DE102008010476A1 - Osteosynthesis clamp for treating fractures of patient, has U-side piece, where clamp is made of shape memory material i.e. nickel-titanium alloy and is pseudo- and super elastic at room- and body temperature - Google Patents

Abstract

The clamp has a round wire, an even U-upper surface (10) and an even U-side piece (12), where transition between the upper surface and the side piece is rounded. The clamp is made of a shape memory material i.e. nickel-titanium alloy, and is pseudo- and super elastic at room temperature and body temperature of a patient. The clamp is formed mirror symmetric to a transverse center plane by the U-upper surface, and the U-side piece encloses an angle between 45 degrees to 90 degrees preferably 74 degrees with the U-upper surface. Free ends of the U-side piece are spherically rounded.

Description

The The invention relates to an osteosynthesis clamp of shape memory material, namely a nickel-titanium alloy.

Osteosynthesis clips made of shape memory material (memory metal) are the EP 0 695 142 B1 and the patent literature discussed therein.

Subject of the DE 297 09 289 U1 is a clip for fixing an osteotomy, which consists of memory metal, preferably a nickel-titanium alloy.

The DE 201 01 918 U1 deals with the stress-strain behavior of memory alloys, in particular their pseudoelastic or superelastic behavior.

at the well-known osteosynthesis of memory metal is the used thermoelastic conversion. The brackets are at lower Temperature spread and implanted in a spread state. she should by warming to body temperature return to their original form, the stapled Hold together bone fragments and apply a compression force on the Exercise fracture gap.

Problematic is the temperature course of the known osteosynthetic clamps before and during implantation and afterwards. With the cooling of the brackets before spreading and their refrigerated storage in splayed Condition go hand in hand with potential handling errors. It can not be ruled out that the warming and reversion of the staples undesirably already in the operational phase. Another uncertainty factor are variations in the body temperature of the patient, z. B. by infection-related fever. The most serious disadvantage However, the known Osteosyntheseklammern is that their Tension for many applications to be desired leaves.

task The invention is to provide an osteosynthesis clamp, the during spreading in the operating room, during implantation and in vivo free from temperature influences and higher clamping and holding forces on the bone fragments allows. The osteosynthesis clamp should be alike suitable for the treatment of fractures and osteotomies be.

The this task solving osteosynthesis clamp consists of a titanium-nickel alloy of such composition that the Clasp at room and body temperature pseudo or superelastic is.

With leaves the osteosynthetic clamp according to the invention achieve very high biomechanical stability. The clamp exercises quickly and without sharp projections a sure high mechanical compression force on the fracture gap out. This is a simple applicability and a high patient comfort guaranteed. The clamp is suitable in place a conventional Zuggurtungsosteosynthese about two parallel Kirschner wires and an eight-speed wire cerclage to kick and special lag screws and / or special angular stable Replace implants. The surgical technique is simplified lowered the error rate and improved the durability of the osteosynthesis.

at In a preferred embodiment, the nickel-titanium alloy, from which the osteosynthetic clamp consists, the following composition: 54.5 Wt% to 57 wt% nickel; Remainder except impurities titanium; Impurities not more than 0.1 wt .-%.

The Abbreviation Gew .-% stands for weight percent.

Of the Proportion of impurities, for example, with cobalt, chromium, iron, Oxygen, hydrogen will generally be about 0.05 wt .-%.

In a preferred embodiment, the alloy (Ni ₅₁ Ti ₄₉ ) consists of 51 at.% Nickel and 49 at.% Titanium.

The Abbreviation at .-% stands for atomic percent.

at A preferred embodiment is the osteosynthetic clamp essentially U-shaped and mirror-symmetrical to a Cross median plane built up by the U-back.

at In a preferred embodiment, the clip has a straight U-back and straight U-thighs. The transition between the U-back and the U-thighs is rounded.

at a preferred embodiment include the U-leg with the U-back an angle of 45 ° to 90 °, preferably 74 °.

at A preferred embodiment is the U-back the osteosynthesis clamp 14.6 mm ± 3 mm long.

at a preferred embodiment, the U-legs of the Osteosynthesis clamp 12 mm ± 8 mm long.

In a preferred embodiment be the osteosynthesis clamp is made of round wire with a diameter of preferably 2.5 mm ± 1 mm.

at a preferred embodiment are the free ends the U-legs rounded spherically, preferably in the form of a kugelkalottenförmigen Knoll.

The Invention will be described below with reference to an illustrated in the drawing Embodiment explained in more detail. Show it:

1 an osteosynthesis clamp in lateral plan view;

2 Stress-strain diagrams of a shape memory material in different temperature ranges; and

3 a diagram showing the temperature dependence of the pseudoelastic strain of the nickel-titanium alloy Ni ₅₁ Ti ₄₉ .

In the 1 shown Osteosynthesekprammer is substantially U-shaped. Her U-back 10 is just. Your U-thighs 12 are also straight and from the U-back 10 bent inwards at an angle of 74 °. The transition between the U-back 10 and the U-thighs 12 the bracket is rounded.

The clip is mirror symmetric to a transverse median plane through the U-back 10 built up. The free ends of the U-thighs 12 are rounded spherical. They have a kugelkalottenförmige dome 14 ,

The clamp consists of round wire of 2.5 mm diameter. The material of the wire is the nickel-titanium alloy Ni ₅₁ Ti ₄₉ .

The maximum lateral display a of the clip in extension of the U-back 10 is 14.60 mm ± 0.30 mm. The length l of the U-legs 12 is about 12 mm.

