Three cases of humeral shaft fracture during police arrest —Biomechanical aspects and reconstruction of events

ObjectivesFirst, to evaluate humeral fracture patterns created by torque and transverse force, to test the breaking force required and evaluate maximum force applied by volunteers; second, to apply the results of these experiments and review relevant literature to three clinical cases of spiral humeral shaft fracture during police arrest with contradicting statements of the involved persons.Material and MethodsThe study consisted of a review of the literature as well as an experimental model study. Controlled torque force and direct force was applied to a set of artificial and human humerus bones. In addition, maximum force was measured in 33 healthy volunteers. Fracture thresholds were compared using t-test.ResultsTorque forces result in spiral fractures, direct force results in transverse fractures of both artificial and human bones. The threshold level for fractures was significantly lower in human bones than in artificial bones. Maximum force was higher in male than in female volunteers. Nevertheless, all volunteers achieved sufficient force to fracture both artificial and human bones.ConclusionThe findings of this study indicate that the humerus fracture in all three clinical cases occurred as a result of torque forces to the arm. Since there were no lesions to the adjacent joints (shoulder, elbow), the injury mechanism concurs with the situation of a resisted arrest.