Plates for Fracture Repair

- See: Orthopaedic Trauma Implants: Know Your Implants (from Synthes web site)

- Discussion: 
    - Bone Healing w/ Plates
    - Characteristics of Metal Implants 

    - concepts:
          - tension side of the fracture:
                 - when plating a fracture the plate should be applied to tension side of the fracture (which is often the convex side);
                 - ideally when bone is plated, the bone itself carries the majority of the compression load;
                 - optimally when a plate tends to close a fracture, placing the plate under tension, a significant portion of the load is
                           supported by bone, thereby diminishing beding moment on the plate;
                 - in this situation there will be little benefit accued from increasing either, the breadth of the plate or the size of screws, but
                           when plate was increased in length from 3-6 inches, the strength of the assembly was doubled;
          - mechanical considerations:
                 - theoretically the most secure plate fixation would be that achieved by having two plates on opposite sides of bone,
                         however, this is biologically unsound;
                 - plating of shafts by two plates at 90 deg is also mechanically sound, but involves soft tissue stripping; 
                         - however, bone is able to heal w/o periosteal callus, provided the endosteal circulation is intact;
          - comminuted frx:
                 - a plate placed across a comminuted segment is known as bridging plate;
                 - if marked comminution is present on the compression side of fracture then non union is more likely;
                 - consider cancellous or cortico-cancellous bone grafts;
                 - cortico-cancellous bone graft can be wedged into a frx gap, w/ appropriate lag screws applied into the graft, along w/
                        dynamic compression applied across the cortico-cancellous graft; 

Dynamic Compression Plates
        - AO foundation: Compression plating (midshaft)

- Prebending vs. Lag Screws:
    - prebending is superior for small bones and for porous bones, while lag screw compression is superior in large and dense bones;
    - another advantage of prebending is that it tolerates incidences of overload;
           - overloaded prebent plate returns to normal function, whereas screw threads are irreversibly stripped;
    - transverse frx:
           - in transverse frxs consider prebending plate inorder to equalize compression; of both cortices;
           - because a lag screws can not be placed, compression must be achieved w/ plates alone (see: dynamic compression plates)
    - oblique frx:
           - attempt to apply lag screw, followed by neutralization plate;
           - it is also possible to place the lag screw thru the plate;
           - neutralization plate is applied w/o dynamic compression;
           - never attempt to insert a lag screw after plate has been applied; 

- Locking Plates: general concepts

 - Methods to Avoid Frx Following Plate Removal:
    - as pointed out by Beaupre GS, et al (1992), plate constructs that used unicortical end screws were significantly weaker than
              bicortical end screws;
    - refracture may occur through unhealed frx site if plate is removed prematurely;
    - plates should be retained for at least 18-21 months to allow bone density to return to its prefrx level before removal of plates;
    - forearm should be protected for six weeks following removal;
    - risk factors for frx:
            - frx w/ initial comminution;
            - plating w/ 4.5-mm DCP;
            - early plate removal;
    - references:
            - Refracture of bones of the forearm after plate removal.
            - Refracture of bones of the forearm after the removal of compression plates
            - Year Book: Refractures After Forearm Plate Removal.  
            - A Comparison of Unicortical and Bicortical End Screw Attachment of Fracture Fixation Plates.
            - Bone weakness after the removal of plates and screws. Cortical atrophy or screw holes?
            - Removal of forearm plates. A review of the complications.

- Misc Plates:
       - One-Third Tubular Plates
       - Reconstruction Plates, 3.5 mm
       - Reconstruction Plates, 4.5 mm
       - Semitubular Plates
       - T Plates

The Effect of Divergent Screw Placement on the Initial Strength of Plate-to-Bone Fixation.

Force transfer between the plate and the bone: relative importance of the bending stiffness of the screws friction between plate and bone.

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

Last updated by Data Trace Staff on Tuesday, May 24, 2016 10:11 am