Being a part of transversospinal muscle group along with semispinalis and multifidus, rotatores comprise the deep layer of deep, or intrinsic, muscles of the back. They can be divided regionally into rotatores colli/cervicis, rotatores thoracis and rotatores lumborum. Rotatores colli and lumborum are often inconsistent, and can be replaced by deep fibers of the multifidus. As rotatores thoracis are the most developed, the emphasis is placed on them during your anatomy classes and in standard textbooks. They are located in the thoracic spine and can be further subdivided into long rotatores and short rotatores, based on the length of their muscle fibers.
|Origin||Rotatores breves: Transverse processes of vertebrae T2-T12
Rotatores longi: Transverse processes of thoracic vertebrae
|Insertion||Rotatores breves: Laminae/Spinous process of vertebra (1 level above origin)
Rotatores longi: Laminae/Spinous process of vertebra (2 levels above origin)
|Actions||Bilateral contraction: Extension of thoracic spine
Unilateral contraction: Rotation of thoracic spine (contralateral)
|Innervation||Medial branches of posterior rami of spinal nerves|
|Blood supply||Dorsal branches of posterior intercostal and lumbar arteries|
This article will describe the anatomy and functions of the rotatores muscles.
Origin and insertion
Rotatores thoracis are small, quadrilateral muscles located between thoracic vertebrae. There are eleven pairs of muscles usually, but some may be absent at either end of the thoracic spine. They are attached as follows:
- Long rotators (rotatores longi): Originate from the transverse processes of thoracic vertebrae and insert into the bases of spinous processes and laminae of thoracic vertebrae located two levels above.
- Short rotators (rotatores breves): They have identical attachments as the long rotators, but extend only one level above their origin. Therefore, they are shorter.
Rotatores occupy the third, or deep layer of the intrinsic back muscles. They are the deepest and shortest transversospinal muscles. Rotatores overlie the muscles of the deepest layer, namely interspinales, intertransversarii and levatores costarum.
The erector spinae muscle group (iliocostalis, longissimus, spinalis) are located lateral to the rotatores. In turn, they are covered by the splenius muscles, spinalis muscles and erector spinae aponeurosis.
Rotatores are innervated by the medial branches of posterior rami of spinal nerves.
Rotatores receive arterial blood from the dorsal branches of posterior intercostal and lumbar arteries. They arise from the supreme intercostal artery and thoracic aorta.
As rotatores colli and lumborum are quite inconsistent and often missing, rotatores thoracis are the most important sub-type acting on the spine. Bilateral contraction results in extension of the vertebral column, while unilateral (one sided) contraction causes contralateral rotation of the thoracic spine.
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However, the rotatores muscles occupy positions of very poor mechanical leverage and studies have shown a minimal contribution of the rotatores towards spine movements. Instead, they function as important stabilizers of the vertebral column, acting as extensible ligaments that adjust their length to support adjacent vertebrae.
More details about the rotatores and deep muscles of the back are provided below: