Anterior Cervical Discectomy and Fusion Alters Whole-Spine Sagittal Alignment

Transcription

1 Original Article htt://dx.doi.org/ /ymj ISSN: , eissn: Yonsei Med J 56(4): , 2015 Anterior Cervical Discectomy and Fusion Alters Whole-Sine Sagittal Alignment Jang Hoon Kim, 1 Jeong Yoon Park, 1 Seong Yi, 2 Kyung Hyun Kim, 1 Sung Uk Kuh, 1 Dong Kyu Chin, 1 Keun Su Kim, 1 and Yong Eun Cho 1 1 Deartment of Neurosurgery, Gangnam Severance Hosital, Sine and Sinal Cord Institute, Yonsei University College of Medicine, Seoul; 2 Deartment of Neurosurgery, Severance Hosital, Yonsei University College of Medicine, Seoul, Korea. Received: November 20, 2014 Revised: January 5, 2015 Acceted: January 17, 2015 Corresonding author: Dr. Jeong Yoon Park, Deartment of Neurosurgery, Gangnam Severance Hosital, Sine and Sinal Cord Institute, Yonsei University College of Medicine, 211 Eonju-ro, Gangnam-gu, Seoul , Korea. Tel: , Fax: sinejy@yuhs.ac The authors have no financial conflicts of interest. Purose: Anterior cervical discectomy and fusion (ACDF) has become a common sine rocedure, however, there have been no revious studies on whole sine alignment changes after cervical fusion. Our urose in this study was to determine whole sine sagittal alignment and elvic alignment changes after ACDF. Materials and Methods: Forty-eight atients who had undergone ACDF from January 2011 to December 2012 were enrolled in this study. Cervical lordosis, thoracic kyhosis, lumbar lordosis, sagittal vertical axis (SVA), and elvic arameters were measured reoeratively and at 1, 3, 6, and 12 months ostoeratively. Clinical outcomes were assessed using Visual Analog Scale (VAS) scores and Neck Disability Index (NDI) s. Results: Forty-eight atients were groued according to oerative method (cage only, cage & late), oerative level (uer level: C3/4 & C4/5; lower level: C5/6 & C6/7), and cervical lordosis (high lordosis, low lordosis). All atients exerienced significant imrovements in VAS scores and NDI s after surgery. Among the radiologic arameters, elvic tilt increased and sacral sloe decreased at 12 months ostoeratively. Only the high cervical lordosis grou showed significantly-decreased cervical lordosis and a shortened SVA ostoeratively. tests revealed that cervical lordosis was significantly correlated with SVA and that SVA was significantly correlated with elvic tilt and sacral sloe. Conclusion: ACDF affects whole sine sagittal alignment, esecially in atients with high cervical lordosis. In these atients, alteration of cervical lordosis to a normal angle shortened the SVA and resulted in recirocal changes in elvic tilt and sacral sloe. Key Words: ACDF, whole sine sagittal alignment, elvic arameters INTRODUCTION Coyright: Yonsei University College of Medicine 2015 This is an Oen Access article distributed under the terms of the Creative Commons Attribution Non- Commercial License (htt://creativecommons.org/ licenses/by-nc/3.0) which ermits unrestricted noncommercial use, distribution, and reroduction in any medium, rovided the original work is roerly cited. Whole-sine sagittal alignment, including cervical lordosis, thoracic kyhosis, and lumbar lordosis, is imortant for maintenance of horizontal gaze and minimization of energy consumtion in the normal state, and there is a close relationshi between whole-sine sagittal alignment and elvic alignment in maintaining global sagittal balance. 1-6 Previous studies have shown that rogression of thoracolumbar deformity influences sagittal and cervical alignment. 1,7-9 Furthermore, surgical correction of 1060 Yonsei Med J htt:// Volume 56 Number 4 July 2015

2 Whole Sine Sagittal Alignment after ACDF sagittal malalignment by techniques such as lumbar edicle subtraction osteotomy (PSO) has been shown to imrove abnormal cervical hyerlordosis to normal lordosis through recirocal alignment changes. 1 The increase in life exectancy and widesread adotion of diagnostic tools such as MRI has increased the incidence of cervical fusion surgery. Among various cervical fusion surgeries, anterior cervical discectomy and fusion (ACDF), introduced by Smith and Robinson, 10 is the most common cervical fusion surgery. ACDF is an established rocedure for the treatment of cervical radiculoathy and myeloathy secondary to degenerative disc disease, and several studies have reorted good fusion success rates and excellent clinical outcomes Whole-sine alignment is known to change after thoracolumbar deformity correction of cervical lordosis. 