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Interspinales Muscles Anatomy

Last updated on: February 26, 2025

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The interspinales muscles represent a crucial yet often overlooked component of the deep postural musculature of the spine. These small, paired muscles run along the spinous processes of adjacent vertebrae and play a significant role in spinal stability and movement. This article provides an in-depth examination of interspinales muscle anatomy, neurovascular supply, function, and clinical significance for medical professionals.

Interspinales Muscles Anatomy

The interspinales are short, paired muscles that connect the spinous processes of adjacent vertebrae. These muscles are most developed in the cervical and lumbar regions, where spinal mobility is greatest, and are often rudimentary or absent in the thoracic region where the spinous processes overlap significantly.

Origin & Insertion

In the cervical region, the interspinales cervicis originate from the superior aspect of the spinous processes of the C3 to T1 vertebrae and insert on the inferior aspect of the spinous processes of the C2 to C7 vertebrae. These muscles are particularly well-developed in this region, reflecting the enhanced mobility of the cervical spine.

The thoracic region displays variable presence of the interspinales thoracis. When present, these muscles typically connect the spinous processes of T1-T2, T2-T3, and T10-T11, T11-T12. Their inconsistent development correlates with the reduced mobility of the thoracic spine due to the ribcage attachments and the overlapping orientation of thoracic spinous processes.

In the lumbar region, the interspinales lumborum are robust and well-defined. They originate from the superior aspects of the spinous processes of L2 to L5 vertebrae and insert onto the inferior aspects of the spinous processes of L1 to L4 vertebrae. The substantial development of these muscles in the lumbar region contributes to the stability required for the load-bearing function of the lower back.

Neurovascular Supply

The neurovascular anatomy of the interspinales muscles follows a segmental pattern, consistent with their metameric development. These muscles receive innervation from the posterior (dorsal) rami of the spinal nerves at their respective levels. This innervation pattern is critical for maintaining proper muscle tone and coordinating the fine movements necessary for spinal stability.

The arterial supply to the interspinales varies by region. The cervical muscles receive blood primarily from branches of the vertebral artery, deep cervical artery, occipital artery, and transverse cervical artery. The thoracic muscles are supplied by the superior intercostal artery, posterior intercostal arteries, and subcostal artery. The lumbar muscles receive their blood supply predominantly from the lumbar arteries, which are direct branches of the abdominal aorta.

Venous drainage follows a similar segmental pattern, with blood returning via the vertebral venous plexus, which communicates with both the internal and external vertebral venous systems. This extensive venous network is significant clinically as it can serve as a pathway for the spread of infection or metastatic disease.

Functional Significance

Despite their small size, the interspinales muscles serve crucial functions in spinal biomechanics. Their primary action is extension of the spine, particularly in the cervical and lumbar regions where they are most developed. However, their significance extends beyond simple movement to include proprioceptive feedback and postural control.

The strategic positioning of these muscles between adjacent spinous processes places them in an optimal position to provide proprioceptive information about the relative position of vertebrae. This proprioceptive function is essential for coordinating the complex movements of the spine and maintaining postural awareness.

Furthermore, these muscles contribute to the maintenance of spinal stability through their role in the deep muscular system. Along with other deep spinal muscles such as the intertransversarii and multifidi, they form an integrated network that provides segmental stability to the spine. This stability is particularly important during dynamic movements when the larger, more superficial muscles generate significant forces.

Origin	Interspinales cervicis: Superior aspect of spinous processes of vertebrae C3-T1 Interspinales thoracis: Superior aspect of spinous process of vertebrae T2, T11 & T12 (variable) Interspinales lumborum: Superior aspects of spinous processes of vertebrae L2-L5
Insertion	Interspinales cervicis: Inferior aspect of spinous processes of vertebrae C2-C7 Interspinales thoracis: Inferior aspect of spinous processes of vertebrae T1, T10 & T11 Interspinales lumborum: Inferior aspects of spinous processes of vertebrae L1-L4
Innervation	Posterior rami of spinal nerves
Blood Supply	Interspinales cervicis: vertebral artery, deep cervical artery, occipital artery, transverse cervical artery Interspinales thoracis: superior intercostal artery, posterior intercostal arteries, subcostal artery Interspinales lumborum: lumbar arteries
Action	Extension of cervical and lumbar spine

Clinical Relevance

The interspinales muscles hold significant clinical relevance for medical professionals across various specialties. Understanding their anatomy and function can inform clinical reasoning and treatment approaches for several conditions.

In cases of chronic low back pain, dysfunction of the deep spinal muscles, including the interspinales, has been implicated. Research suggests that these muscles may atrophy in chronic pain conditions, leading to reduced segmental stability and altered movement patterns. Rehabilitation strategies often target these deep muscles to restore proper function and alleviate pain.

Surgical approaches to the posterior spine must consider the attachment and innervation of the interspinales muscles. Minimally invasive techniques aim to preserve these muscles to maintain postural stability post-operatively and reduce the risk of failed back surgery syndrome.

In the context of spinal trauma, damage to the interspinales may occur with hyperflexion injuries or fractures involving the spinous processes. While these injuries may not be immediately apparent or clinically significant in isolation, they can contribute to post-traumatic instability and pain when combined with other ligamentous or osseous injuries.