Patent Application
20230068307
Not Applicable.
Not Applicable.
Accurate assessment of three-dimensional (3D) joint kinematics is critical for screening, diagnostic, and therapeutic applications in orthopaedics. Such kinematics may include arthrokinematics and osteokinematics, which may further be analyzed in terms of tibiofemoral kinematics. However, relative motion between bone and skin reduces the accuracy of marker-based tibiofemoral kinematic measures. While intracortical pins and biplane imaging can provide precise in vivo bone motion, these options are restricted by cost, availability, patient acceptance and/or ethical considerations. As such, information on tibiofemoral kinematics during knee movement and other functional weight-bearing activities is limited.
Knowledge of 3D motion of the knee (e.g., tibia relative to femur) would aid in diagnosis and treatment of knee related impairment and would benefit understanding, for example, of the influence of gait impairment on knee motion, mechanisms of ligament injury, outcomes of total knee arthroplasty, and effects of assistive devices (e.g., ankle foot orthotics). Such knee related impairment includes, for example, impairment resulting from disorders such as cerebral palsy and the like, impairment resulting from other neurological conditions such as stroke and the like, and impairment from musculoskeletal disorders and the like. Such impairment may include, for example, muscle spasticity, joint degeneration, osteoarthritis and general knee pain.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
There is a need to accurately monitor and characterize in vivo joint motion, such as knee motion, in a non-invasive, cost-effective manner. An aspect of the invention provides a joint arthrometer such as a knee arthrometer for measuring knee laxity. The knee arthrometer includes a femoral frame and a tibial frame. The femoral frame is attachable to a leg about a distal femur. The distal femur and the leg both have a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle. The femoral frame includes a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, and may also include additional femoral arm portions. The first arm portion is configured to contact the leg about the lateral epicondyle, and the second arm portion is configured to contact the leg about the medial epicondyle. The connecting portion connects the first and second arm portions. The femoral motion sensor is coupled to the femoral frame and is configured to measure motion with six degrees of freedom and output femoral motion data associated with the measured motion. The femoral arm portions may contact portions of the leg above the first and second arm portions. The tibial frame is attachable to the leg about a tibia. The tibia has a proximal end, a distal end, and an anterior crest. The tibial frame is attachable to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia. The tibial frame includes a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor. The tibial motion sensor is coupled to the rigid frame portion and configured to measure motion with six degrees of freedom and output tibial motion data associated with the measured motion. The femoral motion data and the tibial motion data are usable, in conjunction, to determine knee laxity and/or tibiofemoral rotations during movement (e.g., step-up and squatting tasks).
Another aspect of the invention provides a method for measuring knee laxity. The method includes attaching a femoral frame to a leg about a distal femur. The distal femur and the leg both have a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle. The femoral frame includes a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism. The first arm portion contacts the leg about the lateral epicondyle, and the second arm portion contacts the leg about the medial epicondyle. The connecting portion connects the first and second arm portions, and the connecting portion is positioned above the anterior side of the leg. The femoral motion sensor is coupled to the femoral frame and configured to measure motion with six degrees of freedom. Additionally, femoral arm portions may further couple the arthrometer to a leg of a test subject. The method further includes attaching a tibial frame to the leg about a tibia. The tibia has a proximal end and a distal end. The tibial frame is attached to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia. The tibial frame includes a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor. The tibial motion sensor is coupled to the rigid frame portion and configured to measure motion with six degrees of freedom. The tibial securing mechanism is attached to the rigid frame portion and positioned about the leg and tibia. The method still further includes moving the tibia relative to the femur in at least one cycle including knee flexion and extension, recording the motion of the femoral motion sensor and recording the motion of the tibial motion sensor through the at least one cycle, and determining knee laxity based on the recorded motion of the femoral and tibial motion sensors.
Yet another aspect of the invention provides for a knee arthrometer and method of efficiently and accurately measuring tibiofemoral bone motion on test subjects performing functional tasks, such as stepping, squatting, treadmill walking, lateral step-down, lunging, and hopping tasks, as well as on test subjects undergoing physical evaluations (e.g., from a physical therapist), such as spasticity evaluations, and also on test subjects wearing orthotics. Measuring tibiofemoral bone motion may include measuring motion of test subjects wearing ankle foot orthotics (e.g., such as a solid ankle foot orthotics prescribed to improve gait). Motion measurements may also be conducted with sensors placed at areas outside of the tibiofemoral region, such as the area near the malleoli and the area near the calcaneus. This method allows for differences in knee kinematics to be determined in real-time, based on calculations performed with respect to a (e.g., Cartesian) coordinate system. The knee arthrometer and associated software (e.g., custom algorithm) can be used together as a knee arthrometer testing system (KATS).
As discussed above, the present invention comprises a knee arthrometer that may include a femoral frame and a tibial frame. The femoral frame may be attachable to a leg about a distal femur and includes a first arm portion, a second arm portion, a connecting portion, and a femoral motion sensor. The first arm portion may be configured to contact the leg about the lateral epicondyle, and the second arm portion may be configured to contact the leg about the medial epicondyle. The femoral motion sensor may be configured to measure motion with six degrees of freedom and output femoral motion data. The tibial frame may include a tibial motion sensor and may be attachable to the leg about a tibia. The tibial motion may be configured to measure motion with six degrees of freedom and output tibial motion data associated with measured motion. The femoral motion data and the tibial motion data may be usable to determine knee laxity and/or provide real-time tibiofemoral measurements.
