GB2392096A - Locking screw - Google Patents

Locking screw Download PDF

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Publication number
GB2392096A
GB2392096A GB0215088A GB0215088A GB2392096A GB 2392096 A GB2392096 A GB 2392096A GB 0215088 A GB0215088 A GB 0215088A GB 0215088 A GB0215088 A GB 0215088A GB 2392096 A GB2392096 A GB 2392096A
Authority
GB
United Kingdom
Prior art keywords
thread
screw
collar
aperture
locking
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
GB0215088A
Other versions
GB0215088D0 (en
Inventor
Gareth Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to GB0215088A priority Critical patent/GB2392096A/en
Publication of GB0215088D0 publication Critical patent/GB0215088D0/en
Publication of GB2392096A publication Critical patent/GB2392096A/en
Pending legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A61B17/8033—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
    • A61B17/8047—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers wherein the additional element surrounds the screw head in the plate hole
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
    • A61B17/86—Pins or screws or threaded wires; nuts therefor
    • A61B17/8605—Heads, i.e. proximal ends projecting from bone
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
    • A61B17/86—Pins or screws or threaded wires; nuts therefor
    • A61B17/8695—Washers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
    • A61B17/86—Pins or screws or threaded wires; nuts therefor
    • A61B2017/8655—Pins or screws or threaded wires; nuts therefor with special features for locking in the bone

Landscapes

  • Health & Medical Sciences (AREA)
  • Orthopedic Medicine & Surgery (AREA)
  • Surgery (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Neurology (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Surgical Instruments (AREA)

Abstract

A locking screw 1 comprising an internally threaded collar 10 with a circumferential cut out allowing the collar to expand and retract. The collar has an arcuate outer surface to engage and rotate in the wall 32 of an aperture 31. The locking screw 1 has a head, a first thread remote from the head, a second thread adjacent to the head and a threadless section between the two threads. The shank supporting the second thread is tapered to expand the collar when the screw is driven into it. Preferably the screw is for bones. The first thread may be cancellous and the second may be a machine thread. A prosthesis is also claimed which may have an aperture with an arcuate wall incorporating a locking bone screw. The aperture in the prosthesis may also have an annular flange to prevent the collar passing through.

