WO1992015248A1

WO1992015248A1 - Self-aligning, joint skew compensating goniometer

Info

Publication number: WO1992015248A1
Application number: PCT/US1992/001740
Authority: WO
Inventors: Beth A. Marcus; Bin An
Original assignee: Exos, Incorporated
Priority date: 1991-03-07
Filing date: 1992-03-06
Publication date: 1992-09-17

Abstract

A self-aligning, joint skew and joint axis shift compensating goniometer (20) for measuring a joint angle in a measurement plane including a first, concave member (2) for aligning the goniometer body with the long axis of a first body link segment on one side of a joint, and defining in conjunction with the long axis of the body link segment the measurement plane, and a second member defining a planar surface (9) perpendicular to the measurement plane and generally parallel to the second body link segment on the other side of the joint. The members are pivotally interconnected (7) to allow the members to move in relation to each other as the joint is moved, and the goniometer includes an electronic measurement device (16) for determining the angle between the first and second members to indicate the degree of joint motion.

Description

SELF-ALIGNING, JOINT SKEW COMPENSATING GONIOMETER

RELATED APPLICATION This application is a continuation-in-part of application serial number 665,988, filed on March 1 , 1991.

FIELD OF INVENTION This invention relates to a self-aligning, joint skew and joint axis shift compensating goniometer which accuratel measures joint motion even when the adjacent body link segments are misaligned.

BACKGROUND OF INVENTION

Physicians, physical therapists, occupational therapists and other health professionals measure joint motion in assessing the effects of injury, disease and patient progress. Industrial designers and ergonomists also estimate the range of motion of human joints in designing safe and comfortable equipment and work environments.

The most common type of goniometer is the simple mechanical goniometer, which is basically a protractor with elongated pivoting segments. The user places the segments on the body link segments on either side of the joint to be measured and reads the joint angle directly off the goniometer. This goniometer, however, has flat surfaces or edges which must be aligned visually or lay directly on the body link segments in order to accurately measure the joint angle; it has one contact line with the link segment. If the joint or link segments are uneven or swollen, or the joint axis shifts as the joint moves, or is misaligned due to deformity, the goniometer surfaces will not be or stay in contact with the body link segments. When this happens, the user must estimate the joint angle by projecting the goniometer position by eye onto the body surface.

There have also been attempts to automate the goniometer so that it may be used with electronic measuring equipment. For example, in U.S. Patent No. 4,667,685, there is disclosed a goniometer consisting of a brace mechanism having separate brace sections secured to the arm and forearm and connected together by an external hinge to allow the brace sections to move about a pivot axis in the hinge, which must be aligned with the joint axis. The pivoting motion is measured by one or more potentiometers that have a wiper blade that moves as the link segments move. A similar potentiometer goniometer is disclosed in U.S. Patent No. 4,834,057.

These automated goniometers are large, clumsy devices that must be strapped on to the leg or arm. The pivot point must be manually aligned with the joint pivot axis in an attempt to obtain accurate measurements of joint movement. However, if the goniometer is not properly aligned with the body link segments, its measurement of joint movement is only approximate and the device interferes with the natural movement of the joint. There are many motions of a human joint in addition to the major pivot. These include motion of the joint center of rotation and motion of the pivot axes. If the goniometer does not mirror these freedoms, it will shift with respect to the skeleton and cause error in the angle readings. Many designs do shift and therefore have such error. These devices employ a variety of mechanisms and typically the linkage angles are measured with potentiometers. These potentiometers are usually large and subject to inaccuracies due to wear; they are also inherently noisy and so inaccurate. SUMMARY OF INVENTION

It is therefore an object of this invention to provide a goniometer which is self-aligning and self-centering on the long axis of one body link segment to account for body link segment misalignment.

It is a further object of this invention to provide such a goniometer that does not require the pivot axis to be aligned with the joint axis.

It is a further object of this invention to provide such a goniometer that can accurately measure joint angles even when the link segments are misaligned.

It is a further object of this invention to provide such a goniometer that can accurately measure joint angles even when the joint axis shifts during motion.

It is a further object of this invention to provide such a goniometer that can accurately measure joint angles even when the joints are swollen.

It is a further object of this invention to provide such a goniometer which is simple and easy to use and is extremely accurate.

It is a further object of this invention to provide such a goniometer which can be held in place with at least one hand and need not be strapped on to the body link segments on opposite sides of the joint being measured.

