WO2005000124A2

WO2005000124A2 - Device for examining the characteristics of a bone

Info

Publication number: WO2005000124A2
Application number: PCT/IB2004/002481
Authority: WO
Inventors: Harwant Singh
Original assignee: Medicrea International
Priority date: 2003-06-27
Filing date: 2004-06-24
Publication date: 2005-01-06
Also published as: WO2005000124A3

Abstract

This device includes an elongated support (1) including an ultrasound transceiver, a unit for processing the ultrasounds reflected by the bony wall, and a display unit enabling to visualise the position of the elongated support (1) inside the bone during boring. According to the invention, the elongated support (1) includes, at its distal end, at least a series (6) of aligned ultrasound transceivers, transmitting according to directions substantially perpendicular to the longitudinal axis of the elongated support (1).

Description

DEVICE FOR EXAMINING THE CHARACTERISTICS OF A BONE This patent application claims the priorities to : - FR 03 07775, filed on June 27, 2003 ; - US Provisional application N° 60/490,517, filed on July 29, 2003. The present invention relates to a device for examining the characteristics of a bone. The invention is in particular intended to be used for boring a pedicle in a vertebra in order to insert in this pedicle an anchoring means to the vertebra for a given piece of equipment, notably a screw for anchoring vertebral osteosynthesis equipment to the vertebra. Boring a bone is generally carried out blindly, which induces a risk that this boring is carried out poorly. In the particular case of boring the pedicle in a vertebra, because of the smaller diameter of this pedicle, the boring must be altered substantially according to the axis of the pedicle with the risk of damaging this pedicle if the cortical is attacked. As far as possible, the boring instrument should not emerge from the inner or "medial" side, with the risk of reaching into the spinal cord, nor from the outer side, with the risk of reaching into the nervous roots of the rachidial nerves. The boring of a vertebral pedicle is therefore a very tricky operation, largely relying on the practitioner's experience and which depends on the patient's anatomy, which may vary substantially from one patient to the other. This boring is currently realised most frequently manually, by means of a tapered instrument which may be engaged into the pedicle and including a distal end which is either sharp or flattened into a spatula. This instrument may be poked into the cancellous bone and enables to push this cancellous bone aside when the latter is imparted partial rotational movements. For easier insertion of a pedicular screw, it has been contemplated to perform continuous X-ray radiography in order to obtain pictures enabling visualisation of the pedicle and the progress of the boring instrument. The shortcoming of this method is the emission of a significant amount of radiation, which is not desirable, neither for the patient nor for the medical staff, and the provision of limited visualisation only of the position of the boring instrument with respect to the pedicle (in two dimensions). It has also been contemplated to use so-called "navigation" computer systems, calculating co-ordinates in space from a reference point and thereby facilitating the guiding of the boring instrument in the right direction (in three dimensions). The shortcoming of such systems is however their very high costs and a longer duration of intervention. Moreover, they require very accurate determination of said reference point, which implies that they should not be moved at all after said determination, failing which the co-ordinates calculated by the system will not be accurate. The document US 2002/0120197 describes notably a device for drilling a pedicle in a vertebra, including a drilling bit fitted with an ultrasound transducer, a unit for processing the ultrasounds reflected by the bony wall, and a display unit enabling to visualise the position of the drilling bit inside the vertebral pedicle. The use of a drilling bit to drill a vertebral pedicle is assessed by the applicant as particularly dangerous, taking into account the neighbouring presence of the spinal cord and of the roots of the rachidial nerves. Moreover, the signals transmitted by the single transducer according to this prior document, transmitting according to a direction tilted forward by 30 to

