Part 6: Posterior Compartment of Arm

Question 1

Origins of heads of Triceps

Answer 1

Long head: Infraglenoid tubercle of scapula
Lat head: Upper half posterior humerus (surgical neck to deltoid insertion)
Med head: Lower half posterior humerus (medial radial groove and both IM speta)

Question 2

Triceps insertion, action and innervation

Answer 2

I: Post upper surface olecranon process and post capsule
A: Elbow extension, shoulder stabilisation, retracts capsule elb jnt
N: Radial n (C6,7,8) post cord

Question 3

Describe path of Radial N

Answer 3

Continuation of post cord. Leaves axilla via triangular space and spirals down behind humerus behind uppermost fibres of triceps.
Pierces lat IM septum to enter ant compartment in cubital fossa.

Question 4

What are the 4 branches of radial nerve to triceps?

Answer 4

1 to long head
1 to lateral head
2 to medial head

Question 5

Sensory branches of radial nerve in arm

Answer 5

Posterior cutaneous of arm

lower lateral cutaneous nerve of arm

Question 6

Describe profunda brachii course and branches

Answer 6

Enters arm via triangular space. At lat IM septum divides into anterior and post branches running down. Ant pierces septum to run anteriorly to join cubital anastomosis

Question 7

Ulnar nerve path

Answer 7

Enters posterior compartment in lower arm and then passes through humeral and ulna heads in forearm

Question 8

Describe elbow joint

Answer 8

Synovial hinge joint.

2 articulations - humeral radius and humeral-ulnar

Question 9

Describe humeral-radial articulation

Answer 9

Hinge joint

Sphere like capitalum articulates with radial head

Question 10

Describe humeral-ulnar articulation

Answer 10

Hinge joint
Trochlear is grooved surface which articulates with curved ridge of ulnar
This creates carry angle

Question 11

Ligaments of elbow joint

Answer 11

Ulnar collateral: Anterior (strongest, med epcndl to med coronoid), posterior (med olecranon to med coronoid) and middle band (med epcndl to med olecranon) form triangle
Radial collateral: single flat ligament from humerus (below CEO) to annular lig
Annular lig:
radial notch ulnar and slings around head and neck of radius
Capsule:
Surrounds joint - attaches to annular lig not to radius

Question 12

Nerves supply of elbow

Answer 12

Mscn, median, ulnar and radial nerves (Hilton’s law)

Question 13

Movements

Answer 13

flexion and extension