Abstract
The present application concerns a shoulder prosthesis assembly. The shoulder prosthesis assembly comprises a humeral stem including a first articulating coupling means, a base portion of a substantially disc shaped geometry including a second articulating coupling means. Said first articulating coupling means and said second articulating coupling means connect the stem to the base portion. The ratio between the circumference of the disc shaped base portion and the peripheral thickness of the disc shaped base portion is at least 18:1.
Claims
1. A shoulder prosthesis assembly comprising a humeral stem, a first articulating coupling means, a base portion of a substantially disc shaped geometry including a second articulating coupling means, the first articulating coupling means and the second articulating coupling means connecting the stem to the base portion, the base portion being movably coupled to the stem by means of an at least three degrees of freedom coupling, wherein the base portion comprises an inner inlay and is movably coupled to the stem by means of the inlay comprising a ball-and-socket coupling with one blocked rotational degree of freedom, wherein the inlay comprises an axis of rotation and is rotatably coupled to a base of the base portion, wherein a ball head of the ball-and-socket coupling is locked in a socket of the ball-and-socket coupling by a form-fit connection, and wherein the ball-and-socket coupling is positioned offset from the axis of rotation of the inlay.
2. The shoulder prosthesis assembly of claim 1, wherein an outer rim of the base portion is in the form of a polygon or is irregularly shaped.
3. The shoulder prosthesis assembly of claim 1, wherein the at least three degrees of freedom coupling has three rotational degrees of freedom.
4. The shoulder prosthesis assembly of claim 3, wherein the base portion is movably coupled to the stem by means of said ball-and-socket connection.
5. The shoulder prosthesis assembly of claim 3, wherein the base portion is movably coupled to the stem portion by means of a gimbal-mount coupling.
6. The shoulder prosthesis assembly according to any one of the preceding claims, wherein the ratio between the circumference of the disc shaped base portion and the peripheral thickness of the disc shaped base portion is at least 18:1.
7. The shoulder prosthesis assembly of claim 3 comprising a substantially Z-shaped adaptor arranged between said ball-head and said humeral stem.
8. The shoulder prosthesis assembly of claim 7, wherein the adaptor comprises two tapered ends, wherein the central axes of the tapered ends are oriented either offset in one direction and parallel to each other or offset in one direction and under an acute angle to each other.
9. The shoulder prosthesis assembly according to claim 1, wherein said second articulating coupling means of said ball-and-socket connection comprises a spherical articulation cavity or a socket, said spherical articulation cavity including a groove and said socket including a channel, wherein said groove or said channel is oriented parallel or perpendicular to an imaginary line connecting the axis of rotation of said inlay and a rotational centre of said ball-and-socket coupling.
10. The shoulder prosthesis assembly of claim 1, wherein said ball-and-socket connection comprises a ball-head in the form of a spherical cap, a connection interface for connecting said humeral stem with said ball-head being arranged on the base of said ball-head, wherein said connection interface is located offset of the centre of the base of the ball-head.
11. The shoulder prosthesis assembly of claim 10, wherein said ball-head is in the form of a spherical segment and a socket of said ball-and-socket coupling has an opening which is smaller than a largest diameter of said ball-head but larger than a distance between faces of said ball-head.
12. The shoulder prosthesis assembly of claim 1, wherein the base portion is dimensioned such that a distance between the centre of rotation of said at least three degrees of freedom coupling and a base area of said base portion is less than 15 mm.
13. The shoulder prosthesis assembly according to claim 1, wherein at least one portion of a rim of said base portion comprises an increased thickness.
