Functional Anatomy of the Thoracic Spine and Rib Cage

Original Editor - Ewa Jaraczewska

Top Contributors - Ewa Jaraczewska and Jess Bell  

Introduction

The thoracic spine has an important role in the stability and posture of the spinal complex. Thoracic pain is a common clinical presentation that creates burden for the individual, community and workforce. According to research, one-fifth of all people experience thoracic spine pain in their lifetime. A good understanding of the anatomy, physiology, biomechanics and innervation of the thoracic complex enables clinicians to properly evaluate, diagnose and treat various thoracic pathologies. This article discusses the key anatomical structures of the thoracic vertebrae and rib cage, including the bony structures, articulations, ligaments, muscles, nerves and the vascular supply.

Key Terms

Axes: lines around which an object rotates. The rotation axis is a line that passes through the centre of mass. There are three axes of rotation: sagittal passing from posterior to anterior, frontal passing from left to right, and vertical passing from inferior to superior. The rotation axes of the foot joints are perpendicular to the cardinal planes. Therefore, motion at these joints results in rotations within three planes. Example: supination involves inversion, internal rotation, and plantarflexion.

Bursae: reduce friction between the moving parts of the joints. A bursa is a fluid-filled sac. There are four types of bursae: adventitious, subcutaneous, synovial, and sub-muscular.

Capsule: one of the characteristics of the synovial joints. It is a fibrous connective tissue which forms a band that seals the joint space, provides passive and active stability and may even form articular surfaces for the joint. The capsular pattern is "the proportional motion restriction in range of motion during passive exercises due to tightness of the joint capsule."

Closed pack position: the position with the most congruency of the joint surfaces. In this position, joint stability increases. For example, the closed pack position for the interphalangeal joints is full extension.

Degrees of freedom: the direction of joint movement or rotation; there is a maximum of six degrees of freedom, including three translations and three rotations.

Ligament: fibrous connective tissue that holds the bones together.

Open (loose) pack position: position with the least joint congruency where joint stability is reduced.

Planes of movement: describe how the body moves. Up and down movements (flexion/extension) occur in the sagittal plane. Sideway movements (abduction/adduction) occur in the frontal plane. The transverse plane movements are rotational (internal and external rotation).

Thoracic Spine Structure

The thoracic spine is located between the cervical and lumbar spine. It consists of twelve vertebrae, and it is the stiffest part of the spine due to its structure and connection to the rib cage. Thoracic spine mobility affects the mobility of several other structures, including the cervical spine, shoulder joint, and rib cage. For example, thoracic spine extension correlates directly with bilateral arm elevation.

Primary roles of the thoracic spine include:

• protection of the spinal cord
• support for the thorax and abdomen
• providing attachments for the ribs
• allowing for flexibility and mobility of the body

Thoracic Vertebrae

Each thoracic vertebra contains the following structural elements:

• Vertebral body: medium-sized and connected with the next vertebral body via an intervertebral disc.

• Costal facets: articulation surfaces that connect the rib with thoracic vertebrae. They are located on the transverse processes of T1 through T9 (T10 may or may not have a costal facet), and they articulate with the tubercles of the ribs. Each thoracic vertebra has two costal facets, and each pair of facets may have a different inclination angle and shape (flat versus concave) when compared with facets on other thoracic vertebrae. The relative location of the costal facet may be asymmetrical.
• Superior and inferior demi-facets: located on the sides of each vertebral body of T2 through T9. They serve as articulating points for the heads of the ribs. The superior demi-facet is directed posteriorly and slightly lateral and articulates with the corresponding rib. The inferior demi-facet is directed anteriorly and slightly medially and articulates with the rib below.

• Bilateral pedicles: belong to the posterior element of the thoracic vertebra. Together with two laminae, they form the vertebral arch.

• Transverse processes: short and stout. They face in the posterior, inferior and lateral directions. Each transverse process articulates with a tubercle of the rib via the transverse costal facet.

• Spinous process: long and face posteroinferiorly (downward angle). Its primary role is to protect the spinal cord.

• Two superior and two inferior thoracic articular processes: the superior articular surface is flat and faces posterolaterally.

