Does it makes sense to use angle-stable screws on one side of angle-stable implants and conventional screws on the other side?

It is possible but does not make sense. Angular stability leads to an increase in stability and a reduction in micro-movements. If there is angular stability on one side, the non-angle-stable side will be subject to greater stresses, with the possibility of failure of the bone-implant connection. Use of angle-stable screws on either side of an unstable bone area (fracture, osteotomy) is recommended.

Do four, five or more screws have to be inserted in the angle-stable method of internal fixation of long bones as in the conventional technique?

 

In conventional internal fixation, forces are transmitted through the compression pressure and the resulting friction. In angle-stable internal fixation, these are distributed evenly over the entire contact surface of the screws in the bone and are transmitted through the contact points of the plate with the bone surface. According to our own investigations, the first screw next to the fracture transmits about 50 to 60 % of the forces, the second 20 to 30 % and the third screw about 10 %. The load-transmitting quality of additional screws is negligible. This means that it is of crucial importance to insert two to three screws on each side using the angular stability method.

Does it make sense to use monocortical, angle-stable screws?

 

As a rule, it does not make sense to use monocortical screws as the specific advantages of angular stability are not exploited. The longer the screw (optimally obliquely bicortical), the greater the area of load distribution in the bone, the more stable the system and the lower the danger with regard to overloading of bone and implant. There are exceptions, e.g. in the mandible, where use of a bicortical screw would put a nerve at risk.

D. Wolter