Drive systems and devices incorporating drive systems

Abstract

A fixation device may be used for supporting and/or stretching an injured body part. An exemplary fixation device uses a thumb wheel control element to provide controlled rotational micromovements of a joint. The control element and its associated drive system allow for movement along a particular axis, while the position remains fixed with relation to the other axis. In addition, the fixation device may incorporate a drive system that introduces a simultaneous longitudinal translation with rotation, in order to provide for a common point of origin of rotation between the fixation device and the affected body part supported by the fixation device.

What is claimed is: 
     
         1 . A method for adjustably supporting an injured body part with an external fixation device having a first portion rotatably attached to a second portion, comprising the steps of:
 removably attaching the first portion of the external fixation device to a bone at a fixed distance from the bone;   rotating the first portion of the fixation device with respect to the second portion of the fixation device; and   providing longitudinal translation of the point of attachment of the first portion of the fixation device to the bone so that the external fixation device and the bone have a common point of origin of rotation.   
     
     
         2 . A method as in  claim 1 , wherein the amount of longitudinal translation approximates the product of the fixed distance between the first portion of the fixation device and the bone and the cosine of the amount of rotation of the first portion with respect to the second portion of the fixation device. 
     
     
         3 . A method as in  claim 2 , wherein the rotation of the first portion with respect to the second portion and the longitudinal translation occur simultaneously. 
     
     
         4 . A method as in  claim 2 , wherein the rotation of the first portion of the fixation device with respect the second portion of the fixation device occurs in one plane; the method further comprising the step of rotating the first portion of the fixation device with respect to the second portion of the fixation device in a second plane. 
     
     
         5 . A method as in  claim 4 , wherein the second plane of rotation is substantially orthogonal to the first plane of rotation. 
     
     
         6 . A method as in  claim 5 , wherein the fixation device further comprises a control element, the method further comprising the steps of:
 moving the control element between two positions in order to switch between the two planes of rotation of the first portion with respect to the second portion; and   adjusting the control element in order to rotate the first portion with respect to the second portion and to cause longitudinal translation of the point of attachment of the first portion of the fixation device to the bone.   
     
     
         7 . A method for adjusting a fixation device with a first portion and a second portion rotatably connected by an adjustable joint, using a control element, comprising the steps of:
 releasably attaching the first portion of the fixation device to a bone with a bone screw; and   adjusting the control element of the adjustable joint in order to simultaneously rotate the first portion relative to the second portion and translate the position of the bone screw relative to the second portion.   
     
     
         8 . A method as in  claim 7 , wherein the bone screw is longitudinally translated along the length of the first portion, and wherein the first portion is held a fixed distance from the bone. 
     
     
         9 . A method as in  claim 8 , wherein the amount of longitudinal translation approximates the product of the fixed distance of the first portion from the bone and the cosine of the amount of rotation between the first portion and the second portion. 
     
     
         10 . A method as in  claim 9 , wherein the control element is capable of being moved between two positions corresponding to two planes of rotation for the first portion with respect to the second portion. 
     
     
         11 . A method as in  claim 10 , wherein the first plane of rotation is substantially orthogonal to the second plane of rotation. 
     
     
         12 . A method of adjusting a fixation device that includes first and second portions connected by an adjustable joint with a control element capable of moving between at least two positions, the method comprising the steps of:
 adjusting the control element of the adjustable joint in order to rotate the first portion relative to the second portion in a first plane about an origin of rotation;   repositioning the control element; and   adjusting the control element in order to rotate the first portion relative to the second portion in a second plane about the origin of rotation, the second plane being substantially orthogonal to the first plane.   
     
     
         13 . A method as in  claim 12 , wherein the first portion is removably attached to a bone a fixed distance from the bone, further comprising the step of longitudinally translating the point of attachment. 
     
     
         14 . A method as in  claim 13 , wherein longitudinal translation accompanies rotation of the first portion with respect to the second portion so that the fixation device and the bone have a common point of origin of rotation. 
     
     
         15 . A method as in  claim 14 , wherein the amount of longitudinal translation approximates the product of the fixed distance of the first portion from the bone and the cosine of the amount of rotation between the first portion and the second portion. 
     
     
         16 . A method as in  claim 12 , further comprising the step of locking the position of the first portion with respect to the second portion whenever the control element is repositioned. 
     
     
         17 . A method as in  claim 16 , further comprising the step of locking the position of the first portion with respect to the second portion once the first portion has been rotatably adjusted relative to the second portion in both planes of rotation.