Surgical rod measuring system and method

A system and method for measuring a surgical rod are disclosed. The system includes a processor, a probe in communication with the processor and configured to trace along a surface of the implant, a tracking system in communication with the processor and the probe for generating first data representing at least one of linear and rotational movement of the probe during a first trace along the surface of the implant, wherein the processor is configured to receive the first data and generate a first graphical representation of the implant based on the first data, and a display in communication with said processor for displaying the graphical representation of the implant based on the first data. Various methods are also disclosed.

TECHNICAL FIELD

The present disclosure generally relates to medical devices, systems and methods for the treatment of musculoskeletal disorders, and more particularly to systems and methods for determining geometries of a surgical rod, and in particular a spinal rod, to provide stabilization of vertebrae.

BACKGROUND

Spinal disorders such as degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including pain, nerve damage, and partial or complete loss of mobility. For example, after a disc collapse, severe pain and discomfort can occur due to the pressure exerted on nerves and the spinal column.

Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatments of these spinal disorders include discectomy, laminectomy, fusion and implantable prosthetics. During surgical treatment, one or more rods may be attached via fasteners to the exterior of two or more vertebral members in a vertebral fixation system.

Normally when a rod is to be positioned within a fixation system, the rod requires bending and shaping to conform to precise curvature of a spine of a patient. This curvature can require bending of the rod in the sagittal, coronal and/or transverse planes of the patient. Surgeons typically predetermine the required geometries of the spine of the patient and then shape and bend a rod based on visual estimates. The shaped rod is then placed into bone anchors of the fixation system in the patient and the surgeon readjusts the shape and bends of the rod in situ based again on visual estimates in an attempt to best match the required geometries. This disclosure describes an improvement over these prior art technologies.

SUMMARY

Accordingly, a system for measuring an implant is provided. The system includes a processor, a probe in communication with the processor and configured to trace along a surface of the implant, a tracking system in communication with the processor and the probe for generating first data representing at least one of linear and rotational movement of the probe during a first trace along the surface of the implant, wherein the processor is configured to receive the first data and generate a first graphical representation of the implant based on the first data, and a display in communication with said processor for displaying the graphical representation of the implant based on the first data.

In one embodiment, a method for measuring an implant includes moving a probe along a surface of an implant prior to positioning the implant within a patient, tracking movement of the probe to obtain first data representing the implant, storing the first data in a memory, and displaying a first image representing the implant based on the first data.

In one embodiment, a method for measuring a surgical rod includes implanting at least one bone fixation element into a patient, bending the rod prior to positioning the rod within the patient, moving a probe along a surface of the rod prior to positioning the implant within the patient, tracking movement of the probe to obtain first data representing the rod, storing the first data in a memory, displaying a first image representing the rod based on the first data, positioning the rod in the patient, connecting the rod to at least one bone screw, moving the probe along the surface of the rod, tracking movement of the probe to obtain second data of the rod within the patient, storing the second data in the memory, and displaying a second image representing the rod based on the second data.

Like reference numerals indicate similar parts throughout the figures. It is to be understood that the figures are not drawn to scale. Further, the relation between objects in a figure may not be to scale, and may in fact have a reverse relationship as to size. The figures are intended to bring understanding and clarity to the structure of each object shown, and thus, some features may be exaggerated in order to illustrate a specific feature of a structure.

DETAILED DESCRIPTION

The exemplary embodiments of the system and method for measuring a surgical rod are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a spinal fixation system that provides stabilization for treating a vertebral column. It is envisioned that the present disclosure may be employed to treat spinal disorders such as, for example, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor and fractures. It is contemplated that the present disclosure may be employed with other osteal and bone related applications, including those associated with diagnostics and therapeutics. It is contemplated that the disclosed systems and methods may be alternatively employed in a surgical treatment with a patient in a prone or supine position, and/or employ various surgical approaches to the spine, including anterior, posterior, posterior mid-line, medial, lateral, postero-lateral, and/or antero-lateral approaches, and in other body regions. The present disclosure may also be alternatively employed with procedures for treating the lumbar, cervical, thoracic, sacral and pelvic regions of a spinal column. The system and methods of the present disclosure may also be used on animals, bone models and other non-living substrates, such as, for example, in training, testing and demonstration.

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is intended. Any alterations and further modifications in the described devices, instruments, methods, and any further application of the principles of the disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. The following discussion includes a description of a surgical rod measuring system and related methods in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. Reference will now be made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures.

