前腕骨骨折の発生機転に関する研究

〈第2編〉―緩衝作用に関する力学的検討―

抄録

Whether or not f ractural accidents have increased in children cannot be determined only by the statistical data. Fracture may be related to various factors and among them, the protective buffer effect by muscle is one of the most important factors. To clarify the onset process of fracture in the forearm in children which was observed most frequently, experimental studies have been done using a model for the forearm bones made of resin and the forearm samples of cadaver. Stresses of various parts of the bones were measured by the strain gage method, and the following results were obtained.
Under static load bearing, the model presented the stress distribution depending on the form, and the largest stress was obserbed at the distal diaphysis of the model of radius. The stress distribution of forearm sample under static load bearing was greatly influenced by the articular capsule and the distal region of the radius showed the maximum stress. As the model was gradually filled up simulating muscular action, the stresses decreased. When the traction force of the muscle was simulated by the use of a steel wire, the stress distribution depending on the form changed and the stresses reduced. As the muscular action was gradually added to the model, fracture was not apt to occur and then, greater impulsive force was required for the onset of the event in impact load test.
Based on the above results, it is suggested that, if the protective buffer effect by the nerve and muscle acted incoordinately when a child falls down, the greater stress is loaded to the bone tissues, resulting easily in fracture.