14. The shoulder prosthesis assembly according to claim 1, comprising a base portion with a proximal face and an outer rim with a circumference, wherein the proximal face has a concave, convex or conical surface with a height or a depth, wherein the circumference to height ratio or circumference to depth ratio is at least 15:1, preferably larger than 20:1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The drawings used to explain the embodiments show:
(2) FIGS. 1a-1c A first embodiment of an inventive shoulder prosthesis assembly according to the present invention;
(3) FIGS. 2a, 2b the relevant bone anatomy for positioning of a shoulder prosthesis assembly according to FIGS. 1a to 1c:
(4) FIG. 3 a side view of the shoulder prosthesis assembly according to FIGS. 1a to 1c:
(5) FIGS. 4a, 4b a perspective view and a side view of a base portion;
(6) FIG. 5 a Z-shaped adaptor for an inventive shoulder prosthesis assembly according FIGS. 1a-1c;
(7) FIG. 6a, 6b a humeral stem for an inventive shoulder prosthesis assembly according to FIGS. 1a-1c;
(8) FIGS. 7a -7c a ball-head for an inventive shoulder prosthesis assembly according to FIGS. 1a-1c;
(9) FIGS. 8a -8g assembly steps for an inventive shoulder prosthesis assembly according to FIGS. 1a-1c;
(10) FIG. 9 a sectional cut of an assembly between a base portion and a ball-head;
(11) FIG. 10 different Z-shaped adaptors;
(12) FIG. 11 a variant of the shoulder prosthesis assembly with an alternative coupling mechanism in the form of a gimbal-mount coupling;
(13) FIG. 12 a variant of the base portion having bone in growth areas;
(14) FIG. 13 a further embodiment of a base portion with an irregular shape;
(15) FIG. 14 an embodiment of a base portion with areas of increased thickness;
(16) FIGS. 15a -15c components of another embodiment of a shoulder prosthesis assembly according to the present invention;
(17) FIGS. 16a, 16b a shoulder prosthesis assembly using the components as shown in FIGS. 15a -15c;
(18) FIG. 17 a representation of implanted shoulder prosthesis as shown in FIGS. 16a, 16b;
(19) FIGS. 18a, 18b an alternative embodiment of the ball-and-socket coupling;
(20) FIGS. 19a -19f the interplay between the elements of the alternative ball-and-socket coupling according to FIGS. 18a, 18b;
(21) FIG. 20 a further embodiment of a shoulder prosthesis assembly according to the present invention;
(22) FIGS. 21a, 21b a detailed view of the base portion and the ball head of the shoulder prosthesis assembly according to FIG. 20;
(23) FIG. 22 the orientation of the channel relative to the inlay according to the embodiment as shown in FIGS. 20 and 21.
(24) In the figures, the same components are given the same reference symbols.
PREFERRED EMBODIMENTS
(25) With reference to FIGS. 1a to 1c, an inventive shoulder prosthesis assembly 100 is shown. In FIG. 1a an exploded view shows the shoulder prosthesis assembly 100 comprising a humeral stem 10, a ball-head 14, an adaptor 15 and a disc shaped base portion 13, the so-called glenoid disc. Said base portion comprises an outer metal base 11 with an integrated articulation inlay 12. Said articulation inlay 12 is rotatable relative to said outer metal base 11.
(26) FIGS. 1b and 1c show the assembled shoulder prosthesis assembly 100 from two different perspectives. The substantially spherical ball-head 14 is inserted into and articulates within a spherical cavity or socket 17 of the base portion 13. Said socket 17 is thereby located in said articulation inlay 12. The ball-head 14 and the socket 17 form a ball-and-socket connection which allows movement of the humeral stem portion 10 around three rotational degrees of freedom relative to the base portion 13.
(27) In the embodiment shown, the base portion 13 is substantially circular with a central axis of rotation A. Said axis of rotation A coincides with the centre of the socket 17. The outer metal base 11 may comprise a polished or treated base area 16 to prevent from bone ingrowth. Said base area is intended to be arranged against the glenoid cavity.
(28) In accordance of a variant of the invention, the prosthesis assembly 100 could consist of two monoblock components, namely the humeral stem 10 including the spherical ball-head 14 and the base portion 13 including socket 17. Such as to facilitate an adaptation of the spatial relationship of the individual elements of the prosthesis assembly 100 to the patient specific anatomy, or such as to convert a standard primary or reverse prosthesis into the described inventive prosthesis assembly 100, multiple parts may be provided, as the prosthesis assembly 100 is a modular construct of the elements humeral stem 10, adaptor 15, ball-head 14, articulation inlay 12 and outer metal base 11, as shown in figure 1a.