The surgical rod measurement system may include any appropriate surgical tracking system. For example, the surgical rod measurement system may include an optical tracking system, an electromagnetic tracking system, and acoustic tracking system, an ultrasound tracking system, an active device tracking system or any other appropriate tracking systems or combinations thereof. Although the following discussion generally relates to the use of an optical and/or electromechanical tracking system, it will be understood that any appropriate tracking system may be used and the optical and/or electromechanical tracking system is described merely as an example. Exemplary electromagnetic tracking systems are set out in U.S. Pat. No. 6,493,573, issued Dec. 10, 2002, entitled “METHOD AND SYSTEM FOR NAVIGATING A CATHETER PROBE IN THE PRESENCE OF FIELD-INFLUENCING OBJECTS”; U.S. Pat. No. 5,592,939, issued Jan. 14, 1997, entitled “METHOD AND SYSTEM FOR NAVIGATING A CATHETER PROBE; U.S. Pat. No. 6,516,212, issued Feb. 4, 2003, entitled “THREE DIMENSIONAL MAPPING”; U.S. Pat. No. 6,522,907, issued Feb. 18, 2003, entitled “SURGICAL NAVIGATION”; each of which is incorporated herein by reference. Other tracking systems are also described in U.S. Pat. No. 7,835,778, issued Nov. 16, 2010, entitled “METHOD AND APPARATUS FOR SURGICAL NAVIGATION OF A MULTIPLE PIECE CONSTRUCT FOR IMPLEMENTATION”; U.S. Pat. No. 6,470,207, issued Oct. 22, 2002, entitled “NAVIGATIONAL GUIDANCE VIA COMPUTER-ASSISTED FLUOROSCOPIC IMAGING”; each of which is incorporated herein by reference.

In addition, although the tracking system disclosed herein uses a probe in wireless communication with a detector to determine position and rotation data of the rod, other configurations are contemplated. For example, a probe having an active internal guidance system that can include gyroscopes and/or accelerometers can be used to track the position and rotation of the probe during its operation and be in direct communication with the control computer or processor, without the need for the detector. A probe in this type of system can communicate positional and rotational information of the probe to the processor in either a wired or wireless configuration. In addition, since the tracking is relative to the rod itself no wider coordinate system is required. Systems and methods for measuring a surgical rod will now be described with respect toFIGS. 1-12.

In one embodiment, the system for measuring a surgical rod10includes a processor11for receiving positional and rotational data representative of movement of a probe15along a surgical rod21. The data can be stored in a memory13in communication with the processor11. Processor11receives the data and translates the data into a graphical representation22of the surgical rod21. The graphical representation22can then be displayed on a display14. At some point in time after the processor11receives the data, the processor11can determine angular geometries of the rod21. The geometries can include angular measurements in any or all of the transverse, coronal and sagittal planes.

As stated above, a detector12in communication with the processor11can be used to track the position and rotation of the probe15. The detector12may be operably located in any appropriate location such that the detector12is able to detect a tracking element17operably connected to the probe15. For example, in an optical tracking system the tracking element may be one or more reflectors or light emitting diodes (LEDs). In an electromechanical system, the tracking element may be one or more radio transmitters to transmit an electromechanical signal.

It is contemplated that tracking element17can be disposed in or on the detector12, probe15, and/or rod21and be used to obtain rod geometries. For example, the tracking element17can be part of the detector12and obtain rod geometries, before, during and/or after surgery.

It is also contemplated that tracking element17can be in a rod bender (not shown), where the rod geometries can be obtained and transmitted to the processor11via a wired or wireless connection, for example, before, during and/or after surgery.

In a system wherein the probe contains active devices to determine movement as the tracking elements, e.g. gyroscopes and/or accelerators, the probe can contain its own processor and transmitter to receive electronic signals from the tracking elements and transmit the signals to the detector, which in this case can be a receiver. The transmission and reception can utilize radio frequency (RF) technology to transmit and receive the signals. Also, as stated above, a system using the active tracking elements can be hardwired to the processor and thus eliminate the need for the transmitter and receiver (i.e. detector).

The detector12may also be operable to detect other tracking elements located within the range of the detector12. For example, the detector12may also be able to detect other probes (not shown), or detect a location of a rod equipped with a tracking element (not shown). As discussed herein, however, the tracking of the location of the rod21may not be necessary, but can be included based on the selected parameters for the tracking system10, the procedure being performed, user preference, and other appropriate considerations. Nevertheless, if the location of the rod21is to be tracked, the tracking element17is generally affixed to the rod21.

The tracking element can be used to trace the rod. The tracing of the rod does not need to be contiguous and can be started and stopped at various points or portions on the rod. This can be displayed as non-contiguous segments or can be interpolated and shown as one continuous rod. Alternatively, the rod may be held in front of the tracking system in at least one view whereby the tracking system will “see” the rod and store the location of the rod and display it on the screen. A retro-reflective surface such as retro-reflective tape or a marker may be applied to the rod to intensify the signal for the tracking. Yet another alternative of contact or noncontact measurement may be achieved by wrapping a coil around the bent rod.

