Field of the Invention
This application is directed to the field of hip replacement, and particularly to surgical tools and methods for guiding the preparation of the bones in connection therewith.
Description of the Related Art
Hip replacement surgery is common and getting more common by the year. One persistent issue with hip replacement is the relatively high incidence of poor placement of the cup and ball components of the prosthetic hip joint. For example, the cup is optimally placed in a specific alignment with a plane including a rim of the acetabulum of the pelvis. For several reasons an unacceptably high percentage of patients have the cup of the artificial hip joint out of alignment with this plane.
Unfortunately, misalignment can lead to dislocation of the hip as soon as within one year of the implantation procedure. This is particularly problematic because recovery from a hip procedure can take many months. Patients undergoing a revision so soon after the initial implantation will certainly be dissatisfied with their care, being subject to addition redundant surgery. Of course, all surgery carries some degree of risk. These poor outcomes are unsatisfactory for patients and surgeons and are inefficient for the healthcare system as a whole.
Also, in cup placement in total hip arthroplasty, the inclination and anteversion angles are with respect to the Anterior Pelvic Plane (defined as a plane created by the two anterior superior iliac spines (ASIS) and the pubic symphysis). While these anatomical features are visible/palpable while the patient is in a supine position, the majority of total hip replacements are accomplished via a posterolateral approach with the patient in some variation of a lateral position, in which most of these landmarks are not accessible or visible. Historically, navigation for posterior approach hip replacement has been accomplished by registering the anatomical features of the Anterior Pelvic Plane with the patient first in a supine position and, once this plane is recorded by the navigation computer, moving the patient to a lateral position in order to perform hip surgery—with navigation performed with respect to the directly registered Anterior Pelvic Plane. This approach to hip navigation is sub-optimal for surgical workflow because the extra movement of the patient from supine to lateral position takes more surgeon and staff time and requires breaking sterility and re-draping. This is one of the key reasons why hip navigation has failed to be adopted by most of the market.
Additionally, altered leg length is a common patient complaint arising from hip replacement surgery and has been a common cause of medical malpractice lawsuits that arise from hip replacement. Because part of the hip replacement procedure requires precise measurements of patient leg length and joint off-set that are frequently difficult to visualize utilizing conventional instrumentation, there are opportunities to improve the surgeon's performance of these measurements using computer technology.
There is a need for improved systems and methods for providing for proper alignment of hip components with a patient's anatomy during a hip replacement procedure. This can involve techniques for locating one or more anatomical landmarks, e.g., discrete anatomy and/or planes including multiple points. This can involve techniques for confirming alignment of a prosthetic component with an anatomical landmark.
In one embodiment, a method is provided for navigating a hip joint replacement procedure. The method includes advancing a first portion of a jig into a portion of the pelvis. The portion of the pelvis is an anatomical landmark in some techniques. In others it is not. At least one inertial sensor is coupled to the jig. The second portion of the jig is moved relative to the first portion to touch, e.g., sequentially, a plurality of anatomical landmarks. This can include touching two or three landmarks, for example. A cup portion of a replacement joint is placed in the acetabulum by reference to a plane calculated based on data from the at least one of a plurality of inertial sensors.
In another embodiment, a hip joint navigation system is provided. The system includes a jig, a first inertial navigation device and a second inertial navigation device. The jig has an anchor portion adapted to be placed on the hip, e.g., at an anatomical landmark. The jig also has a landmark acquisition probe coupled with the anchor portion. The probe is moveable in at least three degrees of freedom. The first inertial navigation device is configured to be fixed to a pelvis of a patient to track movements of the pelvis. The first inertial navigation device can be immovably connected to the pelvis. The second inertial navigation device is coupled with the landmark acquisition probe. The landmark acquisition probe can be moved to touch a plurality of landmarks. The inertial navigation devices determine the orientation of a plane of the acetabulum based at least in part on the position of the anatomical landmarks.
In another embodiment, a method of navigating a hip replacement procedure is provided. A first hip of a patient is positioned on a surgical table and a second hip is positioned off of the table such that the anterior pelvic plane is disposed upright (e.g., vertically). A jig is coupled with a bone adjacent to a second hip joint. The jig has a moveable orientation guide. An inertial sensor is coupled with the orientation guide. The orientation guide can be an arm of a registration probe in some embodiments. The orientation guide is oriented in a plane substantially parallel to the plane of the table. The orientation of the inertial sensor is recorded as an indication of the orientation of the anterior pelvic plane. If the anterior pelvic plane is vertical the inertial sensor can indicate the plane of the table, which is perpendicular to the anterior pelvic plane. A cup of an artificial hip joint is placed in the acetabulum with reference to the orientation of the anterior pelvic plane based on the orientation of the inertial sensor.
In another embodiment, a system for determining orientation data in connection with a hip joint procedure is provided. The system includes a data capture module, a computational module, and a user interface module. The data capture module is configured to receive inertial data from an inertial sensor. The computational module is configured to provide, based on the inertial data, one or more angles of a proxy acetabular plane relative to an anterior pelvic plane. The user interface module is configured to output a user interface configured to communicate orientation data to a user. One or more of these modules is implemented by one or more processors.
In another embodiment, a method of navigating a hip replacement procedure is provided. A patient is positioned for posterior or posterolateral approach. A jig is coupled with a bone adjacent to a hip joint. The jig comprising a landmark acquisition probe having an inertial sensor coupled therewith. Patient condition can be assessed, and based on the patient condition, a selection can be made between a first plurality of landmarks and a second set of landmarks. The first set of landmarks can be disposed on an acetabular rim. The plurality of landmarks can be disposed off of an acetabular rim. The orientation of the inertial sensor can be recorded when the landmark acquisition probe is in contact with each of the points of the selected plurality. A cup of an artificial hip joint is positioned in the acetabulum with reference to the recorded orientation to the selected plurality of points.
In another approach, a method of navigating a procedure on a hip joint is provided. At least one aspect of the hip joint is characterized pre-operatively. A patient is positioned for posterior or posterolateral approach. A jig is coupled with a bone adjacent to the hip joint (e.g., part of the pelvis). The jig has a landmark acquisition probe having an inertial sensor coupled therewith. The orientation of the inertial sensor is recorded when the landmark acquisition probe is in contact with each of a plurality of landmarks. A cup of an artificial hip joint is positioned in the acetabulum with reference to recorded orientation and to estimations of at least one of anteversion and inclination angles. Estimations of these angles can be based upon the pre-operatively recorded characterization of the hip joint. The recorded orientation can be that of the inertial sensor when the probe is in contact with each of the landmarks.
In another embodiment, a method of navigating a hip replacement procedure is provided. The method includes positioning a patient for posterior or posterolateral approach. A jig is coupled with an acetabular socket of the patient, the jig having an engagement surface formed to closely mate to acetabular bone contours of the specific patient. The jig comprising a registration feature configured to be in a pre-determined orientation relative to the anterior pelvic plane of the patient when the jig is so-coupled. An inertial sensor is coupled with the registration feature such that the inertial sensor generates a signal indicating at least one angle relative to the anterior pelvic plane. A prosthetic cup is placed based on the signal.
In another embodiment, a patient specific jig system for hip replacement is provided. The jig system includes an engagement surface and a registration feature. The engagement surface is formed to closely mate to acetabular bone contours of a specific patient. The registration feature is configured to be in a pre-determined orientation relative to the anterior pelvic plane of the patient when the jig is coupled to closely mate to acetabular bone contours of the specific patient.
In another embodiment, a method of replacing a hip joint is provided. The method includes coupling a trackable member with a limb forming a part of a hip joint of the patient. The limb is moved to at least four points disposed away from a neutral position of the hip. The four points include at least one medial extent, at least one lateral extent, at least one anterior extent, and at least one posterior extent of a patient's range of motion. During the moving step, data is collected from the trackable member indicating the displacement from the neutral position to each of the extents. A socked component of the prosthetic hip joint is placed within the acetabulum. A stem of a femoral component of a prosthetic hip joint is placed into a proximal femur. A ball of the femoral component is placed in the socket component. In the method, when the prosthetic hip joint is in the neutral position, a stem axis connecting the center of rotation of the ball and a centroid of the stem at the mouth of the socket component is in a central zone between the at least four extents. At least one of the steps of placing is performed with the aid of a display of the position and/or orientation of the stem axis relative to the central zone.
