FDP Avulsion/Rupture   

- See: Phalangeal Injury

- Mechanism:
    - results from forceful hyperextension of DIP joint w/ FDP in maximal contraction;
    - classic examples include pts injured by the sudden jerk of a rope, such as starting a lawnmower
           or retraining an animal;
    - tendon may rupture directly from its insertion into bone, or it may avulse bone fragment from base of distal phalanx;
           - it may also rupture at the musculotendinous junction;
    - there is more soft tissue injury and hemorrhage than seen w/ simple laceration, & therefore there is more scarring
           of flexor tendon sheath;
    - ring finger is most often involved (75%);
           - this is due to a weaker insertion, a common flexor muscle belly of middle, ring, and little fingers;
    - anatomy: 
           - avulsed tendon ends retract proximally, & may become entrapped at chiasma of FDS at the level of PIP joint,
                   causing a flexion contracture of the PIP;
           - tendon retracts to the base of the digit or into palm, depending on the force of the avulsion;
           - vinculum prevents excessive retraction;
           - lumbricals prevent proximal retraction of lacerated FDP past the mid-palmar area;
    - diff dx:
           - anterior interosseous nerve paralysis (index and long fingers);
           - trigger finger
           - swan neck deformity (can resemble chronic PIP rupture);
    - classification:
           - Type I   - retracts to the palm;
           - Type II  - retracts to the PIP joint;
           - Type III - bony fragment distal to A4;
    - references:
           - "Rugby finger"--Avulsion of the profundus of the ring finger.  
           - Avulsion of the profundus tendon insertion in athletes.   
           - Misleading fractures after profundus tendon avulsions: a report of six cases.

- Exam:

    - attempt to feel the lump of the tendon in palm;
    - consider AIN palsy
    - references: A simple clinical test to differentiate rupture of flexor pollicis longus and incomplete anterior interosseous paralysis.

- Radiograph:

- Indications for Repair:
    - FDP is difficult to repair if tendon retracts into palm for longer than 7 days because tendon becomes swollen, vinculum
           remains avulsed, & tendon cannot be rethreaded (which would comprimise PIP movement);
    - attempts at repairing the tendon after 2 wks will be unsuccessful;
    - if tendon has retracted into  palm consider tendon excision and DIP fusion
           - DIP fusion most indicated in index finger or use of free tendon graft;
    - reference:
           - [Traumatic avulsion of the flexor digitorum profundus tendon. Report of 20 cases].

- Operative Repair:
    - goal is to reattach the flexor tendon to the point of avulsion;
    - tendon is isolated proximally and the phalanx is exposed distally;
    - tendon is rethread using a silicone flexible tendon;
    - avoid A4 pulley disruption (which will impair DIP flexion);
    - in type I tendon rupture (w/ retraction into palm), the vinicular system has been disrupted, and the tip of the profundus
           tendon will be avascular;
           - hence, the distal end of the tendon should be trimmed;
    - in type II rupture, the blood supply to the tendon is left intact, but fibrosis may develop at the FDS chiasm which might
           limit flexion gliding;
           - any such fibrosis should be debrided;

- Pull Through Technique:
    - repair is uses a 3-O polypropylene suture thru distal end of tendon as double figure of eight, and attached to tendon just
            proximal to bone fragment;
    - pass suture on either side of phalanx thru the periosteum;
    - tie sutures over a plastic button placed directly over finger nail to avoid pressure on the tip of the digit;
    - complications:
           - quadriga may develop if the FDP is excessively advanced;

- Alternatives:
    - chronic rupture:
           - in that case of late FDP rupture with intact FDS, consider whether the functional deficit warrents FDP reconstruction;
           - consider no treatment, or tenodesis or arthrodesis of the distal interphalangeal joint to free tendon grafting;

- DIP Arthrodesis:

- Complications:
    - w/ chronic neglected injury there may be dorsal subluxation of the DIP;

The effect of mitek anchor insertion angle to attachment of FDP avulsion injuries.

Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands.

Comparison of pullout button versus suture anchor for zone I flexor tendon repair.

Comparison of an all-inside suture technique with traditional pull-out suture and suture anchor repair techniques for flexor digitorum profundus attachment to bone.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, September 27, 2016 12:13 pm