FR2902311A1 - Surgical drilling instrument for installing endo-osseous implant, has perforator with assembling zone composed of cooperating zone extended towards shank by receiving zone that is delimited between proximal and distal stops - Google Patents

Abstract

The instrument has a perforator (1) connected with a protective sheath (2) and comprising a cutting edge (4) and a gripping shank (3) at distal and proximal ends respectively. Connection units (5, 6) cooperate a reversible junction between the perforator and the sheath. The perforator has an assembling zone (9) composed of a zone (10) cooperating the connection units and extended axially towards the shank by a zone (11) that receives an assembling unit (12) of the sheath by free rotation. The receiving zone is delimited between a proximal stop (7) and a distal stop (8) of the perforator.

Description

Surgical instrument to be pierced composed of a drill equipped with a sheath

  coaxial protection mounted freely rotating on the drill.

Technical Field of the Invention

  The present invention is in the field of surgical instrumentation, and more particularly tools or dental instruments. It relates to an instrument for piercing the bone material, in view of the installation of an endosseous implant in particular, this instrument combining a drill and a protective sheath surrounding the cutting part of this drill.

State of the art

  Among the surgical instrumentation, including dental instruments are known for piercing the bone material that combine a drill and a coaxial protective sheath surrounding the cutting edge of this drill. More particularly, the drill has at its distal end a cutting portion, which is extended at its proximal end by a gripping tail for its grip by a rotary drive tool. The drill is provided with coaxial junction means with a removable sleeve arranged in a cylinder, which remotely surrounds the cutting portion of the drill bit. This sheath is intended to provide protection of the external environment to the drill when piercing the bone material by the practitioner, to avoid injuring the tissues of the patient surrounding the area to be pierced. The cutting portion of the drill emerges axially out of the sheath at a predefined distance, so that the latter constitutes not only a protective member, but also a depth gauge of the penetration stroke of the drill into the bone material.

  There is the problem of the junction between the drill and the sheath. It is desirable that the sheath be removably mounted on the drill, so as to allow its installation and removal quick and easy. Traditionally, the sheath is attached to the drill either by screwing, as described by US6739872 (TURRI A.), or by elastic interlocking as described by US6514258 (BROWN W. & al.).

  For example according to US6739872, the drill has in its central zone a threaded zone, interposed between the cutting portion and the gripping tail. The sheath is provided with a sleeve having an internal thread, so that it can be installed by screwing on the drill. An axial abutment member is installed on the drill by being screwed onto its threaded zone, to prevent an escape of the sheath towards the distal end of the drill when it is rotated.

  From an adjustment of the axial position of this abutment member along the threaded zone, the sheath is placed in the desired position by the practitioner to obtain its depth gauge function.

  Such a solution has the disadvantage of a transmission of the n rotation movement of the drill to the sheath, which rotate together during the drilling operation. This disadvantage induces a risk of injury to the patient by the sheath when the drill is at the end of the piercing stroke and that the sheath, as a depth gauge, is placed in axial contact with the bone material. It finally comes out for the practitioner the need to be careful to avoid axial contact between the sheath and the bone tissue at the end of drilling, which is not only difficult in the dental field in particular, but in addition renders obsolete the function of the gauge. depth sought for the sheath.

  It has therefore been proposed to mount the sheath on the drill so as to allow its free rotation relative to that of the drill. For example according to US6514258, the sheath has at its proximal end a smooth sleeve interlocking resiliently on a cylinder of the drill. The sheath is threaded on the drill by the distal end of the latter, until it is placed in axial abutment against the distal shoulder of the cylinder via an internal shoulder of complementary shape that includes the sleeve. The latter is made radially deformable, due to the presence of axial peripheral grooves in particular, and has at its proximal end radial claws which cap by elastic deformation of the sleeve the proximal end of the cylinder. The sheath is axially immobilized while being relatively free in rotation due to the junction by axial sliding of the sleeve on the cylinder.

  Such a solution is not satisfactory, because of the unreliability of the junction between the sheath and the drill, which is made by elastic interlocking. It reveals an insecurity of this junction which is detrimental to the interest offered to allow free rotation of the sheath. In addition, the elastic interlocking of the sheath on the drill is made possible from radial and axial stresses which are exerted on the cylinder by the sleeve. These constraints induce consequently a connection in rotation between the sheath and the drill, as weak as it is. When the sheath is placed in axial contact with the bone material at the end of the piercing stroke, these stresses must be overcome until a rotation of the drill bit does not induce a concomitant rotation of the sheath, with the consequence of inducing a risk of bone tissue injury.

