Abstract:
The invention relates to a surgical instrument ( 100; 200 ) comprising:
       an elongated arm ( 111; 207 ) according to a longitudinal axis and having a distal end ( 105; 204 ) mounted with a pivot joint on the elongated arm according to an axis substantially orthogonal to the longitudinal axis;   a drive shaft ( 103; 3 ), substantially coaxial with the elongated arm, comprising means forming a universal joint ( 104; 206 ) facing the pivot joint; and,   distal tool ( 9 ) securely fastened on the drive shaft and rotatively mounted on and in the extension of the distal end of the elongated arm, such that the distal tool has two rotational degrees of freedom, distinct and independent of each other, one being around an axis substantially perpendicular to the longitudinal axis of the elongated arm and the other being around an axis substantially collinear to an own axis of the distal tool, characterised in that the means forming a universal joint comprise a flexible drive sleeve ( 104; 206 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a surgical instrument designed for endoscopic or laparoscopic surgical operations. 
       TECHNICAL BACKGROUND 
       [0002]    Within the scope of minimally-invasive surgery, such as endoscopic or laparoscopic surgery, access to the operating site is made via small incisions in the body of the patient (such as the abdomen or thorax), in which the practitioner places a canula formed by a tube whereof the diameter varies from 3 to 15 mm, via which the practitioner can insert into the body of the patient either an endoscope for obtaining a video image on a monitor, or long and fine instruments for performing a procedure at the operating site. 
         [0003]    The majority of existing instruments is constituted by a fine (typically around 5 mm in diameter) and rigid elongated body (typically around 30 cm long). The proximal end of the instrument comprises a grip handle for the practitioner and the distal end of the instrument is often fitted with a forceps or scissors, optionally capable of transmitting electric current for cutting (monopolar or bipolar). 
         [0004]    The main advantage of laparoscopic surgery is the minimum incisions. However, the main limitation is the decrease in dexterity associated with a remote access by long instruments. Indeed, when the instrument is rigid, its passage via a fixed incision point is a planar kinematic constraint which limits the number of degrees of freedom (DoF) to four: three movements of rotation about the point of incision and a penetration translation movement of the instrument. In particular, with conventional laparoscopic rigid instruments, it is impossible to bend the distal end of the instrument to orient the forceps optimally relative to the practitioner. This is a major application limitation of laparoscopic surgical tools for surgical procedures. 
         [0005]    This has led to the development of novel instruments comprising a distal part exhibiting mobility relative to the principal body of the instrument. For example, for suturing exercise, the surgeon utilises a curved needle. When he carries out this exercise in optimal conditions, the surgeon:
       1. grasps the needle such that the plane of the needle is perpendicular to the axis of the forceps;   2. places the plane of the needle perpendicularly to he edges to be sutured;   3. turns the needle according to an axis perpendicular o its plane to insert into the tissue to be sutured.       
 
         [0009]    Therefore, to make a suture in favourable conditions, there must be provision for placing the axis of the instrument substantially parallel to the edges to be sutured and turning the forceps about its axis. During some interventions, positioning the points of incision relative to the operating site is such that it is not possible to align the axis of the forceps with the edges to be sutured when using rigid instruments, substantially complicating making the suture. This is why instruments have been developed which orient the axis of the forceps relative to the principal axis of insertion of the instrument in the body, due to distal mobility. 
         [0010]    It should be noted that the final rotation movement of the forceps on itself (intrinsic rotation of the forceps), which controls penetration of the needle, must be made with a high precision and a maximal stability of the direction of the axis of the forceps while applying sufficient force to perforate tissue. 
         [0011]    Instruments having a distal mobility are described in documents U.S. Pat. No. 7,338,513, U.S. Pat. No. 7,316,681, U.S. Pat. No. 7,398,707 and US 20080228196. 
         [0012]    The instruments described in these documents are such that the axis of the forceps can be oriented relative to the principal axis of insertion of the instrument according to rotation made about any axis perpendicular to the principal axis of insertion. This is done either by a system with flexible sleeve and cables (document U.S. Pat. No. 7,338,513) or by using two perpendicular pivot joints (document U.S. Pat. No. 7,398,707). In both cases, two rotational degrees of freedom between the principal axis of insertion and the axis of the forceps result from the mechanism used. By using the intrinsic rotation of the axis of insertion, freed by the canula placed at the level of the point of insertion, it is therefore possible to combine three rotations and produce all preferred orientations of the forceps. However, to produce the movement described previously for a suturing exercise, that is, intrinsic rotation of the forceps, in general a complex combination of these three movements and their synchronisation is required at the level of their actuation, making carrying out the exercise very complex. With a design having sleeves and cables (document U.S. Pat. No. 7,338,513), the rigidity of the assembly is insufficient and the axis of the forceps can remain stable and turn on itself when forces are exerted, only with difficulty. With a system having pivots and three combined rotations, a complex robotic system is required to perform synchronisation of movements (document U.S. Pat. No. 7,398,707). 
