2nd metacarpal !
The second metacarpal is the palm bone of the index finger; it is the longest metacarpal and its base barely moves on the wrist.
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What it is
The long bone in the palm leading to the index finger.
What it does
Forms the palm and the knuckle at its head.
Key facts
- Joints with
- Base: trapezium, trapezoid, capitate; head: proximal phalanx; adjacent metacarpals
- Landmarks
- Base, shaft, neck, head (knuckle)
Relations
- Above
- Trapezoid mainly, with the trapezium and capitate on each side
- Behind
- ECRL tendon at the base; extensor indicis and extensor digitorum tendons over the shaft
- In front
- Flexor carpi radialis insertion at the base; oblique head of the adductor pollicis; the deep palmar arch crosses the bases
- Lateral
- First dorsal interosseous; the radial artery enters the palm between it and the 1st metacarpal
- Medial
- First palmar interosseous and second dorsal interosseous
- Below
- Proximal phalanx of the index finger
How to find it
The shaft is followed along the back of the hand from the index knuckle to its base, where a carpal boss may be felt.
On imaging
PA, oblique and lateral views of the hand. On the PA view the 2nd to 5th carpometacarpal joints should show as even, parallel gaps; a lost or overlapping gap at the trapezoid suggests a CMC dislocation. Angulation of a neck fracture is judged on the lateral view. CT is used when a CMC fracture-dislocation is suspected but unclear on radiographs.
Clinical notes
- Carpal boss at the base of the 2nd and 3rd metacarpals can irritate the overlying extensor tendons
- Base fractures can avulse the ECRL insertion and weaken wrist extension
- The radial artery dives into the palm between the bases of the 1st and 2nd metacarpals, a point at risk in dorsal approaches and base injuries of the index ray
Development
The secondary ossification centre is at the head (distal), as in the 3rd to 5th metacarpals.
Test yourself
Think of the answer, then tap the question to see it.
Which is the longest metacarpal, and why does its carpometacarpal joint barely move?
The 2nd metacarpal; its notched base locks around the trapezoid.
Why do 2nd metacarpal neck fractures tolerate less angulation than those of the ring and little fingers?
Its carpometacarpal joint is fixed, so it cannot compensate for angulation.
Which tendons insert on the base of the 2nd metacarpal?
The extensor carpi radialis longus on the back and the flexor carpi radialis on the front.
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 II
- English (TA2)
- 2nd metacarpal
Related
- A1 pulleys
- Adductor pollicis
- Thumb base cartilage
- CMC ligaments
- Deep transverse metacarpal ligament
- Dorsal interossei
- ECRL
- Extensor tendons
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Hand Bones.
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Representative model, for educational purposes only.