Atypical Features of the Thoracic Vertebrae

T1: the superior costal facets of T1 are full costal facets (unlike the demi-facets of T2 through T9 vertebrae). This accommodates the articulation with the first rib. The spinal process is long and almost horizontal.

T9: lacks an inferior demi-facet.

T11/T12: have a pair of full costal facets to allow for the articulation with ribs 11 and 12. The same feature may sometimes be present on T10. The transverse processes lack facets.

T12 transitional (T12 TLTV, Thoracolumbar transitional vertebrae): thoracolumbar transitional vertebrae can occur at T12. A T12 TLTV results "from the overlap or shift of thoracic and lumbar somites at the thoracolumbar junction." It is characterised by the presence of thoracic vertebrae features, such as costal facets and superior articular facets, and lumbar vertebrae features, such as the articular processes. It also has mammillary processes on the posterior surface of the superior articular processes - these serve as an attachment point for the intertransversarii and multifidus muscles. T12 TLTV lacks prominent transverse processes. NOTE: A transitional vertebra, which is known as L1TLTV, occurs less frequently at the lumbar level.

Thoracic Kyphosis

Kyphosis=the natural curve of the thoracic spine.

Thoracic Range of Motion

Thoracic spine range of motion measurements vary depending on the instrument used. A systematic review and meta-analysis by Esteban-González et al. found that the most important part of the performance protocol to measure active thoracic range of motion "is the initial measurement positions adopted by the subjects". Therefore, a standardised performance protocol should be established, and it should include initial measurement positions.

The thoracic spine can be assessed using the following methods:

• Visual observation
• Schober test (tape measure)
• Inclinometer
• Goniometer
• Finger-to-floor distance (FFD)

Visual observation

A postural assessment of the thoracic spine is completed with the patient standing and feet slightly apart. The healthcare practitioner observes the patient's posture from the side view. Thoracic posture is classified as hypokyphosis, normal kyphosis or hyperkyphosis. This assessment is purely based on the clinical experience of the clinician.

Schober test

This test is completed using a tape measure with the patient in stting. T1 and T12 are palpated and marked. The distance between T1 and T12 is measured. Next, the patient is asked to perform thoracic spine flexion as far as they can (end-range flexion), and the clinician measures the distance between the same landmarks. Finally, the difference between the two measurements is recorded. This is the thoracic spine Schober test. Thoracic spine extension is measured by recording the difference between neutral and active end-range thoracic spine extension.

The following values are considered in the normal range:

• Flexion: >2.7 cm
• Extension: >2.5 cm

Inclinometer

This test is completed using a bubble inclinometer with the patient in sitting. The clinician marks the skin over the spine on the C7 and T12 spinous processes. The cephalic foot of the inclinometer is placed on the mark corresponding with C7. The caudal foot of the inclinometer is placed on the mark corresponding with T12. The difference between the two measures is the degree of thoracic kyphosis.

"The gravity-dependent (analogue) inclinometer has criterion validity when measuring thoracic kyphosis, comparable to the lateral thoracic spine radiograph, the gold standard. For those individuals presenting clinically with conditions where progressive kyphosis is problematic, it is possible for the clinician to monitor their condition using inclinometer measurements, potentially reducing the need for repeated radiographs that expose patients to harmful radiation".

Goniometer

The four movements of the thoracic spine (flexion, extension, lateral flexion, and rotation) can be assessed using a goniometer. However, the rotation assessment may not be reliable as it is difficult to differentiate thoracic rotation from lumbar spine rotation. Normal ranges are as follows:

• Flexion: 20-45 degrees
• Extension: 25-45 degrees
• Lateral Flexion: 20-40 degrees
• Rotation: 35 degrees

Finger-to-floor distance

The finger-to-floor distance (FFD) test assesses flexibility of the whole spine. The distance from the middle fingertip to the floor is measured for this test. Lateral flexion can also be measured using the FFD test. For lateral flexion, compare side-to-side results.

Rib Cage Structure

The rib cage consists of 12 pairs of ribs which articulate with the thoracic spine and the sternum.

The ribs are classified as follows:

• True ribs: ribs 1-7 directly articulate with the sternum via costal cartilage
• False ribs: ribs 8-10 indirectly articulate with the sternum via costal cartilage
• Floating ribs: ribs 11 and 12 have no articulation with the sternum.