         [0013]    Other documents describe instruments for which movement of the forceps occurs without resulting from a combination of three rotations. In the document U.S. Pat. No. 7,241,288, the forceps is operated by a system of gears and can be either bent (orientation of the axis of the forceps), or oriented about its axis (intrinsic rotation). However, for controlling one or the other of the movements, a mechanical clutch must be used. The movements are therefore not controlled directly by independent proximal movements. 
         [0014]    The instruments described in the document U.S. Pat. No. 6,913,613 comprise a flexible rod, though rigid to torsion according to its axis, enabling orienting a distal forceps according to its axis and a rigid control rod of the inclination of this forceps relative to an axis of the tool. The two rods extend in a tube. The instrument is difficult to make and is complex. 
         [0015]    An aim of the invention is to provide a surgical instrument being simple in use, and which addresses at least one of the limitations and drawbacks mentioned above. 
       SUMMARY OF THE INVENTION 
       [0016]    To this end, there is provided a surgical instrument comprising;
       an elongated arm according to a longitudinal axis and having a distal end mounted with a pivot joint on the elongated arm according to an axis substantially orthogonal to the longitudinal axis;   a drive shaft, substantially coaxial with the elongated arm, comprising means forming a universal joint facing the pivot joint; and,   a distal tool securely fastened on the drive shaft and rotatively mounted on and in the extension of the distal end of the elongated arm, such that the distal tool has two rotational degrees of freedom, distinct and independent of each other, one being around an axis substantially perpendicular to the longitudinal axis of the elongated arm and the other being around an axis substantially collinear to an own axis of the distal tool, characterised in that the means forming a universal joint comprise a flexible drive sleeve.       
 
         [0020]    It should here be noted that in conventional terms, a universal joint is a kinematic joint used for connecting two shafts and adapted for transmission of the rotational movement of one shaft to another, whatever the angular position of one shaft relative to the other is. There exists several types of universal joint, the flexible drive sleeve being one specific example thereof. 
         [0021]    According to the proposed invention, the enabled direct transmission produces an infinite rotation of the forceps about its own axis, without having to modify the position of the axis of the forceps, or reconfiguring movements or using a clutch system. All rotations are maintained and/or actuated independently. Further, all rotations may be actuated simultaneously if required. It is not necessary to reverse or cancel rotation to describe any movement on the other rotation. Because of this, distal movements are selected optimally to ensure simple control of the instrument while a suturing exercise for example is carried out. Using a flexible drive sleeve as universal joint simplifies manufacturing of the instrument. 
         [0022]    Advantageously, though optionally, the surgical instrument has at least one of the following characteristic, taken individually or in combination:
       the flexible drive sleeve comprises bellows.   the flexible drive sleeve is rigid with regard to torsion stress according to the longitudinal axis, and is flexible and elastically deformable with regard to torsion stress according to any axis perpendicular to the longitudinal axis.   the pivot joint comprises a plurality of linking elements mounted in series.   two adjacent linking elements are mounted relative to one another according to a limited pivot joint.   each linking element is a hollow cylindrical element comprising two lugs extending towards the adjacent linking element, said lugs being opposite one another to define the limited pivot joint.   the elongated arm is hollow and at least partially encloses the drive shaft.   the drive shaft is hollow and at least partially encloses the elongated arm.   the elongated arm comprises a through-hole along the longitudinal axis, one or more cables extending in the elongated arm via the through-hole.   the surgical instrument comprises an actuating cable of the distal tool extending along the longitudinal axis, the actuating cable being surrounded by a sheath.   the surgical instrument further comprises a handle and a transmission system, wherein the handle is connected to the proximal end of the elongated arm, the movements according to the two degrees of freedom being connected by the transmission system to two independent movements produced at the handle.   the surgical instrument is arranged such that the amplitude of rotation of the tool about its own axis is not limited structurally by the transmission system.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Other features and advantages of the invention will become clear from the following description which is only given for illustrative purposes and is in no way limitative and should be read with reference to the attached drawings on which: 
           [0035]      FIG. 1  is a side view of the distal end of a surgical instrument according to a first embodiment of the invention; 
           [0036]      FIG. 2  is a two part view of the surgical instrument of  FIG. 1 . 