Object of the invention

  The object of the present invention is to provide a surgical instrument to be drilled of the type consisting of a drill equipped with a coaxial protective sheath. It is more particularly the object of the present invention to provide such an instrument in which the junction between the drill and the sheath is reliable without impairing the ease of installation and removal of the sheath, in which a gauge function depth of the sheath is not impaired by a risk of bone tissue injury that is likely to result from a possible rotation of the sheath by the drill, and wherein the means of junction between '- dwarf and the drill can be exploited to optimize the functionality of the instrument.

  The inventive step of the present invention consisted in organizing the instrument so as to obtain a junction between the protective sheath and the drill that allows absolute free rotation of the protective sheath relative to the drill when they are assembled. one to another in the use of the instrument by the practitioner. The absolute character of this freedom of rotation is obtained by placing the sheath on the drill in an area of the latter from which it is completely free in rotation and in which it is axially retained between two remote axial abutment means. To allow easy installation of the sheath on the drill, it is threaded around it until a crossing of a first abutment means from a voluntary act of the practitioner, this voluntary crossing being unequivocal in a reverse crossing being prohibited at the moment. This prohibition aims to prohibit a spontaneous withdrawal of the sheath beyond the first stop means. The sheath is thus axially retained between the two abutment means, while being completely freely mounted in rotation on the drill.

  More particularly, the inventive step of the present invention was to separate the area of the drill bit reserved for its junction with the sheath into two distinct zones arranged in extension of one another. A first zone comprises cooperating junction means with complementary junction means which comprises an assembly member of the sheath, and a second zone is arranged to receive this assembly member in a freely rotating manner. This second zone is placed between the first zone which constitutes a first means of axial abutment against a spontaneous escape of the sheath towards the distal end of the drill, and a second axial abutment means placed between the zone of junction that includes the drill and its gripping tail.

  This distinction in two successive zones of respective function of the zone of the drill bit reserved for its junction with the sheath makes it possible to guarantee an easily reversible but nevertheless effective assembly between the drill and the sheath, while guaranteeing an absolute free rotation of the sheath when she is assembled in the forest. This assembly is done voluntarily by the practice, - and can only be broken by a reverse voluntary gesture. In addition, this distinction makes it possible to freely arrange the joining means, which may be furthermore organized for mounting a replacement accessory for the sheath that the drill must rotate, such as a drill bit, without wearing interference with the freely rotating nature of the sheath installed on the drill. More particularly, the junction means that comprises the drill are used to form an axial abutment means for the sheath, and are also likely to be exploitable for a connection in rotation between the drill and an accessory, such as a drill bit , which is a substitute for the sheath and which must be rotated through the drill bit. There emerges a possible double exploitation of the drill, one main for the reception of the sheath and the other alternative and secondary for the reception of another accessory, particularly trephine, which can be rotated by the drill bit. In this case, the drill is likely to be a device guiding the accessory as described below.

  According to a general approach of the present invention, the proposed surgical instrument is a drilling instrument of the type consisting of a drill equipped with a protective coaxial sheath. The drill has at its distal end a cutting portion and at its proximal end a gripping shank by a tool for driving the drill bit in rotation. The sheath is arranged in a cylinder remotely surrounding the drill which emerges at its distal end when they are assembled to one another. The drill and the sheath are provided with cooperating means of reversible connection between them, which are respectively formed in a zone of assembly of the drill, interposed between its cutting part and its gripping tail, and on an assembly member that comprises the sheath, at its proximal end in particular. Counterclockwise axial abutment means are provided on the drill to retain axially between them the sheath installed on the drill. These axial abutment means are composed of a proximal stop means prohibiting an axial displacement of the sheath towards the gripping tail and a distal unambiguous abutment means preventing a spontaneous axial displacement of the sheath towards the end of the end. distal of the forest. It will be understood that the unambiguous nature of the distal abutment member confers on it an ability to authorize its axial crossing by the assembly member from a voluntary gesture of the practitioner and to prohibit a spontaneous reverse crossing of the organ. assembly to the distal end of the drill.

  According to the present invention, a surgical instrument is mainly recognizable in that the assembly area of the drill is composed of two distinct zones which are arranged in the extension of one another. A first zone is a zone of cooperation of the means for joining the drill bit and the sheath between them. This cooperation zone is distinctly axially extended towards the gripping shank by a second receiving zone in free rotation of the assembly member of the sheath. This receiving zone is delimited between the proximal abutment means and the distal abutment means that the drill has, and is an area which is adapted to accommodate in a strictly rotational manner the assembly member that the sheath comprises.

