Yonsei Med J.  2015 Jul;56(4):1060-1070. 10.3349/ymj.2015.56.4.1060.

Anterior Cervical Discectomy and Fusion Alters Whole-Spine Sagittal Alignment

• Kim JH
• Park JY
• Yi S
• Kim KH
• Kuh SU
• Chin DK
• Kim KS
• Cho YE

• KMID: 2366349
• DOI: http://doi.org/10.3349/ymj.2015.56.4.1060

Abstract

PURPOSE
Anterior cervical discectomy and fusion (ACDF) has become a common spine procedure, however, there have been no previous studies on whole spine alignment changes after cervical fusion. Our purpose in this study was to determine whole spine sagittal alignment and pelvic alignment changes after ACDF.
MATERIALS AND METHODS
Forty-eight patients who had undergone ACDF from January 2011 to December 2012 were enrolled in this study. Cervical lordosis, thoracic kyphosis, lumbar lordosis, sagittal vertical axis (SVA), and pelvic parameters were measured preoperatively and at 1, 3, 6, and 12 months postoperatively. Clinical outcomes were assessed using Visual Analog Scale (VAS) scores and Neck Disability Index (NDI) values.
RESULTS
Forty-eight patients were grouped according to operative method (cage only, cage & plate), operative level (upper level: C3/4 & C4/5; lower level: C5/6 & C6/7), and cervical lordosis (high lordosis, low lordosis). All patients experienced significant improvements in VAS scores and NDI values after surgery. Among the radiologic parameters, pelvic tilt increased and sacral slope decreased at 12 months postoperatively. Only the high cervical lordosis group showed significantly-decreased cervical lordosis and a shortened SVA postoperatively. Correlation tests revealed that cervical lordosis was significantly correlated with SVA and that SVA was significantly correlated with pelvic tilt and sacral slope.
CONCLUSION
ACDF affects whole spine sagittal alignment, especially in patients with high cervical lordosis. In these patients, alteration of cervical lordosis to a normal angle shortened the SVA and resulted in reciprocal changes in pelvic tilt and sacral slope.

Keyword

ACDF; whole spine sagittal alignment; pelvic parameters

MeSH Terms

Adult
Aged
Cervical Vertebrae/physiopathology/radiography/*surgery
Cross-Sectional Studies
*Diskectomy
Female
Humans
Lordosis/etiology/*surgery
Magnetic Resonance Imaging
Male
Middle Aged
Neck/surgery
Retrospective Studies
Spinal Diseases/complications/physiopathology/radiography/*surgery
Spinal Fusion/*methods
Spine
Treatment Outcome
Young Adult

Figure

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  Fig. 1 Whole spine AP (A) and lateral (B) radiography after anterior cervical discectomy and fusion with cage only (Zero-P implant; Synthes GmbH Switzerland, Oberdorf, Switzerland) with autobone.

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  Fig. 2 Whole-spine AP (A) and lateral (B) radiography after anterior cervical discectomy and fusion with cage and plate [Allobone spacer (CG bio, Seoul, Korea), and Zephir plate (Medtronic Sofamor Danek Inc., Memphis, TN, USA)].

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  Fig. 3 Radiologic parameters evaluated in this study. Cervical lordosis (Cobb angle between caudal endplate of C2 and caudal endplate of C7), thoracic kyphosis (Cobb angle between cranial endplate of T4 and caudal endplate of T12), lumbar lordosis (Cobb angle between sacral upper margin and cranial L1 endplate), sagittal vertical axis (distance between vertical lines through the center of the C7 vertebral body and the S1 superior posterior corner), pelvic incidence (angle between the line joining the center of the femoral head with the midpoint of the sacral endplate and the perpendicular line from the midpoint of the sacral endplate), pelvic tilt (angle between the line joining the center of the femoral head with the midpoint of the sacral endplate and the vertical line), and sacral slope (angle between the line along the sacral endplate and the horizontal line).

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  Fig. 4 Summarized correlations among sagittal vertical axis (SVA), cervical lordosis, pelvic tilt, and sacral slope. SVA was negatively correlated with cervical lordosis and sacral slope and positively correlated with pelvic tilt. Cervical lordosis was negatively correlated with SVA. Pelvic tilt had a positive correlation with SVA and a negative correlation with sacral slope. Sacral slope had a negative correlation with SVA and pelvic tilt.

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  Fig. 5 Significant radiologic parameters changes according to postoperative time. Preoperative and postoperative states were compared within groups using the Wilcoxon signed-rank test. *p<0.01, †p<0.05.

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