In the system described above, the inertial navigation devices can be replaced with or supplemented by one or more cameras for monitoring distance, linear position, or angular position.
In the system described above, the inertial navigation devices can be replaced with or supplemented by one or more cameras for determining the spatial position of trackers coupled with instruments, such as a stylus. In such a system, the jig can be simplified without requiring moveable portions for example.
In some variations of the methods discussed herein, patient data can be used to enhance the accuracy of orientation of a component, such as the plane of the acetabulum. Patient data can include CT, MRI, X-Ray or other pre-operative planning data.
In another embodiment, a hip joint navigation jig is provided that includes a platform, a cannula coupling device, and a registration jig mounting feature. The cannula coupling device is disposed on the platform and is configured to enable a cannula to be detachably coupled with a bottom surface of the platform. The cannula is configured for detachably coupling the platform with a bone adjacent to a hip joint. The registration jig mounting feature is disposed on the platform. The hip navigation jig also includes registration jig. The registration jig includes an upright member, a rotatable member, and a probe. The upright member is configured to be detachably coupled to the platform at the registration jig mounting feature. The rotatable member is coupled with the upright member for rotation about an axis that is not vertical when the jig is mounted to the bone adjacent to a hip joint and the upright member is disposed generally vertically. The probe had a tip for engaging anatomy. The anatomy engaging tip is disposed at a distal end of an elongate body coupled with the rotatable member for rotation about the axis. The orientation and position of the elongate body of the probe can be adjusted to bring the anatomy engaging tip into contact with a plurality of anatomical landmarks during a landmark acquisition maneuver.
Although the platform can have any shape or configuration, it is elongate in some implementations, for example, including a first end and a second end. The first end can be configured to be oriented inferiorly and the second end to be oriented superiorly when the navigation jig is applied to the patient. If the platform is elongate, the cannula coupling device can be disposed adjacent to the first end, which may be located inferior of the second end when placed on the patient. The cannula coupling device can be detachably coupled with a bottom surface of the platform in some embodiments. The registration jig mounting feature is disposed on a top surface of the platform and can be positioned adjacent to the first end. Again, the first end may be inferior end, just superior to or at the superior portion of the surgical field.
In another embodiment, a hip joint navigation jig is provided that includes an anatomical interface comprising a bone engagement portion. A registration jig is also provided that is coupled, e.g., removeably, with the anatomical interface. A rotatable member is provided for rotation about an axis that is not vertical when the jig is mounted to the bone adjacent to a hip joint and the registration jig is coupled with the anatomical interface. An anatomy engaging probe is coupled with the rotatable member for rotation about the axis and is translatable to enable the probe to be brought into contact with a plurality of anatomical landmarks during a procedure. An inertial sensor is coupled with the probe to indicate orientation related to the landmarks, the sensor being disposed in a different orientation relative to horizontal when the probe is in contact with the landmarks.
These and other features, aspects and advantages are described below with reference to the drawings, which are intended to illustrate but not to limit the inventions. In the drawings, like reference characters denote corresponding features consistently throughout similar embodiments.
A variety of systems and methods are discussed below that can be used to improve outcomes for patients by increasing the likelihood of proper placement of a hip joint. These systems can be focused on inertial navigation techniques, close range optical navigation, or a combination of inertial and optical navigation.
Systems and methods described below can improve prosthetic hip joint placement using navigation in connection with referencing anatomical landmarks, incorporating preoperative custom fit jigs based on imaging, and a combination of pre-operative imaging and landmark referencing. These hip procedures generally guide a prosthetic hip to an orientation within the acetabulum that minimizes the chance of dislocation due to impingement of the femoral neck on the cup or on bones around the acetabulum or other reasons related to suboptimal orientation of the prosthetic. Various techniques leverage population averages of proper placement while others are amenable to patient specific refinements. Also various techniques for registering and confirming the position and/or orientation of the femur pre- and post-implantation are discussed herein, which are useful to control leg length and joint offset at the end of the procedure.
A. Navigation Using Inertial Sensors and Jigs for Referencing Anatomical Landmarks with Posterior Approach
Most hip replacement procedures presently are performed from a posterior approach. In this approach, the patient is positioned on his/her side and the anterior pelvic plane is oriented vertically, e.g., perpendicular to the plane of the table on which the patient is positioned. Most surgeons performing hip replacement are very familiar with this approach and will immediately recognize the benefit of enhanced certainty about the orientation of the relevant anatomy when the patient is in this position.
1. Apparatuses and Methods for Posterior Approach Hip Navigation
The system 100 includes a registration jig 104, an alignment assembly 108 and a landmark acquisition assembly 112. The alignment assembly 108 is rigidly connected to the hip in the illustrated configuration so that motion of the hip cause corresponding motion of sensor(s) in the assembly 108 as discussed below. Sensing this motion enables the system 100 to eliminate movement of the patient as a source of error in the navigation. The landmark acquisition assembly 112 provides a full range of controlled motion and sensor(s) that are able to track the motion, in concert with sensor(s) in the assembly 108. Additional details of systems, devices, sensors, and methods are set forth in U.S. Pat. No. 8,118,815; US US2010/0076505; and U.S. Pat. No. 8,057,479 which are all incorporated by reference herein in their entireties for all purposes. The sensors in assemblies 108, 112 preferably transfer data among themselves and in some cases with external devices and monitors wirelessly, using Bluetooth, wifi® or other standard wireless telemetry protocol.
The registration jig 104 includes a fixation cannula 124 that has a distal end that can be advanced to a pelvic bone at an anatomical location or landmark or other selected location. In the illustrated technique, the cannula 124 is secured by a pin 132 (see
As discussed further below, the cannula 124 can be coupled with other bones in other techniques with a posterior approach. For example, the cannula 124 can be coupled with the ischium or the pubis in other techniques. In some techniques, the cannula 124 is mounted to a pelvic bone but not at a landmark. The hip navigation system 450 discussed below in connection with
As illustrated by
The mount feature 140B enables rotational mounting of the landmark acquisition assembly 112. For example, the mount feature 140B can include a pivotally mounted jig 148 that projects upward to a free end that is adapted to mate with an orientation sensing device as discussed below. The joint 148 permits a registration arm, such as the elongate member 224 discussed below to be tilted downward to touch landmarks at different elevations.
In one technique, the registration jig 104 is preassembled and is driven into a suitable anatomical landmark, such as the ilium. In other techniques, an anchor jig can be mounted off-set from a landmark to be acquired. The ilium will have been previously identified by conventional means, such as by X-ray examination, palpation, or by making an incision and visually inspecting the pelvis. In one technique, the cannula 124, the pin 132, and the platform 136 are separable so that the pin can be placed and the platform 136 coupled to the pin at a later time. The cannula 124 can be coupled with other landmarks in some variations.
The first end 164 of the detachable extension provides several functions. The first end 164 has a device to engage the mount 140A in a secure but releasable manner. The engagement between the extension 160 and the platform 136 minimizes or prevents relative movement therebetween to avoid any mechanical relative movement during navigation procedures so that movement of the orientation device 172 corresponds to movement of the hip. The first end 164 also has a docking device that, as discussed further below, provides a stable and controlled manner to position the landmark acquisition assembly 112 relative to the orientation device 172.
Another example of a parked configuration of the system 100 can be provided. For example, the parked configuration advantageously includes the ability to stably position and hold the devices 172, 204 for substantially no relative movement. In one approach, the orientation sensing device 204 is mounted on the rigid extension 160. Other arrangements could include a mounting post on the platform 136 adjacent to the rigid extension 160.
Where error management is less an issue, the parked configuration 260 can still be useful in that it prevents unwanted swinging or other movement in the surgical field.