It is a further object of this invention to provide such a goniometer in which the joint angle measurement device is small and not subject to wear.

This invention results from the realization that a truly effective, easy to use goniometer can be achieved by employing one concave member that provides more than one contact line on a body link segment to self-align the goniometer with the long axis of the segment and establish a measurement plane, and a second flat member that lies on the other link segment and projects it onto the measurement plane to account for link segment misalignment (deformity) as well as normal joint axis of rotation movement.

This invention features a self-aligning, joint skew and joint axis shift compensating goniometer for measuring a joint angle in a measurement plane including a first, concave member for aligning with a long axis of a first body link segment on one side of a joint, and defining in conjunction with that axis the measurement plane, and a second member defining a planar surface perpendicular to the measurement plane and generally parallel to a second body link segment on the other side of the joint. The goniometer further includes means for pivotably interconnecting the first and second members to allow the members to move in relation to each other as the joint is moved, and means for determining the angle between the first and second members to indicate the degree of joint motion. The planar surface defined by the second member preferably is wider than the body link segment to extend laterally beyond the second body link segment for projecting the angle of the second segment on to the measurement plane to allow measurement of a skewed second body link segment.

In a preferred embodiment, one or both of the first and second members may move in relation to the other member to provide an adjustable distance between the members to account for different size body link segments to avoid swollen joints so that a plurality of joints may be measured on a person, and the device may be used to measure joint angles on different-sized people.

A means for sliding one member in relation to another may be accomplished by including a body divided into sections for holding each member. Sliding may then be accomplished by including a complimentary sliding joint, for example a dovetail joint, on each body section and each sliding member to provide interlocking sliding arrangements. Preferably, the concave member includes inclined surfaces for providing at least two lines of contact with the surface of the link segment. That may be accomplished with a V-shaped block that sits on the body link segment.

In one embodiment, the goniometer includes a 2-piece body or primary member for holding the flat and concave measurements members. In that case, the means for pivotably interconnecting the members may be accomplished by pivotably fastening together the primary member pieces. There may further be included a gripping portion on one primary member piece for facilitating pivoting. The gripping portion may be accomplished with a thumbwheel. One manner of accomplishing sliding of one member in relation to the other is provided by including a pin on one body section engaged with a slot in the other body section to allow but constrain the sliding motion. A high precision sensor such as a Hall-effect sensor (a non-contact joint angle measurement device) proximate the pivotable interconnection between the members may be provided.

DISCLOSURE OF PREFERRED EMBODIMENT

Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

Fig. IA is an axonometric view of a self-aligning, joint skew and joint axis shift compensating goniometer according to this invention;

Fig. IB is a top plan view of goniometer of Fig. IA;

Fig. 1C is a side view of the goniometer of Fig. IA with a side cover removed showing the arrangement of the electronics in the device. Fig. ID is a schematic view of the measurement plane and plane of projection that helps explain the manner in which the goniometer of this invention allows the measurement of skewed joints?

Fig. 2A is a elevational, partly cross sectional view of the flat member of Fig. IA;

Fig. 2B is an end view of the member of Fig. 2A detailing the dovetail joint for providing interlocking, sliding relationship;

Fig. 3A is an elevational view of the body and other member of Fig. IA;

Fig. 3B is an end view of the body and concave member of Fig. 3A similar to that of Fig. 2B detailing the dovetail joint;

Fig. 3C is an axonometric view of the concave member of Figs. IA, 3A, and 3B illustrating its construction;

Fig. 4A is a side view of an alternative goniometer arrangement including a thumbwheel for providing ease of pivoting;

Fig. 4B is a detail of the thumbwheel and sliding flat member of the goniometer of Fig. 4A;

Fig. 5A is an elevational view of another alternative embodiment of the goniometer of this invention showing an alternative means of providing sliding of the flat member and pivoting between the members;

Fig. 5B is a top plan view of the goniometer of Fig. 5A; Fig. 6A is an elevational view of a flat member and pivoting thumbwheel similar to that of Fig. 4B but which also includes a second thumbwheel for sliding the flat member; and

Fig. 6B is a cross-sectional view of the embodiment of Fig. 6A taken along line B-B.

