FR2811219A1 - Prosthesis cement injection syringe has sliding piston actuated by threaded rod and nut fixed to cylinder - Google Patents

Abstract

The syringe consists of a relatively broad cylinder (1) with an outlet channel (3), containing a sliding piston (4) actuated by a threaded rod (60) and a nut (52). The nut acts as a cap for the cylinder's inlet end and is fastened to the cylinder by a threaded skirt (50). The tip (61) of the threaded rod is fixed to the piston, and its outer end is fitted with a non-slip head (63).

Description

The present invention relates to syringes allowing

  cement injection for fixing orthopedic prostheses.

  Orthopedic prostheses are frequently sealed in

  a patient's bone cavity using an appropriate cement.

  The cements used are in the form of powder which the practitioner must mix with a liquid to obtain a paste of suitable consistency, not very fluid, and likely to adhere well.

  to the walls of the bone cavity and the prosthesis to be joined.

  The cement, initially in the form of this paste, sets quickly, in a period of the order of two to three minutes, to give a particularly resistant rigid structure. The duration is therefore short between the moment when the practitioner puts the powder and the liquid in contact, and the moment when everything must be in place in

  the bone cavity and around the prosthesis.

  The short duration constitutes a first difficulty, so that it is necessary to reduce as much as possible the time of preparation and handling of the cement, to allow sufficient time for the practitioner for the correct arrangement of the prosthesis in the bone cavity and for the correct distribution. cement around

the prosthesis before taking it.

  A second difficulty stems from the fact that the paste forming the cement is not very fluid, and does not readily lend itself to injection by a syringe. The injection indeed requires a significant pushing pressure to overcome the friction forces of the paste on the walls of the syringe and to overcome the low viscosity of the paste. The syringes currently used include a piston pushed by hand or by a rack, having a small section so as to produce a high pressure resulting from the manual force available for pushing the piston. The practitioner must prepare the paste in an additional container, mixing the powder and the liquid, then introduce the paste into the elongated cylinder of the syringe, and finally inject the paste into the bone cavity around the prosthesis. Such a device is not satisfactory, in particular by the fact that the practitioner must apply to the piston a large longitudinal pushing force which frequently leads to a lack of precision in the positioning of the syringe and therefore to a lack of precision of the points of cement in the bone cavity, and by the fact that the operations of mixing in an annexed container and then of introduction into the syringe require a non-negligible time which reduces all the time available for the medical positioning operation prosthesis into the bone cavity and cement injection around the prosthesis. The problem proposed by the present invention is to design a new syringe structure for injecting prosthesis cement, making it possible to increase the time remaining available to the practitioner for positioning the prosthesis in the bone cavity and injecting the cement around it. the prosthesis, and making it possible to increase the positioning accuracy of the syringe by reducing the longitudinal force necessary to

actuation of the piston.

  According to another object of the invention, the syringe structure makes it possible to reduce the losses of cement, by ensuring the most complete possible injection of the cement into the cavity

bone around the prosthesis.

  Another object of the invention is to design such a syringe structure which is particularly easy to handle.

  and precise, to avoid aseptic errors.

  To achieve these and other objects, a syringe according to the invention for injecting prosthesis cement comprises a cylinder of relatively squat shape with an outlet channel and with a piston sliding in the cylinder and actuated by an operating member; the operating member comprises an axial threaded rod urging the sliding piston to slide in the cylinder and screwed into a threaded nut integral with the cylinder. Such a thrust screw actuator structure makes it possible, from a relatively low torque exerted by the user, to produce an axial thrust force sufficient to reach the injection pressure necessary despite the large cross section of the cylinder. In other words, it is thus possible to use a cylinder of stocky shape, with a relatively large diameter, making it possible to mix the powder and the liquid inside the

cylinder itself.

  According to an advantageous embodiment, the nut consists of a removable inlet plug attached to the first

end of the cylinder.

  The inlet plug may advantageously comprise a threaded fixing skirt, adapting by screwing to the area

  threaded from the first end of the cylinder.

  In practice, the inner end of the threaded rod can advantageously be engaged in abutment against the outer face

sliding piston.

  The sliding piston can advantageously comprise a generally planar thrust face, a cylindrical lateral face for guiding in the cylinder, and an external face with stiffening ribs. The outer end of the threaded rod may advantageously comprise a gripping head with non-slip peripheral means, for example in the form of a grooved wheel. According to a preferred embodiment, the outlet channel is provided in an outlet plug attached to the second end of the cylinder. For example, the outlet plug may include a threaded fixing skirt, adaptable by screwing

  on the threaded area of the second end of the cylinder.

  Preferably, the bottom of the cylinder is flat. For example, the outlet plug may include a transverse wall with a flat interior surface forming said flat bottom of the cylinder. The outer surface of said transverse outlet plug wall may advantageously include stiffening ribs, ensuring the flatness of the inner surface. Such an arrangement, associated with a flat surface for pushing the piston, makes it possible to reduce material losses, the piston coming to drive all the material into the outlet channel

  when it comes to rest against the flat bottom.

