Abstract:
An widening device for bone cavities extends from a proximal end to a distal end along an extension axis, said distal end having an elastically deformable element suitable to pass from a relaxed configuration for placing the distal end within an osteal body to a deformed configuration for forming a cavity within said osteal body. The elastically deformable element permits to create a bone cavity in a regular and uniform way.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a widening device for bone cavities, for example intervertebral cavities or cavities of the tibial plate, the astragalus, or the wrist.  
         [0002]     Particularly it relates to a widening device suitable to restore collapsed bone structures, for example because of trauma or aging, restoring at least partially the collapsed or degenerated bone structure and creating a cavity to be stabilized, for example, with a following injection of bone cement or another biocompatible material. The present invention relates, for example, to a widening device suitable for kyphoplasty operations.  
         [0003]     The present invention further relates to an injection device for bone cavities, for example intervertebral cavities or cavities of the tibial plate, the astragalus, the wrist and the like. The present invention relates, for example, to a device for kyphoplasty suitable to inject liquid cement in a vertebral body for the reconstruction of the same.  
         [0004]     The present invention further relates to a method for widening and filling bone cavities.  
       BACKGROUND OF THE INVENTION  
       [0005]     Widening devices for use in intravertebral cavities are known to be inserted in a relaxed configuration in a vertebral body and then widened to an expanded configuration to restore the shape of the vertebral body, thereby forming a suitable cavity therein which is subsequently filled, for example with liquid cement, bone bits or bone filler of various types.  
         [0006]     The known wideners are not able to ensure a controlled expansion inside the vertebral body, i.e. they are not suitable to provide a volume-controlled tridimensional cavity having a desired configuration.  
         [0007]     The provision of a cavity having a well defined size is indispensable for the reconstruction of a collapsed vertebral body for example consequently to a trauma or bone degeneration.  
         [0008]     The problem of the present invention is to provide a widening device resolving the drawbacks mentioned with reference to the prior art.  
       SUMMARY OF THE INVENTION  
       [0009]     These drawbacks and limitations are resolved by a widening device in accordance with claim  1 .  
         [0010]     Other embodiments of the widening device according to the invention are described in the subsequent claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Further characteristics and the advantages of the present invention will be better understood from the description below of preferred and non-limiting exemplary embodiments thereof, wherein:  
         [0012]      FIG. 1  is a perspective view of a widening device according to the present invention;  
         [0013]      FIG. 2  is a cut-away view of the widening device from  FIG. 1 ;  
         [0014]      FIG. 3  is a perspective view of the widening device from  FIG. 1  with the addition of accessories;  
         [0015]      FIG. 4A  is a magnification of the detail IV from  FIG. 1 ;  
         [0016]      FIGS. 4B and 4C  are magnifications of the detail IV from  FIG. 1 , according to further embodiments of the present invention;  
         [0017]      FIG. 5A  is a sectional view of the detail IV from  FIG. 1  taken along line V-V from  FIG. 4 ;  
         [0018]      FIGS. 5B-5D  show the detail from  FIG. 5A  comprising a sheath according to different embodiments of the invention;  
         [0019]      FIG. 6  is a sectional view of the device from  FIG. 1 ;  
         [0020]      FIG. 7  is a magnification of the detail VII from  FIG. 6 ;  
         [0021]      FIG. 8  is a magnification of the detail VIII from  FIG. 6 ;  
         [0022]      FIG. 9  is a sectional view of  FIG. 3 ;  
         [0023]      FIG. 10  is a magnification of the detail X from  FIG. 9 ;  
         [0024]      FIG. 11  is a magnification of the detail XI from  FIG. 9 ;  
         [0025]      FIG. 12  is a magnification of the detail XII from  FIG. 9 ;  
         [0026]      FIGS. 13A and 13B  are perspective views of a detail of the device from  FIG. 1  in an expanded configuration, according to further embodiments of the present invention;  
         [0027]      FIGS. 13C and 13D  are axonometric projections of the details from  FIGS. 13A and 13B  respectively;  
         [0028]      FIGS. 14A-14D  are perspective views of a detail from  FIG. 1  in a relaxed configuration and in expanded configurations according to different embodiments, respectively;  
         [0029]      FIGS. 15A-15D  are front views of  FIGS. 14A-14D , respectively;  
         [0030]      FIG. 16A-16D  are insertion diagrams of widening devices in collapsed osteal bodies, in a relaxed configuration;  
         [0031]      FIGS. 17A-17D  are insertion diagrams of the widening devices of  FIGS. 16A-16D  in restored osteal bodies, in an expanded configuration;  
         [0032]      FIG. 18  is a perspective view of an injection device according to the invention, in an open configuration of the device;  
