An observational cohort study design was adopted in this study.
This study was designed to investigate preoperative factors that predict poor outcomes following surgery in patients with proximal-type cervical spondylotic amyotrophy (PCSA) using radiological findings.
We evaluated the preoperative factors associated with poor outcomes using electrophysiological and neurological findings. However, the preoperative factors associated with poor outcomes remained unclear.
Sixty patients with PCSA who underwent surgical treatment of the cervical spine were enrolled. The radiological findings on plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) were evaluated. The cervical lordotic angles, C2–C7 sagittal vertical axis (SVA), and T1 slope were assessed on a lateral radiograph in the neutral position. CT was used to assess the width of the intervertebral foramen and the anterior protrusion of the superior articular process on the axial view. MRI was used to determine the number of levels of compression (NLC) and the presence of a high-intensity area in the spinal cord in the T2-weighted midsagittal view. The preoperative and postoperative strengths of the most atrophic muscles were evaluated using manual muscle testing. Improvements in strength were classified as excellent (five grades recovered), good (more than one grade recovered), fair (no improvement), or poor (worsened).
The prevalence of C5 palsy was 17% (10/60). Patients with poor outcomes had higher NLC and Δ C2–C7 SVA than patients with excellent, good, and fair outcomes (
ΔC2–C7 SVA and NLC may be used as prognostic factors for achieving a poor outcome following surgery in patients with PCSA. More focus is needed on preventing the increase in ΔC2–C7 SVA.
Cervical spondylotic amyotrophy (CSA) was first reported by Sobue et al. [
In this study, 68 patients with PCSA who underwent surgical treatment of the cervical spine between April 1997 and September 2017 at Yamaguchi University Hospital were enrolled. Four patients underwent cervical surgery and multi-muscle transfers simultaneously, two had severe muscle atrophy bilaterally, and two had coexisting rotator cuff tears. Therefore, we excluded these eight patients. Finally, this retrospective study enrolled 60 patients. We collected data on age, hypertension, diabetes mellitus (DM), dialysis, corticosteroid use, Parkinson’s disease, surgical approach, the duration of clinical history (DCH), the duration of postoperative follow-up (DPF), and radiological findings. The mean age of the patients was 61.3±9.8 years. An anterior approach was the preferred method of treatment for multilevel cervical myelopathies when less than three surgical segments were involved, regardless of the alignment of the cervical spine. A posterior approach was the preferred method of treatment for multilevel cervical myelopathies when three or more surgical segments were involved. When the alignment of the cervical spine was kyphotic (see evaluation of radiological findings: α <−5°), since 2014, we performed fixation with instrumentation in addition to laminoplasty. All 60 patients showed severe unilateral atrophy of the shoulder girdle muscles; however, the intrinsic muscles remained intact. When patients had muscle atrophy of the forearm and/or hand, in addition to the shoulder girdle muscles, we suspected amyotrophic lateral sclerosis (ALS) and other motor neuron diseases. To differentiate motor neuron diseases, such as ALS and PCSA, we performed preoperative electromyography on 35 patients. When ALS and other motor neuron diseases were suspected, we consulted neurologists preoperatively. Along with the neurologists, we determined that patients with PCSA did not have these diseases preoperatively.
This study was approved by the Institutional Review Board of Yamaguchi University Hospital (IRB approval no., H30–170). Informed consent was obtained from all individual participants included in the study.
The radiological findings on plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) were evaluated. The cervical lordotic angles (cervical curvature, α; Cobb angle, β), K line, C2–C7 sagittal vertical axis (SVA), T1 slope, and diameter of the canal at the C5 vertebral level (C5 canal) were assessed on a lateral radiograph in the neutral position (
In this study, C5 palsy was defined as a motor decline of the deltoid muscle function by at least one level in a standard manual muscle testing (MMT) within a 6-week postoperative period [
We examined the strength of the deltoid and biceps brachii muscles, forearm supination, and grip strength on the affected and healthy sides and the presence of sensory disturbance on the radial side in the affected upper extremity.
Statistical analyses were performed using StatFlex ver. 7.0 (Artech Co. Ltd., Osaka, Japan;
Parameters examined as possibly associated with the surgical outcomes, included surgical approaches (anterior approach versus posterior approach), K line, age, DCH, DPF, alignment, α, β, preoperative and postoperative C2–C7 SVA, ΔC2–C7 SVA, preoperative and postoperative T1 slope, ΔT1 slope, range of motion at C4–C5 and C5–C6 intervertebral levels, C5 canal, SAP and WIF at C4–C5 intervertebral levels on the bilateral side on axial CT, HIA, NLC, and D on T2-weighted sagittal MRI. Univariate statistical analyses were performed using the Mann-Whitney
In this study, a dummy variable indicating the occurrence of poor outcomes was set as the objective variable, and all aforementioned parameters were set as the explanatory variables.
