Interossei
Interossei Key Points
- There is some inconsistency among anatomy resources regarding the interossei. Whilst all agree there are 4 dorsal interossei some report there are only 3 palmar interossei. This is due to the pollical palmar interosseous (PPI) which was traditionally thought to be part of either adductor pollicis or flexor pollicis brevis. Several anatomists since have proven this isn't the case and the PPI is a true interosseous muscle. Radiological investigations also support this (see the radiopedia link).
- Each hand has 8 interossei - 4 dorsal and 4 palmar
- All interossei innervated by the deep branch of ulnar nerve.
- The palmar interossei are sometimes divided into 1 pollical and 3 central palmar interossei. The pollical interossei is absent in 20% of individuals. This means 80% of the population have a PPI making the anatomical norm to have 4 palmar interossei.
- Both Dorsal and Palmar interossei have their origins on the metacarpal and insert on the extensor expansion.
- The palmar interossei adducts the fingers towards the middle finger whereas the dorsal interossei abduct (Remember DORSAL SPREAD)
- Another way to remember this is PAD and DAB (P palmar interossei,
Diagram illustrating palmar interossei
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Diagram illustrating dorsal interossei
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