Source: http://patents.com/us-10130495.html
Timestamp: 2019-10-16 17:15:13
Document Index: 515685213

Matched Legal Cases: ['Application No. 08', 'Application No. 2009', 'Application No. 1101893', 'Application No. 07', 'Application No. 08', 'Application No. 08', 'Application No. 60', 'Application No. 60']

US Patent # 1,013,0495. Prosthetic ankle and foot combination - Patents.com
United States Patent 10,130,495
Moser , et al. November 20, 2018
Prosthetic ankle and foot combination
A prosthetic ankle and foot combination has an ankle joint mechanism constructed to allow damped rotational movement of a foot component relative to a shin component. The mechanism provides a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistances, and with independent variation of damping resistances in the plantar-flexion and dorsi-flexion directions. An electronic control system coupled to the ankle joint mechanism includes at least one sensor for generating signals indicative of a kinetic or kinematic parameter of locomotion, the mechanism and the control system being arranged such that the damping resistances effective over the range of motion of the ankle are adapted automatically in response to such signals. Single and dual piston hydraulic damping arrangements are disclosed, including arrangements allowing independent heel-height adjustment.
Moser; David (Hampshire, GB), Sykes; Andrew John (Surrey, GB), Harris; Graham (Hampshire, GB), Lang; Stephen Terry (Hampshire, GB), Abimosleh; Fadi (Springboro, OH), Zahedi; Mir Saeed (London, GB)
Blatchford Products Limited
Blatchford Products Limited (Hampshire, GB)
Family ID: 1000003657667
14/823,645
US 20150351938 A1 Dec 10, 2015
13150694 Jun 1, 2011 9132023
12035717 Jul 26, 2011 7985265
11956391 Nov 5, 2013 8574312
60891075 Feb 22, 2007
60869959 Dec 14, 2006
Current CPC Class: A61F 2/6607 (20130101); A61F 2/68 (20130101); A61F 2220/0033 (20130101); A61F 2002/30359 (20130101); A61F 2002/5006 (20130101); A61F 2002/5018 (20130101); A61F 2002/5033 (20130101); A61F 2002/5035 (20130101); A61F 2002/5036 (20130101); A61F 2002/5038 (20130101); A61F 2002/5043 (20130101); A61F 2002/6614 (20130101); A61F 2002/6621 (20130101); A61F 2002/6642 (20130101); A61F 2002/6657 (20130101); A61F 2002/6854 (20130101); A61F 2002/704 (20130101); A61F 2002/708 (20130101); A61F 2002/74 (20130101); A61F 2002/745 (20130101); A61F 2002/748 (20130101); A61F 2002/764 (20130101); A61F 2002/7625 (20130101)
Current International Class: A61F 2/66 (20060101); A61F 2/68 (20060101); A61F 2/74 (20060101); A61F 2/76 (20060101); A61F 2/70 (20060101); A61F 2/30 (20060101); A61F 2/50 (20060101)
37637 February 1863 Parmelee
2470480 May 1949 Fogg
2490796 December 1949 Gettman et al.
2541234 February 1951 Fulton
2657393 November 1953 Haller
2699554 January 1955 Comelli
2843853 July 1958 Mauch
2851694 September 1958 Valenti
3871032 March 1975 Karas
4010829 March 1977 Naito et al.
4051558 October 1977 Vallotton
4212087 July 1980 Mortensen
5030239 July 1991 Copes
5044360 September 1991 Janke
5383939 January 1995 James
5913901 June 1999 Lacroix
5957981 September 1999 Gramnas
6033440 March 2000 Schall et al.
6080197 June 2000 Chen
6398817 June 2002 Hellberg et al.
6443993 September 2002 Koniuk
6517585 February 2003 Zahedi et al.
6863695 March 2005 Doddroe et al.
7341603 March 2008 Christensen
7507259 March 2009 Townsend et al.
7611542 November 2009 Bourne et al.
7883548 February 2011 Lang et al.
7985265 July 2011 Moser et al.
8246695 August 2012 Mosler
9132023 September 2015 Moser
2002/0052663 May 2002 Herr et al.
2002/0082712 June 2002 Townsend et al.
2002/0138153 September 2002 Koniuk
2004/0044417 March 2004 Gramnas
2004/0054423 March 2004 Martin
2004/0064195 April 2004 Herr
2004/0236435 November 2004 Chen
2005/0015157 January 2005 Doddroe et al.
2005/0109563 May 2005 Vitale et al.
2005/0192677 September 2005 Ragnarsdottir et al.
2005/0267601 December 2005 Chen
2006/0069448 March 2006 Yasui
2006/0069449 March 2006 Bisbee, III et al.
2006/0235544 October 2006 Iversen et al.
2006/0249315 November 2006 Herr et al.
2007/0043449 February 2007 Herr et al.
2007/0073514 March 2007 Nogimori
2008/0004718 January 2008 Mosler
2008/0262635 October 2008 Moser et al.
2008/0281435 November 2008 Abimosleh et al.
2008/0300692 December 2008 Moser et al.
2008/0306612 December 2008 Mosler
2012/0130508 May 2012 Harris et al.
2014/0039645 February 2014 Moser et al.
2014/0067086 March 2014 Moser et al.
101518473 Sep 2009 CN
818 828 Oct 1951 DE
21 01 303 Jun 1972 DE
0 549 855 Mar 1996 EP
0 948 947 Oct 1999 EP
1 068 844 Jan 2001 EP
643734 Sep 1950 GB
2 234 907 Feb 1991 GB
2 305 363 Apr 1997 GB
2 328 160 Feb 1999 GB
59183747 Oct 1984 JP
59189843 Oct 1984 JP
2001-514925 Sep 2001 JP
2004-506480 Mar 2004 JP
2008-536614 Sep 2008 JP
2009-515628 Apr 2009 JP
WO 93/06795 Apr 1993 WO
WO 96/25898 Aug 1996 WO
WO 99/00075 Jan 1999 WO
WO 00/76429 Dec 2000 WO
WO 02/15826 Feb 2002 WO
WO 03/086245 Oct 2003 WO
WO 2006/112774 Oct 2006 WO
WO 2007/027808 Mar 2007 WO
WO 2007/054736 May 2007 WO
WO 2008/071975 Jun 2008 WO
WO 2008/103917 Aug 2008 WO
WO 2012/104591 Aug 2012 WO
Office Action for European Application No. 08 730 531.4 dated Feb. 7, 2017. cited by applicant .
"Anatomic and Biomechanical Characteristics of the Ankle Joint and Total Ankle Arthroplasty", Total Ankle Arthroplasty, Dec. 5, 2005, Springer Vienna, ISBN 978-3-211-21252 (print) 978-3-211-27254-1 (online), pp. 25-42. cited by applicant .
Combined Search and Examination Report for Great Britain Application No. GB1201875.0 dated Apr. 12, 2012. cited by applicant .
Endolite Global--Echelon VT Foot--Prescription [online][retrieved May 7, 2012]. Retrieved from the Internet: <URL: http://www.endolite.co.uk/products/feet/echelon_vt/echelon_vt_foot.html&g- t; 1 page. cited by applicant .
Furman, Bess; "Progress in Prosthetics" U.S. Department of Health, Education, and Welfare; 1964. cited by applicant .
Hayes, W. C. et al.; "Leg Motion Analysis During Gait by Multiaxial Accelerometry: Theorectical Foundations and Preliminary Validations", Journal of Biomechanical Engineering, vol. 105 (1983) 283-289. cited by applicant .
Hydraulik Ankle Unit Manual; Mauch Laboratories, Inc., Mar. 1988. cited by applicant .
