PROSTHETIC UNIT

Abstract: A prosthetic unit in the form of an ankle unit comprises an ankle block (11) having a first end (12) and a second end (13): the first end (12) being adapted for attachment to, or for incorporation in, a socket for securing over a leg stump so as to establish a first longitudinal axis (L1), and the second end (13) defining a first bore (17) to define an ankle axis (18) substantially perpendicular to the first axis (L1) and a second, locating, bore (19); a foot member (20) defining a working surface (21) and a third bore (Y) and a second longitudinal axis (L3) defined by, or by way of, the working surface (21); stop means (24, 25, 40) whereby the foot member (20) can be aligned relative to the ankle block (1) in one of at least two positions; and a pivot member extending through the first bore (17) and third bore (Y) to enable the foot member (20) to rotate about the ankle axis (18). The stop means (24, 25, 40) comprises: a series of at least two recesses (24, 25) on the foot member (20), each recess (24, 25) being equidistant from the third bore (Y); and a locking member (40) extending through the second, locating, bore (19) and demountably engaging one of the recesses (24, 25) in the series so as to maintain the second longitudinal axis (L3) at a fixed angular alignment relative to the first longitudinal axis (L1). Typically the stop means comprises limit stops on either the foot member (20) or the ankle block (11) and an abutment on either the ankle block (11) or the foot member (20); the foot member (20) being free to pivot about the ankle axis (18) over an angle defined by the path over which the abutment can travel from a limit established by a first limit stop to that established by a second. If necessary the limit stops or the abutment or both can incorporate dashpot or cushioning means to avoid excessive impact between abutment and end stop.

Description: PROSTHETIC UNIT TECHNICAL FIELD This invention relates to a prosthetic joint device it is particularly, though not exclusively, one for use in relation to a lower limb. BACKGROUND ART If a person suffers the loss of all or part of a lower limb it is common for that person to be equipped with a prosthetic device to enable them to walk and sit. With the advent of modern materials and design and fabrication techniques a person equipped in this way can participate in athletic and other sporting activities. To this end it is known for a prosthetic device to be provided specially designed or adapted for use in relation to a particular activity. DISCLOSURE OF IN VΈNTION According to the present invention there is provided a prosthetic unit in the form of an ankle unit comprising an ankle block (11) having a first end (12) and a second end (13): the first end (12) being adapted for attachment to, or for incorporation in, a socket for securing over a leg stump so as to establish a first longitudinal axis (LI), characterised in that the second end (13) of the ankle block (11) defines a first bore (17) to define an ankle axis (18) substantially perpendicular to the first axis (LI) and a second, locating, bore (19); and the unit further includes a foot member (20) defining a working surface (21) and a third bore (Y) and a second longitudinal axis (L3) defined by, or by way of, the working surface (21); stop means (24, 25, 40) whereby the foot member (20) can be aligned relative to the ankle block(ll) in one of at least two positions; and a pivot member extending through the first bore (17) and third bore (Y) to enable the foot member (20) to rotate about the ankle axis (18). According to a first preferred version of the present invention the stop means (24, 25, 40) comprises: a series of at least two recesses (24, 25) on the foot member (20), each recess (24, 25) being equidistant from the third bore (Y); and a locking member (40) extending through the second, locating, bore (19) and demountably engaging one of the recesses (24, 25) in the series so as maintain the second longitudinal axis (L3) at a fixed angular alignment relative to the first longitudinal axis (LI). Typically the stop means comprises limit stops on either the foot member (20) or the ankle block (11) and an abutment on either the ankle block(ll) or the foot member (20); the foot member (20) being free to pivot about the ankle axis (18) over an angle defined by the path over which the abutment can travel from a limit established by a first limit stop to that established by a second. The limit stops