In one basic method, the jigs discussed above are connected to the pelvic bone, the system 100 is put into the parked configuration 260, and the sensors are initialized. The initializing can include synchronizing at least two sensors. In some cases, the initializing can include zeroing one or more sensors. In this context, “zeroing” is a broad term that includes any method of eliminating accumulated error in the system, including any form of resetting of the sensors, and/or confirming in one device that the data from the other device is reliable for at least a fixed period.
After the optional step illustrated in
The extended configuration 264 is one in which the distal end 228 of the elongate member 224 is adapted to touch an anatomical landmark located between the medial cephalad-caudal plane of the patient and the acetabulum of the pelvis.
Depending on the sensors used and the timing of landmark acquiring step of
The extended configuration 272 is one in which the distal end 228 of the elongate member 224 is adapted to touch an anatomical landmark located anteriorly of the acetabulum.
Once landmarks have been acquired, the system 100 can determine the bearing of three landmarks including that of the attachment location of the cannula 124, if the pin is attached to a relevant landmark. The system can calculate the orientation of the orientation device 172 relative the plane containing these three (or in other methods another group of three or more) landmarks. From this, a variety of post processing can be performed. For example, the orientation (anteversion and/or abduction) can be adjusted based on the known mean orientation of the plane containing these three (or another three or more, if used) landmarks from the pelvic anatomic reference planes.
One variant of the system 100 enables a user to select between multiple sets of landmarks for use in the above calculations. The method discussed above exploits the use of three points that are off of the acetabular rim. These points are less impacted by local prominences at the rim that may be due to disease or deformity. Thus, they have a lower likelihood of requiring intra-operative improvisation. On the other hand, another set of landmarks can be selected where the rim is free of deformities, which might be confirmed pre-operatively. For example, two or three points can be selected on the acetabular rim for landmark acquisition. The on-rim landmarks are advantageous in that they are easier to access through a smaller incision. For example, on-rim points can include the center of the posterior insertion of the transacetabular ligament, the center of the anterior insertion of the transacetabular ligament and the most superior point on the rim. A group of anatomical landmarks including one or more extra-acetabular landmarks can include the ilium (where the registration jig 104 or other anchor member can be inserted), the lowest point of the acetabular sulcus of the ischium, and the prominence of the superior pelvis ramus.
Some techniques involve referencing a fourth point. The fourth point can be used in connection with some forms of patient specific registration. The fourth point can be extra-acetabular or can be disposed on the acetabular rim. An example of an acetabular landmark is the acetabular notch. Other landmarks are discussed herein, for example in connection with
The posterior approach systems are advantageously configured to allow intra-operative selection between on-rim and off-rim points. For example, if the rim looks free of deformities pre-operatively but when exposed presents differently, the surgeon can select an off-rim landmark set.
Several techniques for enhancing the accuracy of the relationship between the sensed landmarks and the location of calculated anatomical features, such as the anterior pelvic plane or angle of the acetabulum can be employed. For example, user input can be collected indicating whether the hip being treated is on the left or the right side of the patient and whether the patient is male or female. A more refined estimation of the model can be provided based on a characterization of a study group. For example, hip joints of a group of 30 or more patients can be studied to identify the correspondence between a feature that can be accessed in one approach and an anatomical feature of more surgical relevance that cannot. A group of subjects can be studied for any number of demographic characteristics such as gender, age, weight, height or any other variable in a relevant population. For those sub-groups, a correlation or transformation between a measured parameter and a parameter that cannot be measured but is desirable to know can be generated. Once such a correlation or transformation is established, transforming a measured feature into the unmeasurable but useful to have feature can be achieved by operating software on a processor. The software can be programmed to calculate one or two angles, e.g., inclination and anteversion based on a registered pelvic plane, such as a proxy acetabular plane. Such a system can be used to generate in real time the angles of a free hand instrument relative to the anatomy, e.g., relative to an acetabulum in placing a hip socket component.
Additionally, data from the use of pre-operative imaging or positioning (discussed below) can be used to enhance the accuracy of these calculations. Thus, the posterior approach systems preferably are configured to take user input directly by actuating buttons on the orientation device 172 or by connecting an auxiliary data storage device, such as a flash memory device, to the system or by any means of other communication with the system, including wifi connection, Bluetooth, Internet connection among others.
In some techniques, the posterior approach systems described herein are adapted to determine, monitor, and confirm proper leg length and joint offset outcome in a hip replacement. For example, the system 100 can calculate and store components of a leg length metric, e.g., a vector along the superior-inferior axis (leg length) and/or along the medial-lateral axis (offset). In one approach, the device 172 has a display that indicates when the femur is in the same position pre- and post-operatively. For example, it can indicate “0” meaning no displacement causing a leg length change and “0” indicating no movement of the femur farther away from the cephalad-caudal mid-plane of the patient pre- and post-operatively. For enhanced accuracy, a plurality of points, e.g., three points, can be marked acquired and/or marked on the femur. The points can be spaced apart by an amount sufficient to provide increased accuracy. These three points can be used to confirm proper placement of the femur in abduction, rotation, and flexion.
One enhancement involves referencing the femoral neck to assure that after implanting the hip joint, the femur is positioned properly rotationally. For example, it may be desired to make sure that a feature of the femur like the greater trochanter resides in the same rotational orientation relative to an axis extending through the center of rotation of the femoral head and perpendicular to the plane of the acetabulum. To assure a substantially unchanged rotation orientation post-implantation, the system 100 can record one or more, e.g., three points on the femoral neck pre- and post-implantation. Three points that would be convenient from either the posterior approach or the anterior approach (discussed below in connection with
The foregoing are some steps that can be used to determine and store a variety of parameters useful in a navigated hip procedures. After some or all of these steps have been performed, in one embodiment, the acetabulum can be prepared for receiving a cup. For example, the acetabulum can be reamed in a conventional manner. In some embodiments, the reamer can be coupled with an orientation device containing an inertial sensor to guide the reaming process. This is discussed in some detail in US2010/0076505, published Mar. 25, 2010 which is incorporated by reference herein in its entirety for this purpose and for all disclosure therein generally.
Depending on the sensors and the timing of cup placement step of
The system 100 can be configured to provide a pre- and/or post-operative estimation of an angle relative to the angle of the table. In the posterior approach, the patient is placed on his/her side. In this approach, there is more chance for the patient's position to shift intra-operatively. In one embodiment, an alignment rod can be coupled with the sensing device 204 and aligned with the plane of the table. The orientation of the sensing device 204 when so aligned is recorded in the system. Later in the procedure, one or more angles is calculated and displayed to the user based on the assumption that the pelvis has not moved. At such later stages, the orientation of the sensing device 204 can be confirmed again relative to the table to provide information about whether the patient has moved. If significant movement has occurred, such that any assumptions of no movement are violated, some or all of the landmark acquisition steps can be repeated. Alternatively, the movement of the pelvis can be tracked by the sensing device and corrected for. The manner of incorporating the table orientation with landmark acquisition is discussed in greater detail below.
The user will have placed the artificial ball of the replacement hip join in the proximal femur and thereafter can place the ball in the cup, which was properly oriented using the techniques discussed above.
Once leg length and offset are determined post-operatively, they can be compared the pre-operative measurements (
Because hip replacement procedures involve an open surgical field with a substantial amount of exposed tissue and blood the line of sight the camera 412 to the scales can become obstructed. In one embodiment, a hood is provided above the window 418. The hood keeps most of the blood and tissue out of the space where the camera views the scales. Additionally, a scrubber component, e.g., a thin rubber member, can be provided above the scales 226, 226A (discussed below) to prevent this tissue or fluids from entering into the field of view laterally.
