J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website https://www.jocmr.org

Review

Volume 13, Number 7, July 2021, pages 367-376

The Role of Cervical Muscles Morphology in the Surgical Treatment of Degenerative Disc Disease: Clinical Correlations Based on Magnetic Resonance Imaging Studies

Figure 1. Axial T2 MRI image that demonstrates the muscle layers of the cervical spine of a 40-year-old asymptomatic woman at C5/C6 level. MRI: magnetic resonance imaging; LCA: longissimus capitis; LC: longus colli; LS: levator scapulae; MU: multifidus; SCA: scalenus anterior; SC: splenius capitis; SMC: semispinalis capitis; SCM: sternocleidomastoid; SMCe: semispinalis cervicis; T: trapezius.

**Table 1.** MRI-Based Studies of Cervical Spine Musculature of Patients That Underwent an Anterior Approach for Degenerative Disc Disease
Authors/year of publication	Type of study	Number of patients	Type of surgery	Conclusions
MRI: magnetic resonance imaging; ACDF: anterior cervical discectomy and fusion; VBA: vertebral body area; ASD: adjacent segment degeneration.
Choi et al, 2016 [19]	Retrospective case-control study	243 divided in fusion and no fusion groups	ACDF	Increased dimensions of extensor semispinalis cervicis at C5/C6 level was found positively correlated with a successful and quicker fusion process.
Matsumoto et al, 2012 [20]	Prospective case-control study	31 patients that were operated with ACDF approach, and 32 healthy adults as control group	ACDF	Posterior cervical muscles were not different significantly between the two groups with only a small decrease in the cross-sectional area (CSA) in the ACDF group. These changes were not significantly correlated to pain or functionality scores.
Thakar et al, 2014 [21]	Retrospective case-control study	67 patients with cervical spondylotic myelopathy and normal subjects	Anterior cervical corpectomy-fusion-plating	Normal population has significant higher ratios of CSAs of the superficial, deep flexor (DF), and deep extensor (DE) paraspinal muscles than patients’ group (P < 0.001). Higher age patients and female patients had a lower total extensor CSA/VBA ratio (P < 0.001), while a longer duration of symptoms significantly predicted a greater total flexor/total extensor CSA ratio (P = 0.02). Among the muscle area ratios, the DF/DE ratio demonstrated a negative correlation with segmental angle change in the subgroup with preoperative straight or kyphotic segmental angles (P = 0.04 in the single corpectomy group, P = 0.01 in the two-level corpectomy group). There was no correlation of any of the muscle ratios with change in Nurick grade.
Thakar et al, 2019 [22]	Prospective study	45 patients with single level radiculopathy-myelopathy or myelopathy	ACDF	Deep flexors areas as well as the ratio of deep flexors areas to deep extensors areas have a significant prognostic value of Nurick grade improvement.
Wong et al, 2020 [23]	Retrospective case-control study	32 patients with adjacent level disease after a two-level ACDF procedure; 30 patients that did not have this complication	ACDF	Asymmetry of fat at C5 (coefficient: 0.06), standardized measures of C7 lean (coefficient: 0.05) and total CSA measures (coefficient: 0.05) were the strongest predictors of early onset ASD.

Table 1. MRI-Based Studies of Cervical Spine Musculature of Patients That Underwent an Anterior Approach for Degenerative Disc Disease

Authors/year of publication

Type of study

Number of patients

Type of surgery

Conclusions

MRI: magnetic resonance imaging; ACDF: anterior cervical discectomy and fusion; VBA: vertebral body area; ASD: adjacent segment degeneration.

Choi et al, 2016 [19]

Retrospective case-control study

243 divided in fusion and no fusion groups

ACDF

Increased dimensions of extensor semispinalis cervicis at C5/C6 level was found positively correlated with a successful and quicker fusion process.

Matsumoto et al, 2012 [20]

Prospective case-control study

31 patients that were operated with ACDF approach, and 32 healthy adults as control group

ACDF

Posterior cervical muscles were not different significantly between the two groups with only a small decrease in the cross-sectional area (CSA) in the ACDF group. These changes were not significantly correlated to pain or functionality scores.

