Abstract:
The device according to the invention is composed of an axially perforated cylinder having at least one split end so as to form at least two independent sectors. The material of which the cylinder is made is a Ni—Ti alloy with hot, cold or superelastic shape memory. The cylinder is inserted in a hole that passes through the fracture region and is heated with an electric scalpel, causing the independent sectors of the split end to open out and accordingly compact and couple the two fractured segments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. PCT/IB99/00801 filed on May 4, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a synthesis device for orthopaedia and traumatology. 
     More particularly, the present invention relates to a device for the synthesis of a bone fracture after its reduction by means of a body which allows to fix the fractured region, keeping it in the correct position for the time required by the bone to strengthen. 
     Various devices used to perform this operation are known. 
     Among these, the devices most frequently used are screws of the self-tapping or through type, possibly cooperating with plates which are arranged laterally to the bone in the region where the fracture is present. 
     All these devices are very troublesome to position and also have problems linked, among other issues, to the compactness of the bone in the fractured region. 
     More particularly, screws of the self-tapping type rely on a good grip of the thread, but this does not always occur. 
     Through screws associated with external plates are very bulky and must usually be removed when the bone has consolidated in the fracture region. 
     Substantially U-shaped brackets are also known which are made of materials having shape memory; their wings are inserted in two holes formed in the bone on opposite sides with respect to the fracture line. 
     These brackets, when heated, shorten in the intermediate region between the two ends inserted in the bone or the two ends bend toward each other, connecting the fracture. 
     However, these brackets have the drawback that they act only by traction in the external cortical region of the bone and in many cases do not allow to control the fracture region and keep it in the correct position. 
     U.S. Pat. No. 5,584,695 discloses an apparatus for anchoring a prosthetic tooth  21  to a patient&#39;s jawbone  22  including a root screw  26 , with a longitudinal bore  29 , for implantation in the jawbone  22 , and a temperature-sensitive shape-memory cylindrical coupling pin  34  for fixing a stump  35 , with its own longitudinal bore  39  and mounting the prosthetic tooth  21 , to the root screw  26 . The coupling pin  34  extends into the aligned bores  29  and  39 , and at temperatures below its transformation temperature range (TTR) the coupling pin  34  is thinner than the diameters of such bores  29  and  39  for easy insertion and extraction therefrom, while at temperatures above its TTR the coupling pin  34  expands inside the bores  29  and  39  to lock the mounting stump  35  to the root screw  26 . In one specific embodiment (FIG.  2 C), the cylindrical coupling pin  34  has a forked end portion  47  with two or more prongs  48  which open up at temperatures above the TTR for locking the coupling pin  34  into either or both bores  29  and  39 . 
     FR-A-2727304 discloses a self-locking medullary canal bone implant having at least one section made from a metal alloy with a shape memory effect, situated at one or both ends or along its whole length. The implant is shaped for convenient positioning and its shape changes on heating or cooling so that it grips the inside of the bone and holds firmly in place. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a synthesis device for orthopaedia and traumatology which can advantageously overcome the described problems. 
     A consequent primary object is to pprovide a device which can be easily inserted in the fracture region and is capable of keeping the fractured region correctly aligned. 
     Another object is to provide a synthesis device which, once inserted, can compact the fracture region. 
     Another object is to provide a synthesis device which has small dimensions, so that it can be left in the bone also after said bone has consolidated in the fracture region. 
     In accordance with the invention, there is provided a synthesis device for orthopaedia and traumatology as defined in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become apparent from the description of some embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a partial sectional view of the device according to the invention; 
     FIGS. 2 a ,  2   b  and  2   c  are views of three types of the same device with a different number of sectors of the end parts; 
     FIG. 3 is a view of the individual synthesis device installed to lock a region after reduction of the fracture; 
     FIG. 4 is a view of the insertion of the device of FIG. 3 by means of an auxiliary guiding tool; 
     FIG. 5 is a view of the correct positioning of the device and of the extraction of the auxiliary guiding tool; 
     FIG. 6 is a view of the activation of the device by means of an electric scalpel; 
     FIG. 7 is a view of the arrangement of two devices in an extensive fracture; 
     FIG. 8 is a view of a step of the insertion of the device with intramedullary placement; 
     FIG. 9 is a view of the activation of the device of FIG. 8; 
     FIG. 10 is a view of the device used for Austin osteotomy of the first metatarsus; 
     FIG. 11 is a view of two cylinders associated with a flat frame; 
     FIG. 12 is a view of the connection of the device of FIG. 11 for reducing a fracture; 
     FIG. 13 is a front view of the deformation of the flat frame with shortening of the center distance between the two cylinders; 
     FIG. 14 is a view of the curved shape assumed by the flat frame after heating. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the above figures, the synthesis device according to the invention is composed, of a cylindrical body, generally designated by the reference numeral  10 , which has a median region  11  and two end regions  12  and  13 . 
     In the illustrated embodiment, each one of the end regions  12  and  13  is divided into sectors, respectively  12   a  and  13   a , which are divided along diametrical planes. 
     The entire cylinder is crossed by an axial hole designated by the reference numeral  14 . 
     FIGS. 2 a ,  2   b  and  2   c  illustrate different shapes of the end regions, respectively divided into 4, 3 and 2 sectors; the axial hole  14  is always provided in each case. 
     The synthesis device is made of a Ni—Ti alloy with thermoelastic transformation and shape memory. 
     Substantially, the device is produced with a shape which is different from the one shown in FIG.  1  and is given to said cylinder with a known technology. 
     The cylinder has a memory of the previous shape which is known as: 
     hot memory, when the split end begins to open out at 35° C., stops opening at 55° C. and malleability occurs at 20° C.; 
     cold memory, when the split end begins to open out at 20° C., stops opening at 35° C. and malleability occurs at 10° C. 