One advantage of the system 400 is that the camera 412 can automatically process the image captured through the window 418 and thereby determine the position of the elongate member 224 relative to the sliding support 420. A further advantage of this is to eliminate one step from the navigation process, e.g., to eliminate the need to enter the linear dimension into the system 400. Eliminating the step can reduce time and/or personnel in the operating room. Also, the camera 412 can be configured to read a much higher resolution than can be read by a clinician. This can provide greater accuracy in the system overall. Not only that, but the camera can be configured to make fewer or no errors in reading the position, which can improve outcomes overall. For example, miniature cameras can produce data in JPEG or other image format that a processor in one or both the orientation devices 172, 204A can process to extract the linear position of the elongate member 224.
A further modified embodiment is described in
2. Posterior Approach Systems Adapted for Accelerometer Sensitivity
The jig 454 includes a hollow fixation member 466 and a platform 468 for coupling a plurality of devices to the pelvis. The platform has a generally T-shaped configuration including a first portion 468A coupled with the proximal end of the fixation member 466 and a second portion 468B disposed transversely to the first portion 468A. The first portion 468A provides a support for a cradle 476 discussed further below. The second portion 468B can include a plurality of docking devices 469 for coupling directly or indirectly with the orientation device 172. The T-shaped configuration provides the advantage that the docking devices 469 can be disposed father away from the surgical site than is the case with the system 100. This reduces any intrusion of the orientation device 172 into the working field.
In some cases, the fixation member 466 provides adequate stability in anchoring the system 450 to the pelvis. In other situations, the jig 454 can be coupled with the pelvis from the second portion 468B. For example, a slot 470 can be formed in the second portion 468B on one or both sides of location where the first portion 468A extends from the second portion 468B. The slots 470 can extend from a lateral edge of the second portion 468B toward location where the first portion 468A extends from the second portion 468B. The slots 470 can include a plurality of channels 471 configured to receive fixation pins (e.g., Steinmann pins) that can be advanced into the pelvis. The channels 471 extend generally parallel to the fixation member 466. The fixation pins can be securely connected to the second portion 468B in the channels 471 by a clamp device 472. The clamp device can include a screw configured to draw the portions of the second portion 468B on either sides of the slot 470 toward each other and thus to create large frictional forces on the pins in the slots 471.
The slots 470 preferably are aligned such that a plane extends along both of the slots 470 along their length. Because the slots 470 are long and slender this plane can be readily visualized in an X-ray image. It is preferred that the jig 454 be aligned to the pelvis such that the plane extending along the slots 470 is perpendicular to an axis of the patient (e.g., the intersection of the medial lateral plane and the transverse mid-plane of the patient). This feature provides a convenient way to visually confirm proper positioning of the jig 454 in one embodiment.
The fixation member 466 includes a registration feature 473 and a foot 474 adjacent to a distal end thereof and a coupling 475 adjacent to the proximal end thereof for connecting to the platform 468. The foot 474 includes a plurality of spaced apart spikes extending from a distal end thereof capable of preventing or limiting rotation of the jig 454 when the fixation member 466 is connected to the pelvis.
The coupling 475 generally secures the platform 468 to the fixation member 466. In some embodiment, the coupling 475 has a rotational capability that enables the platform to be positioned at selective locations about the longitudinal axis of the pin 466, for example to enable the platform 468 to be initially positioned in the correct orientation or to be moved during or after the procedure to make space for other surgical devices. One arrangement provides matching splines that extend parallel to the longitudinal axis of the fixation member 466. This arrangement would permit splines on an upper portion of the coupling 475 to be disengaged from splines on a lower portion of the coupling 475. When disengaged, the platform 468 and the upper portion of the coupling 475 can be rotated relative to the lower portion of the coupling 475. The splines can thereafter be re-engaged.
The jig 454 also preferably includes a cradle 476 that can be used to hold a probe arm 477. The cradle 476 includes a U-shaped recess having a width between two upright members that is about equal to the width of an arm 477 of the landmark acquisition system 462.
The cradle 476 can provide other convenient functions even if the sensing devices in the sensor 204 are not subject to sources of accumulated error. As discussed elsewhere herein, for confirmation of accuracy of the system or to provide a simplified reference frame not requiring landmark acquisition, it may be desirable at some point of the procedure to use the probe arm 477 and the sensor 204 to estimate the plane of the surgical table upon which the patient is resting. If, as discussed above, the plane intersecting the slots 470 is oriented perpendicular to the axis of the patient when the jig 454 is mounted to the pelvis, the cradle will be parallel to the axis of the patient. If the fixation member 466 is oriented vertically, the arm 477 will be parallel to the plane of the table when in the cradle 476. The system 450 can thus use the plane of the table as a reference frame for guiding the placement of the cup without registering landmarks. Or, the plane of the table can be used in combination with registering the anatomy about the acetabular rim, as discussed above, to increase the accuracy of navigating the cup.
The cradle 476 also provides a convenient home position that keeps the arm 477 stationary and out of the way of other surgical instruments.
The jig 454 also includes a pivot feature 478 that is disposed horizontally.
The registration feature 473 is a convenient way to enhance the accuracy of the sensor 204. In particular, in one variation of the method discussed above, a distal tip of the probe arm 477 is brought into contact with the registration feature 473. In one embodiment, the registration feature 473 is a notch configured to receive and temporarily retain the tip. Thereafter, the user can interact with the orientation device 172 to initialize accelerometers within the sensor 204. Thereafter the points to be acquired can be sequentially contacted and the orientation and position of the sensor 204 can be sequentially recorded in the system 450. Because the accelerometers are initialized close to the points to be acquired, accuracy of the reading is enhanced as the angular error resulting from an error in the scale factor of the accelerometers is minimized due to the small arc from the registration feature. For example, the jig 454 is configured to enable the landmark acquisition assembly 458 to reach all points to be registered by moving less than about 45 degrees from an initial or home position in some embodiments. In other embodiments, the jig 454 is configured to enable the landmark acquisition assembly 458 to reach all points to be registered by moving less than about 25 degrees from the initial position. In other embodiments, the jig 454 is configured to enable the landmark acquisition assembly 458 to reach all points to be registered by moving less than about 15 degrees from the initial position.
The jig 454 also is configured to interact well with the soft tissue that is disposed around the surgical site in the posterior approach. In this approach, an incision is made in soft tissue that is kept as small as possible. In one approach, the fixation member 466 is positioned at the end of the incision. Where the incision is made as minimal as possible, the jig 454 can also function as a retractor. The T-shaped configuration is particularly well suited for this function because the first portion 468A of the platform 468 can be received between the middle and ring fingers of the user with the second portion 468B in the palm of the hand. With the foot 474 gripping the pelvis, the jig 454 can be tilted from the platform 468 away from the hip joint to retract the tissue away.
3. Workflow Considerations for Posterior Approach
As noted above, a workflow problem arises in typical hip replacement procedures in that anatomical features that can be more easily references are unavailable in the traditional posterior approach for operating on the joint.
By performing a CT-based study of a large number of human pelvises, the assignee of this application has been able to calculate a population-based average relationship between multiple planes created by various points in, on or around the acetabulum that are accessible during posterior approach hip replacement (each plane, an “Acetabular Plane”), and the Anterior Pelvic Plane. One of the key features of posterior hip navigation for some embodiments disclosed herein is the ability of a module, e.g., software incorporated into a processor, which may be on a computer, or one or both of the orientation device 172 and sensor 204, to calculate a transformation from one reference frame to another. As described in more detail elsewhere herein, several points are referenced in, on or around the acetabulum and from these points a proxy Acetabular Plane is calculated.
Next, in certain embodiments described herein a module operable to process an algorithm, e.g., by executing software in one or both of the orientation device 172 and sensor 204 alone or with a separate computer, is able to calculate a transformation from the proxy Acetabular Plane to Anterior Pelvic Plane. The approach indirectly registers the Anterior Pelvic Plane without requiring a direct supine registration and subsequent patient movement and re-draping necessary in standard navigation. A module in certain embodiments described herein is then able to provide the user real time navigation data of the orientation of a hip instrument (e.g., the impactors 300, 300A) with respect to the Anterior Pelvic Plane.