The prevalence of C5 palsy was 17% (10/60). Postoperative C5 palsy was ipsilateral to the preoperative PCSA symptoms in nine of 10 patients. Paralysis was noted after a mean duration of 5.1 days (range, 0–18 days) postoperatively. Six patients underwent anterior decompression with spinal fusion (C4–C6), and four patients underwent laminoplasty (C3–C7) with foraminotomy (two patients: C5–C6 and two patients: C4–C5 and C5–C6). No patient underwent fixation with instrumentation. One patient had full recovery after 2 years and was categorized into group 2. However, nine patients with C5 palsy did not show adequate improvements even after ≥2 years postoperatively. These patients were categorized into group 1. The characteristics and neurological findings of the patients in groups 1 and 2 are shown in
We used univariate analyses to compare the aforementioned parameters between the two groups. Postoperative C2–C7 SVA, ΔC2–C7 SVA, and NLC differed significantly between groups 1 and 2 (
Postoperative C2–C7 SVA and ΔC2–C7 SVA significantly differed between groups 1 and 2 in the posterior approach (
In the MLRA, the dummy variable representing group 1 was set as the objective variable, and all factors were set as the explanatory variables. Using the forward stepwise method, group 1 had higher NLC and ΔC2–C7 SVA than group 2 (
The prevalence of C5 palsy was 17% (10/60). It was 18% and 15% in the anterior and posterior approaches, respectively. The average reported prevalence of C5 palsy following surgery for CCM for the anterior approach is 6.7% (range, 1.6%–9.1%) [
Factors associated with group 1 were ΔC2–C7 SVA and NLC. NLC was a preoperative factor. Thus, avoiding an increase in ΔC2–C7 SVA is important for surgeons. Rao et al. [
In this study, a larger SAP, WIF narrowing, and a posterior shift of the spinal cord were not associated with C5 palsy (
This study has few limitations that should be kept in mind when interpreting the results. The sample size was relatively small. The study may have been underpowered to identify any significant difference in surgical outcomes. However, to the best of our knowledge, this is the first study that identified preoperative factors related to poor outcomes using radiological examinations.
In conclusion, ΔC2–C7 SVA and NLC may be used as prognostic factors for achieving poor surgical outcomes following surgical treatment in patients with PCSA. More focus is needed on preventing the increase in ΔC2–C7 SVA.
No potential conflict of interest relevant to this article was reported.
Yasuaki Imajo gathered and analyzed data. Norihiro Nishida, Masahiro Funaba, Yuji Nagao, and Hidenori Suzuki gathered data. Takashi Sakai was an advisor. All authors read and approved the final manuscript.
The authors acknowledge Prof. Kiyoshi Ichihara, Department of Clinical Laboratory Sciences, Faculty of Health Sciences, Yamaguchi University Graduate School of Medicine, who performed all of the statistical analysis and supported manuscript preparation.
Computed tomography.
Magnetic resonance imaging (MRI). Posterior shift of the spinal cord at C4–C5 on the mid-sagittal MRI (arrows).
Measures and definitions on plain radiographs
Variable | Definitions |
---|---|
The angle between parallel lines to the posterior surface of the C2 and C7 vertebral bodies. | |
β | The angle between the C2 and C7 lower endplates. |
SVA | The distance between the C2 plumb line and the posterior superior endplate of C7. |
T1 slope | The angle between the horizontal plane and the T1 upper endplate. |
C5 canal | The diameter of the canal at the C5 vertebral level. |
K–line | A straight line that connects the midpoints of the spinal canal at C2 and C7 |
γ | The intervertebral range at the C4–C5 intervertebral levels was assessed using lateral radiographs in flexion and extension positions. |
δ | The intervertebral range at the and C5–C6 intervertebral levels was assessed using lateral radiographs in flexion and extension positions. |
α, cervical curvature; β, Cobb angle; SVA, the C2–C7 sagittal vertical axis.