International Search Report and Written Opinion for International Application No. PCT/GB2007/004785, dated Apr. 29, 2008. cited by applicant .
International Search Report and Written Opinion for International Application No. PCT/GB2012/000112, dated Apr. 24, 2012. cited by applicant .
International Search Report and Written Opinion for International Application No. PCT/US2008/054741, dated Jul. 2, 2008. cited by applicant .
Michael, J. et al.; "Hip Disarticulation and Transpelvic Amputation: Prosthetic Management"; Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles, 2.sup.nd edition, Ch. 21B; 1992. cited by applicant .
Morris, J. W.; "Accelerometry--A Technique for the Measurement of Human Body Movements", Journal of Biomechanics (1973) 726-736. cited by applicant .
Murphy, Eugene F.; "The Swing of Walking with Above-Knee Prostheses" Bulletin of Prosthetics Research, Veterans Administration; Spring 1964. cited by applicant .
Office Action for Japanese Application No. 2009-551033 dated Sep. 11, 2012. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated Jul. 30, 2013. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated Jul. 5, 2012. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated Jun. 18, 2010. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated May 10, 2011. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated Sep. 16, 2013. cited by applicant .
Office Action for U.S. Appl. No. 11/956,391; dated Sep. 18, 2009. cited by applicant .
Office Action for U.S. Appl. No. 12/035,717; dated Apr. 21, 2010. cited by applicant .
Office Action for U.S. Appl. No. 12/035,717; dated Aug. 5, 2009. cited by applicant .
Office Action for U.S. Appl. No. 13/150,694, dated Dec. 17, 2014. cited by applicant .
Office Action for U.S. Appl. No. 13/150,694, dated Dec. 30, 2013. cited by applicant .
Office Action for U.S. Appl. No. 13/150,694, dated Dec. 4, 2012. cited by applicant .
Office Action for U.S. Appl. No. 13/150,694, dated Jul. 19, 2013. cited by applicant .
Office Action for U.S. Appl. No. 13/150,694, dated May 9, 2014. cited by applicant .
Office Action for U.S. Appl. No. 13/364,786, dated May 22, 2013. cited by applicant .
Office Action for U.S. Appl. No. 14/073,394; dated Jan. 28, 2014. cited by applicant .
Roylance, David; "Engineering Viscoelasticity" Department of Materials Science and Engineering, Massachusetts Institute of Technology; Oct. 24, 2001. cited by applicant .
Search Report for Great Britain Application No. 1101893.4 dated May 11, 2011. cited by applicant .
Segal, et al.; "Kinematic Comparisons of Transfemoral Amputee Gait Using C-Leg and Mauch SNS Prosthetic Knees;" The Journal of Rehabilitation Research and Development, vol. 43, No. 7; pp. 857-870; dated Nov./Dec. 2006; Figure 3. cited by applicant .
Sowell, T.T.; "A preliminary clinical evaluation of the Mauch hydraulic foot-ankle system"; Prosthetics and Orthotics International; vol. 5, pp. 87-91; 1987. cited by applicant .
Starker, Felix et al.; "Remaking the Mauch Hydraulic Ankle", Capabilities, vol. 18 No. 1, Winter 2010; Northwestern University. cited by applicant .
Wagner, Edmond M.; "Contributions of the Lower-Extremity Prosthetics Program", Artificial Limbs: A Review of Current Developments; National Academy of Sciences National Research Council; May 1954. cited by applicant .
Office Action for European Application No. 07 848 527.3 dated Feb. 25, 2014, 6 pages. cited by applicant .
Office Action for European Application No. 08 730 531.4 dated Mar. 21, 2014, 4 pages. cited by applicant .
Office Action for European Application No. 08 730 531.4 dated Jun. 17, 2016, 3 pages. cited by applicant .
Decision, IPR2015-00640, U.S. Pat. No. 8,740,991 B2, dated Jul. 31, 2015, 29 pages. cited by applicant .
Decision, IPR2015-00642, U.S. Pat. No. 8,574,312 B2, dated Jul. 31, 2015, 25 pages. cited by applicant .
Decision, IPR2015-00641, U.S. Pat. No. 8,574,312 B2, dated Jul. 31, 2015, 29 pages. cited by applicant .
Office Action for U.S. Appl. No. 14/051,775 dated Nov. 25, 2014. cited by applicant .
Office Action for U.S. Appl. No. 14/051,775 dated Jun. 12, 2015. cited by applicant .
Office Action for U.S. Appl. No. 15/227,514 dated Apr. 26, 2017, 21 pages. cited by applicant .
Winter, David A.; Kinematics 1.3.2 and Kinetics 1.3,3; Biomechanics and Motor Control of Human Movement, Fourth Edition; 2009; 3 pages. cited by applicant.
Primary Examiner: Watkins; Marcia
This is a continuation of U.S. application Ser. No. 13/150,694, filed Jun. 1, 2011, which is a continuation of U.S. application Ser. No. 12/035,717, filed Feb. 22, 2008, which claims the benefit of Provisional Application No. 60/891,075 filed Feb. 22, 2007. U.S. application Ser. No. 12/035,717 is a continuation-in-part of U.S. application Ser. No. 11/956,391 filed Dec. 14, 2007, which claims the benefit of Provisional Application No. 60/869,959 filed Dec. 14, 2006. The entire contents of such applications are incorporated by reference in the present application.
1. A prosthetic ankle joint assembly comprising a proximal mounting interface, a distal mounting interface, and a joint mechanism interconnecting the proximal and distal mounting interfaces and constructed to allow damped rotational movement of the distal mounting interface relative to the proximal mounting interface about a medial-lateral joint flexion axis, wherein: the joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistance associated with ankle motion in a dorsi-flexion direction; the ankle joint assembly further comprises a control system coupled to the ankle joint mechanism and having sensors for generating signals indicative of kinetic and kinematic parameters of locomotion; the joint mechanism and the control system are arranged such that the damping resistance effective over said range of motion and associated with motion in the dorsi-flexion direction is adapted automatically in response to the signals; and wherein the control system is arranged to generate signals indicative of a first speed of locomotion and of a second speed of locomotion which is higher than the first speed of locomotion, and to cause the damping resistance in the direction of dorsi-flexion to be set to a first level when the speed of locomotion is at the first speed of locomotion and to be set to a second level when the speed of locomotion is at the second speed of locomotion, wherein the first level is higher than the second level.
2. The assembly according to claim 1, arranged such that damping resistance is a predominant resistance to ankle joint flexion over said part of said range of ankle motion.
3. The assembly according to claim 1, wherein said at least one sensor of the sensors is an accelerometer mounted on a foot component.
4. The assembly according to claim 1, wherein the control system is arranged such that the damping resistance in the direction of dorsi-flexion is reduced in response to said signals indicating increased speed of locomotion.
5. The assembly according to claim 1, wherein the joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of a foot component and a shin component, the piston and cylinder assembly including at least one adjustable damping control valve arranged to vary a degree of hydraulic damping resistance to said translational piston movement, and wherein the joint mechanism further comprises an actuator coupled to the at least one valve for adjusting the valve during locomotion.
6. The assembly according to claim 1, wherein the ankle joint mechanism is further arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistance associated with ankle motion in a plantar-flexion direction and the ankle joint mechanism and the control system are arranged such that the damping resistance effective over said range of ankle motion and associated with motion in the plantar-flexion direction is adapted automatically in response to said signals, and wherein the control system has a further sensor for generating a further signal indicative of a walking environment and the control system is arranged to cause the damping resistance in the direction of plantar-flexion to be decreased when the signals are indicative of walking down an incline and increased when the signals are indicating of walking up an incline.
