Patent Application
20120330191
The present invention relates to the field of intramedullary rod tracking and, more particularly, to a system and a method for tracking an intramedullary rod and detecting deformation of the rod with regard to the curvature of the rod as it is inserted into an object, such as a bone, and more particularly, into a medullary cavity of a bone.
The use of intramedullary nails or rods is well known and an established form of treatment of fractures in long bones, especially, for example, in the femur, tibia or humerus. The intramedullary rod may be inserted into a medullary cavity of a bone to treat bone fractures in orthopedic surgery and intramedullary tumors occurring in some forms of cancer. The rod includes at least one fixing hole arranged at the distal end and/or the proximal end thereof to aid in attachment thereof to the bone. The fixing hole may have an internal thread for mating with a cross lock or screw inserted in the fixing hole through the bone. A targeting device including an aiming arm may be used outside of the bone to determine where a transverse hole should be drilled to insert the cross lock or screw through the fixing hole. In some cases, however, the rod may bend during insertion of the rod into the bone such that the aiming arm must be adjusted to take the bending of the rod into account.
There is accordingly a need in the art for improved methods and systems as well as devices that at least partially overcome the above-mentioned problems. Specifically, there is a need in the art for an improved system and method with regard to intramedullary rod tracking which is easy to handle when determining a possible deformation of an intramedullary rod, and wherein manufacturing the device is uncomplicated and the components used therein are simple.
The present invention relates to a tracking system for an intramedullary rod and a method for tracking an intramedullary rod being inserted in a medullary canal. The present invention also relates to an improved tracking system including simple built-up components.
The present invention further relates to a system and a method for obtaining a three-dimensional view of the intramedullary rod being inserted into the medullary cavity with minimal experience of the operator.
The present invention also relates to a method which compares a deviation of a curvature between the intramedullary rod before and after implantation into a bone. The difference of these measurements determines the deviation, which is further used to aid in aligning an aiming device with a bore extending through the intramedullary nail.
In accordance with an exemplary embodiment of the present invention, a tracking system for an intramedullary rod comprises a probe insertable into the rod and movable toward a distal end of the rod. The probe further includes a deflection detection element. The probe is slidably receivable within a head portion attachable to a proximal end of the intramedullary rod. The system further comprises a logging unit adapted to detect relative movement between the probe and the head portion. By inserting the probe into the rod, the relative movement between the probe and the head portion is measured. The logging unit uses the relative movement to determine the depth of the probe within the cavity and to obtain the orientation of the probe (rotation) with regard to the three-dimensional information of a bending obtained based on the determined deflection. Thus, a three-dimensional view of the rod inserted in the medullary cavity may be obtained. The probe may also be rotated relative to the rod. It may also be possible to measure an amount of deflection as the probe is removed from the rod to verify the accuracy of the information obtained by inserting the probe into the rod.
In an exemplary embodiment, the logging unit recognizes at least one parameter from the relative movement and uses the at least one parameter to determine the current path of the intramedullary rod. The parameter or combination of parameters is selected from the group consisting of an amount of rotation of the probe with regard to a reference orientation between the head and the probe; an amount of deflection of the probe with regard to a reference orientation; and an amount of insertion of the probe relative to the head portion. The deflection detection element may be adapted to detect a deflection of the probe while the logging unit is configured to simultaneously collect the amount of deflection detected, the depth of insertion of the probe and the amount of rotation thereof.
The logging unit may also be configured to determine the current path of the intramedullary rod by comparing the relative movement against an expected movement of the probe. The expected movement may be predetermined by inserting the probe into the intramedullary rod before the rod is inserted into, for example, a patient.
In another exemplary embodiment, the deflection detection element may be one of a laser/mirror triangulation device, a tension stripe, a strain gauge strip, and/or a magnetic sensor, the deflection detection element being formed of simple components which are easy to handle during manufacturing. The above-identified deflection detection devices have a high degree of reliability and an appropriate resolution and accuracy for measuring the deflection of the probe. Any of the above-mentioned elements of the probe may be easily connected to the logging unit through the stem via an electrical connection such as, for example, a wire.
