. Of these, 120 patients received standing whole spine coronal radiographs at or beyond 2 years after surgery. Among them, 50 patients had coronal Cobb angles greater than 10° at final follow-up at 4
ACCEPTED MANUSCRIPT the region of thoracolumbar and were enrolled in the study. We divided all cohorts into two groups according to the magnitude of curve progression during the follow-up period. Sixteen patients who showed more than 5° increases of the Cobb angle were assigned to the progression (P) group, and 34 patients who showed less than 5° increases of the Cobb angle were assigned to the non-progression
RI PT
(NP) group. We then compared parameters between P and NP groups to identify risk factors associated with the progression of the coronal Cobb angle at thoracolumbar region.
Patients with follow-up periods of less than 2 years as well as those who did not undergo standing
SC
whole spine radiography after 2 years were excluded. In addition, patients with trauma, congenital lesions, and prior spinal surgery were also excluded. All retrospective cohorts underwent fusion
M AN U
surgery due to decompressive laminectomy and short segment lumbar fusion to address spinal stenosis and instability, not to correct scoliosis.
Of the 50 patients who met our inclusion criteria, 29 underwent 1 level lumbar fusion surgery consisting of total bilateral facetectomy, posterior lumbar inter-body fusion, and pedicle screw
TE D
fixation. The other 21 patients underwent 2 level lumbar fusion surgery in the same manner. The level of fusion surgery was selected according to the symptomatic lesion and the range of surgery was
EP
confined to the lumbosacral region (L2 to S1).
AC C
Radiological Measurements
We measured parameters that may affect progression of the Cobb angle. First, we identified the location of the apical vertebra (AV) of the major curve whether in the thoracic region or lumbar region. The apical vertebral rotation (AVR) of the major curve was assessed according to the Nash & Moe classification (8). The apical vertebral translation (AVT) of the major curve was measured by the horizontal distance between the central sacral vertical line (CSVL) and the apex. The C7 translation (C7T) is equal to coronal imbalance, or the horizontal distance between CSVL and C7 plumb lines in 5
ACCEPTED MANUSCRIPT the coronal view. We also considered the number of vertebrae of the major curve, and the number of vertebrae between the apical vertebra and stable vertebra (AV-SV distance). Vertebral spur formation of the major curve on each side - concave and convex - was graded according to the Nathan classification (9). We calculated the average grade per level of Nathan score on each side and
RI PT
compared each separately. Lumbar lordosis between L1 and S1 was also measured in the sagittal plane. Disc degeneration grade of the apical vertebra of the major curve was assessed by Schneiderman classification (14) using T2-weighted sagittal MRI scans. Both upper and lower discs
SC
of the apical vertebra were evaluated according to this grading system. In addition, facet degeneration of the upper instrumented vertebra (UIV) was graded according to the classification system described
M AN U
by Pathria et al. (10) using the bone setting of the axial CT scan. Grade 1 (normal) represents normal facet joint space (2/4mm width) without spur; Grade 2 (mild degeneration) represents narrowing of the facet joint space (
S1878-8750(16)00139-X
DOI:
10.1016/j.wneu.2016.01.051
Reference:
WNEU 3655
To appear in:
World Neurosurgery
Received Date: 17 September 2015 Revised Date:
11 January 2016
Accepted Date: 13 January 2016
Please cite this article as: Lee N, Yi S, Shin DA, Kim KN, Yoon DH, Ha Y, Progression of coronal Cobb angle after short segment lumbar inter-body fusion in patients with degenerative lumbar stenosis, World Neurosurgery (2016), doi: 10.1016/j.wneu.2016.01.051. 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.
ACCEPTED MANUSCRIPT
Progression of coronal Cobb angle after short segment lumbar inter-body fusion in patients with degenerative lumbar stenosis
RI PT
Risk factor analysis of progression of scoliosis after lumbar fusion
Department of Neurosurgery, Spine and Spinal Cord Institute,
AC C
EP
TE D
M AN U
Yonsei University College of Medicine, Seoul, Korea
SC
Nam Lee, MD; Seong Yi, MD, PhD; Dong Ah Shin, MD, PhD; Keung Nyun Kim, MD, PhD; Do Heum Yoon, MD, PhD; Yoon Ha, MD, PhD
Correspondence to: Yoon Ha Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Severance Hospital, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea, tel: 82-2-2228-2165, fax: 82-2-393-9979, e-mail: [email protected]
1
ACCEPTED MANUSCRIPT Abstract Objectives: The progression of scoliosis after fusion surgery is a poor prognostic factor of long-term outcomes in patients with degenerative lumbar stenosis (DLS). We aimed to investigate changes in
RI PT
coronal alignment and to identify risk factors related to progression of scoliosis after fusion
Methods: 540 patients with symptomatic DLS treated by short segment lumbar fusion surgery.
SC
Among them, 50 patients had coronal Cobb angles greater than 10° at final follow-up. Sixteen patients had increases greater than 5° (progression, P group), and 34 patients less than 5° (non-
M AN U
progression, NP group). Radiological parameters that may affect the progression of scoliosis were compared.
Results: The mean progression of the Cobb angle was 7.92° in the P group, and 1.25° in the NP group.
