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Zone 1 Flexor Injuries


- See:
      - FDP Avulsion
      - FDP Lacerations
      - tendon pull thru technique

       

- Anatomy:
      - in zone 1, FDP has emerged from between & beneath decussating FDS and travels to its insertion in the distal phalanx;
      - zone 1 contains: A4, C3, and A5 pulley;
             - A4 pulley must be preserved, otherwise the majority of active PIP flexion will be lost;

- Injury Pattern:
      - most injuries are due to lacerations, but traumatic rupture from phalangeal attachment may occur; (see: FDP avulsion:)

- Exam:
    - when FDP is divided in zone 1, there is loss of active flexion of distal phalanx, as well as a hyperextension instability of distal IP joint;
           - this results in instability, esp when these injuries are in index & middle figners, because w/ unstable pinch, pts tend to drop things easily;
    - if tendon has retracted into the proximal finger or palm after rupture or laceration, pt will be unable to actively move distal phalanx;
           - dx is made by asking him to flex distal phalanx & watching level of ability to flex digit;
    - if proximal end of flexor profundus becomes caught at the level of sublimis chiasm, it may affect the range of activemovement at PIP joint;
           - in this area repair may be delayed upto 3 weeks;
           - if tendon is held by vinculum, some active flexion may be possible;
           - if tendon has retracted into the palm, it is difficult to reattach stump if injury is beyond 10 days old;

- Treatment Options for Zone 1 Lacerations:
    - treatment may consist of direct repair or tendon advancement;
    - for tendon lacerations w/in 1 cm of insertion, profundus tendon can be advanced and attached to the distal phalanx;
    - for clean, fresh, sharp lacerations more than 1.5 cm away from the insertion, primary tenorrhaphy is the treatment of choice;

- Surgical Technique:
    - wound edges are extended, debrided, and irrigated;
    - proximal tendon edge of tendon is identified;
         - typically the proximal tendon edge can be found just proximal to the PIP joint and is restrained by the viniculum;
         - it may be necessary to open either the C2 or C1 pulleys for tendon retrieval;
    - distal tendon edge
         - if digit was flexed at time of injury, then distal tendon stump will be short;
         - determine how far the laceration is to the insertion of the tendon;
    - tendon exposure and opposition:
         - w/ an especially short distal tendon stump, open the C3-A5 sheath;
         - through the appropriate proximal window (C2 or C1), a core suture is placed;
         - this core suture is then passed underneath the A4 pulley, and subsequently the proximal tendon stump is passed proximally;
                - the tendon is temporarily anchored by passing a 25 gauge needle thru the annular pulley;
    - tendon repair:
         - if laceration is more than 1 cm from insertion, perform primary repair using standard repair techniques;
    - tendon advancement:
         - see tendon pull thru technique

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Tenodesis for Restoration of Distal Interphalangeal Joint Flexion in Unrepairable Flexor Digitorum Profundus Injuries