     Due to the above-defined temperatures, the sectors of the split end return to the memorized shape, which is then maintained. 
     FIG. 3 illustrates the device in position for compacting a fractured region of a bone  15 , wherein the already-reduced fracture line is designated by the reference numeral  16 . 
     The operations for placing the synthesis device are shown in FIGS. 4,  5  and  6 . 
     After reducing the fracture, whose line is again designated by the reference numeral  16 , the bone being again designated by the reference numeral  15 , a through hole  17  is formed and the device  10  is inserted by means of an auxiliary guiding tool  18  which is constituted by a handle body  19  which has, at its end, a needle  20  which has a slightly smaller diameter than the hole  14  that passes through the device  10 . 
     With this auxiliary guiding tool it is possible to insert the device in the hole  17  as shown in FIG.  5 . 
     The length of the device is chosen so as to be slightly greater than the length of the bone in the fractured region, so that its ends, designated by the reference numerals  21  and  22 , protrude by approximately 2 mm from the outer cortical region of the bone, designated by the reference numeral  23 . 
     The end of an electric scalpel  24  is then inserted in the hole  14  as shown in FIG.  6 . 
     The heating produced by the electric scalpel causes the device to return to the memorized shape, opening out the sectors  12   a  and  13   a  with a particularly large spacing in the end regions. 
     In this way, in addition to maintaining the reduction of the fracture for the insertion of the device, compression of the two segments of the bone at the fracture line is also achieved. 
     Conveniently, the device has a diameter of approximately 3 mm, with an axial hole of 1 mm, but these dimensions, as well as the length, can differ according to requirements. 
     FIG. 7 illustrates a reduction of an extensive fracture by means of two. synthesis devices, now generally designated by the reference numerals  25  and  26 , while the bone is again designated by the reference numeral  15  and the fracture line is again designated by the reference numeral  16 . 
     FIGS. 8 and 9 illustrate the synthesis device fitted in an intramedullary manner. 
     In this case, the device, now designated by the reference numeral  27 , is first placed on one fractured bone segment, designated by the reference numeral  28 , while the second segment, designated by the reference numeral  29 , is displaced in order to allow the operation. 
     The second segment  29  is then moved into its correct position, so that the synthesis device  27  is in an intramedullary position. 
     Two holes, designated by the reference numerals  30  and  31  respectively, are formed beforehand in the two segments and are located at the two ends of the device  27 . 
     After reducing the fracture as shown in FIG. 9, the electric scalpel, now designated by the reference numeral  32 , is inserted; said scalpel heats and causes the spacing of the end sectors of the synthesis device  27 . 
     Also in this case, by way of said spacing the fracture line, now designated by the reference numeral  33 , is compressed. 
     FIG. 10 illustrates the use of the synthesis device, now designated by the reference numeral  34 , for Austin osteotomy of the first metatarsus. 
     In this case, after producing a cut, with a known technique, along the broken line  35  and after correctly positioning the two bone parts  36  and  37 , a blind hole is formed and the synthesis device  34  is inserted therein. 
     Heating by means of an electric scalpel allows the sectors, now designated by the reference numeral  38 , to open out on the outer cortex and allows the sectors of the other end, now designated by the reference numeral  39 , to open out in the spongy region of the head. 
     FIGS. 11,  12 ,  13  and  14  illustrate a synthesis device which constitutes a different embodiment of the inventive concept. 
     In this case, two cylinders, now designated by the reference numerals  40  and  41 , are associated at right angles with a flat frame  42  which has perforated regions  43 . 
     The two cylinders  40  and  41  have free ends which are again divided into sectors, now designated by the reference numerals  40   a  and  41   a , and there is again an axial hole designated by the reference numeral  44 . 
     The entire unit is monolithic and again made of the same alloy having shape memory. 
     In this case, the memorized shape is such that heating, again performed by means of an electric scalpel, in addition to opening out the end sectors  40   a  and  41   a  of the cylinders  40  and  41 , also bends the flat frame as shown in FIG. 14, so as to adapt to the rounded shape of the bone, now designated by the reference numeral  45 . 
     The flat frame again changes shape, curving the two connections  46  and  47  and thus tending to move the cylinders  40  and  41  mutually closer. 
     This produces the compression of the fracture line designated by the reference numeral  48 . 
     From the description and the illustrations it is evident that the intended aim and all of the objects have been achieved. 
     The new synthesis device for orthopaedia and traumatology is very simple and easy to install. 
     Once the fracture or osteotomy has been reduced, the bone is prepared as if to place a screw and then the metal cylinder is inserted, with the suitable guiding tool as shown, in the hole prepared beforehand. 
     It is then sufficient to insert an electric scalpel in the axial hole of the cylinder to open out the sectors and/or deform the plate. 
     After the installation and opening out of the device, optimum and prolonged compression between the fragments is provided. 
     The compression force can vary between 3 and 5 kg depending on the diameter and length of the metal cylinder. 
     As mentioned, the device can be used as a means for intramedullary synthesis. 
     In this case, the sectors that open out grip the internal cortex. 
     The main recommendations for the use of the synthesis device are fractures and osteotomies of the metatarsi and metacarpi, arthrodeses of the interphalangeal articulations through an intramedullary pathway, arthrodeses of the first metatarsal-phalangeal joint, clavicular fractures through an intramedullary pathway, Austin osteotomy of the first metatarsus, etcetera. 
     The main indications for using the device provided with a flat frame are fractures of the distal diaphysis and epiphysis of the radium, ulnar fractures, clavicular fractures, etcetera. 
     The embodiments may obviously be different as convenient starting from the same inventive concept and always using a material with shape memory. 
     The disclosures in Italian Patent Application No. PD98A000110 from which this application claims priority are incorporated herein by reference.