         [0033]      FIG. 19  is a perspective view of the injection device from  FIG. 18 , in a closed configuration of the device;  
         [0034]      FIG. 20  is a side view of the injection device from  FIG. 18  in an initial injection step configuration;  
         [0035]      FIG. 21  is a side view of the injection device from  FIG. 18  in a final injection step configuration;  
         [0036]      FIG. 22  is a perspective view of the injection device from  FIG. 18  as being inserted in an osteal body, for example a vertebral body, at the beginning of the injection step;  
         [0037]      FIG. 23  is a perspective view of the injection device from  FIG. 18  as being inserted in an osteal body, for example a vertebral body, at the end of the injection step;  
         [0038]      FIG. 24  is a perspective view of an injection device according to a further embodiment of the invention;  
         [0039]      FIG. 25  is a cut-away sectional view of the device from  FIG. 24 ;  
         [0040]      FIG. 26  is a sectional view of the device from  FIG. 24 , at the beginning of the injection step;  
         [0041]      FIG. 27  is a sectional view of the device from  FIG. 24 , at the end of the injection step;  
         [0042]      FIG. 28  is a perspective view of the injection device from  FIG. 24  as being inserted in an osteal body, at the beginning of the injection step;  
         [0043]      FIG. 29  is a perspective view of the injection device from  FIG. 24  inserted inside an osteal body, for example a vertebral body, at the end of the injection step;  
         [0044]      FIG. 30  is a perspective view of a device for the insertion either of bone bits or bone filler in an osteal body, for example a vertebral body. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]     The elements or element parts in common between the embodiments described below will be indicated with the same numerals.  
         [0046]     With reference to the above figures, with  4  has been generally indicated a widening device suitable to provide a cavity within an osteal body, for example a vertebral body  6 , a tibial plate  6 ′, an astragalus  6 ″, a wrist  6 ′″ asnd the like.  
         [0047]     By ‘widening device’ it is intended a widening device suitable for restore collapsed osteal structures, for example because of trauma or aging, by restoring at least partially the degenerated or collapsed osteal structure and by creating a cavity to be stabilized, for example by subsequent injection of osteal cement or other biocompatible material.  
         [0048]     The widening device  4  has an elongate shape as a whole and develops along an extension axis X, between a proximal end  8  and a distal end  10 .  
         [0049]     Herewith below, by axial direction will be designated a direction parallel to the extension axis X, and by radial direction will be designated a perpendicular direction to the extension axis X and incident thereto.  
         [0050]     The widening device  4  comprises a cylindrical shank  12 , extending from the proximal end  8  to the distal end  10 .  
         [0051]     The shank  12  comprises a first through hole  13  arranged on the side of the proximal end  8 .  
         [0052]     To the shank  12  there is associated a tube  14  externally and coaxially thereto, relative to axis X, such as to at least partially cover the shank  12 . The tube  14  extends between a first end  14 ′, facing the proximal end  8 , and a second end  14 ″, facing the distal end  10 .  
         [0053]     The tube  14  comprises an aperture  16  having an axial extension L, arranged on the side of first end  14 ′.  
         [0054]     At the proximal end  8  the shank  12  is provided with a threaded length  24  for a knob  28  to be associated thereto according to a screw-nut type coupling.  
         [0055]     To the shank  12  and tube  14  is further coaxially associated a sleeve  32 , arranged between the distal end  10  and the proximal end  8 .  
         [0056]     The sleeve  32  comprises a pin  36  mechanically connecting the sleeve  32  with the shank  12  and the tube  14  such as to rotatably lock both of them, relative to the X axis.  
         [0057]     The pin  36  has a smaller diameter than said extension L of aperture  16 .  
         [0058]     Particularly, in an assembly configuration, said pin  36  is inserted in the sleeve  32  such as to intercept the first hole  13  of shank  12  and aperture  16  of tube  14 . Furthermore, in an assembly configuration, the second end  14 ″ of tube  14  comprises the distal end of shank  12  therein.  
         [0059]     The profile of end  14 ″ of tube  14  identifies a first strike  38 .  
         [0060]     Between the sleeve  32  and the knob  28  there is inserted a spacer  40 , coaxial with the shank  12 , said spacer  40  at least partially intercepting the threaded length  24 .  
         [0061]     Between the spacer  40  and the knob  28  there is inserted, coaxially with the shank  12 , a stop element  44 , suitable to receive the knob  28  in abutment. Preferably, the stop element  44  is one-piece with the tube  14  at the first end  14 ′.  
         [0062]     The spacer  40  and the tube  14  are suitable to axially slide along the extension axis X relative to shank  12 .  
         [0063]     Particularly, the spacer  40  can axially slide relative to shank  12  for a length being almost equal to the axial distance between the end of spacer  40  facing the stop element  44  and the stop element.  
