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Bennett’s Fracture Dislocation

- See:  
      - Rolando's fracture
      - Thumb Fractures/Dislocations
      - X-ray Studies

- Discussion:
    - most frequent of all thumb frx;
    - described in 1882 by Dr. Edward Bennet;
    - it is a frx dislocation, intra-articular frx at base of carpometacarpal joint of the thumb;
    - involves an oblique intraarticular metacarpal frx (known as the palmar beak fragment) which remains
             attached to the palmar beak ligament;
    - anatomy of CMC joint

    - mechanism of frx:
           - results from axial blow directed against the partially flexed metacarpal; (ie. from fist fights)
    - frx starts at ulnar base of thumb metacarpal;
           - palmar ulnar aspect of thumb is normally stabilized by strong ligaments;
           - disruption of the ulnar fragment destabilizes thumb;
    - volar frx fragment remains attached to CMC by volar anterior oblique lig;
           - anterior oblique ligament anchors volar lip of metacarpal to  tubercle of the trapezium;
           - hence, small volar lip fragment remains attached to anterior oblique ligament which is attached to trapezium;
    - distal metacarpal fragment (containing most of articular surface) is displaced proximally, radially, & dorsally by pull of APL;
           - displaced metacarpal is also rotated in supination by the pull of APL;
           - metacarpal head is also displaced into palm by pull of ADP;

- Radiographs:
    - oblique frx line with a triangluar fragment at ulnar base of metacarpal;
    - triangular fragment remains attached to trapezium w/ proximal displacement of the metacarpal;
    - note size of the volar lip fragment and the amount of displacement of shaft;

- Prognositic Features:
    - location and displacement of the fracture;
    - extent of crush or impaction at the metacarpal;
    - presence or absence of shearing or impaction injury to radial side of articular surface of the trapezium;

- Reduction:
    - the metacarpal shaft is displaced dorsally and radial direction due to the force of the abductor pollicis longus and adductor pollicis;
    - reduction is accomplished w/ longitudinal traction on end of thumb, in addition to abduction and extension of thumb metacarpal;
    - thumb is pronated to bring it into opposition w/ non-displaced palmar fragment;
    - because the thumb CMC joint is incongrouos, upto 2 mm of articular displacement is well tolerated in Bennet fractures;

- Percutaneous Pin Fixation:


     - consider closed reduction and percutaneous pin fixation when there is less than 3 mm of displacement, when
             the beak of the fragment involves less than 50% of the palmar slope of the metacarpal, and when the concave
             dome of the metacarpal is maintained;
     - use 0.45 inch K wires to maintain reduction but do not attempt to spear small volar lip fragment with the wires;
                - pins stabilize first metacarpal to trapezium or second metacarpal;
     - may accept slight joint incongruity;
     - if reduction not possible ORIF w/ AO cortical screw;
     - spica cast for 4-6 weeks;

- Open Reduction:
    - consider open reduction and internal fixation when there is more than 3 mm of fracture displacement;
    - 2.5 cm transverse incision is made over radial base of thumb metacarpal;
    - dorsal sensory branches of radial nerve are identified & protected;
    - EPB & APL are identified and retracted;
    - radial artery is protected and retracted ulnarly;
    - by traction of thumb metacarpal, trapezial frx is visualized & reduced;
    - frx reduction is provisionally secured w/ K wire;
    - implants:
            - if only 0.028-inch Kirschner Wires are used to secure trapezial frx, additional immobilization is required for six weeks;
            - if radial fragment is of adequate size, 2.0-mm or 2.7 mm cortical lag screw is used;
            - threaded or non threaded K wires (small sized fragments)
            - 2.7 mm T or L plates
            - 2.0 mm condylar plate

- References:
Open reduction and internal fixation versus closed reduction and percutaneous fixation in the treatment of Bennett fractures: A systematic review.

Long-term patient-reported outcomes following Bennett’s fractures

7-year follow-up after open reduction and internal screw fixation in Bennett fractures

Treatment of Bennett, Rolando, and vertical intraarticular trapezial fractures.

Trapeziometacarpal-I--Symposium: The Classic: On Fracture of the Metacarpal Bone of the Thumb.

Functional cast immobilization of thumb metacarpophalangeal joint injuries.

Fractures at the base of the thumb: treatment with oblique traction.

Post-traumatic instability of the metacarpophalangeal joint of the thumb.

Bennett's fracture.

Fractures of the basal joint of the thumb.

A long-term study following Bennett's fracture.

Bennett's fracture.

Long-term evaluation of Bennett's fracture. A comparison between open and closed reduction.

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