  More particularly, the assembly area of the drill bit successively comprises from its cutting portion towards the gripping tail the cooperation zone, the distal abutment means, the receiving zone and the proximal abutment means.

  The proximal end of the junction means which the drill comprises is advantageously constitutive of the distal abutment means. For example, in the case where the joining means are of the screw type, the distal stop means is advantageously constituted by the proximal end thread of a threaded zone of the drill constituting the cooperation zone.

  The proximal abutment means is indifferently axially fixed on the drill or mounted via means for adjusting its axial position on the drill. In each of these alternative cases and to offer the practitioner the possibility of having depth gauge sheaths for different drill strokes, the sheath is part of a set of sheaths having characteristics of different axial dimensions and other similar ones. . These arrangements are advantageous insofar as for the same instrument of the present invention, it is possible to propose to the practitioner two variants, one offering a faculty of adjusting the axial position of the proximal abutment means, the other being obtained at lower costs.

  For example and according to a first variant embodiment, the proximal abutment means being fixed, the axial dimension of the axial extension of the junction means that includes the sheath is at most equal to the axial extension of the receiving zone. To offer different depth gauge characteristics, the sheath is in this case likely to be part of a first set of sheaths of different lengths, for the same given axial extension of the junction means that includes the sheaths of the first set .

  For example still and according to a second embodiment, the axial position along the drill bit of at least one of the abutment means, and in particular the proximal abutment means, is adjustable. In order to offer different depth gauge characteristics, the sheath participates in a second set of sheaths of the same length for different axial ends of the junction means that comprise the sheaths of this second set.

  According to one embodiment of the cooperating junction means, these are of the screw type, which combine external threads formed in the zone of cooperation of the drill with internal threads formed in a sleeve constituting the body of the drill. assembly that includes the sheath.

  Preferably, the instrument comprises at least one substitute accessory of the sheath, which is provided with mounting means cooperating with the junction means of the drill for assembling them in rotation with each other. More particularly, the junction means that the drill advantageously comprises both an axial abutment means for the sheath and a rotational connection means between the drill and the accessory. Such an accessory consists in particular of a drill bit adapted to be rotated by the drill, which is joined to the latter by screwing.

  More particularly, the bit is mountable on a drill so that the cutting edge of the bit forming tool at its distal end and the distal end of the drill are flush. However, it is advantageous to use the drill as a guide member of the bit, and more particularly of the tool, during its penetration into the bone for the removal of a cohesive bone core. According to this aspect, the drill is a guide device on which the bit is mounted by means of removable mounting means cooperating with the connecting means that includes the drill. In particular, the junction means that includes the drill bit and the mounting means that comprises the drill bit tool are of the screw type. The tool is installed on the drill by screwing by being brought into axial support against the proximal stop means that the drill, while maintaining its grip on the connecting means through the mounting means. These arrangements are such that the drill, which emerges out of the distal outlet of the tool, can be used to guide the trephine in the bone material. More particularly, a shallow pre-hole is likely to be operated by the practitioner by means of the drill provided with the sheath, then, the sheath being removed and the drill bit being installed, this drill hole is used to guide the drill during the approach of the bone material by the trephine. These provisions make it possible to obtain a sample of a cohesive bone core and a removal of it from the trephine which are reliable and easy.

  According to these provisions, the tool can be removed from the guide device, including the drill, after removal of the core, to allow its easy removal. The tool released from the drill is opening at its proximal end initially used for its threading on the joining means that includes the drill. This axial outlet of the tool makes it possible to offer the practitioner axial access to the core for removal. More particularly, the axial recess of the tool is more particularly axially open at its proximal end, to form an axial window constituting means for thrusting the core removed from the tool by providing easy access for the practitioner. The advantage of the removable mounting of the tool on the guide device, and notammP ^ + drill, is not only to allow isolation of the tool after the operation of sampling the core to facilitate the extraction of this last out of the tool, but also to allow to release an axial outlet of the tool at its proximal end to form the axial window. This axial window includes a passage for a pushing instrument, such as a cannula, a probe or similar instrument allowing the practitioner to easily remove by pushing the core removed from the tool without the risk of damaging it.

