DEVICE FOR OSTEOSYNTHESIS

Abstract: An osteosynthesis device including a pair of support plates (1, 2) for carrying fixation elements for fixing the device to a bone, a ball joint (3) connected to one of the support plates and including a rotatable ball element (4) releasably lockably supported in the ball joint, a hinge joint (6) connected to the other support plate; and a rigid distance piece (5) which is connected to the ball element and which is connected to the hinge joint such that the distance piece (5) is rotatably positionable about only a single axis (x-x) of the hinge joint into selected releasably locked positions.

Description: Device for Osteosvnthesis Technical Field The invention relates to a device for osteosvnthesis. According to one preferred aspect of the invention, there is disclosed a device for osteosvnthesis which is particularly useful for fixing fractured ends of curved relatively small bones, for promoting the healing of such bones. Background Art Known osteosvnthesis devices, which in particular are intended to fix curved and relatively small bones, include support plates which carry fixation means and which are interconnected by a ball joint. In such osteosvnthesis devices, the greatest possible degree of angular positioning of the two retainer or support plates relative to one another is appropriately provided according to the circumstances. On the other hand, however, once these osteosvnthesis devices are in their set position, it must be ensured that any involuntary shifting is absolutely excluded. In the previously-known osteosvnthesis devices, this is achieved by double-ball joint connection which is securable by fixing means. Examples of these conventional osteosvnthesis devices are described in US Patent No. 4.988.349. the disclosure of which is incoφorated herein by reference. While conventional osteosvnthesis devices work admirably, there exists the need to provide improved osteosvnthesis devices which achieve improved functionality and results. Disclosure of the Invention In accordance with one preferred aspect of the invention, there is provided an osteosynthesis device of the type in question in which only one ball head of a ball joint is used, while the other support plate is connected via a joint which is mobile in one direction. According to another preferred aspect of the invention, it is proposed that a ball joint with a ball head is connected with one support plate of an osteosynthesis device, while a hinge-like joint which is securable in only one plane is connected with the other support plate of the osteosynthesis device. By virtue of the fact however that this joint is mounted on a rotatable pin. and which is thus rotatable about an axis extending transversely to the joint axis, a relatively large degree of mobility and of facility of alignment of the joint is provided, and greater strength is still achieved in one plane, as the actual hinge¬ like joint is movable in only one plane, so that a great degree of strength is achieved in the other plane. The technical characteristics of the invention may be understood from the following detailed description of some possible examples of preferred embodiments thereof with reference to the drawings. Brief Description of Drawings Fig. 1 is a detail perspective view of an osteosynthesis device for promoting the healing of fractured bones which includes an interconnection in accordance with one preferred embodiment of the invention of two support plates of the device: and Fig. 2 is a partial cross-section view of the device of Fig. 1 taken along plane II-II of Fig. 1. Best Mode for Carrying Out the Invention The numerals 1 and 2 refer in the drawings to respective support plates of the osteosynthesis device, serving to secure suitable means for fixation of the device to a fractured bone. Supports plates 1 and 2 may support fixation means of the type described in US Patent No. 4,988.349. including clamping members adjustably screwed to sliding blocks slidingly connected in slide guides la and 2a respectively of support plates 1 and 2. and including bone screws clamped by the clamping members. The precise type of fixation means carried by support plates 1 and 2 may be any one of many, as understood by a skilled person in the art. A ball joint 3 is connected in a known manner to support plate 2. The ball joint 3 includes a ball head 4. and connected to and extending from the ball head 4 there is a rigid distance piece 5. In particular, the ball joint 3 includes a cylindrical element 3 a which is connected to support plate 2 and which includes a threaded portion at its outer surface arranged distally from support plate 2. The ball joint 3 further includes a locking nut 3b having an intemal seat in which ball 4 is lodged, and having an internally threaded such that locking nut 3b is screwed onto cylindrical element 3a. In a non-locked position of locking nut 3b, ball 4 is free to rotate in the intemal seat of locking nut 3b. and when the locking nub 3b is tightened ball 4 is pushed to engage against a corresponding seat portion of cylindrical element 3 a so as to block the movement of the ball 4. in a known manner. In conventional devices, distance piece 5 would be connected at its end opposite ball 4 to another ball of a double-ball joint, which other ball would be connected to support plate 1 in a manner completely similar to the connection of ball 4 to support plate 2 by means of joint 3. In accordance with the invention however, distance piece 5 opens into a joint 6. which is pivotable about the pivot axis x-x. A securing screw 8 serves to block this pivotal movement. In particular, the joint 6 includes a locking portion 6a rigidly connected to distance piece 5 and supported by a carrier 7 in a manner such that locking portion 6a may rotate into different locked positions only about axis x-x. In particular, carrier 7 includes a pair of lateral fork portions 7a and 7b each having concave inner surfaces 7c which together form a seat for locking portion 6a. Radial teeth are provided on inner surfaces 7c of lateral fork portions 7a and 7b for improving the locking grip on locking portion 6a. as seen in Fig. 2 in which locking portion 6a has been omitted. A stem 8a of securing screw 8 extends through fork portion 7b and through a through channel in locking portion 6a. and is screwed into the opposite fork portion 7a, so that securing screw 8 may be adjusted to mutually space or bring closer together the fork portions 7a and 7b for allowing rotation of locking portion 6a about axis x-x or altematively for blocking the movement of locking portion 6a. A channel 7d is provided between fork portions 7a and 7b which extends in plane II-II and outside of which the distance piece 5 extends, for substantially permitting rotation of locking portion 6a only about axis x-x. Carrier 7 is rotatable about the longitudinal axis y - y of support plate 1 (Fig. 2) with respect to support plate 1, and can be secured and locked in place with respect to support plate 1 by means of a fixing screw 9. In particular, a pin la extends from an end plate lb of support plate 1 and is lodged in a axial cavity 7e of carrier 7 such that carrier 7 is rotatable about axis y-y with respect to support plate 1. Fixing screw 9 is screwed into the lateral surface of carrier 7 and may be rotated so as to engage pin la sufficiently to block the rotation of carrier 7. Cylindrical element 3 a is rotatably connected to support plate 2 in a similar manner about the longitudinal axis of support plate 2. and may be selectively locked in place by means of fixing screw 10. By means of the arrangement of parts herein described, rotary movements about the curved arrows 12 and 13 (Fig. 1) are possible, and yet good securement and blocking of the overall arrangement can be achieved.

