WO1988008281A1 - External fixation device - Google Patents

External fixation device Download PDF

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Publication number
WO1988008281A1
WO1988008281A1 PCT/EP1987/000235 EP8700235W WO8808281A1 WO 1988008281 A1 WO1988008281 A1 WO 1988008281A1 EP 8700235 W EP8700235 W EP 8700235W WO 8808281 A1 WO8808281 A1 WO 8808281A1
Authority
WO
WIPO (PCT)
Prior art keywords
pin
bone
fixation device
external fixation
clamped
Prior art date
Application number
PCT/EP1987/000235
Other languages
French (fr)
Inventor
Slobodan Tepic
Original Assignee
Synthes Ag
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 Synthes Ag filed Critical Synthes Ag
Priority to JP62503064A priority Critical patent/JPH0628668B2/en
Priority to MX011288A priority patent/MX167618B/en
Priority to DE8787903291T priority patent/DE3783916T2/en
Priority to EP87903291A priority patent/EP0313556B1/en
Priority to BR8707717A priority patent/BR8707717A/en
Priority to PCT/EP1987/000235 priority patent/WO1988008281A1/en
Priority to CA000565582A priority patent/CA1329346C/en
Publication of WO1988008281A1 publication Critical patent/WO1988008281A1/en
Priority to US07/465,575 priority patent/US5024618A/en

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
    • A61B17/60—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 for external osteosynthesis, e.g. distractors, contractors
    • A61B17/64—Devices extending alongside the bones to be positioned
    • A61B17/6466—Devices extending alongside the bones to be positioned with pin-clamps movable along a solid connecting rod

Definitions

  • This invention relates to an external fixation device for osteosynthesis, comprising pins adapted for being passed through the bone fragments being joined, a plurality of at least two clamps for fastening said pins and at least one longitudinal rod interconnecting said individual clamps to form a single frame with the bone fragments disposed in required positions relative to each other.
  • fixateur esters comprising a range of components which are variably connectable with each other and with the fragments of a fractured bone by way of pins to form a support network holding the bone fragments in a desired positional relationship for the purposes of re-union.
  • the principle of external fixation entails load transfer from bone to an external frame by means of pins (or wires in the case of Ilizarov-type devices). Length of the pins must allow forclearing soft tissues covering the fractured bone, as well as for post-surgical treatment. The resulting distance between the treated bone and the external frame produces undesirable mechanical conditions at pin-bone interface. Parametric analyses of stress concentrations for commenly used frame configurations showed extremly high stress levels at pin-bone interface ("Parametric Analyses of Pin-Bone Stresses in External Fracture
  • the invention as claimed is intended to remedy these drawbacks. It solves the problem of how to design an external fixation device which couples the reaction force with the reaction moment between the pin and the rod in such a way as to keep the pin angulation at zero within bone cortices. This completely eliminates stress concentration at pin-bone interface due to bending moments on the pin.
  • Fig. 1 is a schematic view of an external fixation device according to the state of the art applied to a fractured bone
  • Fig. 2 is a diagrammatic view of loads and deformations in a device according to the state of the art
  • Fig. 3 is a sectional view of the pin-bone interface showing stress distribution in the device according to Fig. 1;
  • Fig. 4 is a diagrammatic view showing conditions necessary for eliminating bending moment on the pin between bone cortices in a device according to the invention:
  • Fig. 5 is a sectional view showing reduced stresses at pin-bone interface in a device according to the invention.
  • Fig. 6 is a sectional view of a device according to the invention showing loads and deformations of the unilateral frame
  • Fig. 7 is a sectional view and a cross-section of a device according to the invention showing a clamp with a gliding kinematic pair
  • Fig. 8 is a sectional view of a device according to the invention showing a clamp designed as a four-bar linkage
  • Fig. 9 is a sectional view of a device according to the invention showing a clamp designed as a flexible four-bar linkage
  • Fig. 10 is a sectional view of a device according to the invention showing a clamp made as a composite structure
  • Fig. 11 is a sectional view of a device according to the invention showing a coupled pair of clamps.
  • Fig. 1 represents a fractured bone 1 fixed by means of an external fixation device, whereby pins 3 are inserted through bone fragments 1 and fixed to longitudinal rods 4 by means of clamps 5. Transmission of force 6 is achieved partly or completely in case of comminuted fracture 2 through external frame 3,4,5.
  • Fig. 2 shows a deformation of the pin 3 under load 6 to position 3a.
  • Reaction forces 8 in case of symmetrical bilateral frame shown will equal one half of the axial load 6.
  • the corresponding diagramm shows bending moment of the pin 3.
  • Reaction moments 9 depend on the pin length and bone diameter. Between bone cortices 7 bending moment is constant.
  • Fig. 3 shows the resultant stress distribution 10 and 11 at pin-pone interfaces due to mainly high bending moment between cortices 7.
  • Fig. 4 shows deformations of the pin 3 into position 3a due to load 6 provided that reaction moments 21 are high enough to eliminate bending moment 22 between cortices 7.
  • the magnitude of compensating bending moment 21 is equal to the product of the reaction force 8 with the free pin length 12.
  • Fig. 5 shows the resultant stress distribution 23 in the device according to Fig. 4.
  • Fig. 6 shows the kinematic constraint necessary to produce conditions described by Fig. 4. If the clamped extremity 30 of the pin 3 is forced to move on a circular trajectory 24 with the center 25 within the near cortex 7 the reaction moment 21 will be equal to the product of the reaction force 8 multiplied by the radius 26 of the circle 24. Radius 26 is equal to the free pin length 12. Trajectory 24 should remain fixed with reference to the longitudinal rod 4.
  • Fig. 7 shows a preferred embodiment of the clamp 5. It consists of a glider 27 which clamps pin extremity 30. Glider 27 is free to move within the circular groove 29 machined in the clamp body
  • Fig. 8 shows a further preferred embodiment whereby kinematics of the pin extremity 30 is achieved by the four-bar linkage 32.
  • the latter consists of a pin bar 33 clamping the pin 3 a rod bar 34 clamped to the longitudinal rod 4 and two side bars 35 and 36.
  • the four bars are connected by means of joints 37.
  • the center of rotation of the bar 33 with respect to the bar 34 lies at the intersection 25 of the axis 38 and 39 of the side bars 35 and 36.
  • pin extremity 30 will move on approximately circular trajectory 24.
  • Fig. 9 shows a further preferred embodiment whereby the four-bar linkage 32 is realized by connecting the bars 33,34,35,36 by flexible sections 40.
  • the whole four-bar linkage 32 may be manufactured from one single piece of metal.
  • Fig. 10 shows a further preferred embodiment whereby circular kinematic trajectory 24 is realized by connecting sections 41 and 42 of clamp 5 with a composite structure 43 consisting of fibers 44 within an elastomer matrix 45.