In certain systems described herein, a further advantage is that the systems are able to implement the plane transformation algorithm to calculate an Anterior Pelvic Plane from one of any number of proxy Acetabular Planes that the surgeon chooses to register. This enables the surgeon to have greater flexibility in Acetabular Plane landmark selection to take into account the quality or accessibility of certain landmarks. For example, in cases of minimal deformity around the acetabular rim, the surgeon may choose to register landmarks around the rim, which are easily accessible. In cases where there is great deformity or high presence of osteophytes on the acetabular rim, the surgeon may instead choose to register an Acetabular Plane based on extra-acetabular landmarks (or described as “off-rim” elsewhere herein) outside of the rim that are unaffected by disease or prior hip replacement surgery.
Examples of anatomical landmarks that may be used to create a proxy Acetabular Plane and that are shown in
Extra-Acetabular Landmarks (Ischium/Ilium/Pubis)
Acetabular Rim Landmarks
Additional points can be combined with either of the groups of points listed above. For example, in one embodiment, point “D” is used. Point D is the midpoint of the inferior border of the acetabular notch. As discussed in connection with
A further key benefit of certain embodiment discussed herein is that the foregoing plane transformation capabilities increase the accuracy of the transformation between the proxy Acetabular Plane registered and the Anterior Pelvic Plane above the general population average data by the user inputting certain patient-specific information, such as gender.
Additionally, certain embodiments of systems including one or more of the orientation device 172, sensor 204, or a separate computer may have modules that are operable, e.g., by processing software, to allow the user to input an angular or plane relationship between an proxy Acetabular Plane and Anterior Pelvic Plane that the surgeon measured based on pre-operative imaging, allowing for a partial or whole plane transformation based on patient-specific data rather than population data. By way of example, the surgeon may choose to pre-operatively measure an angle created by (a) landmarks that are both visible on an A/P pelvis x-ray and that can be referenced during posterior hip replacement, and (b) landmarks that are both visible on the pelvis x-ray and that are directly associated with inclination measurement in the Anterior Pelvic Plane. If this angular relationship is inputted into a module of a system including one or more of the orientation device 172, the sensor 204, or a separate computer, which module is capable of making calculations processing software and the surgeon registers the landmarks described in (a), inclination navigation will be based specifically on that patient rather than a population average. Landmarks (D) and (H) listed above are examples of landmarks that are both visible on an A/P pelvis x-ray and that can be referenced to create a proxy Acetabular Plane in posterior hip replacement.
These aspects of the systems adapted for posterior approach hip joint replacement can greatly enhance both workflow and accuracy in such procedures.
B. Navigation Using Inertial Sensors and Jigs for Referencing Anatomical Landmarks with Anterior Approach
1. Apparatuses for Anterior Approach Hip Navigation
The docking devices 538 are configured to couple with detachable mounting devices that securely but temporarily couple sensor to the anchor system 504. The two docking device 538 on the top surface of the platform 536 enable the anchor system 504 to be used for either left or right hip procedures. As shown in
The platform 536 also can have a channel 540 disposed away from the cannula 516. The channel 540 can have a lumen disposed along an axis substantially parallel to the lumen 532 of the cannula 516. In one embodiment, the anchor system 504 is configured to securely couple the platform 536 to the hip by placement of two spaced apart pins 544A, 544B.
The pins 544A, 544B can take any suitable form but preferably have the same cross-sectional profile as the lumens in the cannula 520 and in the channel 540, e.g., they can be circular in cross-section. The pins 544A, 544B can be modified Stienmann pins, e.g., configured to extend at least about 5 cm above the platform 536 and having a diameter of about 4 mm.
The anchor system 504 also has a locking device 556 for securing the platform 536 to the pins 544A, 544B. In one embodiment, the portion of the platform disposed around the pins comprises medial and lateral portions 560M, 560L that can move away from each other to release the pins 544A, 544B or toward each other to frictionally engage the pins. For example, a pair of hex-driven screws can engage the medial and lateral portion 560M, 560L to translate them toward and away from each other respectively. The locking device 556 preferably is quickly and easily removed from the pins such that other instrument, such as X-Ray or other diagnostic devices can be brought into the vicinity of the surgical field during the procedure. Preferably the pins 544A, 544B have markings along their length such that if the platform 536 is removed for imaging or other reasons it can be quickly re-positioned at the same elevation.
The cannula 520 also has a foot 568 adjacent to or at the distal end 528 to minimize or eliminate error that could arise due to uneven penetration depth of the anchor system 504 when compared to the position of a distal probe of the landmark acquisition system 512 when landmarks are being acquired. The foot 568 can include an annular projection disposed outward of the cannula 520. Preferably the foot 568 extends laterally from the outer surface of the cannula 520 by a distance equal to or greater than the wall thickness of the cannula 520. In some embodiment, the surface area beneath the foot is equal to or greater than the surface area of the cannula when viewed in cross-section at a location where the foot 568 is not located, e.g., at an elevation about the foot 568.
The alignment assembly 508 is similar to those hereinbefore described. It can have a rigid extension 570 configured to detachably secure a orientation device 172 to the docking device 538.
The landmark acquisition assembly 512 is similar to those hereinbefore described, but is configured to be unobstructed in use by soft tissue anterior to the pelvis of the patient. In one embodiment, an extension 578 is provided to elevate a pivoting and sliding mechanism 582. The pivoting and sliding mechanism enables a probe arm 584 to slide away from the extension 578 toward the location of landmarks to be acquired. The pivoting and sliding mechanism 582 can be similar to any of those discussed above. The distal (lower) end of the extension 578 can be coupled to the platform 536 in any suitable way. For example, the distal end can include a pin-like projection that is received in, e.g., friction fit in, an aperture 578A having the same shape. Detents or other locking features can be provided to securely connect the extension to the platform 536 in the aperture 578A.
The probe arm 584 can be configured as an elongate member with a plurality of markings, discussed below. A distal end of the probe arm 584 can include an angled tip 586 that assists in probing anatomy in some techniques, e.g., portions of the femur for leg length and femoral head positioning confirmation. In the posterior approach, the angled tip 586 is used to directly contact anatomy.
In the anterior approach, the angled tip 586 is coupled with a probe extension 590 configured to contact selected anatomy. The probe extension 590 has an upright member 592 that is configured to extend, in the anterior approach, between the elevation of the probe 584 down toward the elevation of the tissue to be probed. A foot 594 on the distal (lower) end of the upright member 592 is configured to engage the tissue in a way that minimizes error due to uneven tissue compression between the point of mounting of the pin 544A and the foot 594. For example, the foot 594 can have a cross configuration that spreads out the force or pressure applied by the landmark acquisition system 512 in use. The proximal end of the extension 590 includes a coupler 596 that connects a distal end of the probe arm 584 with the upright member 592. Preferably the coupler 596 is easily manipulable by the user to modify connect to the probe arm 584. The coupler can include an L-shaped member with an aperture configured to receive the tip 586 of the probe arm 584. A set screw can be advanced through the L-shaped portion to lock the arm 584 in place. The L-shaped portion is configured to couple to the arm 584 such that the tip of the angled tip 586 rests on a projection of the longitudinal axis of the upright member 592.
2. Example Methods for Navigating Using the Anterior Approach
The system 500 can be used to navigate from an anterior approach in the following ways. The orientation device 172 and the sensor 204 can be paired such that they are in wireless communication with each other. This permits one or other of the device 172 and sensor 204 to control the other, store data from the other, and/or display information based on signals from the other. In one method, the orientation device 172 has a display that confirms to the surgeons certain angles based on the data sensed by the sensor 204. The pairing the device and sensor 172, 204 can involve coupling them together and comparing sensor output between the two devices at a plurality of orientations, e.g., horizontal, vertical, and angled at 30 degrees. Some of these positions may be repeated with a plurality of attitudes, e.g., vertical with left side up, vertical with right side up, and vertical with top side up.
