Mateusz Gładysz FESSH prep

FESSH prep Anatomy Origin and insertion of the lumbricals, relative strength of lumbricals and interossei, variation in interosseous heads and insertions, motor supply of the fourth lumbrical, lumbrical plus finger

Interosseous and lumbrical muscles of the hand

Last reviewed v1.0

FESSH-077Anatomy●○○ basic

Regarding the anatomy of the interosseous and lumbrical muscles of the hand:

  1. 1.Dissection studies support the classic description of the palmar interossei as single-headed muscles that insert into the extensor apparatus.

  2. 2.The lumbrical muscles arise from the flexor digitorum profundus tendons and insert into the lateral band of the extensor mechanism.

  3. 3.The lumbricals generate more of the intrinsic motor force of the finger than the interossei.

  4. 4.The fourth lumbrical receives its motor branch from the median nerve.

  5. 5.In a lumbrical plus finger, attempted flexion produces paradoxical extension of the interphalangeal joints.

FESSH marking: +1 per correct statement, 0 for blank, −1 for incorrect. Click the same TRUE/FALSE button twice to clear it.

Question ID
FESSH-077
First published
Last reviewed
Version
v1.0
Answer key and explanations — open after answering

  1. 1. Dissection studies support the classic description of the palmar interossei as single-headed muscles that insert into the extensor apparatus.

    False

    Eladoumikdachi and colleagues reviewed the literature and dissected 14 fresh cadaver hands. More than one head was present in 38% of palmar and 75% of dorsal interossei, and the palmar interossei could also insert onto bone and onto the volar plate. The authors concluded that classic descriptions of the interosseous insertions are oversimplified.

    • Eladoumikdachi F, Valkov PL, Thomas J, Netscher DT. Anatomy of the intrinsic hand muscles revisited: part I. Interossei. Plast Reconstr Surg. 2002;110(5):1211-24. PMID 12360058

  2. 2. The lumbrical muscles arise from the flexor digitorum profundus tendons and insert into the lateral band of the extensor mechanism.

    True

    Wang and colleagues describe the lumbricals as originating from the flexor digitorum profundus tendons and inserting onto the lateral band of the extensor tendons. Both attachments move, so each lumbrical links the flexor and extensor systems of its finger.

    • Wang K, McGlinn EP, Chung KC. A biomechanical and evolutionary perspective on the function of the lumbrical muscle. J Hand Surg Am. 2014;39(1):149-55. PMID 24369943

  3. 3. The lumbricals generate more of the intrinsic motor force of the finger than the interossei.

    False

    The lumbricals have the smallest physiological cross-sectional area of any muscle in the upper limb, and their motor function is estimated at about one-tenth of that of the interossei. They are rich in muscle spindles, which points to an important role in sensory feedback from the finger joints rather than in force generation.

    • Wang K, McGlinn EP, Chung KC. A biomechanical and evolutionary perspective on the function of the lumbrical muscle. J Hand Surg Am. 2014;39(1):149-55. PMID 24369943

  4. 4. The fourth lumbrical receives its motor branch from the median nerve.

    False

    In a dissection of 10 fresh-frozen cadaver hands, Chim and colleagues found a consistent motor branch to the fourth lumbrical and the third palmar interosseous arising from the deep branch of the ulnar nerve in every specimen. The median nerve supplies the lumbricals of the index and middle fingers.

    • Chim H, Shekouhi R, Ahmed SH, Matsui C, Vonu P, Sullivan B. Anatomical Characterization of the Motor Branch to the Fourth Lumbrical: A Cadaver Study. J Hand Surg Am. 2025;50(11):1401.e1-1401.e7. PMID 39797860
    • Wang K, McGlinn EP, Chung KC. A biomechanical and evolutionary perspective on the function of the lumbrical muscle. J Hand Surg Am. 2014;39(1):149-55. PMID 24369943

  5. 5. In a lumbrical plus finger, attempted flexion produces paradoxical extension of the interphalangeal joints.

    True

    Paradoxical finger extension is the classical presentation of lumbrical plus syndrome, a subtle complication of flexor digitorum profundus lesions. Schuind and colleagues described an additional sign in three cases, increased metacarpophalangeal flexion when making a fist; lumbrical tenotomy corrected the paradoxical interphalangeal extension.

    • Schuind FA, Moungondo F, Van Wetter P. A New Clinical Sign of Lumbrical Plus Finger. J Hand Surg Am. 2018;43(6):573.e1-573.e4. PMID 29223629