One aspect of the present invention includes a knee arthrometer for measuring knee laxity comprising a femoral frame attachable to a leg of a test subject about a distal femur of the leg, the distal femur and the leg both having a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle, the femoral frame comprising a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, the first arm portion configured to contact the leg about the lateral epicondyle, the second arm portion configured to contact the leg about the medial epicondyle, the connecting portion connecting the first and second arm portions, the femoral motion sensor coupled to the femoral frame and configured to measure motion with six degrees of freedom and output femoral motion data associated with the measured motion; and a tibial frame attachable to the leg about a tibia, the tibia having a proximal end, a distal end, and an anterior crest, the tibial frame attachable to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia, the tibial frame comprising a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor, the tibial motion sensor coupled to the rigid frame portion and configured to measure motion with six degrees of freedom and output tibial motion data associated with the measured motion, wherein the femoral motion data and the tibial motion data are usable, in conjunction, to determine knee laxity.
The connecting portion may be curved to extend over the anterior side of the distal femur to accommodate the leg. The connecting portion may be sprung to bias the first arm portion toward the medial side of the leg and bias the second arm portion toward the lateral side of the leg such that the femoral frame is capable of being clamped to the leg. The femoral frame may be U-shaped, and the femoral securing mechanism may comprises a femoral securing strap, the femoral securing strap being attachable to the first arm portion and second arm portion and positionable about the posterior side of the leg. The femoral securing strap may be expandable, the femoral securing strap being configured to bias the first arm portion toward the second arm portion when attached to the first and second arm portions such that the femoral frame is capable of being clamped to the leg. The first and second arm portions may comprise an end opposite the connecting portion and a deformable contact pad coupled to the arm portion near the end, the deformable contact pad configured to contour to the leg. The tibial frame may further comprise a placement guide, the placement guide extending proximally and distally from the rigid frame portion and configured to guide a user in placing the tibial frame. The tibial securing mechanism may comprise a tibial securing strap, the tibial securing strap attachable to the rigid frame portion and positionable about the leg and tibia. The tibial securing strap may be expandable and configured to secure the tibial frame to the leg about the tibia. The tibial securing strap may comprise a hook and loop fastener and be configured to secure the tibial frame to the leg about the tibia. The connecting portion of the femoral frame may be positionable above the anterior side of the leg. The femoral motion sensor may be coupled to the connecting portion of the femoral frame. The tibial frame may be positionable over the anterior crest of the tibia.
Another aspect of the present invention includes a method for measuring knee laxity comprising: attaching a femoral frame to a leg of a test subject about a distal femur of the leg, the distal femur and the leg both having a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle, the femoral frame comprising a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, the first arm portion contacting the leg about the lateral epicondyle, the second arm portion contacting the leg about the medial epicondyle, the connecting portion connecting the first and second arm portions, the connecting portion positioned above the anterior side of the leg, the femoral motion sensor coupled to the femoral frame and configured to measure motion with six degrees of freedom; attaching a tibial frame to the leg about a tibia, the tibia having a proximal end and a distal end, the tibial frame attached to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia, the tibial frame comprising a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor, the tibial motion sensor coupled to the rigid frame portion and configured to measure motion with six degrees of freedom, the tibial securing mechanism attached to the rigid frame portion and positioned about the leg and tibia; moving the tibia relative to the femur in at least one cycle including knee flexion and extension; recording the motion of the femoral motion sensor and recording the motion of the tibial motion sensor through the at least one cycle; and determining knee laxity based on the recorded motion of the femoral and tibial motion sensors. The determining of the knee laxity may be based on calculations defined by a Cartesian coordinate system.
This method may further include moving the tibia in a first stage including a set of cycles; recording the motion of the femoral and tibial motion sensors during the first stage; and determining, based on the recorded motion during the first stage, a knee axis of rotation. The first stage may comprise three cycles, wherein for each cycle the tibia may be moved relative to the femur from an angle of fifteen degrees to an angle of sixty degrees and back to the angle of fifteen degrees.
This method may yet further include moving the tibia such that the knee may be at terminal extension during a knee laxity test in a second stage including a set of cycles, and holding the tibia such that the knee is at the terminal extension for a set period of time; recording the motion of the femoral and tibial motion sensors during the second stage; and determining, based on the recorded motion during the second stage and the knee axis of rotation, a first orthogonal coordinate system relative to the femur and a second orthogonal coordinate system relative to the tibia. The first orthogonal coordinate system may comprise a first axis along the knee axis of rotation, a second axis extending in an anterior direction, and a third axis extending in a proximal direction, and wherein the second orthogonal coordinate system may be coincident with the first orthogonal coordinate system when the knee is at terminal extension.
This method may yet further still include moving the tibia through a range of motion including flexion and extension from terminal extension to an angle of approximately seventy degrees relative to the femur, internal and external rotation, varus and valgus rotation, and anterior and posterior rotation in a third stage including a set of cycles; recording the motion of the femoral and tibial motion sensors during the third stage; determining cardan angle values between the first and second orthogonal coordinate systems; and determining translation distances of the second orthogonal coordinate system relative to the first orthogonal coordinate system. The determining of the knee laxity may include determining, based on the third set of cycles and corresponding recorded motion, a dynamic flexion and extension angle, an internal and external rotation value, and a varus and valgus rotation value, and an anterior and posterior rotation value.
