Dr. Ebraheim’s educational animated video describes fractures of the metacarpals of the hands.
There are five metacarpal bones in the hand located between the phalanges and the carpal bones. The metacarpal bone is divided into head, neck, shaft, and base. Metacarpal shafts give attachments to four dorsal and three palmar interossei muscles. The metacarpal base gives attachment to abductor pollicis longus, extensor carpi radialis longus, extensor carpi radilais brevis, extensor carpi ulnaris. The 1st, 4th and 5th metacarpals are mobile, while the 2nd and 3rd metacarpals are the rigid central pillar.
Normal metacarpal movements :
•2nd and 3rd : 5degrees
•4th: 20 degrees
•5th: 30 degrees
Commonly known metacarpal fractures:
1-Bennett fracture: fracture of the base of the first metacarpal bone which extends into the carpometacarpal (CMC) joint. Two part intra-articular fracture with CMC subluxation.
2-Reverse Bennett fracture: fracture of the base of the fifth metacarpal bone which extends into the carpometacarpal joint. Intra-articular fracture of the base of the 5th metacarpal. The extensor carpi ulnaris is pulling on the 5th metacarpal.
3-Rolando fracture: comminuted intra-articular fracture through the base of the first metacarpal bone. 3 or more fragments, intra-articular.
4-Boxer’s fracture: fracture of the fourth and/or fifth metacarpal neck. Fracture caused by axial loading such as striking an object with a closed fist.
Metacarpal fractures account for 30-50% of hand fractures. Metacarpal head fractures usually need surgery as it is intra-articular. Look for “fight bites” as this indicates open fractures. Metacarpal head fractures usually need ORIF especially displaced fractures & less than 25% articular surface involved. If badly comminuted, consider a short period of splinting followed by early active motion or consider external fixation. There is high incidence of stiffness with these fractures.
Metacarpal neck fractures the most common site of metacarpal fractures is at the metacarpal neck. Acceptable angulation of the fracture:
•2nd & 3rd metacarpals: 15 degrees.
•4th metacarpal: 30 degrees.
•5th metacarpal: 40 degrees
If the fracture exceeds any of these degrees of angulation, attempt reduction and splinting. Reduction can be done with the Jahss technique: digital longitudinal traction. Flex the MCP/PIP joints and apply a dorsally directed force along the phalynx. Next splint the fracture in the safety position. The wrist should be immobilized in 20 degrees of extension and the MCP in 60-70 degrees of flexion.
Metacarpal shaft fractures: x-rays : AP, lateral and oblique films. 30 degrees pronation shows the 2nd & 3rd metacarpal shafts and the 4th & 5th metacarpal base and CMC joint. 30 degrees supination views shows the 4t & 5th metacarpal shafts and the 2nd & 3rd metacarpal bases and CMC joints. Conservative treatment (immobilization) if: undisplaced fractures, no rotation, accepted angulation:
•2nd & 3rd metacarpal: less than 15 degrees
•4th metacarpal: less than 30 degrees.
•5th metacarpal: less than 40 degrees
Acceptable shortening. The wrist should be immobilized in the “safe position”.
Indications for surgical treatment include open fractures, marked displacement, unaccepted angulation/ shortening, rotation, multiple metacarpal fractures.
Options for fixation: k-wires, intramedullary fixation, plates & screws.
Common complications:
1-Malrotation
2-For each 2 mm of shortening there will be 7 degrees of extensor lag at the MCP joint (some may disagree with this), some may accept shortening up to 5 mm.
Metacarpal base fractures: the typical site for metacarpal base fractures is at the base of the fifth metacarpal. Prognosis is guarded. 
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Background music provided as a free download from KZfaq Audio Library.
Song Title: Every Step