As noted above, the components discussed herein can be provided as a kit that enables the surgeon to select among different surgical approaches, e.g., posterior and anterior approaches. The orientation device 172 and sensor 204 may operate differently in these different approaches. Thus, in one method the user will enter into one or both of the orientation device and sensor 172, 204 which approach is being used. This will implement a software module in the orientation device 172 (or in the sensor 204 is the processor running the software is located there) corresponding to the selected approach.
In various embodiments suitable for the anterior approach, the orientation device 172 and the sensor 204 can both have a plurality of sourceless sensors. These components can have both accelerometers and gyroscopes in some embodiments. Some gyroscopes are subject to accumulated error that can be significant in the time frames relevant to these methods. Accordingly, various methods are provided to prevent such errors from affecting the accuracy and reliability of the angles displayed to the surgeon by the system 500. Some approaches can be performed with accelerometers only. For example, variations of the anterior approach can be performed with accelerometers with somewhat less but still acceptable accuracy using accelerometers only. The reduction in accuracy of the accelerometers is balanced against the benefit of eliminating the accumulated error that arises with some gyroscopes. The resolution of accelerometers is sufficient because the points navigated are relatively far apart.
The calculations performed by the system 500 are unique to the hip being treated in some embodiment, so the system receives input of the hip being treated.
The foot 568 is placed on a selected anatomical location, e.g., on the ASIS as discussed above. With the cannula 520 in an approximately vertical orientation the platform 536 is secured to the hip. Securing the platform 536 to the hip can be done in any suitable way, such as with two spaced apart Stienmann pins. Thereafter, the orientation device 172 and the sensor 204 are attached to the platform 536 in the manner shown in
In some embodiment, a frame of reference based on the plane of the table can be input into the system 500. The table reference frame can be a secondary reference frame. In one technique, the sensor 204 is moved from the platform dock position of
At the surgeon's discretion the system 500 can be used to navigate a condition of the femur prior to hip replacement. A mark Fm may be made on the proximal femur. Thereafter the sensor 204 can be initialized or zeroed such as by placing it back in the dock position on the platform (as in
The process to record the contralateral ASIS can be repeated for one or more additional points. The sensor 204 can be docked to the platform as in
Once the foregoing points of the pelvis have been navigated and the data recorded into the orientation device 172 the anterior pelvic plane can be calculated from data indicating the navigated points. The orientation of the anterior pelvic plane is a baseline for placement of the cup portion of a hip prosthesis.
The sensor 204 and the orientation device 172 can at this point be used to guide placement of the cup 360 in the prescribed orientation. Prior to placement the impactor 300, 300A is provided. For example, the impactor 300A can be provided by selecting the appropriate tip component 348 onto the distal end of the shaft 316A. The tip component 348 is coupled with the cup 360, e.g., by threads. The rotational orientation of the cup 360 to the shaft 316A that is most convenient given hole patterns and position of the sensor 204 is selected by matching up the flats 350A, 350B as appropriate. During the process of providing the impactor 300 the sensor 204 can be docked to the platform 536 and source of accumulated error can be eliminated just prior to navigating the cup 360 into place in the acetabulum.
In one technique, the cup 360 is inserted into the acetabulum and placed to approximately the correct orientation. Thereafter the sensor 204 is connected to a docking device 338 on the impactor as shown in
Any of the foregoing combinations of table and landmark reference frames provides redundancy that ensures that the angle information provided to the user is accurate and reliable such that the procedures performed will be better contained within the “safe zone”.
When the correct angles are achieved, a tool is used to strike the proximal end of the impactor 300 to lodge the cup 360 in place at the desired angle. In some techniques, the sensor 204 is removed prior to striking the proximal end of the impactor 300. The system 500 includes a module that monitors signals from the sensor 204 and if a large deviation in the readings occurs, the module prevents the angles on the display of the orientation device from changing. This “freezing” of the display is both a safety and an accuracy precaution because a large force due to impact can affect the accuracy of the sensor 204.
If femoral landmarks are acquired in the procedure prior to separating the natural joint, the same landmarks can be acquired after the prosthetic joint is placed to confirm that the replacement of the joint has not changed either the length of the leg, the off-set of the leg from the trunk of the patient or both. For example, the sensor 204 can be docked to the docking device 538A as shown in
In one variation a plurality of points, e.g., three points, on the femur are acquired before and after the joint is replaced. This approach enables a further confirmation that the rotation orientation of the neck of the femur relative to an axis extending through the center of the cup 360 perpendicular to the plane of the acetabulum is unchanged after the procedure.
Of course, the femur registration procedures enable correction of diagnosed deformities including excessive leg length offset and joint offset, as well as mal-orientation of the femoral neck in the natural joint. In other words, the surgeon can begin the procedure with the intent of adding some offset or changing rotational orientation to improve the patient's bone positions and/or orientations post-operatively.
C. Navigation Using Pre-Operative Imaging or Characterization
Although the foregoing approaches can improve the standard of care currently in place, further increases in accuracy and even better outcomes and streamlining of the procedure can be provided if the system is configured to account for patient specific anatomical variability.
1. Navigation Using Inertial Sensors and a Custom Jig
In one approach, a pre-operative three-dimensional characterization of the acetabulum is performed using any suitable technology, such as CT scan or MRI. This pre-operative procedure can be performed to fully characterize the pelvis and, in some cases, the proximal femur. Thereafter, the shape, location and orientation of the acetabulum are known. Also, the bony features around the acetabulum are known. From this data, a custom jig 700 can be fabricated specific to the patient. The custom jig 700 not only has features that are specific to the individual patient's anatomy but also a registration feature 702 that will be at a known orientation to the plane of the acetabulum and to the anterior pelvic plane.
Once the sensor 204 is mounted to the pin 732, the jig 700 can be removed from the surgical area. For example, the jig 700 can be made of material can be cut along a line 742 in a lateral edge of the jig. A saw or rongeur can be used to cut through the jig 700. Thereafter, the majority of the body of the jig 700 can be removed from the surgical area.
A second sensor 204 is attached to a cup impactor, which may be the same as in
2. Navigation Using Inertial Sensors and a Cannulated Guide
A custom jig 750 is formed by the process discussed above in connection with the jig 700. The jig 750 has many of the same components as those of the jig 700, including a registration feature 752 extending between the anterior and posterior surfaces 754, 758. A guiding mark 738 can be provided on the anterior surface 754 to align the sensor 204 rotationally about the pin 732. The jig 750 also has a guide channel 762 located generally centrally in the jig 750. The guide channel 762 has an anterior opening on the anterior surface 754, a posterior opening on the posterior surface 758, and a wall extending between these openings. The wall is disposed about a central axis A. The position and orientation of the axis A can be determined based on the pre-operative characterization of the acetabulum. In one embodiment, an MRI or CT scan reveals an optimal axis for delivering a prosthetic cup along. The wall forming the guide channel 762 is formed about the axis A which coincides with this optimal axis when the jig 750 is placed on the specific patient's acetabulum.
In one variation, the impactor 300A has a central channel that coincides with the axis A when the impactor is placed into the guide channel 762 and the shoulder 766 abutted with the surface 754. A guide pin can be advanced through this channel and into the acetabulum. The guide pin can be lodged in the base of the acetabulum. The sensor 204 coupled with the pelvis by the pin 732 can be removed because the guide pin placed through the channel of the impactor 300A provides a mechanical way of tracking movement of the hip. Thereafter the impactor 300A with the cup mounted thereon can be slide over the guide pin and into place in the acetabulum.
In a further variation, the sensor 204 coupled with the impactor 300A can also be removed. In this further variation, the guide pin is configured along with the cup to prevent tilting of the prosthetic cup relative to the axis A. In particular, an interface between the guide member and the cup of the hip prosthesis could be made to have sufficient length along the axis A that tilting is prevented by this interface. In some cases, the cup 360 is coupled to the impactor 300, 300A. A variation of the impactor 300, 300A can be tubular or have another feature for interfacing with, e.g., tracking along the guide pin in the pelvis.