         [0064]     The tube  14  can axially slide relative to shank  12  to the extent of the backlash present between the aperture  16  and the pin  36 .  
         [0065]     At the distal end  10 , to the shank  12  there is associated a cylindrical terminal  48  which, on the opposite side to the shank  12 , comprises a second strike  52 , of a substantially greater diameter than the diameter of shank  12 .  
         [0066]     Preferably, the terminal  48  is removably associated to shank  12 , such as by means of a threaded connection.  
         [0067]     According to an embodiment, the terminal  48  comprises a pivot suitable to be screwed to the free end of shank  12 , and the pivot head provides said first strike  38 .  
         [0068]     An elastically deformable element  56  is mounted along the extension axis X, coaxially to the terminal  48 .  
         [0069]     The elastically deformable element  56  is cylindrical and hollow as a whole and is suitable to be fitted on terminal  48 .  
         [0070]     Preferably, the elastically deformable element  56  comprises a central body  57  with a diameter d, axially defined by a first and second collar  58 ′, 58 ″ with a diameter D greater than the diameter d of the central body  57 .  
         [0071]     The elastically deformable element  56  further comprises an inserting portion  59 , connected to first collar  58 ′ and axially extending from the opposite side to second collar  58 ″.  
         [0072]     The inserting portion  59  is suitable to be inserted in the inner diameter of tube  14  and extends such that, in an assembly configuration and in the relaxed configuration, between the inserting portion  59  and shank  12  an axial backlash G is identified.  
         [0073]     Preferably, the axial backlash G is almost equal to the axial extension L of aperture  16 . The axial distance between the first and second collars  58 ′, 58 ″ is almost equal to the distance between the first and second strikes  38 , 52 ; in other words, in a relaxed configuration, the central body  57  is inserted with substantially no backlash between both strikes  38 , 52 .  
         [0074]     In the relaxed configuration, the elastically deformable element  56  is not subjected to axial loads and is substantially parallel to the extension axis X.  
         [0075]     Advantageously, relative to a perpendicular plane to the extension axis X, the elastically deformable element  56  has a variable thickness along said extension axis X; in other words, the radial thickness of the elastically deformable element  56  varies advantageously along a parallel direction to said extension axis X.  
         [0076]     The elastically deformable element  56  is preferably made of a polymeric material, an elastomer, a rubber and the like. The preferred materials to be used are characterized by a high modulus of elasticity value, such as to ensure high distraction forces and resistance to considerable loads, as well as characterized by a low ratio of the modulus of elasticity and the yield stress, such as to minimize the risk of yield due to great deformation.  
         [0077]     Furthermore, metal, composite or polymeric materials, as well as shape-memory, metal or polymeric materials can also be used.  
         [0078]     Preferably, the deformable element  56  comprises at least one tab  60  which, in the relaxed or undeformed configurations, extends substantially parallel to axis X.  
         [0079]     According to a further embodiment, the elastically deformable element  56  comprises at least one tab  60  having a prevalent extension along a median line M, between a first collar  58 ′ and a second collar  58 ″, said median line M extending so that a line, which is parallel to axis X and which passes through an intersection point between the tab  60  and the first collar  58 ′, does not pass through an intersection point between the tab and the second collar  58 ″.  
         [0080]     According to a preferred embodiment, the elastically deformable element  56  comprises at least one tab  60  which, in a relaxed or undeformed configuration, extends along a helicoidal path with respect to said axis X. The tab  60  extends along a helicoidal path with respect to axis X, according to a helix angle a. In other words, the elastically deformable element  56  comprises at least one tab  60  having a preferred extension along a median line or axis M, said median axis M having a helicoidal extension with respect to said axis X.  
         [0081]     Said median axis M extends according to a helix angle α, said angle being defined between a line perpendicular to a line parallel to axis X and passing through said median axis M, and said median axis M.  
         [0082]     By median axis M of the tab it is intended a line passing through a median line of the tab which is also a curvilinear symmetry axis for the tab.  
         [0083]     The helix angle α is preferably comprised between 60 and 85 degrees, and most preferably is equal to 80 degrees. According to an embodiment, said helix angle a is constant, along the extension of the tab  60 . According to another embodiment, the helix angle α is variable along the extension of the tab  60 ; in other words the tab  60 , along its extension, wraps around axis X according to a variable helix angle α.  
         [0084]     Preferably, the helix angle α is greater near first and second collars  58 ′, 58 ″.  
         [0085]     According to an embodiment, said tab  60  along its helicoidal extension presents a thickness, being measured with respect to a radial direction incident with said axis X and contained in a plane perpendicular to said axis X, said thickness being variable along the helicoidal extension of the tab  60 .  