  The screw may advantageously comprise several threads having a relatively long pitch, for example four threads whose pitch is approximately 8 to 15 mm, advantageously approximately 12 mm. In this way, the practitioner can advance the piston according to its total stroke in a relatively small number of turns of the screw, while producing a large axial thrust force effectively expelling the cement through the outlet channel, without however having to exert significant torque on the screw. Thus, the efforts to be deployed by the practitioner are reduced, so that the practitioner can easily maintain a precise position of the syringe during the injection. Other objects, characteristics and advantages of the

  present invention will emerge from the following description of modes

  of particular embodiments, made in relation to the appended figures, among which: - Figure 1 is an exploded perspective view of a syringe according to an embodiment of the present invention; - Figure 2 is a longitudinal section of the cylinder of the syringe of Figure 1, along the diametrical plane A-A of Figure 3; - Figure 3 is a cross section of the barrel of the syringe of Figure 1; - Figure 4 is a perspective view of the piston of the syringe of Figure 1; - Figure 5 is a view of the outer face of the piston of Figure 4; - Figure 6 is a section along plane B-B of Figure 5; - Figure 7 is a detail view of the area C of Figure 6, on a larger scale; - Figure 8 is a side view of the push screw of Figure 1; - Figure 9 is a longitudinal section of the screw of Figure 8; - Figure 10 is a top view of the screw of Figure 8, showing the shape of the gripping head; - Figure 11 is a side view of the inlet plug in the syringe of Figure 1; - Figure 12 is a top view of the plug of Figure 11; - Figure 13 is a longitudinal section of the plug of Figure 11; - Figure 14 is a top view of the outlet plug in the syringe of Figure 1; - Figure 15 is a section along the plane D-D of Figure 14; and - Figure 16 is a perspective view showing the outer face

  of the outlet plug of figure 1.

  In the embodiment illustrated in the figures, a syringe for injecting prosthetic cement according to the invention comprises a cylinder 1, an outlet plug 2 with outlet channel 3, a piston 4 slidably mounted in the cylinder 1, a plug

  inlet 5, and a push screw 6.

  Cylinder 1 is relatively stocky in shape, i.e.

  say having a relatively large inside diameter for a relatively short length L, for example a length L between 1.5 times and 3 times the inside diameter. In practice, in the embodiment illustrated in the figures, the length L is close to twice the inside diameter. You can choose for the inside diameter a value at least equal to the value allowing to easily mix the powder and the liquid to form the cement inside the cylinder. In practice, the

  inside diameter can be between approximately 3.5 and 5.5 cm.

  An inside diameter of around 4.5 cm is a compromise

advantageous.

  The cylinder 1 has a first end 10 having a threaded area 11, and a second end 12 having a threaded area 13. The outer face of the cylinder 1 may have ribs

longitudinal gripping 14.

  The outlet plug 2 comprises a threaded fixing skirt 20, which is screwed onto the threaded zone 13 of the second end 12 of the cylinder 1. The outlet plug 2 also includes a transverse wall 21 with a flat inner surface 22 forming a flat bottom for cylinder 1. The outer surface 23 of transverse wall 21 has stiffening ribs 24. The stiffening ribs 24 are radial, starting from the axial tube forming the outlet channel 3, as far as the peripheral zone of the transverse wall 21. The fixing skirt 20 has an outer face provided with non-slip longitudinal ribs 25. The outlet channel 3 is through, with an outlet orifice 30 and with an inlet orifice 31 which opens into the internal cavity 32 delimited by the fixing skirt 20 and

the transverse wall 21.

  The inlet plug 5 is shaped to be removable and attached to the first end 10 of the cylinder 1. The inlet plug comprises a threaded fixing skirt 50, which is adapted by screwing onto the threaded area 11 of the first end 10 of cylinder 1. The fixing skirt 50 has a surface

  external device provided with longitudinal ribs 51 anti

  sliding. The fixing skirt 50 is connected to a coaxial nut 52 which has an axial hole 53 tapped with a smaller diameter than the diameter d of the cylinder 1. For example, the diameter of the axial hole 53 tapped is close to half the diameter d

inside of cylinder 1.

  The sliding piston 4 comprises a generally planar push face 40, a lateral cylindrical guide face 41, adapted to slide without play in the cylinder 1 and having a length of the order of 1 cm to ensure good guidance and good stabilization. of the sliding piston 4 during its longitudinal sliding in the cylinder 1. The sliding piston 4 further comprises an external face 42 with stiffening ribs 43, with a cylindrical central housing 44. The edges of the thrust face, for example in zone C illustrated in FIG. 6, include a flexible sealing lip 45, better represented by

  section on a larger scale in Figure 7.

