| The pincers compressing external fixator(PCEF) was economic, practical, less invasive and easy to operate in treatment of olecranon fracture. The recovery of the function of elbow joint was satisfactory: 98.88 per cent of patients recovered excellently, which was one of the best therapies of all clinical reports. A method of 3 - dimensional finite element calculation was set up to study biomechanics of treatment of olecranon fracture with PCEF, so as to find the best site and the optimal strength of fixation and the ideal range of elbow joint's activity according to the elastic fixation rule in fracture treatment, and to clarify PCEF's work principle. The study presented scientific and objective datum in clinical therapy, improve its curative effect, and made PCEF's therapy popular in primary hospitals. The results showed:1 .Because of the biceps and triceps' contract force and the reacting force of trochlea humeri, compressive stress was produced in the front of olecranon, while tensile stress in the back. The stress caused olecranon fracture. The place of most fracture lied between the tine and the middle, and most of fracture line was transverse or oblique.2.The site of jaws and hook of PCEF were placed in the back of olecranon. Farther was the force line of PCEF from neutral axis, better was its effect.3.The best fixation strength of PCEF was 50 N in transverse fracture, and was 25 N in oblique fracture and comminuted fracture.4.When the broken limb exercised, the muscle force of triceps was not more than 70 N, and the range of activity of elbow joint was between 60?and 90 .5.The therapy meets the elastic fixation rule in fracture treatment.
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