WO1990012550A1

WO1990012550A1 - Self-reinforced surgical materials and devices

Info

Publication number: WO1990012550A1
Application number: PCT/FI1990/000113
Authority: WO
Inventors: Pertti Törmälä; Timo Pohjonen; Pertti Helevirta; Seppo Vainionpää; Markku Tamminmäki; Pentti Rokkanen; Esa Partio
Original assignee: Biocon Oy
Priority date: 1989-04-26
Filing date: 1990-04-24
Publication date: 1990-11-01
Also published as: EP0422177A1; AU5233293A; FI88111C; AU5530190A; JPH03505537A; FI891973A; FI88111B; FI891973A0

Abstract

This invention describes self-reinforced, absorbable surgical materials and/or implants and/or their parts and/or components, which can be implanted into the living tissue or on its surface for the purpose of e.g. to repair tissue damages, to join tissues or their parts to each other, to augment tissues or their parts, to separate tissues or their parts from each other and/or from their surroundings, and/or to conduct material between tissues or their parts and/or out of tissues or from the outside into the tissues, for which self-reinforced materials and/or implants or their parts and/or components is characteristic that their reinforcing elements are wound at least partially around some axis penetrating the implant. These implants have better and more isotropic strength properties than the known self-reinforced implants.

Description

Self-reinforced surgical materials and devices

In surgery it is known to use implants or their parts o components- which are manufactured at least partially of a absorbable polymer and/or of a polymer composite containing reinforcing elements, for fixation of bone fractures, osteotomies or arthrodeses, joint damages, tendon and ligamen damages etc. Such implants are e.g. rods, screws, plates, intra edullary nails and clamps, which have been described i the professional literatures of material- technique and medicine.

U.S. Pat. No. 3 620 218, E. Schmitt and R. Polistin "Cylindrical Prosthetic Devices of Polyglycolic Acid" an U.S. Pat. No. 3 739 733, E. Schmitt and R. Polistin "Polyglycolic Acid Prosthetic Devices" describe implants like rods, screws, plates and cylinders which have bee manufactured of polyglycolic acid.

U.S. Pat. No. 4 052 988, N. Doddi, C. Versfelt and D asserman "Synthetic Absorbable Surgical devices o Polydioxanone" describes absorbable sutures and other surgica devices manufactured of polydioxanone.

U.S. Pat. No. 4 279 249, M. Vert, F. Chabot, J. Leray and P Christel "New Prosthesis Parts, Their Preparation and Thei Application" describes osteosynthesis devices which have bee manufactured of polylactide or of copolymer containing plent of lactide units, which matrix has been reinforced wit reinforcing elements which have been manufactured o polyglycolide or of copolymer including mainly glycolic aci units.

DE 29 47 985 A 1, S. Belych, A. Davydov, G. Chromov, A Moscenskij, I. Movsovic, G. Rojtberg, G. Voskresenskij, G Persin and V. Moskvitin "Biodestruktiver Stoff fύ Verbindungselemente fϋr Knochengewebe" describes at leas partially degradable composites which comprise e.g. a copolymer of methylmethacrylate and N-vinylpyrrolidone, which has been reinforced with polyamide fibres or with oxycellulose fibres.

U.S.- Pat. No. 4 243 775, M. Rosensaft and R. Webb "Synthetic Polyester Surgical Articles" describes surgical products manufactured of copolymer of glycolic acid and trimethylene carbonate.

U.S. Pat. No. 4 329 743, H. Alexander, R. Parsons, I. Strauchler and A. Weiss "Bioabsorbable Composite Tissue Scaffold" describes a composite of a bio-absorbable polymer and carbon fibres, which composite is suitable for manufacturing surgical articles.

U.S. Pat. No. 4 343 931, T. Barrows "Synthetic Absorbable Devices of Poly(estera ides)" describes absorbable polyesteramides, which are suitable for manufacturing of surgical implants.

^'. Pat. Appl. EPO 0 146 398, R. Dunn and R. Casper " Method of Producing Biodegradable Prosthesis and Products therefrom" describes a method for manufacturing of biodegradable prostheses about biodegradable polymer matrix which is reinforced with biodegradable ceramic fibres.

. WO 86/00533, J. Leenslag, A. Pennings, R. Veth and H. Janse "Bone Implant" describes an implant material fo reconstructive surgery of bone tissue, which material comprises a biodegradable porous polymer material an biodegradable or biostable fibres.

