Abstract: A tool for use in removing broken or inoperative screw fasteners. The tool has a tubular-shaped extension at one end with cutting teeth projecting axially from the extension. The teeth can cut around a fastener when the tool is rotated in one direction to provide a stub end on the fastener over which the extension fits. The extension is then tightened on the stub end and teeth, extending radially inwardly from the extension, tightly grip the stub end so that the fastener can be unscrewed on reverse rotation of the tool.

Abstract: A tension spring capable of large elastic deformation and having a high resistance to breakage and particularly, but not exclusively, for use as an artificial prosthetic ligament. The spring comprises an elongate elastic core having a low modulus of elasticity and defining opposed ends. A tensionable wrapping of thread having a high resistance to breakage is disposed in contact about the core to compress the core and to cause it to elongate axially upon opposite relative axial displacement of opposed ends of the wrapping secured to traction means.

Abstract: An extensometer for detecting traumatized ligaments where the elongation of the ligament is either abnormally large or abnormally small compared to the elongation measured on a healthy ligament for an angle of flexion of the knee. The extensometer includes at least one flexible member having a strain gauge secured thereto to measure deflexion of the flexible member from its normal configuration. The flexible member has a free end and is secured at its opposed end to a support base. A clamping member is provided to retain the free end of the flexible member on a ligament while maintaining the support base substantially stationary with respect to the ligament whereby elongation of the ligament is detected by the deformation of the flexible member from its initial configuration.