Each rib has the following anatomical components:

• Head with two articular facets
• Tubercle
• Neck
• Shaft
• Costal groove

Not all ribs have the same structure. There are atypical ribs which are characterised by the following features:

• Rib 1 has two costal grooves and one articular facet
• Rib 2 has a tuberosity on its superior surface for the attachment of the serratus anterior muscle
• Rib 10 has only one articular facet
• Ribs 11 and 12 have one articular facet with no neck

  The thoracic spine and the ribs are considered a single unit that influences shoulder joint movement. Synchronised activities occur between the ribs and the shoulder joint; therefore, any chest wall procedures may lead to shoulder dysfunction.

Bones, Articulations and Kinematics of the Thoracic Spine

Bones and Articulations

Bones	Articulations	Characteristics	Key palpation points
Vertebral body	Intervertebral disc joint (IVD)	Located between the bodies of each vertebra. An intervertebral disc separates the vertebral bodies. Provides shock absorption, distributes load and allows flexibility.
Articular processes	Zygapophyseal joint (ZP)	Formed between the articular processes of each thoracic vertebra. Located on the left and right sides of the spine. Guides thoracic spine movement. No weight-bearing action.
Rib and vertebral body	Costovertebral joint (CV)	The heads of ribs 2-9 articulate with the bodies of two adjacent vertebrae: the superior costal facet of the corresponding vertebra, the inferior costal facet of the superior vertebra, and the intervertebral disc between the two vertebrae. The heads of the 1st, 10th, 11th and 12th ribs articulate with only one vertebra. Provide thoracic stabilisation, load bearing, and thoracic spine and chest wall movement. The motion of the ribs is known as a "pump-handle" or a "bucket handle" motion, which results in raising and lowering the sternal end of the rib. A strong contributor to respiratory effort.	The patient is sitting or standing with their back towards you, trunk flexed, and scapula protracted. To palpate the first rib, locate the C7 vertebra by palpating its long spinous process. The first rib is about two centimetres lateral and slightly inferior to the C7 spinous process. Trapezius and levator scapulae cover the first rib. This may make it difficult to palpate the first rib. The same method is applied to the second rib. Ribs three and four are located under the medial end of the spine of the scapula. Rib seven is under the inferior angle of the scapula. The costal angle of rib nine is at the level of the spinous process of the L1.
Rib and transverse processes	Costotransverse joint (CT)	Articular facet on the tubercle of ribs 1-10 articulates with the transverse process of the corresponding vertebrae (T1-T10). No CT joint exists between ribs 11/12 and T11/T12. Facilitate upward and outward movement of the ribs during respiration.
Ribs and sternum	Sternocostal joint (SC) (chondrosternal joint) and Costochondral joint (CC)	SC: direct articulation of the costal cartilage with the sternum CC: rib articulates with its costal cartilage Provide strength and allows flexibility of the ribcage. The rib-joint stiffness gradually decreases from T2 (the most stiff) to T10 (the least stiff). The first SC joint assists with inspiration by helping to increase the anteroposterior diameter of the thorax. Protect the internal organs (lungs, heart and thymus gland).	The sternum is located on the anterior wall of the thorax, in the middle of the rib cage. The second costal cartilage marks the superior portion of the sternum. The xiphoid process is located on the sternum's inferior end at the seventh costal cartilage level. You can palpate the xiphoid process by finding the small, pointed projection at the end of the sternum. The xiphoid process articulates directly with the costal cartilage of ribs seven and indirectly with the cartilage of ribs eight, nine, and ten.