The publication D. Tune "A High Strength Absorbable Polyme for-,Internal Bone Fixation", 9th Annual Meeting of the Societ for Biomaterials, Birmingham, Alabama, April 27 - May 1, 1983", p. 17, describes a high strength absorbable polylactide /with an initial tensile strength about 50-60 MPa and whic mater±si retaiώs a significant part of its initial strengt 8-12 weeks after the implantation. This material can b considered suitable to be applied as basic material i manufacturing of internal bone fixation devices which ar totally absorbable in living tissues.

The publication D. Tune, M. Rohovsky, W. Lehman, A. Strogwate and F. Kummer "Evaluation of Body Absorbable Bone Fixatio Devices", 31st Annual ORS, Las Vegas, Nevada, Jan. 21-24, 1985, p. 165, describes high strength, totally absorbabl polylactide (initial strength 57,1 MPa), which was used as plates and screws for fixation of canine radial osteotomies.

The publication D. Tune, M. Rohovsky, J. Zadwadsky, J. Spieke and E. Strauss "Evaluation of Body Absorbable Screw i Avulsion Type Fractures", The 12th Annual Meeting of th Society for Biomaterials, Minneapolis - St. Paul, Minnesota, USA, May 29 to June 1, 1986, p. 168, describes the applicatio of high strength polylactide screws in fixation of avulsion type fractures (fixation of canine calcaneous osteotomy).

U.S. Pat. No. 4 776 329, R. Treharne "Resorbable Compressin Screw and Method", describes a compression screw equipment comprising a non-absorbable compression parts and a screw. A least the head of the screw comprises material, which i resorbable in contact with tissue fluids.

Self-reinforced absorbable fixation devices have significantl higher strength values than the non-reinforced absorbable fixation devices. U.S. Pat. No. 4 743 257, P. Tδrmala, P Rokkanen, J. Laiho, M. Tamminmaki and S. Vainionpaa "Materia for Osteosynthesis Devices", describes a self-reinforce surgical composite material, which comprises an absorbabl polymer or copolymer, which has been reinforced with absorbable reinforcing elements, which have the same chemica element composition as the matrix.

FI Pat. Appl. No. 87 0111, P. Tδrmala, P. Rokkanen, S Vainionp a, J. Laiho, V.-P. Heponen and T. Pohjonen "Surgica Materials and Devices", describes self-reinforced surgical bone fracture fixation devices which have been manufactured at least partially of fibrillated absorbable material(s) .

According to the publication T. Pohjonen, P. Tδrmala, J. Mikkola, J. Laiho, P. Helevirta, H. Lahde, S. Vainionpaa and P. Rokkanen "Studies on Mechanical Properties of Totally Biodegradable Polymeric Rods for Fixation of Bone Fractures", VIth International Conference PIMS, Leeuwenhorst Congress Centre, Holland, 12-14 April 1989, p. 34/1-34/6, self-reinforced absorbable surgical materials have excellent strength properties, e.g. SR-polyglycolide had bending strength 415 MPa and SR-polylactide 300 MPa.

Also in the publication D. Tune and J. Jadhav "Development of Absorbable Ultra High Strength Polylactide", Am. Chem. Soc, 196th ACS Meeting, Abstracts of Papers, L.A. , California, Sept. 25-30, 1988, p. 383-387, a good tensile strength (300 MPa) for fibrillated SR-polylactide was measured.

The publication E. Partio, 0. Bδstman, S. Vainionpaa, H.

Patiala, E. Hirvensalo, K. Vihtonen, P. Tδrmala and P. Rokkanen "The Treatment of Cancellous Bone Fractures with

Biodegradable Screws", Acta Orthop. Scand., 59(5), 1988, p.

18, describes the fixation of cancellous bone fractures with self-reinforced absorbable screws, which have a flat head, which head can be located to a slot at the tip of the screwdriver in order to drive the screw into a channel mad into the bone.

Although the known self-reinforced absorbable surgical composites have certain good mechanical strength properties, they have the disadvantage that the mechanical strength properties are strongly anisotropic. Because the known self reinforced absorbable composites, which have been manufacture e.g. with the sintering technique or with fibrillatio (drawing) technique, are parallel reinforced, the bindin forces between, the reinforcing elements are determined by the strength of the matrix and of the boundary surface betwee matrix and reinforcing elements. The parallel reinforcin means here that reinforcing elements, like fibres, threads fibrils or bundles of them form parallel structures into the matrix.

Typically the tensile strength of the reinforcing elements i hundreds or thousands of MPa, but the internal strength of th matrix and of the matrix - reinforcing element boundary i only the order of magnitude of 10-100 MPa. As a consequence of this structural anisotropy the fracture of self-reinforce absorbable composites occurs relatively easily as th delamination between the parallel reinforcing element layer or between the parallel reinforcing elements, when th external forces affect to the implant from such a direction that the reinforcing elements cannot carry those externa forces. Accordingly, the delamination means the fracture o the composite material along the matrix between th reinforcing elements or along the boundary surface between th matrix and the reinforcing elements.