1,7-9 Although cervical fusion surgeries, including ACDF, have become common sine rocedures, whole sine alignment changes after ACDF have not reviously been investigated in detail. We hyothesized that there might be recirocal changes in whole-sine sagittal alignment, including thoracolumbar angle and elvic alignment, followed by changes in cervical alignment after ACDF. We therefore designed this study to assess changes in whole-sine sagittal alignment and elvic alignment after ACDF. College of Medicine (No ). To comare various situation-related oerations, atients were divided according to oerative method [cage only: Zero-P imlant (Synthes GmbH Switzerland, Oberdorf, Switzerland) with autobone; cage & late: allobone sacer (CG Bio, Seoul, Korea) and Zehir late (Medtronic Sofamor Danek Inc., Memhis, TN, USA)] (Figs. 1 and 2), oerative level (uer level: C3/4, C4/5; lower level: C5/6, C6/7), and reoerative cervical lordosis (high cervical lordosis: reoerative cervical lordosis >12.5 ; low cervical lordosis: reoerative cervical lordosis <12.5 ). 15,16 Preoerative cervical lordosis was classified relative to the mean angle of all atients (12.5 ) (Table 1). Outcome assessment & statistical methods Arm ain and neck ain were assessed by self-reorted MATERIALS AND METHODS Subjects and study design This retrosective, cross-sectional study included atients who were diagnosed with single-level cervical disc herniation. Forty-eight consecutive atients who had undergone single-level ACDF due to cervical disc herniation with only radiculoathy, not myeloathy, from January 2011 to December 2012 were enrolled in this study. We excluded atients treated for non-degenerative uroses such as trauma, tumor, or infection, as well as atients who had undergone multi-level ACDF, lumbar oerations, or other sine oerations in order to minimize the ossible imacts of surgery on segments other than the cervical sine on whole sagittal balance. In addition, we also excluded atients who had thoracic and lumbar sine athologies on routine whole-sine sagittal MRI images, as other segment athologies besides cervical disc herniation might affect whole sagittal alignment. This roject was aroved by the Institutional Review Board of Gangnam Severance Hosital, Yonsei University A Fig. 1. Whole sine AP (A) and lateral (B) radiograhy after anterior cervical discectomy and fusion with cage only (Zero-P imlant; Synthes GmbH Switzerland, Oberdorf, Switzerland) with autobone. A Fig. 2. Whole-sine AP (A) and lateral (B) radiograhy after anterior cervical discectomy and fusion with cage and late [Allobone sacer (CG bio, Seoul, Korea), and Zehir late (Medtronic Sofamor Danek Inc., Memhis, TN, USA)]. B B Yonsei Med J htt:// Volume 56 Number 4 July

3 Jang Hoon Kim, et al. Table 1. Demograhic Data Total Oerative method Oerative level Cervical lordosis Cage only Cage & late C3/4 & 4/5 C5/6 & 6/7 High lordosis Low lordosis No (58%) 20 (42%) 13 (27%) 35 (73%) 21 (44%) 27 (56%) Age (yrs) 52.9± ± ± ± ± ± ±10.3 Sex Male Female O method Cage only* Cage & late O level C3/ C4/ C5/ C6/ *Cage only grou received a Zero-P imlant (Synthes GmbH Switzerland, Oberdorf, Switzerland) with autobone. Cage & late grou received an allobone sacer (CG Bio, Seoul, Korea) and Zehir late (Medtronic Sofamor Danek Inc., Memhis, TN, USA). Patients were divided into two grous according to cervical lordosis angle: high C-lordosis (>mean reo. cervical lordosis ) and low C-lordosis (<mean reo. cervical lordosis ). Among 48 atents, 25 were male, and the mean age was 52.9 years (Table 1). Arm ain and neck ain were assessed using VAS and NDI, resectively. There was a significant, sequential imrovement in both VAS scores and NDI s ostoeratively, relative to the reoerative state (VAS: 6.9± 1.1 reoeratively, 1.6±1.8 at 1 month, 1.1±0.6 at 3 months, 1.5±1.2 at 6 months, and 0.6±0.6 at 12 months ostoeratively; NDI: 20.0±6.8 reoeratively, 7.9±6.5 at 1 month, 6.9±5.3 at 3 months, 6.1±4.6 at 6 months, and 3.6±3.4 at 12 months ostoeratively). Cervical lordosis, elvic tilt, and sacral sloe changed ostoeratively relative to the reoerative state. Cervical lordosis significantly decreased at ostmeasurements using the Visual Analog Scale (VAS) and Neck Disability Index (NDI), resectively. Patients were