Torsion Fractures of the Leg. ( Zurich). This article offers twenty-two clinical observations on the production of spiral fractures of the bones of the leg, together with conclusions as to the reproduction of this variety of fracture experimentally by torsion. Every torsion executed by a one-sided lever ( force) is associated with some bending of the bone, which bending will be greater in inverse proportion to the length of the lever. The level of the fracture is determined by the weakest cross-section of the bone. The spiral shape of the line of fracture is an expression of the torsion. The beginning of the spiral fract ure and the ending of the same are dependent on the situation of the axis of torsion and on the disposition of the greatest ten sion from bending. The ascent of the spiral depends in greater part on the elasticity of the bone. For the leg the following mechanism obtains. External rotation of the foot by force acting on the anterior half of the foot causes a spiral fracture in the lower half of the tibia with the fracture terminating posteriorly and a fracture of the fibula at a higher level. The direction of the spiral is right sided on the left foot and vice versa for the right. Inward rotation of the foot by forces acting on the an terior half of the foot causes a spiral fracture of the fibula at a low level, eventually with fracture of the internal malleolus. The spiral is left on the left side and right on the right side. External rotation by forces acting on the outer surface of the heel also cause a low fracture of the fibula and fracture of the internal malleolus. The spiral passes to the right on the left side and vice versa on the right side. Inward rotation of the foot by forces acting on the inner surface of the heel causes a torsion fracture in the lower half of the tibia with terminal fracture on its posterior surface and a fracture of the fibula at a lower level. The spiral is right sided on the right side and left sided on the left side. Beitriige zur klinischen Chirurgie, Band xxvii, Schluss, Heft 3.