FR2909858A1 - Shoulder articulation prosthesis for treating proximal fractures, has connecting wedge connecting humeral rod to humeral bony tuberosity to be healed by osteosynthesis, where rod is implanted in medullar channel of humerus - Google Patents

Abstract

The prosthesis has a humeral rod implanted in a medullar channel of a humerus (10) fractured at a level of an upper proximal part (13), where the prosthesis is made of stainless steel. A hemispherical artificial humeral head is connected to a proximal end of the rod and adapted to be positioned against a coil (22) of a scapula (20) to form a rotule connection. A connecting wedge connects the rod to a humeral bony tuberosity to be healed by osteosynthesis.

Description

The present invention relates to the field of shoulder prostheses. he

  There are different types of shoulder prostheses on the market to be implanted in humans. In particular, these prostheses can be used when it is necessary to reconstruct the upper end of the humerus, that is to say when it is necessary to treat the proximal fractures of the humerus in order to reconstitute the kneecap connection with the glenoid of the shoulder. When such a fracture is noted, the proximal part is generally fractured into several bone fragments, including the articular humeral head and bone tuberosities, which nevertheless remain attached to the muscles via tendons. In this case, the two or three bony tuberosities and the articular head are no longer correctly positioned relative to each other on the one hand, and with respect to the diaphyseal portion of the humerus and the glenoid of the shoulder of the 'somewhere else. Beyond the pain that it generates in the patient, the shoulder joint is generally no longer possible. The objective of the treatment is to reform the kneecap connection between the end of the humerus and the glenoid of the shoulder with or without preservation of the articular head. For this, a metallic humeral stem, also called a nail, is implanted in the medullary canal of the fractured humerus. The humeral stem is either implanted into the medullary canal or the humerus using special tools, or sealed in this canal using a suitable cement. Most often, the medullary canal of the humerus has been tapped for this purpose. The distal portion of the humeral stem, that is to say its lower part, can also be secured to the humerus to prevent inadvertent movement (rotation on itself, pivoting, longitudinal movement). For this, through holes are provided in the distal portion of the humeral stem to receive screws implanted through the bone. Then, in order to reform the proximal part of the humerus, it is necessary to replace the bone tuberosities under the joint head. Two main solutions are conceivable, the 2909858 2 choice resulting from different criteria such as the age of the patient, the presence or absence of osteoarthritis, the state of the humeral head. In a first case, the fractured articular humeral head is still usable, that is to say that the hemispherical portion of the humerus which usually cooperates with the glenoid of the shoulder to form the ball joint is still intact, or can still be reconstituted using bone fragments by osteosynthesis. The various fragments are partially or totally detached from the bone and it is then simply necessary to reform the humeral head by joining them together. In this case, the metal humeral stem intended to be implanted in the medullary canal of the fractured humerus as described above has a proximal end provided with several through orifices arranged at several levels and in different orientations. Once the fragments are brought closer to each other around the proximal end of the shaft, screws are threaded therethrough to engage the orifices of the proximal end of the humeral shaft. According to another complementary or alternative method, suture threads pass through orifices made in the fragments to be brought together, orifices made in the proximal portion of the humerus and the orifices formed in the proximal portion of the humeral stem. The purpose of this procedure is to bring together the various bone fragments, including the humeral head, to return to their respective initial positions before the fracture, and then to hold them firmly in place using the screws and / or son so that a natural osteosynthesis can occur in order to refold the current fragments between them to reform the proximal part of the humerus.

