Blocking ring for osteosynthesis device and osteosynhesis device including such ring

[0001] The present invention relates to a locking sleeve for a retaining pin to be screwed into the bone part. The invention also relates to an assembly comprising said sleeve and a ring to be inserted into the opening of the holding plate. Finally, the invention relates to an osteosynthesis device.

[0002] The osteosynthesis device consists of a holding plate, at least two pins to be screwed into two bone parts, and locking bushes to ensure the fixing of the pins, and thus the connection of the holding plate with two bone parts.

[0003] A serious problem in this technical field is the creation of an osteosynthesis device offering both effective locking of the mandrels to prevent them from unscrewing under mechanical stress and vibrations, and easy removal of the mandrel when the physician wants to remove the osteosynthesis device.

[0004] Patent EP-1 583 478 discloses an osteosynthesis device in which the axes of the mandrels and the locking sleeves are angled. In this osteosynthesis device, the holes in the retaining plate are threaded and surround an intermediate sleeve that has a threaded groove surrounding the mandrel and a locking sleeve. WO 2004/069067 A discloses the features of the preamble of claim 1.

[0005] To embed the osteosynthesis device, the doctor, after drilling the holding plate in at least two places selected to ensure its attachment to the bone part, drills said bone part, guiding the drill perpendicular to the holding plate. He then places the intermediate sleeve and screw the threaded rod into the bone to the desired length. He inserts the locking sleeve onto the mandrel and screws said locking sleeve into the intermediate sleeve.

[0006] It is understood that due to the angular displacement between the axes of the mandrel and the locking sleeve, during screwing a progressive wedging of the locking sleeve in the intermediate sleeve is realized. Irreversible locking of the plunger in relation to the holding plate is thus achieved.

[0007] Said device is effective but has several disadvantages. [0008] First of all, the tolerance for the angular difference between the axes of the mandrel and the locking sleeve is insufficient. Manufacturing the intermediate sleeve is therefore difficult, resulting in increased manufacturing costs.

[0009] Furthermore, this angle difference, even if it provides effective locking, has the disadvantage that locking already occurs at the beginning of the screwing in of the locking sleeve. Therefore, it may happen that the locking sleeve only insufficiently penetrates the holding plate.

[0010] Finally, in the case of a thin plate (for example, less than 3 mm), the intermediate sleeve and the locking sleeve should be partially inserted into the bone part to allow good blockage of the device. This does not allow the use of a state of the art device for upper bones (arms, forearms, hands, wrists, face) that are too thin. The invention aims to overcome the limitations of the prior art osteosynthesis devices and is defined by the features of claim 1.

[0012] The present invention achieves its purpose by proposing a locking bushing for a threaded retaining mandrel for screwing into a bone part, said bushing having a first part having an axial groove for receiving said retaining mandrel, and the rim of said first part being threaded for cooperate with the holding plate, the said sleeve being characterized in that it additionally includes, in extension of said first part, a second part thinner than the thickness of the first part and having an identical axial groove, while said second part is deformable and thus capable of being locked by deformation of said sleeve on said mandrel.

[0013] According to a preferred embodiment, the groove in the first sleeve part is threaded.

[0014] Preferably, the first sleeve part has an outer cylindrical or truncated cone shape.

[0015] The invention also relates to an assembly comprising a sleeve according to the invention and a ring, said ring being intended to be inserted into the opening of the holding plate, and the ring comprising a threaded cut similar to a truncated cone, threaded according to the thread of the sleeve and the radial gap.

[0016] Preferably, the ring comprises a radial gap.

[0017] According to a particular embodiment, the ring has a convex rim intended to cooperate with the concave opening of the holding plate.

[0018] The invention ultimately relates to an osteosynthesis device comprising a retaining plate comprising at least two holes, pins to be inserted into said holes for screwing into the bone part, and locking sleeves or assemblies according to the invention.