The ends of the U-thighs 12 have from the outer edge of the U-back 10 a maximum distance b of 15.39 mm ± 0.50 mm. The minimum distance c of the ends is 4.5 mm + 0.5 mm / -0.2 mm.

The stress-strain diagram of a shape memory material in 2 bottom left shows a low temperature range in which a thermoelastic conversion is possible. Of course, the invention does not make use of such a conversion.

At a sufficiently low temperature, the shape memory material is at the origin 16 stress-strain diagram in the martensitic phase. The initial steep linear increase 18 The diagram according to Hook's law shows that the martensitic material initially behaves elastically under increasing strain. When a limit voltage is reached, however, the strain increases virtually without further increase in voltage. The material flows like a plastic body. The tension plateau 20 The diagram marks the transition to the austenitic phase, in which the material initially behaves elastically under further increasing strain.

Upon heating of the shape memory material, the transition to the austenitic phase begins at the transition temperature A _s . At the temperature A _f , the phase transition is completed.

Upon cooling of the shape memory material, the transition into the martensitic phase begins at the transition temperature M _s . At the temperature M _f , the phase transition is completed.

A prior art thermoelastic conversion osteosynthesis clamp is in the austenitic phase at human body temperature. It is cooled below the temperature M _f and spread in the martensitic phase. When heated to body temperature, the osteosynthetic clamp returns to the austenitic phase and its original shape.

The low temperature range of the stress-strain diagram closes in the middle of the 2 towards a higher temperature towards a pseudo or superelastic region, in which above the temperature A _f and below a temperature M _d, a stress-induced martensite formation is possible. The initially steep linear increase 22 of the diagram according to Hooke's law shows that the material in austenitic phase initially behaves elastically under increasing deformation stress. It will again be a tension plateau 24 reached, at which the strain grows almost without further increase in voltage and a voltage-induced transition takes place in the martensitic phase. The latter again behaves elastically under further increasing deformation stress.

As the strain voltage decreases, the martensitic to austenitic phases revert. The stress-strain diagram shows a pronounced hysteresis with a significantly lower voltage plateau during the reverse transformation 26 , After reaching Hook's area 22 takes the tension proportional to the strain, until the starting point 28 in the diagram and the original form are reached again.

The Ni ₅₁ Ti ₄₉ alloy that makes up the osteosynthesis clamp is pseudo or superelastic at room temperature as well as at body temperature. On the voltage plateaus 24 . 26 in the pseudo or superelastic region of its stress-strain diagram, strain values of up to 8% can be achieved. However, the strain is strongly temperature-dependent (cf. 3 ). The alloy Ni ₅₁ Ti ₄₉ has its maximum strain in the range of room temperature and body temperature.

The osteosynthesis clamp consisting of the alloy Ni ₅₁ Ti ₄₉ is spread at room temperature and then implanted. It returns to discharge of the spreading force temperature unaffected in their original form.

To the pseudo or superelastic region of the stress-strain diagram 2 is followed by a high temperature range above the temperature M _{d in the} upper right, in which a stress-induced transition into the martensitic phase is no longer possible. In this area, the material has no shape memory.

10

U-back

12

U-leg

14

knoll

16

origin

18

Hook'scher Area

20

voltage plateau

22

Hook'scher Area

24

voltage plateau

26

voltage plateau

28

starting point

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0695142 B1 [0002]
• - DE 29709289 U1 [0003]
• - DE 20101918 U1 [0004]

Claims (12)

Osteosynthesis clamp made of shape memory material, namely a nickel-titanium alloy, characterized by a nickel-titanium alloy of such composition that the Clasp at room and body temperature pseudo or superelastic is. Osteosynthesis clamp according to claim 1, characterized by an alloy of the following composition: 54.5% by weight up to 57% by weight nickel; Remainder except impurities titanium; impurities not more than 0.1% by weight. An osteosynthesis clamp according to claim 1 or 2, characterized by an alloy (Ni ₅₁ Ti ₄₉ ) consisting of 51 at.% Nickel and 49 at.% Titanium. Osteosynthesis staple according to one of claims 1 to 3, characterized in that the staple is substantially U-shaped and mirror-symmetrical to a transverse median plane through its U-back ( 10 ) is constructed. Osteosynthesis clamp according to claim 4, characterized in that it has a straight U-back ( 10 ) and straight U-legs ( 12 ), and that the transition between the U-back ( 10 ) and U-legs ( 12 ) is rounded. Osteosynthesis clamp according to claim 4 or 5, characterized in that the U-limbs ( 12 ) with the U-back ( 10 ) enclose an angle of 45 ° to 90 °, preferably 74 °. Osteosynthesis clamp according to claim 5 or 6, characterized in that the U-back ( 10 ) Is 14.6 mm ± 3 mm long. Osteosynthesis clamp according to one of claims 5 to 7, characterized in that the U-legs ( 12 ) Are 12 mm ± 8 mm long. Osteosynthesis clamp according to one of the claims 1 to 8, characterized in that the clip of round wire consists Osteosynthesis clamp according to claim 9, characterized that the wire has a diameter of 2.5 mm ± 1 mm has. Osteosynthesis clamp according to one of claims 4 to 10, characterized in that the free ends of the U-legs ( 12 ) are rounded spherical. Osteosynthesis clamp according to claim 11, characterized in that the U-legs ( 12 ) at the end of a kugelkalottenförmige dome ( 14 ) to have.