In a second case where it is impossible to preserve the articular humeral head, a prosthesis comprising a metal artificial head mounted at the proximal end of a humeral stem is used, as described in FR-A-2 773 469 or FR-A-2 727 857. The bone tuberosities are then arranged by approximation 35 under the artificial humeral head and then fixed between them (between the diaphysis and the head) in the manner previously described with the aid of 2909858 3 screws and / or suture son to then weld by osteosynthesis. However, these different types of prostheses are not yet satisfactory because the fixation of the humeral stem and bone tuberosities is not optimal. Indeed, the humeral stem of the prosthesis must be implanted very precisely in relation to the bone that receives it. The slightest positioning error of the orifices of the distal portion of the humeral stem may indeed be reflected on the position of its proximal portion, where 10 are located the tuberosity and possibly the artificial head. However, the practitioner who must implant screws in these holes must be able to do so with great precision because it works almost blind, once the stem implanted in the humerus. It is usually only after X-ray verification that he knows if the prosthesis is well positioned. In addition, even if the humeral stem is perfectly implanted and secured to the diaphyseal portion of the fractured humerus, the use of screws and / or sutures coming into the orifices of the proximal portion of the humeral stem poses many problems. It is thus extremely difficult for the practitioner to know where these orifices are actually located because the tuberosities obscure them. However, an error of a few tenths of a millimeter in the repositioning of a tuberosity is enough to cause the formation of a reconstruction unsuitable for the glenoid.

In addition, poor positioning of the fragments between them may lead to poor osteosynthesis of these, likely to result in incomplete welding. This can result in significant pain for the patient, sometimes months after the operation, and possibly the need for a new intervention to replace the poorly installed prosthesis. An object of the present invention is therefore to solve the problems mentioned above with the aid of a simple, reliable and inexpensive solution. For this, the invention proposes to provide an intermediate part to facilitate the positioning of the tuberosities.

More specifically, the subject of the present invention is a shoulder joint prosthesis comprising: a humeral stem intended to be implanted in the medullary canal of a fractured humerus at its upper part, and a head substantially hemispherical artificial humeral connected to the proximal end of the humeral stem and adapted to be positioned against the glide of the shoulder scapula to form a ball joint, and characterized in that it further comprises a shim connecting the humeral stem to at least one humeral bone tuberosity to heal by osteosynthesis. According to preferred embodiments of the present invention. The wedge is arranged around the humeral stem and under the artificial humeral head so as to be surrounded by several bony tuberosities intended to be fixed on said wedge; the wedge has a through orifice having a section substantially identical to that of the humeral stem so as to be slid along said rod before being fixed to each bone tuberosity; the prosthesis further comprises stop means for preventing rotation of the intermediate shim with respect to the humeral stem; the stop means comprise a notch provided in the wedge and communicating with the orifice of the wedge and a rib binding the humeral stem and the artificial humeral head, this rib cooperating with said notch once the wedge in the fixing position; - The prosthesis further comprises self-tapping screws provided to traverse each bone tuberosity and come to fix in the hold; the shim is made of a synthetic resin, for example a polymer such as ultra-high density polyethylene; and 2909858 5 - the wedge is made of bone tissue from the humeral head of the patient. The invention will now be described in more detail with reference to a particular embodiment given by way of illustration only and shown in the appended figures in which: - the figure schematic scapula manner; Figure 2 is a perspective view similar to the upper proximal figure; Figure 3 is a top view of the fractured humerus with corolla-shaped bony tuberosities; Figure 4 is a sectional view of a humeral prosthesis according to the present invention, prior to its implantation in the medullary canal of the humerus; - Figure 5 is a sectional view of the prosthesis implanted in the fractured humerus; Figure 6 is a top view of a prosthesis connecting wedge; and FIG. 7 is a sectional view along the line VII-VII of FIG. 6. FIG. 1 represents, in perspective, a portion of a human humerus 10, more specifically the proximal portion located close to the scapula. 20 shoulder. This humerus portion comprises a diaphyseal portion 12 and an upper epiphyseal portion 13 located in the immediate vicinity of the scapula. The epiphyseal portion 13 comprises a humeral head 14 of substantially hemispherical shape adapted to cooperate with the glenoid 22 of the scapula 20 to form a ball joint. Figure 2 shows the fractured humerus at its epiphyseal portion 13. In particular, the proximal portion 14 is broken into several bone fragments 15, including a hemispherical portion of the articular head and two bony tuberosities which are still related to muscles via tendons 16. 1 is a perspective view showing a proximal portion of a humerus and a 1 and where the humerus is fractured at a portion 2909858 6 Thus, as shown in FIG. Figure 3, the set of fragments 15 forms an open corolla when looking at the bone from above. This configuration corolla can be particularly painful for the patient and especially prevents any rotation of the arm relative to the shoulder. It is therefore necessary to reform the connection ball joint destroyed by the fracture. Therefore, the invention proposes to solve this problem simply and effectively. As can be seen in FIG. 3, the humerus 10 has an internal medullary canal 11 capable of receiving a humeral prosthesis 10 which is the subject of the present invention. As explained in the introductory part of the description, the prosthesis 30 of the present invention has the function of replacing the initial humeral head 14 of FIG. 1 in order to reconstitute the ball joint with the glenoid 22 of the scapula 20.

