The ulnar nerve arises from the medialcord of the brachial plexus (C8 and T1), Gives off no cutaneous or motorbranches in the axilla or in the arm. It enters the forearm from behind themedial epicondyle
In the distal third of the forearm, it givesoff its palmar and posterior cutaneousbranches. The palmar cutaneous branch suppliesthe skin over the hypothenar eminence The posterior branch supplies the skinover the medial third of the dorsum ofthe hand and the medial one and a halffingers.
Not uncommonly, the posterior branchsupplies two and a half instead of oneand a half fingers. NB: It does not supply the skin over thedistal part of the dorsum of these fingers.
Entering the palm by passing in front ofthe flexor retinaculum, The superficial branch of the ulnar nervesupplies the skin of the palmar surface ofthe medial one and a half fingers, including their nail beds
Muscles supplied: Flexor carpi ulnaris Flexor digitorum profundus(medial half) Muscles of the hypothenar eminence Adductor policis Third and fourth lumbricals Interossei Palmaris brevis
Mainly the type of nerve traumadepends on the mechanism of injury: Neuropraxia Axonotemesis Neurotemesis
The ulnar nerve is most commonly injured atthe elbow, where it lies behind the medialepicondyle, The injuries at the elbow are usuallyassociated with fractures of the medialepicondyle. At the wrist, where it lies with the ulnar arteryin front of the flexor retinaculum. The superficial position of the nerve at thewrist makes it vulnerable to damage fromcuts and stab wounds
Injuries of the ulnar nerve at elbow:Motor: The flexor carpi ulnaris and the medial half of theflexor digitorum profundus muscles are paralyzed. The paralysis of the flexor carpi ulnaris can beobserved by asking the patient to make a tightlyclenched fist. Normally, the synergistic action of the flexor carpiulnaris tendon can be observed as it passes to thepisiform bone; the tightening of the tendon will be absent if themuscle is paralyzed.
The profundus tendons to the ring and little fingers willbe functionless, The terminal phalanges of these fingers are thereforenot capable of being markedly flexed. Flexion of the wrist joint will result in abduction, owingto paralysis of the flexor carpi ulnaris. The medial border of the front of the forearm willshow flattening owing to the wasting of theunderlying ulnaris and profundus muscles. The small muscles of the hand will be paralyzed,except the muscles of the thenar eminence and thefirst two lumbricals, which are supplied by the mediannerve.
The patient is unable to adduct and abduct the fingersand consequently is unable to grip a piece of paperplaced between the fingers. It is impossible to adduct the thumb because theadductor pollicis muscle is paralyzed. If the patient is asked to grip a piece of paper betweenthe thumb and the index finger, he or she does so bystrongly contracting the flexor pollicis longus and flexingthe terminal phalanx (Froments sign). The metacarpophalangeal joints become hyperextendedbecause of the paralysis of the lumbrical and interosseousmuscles, which normally flex these joints. The interphalangeal joints are flexed, owing again to theparalysis of the lumbrical and interosseous muscles, whichnormally extend these joints through the extensorexpansion.
The flexion deformity at the interphalangeal joints ofthe fourth and fifth fingers is obvious because the firstand second lumbrical muscles of the index andmiddle fingers are not paralyzed. In long-standing cases the hand assumes thecharacteristic claw deformity (main en griffe). Wasting of the paralyzed muscles results in flatteningof the hypothenar eminence and loss of the convexcurve to the medial border of the hand. Examination of the dorsum of the hand will showhollowing between the metacarpal bones caused bywasting of the dorsal interosseous muscles.
Sensory: Loss of skin sensation will be observedover the anterior and posterior surfacesof the medial third of the hand and themedial one and a half fingers.
Vasomotor Changes The skin areas involved in sensory loss arewarmer and drier than normal becauseof the arteriolar dilatation and absenceof sweating resulting from loss ofsympathetic control
Injury of ulnar nerve at wrist:Motor: The small muscles of the hand will beparalyzed and show wasting, except for themuscles of the thenar eminence and thefirst two lumbricals. The clawhand is much more obvious inwrist lesions because the flexor digitorumprofundus muscle is not paralyzed, andmarked flexion of the terminal phalangesoccurs.
Sensory: The main ulnar nerve and its palmar cutaneousbranch are usually severed The posterior cutaneous branch, which arisesfrom the ulnar nerve trunk about 2.5 in. (6.25cm) above the pisiform bone, is usuallyunaffected. The sensory loss will therefore be confined tothe palmar surface of the medial third of thehand and the medial one and a half fingersand to the dorsal aspects of the middle anddistal phalanges of the same fingers.
Vasomotor and trophic changes: These are the same as those describedfor injuries at the elbow. It is important toremember that with ulnar nerveinjuries, the higher the lesion, the lessobvious the clawing deformity of thehand.
Surgical management & Medical mx: Exploration and suture of the divided nerve Anterior transposition of nerve at the elbowjoint Metacarpophalengeal flexion can beimproved by extensor carpi radialis longus tointrinsic tendon transferes or Looping a slip of flexor digitorum supeficialisaround the opening of the flexorsheath(Zancolli procedure) Admistration of analgesics if nerve lesion isassociated with fracture
Index abduction can be improved bytransfering extensor policis brevis orextensor indicis to interosseous insertionon the radial side of the finger.
faradism Ift Passive movements, can be autoassisted Hydrotherapy Electro diagnosis Tens
If there is no recovery after nervedivision,hand function is significantlyimpaired Grip strength is lost because the primarymetacarpophalangial flexors are lost Pinch is poor because thumb adductionand index finger abduction is weakened.
Apley’s othopaedic textbook Snell’ clinical anatomy www.physiopedia.com Cleveland clinic journal of medicine www.pubmed.com Essential physical medicine andrehabilitation.