FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a screwing device, a kit and an assembly for the insertion and positioning of a bone anchor in a bone of a patient, wherein the bone anchor is configured for guiding a marker of a navigation system within said bone of the patient.

[0002] The disclosure relates to the field of surgical tools adapted for use in combination with computer-assisted technologies used by surgeons to guide or "navigate” in real time within the confines of the patient body, notably, skull or vertebral column, during surgery. The disclosure also relates to the field of surgical instrumentation for targeted administration of a drug via catheters, wherein a targeted region of the body may notably the brain.

BACKGROUND OF THE DISCLOSURE

[0003] For several years, gene therapy for neurological diseases has experienced intensive research growth. Beneficial results in several clinical studies, together with improved vector technology have advanced gene therapy for the central nervous system (CNS) in a new era of development. Although most initial strategies have focused on orphan genetic diseases, such as lysosomal storage diseases, more complex and widespread conditions like Alzheimer's disease, Parkinson's disease, epilepsy, or chronic pain are increasingly targeted for gene therapy. Increasing numbers of applications and patients to be treated will require improvement and simplification of gene therapy protocols to make them accessible to the largest number of affected people. Although vectors and manufacturing are a major field of academic research and industrial development, there is a growing need to improve, standardize, and simplify delivery procedures. Delivery procedures are the major issue for CNS therapies in general, and particularly for gene therapy. [0004] Gene therapy products can be delivered by various routes of administration, using either ex vivo or in vivo strategies. Although not limited thereto, the present invention finds advantageous application in the in vivo gene therapy which requires direct introduction of the vector (carrying the therapeutic gene) into the patient by local administration. Indeed, local administration of low doses of vector limits biodistribution and the risk of immunogenicity or toxicity due to adeno-associated-virus (AAV) vectors capsid or expression of the transgene. In this context, it is therefore of the greatest importance to be able to correctly target the desired region of interest for drug delivery. Among different techniques available, catheters may be used for the delivery of the therapeutics agents, for example by intrathecal lumbar administration, intracisternal administration or intraparenchymal administration. For example, in the case of intraparenchymal administration, in order to correctly introduce the catheters into the brain tissues, a hollow bone anchor may be previously screwed into the skull the patient so as to be used as inlet through which the catheter is inserted. Neuronavigation or stereotactic technics are used in order to help the surgeon during the positioning of the bone anchor.

[0005] The invention also applies to any other kind of treatment or therapy requiring an accurate positioning of a bone anchor. For example, the invention applies to therapy involving infusion of RNA or any protein or even drugs in the brain through catheters guided by accurately placed catheter.

[0006] In this context, there is a need for developing tools and procedures allowing to correctly place the bone anchors within the right position on the skull and with the correct orientation of the hollow passage that will guide the catheter in the brain. Moreover, those tools and procedures should be designed to benefit from the intraoperative information provided by the neuronavigation or stereotactic technics.

SUMMARY

To this end, according to a first aspect, the present disclosure relates to a screwing device for insertion and positioning of a bone anchor in a bone of a patient wherein the bone anchor is configured for guiding a marker of a navigation system within said bone of the patient, the marker comprising a head and a rod extending from the head along a marker axis, the marker being configured to enable a detection of an orientation of the marker axis by a navigation system. The bone anchor has a proximal portion and a distal portion, and comprises a first axial passage extending between said proximal portion and said distal portion for receiving the lead-type member, said distal portion comprising a fixation portion for being fixedly positioned in the bone, and said proximal portion comprising a force-receiving structure configured to cooperate reversibly with the screwing device to receive applied torque therefrom. The screwing device has a proximal portion and a distal portion, said screwing device comprising a second axial passage between said proximal portion and said distal portion, said distal portion comprising a force-transfer structure configured to cooperate reversibly with the force-receiving structure of the bone anchor in order to transfer an applied torque thereto, wherein an axis of the second axial passage is configured to coincide with an axis of the first axial passage when the screwing device cooperates with the bone anchor for receiving the rod the marker through the first and second axial passages of bone anchor and the screwing device, wherein the screwing device comprises a positioning arrangement configured to maintain the marker in a fixed position with respect to the screwing device when the rod of the marker is inserted in the second axial passage.

