Normal and Pathological Spinal Muscle


Fig. 1

The four cervical muscle groups [1]



Deep Muscles


The deep muscles are pure intrinsic muscles.



Longus Colli


Longus colli is an anterior intrinsic muscle of the lower cervical spine.


It is immediately prever tebral and presents three fascicles (Fig. 2).


  1. 1.

    Para-median longitudinal deep fascicle extending from the body of C2 to that of T3,


     

  2. 2.

    Ascending upper oblique fascicle extending from the transverse processes of C3–C6 to the anterior tubercle of the atlas,


     

  3. 3.

    Descending lower oblique fascicle which extends from the transverse processes of C4–C7 to the bodies of T2 and T3.


     

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Fig. 2

Longus colli and supra- and infrahyoid muscles: (a) left lateral view, (b) anterior view


These three fascicles create a diamond construct in which the bodies and discs of the lower cervical spine are inscribed. Longus colli is a flexor which flattens the cervical lordosis. It also has a stabilizing function to which we shall return.



The Intertransversarius


The intertransversarius is a muscle that extends throughout the spine and is considered as an intrinsic lateral muscle.



The Transversarius Spinalis


The transversarius spinalis extends along the entire length of the column; it is a posterior intrinsic muscle divided into three layers: semi-spinous fascicles, long fascicles (multifidus), and short fascicles (rotatores).


The Peripheral Muscles


These are totally extrinsic muscles.


The supra- and infrahyoid muscles are anterior extrinsics.


The mylohyoideus (mylohyoid) is the only suprahyoid muscle; there are, on the other hand, four infrahyoid muscles, thyrohyoid, sternohyoid, sternothyroid, and omohyoid. All these muscles act mainly in phonation but have an action of cervical flexion against resistance. Poisson [2], recently demonstrated by an isometric and electromyographic force study on rugby players, that the protection of the teeth with a buccal protection system had an effect of increase of force of the cervical flexors and thus, a priori, a protective effect of the cervical spine (Fig. 3).

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Fig. 3

Activation of the supra- and infrahyoid muscles by clamping on a dental protective gutter [2]


The Sternocleidomastoid (SCM)


The SCM includes a fascicle that originates on the clavicle and a second on the sternal manubrium. It ends on the cranial side at the level of the mastoid but also on the upper occipital line. This muscle constitutes a large muscular band obliquely extending downward and forward and contains three fascicles: a deep cleidomastoideus and two superficial (cleido-occipital posteriorly, covering the deep and sterno-mastoideus anteriorly, ending in a true tendinous attachment to the sternal manubrium (Fig. 4). This muscle, innervated by the accessory nerve (XIth cranial nerve), has an action in the sagittal plane which varies according to whether or not the cervical column is locked in flexion, by the longus colli in particular; the contraction of the two SCM induces in the first case a flexion and in the second a hyper-extension [1]. In an unilateral contraction, SCM causes a homolateral inclination and a contralateral rotation: this is the attitude observed in the congenital torticollis where there is retraction of this muscle (Fig. 5).

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Fig. 4

Anatomy of the sternocleidomastoid muscle (left lateral view)


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Fig. 5

Actions of the sternocleidomastoid muscle


The Trapezius


It is a muscle which is at the same time cervical and thoracic since it inserts superiorly on the external occipital protuberance, inferiorly on the spinous processes down to T11 and ends on the shoulder girdle on the lateral third of the clavicle for its clavicular fascicle, on the acromion for its acromial fascicle and on the spine of the scapula for its spinal fascicle. This muscle is innervated by the accessory nerve (XIth cranial nerve) and by the cervical plexus (C2 and C3). It is an essential stabilizer of the head in the sagittal plane and an extender when the two muscles contract. Like the SCM, its unilateral contraction causes a homolateral inclination and a contralateral rotation (Fig. 6).

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Fig. 6

Trapezius muscle action in tilt-rotation


The Intermediate Muscles Extending Upwards


These are intrinsic muscles with proximal insertion on the base of the skull and distal insertion on the upper cervical spine.


Three anterior sub-occipital muscles (Fig. 7) [3]:



  • The longus capitis which is positioned between the basilar process of the occiput and the anterior tuberculum of C3–C6.