Claims: Claims 1. Osteosynthesis device with support plates (1. 2) for carrying means for fixing the device to a bone, said support plates being interconnected by a ball joint (3), the device being characterised in that connected with the ball head (4) of the ball joint (3) is a rigid distance piece (5). which is connected at another end with a joint (6) which is displaceable in one plane and which is mounted on a carrier (7) which is rotatable about an axis (y-y) extending transversely to the joint axis (x-x). 2. Osteosynthesis device according to claim 1. characterised in that the joint (6) and the rotary movements of the carrier (7) may be blocked. 3. An osteosynthesis device comprising: a pair of support plates (1, 2) for carrying fixation elements for fixing the device to a bone; a ball joint (3) connected to a first one of said support plates and including a rotatable ball element (4) releasably lockably supported in the ball joint; a hinge joint (6) connected to a second one of said support plates; and a rigid distance piece (5) which is connected to said ball element and which is connected to said hinge joint such that said distance piece (5) is rotatably positionable about only a single axis (x-x) of the hinge joint into selected releasably locked positions. 4. The osteosynthesis device of claim 3 wherein said hinge joint is rotatably connected to said second support plate about a rotation axis (y-y) and wherein said rotation axis (y-y) extends essentially perpendicularly to said single axis (x-x). 5. The osteosynthesis device of claim 4 wherein said ball joint (3) is connected to said first support plate about a rotation axis. 6. The osteosynthesis device of claim 3 wherein said hinge joint (6) comprises: a locking portion (6a) rigidly connected to said distance piece; a carrier (7) connected to said second support plate at a first end thereof and comprising a pair of lateral fork portions (7a.7b) arranged at a second end thereof, said fork portions defining an expanding and contracting seat in which said locking portion is accommodated: and means (8) for releasably contracting said seat of said fork portions for releasably blocking said locking portion in selected releasably blocked positions; 7. The osteosynthesis device of claim 6 wherein said fork portions define a channel (7d) extending in a plane which is perpendicular to said single axis (x- x). said distance piece extending outside said channel.

Inventors: PENNIG DIETMAR, PENNIG, DIETMAR
Applicants: PENNIG DIETMAR, PENNIG, DIETMAR
Application year: 1996
Main classification: A61B17
IPC codes: A61B17