Abstract
The present invention relates to a guide for positioning a resurfacing head implant into the appropriate position and angles on the femur bone. The present invention therefore provides a guide system for an implantable device (e.g. a resurfacing head implant), said guide system comprising a first component arranged to act as a clamp and a second component arranged to interact with the first component to prevent movement of said first component when clamped.
Claims
1. A guide system for an implantable device, said guide system comprising a first component arranged to act as a clamp; and a second component arranged to engage an outer surface of and interact with the first component to restrict or prevent movement of said first component when clamped; wherein the first component comprises at least one actuating portion and at least one jaw portion; wherein the at least one actuating portion and at least one jaw portion each comprises opposing arms arranged either side of a hinge region; and wherein the actuating portion and jaw portion are arranged on either side of the hinge region such that when the actuating portion is compressed the jaw portion expands, and when the actuating portion is relaxed the jaw portion closes.
2. The guide system of claim 1, wherein said first component comprises a proximal region, said proximal region comprising an actuating portion and proximal jaw portion formed by the walls of said first component, said proximal region further comprising a cavity defined by the walls of said first component between the actuating portion and proximal jaw portion and wherein the cavity permits access to a distal region of the first component.
3. The guide system of claim 1, wherein the hinge region lies substantially perpendicular to the longitudinal axis of the first component.
4. The guide system of claim 1, where the hinge region is formed from the same material as the first component and is integral with the first component, the first component and the hinge region being a single piece.
5. The guide system of claim 1, wherein the at least one actuating portion comprises at least two opposing arms.
6. The guide system of claim 1, wherein the first component comprises a distal jaw portion being positioned at a distal region of the first component, wherein said distal region further comprises a locking mechanism to restrict or prevent opening of the distal jaw portion when said locking mechanism is activated, wherein said locking mechanism comprises a latch.
7. The guide system of claim 6, wherein said latch is releasable and is configured either: (i) to have one locking position; or (ii) to have a plurality of locking positions which allow a stepped progression of tightening the distal jaw portion.
8. A guide system for an implantable device, said guide system comprising a first component arranged to act as a clamp, said first component comprising at least one actuating portion and at least one jaw portion, said actuating and jaw portions arranged either side of at least one hinge region, said actuating portion being positioned at a proximal region of the first component and said jaw portion being positioned at a distal region of the first component, wherein said distal region further comprises a locking mechanism formed as a latch on the jaw portion to restrict or prevent opening of the distal jaw portion when said locking mechanism is activated.
9. The guide system according to claim 8, wherein the distal jaw portion comprises arms that are defined preoperatively to fit to a specific patient's bone and thereby orientate the guide system according to a preoperative plan.
10. The guide system according to claim 8, wherein the distal jaw portion comprises arms that are defined to fit approximately to certain size ranges of femoral necks without patient specific adaptations.
11. The guide system of claim 10, wherein the arms of the distal jaw portion are substantially the same length.
12. The guide system of claim 10, wherein the arms of the distal jaw portion are not the same length.
13. The guide system of claim 8, wherein the distal jaw portion comprises at least one gripping portion, wherein the gripping portion is profiled to increase frictional force with the intended item to be gripped.
14. The guide system of claim 13, where the gripping portion comprises a plurality of flexible fingers.
15. The guide system of claim 8, wherein the first component further comprises a portion between the proximal region and the distal jaw portion which has a ballooned profile, wherein the profile is approximately spherical.
16. The guide system of claim 8, further comprising a second component, wherein the second component is a locking collar which is configured to be placed over the proximal region of the first component to prevent the proximal jaw portion from opening.
17. A guide system for an implantable device, said guide system comprising a first component arranged to act as a clamp, said first component comprising at least one actuating portion and at least one jaw portion, said actuating and jaw portions arranged either side of at least one living hinge, said actuating portion being positioned at a proximal region of the first component and said jaw portion being positioned at a distal region of the first component, wherein said distal region further comprises a locking mechanism formed as a latch on the jaw portion to restrict or prevent opening of the distal jaw portion when said locking mechanism is activated.
Description
(1) Examples of the invention will now be described by referencing to the accompanying drawings:
(2) FIG. 1-15 shown the patent specific head guide.
