CT is NOT Appropriate for Evaluating Hand Extensor Tendon Injury
CT has limited use for the diagnosis of soft-tissue injuries of the hand, including extensor tendon injuries, and is not indicated for this purpose. 1
Initial Imaging Approach
Start with plain radiographs to detect fracture fragments associated with extensor tendon injuries, as large bony avulsions may require open reduction and internal fixation 1. Radiographs are particularly useful for:
- Osseous "mallet" injuries (bony avulsion at the extensor mechanism insertion to the distal interphalangeal joint) 1
- Determining if >1/3 of the articular surface is involved (surgical indication) 1
- Identifying palmar displacement of the distal phalanx or interfragmentary gap >3 mm (surgical indications) 1
When Soft Tissue Evaluation is Needed
If radiographs show bone involvement is excluded or equivocal, and soft tissue tendon evaluation is required, MRI without IV contrast is the imaging modality of choice 1. MRI is ideal for:
- Evaluating tendon injuries and surgical planning 1
- Detecting injury to the central slip or extensor hood in equivocal cases 1
- Assessing extensor hood injuries (sensitivity ranges 28-85%) 1
- Evaluating normal sagittal bands of the extensor hood (sensitivity 89-92%) 1
Why CT Fails for Tendon Evaluation
CT cannot evaluate concomitant ligamentous or tendon injuries, unlike MRI 1. The fundamental limitation is that CT is designed for osseous structures, not soft tissues 1.
Limited Research Support
While some research suggests CT can detect tendon abnormalities in trauma settings 2, 3, and specialized techniques like dual-energy CT at 140 keV can improve tendon visualization 4, these are not standard practice and the ACR Appropriateness Criteria explicitly state CT has limited use for hand soft-tissue injuries 1.
Alternative Imaging: Ultrasound
Dynamic ultrasound is an equivalent alternative to MRI for evaluating extensor tendon injuries 1. US allows:
- Direct visualization of joint malalignment without fracture 1
- Assessment of tendons and vascular structures 1
- Real-time dynamic examination 1
Clinical Pitfall
Do not order CT for suspected pure extensor tendon injury—this wastes time and resources while providing no clinically useful information about the tendon itself 1. CT is only appropriate when evaluating for occult fractures of the upper extremity, not tendon pathology 1.