Endoprosthesis for a joint.

p0001The invention relates to an endoprosthesis for a joint according to the preamble of claim 1.

p0002Such prostheses generally consist of a connecting piece with a stem that is inserted into the medullary canal of a resected long bone and is fixed there, for example, by the use of cement.

p0003Known articular wear at the distal end of a joint head which is either fixed or connected by means of a conical interface form and locks with the stem.

p0004For a given shape of the medullary cavity of the bone s leading stem to the fitting result from the natural individual shape of the medullary canal problems concerning the position of the condyle relative to the glenoid. So the connector undergoes due to a quasi-torsion of the bone from the distal to proximal end, which magnitudes may have up to 45 °, during the driving of the stem into the medullary cavity of a Drehung.Aufgrund a given roundness of the condyle is an optimal cooperation of the condyle with the then acetabulum no longer guaranteed after the installation of the fitting.

p0005The invention is now the object of developing an endoprosthesis for a joint of the aforementioned type so that an individual adjustment of the joint position despite a predetermined shape of the inserted into the medullary canal of the long bone stem is possible.

p0006The object is solved by a stent having the features of claim 1.

p0007Further advantageous embodiments result from the dependent claims.

p0008According to this proposed solution is an attachable from a connector with a fixable in a long bone stem and a conical plug-in pin which is engageable with a conical receptacle of a settable on the fitting joint head in a self-locking connection, and an on bony counterpart of the replaced joint acetabular cup existing endoprosthesis formed so that the rotational position of the joint head is adjusted and fixed on the cone of the connecting piece.

p0009According to this proposal, it is possible, after driving the stem of the fitting in the medullary canal of the long bone, said unavoidable natural individual shape of the medullary canal follows to put the joint head on the plug cone of the fitting, adjust its position optimally by turning on the plug-in cone and to fix this.

p0010Preferably, the fixing of the rotational position by means of concentrically around the conical plug-in sleeve of the swivel head arranged bores and by a fixing pin on the end face of the connecting piece, whereby the fixing pin engages in one of the bores so that the fixing pins, the angular position of the joint head on the connecting piece arretiert.Nach the adjusting the rotational position of the condyle is the self-locking connection between the conical receptacle in the joint head and the conical pin on the connector made, so that the rod end load retained in its position.

p0011According to a further advantageous embodiment of the prosthesis is not only the joint head on the connector in its position adjusted and set, but also the Gelenkpfannenteil.Diese measure increases the range of possibilities of joint positions considerably, so that an optimal adjustment of the joint in matching anatomical features is guaranteed.

p0012For this purpose Preferably, the acetabular cup from a attachable to the bone base with a central pin which is driven into the bone, and in which a conical plug-in sleeve is formed, as well as a a joint socket simulating adaptation part which a conical plug-in pin .The connection between the pad and the adaptation part is done via a self-locking taper connection between the conical plug-in pin of the pad and the spigot of the adaptation part.

p0013Before production of the self-locking taper connection, the rotational position of the adaptation part to the substrate can be adjusted, and by simply rotating it about the axis of its conical plug-in pin. The fixation of the rotary position can take place on the other hand by means of concentrically around the plug-in pin part of the adaptation bores arranged on the one hand and by at least one fixing pin on the end face of the support, wherein the fixing pin engages in one of the bores.

p0014After adjustment of the rotational position and their fixing by means of the fastening pin the self-locking taper connection is made, so that the adaptation part load held in position.

p0015The fixing of the base of the joint socket part on the bone can be carried out by at least one drivable in the bone plug on the underside of the pad.

p0016The cooperating with the joint head after installing the prosthesis part of the joint socket portion, ie the adaptation part, for optimal function of the prosthesis from a plastic with low friction coefficient.

p0017For a cementless fixation of the stem of the connecting piece in the long bones and the center pin of the base of the joint socket portion whose surface structure can be modeled to cancellous bone.

p0018The invention will be explained in more detail with reference to the drawings. In the drawing:<ul><li>1 shows a side view of a connecting piece of the endoprosthesis with a swivel head,</li><li>Figure 2 is a view of the underside of the joint head in the direction of arrow A in Fig. 1,</li><li>Figure 3 is a side sectional view of the joint socket portion with pad and adaptation part,</li><li>Figure 4 is a view of the underside of the adaptation part of the joint socket part in the direction of the arrow B in Fig. 3, and</li><li>5 shows a sectional view of a further embodiment of the adaptation part of the joint socket part.</li></ul>

p0019According to Figure 1, the connector 1 from a fixable in a long bone stem 15.Am joint end, the connecting piece 15 a conical insert pin 3. On the conical plug-in pin 3 a joint head 2 is plugged. For this purpose, the joint head 2 on a conical receptacle. 4 The connection between the joint head 2 and the connection piece 1 is carried out via a self-locking taper connection between the plug-in pin 3 and the plug-in sleeve 4th

p0020As shown in Fig.2, has the joint head 2 arranged concentrically on its underside around the conical plug-in sleeve 4 holes fifth After the placing of the joint head 2 on the conical plug-in pin 3 of the connecting piece 1 may whose position can be set by turning on the plug-in pin 3, and are fixed by an engagement of a fastening pin 6 on the end face of the connecting piece 1 in one of the bores 5 in the joint head 2nd After preparation of the self-locking taper connection between the joint head 2 and the connector 1 of the joint head is load firmly in place on the connector 1 held.

p0021The acetabular cup according to Figure 3 consists of a base which is fixed to the bone and an adaptation part 11. The base 8 has a central spigot 9, the wird.Im inserted into the bone interior of the center pin 9 is provided a conical receptacle 10 , The adaptation part 11 has a conical plug-in pin 12, which is plugged into the conical socket 10 of the pad eighth Prior to making a self-locking taper connection between the spigot 12 of the adaptation part 11 and the conical socket 10 in the central pin 9 of the support 8, the adaptation part may be rotated 11 by the plug-in pin 12 to adjust the position of the designed as a joint socket adaptation part eleventh

p0022According to Figure 4, the adaptation part 11 concentrically arranged on its underside to the plug-in pin 12 holes 13 for fixing its position relative to the base. 8

p0023The fixing of the position of the adaptation part 11 with respect to the base 8 is performed by engaging at least one fastening pin 14 on the front side of the base 8, 3 of which two pieces are shown in FIG. After preparation of the self-locking taper connection between the base 8 and the adaptation part 11 it is held firmly in the load adjusted position.

p0024For the fixing of the pad 8 to the bone has this on its side facing the bone side on at least one drivable in the bone pins 16, 3 of which two pieces are shown in FIG.

p0025In the illustrated embodiment, the base 8 of the fixing pin 14 forms with the stud 16 a structural unit in the form of a pin.

p00265 shows a slightly modified embodiment of the adaptation part 11 is shown. Notwithstanding the adaptation part shown in Figure 3 has its embodiment according to Figure 5, a different design of the actual joint socket on, with a roof-shaped bulge, which further surrounds the joint head.

p0027In known manner, the joint socket, the actual performing adaptation part 11 is manufactured from a plastic with a low coefficient of friction.

p0028As indicated in Figure 1 and Figure 3, the surface structures of the stem 15 of the connecting piece 1 and the center pin 9 of the pad 8 to the cancellous bone modeled so that the fixation of the endoprosthesis in the bone without cement can advantageously be carried out.