7. A prosthetic ankle joint assembly comprising a proximal mounting interface, a distal mounting interface, and a joint mechanism interconnecting the proximal and distal mounting interfaces and constructed to allow damped rotational movement of the distal mounting interface relative to the proximal mounting interface about a medial-lateral joint flexion axis, wherein: the joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistances associated with ankle motion in plantar-flexion and dorsi-flexion directions; the ankle joint assembly further comprises a control system coupled to the joint mechanism and having sensors for generating signals indicative of kinetic and kinematic parameters of locomotion; the joint mechanism and the control system are arranged such that the damping resistance effective over said range of motion and associated with motion in the dorsi-flexion direction is adapted automatically in response to the signals; and wherein the control system is arranged to generate signals indicative of a first speed of locomotion and of a second speed of locomotion which is higher than the first speed of locomotion, and to cause the damping resistance in the direction of dorsi-flexion to be set to a first level when the speed of locomotion is at the first speed of locomotion and to be set to a second level when the speed of locomotion is at the second speed of locomotion, wherein the first level is higher than the second level.
8. The assembly according to claim 7, wherein the control system has a further sensor for generating a further signal indicative of a walking environment and is arranged to generate signals indicative of ground inclination and to cause the damping resistance in the direction of plantar-flexion to be decreased when the signals are indicative of walking down an incline and increased when the signals are indicative of walking up an incline.
9. The assembly according to claim 7, wherein one sensor of the sensors is an accelerometer.
10. The assembly according to claim 7, wherein the control system is arranged such that the damping resistance in the direction of dorsi-flexion is reduced in response to said signals indicating increased speed of locomotion.
11. The assembly according to claim 7, wherein the joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the proximal mounting interface and the distal mounting interface, the piston and cylinder assembly including at least one adjustable damping control valve arranged to vary a degree of hydraulic damping resistance to said translational piston movement, and wherein the joint mechanism further comprises an actuator coupled to the at least one valve for adjusting the valve during locomotion.
12. A prosthetic ankle and foot combination comprising a foot component and an ankle joint mechanism, the ankle joint mechanism including a shin component and being constructed to allow damped rotational movement of the foot component relative to the shin component about a medial-lateral joint flexion axis, wherein: the ankle joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistance associated with ankle motion in a dorsi-flexion direction; the combination further comprises a control system coupled to the ankle joint mechanism and having sensors for generating signals indicative of a kinetic parameter of locomotion and a kinematic parameter of locomotion; the ankle joint mechanism and the control system are arranged such that the damping resistance effective over said range of motion and associated with motion in the dorsi-flexion direction is adapted automatically in response to said signals; wherein the control system is arranged to generate signals indicative of a first speed of locomotion and of a second speed of locomotion which is higher than the first speed of locomotion, and to cause the damping resistance in the direction of dorsi-flexion to be set to a first level when the speed of locomotion is at the first speed of locomotion and to be set to a second level when the speed of locomotion is at the second speed of locomotion, wherein the first level is higher than the second level.
13. The combination according to claim 12, wherein one sensor of the sensors is an accelerometer mounted on the foot component.
14. The combination according to claim 12, wherein the control system is arranged to cause the damping resistance to plantar-flexion to be set to a third level when the speed of locomotion is at the first speed of locomotion and to be set to a fourth level when the speed of locomotion is at the second speed of locomotion, wherein the third level is lower than the fourth level.
15. The combination according to claim 12, wherein the joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the foot component and the shin component, the piston and cylinder assembly including at least one adjustable damping control valve arranged to vary a degree of hydraulic damping resistance to said translational piston movement, and wherein the joint mechanism further comprises an actuator coupled to the at least one valve for adjusting the valve during locomotion.
16. A prosthetic ankle and foot combination comprising a foot component and an ankle joint mechanism, the ankle joint mechanism including a shin component and being constructed to allow damped rotational movement of the foot component relative to the shin component about a medial-lateral joint flexion axis, wherein: the joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistances associated with ankle motion in plantar-flexion and dorsi-flexion directions; the ankle joint assembly further comprises a control system coupled to the joint mechanism and having sensors for generating signals indicative of kinetic and kinematic parameters of locomotion; the joint mechanism and the control system are arranged such that the damping resistance effective over said range of motion and associated with motion in the dorsi-flexion direction is adapted automatically in response to the signals; and the control system is arranged to generate signals indicative of a first speed of locomotion and of a second speed of locomotion which is higher than the first speed of locomotion, and to cause the damping resistance in the direction of dorsi-flexion to be set to a first level when the speed of locomotion is at the first speed and to be set to a second level when the speed of locomotion is at the second speed of locomotion, wherein the first level is higher than the second level.
17. The combination according to claim 16, wherein one sensor of the sensors is an accelerometer mounted on the foot component.
18. The combination according to claim 16, wherein the control system is arranged to cause the damping resistance to plantar-flexion to be set to a third level when the speed of locomotion is at the first speed of locomotion and to be set to a fourth level when the speed of locomotion is at the second speed of locomotion, wherein the third level is lower than the fourth level.
19. The combination according to claim 16, wherein the joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the distal mounting interface and the proximal mounting interface, the piston and cylinder assembly including at least one adjustable damping control valve arranged to vary a degree of hydraulic damping resistance to said translational piston movement, and wherein the joint mechanism further comprises an actuator coupled to the at least one valve for adjusting the valve during locomotion.
Amongst other known prosthetic ankle systems is that of U.S. Pat. No. 3,871,032 (Karas). This system contains a damping device having a dual piston and cylinder assembly with tappet return springs acting continuously to return the ankle to a neutral position. EP-A-0948947 (O'Byrne) discloses a prosthetic ankle having a ball-and-socket joint with a chamber filled with a silicone-based hydraulic substance, the joint having a visco-elastic response. In one embodiment, the chamber contains solid silicone rubber particles suspended in a silicone fluid matrix. US2004/0236435 (Chen) discloses a hydraulic ankle arrangement with adjustable hydraulic damping and resilient biasing members mounted anteriorly and posteriorly of an ankle joint rotation axis. In WO00/76429 (Gramtec), a leg prosthesis is described having an ankle joint allowing heel height adjustment by way of a hydraulic piston and linkage arrangement. Elastic components absorb shock during walking. US2006/0235544 (Iversen et al) discloses a hydraulic ankle mechanism with a rotary vane.
The electronically controlled ankle disclosed in WO2003/086245 (Martin) has a magnetorheological (MR) fluid-controlled ankle component. WO2007/027808 (Ossur) discloses an electronically controlled ankle joint in which the angle of foot springs about an ankle joint is altered by means of a motorised coupling.
According to a first aspect of the present invention, a prosthetic ankle and foot combination comprises a foot component and an ankle joint mechanism, the ankle joint mechanism including a shin component and being constructed to allow damped rotational movement of the foot component relative to the shin component about a medial-lateral joint flexion axis, wherein: the ankle joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistances associated with ankle motion in the plantar-flexion and dorsi-flexion directions respectively; the combination further comprises a control system coupled to the ankle joint mechanism having at least one sensor for generating signals indicative of a kinetic and/or kinematic parameter of locomotion and/or walking environment; and the ankle joint mechanism and the control system are arranged such that the damping resistances effective over the said range of motion and associated with motion in the plantar-flexion and dorsi-flexion directions are adapted automatically in response to the said signals. Preferably, the damping resistance is the predominant resistance to ankle joint flexion over at least part of the said range of ankle motion.
