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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.