Ulnar Claw vs Hand of Benediction

Question 1

What are the ulnar claw and hand of benediction?

Answer 1

Two characteristic signs of peripheral nerve damage

Question 2

When is the ulnar claw deformity seen?

Answer 2

In long standing ulnar nerve damage at the wrist

Question 3

What does the ulnar claw affect?

Answer 3

The little and ring fingers of the hand

Question 4

What happens to the little and ring fingers of the hand in ulnar claw?

Answer 4

They are hyperextended at the MCP joint, and flexed at both IP joinsts

Question 5

What muscles are affected by an ulnar nerve lesion in the wrist?

Answer 5

Medial two lumbricals
Interossei
Hypothenar muscles
Adductor pollicis

Question 6

What do the medial two lumbricals do?

Answer 6

Flexes at the MCP joints and extends the IP joints of the little and ring fingers

Question 7

What do the interossei do?

Answer 7

Abducts and adducts the fingers

Question 8

What do the hypothenar muscles do?

Answer 8

Flexes, abducts, and opposes the little finger

Question 9

What does the adductor pollicis do?

Answer 9

Adducts the thumb

Question 10

What are the important muscles to consider in the ulnar claw?

Answer 10

The medial lumbricals

Question 11

What happens if the medial lumbricals are paralysed?

Answer 11

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

Question 12

Why are the MCP joints hyperextended in the ulnar claw?

Answer 12

Due to unopposed extension from the long extensor muscles in the posterior compartment of the forearm

Question 13

Why are the IP joints flexed in the ulnar claw?

Answer 13

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

Question 14

What happens in a high ulnar nerve injury?

Answer 14

Some muscles in the anterior forearm are paralysed, in addition to the hand muscles

Question 15

What muscles in the anterior forearm are paralysed in a high ulnar nerve injury?

Answer 15

Medial half of the flexor digitorum profundus

Flexor carpi ulnaris

Question 16

What does the medial half of the flexor digitorum profundus do?

Answer 16

Flexes at the distal IP joints of the ring and little fingers

Question 17

What does the flexor carpi ulnaris do?

Answer 17

Flexes and adducts the risk

Question 18

How does the ulnar claw differ when there is a high ulnar nerve injury?

Answer 18

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

Question 19

Why is the effect of a high ulnar nerve injury known as the ulnar paradox?

Answer 19

Because you would expect a more debilitating injury to produce a more pronounced deformity, but actually the opposite occurs

Question 20

Why does the hand of benediction occur?

Answer 20

As a result of median nerve damage at the elbow

Question 21

How does the hand of benediction differ from the ulnar claw?

Answer 21

It is only apparent if the patient is asked to make a fist, whereas the ulnar claw is produced spontaneously

Question 22

What muscles are affected if the median nerve is lesioned at the elbow?

Answer 22

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

Question 23

What do the lateral two lumbricals do?

Answer 23

Flexes at the MCP joints and extends at the IP joints of the index and middle fingers

Question 24

What happens if a patient with median nerve damage is asked to make a fist?

Answer 24

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.