DE19630298A1 - Total shoulder arthroplasty - Google Patents

Abstract

The invention concerns a complete endoprosthesis for the shoulder with a shaft (10) and an interchangeable head (20) which can be affixed to the shaft (10) and which is shaped like a mushroom head and symmetrical to a center line (M) and with a connecting side (211) for the shaft (10) constructed on the underside of the head (20), whereby the connecting side (211) of the head (20) on its underside runs in a direction not perpendicular to the center line (M) of the head (20). The head (20) can be fastened to the sh aft (10) in different positions (A, B, C, D) which turn about its axis of attachment (W).

Description

The object of the invention relates to a shoulder Total endoprosthesis with a shaft and a replaceable one head attachable to the shaft with a mushroom-shaped head a central axis M symmetrical shape and with one on the Bottom of the head trained connection side for the Shaft.

The total shoulder arthroplasty was developed in the 50s by C.S. Neer developed. The removed part of the Humeral head of the humerus has about the same head Shape of a spherical section, also as a mushroom-shaped Called shape. The well-known head, which is a symmetrical Has shape, is attached to a shaft, the one Insert part for insertion into the humerus and at the end a usually plate-shaped connection side, on which the head is attached. The heads can be made from one body-compatible material, such as titanium, cobalt-chrome, ceramic with or without a coating. For the heads and shafts are available with different body sizes different dimensions of the same shape are available.

The problem now arises that complications with the Implantation of the shoulder prosthesis with shaft and head can occur if, for example, the shoulder prosthesis in at a wrong angle with respect to the glenoid  (Shoulder joint socket) or humeral head of the humerus is implanted, which leads to dislocation. In one So far, it is necessary to use the entire shoulder prosthesis remove and re-implant to ensure the optimal fit of the shaft and thus of the head attached to the shaft to reach.

The invention has for its object the correction of Seat of implanted shoulder prostheses with shaft and head without removing the entire prosthesis and the further also an improved possibility of balancing Defects in the area of the shoulder joint using a to achieve implanted head.

To achieve the object, the invention proposes that Bottom of the head for the total shoulder arthroplasty in with respect to the central axis (M) of the head to train. According to the invention, one obtains one in principle asymmetrical head for the implantation of the space between the humeral head and the glenoid depending on its position fills the shaft differently.

Advantageous configurations of the head according to the invention are the characteristic features of the subclaims.

According to the invention, the underside of the head is in relation to the Center axis M of the head is asymmetrical, so that the Center axis M of the head with respect to the fastening axis W of the head on the shaft inclined at an acute angle runs. This means that when turning the on the shaft mounted head around its mounting axis W die Axis of symmetry, namely the central axis of the head a conical surface around the mounting axis when the Head moved around. This means that the head in the Top view viewed with respect to the mounting axis assumes asymmetrical position on the shaft and thereby can be shifted accordingly by rotation and in this way  to fill different spaces in the shoulder joint area can

In particular, it is suggested the bottom that the Forms connection side of the head towards the shaft with respect to the perpendicular position to the central axis M of the head under one to form an acute angle α inclined, the Angle is preferably between 5 to 20 °. In particular suggested heads with different angles α as To train a module system, for example a series mushroom-shaped heads of different sizes as a series, these being inclined at an angle of 5 °, 10 ° or 15 ° Connection side are formed.

According to a further proposal of the invention, the head with a protruding wedge-shaped neck part, the Underside in relation to the central axis M of the head forms inclined connection side. To be favoured Head and neck part made from one part, but it is also possible to manufacture head and neck in two parts and then to connect during assembly or beforehand.

In a preferred development of the invention Head for a shoulder prosthesis is proposed that the Head crooked with a neck part in the shape of a cut circular cylinder is formed, its crooked clipped cross-sectional area the bottom and Forms connection side of the head to the shaft.

For attaching the head to the shaft suggested that the head be attached to one at the Connection side of the shaft formed a pin the pin has a correspondingly formed blind hole, the Central axis of the pin and the central axis of the blind hole Form the attachment axis of the head on the shaft, such that when the head is placed on the shaft the Central axis of the head to the attachment axis of the head is inclined at an acute angle.  

According to the invention, the head with the neck part is on the shaft in different rotated around its mounting axis Positions attachable, each being asymmetrical is always trained in relation to its space constant fastening axis filled differently. This makes it possible, even with an implanted shoulder prosthesis to achieve a correction of the head position without the The shaft should be removed surgically and reinserted. According to the invention, it is also possible for one implanted shoulder prosthesis with only a small minimal engagement the position of the head by rotating around the To change mounting axis W and thus a desired Make correction.