In this invention we have found unexpectedly that in such self-reinfoced absorbable surgical material or implan (device) or its part and/or component, where the reinforcin elements have been twisted at least partially around som axis which penetrates the implant, the tendency to the fracture by means of the delamination has been almos completely eliminated or it has at least significantly reduce when compared to the fracture behaviour of known self reinforced absorbable materials and implants.

This invention describes self-reinforced, absorbable surgica materials and/or implants and/or their parts and/o components, which can be implanted into the living tissue on its surface for the purpose of e.g. to repair tiss damages, to join tissues or their parts to each other, augment tissues or their parts, to separate tissues or the parts from each other and/or from their surroundings, and/ to conduct material between tissues or their parts and/or out"^" of tissues or from the outside into the tissues, for which aelf-reinforced materials and/or implants or their parts and/or components is characteristic that their reinforcing elements are wound at least partially around some axis penetrating the implant.

The reinforcing elements can be typically oriented molecular chains, molecule chain groups or their parts, oriented crystalline lamellae or spherulites, fibrils or their parts or corresponding morphological structural elements. They can also be fibres, filaments, film fibres, threads, braids, - non-vowen* .structures, networks, meshes, knits or vowen structures or corresponding.

Because the reinforcing elements do not form in the materials of the invention coherent straight planar structures, th delamination surfaces in the materials of the invention ar at least partially curved and/or partially or completel eliminated depending on in which way the reinforcing elements have been wound around some axis penetrating the implant. As a consequence the materials of the invention have mor isotropic strength properties than the known self-reinforce absorbable materials and implants have. Therefore the implant of the invention have a better reliability in operation an they have more many-sided applications than the known implant have.

According to a specially advantageous embodiment the invente implants, their parts or components contain at least one hole hollow or cavity, around which the reinforcing elements hav -been wound at least partially. Such implants have several advantages in comparison to the known ones. When the implan contains a hole, hollow or cavity or corresponding, the mas of the implant is smaller than the mass of the solid implant This means advantageously a smaller amount of foreign materia in the tissues of the patient in the former case. A hole, hollow or cavity increases also the surface area of the implant which accelerates its hydrolysis in living tissues. A hollow inside of the implant can be used also to guide the implant into the tissue e.g. with a suitable guiding device. Additionally, a metallic rod, wire etc. which has been pushed into the hole, hollow or cavity, can act as an x-ray positive probe, which shows during the operation the exact position of the implant in the tissues. It is also possible to use the long hole or cavity inside of a self-reinforced absorbable screw of the invention as the screwdriver socket during the implantation of the screw by inserting the tip of the screwdriver into the hole so that the torque force from th screwdriver is divided along the screw axis. As a consequenc of spiral orientation such screws resist clearly highe torque forces than the known parallel fibre reinforced or non-reinforced absorbable screws because the torque force i received as tensile stresses by the wound reinforcing element which typically have very high tensile strength. In th known non-reinforced and self-reinforced screws the torqu forces are received by the screw material mainly as shear forces.

According to an advantageous embodiment the implant of th invention is an intramedullary nail, which is at leas partially hollow and where the reinforcing elements hav been wound at least partially around the long axis of the intramedullary nail. The cross-sectional form of such a intramedullary nail can be e.g. a circle, an ellipse, triangle, a quadrangle, a polygone or like a four-leave clover, kidney-like etc. Figure 1 shows some typica embodiments of the cross-sectional form of the intramedullar nail. It is self-evident that also other forms of the cross section than those given in Figure 1 can be applied in th intramedullary nails of the invention.

According to an advantageous embodiment the wall th intramedullary nail contains at least one elongated groove or hole, which has been formed by bending the wall of th intramedullary nail inside or by splitting it at least partially or by making at least one hole into the wall of th implant. The elongated groove or hole(s) give to th intramedullary nail flexibility in such an amount that th intramedullary nail does not split easily the bone, when th intramedullary nail is hammered into a tight drill hole insid of the bone. Figure 2 shows typical cross-sectional forms of intramedullary nails, which have in their wall a groove, a fissure ^*όr holes to increase its flexibility.

Figure 3 shows some examples in perspective view of intramedullary nails of the invention. On the surface of th intramedullary nail of Figure 3a spirally oriented lines have been drawn, describing the orientation of reinforcin elements.

