4th metacarpal !
The fourth metacarpal is the palm bone of the ring finger; it is the thinnest metacarpal and moves slightly at the wrist.
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What it is
The long bone in the palm leading to the ring finger.
What it does
Forms the palm and the knuckle at its head.
Key facts
- Joints with
- Base: capitate, hamate; head: proximal phalanx; adjacent metacarpals
- Landmarks
- Base, shaft, neck, head (knuckle)
Relations
- Above
- Hamate and part of the capitate
- Behind
- Extensor digitorum tendon to the ring finger, linked to its neighbours by the juncturae tendinum
- Lateral
- Third dorsal interosseous and second palmar interosseous
- Medial
- Fourth dorsal interosseous
- Below
- Proximal phalanx of the ring finger
How to find it
Felt along the back of the hand between the middle and little finger rays; in a fist its head is the knuckle between those of the middle and little fingers.
On imaging
Metacarpal sign: on a PA view a line drawn along the heads of the 4th and 5th metacarpals normally passes beyond the head of the 3rd; when it cuts through the 3rd, the 4th is short.
Clinical notes
- Neck fractures of the 4th often come with a 5th metacarpal (boxer's) fracture from the same punch
- Shaft fractures are partly splinted by the deep transverse metacarpal ligaments to the 3rd and 5th metacarpals, which limits shortening
- Fracture-dislocations of the 4th and 5th carpometacarpal joints at the hamate follow a punch and are easily missed on the PA view alone
Development
Ossifies in cartilage: a primary centre appears in the shaft before birth and one secondary centre later forms at the head, not at the base as in the 1st metacarpal. On a child's X-ray the open plate near the head shows as a dark line that can be read as a fracture.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
In which conditions is a short 4th metacarpal seen?
Pseudohypoparathyroidism and Turner syndrome; the knuckle sinks to a dimple in a fist.
What is the metacarpal sign on a PA hand X-ray?
A line along the heads of the 4th and 5th metacarpals that cuts through the 3rd head means the 4th metacarpal is short.
Which fracture often accompanies a 4th metacarpal neck fracture from a punch?
A 5th metacarpal (boxer's) fracture from the same punch.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- ossa metacarpi TA2 1264
- Official Spanish (DeCS)
- Hueso metacarpiano IV
- English (TA2)
- 4th metacarpal
Related
- A1 pulleys
- CMC ligaments
- Dorsal interossei
- Extensor tendons
- FDP tendons
- Finger joint capsules
- Lumbricals
- Knuckle collateral ligaments
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Hand Bones; 8.5 Development of the Appendicular Skeleton (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
