ulnar nerve anatomy & injury

1. Ulnar nerve
- Dr. Naresh Bone
DNB Ortho resident
KIMS, Secunderbad.

2. Anatomy
• Origin : Ulnar nerve derived from
Medial cord of brachial plexus
• Root value : C8-T1

3. Course
• In the Axilla – it descend on the
medial side of 3rd part of axillary
artery between it & axillary vein
• In the Arm – lies posteromedial to
brachial artery in anterior
compartment of upper ½ arm

4. • Pierces medial intermuscular septum at
the Arcade of struthers ~8 cm from
medial epicondyle & lies medial to the
triceps
• The Arcade of Struthers is an aponeurotic
band extending from medial IM septum
to the medial head of triceps.
• At the Elbow , it passes behind the medial
epicondyle where it can be palpated with
a finger.

5. Cubital tunnel
• Roof
• formed by FCU fascia and Osborne's
ligament (travels from the medial
epicondyle to the olecranon)
• Osborne's ligament a.k.a cubital
retinaculum
• Floor
• formed by posterior and transverse bands
of MCL and elbow joint capsule

6. • It enters the forearm by passing
between two heads of flexor carpi
ulnaris.
• It runs medial side of the forearm in
between the flexor carpi ulnaris and
the flexor digitorum profundus
muscles.
• The ulnar artery and nerve enter the
hand by passing superficial to the
flexor retinaculum
• And immediately lateral to the
pisiform bone

7. Guyon's canal
• Roof - Palmar carpal ligament
• Floor - Transverse carpal ligament,
hypothenar muscles
• Ulnar border - pisiform and
pisohamate ligament
• Radial border - hook of hamate

8. Motor innervation
• Forearm – a) Flexor carpi ulnaris
b) Flexor digitorum profundus (3rd & 4th finger)
• Hypothenar muscles - a) abductor digiti minimi
b)opponens digiti minimi
c)flexor digiti minimi
• Thenar – a) adductor pollicis
b) deep head of flexor pollicis brevis (FPB)
• Fingers – a) interossei (dorsal & palmar)
b) 3rd & 4th lumbricals

9. Sensory innervation
• Sensory branches of ulnar nerve –
a) dorsal cutaneous branch
b) palmar cutaneous branch
c) superficial terminal branches

10. Action of interossei
• Palmar – ADduct
• Dorsal –ABduct
(PAD-DAB)

11. Examination :
• Palmar interossei : Adducting finger
against piece of paper
• Dorsal interossei : Resisted abduction
of fingers

12. Action of lumbricals :
• Flexion of metacarpo-phalangeal
joint
• And extension of inter-phalangeal
joint

13. Cubital tunnel syndrome
• Entrapment of ulnar nerve around the elbow
joint.
• Sites of compression (proximal to distal) :
a) medial intermuscular septum
b) Arcade of Struthers
c) medial epicondyle (osteophytes)
d) cubital tunnel retinaculum (Osborne's
ligament)
e) aponeurosis of the two heads of the FCU
(arcuate ligament)

14. Etiology :
• Patient is lying down with the elbows
flexed
• Prolonged elbow flexion –while reading
or using a mobile phone
• compressed within the cubital tunnel (by
bone abnormalities, ganglia or
hypertrophied synovium)

15. Symptoms :
• Numbness and tingling in the little and the ulnar half of the ring finger
• Night symptoms
• caused by sleeping with arm in flexion

16. Physical examination :
• Inspection and palpation
a) interosseous and first web space atrophy
b) ring and small finger clawing
• Ulnar nerve thickening seen in Hansen disease

17. • Sensory
decreased sensation in ulnar 1-1/2 digits
• Motor
loss of the ulnar nerve results in paralysis of intrinsic muscles
(adductor pollicis, deep head FPB, interossei, and lumbricals 4
and 5)

18. Froment’s sign
• Ask the pt to hold paper between thumb &
index finger
• The examiner then attempts to pull the paper
out
• Inability to hold the paper or Flexion of
interphalangeal joint
Indicate – weakness of adductor pollicis
muscle & now pt depend on Flexor pollicis
longus which flexes the thumb

19. Pressure provocation test
• Examiner places fingers over
proximal to cubital tunnel elbow in
20’ flexion & forearm in supination
for 60 sec
• Positive –Symptom develop along
Ulnar nerve distribution

20. Diagnosis
• Electromyography (EMG) & nerve conduction velocity (NCV)
-used to localize areas of compression and neuropathy.

21. Treatment