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