THE BIOMECHANICS OF THE COMBINED KIRSCHNE R WIRE OSTEOSYNTHESIS IN A HUMAN-MODEL FOR DORSAL UNSTABLE DISTAL RADIUS FRACTURE (COLLES FRACTURE)

In an experimental study, the biomechanical qualities of the combined Kirschner wire osteosynthesis (KWO) in the unstable Colles' fracture w ere analyzed. This type of pin fixation is our preferred osteosynthesi s in the treatment of unstable Colles' fracture because it allows imme diate functional therapy. It represents a modification of Kapandji's d ynamic KWO, compensating for the insufficient volar stability by means of the conventional static KWO. Clinical experience according to the anatomical and functional results, was very encouraging suggesting tha t a clinical concept based on the biomechanical principles of combined KWO and its single components should be constituted. Simulation of th e unstable Colles' fracture was realized by dorsal wedge osteotomy of the distal end of the radius using cadaveric material. This fracture m odel was subsequently pinned using the different KWO types and tested by a standardized vector energy testing device regarding its stability in the four main loading directions. The combined KWO unifies the adv antage of volar stability of the conventional KWO with the high dorsal stability of dynamic KWO. The main functional principle of dynamic KW O with regard to its axial stability consists in the repositioning of the dorsal bone fragmentation zone and hence the reconstitution of cor tical load transmission. Besides its good stabilization, dynamic KWO a lso leads to optimal alignment of the distal metaphyseal fragment. Fur thermore, the experiments yielded important information about technica l aspects of the surgical procedure, which helps us to avoid anatomica l and functional deficiencies. Based on these experimental findings, t he surgical technique of combined KWO was standardized.