(29) Referring to FIGS. 2a and 2b, the relevant bone anatomy for positioning of the shoulder prosthesis assembly 100 inside the humeral-scapular joint is shown. FIG. 2a shows the scapula 51 and the humerus 50, with resected humeral head 55. Parts of the bone of the scapula 51, namely the coracoid process 52, acromion process 54 and the glenoid 53 engage with the base portion 13 by means of the outer metal base 11, as shown in FIG. 2b, wherein the humeral stem portion 10 is fixated into the bone of the humerus 50. The base portion 13 is constrained by the coracoid process 52, the acromion process 54 and the glenoid 53, but not rigidly fixated, thus more or less floating within the joint capsule. The forces directed towards the cranial and medial sides of the rotator cuff, deltoid muscle and shoulder capsule pull the shoulder prosthesis assembly against the bony structures and keep it in place.
(30) With reference to the description in relation to FIGS. 1a to 1c and 2a, 2b, the shape for the base portion 13 is circular. During movements of the arm for daily activities, rotational moments and forces may cause the non-fixated base portion to rotate over the glenoid 53. However, the constant distance of the centre of rotation of the socket 17 to the outer diameter of the base portion 13 guarantee a constant position of the centre of rotation of the ball-and socket connection.
(31) FIG. 3 shows a side view of the shoulder prosthesis assembly 100. In this figure, the centre of rotation 19 of the ball-and-socket connection between the ball head 14 and the socket 17 is shown. The ratio between the diameter Dand hence of the circumferenceof the base portion 13 and the distance c of the centre of rotation 19 to the base area 16 results in a far distalised and medialised centre of rotation 19 in comparison to the natural shoulder. As a result, the deltoid muscle will be active throughout the full range of motion and compensate for deficiency of the infra-spinatus muscle.
(32) FIGS. 4a and 4b show a perspective view and a side view of the base portion 13. The base portion 13 comprises the outer metal base 11 as well as the articulation inlay 12. A spherical cavity forming the socket 17 is arranged centrally on said articulation inlay 12. In the embodiment as shown in FIG. 4b the rotation centre 19 of the ball-and-socket joint is arranged at a distance of approximately half the diameter of the socket 17 from the proximal end of the base portion 13. Further, the socket 17 intersects with a pocket 18. The pocket 18 is substantially perpendicular to the base portion 13 and has a depth which reaches to at least the largest circumference of the socket 17. Further, the width of the pocket 18 is significantly smaller than a border circumference 20 of the socket 17.
(33) FIG. 5 shows a Z-shaped adaptor 15 comprising a first tapered end 21 and a second tapered end 22 with substantially parallel axes. Both tapered ends 21, 22 comprise a recess 23, 24 at the end of the taper. The recesses 23, 24 serve as anti-rotation face as described in greater detail for the FIG. 7.
(34) FIGS. 6a and 6b show the humeral stem 10. The humeral stem 10 comprises a shaft portion 25, a proximal end 26 and a female taper-connection 27 with an integrated antirotation protrusion 28 at the bottom of the female taper-connection 27.
(35) FIGS. 7a to 7c show the ball-head 14 comprising an outer geometry which is based on a full sphere with at least a first cut-off section 29, wherein the first cut-off section 29 is significantly smaller than a hemisphere, thus resulting in an overall shape of the ball-head as sphere with a face 33, or spherical cap. The ball-head comprises a second cut-off section 30, substantially aligned with the first cut-off section 29. The second cut-off section 29 is significantly smaller than a hemisphere. The resulting shape of the ball-head 14 is a disc with a spherical outer geometry, or spherical segment. The first cut-off section 29 comprises an attachment means 31 to be attached to the humeral stem 10 or with the adaptor 15. In the embodiment shown, the attachment means 31 is in the form of a female taper connection with an integrated anti-rotation protrusion 32 at the bottom of the taper connection. Further, the attachment means 31 is located eccentrically on the face 33 at a distance w from the centre of said face 33, providing a larger range of motion for the ball-and-socket joint in defined directions, in comparison to other directions.
