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Deforming Forces: in Both Bone Forearm Frx



- Deforming forces:
    - Biceps brachii and Supinator inserts into the proximal1/3 of the radius;
         - these muscles are the supinators of the forearm;
    - Pronator Teres, originating above the elbow medially, inserts into the middle third of the radius;
         - when frx is distal to insertion of pronator teres, proximal fragment lies in neutral rotation, and the distal fragment is pronated;
    - Pronator Quadratus, located on the anterior aspect of the lower forearm, inserts into the distal third of the radius;
         - when the fracture is distal to the insertion of the pronator teres muscle, the proximal fragment lies in neutral rotation, and the distal fragment is pronated;
    - Brachioradialis
         - assists in elbow flexion & is also semipronator & semisupinator of forearm of forearm, bringing it from supine or prone position to neutral rotation;
    - extensors and abductors of the thumb act with Brachioradialis muscle in fractures of the distal third of the radius and pull the distal fragment of the radius proximally;
    - Flexor muscles of the forearm:
         - tend to pull the distal fragments anteriorly and produce dorsal bowing of the radius and ulna during healing;

- Proximal Third Frx :
    - see pediatric proximal 1/3 forearm frx
    - above insertion of pronator teres;
    - proximal fragment of radius is supinated & flexed because of unopposed action of biceps brachii & supinator, and the distal fragment is pronated by the action of the pronator teres & pronator quadratus muscles;
    - to obtain alignment of the fracture, the distal fragment should be supinated;

- Middle Third Fractures:
    - below pronator teres teres;
    - proximal fragment is held in neutral rotation, as action of supinator is countered by the pronator teres;
    - proximal fragment is drawn into flexion by action of biceps;
    - distal fragment is pronated & drawn toward ulna by pronator quadratus;
    - to achieve anatomic reduction, distal fragment is brought into neutral rotation;

- Lower 1/3 of Forearm Fractures:
    - distal fragment of the pulled radius is pronated & pulled inward by pronator quadratus;
    - overriding & shortening are caused by obliquity of frx & pull of muscles


The effects of angular and rotational deformities of both bones of the forearm. An in vitro study.