Clinical Reasoning and Pathologies of the Thoracic Spine

Original Editor - Jess Bell based on the course by Tanya Bell-Jenje
Top Contributors - Jess Bell, Lucinda hampton, Kim Jackson, Rucha Gadgil, Olajumoke Ogunleye and Carin Hunter

Introduction

The thoracic spine is a complex area that has been largely overlooked in research. While only 13 percent of individuals specifically report thoracic pain each year, it is now recognised that the thorax can be a silent contributor to other distal and proximal conditions. Moreover, a number of non-mechanical pathologies can masquerade as musculoskeletal thoracic pain. All of these conditions must be considered when assessing patients who have thoracic pain.

Muscles of the Thorax

There are 112 muscle attachments in the thorax. This page looks at some of the muscles that can affect the thorax. Additional information on thoracic spine musculature is available here.

Intercostals

There are 11 pairs of intercostal muscles. Each muscle has three layers arranged from superficial to deep:

• External
• Internal
• Innermost

The intercostal nerves mostly come from the anterior rami of the T1 to T11 spinal nerves. Along with the intercostal artery and vein, these nerves run between the intermediate and deep layers of the intercostal muscles. The T7 to T11 intercostal nerves leave the thoracic wall and enter the abdominal wall to innervate the abdominal peritoneum. They supply the:

• Ribs and costal cartilages
• Intercostal muscles (all layers)
• Parietal pleura, which lines the inner surface of the thoracic cavity, including the diaphragm, pericardium and thoracic aorta

Because of this shared innervation, diseases of the thoracic wall or cavity may masquerade as dermatomal pain arising from the thoracic spine. Thus, it is essential to constantly assess a patient for red flags. If a patient has a poor response to treatment, this can indicate a more serious pathology and is considered a key red flag.

Iliocostalis

Iliocostalis is the most lateral of the erector spinae muscles. It is divided into three parts:

• Iliocostalis cervicis
• Iliocostalis thoracis
• Iliocostalis lumborum

Iliocostalis lumborum originates at the iliac crest and inserts into the L1 to L4 lumbar transverse processes, the angle of ribs 4 to 12, and the thoracolumbar fascia. Iliocostalis cervicis and thoracis have attachments as high as the upper 6 ribs and the transverse processes of C4. Iliocostalis, therefore, links lumbo-pelvic dysfunction with thoracic dysfunction. Hypertonicity in this muscle can potentially have an impact on the thoracic rings.

Pectoralis Major

Pectoralis major makes up the bulk of the chest muscles. It is a thick, fan-shaped muscle that originates at the:

• Anterior sternum (down to the xiphoid process)
• Clavicle
• 6th rib (sternal end)
• Upper 6 costal cartilages
• Aponeurosis of the external oblique

It inserts into the lateral lip of the bicipital groove on the humerus.It also has fascial links with latissimus dorsi.

Overactivity of pectoralis major is associated with thoracic kyphosis and anterior translation of the humerus. Horizontal clavicles are a clinical sign of overactivity in this muscle. Pectoralis stretching can help to reduce kyphosis, as well as forward head position / rounded shoulder position and upper-crossed syndrome.

Figure 1. Exercise to reduce thoracic kyphosis.

The exercise shown in Figure 1 can be used to improve thoracic and scapula motor control. It can also reduce thoracic kyphosis by increasing the activity of the middle and lower fibres of trapezius and reducing overactivity in the upper fibres of trapezius.

NB: it is important to improve activation of lower trapezius in patients who have an increased thoracic kyphosis. The cue “down and out” should be given during exercises, rather than “down and in”.

See also Scapular Dyskinesia

Rhomboid Major and Minor

The rhomboids consist of two muscles:

• Rhomboid major
  • A quadrangular muscle
  • Inferior to rhomboid minor
  • Originates at the T1 to T4 spinous processes
  • Inserts into the medial margin of the scapula below the root of the inferior angle
• Rhomboid minor
  • A cylindrical muscle
  • Originates at the ligamentum nuchae and C7 and T1 vertebra
  • Inserts into the medial margin at the root of the spine of the scapula

Overactivity in these muscles leads to:

• Inverted thoracic spine (also known as a lordotic thoracic spine) with compression forces on the facets
• Downward rotation of the scapula, which loads the cervical spine
• Dural irritation

Serratus Anterior

Figure 2. Hug an aunt stretches for serratus anterior.