For this purpose, as can be seen in FIGS. 4 and 5, the humeral prosthesis 30 comprises a humeral stem 31 made of a rigid material adapted to be implanted in the human body, such as a stainless steel. The humeral stem 31 is slightly curved to reproduce the shape of the humerus 10, especially in its epiphyseal region 13. A plate 32 is fixed perpendicular to the humeral stem 31, at its proximal end 33. The plate 32 supports a artificial humeral head 34 of a type known per se, of substantially hemispherical shape and made of the same material 25 as that constituting the humeral stem 31. More precisely, the artificial humeral head 34 is force-fitted on a conical protrusion 35 which stands on the Platinum 32. A reinforcing rib 36 joins the proximal end 33 of the humeral rod 31 and the lower face 37 of the plate 32, opposite the conical protrusion 30. The lower face 37 of the plate 32 is also provided with tooth-like roughnesses 38 disposed near the reinforcing rib 36. As can also be seen in FIG. 4, the prosthesis 30 conforms the present invention further comprises a shim 40.

The shim 40, shown in more detail in FIGS. 6 and 7, is made either of a synthetic resin, for example a polymer such as ultra high density polyethylene, or machined in the bone of the humeral head. initial patient. In fact, in the present case, the initial humeral head 14 can not be reconstituted identically with the help of the bone fragments 15 created during the fracture. Only the bone tuberosities closest to the diaphyseal portion 12 of the humerus 10 are preserved. Thus, it is possible to use the hemispherical fragment of the patient to achieve the wedge 40. In this way, the bone compatibility is ideal and this solution facilitates the subsequent osteosynthesis that is necessary for the prosthesis 10 to be effective. The shim 40 thus has a substantially cylindrical shape, with a through orifice 41 having a section substantially identical to that of the humeral stem 31 so as to be slidable along the latter before being fixed to each bone tuberosity 15. A notch 42 is also defined in the shim 40. This notch 42 opens into the orifice 41 and has a thickness substantially identical to the thickness of the reinforcing rib 36 so as to form locking means in rotation of the shim 40 in relation to the humeral stem 31.