           [0037]      FIGS. 3   a  and  3   b  are side views of the surgical instrument of  FIG. 1 , the distal end being in a fully folded position and in a straight position respectively; 
           [0038]      FIG. 4  is an exploded side view of a surgical instrument according to a second embodiment of the invention; 
           [0039]      FIG. 5  is a side view of the distal end of the surgical instrument of  FIG. 4 ; 
           [0040]      FIGS. 6   a  and  6   b  are side views similar to  FIGS. 3   a  and  3   b  applied to the surgical instrument of  FIG. 1 ; 
           [0041]      FIGS. 7   a  and  7   b  are cross section views of he driving mechanism of the pivot joint of the distal end of the surgical instrument of  FIG. 4 , in a fully folded position and in a straight position respectively; 
           [0042]      FIG. 8  is an exploded view of a surgical instrument according to a third embodiment of the invention, 
           [0043]      FIG. 9  is a cross section of the distal end of the surgical instrument of  FIG. 8 ; 
           [0044]      FIGS. 10   a  and  10   b  are mechanical illustrations of the drive of the pivot joint of the distal end of the surgical instrument of  FIG. 8 , in a straight position and in a fully folded position respectively where only the active wires are shown; 
           [0045]      FIG. 11  is an exploded perspective view of a surgical instrument according to a fourth embodiment of the invention; 
           [0046]      FIG. 12  is an enlarged view, in an exploded perspective view, of the portion referenced as A of the surgical instrument of  FIG. 11 ; 
           [0047]      FIG. 13  is a perspective view of the surgical instrument of  FIG. 11 , the distal end being in a straight position; 
           [0048]      FIG. 14  is a cross sectioned view of the surgical instrument of  FIG. 11 , the distal end being in a straight position; 
           [0049]      FIG. 15  is a perspective view of the surgical instrument of  FIG. 11 , the distal end being in a fully folded position; 
           [0050]      FIG. 16  is a cross sectioned view of the surgical instrument of  FIG. 11 , the distal end being in a fully folded position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    In reference to  FIGS. 1 and 2 , we will describe a first embodiment of a surgical instrument according to the invention. 
         [0052]      FIG. 1  illustrates the distal part of a surgical instrument  1  according to a first embodiment of the invention. The surgical instrument  1  comprises an elongated arm  11 , here in a cylindrical revolution shape according to a longitudinal axis (not shown). The elongated arm is hollow and has, on a distal part, an opening on a semi-circumference terminating longitudinally via linking means comprising an axis  10  substantially orthogonal to the longitudinal axis of the elongated arm  11  and extending according to a diameter of a section of said elongated arm  11 . These linking means connect the elongated arm to a distal end  2  comprising, in this respect, complementary linking means. This forms a pivot joint between the elongated arm  11  and the distal end  2 . The distal end  2  here is hollow, cylindrical in revolution in shape about an axis and open on a semi-circumference approximately over the entire length of the distal end  2 , except at the level of an end face  12 . The section of the distal end  2  is almost identical to that of the elongated arm  11 . Accordingly, in an unfolded position, as illustrated in  FIGS. 1 and 2 , the distal end  2  extends in the longitudinal extension of the elongated arm  11 , the longitudinal axis of the elongated arm  11  coinciding with the axis of the distal end  2 . The end face  12  comprises a section of a shaft extending in projection towards the exterior along the axis of the distal end  2 . A distal tool  9 , here a forceps, is mounted in rotation on the section of shaft of the end face  12 , in an extension according to the axis of the distal end  2 . At the level of a proximal end, the elongated arm  11  comprises an end face comprising an axial bore  13 , the longitudinal axis of the elongated arm  11 . 
         [0053]    Mounted substantially coaxially with elongated arm  11 , the surgical instrument  1  according to the invention comprises a drive shaft  3  which extends in the elongated arm  11  from the bore  13  to the distal tool  9  with which it is solid to be able to drive it in a rotation movement about its axis. The drive shaft  3  here is free to turn according to its axis and slide according to a translation movement relative to the elongated arm  11  axis. The drive shaft  3 , comprises, at its distal end, means forming a universal joint  4 ,  5 ,  6 ,  7  and  8  which extend, as shown in  FIG. 1 , into the openings made on a semi-circumference of the distal end  2  and of the elongated arm  11 . The universal joint is thus facing the pivot joint, that is it is arranged to accompany the rotational movement of the pivot joint. 
         [0054]    Here, in the embodiment of the invention described, the means forming universal joint comprise a first Cardan joint  4 ,  5  mounted in series with a second Cardan joint  7 ,  8  by a portion  6  of the drive shaft. In the present text as in conventional terms, a Cardan joint refers to a mechanical linking system comprising two and elements mounted on either side of a central element, where each end element is mounted in a pivot joint with the central element. In addition, the axes of the two pivot joints between the central element and the two end elements respectively are perpendicular (that is, orthogonal and secant) and therefore join at the same point, enabling transmission of angular rotation movement between two shafts extending respectively from the end elements. 
         [0055]    In the example presented in  FIGS. 1 and 2 , the Cardan joints comprise a central piece in the form of a brace, the branches of the brace forming axes on which the end pieces  4 ,  5  and  7 ,  8  are mounted in a pivot joint. 
         [0056]    The function fulfilled by the distal tool  9  is controlled by a cable which extends inside the drive shaft  3  which is hollow for this purpose. The cable is made of resistant metal but still remains sufficiently flexible to follow the movement of the distal end  2  when the pivot joint is used about the axis  10 . 
         [0057]    In reference to  FIGS. 3   a  and  3   b , a brief description follows of the functioning of the surgical instrument  1  according to the invention.  FIG. 3   a  illustrates the folded position at around 90°, while  FIG. 3   b  illustrates the unfolded position. In both cases, rotation movement  15  applied to the proximal end of the drive shaft causes a rotation movement  14  of the distal tool  9 . A perfect transmission of this rotation movement is ensured by the means forming a universal joint, and this being irrespective of the degree of folding of the distal end  2  turning about the axis  10  of the pivot joint. A transition from the folded position to the unfolded position (or between two different folded positions) occurs via translation movement of the drive shaft  3  according to its axis. When the proximal end of the drive shaft is shifted according to this translation movement, an operator controls the orientation of the distal tool  9 . This does away with the presence of cables to complete this orientation. In fact, this translation movement modifies the distance between the axis  10  of the pivot joint between the elongated arm  1  and the distal end  2  and orthogonal projection of any point of the distal tool  9  on the axis of the elongated arm  11 . The rigidity of the distal end  11  causes a rotation movement about the axis  10  to produce a folded position (or unfolded), the drive shaft following the movement as a result of the means forming a universal joint. 
