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Low Ulnar Nerve Injury

- See:
      - Claw Hand:
      - Tendon Excursion:
      - Nerve Repair:
      - Combined Injuries of the Median and Ulnar Nerves:

- 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;
                          - references:
                                 - Closed rupture of the deep transverse metacarpal ligament: diagnosis and management
                                  - Abducted, hyperextended small finger deformity of noneurologic etiology
           - treatment:
                  - transfer EDQ to radial side of digit, volar to intermetacarpal ligament if claw deformity exists;
                  - as a requirement for this procedure, one must be sure that pt has good EDC function to the little finger;
          - reference:
                  The abducted little finger in low ulnar nerve palsy.

- Operative Procedures:
    - adductor pollicis deficit:
         - adductor pollicis substitution by FDS of long finger passed thru interosseous membrane, over & under ECU  as distal pulley;
                 - crossing beneath EDC, and into adductor insertion, anchoring tendon into bone;
         - boyles procedure:
                 - transfer of BR (reroute around 3rd MC to adductor pollicis);
         - mp arthrodesis
                 - if tendon transfer is not possible due to of lack of motors, MP arthrodesis of hypermobile thumb MP joint will provide
                         stability and some improvement in strength;
    - intrinsic muscles deficit:
         - burkhalter transfer
         - APL transfer to first dorsal interosseous;
         - reference:
                 Abductor pollicis longus transfer for replacement of first dorsal interosseous

Studies on the hand in ulnar nerve paralysis. A clinical experimental investigation in normal and anomalous innervation

Restoration of pinch in ulnar nerve palsy by transfer of split extensor digiti minimi and extensor indicis.

Tendon transfer for median and ulnar nerve paralysis

Reconstruction of pinch in ulnar intrinsic palsy. 
      Brown PW. Orthop Clin North Am. 1974:5:323.

Tendon transfers for ulnar nerve palsy. Evaluation of results and practical treatment considerations