60 degrees and subjected to the rotation of the drilling bit, appears unable to provide perfectly reliable results in terms of analysis accuracy of the bony zone affected by the boring. The present invention aims at remedying all the shortcomings of the prior techniques. The device affected by said invention includes, in a manner known in itself, an elongated support including an ultrasound transceiver, a unit for processing the ultrasounds reflected by the bony wall, and a display unit enabling to visualise the position of the elongated support inside the bone during boring. According to the invention, the elongated support includes, at its distal end, at least a series of aligned ultrasound transceivers, transmitting according to directions substantially perpendicular to the longitudinal axis of the elongated support. Ultrasounds are thus transmitted according to a direction substantially perpendicular to the longitudinal axis of the elongated support, and therefore substantially perpendicular to the bony wall under examination, which enables reflection of the ultrasounds under the best conditions, and the series (one or several series) of aligned ultrasound transceivers enable examination of the bony wall over an elongated zone, which enables cross-referencing of the signals received by each of the transceivers and therefore to make reliable the determination of the distance between the elongated support and the bony wall. The device according to the invention thus enables to determine the characteristics of the bone around a boring operated in this bone and to ensure that the bony wall has not been bored when proceeding to said boring operation. In the case of a vertebral pedicle, the device according to the invention also enables to determine the position of the boring with respect to the outer wall of the vertebral pedicle, and, if required, to demonstrate that this boring has not emerged from the side of the spinal cord nor from the side of the roots of the rachidial nerves. The elongated support may include only one series of ultrasound transceivers, or two series of ultrasound transceivers transmitting in directions diametrically opposed. It is thus not necessary to rotate the elongated support by 360 degrees to obtain a picture of the distance of the bony wall over the whole circumference of the bone examined, but only over 180 degrees to obtain this same result. In such a case, the display unit is advantageously designed to display the pictures produced by both series of ultrasound transceivers below one another, by reversing the picture produced by the second series of ultrasound transceivers. This display unit thus enables to visualise simultaneously both zones diametrically opposed of the bony wall under examination with respect to a reference axis formed by the adjoining edges of both pictures, and therefore to visualise immediately the distance of each of these zones with respect to this reference axis; it is thus easy to determine the correct boring, wherein both bony zones lie substantially at equal distance from said reference axis. Said elongated support may serve only for the examination of the characteristics of the bone and may be composed of a simple rod employed for inserting the series of transceivers into the bone, this instrument being used jointly or not with a conventional boring instrument. Preferably, however, said elongated support comprises a distal end shaped in order to realise a boring in of the cancellous bone. It is thus possible to perform the boring of the cancellous bone by means of said elongated support while controlling simultaneously the quality of the bone wherein this boring is conducted. Said distal end may be shaped so as not to cut into the cancellous bone, but to move aside and/or to compact laterally said cancellous bone, thereby compressing and compacting the cancellous bone round said support. This distal end may be in the form of so-called "square" tip, i.e. in the form of a pyramid with four lateral faces; it is preferably in the form of a flattened spatula, such as a "Steffee spatula". This compressed cancellous bone, when healthy, advantageously provides a picture which is particularly loud and clear. When the distal end of the elongated support has a flattened shape, each series of ultrasound transceivers may extend at the medial zone of a flattened face of this distal end or at the edge of this distal end. Alternately, particularly when the elongated support comprises a distal end enabling to bore the cancellous bone, this elongated support may include a series of ultrasound transceivers mounted on at least one rod, such rod being engaged into the elongated support and liable to slide with respect thereto between a retraction position of the rod, wherein the ultrasound transceivers are situated inside the elongated support, and a active position, wherein these ultrasound transceivers enable examination of the bone. In inactive position, the ultrasound transceivers are perfectly protected against loads subjected by the elongated support during introduction into the bone or during the boring performed by its distal end. When the elongated support has a distal end flattened as a spatula, the reception cavity of said rod may emerge at the transition zone between this distal end and the remainder of the elongated support, the rod being situated, in active position, along a flattened face formed by said distal end. At least one series of ultrasound transceivers may be placed under a protective plate. The device may include means enabling to determine an accurate penetration depth of the elongated support into the bone and to ensure that this support remains at the same penetration depth during a given examination. Notably, these means may be in the form of a back-up washer integral with a sleeve engaged frictionally on the elongated support, such washer being positioned adequately with respect to the elongated support according to the penetration depth required and abutting against the bone during examination of this bone. These means may include means for locating several determined penetration depths, notably a graduation on the elongated support, facing said washer or said sleeve. Advantageously, said elongated support has an outer diameter at most equal to three or four millimetres. This diameter may however be different, for instance, 5 to 6 mm. The device may include visualisation means, in particular an additional display unit, enabling to visualise the bony wall in a plane perpendicular to the alignment direction of the ultrasound transceivers, as detected by one of the transceivers of each series. It is thus possible, by rotating the elongated support, to visualise the bony wall over a sector or over its whole circumference, and therefore to determine the radial position of the elongated support with respect to said wall. The invention also relates to a method enabling to examine the characteristics of a bone, and to a bone boring method. The method enabling to examine the characteristics of a bone consists in boring into the bone, then in inserting the elongated support of the device according to the invention as mentioned above in this boring. The boring method comprises