With the invention there are four different ones Correction options during and after a Implantation of the shoulder prosthesis by changing the Head position possible, in relation to the humeral head and forward, backward, upward with respect to the pan and down.

In particular, it is possible to easily get a wrong one Angular position of the implanted shoulder prosthesis using the head designed according to the invention also after the Correct implantation.

The invention also enables an implanted Shoulder prosthesis, which has a symmetrical head, if necessary, replace it and replace it with one to replace head according to the invention. Again, there is only one minimal intervention required and no removal of the entire prosthesis, especially not in the upper arm inserted prosthetic stem.

The four correction options listed above a shoulder prosthesis for the seat of the same head enable, it is proposed to position each in  offset at an angle of 90 ° to each other Arrange mounting axis around. For this, the head according to the invention on its inclined connection side positioning pin protruding from the connection side and one of the number of positions of the head number of position holes on the shaft corresponding to the shaft Connection side of the shaft for inserting the Positioning pin of the head can be provided.

In a further development of the invention, the angle is preferred between the fastening axis and the central axis of the head the angle at which the connector side of the head is related is inclined to the vertical position to the central axis trained and is preferably in the range of 5 to 20 °.

When designing the head according to the invention with a asymmetrical shape in the form of a with respect to the Central axis inclined connection side, preferably through Formation of an approximately wedge-shaped neck part proposed that the neck part wedge-shaped to a Edge of the mushroom-shaped headboard towards zero tapered, so viewed in cross-section a long pointed one Triangle forms.

With the head according to the invention, it is possible in one wrong angle implanted shoulder prostheses on simple Way to correct with minimal intervention by either a normal head with no asymmetry against one head replaced according to the invention in asymmetrical form or an existing asymmetrical head in a different position is brought on the shaft.

The head according to the invention when the head is highly implanted allows the space between the glenoid and the approach of the Enlarge rotator cuff in the shoulder area and at the same time close the space between the acromyon and humeral head downsize. This is achieved in that the neck part in wedge-shaped area forms an elevation of the head so that  in the end by the head according to the invention in the position at the corresponding position Rotator cuff is reached to the space between Reduce acromyon and head at the same time. The change of these two levels is symmetrical with the previously known ones Head prosthesis not possible.

Another possibility when using the invention asymmetrical head for the correction is that the Version angle of the head to the front with implanted shaft and backwards by changing the position of the head on the Shaft can be changed, in particular reduced.

In cases where the shoulder socket is in the upper Part is eroded, the elevation Rotator cuff between head and shoulder joint socket compresses because of erosion of the shoulder socket large space between the upper part of the head and the upper part the shoulder joint socket is created. This can be done through the head according to the invention by inserting into the corresponding Position on the shaft can be corrected because of the asymmetrical design of the head of the invention in the upper part can be increased in the corresponding Position.

Lower erosion of the shoulder joint socket can result in a Loosen the subscapilarus tendon, using it of a larger known head it creates a tension on the Subscapilarus and infraspinatus tendon can come, however also to loosen the supraspinatus tendon. If according to the invention, however, an asymmetrical large head, a tension on the Subscapilarus and infraspinatus tendon can be reached without Apply pressure upwards on the supraspinatus tendon.

The invention is based on the drawing and Examples explained. Show it  

Fig. 1a-c is a side view, a longitudinal section and bottom view of a conventional symmetrical head for a shoulder prosthesis,

Fig. 2a-c is a side view, longitudinal section and bottom view of a head according to the invention formed in an asymmetrical shape,

Fig. 3 is a side view of a shoulder prosthesis with a shank and head of the prior art,

Fig. 4, 5, 6, 7, the side view of a shoulder prosthesis with a shank and head according to the invention mounted in various positions on the shaft,

Fig. 8 is a schematic representation of the top view of the different positions of the head according to the invention on the shaft,

Fig. 9a, b schematic representation of an implanted shoulder prosthesis in side view and top view.