Kinematics

• T7–T10 are responsible for 74% of the T1–T12 sagittal movement. However, these ranges change slightly with ageing:
  • 20-30 years: 78.5% of the total thoracic spine range of motion comes from the T7–T10 segment
  • 30–45 years.: 72.8% of the total thoracic spine range of motion comes from the T7-T10 segment
  • Over 45 years: 69.8% of the total thoracic spine range of motion comes from the T7-T10 segment

• The T10–T12 vertebral segment was found to be relatively fixed during peak respiratory movement
• Due to their limited mobility, the sternum, first shorter ribs, and first intervertebral discs can be considered the passive elements of the thoracic spine

Joint	Type of joint	Plane of movement	Motion	Kinematics	Closed pack position	Open pack position
Intervertebral disc joint	Cartilaginous joint, symphysis	Coronal Saggital Transverse	Rotation Flexion/Extension Lateral flexion	Rotation: nine degrees at T1 with an incremental decrease to two degrees at T12. Flexion/Extension: four degrees at T1 with an incremental increase to twelve degrees at T12. Lateral flexion: six to seven degrees per vertebral segment.	Full extension	Midway between flexion and extension
Zygapophyseal joint	SynovialPlane joint
Costovertebral joint	Synovial Plane joint		Gliding which produces the rising and lowering of the sternal end of a rib
Costotransverse (upper ten ribs only)	Plane joint (glide joint)		Joints 1-6: slight gliding and internal rotation of the neck of the ribs 1-6. Joints 7-10: posteromedial translation of neck of ribs 7-10. Joints 1-10: anterior and lateral chest expansion during inhalation.
Costochondral joints	Cartilaginous joints		No movement occurs in these joints
Sternocostal joint	Rib 1: Cartilaginous joint Ribs 2-12: Synovial, plane joint		No movement occurs in the first sternocostal joint (synarthrosis type of joint). Slight bending and twisting actions in other joints.

Thoracic Spine Ligaments

Key ligaments	Origin	Insertion	Action/role	Key palpation points
Anterior longitudinal ligament	Anterior portion of the vertebral body at the base of the skull	Anterior portion of the vertebral body at the sacrum	Limits extension of the vertebral column. Reinforces the intervertebral disc.
Posterior longitudinal ligament	Body of C2	Posterior surface of the sacrum	Limits flexion of the vertebral column. Reinforces the intervertebral disc.
Ligamentum flavum: A series of short ligaments that connect the laminae of each vertebra. There are two ligamenta flava at each vertebra. Each ligament is divided into: Medial portion: passes to the back of the next lower lamina and across the gap between adjacent vertebrae, fusing with the interspinous ligament Lateral portion: passes in front of the zygapophyseal joint, attaches to the anterior aspect of the inferior and superior articular processes and forms the anterior capsule. Most lateral fibres extend beyond the superior articular process to the pedicle below.	The lower half of the anterior surface of the lamina above	The posterior surface and upper margin of the lamina below	High elastin content prevents this ligament from buckling into the spinal canal. Assists with thoracic spine flexion and extension. Compresses the intervertebral discs.
Intertransverse ligaments	Transverse processes of the vertebra above	Transverse processes of the vertebra below	Contributes to the stability of the thoracic spine. Limits lateral flexion.	Apply the finger rule to palpate the transverse processes of the thoracic vertebra. To palpate the transverse processes of the T1 and T2 vertebrae, start by palpating the inferior margin of the spinous process of the corresponding thoracic vertebrae. Next, add one finger width in the lateral direction to palpate the T1 and T2 transverse processes. For T3 and T4, add 2 fingers width laterally from the inferior margin of the spinous process of T3 and T4. The lateral border of the top finger indicates the location of the transverse process. For T5 through T8, add 3 fingers width - the lateral border of the top finger will point at the transverse processes of the corresponding vertebrae. For T9 and T10, apply the two-finger rule and for T11 and T12, the one-finger rule.
Interspinous ligaments	Spinous processes of the vertebra above, between the ligamenta flava anteriorly and the supraspinous ligament posteriorly	Spinous processes of the vertebra below between the ligamenta flava anteriorly and the supraspinous ligament posteriorly	Limits forward flexion of the vertebral column.	To palpate the spinous processes of the thoracic spine, you can use the bony landmarks of the scapula: The inferior angle of the scapula corresponds to the T7 spinous process. The spine of the scapula corresponds to the T3 spinous process. The superior angle of the scapula corresponds to the T1 spinous process and the second rib. Note: this palpation method may not be reliable for individuals with scapula pathology (e.g. following stroke).
Supraspinous ligament	Tip of the spinous processes of the vertebra above from the seventh cervical vertebra to the third or fourth lumbar vertebra	Tip of spinous processes of the vertebra below	Prevents the separation of the spinous processes during forward flexion, thus limiting thoracic spine flexion.	An alternative method: To palpate the spinous processes of the thoracic spine, start by palpating the 12th rib. Follow the rib contour medially to find the spinous process of T12. From T12, start palpating along the spine in the cephalic direction to palpate the remaining spinous processes.
Radiate ligament: Superior band Inferior band Central band	Head of the rib	Two vertebral bodies and the intervertebral disc	Stabilise and allow some rib motion on the thoracic vertebra.
Costotransverse ligament	Dorsal surface of the neck of the rib	Anterior surface of the transverse process of the vertebra
Superior costotransverse ligament Anterior superior costotransverse ligament (ASCT) Posterior superior costotransverse ligament (PSCT)	ASCT: crest on the superior border of the neck of the rib PSCT: crest border of the superior rib	ASCT: anterior surface of the transverse process of the vertebra above PSCT: inferior border of the transverse process of the vertebra above
Lateral costotransverse ligament	Posterior surface of the tip of the transverse process	Nonarticular part of the tubercle of the analogous rib
Radiate sternocostal ligaments	Front and back of the sternal ends of the cartilages of the ribs 1-7	Anterior and posterior surfaces of the sternum.	Reinforce the sternocostal joint capsule	The sternum is located on the anterior wall of the thorax in the middle of the rib cage. The second costal cartilage marks the superior portion of the sternum. The xiphoid process is located on the sternum's inferior end at the seventh costal cartilage level. You can palpate the xiphoid process by finding the small, pointed projection at the end of the sternum. The xiphoid process articulates directly with the costal cartilage of ribs seven and indirectly with the cartilage of eight, nine, and ten.