(36) FIGS. 8a to 8g depict the assembly steps of the different components into a prosthesis assembly 100. In a first step, the articulation inlay 12 is snapped into the outer metal base 11, forming the base portion 13. In a second step, shown in FIG. 8a, the ball-head 14 is inserted into the socket 17 of the articulation inlay 12. The ball-head 14 is inserted by orienting both faces of the ball-head 14 perpendicular to the sidewalls of pocket 18. When a first end-position is reached, as shown in FIG. 8b, the ball-head 14 and the socket 17 are concentrically aligned. Then, the ball-head 14 is turned by 90 into a second end-position wherein the attachment means 31 are accessible through pocket 18, as shown in FIG. 8c.
(37) In a next step, shown in FIG. 8d, the adaptor 15 is placed into the attachment means 31 of the ball-head 14 with the first tapered end 21. Thereby, the recess 23 of the first tapered end 21 match with the anti-rotation protrusion 32 of the attachment means 31. Once the adaptor 15 is fully inserted into the attachment means 31, as shown in FIG. 8e, the ball-head 14 is prevented from rotating far enough to reach the assembly orientation as illustrated by FIGS. 6a and 6b. Therefore the ball-head 14 is locked within the socket 17 by a form fit connection.
(38) Excessive movement of the arm which exceeds the range of motion of the shoulder prosthesis assembly 100 may cause the humeral stem 10 to impinge with the base portion 13. This will result in a momentum which in state of the art designs may cause a luxation of both implant components. The positive fit between the ball-head 14 and the socket 17 prevents the occurrence of such a luxation with a shoulder prosthesis assembly 100 according to the present invention.
(39) In a next step, shown in FIG. 8f, the humeral stem 10 is assembled with the second tapered end 22 of the adaptor 15. Thereby, the second recess 24 of the second tapered end 22 matches with the anti-rotation protrusion 28.
(40) In matters of the anti-rotation faces, a taper connection is designed for transfer of rotational forces. The form-fit of the mating faces will resist any rotational moments around the axes of each taper connection.
(41) The final configuration of the shoulder prosthesis assembly 100 is shown in FIG. 8g.
(42) FIG. 9 shows the assembly between the base portion 13 and the ball-head 14 as a sectional cut. As may be seen in this figure, the ball-head 14 is locked within the socket 7 in a form-fitting manner in the area 60 located beneath a rim of the socket 17.
(43) As shown in FIG. 10, different adaptors 15a-15d allow adapting the spatial relationship of the individual elements of the shoulder prosthesis assembly 100 to the specific patient anatomy. The distance X between the central axes of the first tapered end 21 and the second tapered end 22, the length L of the adaptor 15 as well as the angle a between the central axes of the first tapered end 21 and the second tapered end 22 may vary. By this variation, it is possible to individually distalize and lateralize the humeral bone and humeral stem 10 in relation to the centre of rotation 19 of ball-head 14.
(44) FIG. 11 shows a variant of the present invention with an alternative coupling mechanism, namely a gimbal-mount coupling 40. The base portion 13 comprises a circular inner inlay 41 which is rotatably coupled to the outer metal base 42. Further, an inner ring 43 with a first axis of rotation 44 is rotatably coupled to the circular inner inlay 41. A centre portion 46 is rotatably coupled to the inner ring 43 via a second axis of rotation 45. The centre portion 46 furthermore comprises connection means 47 for connecting to the humeral stem 10 or to the adaptor 15.
(45) The rotation axis of the inner inlay 41 is oriented substantially perpendicular to the outer metal base 42 and does not intersect the first axis of rotation 44 or the second axis of rotation 45. The eccentric position facilitates a further distalised centre of rotation without increasing the diameter of the glenoid disc.