The intramedullary nails can include also holes through which they can be fixed into bone e.g. with screws as is show schematically in a cross-sectional Figure 3e.

The fixation devices of the invention can be manufactured o absorbable (biodegradable or resorbable) polymers, copolymers, polymer mixtures or composites which have been described in many publications, like e.g. in the following inventions: U.S. Pat. No. 3 297 033, U.S. Pat No. 3 636 956, U.S. Pat. No. 4 052 988, U.S. Pat. No.4 343 931, U.S. Pat. No. 3 969 152 U.S. Pat. No. 4 243 775, FI Pat. Appl. No. 85 5079, FI Pat. Appl. No. 86 0366, FI Pat. Appl. No. 86 0440 and FI Pat. Appl. No.. 88 5164.

Table 1 gives some known biodegradable polymers, which ca be used as such or as mixtures as raw materials of th implants of the invention both as matrix material (as binding polymer) and/or as reinforcing elements. Table 1. Absorbable polymers

1. Polyglycolide (PGA)

Copolymers of σlvcolide;

2. Glycolide/L-lactide copolymers (PGA/PLLA) 3. Glycolide/trimethylene carbonate copolymers (PGA/TMC)

Polylactides (PLA)

Stereocopol mers of PLA;

4. Poly-L-lactide (PLLA)

5. Poly-DL-lactide (PDLLA) 6. L-lactide/DL-lactide copolymers

Copolymers of PLA:

7. Lactide/tetramethylglycolide copolymers

8. Lactide/trimethylene carbonate copolymers

9. LactideΛf-valerolactone copolymer. 10. Lactide/£-caprolactone copolymer

11. Polydepsipeptides

12. PLA/polyethylene oxide copolymers

13. Unsymmetrically 3,6-substituted poly-l,4-dioxane-2,5 diones 14. Poly-^β-hydroxybutyrate (PHBA)

15. PHBA/cT-hydroxyvalerate copolymers (PHBA/HVA)

16. Poly-β-hydroxypropionate (PHPA)

17. Poly-p-dioxanone (PDS)

18. Poly-3^"-valerolac one 19. Poly-e-.caprolactone

20. Methylmethacrylate-N-vinyl pyrrolidine copolymers

21. Polyesteramides

22. Polyesters of oxalic acid

23. Polydihydropyrans 24. Polyalkyl-2-cyanoacrylates

25. Polyurethanes (PU)

26. Polyvinylalcohol (PVA)

27. Polypeptides

28. Poly-β-malic acid (PMLA) 29. Poly-β-alkanoic acids

30. Polyvinylalcohol (PVA)

31. Polyethyleneoxide (PEO)

32. Chitine polymers

Reference: S. Vainionpaa, P. Rokkanen and P. Tδrmala, Proσ Polvm. Sci., 14, 1989, p. 679-716.

It is self-evident that also other absorbable polymers th those given in Table 1 can be applied in manufacturing t devices or their parts of this invention. E.g. the followi publications give absorbable (biodegradable) polymers whic can be applied in this connection: U.S. Pat. No. 4 700 704, U.S. Pat. No. 4 653 497, U.S. Pat. No. 4 649 921, U.S. Pat. No. 4 559 945, U.S. Pat. No. 4 532 928, U.S. Pat. No. 4 605 730, U.S. Pat. No. 4 441 496, U.S. Pat. No. 4 435 59 and U.S. Pat. No. 4 559 945.

The implants of the invention can be manufactured o absorbable polymers or copolymers by using one polymer o polymer mixture. The devices can be reinforced in addition to self-reinforcing also with fibres which are manufacture of other resorbable polymer or polymer mixture or with fibre which are manufactured of a resorbable ceramic materia (like with β-tricalciumphosphate fibres or with CaAl-fibres; see e.g. EPO Appl. 146 398) and/or with biostable fibres like glass-,^" carbon- or polymeric fibres.

The devices of the invention can contain also layered part comprising e.g. (a) a flexible surface layer which increase the toughness of the implant and/or acts as a hydrolysi barrier and (b) a stiff inner layer.

The surgical devices of the invention can be manufactured o absorbable polymers and of possible absorbable and/o biostable reinforcing fibres by means of different method like with methods known in plastics technology. Such method are e.g. injection moulding, extrusion as such or combined with fibrillation and forming (see e.g. FI Pat. Appl. No.

87 OZll) or compression moulding, where the samples are forme from the raw materials by means of heat and/or pressure.

The devices of the invention can be manufactured from th above raw materials also by means of so called solution techniques. Here at least part of the polymer is dissolved i a suitable solvent or it is plasticized with a solvent an the material or material mixture is compressed to a devic or preform by means of pressure and possibly applying heat so that the dissolved or plasticized polymer glues the material to a macroscopical sample, from which the solvent ca be removed by evaporation.