  • The rectus capitis anterior located between the anterior limit of the occipital foramen and the lateral mass of the atlas.



  • The rectus capitis lateralis, parallel to the preceding one.



  • These three muscles are flexors and homolateral rotators.


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Fig. 7

Anterior sub-occipital muscles and scaleni


Four posterior sub-occipital muscles (Fig. 8):



  • The rectus capitis posterior major positioned between the inferior nuchal line of the occiput and the axis spinous process; it extends and inclines the head but has no real rotatory action.



  • The rectus capitis posterior minor, more medial, situated between the inferior nuchal line and the posterior ring of the atlas; it is an extensor.



  • The obliquus capitis inferior positioned between the transverse process of the atlas and the spinous process of the axis and which operates on the atlas, according to Kapandji [3] with the opposite obliquus capitis inferior acting as a pair of reins (Fig. 9). It controls homolateral rotation of the atlas.


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Fig. 8

Sub-occipital posterior muscles: (a) posterior view, (b) left lateral view


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Fig. 9

Stabilizing action on C1–C2 of the obliquus capitis inferior


The three following muscles are positioned between the skull and the spine and lie between the plane of the posterior sub-occipital muscles which have just been described and the trapezius; those are:



  • The semispinalis capitis extending from the superior nuchal line to the transverse processes from C3 to T5 (Fig. 10).



  • The longissimus capitis which extends from the mastoid process to the transverse processes from C3 to T1.


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Fig. 10

Posterior muscles from the neck to the head


These two muscles are pure extensors with a tilt component for the longissimus capitis.



  • The splenius capitis is inserted on the mastoid and the superior nuchal line and ends on the cervical spinous process. It is a powerful extensor and a homolateral rotator; it has in this movement a synergistic action with the controlateral SCM.


The Intermediate Muscles Extending Downwards


These are rather extrinsic muscles with a proximal insertion on the cervical spine but distal insertion at a distance on the thoracic spine, the ribs, or the scapula.


Scaleni


There are three (Fig. 7)



  • The scalenus anterior which extends from the anterior tubercle of the transverse processes from C3 to C6 to the upper surface of the first rib.



  • The scalenus medius which extends from the edge of the transverse process gutters of C2–C7 and ends on the same first rib behind the subclavian artery.



  • The scalenus posterior that extends from the posterior transverse tubercle of C4–C6 and ends on the second rib.


Besides their respiratory role, these muscles are flexors and lead to a homolateral inclination with contralateral rotation.



The Longissimus Cervicis


It extends from the transverse processes of the last four cervical vertebrae to those of the first five thoracic vertebrae; it is a powerful extensor.



The Ilio-Costalis (Fig. 10)


It has nearly the same origin as the preceding muscle; more lateral, it ends on the posterior arch of the first pair of ribs.



The Epi-Spinalis


It extends between the spinous processes of C2 to C7 and participates in the constitution of the star-like formation of muscles around the spinous process of C2; we have shown only the cranial insertions in Fig. 8.



The Splenius Cervicis


It extends from the transverse processes of C1 to C3 to the spinous processes of the first five thoracic vertebrae; it is a direct extensor.



The Levator Scapulae


It is inserted on the tip of the transverse processes of the first four cervical vertebrae and after a tortuous path joins the superior medial angle of the scapula; if the scapula is fixed, it causes a homolateral extension-inclination.


Thoraco-Lumbar Muscles


The thoraco-lumbar muscles can be simplified by division into three groups (Fig. 11)


  1. 1.

    The posterior or dorsal group which will extends inferiorly towards the lumbo-sacral junction.


     

  2. 2.

    The lateral group with the psoas and the quadratus lumborum.


     

  3. 3.

    Finally, the anterior or ventral group with the muscles of the abdominal wall.


     

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Fig. 11

(a) The three groups of thoraco-lumbar muscles. Dorsal group, lateral group, ventral group. (b) Horizontal cut at the lumbar level of the posterior thoraco-lumbar muscles; note the difference in surface between the psoas and the paravertebral muscles. (Conservatory of Anatomy, Montpellier—Pr F. Bonnel)


The set of posterior and lateral groups envelops the spinal column as the muscles of the thigh envelop the femur to realize a composite beam which has a protective function, we will return to this in the chapter on functional anatomy (Chap. 30) (Fig. 12).