FIGS. 4 and 5 illustrate the method used to position the wedge 40 on the humeral stem 31, then to fix the fragments 15 on said wedge 40. In a first step, the wedge 40 is slipped on the humeral stem 31 thanks to its orifice 41, and until its bearing surface 43 abuts against the lower face 37 of the plate 32, as shown in Figure 6. In this position, the reinforcing rib 36 enters the notch 42 and the roughnesses 38 abut against the bearing surface 43 of the shim 40. Once the prosthesis 30 is assembled, the humeral stem 31 is slipped inside the medullary canal 11 of the humerus 10, then it is sealed in known manner, for example with a suitable cement. In this position, the wedge 40 is thus surrounded by the remaining bone fragments (head portion and tuberosities) which are still configured in the shape of a corolla but which have been reduced by cutting at the lines referenced F. The wedge 40 is moreover designed so that once the bone fragments are returned to their initial position before fracture, it is in contact with them. The practitioner then brings all the cut portions of bone fragments 15 closer to each other, i.e. centripetally towards the shim 40, and screws self-tapping screws 50 therethrough for keep in position. For this purpose, the practitioner may, contrary to the prior art, choose to place the self-tapping screws 50 at any location of each bone fragments 15. The material constituting the wedge 40 being easy to pierce, the practitioner simply continue the screwing of the self-tapping screws 50 in the hold 40 without it being necessary to have predrilled holes therein. The practitioner also does not need to use sutures, which avoids having to make orifices in the bone fragments 15 and in the diaphyseal portion 12 of the humerus 10. Thus, the wedge 40 and the bone fragments 15 (head portion and tuberosities) being devoid of pre-holes or through orifices, the practitioner is free to place the self-tapping screws 50 at the places where the fixation will be optimal to allow good osteosynthesis of the Bone fragments 15. Unlike the prior art, the practitioner has the possibility of positioning very precisely the artificial humeral head 34 relative to the glenoid 22 without having to wonder if the humeral stem 31 will then be well placed for the subsequent fixation of the In other words, since the proximal portion 33 of the humeral stem 31 is devoid of a through hole for receiving screws or sutures, the practitioner does not have to It is important to consider whether the humeral stem 31 is well oriented in the medullary humeral canal 11. It should simply focus on the position of the artificial humeral head 34 with respect to the glenoid 22. Thus, the osteosynthesis weld The remaining bone fragments can be easily and optimally formed as long as they are perfectly positioned relative to one another and firmly attached to the shim 40. The risk of poor fixation of the bone fragments is significantly reduced. 9 also makes it possible to increase the implantation success rate of humeral prostheses compared to the prior art. The post-operative complications are furthermore significantly reduced, in particular at the level of the welding of the bone fragments between them and the collaboration between the artificial humeral head 34 and the glenoid 22 of the shoulder. The wedge 40 is a very easy piece to achieve with very small accuracy tolerances. It has a simple form adapted to be performed in a patient's bone. It is easy to handle and put in place by the practitioner, causes no rejection phenomenon and allows a firm and reliable fixation of the bone fragments 15. It goes without saying that the detailed description of the subject of the invention, given By way of illustration only, in no way constitutes a limitation, the technical equivalents also being within the scope of the present invention. Thus, the artificial humeral head 34 can be made in one piece with the humeral stem 31.

Claims (8)

  A shoulder joint prosthesis (30) comprising: - a humeral stem (31) intended to be implanted in the medullary canal (11) of a fractured humerus (10) at its upper proximal portion (13) , and a substantially hemispherical artificial humeral head (34) connected to the proximal end (33) of the humeral stem (31) and adapted to be positioned against the glenoid (22) of the scapula (20) to form a link patella, characterized in that it further comprises a wedge (40) for connecting the humeral stem (31) to at least one humeral bone tuberosity (15) to be healed by osteosynthesis.   2. Prosthesis according to claim 1, characterized in that the shim (40) is arranged around the humeral stem (31) and under the artificial humeral head (34) so as to be surrounded by several bone tuberosities (15) intended to be fixed on said shim (40).   3. Prosthesis according to claim 2, characterized in that the wedge (40) has a through hole (41) having a substantially identical section to that of the humeral stem (31) so as to be slid along said rod ( 31) before being attached to each bone tuberosity (15).   4. Prosthesis according to claim 3, characterized in that it further comprises stop means (36, 42) for preventing the rotation of the wedge (40) relative to the humeral stem (31).   5. Prosthesis according to claim 4, characterized in that the stop means comprise a notch (42) provided in the shim (40) and communicating with the orifice (41) of the shim, and a rib (36) binding the humeral stem (31) and the artificial humeral head (34), this rib (36) cooperating with said notch (42) once the shim (40) in the fixing position.   6. Prosthesis according to any one of the preceding claims, characterized in that it further comprises self-tapping screws (50) provided to pass through each bone tuberosity (15) and to be fixed in the wedge (40). 2909858 11   7. Prosthesis according to any one of the preceding claims, characterized in that the shim (40) is made of a synthetic resin, for example a polymer such as ultra high density polyethylene. 5   8. Prosthesis according to any one of claims 1 to 7, characterized in that the wedge (40) is made of a bone tissue from the humeral head (14) of the patient.