Muscles of the Thoracic Spine and Rib Cage

The thoracic spine and rib cage muscles can be grouped according to their function and location.

When grouped according to function, the muscles of the thoracic spine and rib cage can be organised as follows:

• Thoracic Spine Flexors: internal obliques, rectus abdominus, and external obliques
• Thoracic Spine Extensors: multifidus, semispinalis thoracis, erector spinae
• Thoracic Spine Lateral flexors: erector spinae, internal obliques, external obliques
• Thoracic Spine Rotators: levatores costrum, multifidus, semispinalis thoracis, rotatores thoracis, internal obliques, external obliques
• Rib Mobilisers: levatores costrum, intercostals, serratus posterior superior and inferior

When grouped according to location, the muscles of the thoracic spine and rib cage can be divided as follows:

• The back muscles:
  • Superficial: semispinalis thoracis
  • Middle: rotatores thoracis, erector spinae, spinalis thoracis
  • Deepest: multifidus, levatores rostrum
• The rib muscles: levatores costarum, intercostals, serratus posterior superior and inferior
• The abdominal wall muscles: internal obliques, rectus abdominus, external obliques, diaphragm

The following tables group muscles according to their function. Please note that when a muscle has multiple functions, it is included in all relevant tables. These tables only list muscle actions associated with the thoracic spine and rib cage. Actions related to other regions/joints are discussed in the relevant page.

Thoracic Spine Flexors

Muscle	Origin	Insertion	Innervation	Action
Internal obliques	Thoracolumbar fascia Iliac crest Inguinal ligament	Lower four ribs Linea alba Pubic crest	Lower intercostal nerves Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve	Bilateral action: Thoracic spine flexion
Rectus abdominus	Pubis, pubic symphysis	Xiphoid process of the sternum Costal cartilage of ribs 5-7	Thoracoabdominal nerves	Thoracic spine flexion
External obliques	Ribs 5-12	Linea alba Pubic tubercle Iliac crest	Intercostal nerves T7-T11 and the T12 subcostal nerve	Bilateral action: Thoracic spine flexion