         [0058]    In reference to  FIGS. 4 and 5 , a second embodiment of a surgical instrument  100  according to the invention will now be described. The surgical instrument  100  according to the invention comprises an elongated arm  111 , here cylindrical in revolution in shape according to a longitudinal axis (not shown). The elongated arm  111  distally comprises a base linking element  101  comprising an axis  110  substantially perpendicular to the longitudinal axis of the elongated arm  111 . The elongated arm  111  further comprises a second linking element  102  comprising a bore  112  at a proximal end and an axis  110  similar to the axis  110  of the base linking element  101  and situated at a distal end of the second linking element  102 . The second linking element  102  is mounted in rotation on the base linking element  101  by cooperation of the axis  110  of the base linking element  101  and the bore  112  of the second linking element  102 , thus forming a pivot joint. The elongated arm  111  further comprises a third linking element  105  comprising, at a proximal end, a bore  112  similar to the bore  112  of the second linking element  102 . Similarly, the third linking element  105  is mounted in rotation on the second linking element  102  by cooperation of the axis  110  of the second linking element  102  with the bore of the third linking element  105 , thus forming a second pivot joint. This third linking element  105  forms the distal end of the elongated arm  111 . Mounted on a distal end of the third linking element is the distal tool  9 , here a forceps, in an extension of the third linking element  105 . The latter is mounted in rotation about a longitudinal axis of the third linking element  105  on the latter. As a variant embodiment, several linking elements  102  can be mounted in series between the base linking element  101  and the third linking element  105  bearing the distal tool  9 . Accordingly, the distal tool  9  is mounted in rotation on and in the extension of the distal end of the elongated arm  111 . The distal end of the elongated arm  111  formed by the third linking element  105  is mounted according to a pivot joint on the latter. 
         [0059]    Mounted substantially coaxially with the elongated arm  111 , the surgical instrument  100  according to the invention comprises a drive shaft  103  which extends about the elongated arm  111  from substantially a proximal end of said elongated arm  111  and substantially a proximal part of the base linking element  101 . A drive sleeve  104  is mounted firmly on a distal end of the drive shaft  103  in the extension of the latter. The drive sleeve  104  is mounted on the distal tool  9  so as to drive it in rotation movement about its axis. The drive sleeve  104  is arranged to extend about the base linking element  101 , of the second linking element(s)  102  and of the third linking element  105 , once mounted, as illustrated in  FIG. 5 . The drive shaft  103 , and consequently the sleeve  104 , is free to turn according to its axis relative to the elongated arm  111 . The drive sleeve  104  forms means forming a universal joint. The drive sleeve  104  is rigid with regard to torsion stress according to the longitudinal axis, and is flexible and deformable elastically with regards to torsion stress according to any axis perpendicular to the longitudinal axis. Torsion according to an axis corresponds to the twisting about such axis produced by the action of two opposing couples acting in parallel planes. In the embodiment of  FIGS. 4 and 5 , the drive sleeve comprises bellows which is rigid with regard to torsion stress according to the longitudinal axis, so as to transmit the rotation movement about this axis of the drive shaft  103  to the distal tool  9 , and which is flexible and deformable elastically with regard to torsion stress according to any axis perpendicular to the longitudinal axis, so as to deform easily when pivot joints are used between the base linking element  101  and second  102  and third  105  linking elements (cf.  FIGS. 6   a  and  6   b ). The bellows may for instance be metallic. Any other adapted material can be used to make said bellows. 
         [0060]    The function fulfilled by the distal tool  9  is controlled by a cable which extends inside the elongated arm  111  which is hollow, for this purpose. The cable is made of resistant metal but still remains sufficiently flexible to follow movement of the distal end when pivot joints are used about axes  110 . Similarly, using pivot joints between the base linking element  101  and second  102  and third  105  linking elements is achieved by means of two cables  130  and  131  (cf.  FIGS. 7   a  and  7   b ) extending inside the elongated arm  111  substantially parallel relative to one another and relative to the longitudinal axis of the elongated arm  111 , on the one hand, and on the other hand, spaced apart on either side of said longitudinal axis. Each cable  130  (resp.  131 ) comprises a distal end  132  (resp.  133 ) securely fastened with the third linking element  105 . Traction force  135  on one of the cables utilises the abovementioned pivot joints as is illustrated in  FIG. 7   b . These different cables can be enclosed by a sheath which protects them, but which also allows the length of the cable or cables placed according to the principal axis of insertion to be independent of the flexion of the surgical instrument and force these cables to follow curvature of the principal axis. This avoids for instance that pulling cable actuating distal tool  9  creates forces on the surrounding structure when distal tool  9  is pivoted with respect to elongated arm  207 . 
