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Distal Radius Frx: Dorsal Angulation


- See:
            - Reduction of Dorsal Angulation

- Discussion:
    - measured on lateral, from angle created between articular surface of distal radius & line perpendicular to long axis of radius;
    - normal volar tilt measures between 0 to 22 degrees (mean 11 to 14.5 deg);
          - rare individuals may even have a dorsal tilt (which for them is normal);
    - dorsal tilt decreases moment arm of finger extensors, making wrist less efficienct;
    - w/ dorsal tilt deformity, there will be significant transfer of load onto ulna;
          - normally 82% of compressive load across the wrist is borne by radio-carpal joint, and 18% is borne thru the ulnocarpal joint;
          - w/ a 45-deg dorsal angulation deformity, 65 % of axial load across carpus is directed onto ulna;
          - remaining loads on radius will be concentrated on dorsal aspect of scaphoid fossa;

- Acceptable Reduction:
    - most orthopaedist will generally not accept any angulation past neurtal;
          - consider obtaining a lateral radiograph of the opposite wrist for comparison;
          - note that some patients may be predisposed to ulnar mid carpal instability, and hence, even an "acceptable reduction" w/ 5 deg volar tilt may cause symptoms;
                 - note whether there is abnormal dorsal tilt of the lunate;
    - as pointed out by Jupiter (1991), dorsal tilt greater than 20 deg will often become symptomatic w/ pain at radiocarpal articulation, as well as in limited grip strength, if angulation is not reduced;
    - when radial shortening occurs w/ dorsal tilt, there may be dysfunction of the distal R-U joint, manifested by limited rotation of forearm & impingement of ulna on radius;
    - Fractures of the distal end of the radius.
- Assoicatted Findings in Acute Injury:
    - see unstable distal radial frx;
    - in younger patients w/ distal radius frx, mid-carpal instability may be found in association w/ excessive dorsal tilt;
            - look for dorsal tilt of the lunate (DISI deformity);
    - comminution:
          - dorsal surface is frequently comminuted;
          - if comminution extends volar to midaxial plane of radius, then cast immobilization will frequently fail;
                 - expect increase in comminution w/ incr in amount of dorsiflexion;
                 - high-loading angles, (70-90 deg), have much more comminution than low loading angles of 20 to 40 deg;

- Effects of Chronic Dorsal Tilt:
    - in chronic cases, a malunion w/ excessive dorsal tilt may lead to ulnar mid carpal instability;
    - w/ healed fractures, symptotomatic dorsal angulation greater than 20 deg can be managed w/ a corrective opening wedge radial osteotomy

Midcarpal instability caused by malunited fractures of the distal radius.