- 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 the bone, or it may avulse bone fragment from the 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;
- Exam:
- attempt to feel the lump of the tendon in
palm;
- Radiographs: 
- 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;
- 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 Thru 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;
A simple clinical test to differentiate rupture of flexor pollicis longus and incomplete anterior interosseous paralysis.
Rugby finger: Avulsion of the profundus of the ring finger. PG Lunn and DW Lamb. J. Hand Surg. Vol 9-B. p 69-71.
Misleading fractures after profundus tendon avulsions: a report of six cases.
Avulsion of the profundus tendon insertion in athletes. JP Leddy and JW Packer. J. Hand Surgery. Vol 2-A. 1977. p 66-69.