In another exemplary embodiment, the above-identified deflection detection element may be arranged at least partially inside the probe such that the deflection detection element is protected against an inner wall of the intramedullary rod. The laser/mirror triangulation device may be constructed using an interferometry measurement method as disclosed in U.S. Pat. No. 5,541,731 and U.S. Pat. No. 5,751,588 for general construction purposes.
In another exemplary embodiment, the logging unit may be a microprocessor having re-writable memory for storing data corresponding to the parameters recognized from the relative movement. The parameters may be one or more of an amount of deflection measured; an amount of insertion; and an amount of rotation for current procedure and/or for a plurality of past procedures.
In addition to the deflection detection element, the probe may also include a sensor for determining a position of a locking hole in the intramedullary rod. Thus, two different sensors may be used for obtaining information with regard to the three-dimensional imaging of the intramedullary rod and the detection of the locking hole. Having a lock hole detection sensor in addition to the deflection detection element ensures that the respective results are obtained independently from each other to provide reliability and redundancy.
In a further exemplary embodiment, the probe may comprise pads arranged along an outer surface thereof for centering the probe in the intramedullary rod. The pads may be preferably arranged in such a way that the probe is centered in the cavity of the intramedullary rod over its entire length. This will help obtain a reliable measurement of the deflection and also protect the probe against the inner surface of the intramedullary rod. The pads may have a triangular shape extending including a point extending radially outward relative to the longitudinal axis of the probe, which in one exemplary embodiment, may be in the shape of a cylinder.
In a further embodiment, the system may include a control unit connectable to the logging unit. The control unit may be adapted to calculate a difference between a curved trajectory of the probe in a deformed intramedullary rod and a straight and/or non-deformed intramedullary rod using the data collected by the logging unit. The control unit has a display on which the calculated difference may be displayed in terms of a number with digits and a sign. This display preferably provides the results of the measurements in an efficient manner such that the displayed number may be entered in the aiming device for the correction of the alignment of the aiming arm such that a hole may be drilled at the correct position in the bone for a bone fixation element to be inserted through the bone into the locking hole of the intramedullary rod.
In another exemplary embodiment of the present invention a method for tracking an intramedullary rod being inserted in a medullary cavity of a bone comprises inserting a probe attached to a probe stem into the rod, and locating and fixing a head at a proximal end of the rod, wherein the probe stem is slidably arranged with respect to the head. Further, the method comprises moving the probe in the rod, and while moving the probe in the rod in the direction of the proximal end of the rod, measuring relative movement between the probe and the head portion. The relative movement measure may be one or a combination of: the deflection of the probe; the distance the probe has been inserted in the rod; and/or the orientation of the probe with respect to a reference orientation. The data may be associated with each other, i.e. the deflection of the rod, the distance the probe has been inserted into the rod and the orientation of the probe with regard to a reference orientation, are collected. In an exemplary embodiment, for each point in time at which data is collected, there will be the information about distance, deflection and orientation. The method provides an easy to use intuitive procedure for obtaining tracking information about the intramedullary rod.
In an exemplary embodiment, the deflection of the probe may be measured by any sensor device capable of detecting deflection or bending of the probe. In particular, the deflection of the probe may be measured using one of a laser/mirror triangulation device, a tension stripe, a strain gauge strip, and a magnetic sensor.
In another exemplary embodiment, the deflection of the probe may also be measured as the probe is moved proximally toward a proximal end of the rod to verify the previously measured values. Thus, the necessary removal of the probe from the rod may provide additional information, minimizing the time and/or interaction of the probe with the intramedullary rod.
According to a further exemplary embodiment of the invention a method for tracking insertion of an intramedullary rod with a channel into a medullary cavity of a bone comprises measuring the intramedullary rod before implantation into the medullary cavity thereby generating reference data. Further, the method comprises measuring the intramedullary rod after implantation into the medullary cavity and calculating correction value(s) for adjustment of an aiming device to aligning the aiming device with the actual position of locking hole(s) in the intramedullary rod after insertion.