Advantageously, the control system is programmed to generate signal indicative of terrain, e.g. ground inclination, and to vary the degree of damping resistance in the direction of both ankle dorsi-flexion and ankle plantar-flexion. Particular benefits are achieved if the damping resistance in the direction of plantar-flexion is automatically decreased when the control system generates signals indicative of walking down an incline and increased when indicative of walking up an incline, compared with a level of resistance in that direction set for walking on the level. Conversely, it is preferable that the control system operates such that the damping resistance in the direction of dorsi-flexion is increased compared with the level walking resistance level in the dorsi-flexion direction when the control system signals are indicative of walking down an incline and decreased when the signals are indicative of walking up an incline.
The control system may also be capable of detecting walking on stairs as another kind of terrain variation. In such a case, the damping resistance may also be automatically adjusted in response to signals generated by the control system, the resistance in the direction of plantar-flexion being decreased when the signals are indicative of walking upstairs and increased when the signals are indicative of walking downstairs.
Another parameter that may be used for altering damping resistance is walking speed (or step period or its reciprocal step rate, commonly referred to as "cadence"). As the speed of walking or cadence value increases, the control system preferably decreases the resistance of the hydraulic damping in the direction of dorsi-flexion. Conversely, when the user is walking more slowly, the resistance in the direction of dorsi-flexion is increased. In addition, resistance in the plantar-flexion direction is increased when walking faster and decreased when walking slower.
Various ways of indicating kinetic or kinematic parameters of locomotion may be used. One preferred sensor is an accelerometer, typically a two-axis accelerometer, mounted in the foot component. It will be appreciated that such an accelerometer can produce signals indicative of foot component inclination, as well as gait characteristics such as acceleration or deceleration at heel strike. Foot component angular velocity can also be measured by processing the sensor output in the control system to integrate the acceleration output over time. Techniques for processing output signals from an accelerometer to obtain kinetic and kinematic parameter data such as those referred to above are set out in Morris, J. W "Accelerometry--A Technique for the Measurement of Human Body Movements", Journal of Biomechanics, 1973, pages 726-736. Additional information is contained in Hayes, W. C et al. "Leg Motion Analysis During Gait by Multiaxial Accelerometry: Theoretical Foundations and Preliminary Validations", Journal of Biomechanical Engineering, 1983, vol. 105, pages 283-289. The content of these papers is incorporated in this specification by reference.
Such a sensor may be used for sensing cadence (step rate) and the amplitude of ankle flexion. Measurement of the piston stroke indicates the magnitude of flexion. Changes to the signal characteristics may be used to indicate indirectly step rate, for example, the time taken to reach a particular flexion angle or, alternatively, measurement of the time taken for the ankle angular velocity to indicate a change from plantar-flexion to dorsi-flexion.
Hydraulic damping resistance is preferably introduced in the prosthesis described above by means of a joint mechanism in the form of a hydraulic piston and cylinder assembly. In the case of this being a linear piston and cylinder assembly, it is connected to an associated linkage arranged to convert between translational piston movement and rotational relative movement of the foot component and the shin component. The piston and cylinder assembly includes at least one damping control valve which is adjustable during locomotion by an actuator coupled to the valve. The valve is arranged such that, when adjusted, it varies the degree of hydraulic damping resistance to the piston movement. Independent control of damping resistance in the directions of dorsi-flexion and plantar-flexion may be achieved by having two such valves with respective associated non-return valves.
In preferred embodiments of the invention, control of the damping resistance is such that, at an angular position within at least part of the range of ankle motion, the resistance can be any of several (e.g. at least three) different levels. Indeed, the resistance is preferably continuously variable. It is possible to maintain the damping resistance, preferably in the case of both resistance to plantar-flexion and resistance to dorsi-flexion, at a set level so long as the walking characteristics indicated by the sensor or sensors of the control system do not change. This means, for instance, that a valve in a hydraulic circuit within the ankle joint mechanism can be adjusted to any of several different positions having respective different orifice areas according to signals produced by the control system and that, once the valve has been adjusted to provide a particular orifice area, no further adjustment of the valve may be needed so long as the walking characteristics or parameters indicated by the sensors do not change. This has advantages in terms of minimising power consumption. However, when power and energy limitations permit it, the damping resistance can be altered on each step such that, for example, the resistance to motion in the direction of dorsi-flexion can be increased as the angle of dorsi-flexion increases, i.e. increasing from a variable resistance level governed by signals generated in the control system in response to sensor outputs, to a higher level of resistance beyond a given dorsi-flexion angle. Different damping resistance relationships to sensed walking characteristics may be used, as follows.
The change in damping resistance may be linearly proportional to a sensed characteristic such as ground inclination or walking speed. This may apply to one or both of resistance in the direction of dorsi-flexion and resistance in the direction of plantar-flexion.
Changes in ground inclination may be sensed indirectly by measuring a gait characteristic such as the timing or duration or specific gait events or phases, e.g. the time taken for the foot to reach a flat-foot state or to stop plantar flexing after heel-strike. In such a case, the resistance to movement in the direction of plantar-flexion may be adjusted to prevent the duration of plantar-flexion exceeding a predetermined maximum. In particular, the maximum plantar-flexion duration allowed is never greater or less than a predefined or programmable time, depending on walking requirements.
The change in damping resistance may also be governed as a function of a gait measurement such as the acceleration recorded at heel-strike. In such a case, the resistance in the direction of plantar-flexion is adjusted to limit the maximum acceleration occurring during the loading response phase of gait to a predetermined or programmed value.
The changes in resistance in the direction of plantar-flexion and dorsi-flexion respectively may be mutually adapted, i.e. according to one another. Thus, in the case of walking down an incline, a decrease in plantar-flexion resistance compared with the value for level walking, may be automatically accompanied by an increase in dorsi-flexion resistance by a predetermined or programmable factor.
According to another preferred scheme of operation, the control system may store a database of damping resistance settings for movement in both dorsi-flexion and plantar-flexion directions, which database is derived from clinical testing data. In this embodiment, a look-up table of settings is stored in the control system memory. The stored data is obtained from test results with a variety of users, rather than values obtained specifically for the individual user.
The sensitivity of changing damping resistance in response to changing walking requirements may be defined in different ways. For instance, the changes in walking requirements may be determined on an individual step-by-step basis. Alternatively, the changes in walking requirement may be determined based on a measured average of a previous number of steps of a specific variable such as gait speed and inclination or other measured gait variable. The changes in walking requirements may be subdivided into bands defining response sensitivity. For instance, walking speed may be subdivided into cadence (step-rate) bands or ranges. Similarly, changes to ground inclination may be subdivided into bands of a few degrees at a time. The limits of such bands may be uniformly distributed over the range of the relevant parameter or characteristic, or non-uniformly. Such limits may be predetermined or programmable, or they may be continuously or step-wise self-adaptive, such adaptation being based on clinical testing with a variety of amputees or upon responses measured with an individual user. Another aspect of the invention provides a lower limb prosthesis comprising a shin component, a foot component, and a joint mechanism interconnecting the foot and shin components and arranged to allow damped pivoting of the foot component relative to the shin component about a medial-lateral joint flexion axis during use, wherein the joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the foot component and the shin component, the piston and cylinder assembly including an adjustable damping control valve arranged to vary the degree of hydraulic damping resistance to the said translational piston movement at least insofar as such movement is associated with flexion of the foot component relative to the shin component, and wherein the prosthesis further comprises a valve control system including at least one sensor for generating signals indicative of a kinetic or kinematic parameter of locomotion and, coupled to the control valve, an actuator for adjusting the valve, the control system being arranged to adjust the valve during locomotion thereby to vary the hydraulic damping resistance of the joint mechanism to flexion in response to the signals from the sensor. The invention also includes a prosthetic ankle and foot combination and a prosthetic ankle joint each having the above features.
