Flexion Deformity at the DIP Joint After Laceration
A flexion deformity at the DIP joint following a laceration most likely indicates a flexor digitorum profundus (FDP) tendon injury that requires surgical repair, ideally performed early but with acceptable outcomes even when delayed up to several weeks.
Immediate Assessment and Diagnosis
The clinical presentation of a flexion deformity at the DIP joint after laceration strongly suggests complete or partial disruption of the FDP tendon 1. Key examination findings to confirm this diagnosis include:
- Loss of active DIP joint flexion when testing isolated FDP function (holding the PIP joint in extension while asking patient to flex the DIP joint) 1
- Radiographic evaluation is essential to exclude associated fracture fragments, particularly volar base avulsion fractures of the distal phalanx, which may require open reduction and internal fixation if the fragment involves more than one-third of the articular surface 2, 3
- Zone of injury classification: Zone I injuries occur distal to the FDS insertion, while Zone II injuries occur within the flexor sheath where both FDP and FDS may be involved 1
Treatment Algorithm
Surgical Repair is the Primary Treatment
Surgical repair of the lacerated FDP tendon should be performed to restore DIP joint function, as non-operative management will result in permanent loss of active DIP flexion 1. The timing and approach depend on several factors:
Timing of Repair
- Early repair (within 2 weeks) is preferred when possible 1
- Delayed repair (2-96 weeks post-injury) can still achieve satisfactory outcomes in isolated FDP lacerations, with 82% of Zone I repairs and 73% of Zone II isolated FDP repairs achieving good to excellent total active motion 1
- The critical determination is made intraoperatively based on tendon quality, retraction distance, and presence of adhesions 1
Surgical Outcomes by Injury Pattern
- Isolated FDP lacerations in Zone I: Average postoperative DIP flexion of 35° with 82% achieving good to excellent range of motion 1
- Isolated FDP lacerations in Zone II: Average postoperative DIP flexion of 36.5° with 73% achieving good to excellent outcomes 1
- Combined FDP and FDS lacerations in Zone II: Less favorable results with only 45% achieving good to excellent outcomes when only FDP is repaired 1
Special Considerations
If a volar avulsion fracture is present (flexor digitorum profundus avulsion), this typically requires surgical fixation as these injuries result from forceful extension of a flexed DIP joint and will not heal with conservative management alone 3. Large fracture fragments involving significant articular surface mandate open reduction and internal fixation 2.
Post-Operative Management
Following tendon repair, a structured rehabilitation protocol is essential:
- Immobilization period varies based on repair technique and surgeon preference, but early controlled motion protocols are generally favored to prevent adhesion formation while protecting the repair 1
- Splinting of the DIP joint in slight flexion initially, with gradual progression to active motion under hand therapy guidance 3
Common Pitfalls to Avoid
- Delaying diagnosis: Failure to recognize complete FDP laceration early may complicate later repair due to tendon retraction and adhesion formation 1
- Missing associated injuries: Always obtain radiographs to identify fracture fragments that may alter surgical planning 2, 3
- Assuming partial function means intact tendon: Tendinous interconnections between adjacent FDP tendons or lumbrical contributions may permit partial DIP flexion despite complete proximal tendon laceration 4
- Inadequate immobilization of mallet finger: If the injury pattern is actually a dorsal avulsion (mallet finger) rather than volar laceration, strict splint immobilization for 8 weeks in full extension is required 3