(46) FIG. 12 shows a variant of the base portion 13 comprising three bone in growth areas 61.1, 61.2, 61.3. The bone in growth areas 61.1, 61.2, 61.3 are located on the base portion 13 such as to engage with the glenoid 53, coracoid 52 and acromion 54.
(47) FIG. 13 depicts a further embodiment of the base portion 13. In this embodiment, the base portion 13 is irregularly shaped and comprises a protrusion 63 which may be positioned between the coracoid 52 and the acromion 54. The protrusion 63 prevents rotation of the 10 base portion 13.
(48) Another variant of the base portion 13 is shown in FIG. 14. The base portion 13 comprises two areas of increased thickness, namely a first engagement surface 64 engaging with the coracoid 52 and a second engagement surface 65 engaging with acromion 54. The two engagement surfaces 64, 65 allow for a better stress distribution on the bone.
(49) FIGS. 15a to 15c show components of another embodiment of a shoulder prosthesis assembly 110 according to the present invention. In this embodiment, the ball-head 81 comprises a central taper connection 82 and two cut-off faces 83, 84, as shown in FIG. 15a. The base portion 89 is substantially circular in shape and has a thin base 90 and a substantially centrally positioned male taper 91, as seen in FIG. 15b. FIG. 15c shows a 20 stem-extension 85, comprising a cavity 86 and a stem 87 with a tapered end 88.
(50) FIGS. 16a and 16b show a shoulder prosthesis assembly 110 using the components as described in connection with FIGS. 15a to 15c. In a first assembly step, the ball-head 81 is inserted into the cavity 86 of the stem-extension 85. In a next step, the base portion 89 is connected to the ball-head 81. Finally, the humeral stem 10 is connected to the stem25 extension 85.
(51) The implanted shoulder prosthesis assembly 110 according to FIGS. 16a and 16b is shown in FIG. 17. The humeral stem 10 is inserted into the humeral bone 50. The base portion 13 engages with the glenoid 53, acromion 54 and the coracoid 52.
(52) FIGS. 18a and 18b show an alternative embodiment for the ball-in-socket joint coupling. FIG. 18a represents the substantially circular base portion 120. The base portion 120 comprises an inner inlay 121 and an outer metal base 122. The inner inlay 121 is rotatably coupled to the outer metal base 122 such as to be rotatable around a fourth axis of rotation 126, which is substantially perpendicular to outer metal base 122. The inner inlay 121 comprises a spherically shaped cavity 127 with an intersecting pocket 124. The spherical articulation cavity 127 is positioned offset from the centre of the base portion 120. The inner inlay 121 further comprises a nose 123. The nose 123 is preferably circular or hemispherical with a diameter 125 being larger than 2 mm but smaller than 15 mm. The nose 123 is directed towards the centre of the spherical cavity 127, wherein the central axis of the nose 123 intersects with the centre of spherical cavity 127.
(53) FIG. 18b depicts the ball-head 130. The ball-head 130 comprises a connection interface 131, preferably in the form of a female taper. Additionally, the ball-head 130 comprises a groove 132 along a circular largest circumference. The groove 132 has side walls 133, wherein a distance between the side-walls 133 is equal to or larger as diameter 125. The depth 134 of the groove 132 is equal or larger than the length of the nose 123.
(54) FIGS. 19a to 19c show the interplay between the described elements according to FIGS. 18a and 18b. The ball-head 130 is assembled into the spherical articulation cavity 127 of the inner inlay 121 by orienting faces of the ball-head 131 such that they are aligned with the sidewalls of pocket 124. In this way, the nose 123 may be inserted into groove 132, as seen in FIG. 19a. When a first end-position, shown in FIG. 19b, is reached, the ball-head 131 is turned by approximately 90 into a second end-position, as shown in FIG. 19c. In this second end-position, the connection interface 131 is accessible through pocket 124. This allows the introduction of the adaptor 15 into the connection interface 131, as may be seen in FIG. 19d. Finally, the humeral stem 10 is connected with the adaptor 15, as shown in FIG. 19e.
