J Korean Neurosurg Soc.  2017 Sep;60(5):577-583. 10.3340/jkns.2017.0505.007.

The Predictable Factors of the Postoperative Kyphotic Change of Sagittal Alignment of the Cervical Spine after the Laminoplasty

• Lee JS
• Son DW
• Lee SH
• Kim DH
• Lee SW
• Song GS

• KMID: 2457965
• DOI: http://doi.org/10.3340/jkns.2017.0505.007

Abstract

OBJECTIVE
Laminoplasty is an effective surgical method for treating cervical degenerative disease. However, postoperative complications such as kyphosis, restriction of neck motion, and instability are often reported. Despite sufficient preoperative lordosis, this procedure often aggravates the lordotic curve of the cervical spine and straightens cervical alignment. Hence, it is important to examine preoperative risk factors associated with postoperative kyphotic alignment changes. Our study aimed to investigate preoperative radiologic parameters associated with kyphotic deformity post laminoplasty.
METHODS
We retrospectively reviewed the medical records of 49 patients who underwent open door laminoplasty for cervical spondylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament (OPLL) at Pusan National University Yangsan Hospital between January 2011 and December 2015. Inclusion criteria were as follows: 1) preoperative diagnosis of OPLL or CSM, 2) no previous history of cervical spinal surgery, cervical trauma, tumor, or infection, 3) minimum of one-year follow-up post laminoplasty with proper radiologic examinations performed in outpatient clinics, and 4) cases showing C7 and T1 vertebral body in the preoperative cervical sagittal plane. The radiologic parameters examined included C2-C7 Cobb angles, T1 slope, C2-C7 sagittal vertical axis (SVA), range of motion (ROM) from C2-C7, segmental instability, and T2 signal change observed on magnetic resonance imaging (MRI). Clinical factors examined included preoperative modified Japanese Orthopedic Association scores, disease classification, duration of symptoms, and the range of operation levels.
RESULTS
Mean preoperative sagittal alignment was 13.01° lordotic; 6.94° lordotic postoperatively. Percentage of postoperative kyphosis was 80%. Patients were subdivided into two groups according to postoperative Cobb angle change; a control group (n=22) and kyphotic group (n=27). The kyphotic group consisted of patients with more than 5° kyphotic angle change postoperatively. There were no differences in age, sex, C2-C7 Cobb angle, T1 slope, C2-C7 SVA, ROM from C2-C7, segmental instability, or T2 signal change. Multiple regression analysis revealed T1 slope had a strong relationship with postoperative cervical kyphosis. Likewise, correlation analysis revealed there was a statistical significance between T1 slope and postoperative Cobb angle change (p=0.035), and that there was a statistically significant relationship between T1 slope and C2-C7 SVA (p=0.001). Patients with higher preoperative T1 slope demonstrated loss of lordotic curvature postoperatively.
CONCLUSION
Laminoplasty has a high probability of aggravating sagittal balance of the cervical spine. T1 slope is a good predictor of postoperative kyphotic changes of the cervical spine. Similarly, T1 slope is strongly correlated with C2-C7 SVA.

Keyword

Laminoplasty; Spondylosis; Myelopathy; Kyphosis; Spinal cord diseases/surgery; Cervical vertebrae

MeSH Terms

Ambulatory Care Facilities
Animals
Asian Continental Ancestry Group
Busan
Cervical Vertebrae
Classification
Congenital Abnormalities
Diagnosis
Female
Follow-Up Studies
Gyeongsangnam-do
Humans
Kyphosis
Laminoplasty*
Longitudinal Ligaments
Lordosis
Magnetic Resonance Imaging
Medical Records
Methods
Neck
Orthopedics
Postoperative Complications
Range of Motion, Articular
Retrospective Studies
Risk Factors
Spinal Cord Diseases
Spine*
Spondylosis

Figure

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  Fig. 1 Measurement of radiologic parameters, including C2–C7 SVA, C2–C7 lordosis and T1 slope in cervical lateral radiographs. SVA: sagittal vertical axis.

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  Fig. 2 Scatter plots showing a positive correlation between T1 slope and loss of cervical lordosis (r=0.302). CA: cobb angle.

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  Fig. 3 ROC analysis was performed to determine the cut-off value of T1 slope that induced significant postoperative kyphotic change. T1 slope above 29° could serve as a threshold for significantly increased risk of postoperative kyphotic change (p=0.026, area under curve=0.687, sensitivity=63%, specificity=69%). ROC: receiver operating characteristic.

• 

  Fig. 4 Schematic image of alteration of cervical lordosis after laminoplasty in patients with OPLL. A: Patients with high T1 slope had needed more lordotic force. Postoperatively, center of gravity moved forward and cervical spine accelerated kyphotic. B: Patients with low T1 slope had relatively less influence of the operation than high T1 slope. OPLL: ossification of the posterior longitudinal ligament.

Reference

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