Humeral fracture in arm wrestling: bone morphology as a permanent risk factor. Indications for safety measures in arm wrestling.

Background. Arm wrestling has been recognized as a popular and potentially dangerous competition. Reports on injuries related to arm wrestling are increasing. The most important of these injuries are humeral shaft fractures. The generally accepted theory states that the shoulder joint is actively internally rotated against the opponent while the elbow is fixed in flexion resulting in enormous violent torque forces across the humeral shaft. Methods. The reported fracture morphology seems similar so we theorized that the basis of this fracture type is the bone structure. There is no experimental model of the arm wrestling fracture other than a virtual one. We assess morphology of the humeral bone by means of the bone cutting procedures and to verify the theory that the structure of humeral bone is a basis of the arm-wrestling fracture by means of newly developed model on human bones. Results. Results of the study suggest that the humeral shaft fracture morphology during arm wrestling is based on the spiral structure of the bone combined with the direction of the revolving, rotational force during the match. Conclusion. The safety rules of the arm-wrestling match based on results of our experimental study and the literature metaanalysis are also formulate.