Theory of Dynamic Compression Plates


- See:
      - DCP and LC-DCP, 3.5 mm
      - DCP, 4.5 mm
      - LC-DCP, 4.5 mm in Pure Titanium

- Discussion:
    - compression is appied by eccentric insertion of screws;
    - slot for compression has a sloping surface at one end;
           - when the spherical head of the screw impinges on this surface, plate moves away from the fracture, thereby compressing
                     fracture plane;
    - if more compression is necessary, subsequent screws may be inserted in compression mode, but it is rarely necessary for more than
           two screws to be loaded;
           - when additional compression is added, the tension on initially inserted screws must be released by backing off 1-2 turns;
           - each scew is then tightened in turn when all screws have been inserted;
    - usage of two load screws in the main fragments for axial compression;
    - after one scew has been inserted in load position in each main fragment, producing 1 mm of displacement, horizontal track in main
           fragment still permits 1.8 mm of displacement;
    - second screw, therefore, can be inserted in the next hole w/o being blocked by the first screw;
           - first screw, however, must be slightly loosened before further1 mm compression can be produced by the second screw;
    - note: that the first screw is inserted in the fragment whose spike is farthest from the plate;
           - following this, after axial compression is applied, oblique lag screw is inserted for interfragment compression;
    - after insertion of at least 2 screws on each side of frx, (4 cortices on each side of frx), a screw is be placed throug 1 cortex only
           in most proximal and distal palte holes; - this prevents a stress riser;
    - note: stratedgy for plating frx may be dictated by frx configuration
           - transverse fractures are stronger in compression than oblique frx
           - oblique fractures are stronger in rotation than transverse frx

- Limited Contact Dynamic Compression Plate:
       - characterized by less than 50% contact between the plate and the bone.
       - allows for preservation of blood supply and less osteoporosis underneath the plate;



- References:
      - Optimizing compression: Comparing eccentric plate holes and external tensioning devices.

      - Can DCP and LCP plates generate more compression? The effect of multiple eccentrically placed screws and their drill guides.

      - General principles for the clinical use of the LCP.

      - Biomechanical testing of the LCP--how can stability in locked internal fixators be controlled?



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, November 14, 2016 5:50 am