There is shown in Figs. IA, IB goniometer 20 according to this invention. Goniometer 20 includes main body section 1 to which is slidingly attached concave member 2 having a V-shaped concave section 26. Member 2 is adapted to slide in a direction of arrow 11 on mating surface 22 of body section 1. Side covers 3 and 4 provide access to the interior of section 1 that houses a data-captive switch operated by button 6 and the electronic device used to measure the angle between first sliding member 2 and second sliding member 9. Member 9 itself is interlockingly, slidingly engaged with second body section 8 having engaging surface 24. Projecting, knurled thumb-operated section 26 is provided so that the operator may grasp body 1 in the hand and pivot member 8, and thus member 9 having flat surface 28, with the thumb. Member 8 pivots in relation to member 1 on axis 21.

In Fig. IB, extension 14 of body member 8 fits within body member 1 and is pivotably secured thereto with pin 7. Magnet 15 is glued to section 14 so that it pivots therewith for interacting with Hall-effect sensor 16 mounted in body l to provide an accurate, non-contact, non-wearing means of measuring the angle between members 2 and 9 as an indication of the angle of the joint.

Fig. 1C shows the inside of body 1 of goniometer 20 having cover 4 removed to show that the three wires from Halleffect sensor 16, and two wires from switch 6, run out through cable 127 to a computer or another device for capturing the signal from Hall-effect sensor 16 on operation of button 6 to allow the determination of the angle between measurement members 2 and 9.

Fig. ID illustrates the theory of operation of the goniometer of this invention. One body link segment such as proximal phalanx segment 27 has placed thereon concave member 2. The line at which the inclined surfaces of V-block 26 meet forms, with the axis of proximal phalanx 27, a plane of measurement of the PIP joint connecting the proximal and middle phalanx 29. In the example of Fig. ID, middle phalanx 29 is skewed off at an angle to proximal phalanx 27. Flat surface 28 of block 9 is placed on body link segment 29. Planar surface 28 is perpendicular to measurement plane 23 and generally parallel to second body link segment 29. Surface 28 is wide enough to extend laterally beyond that second body link segment for projecting the angle of the segment onto the measurement plane as shown by line 31 to allow accurate measurement of the flexion angle of the joint. This sliding, pivoting arrangement with one concave member and one flat member allows measurement of the flexion/extension angles of every joint in hand as well as those and other angles of other joints such as the elbow, knee, hip and shoulder. The arrangement shown in Fig. IA provides 115° of flexion and 90° of extension for measuring a wide range of joint movements.

Member 9 need not have a flat surface as long as the portion of the member used to contact the body link segment defines a planar surface. Such an arrangement may be accomplished with flat surface 28 or, alternatively, two members that would each contact a body link segment along a line so that the two lines would define a plane. Such an arrangement could be accomplished with a pair of cylinders or other structural members that rested on a body link segment.

The V-shaped block 2 provides an easy and accurate means for the user to align member 2 with one body link segment. The planar surface 28 of second measurement member 9 provides a means to measure the flexion/extension of a skewed joint. Providing sliding motion between the members allows the device to be used to avoid at abnormally large knuckles and also allows the device to accommodate a variety of patients with different hand sizes, as well as allowing one device to be used to measure all of the finger joints of single patient. The sliding, interlocking arrangement of member 9 with member 8 is shown in more detail in Figs. 2A and 2B. Slot 35 (see Fig. IB) is provided in member 9. Through this slot bolt 10 is threaded into body 8. The head of bolt 10 projects slightly down through this slot so that its motion is limited by shoulders 34 and 34a that act as stops for the sliding movement. Hole 36 is provided for accepting pin 21 that allows the pivoting between member 8 and member 1. Member 9 is provided with an interlocking sliding arrangement on member 8 using dovetail joint 32.

Member 2 is slidingly interlocked with body 1 in the similar fashion as shown in Figs. 3A-3C. Member 2 includes projecting partial dovetail members 44 and 46 that interlock with mating dovetail surface 22 of body member 1 to provide dovetail joint 42. Back ends 4a and 3a of cover members 4 and 3, respectfully, provide a stop at one end to prevent member 2 from sliding off of the surface 22. The lobe at the other end of covers 4 and 3, such as lobe 48, provide a stop at the other end for allowing member 2 to be to and fro on body member 1 to account for body link segments of different lengths and also to provide room for enlarged joints. Because the front part of member 2 towards pivot 21 does not include dovetail sections, when member 2 is slid all the way up against stop 48 it projects right up to pivot 21.