Description

Title: Locking Screw The present invention relates to a locking screw,
especially for securing a medical prosthesis to a bone. It is known to provide a locking bone screw to secure prostheses to bones. Such locking screws have two components. One component is an internally-threaded annular collar with a circumferential cut out allowing the collar to expand and contract. The collar has an arcuate outer surface to engage and rotate in an arcuate wall of an aperture in a prosthesis. The other component is a screw having a continuous and constant thread extending from a screw shank which tapers outwards towards the screw head. In use the collar is inserted in the prosthesis and the screw placed into threaded engagement with the collar. The screw can then be screwed into the bone. Before the screw is screwed filly into the bone and collar, the screw can toggle relative to the prosthesis so its angle can change as the collar can rotate in the aperture of the prosthesis. However when the screw is fully screwed into the bone and collar, the widened taper of the shank of the screw expands the collar so locking the collar in the aperture and the screw in the collar.
A problem with this known arrangement is that an ideal screw thread for engaging bone tissue is not always the ideal screw thread for engaging the collar.
The invention seeks to provide an improved locking screw, especially for bones.
According to the present invention there is provided a locking screw comprising: a) an internally-threaded annular collar with a circumferential cut out allowing the collar to expand and contract, said collar having an arcuate outer surface to engage and rotate in an arcuate wall of an aperture, b) a screw having a head at one end of a screw shank, a first thread on the screw shank extending from the screw end remote from the head towards the head, a second thread on the shank adjacent the head, and a threadless section of shank or lag between the first and second thread, said shank supporting the second thread being tapered such that it expands the collar when screwed into the collar.
Preferably the locking screw is a locking bone screw.
Preferably the first thread is a cancellous thread such as an ISO standard bone thread.
Preferably the second thread is a machine thread such as an ISO machine thread.
The invention also extends to a prosthesis with an aperture with an arcuate wall incorporating the above defined locking bone screw. Preferably the aperture has an annular flange at one end of the aperture to prevent the collar passing through said end of the aperture.
An embodiment of the invention will now be described with reference to the accompanying drawings in which:
Figure I shows a collar and screw in an aperture of part of a prosthesis.
Figure 2 shows a cross section and end view of a collar, and Figure 3 shows a side and end view of the screw.
Referring to Figure I there is provided a locking bone screw l having an annular collar l O and screw 20 in an aperture 31 of a prosthesis 30.
Referring more particularly to Figure 2, annular collar 10 has an internal thread 1 1. A circumferential cut out l 2 is provided allowing the collar to expand and contract. Collar l O may be formed of resilient material such as metal, e.g. titanium-based metal. Collar 10 has an arcuate outer surface 13 to engage and rotate in an arcuate wall 32 of aperture 31 in prosthesis 30.
As shown in Figure 3, screw 20 has a head 21 at one end of a screw shank 22. Screw 20 may be of metal such as titanium-based metal. Screw head may have a hexagonal recess 21A to receive a tool (not shown) to rotate the screw.
A first thread 23 on the screw shank extends from the screw end 24 remote from the head 21 towards the head 21. First thread 23 is a cancellous thread such as an ISO standard bone thread.
A second thread 25 is provided on the shank 22 adjacent the head. The shank section 22A supporting thread 25 tapers outwards toward the end of head 21. The second thread 25 is a machine thread such as an ISO machine thread.
A threadless section or lag 26 of the shank is provided between the first and second thread.
First thread 23 and second thread 25 are of a size to engage with the internal thread 11 of collar 10. However when first thread 23 is engaged with internal thread 11 of collar 10, collar 10 is able to rotate in aperture 31 allowing the screw 20 to toggle relative to the prosthesis. When second thread 25 is fully engaged with internal thread 11 (i.e. the screw 20 is fully screwed into collar 10 as shown in Figure 1), the tapered shaft supporting thread 25 expands collar 10 so its arcuate outer surface 13 locks against the arcuate wall 32 of aperture 31 in prosthesis 30.
It is preferred that an annular flange 33 is provided at one end of the aperture 31 to prevent the collar passing through this end of the aperture, so preventing separation of the screw 20 from the prosthesis 30. Flange 33 also limits rotation of the collar 10 in aperture 31.
In use screw 20 is placed in collar 10 in the prosthesis aperture 31, and is screwed into a bone using a tool with the thread 23 engaging the bone tissue. The desired angle of the screw is achieved as it can toggle relative to the prosthesis. The collar 10 finally locks in the aperture 31 as the head 21 is screwed into the collar.
Because the thread 25 is a machine thread it engages well with the metal collar to prevent it unscrewing itself, and the bone thread 23 bonds well with bone.
Once the prosthesis is connected to the bone, after a period of time, fibrous growth fortes around the threadless section or lag in shank 22 which helps prevent the screw from unscrewing out of the bone.
The invention may take a form different to that specifically described above.
The locking screw of the invention may be sold separately or in conjunction with a prosthesis.
The locking screw of the invention may be of particular use when used in a wrist prosthesis as defined in our copending application no The locking bone screw may have applications outside medical application, i.e. used to secure fittings to material other than bones.
Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims (8)