FIG. 4Cis a perspective view of one particular embodiment of a surgical rod21having a marker45disposed on its surface (e.g., retro-reflective tape, strip, coil, etc.) that enhances the signal for tracking rod measurements in accordance with the principles of the present disclosure. The marker45may extend the entire length of the rod21. In this embodiment, the marker45runs longitudinally on the rod to rod end46. The tracking system may register the shape of the rod using the marker45along the length of the rod21without the need to trace a probe along the length of the surface of the rod21. The marker45may be implantable with the rod21or may be taken off the rod21before implantation.

FIG. 4Dis a perspective view of one particular embodiment of a probe50that tracks rod measurements in accordance with the principles of the present disclosure. The probe50comprises proximal end51having a control button52to activate the upper tracking element54and lower tracking element60. At the distal end58of the probe50, there are arms62configured to receive a rod between ends64. In the embodiment shown, a lower tracking element60is disposed in the rod receiver that can be coupled to upper tracking element54or transmit to the computer processor (not shown). The user grips probe50at its proximal end51and traces the probe50longitudinally along the rod so as to obtain geometries of the rod. The probe50can contact the rod during the tracing or in an alternative embodiment the probe50can surround the circumference of the rod without contacting the rod to obtain the geometries of the rod. Arms62are spaced apart at a greater distance than the diameter of the rod to allow the user to trace the probe15along the rod. The probe15, in some embodiments, can communicate positional and rotational information of the rod and/or probe to the processor in either a wired or wireless configuration. It is contemplated that upper tracking element54and/or lower tracking element60can directly transmit data about the geometries of the rod and/or position to the processor without the need for a sensor. In some embodiments, the upper tracking element54and/or lower tracking element60can have imaging sensors to assist in measuring rod geometries (e.g., angles, position, rotation, etc.).

The tracing methods described above can be used separately or in tandem. Additionally, the graphical representation of the rod can be viewed in one of many views such as coronal, sagittal, A-P, lateral, or rotationally as a 3D image. Lastly, because the graphical representation of the rod is in 3d coordinates, the system can automatically or as directed by a user, display any and/or all of the numeric information related to that data be it distances, angles, curves, radii, etc.

The system10can also include input/output devices16such as, for example, a keyboard, trackball, touch screen, mouse, printer, etc. The input/output devices16can be used to calibrate the system, position and/or rotate the graphical image22on the display14, control the display14, select points of reference on the graphical image22, and/or perform various other functions of the system.

As a general rule, after making the decision to implant a fixation system into a patient, a surgeon will take a plurality of spinal measurements of the patient and determine the precise geometries required for the spinal rod. That is, the surgeon determines a number of bends and angles of the bends to the rod required in the sagittal, coronal and/or transverse planes. These predetermined/preoperative measurements are brought into the operating room where the rod21is initially bent on a back table20prior to being positioned within the patient40. The preoperative measurements can also be input into the measuring system10and stored in memory13for later use in confirming the proper bending of the rod21, as will be described below. Once the surgeon18is satisfied with the bending of the rod21, the rod21is taken from the back table20and positioned in fasteners (e.g., bone screws)41previously implanted into the patient40on the operating table30. The surgeon18can again adjust the bends in the rod21. The surgeon18then tightens the set screws42onto the rod21to secure the rod21in the fasteners (e.g., bone screws)41. The surgeon18now has yet another opportunity to adjust the bends in the rod21before closing the patient40. The present invention assists the surgeon in the operating room by providing the surgeon with a precise and accurate method to confirm that a rod is properly bent according to the pre-operative measurements and calculations and that the final construct remains within therapeutic limits through reduction, tightening, and/or final implantation of the rod.

In operation, the system for measuring a surgical rod10is located in the operating room with the surgeon18. Initially, in step s1the surgeon according to the pre-operative (or intra-operative) geometries determined by the surgeon bends the rod21on the back table20. The bending step may include multiple bends in different planes to correct lordotic/kyphotic and scoliotic bends which may require bending the rod in sagittal, coronal, and transverse planes. At step s2, the probe15is placed at one end of the rod21. (SeeFIG. 5). In step s3the system is initialized, which includes determining an initial position and orientation of the probe15. This initialization can occur by providing an input to the processor11. Such an input can be from a touch screen, a keyboard, foot pedal or a button (not shown) on the probe15itself. Next, in step s4the probe15is moved along the rod21to trace the rod21. (SeeFIG. 6.) During the tracing step the processor11continually receives position and orientation (e.g. linear and rotational movement) data of the probe15, and by extension the 3D coordinates of the rod. The data may be XYZ coordinates, polar coordinates, or built on some reference frame within the data. This can be started and stopped multiple times along the rod. In step s5the processor stores the data in memory13. In step s6processor11can read the data from memory13and create the graphical representation22of rod21and displays on display14a graphical representation22of rod21. (SeeFIG. 7.) Since the data of the tracing of the rod21is stored in memory13, in step s7processor11calculates the geometries50of the graphical representation22of the rod21. That is, processor11determines the angles between various points on the graphical representation. (SeeFIG. 8.) These points can be selected automatically by the processor11or can be manually selected using one of the input devices16described above. Other characteristics of the rod21, may also be input into the system. For example, if the surgeon would like specific radii or specific lengths for portions or all of the rod21, then the processor11may receive that input and calculate the rod shape based on that input information in accordance with the data. In step s8the actual value of the measurements can be displayed on display14so that the surgeon can confirm that the rod21has been bent according to the predetermined geometries. If it is determined in step s9that the angles/geometries/measurements do not match the predetermined geometries the process can be repeated until the surgeon is satisfied with the results.