3. Navigation Using Inertial Sensors and Pre-operative Imaging
In another technique using less comprehensive imaging, a correspondence between one or more linear dimensions and an angle can be exploited to enhance accuracy. For example, a clinician can use an X-ray or other standard radiographic imaging device to provide an anterior pelvic bone image. This image can be read to derive the location of the anterior pelvic plane and a dimension on the anatomy. For example, an angle between top and bottom landmarks around the acetabulum (as further describe below) and a trans-ischial line or other anatomic medial-lateral reference line can be a useful patient specific variable to minimize patient-to-patient variation in at least one relevant angle, e.g., the abduction angle.
Patient specific data can be provided for use by the surgeon based on best medical judgment. For example, any of the systems herein can be used in a mode that is based on broad population studies. Such studies can define a distribution of patients with sufficient clarity and detail to enable significant improvement over the current standard of care. In one mode, the dimensions taken from radiograph or CT can be used to inform the surgeon whether some patient specific adjustments should be considered. Alternatively, patient specific adjustments can be coded into the system 100 so that they are transparent to the doctor. Such adjustments can be downloaded to either or both of the devices 172, 204 or into a separate monitor or control device that communicates wirelessly with the devices 172, 204. Thus, the system 100 can either fully implement patient specific adjustment, e.g., for anteversion, abduction, leg length, joint offset, or other parameter or can enable the surgeon to make a judgment as to whether to do so.
4. Navigation Using Drift Insensitive Inertial Sensors
In one variation, one or both of the devices 172, 204 can comprise only accelerometers and can be configured as tilt meters, or the devices could be put into a mode that relies mostly on the accelerometer data or otherwise be configured to be insensitive to accumulated errors that arise from integration of data. If the patient is set in a reproducible and stable position, patient movement and mis-orientation can be eliminated. This enables some methods to be performed without using rate sensor data. In one variation of this tilt-meter approach, one or both of the sensors 172, 204 can be configured to inform the surgeon if a condition is sensed that suggests a landmark acquisition approach would yield a superior alignment outcome. This method can advantageously be used for procedures that do not require complex movements, like freehand motions. Where freehand motion is involved, incorporating some indication of heading (gyroscopes, magnetometer, or other indication of heading) would be useful.
5. Navigation Using Inertial Sensors to Track Motion to Define a Patient-Specific Safe Zone
In another technique illustrated by
In one hip replacement technique a sensor S is coupled with the femur. The sensor can be coupled above the knee to prevent movements at the knee from affecting the measurements made. The sensor S can be connected below knee if the knee is immobilized. The sensor S can be initialized and otherwise prepared to record accurate readings. Thereafter one or more movements of the hip joint can be performed with the output of the sensor recorded and processed. The movements can include, for example, movement in anterior and posterior (A-P) directions to the full extent of the range of motion and movement in medial and lateral (M-L) directions to the full extent of the range of motion. These motions define the patient's natural range of motions in these planes.
Based on the extents of motion in the A-P and M-L directions, a cone of motion CM can be defined. The cone of motion CM can be defined as originating at a point defined as the center of rotation of the femoral head and extending out from the acetabulum to a circular base located a distance from the center of rotation equal to the distance to the mount point of the sensor. The circular base can be defined as having a radius equal to the average extent of motion in the A-P and M-L directions. In
Placement of the cup of the hip prosthesis is dictated by some metric of centering within the cone of motion. For example, the cup can be centered such that an axis extending perpendicular to the plane of the entrance to the cup crosses the circular base of the cone of motion precise in the center of the cone. In some systems, the orientation of the cup is controlled such that the crossing point of the axis so projecting is closer to the center of the circular base than it is to the periphery of the circular base. In other systems, the orientation of the cup is controlled such that the crossing point of the axis so projecting is within a distance from the center point that is less than 25% of the radius of the circular base.
In a class of patients, the movement of the hip is not symmetrical in each of the A-P and M-L directions. As such, the cone of motion can have a more complex geometry. For example, the cone of motion can originate at the center of rotation of the femoral head and extend to a base having an oblong shape, for example shortened in the medial direction, but longer in the lateral, anterior, and/or posterior directions. Various metrics of “within the safe zone” can be defined based on these irregular shaped cones. For example the geometric center of a complex base shape can be calculated and the cup of the prosthetic joint can be centered such that an axis extending perpendicular to the plane of the entrance to the cup crosses the irregular shaped base of the cone of motion at or within some maximum distance of the centroid of the cone.
Any suitable set of motions can be used to obtain the center of rotation of the femoral head and/or the boundaries of the base of the cone of motion. Examples of methods for determining the center of rotation of a femoral head using inertial sensors are discussed in U.S. Pat. No. 8,118,815, which is hereby incorporated by reference for this and all other purposes. A more complete perimeter of the base of the cone of motion can be directly recorded using sensors that are capable of tracking both position and orientation. For example, several other points between the A-P and M-L direction can be taken so that six, eight, ten, twelve or more extents are recorded. In other embodiments, arcuate motions of along all or portions of the perimeter of the base of the cone of motion can be traced and recorded. Because several degrees of freedom of the sensor S are constrained, the sensor can operate based on accelerometers only in some approaches, which simplifies sensor S and enables it to be disposable and/or less expensive to make. Such approaches may be most accurate if rotations about a vertical axis are minimized or eliminated.
In one embodiment, the procedure illustrated in
In other embodiments, cannulated systems can be used to minimize the number of steps during which inertial sensors are used. For example, once the origin and direction of the axis connecting the center of rotation and the intersection with the base of the cone of motion are determined, a guide member can be placed via a cannulated impactor (or other cannula). The guide member can dock with an impactor-mounted cup. The cup can be slid over the guide member into place in the acetabulum. The direction and origin information collected in the steps illustrated by
If the patient's joint is subject to extensive disease, a cone of motion can be established by a combination of data collected in motions similar to those discussed above in connection with
D. Modular System for Anterior or Posterior Approach to Navigation Using Inertial Sensors and Anatomical Landmark Acquisition Jigs
The system 900A includes a jig 904A that is adapted for hip joint navigation from a posterior approach. The jig 904A is similar in some respects to the jig 454, and any consistent description thereof is incorporated herein. The jig 904A includes a platform 908, a cannula coupling device 912, and a registration jig mounting feature 914. The platform 908 can have any shape, but in some implementations can be elongate, e.g., having a first end 916 and a second end 920. The elongate shape enables at least a portion of the jig 904A to be low profile in one direction and to provide a plurality of positions along a length for coupling devices to the jig. The first end 916 is configured to be oriented inferiorly and the second end 920 to be oriented superiorly when the navigation jig is applied to the patient. The medial-lateral dimensions or extent can be minimized to not obstruct the surgical field or the surgeon.
The cannula coupling device 912 is disposed adjacent to the first end 916 and is configured to enable a cannula 924 to be held adjacent to a bottom surface of the platform 908. The cannula 924 can have a top surface connected to a bottom surface of the platform 908. A connection between these components can be secured by a device disposed above within or below the platform 908. In one form, a proximal structure of the cannula 924 can be received within a bottom recess of the platform 908 and can be held within the recess by a compression device, such as a set screw S. Details of several variants of cannula coupling devices 912 are discussed below in connection with
An anterior approach cannula 926 is shown in
The registration jig mounting feature 914 is disposed on a top surface 932 of the platform 908 adjacent to the first end 916. In one form, the mounting feature 914 includes an elevated portion of the platform. The mounting feature can include one or more, e.g., two recesses into which pins can be received. In one embodiment, the elevated portion includes a window, e.g., a through hole, for viewing such a pin to confirm correct placement. As illustrated in
The hip navigation jig 904A also includes registration jig 940. The registration jig 940 can have some features similar to those discussed above. The registration jig 940 includes an upright member 942, a rotatable member 948, and a probe 952. The upright member 942 is configured to be detachably coupled to the platform 908 at the registration jig mounting feature 914. For example, a plurality of (e.g., two) pins can project from a lower surface of the upright member 942, the pins being configured to be received in corresponding recesses in the registration jig mounting feature 914. One of such pins is visible through the window in the registration jig mounting feature 914 seen in
The incline of the second portion 946 also provides a simple way to incline an angle of rotation of the rotatable member 948 relative to a vertical axis. The rotatable member 948 is coupled with the upright member 942 for rotation about an axis A that is not vertical when the jig is mounted to the bone adjacent to a hip joint and the upright member is disposed generally vertically. This arrangement is one way to enable a navigation system employing inertial sensors to eliminate the need to manage sensor drift. As discussed above, certain sensors, such as gyroscopes, are more subject to accumulated errors (drift). The orientation of the axis A enables the jig 904 to be used in a system that includes accelerometers and other sensors that are sufficiently sensitive if activated and moved about axes that are not vertical.