It is natural that the devices of the invention can includ additionally different kind of additives or auxiliary materials to facilitate the processing of the material (e.g. stabilizators, antioxidants or plasticizers) or to chang its properties (e.g. plasticizers or powder-like cerami materials or biostable fibres like polyaramide-or carbo fibres), or to facilitate its use (e.g. colours).

According to one advantageous embodiment the devices of th invention contain some bioactive material or materials, lik antibiotic or chemotherapeutic additives facilitating th healing of the wound, growth hormone, antifertilizatio additive, anticoagulant (like heparine) etc. Such bioactive implants are especially advantageous in clinical use, becaus they have in addition to the mechanical function als biochemical, medicinal etc. effects in different tissues.

Because the materials of the invention have good mechanica properties, they can be processed mechanically into differen forms. E.g. the plate preforms can be rolled, compressed stamped, upset, bent etc. either when cooled to a temperatur below the room temperature or at the room temperature or a an elevated temperature. They can be processed also b drilling, grinding, milling etc. or with other methods of mechanical processing or by other methods like lase processing or water jet cutting or ultra sound cutting. Th rods and tubes of the invention can be processed also wit the corresponding methods. E.g. it is possible to rol threads on the surface of a rod or a tube by rolling a rod or a tube between rotating (possibly heated) rolls (usuall 2-3 rolls) which rolls have been grooved in a suitable way This kind of rolling of the threads is in a common use i metal industry, but so far, this method has not been applie in the processing of absorbable polymeric materials. It is possible also to upset a head to the rod, and rods can be wound to helices, bent to clamps etc.

The invention and its function has been illustrated with the following non-limiting examples.

Example 1.

Polyglycolide surures (Dexon^R; size 2 USP, manufacturer Davis+Geck, England) were collected to a parallel thread bundle and the bundle was wound around its long axis in such way that the threads were wound in relation to the long axis of the thread bundle to an angle of 45° (Figure 4a shows schematically the parallel thread bundle and Figure 4b the wound thread bundle). The wound thread bundle was located into a cylindrical compression mould (length 70 mm, diameter 3.2 mm) and it was sintered (T = 218°C, time 5 min, pressure 2000 bar) to a self-reinforced rod, where the reinforcing elements (threads) were wound around the long axis of the rod (a spiral reinforced rod). The rod is shown in Figure 4c which shows also schematically the orientation of reinforcing threads. As a comparison material a corresponding rod was manufactured by sintering a parallel thread bundle to a rod.

The torsional load carrying capacity of the spiral reinforced rod was measured by fixing the ends of the rod into a torsional strength measurement device and by winding the other end of the rod in the same direction where the spiral reinforcement had been wound in the rod. As a comparison the torsional load carrying capacity of the parallel thread reinforced rods was measured. The maximum force of torsional load was for spiral reinforced rods 18 N and for parallel thread reinforced rods 10 N.

Example 2.

Melt spinning and (hot) drawing method was applied t manufacture fibres of the following absorbable polymers: poly-L-lactide (Mw 260 000, L-lactide/D-lactide copolymer (molar ratio 90/10), glycolide/lactide copolymer (molar ratio 90/10) and poly-β-hydroxy butyrate (Mw ca. 700 000). The polymers were manufactured by Boehringer/Ingelheim (Germany), CCA biochem (Holland) and ICI (England).

According to the principles of Example 1 the above fibres were applied to manufacture spiral reinforced and parallel reinforced absorbable (self-reinforced) rods by the sintering technique. The torsional load carrying capacity of each rod was measured according to the method of Example 1. The torsional load carrying capacities of the spiral oriented rods were 1.3-2 times higher than those of parallel fibre reinforced rods.

Example 3.

Dexon^R -sutures (size USP 1) were applied to manufacture absorbable, self-reinforced screws with the following dimensions: the total length 120 mm, the diameter of the screw core 6 mm, the length of the threaded part 20 mm (in the tip of the screw), the maximum thread diameter 8 mm, the maximum diameter of the head 9 mm. The screws were manufactured by sintering Dexon sutures in a hydraulic screw mould. The sintering coditions were: T = 215-225°C, the compression time 10 min and the pressure 2000 bar.