Abstract

This external fixation device for osteosynthesis comprises pins (3) adapted for being passed through the bone fragments (1) being joined, a plurality of at least two clamps (5) for fastening said pins (3), and at least one longitudinal rod (4) interconnecting said individual clamps (5) to form a single frame with the bone fragments (1) disposed in required positions relative to each other. The clamps (5) are designed in such a way that they allow movement of the axially clamped extremity (30) of said pin (3) on a trajectory (24) approximating the arc of a circle and maintaining approximately orthogonality between said clamped pin extremity (30) and said trajectory (24), whereby the center (25) of said circle is located approximately within the near bone cortex (7) where said pin (3) enters said bone fragment (1) and the radius (26) of said circle corresponds to the free length (12) of said pin (3).

Description

EXTERNAL FIXATION DEVICE Background of the Invention
This invention relates to an external fixation device for osteosynthesis, comprising pins adapted for being passed through the bone fragments being joined, a plurality of at least two clamps for fastening said pins and at least one longitudinal rod interconnecting said individual clamps to form a single frame with the bone fragments disposed in required positions relative to each other.
Various proposals have been made for orthopaedic external fracture fixing apparatus, so-called "fixateur externes" comprising a range of components which are variably connectable with each other and with the fragments of a fractured bone by way of pins to form a support network holding the bone fragments in a desired positional relationship for the purposes of re-union.
The principle of external fixation entails load transfer from bone to an external frame by means of pins (or wires in the case of Ilizarov-type devices). Length of the pins must allow forclearing soft tissues covering the fractured bone, as well as for post-surgical treatment. The resulting distance between the treated bone and the external frame produces undesirable mechanical conditions at pin-bone interface. Parametric analyses of stress concentrations for commenly used frame configurations showed extremly high stress levels at pin-bone interface ("Parametric Analyses of Pin-Bone Stresses in External Fracture
Fixation Devices" R.Huskes, E.Y.S.Chao, and T.E.Crippen, Journal of Orthopaedic Research, Vol 3, 341-349, 1985).
None of the known external fixation devices has been able to reduce the stress concentration factors to an acceptable level.
High stress levels at pin-bone interface are likely to contribute to, if not even to directly induce, pin loosening and the known clinical complications that follow.
Most of the stress concentration at pin-bone interface is produced by pin angulation within cortices under functional loading as well as preloading.
Summary of the Invention
The invention as claimed is intended to remedy these drawbacks. It solves the problem of how to design an external fixation device which couples the reaction force with the reaction moment between the pin and the rod in such a way as to keep the pin angulation at zero within bone cortices. This completely eliminates stress concentration at pin-bone interface due to bending moments on the pin.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For the better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which are illustrated and described preferred embodiments of the invention.
Brief Description of the Drawings
In the drawings:
Fig. 1 is a schematic view of an external fixation device according to the state of the art applied to a fractured bone;
Fig. 2 is a diagrammatic view of loads and deformations in a device according to the state of the art;
Fig. 3 is a sectional view of the pin-bone interface showing stress distribution in the device according to Fig. 1;
Fig. 4 is a diagrammatic view showing conditions necessary for eliminating bending moment on the pin between bone cortices in a device according to the invention:
Fig. 5 is a sectional view showing reduced stresses at pin-bone interface in a device according to the invention;
Fig. 6 is a sectional view of a device according to the invention showing loads and deformations of the unilateral frame;
Fig. 7 is a sectional view and a cross-section of a device according to the invention showing a clamp with a gliding kinematic pair; Fig. 8 is a sectional view of a device according to the invention showing a clamp designed as a four-bar linkage;
Fig. 9 is a sectional view of a device according to the invention showing a clamp designed as a flexible four-bar linkage;
Fig. 10 is a sectional view of a device according to the invention showing a clamp made as a composite structure;
Fig. 11 is a sectional view of a device according to the invention showing a coupled pair of clamps.
Description of the Preferred Embodiments
Fig. 1 represents a fractured bone 1 fixed by means of an external fixation device, whereby pins 3 are inserted through bone fragments 1 and fixed to longitudinal rods 4 by means of clamps 5. Transmission of force 6 is achieved partly or completely in case of comminuted fracture 2 through external frame 3,4,5.
Fig. 2 shows a deformation of the pin 3 under load 6 to position 3a. Reaction forces 8 in case of symmetrical bilateral frame shown will equal one half of the axial load 6. The corresponding diagramm shows bending moment of the pin 3. Reaction moments 9 depend on the pin length and bone diameter. Between bone cortices 7 bending moment is constant. Fig. 3 shows the resultant stress distribution 10 and 11 at pin-pone interfaces due to mainly high bending moment between cortices 7.
Fig. 4 shows deformations of the pin 3 into position 3a due to load 6 provided that reaction moments 21 are high enough to eliminate bending moment 22 between cortices 7. The magnitude of compensating bending moment 21 is equal to the product of the reaction force 8 with the free pin length 12.
Fig. 5 shows the resultant stress distribution 23 in the device according to Fig. 4.
Fig. 6 shows the kinematic constraint necessary to produce conditions described by Fig. 4. If the clamped extremity 30 of the pin 3 is forced to move on a circular trajectory 24 with the center 25 within the near cortex 7 the reaction moment 21 will be equal to the product of the reaction force 8 multiplied by the radius 26 of the circle 24. Radius 26 is equal to the free pin length 12. Trajectory 24 should remain fixed with reference to the longitudinal rod 4.
Fig. 7 shows a preferred embodiment of the clamp 5. It consists of a glider 27 which clamps pin extremity 30. Glider 27 is free to move within the circular groove 29 machined in the clamp body
28. To reduce the friction rollers 13 may be interposed between gilder 27 and clamp Cody 28.
Fig. 8 shows a further preferred embodiment whereby kinematics of the pin extremity 30 is achieved by the four-bar linkage 32.
The latter consists of a pin bar 33 clamping the pin 3 a rod bar 34 clamped to the longitudinal rod 4 and two side bars 35 and 36. The four bars are connected by means of joints 37. The center of rotation of the bar 33 with respect to the bar 34 lies at the intersection 25 of the axis 38 and 39 of the side bars 35 and 36. For small deformations pin extremity 30 will move on approximately circular trajectory 24.
Fig. 9 shows a further preferred embodiment whereby the four-bar linkage 32 is realized by connecting the bars 33,34,35,36 by flexible sections 40. The whole four-bar linkage 32 may be manufactured from one single piece of metal.
Fig. 10 shows a further preferred embodiment whereby circular kinematic trajectory 24 is realized by connecting sections 41 and 42 of clamp 5 with a composite structure 43 consisting of fibers 44 within an elastomer matrix 45.
If only two pins 3 are used in each bone segment 1 an additional kinematic constraint is needed to prevent rotation of the bone segment 1 in the frame plane. This may be achieved by an additional bar linkage 31 connecting pin extremities 30 or the respective elements 33 of the clamp mechanism as shown in Fig. 11.