As described above, the way in which damping resistance may be varied can be programmable so that, for instance, the control system is arranged to have a "teach" mode in which a prosthetist may select and store damping resistance settings for different speeds of walking and different terrains (e.g. ascending stairs or an incline, descending stairs or an incline, and walking on level ground), these settings being determined during test sessions with the amputee. Alternatively, a self-tuning system may be used whereby control parameters are automatically adjusted towards specific values under known walking conditions. As a further alternative, settings may be stored in a database or as a look-up table derived from clinical tests on a variety of patients, the settings having related to sensed or computed parameters. A combination of these methods may be used.
In accordance with the principle outlined above, the valve control system may be arranged to generate a signal indicative of a kinetic or kinematic parameter which varies during individual gait cycles and to drive the valve so as to increase and decrease hydraulic resistance to flexion during each of a plurality of gait cycles, the direction, magnitude and timing of such changes in resistance being dynamically adjustable during locomotion. In one embodiment the system operates such that the hydraulic resistance to dorsi-flexion is increased to a maximum value during the stance phase of the gait cycle, the time at which the maximum value is reached being altered in the stance phase, for example occurring later in the stance phase, when the signal indicative of terrain indicates walking down stairs or up an incline compared with the time at which the maximum value is reached when the said signal indicates walking on level ground.
According to another aspect of the invention, a prosthetic ankle and foot combination comprises a foot component and a hydraulic ankle joint mechanism, the ankle joint mechanism including a proximal shin component and being constructed to allow damped rotational movement of the foot component relative to the shin component about a medial-lateral joint flexion axis, wherein the ankle joint mechanism is arranged to provide (a) continuous hydraulically damped ankle flexion during walking relative to a present reference angular position of the foot component with respect to the shin component and (b) adjustment of the reference angular position. The adjustment of the reference angular position may also be damped, preferably hydraulically, and may be user adjustable. Once the reference angular position has been set, the range of rotational movement of the foot component relative to the shin component is preferably a single fixed range. Within that range or at least a major part of it, adaptive damping control is effected, the relationship between damping resistance levels being defined according to changing requirements of locomotion such as terrain (surface inclination and/or stairs, and walking speed or cadence). Within the range of rotational movement, damping resistance is preferably continuously variable or variable in a series of steps such that, typically, whilst the walking requirements remain constant, a programmed damping resistance level in a given direction (plantar-flexion, dorsi-flexion, or both) is maintained throughout the gait cycle and remains constant from step-to-step. It is also possible for dynamic damping of flexion during walking to be manually varied rather than automatically adaptively varied.
The mechanism may comprise a second valve element defining another orifice through which hydraulic fluid is driven when the first piston element moves in response to rotation of the foot component relative to the shin component, the first and second valves being constructed and arranged such that the first valve and the second valve independently determine the damping resistance of the mechanism to flexion in the dorsi-flexion and plantar-flexion directions respectively.
Accordingly, in one preferred embodiment, the ankle joint mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the shin component and the foot component; the piston and cylinder assembly comprises first and second piston elements which are substantially coaxial and substantially aligned with the shin axis; the first piston element has a neutral position in the assembly and is located in a cylinder so as to drive hydraulic fluid through an orifice when moved from the neutral position in response to pivoting of the foot component from a preset reference angular position relative to the shin component, the fluid flow through the orifice damping the said pivoting; and the second piston element is arranged to drive hydraulic fluid through a locking valve in response to pivoting of the foot component relative to the shin component, which valve can be closed to lock the second piston element thereby to set the said reference angular position corresponding to the neutral position of the first piston element. In this way it is possible to allow dorsi-plantar-flexion of the ankle over a limited range of movement with largely damped, as opposed to resilient, resistance to motion, resulting in an ankle which is able easily to flex under load according to changing activity requirements without generation of high reaction moments which would otherwise cause discomfort and compromise the function of the prosthesis.
The position of the foot component relative to the shin component at a given position of the first piston element may be independently adjusted by opening the normally closed locking valve and causing the second piston element to move in the assembly until a required relative orientation of the foot component and the shin component is reached, whereupon the locking valve is closed again. The "given position" of the first piston element is referred to above as the neutral position. Although this so-called neutral position may be defined by resilient elements in the mechanism biasing the first piston element towards a particular position in the cylinder, the "neutral" position may be notional in the sense that it is not defined by any characteristic or feature of the piston and cylinder assembly as such, but may be merely a position selected by the user or prosthetist for the purpose of setting the reference angular position by adjusting the position of the second piston element.
In the case of one piston element being slidable in a bore formed in the other, the former element may comprise two pistons interconnected by a piston rod which slides in the bore as well as being slidable within the cylinder referred to above. The space between the two pistons contains a dividing wall dividing the space into two variable volume chambers interconnected by a first passage containing a valve element. This valve element is typically drivable over a range of positions by a servo motor or a stepper motor under electronic control in order to vary the area of the orifice and, therefore, the resistance to movement of the first piston element and, consequently, rotation of the ankle joint during use (i.e. during locomotion, whether it be walking, running, climbing or descending ramps and stairs, and so on). Such an arrangement may be duplicated, albeit with oppositely directed respective non-return valves as well, for servo or stepper motor controlled damping resistances independently for the directions of dorsi-flexion and plantar-flexion, as will be described in more detail below.
In this preferred embodiment, the so-called "other" piston element constitutes at least part of the dividing wall, both piston elements being slidable within a common cylinder. Conveniently, both piston elements are dual piston components, each having two pistons interconnected by a respective piston rod, the cylinder being a transverse wall dividing the space between the two pistons of the piston element having the above-mentioned internal bore. This transverse wall contains a valved second passage linking the chambers formed on opposite sides of the transverse wall. It is preferably this second passage with which the locking valve is associated, the first passage or passages containing the damping orifice.
In other variants of the invention, differential control of the resistance to flexion in the dorsi direction and plantar direction respectively may be provided using, for instance, two damping control valves in respective passages which function in parallel, i.e. one allowing the flow of fluid in one direction from a variable volume chamber which varies in size with movement of the first piston element, and the other allowing the flow of fluid in the opposite direction to the variable volume chamber. Non-return valves may be used to define the direction of flow in each case. Separate electrical actuators may be provided for each damping control valve to allow dynamic variation of resistance to flexion in each direction. Alternatively, one or both may be manually presettable. It is particularly preferred that the valve control system is adapted such that the actuator drive signal fed to the output control valve actuator for dorsi-flexion damping control causes the damping control valve to increase the orifice area as the indicated walking speed increases, thereby decreasing dorsi-flexion damping resistance with increasing walking speed and vice-versa.
The invention also includes a prosthetic ankle and foot combination comprising a foot component and an ankle joint mechanism, which mechanism includes a proximal mounting interface, the joint mechanism being arranged to allow limited damped pivoting of the foot component relative to the mounting interface about a medial-lateral joint flexion axis during use, wherein: the mechanism comprises a hydraulic piston and cylinder assembly and an associated linkage arranged to convert between translational piston movement and rotational relative movement of the proximal mounting interface and the foot component; the piston and cylinder assembly comprises first and second piston elements which are substantially coaxial and substantially aligned with the shin axis; the first piston element has a neutral position in the assembly and is located in a cylinder so as to drive hydraulic fluid through an orifice when moved from the neutral position in response to pivoting of the foot component from a preset reference angular position relative to the proximal mounting interface, the fluid flow through the orifice damping the said pivoting; and the second piston element is arranged to drive by hydraulic fluid through a locking valve in response to pivoting of the foot component relative to the proximal mounting interface, which valve can be closed to lock the second piston element thereby to set the said reference angular position corresponding to the neutral position of the first piston element. As an alternative to setting the reference angular position via a hydraulic device, other mechanical adjustment devices may be used to adjust the position of the ankle interface (pyramid device or shin clamp) to accommodate changes to heel height.