Two types of screws were manufactured:

A) Screws with the structure of the invention were manufactured by winding Dexon suture (size USP 1) around a rotating, polished metallic (steel) mandrel with the filament winding techniques by changing the winding angle between- 60° - 0° - +60°, where 0° - the direction perpendicular to the long axis of the mandrel and +60° = the maximum and the minimum values of the winding angle on the both sides of the perpendicular direction. The length of the mandrel was 140 mm. The maximum thickness of the mandrel was 3 mm at the one end and 2 mm at the other end. The cross-section of the

SUBSTITUTESHEET mandrel was a square. The filament wound preform was cut t the length of 125 mm and it was sintered to a headless scre preform with the 20 mm long thread part at its tip leavin the metal mandrel inside of the screw preform. The above screw mould was applied. The head was upset with th compression moulding technique to the other end of the scre preform (to the end where the metal mandrel was thicker) . The screw head was upset in such a way that the metal mandrel was uncovered 5 mm. The metal mandrel was drawn out of the screw, which left inside of the screw a square hol penetrating the screw.

B) Corresponding screws were manufactured of Dexon paralle thread bundles, where the reinforcing elements (Dexon threads) were oriented parallel with the long axis of the screw.

The torsional load carrying capacity of the spiral oriente screw was measured by pushing into the hole inside of th screw a long tip of a screwdriver which fitted tightly int the hole. The handle of the screwdriver and the tip of the thread part of the screw were fixed to the torsional strengt measurement apparatus and the torsional load carrying capacit was measured by winding the handle of the screwdriver aroun its long axis until the screw broke. A similar measuremen was done for parallel thread reinforced screws. The torsiona load carrying capacity of the spiral reinforced screws was 1. times higher than that of the parallel thread reinforce screws.

Example 4.

Linen weave type fabric was woven of glycolide/lactide suture (Vicryl^R, size 1 USP) by using Vicryl sutures both as warp an weft yarns. The fabric was rolled up to a ca. 8 mm thick an 40 mm long roll, which was flattened to a 5 mm thick fla roll which was pushed into a compression mould cavity wit dimension 5 x 15 x 40 mm which was open from one long, narro side. A suitable rectangular steel plate was compressed on th fabric roll, the mould was evacuated and the fabric wa sintered at ca. 180°C (time 10 min, pressure 2000 bar) to self-reinforced rod with dimensions 5 x 5 x 40 mm and with square cross-section. A layered rod was made for compariso by filling the mold with (5 x 40 mm) Vicryl fabric strip and by sintering them together.

Figure 5a shows schematically a rod according to th invention. Here a spiral orientation of the fabric has been described with a thick spiral line at the end of the rod an the positions of the warp and weft yearns on the surface o the rod have been described with thin lines. Figure 5b show the corresponding layered rods with the fabric layers in vertical position. (During the compression of this rod the fabrics were in a horizontal position. )

5 mm long parts were milled from the rods and they were cas partially into epoxy plastic (EP) according to the schemati side views of Figures 5c and 5d. The shear strength of th material of the invention (Figure 5c) and the shear strengt of the layered material in the direction of the plane of th layers (Figure 5d) was measured by loading the partiall into the epoxy cast samples in the direction given by th arrow. The measurements gave for the shear strength of th material of the invention the value of 80 MPa and for the layered material the value of 45 MPa.

Spiral reinforced rods and layered rods were split by sawin in the direction of their long axis. The layered rods wer split ^' n the plane of the fabrics. Accordingly spira reinforced rods shown schematically in Figure 5e and layere rods (Figure 5f) were obtained. The layered rod which is see in Figure 5f has been wound 90° around its long axis afte splitting if compared to the rod of Figure 5b. The rods we hydrolyzed 3 weeks in distilled water (T = 37°C) and thei bending strengths were measured with three point bending method by supporting the rods from their both ends and by loading them in the middle of the rod (shown by arrows in Figures 5e and 5f). The details of the bending test arrangements are given in the publication P.' Tδrmala et al. "Ultra high strength absorbable self-reinforced polyglycolide (SR-PGA) composite rods for internal fixation of bone fractures: in vitro and in vivo study", J. Biomed. Mater. Res. , in press. The bending strength of the hydrolysed rods of the invention was 40 MPa and of the layered rods 25 MPa.

Example 5.

Compression moulding technique was applied to manufacture of poly-L-lactide (Mw ca. 700 000, manufacturer CCA biochem, Holland) 5 mm thick plates, which were drawn and rolled at an elevated temperature (rolling temperature > 90°C) to 0.4 mm thick films. A 30 mm wide piece of the film was heated to ca. 90°C and rolled according to Figure 5a to a roll which was sintered to a spiral oriented rod with dimensions 5 x 5 x 30 mm in the mould of Example 4 at temperature 175°C.

