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Ulnar Nerve Injury, Treatment of Ulnar Nerve Injury, Pathomechanics
Loss…
Ulnar Nerve Injury
CLAW HAND
It is a deformity with hyperextension of the
metacarpophalangeal joints and flexion of the interphalangeal joints of the fingers.
(intrinsic minus hand)
-
Clinical Features
These include the
- classical deformity,
.
- loss of sensation along the ulnar nerve distribution and
.
- wasting of the hypothenar muscles,
intrinsic muscles of the hand leading to hollow intermetacarpal spaces on the dorsum of the hand
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causes
General Causes
Local Causes
Causes in the axilla
- Crutch pressure.
- Aneurysm of the axillary vessels
Causes in the arm
- Fracture shaft of humerus.
- Gunshot and penetrating injuries.
Causes at the elbow
- Compression by the accessory muscle (anserine epitrochlearis).
- Fracture lateral epicondyle of humerus.
- Repeated occupational strains.
- Recurrent subluxation of the nerve.
- Compression by the osteophytes as in rheumatoid and osteoarthritis.
- Cubitus valgus deformity due to various causes results in repeated friction of
the nerve giving rise to tardy (late) ulnar nerve palsy.
Causes in the forearm
- Fracture both bones forearm.
- Incised wounds, gunshot wounds and penetrating injuries of the forearm
Causes at the wrist
- Compression by osteophytes.
- Fracture hook of the hamate.
- Compression by ganglion.
- Wrist injuries.
Causes in the hand
- 1 more item...
- Metabolic diseases,
- collagen diseases,
- malignancies,
- endogenous or exogenous toxins;
- thermal, chemical or mechanical trauma,
etc. can cause injury to the peripheral nerves
-
-
Pathomechanics
Loss of intrinsic muscle function due to ulnar nerve
injury results in
- loss of flexion at MP joints & extension of IP joints of the fingers.
.
- In a bid to bring about the flexion of the MP joints,
the long finger flexors overact pulling the IP joints
and wrist into more flexion.
.
- This causes a tenodesing (pulling) effect on the long finger extensors.
.
- The extensors cannot extend the IP joints without the
of the MP joint in neutral or slightly flexed position, which is normally brought about by the intrinsic.
.
- This along with the compensatory over action of the long finger extensors to bring about the lost extension of the MP joints results in hyper-extension of the MP joints and the classical deformity
.
- This is called the intrinsic minus hand:
.
- The thumb is also adducted by its long extensors because the
intrinsics and the abductors are paralyzed
What is ulnar paradox?
The higher the lesion of the median and ulnar nerve injury,
the less prominent is the deformity and vice versa. This is
because in higher lesions the long finger flexors are
paralyzed. The loss of finger flexion makes the deformity
look less obvious.
At a glance: Ulnar nerve injury
.
- Ulnar nerve root value is C8T1
.
- Injury causes ulnar clawing
.
- Total clawing when median nerve is also affected
.
- Froment’s sign is a reliable test
.
- For quick clinical evaluation after injury, the tip of the
little finger is tested for sensation
.
- Ulnar paradox—higher the lesion less is the deformity
& vice versa
.
- Correction is by tendon transfers if all criteria are met
.
- If no tendons are available for transfer, MP joint is
stabilized by capsulodesis, tenodesis or arthrodesis
.
- All surgeries aim at correcting the hyperextension at
MP joint