[0007] The screwing device hence forms an interface enabling a complete and fixed connection between the bone anchor and the marker of the navigation system to ensure a reliable and accurate placement of the bone anchor. Indeed, thanks to such features, the marker (such as an electromagnetic or optic marker), designed to be detected by an appropriate detection or navigation system to provide an orientation in space (and, preferably, also a position) of the respective marker axis AM, can be inserted through the first and second axial passages of the bone anchor and the screwing device and held in position simultaneously when said bone anchor and screwing device are reversibly engaged with each other. As a result, an accurate determination of the orientation of the first axial passage is available. By tracking the orientation of the marker axis AM, an operator is able to make sure that, during insertion of the bone anchor in a tissue of the patient, the orientation of the first axial passage (and, therefore, the orientation of the bone anchor) is consistent with a corresponding desired orientation. [0008] According to other advantageous aspects of the invention, the kit includes one or more of the following features, taken alone or in any possible combination:

- the positioning arrangement is arranged at a proximal extremity of the proximal portion of the screwing device,

- the positioning arrangement comprises a resting surface arranged so that a transverse surface of the head of the marker rests on said resting surface when the rod of the marker is inserted in the second axial passage, and a contact surface arranged to contact a lateral surface of the marker when the rod of the marker is inserted in the second axial passage,

- the positioning arrangement comprises an imprint having a complementary shape to at least a lower portion of the head of the marker from which the rod extends,

- the second axial passage has an internal diameter configured to prevent radial motion of the rod of the marker, and a length configured so that an end of the rod of the marker is flush with an end opening of the bone anchor when the screwing device cooperates with the bone anchor,

- the screwing device comprises at its distal portion a shaft portion and at its proximal portion a handle portion;

- the force-transfer structure of the screwing device includes at least one protrusion having a complementary shape to at least one cavity of the force-receiving structure;

- the force-transfer structure of the screwing device includes at least one cavity having a complementary shape at least one protrusion of the force-receiving structure.

[0009] According to a second aspect, the disclosure relates to a kit for the insertion and positioning of a bone anchor in a bone of a patient wherein the bone anchor is configured for guiding a marker of a navigation system within said bone of the patient, the marker comprising a head and a rod extending from the head along a marker axis, the marker being configured to enable a detection of an orientation of the marker axis by a navigation system, said kit comprising;

- a screwing device according to any of claims 1 to 8, and

- at least one bone anchor having a proximal portion and a distal portion, said bone anchor comprising a first axial passage extending between said proximal portion and said distal portion for receiving the lead-type member, said distal portion comprising a fixation portion for being fixedly positioned in the bone, and said proximal portion comprising a force-receiving structure configured to cooperate reversibly with the screwing device to receive applied torque therefrom; wherein axes of the first and second axial passages are configured to coincide when the screwing device cooperates with the bone anchor for receiving the rod of the marker through the first and second axial passages of bone anchor and the screwing device.

[0010] The first axial passage may have an internal diameter configured to prevent radial motion of the rod of the marker, and a length configured so that a distal end of the rod of the marker is flush with a distal opened end of the bone anchor when the screwing device cooperates with the bone anchor.

[0011] The fixation portion comprises external threading adapted to advance the bone anchor into the bone.

[0012] The force-receiving structure of the bone anchor comprises at least two lobes.

[0013] The force-receiving structure of the bone anchor comprises at least one notch.

[0014] According to a third aspect, the disclosure relates to an assembly comprising:

- the kit as defined previously, and

- a marker of a navigation system, the marker comprising a head and a rod extending from the head along a marker axis, the marker being configured to enable a detection of an orientation of the marker axis by a navigation system.