The layered rod according to Figure 5 b was manufactured by filling the cavity of the mould of Example 4 with 5 x 30 mm big strips which were cut from the drawn and rolled film.

Analogously with the tests described in Figures 5c and 5d the shear strength of the spiral oriented and of the parallel film oriented rod was measured. The shear strength of the spiral oriented rods was 120 MPa and of the parallel oriented mat-trial 40 MPa.

Example 6.

P o l y - L - l a c t i d e ( Mw c a . 2 6 0 0 00 , manu f a cturer Boehringer/Ingelheim, Germany) was extruded to a cylindrical preform with diameter of 4 mm. The extruded preform was drawn through a conical die (conical angle of the die 25° , length of the die 25 mm) . The diameter of the circular hole at the tip of the die was 2. 6 mm. The drawing was done at a temperature between the glass transition temperature (Tg) and the melting temperature (T_m) of the polymer. Typical drawing temperatures were between 90°C and 150°C. The drawin was repeated for the drawn prefom by using an other die wit the hole tip diameter of 1.2 mm. The final self-reinforce (parallel fibre reinforced) rod had the diameter of 1.15 mm. The rod was cut into 20 mm long pieces. Part of the rods wer transformed to spiral reinforced by winding the ends of the rods at the opposite directions at 90°C tempereature so tha the final orientation of the reinforcing fibrils deviated ca. 45° from the direction of the long axis of the rod. Th torsional load resistance of spiral reinforced and paralle reinforced rods was measured at room temperature. The spira reinforced rods had about 1.4 times higher torsional load carrying capacity in comparison to the parallel fibre reinforced rods, when the spiral oriented rods were loade in the same direction where the spiral reinforcement wa oriented.

Example 7.

A. Parallel fibre reinforced, self-reinforced cylindrica polylactide rods were manufactured by sintering poly-L-lactid (PLLA) fibres (Mw 700 000, T_m ca. 180°C) and L-lactide/D lactide (PLDLA) copolymer fibres (molar ratio L-lactide/DL lactide = 90/10, T_m of the fibres = 150°C) together at T = 175°C in such a way that PLDLA-fibres melted and wetted PLLA fibres (PLDLA formed the binding matrix around the PLLA fibres). The dimensions of the rods were: the length 60 mm the diameter 4.8 mm.

B. Self-reinforced polylactide preforms were manufactured b the filament winding technique by winding PLLA-fibres an PLDLA-fibres (weight ratio 1:1) around a cylindrical mandre (diameter 3.8 mm) and by sintering the preforms in cylindrical mould (sintering temperature = 175°C) int cylindrical tubes with the outer diameter of 4.8 mm. The mandrel was removed from the inside of the tube and anothe mandrel was pushed into the hole inside of the tube. This mandrel had a longitudinal 1 mm deep and broad groove on its surface. A schematic cross-sectional Figure 6a shows the self- reinforced tube and the mandrel, which has a longitudinal groove. The tube was heated to 110°C and it was deformed with a heated tool so that part of the tube wall yielded into the groove of the mandrel according to the Figure 6b. The tube was cooled to the room temperature, the tool and the mandrel were removed giving an intramedullary nail according to the Figure 6c.

The application of the grooved tubes (see Figure 6c) and of the comparative solid rods as intramedullary nails were tested with 20 femurs of rabbits. A drill hole with the length of 60 mm and diameter of 4.5 mm was drilled into each femur from their proximal end. The dircetion of the drill hole was parallel with the long axis of the femur. Soli intramedullary rods of paragraph A were tapped into the drill hole of 10 femurs. An intramedullary nail according to paragraph B was tapped into the drill hole of other 10 femurs. 2 of the femurs split when the solid rods were tapped into th drill holes. The tapping of the hollow, groove intramedullary nails into the drill holes occurred withou problems in all cases.

Example 8.

Dexon^R sutures (size 1 USP) were braided to three-dimensiona cylindrical, longitudinal braid by so called 3-D techniqu (Figure 7 gives schematically the location of the Dexo sutures in the braid structure). The thickness of the brai was ca. 6 mm. The braid was sintered in a cylindrical screw mould into self-reinforced screws (the length of the full threaded screw was 40 mm, with maximum diameter of the hea 8 mm, maximum thread diameter 4.5 mm, and minimum threa diameter 3.2 mm). Sintering conditions were: T =208-215°C time = 10 min, pressure = 2000 bar. Corresponding screws were manufactured of Dexon sutures by filling the mould cavity with parallely oriented Dexon threads and by sintering them to screws.

The torsional strengths of the screws were measured.