Serratus anterior is a fan-shaped muscle. It lies deep to the scapula and pectoral muscles:

• It originates on the superolateral surfaces of the upper 8 or 9 ribs
• It runs backwards and inserts along the superior angle, medial border, and inferior angle of the scapula

This muscle is a powerful protractor (abductor). It is also involved in upward rotation (which allows for overhead activity), posterior tilt and external rotation of the scapula. It holds the scapula flat against the rib cage and can mobilise the thoracic spine into kyphosis. 

The exercises shown in Figure 2 are useful for:

• Inverted thoracic spine (see above)
• Possible dural pain
• Targeting the various digitations of serratus anterior

External Oblique vs Serratus Anterior

External oblique, internal oblique and transversus abdominis are the three anterolateral abdominal wall muscles. The external oblique is the largest, thickest and most superficial of these muscles:

• It attaches to the lower 6 or 7 ribs (and, therefore, can affect the activity of the diaphragm)
• It runs obliquely from superior-lateral to inferior-medial
• It inserts on the iliac crest

The external oblique and serratus anterior interdigitate from the 5th to the 9th ribs. The opposing action of these muscles (e.g. during rowing or coughing) creates a stress reaction, which is a major contributor to stress fractures.

The Diaphragm

The diaphragm is a dome-shaped muscle of respiration that is innervated by the phrenic nerve (C3-5). The superior portion of the diaphragm originates at the:

• Xiphoid process anteriorly
• The lower 6 costal cartilages of the thorax laterally via digitations that cross those of transversus abdominis
• The first two lumbar vertebrae posteriorly

It converges into a central tendon which forms the dome’s crest. The peripheral segment attaches to the chest wall and abdominal cavity.

The diaphragm is connected via fascia to the:

• Aortic system
• Inferior vena cava
• Liver
• Psoas muscles
• Quadratus lumborum
• Transversus abdominis
• Pelvic floor
• Cardiac system (pleura and pericardium)
• Deep and median neck fascia
• Occiput
• Dura
• Phrenic-oesophageal ligaments
• Kidneys

The diaphragm and intercostals are the only muscles that are active during quiet inspiration. During quiet exhalation, the diaphragm, rib cage and chest wall relax and return to their original position, which expels the air from the lungs.

The diaphragm is, therefore, essential for optimal respiratory physiology. It also affects many other systems as well, including the nervous system, muscle and postural systems, as well as the lymphatic system.

The Effect of Diaphragmatic Bracing on the Thoracic Spine

Diaphragmatic bracing in low load situations can occur in:

• Chronic low back pain
• PTSD
• Panic attacks
• COVID-19

Figure 3. 90/90 bridge with ball and balloon exercise.

Patients who engage this bracing strategy may present with back, thoracic, neck and rib pain. Bracing fixes the thoracic wall and reduces thoracic mobility. It can lead to:

• Hypocapnia (i.e. decrease in carbon dioxide levels)
• Increased respiratory rate
• Apical breathing
• Irregular respiratory rate

Normally, ribs 1 to 7 posteriorly rotate during full inspiration and anteriorly rotate during full expiration. It is important to teach patients correct respiration as optimal breathing mechanics promote synchronous movement of the ribs.

The 90/90 bridge with ball and balloon exercise (see Figure 3) was created to enhance function and breathing, improve posture and stability and to reduce pain.

Pathologies

Spinal Masqueraders

In some instances, thoracic pain may have non-mechanical origins. Visceral or systemic conditions that present as thoracic pain are known as spinal masqueraders. Examples of thoracic spinal masqueraders include:

• Pneumothorax
• Pleuritic pain
• Coronary heart disease
• Oesophageal pain
• Tumours (e.g. lung)
• Liver and spleen conditions
• Herpes zoster
• Seronegative arthritis
• Ankylosing spondylitis
• Pneumonia
• Malignant lymphoma
• Stomach ulcers

Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) is a group of disorders that cause compression of the nerves, arteries or veins as they exit the thoracic outlet. TOS typically occurs in three places:

• Scalene triangle
• Costoclavicular space
• Retropectoral space

Postural / thoracic kyphosis, tight bra straps, overactive subclavius, and the presence of a cervical rib can narrow the costoclavicular space and create neurovascular symptoms. Structures usually affected in TOS are the:

• Subclavian artery and vein
• Axillary artery and vein
• Brachial plexus

There are three types of TOS:

1. Neurogenic (i.e. brachial plexus)
   • Most common type (approximately 95 percent of cases)
   • Symptoms include:
     • Pain
     • Weakness
     • Heaviness in the arm
     • Paraesthesia
   • Neurogenic symptoms tend to be worse with overhead activities or when the patient's arm is dangling at his / her side
2. Venous (i.e. subclavian vein) - also known as Paget–von Schroetter syndrome
   • Symptoms include:
     • Swelling
     • Pain
     • Bluish discolouration
3. Arterial (i.e. subclavian artery)
   • Least common type
   • Symptoms include:
     • Pain
     • Coldness
     • Paleness in the arm

TOS is often missed by clinicians - the average time to diagnosis is 60 months. TOS may be mistaken for carpal tunnel, cervical nerve root compression, psychosocial issues, complex regional pain syndrome, fibromyalgia, MS etc.