  According to another embodiment of the cooperating joining means, these are of the elastic deformation type of the assembly member. More particularly, it will be understood that, starting from the dissociation of the assembly zone that the drill has in two distinct zones successively respectively of cooperation and of reception, the nature of the junction means is likely to be arbitrary without altering the faculty. offered a rigorously freely rotating assembly of the sheath on the drill. Such junction means are intended to allow their passage by elastic deformation along the junction means that includes the drill, then to take axially support against them from their return to spontaneous initial position.

Description of the figures.

  The present invention will be better understood on reading the description which will be made of embodiments, in connection with the figures of the attached plates, in which: Fig.1 to Fig.4 are diagrams in section showing a first preferred embodiment of a surgical instrument of the present invention, which illustrate successively the methods of assembly between a drill and a constituent sheath of this instrument.

  FIGS. 5 to 7 are cross-sectional diagrams representing a second variant embodiment of a surgical instrument of the present invention, which successively illustrate the methods of assembly between a drill and a sheath constituting this instrument. Fig.8 is a sectional diagram illustrating a surgical instrument according to the first embodiment shown in Fig.1 to fig.4, -'--, s which the drill is associated with a replacement bit of the sheath.

  In Fig.1 to Fig.7, a surgical instrument associates a drill 1 for drilling the bone material and a protective sheath 2. The drill 1 consists of an axially extended element, which comprises at its proximal end a gripping shank 3 of the drill bit 1 by a rotary drive tool, and at its distal end a cutting portion 4. The sheath 2 is arranged in cylinder 13 surrounding coaxially remotely drill 1, the latter emerging out of the distal end of the sheath 2 when assembled to one another as shown in Fig.4 and Fig.7. It emerges that the sheath 2 provides protection of the external environment surrounding the piercing area in the bone material to avoid injuring the patient, and is furthermore for the practitioner a gauge with regard to the depth of penetration of the drill 1 inside the bone material. The drill 1 and the sheath 2 comprise respective means 5,6 cooperating with each other for their reversible junction with each other. Stop means 7,8 prohibit a spontaneous escape of the sheath 2 beyond the drill 2.

  More particularly, a proximal abutment means 7 prohibits a spontaneous escape of the sheath 2 towards the proximal end of the drill 1, whereby a distal abutment means 8 prohibits a spontaneous escape of the sheath 2 towards the end. distal of the drill 1.

  It is desired that the joining means 5,6 do not hinder a dissociation of the rotational mobility of the drill 1 and the sheath 2 when they are assembled to one another. More particularly, it is desired that the sheath 2 is absolutely and rigorously mounted free to rotate on the drill 1 in the position of use of the instrument by the practitioner, so that the contacting of the sheath 2 axially against the tissue the patient's bone at the end of the drilling operation, is not a cause of injury despite the rotational movement of the drill 1.

  For this purpose, the drill 1 comprises an assembly zone 9 with the sheath 2 in which the junction means 5 are arranged. This assembly zone is composed of two successive zones 10, 11 arranged in extension one of the 'other. A first zone is a zone of cooperation between the junction means 5 of the drill 1 and the junction means 6 of the sheath 2; a second zone is a reception zone 11 in free rotation of an assembly member 12 of the sheath 2 integrating the junction means 6 equipping the latter. The receiving zone 11 is formed between the distal abutment means 8 formed by the proximal end of the junction means 5 that comprises the drill 1, and the proximal abutment means 7. Axial abutment members that are antagonistic to these abutment means are formed on the sheath, being formed respectively by the proximal end face 14 and the distal end face 15 of the assembly member 12. It follows that the drill 1 comprises successive .., since its part 4 to the gripping tail 3, the cooperation zone 10, the distal abutment means 8, the receiving zone 11 and the proximal abutment means 7. When fitting the sheath 2 to the drill 1, the sheath 2 is introduced axially through its proximal opening on the drill 1, from the distal end of the latter as shown in Fig.2, Fig.3 and Fig.6. The junction means 6 that comprises the sheath 2 are related to the junction means 5 that includes the drill 1, as shown in Fig.3 and Fig.6, until crossing the latter by the assembly member 12 that includes the sheath 2. This crossing allows to place the assembly member 12 of the sheath 2 in the receiving zone 11 of the drill 1, as shown in Fig.4 and Fig.7 . In order to prevent the sheath 2 from floating on the drill 1, the radial dimension of the junction means 6 that the sheath 2 comprises corresponds to that of the receiving zone 11, a slight radial clearance being possible to ensure that no rotation is established between the drill bit 1 and the sheath 2. In order to guarantee the depth gauge function of the sheath 2, the axial dimension D1 of the junction means 6 that the sheath 2 comprises, and in particular the axial dimension of the member 12, corresponds to the axial dimension D2 of the receiving zone 11. A slight axial play is likely to be provided between the assembly member 12 and the receiving zone 11 delimited between the proximal stop means 8 and the distal abutment means 7. When the sheath 2 is placed in contact against the proximal abutment means 7 under the effect of the thrust exerted as a result of its axial contact with the bone tissues at the end of the piercing, this setting contact is simply slippery, the surface condition respectively of the proximal abutment means 7 and the end face 14 of the connecting member 12 being adapted to provide such sliding.