or the abutment or both can incorporate dashpot or cushioning means to avoid excessive impact between abutment and end stop. BRIEF DESCRIPTION OF DRAWINGS An exemplary embodiment of the invention will now be described with reference to the accompanying drawing of am ankle prosthesis of which: Figure 1 is a side view of a first component; Figure 2 is a front view in direction A of Figure 1 ; and Figure 3 is an end view in direction B of Figure 1; Figure 4 is a side view of a second component; Figure 5 is a front view in direction C of Figure 4; and Figure 6 is a plan view from beneath in direction D of Figure 4; Figure 7 is a side view of a third component serving to link the first and second components; and Figure 8 shows an assembly of the first, second and third components. MODES FOR CARRYING OUT THE INVENTION Figures 1 to 3 show an ankle block 11 having a first end 12 whereby the block is securely incorporated into a prosthesis member which closely fits a residual limb (in this case a lower limb) of a user so as to define a first longitudinal axis LI. Second end 13 is bifurcated having limbs 14, 15 on either side of recess 16. Bore 17 extends through limbs 14, 15 to define an ankle axis 18 perpendicular to the first longitudinal axis LI. Bore 19 extends through limbs 14, 15 to define an axis X and serves to retain a locking device as will be described hereafter. Figure 4 to 6 shows a foot member 20 having a working surface 21 to which a ground contacting pad can be attached by means of a threaded bore. Bores 22, 23 each serve to accept dowel pins located in a ground locating member so as to resist rotation of the ground engaging member relative to the foot member 20. The working surface 21 defines a longitudinal axis L2. Rolling bore Y extends through the foot member 20 and defines ankle axis L3 . A series of recesses 24, 25 are located on periphery 26 of the member 20. The recesses 24, 25 are identical in form, equidistant from the ankle axis 13 and extend fully across the face 26. The ankle block 11 and the foot member 20 are assembled so that working surface 21 faces away from ankle block 11 and ankle axis 18 is coaxial with axis L3. A pivot pin is then inserted to extend bore 17 and bore 24 so that the foot member 20 is pivotably retained for relative rotation about axis 18. The assembled ankle block 11 and foot member 20 form an ankle unit in which the angular alignment of axis L2 relative to axis LI can be adjusted to suit the user. In this case use is made of a captive locking pin which will now be described with reference to Figure 7. Locking pin 40 has secured near one end 41 a stop washer 42. There is also provided at end 41 a threaded bore 43 in which a tommy bar can be inserted in order to rotate the locking pin 40 as will be described hereafter. At end 44 the locking pin 40 is provided with a threaded bore 45 in which a bolt is mounted to retain a second stop washer once the locking pin 40 is located in bore 19. The locking pin 40 is cut away over part of its length to provided a recess 46. To use the locking pin 40 in the assembled ankle unit the pin 40 is mounted in bore 19 and secured by means of end washer 42 and a further washer retained by a bolt in bore 43. In this way the pin 40 is prevented from moving axially within bore 19 but is readily rotated therein. The user rotates pin 40 until the recess 46 opens into bore 19. The user then selects an appropriate alignment for axis L2 relative to axis LI and corresponding to the alignment of either recess 24 or 25 with bore 19 and moves the foot member 20 relative to the ankle block 11 accordingly. As the recess 46 is presented to the bore 19 during this alignment operation the pin 40 presents no obstruction to the relative movement of foot member 20 and ankle block 11. Once the desired alignment is achieved the user rotates the pin 40 about axis X so as to move the recess 46 out of the bore 19 and replace it with a portion of the pin 40. This portion of the locking pin engages with whichever of recesses 24, 25 lies in the bore 19. Rotation of pin 40 is achieved by means of a small tommy bar inserted in bore 43. The locking pin now serves to prevent any further relative motion between foot member 20 and ankle block 11. When necessary the user can readily realign the foot member 20 and ankle block 11 by rotating pin 40 to cause recess 46 to enter the bore 19 and so disengage the pin 40 from the recess in which it has previously been located, the user then moves the