Yet another aspect of the present invention includes a knee arthrometer for measuring knee tibiofemoral kinematics comprising: a femoral frame attachable to a leg of a test subject about a distal femur of the leg, the distal femur and the leg both having a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle, the femoral frame comprising a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, the first arm portion configured to contact the leg about the lateral epicondyle, the second arm portion configured to contact the leg about the medial epicondyle, the connecting portion connecting the first and second arm portions, the femoral motion sensor coupled to the femoral frame and configured to measure motion with six degrees of freedom and output femoral motion data associated with the measured motion; and a tibial frame attachable to the leg about a tibia, the tibia having a proximal end, a distal end, and an anterior crest, the tibial frame attachable to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia, the tibial frame comprising a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor, the tibial motion sensor coupled to the rigid frame portion and configured to measure motion with six degrees of freedom and output tibial motion data associated with the measured motion, wherein the femoral motion data and the tibial motion data are usable, in conjunction, to determine tibiofemoral kinematics in real-time.
The connecting portion may be curved to extend over the anterior side of the distal femur to accommodate the leg. The connecting portion may be sprung to bias the first arm portion toward the medial side of the leg and bias the second arm portion toward the lateral side of the leg such that the femoral frame is capable of being clamped to the leg. The femoral frame may be U-shaped. The femoral securing mechanism may comprise a femoral securing strap, the femoral securing strap attachable to the first arm portion and second arm portion and positionable about the posterior side of the leg. The femoral securing strap may be expandable, the femoral securing strap being configured to bias the first arm portion toward the second arm portion when attached to the first and second arm portions such that the femoral frame is capable of being clamped to the leg. The first and second arm portions may comprise an end opposite the connecting portion and a deformable contact pad coupled to the arm portion near the end, the deformable contact pad configured to contour to the leg. The contact pad may comprise a plurality of posts configured to contour to the leg. The plurality of posts of the contact pad may comprise a material configured to grip to the leg. The tibial frame may further comprise a placement guide, the placement guide extending proximally and distally from the rigid frame portion and configured to guide a user in placing the tibial frame. The tibial securing mechanism may comprise a tibial securing strap, the tibial securing strap being attachable to the rigid frame portion and positionable about the leg and tibia. The tibial securing strap may be expandable and configured to secure the tibial frame to the leg about the tibia. Therein the tibial securing strap may comprise a hook and loop fastener and may be configured to secure the tibial frame to the leg about the tibia. The connecting portion of the femoral frame may be positionable above the anterior side of the leg. The femoral motion sensor may be coupled to the connecting portion of the femoral frame. The tibial frame may be positionable over the anterior crest of the tibia. The femoral frame further may comprise femoral arm portions. The femoral frame may further comprise wire retention members. The femoral frame may further comprise being configured to secure the femoral sensor. The tibial frame may further comprise posts configured to secure the tibial sensor. The tibial frame may further comprise an upper femoral securing mechanism.
Yet another aspect of the present invention includes a method for measuring tibiofemoral kinematics comprising: attaching a femoral frame to a leg of a test subject about a distal femur of the leg, the distal femur and the leg both having a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle, the femoral frame comprising a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, the first arm portion contacting the leg about the lateral epicondyle, the second arm portion contacting the leg about the medial epicondyle, the connecting portion connecting the first and second arm portions, the connecting portion positioned above the anterior side of the leg, the femoral motion sensor coupled to the femoral frame and configured to measure motion with six degrees of freedom; attaching a tibial frame to the leg about a tibia, the tibia having a proximal end and a distal end, the tibial frame attached to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia, the tibial frame comprising a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor, the tibial motion sensor coupled to the rigid frame portion and configured to measure motion with six degrees of freedom, the tibial securing mechanism attached to the rigid frame portion and positioned about the leg and tibia; moving the tibia relative to the femur in at least one cycle including at least one of knee flexion and extension, internal-external knee movement, and adduction-abduction knee movement; recording the motion of the femoral motion sensor and recording the motion of the tibial motion sensor through the at least one cycle; and determining tibiofemoral kinematics in real-time based on the recorded motion of the femoral and tibial motion sensors. This method may further comprise: moving the tibia in a first stage including a set of cycles; recording the motion of the femoral and tibial motion sensors during the first stage; and determining, based on the recorded motion during the first stage, a knee axis of rotation.
The first stage may comprise three cycles, wherein for each cycle the tibia may be moved relative to the femur from a first angle to a second angle different than the first angle. The tibia may comprise each tibia of the test subject and the knee may comprise each knee of the test subject, the method further comprising: moving the tibias such that the knees are brought together; recording the motion of the femoral and tibial motion sensors; and determining, based on the recorded motion, a Cartesian coordinate system. The tibia may comprise each tibia of the test subject and the knee may comprise each knee of the test subject, the method further comprising: moving the tibias such that the knees are outward from one another; recording the motion of the femoral and tibial motion sensors; and determining, based on the recorded motion, a Cartesian coordinate system. The tibia may comprise each tibia of the test subject and the knee comprises each knee of the test subject, the method further comprising: moving the tibias such that the knees are neutral to one another; recording the motion of the femoral and tibial motion sensors; and determining, based on the recorded motion, a Cartesian coordinate system. The Cartesian coordinate system may define a search space for calculating a knee angle of rotation.