TOS can be diagnosed using the following tests and investigations:

• Adson’s test
• Elevated arm stress test (Roos test)
  • It has been found that using the Adson and Roos tests as a cluster results in higher specificity than using these tests on their own
• Upper limb tension test
• Nerve conduction study (0ften negative)
• MRI in elevation
• Doppler / duplex ultrasound
• Scalene blocks can be used as a diagnostic tool
• Warm and cold thermal detection also has good reliability

Stress Fracture of the Ribs

Stress fractures of the ribs are typically associated with sports that have:

• High strain magnitudes (e.g. weightlifting)
• High load repetitions (e.g. golf, rowing, throwing, over-training)

They tend to occur when the opposing actions of serratus anterior and external oblique generate pulling forces and, consequently, a stress reaction (see above).

Rowing:

• The incidence of rib stress fractures in rowing is between 6 and 12 percent:
  • Occurs most often in ribs 5 to 9
  • Typically antero-lateral, but can be postero-lateral

Golf:

• Most commonly occurs on the lead-side (i.e. non-dominant side) and affects the postero-lateral ribs
• Ribs 4 to 6 are most often affected

Rib stress fractures are diagnosed based on history and bone scans, CT or MRI. Patients usually require 3 to 9 weeks off sports. Patients tend to present with:

• History of insidious onset (overload) with sudden pain
• Pain with deep breathing, coughing, sneezing, turning in bed
• Inability to sleep on the affected side
• Severe, specific, palpable pain on examination
• Positive rib spring
• Altered breathing mechanics
• Pain with push-up and with resisted serratus anterior testing
• Pain with sit-up, including with an oblique bias

Manubriosternal Joint Pain

Manubriosternal joint pain often occurs as a result of an acceleration / deceleration injury (e.g. throwing, serving). Sclerosis of this joint is also seen in various types of arthritis, including:

• Axial spondyloarthritis / ankylosing spondylitis
• Reactive arthritis / Reiters
• Psoriatic arthritis
• Rheumatoid arthritis

Costochondritis

Costochondritis is inflammation of the costochondral or chondrosternal joints. It is more common in adults aged over 40 years. In 90 percent of patients, more than one rib is affected. The ribs most frequently affected are ribs 2 to 5.

• Mild to severe localised pain, but may refer to the shoulder, neck and arms
• It is important to rule out seronegative arthritis, pneumonia, cardiovascular and malignant disorders
• It is treated with NSAIDs and it can take weeks or months to resolve

Costochondritis can be mistaken for Tietze syndrome, but this condition is characterised by swelling of a single costal cartilage. Ribs 2 or 3 are usually affected and it is more common in younger patients.

Cervical Facet Pain

It is well established that cervical discs, as well as cervical facet joints refer pain to the upper thorax.

Thoracic Disc Pathology

Thoracic disc pathology is rare and individuals are often asymptomatic. One of the reasons it is so rare is due to the thickness of the thoracic disc - it is thinner than in other regions. The ratio of the thoracic disc to the vertebral body is 1:5 (vs 2:5 in the cervical spine and 1:3 in the lumbar spine).

Figure 4. Spinal dermatomes.

In 75 percent of cases, thoracic disc pathology occurs at T8 or below, peaking around T11 or T12. Only 1 percent of prolapses with severe myelopathy occur in the thoracic spine.

There are two types of disc pathology:

• Central thoracic pain (myelopathic):
  • Leg paralysis and spinal cord compression
  • Bladder and bowel impairment
• Dermatomal unilateral pain (radicular)
  • Compression of the nerve root
  • Pain follows the intercostal dermatomal route (see Figure 4)

Summary

• It is beneficial to restore a neutral thoracic spine
• Serratus anterior is key to restoring an optimal thoracic kyphosis from a dysfunctional inverted position
• Teaching correct respiration is important as good breathing mechanics prompt synchronous movement of the ribs
• As there are many thoracic spinal masqueraders, red flags should be constantly assessed:
  • A key red flag to consider is a poor response to treatment