Osteosynthesis means for the connection of bone fracture segments

Abstract: Osteosynthesis means comprising a plate (3) secured to one bone fracture segment (1), and at least a screw (8) inserted inside a hole (9) on the plate (3) and screwed into corresponding holes (11, 12) in the bone segments; characterised by the fact that they comprise an angle joint (13) located between the screw (8) and the hole (9) in the plate (3), and designed to enable the axis of the screw (8) to be positioned in relation to the plate (3) at any angle within a conical surface whose axis coincides with that of the hole (9) in the plate (3).

Description: The present invention relates to osteosynthesis means for the treatment of bone fractures and in particular for the connection of bone fracture segments. The assemblies currently employed for the treatment of bone fractures substantially comprise a plate secured surgically to one of the bone fracture segments, e.g. by means of one or more screws inserted through holes on the plate and screwed into matching holes on the bone segment; and at least one screw inserted through a further hole on the plate and screwed into a matching hole on both segments. Once the bone segments are firmly knit, the various elements in the assembly are removed. Said second screws inserted inside the second segment for connecting it to the first are longer than those connecting the plate to the first segment, and must be positioned at a predetermined angle in relation to the plate, so as to fit precisely inside the matching holes on the second segment. Assemblies of the type briefly described above present a number of drawbacks. Firstly, they fail to provide for correct support between the plate and mating segment when the screws connecting the two segments are screwed inside the respective holes on the same. This is due to the axes of said screws forming a predetermined angle in relation to the plate, which permits no or only a very small amount of adjustment, i.e. that permitted by the slack between the hole in the plate and the screw shank. Very rarely, however, does said angle correspond to that formed between the axes of the holes in the bone segments and the plate supporting surface on the bone. Secondly, assembly of the various component parts involved to the bone segments is not only difficult but requires considerable care and skill. Thirdly, the versatility of assemblies of the aforementioned type is extremely limited, by virtue of the size and shape of the component parts depending on the geometrical characteristics of the bone segments for connection. Fourthly, known assemblies of the aforementioned type may lead to complications and delayed healing of the fracture in the period immediately following the surgical operation. During this period, in fact, absorption generally takes place at the fracture surfaces, thus altering the position of the ends of the bone segments, which, using known assemblies of the aforementioned type, are prevented from moving by the rigid restraints consisting of the plate and respective screws. This results in undue stress on the fracture surfaces, which may even be caused to move away form each other. Finally, the mechanical strength and stability of the connection provided for by such assemblies are fairly poor, so that steps must be taken for preventing relative movement of the bone segment in the period immediately following surgery. From the document DE-A-30 27 148, also osteosynthesis devices for connection of bone fracture segments are known, wherein a support plate is provided with at least one hole having an angle joint engaged by a screw, which is screwed into corresponding holes of the bone segments. The angle joint includes an adjustable element, which is either spherical or cylindrical. Only one angle joint is provided for a screw to be screwed in the coaxial holes of both bone sagments. The plate contacts both bone segments, and is provided with other holes to be engaged by other screws, some of which are screwed only in one of the bone segments, and some in the other bone segment. All the screw has a shank which is entirely threaded. It is also known from the document US-A-3 842 825 another osteosynthesis device particularly for connection of bone fractures in the upper end of a femur. This device includes a spoon-shaped plate adapted to contact only one segment of the fracture. The bowl portion of the plate is provided with with a central hole and four ovular holes. The femur is firstly drilled to house therein a guide wire, which is then inserted into the central hole of the plate. Then, guided by this wire, four parallel bores are drilled into the femur through the ovular holes. Then corresponding screws are directly inserted in the ovular holes, to be screwed in both bone segments by means of an intricate screwdriver. The bowl portion of the plate is also provided with a pair of other holes, where a pair of plow bolts are previously inserted to connect, by means of nuts, a cover plate covering the heads of the four screws. Finally, the handle portion of the plate is connected to the contacted segment by other screws. The aim of the present invention is to provide osteosynthesis means for the connection of bone fracture segments of the type briefly described above, and designed to overcome the drawbacks of the known devices, i.e. provided with means enabling highly accurate positioning and strong, reliable connection of the bone segments; fast easy assembly; maximum versatility in terms of application; and rapid healing of the bone fracture. With these aim in view, according to the present invention, there is provided an osteosynthesis device for the connection of bone fracture segments, comprising a support plate adapted to be secured to one of the bone fracture segments; at least one screw for insertion into at least one corresponding hole in said support plate and adapted to be screwed into