(3) FIG. 1 shows head guide main body.
(4) FIG. 2 is an exploded view showing all four parts, main body, collar, collar insert and drill tube.
(5) FIG. 3 is the main body in the expanded/open position.
(6) FIG. 4 is another view of the main body in the expanded/open position.
(7) FIG. 5 shows the 2 part collar (collar and insert).
(8) FIGS. 6-16 show the sequence of use of the patent specific head guide.
(9) FIG. 6 shows the guide main body in the expanded/open position being fitted to the femur bone.
(10) FIG. 7 shows the main body assembled on the femur bone with the latch secured.
(11) FIG. 8 is an exploded view showing all 4 parts being assembled together.
(12) FIG. 9 shows a hole being drilled into the femur bone.
(13) FIG. 10 shows the partially assembled guide, with collar insert removed with a guide rod inserted in the drilled hole.
(14) FIG. 11 is a partially cross sectioned view showing the planar face drill advancing over the guide rod.
(15) FIG. 12 is a partially cross sectioned view showing the planar face drill at full depth.
(16) FIG. 13 is a partially cross sectioned view showing the completed face cut and with the guide rod still in position.
(17) FIG. 14 shows a separate rotary cutter advancing over the guide rod.
(18) FIG. 15 shows the separate rotary cutter at full depth.
(19) FIG. 16 shows the final head implant in position on the femoral bone.
(20) FIGS. 17-19 show an alternative embodiment generic (non-patient specific head guide)
(21) FIG. 17 is the main body in the expanded/open position.
(22) FIG. 18 is an exploded view showing all three parts, main body, collar and drill tube.
(23) FIG. 19 shows all three parts assembled together on the femur bone.
(24) FIGS. 20-37 show an alternative embodiment head guide
(25) FIG. 20 is the guide body in the relaxed state.
(26) FIG. 21 is the guide body in the expanded state.
(27) FIG. 22 is another view of the guide body in the relaxed state.
(28) FIG. 23 is another view of the guide body in the expanded state.
(29) FIG. 24 is the assembled guide.
(30) FIG. 25 is an exploded view of FIG. 24.
(31) FIG. 26 is another exploded view of the assembled guide.
(32) FIG. 27 shows the guide main body on a femur bone.
(33) FIG. 28 shows a cross section of the guide body as it is expanded over the femoral head.
(34) FIG. 29 shows a cross section of the guide body assembled on a femur bone.
(35) FIG. 30 shows the assembled guide on a femur bone.
(36) FIG. 31 is an exploded view of FIG. 30.
(37) FIG. 32 shows the assembled guide on a femur bone with a drill about to be inserted.
(38) FIG. 33 shows the partly assembled guide on a femur bone with a guide rod placed in the drilled hole.
(39) FIG. 34 is a cross sectioned view of FIG. 33
(40) FIG. 35 is a cross sectioned view of the partly assembled guide on a femur bone with a planar face cutter about to slide onto the guide rod.
(41) FIG. 36 is a cross sectioned view of the partly assembled guide on a femur bone with a planar face cutter having cut to its fullest extent.
(42) FIG. 37 is a cross sectioned view of the femur bone with guide rod inserted showing the completed planar face cut.
(43) The patent specific head guide will now be described with reference to FIGS. 1-5.
(44) In FIG. 1 it can be seen that the main body [1] is manufactured as a single part consisting of two approximately cylindrical rings, one at each end with a multitude of connecting struts [6] (for example two, four or six struts). One ring is intended to be positioned around the femoral neck (neck ring [7]) and the other is positioned at the opposite side of the femoral head (head ring pp. The neck ring [7] has an integral hinge [5] on one side and an opening [15] at the other side. The head ring [2] has an integral hinge [4] on one side and an opening [16] on the other side. The two hinges are arranged to be axially aligned, so that they act together (similar to two hinges on a gate or door). The head ring has two paddle features [3] which extend outwards to the other side of the hinge [4]. When the paddles are pressed together in the direction of arrows [18] (for example between thumb and forefinger) the two halves of the main body, are hinged apart in the direction of arrows [17] (similar to a hair claw) as shown in FIGS. 3 and 4. This allows it to be assembled over the femoral head/neck bone, either from one end or from the side during the resurfacing operation (as shown in FIG. 6). The free position of the guide main body is closed (as in FIG. 1) so that it returns to this position as the grip on the paddles is relaxed.
