Treatment of Volar Base Thumb Distal Phalanx Avulsion Fracture
Flexor digitorum profundus (FDP) avulsion fractures at the volar base of the thumb distal phalanx require surgical reattachment if seen within 10 days of injury. 1
Initial Assessment and Imaging
- Obtain at minimum a 2-view radiographic examination of the thumb (PA and lateral), though adding an oblique projection increases diagnostic yield 2
- Radiographs are sufficient to detect the fracture fragment and assess for displacement 2
- Critical radiographic parameters to evaluate:
- Size of the avulsion fragment
- Degree of displacement
- Presence of joint subluxation or palmar displacement of the distal phalanx 2
Treatment Algorithm
If Presenting Within 10 Days of Injury:
- Operative reattachment of the FDP tendon is indicated 1
- This is the standard of care for acute profundus avulsion injuries regardless of fragment size 3, 1
- These injuries result from forceful extension of the distal interphalangeal (DIP) joint when in a flexed position 3
If Presenting More Than 10-14 Days After Injury:
Treatment must be based on specific clinical findings 1:
- If the tendon stump is distal to the interphalangeal joint: Secondary advancement of the stump can often be performed 1
- If the tendon stump has retracted to the palm: Options include:
- Decision factors include:
- Location of retracted tendon stump (digit vs. palm)
- Passive mobility of the digit
- Patient's functional demands and occupation 1
Surgical Approach Considerations
- For volar-based avulsion fractures of the proximal phalanx (analogous anatomy), a volar A1 pulley approach provides direct access to the fracture fragment and allows anatomic restoration 4
- This principle applies to thumb distal phalanx volar avulsions where direct volar access facilitates tendon reattachment 4
Critical Management Principles
- Time is the most critical factor: Outcomes deteriorate significantly after 10-14 days due to tendon retraction, muscle contracture, and scarring 1
- Unlike mallet finger (dorsal avulsion), these volar avulsions cannot be managed conservatively with splinting alone 3, 1
- The thumb's functional importance for pinch and grip makes surgical intervention the priority to restore FDP function 1
Common Pitfalls to Avoid
- Do not attempt conservative splinting for these injuries - unlike dorsal avulsions (mallet finger), volar FDP avulsions require surgical reattachment 3, 1
- Do not delay referral - waiting beyond 10 days significantly complicates surgical options and worsens outcomes 1
- Ensure the injury is not mistaken for a simple contusion or sprain, as the clinical presentation may be subtle initially 3