  The push screw 6 constitutes an operating member for actuating the sliding piston 4 sliding in the cylinder 1. The push screw operating member 6 comprises an axial threaded rod 60 shaped to be screwed into the nut 52 of the inlet plug 5. Preferably, the threaded rod 60 has four threads having a pitch of approximately 8 to 15 mm, advantageously approximately 12 mm. The inner end 61 of the threaded rod is cylindrical, devoid of thread, and shaped to engage in abutment against the outer face 42 of the sliding piston 4. In practice, the cylindrical inner end 61 engages in the central housing 44 corresponding cylindrical sliding piston 4. The outer end 62 of the threaded rod 60 comprises

  a gripping head 63 with non-slip peripheral means.

  For example, the gripping head 63 is in the form of a wheel

  grooved, with six grooves such as groove 64.

  A mode of use of the syringe according to the invention is described below. The practitioner prepares the syringe, with the sliding plunger 4 engaged in the cylinder 1 near its first end 10, with the inlet plug 5 adapted on said first end 10, and with the pushing screw 6 slightly screwed into the nut 52 and pressing against the sliding piston 4. The cap

output 2 is removed.

  The practitioner introduces the liquid inside the cylinder by its second end 12 facing upwards, then introduces the powder intended to form the cement. Using a spatula which he introduces into the cylinder through the second end 12, he mixes the mixture inside the cylinder 1, already in place. We understand that this is made possible by the relatively large diameter d of the cylinder 1, combined with its length L

relatively small.

  After stirring, the practitioner adapts the outlet plug 2 to the second end 12 of the cylinder 1, and screws the screw

  push 6. The syringe is now ready for use.

  During the injection, the user has the outlet channel 3 in the injection zone of the bone cavity, and screws the pushing screw 6 by maneuvering the gripping head 63. It suffices to exert a relatively torque. reduced to achieve a significant pushing force thanks to the threads of the threaded rod 60

engaged in nut 52.

  At the end of screwing, the flat push face 40 of the sliding piston 4 comes to bear against the flat and parallel inner surface 22 of the outlet plug 2, driving all of the dough through the outlet channel 3. If necessary, the practitioner can also unscrew the outlet plug 2, then push the residue of the dough through the outlet channel using a tool

  3. This avoids any loss of material.

  It will be noted that the syringe structure illustrated in the drawings is intended to be manufactured by molding plastic material, with a non-negligible saving of material. For example, the push screw 6 is a hollow structure, with a longitudinal internal cavity 65 open through the gripping head 63. Likewise, the sliding piston 4 is a hollow structure stiffened by the stiffening ribs 43. It is likewise also of the outlet plug 2 with its ribs of

stiffening 24.

  The syringe structure according to the invention allows the cement to be mixed directly in the cylinder 1, then a push

  easy by screwing the push screw 6.

  The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field.

of the claims below.

Claims (6)

  1 - Syringe for injecting prosthesis cement, comprising a cylinder (1) of relatively stocky shape with an outlet channel (3) and with a piston (4) sliding in the cylinder (1) and actuated by an operating member, characterized in that the operating member comprises an axial threaded rod (60) urging the sliding piston (4) to slide in the cylinder and screwed into a threaded nut (52) integral with the cylinder (1). 2 - Syringe for injecting prosthetic cement according to claim 1 characterized in that the nut is constituted by a removable inlet plug (5) attached to the first end (10) of the cylinder (1).   3 - Syringe for injecting prosthesis cement according to claim 2 characterized in that the inlet plug (5) comprises a threaded fixing skirt (50), adapting by screwing onto the threaded zone (11) of the first end (10) of the cylinder (1). 4 - Syringe for cement injection of prostheses according to   any one of claims 1 to 3 characterized in that   the inner end (61) of the threaded rod (60) is engaged in   support against the external face (42) of the sliding piston (4).   - Syringe for injecting prosthesis cement according to claim 4 characterized in that the sliding piston (4) comprises a generally planar push face (40), a cylindrical lateral face (41) for guiding in the cylinder, and a face   external (42) with stiffening ribs (43).   6 - Syringe for injecting prosthetic cement according to   any one of claims 1 to 5 characterized in that   the outer end (62) of the threaded rod (60) comprises a   gripping head (63) with non-slip peripheral means.   7 - Syringe for cement injection of prostheses according to   any one of claims 1 to 6 characterized in that the   outlet channel (3) is provided in an attached outlet plug   on the second end (12) of the cylinder (1).   8 - Syringe for injecting prosthesis cement according to claim 7 characterized in that the outlet plug (2) comprises a threaded fixing skirt (20), adapting by screwing on the threaded zone (13) of the second end (12) of the cylinder (1). 9 - Syringe for cement injection of prostheses according to   any one of claims 7 or 8 characterized in that   the outlet plug (2) comprises a transverse wall (21) with a flat inner surface (22) forming a flat cylinder bottom (1) and with an outer surface (23) comprising ribs stiffening (24).   10 - Syringe for cement injection of prostheses according to   any one of claims 1 to 9 characterized in that the   screw has four threads having a pitch of 8 to 15 mm approximately, advantageously about 12 mm.