Radiological and biomechanical analysis of humeral fractures occurring during arm wrestling

BACKGROUND Arm wrestling has recently become one of the most popular sports among young people, mainly due to its simplicity and spectacularity. Yet, unfortunately it is also injury prone. The aim of the study was to perform a biomechanical analysis of the forces which act during arm wrestling, as well as to explain the mechanism of the occurrence of humeral fractures of a similar topology as observed on X-rays. MATERIAL/METHODS During the period 2001 to 2008 nine cases of humeral fractures resulting from arm wrestling were consulted and treated at the Clinic. The assessment of the limb condition included an interview and the examination of the fractured extremity. All the patients underwent surgical treatment, using the method of open reduction and internal fixation. The virtual dynamic model of the upper limb was established on the basis of a series of computer tomography scans of the bone, and literature data. The biomechanical analysis was carried out using the Finite Elements Method (FEM). RESULTS There were five cases of the 12-B1 type in the AO Classification with butterfly fragments in five cases, and four of the 12-A1 type without the butterfly fragment. The maximum bone stress resulting from torsional loading which occurs during arm wrestling amounted to 60 MPa and was located 115 mm above the elbow on the medial - posterior side of the humeral. CONCLUSIONS The strength analysis carried out during arm wrestling revealed that the forces of the acting muscles significantly exert stresses within the distal third of the humeral.