GB2323533A

GB2323533A - Orthopaedic modular compression screw

Info

Publication number: GB2323533A
Application number: GB9706050A
Authority: GB
Inventors: Ioannis Karnezis
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-03-25
Filing date: 1997-03-25
Publication date: 1998-09-30
Anticipated expiration: 2017-03-25
Also published as: DE29805443U1; GB2323533B; GB9706050D0

Abstract

An orthopaedic device for compressing two bone fragments together, comprises first (Figure 1) and second (Figure 2) independently formed, but interfitting components. Each component comprises an externally threaded potion 1, 8 for engaging with one of the bone fragments, and a non-threaded portion 3, 7. The second component (Figure 2) has a hollow interior and the non-threaded portion 3 of the first component is insertable into this hollow interior. A screwdriver 16 (Figure 5) is used to cause relative rotation of the first and second components whereby their threaded portions engage with bone fragments 14 and 15 so as to compress them together.

Description

2323533 ORTHOPAEDIC MODULAR COMPRESSION SCREW SYSTEM The present invention

relates to orthopaedic devices and is concerned particularly, although not exclusively, with orthopaedic devices of the compression screw type for creating compression between bone fragments or for securing orthopaedic implants in the bone.

At present the use of orthopaedic compression screws involves the process of compressing two bone fragments together by the use of bone screws able to be anchored in one fragment and compress the other fragment with the screw head with or without the use of a washer. In addition, screws are used to secure internal fixation implants such as intramedullary nails in bone. With the presently used devices the screw head is left protruding from the bone and commonly it causes problems of irritation of the soft tissues and pain. In addition the screw is not securely engaged in both bone fragments and this commonly results in loss of stability of the screw-bone structure.

According to the present invention there is provided an orthopaedic device comprising two independent components, each comprising a respective externally- threaded securing means for engaging with a bone. The two externally-threaded securing means may comprise threads of geometric features different from each other. One component's non- threaded part is a solid tubular shaft, that can be inserted and secured in a hollow tubular shaft of the other component, in a way that the two components can be rotated independently. The two components together are thus constructing an orthopaedic implant that can be inserted in bone and develop compression between bone fragments or secure internal fixation implants such as intramedullary nails, without any part of the implant protruding from the outer bone surface.

Preferably the threaded part of each component is disposed substantially at one end of the component leaving the remaining outer surface of the component externally smooth.

Preferably the hollow tubular component comprises a stopping means protruding from its inner hollow surface at the one end of the non-threaded section, which prevents dismounting of the two components once they are mounted together.

The invention may be carried into practice in various ways, but an embodiment will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows a plan view of component A, Figure 2 shows a plan view of component B, Fieure 3 shows a cross-section view of component B, Figure 4 shows a plan view of the two components mounted together, Figure 5 shows a plan view of the orthopaedic modular compression screw system in use, during insertion of the device through two bone fragments, Figure 6 shows a plan view of the orthopaedic modular compression screw system in use, during application of compression between the two bone fragments, and Figure 7 shows a plan view of the orthopaedic modular compression screw system in use as a bone anchorage means for an orthopaedic implant of the intramedullary bone nail type.

Referring to Figure 1, component A comprises a screw threaded part 1, a conical neck part 2, a solid tubular shaft 3 and an end 4 capable of receiving an appropriate screwdriver for insertion of the component in bone.

Referring to Figure 2, component B comprises a hollow tubular shaft open at both ends 5 and 6.

Component B is externally partly smooth 7 and partly threaded 8. Part of the externally smooth hollow tubular part 7 of component B is longitudinally slotted 9 starting from the end 6 through the whole of its thickness in order to permit some temporary expansion during insertion of the solid tubular shaft 3 of component A. The end 5 of the hollow tubular shaft is capable of receiving an appropriate screwdriver for insertion of the component in bone.

Referring to Figures 1, 2 and 3, the dimensions of the hollow inner surface 10 of component B are sufficiently large to accommodate the solid tubular shaft 3 of component A. The inner hollow surface 10 of component B comprises a stopping means 11 internally protruding from the hollow surface of the externally smooth section 7 of component B to prevent dismounting of the components A and B once they are mounted together.