required to undergo cervical MRI, CT, and whole-sine radiograhy reoeratively, as well as serial whole-sine radiograhy at the 1-, 3-, 6-, and 12-month ostoerative followus. Cervical lordosis, thoracic kyhosis, lumbar lordosis, sagittal vertical axis (SVA), and elvic arameters (elvic incidence, elvic tilt, and sacral sloe) were measured reoeratively and at all follow-us. Cervical lordosis was measured by determining the Cobb angle between the caudal endlate of C2 and the caudal endlate of C7. Thoracic kyhosis was measured by determining the Cobb angle between the cranial endlate of T4 and the caudal endlate of T12, while lumbar lordosis was measured by determining the Cobb angle between the sacral uer margin and the cranial L1 endlate (Fig. 3). SVA was measured as the distance between vertical lines through the center of the C7 vertebral body and the S1 suerior osterior corner. Pelvic incidence was measured as the angle between the line joining the center of the femoral head with the midoint of the sacral endlate and the erendicular line from the midoint of the sacral endlate. Pelvic tilt was measured as the angle between the line joining the center of the femoral head with the midoint of the sacral endlate and the vertical line. Sacral sloe was measured as the angle between the line along the sacral endlate and the horizontal line (Fig. 3) All radiologic arameters were evaluated using PACS software and a PACS workstation (Cen- tricity 3.0, General Electric Medical System, Milwaukee, WI, USA). Statistical comarisons were erformed based on the measured follow-u radiologic date. SPSS for Windows (version 15.0 K; SPSS Inc., Chicago, IL, USA) was used for statistical analyses. The Wilcoxon signed-rank test was used for intragrou comarisons reoeratively and at ostoerative 1, 3, 6, and 12 months. For intergrou comarisons, the Mann-Whitney U test was used, and the Pearson correlation test was used to assess the significance of differences in radiologic arameters among grous. s less than 0.05 were considered statistically significant. RESULTS 1062 Yonsei Med J htt:// Volume 56 Number 4 July 2015

4 Whole Sine Sagittal Alignment after ACDF Cervical lordosis Thorasic kyhosis cervical lordosis, and elvic tilt revealed that these factors changed significantly ostoeratively comared to the reoerative state. Cervical lordosis was significantly lower at ostoerative 3 months in the cage-&-late grou than reoeratively (-11.5 to -5.9 ; <0.05) (Table 2). Pelvic tilt was significantly higher at ostoerative 6 and 12 months in the cage-&-late grou than reoeratively (reoeratively 12.2 to 15.5 at ostoerative 6 months and 17.1 at ostoerative 12 months; <0.05) (Table 2). Lumbar lordosis Pelvic tilt Sacral sloe Sagittal vertical axis Pelvic incidence Fig. 3. Radiologic arameters evaluated in this study. Cervical lordosis (Cobb angle between caudal endlate of C2 and caudal endlate of C7), thoracic kyhosis (Cobb angle between cranial endlate of T4 and caudal endlate of T12), lumbar lordosis (Cobb angle between sacral uer margin and cranial L1 endlate), sagittal vertical axis (distance between vertical lines through the center of the C7 vertebral body and the S1 suerior osterior corner), elvic incidence (angle between the line joining the center of the femoral head with the midoint of the sacral endlate and the erendicular line from the midoint of the sacral endlate), elvic tilt (angle between the line joining the center of the femoral head with the midoint of the sacral endlate and the vertical line), and sacral sloe (angle between the line along the sacral endlate and the horizontal line). oerative 1 and 3 months (reoeratively to at ostoerative 1 month and at ostoerative 3 months; <0.05) (Table 2). Pelvic tilt was significantly higher ostoeratively than at reoerative 12 months (12.0 to 15.0 ; <0.05) (Table 2). Sacral sloe was significantly lower at 12 months ostoeratively than reoeratively (36.9 to 34.8 ; <0.05) (Table 2). Other radiologic arameters (SVA, thoracic kyhosis, lumbar lordosis, and elvic incidence) did not show any significant differences between reoerative and ostoerative states (Table 2). Effect of oerative method: cage only versus cage & late There were 28 atients in the cage-only grou (58%) and 20 atients in the cage-&-late grou (42%). There were no significant differences in mean age (cage only: 51.4 years; cage & late: 55.0 years) or sex (cage only: 15 men, 13 women; cage & late: 10 men, 10 women) between these two grous (Table 1). Intergrou comarisons of radiologic arameters revealed that cervical lordosis was the only factor that differed significantly between grous. Cervical lordosis at 3 months was in the cage-only grou comared to -5.9 in the cage-&-late grou (<0.05) (Table 2). Intragrou comarison according to oerative method, Effect of oerative level: uer level (C3/4, C4/5) and lower level (C5/6, C6/7) There were 13 atients in the uer-level grou (27%) and 35 atients in the lower-level grou (73%). There were no significant differences in mean age (uer level: 56.2 years; lower level: 51.7 years) or sex (uer level: 7 men, 6 women; lower level: 18 men, 17 women) between grous (Table 1). Intergrou comarisons of radiologic arameters, SVA, and cervical lordosis showed significant differences. SVA reoeratively and at 1, 3, and 12 months ostoeratively was significantly different between grous (uer level: 30.7, 29.4, 21.0, and 29.2 mm; lower level: -17.9, -9.0, -10.3, and mm, resectively; <0.01 reoeratively and 1 month; <0.05 at 3 and 12 months) (Table 2). Cervical lordosis reoeratively and at 1, 3, and 12 months ostoeratively was also significantly different between grous (uer level: -20.0, -18.2, -20.1, and ; lower level: -9.6, -6.3, -9.3, and -10.6, resectively; <0.01 at 12 months; <0.05 reoeratively and at 1, 3, and 12 months ostoeratively) (Table 2). Intragrou comarison according to oerative level, cervical lordosis, elvic tilt, and sacral sloe revealed significant changes ostoeratively relative to the reoerative state. Cervical lordosis significantly decreased at ostoerative 1 month in the lower-level grou (-9.6 to -6.3 ; <0.05) (Table 2). Pelvic tilt was significantly higher at ostoerative 12 months in the uer-level grou (12.7 to 19.4 ; <0.05) (Table 2). Sacral sloe was significantly lower at ostoerative 12 months than reoeratively in the uer-level grou (35.7 to 31.6 ; <0.05) (Table 2). Effect of cervical lordosis: high lordosis and low lordosis There were 21 atients in the high-lordosis grou (44%) and 27 atients in the low-lordosis grou (56%). There were no significant differences in mean age (high lordosis: 51.1 years; low lordosis: 53.8 years) or sex (high lordosis: 12 men, 9 Yonsei Med J htt:// Volume 56 Number 4 July

5 Jang Hoon Kim, et al. Table 2. Radiologic Parameters Preoeratively and at 1, 3, 6, and 12 Months Postoeratively Total±SD Oerative method Oerative level Cervical lordosis ǁ Cage only±sd Cage & late±sd Uer level±sd Lower level±sd High C-lordosis Low C-lordosis SVA (mm) Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo * Posto. 12 mo * Cervical lordosis ( ) Preo Posto. 1 mo , *, Posto. 3 mo , *, Posto. 6 mo , Posto. 12 mo * Thoracic kyhosis ( ) Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Lumbar lordosis ( ) Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Pelvic incidence ( ) Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Pelvic tilt ( ) Preo Posto. 1 mo Posto. 3 mo Yonsei Med J htt:// Volume 56 Number 4 July 2015

6 Whole Sine Sagittal Alignment after ACDF Table 2. Radiologic Parameters Preoeratively and at 1, 3, 6, and 12 Months Postoeratively (Continued) Oerative method Oerative level Cervical lordosis ǁ Cage only±sd Cage & late±sd Uer level±sd Lower level±sd High C-lordosis Low C-lordosis Total±SD Posto. 6 mo Posto. 12 mo Sacral sloe ( ) Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo SVA, sagittal vertical axis. Intragrou reo. versus osto. comarisons were erformed using the Wilcoxon signed-rank test; *<0.01, <0.05. Intergrou comarisons were erformed with the Mann-Whitney test; <0.01, <0.05. ǁ Patients were divided into two grous according to cervical lordosis angle: high C-lordosis (>mean reo. cervical lordosis ) and low C-lordosis (<mean reo. cervical lordosis ). women; low lordosis: 13 men, 14 women) between the two grous (Table 1). Intergrou comarisons of radiologic arameters revealed significant differences in SVA and cervical lordosis. SVA reoeratively and at 1 and 3 months ostoeratively was significantly different between grous (high lordosis: 17.5, 16.2, and 11.1 mm; low lordosis: -20.7, -10.5, and mm, resectively; <0.01 reoeratively; <0.05 at 1 and 3 months) (Table 2). Cervical lordosis reoeratively and at 1, 3, and 6 months ostoeratively was significantly