In FIG. 1a to 1c, a commercially available symmetrical head for a shoulder prosthesis (Shoulder endoprosthesis) is shown, which has a substantially mushroom-like shape, and is symmetrical to the central axis M. The height H and the diameter E of the head 20 can be chosen differently for different head sizes. On its connection side 201 for attachment to the shaft, the head 20 is flat and has the slightly conical blind hole 202 in the center. Further centering holes 203 a, b, c, d can be formed around the blind hole on the connection side 201 . The attachment of the head 20 according to FIGS. 1 a, b, c takes place on the head plate 101 of a shaft 10 , as can be seen in FIG. 3. Here, a pin 102 with a pin axis is formed on the head plate 101 of the shaft 10 , which determines the fastening axis W and which, in the case of the formation of a symmetrical head 20 according to the prior art, with the central axis M of the head 20 during assembly, as in FIG Fig. 3 clearly coincides. The head 20 is plugged onto the pin 102 with its blind hole and fixed, for example, by the taper of the fits. When the head 20 is rotated about the central axis M, which is equal to the fastening axis W, according to FIG. 3, nothing changes with respect to the space which the head 20 fills.

In FIGS. 2a, b, an inventively formed head 20 is c shown, having a mushroom-shaped symmetrical head portion 20 a and has, on its underside, namely the connection side towards the shaft an asymmetric neck portion 21, for example in the form of an obliquely truncated circular cylinder. The obliquely cut surface of the neck part 21 forms the connection side 211 . The angle α of the inclined side terminal 211 with respect to the vertical plane 201a to the center axis M of the mushroom-shaped head part 20 a of the head is between 5 to 15 °, in the example shown it is 10 °.

Corresponding to the underside of the head 20 , which is inclined with respect to the central axis M and forms the connection side 211 , the fastening axis W of the head 20 according to FIGS. 2a, 2b, 2c also extends at an appropriate angle α to the central axis M.

The dimensions, namely the diameter E of the mushroom-shaped part 20 a, which is symmetrical to the central axis M, and the height H can also be varied. The angle of inclination α can be varied, for example, by appropriately designing the maximum height G of the wedge-shaped neck part 21 . The neck part 21 is preferably designed such that it extends from a maximum height G on one side to zero, ie to the lower edge of the symmetrical mushroom-shaped part 20 a.

To attach the head 20 to the shaft, a conical blind hole 202 is again formed in the center from the connection side 211 , the central axis of which is perpendicular to the connection side 211 and at the same time represents the fastening axis W. As can be seen from FIG. 4, the head 20 according to FIGS. 2a, 2b, 2c is in turn placed on the shaft 10 , which is formed with a projecting pin 102 for fitting the head, as described in FIG. 3. As a result of the asymmetrical design of the head according to the invention according to FIGS. 2a, b, c, the central axis M of the head 20 and the fastening axis W of the head 20 do not coincide, but are inclined towards one another in accordance with the wedge-shaped angle of the neck 21 attached.

Depending on the position in which the head 20 according to the invention with the neck 21 is now placed on the head plate 101 of the shaft, there are different fillings of space by the head above the shaft. In Figs. 4, 5, 6, 7, the four positions are shown, which are formed by respectively successively reacting the head 20 on the shaft 10 by 90 °. By implementing the head 20 according to the invention with the neck 21 in the asymmetrical configuration, a different space filling above the head plate of the shaft is achieved, that is to say a different space filling of an implanted shoulder prosthesis in the region of the shoulder joint with the same head in each case.

In the design and arrangement of the head according to FIG. 4, the lifting of the head in the lower region ensures that it is arranged in position C in the direction of the humeral head, as can also be seen from the schematic illustration according to FIG. 8.

In the arrangement shown in position A of FIG. 5, however, the head is in its maximum position disposed downward by arranging the maximum wedge of the neck 21 in the upper region of the shaft.

Positions B and D show the corresponding displacements of the head 20 to the front and to the rear depending on the arrangement of the head on the head plate 101 of the shaft 10 , as can also be seen from FIG. 8.

As shown in FIGS. 4 to 7, it is thus possible in a simple manner, even in the case of an implanted shaft, by means of minimal intervention only by changing the position of the head 20 according to the invention with the neck 21 on the shaft head plate 101, incorrect positions in the region of the shoulder joint to balance on pan and / or humeral head.

In order to enable a simple fixation of the head according to the invention on the head plate 101 of the shaft, four centering holes are provided on the head plate of the shaft in a circle around the fastening axis W and at a corresponding distance on the underside, ie connection side 211 , of the head 20 form a protruding positioning pin 22 which is then inserted into one of the respective centering holes on the shaft plate in order to fix the positions shown in FIGS . 4 to 7.