[0015] According to a fourth aspect, the disclosure relates to a method of mounting an assembly as defined previously, comprising steps consisting in:

- assembling the screwing device and the bone anchor, the force-transfer structure of the screwing device cooperating with the force-receiving structure of the bone anchor and axes of the first and second axial passages coinciding,

- mounting the marker on the screwing device, the rod being inserted in the first and second axial passages, and the marker being maintained in a fixed position with respect to the screwing device by the positioning arrangement of the screwing device. [0016] According to another aspect, the disclosure proposes a method of inserting a bone anchor in a bone of a patient comprising steps consisting in:

- implementing the method of mounting the assembly as defined previously,

- mounting the marker on the screwing device, the rod being inserted in the first and second axial passages, and the marker being maintained in a fixed position with respect to the screwing device by the positioning arrangement of the screwing device,

- putting the distal portion in contact with the bone and applying a torque to the screwing device, the fixation portion of the bone anchor penetrating the bone,

- monitoring in real time the orientation of the marker axis by a navigation system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a perspective view of an assembly comprising a kit according to a first embodiment of the invention, and a marker of a navigation system according to a first example of implementation, the kit comprising a bone anchor and a screwing device, the bone anchor having a force-receiving structure and the screwing device having a force-transfer structure to transfer a torque from the screwing device to the bone anchor.

[0018] Figure ! is a perspective view of the assembly of figure 1 as the screwing device is mounted on the bone anchor and the marker is mounted on the screwing device,

[0019] Figure 3 is a view in section along the orientation referenced III-III on figure 2 of the assembly of figure 2 in a mounted state, a rod of the marker being arranged within first and second axial passages of the screwing device and the bone anchor, and a head of the marker being arranged within an imprint of a positioning arrangement of the screwing device.

[0020] Figure 4 is an enlarged view of detail referenced IV on figure 3.

[0021] Figure 5 is an enlarged view of detail referenced V on figure 3. [0022] Figure 6 is a perspective view of an assembly comprising a kit according to a second embodiment of the invention, and a marker of a navigation system according to a second example of implementation.

[0023] Figure 7 is a view in section along the orientation referenced VII- VII on figure 6 of the assembly of figure 6 in a mounted state,

[0024] Figure 8 is an enlarged view in perspective of a variant of the kit according to the second embodiment of figure 6.

[0025] Figures 9 and 10 are enlarged views in perspective and Figure 11 is a view in longitudinal section of an assembly comprising a kit according to a third embodiment of the invention.

[0026] Figure 12 is a schematic view of a method of inserting a bone anchor in a bone of a patient implementing the assembly of figure 1.

DETAILED DESCRIPTION

[0027] An assembly (2) according to the invention is shown on figures 1 to 11.

[0028] The assembly (2) is configured to allow an operator 3 to insert and position a bone anchor 10 in a bone 5 of a patient, for instance a skull of the patient.

[0029] More precisely, the assembly 2 comprises a kit 1 including said bone anchor 10, as well as a screwing device 20. It should be noted that the kit 1 may include more than one bone anchor 10, of the same of different kind, as the same screwing device 20 may be used to insert and position several bone anchors 10.

[0030] The bone anchor 10 is configured to guide a marker M of a navigation system 4 within the bone 5. More precisely, the bone anchor 10 is configured to guide said marker M once the bone anchor 10 has been fixedly attached to the bone 5.

[0031] The marker M has a generally cylindrical and elongated shape extending along a marker axis AM. More specifically, the marker M comprises a head 30 and a rod 35 extending from a lower portion 31 of the head 30 along the marker axis AM. The marker M, of any suitable kind such as an electromechanical or optic probe, is configured to enable a detection of an orientation and possibly the position of the marker axis AM by navigation system 4.

[0032] The rod 35 is cylindrical along the marker axis AM, for example of circular crosssection. The rod 35 has a length measured along the marker axis AM between opposite proximal 36 and distal 37 ends.

