DEVICE FOR MEASURING FEMUR DISPLACEMENT AND METHOD OF MAKING ORTHOPEDIC MEASUREMENTS DURING A SURGICAL PROCEDURE TO CORRECT A DAMAGED HIP

Abstract

A device for measuring femur bone displacement during total hip arthroplasty includes a base element immovably mounted to the pelvis and a measurement arm, detachably mounted to the base element via a support, and the measurement arm is fitted with a microprocessor computing system with a display screen. The measurement arm includes at least two movable links, serially connected with each other and with support by rotary joints with at least one (and preferably three) degrees of freedom, whereby both movable links are fitted with an accelerometer (preferably a three-axis accelerometer) and/or a magnetic field sensor and/or a gyroscope, preferably forming together an integrated acceleration, magnetic field and gyroscopic sensor unit.

Claims

1.-18. (canceled)

19. A device for measuring femur bone displacement during a surgical procedure to correct a damaged hip, especially during a total hip arthroplasty, includes a base element immovably mounted to the first measured element, and a measurement arm, detachably mounted to the base element via a support, whereby the measurement arm is fitted at least with an accelerometer located in the support and connected with a computing system unit, wherein the measurement arm includes at least two movable links, connected serially to each other and to support by means of rotational joints of at least one degrees of freedom, and both movable links are fitted with an accelerometer and/or a magnetic field sensor and/or a gyroscopic sensor.

20. The device according to claim 19, wherein the measurement arm support is connected with first movable link by means of a Cardan joint or a spherical joint, and the first movable link is connected to second movable link by means of revolute, Cardan or spherical joints, and the first movable link is fitted with microprocessor computing system with a display screen.

21. The device according to claim 19, wherein it is fitted with marker mounted to the femur by means of a screw connection.

22. The device according to claim 20, wherein the second movable link is fitted with indicator of the position of characteristic points of the patient's pelvis or femur or marker.

23. The device according to claim 21, wherein the measurement arm includes movable end link, connected to second movable link by means of a spherical joint or a Cardan joint, detachably connected with marker.

24. The device according to claim 23, wherein the movable end link is fitted with an accelerometer and/or a magnetic field sensor and/or a gyroscopic sensor.

25. The device according to claim 24, wherein the accelerometer, the magnetic field sensor and the gyroscopic sensor form together an integrated sensor unit.

26. The device according to claim 25, wherein a microprocessor computing system, mounted on support or on either movable link of the measurement arm, is fitted with display screen.

27. The device according to claim 19, wherein the second movable link is connected to first movable link by means of a revolute joint.

28. The device according to claim 19, wherein it has a two-piece support consisting of lower support and upper support, connected by means of a joint fitted with a motion locking mechanism.

29. The device according to claim 19, wherein accelerometers (with not more than three axes) are mounted on support and on three movable links.

30. The device according to claim 19, wherein the support is serially connected with at least five movable links and movable end link connected by means of revolute joints with one degree of freedom, whereby a three-axis accelerometer is mounted on at least every other link and the device is fitted with a microprocessor computing system with display screen and control buttons.

31. The device according to claim 30, wherein it is fitted with marker mounted to the femur by means of a screw connection, whereby movable end link is connected to marker by means of a quickly detachable connection.

32. The device according to claim 30, wherein it has a two-piece support consisting of lower support and upper support, connected by means of a joint fitted with a motion locking mechanism.

33. The device according to claim 30, wherein revolute joints constitute local narrowings of the material, where elastic deflections take place.

34. A method of making orthopedic measurements during total hip arthroplasty using the device for measuring femur bone displacement as claimed in claim 30, wherein across the entire range of movement of the measurement arm the angle of axes of all revolute joints to the vertical remains greater than 30.

35. The method according to claim 30, wherein a microprocessor computing system is used to determine, based on the reading of the gravitation vector direction from accelerometers located on adjacent links of the measurement arm, the angular position of revolute joint located between the links and subsequently to determine, based on angular positions of revolute joints, the position of movable end link relative to upper support, whereby the measurement is made at least twice, and the operating surgeonusing the display screen and buttonscontrols such measurement and reads the data indicating the difference between the first and the last position in directions of relevance to the patient.

36. The method according to claim 35, wherein the measurement includes reading of data from the sensors over a certain period of time, during which the patient and the device can be immovable or can be moved by the operating team.

Description

BRIEF DESCRIPTION OF THE DRAWINGS AND EXAMPLES

[0029] For a more complete understanding of the invention, reference should be made to the embodiments presented on the drawing, wherein:

[0030] FIG. 1measurement arm (perspective view) with two movable links,

[0031] FIG. 2view of the bottom horizontal plane of a detail of the arm from FIG. 1,

[0032] FIG. 3measurement arm (perspective view) with three movable links,

[0033] FIG. 4measurement arm (perspective view) with three movable links and a two-piece support, fitted with one three-axis accelerometer on each link and one on the upper part of the support,

[0034] FIG. 5measurement arm (side perspective view) with six movable links and a two-piece support, fitted with seven three-axis accelerometers, one on each link and one on the upper part of the support,

[0035] FIG. 6top perspective view of the measurement arm shown in FIG. 6.

EXAMPLE I(FIGS. 1 AND 2)

[0036] The device for measuring femur bone displacement during total hip arthroplasty includes base element 1 mounted to the pelvis by means of a screw in a manner preventing it from dislocation during the surgical procedure, marker 10 whose displacement relative to the pelvis is measured and which is mounted to the femur by means of a screw connection and measurement arm, detachably mounted to base element 1. The measurement arm includes support 2 mounted to base element 1, movable link I-4 and movable link II-6 with indicator 7. Links 4 and 6 are connected to each other and to the support by means of spherical joint 3. Acceleration sensors, magnetic field sensors and gyroscopic sensors together forming an integrated sensor unit 9 are located on support 2 and on each link 4 and 6. Microprocessor computing system with a display screen 5 and control buttons is mounted on link 4. Its purpose is to compute data provided by sensors and to communicate with the operator (surgeon).

