Ulnar Claw vs Hand of Benediction Flashcards
What are the ulnar claw and hand of benediction?
Two characteristic signs of peripheral nerve damage
When is the ulnar claw deformity seen?
In long standing ulnar nerve damage at the wrist
What does the ulnar claw affect?
The little and ring fingers of the hand
What happens to the little and ring fingers of the hand in ulnar claw?
They are hyperextended at the MCP joint, and flexed at both IP joinsts
What muscles are affected by an ulnar nerve lesion in the wrist?
Medial two lumbricals
Interossei
Hypothenar muscles
Adductor pollicis
What do the medial two lumbricals do?
Flexes at the MCP joints and extends the IP joints of the little and ring fingers
What do the interossei do?
Abducts and adducts the fingers
What do the hypothenar muscles do?
Flexes, abducts, and opposes the little finger
What does the adductor pollicis do?
Adducts the thumb
What are the important muscles to consider in the ulnar claw?
The medial lumbricals
What happens if the medial lumbricals are paralysed?
There is a loss of flexion at the MCP joints, and a loss of extension at the IP joints, leading to an imbalance between the intrinsic and extrinsic muscles of the hand, producing the claw deformity
Why are the MCP joints hyperextended in the ulnar claw?
Due to unopposed extension from the long extensor muscles in the posterior compartment of the forearm
Why are the IP joints flexed in the ulnar claw?
Due to unopposed flexion from the long flexor muscles in the anterior compartment of the arm. The extensor muscles cannot extend the IP joint, as their energy is dissipated in hyperextending the MCP joints
What happens in a high ulnar nerve injury?
Some muscles in the anterior forearm are paralysed, in addition to the hand muscles
What muscles in the anterior forearm are paralysed in a high ulnar nerve injury?
Medial half of the flexor digitorum profundus
Flexor carpi ulnaris
What does the medial half of the flexor digitorum profundus do?
Flexes at the distal IP joints of the ring and little fingers
What does the flexor carpi ulnaris do?
Flexes and adducts the risk
How does the ulnar claw differ when there is a high ulnar nerve injury?
There will not be any flexion at the distal IP joints of the ring and little fingers, because the flexor digitorum profundus is paralysde, and so the ulnar claw only consists of hyperextension at the MCP joints and flexion at the proximal IP joints, producing a much less evident hand claw
Why is the effect of a high ulnar nerve injury known as the ulnar paradox?
Because you would expect a more debilitating injury to produce a more pronounced deformity, but actually the opposite occurs
Why does the hand of benediction occur?
As a result of median nerve damage at the elbow
How does the hand of benediction differ from the ulnar claw?
It is only apparent if the patient is asked to make a fist, whereas the ulnar claw is produced spontaneously
What muscles are affected if the median nerve is lesioned at the elbow?
Long flexors in the anterior compartment of the (except the medial half of the flexor digitorum profundus and the flexor carpi ulnaris)
Lateral two lumbricals
What do the lateral two lumbricals do?
Flexes at the MCP joints and extends at the IP joints of the index and middle fingers
What happens if a patient with median nerve damage is asked to make a fist?
They will be able to flex the little and ring fingers, as this action is performed by the medial half of the flexor digitorum profundus and medial two lumbricals, but they will not be able to flex the index and middle fingers.