         [0061]    Operation of the surgical instrument  100  according to the invention will now be described in brief.  FIG. 6   b  ( 7   b ) illustrates the folded position at around 90°, while  FIG. 6   a  ( 7   a ) illustrates the unfolded position. In both cases, a rotation movement  120  applied to the proximal end of the drive shaft causes rotation movement  121  of the distal tool  9 . Perfect transmission of this rotation movement is ensured by the means forming a universal joint (drive sleeve  104 ) and, this being irrespective of the degree of folding of the distal end turning about axes  110  of the pivot joints. Transition from the folded position to the unfolded position (or between two different folded positions) occurs via translation movement  135  of one of the cables  130 ,  131  according to its axis. An operator controls orientation of the distal tool  9  by moving one of these cables according to this translation movement. 
         [0062]    In reference to  FIGS. 8 and 9 , a third embodiment of a surgical instrument  200  according to the invention will now be described. The surgical instrument  200  according to the invention comprises an elongated arm  207 , here cylindrical in revolution in shape according to a longitudinal axis (not shown). The elongated arm  207  is hollow and distally comprises a base linking element  201  hollow, comprising two lugs extending in the extension of the elongated arm  207  and opposite one another to define an axis  210  substantially perpendicular to the longitudinal axis of the elongated arm  207 . The elongated arm  207  further comprises second hollow linking elements  202 ,  203  (also called intermediate linking elements), comprising two lugs extending in the extension of said second linking elements  202 ,  203  and opposite one another to define an axis  210  similar to the axis  210  of the base linking element  201  and located at a distal end of the second linking elements  202 ,  203 . The second linking element  202  is mounted in rotation relative to the axis  210  on the base linking element  201 , thus forming a pivot joint. Similarly, the second linking elements  202  and  203  are mounted in rotation relative to their mutual axis  210 , thus forming a second pivot joint. The elongated arm  207  further comprises a third hollow linking element  204  (also called and linking element). Similarly, the third linking element  204  is mounted in rotation relative to the axis  210  on the second linking element  203 , thus forming a third pivot joint. This third linking element  204  forms the distal end of the elongated arm  207 . 
         [0063]    Mounted on a distal end of the third linking element  204  is the distal tool  9 , here a forceps, in an extension of the third linking element  204 . The distal tool  9  is mounted in rotation about a longitudinal axis of the third linking element  204  on the latter. As a variant embodiment, more than two linking elements  202 ,  203  can be mounted in series between the base linking element  201  and the third linking element  204  bearing the distal tool  9 . Accordingly, the distal tool  9  is mounted in rotation on and in the extension of the distal end of the elongated arm  207 . The distal end of the elongated arm  207  formed by the third linking element  204  is mounted according to a pivot joint on the latter. 
         [0064]    As a variant embodiment, the third linking element  204  is mounted directly in series on the base linking element  201 . As another variant embodiment, a single second linking element  202  is mounted in series between the third linking element  204  and the base linking element  201 . 
         [0065]    All the linking elements ( 201 ,  202 ,  203 ,  204 ) are segmented elements which, when mounted in series, fulfil the pivot function. This assembly of linking elements ( 201 ,  202 ,  203 ,  204 ) can be similar to a set of hollow vertebrae of substantially cylindrical form, each of the vertebrae being mounted with the preceding vertebra with a pivot joint according to a pivot axis  210  perpendicular to the longitudinal axis of the elongated arm  207 . Such pivot joint is also referred as a limited pivot joint or wedged pivot joint, as the angular amplitude of the pivot is structurally restricted by the form of the linking elements. All the axes of the pivot joints  210  are parallel such that the total angle of flexion is the sum of the angles of rotation between each pair of vertebrae. The series of the limited pivot joints produces an accumulative pivot with respect to the whole body, which corresponds to the overall pivot joint. 
         [0066]    According to a preferred embodiment, the hollow vertebrae have a substantially cylindrical form. They can be assembled with others like puzzle pieces, by having one piece slide relative to the other according to the axis of the pivot  210 . Accordingly it is not necessary to provide a rod to physically form the pivot joint which is in reality ensured by cooperation of the lugs of each vertebra with a complementary form arranged on the following vertebra, this complementary form for example being a notch made from the edge of the cylinder forming the vertebra. Such an arrangement considerably simplifies assembling of the assembly. In addition, such a configuration also has the advantage of forming a pivot joint without introducing dents or additional structure in the internal wall or in the external wall of the vertebra, ensuring no loss of room inside the vertebra on the one hand, and on the other hand ensuring a smooth surgical instrument without an element which might impede its displacement in the insertion trocar of the surgical instrument. It should be noted that the vertebrae are kept in a nested position in one another by any means, but will preferably be held by the actuating cables of the pivot joints passing through the vertebrae, and/or the elements placed inside the vertebrae and ensuring this position is kept especially by overlapping of the pieces. Other methods of coupling the vertebrae are feasible, for example by arranging a cavity on the surface of the vertebra, this cavity cooperating with an embossing extending from the inner surface of the lug, enabling fixing via clipping for example. According to a preferred embodiment, though not necessary, all the vertebrae are identical. 