different between grous (high lordosis: -25.9, -17.6, -17.8, and ; low lordosis: -2.5, -2.8, -3.8, and -6.7, resectively; <0.01) (Table 2). Intragrou comarison according to cervical lordosis revealed that only the high-cervical-lordosis grou showed significant changes in SVA, cervical lordosis, elvic tilt, and sacral sloe ostoeratively comared to the reoerative state. SVA was significantly shorter at 6 and 12 months ostoeratively than the mean reoerative in the high-lordosis grou (17.5 to 4.5 and 5.6 mm, resectively; <0.01) (Table 2). Cervical lordosis was also significantly lower at ostoerative 1, 3, 6, and 12 months relative to the mean reoerative (-25.9 to -17.6, -17.8, -18.4, and -17.9, resectively; <0.01 at 1, 3, and 12 months; <0.05 at 6 months) (Table 2). Pelvic tilt also showed a significant increase at ostoerative 12 months relative to the reoerative mean (12.0 to 16.7 ; <0.05) (Table 2). Sacral sloe was significantly lower at ostoerative 12 months than reoeratively (36.4 to 33.3 ; <0.05) (Table 2). test test results are summarized in Fig. 4 and Table 3. As we found statistically significant changes in SVA, cervical lordosis, elvic tilt, and sacral sloe after ACDF, we erformed a Pearson correlation test for SVA, cervical lordosis, elvic tilt, and sacral sloe. SVA was negatively correlated with cervical lordosis and sacral sloe and ositively correlated with elvic tilt (Table 3, Fig. 4). Cervical lordosis only showed a negative correlation with SVA (Table 3, Fig. 4). Pelvic tilt was ositively correlated with SVA yet negatively correlated with sacral sloe (Table 3, Fig. 4). Sacral sloe was negatively correlated with SVA and elvic tilt (Table 3, Fig. 4). DISCUSSION Over the last decade, areciation of the critical role of nor- Yonsei Med J htt:// Volume 56 Number 4 July

7 Jang Hoon Kim, et al. Pelvic tilt (+) (-) SVA (-) Cervical lordosis Sacral sloe Fig. 4. Summarized correlations among sagittal vertical axis (SVA), cervical lordosis, elvic tilt, and sacral sloe. SVA was negatively correlated with cervical lordosis and sacral sloe and ositively correlated with elvic tilt. Cervical lordosis was negatively correlated with SVA. Pelvic tilt had a ositive correlation with SVA and a negative correlation with sacral sloe. Sacral sloe had a negative correlation with SVA and elvic tilt. mal whole-sine sagittal alignment and sagittal elvic alignment in the maintenance of an economic osture and minimal energy consumtion has been increasing. 1-6 Wholesine sagittal alignment and elvic alignment are closely related and can change simultaneously, and sagittal sinoelvic alignment is a comlex chain of correlation from the elvis to the occiut such that changes in one region of the sine can result in recirocal changes in other sinoelvic regions. 1-6 Previous studies have tended to focus on the effects of changes in the lower sine (elvis, lumbar, and thoracic sine) on the uer art (cervical sine). 1,8 These studies reorted that changes in the balance of the thoracolumbar sine caused recirocal changes in the whole sagittal sine and cervical sine alignment. 1,8,9 Develoment of sinal instrumentation and osteotomy techniques, such as PSO, has enabled surgical correction of thoracolumbar deformity and ositive sagittal malalignment. 8 Lumbar PSO to correct sagittal malalignment has been shown to imrove abnormal cervical hyerlordosis to normal lordosis through recirocal change. 1,8 In contrast, however, it is not known whether cervical lordosis changes after cervical sine surgery, or how this may affect whole sine sagittal alignment and elvic alignment. We investigated 48 atients who underwent single-level ACDF for cervical disc herniation. Cervical deformity is not a common disease, in contrast to thoracolumbar deformity; thus, it is challenging to determine whole-sine sagittal alignment changes after cervical deformity correction. ACDF is (-) the most common cervical fusion rocedure; therefore, our goal was to assess whether there were whole-sine sagittal alignment changes after ACDF and to find significant factors that influenced such changes. We did not observe any change in SVA after ACDF; however, cervical lordosis, elvic tilt, and sacral sloe did change after ACDF in the overall grou of atients (Table 2). As SVA did not change after ACDF, we could not distinguish whether the change in elvic alignment (elvic tilt and sacral sloe) was associated with ACDF or whether it occurred indeendently of ACDF. To determine the relationshis among radiologic arameters, we erformed correlation tests of significant variables. We found that the correlation between cervical lordosis and SVA and the changes in SVA resulted in changes to elvic tilt and sacral sloe angles (Table 3, Fig. 4). To find oeration-related or atient factors that influenced SVA and elvic alignment, we comared oerative methods (cage only versus cage & late), oerative level (uer level versus lower level), and reoerative cervical lordosis (high cervical lordosis versus low cervical lordosis). 