         [0086]     The at least one tab  60  is formed in the elastically deformed element  56  by means of longitudinal grooves  64  if the tab has a longitudinal extension parallel to axis X; otherwise the tab  60  is formed in the elastically deformed element  56  by means of helicoidal grooves  64 ′ if the tab has a helicoidal extension with respect to axis X. Said helicoidal grooves  64 ′ may be obtained by a CNC machine having a working head which moves along a helicoidal direction so as to cut away material from a solid tubular element and to obtain said grooves.  
         [0087]     Advantageously, at ends facing the first and second collars  58 ′, 58 ″, respectively, the grooves  64 , 64 ′ end with slots  68 , for example of a circular shape.  
         [0088]     According to an embodiment, each tab  60  has a central portion  72  and two side portions  76 ′,  76 ″ being axially arranged on opposite sides to the central portion  72 .  
         [0089]     The side portions  76 ′,  76 ″ are in turn connected to the respective collars  58 ′, 58 ″ through attachment portions  80 ′,  80 ″.  
         [0090]     According to an embodiment, the tabs  60  have a midplane S perpendicular to the extension axis X and positioned in the middle of central portion  72 ; in other words, the side portions  76 ′,  76 ″ and the attachment portions  80 ′,  80 ″ have the same axial extension. According to further embodiments, the side portions  76 ′, 76 ″ and/or the attachment portions  80 ′, 80 ″ have different axial extensions.  
         [0091]     According to further embodiments, the tabs  60  have only one side portion  76 ′ or  76 ″ and do not exhibit the midplane S, i.e. the central portion is directly connected to the respective collar  58 ′ or  58 ″.  
         [0092]     Furthermore, the central body  57  can have an outer diameter varying along the longitudinal extension of the same.  
         [0093]     Such as for example illustrated in  FIG. 5 , each tab  60  advantageously has radial thicknesses varying along the extension axis X. This variation in the thicknesses can be discrete, such that the elastically deformable element  56  has marked variations in the thickness for example at the interface areas between the central portion  72  and the side portions  76 ′, 76 ″ or between the side portions  76 ′, 76 ″ and the attachment portions  80 ′, 80 ″. According to a further embodiment this variation in the thicknesses is gradual and continuous, i.e. said interface areas between the central portion  72  and the side portions  76 ′, 76 ″ or between the side portions  76 ′, 76 ″ and the attachment portions  80 ′, 80 ″ are suitably linked up to one another in the thicknesses thereof.  
         [0094]     For example, at the central portion  72 , the greater thickness of each tab  60  gradually decreases towards the attachment portions  80 ′, 80 ″.  
         [0095]     Furthermore, each tab  60  has, relative to a perpendicular plane to the extension axis X, a section shaped like a ring sector, having a minor arch  84  facing the axis X and a major arch  88  facing outwardly.  
         [0096]     Preferably, the elastically deformable element  56  has a plurality of tabs  60 ; according to some preferred embodiments, such as illustrated for example in  FIGS. 14A-14D , the elastically deformable element  56  has three or four tabs symmetrically or asymmetrically arranged relative to the extension axis X.  
         [0097]     According to an advantageous embodiment, said elastically deformable element  56  comprises a sheath  92  extending between the attachment portions  80 ′, 80 ″ such as to wrap or cover said tabs  60 .  
         [0098]     In the relaxed configuration of the elastically deformable element  56 , the sheath  92  has a substantially axial-symmetrical extension coaxial with the extension axis X. According to an embodiment, the sheath  92  has a cylindrical extension, with a substantially constant diameter, such as to at least partially adhere to tabs  60  also in a relaxed configuration. According to a further embodiment, the sheath  92  has a cylindrical extension with a varying diameter such as to adhere, in a relaxed configuration, to the elastically deformable element  56  at the collars  58 ′, 58 ″. According to a further embodiment, the sheath  92  has an ellipsoidal extension as a whole in a relaxed configuration, having a varying diameter along the extension of said axis X, for example such as to come in contact with tabs  60  at the collars  58 ′, 58 ″ and not at the central portion  72  of tabs  60 . Furthermore, the sheath  92  can be double-lobe shaped or however have a varying section along the longitudinal extension of sheath  92 , said section being taken on a perpendicular plane to axis X.  
         [0099]     According to an embodiment the sheath  92  has a constant thickness along the extension thereof. According to a further embodiment, such as illustrated in  FIG. 5D , the sheath  92  has a varying thickness along the extension thereof; for example the sheath  92  has a thickening  93  at the connecting portions to the elastically deformable element  56  and a thinning  94  in a portion comprised between said connecting portions and facing for example the central body  57  of tabs  60 .  
         [0100]     Preferably, the sheath  92  is made of an elastic material such as a polymer, an elastomer, a rubber, and is suitable to be matched to the tabs  60  in the deformed configuration.  