(45) The internal surfaces [8] of the neck ring are defined preoperatively to exactly fit to the specific patient's bone and hence to orientate the guide according to a preoperative plan. The neck ring has a latch [9] at the opening side (opposite the hinge) for fastening it closed. The latch can be opened manually with release tag [10] to remove it after use. As the neck ring extends almost fully round the femoral neck, it will only fit and close properly in the distinct position it is intended to fit.
(46) All parts of the head guide are shown in FIG. 8, main body [1], collar [12], collar insert [13] and drill tube [14]. The collar [12] has a sliding fit onto the main body [1] and is held in position by two latches [19]. Once fitted, the collar captivates the head ring in the closed position, therefore once the neck ring latch [9] is closed and the collar [12] assembled, the guide is very firm and stable on the femur bone. The collar insert [13] fits into the collar via a bayonet fitting (the collar insert [13] has a male bayonet fitting [21] and the collar [12] has female bayonet fitting [20] which is shown clearly in FIG. 5.
(47) The in-use function of the patent specific head guide will now be described with reference to FIGS. 6-16.
(48) The paddles are pressed together (for example between thumb and forefinger) to assemble the main body over the femoral head/neck bone, either from one end or from the side as shown in FIG. 6. It is then allowed to close over the head/neck and manipulated to the position of the planned fit. The latch [9] will close once this distinct position is found as shown in FIG. 7. The other parts are then assembled onto the main body (collar [12], collar insert [13], and drill tube [14] as shown in FIG. 8. The spiked end of the drill tube is tapped into the femoral head and a drill [22] (for example 5 mm in diameter) is then passed through the drill tube to drill a hole into the femur bone corresponding to the central longitudinal axis of the resurfacing head implant as shown in FIG. 9. The drill tube and insert are removed (leaving the collar [12] in place) and a guide rod [23] is inserted into the drilled hole with the head guide still in position as shown in FIG. 10. A separate face drill [24] is then advanced (as shown in FIGS. 11 and 12) to machine a flat counter-bored surface on the head of femur. This face drill has a bore to fit precisely over the guide rod and a flange feature [11] which stops against the collar [12] to limit the depth of the counter-bore to a planned position. This counter-bore [25] later acts as a datum surface which a separate cylinder/chamfer cutter [24] stops cutting against and it corresponds exactly with the internal planar surface of the resurfacing head implant. Therefore it can be seen how the patient specific guide controls all aspects of head implant position according to the pre-operative plan. The patient specific guide is removed (leaving the guide rod [23] in position as shown in FIG. 13) by first unlatching and removing the collar [12], then releasing the neck ring latch [9] via tab [10] and then expanding it open to remove it from the femur. A cylinder/chamfer cutter [24] is then employed to complete the machining of the head of femur which is also controlled by the by the guide rod and stops cutting when it reaches the counter-bore surface [25] as shown in FIGS. 14 and 15. Finally the guide rod is removed, a stem over-drill (not shown) is used to enlarge the central hole to accept the head implant stem and the femur bone is then fully prepared ready for the head implant [26] (shown in final position in FIG. 16).
(49) An alternative embodiment, the generic (non-patient specific) head guide will now be described with reference to FIGS. 17-19. It is very similar to the patent specific head guide, therefore only the features which are different will be described.
(50) This embodiment is a standard version of the head guide (not patient specific). It can be seen in FIG. 17 that the neck ring consists of two half rings with an integral hinge [27] on one side and an opening [29] at the other side. In this embodiment the neck ring latch [28] has a multitude of engaging positions [30] in the form of a ratchet, however alternatively there is only one latch position (similar to the patient specific version). There are three parts to this guide, consisting of main body [31], insert [32] and drill tube [33] as shown in FIG. 18.