[0037] During the surgical procedure and prior to femoral head dislocation, the surgeon mounts the base to the pelvis and the marker to the femur. Subsequently he/she mounts the measurement arm support to the base and brings the tip of link II to the marker. After pushing a button, the measurement system memorizes the differences between angular positions of each link and the support. In this way, the surgeon determines the marker's position relative to the support, and thus to the base and the pelvis. Subsequently the surgeon removes the measurement arm support from the base and proceeds to replace the hip joint. After replacing the femoral head and the acetabular cup, he/she once again mounts the measurement arm to the base and measures the marker's position in the system immovably connected with the base. Subsequently the surgeon sets link II of the measurement arm in the direction in which he/she wishes to measure displacement (translation, offset) and after pressing the corresponding button the system displays a view of the positional difference (before and after hip replacement) in the selected direction.

EXAMPLE II(FIG. 3)

[0038] The device for measuring femur bone displacement during total hip arthroplasty includes base element 1 mounted to the pelvis by means of a screw in a manner preventing it from dislocation during the surgical procedure, marker 10 whose displacement relative to the pelvis is measured and which is mounted to the femur, preferably by means of a screw connection and measurement arm, detachably mounted to base element 1. The measurement arm includes a support mounted to the base element, movable link I-4, movable link II-6 and movable end link III-11 mounted to the marker 10. The form of the marker corresponds to the form of the base element. The links are connected to each other and to the support by means of spherical joints 3. Acceleration sensors, magnetic field sensors and gyroscopic sensors together forming an integrated sensor unit 9 are located on the support and on each link. Microprocessor computing system with a display screen 5 and control buttons is mounted on link I-4. Its purpose is to compute data provided by sensors and to communicate with the operator (surgeon).

EXAMPLE III(FIG. 4)

[0039] The device includes: base element 1, lower section of support 2, upper section of support 12, measurement arm link 4, measurement arm link 6 with microprocessor computing system located on it with a display screen 5 and control buttons, movable end link 11, marker 10, as well as four three-axis accelerometers 9 mounted on links 12, 4, 6, 10, respectively.

[0040] Both base 1 and marker 10 take the form of a hollow truncated cone with three sharp spikes protruding downwards and are mounted to the bone by means of a centrally located screw. The measurement arm support includes both lower support 2 and upper support 12 which can linearly move relative to each other after releasing securing lever 15. Lower support 2 is connected with base 1 by means of quickly detachable connection 8 taking the form of an incised sleeve with swellings at the end, inserted into a corresponding socket in base element 1. Rotation of the sleeve relative to base element 1 is blocked by pin 16. After inserting sleeve 8 into base 1 the sleeve is protected against sliding out by pushing rod 13 fitted with handle 14 into it. Link 4 of the measurement arm is connected with upper support 12 by means of spherical joint 3, link 6 of the measurement arm is connected with link 4 of the measurement arm by means of revolute joint 17, movable end link 11 is connected with link 6 by means of spherical joint 3. Furthermore, movable end link 11 is connected with marker 10 by means of quickly detachable connection 8, fitted with locking pin 16 and securing rod 13 with handle 14, identically to the connection of lower section of support 2 with base element 1.

[0041] The optional device presented in FIG. 4owing to the division of the support into two elementsallows for positioning these two elements relative to each other in the first phase of the procedure so as to better adjust the device's position to the patient's anatomy.

EXAMPLE IV(FIGS. 5 AND 6)

[0042] The device includes: base element 1, lower support 2, upper support 12, movable links 18, 19, 20, 21, 22 of a measurement arm, microprocessor computing system with a display screen 5 and control buttons, movable end link 11, marker 10, as well as seven three-axis accelerometers 9 mounted on links 12, 18, 19, 20, 21, 22, 10, respectively.

[0043] Both base element 1 and marker 10 take the form of a hollow truncated cone with three sharp spikes protruding downwards and are mounted to the bone by means of a centrally located screw. The measurement arm two-piece support includes both lower support 2 and upper support 12 which can linearly move relative to each other after pressing securing lever 15. Lower support 2 is connected with base 1 by means of quickly detachable connection 8 taking the form of an incised sleeve with swellings at the end, inserted into a corresponding socket in base element 1. Rotation of the sleeve relative to base element 1 is blocked by pin 16. After inserting sleeve 8 into base 1 the sleeve is protected against sliding out by pushing rod 13 fitted with handle 14 into it. To upper support 12 is mounted the measurement arm including links 18, 19, 20, 21, 22 and movable end link 11 all connected with one another and the upper part of the support by means of revolute joints 23 and forming a serial kinematic chain. Upper support 12, links 18, 19, 20, 21, 22 and movable end link 11 are made of plastic as a single piece, while revolute joints 23 take the form of local narrowings of the material, where elastic deflections take place. To link 21 is mounted microprocessor computing system with display screen 5 and control buttons. Movable end link 11 is connected with marker 10 by means of quickly detachable connection 8, fitted with locking pin 16 and securing rod 13 with handle 14, identically to the connection of lower section of support 2 with base element 1.

[0044] Increasing the number of movable elements improves measurement accuracy. With six movable elements 18, 19, 20, 21, 22 and 11 a kinematic chain with 6 degrees of freedom is formed. The operated limb constitutes a free rigid link suspended in space, with 6 degrees of freedom of movement: 3 linear movements along axes x, y, z and 3 rotational movements around said axes, which means that the measuring arm with a system of six elements ensures the greatest accuracy of intraoperative measurements.