Trocar with two convex distal surfaces

Field of the invention

The present invention relates to a trocar which is designed to penetrate e.g. an abdominal wall

Technical background

Disposable trocars are used together with tubular sheath at present as devices that guide medical instrument into a patient. U.S. Patent 5, 314, 417 discloses a needle unit and a tubular sheath, wherein the trocar is pointed at its distal end and can penetrate an abdominal wall.

In osteosynthesis a fracture may be supplied with e.g. a nail or screws securing a plate. To arrive e.g. with the screws at the bone without harming the surrounding tissue, tubular sheaths are used here. To occlude the tubular sheath, a needle unit, the so-called trocar, is used with an outer diameter equal to the inner diameter of the said tubular sheath.

There may be a need for a trocar that is designed such that it slides more easily through human tissue and may be restrict the tissue harm to an unavoidable minimum.

Summary of the invention

This need may be met by a trocar according to the independent claim. Embodiments of the invention are described in the dependent claims.

According to a first aspect of the present invention, a trocar comprises an elongated cylindrical section with a radius R and a distal part adjacent to the cylindrical section.

The distal part comprises two convex surfaces. The two convex surfaces are sy mmetrical to each other with respect to an axis of the trocar. The distal part further comprises two curved ridges. Each curved ridge is defined by one of the two convex surfaces and the adjacent cylindrical section. Two endpoints of each lateral curved ridge spanning a chord at a distal end of the distal part. The distal part further comprises a rounded distal ridge at the distal end, the distal ridge is defined by the two convex surfaces. The length of each chord and the length of the distal ridge is equal to the radius R of the cylindrical section.

Preferably, the trocar has a flattened blade-shaped tip to better penetrate tissue. The two convex surfaces defining an acute apex angle which complies with a bevel angle of a sheath used with the trocar.

In the following, possible details and advantages of the present invention according to the first aspect and embodiments thereof will be explained.

Herein, the term "distal" can be interpreted such that distal means away from a surgeon during an operation.

According to an embodiment of the present invention the convex surfaces have a radius of curvature in a range between 2 mm and 12 mm, preferably between 4 mm and 8 mm, more preferably between 5 mm and 7 mm.

According to a further embodiment, the radius R of the cylindrical section is in a range between 1,5 mm and 5 mm, preferably between 2,5 mm and 3,5 mm.

According to a further embodiment, the distal ridge has a radius of curvature of about 3 mm at most, preferably in a range between 0,05 mm and 0,4 mm.

According to a further embodiment, the elongated cylindrical section has a length in a range between 40 mm and 180 mm, preferably between 110 mm and 140 mm..

According to a further embodiment, the distal part has a length in a range between 4 mm and 30 mm.

According to a further embodiment, the two convex surfaces defining an acute apex angle (θ) with a range from 20° to 60°, preferably from 25° to 40°.

The aspects defined above and further aspects, features and advantages of the present invention can be derived from the examples of embodiments described hereinafter.

The invention will be described in more detail hereinafter with reference to examples of embodiments but to which the invention is not limited.

Brief description of the drawings

Fig. 1 shows a schematic side view of a trocar according to an embodiment of the present invention.

Fig. 2 shows a further side view onto the distal extremit of the trocar according to Fig. 1.

Fig. 3 to Fig. 7 show different perspective views of the trocar.

In the figures, reference signs designate like elements. Furthermore, it is to be noted that the figures showing the perspective views are only schematically and not to scale.

Fig. 1 and Fig. 2 show a trocar 1 with a an elongated cylindrical section 2 with 137,1 mm length and a radius R of 2,95 mm, and a distal part 3 with a axial length of 10,4 mm adjacent to the cylindrical section 2. The distal part 3 comprises two convex

surfaces 4a, 4b. The two convex surfaces 4a, 4b are symmetrical to each other with respect to an axis 5 of the trocar 1. The distal part 3 further comprises two curved ridges 6a, 6b. Each curved ridge 6a, 6b is defined by one of the two convex surfaces 4a, 4b and the adjacent cylindrical section 2. Two endpoints 7a, 8a, 7b, 8b of each lateral curved ridge 6a, 6b geometrically span a chord 9a, 9b at a distal end 10 of the distal part 3.

The distal part 3 further comprises a rounded distal ridge 11 at the distal end 10, the distal ridge is defined by the two convex surfaces 4a, 4b each has a radius of curvature of 6 mm. Further, two endpoints of the distal ridge 11 geometrically span a chord 9c at a distal end 10 of the distal part 3. Further, the two convex surfaces 4a, 4b define an acute apex angle (θ) of 30°. The distal ridge has a radius of curvature of 0,2 mm. The length of the said three chords is equal to the radius R of the cylindrical section 2. In this embodiment the chords of the lateral curved ridges and the distal ridge, and the associated end points are in line with each other.

The Figs. 3 to 7 show a trocar in different perspectives. Fig. 6 shows a sheath with an inner diameter of 5,9 mm.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "one" does not exclude a plurality. Also elements described in association with different embodiments and aspects may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.