The determining of the tibiofemoral kinematics in real-time may include determining tibiofemoral kinematics resulting from measurements taken during a step-up test. The determining the tibiofemoral kinematics in real-time may include determining tibiofemoral kinematics resulting from measurements taken during performance of a squatting test. The squatting test may comprise the test subject performing a neutral dual limb squatting task, a Valgus squatting task, and/or a Varus squatting task.
Yet another aspect of the present invention includes a method for measuring tibiofemoral kinematics comprising: attaching a femoral frame to a leg of a test subject about a distal femur of the leg, the distal femur and the leg both having a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle, the femoral frame comprising a first arm portion, a second arm portion, a connecting portion, a femoral motion sensor, and a femoral securing mechanism, the first arm portion contacting the leg about the lateral epicondyle, the second arm portion contacting the leg about the medial epicondyle, the connecting portion connecting the first and second arm portions, the connecting portion positioned above the anterior side of the leg, the femoral motion sensor coupled to the femoral frame and configured to measure motion with six degrees of freedom; attaching a tibial frame to the leg about a tibia, the tibia having a proximal end and a distal end, the tibial frame attached to the leg about the tibia closer to the proximal end of the tibia than the distal end of the tibia, the tibial frame comprising a tibial securing mechanism, a rigid frame portion, and a tibial motion sensor, the tibial motion sensor coupled to the rigid frame portion and configured to measure motion with six degrees of freedom, the tibial securing mechanism attached to the rigid frame portion and positioned about the leg and tibia; moving the tibia relative to the femur in at least one cycle of a functional task; recording the motion of the femoral motion sensor and recording the motion of the tibial motion sensor through the at least one cycle; and determining tibiofemoral kinematics based on the recorded motion of the femoral and tibial motion sensors.
The determining of the tibiofemoral kinematics may be based on calculations defined by a Cartesian coordinate system. The determining of the tibiofemoral kinematics may be based on calculations defined by an orthogonal coordinate system.
These are merely some of the innumerable aspects of the present invention and should not be deemed an all-inclusive listing of the innumerable aspects associated with the present invention. These and other aspects will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure.
Reference characters in the written specification indicate corresponding items shown throughout the drawing figures.
Referring to
The femoral frame 22 is attachable to a leg 28 about a distal femur 30. The distal femur 30 and the leg 28 both have a medial side, a lateral side, an anterior side, a posterior side, a lateral epicondyle, and a medial epicondyle. The femoral frame 22 includes a first arm portion 32, a second arm portion 34, a connecting portion 36, a femoral motion sensor 38, and a femoral securing mechanism 40. The first arm portion 32 is configured to contact the leg 28 about the lateral epicondyle. The second arm portion 34 is configured to contact the leg 28 about the medial epicondyle. The connecting portion 36 connects the first 32 and second 34 arm portions. The femoral motion sensor 38 is coupled to the femoral frame 22 and is configured to measure motion with six degrees of freedom and output femoral motion data associated with the measured motion. Generally the femoral motion sensor 38 is positioned on the connecting portion 36, but it can alternatively be positioned elsewhere on the femoral frame 22. The femoral securing mechanism 40 secures the femoral frame 22 to the leg 28.
The connecting portion 36 is curved to extend over the anterior side of the distal femur 30 to accommodate the leg 28. The connecting portion 36 may be sprung to bias the first arm portion 32 toward the medial side of the leg and bias the second arm portion 34 toward the lateral side of the leg such that the femoral frame 22 is capable of being clamped to the leg 28. This configuration secures the femoral frame 22 to the leg 28. For example, and without limitation, the femoral frame 22 may be U-shaped.
The femoral securing mechanism 40 is a femoral securing strap (e.g., as shown in
The first and second arm portions 32, 34 may each include an end opposite the connecting portion 36 and a deformable contact pad 42 coupled to the arm portion near the end. The deformable contact pad 42 is configured to contour to the leg 28. The deformable contact pad 42 may improve patient comfort and/or facilitate securing of the femoral frame 22 to the leg 28.
The tibial frame 24 is attachable to the leg 28 about a tibia 44. The tibia has a proximal end, a distal end, and an anterior crest. The tibial frame 24 attaches to the leg 28 about the tibia 44 closer to the proximal end of the tibia 44 than the distal end of the tibia. The tibial frame includes a tibial securing mechanism 46, a rigid frame portion 48, and a tibial motion sensor 50. The tibial motion sensor 50 is coupled to the rigid frame portion 48 and is configured to measure motion with six degrees of freedom and output tibial motion data associated with the measured motion. The femoral motion data and the tibial motion data are usable, in conjunction and by a processor, to determine knee laxity as described in greater detail later herein. The femoral motion sensor 38 and/or the tibial motion sensor 50 may communicate with the processor using a wired or wireless data and/or power connection.
The tibial frame 24 may further comprise a placement guide 52. The placement guide 52 extends proximally and distally from the rigid frame portion 48 and is configured to guide a user in placing the tibial frame 24. For example, and without limitation, the placement guide 52 is a protrusion, rod, or the like, having an end opposite the rigid frame portion 48. The user may place the tibial frame by centering the end of the placement guide 52 relative to the knee (e.g., centered on the patella or more specifically the tibial tuberosity).