The 3-D braided screws of the invention showed the torsional strength of 1.4 NM. The parallel thread reinforced screws showed the torsional strength of 0.8 NM.

Example 9.

3-D braided preforms were manufactured according to Example 8 of PLLA-fibres and of PLDLA-fibres (weight ratio 1:1). The preforms were sintered in a cylindrical mould to 120 mm long and 2.6 mm diameter rods at the temperature 175°C. A 20 m long thread (maximum thread diameter 3.2 mm) was rolled to the other end of the rods by locating the other end of the rod between three hot (T = 100°C) rolls, which were rotatin according to the schematic cross-sectional Figure 8. Th surfaces of the rolls were equipped with grooves with th thread profile. The partially threaded rods were cut to 3 mm long pieces and a flat head with the maximum diameter of the head 6 mm was upset to the non-threaded end of the rod b compression moulding in a hot mould (T >100°C).

A vertical osteotomy was done into the distal end of the femu of a rabbit into the cancellous bone area. The osteotomy wa fixed with two screws which were manufactured with the abov method. The fixation technique is shown schematically in a anteroposterial view (cross-section) in the Figure 9. Afte one year's follow-up time it was found that the osteotom had healed well.

Example 10.

Three-dimensional braiding technique was applied to braid o Dexon^R sutures (size USP 1) a tube-like preform with the maximum diameter of 3 mm and with the wall thickness of 1 mm. The Figure 10 shows schematically the structure of the preform. Part of Dexon threads can be seen at the cut end of the preform.

A 40 ram long piece of preform was located into the cavity of an injection mould. The cavity had the form of a screw (length 40 mm, maximum therad diameter 4.5 mm, minimum thread diameter 3.2 mm, maximum diameter of the flat head 8 mm). The mould cavity of the mould was filled with polyglycolic acid (manufacturer Boehringer/Ingelheim, Germany) melt by applying the injection moulding technique (injection moulding machine: model Battenfeldt, Austria) . The polyglycolide melt filled the cavity, the medullary cavity inside of the Dexon thread preform and covered also the Dexon preform. The cavity was cooled rapidly. The same mould was applied to manufacture screws of polyglycolide melt without Dexon thread braid reinforcement. The spiral reinforced screws (including the Dexon thread braid) showed the shear strength of 120 MPa and the non-reinforced screws showed the shear strength of 75 MPa.

Claims

1. Self-reinforced, absorbable surgical materials and/o implants (devices) and/or their parts and/or components which can be implanted into the living tissue or on its surface for the purpose of e.g. to repair tissue damages, t join tissues or their parts to each other, to augment tissue or their parts, to separate tissues or their parts from eac other and/or from their surroundings, and/or to conduc material between tissues or their parts and/or out of tissue or from the outside into the tissues, c h a r a c t e r i z e d in that the reinforcing element of self-reinforced materials and/or implants or their part and/or components are wound at least partially around som axis penetrating the implant.

2. Materials, implants or their parts or components accordin to Claim 1, c h a r a c t e r i z e d in that thei reinforcing elements are oriented molecular chains, molecul chain groups or their parts, oriented crystalline lamella or spherulites, fibrils or their parts or corresponding morphological structural elements.

3. Materials, implants or their parts or components accordin to Claim 1 or 2, c h a r a c t e r i z e d in that thei reinforcing elements are fibres, filaments, film fibres threads, braids, non-vowen structures, networks, meshes, knits or vowen structures or corresponding fabrics.

4. Materials, implants or their parts or components accordin to any claim of Claims 1-3, c h a r a c t e r i z e d i that they include at least one hole, hollow or cavity, arou which the reinforcing elements are wound at least partiall

5. A method to manufacture a material, implant or its part component according to any claim of Claims 1-4, c h a r a c t e r i z e d in that the reinforcing elemen are located into a mould into which the melt of the matrix polymer is injected or the reinforcing elements are transformed into such a physical state where they are bound at least partially to each other.

6. A method to manufacture a material, implant or its part or component according to any claim of Claims 1-4, c h a r a c t e r i z e d in that it is deformed to the desired shape with mechanical twisting, rolling, compression, stamping, drawing, upsetting or bending or by combining different deformation methods.

7. An implant, its part or component according to any claim of Claims 1-6, c h a r a c t e r i z e d in that it is a rod, nail, bolt, intramedullary nail, screw, clamp, tube, plate or rivet.

8. An intramedullary nail according to Claim 7, c h a r a c t e r i z e d in that it is at least partially hollow and/or in its wall is at least one longitudinal groove or hole, which has been formed by bending the wall inside and/or by splitting or perforating it at least partially.