Levatores Costarum Muscles Anatomy

The levatores costarum muscles (L. levator, a lifter) are 12 fan-shaped muscles that elevate the ribs, but their role, if any, in normal inspiration is uncertain. They may play a role in vertebral movement and/or proprioception.

The Levatores Costarum muscles represent a clinically significant yet often overlooked group in thoracic anatomy. These twelve paired muscles play crucial roles in respiratory mechanics and vertebral stability, deserving detailed examination by clinicians involved in thoracic, pulmonary, and musculoskeletal medicine.

Levatores Costarum Muscles Anatomy

The Levatores Costarum muscles originate from the transverse processes of the seventh cervical vertebra (C7) and the first through eleventh thoracic vertebrae (T1-T11). They insert onto the rib directly below their vertebral origin, specifically on the superior border and external surface between the tubercle and angle of the rib. This arrangement creates an oblique orientation where each muscle spans from a superior vertebra to an inferior rib.

These muscles are categorized into two distinct types: Levatores Costarum Breves and Levatores Costarum Longi. The Breves, more numerous and consistent, extend from their vertebral origin to the immediately adjacent rib below. The Longi, found primarily in the lower thoracic region, span beyond the adjacent rib to insert on the second rib below their origin. This extended architecture provides additional mechanical advantage for respiratory movements in the lower thoracic cage.

Histologically, the Levatores Costarum demonstrate a predominance of type I slow-twitch muscle fibers, consistent with their role in maintaining postural support during respiration. Their fascicular arrangement allows for fine-tuned control during the respiratory cycle while providing stability to the thoracic vertebrae.

Neurovascular Supply

Innervation of the Levatores Costarum comes from the dorsal rami of the spinal nerves at the corresponding vertebral levels (C8 and T1-T11). This segmental innervation pattern aligns with their metameric embryological development. The posterior intercostal arteries, branches of the thoracic aorta, provide the primary blood supply, with venous drainage occurring through accompanying posterior intercostal veins that ultimately return to the azygos system.

Functional Significance

The Levatores Costarum serve dual functional roles in thoracic biomechanics. Primarily, they act as accessory muscles of respiration, specifically during deep or forced inspiration. When contracting bilaterally, they elevate the ribs, increasing the anteroposterior diameter of the thoracic cavity. This action becomes particularly significant during increased respiratory demand, such as in patients with chronic obstructive pulmonary disease (COPD) or during high-intensity exercise.

Their secondary function involves lateral flexion of the vertebral column when contracted unilaterally. This action contributes to thoracic spinal mobility and postural control. Additionally, these muscles provide proprioceptive feedback regarding thoracic position due to their rich supply of muscle spindles.

Recent biomechanical studies suggest that the Levatores Costarum also function as dynamic stabilizers of the thoracic spine, particularly during rotational movements. Their activation patterns during various respiratory phases reveal complex coordination with other thoracic musculature, including the intercostals and transversospinalis group.

Clinical Implications

The Levatores Costarum hold significant relevance in various clinical contexts. In respiratory disorders, particularly those involving increased work of breathing, these muscles may undergo compensatory hypertrophy. This adaptation can be observed radiographically and during physical examination in patients with advanced pulmonary disease.

Dysfunction of these muscles has been implicated in thoracic spine disorders, including segmental hypomobility and facet joint syndrome. Their close anatomical relationship with the thoracic facet joints makes them susceptible to reflex inhibition following joint dysfunction. Conversely, trigger points within the Levatores Costarum can refer pain to the adjacent intercostal spaces, potentially mimicking pleuritic or cardiac pain.

Surgical approaches to the posterior thoracic spine necessitate careful consideration of these muscles. Their segmental innervation means that surgical disruption can lead to localized weakness and potential respiratory compromise, particularly in patients with pre-existing pulmonary insufficiency.

Advanced Imaging and Assessment

Modern imaging modalities have enhanced our understanding of these muscles. High-resolution MRI can delineate the Levatores Costarum from surrounding musculature, allowing assessment of their morphology in various pathological states. Ultrasonography offers dynamic evaluation of these muscles during respiratory cycles, providing insights into their functional recruitment patterns.

Electromyographic studies demonstrate that the Levatores Costarum exhibit phasic activation during deep inspiration, with increased recruitment during elevated respiratory demands. This activation pattern suggests their role as a respiratory reserve, mobilized when primary respiratory muscles approach fatigue thresholds.

Developmental Anatomy

Embryologically, the Levatores Costarum derive from the epimeric compartment of the paraxial mesoderm, sharing origins with other deep back muscles. Their development follows the segmental pattern of the thoracic vertebrae, with complete differentiation occurring by the late fetal period. This developmental trajectory explains their consistent metameric arrangement and segmental innervation pattern.

Evolutionary perspectives suggest that these muscles have been conserved across mammalian species, indicating their fundamental importance in thoracic function. Comparative anatomical studies reveal similar architectural patterns in quadrupeds, although with variations reflecting the different gravitational challenges of bipedal versus quadrupedal locomotion.

Therapeutic Considerations

For medical professionals, understanding the Levatores Costarum has therapeutic implications. Manual therapy techniques targeting these muscles can improve thoracic mobility and respiratory mechanics. Specific rehabilitation protocols emphasizing their activation may benefit patients with thoracic spine dysfunction or respiratory insufficiency.

Respiratory rehabilitation programs increasingly incorporate techniques to strengthen these muscles, particularly in post-surgical patients or those with chronic respiratory conditions. Progressive loading exercises focusing on thoracic extension and rotation can enhance their functional capacity and contribute to improved respiratory efficiency.

The interface between the Levatores Costarum and adjacent fascial structures represents an emerging area of clinical interest. Fascial manipulation techniques directed at thoracolumbar fascia can influence the function of these muscles, potentially addressing both respiratory and postural dysfunctions.

Resources for Medical Professionals

• Gray H, Williams PL, Bannister LH. Gray’s Anatomy: The Anatomical Basis of Medicine and Surgery. 41st ed. Elsevier; 2020. https://www.elsevier.com/books/grays-anatomy/standring/978-0-7020-7705-2
• Standring S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2021. https://www.elsevier.com/books/grays-anatomy/standring/978-0-7020-7926-1
• Netter FH. Atlas of Human Anatomy. 7th ed. Elsevier; 2018. https://www.elsevier.com/books/atlas-of-human-anatomy/netter/978-0-323-39322-5
• Bordoni B, Varacallo M. Anatomy, Head and Neck, Levatores Costarum Muscle. StatPearls Publishing; 2022. https://www.ncbi.nlm.nih.gov/books/NBK541055/