[Biological internal fixation -- guidelines for the rehabilitation]

The process of fracture healing restores the biological and mechanical state of the bone tissue. In contrast to other tissues, bone has the unique capacity to heal through a real repair process resulting not in a scar but in a regular reconstitution of its original tissue structure. During the last two decades, the understanding of bone biology continuously evolved leading to the new concept that preservation of the viability of the bone fragments is the key to unimpaired fracture healing. The biological fracture management provides environmental conditions that allow the natural healing process to occur as quickly and undisturbed as possible. In comminuted diaphyseal and metaphyseal fractures, the reduction process strives for restoration of proper length and axial and torsional alignment. Thereby, the reduction technique is mainly indirect, i.e. without direct visualization of the fracture area. The primary stability of an osteosynthesis seems to be of secondary importance for achieving sound bone healing. Stabilization can either be performed with an intramedullary nail or a bridging plate. The new biological plating technique imitates the concept of intramedullary fixation. It requires the use of a long implant working with improved leverage. This reduces both, the loading of the screws and the loading of the plate. The good healing capacity of viable fragments and their integration into the fracture callus protects the implant (especially a plate) from fatigue failure. To help to accomplish this new concept of biological plate fixation, new implants such as the Locking Compression Plate (LCP) have been introduced. The mechanical efficiency of this new plate generation is enhanced due to its possibility for angular stability screw insertion; load transfer by friction can be replaced by a load transfer by interlocking (internal fixator), reducing the biological interference of this implant (no contact implant). Functional rehabilitation with painfree mobilization needs to be performed carefully because the loading capacity of the biological plate osteosynthesis is low until radiological signs of bone healing via callus formation is visible. Clinical signs of overload and radiological indicators of potential mechanical failure of the fixation have to be identified by the general practitioners, and the compliance of the patient has to be controlled during the rehabilitation phase to avoid complications after biological internal fixation.