Intramedullary device for pinning bones

Details Intramedullary device for pinning bones Intramedullary device for pinning bones

1998-03-28

1999-10-26

Buiz, Michael

Surgery

Instruments

Orthopedic instrumentation

606 72, 606 63, A16B 1700

Patent

active

059719869

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an intramedullary device for pinning bones.
In particular, the present invention may be used to advantage, though not exclusively, in the treatment of long bones, such as the femur and/or humerus, to which the following description refers purely by way of example.


BACKGROUND ART

For bone treatment in general, a pinning device, as described in Patent Application n. TO94A000407 filed on May 20, 1994 by the present Applicant, is used comprising a cannulate metal rod, which is inserted inside the medullary canal of the bone; and an anchoring or pinning assembly for releasably connecting one or both end portions of the cannulate rod to respective portions of the bone.
The anchoring assembly comprises two or more deformable metal pins and, for each pin, a respective guide conduit formed inside the cannulate rod. Each conduit has an inside diameter approximately equal to but no smaller than the outside diameter of the respective pin, so as to guide the pin along a given path, and the pins are connected positively to a common slide, which is movable from the outside by means of a mechanical device for moving the pins simultaneously to and from a forward pinning position, in which respective deformed end portions of the pins project outwards from the rod and are inserted in use, inside the respective bone portion.
Though widely used, by permitting withdrawal of the pins from the bone when the fracture heals, known devices of the above type are not altogether satisfactory, mainly on account of the considerable force normally required to remove the pins.
This is substantially due to the inside diameter of each guide conduit being comparable with the outside diameter of the respective pin, so that, when withdrawing the pin, fairly severe friction components opposing withdrawal are generated between the pin and the conduit. For this reason, the pins are connected to said mechanical device, which not only increases the cost of producing the device, but, by comprising a single slide common to all the pins, also creates problems when, for various reasons, the pins must be withdrawn separately.
Moreover, the conduits of known devices of the above type are at times fairly difficult to form, due to their normally being formed by drilling and subsequently milling a solid portion of the rod.


DISCLOSURE OF INVENTION

It is an object of the present invention to provide a straightforward, low-cost intramedullary device, designed to overcome the aforementioned drawbacks.
According to the present invention, there is provided an intramedullary device for pinning bones, the device comprising an elongated body insertable inside a bone and having a respective axis; and connecting means for connecting said elongated body to the bone; said connecting means comprising at least one deformable pin, and guide means for guiding said pin along a respective given path into an extracted operating position wherein the pin projects outwards of said elongated body; and said guide means comprising a guide surface extending along at least a portion of said path; characterized in that said guide means also comprise radial constraint means distinct from said elongated body, located facing and at a distance from said guide surface, and having a supporting portion for supporting said pin and which is smaller than said guide surface; fastening means being provided for connecting said constraint means to said elongated body.


BRIEF DESCRIPTION OF DRAWINGS

A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
FIGS. 1 and 2 show longitudinal sections of a first preferred embodiment of the intramedullary device according to the present invention, as applied to a humerus and in two different operating positions;
FIG. 3 shows a larger-scale side view of a detail in FIGS. 1 and 2;
FIG. 4 shows a section along line IV--IV in FIG. 3;
FIGS. 5a to 5e show sections along respective lines a--a, b--b, c--c, d--d, e-

REFERENCES:
patent: 5702397 (1997-12-01), Goble et al.
patent: 5814047 (1998-09-01), Emilio et al.

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