         [0067]    Ensuring the pivot function by a set of vertebrae such as described hereinabove has numerous advantages. First, as already pointed out, specific assembling (by nesting/puzzle, and even by clipping) maintains a large enough inner space for placing the other mechanical functions necessary for the surgical instrument. In addition, the proposed arrangement uses small-sized pieces and guarantees an outer diameter of the surgical instrument of the order of 5 mm, ensuring considerable angular amplitude of the pivot and satisfactory rigidity of the assembly for manipulation of the surgical instrument. In fact, using a series of successive vertebrae easily produces the angular amplitude generally used of the order of 90°, since each pivot between two successive vertebrae permits angular amplitude of at least 20° (corresponding to what qualifies as a limited pivot joint). Also, the proposed arrangement ensures the required rigidity for good manipulation of the surgical instrument, especially torsional rigidity according to the axes orthogonal to the axis of the overall pivot, this being due especially to the full cylindrical form of the vertebrae and to their particular coupling. In addition, the fact that the axes of the pivots  210  are perpendicular to the longitudinal axis of the elongated arm  207  allows the lugs of the vertebrae to be arranged in the body of the cylinder according to a diametrical axis, preventing them from projecting relative to the outer wall of said cylinder. 
         [0068]    Mounted substantially coaxially with the elongated arm  207 , the surgical instrument  200  according to the embodiment presented in  FIGS. 8 to 10  comprises a drive shaft  3  which extends in the elongated arm  207  from substantially a proximal end of said elongated arm  207  and substantially a proximal part of the base linking element  201 . A drive sleeve  206  is mounted solid on a distal end of the drive shaft  3  in the extension of the latter. The drive sleeve  206  is securely fastened with the distal tool  9  so as to drive it in rotation movement about its axis. The drive sleeve  206  is arranged to extend within the base linking element  201 , the second linking elements  202 ,  203  and the third linking element  204 , once mounted, as illustrated in  FIG. 9 . The drive shaft  3 , and consequently the sleeve  206 , is free to turn according to its axis relative to the elongated arm  207 . The drive sleeve  206  forms means forming a universal joint. The flexible drive sleeve is rigid with regard to torsion stress according to the longitudinal axis, and is flexible and deformable elastically with regard to torsion stress according to any axis perpendicular to the longitudinal axis. In the embodiment of  FIGS. 8 and 9 , the drive sleeve comprises bellows which are rigid with regard to torsion stress according to the longitudinal axis, so a to transmit rotation movement about this axis of the drive shaft  3  to the distal tool  9 , and flexible and deformable elastically with regard to torsion stress according to any axis perpendicular to the longitudinal axis, so as to deform easily when pivot joints are used between the base linking element  201  and second  202 ,  203  and third  204  linking elements. The bellows may for instance be metallic. Any other adapted material can be used to make said bellows. 
         [0069]    The function fulfilled by the distal tool  9  is controlled by a cable which extends inside the drive shaft  3  which is hollow, for this purpose. The cable is made of resistant metal but still remains sufficiently flexible to follow the movement of the distal end when pivot joints are used about axes  210 . Similarly, using pivot joints between the base linking element  201  and second  202 ,  203  and third  204  linking elements is achieved by means of a cable  212  (cf.  FIGS. 10   a  and  10   b ) extending inside the elongated arm  207  from the proximal part of the base linking element  201 . The cable  212  comprises a distal end  211  securely fastened with the third linking element  204 . Part  214  of the cable extends outside the elongated arm  207 , opposite the second linking elements  202 ,  203 . Traction force  213  on the cable utilises the above pivot joints, as is illustrated in  FIG. 10   b . As a variant, a second cable can be used, located diametrically opposite the cable  212 . As another variant, the part  214  of the cable extends inside the second linking elements (if a second cable is used, the latter can also extend inside the second linking elements). These different cables can be enclosed by a sheath which protects them, but which also allows the length of the cable or cables placed according to the principal axis of insertion to be independent of the flexion of the surgical instrument and force these cables to follow curvature of the principal axis. This avoids for instance that pulling cable actuating distal tool  9  creates forces on the surrounding structure when distal tool  9  is pivoted with respect to elongated arm  207 . 
         [0070]    The function of the surgical instrument  200  according to the invention will now be described in brief.  FIG. 10   b  illustrates the folded position at around 90°, while  FIG. 10   a  illustrates the unfolded position. In both cases, rotation movement applied to the proximal end of the drive shaft causes rotation movement of the distal tool  9 . Perfect transmission of this rotation movement is ensured by the means forming a universal joint (drive sleeve  206 ) and, this being irrespective of the degree of folding of the distal end turning about axes  210  of the pivot joints. Transition from the folded position to the unfolded position (or else between two different folded positions) is done via translation movement  213  of the cable  212  according to its axis. An operator controls the orientation of the distal tool  9  by moving this cable according to this translation movement. 
