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Boxer’s Fracture (Metacarpal Neck)

- See:
       - Metacarpal Neck Frx
       - Metacarpal Shaft Frx

- Discussion:
    - metacarpal neck frx involving little finger;
    - only collateral ligaments, remain attached to the proximal phalanx, & therefore metacarpal head is freed from any proximal stabilizing influence;
    - metacarpal head tilts volarly causing joint to lie in hyperextension & collateral ligaments become slack;
               - if joint is allowed to remain in hyperextension, collateral ligaments will shorten, leading to limited MCP flexion;
    - little finger CMC articulation allows flexion extension arc of 20-30 deg in addition to a rotatory motion facilitating little finger opposition to thumb;
    - ring metacarpal provides 10-15 deg of mobility;
    - diff dx:
             - transverse metacarpl shaft frx this frx may be ammenable to a 4 holed plate;
             - frx of metacarpal head;
                       - infrequent variant of boxer's frx;
                       - in this injury, impact is recieved directlly on metacarpal head, producing frx thru joint surface;
                       - requires operative fixation;

- Radiographs:
    - true lateral radiograph is necessary with these fractures in order to measure the angle of displacement of the distal fragment;
    - normal metacarpal neck angle is about 15 deg & therefore  a measured angle on film of 30 deg actually = 15 deg;
    - when displaced, angulate with dorsal angulation at frx line & distal metacarpal head displaces palmarward;


- Non Operative Treatment:
      - clawing results from the palmar displacement of the metacarpal head & resulting imbalance of extrinsic tendons;
      - may have cosmetic deformity, but good function;
      - methods of reduction:
               - because collateral ligaments are the only remaining attachment to metacarpal head, collaterals must be placed in a tightened position to control distal fragment and achieve reduction;
               - MP joint is flexed 90 deg to produce tightening of MP collateral ligaments;
               - flexed metacarpal is directed dorsally, which effects reduction of metacarpal head by correction of volar angulation;
    - accetable reduction:
            - on lateral view if angulation > 30-40 deg, a functional deficit (pseudoclawing) may result - consider percutaneous pin fixation.
            - in the report by Ali et al (JHS Vol 24-A. July 1999), 30 deg of angulation resulted in loss of 22% of finger ROM;
            - on AP view, little or no anglation should be accepted, since this indicates mal-rotation of the digit;
            - references:
                      - Biomechanical effects of angulated boxer's fractures.  
                      - Fractures of the fifth metacarpal neck: is reduction or immobilisation necessary?


      - casting technique:
             - no matter what casting technique is used, it is essential to "buddy tape" the little and ring fingers (with an intervening layer of cast padding) in order to control fracture malrotation;


- Operative Treatment:


Year Book: Functional Treatment of Metacarpal Fractures: 100 Randomized Cases With or Without Fixation.

Immediate mobilization of fractures of the neck of the fifth metacarpal.

Fractures of the metacarpal neck of the little finger.

[Osteosynthesis using perpendicular pins in the treatment of fractures and malunions of the neck of the 5th metacarpal bone.]

Conservative treatment of boxer's fracture: a retrospective analysis.

Intra-articular fractures at the base of the fifth metacarpal. A clinical and radiographical study of 64 cases.

Biomechanical effects of angulated boxer's fractures.

Immediate mobilization gives good results in boxer's fractures with volar angulation up to 70 degrees: a prospective randomized trial comparing immediate mobilization with cast immobilization.