The tibial securing mechanism 46 may be configured as a tibial securing strap. The tibial securing strap is attachable to the rigid frame portion 48 and is positionable about the leg 28 and tibia 44. The tibial securing strap may be expandable and is configured to secure the tibial frame 24 to the leg 28 about the tibia 44. For example, and without limitation, the tibial securing strap may be a hook and loop fastener and stretchable material such that the tibial frame 24 is securable to the leg 28 about the tibia 44. The tibial frame 24 may be configured to be positionable over the anterior crest of the tibia 44.
In operation, an electromagnetic motion tracker measures the position and orientation of the tibial motion sensor 50 relative to the femoral motion sensor 38. For example, and without limitation, the electromagnetic motion tracking system, tibial motion sensor, and femoral motion sensor may be of the type used in the Polhemus™ Patriot™ system, and in particular the Polhemus™ Patriot™ two sensor 6DOF (e.g., six degrees of freedom) electromagnetic tracker. The femoral motion sensor 38 is attached to the femoral frame 22 that is positioned on the distal femur. The tibial motion sensor 50 is attached to the tibial frame 24 that is placed on the shin (tibia). The femoral frame 22 is placed over the distal femur such that rubber covered pegs (e.g., contact pads 42) on the interior of the frame surround the medial and lateral epicondylar eminences. The opening of the femoral frame 22 is increased prior to placement on the femur and when released, pressure is applied to the femur by the femoral frame 22, holding it in place. A strap that goes under the femur helps secure the femoral frame 22. The patient is in a seated position when the femoral frame 22 is positioned by the operator such that the femoral motion sensor 38 is above the epicondylar axis of the femur. Different sized femoral frames 22 accommodate different sized knees.
The tibial frame 24 is placed over the anterior crest of the tibia 44 such that the tibial motion sensor 50 is located on the flat surface of the tibia just medial to the crest. A guide (e.g., placement guide 52) is used to assist the operator in placing the tibial frame 24. The tip of the guide is placed on the tibial tuberosity such that the distal distance of the tibial frame 24 from the knee is consistent. A strap (e.g., tibial securing mechanism 46) wraps around the calf and secures the tibial frame 24 to the tibia 44.
During measurements, outputs of the electromagnetic motion tracker are the six degree-of-freedom translations and orientations of the tibial motion sensor 50 relative to the femoral motion sensor 38. The preferred orientation output of the motion tracker is in the form of Euler Parameters (quaternions). The measured orientation data is converted into a rotation matrix designated as “A” in
Referring now to
In Stage 1 (
In Stage 2 (
In Stage 3, the tibia 44 is moved through its dynamic passive range of motion. This may include flexion-extension from terminal extension to˜70 degrees, internal external-rotation, varus-valgus rotation, and anterior-posterior translation. The output of Stage 3 is Cardan angles and translation of the tibia 44 (e.g., the tibial orthogonal coordinate system) relative to the femur 30 (e.g., the femoral orthogonal coordinate system). One or more of the outputs are in coordinates relative to/in the femoral orthogonal coordinate system.
With reference general to
Stage 2 moves the knee into terminal extension (e.g., for the laxity test described above, when the subject is sitting on a plinth, a therapist, for example, would move the leg to terminal extension). Motion tracker output of the femoral motion sensor 38 and tibial motion sensor 50 at this static position is used to define the remaining axes of the femoral orthogonal coordinate system. A vector is created from an origin of the femoral orthogonal coordinate system to an origin of the tibial motion sensor 50. The cross product between the femoral orthogonal coordinate system x-axis and the vector between the femoral orthogonal coordinate system and the tibial motion sensor 50 frame origin defines the y-axis of the femoral orthogonal coordinate system. The y-axis points anteriorly from the femur. The cross-product between the femoral orthogonal coordinate system x-axis and y-axis defines femoral orthogonal coordinate system z-axis. The z-axis approximately acts along the long axis of the femur and points in the proximal direction. A rotation matrix from the femoral motion sensor 38 to the femoral orthogonal coordinate system is then defined. This rotation matrix, along with the origin of the femoral orthogonal coordinate system in femoral motion sensor 38 coordinates, defines the location and orientation of the femoral orthogonal coordinate system relative to the femoral motion sensor 38. This is designated “B” in
In the Stage 2 terminal extension position, a tibial orthogonal coordinate system is defined. The tibial orthogonal coordinate system is coincident with the femoral coordinate system with its origin translated distally a set distance from the femoral orthogonal coordinate system along the z-axis of the femoral coordinate system. The origin location and orientation of the tibial orthogonal coordinate system relative to the tibial motion sensor 50 is then determined. This is designated “C” in
Motion of the tibial orthogonal coordinate system relative to the femoral coordinate system, E, during the passive motion of Stage 3 is used to calculate joint laxity including the dynamic flexion/extension angle, internal/external rotation, anterior/posterior translation, and varus/valgus rotation of the tibia 44 relative to the femur 30. The algorithm details and mathematical equations used in these determinations/calculations are illustrated in
As illustrated in
As illustrated in
With respect to the measurements and calculation of KAoR, current techniques for searching for two KAoR axis points (e.g., one medial, one lateral) are performed at a high level, where relative motion for all points in the search space is calculated and then the minimum is found. Rather than resolving the points using an orthogonal coordinate system as in the first embodiment (e.g., see
Although the algorithm of the second embodiment is described in connection with the knee arthrometer 200, the knee arthrometer 20 described above can likewise be used in conjunction with the algorithm of the second embodiment. Additionally, the algorithm of the second embodiment can be used for measuring knee laxity as described above in the first embodiment, as well as for measuring dynamic functional tests (e.g., step-up/squat as shown in
In Stage 1 of the algorithm of the second embodiment, the determination of the values for the KAoR search space are determined as described above. The rotation matrix “A” as described above is calculated, and points of knee axis rotation are found (see
In Stage 2, the rotation matrix “B” as described above and the rotation matrix “A” (at stage 2 terminal extension) are calculated. The ultimate output from Stage 2 is the solution of the rotation matrix “C” as described above.
