HLTH1008 Chap.11 Elbow, Forearm, Wrist and Hand
Elbow, Forearm, Wrist and Hand
This chapter covers the joints and nerves from the elbow to the fingers. It describes the three joints of the elbow, the carrying angle with its two sets of published values, pronation and supination, the collateral and annular ligaments, and the prime movers of the elbow and forearm.
It then compares ulnar nerve lesions at the elbow and the wrist, sets radial, median and ulnar injuries side by side, and finishes with the radiocarpal joint, the scaphoid, Colles fracture and the anatomical snuff box. The nerve lesions are presented as comparisons so that one clinical clue points to one nerve and one level. The carpal bones and snuff box close the chapter because they appear on wrist and hand stations.
What this chapter covers
- 01
Humeroulnar, humeroradial and radioulnar joints
- 02
Carrying angle
- 03
Pronation and supination
- 04
Elbow ligaments and pulled elbow
- 05
Prime movers of the elbow and forearm
- 06
Ulnar nerve lesions at two levels
- 07
Radial and median nerve lesions
- 08
Wrist joints, scaphoid and snuff box
Worked example · free
Radial nerve injury above or below the groove
- +1Wrist drop at either level means the wrist and finger extensors have lost their radial supply.
- +1Test elbow extension, the action of triceps.
- +1If the elbow cannot be extended, the lesion lies above the radial groove.
- +1If elbow extension is preserved, the lesion is at or below the groove.
Key terms
- Humeroulnar joint
- The hinge joint between the trochlea of the humerus and the trochlear notch of the ulna.
- Annular ligament
- The ring that holds the radial head against the ulna.
- Cubitus valgus
- An outward angle of the forearm at the elbow, normal as the carrying angle.
- Claw hand
- Flexed medial fingers after loss of ulnar-supplied hand muscles.
- Wrist drop
- Inability to extend the wrist after radial nerve injury.
- Scaphoid
- The carpal bone most often injured, prone to proximal necrosis.
- Anatomical snuff box
- The hollow between the thumb extensor tendons over the scaphoid.
- Carpal tunnel syndrome
- Compression of the median nerve at the wrist, causing pain and numbness.
- Colles fracture
- A distal radius fracture with posterior displacement, the dinner-fork deformity.
- Carrying angle
- The lateral angle of the extended, supinated forearm to the humerus.
Elbow, Forearm, Wrist and Hand FAQ
What is the carrying angle and how large is it?
It is the lateral angle between the long axes of the humerus and the forearm with the elbow extended and supinated, a physiological cubitus valgus that keeps a carried load clear of the thigh. One lecture gives 8 to 15°, the biomechanics lecture 10 to 15° in males and 15 to 20° in females.
Which muscles are lost when the ulnar nerve is injured at the wrist?
The hypothenar muscles, the deep head of flexor pollicis brevis, the palmar and dorsal interossei, the medial two lumbricals and adductor pollicis, with sensory loss over the medial hand and one and a half fingers. The forearm muscles are spared because their branches leave above the wrist.
What is a pulled elbow?
In young children a sudden pull on a pronated forearm can slip the radial head out of the annular ligament. The workshop answer describes the distal attachment of the ligament tearing and the radial head displacing, which is why the answer names the ligament rather than a fracture.
What is the difference between golfer's elbow and tennis elbow?
Golfer's elbow is irritation of the common flexor origin on the medial epicondyle, mainly flexor carpi radialis and pronator teres. Tennis elbow is irritation of the common extensor origin on the lateral epicondyle, where the lecture singles out extensor carpi radialis brevis.
Why is the scaphoid prone to avascular necrosis?
It is the carpal bone most often injured, and its blood supply enters at its distal end. A fracture can cut off the proximal part from that supply, which is why the proximal fragment is the one at risk of necrosis.
Exam move
Draw the elbow from the front and mark the three joints and the carrying angle with both sets of values. Make a table of the elbow and forearm prime movers. Then build a three-row comparison of the radial, median and ulnar nerves with the site of injury, the lost muscles and the skin area, and practise the two-level ulnar question until the difference is automatic.
Finish with the carpal bones and the boundaries of the snuff box. Draw the hand and shade the skin areas of the median, ulnar and radial nerves, then add the C6, C7 and C8 dermatomes to see where the two maps agree and differ.
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