Thoracic Spine Extensors

Muscle	Origin	Insertion	Innervation	Action
Transversospinalis muscle group: Multifidus (MF) Semispinalis Thoracis (ST)	MF: Transverse processes of T1-T12 ST: Transverse processes of T6-T10	MF: Spinous process of the vertebra above ST: Spinous processes of C6 to T4	Medial branches of the posterior rami of the spinal nerves in the corresponding thoracic region	Bilateral action: Thoracic spine extension
Erector spinae: Iliocostalis thoracis (ICT) Longissimus thoracis (LT) Spinalis thoracis (ST) Illiocostalis lumborum (ICL)	ICT: ribs 7-12 LT: transverse processes of L1-L5 and the thoracolumbar fascia ST: spinous processes of T11-L2 ICL: iliac crest	ICT: ribs 1-6 and the transverse process of C7 LT: transverse processes of T1 to T12, ribs 4-12 ST: spinous processes of T2-T8 ICL: L1-L4 lumbar transverse processes, angle of ribs 4-12 and thoracolumbar fascia	Dorsal rami of spinal nerves

Thoracic Spine Lateral Flexors

Muscle	Origin	Insertion	Innervation	Action
Erector spinae: Iliocostalis thoracis (ICT) Longissimus thoracis (LT) Spinalis thoracis (ST) Illiocostalis lumborum (ICL)	ICT: ribs 7-12 LT: transverse processes of L1-L5 and the thoracolumbar fascia ST: spinous processes of T11-L2 ICL: iliac crest	ICT: ribs 1-6 and the transverse process of C7 LT: transverse processes of T1 to T12, ribs 4-12 ST: spinous processes of T2-T8 ICL: L1-L4 lumbar transverse processes, angle of ribs 4-12 and thoracolumbar fascia	Dorsal rami of spinal nerves	Unilateral action:  ipsilateral side flexion and rotation of the vertebral column
Internal obliques	Thoracolumbar fascia Iliac crest Inguinal ligament	Lower four ribs Linea alba Pubic crest	Lower intercostal nerves Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve	Unilateral action: thoracic spine lateral flexion and/or rotation to the ipsilateral side
External obliques	Ribs 5-12	Linea alba Pubic tubercle Iliac crest	Intercostal nerves T7-T11 and the T12 subcostal nerve	Unilateral action: thoracic spine lateral flexion to the ipsilateral side and rotation to the contralateral side

Thoracic Spine Rotators

Muscle	Origin	Insertion	Innervation	Action
Levatores costarum	Transverse processes of C7-T11	Rib just below	Lateral branches of the posterior rami of spinal nerves C8-T11.	Assist with contralateral rotation
Transversospinalis muscle group: Multifidus (MF) Semispinalis Thoracis (ST)	MF:Transverse processes of T1-T12 ST: Transverse processes of T6-T10	MF: Spinous process of the vertebra above ST: Spinous processes of the upper four thoracic and lower two cervical vertebrae	Medial branches of the posterior rami of the spinal nerves in the corresponding thoracic region
Rotatores thoracis	Transverse processes of T2-T12	The lamina of the vertebra above		Assist with contralateral rotation Provide proprioception and stabilisation of the spine.
Internal obliques	Thoracolumbar fascia Iliac crest Inguinal ligament	Lower four ribs Linea alba Pubic crest	Lower intercostal nerves Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve	Ipsilateral trunk rotation
External obliques	Ribs 5-12	Linea alba Pubic tubercle Iliac crest	Intercostal nerves T7-T11 and the T12 subcostal nerve	Contralateral trunk rotation

Ribs Mobilisers

Muscle	Origin	Insertion	Innervation	Action
Levatores costarum brevis and longus	Transverse processes of C7-T11	Rib just below	Lateral branches of the posterior rami of spinal nerves C8-T11.	Rib elevation
Intercostal muscle: Innermost intercostal (INI) Internal intercostals (II) External intercostals (EI)	The inferior border of the rib above	Superior border of the rib below	Anterior rami of spinal nerves T1-T11	INI and II: rib depression during expiration EI: rib elevation during inspiration
Serratus posterior superior	Ligamentum nuchae and the spinous processes of C7-T3	Superior borders of ribs 2-5	Intercostal nerves T2-T5.	Rib elevation
Serratus posterior inferior	Spinous processes of T11-L2	Inferior borders of ribs 9-12	Anterior rami of the T9-T11 spinal nerves Subcostal nerves (T12)	Rib depression