As in the registration devices discussed above, other degrees of freedom of rotation and position can be provided in the registration jig 940 and such description is incorporated here.
The probe 952 had a tip 956 for engaging anatomy. The anatomy engaging tip 956 is disposed at a distal end of an elongate body 960 coupled with the rotatable member for rotation about the axis. The orientation and position of the elongate body 960 of the probe can be adjusted to bring the anatomy engaging tip into contact with a plurality of anatomical landmarks during a landmark acquisition maneuver. Such adjustments can be by sliding through a sliding support, similar to those hereinbefore described.
The upright member 942 can include a cradle 954 that allows the elongate body 960 of the probe 952 to be held in place when not in use during a procedure. The cradle 954 can be used to latch the sensor 204, as discussed above. In various implementations, the system 900 does not require any steps of zeroing, however, since the sensors are configured to be generally drift insensitive. Eliminating sensitivity to drift can be achieved by configuring the sensor 204 as a tilt meter, and/or by using any sort of inertial sensor that will not introduce excessive error due to drift during the procedure time. As such, even sensors that have some drift can be used, so long as their accumulation of error does not reach a significant level until during the procedure. The cradle 954 could be used to zero error if a procedure was unexpectedly long and the sensor were subject to some drift. In one advantageous embodiment, the sensor 204 can operate solely with signals from accelerometers, which are insensitive to drift.
The registration jig 940 can include a sensor mounting feature 964 disposed thereon for movement with the probe 952. For example, the sensor mounting feature 964 can be located at a proximal end of the elongate body 960. This location is one of convenience, placing the sensor 204 at the proximal end. However, the sensor mounting feature 964 and the sensor 204 could be located on a side surface of the elongate body 960.
As discussed herein, the orientation of the axis of rotation A of the rotatable member 948 enables the change of orientation of the sensor 204 to be other than in the horizontal plane. This is accomplished by orienting the axis A other than in the vertical direction. With this arrangement, it is possible to configure at least the sensor 204 as a tilt meter, e.g., using primarily or only accelerometers to output a signal indicative of orientation of a component, such as of the prove 952. Example of angles or ranges of angles of the axis A that can be provided include about 20 degrees from horizontal, about 30 degrees from horizontal, about 45 degrees from horizontal, at less than about 60 degrees from horizontal.
Because the system 900 can be adapted for posterior approach or for anterior approach (discussed below), the cannula 924 should be made removable from the platform 908 in the operating room or at a back table in preparation for surgery. As such, the connection between the cannula 924 and the platform 908 can be made orientation specific. This reduces a potential source of operator error, i.e., the home point feature 968 always faces toward the surgical field from the hip bone attachment location, e.g., faces inferiorly if the jig 904 is mounted to a superior location of the surgical field. For example, a projection on a proximal portion of the cannula 924 and a corresponding projection in a recess on the lower side of the platform 908 can define only one rotational orientation of the cannula relative to the platform in which these components can be coupled.
As discussed above, the cannula 926 is provided in the system 900 to enable a surgeon to switch to an anterior approach. Anterior approach is discussed in great detail above, e.g., in connection with
In one method to maximize the accuracy of the landmark acquisition, jig 904B is coupled with the patient in an anterior approach. The tip 956 is put into contact with the home point feature 968B. Thereafter, user input can be applied to the surgical orientation device 172A to indicate that the tip 956 is in the home point feature 968B. Thereafter, the system registers movements and landmark acquisition in the manner discussed above. These data provide a basis to guide the placement of the acetabular cup, as discussed above.
The placement of the acetabular cup using a device such as the impactor 300A can be an operation that benefits from inertial sensors that may include one or more drift-sensitive sensors, e.g., gyroscopes. The system 900 provides a calibration mount 998 for coupling a sensor 204 in a known, fixed position and orientation relative to the surgical orientation device 172A. The calibration mount 998 is a docking device that positions the sensor 204 just prior to a step of eliminating any potential source of accumulated error, e.g., zeroing a drift-sensitive sensor.
In one method, a pin or other fixation member is advanced through the gap G and into the bone. The platform 908 is positioned on the fixation member at an appropriate height and the pin securement device 970 is affixed to the fixation member. The fixation member can be a Steinmann pin or other similar device. In one technique, the tapered member 978 is a threaded elongate body that is advanced along internal threads formed in the platform 908 until the tapered surface thereof acts on the tapered surface 976 to shift the compression member 972 laterally to narrow the gap G. Further advancement of the tapered member 978 further shifts the compression member 972 to enhanced securement of the fixation member. The method can be repeated for a second pin, where one pin extends through the cannula 924 and one extends parallel to the cannula 924, but off-set superiorly therefrom on the patient.
In one method, pins or other fixation members are placed in the fixation pin securement device 970A and the cannula coupling device 912. In the illustrated embodiment, these devices can employ similar clamping mechanisms. Thereafter, screws 982 are advanced to cause the compression member 972 to pivot about the pin or shaft 980 from a first position in which the gap G provided between a clamping surface of the compression member 972A and a rigid surface of the platform 908 is larger to a second position in which the gap G is smaller. The second position is a clamped position for the fixation member and will retain the platform in position until the screw 982 is withdrawn enlarging the gap G.
While the systems discussed above are well suited for specific approaches, the system 900 can be adapted for a posterior approach or for an anterior approach. This provides a great deal of flexibility to the surgeon and only adds minimal additional components to a universal kit. The orientation of the axis of rotation A (see
In the illustrated embodiment, a jig system 804 is provided for connecting to patient bone. The jig system 804 can include any of the features of any of the jig systems discussed herein. For simplicity, the jig system is illustrated with that of
This data can at least be used to determine the heading of and in some cases six degrees of freedom of a stylus 816. The stylus has a distal end 828 configured to touch landmarks as part of a landmark acquisition maneuver, as discussed above. A proximal (or other) portion 832 of the stylus 816 has an array of trackers 836 that can be tracked by the cameras 812 to provide orientation, position, heading, attitude, or other combinations of spatial characteristics of portions of the stylus 816 or anatomy with which it is coupled.
The cameras 812 can operate without any additional sensor, such as inertial sensors. In some embodiments, the cameras 812 are used in concert with inertial sensors to confirm or to improve accuracy of the sensors. For example, drift in a rate sensor, e.g., accumulated errors, can be monitored by comparing the output of the rate sensor with the viewed position from the cameras. The system can intervene if the sensor output drifts too much, for example, telling the user to reset the rate sensors.
Another optical device such as a laser or an IR emitter 814 can be provided in the orientation device 172A. An IR emitter can be useful to illuminate the fiduciaries to make them more readily detectable by the cameras under the intense lighting in the surgical field.
Although these inventions have been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that this application extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the inventions have been shown and described in detail, other modifications, which are within the scope of the inventions, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the application. For example, the application contemplates the connection hub alone or in combination with any of the other modules could comprise a separate aspect. Or, any one or a combination of the modules could be directly connected to an umbrella hub or overhead support to form another separate aspect. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed embodiments. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.
Similarly, this method of disclosure, is not to be interpreted as reflecting an intention that any claim require more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment.
Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application including U.S. provisional application No. 61/683,167, filed Aug. 14, 2012, and U.S. provisional application No. 61/761,617, filed Feb. 6, 2013, are hereby incorporated by reference under 37 CFR 1.57.
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