1. A locking screw comprising: a) an internally-threaded annular collar with a circumferential cut out allowing the collar to expand and contract, said collar having an arcuate outer surface to engage and rotate in an arcuate wall of an aperture, b) a screw having a head at one end of a screw shank, a first thread on the screw shank extending from the screw end remote from the head towards the head, a second thread on the shank adjacent the head, and a threadless section of shank or lag between the first and second thread, said shanlc supporting the second thread being tapered such that it expands the collar when screwed into the collar.
2. A locking screw according to claim 1, wherein the locking screw is a locking bone screw.
3. A locking screw according to claim I or 2, wherein the first thread is a cancellous thread such as an ISO standard bone thread.
4. A locking screw according to claim 1, 2 or 3, wherein the second thread is a machine thread such as an ISO machine thread.
5. A prosthesis with an aperture with an arcuate wall incorporating a locking bone screw according to any preceding claim.
l
6. A prosthesis according to claim 5, wherein the aperture has an annular flange at one end of the aperture to prevent the collar passing through said end of the aperture.
7. A locking screw substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
8. A prosthesis with a locking screw substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
GB0215088A 2002-06-29 2002-06-29 Locking screw Pending GB2392096A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0215088A GB2392096A (en) 2002-06-29 2002-06-29 Locking screw

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0215088A GB2392096A (en) 2002-06-29 2002-06-29 Locking screw

Publications (2)

Publication Number Publication Date
GB0215088D0 GB0215088D0 (en) 2002-08-07
GB2392096A true GB2392096A (en) 2004-02-25

Family

ID=9939548

Family Applications (1)

Application Number Title Priority Date Filing Date
GB0215088A Pending GB2392096A (en) 2002-06-29 2002-06-29 Locking screw

Country Status (1)

Country Link
GB (1) GB2392096A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006113257A1 (en) * 2005-04-14 2006-10-26 Warsaw Orthopedic, Inc. Anti-backout mechanism for an implant fastener
US7655009B2 (en) 2003-12-01 2010-02-02 Smith & Nephew, Inc. Humeral nail
USD734853S1 (en) 2009-10-14 2015-07-21 Nuvasive, Inc. Bone plate
US9615866B1 (en) 2004-10-18 2017-04-11 Nuvasive, Inc. Surgical fixation system and related methods

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2173565A (en) * 1985-04-03 1986-10-15 Hatif Himoud Expansion screw for surgical use
US5741258A (en) * 1993-01-25 1998-04-21 Synthes (U.S.A.) Lock washer for bone plate osteosynthesis
US20010014807A1 (en) * 1997-08-04 2001-08-16 Erik J. Wagner System and method for stabilizing the human spine with a bone plate
WO2001078615A1 (en) * 2000-04-19 2001-10-25 Synthes Ag Chur Bone fixation assembly
WO2002054964A1 (en) * 2000-12-21 2002-07-18 Madhavan Pisharodi Plate system for bridging and stabilizing spaced apart bone segments

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2173565A (en) * 1985-04-03 1986-10-15 Hatif Himoud Expansion screw for surgical use
US5741258A (en) * 1993-01-25 1998-04-21 Synthes (U.S.A.) Lock washer for bone plate osteosynthesis
US20010014807A1 (en) * 1997-08-04 2001-08-16 Erik J. Wagner System and method for stabilizing the human spine with a bone plate
WO2001078615A1 (en) * 2000-04-19 2001-10-25 Synthes Ag Chur Bone fixation assembly
WO2002054964A1 (en) * 2000-12-21 2002-07-18 Madhavan Pisharodi Plate system for bridging and stabilizing spaced apart bone segments

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7655009B2 (en) 2003-12-01 2010-02-02 Smith & Nephew, Inc. Humeral nail
US9615866B1 (en) 2004-10-18 2017-04-11 Nuvasive, Inc. Surgical fixation system and related methods
WO2006113257A1 (en) * 2005-04-14 2006-10-26 Warsaw Orthopedic, Inc. Anti-backout mechanism for an implant fastener
US7931681B2 (en) 2005-04-14 2011-04-26 Warsaw Orthopedic, Inc. Anti-backout mechanism for an implant fastener
USD734853S1 (en) 2009-10-14 2015-07-21 Nuvasive, Inc. Bone plate
USD754857S1 (en) 2009-10-14 2016-04-26 Nuvasive, Inc. Bone plate

Also Published As

Publication number Publication date
GB0215088D0 (en) 2002-08-07

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