         [0071]    In reference to  FIGS. 11 to 16 , a fourth embodiment of a surgical instrument  300  according to the invention will now be described. The surgical instrument  300  according to the invention comprises an elongated arm  307  having a form similar to the elongated arm  207  of the surgical instrument  200  according to the third embodiment of the invention. Accordingly, the elongated arm  307  comprises one or more linking elements making up the pivot function, where the set of linking elements can be similar to a set of hollow vertebrae, each of the vertebrae being mounted according to an axis pivot joint perpendicular to the axis of the elongated arm with the preceding vertebra. 
         [0072]    More precisely, in the fourth embodiment presented, the elongated arm  307  comprises five linking elements ( 301 ,  302 ,  303 ,  304 ,  305 ) forming the pivot joint (also called overall pivot joint). The elongated arm  307  is hollow and distally comprises a hollow base linking element  301 , comprising one set of pivot lugs (female side only) extending in the direction of the elongated arm  307  and opposite one another to define an axis  310  substantially perpendicular to the longitudinal axis of the elongated arm  307 . The elongated arm  307  further comprises hollow intermediate linking elements ( 302 ,  303 ,  304 ), comprising two lugs extending in the extension of said intermediate linking elements ( 302 ,  303 ,  304 ) and opposite one another to enable rotation about an axis parallel to the axis  310  of the base linking element  301  and located at a distal end of the intermediate linking elements ( 302 ,  303 ,  304 ). The intermediate linking element  302  is mounted in rotation relative to the axis  310  on the base linking element  301 , thus forming a first limited pivot joint (also called wedged pivot joint, as the form of the linking elements naturally restrict the amplitude of the pivot). Similarly, the intermediate linking elements ( 302 ,  303 ,  304 ) are mounted in mutual rotation relative to the axis  310 , thus forming a second and third limited pivot joint. The elongated arm  307  further comprises a hollow end linking element  305 . Similarly, the end linking element  305  is mounted in rotation relative to the axis  310  on the final intermediate linking element  304 , thus forming a fourth limited pivot joint. This end linking element  305  forms the distal end of the elongated arm  307 . The series of the limited pivot joints produces an accumulative pivot with respect to the whole body, which corresponds to the overall pivot joint. All the axes of the pivot joints  310  are parallel such that the total angle of flexion is the sum of the angles of rotation between each pair of linking elements. 
         [0073]    In addition, the vertebrae are pierced to allow two cables ( 312 ,  314 ) placed on either side of the axis of the pivot  310  to slide. The cables ( 312 ,  314 ) are attached to the final vertebra and slide in the openings of the others, which allow all the pivots to be actuated after mounting and therefore flexes by pulling on one or the other of the two cables ( 312 ,  314 ). 
         [0074]    Mounted substantially coaxially with the elongated arm  307 , the surgical instrument  300  comprises a drive shaft  3  which extends in the elongated arm  307  from substantially a proximal end of said elongated arm  307  to substantially a proximal part of the base linking element  301 . The drive shaft  3  comprises, at its distal end, means forming a universal joint which extend in the cavity formed by the different linking elements, these means forming a universal joint comprising at least one Cardan joint. The means forming a universal joint preferably comprise at least two Cardan joints. To maintain the full range of motion (longitudinal and radial rotation), the means forming a universal joint more preferably comprise as many Cardan joints as pivot axes  310  formed by the vertebrae ( 301 ,  302 ,  303 ,  304 ,  305 ). Accordingly, in the example presented in  FIGS. 11 to 16 , four Cardan joints ( 320 ,  330 ,  340 ,  350 ) are provided, respectively positioned at the level of the pivot axes  310  formed between the different linking elements ( 301 ,  302 ,  303 ,  304 ,  305 ), that is adjacent to the corresponding pivot joint. According to a preferred aspect of this embodiment, the axes of the two pivot joints defining each Cardan joint intersect with the pivot axis  310  at the level where it is positioned. 
         [0075]    As pointed out earlier, a Cardan joint s a mechanical linking system comprising two end elements mounted on either side of a central element, where each end element is mounted in a pivot joint with the central element. In the embodiment presented in  FIGS. 11 to 16 , the pivot joints between the pieces forming the Cardan joint are made by a sliding guide of one surface on another. To achieve this, end pieces having at their end of the surfaces sliding on the surface of the central piece can be provided for example, these central and end pieces also comprising sliding guide means. 
         [0076]    Accordingly, as is evident from  FIG. 12 , the central piece  322  of the Cardan joint  320  is preferably a sphere in which two grooves are hollowed out in two perpendicular diametrical planes, preferably according to two diametrical circles. More preferably, each groove forms a circle around the sphere. The end pieces  321  and  323  have as such ends formed to be able to slide on the sphere  322 , having hollow/concave surfaces with for example a semi-cylindrical or semi-spherical form complementary to the sphere  322 . The contact surfaces at the ends of the end pieces  321  and  323  also preferably comprise a ridge in projection whereof, said ridge having a form corresponding to the geometry of the hollow grooves in the sphere  322 , such that the ridge in projection serves as guide rail for sliding of the end pieces  321  and  323  on the central piece  322 . The end pieces  321  and  323  also have a general cylinder form. In a preferred embodiment, two successive Cardan joint could have a common end piece (corresponding to the end piece positioned between the two spheres of the two Cardan joints) having the form of a cylinder with at its two ends a hollow surface formed for sliding on the spheres. 