In Stage 3, the rotation matrix “A” (at each time step of Stage 3 acquisition) is calculated, and the rotation matrix “D” and the rotation matrix “E” as described above are solved. From Stage 3, a vector from knee to tibia is calculated, and a projection of the knee to tibia vector onto a knee axis (x-, y- and/or z-axes) is performed.
As described above, the KAoR is the axis where the tibia rotates around the femur during motion. The KAoR anatomically lies close to an axis in the femur that passes through the medial and lateral epicondyles. Tests conducted with test subjects using knee arthrometer 200 were conducted as follows. The femoral frame 220 was placed on a leg (e.g., 280) of a test subject such that the five (rubber tipped) posts (e.g., 221) were placed around each of the protruding medial and lateral epicondyles of the subject to create a circle target area. The center of the circle target area serves as a starting point for the KAoR search space (see, e.g., Stage 1 in
In testing (e.g., during Stage 3, after defining anatomical coordinate systems in Stages 2 and 3), test subjects wearing the knee arthrometer 200 performed knee movement tasks that included (i) a step-up onto a (e.g., 20 cm) box such as the box 1000 in
The algorithm of the second embodiment defines the KAoR based on (e.g., knee flexion-extension) cycles captured over a 6 second period (e.g., in Stage 1). Sensor measurements from a weight bearing anatomical position were used to define any remaining orthogonal knee axes (e.g., during Stage 2). Standing in anatomical position is essentially putting the leg in terminal extension. There are two ways of acquiring the above-described y-axis, depending on whether subject is sitting on a plinth for laxity or standing for dynamic functional tests (e.g., squatting/step-up).
Stage 1 and Stage 2 are basically the same for laxity and dynamic functional measurements, except as follows. For laxity measurements, the test subject typically sits, whereas in the dynamic functional measurements the test subject typically stands. Stages 1 and 2 are used to determine the anatomical coordinate system based on knee flexion/extension, for example. Stage 3 measures motion of the tibia bone relative to the femur bone using the coordinates defined in Stages 1 and 2. For the laxity test, Stage 3 measures passive motion while a therapist manipulates the limb of the test subject (e.g., in the form of a Lachman's test or similar procedures or acquiring the passive envelope of motion for the knee). For the dynamic functional test, tibiofemoral motion is measured during functional tasks as described above (e.g., squat, etc.).
As an example of how the above-described arthrometer device can be used to measure tibiofemoral motion during functional movements, test subjects performed 3 cycles of each task. The entire data collection, including determination of the KAoR, was then repeated resulting in a total of 6 cycles for each task. Total test time for each test subject was less than 15 minutes. Step-up and squat cycles as described above were extracted from the motion data and time normalized. Ensemble averages of 3D knee motion for each subject provided input to a principal component analysis of the three squat tasks. The results from the test subjects (e.g., measured knee rotations during the step-up task) were within one standard deviation of knee rotations measured on patients using known dual-fluoroscopy techniques. The algorithm shown in
In general, IE motion during squatting was dominated by PC1 which peaks at approximately 50% of the squat cycle. IE PC1 scores are greatest for Varus squatting, indicating this task has the largest internal tibia rotation. IE PC1 scores were smallest for Valgus squatting, with some subjects experiencing external rotation (see
From the results, it has been shown that the knee arthrometer 200 and the algorithm of the second embodiment can efficiently and accurately measure tibiofemoral bone motion in a non-invasive, cost effective manner. Differences in knee kinematics were able to be determined in real-time using the knee arthrometer 200 and the algorithm of the second embodiment, representing an improvement over conventional techniques.
In view of the foregoing, it will be seen that the several advantages of the disclosure are achieved and attained. For example, and without limitation, the knee arthrometer 20/200 provides for objective tests of knee laxity and other knee movements described above, as opposed to the current subjective tests for determining knee laxity. The knee arthrometer 20/200 can be used to assess injury to the knee such as tearing of the anterior cruciate ligament. The knee arthrometer 20/200 can replace the Lachman test and/or anterior drawer test with an objective measure. The knee arthrometer 20/200 provides measurement through dynamic 6 degrees-of-freedom motion which is superior to current testing machines which measure only static single degree-of-freedom displacement. These current machines are inaccurate and are not able to quantify dynamic rotational laxity and/or tibiofemoral motion as the knee arthrometer 20/200 is capable of quantifying. The operation of the knee arthrometer 20/200 also is less dependent on sensor placement relative to other existing machines. This provides for increased measurement repeatability (e.g., when measuring knee laxity throughout a treatment regimen).