[0019] Other features and advantages of the invention will become apparent upon reading the following description of a particular embodiment of the invention, given as a guide rather than limiting, with reference to the accompanying drawings, in which:

- fig. 1 schematically illustrates the osteosynthesis device,

- fig. 2 is a longitudinal cross-sectional view of the osteosynthesis device mounted on the bone part comprising the sleeve according to the first embodiment of the invention,

- fig. 3 shows the device of fig. 1, after cutting off the locking sleeve and the mandrel,

- fig. 4 is a longitudinal cross-sectional view of a part of the osteosynthesis device mounted on the bone part comprising a sleeve according to a second embodiment of the invention, and

- fig. 5 is a view in direction D of the device shown in fig. 4. [0020] Fig. 1 schematically shows an osteosynthesis device for attaching two bone parts 2a, 2b to the holding plate 4. The holding plate 4 includes holes through which the pins 6a, 6b, 6c, 6d pass, at least one of which contains thread 8a, 8b, 8c, 8d for screwing the mandrel into one of the bone parts. The osteosynthesis device includes two pins for each bone part, but it is obvious that in some cases it may contain only one pin for one bone part. It should be noted that the mandrels can be screwed in a direction perpendicular to the plane of the holding plate 4. This is the case for the mandrel 8b. The mandrels can also be screwed in an inclined direction relative to the perpendicular direction. This is the case with mandrels 8a, 8c, 8d.

[0021] Locking sleeves 10a, 10b, 10c, 10d are provided in the holes of the holding plate 4 for attaching the pins to said holding plate.

[0022] Methods of implementing the locking sleeve according to the invention will now be described with reference to Figures 2 to 5.

[0023] Fig. 2 shows a part of an osteosynthesis device comprising a sleeve according to a first embodiment of the invention. One mandrel is shown in this drawing, but it is understood that the osteosynthesis device may include at least two mandrels for fusing two bone parts.

[0024] In Fig. 2, the holding plate 12 is located above the bone part 14. The holding plate comprises an opening 16 in which the pin 18 and a locking sleeve 20 are located.

[0025] According to the invention, the locking sleeve 20 comprises a first portion 22 having an axial groove 24 for the passage of the mandrel 18, said groove may or may not be threaded, the periphery of the first locking sleeve part 22 comprising a thread 26 for screwing it in the hole of the holding plate, and the second part 28, which is an extension of the first part 22, with a smaller thickness than the first part and having an axial groove 30, identical to the turning in the first part.

[0026] The thickness of the second part 28 is selected depending on the material of which the locking sleeve 20 consists, so that after cutting the mandrel and the second part, the remaining part of the second part deforms and presses on the upper remaining part of the mandrel, ensuring its blocking relative to the holding plate.

[0027] The location of the osteosynthesis device is carried out as follows. The doctor drills the holding plate at least in two selected places to ensure its attachment to the bone parts. He then drills each bone part, guiding the drill at right angles to the holding plate. Then places the locking sleeve 20, screwing it partially into the hole 16. He can also screw the locking sleeve 20 completely into the hole 16, in particular when the axial hole of the first locking sleeve part 22 is not threaded. The mandrel 18, the lower part of which includes the thread 32, is then screwed into the bone part to the desired length, and the locking sleeve 20, or at least a second part thereof, performs a secondary function when screwing in to guide the pin during screwing in. If the locking sleeve 20 has not been pre-positioned, it is now completely screwed into the hole 16.

[0028] The physician then cuts off the stem 18 and the sleeve 20 approximately at the base of the second part 28, i.e. in the area of ​​connection between the first part 22 and the second part 28. An indicator, for example a small groove, can be provided around the circumference of the sleeve for precise definition of the position cutting off tool.

[0029] As a result of cutting out, the remaining part 34 of the second part 28 of the locking sleeve 22 is deformed towards the mandrel 18 ,. Locking of the mandrel 18 relative to the locking sleeve 22 and thus relative to the holding plate 12 is thus achieved by clamping.