         [0101]     According to an embodiment, the sheath  92  is associated to the elastically deformable element  56  by glueing at the first and second collars  58 ′, 58 ″.  
         [0102]     According to an advantageous embodiment, the widening device  4  comprises a cylindrical cannula  96  suitable to cover the tube  14  in the length comprised between the distal end  10  and sleeve  32 .  
         [0103]     Preferably, said cannula  96  is provided with a threaded bush  100  at a connecting end  106  facing the sleeve  32 ; the bush  100  acts as an adjusting sleeve to tailor the insertion depth of the widening device  4  inside the osteal body  6 , 6 ′, 6 ″, 6 ′″.  
         [0104]     Advantageously, said cannula  96  is provided with a gripping end  104 , suitable to be locked on the cortex of an osteal body  6 , like a vertebral body  6 , a tibial plate  6 ′, an astragalus  6 ″ or a wrist  6 ′″, such as to form a guide for the widening device  4  to be inserted therein, and also for the insertion of a probe to first inspect the interior of the osteal body  6 ,  6 ′, 6 ″, 6 ′″. Advantageously, the cannula  96  allows the use, i.e. the coupling with endoscopic, microscopic systems and for biopsy sampling.  
         [0105]     Furthermore, the cannula  96  is advantageously suitable to at least partially house a cement injection device  112  to fill the osteal cavity with liquid cement.  
         [0106]     The injection device  112  comprises a grip element  116  suitable to allow the grip by a user and having a pusher  118  for example of a cylindrical shape, integrally connected to the grip element  116 . In an assembly configuration of the injection device  112  on the cannula  96 , the pusher  118  is coaxial to the extension axis X. The grip element  116  further comprises at least one seat  120 .  
         [0107]     On the grip element  116  there is hinged a lid  122 , suitable to rotate from an open position, such as illustrated for example in  FIG. 18 , to a closed position such as illustrated for example in  FIG. 19 .  
         [0108]     The lid  122  further comprises a window  123  and a corresponding graduated scale suitable to measure the relative translation between a control element  126  and the grip element  116 . At an end facing the hinging end of the grip element  116  on lid  122 , the lid  122  ends with a stop  124  having a notch  125 .  
         [0109]     To said grip element  116  there is associated the control element  126  mechanically connected to a plate  130 , of a circular shape having a second hole  134 .  
         [0110]     The control element  126  and the grip element  116  in a closed configuration, where the stop  125  and the plate  130  directly face each other, identify a chamber  135  suitable to house a cement cartridge  136  to be injected.  
         [0111]     Preferably, the control element  126  comprises at least one guide  138  suitable to be at least partially housed within said seat  120 , such that the motion of the control element  126  relative to the grip element  116  is guided substantially along a stroke T according to a direction parallel to axis X.  
         [0112]     A cylindrical needle  140 , hollow and suitable to be housed within the cannula  96 , is mechanically associated to the plate  130  through said second hole  134  such that an injection end  144  of needle  140  is fluidically connected to chamber  135 .  
         [0113]     A further embodiment of an injection device  112 ′ will be now described, such as illustrated for example in  FIGS. 24-29 , wherein the elements or parts in common with the embodiment illustrated above will be indicated with the same numeral provided with primes.  
         [0114]     The injection device  112 ′ has a cartridge configuration as a whole, of main extension P. The injection device  112 ′ comprises a hollow grip element  116 ′ of a cylindrical shape suitable to be held by a user. At an inner side wall  150  the grip element  112 ′ comprises a first threading  152  with pitch M′. Opposite to the first threading  152 , relative to the main extension P, the grip element  112 ′ comprises a flange  154  having longitudinal guides  156  arranged parallel to the main extension P.  
         [0115]     A first cylindrical and hollow ring nut  158  is suitable to mesh with said first threading  152  at a first control portion  160  such as to be coaxially mounted to the grip element  116 ′ and internally thereto.  
         [0116]     The first ring nut  158 , opposite to the first control portion  160 , comprises a second control portion  162  provided at an inner part, i.e. towards the extension axis P, with an inner threading of pitch M″, other than said pitch M′. Advantageously, pitch M″ of second threading  164  is greater than pitch M′ of first threading  152 ; preferably pitch M″ is about twice the pitch M′.  
         [0117]     The first ring nut  158 , opposite to the second threading  164 , comprises a neck  166  provided with a notch  168 . At the neck  166 , to the first ring nut  158  there is associated a control element  126 ′ preferably in the form of a hollow knob. Particularly, the control element  126 ′ is removably fastened to the neck  166 , through a bayonet-type arrangement, by means of at least one stake  170  suitable to be locked within said notch  168 . Between the control element  126 ′ and the neck  166  there is interposed a barrel  172  for the at least one stake  170  to be mounted thereto; the barrel  172  is provided with a spring  173  such as to force said stake against the corresponding notch  168 .  
