this invention improves upon existing designs by directly measuring , independently from input variables , the axial force generated while assembling modular implant components . in a preferred embodiment of the present invention , this is accomplished by using a spring ( or springs ) to measure the true axial force being exerted . springs deflect a predictable amount under load . if this deflection is measured and the spring rate is known , a force can be calculated . in one embodiment this deflection can be measured using a scale . this scale may be labeled with force as the units . the scale may also represent a range of desirable loads . this range may be labeled with text , or color coded , to indicate adequate or inadequate assembly loads . in another embodiment of the present invention , the required spring deflection may activate a trigger that alerts the user that the desired load has been reached . this trigger may release a button , make a sound , switch on a light or provide some other means of indication . in another embodiment of the present invention , the force may be measured by a piezoelectric element whose voltage can be calibrated to a load . this voltage can be communicated to a user by means of a scale , light , sound , sensation ( e . g . shock ), etc . fig1 shows an implant assembly tool formed in accordance with the present invention . some sections of the tool have been cut away in fig1 for clarity . by closing handles 1 , shaft 2 is drawn up away from nose 3 . this applies the assembly forces for the modular device attached at location 4 . fig2 shows an embodiment using springs to measure direct axial tension . shaft 5 is attached to the implant . housing 6 , is attached to handle 7 by means of a mechanical linkage . elements 5 and 6 move in opposite directions with respect to one another . the motion causes compression on spring ( s ) 8 . in this embodiment the spring deflection is measured in a discrete amount by a triggering mechanism 9 . fig3 shows an embodiment of the present invention that measures tension incrementally , using a scale 10 . fig4 shows an embodiment of the present invention that measure tension discretely , using a button indicator 11 . still other embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure , and are considered to be within the scope of the present invention .
this invention provides for a tool that produces , and directly and accurately measures , an axial force used to assemble two members of a modular implant , specifically , a modular hip implant .