         [0077]    In the present embodiment, shoulders preferably prevent the sliding according to the axis of the drive shaft  3  and the contact between the sliding surfaces is maintained by external pressure, due especially to the mechanical assembling of the different pieces. As pointed out earlier, the spheres are preferably placed such that their centre belongs to the pivot axis of the vertebrae, such that the axes of the pivot joint made by the contact surfaces intersect the pivot axis of the vertebrae. All the pieces forming the Cardan joints are small enough to be nestled inside the vertebrae. The outer diameter of the cylinders forming the and pieces of the Cardan joints is preferably adjusted to the inner diameter of the vertebrae so that the cylinders can slide inside the vertebrae, thus facilitating assembling of the assembly, since the cylinders and spheres forming the Cardan joints can be inserted and slide inside the vertebrae according to the longitudinal axis of the elongated arm  307 . 
         [0078]    Assembling such a set of Cardan joints therefore consists of inserting in the vertebrae ( 301 ,  302 ,  303 ,  304 ,  305 ) and stacking between them a succession of cylindrical elements and spherical elements, respectively forming the end elements and central elements of the Cardan joints ( 320 ,  330 ,  340 ,  350 ). Accordingly, the ridge in projection of a cylinder is inserted into the groove of the sphere in which the ridge in projection of the preceding cylinder is not inserted, the ridges in projection of two consecutive cylinders in contact with the sphere connecting it therefore being orthogonal. It is ensured that the centre of the spheres is positioned according to the pivot axis of the corresponding vertebrae. The assembly is then blocked in translation by the stacked axis corresponding to the longitudinal axis of the elongated arm  307 , by a screw system, for example. Transmission of the intrinsic rotation of the distal part is then possible between the most proximal cylinder and the most distal cylinder by relative shifts of the cylinders and of these spheres which respect Cardan kinematics. Advantageously, transmission can overall remain homokinetic if, for each intermediate cylinder, the ridges in projection of the ends are machined orthogonally relative to one another, and if the number of Cardan joints is even. 
         [0079]    As for the others embodiments, a distal tool  9 , for example a forceps, is mounted on a distal end of the end linking element  305 , in its extension. The distal tool  9  is mounted in rotation about a longitudinal axis of the element end linking element  305  on the latter. This distal tool  9  is preferably actuated by a cable extending inside the elongated arm  307 . More preferably, the cylindrical and spherical pieces forming the transmission by Cardan joints are pierced by through-holes according to the principal axis of the instrument when the latter is not flexed. These different holes made in the pieces of the Cardan joints allow a flexible mechanical cable  360  to pass through for transmission of traction force to actuate the distal tool  9  placed at the distal end of the instrument, or of electric cables (not shown) for transmission of a signal, a command or a monopolar and/or bipolar current. This or these cables are preferably enclosed by a sheath  361  which on the one hand protects this or these cables, but also the length of the cable or cables placed according to the principal axis of insertion is independent of the flexion of the surgical instrument and force these cables to follow curvature of the principal axis. This avoids for instance that pulling cable actuating distal tool  9  creates forces on the surrounding structure when distal tool  9  is pivoted with respect to elongated arm  207 . 
         [0080]    Operation of the surgical instrument  300  according to the invention will now be described.  FIGS. 15 and 16  illustrate the folded position at 90°, while  FIGS. 13 and 14  illustrate the unfolded position. In both cases, a rotation movement  370  applied to the proximal end of the drive shaft causes rotation movement  371  of the distal tool  9 . Perfect transmission of this rotation movement is ensured by the means forming a universal joint (Cardan joints  320 ,  330 ,  340 ,  350 ) and, this being irrespective of the angular deflection of the distal end turning about axes  310  of the limited pivot joints. The transition of the folded position to the unfolded position (or between the two different folded positions) occurs via translation movement of one of the cables  312 ,  314  according to its axis. An operator controls the orientation of the distal tool  9  by moving one of these cables according to this translation movement. 
         [0081]    Controlling of the different cables used in the described surgical instrument, for example the actuating cables of the distal tool and/or the actuating cables of the pivot joint, could be done manually by the user, or by means of one or more motors automating operation of the surgical instrument. A motor can also be used to set the drive shaft in rotation about its longitudinal axis. 
         [0082]    The described surgical instrument distinguishes itself from existing instruments by having distal mobility in that the intrinsic rotation movement of the forceps is completely independent of the other movements (especially those which orient the axis of the forceps relative to the principal axis of the instrument) and transmitted directly via rotation movement carried out at the level of the proximal part. 
         [0083]    This allows control of two movements of the distal part from two independent movements engendered at the level of the handle, which are orientation of the axis of the forceps due to rotation about an axis substantially orthogonal to the axis of insertion of the instrument and rotation about the axis of the forceps. 
         [0084]    It is of course possible to make numerous modifications o the invention without departing from the scope thereof.