Figs. 4A and 4B detail an alternative embodiment in which thumb wheel 70 is integral with body section 66 having sliding flat member 68. Thumbwheel 70 is fixed with pivot pin 72 to body member 62 having sliding V-block 64. In use, main body member 62 may be grasped by the user who may then use his or her thumb to catch on wheel 70 to pivot body section 66 and member 68 to the desired position.

As shown in Figs. 5A and 5B, the sliding arrangement of the flat block member 86 of goniometer 80 may alternatively be provided by having a single piece member 86 with slot 99 through which pass pins 90 and 92 affixed to thumbwheel 88. Pin 92 also passes through main body section 82 to provide the pivoting action between members 86 and 84 in the direction of arrow 91. Member 86 may then be slid horizontally in the direction of arrow 93, with pins 90 and 92 both guiding and constraining the motion.

Another alternative means of providing the pivoting action and the sliding of the flat members shown in Figs. 6A and 6B. Thumbwheel 109 of goniometer section 100 has elongated protruding section 101 carrying flat block 102. Section 100 is pivotably attached to the main body section of the goniometer carrying the V-block measurement device (not shown) with a pin 111. Smaller concentric thumb wheel 108 rotatable about pin 111 has cables 104 and 106 running around it and around pulley 110 and fixed to block 102 so that rotation of wheel 108 causes block 102 to slide in the direction of arrow 115, while rotation of thumbwheel 109 in the direction of arrow 117 would cause the whole assembly 100 to pivot to in relation to the main body section.

Although specific features of the invention are shown in some drawings and not others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention.

Other embodiments will occur to those skilled in the art and are within the following claims: What is claimed is:

Claims

Claims:

1. A self-aligning, joint skew and joint axis shift compensating goniometer for measuring a joint angle in a measurement plane, comprising: a first concave member for aligning with the long axis of a first body link segment on one side of a joint, and defining in conjunction with that axis the measurement plane; a second member for defining a planar surface perpendicular to the measurement plane and generally parallel to a second body link segment on the other side of the joint; means for pivotably interconnecting said first and second members to allow the members to move in relation to each other as the joint is moved; and means for determining the angle between the first and second members to indicate the degree of joint motion.

2. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 in which said planar surface extends laterally beyond the second body link segment for projecting the angle of the second body link segment onto the measurement plane to allow measurement of a skewed second body link segment.

3. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 further including means for moving one said member in relation to the other.

4. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 3 further including a base section for holding each said member.

5. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 4 in which said base section and said moving member include a complementary sliding joint for providing an interlocking sliding arrangement.

6. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 further including means for sliding both said members in relation to each other.

7. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 in which said concave member includes inclined surfaces for providing at least two lines of contact with the surface of the link segments.

8. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 7 in which said concave member includes a V-block.

9. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 further including a two-piece base section for holding said members.

10. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 9 in which said means for pivotably interconnecting includes means for pivotably fastening together said two base section pieces.

11. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 10 further including a gripping portion on one base section piece for facilitating pivoting.

12. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 11 in which said gripping portion includes a thumbwheel.

13. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 9 further including means for sliding one member in relation to the other.

14. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 13 in which said means for sliding includes a pin on one base section engaged with a slot in the other base section.

15. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 1 in which said means for determining includes a precision sensor proximate said means for pivotably interconnecting.

16. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 15 in which said sensor is a Hall-effect sensor.

17. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 5 in which said sliding joint is a dovetail joint.

18. A self-aligning, joint skew and joint axis shift compensating goniometer, for measuring the angles of joints between body link segments of variable size, in a measurement plane, comprising: a primary member including pivotably-interconnected primary member pieces; a concave member slidingly attached to one said primary member piece for aligning with the long axis of a first body link segment on one side of the joint, and defining in conjunction with that axis the measurement plane; a flat member slidingly attached to another said primary member piece and having a surface perpendicular to the measurement plane and generally parallel to the second body link segment on the other side of the joint; and means for determining the angle between the concave and flat member in the measurement plane to indicate the degree of joint motion.

19. The self-aligning, joint skew and joint axis shift compensating goniometer of claim 10 in which said concave and flat members are slidingly attached to the respective primary member pieces by interlocking, sliding joints.

20. A self-aligning, joint skew and joint axis shift compensating goniometer of claim 19 in which said sliding joints are dovetail joints.