First Rib

Description[edit | edit source]

First rib 3.png

The first rib is the most superior of the twelve ribs. It is considered an atypical rib. It is an important anatomical landmark and borders of the superior thoracic aperture.[1] The ribs form the main structure of the thoracic cage that protects the thoracic organs. There are 12 pairs of ribs which are separated by intercostal spaces. The first seven ribs progressively increase in length, the lower five ribs begin to decrease in length.  Ribs are highly vascular and trabecular with a thin outer layer of compact bone. Similar to the first rib, the 11th and 12th ribs are considered atypical ribs due to their anatomical features[2].

Anatomy[edit | edit source]

First rib.jpg

When compared to a typical rib, the first rib is

  • Wide and short, consisting of a single articular facet for the costovertebral joint.[3]
  • Has a head, neck and shaft but lacks a discrete angle[4].
  • Has a shaft that is indented laterally which serves as the groove for the subclavian artery.
  • Has another groove for the subclavian vein anterior to the scalene tubercle.
  • Lacks a costal groove on its inferior surface.
  • The only rib that articulates with one thoracic vertebra only (T1).[3]

The first rib has two tubercles. The first tubercle is the transverse tubercle, which is located posterior and lateral to the neck and bears an articular facet for the transverse process of T1. The second tubercle is the scalene tubercle, where the anterior scalene muscle inserts (otherwise known as the Lisfranc tubercle).

Blood Supply[edit | edit source]

The ribs receive their blood supply anterior via the anterior intercostal arteries and posteriorly by the posterior intercostal arteries.[3]The anterior intercostal arteries branch off of the internal thoracic artery, which supply blood for the first seven ribs. The 8th, 9th, and 10th ribs anterior blood supply branches off the musculophrenic artery. All arteries and veins run through the costal groove of each rib.

  • The internal thoracic artery supplies the anterior body wall and its associated structures from the clavicles to the umbilicus. It originates from the first part of the subclavian artery in the base of the neck.
  • The superior intercostal arteries are formed as a direct result of the embryological development of the intersegmental arteries.
  • These arteries are paired structures of the upper thorax which normally form to provide blood flow to the first and second intercostal arteries.[5]
  • Venous drainage is to the intercostal veins.

Innervation[edit | edit source]

The first rib is innervated by the first intercostal nerve.

  • The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the  T1 to T11 thoracic spinal nerves
  • The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum and differ from the anterior rami of the other spinal nerves in that each pursues an independent course without plexus formation.[1]
  • The first intercostal nerve is joined to the brachial plexus through a branch, which is equivalent to the lateral cutaneous branches of remaining intercostal nerves.
  • Another exception with the first intercostal nerve is that there is no anterior cutaneous branch. It is also very small as compared to the remaining nerves[6].

Attachments[edit | edit source]

The first rib has several attachments which are listed below:

  • Anterior scalene muscle: scalene tubercle
  • Middle scalene muscle: between groove for the subclavian artery and transverse tubercle
  • Intercostal muscles: from the outer border
  • Subclavius muscle: arises from the distal shaft and first costal cartilage
  • First digitation of the serratus anterior muscle
  • Parietal pleura: from the inner border
  • Costoclavicular ligament: anterior to the groove for the subclavian vein

Palpation[edit | edit source]

The first rib can be difficult to palpate. To palpate the first rib, find the superior border of the upper trapezius muscle and then drop off it anteriorly and direct your palpatory pressure inferiorly against the first rib. Asking a patient to take in a deep breath will elevate the first rib up against your palpating fingers and make palpation easier.

Examination[edit | edit source]

The first rib can be assessed in sitting, supine, and prone. Using T1 as reference, rotate the patient's head to the side being tested. This allows the first rib to move posteriorly and become more accessible for palpation.

First Rib Assessment on hypomobility in supine:

[7]

Assessing Rib Mobility - Lindgren's Test:

[8]

Pathology/Injury[edit | edit source]

With respect to injury and pathology, the first rib is involved in Thoracic Outlet Syndrome and Pancoast tumours.

Thoracic Outlet Syndrome

Thoracic Outlet Syndrome (TOS) refers to the compression of the neurovascular structures (i.e., the brachial plexus and subclavian vessels) as they exit through the thoracic outlet region (the scalene triangle, the costoclavicular space, and the subcoracoid space).[9] The thoracic outlet is marked by the anterior scalene muscle anteriorly, the middle scalene posteriorly, and the first rib inferiorly. TOS does not specify the structure being compressed. It affects approximately 8% of the population and is 3-4 times as frequent in woman as in men between the age of 20 and 50 years[10]. Signs and symptoms of thoracic outlet syndrome vary from patient to patient due to the location of nerve and/or vessel involvement. Severity of symptoms can range from mild pain with sensory changes to limb threatening complications in severe cases.

Pancoast Tumour

Superior sulcus tumors, commonly known as Pancoast tumors, is a type of lung cancer. [11] It refers to a relatively uncommon situation where a primary bronchogenic carcinoma arises in the lung apex at the superior pulmonary sulcus and invades the surrounding soft tissues. The most common symptoms are chest pain, shoulder pain, and arm pain. Weight loss is frequently present[12].

Common pathologies found in all 12 ribs include:

References[edit | edit source]

  1. 1.0 1.1 Ramsaroop L, Partab P, Singh B, Satyapal K. Thoracic origin of a sympathetic supply to the upper limb: the ‘nerve of Kuntz’revisited. The Journal of Anatomy. 2001 Dec;199(6):675-82.
  2. https://radiopaedia.org/articles/ribs
  3. 3.0 3.1 3.2 Safarini OA, Bordoni B. Anatomy, Thorax, Ribs. InStatPearls [Internet] 2022 Jul 11. StatPearls Publishing.
  4. Marhold F, Izay B, Zacherl J, Tschabitscher M, Neumayer C. Thoracoscopic and anatomic landmarks of Kuntz's nerve: implications for sympathetic surgery. Ann Thorac Surg. 2008;86:1653Y1658.
  5. https://radiopaedia.org/articles/supreme-intercostal-arteries
  6. http://www.mananatomy.com/body-systems/nervous-system/intercostal-nerves
  7. First Rib Palpation Available from: https://www.youtube.com/watch?v=zwDO_VXOItM
  8. Assessment of Rib Mobility - Lindgren's Test Available from: https://www.youtube.com/watch?v=PrDZD1erucI
  9. Li N, Dierks G, Vervaeke HE, Jumonville A, Kaye AD, Myrcik D, Paladini A, Varrassi G, Viswanath O, Urits I. Thoracic outlet syndrome: a narrative review. Journal of Clinical Medicine. 2021 Mar 1;10(5):962.
  10. Citisli V. Assessment of Diagnosis and Treatment of Thoracic Outlet Syndrome, An Important Reason of Pain in Upper Extremity, Based on Literature. J Pain Relief [Internet]. 2015 [cited 2024 Mar 19];4(2):173.
  11. Rahimzadeh P, Ahani A, Antar A, Morsali SF, Zojaji F, Shokooh GD. Erector Spinae Plane Block for the Treatment of Intractable Pain in a Patient with Pancoast Tumor: A Case Report. Anesthesiology and Pain Medicine. 2023 Jun;13(3).
  12. Alifano M, D'aiuto M, Magdeleinat P et-al. Surgical treatment of superior sulcus tumors: results and prognostic factors. Chest. 2003;124 (3): 996-1003.