Four dynamite methods
One way of promoting natural fracture healing is to decrease the stiffness of locked plating constructs by controlled dynamization of the fracture, say US-American orthopedics at the University of Iowa Hospital and Clinics. In their study, the researchers investigated the effect of four different stiffness reduction methods on interfragmentary motion. Their conclusions:
Replacing locked with non-locked diaphyseal screws does not significantly decrease construct stiffness and does not enhance interfragmentary motion.
A longer bridge span primarily increases shear motion, not axial motion.
The use of far cortical locking screws or active plating delivers axial dynamization without introducing shear motion.
The authors applied distal femur locking plates to bridge a metadiaphyseal fracture in femur surrogates, and measured construct stiffness, axial motion and shear motion at the fracture site. The four different methods for stiffness reduction were: replacing diaphyseal locking screws with non-locked screws (NON-LOCKED); bridge dynamization (BRIDGE) with two empty screw holes proximal to the fracture; screw dynamization with far cortical locking screws (FCL); and plate dynamization with active locking plates (ACTIVE). In addition, a locked construct with a short bridge span was used as non-dynamized control group (LOCKED).
NON-LOCKED constructs had a similar stiffness, axial motion and shear motion as controls, while BRIDGE constructs reduced stiffness by 45 % versus controls (p<0.001). Again versus controls, FCL and ACTIVE constructs reduced stiffness by 62 % and 75 % respectively, and significantly increased axial motion, but not shear motion.