         [0118]     The control element  126 ′ comprises a bell  174  suitable to house said barrel  172  and suitable to be at least partially inserted in the first ring nut  158  from the neck  166 . The bell  174  axially ends with a stop surface  175 , such as of a disc-shape type.  
         [0119]     In an assembly configuration, the control element  126 ′, the barrel  172  and the first ring nut  158  are preferably rotatably integral to one another.  
         [0120]     To the grip element  116 ′, opposite to the first threading  152 , there is associated a second ring nut  176  having an outwardly threaded portion  178  suitable to mesh with the second threading  164 . Opposite to the outwardly threaded portion  178 , along extension P, the second ring nut  176  comprises at least one pivot  180  suitable to be housed within said longitudinal guides  156 , such as to longitudinally slide therealong; furthermore, the second ring nut  176  comprises an abutment surface  182  of a circular ring shape. To the second ring nut  176  is further associated a cylindrical plug  184 , arranged at the opposite end of the control element  126 ′, and preferably comprising a threaded ring  186  suitable to be screwed on the threaded bush  100 .  
         [0121]     In an assembly configuration, the first ring nut  158  and the second ring nut  176  are coaxially and partially mounted within the grip element  116 ′ such as to define a substantially cylindrical chamber  135 ′.  
         [0122]     The injection device  112 ′ is suitable to contain within said chamber  135 ′ a substantially cylindrical syringe  188  comprising a syringe body  190  enclosing a cement cartridge  136 ′ to be injected, a pusher  118 ′ being associated thereto, which is suitable to compress said cement cartridge  136 ′. The cement cartridge  136 ′, opposite to the pusher  118 ′, is fluidically connected to a needle  140 ′ and according to an embodiment, the syringe body  190  is one-piece with the needle  140 ′.  
         [0123]     As illustrated for example in  FIG. 30 , the cannula  96  is further suitable to be connected to a funnel  200 , at the proximal end. Said funnel  200  is suitable to allow bone bits, i.e. bone fragments, such as taken from the iliac crest or generally bone substitute to be inserted therein.  
         [0124]     Furthermore, the cannula  96  allows a rammer, i.e. an elongate cylindrical body having a rounded end, suitable to compact the bone bits or the bone substitute inserted therein, to be inserted within the cavity of a vertebral body  6 , tibial plate  6 ′, astragalus  6 ″, wrist  6 ′″, by means of the cannula  96 .  
         [0125]     The operation of the widening device according to the invention will be now described.  
         [0126]     At first, the cortical and sponge tissues of the osteal body  6 , like for example a vertebral body  6 , a tibial plate  6 ′, an astragalus  6 ″, a wrist  6 ′″, are pierced with a punch such as to enable the cannula  96  to be firmly fixed to the osteal body  6 , 6 ′, 6 ″, 6 ′″.  
         [0127]     An endoscope may be firstly inserted in said cannula  96  to inspect the interior of the osteal body  6 , 6 ′, 6 ″, 6 ′″.  
         [0128]     The cannula  96  can then house the widening device  4  therein.  
         [0129]     In order to properly tailor the insertion depth of the widening device  4  the above threaded bush  100  can be used to act as the adjustment sleeve.  
         [0130]     The elastically deformable element can be then expanded  56 .  
         [0131]     Particularly, the knob  28  can be rotated on the threaded length  24  of shank  12 , by holding the sleeve  32  at the same time, such as to cause the shank  12  to be tensioned, which is rotatably locked by the pin  36  of sleeve  32 .  
         [0132]     The shank  12  translatably drags the terminal  48  and the elastically deformable element  56  which in turn pushes the first strike  38  of tube  14 . The tube  14  translates at first towards the proximal end until completely recovering the backlash between the pin  36  and the aperture  16 .  
         [0133]     The rotation of knob  28  generates the compression of the elastically deformable element  56  between the first and second strike  38 , 52 . Following said compression the tabs  60 , subjected to a compression load, tend to inflect outwardly, thereby taking an expanded or deflected configuration, such as arch-shaped.  
         [0134]     While being bent, the tabs  60  can be advantageously encircled by the sheath  92  filling the gaps or grooves  64  between the tabs  60 .  
         [0135]     Once the desired size has been obtained for the osteal cavity the widening device  4  can be disabled.  
         [0136]     By rotating the knob  28  to the opposite direction the elastically deformable element  56  is unloaded and tends to return in the undeformed or relaxed configuration due to the elasticity of tabs  60 . The sheath  92  until being stressed by the action of the tabs  60 , cooperates to the passage from the deformed configuration to the undeformed configuration.  
         [0137]     Therefore, the passage from the deformed configuration to the undeformed or relaxed configuration does not take place by applying another external force, but by removing the initial deformation force, i.e. by unloading the shank  12  and the elastically deformable element  56  accordingly.  