TE D
The P group had significantly longer follow-up periods and lower preoperative Cobb angle. The apical vertebra (AV) of the major curve was more frequently thoracic in the P group. Progression of the Cobb angle was correlated with follow-up period, preoperative Cobb angle and location of AV.
EP
Multivariate regression analysis showed that progression of the Cobb angle was significantly associated with a lower preoperative Cobb angle, and both facet degeneration of the upper
AC C
instrumented vertebra at the fusion site and vertebral spur formation on the concave side also appeared to be associated with progression of the Cobb angle.
Conclusion: The global magnitude of progression of the Cobb angle after short segment lumbar fusion surgery in patients with DLS is similar to the natural curve progression of adult degenerative scoliosis. 2
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
Key Words: degenerative lumbar stenosis, lumbar fusion surgery, progression of the Cobb angle
3
ACCEPTED MANUSCRIPT Introduction Degenerative lumbar stenosis (DLS) is a common disease in the elderly. Short segment lumbar decompression and fusion surgery is a major treatment option for patients with DLS and instability,
RI PT
with excellent clinical outcomes (4, 19). Increasing prevalence of adult degenerative scoliosis (ADS) is of concern as society ages, due to associations between ADS and the development of DLS (15). Therefore, when clinicians advise surgical treatment for DLS, risk of scoliosis progression after fusion surgery should be assessed preoperatively. Risk factors that may affect the progression of curvature
SC
after surgery (selective decompression only) in patients with mild lumbar degenerative scoliosis have been reported, such as spur formation on the concave side of the curve (3). However, these studies did
M AN U
not provide the ADS is defined by any curvature of the spine more than 10° not confined to only lumbar region (11). Short segment decompression and fusion is the most common surgical procedure used to treat DLS. Compared to laminectomy alone, short segment fusion surgery results in wider decompression and restoration of coronal and sagittal alignment (17). However, the normal
TE D
progression of the Cobb angle after short segment lumbar fusion surgery is not clearly understood. Therefore, in this study, we investigated the progression of the coronal Cobb angle at thoracolumbar region after short segment lumbar fusion surgery and identified risk factors associated with curve
EP
progression in patients with DLS.
AC C
Materials and Methods
Institutional review board approval (1-2013-0070) was obtained before initiating this study. Five hundred and forty patients with symptomatic DLS and instability were underwent fusion surgery of either one or two levels of the lumbar spine at our institute between January 2010 and December 2012. Of these, 120 patients received standing whole spine coronal radiographs at or beyond 2 years after surgery. Among them, 50 patients had coronal Cobb angles greater than 10° at final follow-up at 4
ACCEPTED MANUSCRIPT the region of thoracolumbar and were enrolled in the study. We divided all cohorts into two groups according to the magnitude of curve progression during the follow-up period. Sixteen patients who showed more than 5° increases of the Cobb angle were assigned to the progression (P) group, and 34 patients who showed less than 5° increases of the Cobb angle were assigned to the non-progression
RI PT
(NP) group. We then compared parameters between P and NP groups to identify risk factors associated with the progression of the coronal Cobb angle at thoracolumbar region.
Patients with follow-up periods of less than 2 years as well as those who did not undergo standing
SC
whole spine radiography after 2 years were excluded. In addition, patients with trauma, congenital lesions, and prior spinal surgery were also excluded. All retrospective cohorts underwent fusion
M AN U
surgery due to decompressive laminectomy and short segment lumbar fusion to address spinal stenosis and instability, not to correct scoliosis.
Of the 50 patients who met our inclusion criteria, 29 underwent 1 level lumbar fusion surgery consisting of total bilateral facetectomy, posterior lumbar inter-body fusion, and pedicle screw
TE D
fixation. The other 21 patients underwent 2 level lumbar fusion surgery in the same manner. The level of fusion surgery was selected according to the symptomatic lesion and the range of surgery was
EP
confined to the lumbosacral region (L2 to S1).
AC C
Radiological Measurements
We measured parameters that may affect progression of the Cobb angle. First, we identified the location of the apical vertebra (AV) of the major curve whether in the thoracic region or lumbar region. The apical vertebral rotation (AVR) of the major curve was assessed according to the Nash & Moe classification (8). The apical vertebral translation (AVT) of the major curve was measured by the horizontal distance between the central sacral vertical line (CSVL) and the apex. The C7 translation (C7T) is equal to coronal imbalance, or the horizontal distance between CSVL and C7 plumb lines in 5
ACCEPTED MANUSCRIPT the coronal view. We also considered the number of vertebrae of the major curve, and the number of vertebrae between the apical vertebra and stable vertebra (AV-SV distance). Vertebral spur formation of the major curve on each side - concave and convex - was graded according to the Nathan classification (9). We calculated the average grade per level of Nathan score on each side and
RI PT
compared each separately. Lumbar lordosis between L1 and S1 was also measured in the sagittal plane. Disc degeneration grade of the apical vertebra of the major curve was assessed by Schneiderman classification (14) using T2-weighted sagittal MRI scans. Both upper and lower discs
SC
of the apical vertebra were evaluated according to this grading system. In addition, facet degeneration of the upper instrumented vertebra (UIV) was graded according to the classification system described
M AN U
by Pathria et al. (10) using the bone setting of the axial CT scan. Grade 1 (normal) represents normal facet joint space (2/4mm width) without spur; Grade 2 (mild degeneration) represents narrowing of the facet joint space (