Comparison of patients population and neurological findings between the two groups
Characteristic | Group 1 (n=9) | Group 2 (n=51) | |
---|---|---|---|
Age (yr) | 61.8±12.0 | 61.2±9.6 | 0.86 |
Sex | 0.58 | ||
Male | 9 | 45 | |
Female | 0 | 6 | |
Duration of clinical history (mo) | 9.0 (5.8–13.3) | 8.0 (4.3–14.0) | 0.66 |
Duration of postoperative follow-up (mo) | 24.0 (12.0–32.3) | 26.0 (12.3–60.0) | 0.44 |
Surgical procedure | 1.0 | ||
Posterior approach | 4 | 23 | |
Anterior approach | 5 | 28 | |
Preoperative neurological findings | |||
MMT of the deltoid on the affected side | 2.2±0.7 | 2.4±0.7 | 0.54 |
MMT of the biceps brachii muscle on the affected side | 3.2±0.7 | 2.8±0.9 | 0.20 |
MMT of the forearm supination on the affected side | 3.5±0.6 | 2.7±0.9 | 0.09 |
Grip strength on the affected side (kg) | 31.6±10.7 | 26.6±9.8 | 0.25 |
Grip strength on the normal side (kg) | 41.2±6.9 | 34.3±9.9 | 0.11 |
Sensory disturbance | 0.28 | ||
Hypesthesia | 4 | 28 | |
Normal | 5 | 15 | |
Postoperative neurological findings | |||
MMT of the deltoid on the affected side | 1.8±0.8 | 3.9±1.5 | 0.0003 |
MMT of the biceps brachii muscle on the affected side | 2.3±1.1 | 3.9±1.2 | 0.001 |
MMT of the forearm supination on the affected side | 0.7±0.6 | 3.5±1.2 | 0.001 |
Grip strength on the affected side (kg) | 23.5±10.4 | 32.3±11.1 | 0.16 |
Grip strength on the normal side (kg) | 36.4±7.4 | 37.4±0.7 | 0.84 |
Sensory disturbance | 0.03 | ||
Hypesthesia | 8 | 23 | |
Normal | 1 | 24 |
Values are presented as mean±standard deviation, number, or median (interquartile range).
MMT, manual muscle testing.
Comparison of radiological findings between the two groups
Variable | Anterior and posterior approach | Anterior approach | ||||
---|---|---|---|---|---|---|
|
| |||||
Group1 (n=9) | Group 2 (n=51) | Group 1 (n=5) | Group 2 (n=28) | |||
Plain radiography | ||||||
| ||||||
|
10.3±10.4 | 10.4±12.7 | 0.98 | 6.6±12.1 | 9.3±12.5 | 0.66 |
| ||||||
β (°) | 12.3±12.2 | 12.1±14.6 | 0.97 | 6.6±11.9 | 10.9±13.8 | 0.52 |
| ||||||
Alignment | 0.21 | |||||
| ||||||
Straight | 0 of 9 | 2 of 50 | 0.16 | 0 of 5 | 1 of 28 | |
| ||||||
Lordosis | 7 | 29 | 3 | 15 | ||
| ||||||
Kyphosis | 0 | 17 | 0 | 11 | ||
| ||||||
Sigmoid | 2 | 2 | 2 | 1 | ||
| ||||||
K–line ( − ) | 1 | 9 | 1.00 | 1 | 6 | 1.00 |
| ||||||
Pre C2–C7 SVA (mm) | 24.1±9.3 | 21.3±10.6 | 0.48 | 19.8±10.2 | 21.6±11.0 | 0.72 |
| ||||||
Post C2–C7 SVA (mm) | 37.1±18.4 | 23.1±13.2 | 0.01 |
31.0±15.1 | 21.6±11.0 | 0.10 |
| ||||||
ΔC2–C7 SVA (mm) | 13.1±16.8 | 2.2±8.5 | 0.004 |
11.2±18.2 | 1.0±8.2 | 0.047 |
| ||||||
Pre T1 slope (°) | 26.3±4.5 | 24.3±7.6 | 0.47 | 26.3±4.1 | 24.5±7.5 | 0.67 |
| ||||||
Post T1 slope (°) | 25.2±6.3 | 23.6±8.5 | 0.62 | 23.3±2.0 | 23.4±7.5 | 0.98 |
| ||||||
ΔT1 slope (°) | −1.2±5.2 | −0.2±6.2 | 0.66 | −2.9±4.8 | −0.1±6.9 | 0.44 |
| ||||||
Pre T1 slope–β (°) | 15.7±14.3 | 11.5±10.1 | 0.30 | 14.4±17.8 | 11.3±11.0 | 0.61 |
| ||||||
γ (°) | 12.2±5.2 | 9.6±5.0 | 0.17 | 12.1±5.7 | 8.9±4.7 | 0.20 |
| ||||||
δ (°) | 8.9±3.7 | 7.3±4.0 | 0.28 | 7.5±3.0 | 7.4±4.1 | 0.96 |
| ||||||
C5 canal (mm) | 14.0±1.2 | 14.4±1.3 | 0.45 | 14.2±1.4 | 14.7±1.2 | 0.44 |
| ||||||
Computed tomography | ||||||
| ||||||
SAP at C5 level (mm) | ||||||
| ||||||
Affected side | 6.3±1.6 | 6.3±2.2 | 0.99 | 6.8±1.5 | 6.6±2.1 | 0.85 |
| ||||||
Normal side | 6.4±1.6 | 5.2±2.0 | 0.08 | 6.7±1.5 | 5.2±2.0 | 0.13 |
| ||||||
WIF at C4–C5 level (mm) | ||||||
| ||||||
Affected side | 2.4±1.1 | 2.3±0.7 | 0.75 | 2.6±1.3 | 2.4±0.7 | 0.59 |
| ||||||
Normal side | 2.5±1.0 | 2.8±1.3 | 0.58 | 2.7±1.3 | 2.9±1.3 | 0.69 |
| ||||||
Magnetic resonance imaging | ||||||
| ||||||
No. of levels of compression | 2.9 (2–4) | 1.6 (0–3) | 0.001 |
3.0 (2–4) | 1.4 (0–3) | 0.002 |
| ||||||
The presence of HIA (%) | 4 of 9 (44) | 20 of 49 (41) | 1.0 | 2 of 5 (40) | 10 of 27 (37) | 1.0 |
Values are presented as mean±standard deviation, number, number (range), or number (%), unless otherwise stated.