The Diaphragm

Origin

• The sternal part originates from the xiphoid process of the sternum
• The costal part originates from the sixth to twelfth ribs
• The lumbar part originates from the medial and lateral arcuate ligaments, and the bodies of L1-L3 vertebrae

Insertion:

• Central tendon

Innervation:

• Phrenic nerves (C3-C5)

Action:

• Primary muscle involved in respiration
• Separates abdominal and thoracic cavities
• Increases intra-abdominal pressure

Innervation of the Thoracic Spine and Rib Cage

Nerve	Origin	Branches	Motor fibres	Sensory fibres
Ventral rami of thoracic spinal nerves	Spinal nerves	Intercostal nerves	Intercostal muscles Serratus posterior inferior and superior	The skin of the lateral and ventral body walls
Dorsal rami of thoracic spinal nerves			Intrinsic back muscles of the transversospinalis group: semispinalis, multifidus and rotatores Erector spinae	The skin of the posterior portion of the back.
Ventral rami of C3 to C5		Phrenic nerve	Diaphragm	Central tendon part of the diaphragm.

Vascular Supply of the Thoracic Spine and Rib Cage

Artery	Origin	Branches	Supply
Posterior intercostal arteries	Superior intercostal artery (first and second posterior intercostal arteries) Descending thoracic aorta (third to eleventh posterior intercostal arteries)	Dorsal (posterior) branch Spinal, medial and lateral musculocutaneous branches Collateral arteries	Chest wall, parietal pleura, skin and back muscles
Anterior intercostal arteries	Internal thoracic artery (one to six vessels) Musculophrenic arteries (seven to nine vessels)	Superior branch Inferior branch	Intercostal muscles and skin of the intercostal space
Superior phrenic artery	Thoracic aorta	Supreme intercostal artery Deep cervical artery	Posterior aspect of the superior surface of the diaphragm
Musculophrenic artery	Internal thoracic artery	Anterior intercostal arteries seven to nine Branches to the pericardium Branches to rectus abdominis	Intercostal spaces 7-9 Muscles attached to the intercostal spaces 7-9 The inferior part of the pericardium The anterior part of the diaphragm The upper part of rectus abdominis
Pericardiophrenic artery	Internal thoracic artery	Posterior intercostal arteries Bronchial artery Superior phrenic artery Subcostal artery	Pericardium Diaphragm Phrenic nerve
Inferior phrenic arteries: Right inferior phrenic artery (RIPA) Left inferior phrenic artery (LIPA)	Abdominal aorta Celiac axis	Ascending branch Descending branch Superior suprarenal branches	The muscular portion of the diaphragm Internal organs: oesophagus, suprarenal glands, liver, spleen Trunk wall

Clinical Relevance

1. Ankylosing spondylitis is an inflammatory disease affecting the spine, causing pain, stiffness and a loss of motion in the back.
2. Scheuermann's disease is a condition characterised by hyperkyphosis of the thoracic spine. Discogenic changes may also affect the thoracolumbar and lumbar regions.
3. Available movement at the ribs and thoracic vertebrae affects active bilateral arm elevation range of motion. The amount of rib movement can be affected by age and gender: middle-aged males have smaller movement in the upper ribs than young males. Ribs 1-9 are less mobile in females than males. It may be necessary to assess/manage the thoracic spine and the upper ribs when treating individuals with shoulder disorders.
4. Costovertebral strains can develop due to compression and torsional forces applied to the joint.
5. Phrenic nerve injury due to surgery, trauma, or disease can result in diaphragm dysfunction or paralysis. You can learn about diaphragm anatomy and differential diagnosis here. The role of the diaphragm in trunk stability is presented in this course by Rina Pandya.

Resources

• Tachihara H, Junichiro Hamada J. Characteristic Movement of the Ribs, Thoracic Vertebrae while Elevating the Upper Limbs - Influences of Age and Gender on Movements. The Open Orthopaedics Journal 2019,13: 170-176.
• Saker E, Graham RA, Nicholas R, D'Antoni AV, Loukas M, Oskouian RJ, Tubbs RS. Ligaments of the Costovertebral Joints including Biomechanics, Innervations, and Clinical Applications: A Comprehensive Review with Application to Approaches to the Thoracic Spine. Cureus. 2016 Nov 11;8(11):e874.