Anatomy of Humerus

Complete Anatomy of Humerus by Dr. Adnan Sami

1. Humerus Dr. Sami

2. The humerus is a long bone of the upper arm . It is one of the longest bones in the body, which makes it more prone to fractures upon impact. The word “ humerus ” comes from the Latin word for upper arm.

3. Where is the humerus located? The humerus bone is located in the upper arm, between the shoulder joint and the elbow joint . The shoulder joint, also known as the glenohumeral joint, is a ball and socket joint . The ball is the humeral head , and the socket is the glenoid fossa of the scapula. The joint is supported by ligaments , and surrounded by the four rotator cuff muscles and their tendons : the supraspinatus , infraspinatus , teres minor , and subscapularis . These muscles originate on the scapula and insert on the humeral head .

4. Anatomical Position:

5. Parts of Humerus : Proximal End : This is the upper part of your humerus closest to your shoulder. Body or shaft : This is the long, middle portion of your humerus . Distal End : This is the lower area of your humerus that’s closest to your elbow.

6. Proximal Part: Head: . The head is nearly hemispherical in form .   It is directed upward , medialward , and a little backward . It articulates with the glenoid cavity of the scapula to form the glenohumeral joint (shoulder joint ). The head form about one third of the sphere and is much greater than glenoid cavity .

7. Anatomical Neck : The line separating the head from rest of the upper end is called the anatomical neck . The anatomical neck is a slight narrowing below the articular surface of the head . The anatomical neck is obliquely directed, forming an obtuse angle with the body. (More than 90 & less than 18) 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 .

8. Surgical neck : T he surgical neck of the humerus is a bony constriction at the proximal end of shaft of humerus . It is situated distal to the greater tubercle and lesser tubercle , and proximal to the deltoid tuberosity . The surgical neck is a narrow area distal to the tubercles that is a common site of fracture. It makes contact with the axillary nerve and the posterior humeral circumflex artery . Damage to the axillary nerve affects function of the teres minor and deltoid muscles, resulting in loss of abduction of arm (from 15-90 degrees), weak flexion , extension , and rotation of shoulder as well as loss of sensation of the skin over a small part of the lateral shoulder .

9. Greater tubercle : The greater tubercle (greater tuberosity) is a large, posteriorly placed projection that is placed laterally . It provides attachment points for the supraspinatus , infraspinatus , and teres minor muscles , three of the four muscles of the rotator cuff (except subscapularis on lesser tubercle ), a muscle group that stabilizes the shoulder joint . (SIT) The upper surface of the greater tubercle is rounded , and marked by three flat impressions : the highest (" superior facet ") gives insertion to the supraspinatus muscle. the middle (" middle facet ") gives insertion to the infraspinatus muscle. the lowest (" inferior facet "), and the body of the bone for about 2.5 cm, gives insertion to the teres minor muscle. The lateral surface of the greater tubercle is convex , rough , and continuous with the lateral surface of the body of the humerus . It can be described as having a cranial and a caudal

10. Between the greater tubercle and the lesser tubercle is the bicipital groove ( intertubercular sulcus ).

11. Lesser Tubercle : The lesser tubercle of the humerus , although smaller , is more prominent than the greater tubercle : it is situated in front , and is directed medially and anteriorly . The projection of the lesser tubercle is anterior from the junction that is found between the anatomical neck and the shaft of the humerus and easily identified due to the intertubercular sulcus ( Bicipital groove ). The crest of the lesser tubercle forms the medial lip of the bicipital groove and is the site for insertion of teres major and latissimus dorsi muscles . Above and in front it presents an impression for the insertion of the tendon of the subscapularis muscle .

12. Bicipital groove The bicipital groove separates the greater tubercle from the lesser tubercle . It is usually around 8 cm long and 1 cm wide in adults . It lodges the long tendon of the biceps brachii muscle between the tendon of the pectoralis major muscle on the lateral lip and the tendon of the teres major muscle on the medial lip . It also transmits a branch of the anterior humeral circumflex artery to the shoulder joint . The insertion of the latissimus dorsi muscle is found along the floor of the bicipital groove. The teres major muscle inserts on the medial lip of the groove . It runs obliquely downward, and ends near the junction of the upper with the middle third of the bone. It is the lateral wall of the axilla .

13. Distal humerus The distal or lower extremity of the humerus is flattened from before backward , and curved slightly forward ; it ends below in a broad, articular surface, which is divided into two parts by a slight ridge . Projecting on either side are the lateral and medial epicondyles .

14. Articular surface The articular surface extends a little lower than the epicondyles , and is curved slightly forward ; its medial extremity occupies a lower level than the lateral . The lateral portion of this surface consists of a smooth , rounded eminence , named the capitulum little head of the humerus ; it articulates with the cup-shaped depression on the head of the radius , and is limited to the front and lower part of the bone. The trochlea (pulley) is a pulley shaped surface. It articulates with the trochlear notch of the ulna. The medial edge of the trochlea projects down 6 mm more than the lateral edge . This results in the formation of carrying angle .

15. Fossae: Above the front part of the trochlea is a small depression , the coronoid fossa , which receives the coronoid process of the ulna during flexion of the forearm .

16. Above the back part of the trochlea is a deep triangular depression , the olecranon fossa , in which the summit of the olecranon is received in extension of the forearm .

17. Above the front part of the capitulum is a slight depression , the radial fossa , which receives the anterior border of the head of the radius , when the forearm is flexed .

