Imaging for Mallet Finger
Mallet finger can be detected on imaging, with standard radiographs (X-rays) being the primary diagnostic tool that can identify both bony avulsion fractures and assess for joint subluxation. 1, 2
Radiographic Evaluation
- A standard 3-view radiographic examination is necessary for proper evaluation of mallet finger, including posteroanterior (PA), lateral, and oblique views 2
- Radiographs are commonly used to assess for bone involvement in extensor tendon injuries and determine the need for operative fixation 1
- For phalangeal injuries, some centers include a PA examination of the entire hand, while others limit examination to the injured finger 2
- An internally rotated oblique projection, in addition to the standard externally rotated oblique, increases diagnostic yield for phalangeal fractures 2
Imaging Findings in Mallet Finger
- X-rays can identify bony mallet finger, characterized by an avulsion fracture at the base of the distal phalanx 3
- Radiographs can detect palmar displacement of the distal phalanx or an interfragmentary gap >3 mm, which are indications for surgical intervention 1
- X-rays can show fractures involving more than one-third of the articular surface, which typically require operative fixation 1, 4
- Radiographs can identify volar subluxation of the distal phalanx, which is a common complication of mallet finger injuries 5, 4
Advanced Imaging Options
- MRI without IV contrast is especially useful for evaluating soft tissue injuries when radiographs are negative but clinical suspicion remains high 1
- MRI is ideal for evaluating tendon injuries and helping with surgical planning, with high sensitivity and specificity for detecting tendon tears 1
- For metacarpal and digital fractures, CT is usually not indicated during acute injury 1
- Ultrasound has limited utility for evaluating bone injuries in the hand and is not typically used for mallet finger diagnosis 1
Management Considerations Based on Imaging
- If initial radiographs are negative but clinical suspicion remains high, options include placing the patient in a splint and repeating radiographs in 10-14 days, or proceeding to MRI 2
- Left untreated, mallet finger can lead to swan-neck deformity and distal interphalangeal joint (DIPJ) osteoarthritis, which may be visible on later imaging 3
- Surgical fixation is indicated in cases of mallet fractures involving more than one-third of the articular surface and in patients who develop volar subluxation of the distal phalanx, as identified on imaging 4
Common Pitfalls in Imaging
- Relying on only 2 views is inadequate for detecting fractures in the fingers; a 3-view radiographic examination is necessary 2
- Failure to obtain adequate radiographic views may lead to missed diagnosis; a minimum of 3 views is necessary 6
- Delayed diagnosis due to negative initial radiographs can lead to functional impairment 1
- Post-surgical complications such as joint autofusion can be detected on follow-up radiographs 7