Claims

Claims
1. External fixation device for osteosynthesis, comprising pins (3) adapted for being passed through the bone fragments (1) being joined, a plurality of at least two clamps (5) for fastening said pins (3), and at least one longitudinal rod (4) interconnecting said individual clamps (5) to form a single frame with the bone fragments (1) disposed in required positions relative to each other, characterised in that said clamps (5) are designed in such a way that they allow movement of the axially clamped extremity (30) of said pin (3) on a trajectory (24) approximating the arc of a circle and maintaining approximately orthogonality between said clamped pin extremity (30) and said trajectory (24), whereby the center (25) of said circle is located approximately within the near bone cortex (7) where said pin (3) enters said bone fragment (1) and the radius (26) of said circle corresponds to the free length (12) of said pin (3).
2. External fixation device according to claim 1, wherein said clamp (5) comprises a circular groove (29) suitable to receiving glider (27) in which extremity (30) of said pin (3) is clamped in orthogonal relationship and allowing free movement of said glider (27) within and along said circular groove (29).
3. External fixation device according tc claim 1, wherein said clamp (5) comprises a four-bar linkage (32) consisting of a bar (33) in which the extremity (30) is clamped, of a bar (34) which is clamped to the longitudinal rod (4) and two side bars (35,36) interconnecting said two bars (33,34) by joints (37) in such a way that the axis (38,39) of said two side bars (35,36) are intersecting within the near cortex (7).
4. External fixation device according to claim 3, wherein said joints (37) are replaced by flexible sections (40) forming a single framework together with said bars (33,34,35,36).
5. External fixation device according to claim 1, wherein said clamp (5) consists of an element (41) connected to said pin (3), an element (42) connected to said longitudinal rod (4) and an element (43) interconnecting said two elements (41) and (42), whereby element (43) is made of a composite material with elastomer matrix (45) and fibres (44) arranged in such a way that said element (41) is free to move on said trajectory (24).
6. External fixation device according to one of the claims 1 to 5. wherein said plurality of clamps (5) is limited to the number of two per bone fragment and said clamped pin extremities (30) of said pins (3) are connected with a bar (31) assuring synchronism to achieve rotational stability in the plane formed by said bone (1) and said longitudinal rod (4).
PCT/EP1987/000235 1987-04-30 1987-04-30 External fixation device WO1988008281A1 (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
JP62503064A JPH0628668B2 (en) 1987-04-30 1987-04-30 External fixing device
MX011288A MX167618B (en) 1987-04-30 1987-04-30 EXTERNAL FIXING DEVICE FOR OSTEOSYNTHESIS
DE8787903291T DE3783916T2 (en) 1987-04-30 1987-04-30 EXTERNAL FIXATEUR.
EP87903291A EP0313556B1 (en) 1987-04-30 1987-04-30 External fixation device
BR8707717A BR8707717A (en) 1987-04-30 1987-04-30 EXTERNAL FIXATION DEVICE FOR OSTEOSYNTHESIS
PCT/EP1987/000235 WO1988008281A1 (en) 1987-04-30 1987-04-30 External fixation device
CA000565582A CA1329346C (en) 1987-04-30 1988-04-29 External fixation device
US07/465,575 US5024618A (en) 1987-04-30 1990-01-18 External fixation device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP1987/000235 WO1988008281A1 (en) 1987-04-30 1987-04-30 External fixation device

Publications (1)

Publication Number Publication Date
WO1988008281A1 true WO1988008281A1 (en) 1988-11-03

Family

ID=8165185

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1987/000235 WO1988008281A1 (en) 1987-04-30 1987-04-30 External fixation device

Country Status (8)

Country Link
US (1) US5024618A (en)
EP (1) EP0313556B1 (en)
JP (1) JPH0628668B2 (en)
BR (1) BR8707717A (en)
CA (1) CA1329346C (en)
DE (1) DE3783916T2 (en)
MX (1) MX167618B (en)
WO (1) WO1988008281A1 (en)