[0033] The head 30 has a bottom surface 32, to which the proximal end 36 of the rod 35 is attached, extending transversely to the marker axis AM. The head 35 also has a lateral surface 33 extending around the marker axis AM from the bottom surface 32 to a top surface 34. The bottom surface 32 has transverse dimensions that are larger than that, in particular an external diameter, of the rod 35 so as to protrude from the rod 35.

[0034] In a first example of implementation represented in figures 1 to 5, the head 30 is cylindrical along the marker axis AM and of triangular cross-section. The bottom surface 32 as well as the top surface 34 are hence triangular. In a second example of implementation represented in figures 6 to 10, the head 30 is cylindrical of circular crosssection along an axis perpendicular to the marker axis AM. The bottom 32 and top 34 surfaces are hence arcuate and the lateral surface 33 includes opposite flat surface portions and arcuate surface portions.

[0035] The screwing device 20 is configured to maintain the bone anchor 10 in a predetermined orientation during its insertion in a bone 5. The screwing device 20 is further configured to apply torque to the bone anchor 10, thereby allowing its insertion in the bone 5.

[0036] A more precise description of each of the bone anchor 10 and the screwing device 20 will now be provided.

[0037] Bone anchor 10

[0038] As represented in figures 3, 5, 6 and 7, the bone anchor 10 has a first axial passage 11 extending along an anchor axis AA between a proximal portion 10a and a distal portion 10b of the bone anchor 10. The bone anchor 10 further includes a force-receiving structure 13.

[0039] First axial passage 11

[0040] As stated above, the first axial passage 11 extends between the proximal portion 10a and the distal portion 10b of the bone anchor 10. More precisely, the first axial passage 11 of the bone anchor 10 is a through passage extending between proximal I la and distal 1 lb opened ends opening respectively in the proximal portion 10a and the distal portion 10b of the bone anchor 10. Advantageously, the first axial passage 11 is straight.

[0041] Moreover, the first axial passage 11 is configured to receive at least a part of the rod 35 of the marker M. In particular, an internal diameter of the first axial passage 11 is suitable for the insertion of the marker M in said first axial passage 11. Preferably, the internal diameter of the first axial passage 11 is chosen, with respect to the external diameter of the marker M, to allow insertion of the rod of the marker M in the first axial passage 11, while preventing radial motion of the marker M in said first axial passage 11. Alternatively or in a complementary manner, the first axial passage 11 could also present any other suitable cross-section than circular adapted to a non-circular cross-section of the rod 35 of the marker M.

[0042] Force receiving structure 13

[0043] The force-receiving structure 13 is included in or located at the proximal portion 10a of the bone anchor 10.

[0044] The force-receiving structure 13 is configured to cooperate reversibly with the screwing device 20 to receive applied torque therefrom, thus causing penetration of the distal portion 10b of the bone anchor 10 in the bone 5. A more precise description of the insertion of the bone anchor 10 by means of the screwing device 20 will be provided below.

[0045] Advantageously, the force-receiving structure 13 of the bone anchor 10 includes at least one protrusion or at least one recess, aimed at cooperating with a corresponding force-transfer structure 23 of the screwing device 20. Preferably, the force-transfer structure 23 has a shape that is complementary to that of the protrusion or the recess of the force-receiving structure 13. In other words, one of the force-receiving structure 13 of the bone anchor 10 and the force-transfer structure 23 of the screwing device 20 includes at least one protrusion, and, for each protrusion, the other one of the forcereceiving structure 13 and the force-transfer structure 23 comprises a corresponding cavity having a complementary shape to that of said protrusion.

[0046] Such feature is advantageous, as it ensures reduced play between the forcereceiving structure 13 and the force-transfer structure 23, thereby allowing an efficient force transfer from the screwing device 20 to the bone anchor 10.