α, C2–C7 curvature; β, C2–C7 cobb angle; Pre, preoperative; Post, postoperative; SVA, sagittal vertical axis; ROM, range of motion; γ, ROM at the C4–C5 intervertebral level; δ, ROM at the C5–C6 intervertebral level; SAP, superior articular process; WIF, width of the intervertebral foramen; HIA, high-intensity area.
p<0.05.
Comparison of radiological findings between the two groups in posterior approach
Variable | Group 1 (n=4) | Group 2 (n=23) | |
---|---|---|---|
Plain radiography | |||
|
15.0±6.5 | 11.9±13.1 | 0.64 |
β (°) | 19.5±9.2 | 13.7±15.8 | 0.49 |
Alignment | 0.15 | ||
Straight | 0 of 4 | 1 of 20 | |
Lordosis | 4 | 14 | |
Kyphosis | 0 | 6 | |
Sigmoid | 0 | 1 | |
K–line (−) | 0 | 3 | 1.00 |
Pre C2–C7 SVA (mm) | 29.4±5.0 | 21.0±11.3 | 0.17 |
Post C2–7 SVA (mm) | 44.8±21.6 | 25.1±15.8 | 0.04 |
ΔC2–C7 SVA (mm) | 15.4±17.4 | 3.6±8.8 | 0.04 |
Pre T1 slope (°) | 26.4±5.5 | 24.1±7.2 | 0.56 |
Post T1 slope (°) | 27.0±9.0 | 23.9±9.8 | 0.56 |
ΔT1 slope (°) | 0.6±5.7 | −0.2±5.3 | 0.78 |
Pre T1 slope–β (°) | 7.0±4.7 | 11.3±10.8 | 0.45 |
γ (°) | 12.3±5.3 | 10.6±5.3 | 0.56 |
δ (°) | 10.7±4.1 | 7.3±3.9 | 0.13 |
C5 canal (mm) | 13.8±1.1 | 14.0±1.4 | 0.81 |
Computed tomography | |||
SAP at C5 level (mm) | 0.76 | ||
Affected side | 5.4±1.4 | 5.8±2.3 | |
Normal side | 6.2±2.1 | 5.1±1.9 | 0.39 |
WIF at C4–C5 level (mm) | 0.92 | ||
Affected side | 2.2±1.1 | 2.3±0.8 | |
Normal side | 2.4±0.7 | 2.6±1.2 | 0.72 |
Magnetic resonance imaging | |||
No. of levels of compression | 2.8 (2 to 3) | 2.0 (0 to 3) | 0.13 |
The presence of HIA (%) | 2 of 4 (50) | 10 of 22 (45.5) | 1.0 |
Pre D at C4–C5 level (mm) | 0.6±0.7 | 0.8±0.9 | 0.93 |
Post D at C4–C5 level (mm) | 1.8±1.3 | 2.3±1.0 | 0.41 |
Values are presented as mean±standard deviation, number, number (range), or number (%), unless otherwise stated.
α, C2–C7 curvature; β, C2–C7 cobb angle; Pre, preoperative; Post, postoperative; SVA, sagittal vertical axis; ROM, range of motion; γ, ROM at the C4–C5 intervertebral level; δ, ROM at the C5–C6 intervertebral level; SAP, superior articular process; WIF, width of the intervertebral foramen; HIA, high-intensity area; D, distance between posterior edge of C4–C5 disc and anterior aspect of spinal cord.
p<0.05.
Factors associated with poor outcomes
Variable | Odds ratio (95% CI) | |
---|---|---|
No. of levels of compression | 0.015 | 5.758 (1.397–23.726) |
ΔC2–C7 sagittal vertical axis | 0.048 | 1.068 (0.992–1.141) |
CI, confidence interval.