Since the pre-operative measurements can be stored in memory13, processor11can use this pre-operative data to determine if the geometries of the rod21are correct by comparing the geometries of the preoperative data with the geometries of the probe data. For example, measurements between different points on the graphical representation22can be compared with corresponding points and angles from the preoperative geometries to determine if the measurements correspond. As with the earlier selection of points, these points can be selected automatically by the processor11or can be manually selected using one of the input devices16described above.

In step s10the implant is positioned within the implanted fasteners (e.g., bone screws)41in the patient40. In some embodiments, the fasteners41can include a tracking element. In an open procedure, the rod21may be positioned within the receivers through a large open wound. In a minimally invasive procedure, the rod21may be advanced through a small incision and laterally guided through the fasteners41. The display may show the fasteners41based on the tracking elements on the fasteners41. The tracking elements41may include extenders attached to the fasteners41to help urge the rod into the fasteners41when the rod is being guided subcutaneously. Thus, the known shape of the rod21can be combined with the known positions of the fasteners41to allow a display to show a guided path for positioning the rod21in the fasteners41.

Additional bending of the rod21may be required at this point to properly seat the rod21in the fasteners (e.g., bone screws)41. The bending may be accomplished in-situ in an open case. Once the rod21is seated in the fasteners41, set screws42can be installed. Tightening of the set screws42may occur at this time or additional bending of the rod21can occur before the set screws42undergo a final tightening onto rod21. Further, after the set screws42are tightened onto rod21, the surgeon18can bend the rod21further. Various combinations of these procedures can occur until the surgeon18is satisfied with the geometries of the rod21and fixation system.

Now that the rod21has been secured in the fasteners (e.g., bone screws)41, the surgeon18can again determine the geometries of the implanted rod21with the aid of the measurement system10. That is, in step s11the probe15is again placed at one end of the rod21. (SeeFIG. 10). In step s12the system is initialized to determine the initial position and orientation of the probe15. Next, in step s13the probe15is moved along the rod21to trace the rod21. (SeeFIG. 11.) During the tracing step the processor11receives position and orientation (e.g. linear and rotational movement) data of the probe15. This process is similar to that of the earlier back table tracing, but differs in that the rod21can only be traced along lengths between the fasteners (e.g., bone screws)41. That is, the data obtained from the trace will have gaps43that represent the positions of the fasteners (e.g., bone screws)41. Conversely, the probe can be placed through the set screws on the rod and get the inverse ofFIG. 12or do both and have almost no gaps. Standard smoothing algorithms exist that could be employed to complete the spaces and show an interpolated continuous line.

In step s14the processor stores the data in memory13. In step s15processor11reads the data from memory13and creates a second graphical representation23of rod21to be displayed on display14. (SeeFIG. 12.) This second graphical representation23represents the geometries of the rod21as positioned in the fasteners (e.g., bone screws)41. The surgeon18can use these graphical representations22/23to determine if the geometries of the rod21are correct. They can be displayed together separately or with the pre-operation data. They can also be overlayed to visually see the differences.

In step s16processor11can now calculate the geometries of the graphical representation23of the rod21. That is, processor11determines the angles between various points on the graphical representation. These points can be selected automatically by the processor11or can be manually selected using one of the input devices16described above. In step s17the actual value of the measurements can be displayed on display14so that the surgeon can confirm that the rod21has been bent according to the predetermined geometries. If it is determined in step s18that the angles/geometries do not match the predetermined geometries the rod21can be bent again in step s19and process can be repeated until the surgeon is satisfied with the results. When the surgeon18is satisfied with the results, the patient can be closed and the operation completed.

In lieu of steps s11thru s13, an imaging device such as an O-arm can be used to scan the position of the rod in the patient. Because the imaging device is also tracked with a tracker17, the 3d position of the rod can be ascertained and displayed as above to then be manipulated and interrogated for measurement data.

As can be seen, the system and methods for measuring a surgical rod can greatly assist a surgeon during the installation of the fixation system. Further, system and methods for measuring a surgical rod can provide an accurate confirmation of the geometries of the fixation system.