  On the illustrated embodiments, the proximal stop member 7 is integrated in the drill 1 and is fixed in axial position. It emerges that in order to make it possible to vary the emergence dimension D3 of the drill bit 1, it is necessary for the practitioner to choose a sheath 2 of length adapted to the desired stroke of the drill bit 1 of a first set of sheaths 2 of length LI different. According to an embodiment not shown, the proximal abutment means 7 is mounted axially movably along the drill bit 1 so as to adapt its position according to the desired stroke of the drill bit 1. In this case, it is necessary for the practitioner to choose a sheath 2 of an axial dimension D1 adapted junction means 6, and more particularly the assembly member 12, among a set of sheaths 2 of the same length L1. It will be noted that, in a similar manner, the junction means 5 that the drill 1 comprises as constituting the distal abutment means 8 are capable of being mounted movably along the drill 1 to adapt the axial position of the sheath 2 along the drill 1 depending on the neck, desired penetration of the drill bit 1 in the bone material.

  In FIGS. 1 to 4, the cooperating joining means 5, 6, respectively formed on the drill 1 and on the sheath 2 are of the screw type. More particularly, the drill 1 comprises in the cooperation zone 10 a cylinder 16 provided with an external thread, while the sheath 2 has an internal thread which is formed on the assembly member 12 arranged in a sleeve. The proximal end thread of the junction means 5 that comprises the drill 1 constitutes the distal abutment means 8, against which the proximal end face 15 of the assembly member 12 comes into axial support when it is placed. in the reception area 11.

  The organization of the connection means by screwing type allows an operation of the junction means 5 that includes the drill 1 to associate an accessory 17 in substitution of the sheath 2, as shown in Fig.8. Such an accessory 17, in particular bit, can be rotated by the drill 1 from a cooperation of the junction means 5 of the drill 1 with cooperating mounting means 18 that includes the accessory 17. When the accessory 17 is mounted on the drill, the cooperation between the mounting means 18 and the junction means 5 is maintained despite the axial abutment of the accessory 17 by its proximal end face 23 against the proximal abutment means 7. It emerges that the accessory 17 can be rotated by the drill bit 1 being axially pressed against the proximal stop means 7.

  According to a variant not shown, the tip of the drill 1 is likely to be flush with the distal outlet of the accessory 17, including the drill bit. However, and according to the illustrated embodiment, the drill bit 1 is able to emerge out of the distal opening of the bit 17, to constitute a guide member for the latter during its penetration into the bone material. It will be noted that in the case where the proximal abutment means 7 is mounted axially movably along the drill bit 1, this mobility constitutes means for adjusting the distance D4 of emergence of the drill bit 1 out of the bit 17.

  More particularly, the drill bit 1 constitutes a device for guiding the drill bit 17 during its penetration into the bone material. Such a bit 17 consists of a tool 19 of cylindrical shape consisting generally of a wall of revolution delimiting an axial recess 20 for housing a core ossei ',. ^ To take. The proximal outlet of this recess 20 can be exploited to remove the removed bone core. The joining means 5 that includes the drill bit 1 are used to cooperate with removable mounting means 18 of the tool 19 on the drill bit 1. In the exemplary embodiment illustrated, these mounting means 18 comprise more particularly a barrel 21 arranged at the proximal end of the tool 19 which receives the externally threaded cylinder 16 constituting the joining means 5 that includes the drill 1. The drill 1 emerging at the distal end of the tool 19, it is operated to form a pre-hole in the bone material and a guide member of the tool 19 during the coring operation.

  It emerges that the drill bit 1 can be used in a first é + ^^ e being associated with the protective sheath 2 to practice a pre-hole in the bone material. This pre-hole being made, the sheath 2 is removed and is replaced by the tool 19 constituting the bit 17 to practice in a second step a collection of a cohesive bone core. The trephine is guided in its stroke inside the bone mass by the drill, whose distal tip is a guide finger introduced into the pre-hole prior to contacting the trephine against the bone material. .