Thakar et al, 2014 [21]

Retrospective case-control study

67 patients with cervical spondylotic myelopathy and normal subjects

Anterior cervical corpectomy-fusion-plating

Normal population has significant higher ratios of CSAs of the superficial, deep flexor (DF), and deep extensor (DE) paraspinal muscles than patients’ group (P < 0.001). Higher age patients and female patients had a lower total extensor CSA/VBA ratio (P < 0.001), while a longer duration of symptoms significantly predicted a greater total flexor/total extensor CSA ratio (P = 0.02). Among the muscle area ratios, the DF/DE ratio demonstrated a negative correlation with segmental angle change in the subgroup with preoperative straight or kyphotic segmental angles (P = 0.04 in the single corpectomy group, P = 0.01 in the two-level corpectomy group). There was no correlation of any of the muscle ratios with change in Nurick grade.

Thakar et al, 2019 [22]

Prospective study

45 patients with single level radiculopathy-myelopathy or myelopathy

ACDF

Deep flexors areas as well as the ratio of deep flexors areas to deep extensors areas have a significant prognostic value of Nurick grade improvement.

Wong et al, 2020 [23]

Retrospective case-control study

32 patients with adjacent level disease after a two-level ACDF procedure; 30 patients that did not have this complication

ACDF

Asymmetry of fat at C5 (coefficient: 0.06), standardized measures of C7 lean (coefficient: 0.05) and total CSA measures (coefficient: 0.05) were the strongest predictors of early onset ASD.

**Table 2.** MRI-Based Studies of Cervical Spine Musculature of Patients That Underwent a Posterior Approach for Degenerative Disc Disease
Authors/year of publication	Type of study	Number of patients	Type of surgery	Conclusions
MRI: magnetic resonance imaging; CSA: cross-sectional area; QOL: quality of life; CSM: cervical spondylotic myelopathy.
Ashana et al, 2017 [24]	Retrospective study	61	18 laminoplasty and 43 laminectomy and fusion patients	Authors found a 2.19 times increase of the degree of atrophy in patients who sustained laminectomy and fusion. This study concluded that paraspinal muscle atrophy is correlated to anatomically larger surgical procedures.
Chen et al, 2019 [25]	Retrospective study	63	36 patients with laminoplasty and posterior muscle-ligament complex preservation, and 27 patients with traditional laminoplasty	The preservation of posterior muscle-ligament complex protects patients from a postoperative muscle volume decrease which was noted in the traditional laminoplasty patients’ group (P < 0.01).
Kim et al, 2020 [26]	Retrospective study	106	Cervical laminoplasty	Higher T1 slope and less regional cross-sectional areas at C7 - T1 level were associated with loss of cervical lordosis.
Kotani et al, 2009 [27]	Retrospective study	84	conventional open-door laminoplasty and deep extensor muscle-preserving laminoplasty	Laminoplasty with deep extensor muscle-preserving approach appeared to be effective in reducing the axial pain and deep muscle atrophy, as well as improving cervical spine function and QOL when compared to conventional open-door laminoplasty.
Kotani et al, 2012 [28]	Prospective study	90	Conventional open-door laminoplasty and deep extensor muscle-preserving laminoplasty	There is a superiority of deep extensor muscle-preserving laminoplasty in terms of postoperative axial pain, QOL, and prevention of atrophy of the deep extensor muscles over conventional open-door laminoplasty for the treatment of CSM.
Lee et al, 2018 [29]	Prospective study	144	Laminoplasty procedure	Statistical analysis revealed that high T1 slope and low summation of CSAs at each level of the semispinalis cervicis is correlated with loss of cervical lordosis. The level of the semispinalis cervicis associated with greater loss of lordosis was the C6 level.