The present invention is directed to a device for determining deformation of an intramedullary rod comprising a longitudinal probe sized and shaped to be inserted into a channel of the rod and including a deflection detection element and a stem coupled to the probe, a head portion including a lumen extending therethrough and a coupling element to attach the head portion to a proximal end of the intramedullary rod. The lumen slidably receives the stem such that the probe is movable relative to the head portion and motion of the probe relative to the head portion corresponds to motion of the probe relative to the intramedullary rod. A logging unit coupled to the head portion detects a distance of travel of the probe relative to the head portion, a rotation of the probe relative to the channel and a deflection of the probe, the distance of insertion detected by measuring a relative movement of the probe with respect to the head portion, the rotation of the probe detected by measuring an amount of rotation of the probe with regard to a reference orientation between the head and the probe, the deflection detected by measuring of deflection of the deflection detection element with respect to the reference orientation. The logging unit aggregates data corresponding to the amount of deflection, the distance of travel of the probe and the amount of rotation along the path of travel of the probe to determine a current path of the intramedullary rod.
In another exemplary embodiment, an aiming device is attached to an intramedullary rod before implantation of the rod into the medullary cavity so that the aiming device may be calibrated to the particular intramedullary rod with which it is to be used. This overcomes problems relating to, for example, manufacturing tolerances which may cause certain features of the rod to deviate from their target positions.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein the same reference numerals are used throughout the several drawings to refer to similar components.
a shows an enlarged schematic view of a tracking system including an alternate deflection detection element according to the present invention;
b show in an enlarged schematic view an exemplary embodiment of a tracking system according to the present invention elucidating a determination of bending of an inserted intramedullary rod; and
a shows a schematic view of a head portion of the tracking system of
b shows a schematic view of a probe of the tracking system of
c shows a schematic view of a probe of the tracking system of
The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to the treatment of bone fractures and, in particular, relates to devices for determining deflection of intramedullary rods during insertion into a bone. It will be understood by those of skill in the art that an intramedullary rod may bend as it is inserted into a medullary canal of a bone, causing a deflection along a length thereof. Exemplary embodiments of the present invention describe a tracking device including a probe that may be inserted into a channel of an intramedullary rod to measure deflection thereof and to determine the position of one or more locking holes extending through the deflected intramedullary rod. It will be understood by those of skill in the art that the measured deflection of the intramedullary rod and/or the position of the locking holes may be used to adjust an aiming device such that an opening of the aiming device aligns with the actual position of the locking hole(s) in the deflected intramedullary rod. It should be noted that the terms “proximal” and “distal” as used herein, refer to a direction towards (proximal) and away from (distal) a surgeon or other user of the device.
As shown in
As shown in
The stem portion 4 may also be substantially longitudinal, extending proximally from a proximal end of the probe 3. The stem portion 4 is sized and shaped to be slidable within the head portion 13. Thus, an outer circumference of the stem 4 may be slightly smaller than an inner circumference of the head portion 13. The inner circumference of the head portion 13 is smaller than an outer circumference of the probe 3 such that the probe 3 cannot be slid within the head portion 13. The head portion 13 provides a sliding support for the probe stem 4. The head portion 13 may also include a coupling element for coupling the head portion 13 to a proximal end of the intramedullary rod 2 such that the head portion 13 remains stationary relative to the intramedullary rod 2 while the probe 3 is movable relative thereto. The head portion 13 may also include a movable element (not shown) configured to measure longitudinal movement of the probe 3 relative to the head portion 13. The movable element may be, for example, a wheel that turns in a first direction (e.g., clockwise) as the probe 3 is moved distally relative to the head portion 13 and an intramedullary rod 2 to which it is coupled and a second direction (e.g., counter clockwise) as the probe 3 is moved proximally relative to the head portion 13. It will be understood by those of skill in the art, however, that the movable element may be any element capable of detecting longitudinal movement of the probe 3 relative to the head portion 13 and the intramedullary rod 2 to which it is coupled.
