Download HUMERUS

HUMERUS
Learning Objectives:
 To know the different bony landmarks of the
humerus
 To understand the attachments of muscles of the
humerus.
 To know the relations of different nerve injuries in
fracture involving humerus
Lecture outlines:
Introduction
Upper end
Body(shaft)
Lower end
Attachments
Clinical correlates
Introduction:
Humerus, the bone of the arm, is the longest and largest bone of the
upper extremity; it is divisible into a shaft and two extremities.
.
The upper End:
Head
The Head, nearly hemispherical in form, is directed upward, medially,
and a little backward, and articulates with the glenoid cavity of the
scapula.
Anatomical neck
The line separating the head from the rest of the upper end is termed
the Anatomical neck .The anatomical neck is obliquely directed,
forming an obtuse angle with the body. It is best marked in the lower
half of its circumference; in the upper half it is represented by a
narrow groove separating the head from the tubercles.
The Lesser Tubercle (tuberculum minus; lesser
tuberosity):
The lesser tubercle, although smaller, is more prominent than the
greater tubercle. It presents as an elevation on the anterior aspect
of the upper end.
The Greater Tubercle (tuberculum majus; greater
tuberosity):
The greater tubercle is an elevation that forms the lateral part of the
upper end. Its posterior aspect is marked by three impressions.
Intertubercular sulcus:
The intertubercular sulcus or biccipital groove separates the lesser
tubercle medially from the anterior part of the greater tubercle. The
groove has two lips the medial lip and the lateral lip.
Surgical neck
The narrow line separating the upper end of the humerus from the
shaft is called the surgical neck.
The Body or Shaft (corpus humeri)
The body is almost cylindrical in the upper half of its extent. It is
prismatic and flattened in the lower end.
The shaft of the humerus is compromised of three borders and three
surfaces.
Borders
Anterior border:
 The upper 1/3rd of the anterior border forms the lateral lip of the
intertubercular sulcus.
 In its middle part it forms the anterior margin of the deltoid tuberosity.
 The lower half of the anterior border is smooth and rounded.
Lateral border:
 The lateral border is prominent only at the lower end, where it
forms the lateral supracondylar ridge.
 In the middle part it is interrupted by the radial or spiral groove.
Medial border:
 The upper part of the medial border forms the medial lip pf the
intertubercular sulcus.
 It is continuous below with the medial supracondylar ridge.
Surfaces
Anterolateral surface:
 This surface lies between the anterior and the lateral borders.
 The upper half of the surface is covered by the deltoid.
 A little above the middle it is marked by a V-shaped deltoid
tuberosity.
 Behind the deltoid tuberosity the radial groove runs downwards
and forwards across the surface.
Anteromedial surface:
 This surface lies between the anterior and medial borders.
 Its upper 1/3rd is narrow and forms the floor of the intertubercular
sulcus.
 A nutrient foramen is present on this surface.
Posterior surface:
 It lies between the medial and lateral borders.
 Its upper part is marked by an oblique ridge.
 The middle 1/3rd is crossed by the radial groove.
The Lower end
 The lower extremity is flattened from before backward, and curved
slightly forward.
 It ends below in a broad, articular surface, which is divided into two
parts capitulum and trochlea, by a slight ridge. Projecting on either
side are the lateral and medial epicondyles.

Capitulum:
 It is the rounded projection which articulates with the head of the
radius.

Trochlea:
 It is a pulley shaped surface.
 It articulates with the trochlear notch of the ulna.
 The medial edge is responsible for forming the carrying angle.
 Medial epicondyle:
 The medial epicondyle is a prominent bony projection on the
medial side of the lower end.
 lateral epicondyle
 The lateral epicondyle is smaller than the medial one and its
anterolateral part has a muscular impression.
 Lateral supracondylar ridge.
 The sharp lateral margin just above the lower end is called the
lateral supracondylar ridge.
 medial supracondylar ridge
 The medial supracondylar ridge is a similar ridge to the medial
aspect.
 coronoid fossa
 The coronoid fossa is a depression just above the anterior aspect
of the trochlea.
radial fossa
 The radial fossa is a depression that is present just above the
anterior aspect of the capitulum.
 olecranon fossa
 The olecranon fossa lies just above the posterior aspect of the
trochlea.
Attachments on the Humerus:
Muscles attached on the upper end of humerus
 Insertion of muscle ON TUBEROSITIES
Subscapularis
Lesser tuberosity of the humerus.
Supraspinatus
Greater tuberosity of the humerus.
Infraspinatus
Greater tuberosity of the humerus.
Teres minor
Greater tuberosity of the humerus
Tendons of these four muscles form a cuff around the anterior, posterior
and superior aspect of shoulder joint and collectively known as
ROTATOR CUFF
 Insertion in the region of bicipital groove
Latissimus dorsi
Floor of the intertubercular sulcus.
Pectoralis major
Lateral lip of the bicipital groove of the humerus.
Teres major
Medial lip of the bicipital groove of the humerus.
Muscles attached on the shaft of Humerus
 Origin of muscles:
Lateral head of the triceps
Upper half of posterior surface of shaft of humerus above radial
groove
.
Medial head of the triceps
Lower half of the posterior surface of the shaft of humerus.
Brachialis
Front of the lower half of the humerus i.e. from the anteromedial and
anterolateral surfaces of the shaft.
 Insertion of muscle
Deltoid
Middle of the lateral surface of the shaft of the humerus.
Coracobrachialis
Into the rough area on the middle of the medial border.
Muscles attached on the lateral lower end of Humerus
 Origin of muscles:
Brachioradialis
Arises from the upper 2/3rd of the lateral supracondylar ridge.
Extensor carpi radialis longus
Arises from the lower 1/3rd of the lateral supracondylar ridge.
Common Extensor Origin
The superficial extensor muscles of the forearm have a common
origin from the lateral epicondyle. This is called the common extensor
origin.
Anconeus
Arises from the posterior surface of the lateral epicondyle.
Muscle attached on medial lower end of Humerus
 Origin of muscle
Pronator teres (humeral head)
Arises from the lower 1/3rd of the medial supracondylar ridge medial
epicondyle of the humerus.
Common Flexor Origin
The superficial flexor muscles of the forearm arise by a common
origin from the anterior aspect of the medial epicondyle. This is called
the common flexor origin.
Attachment of capsular ligaments:
 Capsular ligament of shoulder joint:
Attached to anatomical neck except on medial side where it also
includes a small area of shaft
Also provides an aperture for the tendon of long head of biceps
 Capsular ligament of elbow joint:
Attached on lower end to a line that reaches upper limit of coronoid
and radial fossa anteriorly, olecranon process posteriorly, medially
passes between epicondyle and trochlea and laterally between
capitulum and lateral epicondyle.
Clinical correlates
 Three nerves are liable to injury in fractures involving humerus
 Axillary nerve is damaged in the fractures involving surgical neck of
humerus
 Radial nerve in the radial groove
 Ulnar nerve in the fractures involving fractures of medial epicondyle