Table 2. MRI-Based Studies of Cervical Spine Musculature of Patients That Underwent a Posterior Approach for Degenerative Disc Disease

Authors/year of publication

Type of study

Number of patients

Type of surgery

Conclusions

MRI: magnetic resonance imaging; CSA: cross-sectional area; QOL: quality of life; CSM: cervical spondylotic myelopathy.

Ashana et al, 2017 [24]

Retrospective study

18 laminoplasty and 43 laminectomy and fusion patients

Authors found a 2.19 times increase of the degree of atrophy in patients who sustained laminectomy and fusion. This study concluded that paraspinal muscle atrophy is correlated to anatomically larger surgical procedures.

Chen et al, 2019 [25]

Retrospective study

36 patients with laminoplasty and posterior muscle-ligament complex preservation, and 27 patients with traditional laminoplasty

The preservation of posterior muscle-ligament complex protects patients from a postoperative muscle volume decrease which was noted in the traditional laminoplasty patients’ group (P < 0.01).

Kim et al, 2020 [26]

Retrospective study

106

Cervical laminoplasty

Higher T1 slope and less regional cross-sectional areas at C7 - T1 level were associated with loss of cervical lordosis.

Kotani et al, 2009 [27]

Retrospective study

conventional open-door laminoplasty and deep extensor muscle-preserving laminoplasty

Laminoplasty with deep extensor muscle-preserving approach appeared to be effective in reducing the axial pain and deep muscle atrophy, as well as improving cervical spine function and QOL when compared to conventional open-door laminoplasty.

Kotani et al, 2012 [28]

Prospective study

Conventional open-door laminoplasty and deep extensor muscle-preserving laminoplasty

There is a superiority of deep extensor muscle-preserving laminoplasty in terms of postoperative axial pain, QOL, and prevention of atrophy of the deep extensor muscles over conventional open-door laminoplasty for the treatment of CSM.

Lee et al, 2018 [29]

Prospective study

144

Laminoplasty procedure

Statistical analysis revealed that high T1 slope and low summation of CSAs at each level of the semispinalis cervicis is correlated with loss of cervical lordosis. The level of the semispinalis cervicis associated with greater loss of lordosis was the C6 level.

**Table 3.** Classification of Cervical Spine Muscles Based on Their Function
Function of cervical musculature
Flexion
Sternocleidomastoid
Longus colli
Longus capitis
Rectus capitis anterior
Stylohyoid
Digastric
Mylohyoid
Geniohyoid
Omohyoid
Sternohyoid
Sternothyroid
Extension
Splenius capitis
Splenius cervicis
Semispinalis capitis
Semispinalis cervicis
Longissimus capitis
Longissimus cervicis
Trapezius
Interspinal
Rectus capitis posterior major
Rectus capitis posterior minor
Obliquus capitis superior
Rotation
Sternocleidomastoid
Trapezius
Splenius capitis
Longissimus capitis
Obliquus capitis inferior
Rectus capitis posterior major
Longus capitis
Rotators
Multifidus
Lateral flexion
Scalene
Splenius capitis
Longus colli
Levator scapulae
Iliocostalis cervicis
Intertransversarii

Table 3. Classification of Cervical Spine Muscles Based on Their Function

Function of cervical musculature

Flexion

Sternocleidomastoid

Longus colli

Longus capitis

Rectus capitis anterior

Stylohyoid

Digastric

Mylohyoid

Geniohyoid

Omohyoid

Sternohyoid

Sternothyroid

Extension

Splenius capitis

Splenius cervicis

Semispinalis capitis

Semispinalis cervicis

Longissimus capitis

Longissimus cervicis

Trapezius

Interspinal

Rectus capitis posterior major

Rectus capitis posterior minor

Obliquus capitis superior

Rotation

Sternocleidomastoid

Trapezius

Splenius capitis

Longissimus capitis

Obliquus capitis inferior

Rectus capitis posterior major

Longus capitis

Rotators

Multifidus

Lateral flexion

Scalene

Splenius capitis

Longus colli

Levator scapulae

Iliocostalis cervicis

Intertransversarii