Endoprosthesis for partly or completely replacing the humerus

Abstract: An endoprosthesis (16) for partly or completely replacing the humerus, comprising a head portion (14) which is connected to an elongate shaft portion, wherein the spherically formed head (32) includes openings (36) for fixing a number of bands, whereby the head (32) includes an at least partly circumferentally extending groove (34) distally below its largest diameter to receive a band (38) made of body compatible material wrappen around the head (32).

Description: The present invention refers to an endoprosthesis for partly or completely replacing the humerus according to the preamble of claim 1. An endoprosthesis of this type is disclosed in German Petty Patent DE-U-88 14 434. The endoprosthesis comprises a humerus head portion having a distal end including an inner cone. For a complete replacement, the humerus head portion is connected to a shaft comprising a pair of elongate shaft portions which may be axially connected to each other and which shaft is secured to the distal joint portion through a tapered joint. For a replacement in part the distal end of the shaft is connected to a portion of the humerus not resected. Below the spherical head of the head portion a number of openings is provided for securing bands or, respectively, tissue portions forming the articulate capsule. It is the object of the present invention to provide an endoprosthesis for partly or completely replacing the humerus which endoprosthesis is suited to provide for a particular suitable connection of the bands of the shoulder joint to the prosthesis. According to the invention the object referred to is solved by the features of claims 1. The head of the endoprosthesis according to the invention comprises an at least partly peripherally extending groove distally below the largest diameter for receiving a band extending around the head. The ends of the bands or the tissue forming the articular capsule can be safely fixed in the groove by a band made of body compatible material. According to an embodiment of the invention, the groove is located in a meridian plane of the head. The groove is thus positioned to provide optimum conditions for fixing the tissue and the bands. According to a further embodiment of the invention, the openings are located in a meridian plane adjacent to the groove i.e. positioned proximal with respect to the groove. Additional securing bands may be drawn through the openings. The head and the portion suspending therefrom up to the cone of the known prosthesis are formed solid. Thus this portion of the prosthesis has a substantial weight. According to a further embodiment of the invention it is preferred to provide a short and hollow shaft portion integrally formed on the head. For connecting the shaft portion extending therefrom the head prosthesis portion comprises either an inner cone or an inner thread portion wherein the shaft portion comprises an outer cone or an outer thread portion correspondingly. According to a still further embodiment of the invention the cavity of the hollow head contains a cross wall including a threaded bore for receiving a threaded pin for connecting the head portion and the shaft portion. The screw pin is provided to extend distally through the shaft portion when connecting the head and shaft portion to be screwed into the head portion. Preferred embodiments of the invention are described in detail as follows with reference to the drawings. Fig. 1 shows a side view of an endoprosthesis according to the invention for partly replacing a humerus. Fig. 2 shows an embodiment of a head portion of a humerus endoprosthesis according to the invention. Fig. 3 shows a longitudinal section through the head portion of Fig. 2 and Fig. 4 shows a longitudinal section through a further embodiment of a head portion. The shoulder joint 10 shown in Fig. 1 is formed by a natural shoulder blade 12 including an artificial articulate capsule, for example, and a head portion 14 of an endoprosthesis 16. The head portion 14 to be formed as a rotational head is attached to a shaft portion 18 including a stepped end 20 with a flat 22 cooperating with an end portion 24 of a distal shaft portion which comprises alike flats cooperating with the flat 22, wherein the portions are to be connected to each other by screws. A connection of this type is disclosed in DE-GM 88 14 434. The distal shaft portion includes a lateral strut 26 to be secured to the distal portion 28 of a natural humerus. The head portion 14 is shown in detail in Fig. 2. The head includes a distal shaft portion 30 which proximally ends in a spherical head 32 under an angle corresponding to the anatomic conditions of the humerus. As seen from Fig. 2 the joint between the shaft portion 30 and the head 32 includes an annular groove 34 having an arcuate or circular cross section. The groove 34 is located in a meridian plane with respect to the head 32 which distally is located below the maximum meridian plane. A number of openings 36 is formed in the head 32 in the plane of the maximum diameter or, respectively, the maximum meridian plane. As Fig. 1 shows, the groove 34 receives a body compatible band 38 which is slung around the end portion of bands and capsule tissue to fix these parts to the head portion 14. Bands and capsule tissue are indicated at 40. The openings 36 serve to receive further bands or the like to improve the connection. Fig. 3 shows the longitudinal section through the head portion 14 of Fig. 2. One sees that the distal shaft portion 30 includes an inner cone 42 to receive an outer cone of the shaft portion 18 (Fig. 1). The wall of the shaft portion 30 limiting the inner cone 42 extends partly into the hollow head 32. Thus a cross wall 44 is formed in which a threaded bore 46 is provided coaxially with respect to the shaft portion 30. The threaded bore 46 receives a threaded pin not shown which extends distally through the shaft portion 18 and is screwed in the threaded bore 46 to fix the head portion 14 and the shaft portion 16 with respect to each other. The embodiment shown in Fig. 4 slightly differs from that shown in Fig. 3. With respect to Fig. 3 identical parts bear the same reference numerals but an "a" is added. The distal shaft portion 30a comprises a threaded bore 50 to receive an outer threaded portion of a shaft portion similar to the shaft portion 18 shown in Fig. 1. The threaded bore 46a receives a threaded pin to fix a shaft portion not shown to the head portion 14a.

Claims: An endoprosthesis for partly or completely replacing the humerus, comprising a head portion (14) which is connected to an elongate shaft portion (30), wherein the spherically formed head (32) includes openings (36) for fixing a number of bands, characterized in that the head (32) includes an at least partly circumferentially extending groove (34) distally below its largest diameter which receives a band (38) made of body compatible material wrapped around the head (32) The endoprosthesis of claim 1, characterized in that the groove (34) is located in a meridian plane of the head (32) The endoprosthesis of claim 2, characterized in that the openings (36, 36a) are located in a meridian plane adjacent to the groove (34, 34a). The endoprosthesis of one of claims 1 to 3, characterized in that a hollow shaft portion (30, 30a) suspends from the head (32). The endoprosthesis of claim 4, characterized in that the shaft portion (30) comprises an inner cone (42) to receive an outer cone of the shaft portion (18). The endoprosthesis of claim 4, characterized in that the shaft portion (30a) comprises an inner thread (50) cooperating with an outer threaded portion of the shaft portion. The endoprosthesis of one of claims 4 to 6, characterized in that a cross wall (44, 44a) is provided in the inner cavity of the head (32, 32a) including a threaded bore (46, 46a) to receive a screw pin to connect the head portion (14) to the shaft portion (18).

Inventors: CAPANNA RUDOLFO DR MED, CAPANNA, RUDOLFO, DR. MED.
Applicants: HOWMEDICA GMBH
Application year: 1992
Main classification: A61F2
IPC codes: A61F2