Other aspects of the invention provide for using the device and techniques described herein for evaluations relating to issues such as (i) muscle spasticity and/or (ii) other impairments such as those associated with (e.g., treatment of) various other disorders (e.g., such as evaluating the impact of ankle foot orthotics on test subjects, where ankle foot orthotics are prescribed to individuals suffering from issues such as foot drop as a result of disorders such as cerebral palsy). For example, muscle spasticity affects millions of people worldwide, but it is very difficult for health care professionals (e.g., physical therapist) to manually assess the severity of a patient's muscle spasticity with accuracy, making it difficult to determine the appropriate treatment. To combat these difficulties, an (e.g., automated) method using (e.g., two) sensors as described herein can be utilized for measurement of a spastic joint angle, thereby making diagnosis and treatment of muscle spasticity easier and more accurate. The Tardieu Scale and Modified Tardieu Scale are clinical measures of muscle spasticity for use with patients with conditions such as neurological conditions, where spasticity is quantified by assessing the muscle's response to stretch applied at given velocities. The quality of the muscle reaction is often velocity dependent. The muscle reaction at specified velocities and the angle at which the muscle reaction occurs are incorporated into the measurement of spasticity using the Modified Tardieu Scale. For example, a conventional assessment using the Modified Tardieu Scale involves manipulating the joint rapidly until the therapist feels a sudden resistance, known as the R1 catch. The physical therapist then eases the joint past its “catching point” slowly. Oftentimes, the physical therapist is trying to determine the joint angle at which the muscle spasticity occurs, but since this joint angle is velocity dependent, it can vary depending on how fast the therapist manipulates the foot. The joint angle can be found by estimating the approximate configuration at which the spasticity occurred and using a goniometer to measure the joint angle at that configuration. However, this method is not very accurate in determining the joint angle, a value that physical therapists use to select and evaluate muscle spasticity treatments. This method is also not able to measure the spastic velocity, a value that potentially could make the assessment more consistent. Accordingly, improvements are needed to improve muscle spasticity assessment.
The device and techniques described herein can realize improvements in muscle spasticity assessment. For example, sensors (e.g., 38, 50) such as those described herein can be used to assess muscle spasticity by conducting a Modified Tardieu Assessment. The algorithms described above in
For comparison, in connection with the above-described knee embodiments/measurements, for the knee motion (e.g., flexion extension to determine flexion axis (KAoR)), accurate determination of KAoR is desired for repeatable and anatomically accurate measurement of knee arthrokinematics with respect to plane motion (e.g., particularly with respect to frontal and transverse plane motion). While the KAoR roughly aligns with the epicondyles, these are difficult to accurately palpate. However, for the ankle, malleoli are easy to palpate and the flexion axis determined with probing the malleoli is sufficient.
The above-described algorithms (e.g., see
Experimental results include the following: assessing multiple trials, the average spastic joint angle for a single individual was 4.663 degrees (dorsiflexion). These values are similar to the estimated joint angle as estimated by a physical therapist (e.g., a joint angle of 5 degrees (dorsiflexion) given by a physical therapist that performed the assessment). The average spastic velocity for the test subject was 226.8 degrees per second. There was a clear signature of the spastic joint angle and velocity in each of the trials performed on a single subject. This clear signature allowed for reliable identification of the joint angle and velocity within the code. This method of determining spastic joint angle and velocity was able to reliably produce a joint angle similar to the one estimated by the physical therapist. It was also able to consistently measure a spastic joint velocity. Because of this, the two-sensor method of determining spastic joint angle and velocity represents a replacement option for a conventional Modified Tardieu Assessment. This method can identify the moment of muscle spasticity, output the spastic joint angle and velocity, and produce a graph of these values, and therefore can assess abnormal muscle reaction using electromagnetic sensors such as those described herein. Placement of the sensors via a rigid attachment system is envisioned, as well as adaptation for different spastic muscles other than the gastrocnemius.
Thus, while muscle spasticity affects millions of people worldwide, the device and method disclosed herein can aid in the assessment and treatment of these people. The device and method disclosed herein can measure and output the joint angle and velocity at the moment of muscle spasticity, in a manner consistent with estimated joint angle values given by a physical therapist, thereby representing an improvement over conventional techniques (of note, the Modified Tardieu assessment is often used to evaluate the efficacy of drugs used to suppress spasticity, such as Botox).
In addition to the above-described practical applications, the device and methods disclosed herein can also be implemented for use in evaluating the effect of an ankle foot orthotic (AFO) on tibiofemoral motion during certain tasks, such as the above-described step-up task using a step-up box. Ankle foot orthoses are commonly prescribed to improve gait in populations such as those with cerebral palsy and other like disorders causing certain (e.g., knee) impairments. An ankle foot orthotic is a support intended to control the position and motion of the ankle, compensate for weakness, or correct deformities, and can be used to support weak limbs, or to position a limb with contracted muscles into a more normal position. An ankle foot orthotic can also be used to control impairments such as foot drop, known to be caused by a various neurologic and musculoskeletal disorders. An ankle foot orthotic supports the lower limb in cases of ankle or knee weakness or spasticity. Reduction or elimination of (e.g., talocrural) motion can be obtained as well as a reduction in (e.g., subtalar) motion. Moreover, an ankle foot orthotic can be modified to reduce tone or maintain neutral alignment and can further minimize varus/valgus with the addition of additional features such as straps/tabs (e.g., a dynamic force strap and/or medial/lateral tabs or other securing mechanism consistent with those described herein). The overall goal of an ankle foot orthotic is to stabilize the foot and ankle and provide toe clearance during the swing phase of gait, which helps decrease the risk of catching the toe and/or falling. A typical ankle foot orthotic creates an L-shaped frame around the foot and ankle, extending from just below the knee to the metatarsal heads of the foot.