The logging unit 5 may be connected to the head portion 13 through a wired or wireless connection and includes a data handling device for detecting and collecting information regarding an amount/distance of insertion of the probe 3 into the channel 11 of the rod 2, an orientation of the of the probe 3 relative to the intramedullary rod 2 and a bend or curvature of the path of the probe 3. The logging unit 5 may detect the amount or distance of insertion of the probe 3 in the channel 11 of the intramedullary rod 2 by measuring a relative longitudinal movement of the probe 3 with respect to the head portion 13. For example, where the movable element is a wheel, the logging unit 5 may detect the number of turns in the first direction to determine a length or distance of insertion of the probe 3 distally into the channel 11. Thus, the length or distance of insertion of the probe 3 into the rod 2 may be measured automatically by the logging unit 5. The logging unit 5 may also be capable of detecting an orientation of the probe 3 relative to the channel 11 of the rod 2 by measuring a rotation of the probe 3 relative to the head portion 13. Thus, the orientation of the probe 3 in the rod 2 may also be measured automatically by the logging unit 5. The logging unit 5 may measure the length of insertion and the orientation of the probe 3 simultaneously.
Further, the logging unit 5 may detect a deflection or curvature of the probe 3 measured by the deflection detection element 6 which may be connected to the logging unit 5 via a wire or cable passing through the stem 4. Since the probe 3 is sized and shaped for insertion into the channel 11 of the intramedullary rod 2, a deflection or bending of the probe 3 corresponds to a bending of the rod 2 caused by insertion of the rod 2 in the medullary cavity of the bone. This is schematically shown in
The logging unit 5 collects and stores the length, orientation and deflection data. The logging unit 5 may be, for example, a microprocessor having re-writable memory for storing the data. The data measured at the same point in time are associated with one another as a single data reference. Thus, each data reference may contain information regarding a specific time and point along the rod 2 and includes three measurements—the length, orientation and deflection. Moving the probe 3 within the channel 11 of the rod 2 will permit the logging unit 5 to obtain information for several points along the rod 2 so that a map of the rod 2 may be created. Thus, a three-dimensional image of the rod 2 may also be obtained so a sufficient number of points along the rod 2 are measured.
To determine the position of the locking hole 7, which may extend transversely through the intramedullary rod 2, the probe 3 may be rotated and moved within the channel 11 until the sensor 8 indicates alignment with the locking hole 7. While the probe 3 is rotated and/or moved longitudinally within the channel 11, the data regarding the length of insertion, orientation and deflection of the probe 3, and thereby the intramedullary rod 2, is collected.
The control unit 10 may be connected to the logging unit 5. The control unit 10 is a data processing arrangement which calculates a difference between the trajectory of the probe 3 in the actual intramedullary rod 2 and the trajectory the probe would have shown when inserted into the intramedullary rod 2 before it was deformed (e.g., prior to insertion into the medullary cavity of the bone). The difference is calculated using the data references collected by the logging unit 5. For convenience, the control unit 10 may further comprises a display 12 on which the calculated difference is displayed in terms of a number with digits. The display 12 may also display a sign indicating an objective assessment of the differential or corresponding directly to an adjustment which should be made to the aiming device to obtain a desired alignment of the aiming device with corresponding features of the intramedullary rod 2 (e.g., a locking hole 7). In either case, a user of the device 1 may use the data displayed to achieve the desired alignment of the aiming device with the intramedullary rod 2.
a-5c show an exemplary method for tracking the intramedullary rod 2 after it has been inserted in a medullary cavity of a bone. As shown in
Data collected by the logging unit 5 as the probe 3 is moved within the channel 11 may be used to calculate a deformity of the intramedullary rod 2 and subsequently displayed on the control unit 10 to aid in determining a corresponding adjustment that should be made to an aiming device (not shown) for drilling a hole into the bone in alignment with the locking hole 7. As shown in
Although the exemplary embodiments of the present invention and some of its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, composition of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention.
It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art.
The present application claims priority to U.S. Provisional Application Ser. No. 61/380,871 entitled “Intramedullary Rod Tracking” filed on Sep. 8, 2010 to Urs Hulliger and Adrian Baumgartner. The entire contents of this application are incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 61380871 | Sep 2010 | US |
