J Korean Neurosurg Soc.  2021 Sep;64(5):677-692. 10.3340/jkns.2020.0294.

Preoperative Radiological Parameters to Predict Clinical and Radiological Outcomes after Laminoplasty

• Lee SH
• Son DW
• Shin JJ
• Ha Y
• Song GS
• Lee JS
• Lee SW

• KMID: 2519695
• DOI: http://doi.org/10.3340/jkns.2020.0294

Abstract

Many studies have focused on pre-operative sagittal alignment parameters which could predict poor clinical or radiological outcomes after laminoplasty. However, the influx of too many new factors causes confusion. This study reviewed sagittal alignment parameters, predictive of clinical or radiological outcomes, in the literature. Preoperative kyphotic alignment was initially proposed as a predictor of clinical outcomes. The clinical significance of the K-line and K-line variants also has been studied. Sagittal vertical axis, T1 slope (T1s), T1s-cervical lordosis (CL), anterolisthesis, local kyphosis, the longitudinal distance index, and range of motion were proposed to have relationships with clinical outcomes. The relationship between loss of cervical lordosis (LCL) and T1s has been widely studied, but controversy remains. Extension function, the ratio of CL to T1s (CL/T1s), and Sharma classification were recently proposed as LCL predictors. In predicting postoperative kyphosis, T1s cannot predict postoperative kyphosis, but a low CL/T1s ratio was associated with postoperative kyphosis.

Keyword

Cervical vertebrae; Laminoplasty; Spinal cord compression; Ossification of posterior longitudinal ligament; Reference values

Figure

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  Fig. 1. Flow chart diagram of our search mechanism in accordance to the PRISMA. PRISMA : preferred reporting items for systematic reviews and meta-analyses, ACDF : anterior cervical discectomy and fusion.

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  Fig. 2. Schematic images of sagittal radiological parameters. A : Routine sagittal parameters. B : K-line. C : a means length of a vertical line drawn between the postero-inferior edges of C2 and C7, b means the antero-posterior diameter of C4, and LDI of the cervical spine. D : Extension function (EF). E : Anterolisthesis in flexion position. CL : cervical lordosis, SVA : sagittal vertical axis, T1s : T1 slope, LDI : longitudinal distance index, CL(N) : cervical lordosis in neutral position, CL(E) : cervical lordosis in extension position.

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  Fig. 3. Schema of the indication of laminoplasty according to preoperative alignment, diagnosis, K-line, and loss of cervical lordosis. Preop : preoperative, OPLL : ossified posterior longitudinal ligament, CSM : cervical spondylotic myelopathy, LCL : loss of cervical lordosis.

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  Fig. 4. Sufficient indirect decompression (case 1). CL : cervical lordosis, SVA : sagittal vertical axis, T1s : T1 slope, Flex CL : cervical lordosis in flexion position, Ext CL : cervical lordosis in extension position.

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  Fig. 5. Different postoperative alignment and clinical outcomes in two patients with preoperative kyphotic alignment (case 2 [upper] and case 3 [lower]). CL : cervical lordosis, SVA : sagittal vertical axis, T1s : T1 slope, Flex CL : cervical lordosis in flexion position, Ext CL : cervical lordosis in extension position, EF : extension function.

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  Fig. 6. Failure of indirect decompression in patients with preoperative kyphotic alignment (case 3). CL : cervical lordosis, SVA : sagittal vertical axis, T1s : T1 slope.

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  Fig. 7. Failure of indirect decompression following loss of cervical lordosis in preoperative straight alignment patients (case 4). CL : cervical lordosis, SVA : sagittal vertical axis, T1s : T1 slope, Flex CL : cervical lordosis in flexion position, Ext CL : cervical lordosis in extension position, EF : extension function.

Reference

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