         [0138]     The axial backlash between the pin  36  and the aperture  16  on tube  14  ensures that, once the knob  28  has been completely unscrewed, the tabs  60  can completely stretch without having compression loaded residues.  
         [0139]     On the contrary, there would be the risk for the elastically deformable element  56  to be locked inside the osteal body  6 , 6 ′, 6 ″, 6 ′″ or inside the cannula  96 .  
         [0140]     The widening device  4  can be then extracted and the injection device  112 , 112 ′ or the funnel  200  can be subsequently inserted to fill the osteal cavity with liquid cement or bone bits, respectively.  
         [0141]     The operation of the injection device  112  according to an embodiment will be now described.  
         [0142]     Particularly, once the cartridge  136  has been inserted in chamber  135 , and the lid  122  has been closed, one holds the grip element  116  and presses the control element  126 , such as to approach i.e. move the control element  126  backward towards the grip element  116 . The cartridge  136  is compressed between the plate  130  translatably dragged by the grip element  116  and the pusher  118 . The cement contained in the cartridge  136  tends to flow inside the needle  140  and to exit through the injection end  144  of the same.  
         [0143]     During the backward motion of the control element  126 , the same drags the needle  140  which tends to move backwards while the cement is being injected. Consequently, the injection end  144  moves backward during the injection step, by a stroke T equal to the translation stroke of the control element  126 . The amount of cement to be injected can be controlled by directly reading the translation of needle  140  with the aid of a graduated scale on window  123  of lid  122 .  
         [0144]     The operation of the injection device  112 ′ will be now described according to a further embodiment of the invention.  
         [0145]     To assemble the syringe  188  within the injection device  112 ′, the control element  126 ′ is first extracted by disengaging the stake  170  from notch  168  of neck  166 , and the barrel  172  is removed to gain access to chamber  135 ′.  
         [0146]     Thereafter, the syringe  188  provided with needle  140 ′ is inserted in the chamber  135 ′ such as to bring the cement cartridge  136 ′ in abutment against the abutment surface  182  of second ring nut  176 . The control element  126 ′ is then reassembled such as to bring the end surface  175  of bell  174  in contact with the pusher  118 ′. In other words, following the assembly of syringe  188  to the injection device  112 ′, syringe  188  is housed coaxially to the injection device  112 ′ as well as axially constrained from opposite sides, i.e. between the control element  126 ′ and the second ring nut  176 .  
         [0147]     Particularly, following the assembly, the pusher  118 ′ of syringe  188  is in abutment against the stop surface  175  of the control element  126 ′, such as to prevent the pusher  118 ′ to move backwards according to a backward direction r; whereas the syringe body  190  abuts against the abutment surface  182  of second ring nut  176 , such that the syringe body  190  cannot be moved according to a forward motion relative to a forward direction f opposite to said backward direction r.  
         [0148]     The outwardly threaded portion  178  is first engaged on bush  100  such as to house the needle  140 ′ of injection device  112 ′ within the cannula  96  and form a fluidical connection between the cement cartridge  136 , the injection end  144  and the cavity of the osteal body  6 , 6 ′, 6 ″, 6 ′″.  
         [0149]     To perform the injection, one holds the grip element  116 ′ and rotates the control element  126 ′ such as to rotatably drag the first ring nut  158 ; particularly the first ring nut  158 , by screwing on the grip element  116 ′, moves forward, i.e. it translates towards needle  140 ′, according to the forward direction f. The second ring nut  176  meshes in turn with the grip element  116 ′ and, since it cannot rotate relative to the grip element  116 ′ due to the coupling between pivots  180  and longitudinal guides  156  of flange  154 , it translates away from needle  140 ′, according to the backward direction r opposite to said forward direction f. Therefore, following the rotation of the control element  126 ′, the first and second ring nuts  158 , 176  translate along extension P in opposite directions f,r thus approaching each other respectively.  
         [0150]     The abutment surface  182  of second ring nut  176  when being translating urges the cement cartridge  136  which is compressed between the syringe body  190  in abutment against the abutment surface  182  and pusher  118 ′, which cannot move backward according to backward direction r due to the stop surface  175 . The syringe body  190  moves backward together with the abutment surface  182  of second ring nut  176  and drags the needle  140 ′ in its backward motion along the backward direction r. Consequently, following the rotation of the control element  126 ′, needle  140 ′, and particularly the injection end  144  of needle  140 ′, moves backward by a stroke T according to the backward direction r.  