15,16 When we erformed intragrou comarisons between reoerative status and ostoerative 1-, 3-, 6-, and 12-month statuses according to oerative method and oerative level, we did not observe any changes in SVA after ACDF. This means that the oerative methods and levels were not associated with SVA changes after ACDF. We also groued atients according to reoerative cervical lordosis, as revious studies have reorted that correction of thoracolumbar deformity by PSO significantly decreases cervical lordosis and that this results in a recirocal change to correct cervical hyerlordosis. 8 Patients with ositive sagittal malalignment could comensate with abnormally-increased cervical lordosis to maintain horizontal gaze; this correction of sagittal malalignment would result in correction of cervical hyerlordosis through recirocal changes. 8 We divided atients into two grous based on mean reoerative cervical lordotic angle: those with an angle >12.5 were assigned to the high-cervical-lordosis grou, and those with an angle <12.5 were assigned to the low-cervical-lordosis grou. We found that in the high-cervical-lordosis grou, cervical lordosis decreased significantly from ostoerative 1 month to 12 months, and SVA decreased significantly from 6 months to 12 months; additionally, elvic tilt increased and sacral sloe decreased at ostoerative 12 months (Table 2, Fig. 5). Cervical lordosis changed immediately after ACDF and resulted in a change in SVA at ostoerative 6 months. The change in SVA resulted in a change in 1066 Yonsei Med J htt:// Volume 56 Number 4 July 2015

8 Whole Sine Sagittal Alignment after ACDF Table 3. Significant s* among Radiologic Parameters SVA SVA Cervical lordosis Preo. Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Preo. Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Preo Posto. 1 mo Posto. 3 mo Strong correlation Posto. 6 mo Posto. 12 mo Cervical lordosis Preo Posto. 1 mo Posto. 3 mo Strong correlation Posto. 6 mo Posto. 12 mo Pelvic tilt Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Sacral sloe Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Yonsei Med J htt:// Volume 56 Number 4 July

9 Jang Hoon Kim, et al. Table 3. Significant s* among Radiologic Parameters (Continued) SVA Pelvic tilt Sacral sloe Preo. Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Preo. Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Cervical lordosis Preo Posto. 1 mo Posto. 3 mo Posto. 6 mo Posto. 12 mo Pelvic tilt Preo Posto. 1 mo Posto. 3 mo Strong correlation Posto. 6 mo Posto. 12 mo Sacral sloe Preo Posto. 1 mo Posto. 3 mo Strong correlation Posto. 6 mo Posto. 12 mo SVA, sagittal vertical axis. *Pearson correlation test Yonsei Med J htt:// Volume 56 Number 4 July 2015

10 Whole Sine Sagittal Alignment after ACDF SVA (mm) Cervical lordosis ( ) Pelvic tilt ( ) Sacral sloe ( ) Radiologic arameters changes (high cervical lordosis grou) 17.6* Preo Posto 1 m Posto 3 m * * Posto 6 m * * Posto 12 m Fig. 5. Significant radiologic arameters changes according to ostoerative time. Preoerative and ostoerative states were comared within grous using the Wilcoxon signed-rank test. *<0.01, <0.05. elvic tilt and sacral sloe at ostoerative 12 months. This result is the converse of that observed after correction of thoracolumbar deformity by PSO, which changed the elvic tilt and sacral sloe and subsequently decreased the C2 7 lumb line, resulting in recirocal changes to correct cervical hyerlordosis to neutralization in the cervical-hyerlordosis grou. 8 Intragrou comarison of the uer-cervical grou (C3/4 and C4/5) revealed significant elvic tilt and sacral sloe changes at ostoerative 12 months (Table 2). In this grou, reoerative cervical lordosis was hyerlordosis (20.0 ), which means