Clinical Reasoning and Pathologies of the Thoracic Spine

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

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (31/08/2021)

Introduction

Like the cervical and lumbar spine, pain in the thoracic spine can be caused by a number of musculoskeletal structures, including thoracic spine muscles, joints, the disc and the ribs. There are also a number of visceral or systemic conditions that can masquerade as musculoskeletal spinal pain. These all need to be considered when assessing the thoracic spine.

Muscles of the Thorax

There are 112 muscle attachments in the thorax. This page will look at major muscle groups that can have a significant impact on the thorax. Additional information on thoracic spine musculature is available here.

Intercostals

There are 11 pairs of intercostal muscles, each consisting of three layers arranged from superficial to deep:

• External
• Internal
• Innermost

The intercostal nerves mostly come from the anterior rami of the T1 to T 11 spinal nerves and, along with the intercostal artery and vein, they 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:

• 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, including a poor response to treatment, as this may indicate a more serious pathology.

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 six ribs and the transverse processes of C4. Iliocostalis, therefore, links lumbo-pelvic dysfunction with thoracic dysfunction and hypertonicity in this muscle can potentially have an impact on the thoracic rings.

Pectoralis Major

The 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
• Sixth rib (sternal end)
• Upper six costal cartilages
• Aponeurosis of the external oblique

It inserts into the lateral lip of the bicipital groove on the humerus.

Overactivity of pectoralis major is associated with thoracic kyphosis and anterior translation of the humerus.

• Bodybuilders, for example, often have overactive pectoralis major muscles and thoracic dysfunction
  • A key clinical sign to look for is horizontal clavicles

• Pectoralis stretching can help to reduce kyphosis (and forward head position / rounded shoulder position)

NB: pectoralis major also has fascial links with latissimus dorsi (see below).

Figure 1. Exercise to reduce thoracic kyphosis.

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

• NB: activating lower trapezius plays a key role in addressing an increased thoracic kyphosis. The cue “down and out” should be given during exercises, rather than “down and in”.

Rhomboid Major and Minor

The rhomboids consist of two muscles:

• Rhomboid major
  • 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
  • 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 with facet compression forces
• Scapula held in downward rotation with resultant cervical spine loading
• Dural irritation

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 following exercise is useful for:

• Inverted thoracic spine
• Possible dural pain
• Targeting the various digitations of serratus anterior

GROOVI IMAGE ?

External Oblique vs Serratus Anterior

External oblique, along with the internal oblique and transversus abdominis make up the three anterolateral abdominal wall muscles. The external oblique is the most superficial, the largest and thickest of these three 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, with the most inferior extension folding posteriorly and superiorly to the inguinal ligament

External oblique and serratus anterior interdigitate from the fifth to the ninth ribs. The opposing actions of these muscles (e.g. during rowing and coughing) creates a stress reaction, and 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 six costal cartilages of the thorax laterally via digitations that cross those of transversus abdominis BORDONI
• 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

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 (decreased end tidal carbon dioxide)
• Increased respiratory rate
• Apical breathing
• Irregular respiratory rate

Normally, ribs one to seven 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 2) was created to enhance breathing and improve posture and stability in patients to enhance function and / or reduce pain.