  In FIGS. 5 to 7, the cooperating reversible junction means 5,6 respectively formed on the drill bit 1 and on the sheath 2 are of the type with elastic deformation of the fastener member 12. On the example of illustrated embodiment, the drill 1 comprises in the cooperation zone 10 a smooth cylinder 16, whose proximal end face forms a shoulder constituting the distal abutment means 8. The sheath 2 is provided with a deformable assembly member 12, as constituted by a radially deformable sleeve. In the exemplary embodiment illustrated, this sleeve is attached to the proximal end of the sheath 2, by narrow interlocking preferably completed with a seal. This sleeve is composed of fins 22 radially deformable, which are pushed radially outwardly during the passage of the assembly member 12 along the smooth cylinder 16 that includes the drill 1, as shown in FIG. 6. The assembly member 12 having crossed the cylinder 16 smooth and being housed in the area d ... _aption 11, the fins 22 spontaneously resume their natural initial position, taking axially against the support against distal abutment 8 that includes the drill 1, as shown in Fig.7. Preferably, the fins 22 comprise at their distal end a shoe arranged as a push ramp against the fins 22 to promote the elastic deformation of the assembly member 12 during its introduction and its voluntary withdrawal by the practitioner. 30

Claims (10)

claims   1.- Surgical instrument to drill of the type consisting of a drill (1) equipped with a sheath (2) coaxial protection, the drill (1) having at its distal end a cutting portion (4) and at its proximal end a gripping tail (3) by a drill driving tool (1) in rotation, the sheath (2) being arranged in a cylinder (13) remotely surrounding the drill (1) which emerges at its distal end when are assembled to each other, the drill (1) and the sheath (2) being provided with means (5,6) cooperating reversibly junction between them which are respectively formed in an assembly zone (9) of drill (1), interposed between its cutting portion (4) and its gripping tail (3), and on an assembly member (12) that comprises the sheath (2), means (7,8) of axial abutment antagonist being formed on the drill (1) to retain axially between them the sheath (2) installed on the drill (1), these axial abutment means being composed of a proximal abutment means (7) preventing axial displacement of the sheath (2) towards the grasping tail (3) and a distal unambiguous abutment means (8) preventing spontaneous axial displacement of the sheath (2) towards the end of the distal end of the drill (1), characterized in that the assembly zone (9) of the drill (1) is composed of a first cooperation zone (10) of the joining means (5, 6) the drill (1) and the sheath (2) between them, which is distinctly axially extended towards the gripping tail (3) by a second receiving zone (11) in free rotation of the fastener (12) the sheath (2), which is delimited between the proximal stop means (7) and the distal stop means (8) that comprises the drill (1).   2. Surgical instrument according to claim 1, characterized in that the assembly zone (9) of the drill (1) comprises successively from its cutting portion (4) towards the gripping tail (3) the zone of cooperation (10). ), the distal abutment means (8), the receiving zone (11) and the proximal abutment means (7). 15   3. Surgical instrument according to any one of the preceding claims, characterized in that the proximal end of the junction means (5) that comprises the drill (1) is constitutive of the distal abutment means (8).   4. Surgical instrument according to claim 3, characterized in that the proximal abutment means (7) being fixed, the axial dimension (D1) of the axial extension of the junction means (6) that comprises the sheath (2). is at most equal to the axial extension (D2) of the receiving zone (11).   5. Surgical instrument according to claim 4, characterized in that the sheath (2) is part of a first set of sheaths (2) of different lengths, for the same given axial extension of the junction means (6) that comprises the sheaths (2) of this first game.   6. Surgical instrument according to any one of claims 1 to 3, characterized in that the axial position along the drill (1) of at least one of the abutment means (7,8) is adjustable. 20   7. Surgical instrument according to claim 6, characterized in that the sheath (2) is part of a second set of sheaths (2) of the same length (L1) for axial extensions (D2) different from the connecting means ( 6) that comprises the sheaths (2) of this second set.   8. Surgical instrument according to any one of the preceding claims, characterized in that it comprises at least one accessory (17) replacing the sheath (2), which is provided with mounting means (18) cooperating with the means junction (5) of the drill (1) for their assembly in rotation with each other. 10 15 30   9. Surgical instrument according to any one of the preceding claims, characterized in that the cooperating joining means (5,6) are of the screw type.   10. Surgical instrument according to any one of claims 1 to 8, characterized in that the cooperating joining means (5,6) are of the elastic deformation type of the assembly member (12).