(55) The nose 123 eliminates one rotational degree of freedom of the ball-and-socket connection. The ball-head 130 can only rotate along groove 132 and around the central axis of the nose 123. The rotational degree of freedom substantially perpendicular to the base portion 120 is blocked by the interaction of the nose 123 and the side-walls 133 of the groove 132. This missing rotational degree of freedom is compensated by the rotatable coupling between the outer metal base 122 and the inner inlay 121. As the fourth axis of rotation 126 does not intersect with the remaining two axes of rotation of the ball-head 130, the rotation of the ball head around said axis is in a more distal position in comparison to the embodiment of the shoulder prosthesis assembly 100 as shown for FIGS. 1 to 3. This distal shifting of the axis of rotation is shown in FIG. 19f.
(56) FIG. 20 shows a further embodiment of a shoulder prosthesis assembly 140 according to the present invention. The base portion 150 comprises an inner inlay 151 which is rotatably coupled to an outer metal base 152. Further, a ball-head 160 is movingly arranged within a socket 153 of the inner inlay 151. The ball-head 160 and the socket 153 form a ball-and-socket connection. An adaptor 15 is connected to the ball-head 160, said adaptor 15 being further attached to a humeral stem 10.
(57) The socket 153 includes a channel 154 into which two protuberances 161, 162 provided on said ball-head 160 are engaged. The channel 154 as well as the protuberances 161, 162 have a matching hemispherical shape. Without provision of the channel 154 and the protuberances 161, 162 the ball-head 160 would be able to rotate freely around three axes of rotation within the socket. However, the engagement of the two protuberances 161, 162 into the channel 154 restricts rotational movement of the ball-head 160 around one axis, as the two protuberances 161, 162 are form-fittingly engaged within the channel 154. This results in a movement restriction of the ball-and-socket connection in one degree of freedom. In the shown embodiment, the channel 154 has the same shape and width as the two protuberances 161, 162, hence any movement around the blocked rotation axis are prevented. Alternatively, the channel 154 may have a width which is slightly larger than the width of the two protuberances 161, 162. With such an alternative embodiment, the ball-head 160 would be able to carry out small movements around the blocked axis, hence enabling a limited wobbling of the ball-head 160 within the socket 153.
(58) Rotational movement of the ball-head 160 around the two other axes of rotation is enabled by a sliding motion of the two protuberances 161, 162 within the channel 154 and rotational movement of the two protuberances 161, 162 within the channel 154.
(59) FIG. 21a shows a detailed view of the base portion 150 of the shoulder prosthesis assembly 140 according to FIG. 20. The shape of the two protuberances 161, 162 as well as of the ball-head 160 may be clearly recognized in this figure. As may be seen, the ball-head 160 is in the shape of a dome, i.e. of a sphere which is cut by a plane, while the two protuberances 161, 162 are in the form of hemispheres.
(60) FIG. 21b shows a detailed view of the ball-head 160 of the shoulder prosthesis assembly 140 according to FIG. 20. As may be seen, the channel 154 has a hemispherical shape and is arranged on the socket 153 along a great circle. The channel 154 thereby spans the socket 153 from edge to edge.
(61) FIG. 22 depicts the orientation of the channel 154, which is represented by the channel axis 158, relative to the inner inlay 151. In the embodiment shown, the channel 154 is oriented perpendicular to an imaginary line 157 which connects the axis of rotation 156 of the inner inlay 157 and the centre of rotation 156 of the ball-and-socket connection. In other words the angle between the imaginary line 157 and the channel axis 158 is 90.
(62) In a further embodiment (not shown) the channel axis 158 is parallel to the imaginary line 157. In other words the angle between the imaginary line 157 and the channel axis 158 is 0.
(63) As a person having skill in the art recognizes, the orientation of the groove 132 according to the embodiment shown in FIGS. 18 and 19 may likewise be oriented parallel or perpendicular so said imaginary line 157.