[0047] For instance, in a first embodiment shown in figures 1 to 5, the force-receiving structure 13 of the bone anchor 10 presents an external surface with a polygonal, in particular hexagonal, cross-section resulting in six regularly spaced protrusions extending radially with respect to the anchor axis AA. Such force-receiving structure 13 of the bone anchor 10 is intended to cooperate with a force-transfer structure 23 presenting a complementary shape, namely an internal surface with a corresponding polygonal, in particular hexagonal, cross-section resulting in six regularly spaced recesses extending radially with respect to a screwing device axis As.

[0048] In a second embodiment shown in figures 6, 7 and 8, the force-receiving structure 13 of the bone anchor 10 comprises lobes 13o, for example two lobes as in figures 6 and 7 or three lobes in the variant of figure 8. In this case, each lobe 13o forms a protrusion as described previously.

[0049] As will be shown later, in this second embodiment, the force-transfer structure 23 includes recesses (visible in figures 6, 7 and 8) to interlock with said lobes 13o.

[0050] The lobes 13o extend outwards radially, that is to say away from the first axial passage 11. Nonetheless, the lobes 13o may extend in other directions. For instance, the lobes 13o may extend in a direction parallel to that of the first axial passage 11.

[0051] Moreover, the lobes 13o are arranged circumferentially in a regular fashion, namely at an angle of 180° with each other in figures 6 and 7 with two lobes 13o, and at an angle of 120° with each other in the variant of figure 8 with three lobes 13o. Nonetheless, other arrangements can be envisaged where said angles are not equal to each other.

[0052] According to a third embodiment shown in figures 9, 10 and 11, the forcereceiving structure 13 of the bone anchor 10 comprises at least one notch 13n. In this case, each notch 13n forms a recess as described previously.

[0053] As will be shown later, in this embodiment, the force-transfer structure 23 includes protrusions (shown on figure 10) to interlock with said notches 13n.

[0054] Alternatively, the force-receiving structure 13 of the bone anchor 10 may present an external thread configured to cooperate with an internal thread of the force-transfer structure 23 of the screwing device 20. These provisions ensure a tightening of the connection between the bone anchor 10 and the screwing device 20 by the torque applied to the screwing device 20 to insert the bone anchor 10 in the bone 5.

[0055] Fixation portion 12

[0056] Preferably, the bone anchor 10 also comprises a fixation portion 12.

[0057] The fixation portion 12 is located at the distal portion 10b of the bone anchor 10. The fixation portion 12 is configured for fixedly positioning the bone anchor 10 in the bone 5. This ensures that, once inserted, inopportune movement of the bone anchor 10 is prevented.

[0058] Advantageously, the fixation portion 12 comprises external threading configured to advance the bone anchor 10 into the bone 5.

[0059] For instance, the distal portion 10b has a tapered shape extending along a corresponding first longitudinal axis (preferably along the anchor axis AA), in a direction from the proximal portion 10a to the distal portion 10b. In this case, the external threading is threaded on an external surface of the tapered shape, about said first longitudinal axis. [0060] Furthermore, in this case, the first axial passage 11 preferably extends along said longitudinal direction of the tapered shape.

[0061] Screwing device 20

[0062] As shown on the figures, the screwing device 20 has a general elongated shape. Advantageously, for enhanced ease of use by the operator 3, the screwing device 20 comprises a shaft portion at its distal portion 20b, and a handle portion at its proximal portion 20a.

[0063] The screwing device 20 includes a second axial passage 21 extending along a screwing device axis As between the proximal portion 20a and the distal portion 20b. The screwing device 20 further includes the aforementioned force-transfer structure 23.

[0064] Second axial passage 21

[0065] As stated above, the second axial passage 21 extends between the proximal portion 20a and the distal portion 20b of the screwing device 20. More precisely, the second axial passage 21 of the screwing device 20 is a through passage extending between the proximal portion 20a and the distal portion 20b of the screwing device 20. Advantageously, the second axial passage 21 is straight.

