[The fixateur-externe-osteosynthesis without osseous support (external distance-osteosynthesis) in the lower limbs. Biomechanic, surgical and osteoplastic basic principles (author's transl)].

The stability of external distance osteosynthesis for complete tibia and femur defects rests solely on the rigidity of the external support. The rigidity of the external support is an function of the mechanical data of its individual elements, of the hold between the bone and the other system, as well as of the individually optimized construction form. The response of an osseous contact area which is not resistant to compression when external osteosynthesis is applied is mechanically similar to the response to distance osteosynthesis in the presence of a defect. The basic application rules for distance osteosynthesis of the lower limbs are given. The symmetric frame fixator applied in a three-dimensional arrangement is indicated for tibia defects. External distance osteosynthesis of femur defects can only be recommended when plate osteosynthesis alone or plate osteosynthesis in conjunction with a bracket fixator are out of the question. The various application forms for external osteosynthesis of femur defects are described and their indication with respect to knee function given. Although none of the construction forms for defects in the tibia and especially in the femur can eliminate mechanical interfragmental movement of the main fragments, their clinical use has been successfully established; however, surgical and osteoplastic measures must ensure more and more biological stability with time. The necessary surgical techniques and procedures are described. Whereas even extensive defects of the femur can be bridged exclusively with autologous cancellous bone, varied measures are required for the lower leg, depending on the various individual conditions. Should the direct bridging of the main tibia fragments not be appropriate, fibular-tibial synostosis is necessary. The various options for such fibular-tibial osteoplasty which may be required, depending on the individual case, are described.