Discussion: -
lesion of ulnar nerve at or near wrist or base of palm will result in paralysis of hypothenar muscles, all interosseous muscles, 1/2 of FPB, the palmaris brevis, & adductor pollicis; -
in pts w/ low ulnar nerve injury, some intrinsic may continue to function due to martin gruber communication between AIN and the unlnar nerve;
- Clinical Presentation:
- w/ low ulnar nerve palsy, interossei & third & fourth lumbricals are paralyzed;
- there will be loss of hypothenar muscles, interossei, adductor pollicis, and the deep half of the FPB;
- in patients w/ low ulnar nerve injury, some intrinsic f(x) may be maintained due to martin gruber communication between AIN nerve & unlnar nerve;
there will be loss of 50-80 % of pinch strength, 50% loss of grip strength, loss of lateral deviation of fingers, and loss of integration of the PIP and MPJ flexion; -
Froment's sign: - when the patient is asked to adduct the thumb (such as holding a pencil in the web space), patient will instead hyperflex the IP joint to compensate for loss of the adductor;
- MP Joint Instability: - weakness of the adductor pollicis leads to instability of the MP joint; - unopposed action of the thumb extensors leads to MCP hyperextension deformity where as unopposed activity of the thumb flexors lead to IP joint hyperflexion deformity;
- Clawing is present w/ low ulnar nerve injury: - also known as Duchenne's sign;
- clawing of ulnar 2 digits occurs, to lesser degree, long finger cannot be completely extended; - there is hyperextension of MP joint, because of unopposed action of long extensors;
- unopposed long extensors cannot bring about any extension of IP jonts because their energy is dissipated in hyperextending MP joints;
- IP joints are flexed due to unopposed action of long flexors, since extensor expansion is lax due to of paralysis of interossei & lumbricals;
- thus clawing occurs, w/ hyperextension of MP joints & flexion of IP joints;
- wartenberg's sign (little finger abduction) - due to unopposed ulnar insertion of extensor digiti quinti;
- little finger more often has more severe claw deformity, as opposed to ring finger, because of inherent increased laxity in little finger MP joint volar plate;
- in addition, approx 50% of pts have median nerve cross innervation to lumbricals to ring finger, thus preventing claw deformity of the ring finger; -
diff dx:
- rupture of the deep transverse metacarpal ligament;
- note that extreme ulnar deviation of the little finger with extension may indicate a rupture of the deep transverse metacarpal ligament
lesion of ulnar nerve at or near wrist or base of palm will result in paralysis of hypothenar muscles, all interosseous muscles, 1/2 of FPB, the palmaris brevis, & adductor pollicis; -
in pts w/ low ulnar nerve injury, some intrinsic may continue to function due to martin gruber communication between AIN and the unlnar nerve;
- Clinical Presentation:
- w/ low ulnar nerve palsy, interossei & third & fourth lumbricals are paralyzed;
- there will be loss of hypothenar muscles, interossei, adductor pollicis, and the deep half of the FPB;
- in patients w/ low ulnar nerve injury, some intrinsic f(x) may be maintained due to martin gruber communication between AIN nerve & unlnar nerve;
there will be loss of 50-80 % of pinch strength, 50% loss of grip strength, loss of lateral deviation of fingers, and loss of integration of the PIP and MPJ flexion; -
Froment's sign: - when the patient is asked to adduct the thumb (such as holding a pencil in the web space), patient will instead hyperflex the IP joint to compensate for loss of the adductor;
- MP Joint Instability: - weakness of the adductor pollicis leads to instability of the MP joint; - unopposed action of the thumb extensors leads to MCP hyperextension deformity where as unopposed activity of the thumb flexors lead to IP joint hyperflexion deformity;
- Clawing is present w/ low ulnar nerve injury: - also known as Duchenne's sign;
- clawing of ulnar 2 digits occurs, to lesser degree, long finger cannot be completely extended; - there is hyperextension of MP joint, because of unopposed action of long extensors;
- unopposed long extensors cannot bring about any extension of IP jonts because their energy is dissipated in hyperextending MP joints;
- IP joints are flexed due to unopposed action of long flexors, since extensor expansion is lax due to of paralysis of interossei & lumbricals;
- thus clawing occurs, w/ hyperextension of MP joints & flexion of IP joints;
- wartenberg's sign (little finger abduction) - due to unopposed ulnar insertion of extensor digiti quinti;
- little finger more often has more severe claw deformity, as opposed to ring finger, because of inherent increased laxity in little finger MP joint volar plate;
- in addition, approx 50% of pts have median nerve cross innervation to lumbricals to ring finger, thus preventing claw deformity of the ring finger; -
diff dx:
- rupture of the deep transverse metacarpal ligament;
- note that extreme ulnar deviation of the little finger with extension may indicate a rupture of the deep transverse metacarpal ligament
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