corresponding holes in said segments; an angle joint located between said screw and said hole in said support plate for enabling the axis of the screw to be positioned at any angle within a conical surface having an axis coinciding with an axis of said hole in said support plate, said angle joint including an adjustable element having a hole for receiving the shank of said screw, and at least a spherical surface portion; said support plate further comprising a spherical seat formed about said hole in said support plate for receiving said spherical surface portion; characterised in that said screw includes a head and a shank formed of a smooth portion and a threaded end portion; and in that locking means are provided for locking said adjustable element and said screw at a predetermined angle in relation to said support plate, said locking means including a second plate and at least one threaded connecting means for securing said second plate to said support plate, said second plate including a surface portion for engaging a portion of said adjustable element and leaving uncovered the head of said screw to exert a predetermined pressure on said adjustable element in said spherical seat. The present invention will be described in detail, by way of a non-limiting example, with reference to the accompanying drawings, in which: Fig.1 shows a partially-sectioned side view of a first embodiment of the means according to the present invention, employed for connecting two femur segments; Fig.2 shows a plan view of the Fig.1 means; Fig.3 shows a section along line III-III of the Fig.2 means; Fig.4 shows a partially-sectioned side view of a second embodiment of the means according to the present invention; Fig.5 shows a view in perspective of an adjustable element forming part of the Fig.4 means. As shown in Fig.1, the means according to the present invention provide for connecting two bone fracture segments, e.g. femur segments 1 and 2, and substantially comprise a plate 3 secured in any convenient manner to one of said segments, e.g. segment 1, using screws 4 inserted inside holes 5 on plate 3 and screwed into corresponding holes 6 in segment 1. Surface 7 of plate 3 contacting the surface of segment 1 is conveniently designed to rest directly on said segment surface. The means according to the present invention also comprise further screws 8, each designed to fit through a hole 9 on the end portion of plate 3, through a hole 11 in segment 1, and to screw into a hole 12 in segment 2. As shown in Fig.1, only end portion 27 of each screw 8 is threaded, whereas the rest of the shank is smooth, and each threaded portion 27 is shorter than the respective hole 12 in segment 2. The means according to the present invention also comprise an angle joint 13 located between each screw 8 and respective hole 9 in plate 3, and designed to enable the axis of screw 8 to be positioned in relation to plate 3 at any angle within a conical surface the axis of which coincides with that of hole 9. Each angle joint 13 may conveniently be designed as shown in Figs.1 and 2, in which case, it comprises an adjustable element 15 housing head 16 of screw 8, and having a hole 17 for the shank of the same. Each adjustable element 15 also comprises at least a spherical surface portion 18 designed to mate with a spherical seat 19 formed about hole 9 on plate 3, and conveniently consists simply of a ball with a hole 17, as shown in the Fig.1 embodiment. Each adjustable element 15 also presents a seat 20 housing head 16 of screw 8. Means are provided for locking angle joints 13 and securing screw 8 at a predetermined angle in relation to plate 3, said means conveniently comprising a plate 21 secured to plate 3 by means of at least a threaded connecting member 22, and having surface portions 23 designed to exert predetermined pressure on adjustable element 15 for preventing movement of the same. Each of elements 15 may conveniently be formed as shown in Figs, 4 and 5, in which case, it consists of two parts 24, 25 having flat mating surfaces 26 (Fig.5) lying in the equatorial plane of the element. When each adjustable element 15 consists of a ball, therefore, parts 24 and 25 are separated by the equatorial plane of said ball. The Fig.4 embodiment may be employed when the threaded end portion 27 of each screw 8 presents a larger diameter than the screw shank. In this case, by virtue of the diameter of hole 17 in each adjustable element 15 being substantially equal to that of the screw shank, and therefore smaller than that of threaded portion 27, screw 8 may be removed from segments 1 and 2 by simply detaching parts 24 and 25 of each angle joint 13 from plate 3 as described later on. The osteosynthesis means described above are employed as follows. First of all, an assembly is formed comprising plate 3, adjustable elements 15, screws 8, plate 21 and screws 22 for connecting plate 21 and said elements to plate 3. Once holes 11 and 12 have been formed in bone segments 1 and 2, screws 8 are inserted inside holes 11 in segment 1 and screwed inside holes 12 in segment 2. Surface 7 of plate 3 is then placed on segment 1, as shown in Fig.1, which operation is simplified by virtue of angle joints 13, which enable plate 3 to adjust in relation to screws 8, and so achieve perfect mating of surface 7 of plate 3 on segment 1 regardless of the position of the holes 11 and 12. Plate 3 is then secured to segment 1 using screws 4 inserted inside holes 6. The above procedure, therefore, not only provides for extremely straightforward connection of segments 1 and 2, but also for highly accurate mutual positioning of the same. Moreover, the means according to the present invention provide for a high degree of versatility by enabling the connection of bone segments of different shapes and sizes, by virtue of angle joints 13 enabling adjustment of the axes of screws 8. In addition to considerably improving the mechanical strength and