that the change in elvic tilt and sacral sloe after ACDF in the uer-cervical grou was not at the oerative level but was instead due to high cervical lordosis reoeratively. In conclusion, ACDF affects wholesine sagittal balance including SVA, sacral sloe, and elvic tilt between 6 and 12 months ostoeratively by changing cervical high lordosis to neutralization. With the swings of SVA, sacral sloe, and elvic tilt in the high-cervical-lordosis grou all falling with the normal range, there were no differences in clinical results between the high- and low-cervical-lordosis grous ostoeratively in this study. A recirocal relationshi also exists between lumbar lordosis and thoracic kyhosis, and the sagittal thoracic comensatory curve and elvic retroversion can normalize after restoration of lumbar lordosis in adolescent idioathic scoliosis (AIS). 1,21-25 In revious studies, cervical kyhosis in AIS with thoracic hyokyhosis was reorted. We did not have any cases with thoracic kyhosis or lumbar lordosis changes after ACDF. We only included single-level ACDF and atients with cervical lordosis; therefore, we did not observe any recirocal changes in the thoracic and lumbar sine. Blondel, et al. 21 recently reorted normal cervical lordosis from 6.6 to 22.2 for individuals between the ages of 20 and 60 years. The mean cervical lordosis angle in the current study was 12.5, which is within the range of normal s. 8,26 The authors defined high and low cervical lordosis according to the mean reoerative cervical lordosis of all atients (12.5 ) (Table 1). This subjective classification of cervical lordosis is a limitation of this study, and our results may have been different had we included cervical kyhosis atients or other cervical deformities. This study had several limitations: a short follow-u eriod of one year, a small number of atients, no cervical deformity cases, and no clinical differences according to SVA and cervical lordosis change. In addition, we did not determine the cervical fusion rate. However, several studies have shown that almost all cervical fusion rocedures are successful after single-level ACDF; in our study, none of the atients required revision surgery. Nevertheless, long-term follow-u in a larger number of atients, including those with cervical kyhosis and deformities, is required to determine the fusion rate. Radiologic change including cervical lordosis and SVA before and after surgery did not show any clinical relevance or significance. As all reoerative and ostoerative radiologic arameters were within the normal range, there was no clinical difference according to changes in radiologic arameters. In addition, from this study it is imossible to know the exact reasons as to why only high cervical lordosis atients had an altered sagittal alignment and not those in the low-cervical-lordosis grou, as this study only included the one-segment ACDF and the range of high cervical lordosis was within the normal range. From the revious studies on thoracolumbar deformity, PSO was reorted to have changed the elvic tilt and sacral sloe, which changed SVA and resulted in recirocal changes to correct cervical hyerlordosis to neutralization in the cervical-hyerlordosis grou. 8 However, this study did not include abnormal cervical hyerlordosis and kyhosis cases. Further studies that include various cervical deformities with abnormal high cervical lordosis and kyhosis are required. Desite these limitations, ACDF was found to affect whole-sine sagittal alignment and elvic alignment, esecially in atients with high cervical lordosis. After ACDF, cervical lordosis decreased in the high-cervical-lordosis grou, SVA decreased, elvic tilt increased, and sacral sloe decreased in sequential order. Cervical lordosis and wholesine sagittal alignment were strongly correlated after ACDF. Yonsei Med J htt:// Volume 56 Number 4 July