foot member 20 to align the other recess and rotates the locking pin 40 to engage the new recess. Figure 8 shows a user 50 with a leg stump 51 extending below knee 52. The stump 51 has mounted on it a below knee prosthesis 53 comprising a socket 54 of fibre reinforced plastics material which is fabricated to form a close fit around stump 51. The socket 54 is secured to body of the user 50 in a conventional manner to provide for secure usage. In lower end 55 of the socket 54 there is moulded in ankle block 11 (described in connection with Figures 1 to 3) to which is coupled foot member 20 (described in connection with Figures 4 to 6. The assembled prosthesis 53 enables the user 50 to readily establish desired a angle of axis L2 relative to axis LI as described earlier depending on the activity to be undertaken. In an alternative embodiment there is provided an ankle unit similar in most ways to that described in connection with Figures 1 to 8. However in this alternative version the foot member is provided with an extending projection and the ankle block is provided with two stop so that the foot member can freely rotate about axis L3 over a path whose ends are defined by the end stops which serve to limit movement of the projection. This path of free angular movement established by the use of the ends stops is useful for a user who wishes to swim and where the foot member has secured to it, for example, a fin. In either of the embodiments described the limits stops or the abutments fro limiting pivotal movement can incorporate dashpot or cushioning means to avoid excessive impact between abutment and end stop. INDUSTRIAL APPLICABILITY Either described embodiment is directed to facilitating activities of the user especially in an exercising context. The ability to lock the foot unit at a particular angle relative to the longitudinal axis of the rest of the assembly is beneficial for walking. Other activities benefiting from an adjustable arrangement include rowing and skiing.

Claims: CLAIMS 1 A prosthetic unit in the form of an ankle unit comprising an ankle block (11) having a first end (12) and a second end (13): the first end (12) being adapted for attachment to, or for incorporation in, a socket for securing over a leg stump so as to establish a first longitudinal axis (LI), characterised in that the second end (13) of the ankle block (11) defines a first bore (17) to define an ankle axis (18) substantially perpendicular to the first axis (LI) and a second, locating, bore (19); and the unit further includes a foot member (20) defining a working surface (21) and a third bore (Y) and a second longitudinal axis (L3) defined by, or by way of, the working surface (21); stop means (24, 25, 40) whereby the foot member (20) can be aligned relative to the ankle block(ll) in one of at least two positions; and a pivot member extending through the first bore (17) and third bore (Y) to enable the foot member (20) to rotate about the ankle axis (18). A prosthetic unit as claimed in Claim 1 characterised in that the stop means (24, 25, 40) comprises: a series of at least two recesses (24, 25) on the foot member (20), each recess (24, 25) being equidistant from the third bore (Y); and a locking member (40) extending through the second, locating, bore (19) and demountably engaging one of the recesses (24, 25) in the series so as maintain the second longitudinal axis (L3) at a fixed angular alignment relative to the first longitudinal axis (LI). A prosthetic unit as claimed in Claim 2 characterised in that the stop means comprises limit stops on either the foot member (20) or the ankle block (11) and an abutment on either the ankle block(ll) or the foot member (20); the foot member (20) being free to pivot about the ankle axis (18) over an angle defined by the path over which the abutment can travel from a limit established by a first limit stop to that established by a second. A prosthetic unit as claimed in Claim3 characterised in that the limit stops or the abutment or both can incorporate dashpot or cushioning means to avoid excessive impact between abutment and end stop.

Inventors: DIX COLIN, PARSONS ANTHONY JAMES, STURCH RODNEY BRUCE EDWARD, DIX, COLIN, PARSONS, ANTHONY, JAMES, STURCH, RODNEY, BRUCE, EDWARD
Applicants: BYRNE MICHAEL O, DIX COLIN, PARSONS ANTHONY JAMES, STURCH RODNEY BRUCE EDWARD, DIX, COLIN, O'BYRNE, MICHAEL, PARSONS, ANTHONY, JAMES, STURCH, RODNEY, BRUCE, EDWARD
Application year: 1996
Main classification: A61F2
IPC codes: A61F2