According to yet a further aspect of the invention, a prosthetic ankle joint assembly comprises a proximal mounting interface, a distal mounting interface, and a joint mechanism interconnecting the proximal and distal mounting interfaces and constructed to allow damped rotational movement of the proximal mounting interface relative to the distal mounting interface about a medial-lateral joint flexion axis during use, wherein the joint mechanism is arranged to provide a continuous hydraulically damped range of ankle motion during walking with dynamically variable damping resistances associated with ankle motion in the plantar-flexion and dorsi-flexion directions respectively; the ankle joint assembly further comprises a control system coupled to the joint mechanism having at least one sensor for generating signals indicative of a kinetic and/or kinematic parameter of locomotion; and the joint mechanism and the control system are arranged such that the damping resistances effective over the said range of motion and associated with motion in the plantar-flexion and dorsi-flexion directions are adapted automatically in response to the said signals.
Independent control of plantar-flexion damping resistance assists knee stability in above-knee amputee locomotion by managing the ground reaction vector orientation with respect to the knee joint centre specifically to diminish the flexion moment about the knee. This function is useful when for example walking down a ramp; a lower level of resistance to plantar-flexion allows the foot to realign to the walking surface without generating substantial reaction moments which would otherwise cause the knee to become unstable.
According to yet a further variant, a lower limb prosthesis comprises a shin component, a foot component, a joint mechanism interconnecting the foot and shin components and arranged to allow limited damped pivoting of the foot component relative to the shin component about a medial-lateral flexion axis during locomotion, and a control system having at least one sensor for generating signals indicative of at least one characteristic of locomotion, the joint mechanism including a device for adjusting, the limit of dorsi-flexion of the foot component relative to the shin component during locomotion. Typically the control system is arranged to generate signals indicative of walking on stairs or on an incline and to alter the dorsi-flexion limit to increase the maximum degree of dorsi-flexion permitted by the joint mechanism when such signals are produced compared with the degree of dorsi-flexion permitted by the adjusting device when signals are generated indicative of walking on level ground. A further adjusting device may be included for adjusting the degree of damping resistance of the joint mechanism in the directions of dorsi-flexion and plantar-flexion respectively in response to signals from the control system, the control system and the joint mechanism being arranged such that the dorsi-flexion limit and the damping resistances are independently adjustable during locomotion.
Running through the body of the dynamic damping piston 24 so as to interconnect the two annular chambers formed between this piston element and the heel-height adjusting piston element 26 are two passages 34 arranged in parallel, each with a damping control valve 36. (Only one passage and one such control valve is shown in FIG. 1.) Valves 36 are each in the form of a tapered valve element threaded in the body of the dynamic damping piston element 24 and driven by a respective electrical actuator in the form of a servo motor 38 to allow variation in the area of the orifice created by the penetration of the valve element of the valve 36 into the passage 34. (Again, only one servo motor 38 appears in FIG. 1.) It will be appreciated that operation of the servo motors 38 varies the resistance to fluid flow between the outer annular chambers 32A, 32B and hence the resistance to movement of the first piston element 34 with respect to the second piston element 26. Non-return valves 39 (one of which is shown in FIG. 1) located in the passage 34 confine fluid flow in the respective passages to flow in response to dorsi-flexion and plantar-flexion of the ankle joint so that the orifice area of one valve 36 governs the damping resistance in the direction of dorsi-flexion and that of the other valve 36 governs resistance in the direction of the plantar-flexion.
The latter function of the control system 52 is indicated diagrammatically in FIGS. 2 and 3 insofar as signals derived from the sensors 52A, 52B within the valve control system 52 are fed to a microprocessor control unit 52M which processes the received signals to provide indications of surface inclination and walking speed, specifically determining an "inclination factor" and a "walking speed factor". The microprocessor calculates a required resistance level in the form of valve positions for the control valves 36 and provides corresponding output signals on first and second outputs 52MA, 52MB of the control unit 52M to the actuators 38 for the dynamic damping control valves 36 to drive their valve elements to the required positions.
The programming of the microprocessor unit 52M is such that the valve controlling resistance to rotation in the direction of dorsi-flexion is driven towards its open position as the indicated walking speed increases or when an upwardly inclined surface is indicated, and towards its closed position when the indicated speed decreases or when a downwardly inclined surface is indicated (i.e. in order that the resistance to flexion of the ankle is decreased at higher walking speeds and when walking up an incline).
In a similar manner, the microprocessor causes the valve that controls resistance to rotation in the direction of plantar-flexion to move towards its open position as the indicated walking speed decreases or when a downwardly inclined surface is indicated, and to move towards its closed position when the indicated speed increases or when an upwardly inclined surface is indicated (i.e. in order that the resistance to flexion of the ankle is decreased at slower walking speeds and when walking down an incline).
Operation of the ankle joint mechanism for the purpose of heel-height adjustment will now be described in more detail. It will be understood that the inner piston element, i.e. the heel-height adjustment piston element 26, acts as a movable mechanical reference which can be adjusted to compensate for changes in heel-height. The locking valve 40 is normally set locked so that the inner piston element 26 is locked with respect to the cylinder 22. This is the situation during the so-called "dynamic response" mode of the valve control system, the dynamic damping control valve 36 being operated as described above during this mode. In a second mode of the valve control system, a "heel-height setting" mode, the dynamic damping control valve 36 is driven to its fully closed position thereby locking the outer piston element 24, i.e. the dynamic damping piston element, with respect to the inner piston element 26 so that the other moves in concert with it. In other words, the spacing between the two piston elements 24, 26 is fixed. During the heel-height setting mode, the locking valve 40 is driven to its open position, allowing the inner piston element 26 to move in the cylinder 22 in response to rotational forces applied to the foot 10. In this way, providing the damping piston element 24 is set to a predetermined position with respect to the heel-height adjustment piston element 26 beforehand, the foot 10 can be set to a required angle with respect to the shin component 14, whereupon the valve 40 is closed and normal operation of the valve control system in the dynamic response mode can be resumed.
Functioning of the ankle joint mechanism is largely the same as described above in connection with the embodiment of FIG. 1, with reference to FIGS. 2 to 4, the main differences being that only the resistance to dorsi-flexion is dynamically variable and that the pivot axis 20A is a dynamic flexion axis only rather than an axis serving for both dynamic flexion and heel-height adjustment. Instead, in this second embodiment, there is a separate heel-height adjustment axis 56A. One particular feature that this embodiment has in common with the first embodiment is that movement of the two pistons is cumulative in terms of the associated pivoting movement of the foot component with respect to the shin component 14.
Summarizing, it will be seen that, in each of the above-described prostheses, at least one piston is being used to alter alignment when the prosthesis is not being used for locomotion activities, the alignment preferably being controlled electronically to reduce the risk of incorrect adjustment. A second piston, preferably under microprocessor control, is used to adapt damping characteristics of the prosthesis by way of a variable yielding action in real-time according to changing walking conditions, in particular walking speed and surface inclination. Although electronically controlled valves have been disclosed above, the valves may be manually manipulated or adjusted. Linked valve control means ensure, preferably, that the dynamic control valve is closed and not allowed to open when the heel-height adjustment valve is open.