the following steps: a) using the elongated support for boring into the bone; b) carrying out, by means of this elongated support, the whole boring operation in this bone or only a portion of this boring, and c) verifying, by means of the device, the quality or the integrity of the bone at said boring or of said portion of boring. When, at step b above, the boring is conducted only partially, the method comprises renewal the steps b and c as many times as necessary to conduct the whole boring. The quality or the integrity of the bone is thus examined step by step. The invention will be better understood, and other characteristics and advantages thereof will appear, with reference to the appended schematic drawings representing, by way of non-limiting examples, several embodiments of the device affected. Figures 1 and 2 are partial views, respectively lateral and top view, of the distal end of an elongated support included in this device, according to a first embodiment; Figures 3 and 4 are homologue views of Figures 1 and 2, according to a second embodiment of the elongated support; Figures 5 and 6 are homologue views of Figures 1 and 2, according to a third embodiment of the elongated support; Figure 7 is a view of the picture shown by a display unit included in the device, during the examination of a bone, and Figures 8 to 10 are views of pictures displayed by an additional display unit which may be included in this device. Figures 1 and 2 represent, at enlarged scale, the distal end of an elongated support 1 intended for being inserted into a bone in view of boring this bone while enabling examination of the characteristics thereof. Such elongated support 1 is in particular intended for boring into a vertebral pedicle, in order to insert in this pedicle a member serving for anchoring vertebral osteosynthesis equipment, and has henceforth an adapted outer diameter, at most equal to three or four millimetres. The distal end of the elongated support 1 comprises a nose 2 in the form of a flattened spatula, linked with the remainder of the elongated support 1 by oblique transition walls 3 and terminated by a rounded edge 4. The nose 2 forms thus two plane faces 5 on two sides, diametrically opposed. The distal end of the elongated support 1 thus reproduces the form of a so-called "Steffee spatula" instrument, for boring into cancellous bone, by compression and compaction of this cancellous bone, notably in a vertebral pedicle. As represented, the nose 2 includes, on each of its faces 5, two series of aligned ultrasound transceivers 6, transmitting according to directions diametrically opposed, perpendicular to the faces 5. Each series 6 extends over the longitudinal medial axis of the nose 2. The elongated support 1 is part of a device for examining the characteristics of a bone, including moreover a unit for processing the ultrasounds reflected by the bony wall, whereto the ultrasound transceivers are connected, included in the elongated support 1, and a display unit connected to this processing unit, enabling to visualise the position of the elongated support 1 inside the bone during boring. Figure 7 represents a picture 10 which can be shown by this display unit during this boring. This picture is composed of both pictures 10a, 10b produced by each of both series 6 of ultrasound transceivers, which are placed below one another by reversing the picture 10b produced by the second series 6 of ultrasound transceivers. This display unit thus enables to visualise simultaneously both zones 11 diametrically opposed of the bony wall under examination with respect to a reference axis 12 formed by the adjoining edges of both pictures 10a, 10b, and therefore to visualise immediately the distance of each of these zones 11 with respect to this reference axis 12 ; it is thus easy to determine the position of the elongated support 1 (whereof the axis coincides with the axis 12) with respect to these zones 11 , and in particular the correct boring position, wherein both zones 11 lie substantially at equal distance from this reference axis 12. Figures 8 to 10 show three pictures liable to be displayed by an additional display unit included in the device, this additional display unit enabling to visualise the bony wall 11 in a plane perpendicular to the direction of alignment of the ultrasound transceivers, as detected by one of the transceivers of each series 6. Figure 8 shows healthy bone, which appears clearly and in light colour, being delineated therefrom with respect to the dark colour of the liquid (blood or saline solution) wherewith the cavity is filled or the boring by which the elongated support is engaged into the bone. Damaged bone leads to blurred reflection of the ultrasounds (due to dissipation), as shown on Figure 9, and a fractured bone zone does not reflect any ultrasounds, as is the case of the zone situated at the top and on the right on Figure 10. Figures 3 and 4 show an elongated support 1 , very similar to that which has just been described, except that the ultrasound transceivers are placed not on the plane faces 5 but on the longitudinal edges of the nose 2, and that these ultrasound transceivers are placed below protective plates 15. Figures 5 and 6 show, for their own parts, an elongated support 1 also similar to those described above, apart from that it includes two rods 16 supporting series 6 of ultrasound transceivers. Each rod 16 is engaged into a bore 17 included in the elongated support 1 , emerging from a face 3, and may slide with respect to this elongated support 1. As shown, this sliding motion is possible between a retraction position of the rod 7 (cf. lower rod 7 on Figure 5), wherein the ultrasound transceivers are situated inside the elongated support 1 , and an active position (cf. upper rod 7 on Figure 5), wherein these ultrasound transceivers enable examination of the bone. As appears from the foregoing, the invention provides a device for examining the characteristics of a bone whereof the elongated support 1 enables transmission of ultrasounds according to a direction substantially perpendicular to the longitudinal axis of this elongated support 1 , and therefore substantially perpendicular to the bony wall under examination, and comprises at least one series 6 of aligned ultrasound transceivers. This transmission direction enables reflection of the ultrasounds under the best conditions, and the series (one or several series) of aligned transceivers enable examination of the bony wall over an elongated zone, thereby enabling to cross-reference the signals received by each of the transceivers and therefore to make the determination of the distance between the elongated support and the bony wall reliable. This device is particularly suited to boring into a vertebral pedicle, also enabling to determine the position of the boring with respect to the outer wall of the vertebral pedicle, and, if required, to demonstrate that this boring has not emerged from the side of the spinal cord nor from the side of the roots of the rachidial nerves. It goes without saying that the invention is not limited to the embodiment described above by way of example, but it extends to all the embodiments covered by the appended claims.

