- See:
-
Bunnel Test for Intrinsic Tightness:
-
Extensor Mechanism of Digits
-
Lumbrical Muscle Sheaths
-
Lumbical Plus Finger:
- Origin:
- tendons of
FDP tendon in center of palm, just proximal to the flexor sheath and the A1 pulley;
- area of origin varies from 3.5 to 4 cm and extends from level of pisiform bone proximally;
- lumbrical tendons pass volar to the deep transverse metacarpal ligament and insert into the radial
lateral band of each finger;
- Insertion:
- approaches the radial side of the metacarpal bone;
- sends one slip dorsally into central slip;
- sends another slip (called
lateral band) which joins w/ lateral slip from
EDC to form the lateral band;
- Discussion:
- intrinsics
of hand are supplied by distal branches of ulnar and
median
nerves;
- hence, injury to both these nerves, esp ulnar nerve (distally), leads to imbalance between the extrinsic and
intrinsic muscles;
- lumbricals are prime flexors of MP joints;
- they are responsible for well-synchronized flexion of MP joint w/ flexion of the interphalangeal (IP) joints;
- lumbricals, further, in conjugation with the interossei, form that part of the extensor expansion that is chiefly responsible for extension of
the proximal and distal interphalangeal joints;
Nerve supply:
- 1st & 2nd lumbricals:
median:
C7 >
C6;
- 3rd & 4th lumbricals:
ulnar:
C8;
- Action:
- when the lumbrical muscle contracts, it draws the lateral band proximally and
pulls the FDP distally (relaxing the tendon);
- extends IP joints:
- principal extensors of the interphalangeal joints (work horse);
- extends the IP joint, irrespective of MCP joint postion;
- facilitates IP extension by pulling profundi distally (unique ability to relax its on antagonist)
- flexes MCP joint:
- mainly in mechanical way by being pulled by the profundus;
-
Lumbricals are prime flexors of MP joints;
- when MP joints are stabilized, lumbricals bend fingers toward thumb (index finger abduction,
middle finger radial flexion, ring and little finger adduction);
- when fingers are flexed, lumbricals are pulled into carpal canal & recede proximally to the distal end of radius;
-
synergists: dorsal interossei,
palmar interossei,
FDP,
flexor digitorum superficialis;
Movement patterns of interosseus-minus fingers.
Architectural design of the human intrinsic hand muscles.
Lumbrical function: interaction of lumbrical contraction with the elasticity the extrinsic finger muscles and its effect on metaphalangeal joint equilibrium.
DA Ranney et al.
J. Hand Surg. Vol 12-A. 1987. p 566-575.