Associated with a proximal extension 24E of the piston 24 is a piston-stroke range control collar 160. The axial position of this collar 160 is adjustable in response to operation of a linear electro-mechanical actuator 162 fixed to the housing 114. The collar 160 is shaped to provide at least a dorsi-flexion end-stop for the piston 24, thereby limiting the dorsi-flexion of the foot component 10 relative to the housing 114.
The microprocessor system forming part of the control system 52 processes the signals from the sensors to adjust the two dynamic control valves 136 and the piston-stroke range control collar 160 by driving actuators 138, 162 during locomotion thereby to dynamically adjust dorsi-flexion and plantar-flexion damping resistances and flexion range, in particular to dynamically adjust the dorsi-flexion end stop. It will be noted that independent control of damping resistances and end-stop is possible.
Dorsi-flexion damping resistance may be controlled separately from plantar-flexion damping resistance. Dorsi-flexion resistance is decreased with higher speeds of locomotion. In this embodiment, plantar-flexion resistance is increased with speed of locomotion. With regard to the adjustable dorsi-flexion end-stop provided by the range control collar 160 and its associated actuator 162, the control system 52 is arranged to adjust the range control collar 160 downwardly (i.e. in the distal direction) when signals are produced in the control system indicating, e.g. descent of stairs. Further adjustments of the range of flexion are preferably performed in response to other indications of changing terrain.
In yet a further embodiment, using the arrangement shown in FIG. 1, the locking valve 40 for locking the reference piston 26 may be used to facilitate incremental movement of the reference piston 26 during plantar-flexion and dorsi-flexion phases of locomotion. The forces produced during locomotion are used, in this case, physically to move the reference piston 26, valve 36 (FIG. 1) being closed at appropriate times. The control system 52 coordinates valve actuation and monitors the reference piston position.
The bypass passage 34 appearing in FIG. 7 has its non-return valve 39 oriented to allow the flow of hydraulic fluid from the lower chamber 32B to the upper chamber 32A. The other bypass passage (not shown) has its non-return valve oriented in the opposite direction. Accordingly, one of the passages 34 is operative during dorsi-flexion and the other during plantar-flexion. When the locking valve 32 is open, continuous yielding movement of the foot component 10 relative to the ankle joint mechanism 16 about the flexion axis 20A is possible between dorsi-flexion and plantar-flexion limits defined by the abutment of the piston with, respectively, the lower wall and the upper wall of the cylinder containing the piston. The level of damping for dorsi-flexion and plantar-flexion is independently and automatically presettable by the respective adjustable-area orifices by means of a control system (not shown in FIG. 7) like that described above. The control system, as in the embodiments described above with reference to FIGS. 1 and 5, has a sensor 52A in the form of an accelerometer mounted on the foot keel 12A.
It will be understood, therefore, that the angular range magnitude is fixed by the construction and geometry of the ankle-foot prosthesis and its hydraulic joint mechanism. The degrees of dorsi-flexion and plantar-flexion respectively are altered by the alignment of the shin component connection, as described above. It will be understood that alternative alignment interfaces can be used to adjust the positions of the dorsi-flexion and plantar-flexion limits. For instance, an anterior-posterior tilt alignment interface may be provided between the ankle unit 16 and the foot keel 12. Such an interface is provided by a further embodiment of the invention, as will now be described with reference to FIGS. 8 and 9.
Referring to FIG. 8, this further embodiment of the invention takes the form of a two-part ankle joint-mechanism having an ankle unit body 16A which, as before, mounts a shin connection interface 170 for adjustable connection to a shin tube (not shown), and a foot mounting component 16B which incorporates a foot connection interface for receiving a pyramid connector of the known kind on a foot keel (not shown in FIG. 8). The joint mechanism is identical to that described above with reference to FIG. 7 with the exception that the flexion and piston rod connection pivots 20, 48 are housed in the foot mounting component 16B rather than directly in the keel of a prosthetic foot. In the case of FIG. 8, the drawing is a cross-section on a vertical anterior-posterior plane parallel to but spaced from the axis of the shin connection interface 170 and the cylinder housing the piston 24. Consequently, the bypass passage permitting hydraulic fluid flow from the lower chamber 32B to the upper chamber 32A of the cylinder (corresponding to dorsi-flexion, i.e. clockwise rotation of the foot mounting component 16B relative to the ankle unit body 16A about the pivot 20) appears in full lines, whereas the common linking passage 178 between the control valve 176 and the upper chamber 32A is shown with dotted lines.
The ankle unit trunnion 16AA is shown more clearly in FIG. 9. Also visible in FIG. 9 are two valve adjustment spindles 36A, 36B which are accessible on the anterior face of the ankle unit body 16A. These form part of the dynamic damping control valves 36 (or flow resistance adjusters), one of which appears as valve 36 in FIG. 8, and permit continuous electronic adjustment of damping resistance to ankle flexion in the dorsi- and plantar-flexion directions respectively. The servo motors 38 are shown by dotted lines in FIG. 9 in order that the positions of the valve spindles 36A, 36B can be more clearly seen.
When the spool member 182 is in its open position, it allows fluid flow between the bypass passages 34 and the common passage 178 communicating with the upper chamber 32A of the cylinder. Conversely, when the push button 184 is released, the spool member 182 moves to prevent fluid flow between the upper cylinder chamber 32A and the bypass passages 36. It follows that when the pushbutton 184 is released, the ankle unit is hydraulically locked at whichever flexion angle existed at the moment of release. The pushbutton 184 has a detent that allows it to be maintained in its depressed position. This is the normal position of the locking valve 176, in which flow of hydraulic fluid through the bypass passages 36 (FIG. 8) is allowed, with the result that the ankle unit allows yielding dorsi- and plantar-flexion.
Whether the ankle unit is in the form of a two-part assembly for detachable mounting to a foot component, as described above with reference to FIGS. 8 and 9, or in the form of an ankle joint mechanism directly pivotally mounted to a prosthetic foot, as described above with reference to FIG. 7, the joint mechanism allows yielding ankle flexion as shown diagrammatically in FIG. 10. The dotted lines denote plantar-flexion (PF) and dorsi-flexion (DF) limits of a mechanical hydraulic yielding range of flexion of a shin component 56 with respect to a foot component 10. The magnitude of the angular range is fixed by the geometry of the joint mechanism and its damping piston and cylinder assembly. Although in these preferred embodiments, the range magnitude is fixed, the position of the limits with respect to a neutral position indicated by the chain lines in FIG. 10 can be altered by adjusting the alignment of the shin component relative to the foot component using one of the alignable connection interfaces described above. In this way, the flexion range may be biased anteriorly or posteriorly from the position shown in FIG. 10 to create a larger range of motion in either the PF or DF direction. Typical alignment settings result in a dorsi-flexion limit at 2 degrees to 6 degrees tilt anteriorly with respect to the neutral axis, dependent on the foot toe spring stiffness in particular, and the plantar flexion limit at 4 degrees to 10 degrees tilt posteriorly with respect to the neutral axis (shown by the chain lines in FIG. 10).
Providing the manual hydraulic lock is not activated, the unit continuously allows yield in the dorsi-flexion direction (and plantar-flexion direction) up to the dorsi-flexion limit during walking and standing.
