Intrinsic Muscles of the Hand

- See:
      - Dorsal Interossei
      - Lumbricals:
      - Palmar Interossei

- Hypothenar Eminence:
    - muscles of hypothenar eminence are  abductor, flexor, opponens digiti minimi, & palmaris brevis;
    - muscles of hypothenar eminence are innervated by ulnar nerve;

- Thenar Eminence:
    - muscles of thenar eminence are APB, flexor pollicis brevis, & opponens pollicis;
    - muscles of thenar eminence, w/ exception of deep head of FPB, which is innervated by ulnar nerve, are supplied by median;
    - all thenar & hypothenar muscles, except abductor minimi, originate partly from transverse carpal ligament;
    - their insertions are primarily on base of proximal phalanx of thumb & little finger, except for both opponens muscles, 
          which insert on their respective metacarpals.

- Interossei:
    - anatomy:
         - 7 in number, 4 are dorsal & 3 volar.
         - their origin is from the metacarpal shafts.
         - dorsal interossei:
               - 1st & 4th dorsal interossei insert on radial aspect of index & ulnar side of ring fingers;
               - 2nd & 3rd insert on radial & ulnar sides of long finger respectively;
               - occassionally, short masses of muscle originate from carpal bones or from base of metacarpals on dorsum
                     of hand & appear as enlargements similar to cysts or other bone or soft tissue lesions;
                     - these accessory muscle masses are similar to muscle belly of extensor digitorum brevis on the dorsum of the foot;
                     - recognition of these muscle abnormalities is important in diff dx;
               - dorsal Interossie abduct index & ring fingers & adduct long finger to either side of a line drawn through its longitudinal axis;
         - palmar interossei:
               - 1st volar interosseous inserts on ulnar side of index digit, and 2nd & 3rd insert on radial aspect of ring and little fingers;
               - volar interossei are thus positioned to adduct these digits toward the long finger;
               - site of insertion of these muscles accounts for development of ulnar deviation of little finger if motor branch of ulnar nerve is injured;
         - interossei, along w/ 4 lumbricals, also flex MP & extend IP joints;
               - radial interossei tend to insert into bone w/ lesser insertions into extensor hood;
               - volar interossei & lumbricals usually insert into lateral band expansion;
               - lumbricales arise from tendonns of FDP in mid-palmar area & insert into radial aspect of dorsal hood.
    - innervation:
         - all interossei & 3rd & 4th lumbricale s are innervated by ulnar nerve;
         - first and second lumbricales are supplied by median;

- Exam:
    - Bunnel test for intrinsic tightness:
    - side to side confrontational test:
          - bring ulnar sides of little fingers into opposition and press together;
          - bring radial sides of thumbs into opposition and press together;
          - weakness is readily demonstrated, as the fingers on the weakened hand will bunch together;

- Pathologic Conditions:
    - intrinsic minus - claw hand:
    - intrinsic plus hand:
    - saddle deformity:
         - condition which results from traumatic adhesions between interosseous and lumbrical muscles which causes
                symptomatic impingement on the deep transverse metacarpal ligament during intrinsic contraction;
         - etiology: crush injuries or direct blow;
         - clinical findings:
                - pain located in the distal intermetacarpal space;
                - pain w/ prolonged gripping of objects or w/ making a fist;
                - seen most often in ring and long finger;
                - Bunnel test is positive in the majority of patients;
        - treatment release of adhesions between the lubrical and interosseous muscle, in addition to release of the transverse metacarpal ligament;
        - references:
            - Saddle Deformity. Posttraumatic interosseous-lumbrical adhesions: review of eighty-seven cases.

  Flexor digitorum superficialis tendon transfer for intrinsic replacement. Long-term results and the effect on donor fingers.

  Opponensplasty in intrinsic-muscle paralysis of the thumb in leprosy.

  Patterns of movement of totally intrinsic-minus fingers based on a study of one hundred and forty-one fingers.

  Movement patterns of interosseus-minus fingers.

  Abductor pollicis longus transfer for replacement of first dorsal interosseous.

  Architectural design of the human intrinsic hand muscles.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, April 10, 2012 3:53 pm