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U Schümann

Publications and source records attributed to U Schümann.

3 recordsLinked to original sources

[Ilisarov ring fixation and its technical application].

The Ilisarov ring fixator is an extremely versatile external fixation device. There is a wide range of indications for its use, e.g. fractures, pseudarthroses and non-unions, large defects, deformities and limb shortening. The device consists of rings or half-rings, which are connected to each other by threaded rods or plates and to the bone by wires under tension. This design allows neutral fixation, compression or distraction of the bone fragments. Because of its low axial stiffness at low loads and increased stiffness at higher loads, this fixator promotes osteogenesis and reduces strain on the tissues in functional treatment. Surgical intervention for its application is minimally invasive. This is a useful addition to the orthopaedic surgeon's armamentarium, providing proper attention is paid to preoperative planning, the principle rules of frame design and wire insertion technique, and postoperative management.

Biomechanical Phenomena

[Biomechanics of the ring fixator--contributions of individual structural elements].

The mechanical behaviour of the circular external fixation device using thin, pre-tensioned wires is difficult to predict, because the individual elements, such as rings, rods and wires, can be assembled in a large variety of configurations. This behaviour is of particular importance in the treatment of large segmental defects and in bone lengthening, because most of the load is transmitted through the fixator. In this study, the mathematical basis of the widely varying definitions of stiffness under axial, bending and torsional loads is presented. The principal variables influencing a particular configuration and their effects are indicated. Particular consideration must be given to the fact that the wires under tension generate a non-linear behaviour of the frame. The information needed for reporting on different fixator systems is indicated. Finally, the effect of individual structural elements, such as number, direction and tension of the wires, number of threaded rods and distance between the planes of the rings on the different stiffnesses, is presented and discussed with respect to clinical significance.

Biomechanical Phenomena

[Initial modifications of the ring fixator apparatus].

To increase the practicability of Ilisarov's ring fixation apparatus, we introduced the following modifications: Clamping of the fixation wires using a quick collet with a force indicator, which enables reproducibly preuse and rapid clamping. Hardened screws to maintain the tension longer. Production of the olive wire from homogeneous implant steel by the cold-press method. Optimization of the cutting edge at the wire tip. Measurement of tension in the fixation wire. A distractor incorporating a clock and a device showing the distraction achieved so that doctor and patient can better supervise the distraction procedure. Simplifications of the wound dressing.

Biomechanical Phenomena