         [0151]     Furthermore, while screwing and moving forward within the grip element  116 ′, the first ring nut  158  translatably drags the control element  126 ′ towards the second ring nut  176 . Therefore, the stop surface  175  of the control element  126 ′ urges in turn the pusher  118 ′ of syringe  188  according to the forward direction f and further compresses the cement cartridge  136 ′. Following this compression the cement tends to exit through the injection end  144  of needle  140 ′ and from the latter to the inside of the osteal cavity. The pivots  180  slide in the longitudinal guides  156  and by being visible from the outside of the injection device  112 ′, also provide a visual indication of the feeding state of the injection, i.e. the amount of cement being injected. Preferably, near the longitudinal guides  156 , there is provided, for example, a graduated scale to give an indication of the amount of cement being injected.  
         [0152]     Advantageously, by dismounting the control element  126 ′ during any cement injection step, the cement capsule  136 ′ stops being subjected to compression and the cement flow through needle  140 ′ is stopped.  
         [0153]     As may be appreciated from what has been stated above, the widening device allows to overcome the drawbacks of the prior art widening devices.  
         [0154]     Particularly, the widening device according to the invention allows to provide a cavity within an osteal body, such a vertebral body, an astragalus, a tibial plate, a wrist, in a controlled manner, i.e. by providing predetermined expansion configurations which can be adjusted according to different types of osteal bodies and different surgical indications.  
         [0155]     In other words, the widening device ensures an active expansion, by generating a cavity of a defined shape without being subjected to deformations by the bone tissue of the osteal body, the mechanical characteristics of which are typically not isotropic and omogeneous.  
         [0156]     The covering sheath, by filling the grooves comprised between the tabs, ensures continuity to the deformable element thereby preventing the individual tabs from getting entangled within the osteal body tissue, thereby allowing the deformed configuration to return to the relaxed configuration.  
         [0157]     Advantageously, the presence of the sheath covering the tabs prevents any inclusion of bone material within the elastically deformable element, which case may hinder the tab closing motion, i.e. their return to the undeformed configuration.  
         [0158]     Thanks to the helicoidal arrangement of tabs, the device has a solidity of the created volume, it is to say the volume of the device in an expanded configuration, which is greater than the arrangement with longitudinal tabs. By solidity it is intended the ratio between solid and void zones, it is to say between the zone comprising the tabs, which contribute to the widening of the cavity, and the interstices among the tabs which do not exerte any widening action of the osteal tissue. A greater solidity of the deformable element grants a controlled expansion, in spite of the anisotropy of the spongeous tissue in the cavity of the osteal body. A high solidity avoids the event of gripping of the tabs in the spongeous tissue and does not require the use of sheaths or membranes, suitable for fill said voids or interstices among tabs.  
         [0159]     The particular varying-thickness configuration along the tabs both with longitudinal extension and with elicoidal extension, allows to provide greater thicknesses in the tab areas subjected to greater loads and lower thicknesses in the areas where, following the deformation, great bending is desired without yielding the material. In fact, any yield may hinder the elastic return of the deformable portion from the deformed configuration to the relaxed configuration.  
         [0160]     In fact, the return from the deformed configuration to the relaxed configuration takes place due to the elastic return of the material following the removal of the axial force which had caused the deformation, i.e. without applying another external force.  
         [0161]     This elastic return is favoured by the elastic action provided by the sheath which tends to cause both tabs to approach each other, thereby bringing them back to the undeformed configuration.  
         [0162]     By providing the deformable element as one-piece, the resistance of the tabs to high work load is ensured. Particularly, the presence of the slots to the tab ends prevents the risk that any crack may propagate.  
         [0163]     The tabs are therefore beams fitted to the ends, which when subjected to compression, instabilize and inflect outwardly, i.e. away from the extension X axis.  
         [0164]     This arrangement provides a particular stiffness to the deformable portion and allows to vary the stiffness of the tabs by acting on the variation of thicknesses.  
         [0165]     The backward motion of the needle during the cement injection ensures an optimum filling of the osteal cavity because the injection end moves gradually and automatically backward as the cavity is being filled. A uniform and omogeneous distribution of the cement being injected in the bone cavity is thereby ensured. Furthermore, due to the backward motion of the needle, overpressures in the osteal body are prevented which may give origin to leakages of cement dangerous for the spinal marrow if, for example, the osteal body is a vertebral body.  
         [0166]     The configuration of the cannula provided with a tailored bush allows to associate different devices to this cannula for an operation of widening and restoring of an osteal cavity, such as a kyphoplasty operation, after only one access port has been made in the osteal cortical area and only one cannula has been inserted as the guide member. The bush allows to change the axial position of each of the devices being inserted, particularly the insertion depth of the distal end of the widening device and the needle injection end.  
         [0167]     Those skilled in the art, aiming at satisfying contingent and specific requirements, will be able to carry out a number of modifications and variants to the above widening devices, which are all contemplated within the scope of the invention such as defined by the claims below.