stability of the connection, the means according to the present invention also provide for maintaining correct mutual positioning of the bone segments in the period immediately following surgery and pending complete knitting of the same, regardless of whether or not additional precautions are taken. In particular, when more than one screw 8 is employed, the resulting connection also presents a high mechanical resistance to the torques which would otherwise cause the bone segments to rotate about an axis parallel to that of the screws. During the period in which the fracture surfaces are absorbed, the contacting segments may undergo a change, particularly a reduction, in length, which changes are permitted by the special retaining conditions provided for by the means according to the present invention. Any reduction in length of the bone segments is permitted by virtue of the smooth shank portions of screws 8 sliding inside respective holes 11 in segment 1, and by virtue of heads 16 of screws 8 withdrawing from respective seats 20 on adjustable elements 15 and projecting in relation to plate 3 with no impairment in the characteristics of the connection. Moreover, once screws 8 are screwed inside holes 12 in segment 2, compressive stress may be produced as required between the mating surfaces of the fracture, for ensuring fast, safe knitting of the bone segments. Once the bone segments are knit strongly enough to dispense with screws 8, these are removed by simply unscrewing them. In the case of the Fig.1 embodiment, the threaded portions of screws 8 may be withdrawn through holes 17 in adjustable elements 15. In the case of screws 8 of the Fig.4 type, wherein threaded end portions 27 present a larger diameter than the screw shanks, screws 8 may be removed from the bone by detaching parts 24 and 25 of each adjustable element 15, the two-part design of which provides for detaching it easily from the rest of the assembly. Once assembled as required, screws 8 may be locked in position by the locking means on the assembly, consisting of plates 21 and screws 22. By torquing screws 22, sufficient pressure is exerted by surface portions 23 of plates 21 on adjustable elements 15 for preventing any movement of the same. To those skilled in the art it will be clear that changes may be made to both the form and arrangement of the component parts of the embodiments described and illustrated herein.

Claims: An osteosynthesis device for the connection of bone fracture segments (1, 2), comprising a support plate (3) adapted to be secured to one (1) of the bone fracture segments (1, 2); at least one screw (8) for insertion into at least one corresponding hole (9) in said support plate (3) and adapted to be screwed into corresponding holes (11, 12) in said segments (1, 2); an angle joint (13) located between said screw (8) and said hole (9) in said support plate (3) for enabling the axis of the screw (8) to be positioned at any angle within a conical surface having an axis coinciding with an axis of said hole (9) in said support plate (3), said angle joint (13) including an adjustable element (15) having a hole (17) for receiving the shank of said screw (8), and at least a spherical surface portion (18); said support plate (3) further comprising a spherical seat (19) formed about said hole (9) in said support plate (3) for receiving said spherical surface portion (18); characterised in that said screw (8) includes a head (16) and a shank formed of a smooth portion and a threaded end portion (27); and in that locking means (21, 22) are provided for locking said adjustable element (15) and said screw (8) at a predetermined angle in relation to said support plate (3), said locking means (21, 22) including a second plate (21) and at least one threaded connecting means (22) for securing said second plate (21) to said support plate (3); said second plate (21) including a surface portion (23) for engaging a portion of said adjustable element (15) and leaving uncovered the head (16) of said screw (8) to exert a predetermined pressure on said adjustable element (15) in said spherical seat (19). An osteosynthesis device as claimed Claim 1, characterised in that said adjustable element (15) is comprised of a ball (15) having said hole (17) extending therethrough, said hole (17) having an axis passing through the center of said ball (15). An osteosynthesis device as claimed in Claim 1 or 2, characterised in that said adjustable element (15) is comprised of two parts (24, 25) having flat mating surfaces (26) lying in an equatorial plane of said spherical surface portion (18). An osteosynthesis device as claimed in Claim 3, characterised in that said threaded end portion (27) of the shank of said screw (8) has a diameter greater than the diameter of the smooth portion thereof, the diameter of said hole (17) between said two parts (24, 25) being smaller than that of said threaded end portion (27). An osteosynthesis device as claimed in any previous Claim, characterised in that said plate (3) is provided with a first surface adapted to contact the surface of only one (1) of said segments (1, 2), and a second opposite surface; a pair of said holes (9) extending therethrough being formed on an end portion of said support plate (3) and being each provided with said angle joint (13); another portion of said support plate (3) being secured to said one segment (1) by a plurality of threaded connecting means (4) inserted in corresponding holes (5) provided in said other portion, whereby a correct mutual positioning of said segments (1, 2) is maintained during the kitting period thereof solely by the screws (8) of said angle joints (13).

Inventors: CALDERALE PASQUALE MARIO, PIPINO FRANCESCO, CALDERALE, PASQUALE MARIO, PIPINO, FRANCESCO
Applicants: CALDERALE PASQUALE MARIO, PIPINO FRANCESCO, CALDERALE, PASQUALE MARIO, PIPINO, FRANCESCO
Application year: 1990
Main classification: A61B17
IPC codes: A61B17