18. Epicondyles The epicondyles are continuous above with the supracondylar ridges. The lateral epicondyle of the humerus is a large , tuberculated eminence , curved a little forward , and giving attachment to the radial collateral ligament of the elbow joint, and to a tendon common to the origin of the supinator and some of the extensor muscles . Specifically , these extensor muscles include the anconeus muscle , the supinator , extensor carpi radialis brevis , extensor digitorum , extensor digiti minimi , and extensor carpi ulnaris . ( SAD hu because of EX so DUR raho )

19. The medial epicondyle of the humerus is an epicondyle of the humerus bone of the upper arm in humans. It is larger and more prominent than the lateral epicondyle and is directed slightly more posteriorly in the anatomical position . The medial epicondyle is located on the distal end of the humerus . Additionally, the medial epicondyle is inferior to the medial supracondylar ridge . It is also proximal to the olecranon fossa . The medial epicondyle gives attachment to the ulnar collateral ligament of elbow joint , to the pronator teres , and to a common tendon of origin (the common flexor tendon) of some of the flexor muscles of the forearm : the flexor carpi radialis , the flexor carpi ulnaris , the flexor digitorum superficialis , and the palmaris longus . ( PLUS R ) The medial epicondyle protects the ulnar nerve , which runs in a groove on the back of this epicondyle . The ulnar nerve is vulnerable because it passes close to the surface along the back of the bone . Striking the medial epicondyle causes a tingling sensation in the ulnar nerve . This response is known as striking the " funny bone ".

20. The Medial supracondylar crest forms the sharp medial border of the distal humerus continuing superiorly from the medial epicondyle . The Lateral Supracondylar crest forms the sharp lateral border of the distal humerus continuing superiorly from the lateral epicondyle .

21. Shaft or Body: Borders : Its three borders are : Anterior : the anterior border runs from the front of the greater tubercle above to the coronoid fossa below , separating the antero -medial from the antero -lateral surface . Its upper part is a prominent ridge, the crest of the greater tubercle ; it serves for the insertion of the tendon of the pectoralis major muscle. About its center it forms the anterior boundary of the deltoid tuberosity , on which the deltoid muscle attaches ; below , it is smooth and rounded , affording attachment to the brachialis muscle.

22. Lateral : the lateral border runs from the back part of the greater tubercle to the lateral epicondyle , and separates the anterolateral from the posterior surface . Its upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the teres minor muscle , and below this giving origin to the lateral head of the triceps brachii muscle ; its center is traversed by a broad but shallow oblique depression , the spiral groove ( musculospiral groove ). The radial nerve runs in the spiral groove . Its lower part forms a prominent, rough margin, a little curved from backward , forward the lateral supracondylar ridge, which presents an anterior lip for the origin of the brachioradialis muscle above, and extensor carpi radialis longus muscle above, a posterior lip for the triceps brachii muscle, and an intermediate ridge for the attachment of the lateral intermuscular septum.

23. Medial : the medial border extends from the lesser tubercle to the medial epicondyle . Its upper third consists of a prominent ridge , the crest of the lesser tubercle , which gives insertion to the tendon of the teres major muscle . About its center is a slight impression for the insertion of the coracobrachialis muscle , and just below this is the entrance of the nutrient canal , directed downward ; sometimes there is a second nutrient canal at the commencement of the radial sulcus . The inferior third of this border is raised into a slight ridge , the medial supracondylar ridge , which became very prominent below ; it presents an anterior lip for the origins of the brachialis muscle and the pronator teres muscle , a posterior lip for the medial head of the triceps brachii muscle , and an intermediate ridge for the attachment of the medial intermuscular septum .

24. The body or shaft of the humerus is triangular to cylindrical in cut section and is compressed anteroposterior . It has 3 surfaces , namely : Anterolateral surface: the area between the lateral border of the humerus to the line drawn as a continuation of the crest of the greater tubercle . The antero -lateral surface is directed lateralward above, where it is smooth, rounded , and covered by the deltoid muscle; forward and lateralward below, where it is slightly concave from above downward, and gives origin to part of the Brachialis . About the middle of this surface is a rough , rectangular elevation , the deltoid tuberosity for the insertion of the deltoid muscle ; below this is the radial sulcus , directed obliquely from behind, forward, and downward, and transmitting the radial nerve and profunda artery.

25. Anteromedial surface: the area between the medial border of the humerus to the line drawn as a continuation of the crest of the greater tubercle . The antero -medial surface, less extensive than the antero -lateral, is directed medialward above, forward and medialward below; its upper part is narrow , and forms the floor of the intertubercular groove which gives insertion to the tendon of the latissimus dorsi muscle ; its middle part is slightly rough for the attachment of some of the fibers of the tendon of insertion of the coracobrachialis muscle ; its lower part is smooth , concave from above downward, and gives origin to the brachialis muscle .

26. Posterior surface : the area between the medial and lateral borders . The posterior surface appears somewhat twisted , so that its upper part is directed a little medialward , its lower part backward and a little lateralward . Nearly the whole of this surface is covered by the lateral and medial heads of the Triceps brachii , the former arising above, the latter below the radial sulcus .

27. The Deltoid tuberosity is a roughened surface on the lateral surface of the shaft of the Humerus and acts as the site of insertion of deltoideus muscle . The posterorsuperior part of the shaft has a crest, beginning just below the surgical neck of the humerus and extends till the superior tip of the deltoid tuberosity. This is where the lateral head of triceps brachii is attached.

28. The radial sulcus , also known as the spiral groove is found on the posterior surface of the shaft and is a shallow oblique groove through which the radial nerve passes along with deep vessels . This is located posteroinferior to the deltoid tuberosity. The inferior boundary of the spiral groove is continuous distally with the lateral border of the shaft.

29. The nutrient foramen of the humerus is located in the anteromedial surface of the humerus . The nutrient arteries enter the humerus through this foramen.