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Mallet Deformity: (Baseball finger)

- See:
      - Phalangeal Injury
            - Pediatric Mallet Finger
            - Mallet Frx

- Anatomy:
    - extensor mechanism of digits;
    - terminal extensor tendon is comprised of the convergence of lateral bands, and more proximally by terminal fibers of the oblique retinacular ligament;

- Acute Injury:
    - from forcible flexion of the extended DIP joint:
    - following this injury there is unopposed flexion from the FDP;
    - w/ severe flexion deformity of DIP joint in mallet finger injury a secondary hyperextension deformity of PIP (swan neck) joint may occur because of imbalance of the extensor mechanism;
          - as the conjoined tendon slides proximally, the conjoined tendon becomes a secondary extensor of the PIP joint;
    - w/ closed injury, extensive fraying of tendon ends usually occurs at point of separation, which makes surgical repair difficult;
    - radiographs:
          - true lateral to r/o avulsion frx or frx of articular surface;
          - volar subluxation along w/ a significant intra-articular frx (greater than 30% of joint surface) is an indication for surgery;

- Mallet Frx

- Non Operative Rx: (Acute Closed Injuries)
     - the vast majority of patients w/ closed mallet injuries (even those seen one month out from injury) can be treated w/ splinting;
     - continuous splinting of only the DIP joint for 6 to 10 weeks is the usual treatment;
     - note: that patients w/ ligamentous laxity and/or propensity for PIP joint hyperextension may be at special risk for failure with non operative treatment;
     - consider using a thinly padded dorsal aluminum splint;
            - remember that a poorly fitting dorsal splint on an elderly pt, may worsen tendon vascularity;
     - an alternative, is to apply Coband wrap to the DIP joint, and then apply a bent paper clip to the dorsal surface, followed by more Coband;
     - try for mild hyperextension, no pain should occur;
     - avoid forced extension in the acutely swollen finger, rather, position the finger in hyperextension after the swelling has decreased;
            - consider hyperextending the digit to the point at which the skin blanches and then back off extension by 50%;
     - do not immobilized the PIP joint;
     - at no point should the joint be allowed to fall into flexion for at least 6 weeks;
            - after 6 weeks, continue splinting if an extensor lag is present;
            - if extensor lag is not present, a night time splint is worse for 2-3 weeks;

- Indications for Surgery:
    - Open Mallet Finger Injury:
           - consider direct repair;
           - anchor one end of a 4-0 nylon suture on skin & then run it as continuous suture, back & forth through tendon ends from one side of finger to other;
           - consider cross pin fixation of DIP joint to maintain some hyperextension;

- Close Reduction / K wire:
     - insert 0.45 K wire across the fully extended DIP joint;
           - technically, it is easier to place the K wire longitudinally (w/ the pin cut off beneath the skin), but pts may complain of scarring at the pin entrance site;
           - oblique placment of the K wire across the DIP joint may be preferable by the patient, but is technically more difficult;
     - remove pin at 6 wks, but continue night splinting for additional 4 wks;
     - this method may cause osteomyelitis;

- Open Repair:
     - may have high rate of complications;
     - prior to open repair, many will insert a K wire to hold the joint in extension;
     - open repair is most indicated w/ open mallet finger injuries, however, many point out that due to the flimsy nature of tendon at this level, open tendon repair will not be very secure;
           - some advocate washout of the wound (and joint if indicated) but avoiding attempts at suture repair of the tedon;
           - others will attempt to close the tendon and skin in one single layer, using a running simple suture technique;
                 - sutures are removed at 2 weeks, but splint for atleast 6 weeks;
           - alternatively the extensor tendon can be repaired w/ 4-0 or 5-0 Vicryl figure of 8 sutures, w/ knot buried on the inside;
     - w/ a displaced frx fragment, expose joint thru dorsal zig-zag incision;
     - insert a wire loop through the fragment and into the distal phalanx, and tie over felt and a large volar button;
           - take care not to further disrupt or comminute the frx fragment and/or extensor mechanism;
     - in the report by King HJ, et al, 24 of 59 (41%) surgically treated mallet fractures developed postoperative complications;
           - most common complication was marginal skin necrosis on the dorsal aspect of the distal phalanx, but recurrent extension lag, permanent nail deformities, transient infections along the wires and pull-out steel wires and osteomyelitis were also observed;
           - ref: Complications of operative treatment for mallet fractures of the distal phalanx.

- Late Mallet Finger:
    - may lead to swan neck deformity;
    - these pts will probably not respond to splinting (w/ Swan neck);
    - in pts w/o swan neck deformity:
         - DIP is splinted in neutral or slight hyperextension;
         - do not place too much pressure on the dorsum of the finger;
         - PIP is left freee;
         - consider splinting for 4 to 8 weeks;
    - central slip tenotomy.
         - ref: Central slip tenotomy for the treatment of chronic mallet finger: an anatomic study.

Mallet finger: long-term review of 100 cases.

Treatment of chronic mallet finger deformity in children by tenodermodesis.

Complications and prognosis of treatment of mallet finger.

Fowler central slip tenotomy for old mallet deformity.

Central slip tenotomy for chronic mallet finger deformity.

Conservative management of chronic mallet finger.

Mallet finger: comparison between operative and conservative management in those cases failing to be cured by splintage.

Ligaments of the distal interphalangeal joint and the mallet position.