Fixing Fractures With Plates
Because of the large number of locations where fractures occurs and the different bones involved there is a variety of plates available. The dynamic compression plate or DCP allows a sliding technique to be used because of the screw holes being angled away from a central point. Once the screws are inserted and tightened they apply an inwards compression force, bringing the fragments into stronger contact.
The ulna and the ankle lateral malleolus are fixed with thin plates of about one mm in thickness which can be shaped to the area required. Fractures close to a joint need specially designed plates to facilitate fixation and reduce impingement. Upper femoral fractures are often stabilised with a plate which has an angle of 95 degrees to restore the normal anatomy of the upper femoral area.
Internal fixation with this plate demands three dimensional thinking on behalf of the surgeon so that the anatomy can be restored to the normal relationships. Reconstruction plates can be moulded to the contours of the pelvis and acetabulum in three dimensions as they are thinner than dynamic compression plates. If a fracture is next to or just below a joint replacement prosthesis they are often managed with larger plates which also include the ability to use cerclage wiring. High levels of fracture stability can be provided by compression of the fragments and a good restoration of anatomical alignment by the fixation. If firmly stabilised and without any fragment gap then the fracture will heal by primary healing.
Absorption of the dead bone at the site of fracture occurs by the action of osteoclasts, with blood vessels growing into the region and then bone producing cells proliferating. Disruption of the blood supply by the plate can produce some osteoporosis under the plate, leading to reduced bone strength from this and the screw holes once the plate is removed, necessitating careful decisions about the amounts of force to be applied to the area. Internal fixation with a plate involves opening up the fracture site and removing the blood clot, reducing the fragments to an anatomically acceptable alignment. A fracture interrupts the blood supply across and around a fracture and the remaining blood supply is provided by the periosteal bone lining. The periosteum should be preserved and not stripped away during the operation or healing could be delayed from reduced vascular supply. Unstable comminuted fractures are more difficult to fix and bridge plates are used to fix the two main parts and keep the important aspects of the bone in line, the rotation, alignment and length of the bones. However this form of weaker fixation cannot tolerate any significant level of load.
The LISS (Less Invasive Surgical Stabilisation) plating system is a recently developed technique which reduces the contact between the metal and the bone or periosteum, reducing the potential for disruption of the blood supply in the fracture area. Modern designs contour more effectively to the bony anatomy and allow for locking of the screws, which are both advantageous by maintaining the fracture in the correct position whilst allowing increased forces to be applied to it in the healing period. These new designs are most useful in fixing the ends of the bones in fractures of the tibia, femur, radius and humerus. If there is enough room for easy fixation and the fracture is of a more stable type then conventional plating techniques may be used for fixing breaks of the shafts of bones such as the radius, ulna and humerus.
Locking screws are more appropriate if the bone is osteoporotic or the fixation options are limited. Future development will likely lead towards locking techniques being the first option for all fractures, but they are much more expensive and wider use awaits reduction in costs. If the costs of revising the fixation due to malunion by conventional plating are factored in then the more expensive initial system looks more cost neutral. Nailing It was in the 1930s that Kuntscher refined the intramedullary nailing technique which then became the treatment of choice for shaft fractures of the femur. Humeral and tibial fractures as well as femoral breaks nearer the bone ends were the next progression. Early joint movement and weight bearing walking is allowed by this.