Prebending of Plates



- Discussion:
    - exactly contoured plates produce asymmetric compression (ie the near cortex is compressed more than the far cortex);
          - i.e., the far cortex may not be compressed at all;
    - when prebent plate is fixed to the bone, the bend is straightened out;
    - due to its elastic recoil, the plate  has a tendency to recover the bend which was applied by plastic (irreversible) deformation;
    - it therefore exerts a bending moment which tends to close and to compress the far fracture gap;
    - to provide compression of the far cortex the plate is applied after exact contouring but with an additional bend of the plate segment 
          bridging the fracture;
    - w/ respect to stabilization against torque and bending, compression of the far cortex is far more important than that of the near cortex;
    - goals of prebending:
          - goal is to balance forces on the near and far corticies;
          - good stability only requires that the far cortex be compressed enough to maintain contact under physiologic loading w/o being overloaded;
          - it should be noted that it is not aim of prebending to produce equal compression in both cortices;
          - slight prebending, results in minimal compression of the far cortex;
          - if two large an amount of prebending is applied, near cortex is not compressed efficiently;
    - sharp vs smooth bending:
          - bend is such that the mid section of the plate is elevated from the bone surface prior to fixation to the bone;
          - most active portion of prebending spans the distance between the inner screws;
          - therefore a comparitively sharp bend should be applied;
          - angle of bend should be such that an 8 hole, 4.5 mm small DCP should be elevated about 2 mm from the bone surface;
    - order of screw insertion:
          - to fix prebent plate to bone, inner screws should be applied first and the outer last;
                - if outer screws are applied first, near cortex opens because plate is too long in relation to the bone spanned between outer 
                       screw holes;
          - to fix a straight plate to a curved bone (here plate is relatively prebent);
                - outer screw holes are inserted first, which has the effect of shortening the plate as the plate conforms to the bone;
                - the net effect is compression across the frx site


Prebending of Plates
ORIF - Axial compression plating

Humeral shaft fractures: a review

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

Section 28: Bone Plate Analysis and Design

Functional load of plates in fracture fixation in vivo and its correlate in bone healing.

[Pre-bending and and tension adjustment of narrow 4.5 mm AO titanium LC-DCP (limited contact dynamic compression plate)]

[Biochemical and mathematical studies of the pre-bending and pre-stressing of the small fragment DC plate]

A radiological and histological analysis of fracture healing using prebending of compression plates.

[Experimental examinations in plate-prebending--a contribution to the biomechanics of compression osteosynthesis (author's transl)].



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

Last updated by Data Trace Staff on Tuesday, May 24, 2016 10:09 am