However, currently there is limited evidence available on the long term effects of ankle foot orthoses prescriptions or the possible effects of limiting foot and ankle motion on the tibiofemoral joint. This is an important consideration as adults with cerebral palsy are more likely to experience issues such as knee pain and osteoarthritis, resulting in earlier than normal loss of function. The device 20/200 and associated techniques as described herein can be used in conjunction with an ankle foot orthotic in order to investigate the effects of an ankle foot orthotic on patients. The above-described algorithms (see
From the experimental data shown in
In view of the foregoing, it will be seen that the several advantages of the disclosure are achieved and attained, including a portable, inexpensive and quick way to measure, for example, arthrokinematics (e.g., tibiofemoral arthrokinematics), where dynamic joint (e.g., knee) motion can be measured during functional weight bearing tasks. The above-described algorithm(s) allow for quick identification of anatomically-based axes and coordinates. The above-described systems and methods allow for analysis of functional movement during functional tasks including but not limited to stepping tasks and other tasks (e.g., walking), and measurements of joint motion (e.g., including motion at the knee, ankle, and the like). Parameters such as joint angle and velocity at which muscle spasticity occur (e.g., including calf and/or hamstring spasticity) can be measured, for example, at the knee. For example, the ankle can be used to assess calf muscles, while knee flexion/extension can be used to assess hamstring spasticity.
For all of the above-described embodiments and usages, the code and/or obtained sensor data may be stored in a memory of the above-described computer system, and/or in a remote (e.g., cloud) storage system (e.g., in a dedicated database or other centralized storage mechanism). The raw and/or processed sensor data and/or any related graphical or other representations of the data may be processed by the above-described computer system or the like and output for display on a display device such as a TV, monitor, mobile device (e.g., mobile phone or tablet) and the like such that a technician/practitioner/evaluator/therapist/user can view and/or manipulate the data (e.g., the data may be presented in a visual format for presenting certain aspects of the test results, for example as shown in the applicable above-noted figures). For example, a display monitor may be connected (e.g., wired or wirelessly) to the above-described computer system to provide a visual output on the computer system. The computer system may have an operating system with a graphical user interface capable of being used by a user to (i) input, view, execute and/or manipulate the above-described computer code and/or (ii) process the obtained sensor data and any related graphical representations of such data in the manners described above. The operating system may be capable of running software applications such as those described above (e.g., MatLab and the like) for carrying out the above-described techniques and also any necessary post-processing and/or outputting of the obtained sensor data for viewing, such as for viewing by a therapist that is treating/diagnosing a patient/test subject. Additional software for other code/data manipulations and/or for generating other visuals relating to the data may also be present on the computer system.
In the present disclosure, all or part of the units or devices of any system and/or apparatus, and/or all or part of functional blocks in any block diagrams and flow charts may be executed by one or more electronic circuitries including a semiconductor device, a semiconductor integrated circuit (IC) (e.g., such as a processor), or a large-scale integration (LSI). The LSI or IC may be integrated into one chip and may be constituted through combination of two or more chips. For example, the functional blocks other than a storage element may be integrated into one chip. The integrated circuitry that is called LSI or IC in the present disclosure is also called differently depending on the degree of integrations, and may be called a system LSI, VLSI (very large-scale integration), or ULSI (ultra large-scale integration). For an identical purpose, it is possible to use an FPGA (field programmable gate array) that is programmed after manufacture of the LSI, or a reconfigurable logic device that allows for reconfiguration of connections inside the LSI or setup of circuitry blocks inside the LSI. Furthermore, part or all of the functions or operations of units, devices or parts or all of devices can be executed by software processing (e.g., coding, algorithms, etc.). In this case, the software is recorded in a non-transitory computer-readable recording medium, such as one or more ROMs, RAMs, optical disks, hard disk drives, solid-state memory, servers, cloud storage, and so on and so forth, having stored thereon executable instructions which can be executed to carry out the desired processing functions and/or circuit operations. For example, when the software is executed by a processor, the software causes the processor and/or a peripheral device to execute a specific function within the software. The system/method/device of the present disclosure may include (i) one or more non-transitory computer-readable recording mediums that store the software, (ii) one or more processors (e.g., for executing the software or for providing other functionality), and (iii) a necessary hardware device (e.g., a hardware interface).
The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical application to thereby enable others skilled in the art to best utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. Aspects of the disclosed embodiments may be mixed to arrive at further embodiments within the scope of the invention.
As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the disclosure, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
This application claims priority to U.S. provisional application Ser. No. 62/971,704, filed on Feb. 7, 2020, the entirety of which is incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/016872 | 2/5/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62971704 | Feb 2020 | US |
