Humerus

Description

The humerus is a long bone which consists of a shaft (diaphysis) and two extremities (epiphysis). It is the longest bone of the upper extremity.

Structure

Upper Extremity Features

The head of the humerus is the articular surface of the upper extremity, which is an irregular hemisphere.

The anatomical neck is the part between the head and the tuberosities.

The surgical neck is the part between the tuberosities and the shaft.

The greater tuberosity it is located lateral to the head.

The lesser tuberosity is located inferior to the head, on the anterior part of the humerus, Its very prominent and palpable.

Bicipital (intertubercular) groove is located between the two tuberosities. The Biceps tendon is placed here.

Body Features

The body of the humerus has three borders and three surfaces.

Borders

  1. Anterior
  2. Lateral
  3. Medial

Surfaces

  1. Antero-lateral
  2. Antero-medial
  3. Posterior

Function

The humerus serves as an attachment to 13 muscles which contribute to the movements of the hand and elbow, and therefore the function of the upper limb.

Video

Articulations

Glenohumeral joint

Elbow joint

Muscle Attachments

Muscle Attachment
Supraspinatus Greater Tubercle
Infraspinatus Greater Tubercle
Teres Minor Greater Tubercle

Upper Part of the Lateral Border

Subscapularis Lesser Tubercle
Pectoralis Major Upper Part of the Anterior Border
Triceps Brachii Lower Part of the Lateral Border

Lateral Supracondylar Ridge

Brachioradialis Lateral Supracondylar Ridge
Extensor Carpi Radialis Longus Lateral Supracondylar Ridge
Teres Major Crest of the Lesser Tubercle
Coracobrachialis Crest of the Lesser Tubercle
Brachialis Medial Supracondylar Ridge
Pronator Teres Medial Supracondylar Ridge
Latissimus Dorsi Bicipital Groove

Clinical Relevance

Proximal end or Head-Surgical Neck Fracture[2]

  • It is caused by a direct blow on the area or fall on an outstretched hand.
  • It results in damage to the Axillary nerve and Posterior circumflex artery.
  • Axillary nerve damage results in paralysis of deltoid and teres minor muscles.

Shaft-Mid-shaft fracture[2]

  • This fracture causes damage to radial nerve and Profunda brachii artery.
  • Sensory loss can be seen over the dorsal surface of the hand, proximal parts of lateral 3 and a half fingers dorsally.
Wrist drop
  • Radial nerve palsy results in wrist drop.

Distal end-Supracondylar fracture[2]

  • It is a fracture of the distal humerus just above the Elbow joint.
  • Volkmann's Contracture
    It results in damage to the brachial artery and anterior interosseous nerve, the resulting ischemia causes Volkmann's ischaemic contracture.

Other conditions

  • Humerus Varus can be caused due to haematologic, infectious, genetic and neurological disorders.[3]
  • Charcot arthropathy is a rare disorder characterised by debilitating joint destruction.[3]

References

  1. Gray H. Anatomy of the human body [Internet]. 20th ed. Lewis WH, editor. Philadelphia: Lea & Febiger; 1918. Accessed 26 March 2020.
  2. 2.0 2.1 2.2 Jones O. The Humerus (Updated 16 June 2019). Teach Me Anatomy. Accessed 24 March 2020
  3. 3.0 3.1 Mostafa E, Varacallo M. Anatomy, Shoulder and Upper Limb, Humerus. InStatPearls [Internet] 2018 Dec 3. Accessed 26 March 2020