[0030] Thus, when the physician cuts off the stem 18 and the sleeve 20 in the region of the joint between its first part 22 and the second part 28, with the use of appropriate forceps, the forceps of the forceps tend to grip the locking sleeve 20 first and then, joining , for deforming it for final cutting, both of the locking sleeve 20 and the mandrel 18. Thus, the cut free edge of the second part appears, forming the remaining part 34, connected to the first part. The two diametrically opposed portions of said free edge are brought together as a result of shear forces and approximately cover the free, cut-off end of the mandrel 18. The remaining portion 34 of the second portion 28 of the locking sleeve 22, deformed towards the mandrel 18 by tightening it, allows the pin 18 to be locked to the locking sleeve 22 by tightening.

[0031] Thus, the situation of Figure 3 arises, in which elements identical to those in Figure 2 bear the same markings.

[0032] The locking sleeve according to the invention is particularly advantageous in that it provides excellent locking performance for small diameter stems, e.g. 0.8 to 1.8mm diameter, which corresponds to the type of stems used for the wrist bone parts, hand or face.

[0033] Thus, a tensile strength greater than 200 kg, which cannot be greater than 200 kg per one 4 mm diameter mandrel, and a 316L surgical steel sleeve whose second part has a thickness of 1 mm was experimentally found. In this test, the bushing did not have an internal thread. It is understood that the tensile strength will be significantly increased with an internal threaded sleeve. It enables, in particular, excellent tensile strength, even for small diameter mandrels.

[0034] Of course, the locking sleeve according to the invention is also useful and effective with larger diameter mandrels.

[0035] Fig. 4 is a cross-sectional view of a part of the osteosynthesis device comprising a locking sleeve according to a second embodiment of the invention, and in Fig. 5 a top view thereof in the direction D parallel to the axis of the mandrel.

[0036] The locking sleeve 36 includes a first frustoconical portion 38 (thread 40) provided with an axial groove 42 and a second portion 44, in extension of the first portion, comprising an axial groove 46 identical to the groove in the first portion 38. According to the invention, the thickness of the second part is selected depending on the material used, so that said second part is deformable and blocks the mandrel due to deformation during its cutting off.

[0037] The second embodiment of the invention differs fundamentally from the first embodiment in that the locking sleeve is formed on a directionally oriented ring 50 in the opening 50 of the holding plate. To this end, the ring has a convex edge 52 and the opening of the holding plate 12 has a corresponding concave edge 54.

[0038] The location of the mandrel is done in the same way as for the device described in connection with Figs. 2 and 3. The physician initially drills the plate in at least two places. It then creates a concave edge of the hole to allow later insertion of the ring. Then it drills the bone part, depending on the selected tilt of the mandrel, with a drill. The ring 48 is then inserted into the hole in the retaining plate, the insertion being facilitated by the radial gap 50 of the ring 48. The locking sleeve 36 is screwed at least partly on the ring 48 to lock its orientation and guide the mandrel 18. When the stem has already been screwed to the desired length and the locking sleeve has been completely screwed onto the ring 48, the doctor cuts off the locking sleeve 36 and stem 18 in the area of ​​the bottom of the second part 44 of the locking sleeve 36, deforming the remainder of said second part and thus locking the stem 18 .

[0039] In a classical manner, the locking sleeve, in accordance with each embodiment of the invention described, includes one or more of the depressions 56 shown in Fig. 5 to allow the physician, with a suitable screwdriver, to unscrew the stem / sleeve assembly when he wants to remove the plate holding.

Worcel, Alexandre, France; Worcel, Manuel, France;

Worcel, Julia, France; Worcel, Marie, France;

Paoli, Albert, France; Paoli, Edouard, France;

Paoli, Jean, France; Paoli, Myriam, France;

Lombardo-Fiault, Bernard, France; Laumonier, Yves, France; Laumonier, Alain, France;

Laumonier, Bruno, France; Laumonier, Nicolas, France;

Laumonier, Remi, France; Ateliers Laumonier, SAS, France;

Proxy:

Z-13841 EP