[0066] Moreover, the second axial passage 21 is configured to receive at least a part of the rod 35 of the marker M. In particular, an internal diameter of the second axial passage 21 is suitable for the insertion of the rod 35 of the marker M in said second axial passage 21. Preferably, the internal diameter of the second axial passage 21 is chosen, with respect to the external diameter of the marker M, to allow insertion of the rod of the marker M in the second axial passage 21, while preventing radial motion of the marker M in said second axial passage 21. Alternatively or in a complementary manner, the second axial passage 21 could also present any other suitable cross-section than circular adapted to a non-circular cross-section of the rod 35 of the marker M.

[0067] Furthermore, the screwing device 20 and the bone anchor 10 are configured so that the anchor axis AA of the first axial passage 11 and the screwing device axis As of the second axial passage 21 coincide when the screwing device 20 reversibly cooperates with the bone anchor 10, that is to say when the force-transfer structure 23 is engaged with the force-receiving structure 13. Therefore, the assembly comprising the bone anchor 10 in reversible cooperation with the screwing device 20 is adapted to simultaneously receive the rod 35 of the marker M through the first axial passage 11 of the bone anchor 10 and the second axial passage 21 of the screwing device 20. As shown in figure 5, the first 11 and second 2 axial passages have a length configured so that the distal end 37 of the rod 35 of the marker M is flush with the distal opened end 1 lb of the bone anchor 10 when the screwing device 20 cooperates with the bone anchor 10.

[0068] Force-transfer structure 23

[0069] The force-transfer structure 23 is included in the distal portion 20b of the screwing device 20. As mentioned previously, the force-transfer structure 23 is configured to cooperate reversibly with the force-receiving structure 13 of the bone anchor 10 in order to transfer an applied torque thereto, thereby allowing penetration of the distal portion 10b of the bone anchor 10 in a tissue.

[0070] Advantageously, the force-transfer structure 23 of the screwing device includes at least one protrusion or at least one recess, aimed at cooperating with a corresponding recess or protrusion, respectively, of the bone anchor 10.

[0071] For instance, in the first embodiment shown in figures 1 to 5, the force-transfer structure 23 presents a shape complementary to that of the force-receiving structure 13, namely an internal surface with a hexagonal cross-section resulting in six regularly spaced recesses extending radially with respect to a screwing device axis As.

[0072] In the second embodiment of figures 6, 7 and 8, for each lobe 13o of the bone anchor 10, the force-transfer structure 23 comprises two axial teeth extending along the screwing device axis As in a direction from the proximal portion 20a to the distal portion 20b of the screwing device 20, each tooth lying in a respective radial plane of the screwing device 20. Moreover, said teeth define a radial gap between them, each lobe 13o engaging in a corresponding radial gap when the screwing device 20 cooperates with the bone anchor 10. As a result, when operating the screwing device 20, the torque applied by the operator 3 to the screwing device 20 translates into a tangential force applied by said teeth to the lobes 13o, thereby entailing spinning of the bone anchor 10 about the anchor axis AA and its insertion in the bone 5 of the patient.

[0073] In the third embodiment of figures 9, 10 and 114, for each notch 13n of the bone anchor 10, the force-transfer structure 23 comprises a protrusion extending along the screwing device axis As in a direction from the proximal portion 20a to the distal portion 20b of the screwing device 20. Each protrusion is configured to engage in the respective notch 13n when the screwing device 20 cooperates with the bone anchor 10, that is to say when the force-transfer structure 23 is engaged with the force-receiving structure 13. As a result, when operating the screwing device 20, the torque applied by the operator 3 to the screwing device 20 translates into a tangential force applied by each protrusion to the walls of the corresponding notch 13n, which results in the insertion of the distal portion 10b of the bone anchor 10 in the tissue of the patient.

[0074] Alternatively, as mentioned previously, the force-transfer structure 23 of the screwing device 20 may comprise an internal thread configured to cooperate with an external thread of the force-receiving structure 13.