(51) When latched closed, the neck ring is cylindrical in shape and the internal diameter of the cylinder is slightly smaller than the diameter of the cylindrical head cutter for the corresponding head size. The collar [32] is fitted onto the main body via a sliding fit and retained in position by two latch features [35]. A flag [36] extends from the neck ring which is positioned to be in line with the inferior femoral neck. This is a useful visual reference as the first few centimetres of the inferior femoral neck [34] approximately indicated the desired head axis. This can be seen in FIG. 19 where the fully assembled guide is mounted on the femur bone.
(52) In this embodiment the head guide is used to position the guide rod (and therefore the central axis of the head implant) however it does not control the depth of the face drill counter-bore. This is controlled by another means, using the femoral head surface as a datum. The neck ring being cylindrical is not always close fit on the neck (as the patient specific version is) therefore the surgeon must bias it into the appropriate position before drilling the hole in the femur.
(53) An alternative embodiment will now be described with reference to FIGS. 20-37
(54) In FIG. 20-23 the anatomy of the guide body (38) will be described as having a largely cylindrical portion (39) with a bore (42) and partial screw thread (40) with two slot opening (41) ending in a two thinned resilient connections (45) described hereafter as the resilient hinge. To the other side of the resilient hinge is a largely spherical portion (44) with bore (46) with two opening slots (48) and internal jaws (47) defined to make mating contact with the femoral bone (55) shown in later figures. It can be seen in FIGS. 21 and 23, that as the largely cylindrical portion (39) is compressed, for example with a manual grip between thumb and forefinger (not shown), the resilient hinges (45) flex and expansion of the largely spherical portion (44) occurs. The partial screw thread (40) also acts as a finger grip to prevent the fingers slipping off the guide body. As the manual grip is relaxed, the guide body returns to the relaxed state as shown in FIGS. 20 and 22. In FIGS. 24-26 all parts of the assembled guide are identified as guide body (38), locking collar (51), drill guide (50) and spiked tube (49). As shown in these figures, locking collar (51) fits precisely with the largely cylindrical portion of the guide body both on the internal bore (42) and external cylinder with screw thread (40 & 52). Therefore when locking collar (51) is assembled and tightened via the screw thread, both compression and expansion of largely cylindrical (39) and spherical (44) portions are prevented.
(55) In use during a hip resurfacing operation, the guide body must first be assembled over the femoral head (57) as shown in FIGS. 27-29 using the method described above. FIGS. 27 and 29 show the mating fit of the jaw teeth (47) with the femoral neck (56). Preferably the profile of the jaw teeth is defined from a preoperative plan but alternatively could be shaped to fit a generic neck of femur of a certain size or size range. It can be seen how the two opposing jaws mating with the femoral neck control the three dimensional position of the guide relative to the femur bone preferably according to the preoperative plan. When the locking collar is assembled, the guide body becomes rigid and further acts to maintain its position. Furthermore as the locking collar is assembled with the guide body the grip force is increased as now described. A pretension allowance is built into the guide body so that as the locking collar is inserted, it slightly expands the cylindrical bore which compresses the largely spherical portion (38) to the other side of the resilient hinge (45) and tightens the grip on the femoral neck (56). Clearly shown in FIG. 31 is the spiked tube part (49) which fits into the bore (60) of the drill guide. The sharp spikes (58) on the spiked tube penetrate the femoral head slightly and prevents the drill (59) from skating off line as it enters the femoral head. The drill (59) shown in FIG. 32 makes a reference hole in the femur (55) which exactly coincides with the longitudinal axis of the resurfacing head component preferably as defined by the preoperative plan. In FIGS. 33-36 it can be seen that the drill guide (50) has been removed and a guide rod (61) is placed in the drilled hole which also coincides with the longitudinal axis of the resurfacing head component. A rotary cutter (62) then slides over the guide rod (61) and is rotated with a surgical power drill (not shown) to make a planar face cut on the femoral head. The depth of this face cut is controlled by a flange feature (63) on the rotary cutter (62) which makes contact with the end face (64) of the locking collar (51) acting as a stop feature as shown in FIG. 36. This planar cut surface (65) on the femoral head serves as a datum surface that the other rotary cutters stop cutting against and it corresponds exactly with the internal planar surface of the resurfacing head implant. Once the planar face cut is made, the guide is removed by first unscrewing the locking collar and then expanding the guide body over the femoral head, leaving the guide rod in position as shown in FIG. 37.