Referring to Figures 1, 2 and 4, components A 12 and B 13 are mounted by axial insertion of the solid tubular shaft 3 of component A through the open end 6 of component B to construct the orthopaedic compression screw system.

The procedure of inserting the device will now be described with reference to Figures 5, 6 and 7.

Referring to Figure 5 the orthopaedic compression screw system, once mounted, it can be inserted through a hole in two bone fragments 14 and 15 by a screwdriver 16 which engages both ends 4 and 5 of components A and B respectively and drives them in direction 17 by clockwise rotation 18 of the system.

Referring to Figure 6, once the orthopaedic compression screw system is totally inserted in both bone fragments 14 and 15, another screwdriver 19 engages only the end 4 of the solid part of component A 12 which is accessible through the open end 5 of the hollow component B 13. It is therefore possible for the component A 12 to be rotated in a clockwise direction 20 while at the same time component B 13 is not rotating. This effect creates compression 21 between the bone fragment 14 engaged with the threaded part of component A 12 and the bone fragment 15 engaged with the threaded part of component B 13.

It would be appreciated that following this procedure, a strong compression between the two bone fragments is created and since both bone fragment are securely engaged by a significant screw thread length, the fixation is secure and able to successfully resist external loading forces. In addition, no part of the device is protruding beyond the surface of the bone and therefore no problems of soft tissue irritation are expected.

Referring to Figure 7, another application of this invention is described. The orthopaedic compression screw system 22 once mounted in the way described above, can be inserted through a hole 23 of an orthopaedic implant 24 of the intramedullary bone nail type and at the same time to be engaged with bone tissue 25 and 26 at either side of the orthopaedic intramedullary bone nail implant.

It would also be appreciated that according to the last proposed application, increased stability of an orthopaedic implant such as an intramedullary bone nail is expected as strong compression between adjacent bone areas is created and both bone areas are securely engaged by a significant screw thread length. In addition, no part of the screw system used to secure an orthopaedic implant such as an intramedullary bone nail is protruding beyond the outer surface of the bone and therefore no problems of soft tissue irritation are expected.

Claims

1. An orthopaedic device for compressing bone fragments together, comprising first and second independent, interfitting components, each comprising a respective external 1 y-threaded portion for engaging with a 5 bone.

2. A device as claimed in claim 1, wherein each component comprises said external ly-threaded portion, and a non-threaded portion.

3. A device as claimed in claim 2, wherein the second component is of hollow form, and the non-threaded portion of the first component is insertable in the hollow of the second component, in such a way that the two components cab be rotated independently.

4. A device as claimed in claim 2 or 3, wherein the screw-threaded potion of each component is disposed substantially at one end of the component.

5. A device as claimed in claim 4, wherein the non-threaded portion of each component is substantially smooth.

6. A device as claimed in claim 3, 4 or 5, wherein the second component comprises stopping means protruding from the inner hollow surface of its non-threaded portion, and operable to prevent dismounting of the two 20 components, once they are mounted together.

7. A device as claimed in any one of claims 3 to 6, wherein the nonthreaded portion of the first component is capable of receiving a screwdriver for insertion of said first component in bone.

8. A device as claimed in any one of claims 3 to 7, wherein the nonthreaded portion of the second component is formed so as to permit expansion thereof during insertion of the non-threaded portion of the first component.

9. A device as claimed in any one of claims 3 to 8, wherein the threaded portion of the second component is capable of receiving a screwdriver for insertion of the second component in the bone.

10. An orthopaedic device for compressing bone fragments together, substantially as hereinbefore described with reference to Figures 1 to 7 of 10 the accompanying drawings.

11. A method of securing two bone fragments together comprises forming a common hole through the fragments, inserting the device of any one of claims 1 to 10, with the first and second components thereof in interfitting relationship, into said common hole and then causing relative rotation of the first and second components whereby their threaded portions engage with the bone fragments so as to compress them together.

12. A method of securing two bone fragments together, substantially as hereinbefore described with reference to Figures 1 to 7 of the accompanying drawings.