Claims

CLAIMS 1 - Device for examining the characteristics of a bone, including an elongated support (1) including an ultrasound transceiver, a unit for processing the ultrasounds reflected by the bony wall, and a display unit enabling to visualise the position of the elongated support (1) inside the bone during boring, characterized in that the elongated support (1) includes, at its distal end, at least a series (6) of aligned ultrasound transceivers, transmitting according to directions substantially perpendicular to the longitudinal axis of the elongated support (1). 2 - Device according to claim 1 , characterized in that the elongated support (1) includes two series (6) of ultrasound transceivers transmitting in directions diametrically opposed. 3 - Device according to claim 2, characterized in that the display unit is designed to display the pictures (10a, 10b) produced by both series (6) of ultrasound transceivers below one another, by reversing the picture (10b) produced by the second series (6) of ultrasound transceivers. 4 - Device according to anyone of claims 1 to 3, characterized in that said elongated support (1) comprises a distal end shaped in order to realise a boring in of the cancellous bone. 5 - Device according to claim 4, characterized in that the distal end of the elongated support (1) is in the form of a flattened spatula, such as a "Steffee spatula". 6 - Device according to claim 5, characterized in that each series (6) of ultrasound transceivers extends at the medial zone of a flattened face (5) of said distal end or at the edge of this distal end. 7 - Device according to anyone of claims 1 to 5, characterized in that said elongated support (1) includes a series (6) of ultrasound transceivers mounted on at least one rod (16), such rod (16) being engaged into the elongated support (1) and liable to slide with respect thereto between a retraction position of the rod (16), wherein the ultrasound transceivers are situated inside the elongated support (1), and a active position, wherein these ultrasound transceivers enable examination of the bone. 8 - Device according to claim 7, characterized in that the reception cavity of said rod (16) may emerge at the transition zone (3) between this distal end and the remainder of the elongated support (1), the rod (16) being situated, in active position, along a flattened face (5) formed by said distal end. 9 - Device according to anyone of claims 1 to 8, characterized in that at least one series (6) of ultrasound transceivers is placed under a protective plate (15). 10 - Device according to anyone of claims 1 to 9, characterized in that it includes means enabling to determine an accurate penetration depth of the elongated support (1) into the bone. 11 - Device according to anyone of claims 1 to 10, characterized in that it includes visualisation means, in particular an additional display unit, enabling to visualise the bony wall in a plane perpendicular to the alignment direction of the ultrasound transceivers, as detected by one of the transceivers of each series (6). 12 - Method enabling to examine the characteristics of a bone, which uses the device according to anyone of claims 1 to 11 , characterized in that it consists in boring into the bone, then in inserting the elongated support (1) of said device in this boring. 13 - Bone boring method using the device according to anyone of claims

1 to 11 , characterized in that it comprises the following steps: a) using the elongated support (1) for boring into the bone; b) carrying out, by means of this elongated support (1), the whole boring operation in this bone or only a portion of this boring, and c) verifying, by means of the device, the quality or the integrity of the bone at said boring or of said portion of boring. 14 - Bone boring method according to claim 13, characterized in that when, at step b above, the boring is conducted only partially, the method comprises renewal the steps b and c as many times as necessary to conduct the whole boring.