[0075] Positioning arrangement 40

[0076] As apparent from figures 1 to 3, 5 and 7, the screwing device 20 further comprises a positioning arrangement 40 configured to maintain the marker M in a fixed position with respect to the screwing device 20 when the rod 35 of the marker M is inserted in the second axial passage 21.

[0077] In the represented embodiments, the positioning arrangement is arranged within a transverse surface at a proximal extremity 41 of the proximal portion 20a of the screwing device 20, in the form of an imprint 42 having a complementary shape to at least the lower portion 31 of the head 30 of the marker M. Hence, the positioning arrangement 40 comprises a resting surface 43 on which the bottom surface 32 of the head 30 of the marker M rests when the rod 35 is inserted in the second axial passage 21. The positioning arrangement 40 also comprises a contact surface 44 arranged to contact the lateral surface 33 of the marker M when the rod 35 is inserted in the second axial passage 21. [0078] Specifically, in the first embodiment of figures 1 to 5, the contact surface 44 of the imprint 42 has a triangular cross-section, and the resting surface 43 is triangular and extends perpendicular to the screwing device axis As. In the second embodiment of figures 6 and 7, the contact surface 44 of the imprint 42 has flat surfaces facing each other and an arcuate resting surface 43.

[0079] Alternatively or in a complementary manner, the aforementioned first 11 and second 21 axial passages adapted to the cross-section of the rod 35 of the marker M in terms of shape other than circular could be part of the positioning arrangement 40.

[0080] Set-up and operation

[0081] Set-up of the bone anchor 10 will now be disclosed.

[0082] Each bone anchor 10 is associated to a corresponding predetermined desired location in the bone 5 of the patient. Furthermore, each bone anchor 10 is associated to a predetermined desired orientation in space (/'.<?., a direction of the respective first axial passage 11).

[0083] A given bone anchor 10 is brought to cooperate reversibly with the screwing device 20. More precisely, the force-receiving structure 13 of the bone anchor 10 is reversibly engaged with the force-transfer structure 23 of the screwing device 20. As a result, the axis of the first axial passage 11 and the axis of the second axial passage 21 coincide.

[0084] The rod 35 of the marker M is inserted from the proximal extremity 41 of the screwing device 20, through the first 11 and second 21 axial passages of the bone anchor 10 and the screwing device 20 until the head 30 reaches the proximal extremity 41 of the screwing device 20, as shown in figures 3 and 7. The head 30 of the marker M is placed in the imprint 42 so as to be held in the fixed position with respect to the screwing device 20 by the resting surface 43 and the contact surface 44 of the positioning arrangement 40 of the screwing device 20. The distal end 27 of the rod 35 of the marker M is arranged at the level of the distal opened end 1 lb of the bone anchor 10. [0085] Once mounted as described previously, the assembly can be implemented in a method of inserting the bone anchor 10 in the bone 5, for example the skull, of a patient as represented in figure 12.

[0086] In particular, the distal portion 12 of the bone anchor 10 is put in contact with the bone 5 and a torque applied to the screwing device 20 by the operator 3, especially a surgeon, is transmitted to the bone anchor 10.

[0087] The marker M can be detected by the appropriate navigation system 4 to determine in real time the orientation and possibly also a position of the marker axis AM. As the bone anchor 10 penetrates the bone 5, the orientation and possibly the position of the marker axis AM are monitored by the navigation system 4 and displayed or otherwise controlled in real time. As a result, the marker M being fixedly arranged within the screwing device 20 and the bone anchor 10, an accurate determination of the orientation and possibly the position of the bone anchor 10 and hence of its first axial passage 11 is available.

[0088] By tracking the orientation of the marker axis AM, the operator 3 is able to make sure that, during insertion of the bone anchor 10 in the bone 5 of the patient, the orientation of the first axial passage 11 (z.e., the orientation of the bone anchor 10) is consistent with the respective desired orientation.