11 Jang Hoon Kim, et al. ACKNOWLEDGEMENTS The authors thank Se Jin Park, MS at the Deartment of Neurosurgery, Gangnam Severance Hosital, for her great effort in this study. REFERENCES 1. Ha Y, Schwab F, Lafage V, Mundis G, Shaffrey C, Smith J, et al. Recirocal changes in cervical sine alignment after corrective thoracolumbar deformity surgery. Eur Sine J 2014;23: Schwab F, Lafage V, Boyce R, Skalli W, Farcy JP. Gravity line analysis in adult volunteers: age-related correlation with sinal arameters, elvic arameters, and foot osition. Sine (Phila Pa 1976) 2006;31:E Vialle R, Levassor N, Rillardon L, Temlier A, Skalli W, Guigui P. Radiograhic analysis of the sagittal alignment and balance of the sine in asymtomatic subjects. J Bone Joint Surg Am 2005;87: Boulay C, Tardieu C, Hecquet J, Benaim C, Mouilleseaux B, Marty C, et al. Sagittal alignment of sine and elvis regulated by elvic incidence: standard s and rediction of lordosis. Eur Sine J 2006;15: Le Huec JC, Aunoble S, Philie L, Nicolas P. Pelvic arameters: origin and significance. Eur Sine J 2011;20 Sul 5: Scheer JK, Tang JA, Smith JS, Acosta FL Jr, Protosaltis TS, Blondel B, et al. Cervical sine alignment, sagittal deformity, and clinical imlications: a review. J Neurosurg Sine 2013;19: Cil A, Yazici M, Uzumcugil A, Kandemir U, Alanay A, Alanay Y, et al. The evolution of sagittal segmental alignment of the sine during childhood. Sine (Phila Pa 1976) 2005;30: Smith JS, Shaffrey CI, Lafage V, Blondel B, Schwab F, Hostin R, et al. Sontaneous imrovement of cervical alignment after correction of global sagittal balance following edicle subtraction osteotomy. J Neurosurg Sine 2012;17: Lee SH, Son ES, Seo EM, Suk KS, Kim KT. Factors determining cervical sine sagittal balance in asymtomatic adults: correlation with sinoelvic balance and thoracic inlet alignment. Sine J 2015;15: Smith GW, Robinson RA. The treatment of certain cervical-sine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg Am 1958;40-A: Park SB, Jahng TA, Chung CK. Remodeling of adjacent sinal alignments following cervical arthrolasty and anterior discectomy and fusion. Eur Sine J 2012;21: Kaiser MG, Haid RW Jr, Subach BR, Barnes B, Rodts GE Jr. Anterior cervical lating enhances arthrodesis after discectomy and fusion with cortical allograft. Neurosurgery 2002;50: Xie JC, Hurlbert RJ. Discectomy versus discectomy with fusion versus discectomy with fusion and instrumentation: a rosective randomized study. Neurosurgery 2007;61: Lee JY, Park MS, Moon SH, Shin JH, Kim SW, Kim YC, et al. Loss of lordosis and clinical outcomes after anterior cervical fusion with dynamic rotational lates. Yonsei Med J 2013;54: Miao J, Shen Y, Kuang Y, Yang L, Wang X, Chen Y, et al. Early follow-u outcomes of a new zero-rofile imlant used in anterior cervical discectomy and fusion. J Sinal Disord Tech 2013;26: E Miller LE, Block JE. Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery. Sine (Phila Pa 1976) 2011;36: Vrtovec T, Janssen MM, Likar B, Castelein RM, Viergever MA, Pernuš F. A review of methods for evaluating the quantitative arameters of sagittal elvic alignment. Sine J 2012;12: Gardocki RJ, Watkins RG, Williams LA. Measurements of lumboelvic lordosis using the elvic radius technique as it correlates with sagittal sinal balance and sacral translation. Sine J 2002;2: Morvan G, Mathieu P, Vuillemin V, Guerini H, Bossard P, Zeitoun F, et al. Standardized way for imaging of the sagittal sinal balance. Eur Sine J 2011;20 Sul 5: Roussouly P, Nnadi C. Sagittal lane deformity: an overview of interretation and management. Eur Sine J 2010;19: Blondel B, Lafage V, Schwab F, Farcy JP, Bollini G, Jouve JL. Recirocal sagittal alignment changes after osterior fusion in the setting of adolescent idioathic scoliosis. Eur Sine J 2012;21: Ilharreborde B, Vidal C, Skalli W, Mazda K. Sagittal alignment of the cervical sine in adolescent idioathic scoliosis treated by osteromedial translation. Eur Sine J 2013;22: Kim KT, Suk KS, Cho YJ, Hong GP, Park BJ. Clinical outcome results of edicle subtraction osteotomy in ankylosing sondylitis with kyhotic deformity. Sine (Phila Pa 1976) 2002;27: Kim YJ, Bridwell KH, Lenke LG, Rhim S, Cheh G. An analysis of sagittal sinal alignment following long adult lumbar instrumentation and fusion to L5 or S1: can we redict ideal lumbar lordosis? Sine (Phila Pa 1976) 2006;31: Lafage V, Schwab F, Vira S, Patel A, Ungar B, Farcy JP. Sino-elvic arameters after surgery can be redicted: a reliminary formula and validation of standing alignment. Sine (Phila Pa 1976) 2011; 36: Lafage V, Blondel B, Schwab F, Ames CP, LeHuec JC, Smith JS, et al. The crucial role of cervical alignment in regulating sagittal sino-elvic alignment in human standing osture. Presented at the 19th International Meeting on Advanced Sine Techniques 2012; Istanbul Turkey July Yonsei Med J htt:// Volume 56 Number 4 July 2015