Fracture of shaft of little finger metacarpal

Clinical History

The patient sustained an injury to his right hand when he punched a wall.

Imaging Findings

The right hand dominant male, in a fit of anger punched a wall with his right fist. He attended casualty with complaints of pain in his right hand. On examination there was tenderness over the little finger metacarpal. There were no skin wounds, rotational deformity or neurovascular deficits. Range of movements in the little finger joints were reduced due to pain. Radiographs of the right hand revealed a shaft fracture of the little finger metacarpal with a dorsal angulation of 50° (Fig 1).
Under general anaesthesia the fracture was reduced and closed retrograde intramedullary fixation was performed with a 1.8 mm. Kirshner wire. Post operative radiographs showed satisfactory position of the fracture (Fig 2). The right hand was splinted for pain relief, which allowed full mobilisation of the little finger.
Six weeks after operation there was no tenderness at the fracture site. Range of movements was satisfactory with no rotational deformity. Attempts at removal of the Kirshner wire was difficult but with persistence the wire was removed intact (Fig 3). Radiographs after removal of the wire showed satisfactory position of the fracture (Fig 4).

Discussion

Metacarpal shaft fractures are usually caused by direct blow (transverse fractures) and twisting injuries (spiral fractures). Less commonly crushing injuries can cause comminuted metacarpal fractures with significant soft tissue damage. Common problems associated with metacarpal shaft fractures are shortening, angulation and malrotation.
Shortening at fracture site is less common in the middle and ring finger metacarpals due to the deep transverse metacarpal ligaments. Shortening at fracture site produces extensor lag (1).
Most serious of the complications is the malrotation which can significantly affect the hand function while angulation at the fracture site is more of a cosmetic problem. More proximal the fracture more prominent will be the deformity for the same degree of angulation. Dorsal angulation is due to the interosseous muscle action (Fig 5). Angulation at the little and ring finger metacarpals are more acceptable than the one at index and middle finger metacarpals due to more mobile ulnar carpometacarpal joints. Lateral view of the hand is essential to identify the degree of angulation at the fracture site.
Available treatment options include closed reduction and splintage, pinning either transverse (2) or intra medullary (3), plate fixation for multiple metacarpal fractures, external fixation in case of associated soft tissue injury (4). Each has its own advantages and disadvantages (5).
Whatever line of management is chosen the aim should be avoid rotational deformity and stiffness at the metacarpophalangeal and interphalangeal joints. Complications of treatment of metacarpal shaft fractures include residual angulation, stiffness of joints, non union, pin tract infection, breakage of pins. In the case presented the tip of the pin was bent quite acutely and caused difficulty in its removal. Under these circumstances the possibility of breakage of the tip of the pin and refracture due to overzealous attempts to remove the pin should be kept in mind.

Differential Diagnosis List

Final Diagnosis

Fracture of metacarpal shaft of little finger

URL:	https://www.eurorad.org/case/2223
DOI:	10.1594/EURORAD/CASE.2223
ISSN:	1563-4086