Plates for Fracture Repair:

---

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

          - Bone Healing w/ Plates:
          - Characteristics of Metal Implants:
          - Dynamic Compression Plates:
                     - DCP and LC-DCP, 3.5 mm
                     - DCP, 4.5 mm
                     - LC-DCP, 4.5 mm in Pure Titanium:
          - One-Third Tubular Plates:
          - Reconstruction Plates, 3.5 mm:
          - Reconstruction Plates, 4.5 mm;
          - Semitubular Plates:
          - T Plates: 

          - Locking Plates:
                  - out side links:
                          - LCP Locking Compression Plate.
                          - PHILOS
                          - LCP Distal Radius Plates 2.4. 
                  - references:
                          - The Evolution of Locked Plates. 
                          - Revolution in plate osteosynthesis: new internal fixator systems.
                          - "Shimming" a locking plate with washers to correct axial alignment.
                          - Awful considerations with LCP instrumentation: a new pitfall.
                          - Locking compression plate loosening and plate breakage: a report of four cases.
                         

---

- Outside Links: 
    - Orthopaedic Trauma Implants: Know Your Implants

- Discussion:
    - when bone is plated, the bone itself carries the majority of the compression load;
    - 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;
    - note: when plating a fracture the plate should be applied to tension side of the fracture;
    - 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 the 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;
    - 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;

- 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;

- Methods to Avoid Frx Following Plate Removal:
    - as pointed out by Beaupre et al 1992, plate constructs that used unicortical end screws were significantly weaker than bicortical end screws;
    - refracture may occur thru 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.  Rumball-K.  Finnegan-M.  Original Article: J Orthop Trauma. 1990. 4. pp 124-129.
            - A Comparison of Unicortical and Bicortical End Screw Attachment of Fracture Fixation Plates. J. Orthop Trauma. Vol 6, No 3. p 294-300. 1992.
            - Bone weakness after the removal of plates and screws. Cortical atrophy or screw holes.
            - Removal of forearm plates. A review of the complications.

---

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.