The combination described with reference to the FIGS. 7 to 11 is an foot-ankle system that is continuously allowed to yield over a limited range in plantar-flexion and dorsi-flexion. The yielding action is provided by a hydraulic damper coupled to conventional foot elements (i.e. keel, carrier and independent carbon fibre composite heel-toe springs). The ankle is, therefore, free to flex continuously over a limited plantar- and dorsi-flexion range via the hydraulic damper with minimal interference from elastic elements during walking and standing. During standing, the relative positions of the hip, knee and ankle joint centres are such that substantially normal standing postures can be maintained, the moments about each joint being automatically balanced thereby creating limb stability. Moreover, the self-aligning action of the foot-ankle system facilitates improved control of energy transfer between limb segments during locomotion, the user's hip joint being the main driver and the knee joint being the main facilitator of mechanical energy transfer. This biomimetic method of stabilisation of standing stability and balance control has a further advantage in that, while standing on ramps, owing to the yielding action of the hydraulic components, there are no significant reaction moments generated around the ankle which may cause imbalance between joints and discomfort. Since, owing to the limited range of hydraulic yielding, the ankle is free to move, adaptation for walking and standing on inclined surfaces and changes to footwear with various heel heights is achieved automatically. A further advantage of the system is a smoother more progressive transition during roll-over over a variety of terrains.
In all the control embodiments described above, it is preferable that functional parameters such as plantar-flexion and dorsi-flexion resistance levels, profiles (i.e. resistance alteration gradients with respect to time) and timing, as well as dorsi-flexion range of motion are programmably adjustable. Each of the embodiments may include within the control system 52 a receiver for communication with a wireless programming device (not shown). Wireless programming may be performed by a prosthetist during an amputee walking test and tests over different terrains (e.g. stairs and inclined surfaces) to adjust control parameters which may or may not be pre-selected by means such as a look-up table to suit the particular amputee's specific locomotion style and the mechanical properties of attached foot and knee components. Similarly, adaptive control parameters which determine how the above functional parameters are continuously adapted during locomotion and use, such as walking speed, walking surface gradient, and activities such as stair climbing and descent, are also adjustable under prosthetist control, using control software. Specified and/or measured adaptive control parameter values may be entered. This may be achieved using a teaching/playback system. It is also possible to incorporate a self-tuning system whereby control parameters are automatically adjusted towards specific values under known walking conditions. The changes in damping response may be predefined and contained in a database stored in a storage device forming part of the control system 52, the database being drawn from clinical experience and tests with a plurality of amputees. Teaching/playback, database, and self-tuning look-up methods may be used in combination.
The timing of control of valve function and/or other associated dorsi-flexion limiting means are preferably coordinated during locomotion to occur at specific phases of the gait cycle determined from system sensors and using finite state control principles. In this way the control system can be readily adapted to optimize the mechanical characteristics of the prosthesis, thereby to optimize the biomechanics of locomotion.
FIG. 12B illustrates damping control valve actuation from a base resistance level B, a fully closed position D in which the associated piston is locked. The shaded region A illustrates an adjustment range for commencement of the locked state during the stance phase, resistance to flexion in the dorsi-flexion direction increasing following heel strike to a time A which is at a predetermined time interval after a trigger point C represented by the zero-crossing of the shin angular velocity characteristic prior to heel strike HS. Lock commencement at time A is delayed when the control system 52 detects walking on an incline or stairs (compared to level walking). Thus, flexion is restricted and/or limited angularly with respect to heel strike. In effect, gait-cycle by gait-cycle actuation of the valve as shown in FIG. 12B provides variable dorsi-flexion angular limitation. The dotted line in FIG. 12B indicates alteration of the resistance gradient in response to sensed locomotion characteristics.
Over at least the major part of the range of ankle movement, the damping resistance in the direction of dorsi-flexion remains substantially constant during each step of the locomotion cycle. However, the level of damping resistance is allowed to change from step to step according to signals generated in the control system in response to sensor outputs. The same applies to the damping resistance in the direction of plantar-flexion. In general, at any point within the range of ankle movement, the damping resistance can be set to any of several different values in response to such control system signals. Indeed, the level of damping resistance in both dorsi-flexion and plantar-flexion directions is continuously variable over a range of resistance level values, the limits of the resistance level range being determined by the maximum and minimum orifice areas of the dynamic damping control valves.
The control system may be programmed to alter damping resistance from step to step in a number of different ways. In one configuration the change in damping resistance in the directions of both dorsi-flexion and plantar-flexion are linearly related to a sensed parameter. For instance, as shown in FIG. 13A, the damping control valves can be adjusted linearly between their open and closed positions according to surface inclination. The damping levels and the valve settings indicated in FIG. 11A at A represent the dynamic plantar-flexion/dorsi-flexion balance set for level walking.
Referring to FIG. 13B, the control system may be programmed such that the optimum dorsi-flexion and plantar flexion damping levels are unequal for level walking. Such levels are determined by programming the control system to suit an individual amputee's preferred walking characteristics. As shown in the example of FIG. 13B, the optimum level of resistance to rotation in the direction of dorsi-flexion is less than that in the direction of plantar-flexion. However, according to the requirements of the amputee, the opposite may also be true.
Either or both the resistance in the direction of dorsi-flexion and the resistance in the direction of plantar-flexion may be non-linearly related to the sensed surface inclination. In the example shown in FIG. 13C, the response in the direction of plantar-flexion is non-linearly related to surface inclination, while the response in the direction of dorsi-flexion is linear. Either one or both of plantar-flexion and dorsi-flexion responses may be non-linear or linear according to the value of the sensed parameter.
It will be noted that in each of the above examples, the resistance in the direction of plantar-flexion increases with increasing upward surface inclination and decreased with increasing downward surface inclination, whereas the resistance in the direction of dorsi-flexion varies in the opposite sense.
Typical responses in damping resistance to changes in walking speed are shown in FIG. 13D. As will be seen, at a normal walking speed or cadence, the resistance in the direction of dorsi-flexion in this example is higher than the resistance to plantar-flexion. As walking speed or cadence increases, the resistance in the direction of plantar-flexion increases whilst that in the direction of dorsi-flexion decreases. The converse changes apply at slower walking speeds or cadences. In this case, the variation in damping resistances is linear. Non-linear functions may also be programmed in the control system.
The control system may be programmed to follow different sequences for the purpose of adjusting valve openings in response to changes in sensed or computed parameters. Referring to FIG. 14A, a first typical sequence for adapting valve openings to sensed walking surface inclination involves the steps of reading sensor signals indicative of kinetic or kinematic parameter values (step 200), computing the walking surface inclination, preferably on a step-by-step basis, the inclination being compared to preset inclination bands (step 202), whereupon the system then determines whether a change in inclination has occurred (step 204). If no change has occurred, the sequence loops back (loop 206) to repeat the determination of surface inclination and comparison steps 202, 204, this process continuing until a change is detected. When a change is detected, required damping resistance levels are computed, e.g. by reference to a look-up table mapping resistance levels to parameter bands (step 208), whereupon actuating signals are fed to the servo motors (or stepper motors) connected to the valves which control damping resistance to ankle rotation in the direction of plantar-flexion and dorsi-flexion respectively (steps 210A, 210B).
In the preferred embodiments of the invention, optimum levels of damping resistance in the directions of plantar-flexion and dorsi-flexion are obtained to provide an adaptive dynamic balance which suits an individual amputee's gait in different situations and for different walking requirements. The nature of the adaptive dynamic balance is that it has the effect of acting like a brake and an accelerator on the motion of the shin. Optimising these effects for different walking situations produces a more stable gait, placing less physiological demand on the amputee to control proximal joints, i.e. the knee and/or the hip through muscular control, and also with reduced stress at the stump interface.
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