What is the recommended method for immobilizing a flexor tendon tear at the index finger DIP (Distal Interphalangeal) joint?

Immobilization of Flexor Tendon Tear at Index Finger DIP Joint

For a flexor digitorum profundus (FDP) tear at the index finger DIP joint, immobilize using a dorsal protective splint with the wrist in 30 degrees flexion, metacarpophalangeal (MP) joint in 40 degrees flexion, and the DIP joint blocked at 40-45 degrees of flexion to prevent full extension during the early healing phase. 1

Splinting Position and Rationale

The optimal immobilization strategy depends on whether this is post-surgical repair or conservative management:

Post-Repair Immobilization Protocol

Position the hand in a dorsal protective splint with:

• Wrist: 30 degrees flexion 1
• MP joint: 40 degrees flexion 1
• PIP joint: Neutral position (0 degrees) 1
• DIP joint: Blocked at 40-45 degrees flexion 1

This positioning limits excursion of the zone I repair to approximately 3mm in a limited arc (45-75 degrees), applying low loads of force (<500g) to the repair site. 1 The blocked DIP extension prevents excessive tension on the repair during early wound healing phases while still allowing controlled active motion. 1

Alternative Positioning Strategy

An older but effective approach involves:

• MP joint: Full flexion 2
• Interphalangeal joints (PIP and DIP): Full extension 2

This position makes the FDP so redundant that it abolishes all tension at the suture line by taking advantage of the mass action nature of the FDP muscle. 2 When the injured finger is fully flexed at the MP joint while adjacent fingers are fully extended, the FDP of the operated finger becomes maximally relaxed. 2

Duration of Immobilization

Maintain uninterrupted immobilization for 6-8 weeks for optimal healing. 3 This duration applies to both:

• Acute soft-tissue mallet finger injuries 3
• Post-surgical flexor tendon repairs 1, 3

The 6-8 week period has been shown to be highly effective, safe, and reproducible for both acute and chronic lesions. 3

Early Active Motion Considerations

If implementing an early active motion protocol:

• Use relaxed composite flexion to apply active tension to both the uninjured flexor digitorum superficialis (FDS) and repaired FDP 1
• This applies controlled excursion while maintaining the protective blocked DIP extension 1
• Studies show this approach achieves mean total active range of motion of 142 degrees (PIP 95 degrees plus DIP 47 degrees), representing 81% of normal function 1

Evidence for Flexion vs. Extension Fixation

Recent evidence favors flexion fixation positioning: Patients who slept with their injured fingers in the flexed position achieved significantly better outcomes than those using extension fixation, with 44% achieving excellent Strickland ratings versus 28% in the extension group (p=0.040). 4 The flexion fixation group demonstrated higher %TAF (total active flexion) and greater active flexion angle of the DIP joint (p=0.008 and p=0.025 respectively), without increasing extension limitation. 4

Critical Pitfalls to Avoid

Do not allow full DIP extension during the first 6-8 weeks - this creates excessive tension on the repair site and increases rupture risk. 1

Avoid complete immobilization without any motion protocol - while the joint must be protected, complete immobilization can lead to adhesions and poor functional outcomes. 5 Tensile loading of the tendon stimulates collagen production and guides normal alignment of newly formed collagen fibers. 5

Do not convert closed injuries to open ones unnecessarily - external splinting should be prioritized even in the presence of open injury due to unacceptable complication rates with surgical conversion. 3

Surgical Fixation Alternative

If external splinting fails or is not tolerated, transarticular Kirschner wire placement at the DIP joint for 6-8 weeks is the preferred surgical option. 3 This provides rigid immobilization while avoiding the complications of more extensive surgical procedures. 3