Palmar Interossei (Hand)
| Palmar Interossei (Hand) | |
|---|---|
| Muscle Type | |
| Origin | 1st: Base MC1 ulnar side
2nd: Length of MC2, ulnar side 3rd: Length of MC4, radial side 4th: Length of MC5, radial side |
| Insertion | 1st: Ulnar side thumb
2nd: Ulnar side index finger 3rd: Radial side ring finger 4th: Radial side little finger |
| Action | Adduction of thumb, index, ring, and little fingers towards the midline (axial line) through the third digit. Assists in flexion of MCPJs and extension of ICPJs of the three fingers. |
| Synergists | Abductor Digiti Minimi (Hand), Lumbricals |
| Antagonists | |
| Spinal innervation | C8, T1 |
| Peripheral Innervation | Ulnar Nerve |
| Vasculature | |
Manual Muscle Testing
The interossei muscles of the hand – four dorsal and three palmar – are tested by finger abduction and adduction movements.
The dorsal interossei abduct the index, middle, and ring fingers (away from the midline of the hand), while the palmar interossei adduct the index, ring, and little fingers (toward the hand’s midline).
Manual muscle tests typically have the patient extend the fingers and spread them apart or squeeze them together, against the examiner’s resistance. To isolate these motions in an exam, the fingers are usually tested in extension (to minimize the flexion force and better target pure abduction/adduction).
Palmar Interossei
Patient: Sitting or supine
Fixation: Stabilisation of adjacent digits
Test and Pressure:
1st: Adduction of the thumb towards the index finger (synergistic with adductor pollicis and 1st dorsal interosseous). Hold thumb and pull it radially
2nd: Adduction of the index finger towards the middle finger. Hold the index finger and pull towards the thumb
3rd: Adduction of ring finger towards middle finger. Hold the ring finger and pull to the little finger
4th: Adduction of little finger towards ring finger. Hold the little finger and pull ulnarly.
The dorsal interossei abduct the index, middle, and ring fingers (away from the midline of the hand), while the palmar interossei adduct the index, ring, and little fingers (toward the hand’s midline). The dorsal interossei abduct the index, middle, and ring fingers (away from the midline of the hand), while the palmar interossei adduct the index, ring, and little fingers (toward the hand’s midline).
A common clinical method for palmar interossei is the paper pull test: the patient holds a sheet of paper between two fingers (preventing adduction) and the examiner attempts to pull it out – failure to maintain grip indicates weakness in the respective palmar interosseus.