A total shoulder prosthesis in the implanted state is shown schematically in FIG. 9a. The humerus 1 with humeral head 1 a has the cut surface 1 b, via which the shaft 10 is inserted into the humerus. The head plate 101 delimits the cut surface 1 b. The shoulder blade 2 with the shoulder joint socket 2 a (glenoid) forms the joint space with the humeral head 1 a. The rotator cuff is labeled 3. The head 20 according to the invention with the neck 21 is fastened in the corresponding position on the shaft plate 101 of the shaft 10 in accordance with the course of the cut surface 1 b, glenoid 2 a and the required angular position of the humerus. If the spatial conditions in the shoulder joint area change, it is also possible after the implantation to change the position of the head 20 by rotation about the fastening axis W and thus to achieve a different space filling and improved joint function. In particular, the corrections described at the outset can be carried out with the head 20 with the neck 21 according to the invention.

Claims (12)

1. total shoulder endoprosthesis with a shaft and a head which can be exchangeably fastened to the shaft, with a mushroom-shaped shape symmetrical to a central axis M and with a connection side for the shaft formed on the underside of the head, characterized in that the connection side ( 211 ) forms the connection side Underside of the head ( 20 ) is designed to run obliquely with respect to the central axis (M) of the head. 2. Shoulder endoprosthesis according to claim 1, characterized in that the underside of the head (20) with respect to the central axis (M) of the head (20), the connection side (211) forming member is formed asymmetrically, so that the central axis (M) of the head is inclined at an acute angle with respect to the fastening axis (W) of the head on the shaft ( 10 ). 3. total shoulder endoprosthesis according to claim 1 or 2, characterized in that the connecting side ( 211 ) forming the underside of the head ( 20 ) with respect to the perpendicular position to the central axis (M) of the head ( 20 ) inclined at an acute angle α is progressive. 4. Total shoulder prosthesis according to one of claims 1 to 3, characterized in that the head ( 20 ) is formed with a projecting wedge-shaped neck part ( 21 ), the underside of which is inclined with respect to the central axis (M) of the head ( 20 ) running connection side ( 211 ) forms. 5. total shoulder endoprosthesis according to one of claims 1 to 4, characterized in that the head ( 20 ) is formed with a neck part ( 21 ) in the form of a crooked circular cylinder whose crooked cross-sectional area, the underside and connection side ( 211 ) of the head ( 20 ) forms. 6. shoulder total endoprosthesis according to one of claims 1 to 5, characterized in that the head ( 20 ) for attachment to a on the connection side ( 101 ) of the shaft ( 10 ) formed pin ( 102 ) a correspondingly formed the pin ( 102 ) Has a blind hole ( 202 ), the central axis of the pin ( 102 ) and the central axis of the blind hole ( 202 ) forming the fastening axis (W) of the head ( 20 ) on the shaft, such that when the head is placed on the shaft ( 10 ) ( 20 ) the central axis (M) of the head ( 20 ) is inclined at an acute angle to the fastening axis (W) of the head ( 20 ). 7. total shoulder endoprosthesis according to one of claims 1 to 6, characterized in that the head ( 20 ) on the shaft ( 10 ) in different about its fastening axis (W) rotated positions (A, B, C, D) can be fastened. 8. total shoulder endoprosthesis according to one of claims 1 to 7, characterized in that the positions of the head ( 20 ) on the shaft ( 10 ) are arranged offset at an angle of 90 ° to each other. 9. shoulder total endoprosthesis according to one of claims 1 to 8, characterized in that the head ( 20 ) on its connection side ( 211 ) forming the underside has a positioning pin ( 22 ) projecting over the connection side ( 211 ) and one of the number of positions of the head ( 20 ) on the shaft ( 10 ) corresponding number of position holes ( 203 a, b, c, d) on the connection side ( 101 ) of the shaft ( 10 ) for inserting the positioning pin ( 22 ) are formed. 10. Total shoulder prosthesis according to one of claims 1 to 9, characterized in that the angle between .   11. Total shoulder endoprosthesis according to one of claims 1 to 10, characterized in that the neck part ( 21 ) tapers in a wedge shape towards an edge side of the mushroom-shaped head ( 20 ) towards zero. 12. total shoulder endoprosthesis according to one of claims 1 to 11, characterized in that the connection side or underside ( 211 ) of the head ( 20 ) at an angle α of 5 to 20 ° from the in relation to the central axis (M) considered vertical position is inclined.