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US5318575A (en) * 1992-02-03 1994-06-07 United States Surgical Corporation Method of using a surgical repair suture product
US5417698A (en) * 1992-10-09 1995-05-23 United States Surgical Corporation Apparatus for tightening elongated wound closure elements
US5355913A (en) * 1992-10-09 1994-10-18 United States Surgical Corporation Surgical repair device
US5356412A (en) * 1992-10-09 1994-10-18 United States Surgical Corporation Sternum buckle with rotational engagement and method of closure
US5330489A (en) * 1992-10-09 1994-07-19 United States Surgical Corporation Sternum closure buckle
US6162224A (en) * 1995-02-15 2000-12-19 Acumed, Inc. External fixator for repairing fractures of distal radius and wrist
US6171309B1 (en) 1995-02-15 2001-01-09 Acumed, Inc. External fixator for repairing fractures of distal radius and wrist
US5743898A (en) * 1995-05-12 1998-04-28 Electro-Biology, Inc. Method and apparatus for external fixation of small bones
US5662650A (en) 1995-05-12 1997-09-02 Electro-Biology, Inc. Method and apparatus for external fixation of large bones
US5976125A (en) * 1995-08-29 1999-11-02 The Cleveland Clinic Foundation External distractor/fixator for the management of fractures and dislocations of interphalangeal joints
DE19635975C1 (en) * 1996-09-05 1998-07-30 Richard Dipl Ing Skiera Fastening device for bones and bone fragments
ATE349960T1 (en) * 1997-01-14 2007-01-15 Res Corp Technologies Inc BONE PIN WITH ROTARY CUTTING TIP
US20070012372A1 (en) * 2005-07-01 2007-01-18 Jay Richard M Cover for fixation pin
WO2009094478A1 (en) * 2008-01-22 2009-07-30 Stout Medical Group, L.P. Expandable orthopedic device and method
US9962188B2 (en) 2013-10-29 2018-05-08 Cardinal Health 247. Inc. External fixation system and methods of use

Citations (3)

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Publication number Priority date Publication date Assignee Title
FR1569090A (en) * 1968-04-12 1969-05-30
FR2442044A1 (en) * 1978-11-24 1980-06-20 Barbiero Aldino EXTERNAL MONOLATERAL OSTEOSYNTHESIS APPARATUS
US4584995A (en) * 1984-04-26 1986-04-29 Orthotic Limited Partnership External fixation device

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US1789060A (en) * 1928-09-29 1931-01-13 King Scheerer Corp Bone-fracture clamp
GB347495A (en) * 1930-05-09 1931-04-30 Earl Edward Youngren Improvements in and relating to surgical apparatus
US2435850A (en) * 1945-07-16 1948-02-10 John R Siebrandt Splint and guard construction
US3985127A (en) * 1975-06-11 1976-10-12 Mstislav Vasilievich Volkov Apparatus for surgical treatment of the knee joint
CH628798A5 (en) * 1978-06-27 1982-03-31 Synthes Ag BONE REDUCTION DEVICE.
US4185623A (en) * 1978-07-18 1980-01-29 Oganesian Oganes V Apparatus for restoration of hip joint mobility
US4393868A (en) * 1981-02-20 1983-07-19 Ace Orthopedic Manufacturing Inc. Colles fracture fixature device
US4757809A (en) * 1984-04-26 1988-07-19 Orthotic Limited Partnership Pin clamp
FR2595045B1 (en) * 1986-02-28 1991-12-27 Hardy Jean Marie DEVICE FOR IMMOBILIZING A BONE ELEMENT, PARTICULARLY FOR ORTHOPEDIC INTERVENTION

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1569090A (en) * 1968-04-12 1969-05-30
FR2442044A1 (en) * 1978-11-24 1980-06-20 Barbiero Aldino EXTERNAL MONOLATERAL OSTEOSYNTHESIS APPARATUS
US4584995A (en) * 1984-04-26 1986-04-29 Orthotic Limited Partnership External fixation device

Also Published As

Publication number Publication date
US5024618A (en) 1991-06-18
EP0313556B1 (en) 1993-01-27
DE3783916T2 (en) 1993-05-19
DE3783916D1 (en) 1993-03-11
JPH01502719A (en) 1989-09-21
JPH0628668B2 (en) 1994-04-20
BR8707717A (en) 1989-10-31
EP0313556A1 (en) 1989-05-03
MX167618B (en) 1993-03-31
CA1329346C (en) 1994-05-10

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