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Fig. 12

Composite spinal beam


Posterior Muscle Group


The Deep Plane


The deep plane (Fig. 13) consists of the inter-spinous muscles and the inter-transversal muscles, the segmental muscles situated between the spinous processes and between the transverse processes, respectively.

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Fig. 13

Deep posterior muscles


The transversus spinosus that exists at the cervical level is situated, according to Trolard, between the tip of the transverse process and the spinous processes or the laminae of the four overlying vertebrae. They are therefore muscular rafters (like the supports of a roof) which is commonly called the multifidus. More laterally and more superficially, we find the epi-spinalis of the thorax and the semi-spinous. The latter is purely thoracic and is situated between the transverse processes of the thoracic vertebrae and the spinous processes of the lower cervical vertebrae.


The spinalis thoracis also exists in the neck. It is more superficial and extends from the lateral surfaces of spinous processes from the thoracic region to the upper lumbar region where it is very close to the multifidus.


The longissimus thoracis, which extends from the longissimus capitis and the longissimus cervicis, unites downwards with the ilio-costalis to constitute the lumbo-sacral common mass. It inserts into the accessory processes of the lumbar vertebrae, the transverse processes of the thoracic vertebrae, and the posterior arch of the ribs.


The ilio-costal inserts on the posterior arch of the ribs and on the iliac crest.


About these deep posterior muscles, we can make three observations:



  • According to Kapandji [3], the third lumbar vertebra at the apex of the lumbar lordosis, horizontal in the sagittal plane, is a true muscular relay (Fig. 14) since it receives from superiorly the longissimus and epi-spinalis thoracis and from inferiorly, the multifidus. This muscular disposition is reminiscent of that of the muscles around the posterior arch of C2.



  • Functionally, these posterior deep muscles are extensors and have rather a stabilizing function as shown by their composition in type 1 fibers (slow) and type 2 fibers (fast). Jorgensen [4] and Bagnall [5] demonstrated that these muscles were more rich in slow fibers than the superficial posterior muscles. It is interesting to note that in degeneration (or natural aging) these deep posterior muscles degenerate first and are replaced by fat and this normally occurs, from caudad to cephalad, from the lumbo-sacral junction to the upper lumbar spine.



  • Finally, at the base, the ilio-costalis, longissimus, and multifidus, although constituting the lumbo-sacral common mass, are separated by cleavage planes containing fat tissue. The multifidus—longissimus space can easily be dissociated with a finger and thus we can easily reach the articular processes or the transverse processes (classic Wiltse approach [6]) (Fig. 15).


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Fig. 14

Concentric termination of the muscles like a star on the spinous process of L3: (a) left lateral view, (b) posterior view


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Fig. 15

Wiltse approach [6] between the multifidus and the longissimus


The Intermediate Plane


It consists of the serratus posterior—superior and inferior (Fig. 16). The serratus posterior superior is situated between the spinous processes of the last two cervical vertebrae and those of the first two thoracic vertebrae and the first ribs.

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Fig. 16

Posterior muscles of the medium plane


The serratus posterior inferior is inserted on the spinal processes of the last thoracic vertebrae and the first lumbar vertebrae and ends on the caudal margin of the last four ribs. These two muscles have a function in inspiration.


The Superficial Plane


It consists of the trapezius , the rhomboideus, the latissimus dorsi, which are mobilizers of both the spine and the scapular girdle.


Lateral Muscle Group


These lateral muscles are located in the lumbar spine (Fig. 17).


  1. 1.

    The ilio-psoas consists of three heads (small and large psoas and iliac). It is innervated by the femoral nerve and has an action of lateral bending-rotation of the hip. Its action on the vertebral column is discussed: its contraction causes a homolateral inclination and a contralateral rotation (Fig. 18). In the sagittal plane, it is a lordosing muscle with lumbo-sacral flexion, as shown in the diagram of Kapandji [3] (Fig. 19).

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Apr 25, 2020 | Posted by in ORTHOPEDIC | Comments Off on Normal and Pathological Spinal Muscle

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