METHOD FOR CONTROLLING THE VISCOSITY OF ORTHOPEDIC BONE CEMENT

Abstract

Some embodiments are directed to a method for controlling the viscosity of orthopedic bone cement during its curing in percutaneous vertebroplasty by allowing a controlled heating and/or cooling of the cement during the injection that leads to a dynamic and full control of the viscosity of the cement during the injection.

Claims

1. A method for a dynamic control of the viscosity of an orthopedic bone cement during curing by acting on a bone cement temperature in percutaneous vertebroplasty, within an injection device that includes a syringe, a percutaneous needle connected to the syringe via a pipe, including an active heat exchanger, the method comprising: A. defining the time t.sub.o, time at which the radiologist starts the mixing process of the bone cement; B. filling the syringe with the prepared bone cement; C. defining for the bone cement a target viscosity * to be reached or maintained, the target viscosity * being in the range [.sub.min.sub.max], .sub.min being the minimal threshold viscosity of the cement which has to be reached for beginning the injection and .sub.max being the maximum threshold viscosity of the cement above which the injection is no longer possible; D. beginning the injection of the bone cement into the vertebra; E. at instant t during the injection: e1) measuring an effective temperature T of the bone cement at an outlet of the active heat exchanger and measuring an effective temperature T.sub.i of the bone cement at an inlet of the active heat exchanger; e2) computing the pressure drop P=P.sub.oP.sub.i along the pipe between the outlet of the syringe and a given intermediate point, P.sub.o being the pressure measured at the outlet of the syringe and P.sub.i being the pressure measured at the given intermediate point on the pipe, the length between those two points being denoted as L.sub.sensor; e3) computing a flow rate Q of the bone cement in the pipe; e4) computing a shear rate {dot over ()}.sub.p at the wall of the pipe as a function of the flow rate Q, the cross-section dimensions of the pipe and the intrinsic physical parameters of the cement; e5) calculating the instant viscosity (t,T,{dot over ()}.sub.P) if Q is nonzero, as a function of time t, temperature T, pressure drop P and shear rate {dot over ()}.sub.p, itself function of the flow rate Q; .sub.0(t,T) if Q has a zero value, as a function of time t and temperature T. e6) computing a set point temperature T(*)t associated to the target viscosity * and the instant viscosity , * being function of the flow rate Q and the time t; e7) calculating the difference .sub.T between the previously determined set point temperature T(*)t and the effective temperature at the outlet of the heat exchanger T; e8) controlling the cooling or the heating of the bone cement throughout the control of the active heat exchanger as a function of .sub.T; F. at instant t+t, repeating step E until the end of the injection, unless the instant viscosity (t,T,{dot over ()}.sub.P) and/or .sub.0(t,T) has reached the maximum threshold viscosity .sub.max.

2. The method according to claim 1, wherein step F further comprises the redefinition of the target viscosity * before repeating step E until the end of the injection, unless the instant viscosity (t,T,{dot over ()}.sub.P) and/or .sub.0(t,T)has reached the maximum threshold viscosity .sub.max.

3. The method according to claim 1, wherein the step e2) of computing the pressure drop P is realized between the outlet of the syringe and the outlet of the needle.

4. The method according to claim 1, wherein the step e2) of computing the pressure drop P is realized between the outlet of the syringe and the outlet of the active heat exchanger.

5. The method according to claim 1, wherein the instant viscosity (t,T,{dot over ()}.sub.p), if the flow rate is nonzero, is calculated according to modified Power Law as defined by formula (2) in the case of a pipe having a cylindrical geometry of radius r: $\begin{array}{cc}\left(t,T,{\stackrel{.}{}}_p\right)=a_{T_0}\left(T\right).Math.K\left(t\right).Math.{\left(a_{T_0}\left(T\right).Math.{\stackrel{.}{}}_p\right)}^{n\left(t\right)-1}.Math..Math.\mathrm{with}.Math..Math.a_{T_0}\left(T\right)=\exp \left(\frac{-E_a}{R}.Math.\left(\frac{1}{T}-\frac{1}{T_0}\right)\right)& \left(2\right)\end{array}$ with: E.sub.a being the activation energy in J.mol.sup.1, T being the effective temperature of the bone cement at the outlet of the active heat exchanger, T.sub.0 being a reference temperature at which the viscosity .sub. is known, R being the gas constant, n(t) being the flow index of the bone cement at the current time t, n is either a known constant or defined as a function of t.sub.0 and t. being the shear rate at the wall of the pipe being given by formula (3): $\begin{array}{cc}{\stackrel{.}{}}_p=\frac{Q}{.Math..Math.r^3}.Math.\frac{3.Math..Math.n\left(t\right)+1}{n\left(t\right)}& \left(3\right)\end{array}$ with r being the radius of the pipe. K(t) being given by formula (4): $\begin{array}{cc}Q={\left(\frac{.Math..Math.P}{L_{\mathrm{sensor}}}\right)}^{1/n\left(r\right)}.Math.{\left(\frac{r}{2.Math..Math.K\left(t\right)}\right)}^{1/n\left(t\right)}.Math.\left(\frac{.Math..Math.n\left(t\right).Math.r^3}{3.Math..Math.n\left(t\right)+1}\right)& \left(4\right)\end{array}$

6. The method according to claim 1, wherein the instant viscosity (t) is calculated according to the differential equation (5):
{dot over ()}(t,T,{dot over ()}.sub.p)=f((t,T,{dot over ()}.sub.p)) (5) wherein the time derivative fi of the viscosity is defined as a function the instant viscosity .

7. The method according to claim 1, wherein the set point temperature T(*)t is calculated according to a chosen control strategy either via $\underset{T}{\mathrm{argmin}.Math.}.Math.\stackrel{.}{}$ or using the inverse solution of equation (5).

8. The method according to claim 1, wherein the step of measuring the flow rate Q of the bone cement in the pipe comprises a step of measuring a moving speed V.sub.pist of the piston of the syringe, the piston being driven to vary the volume of the cement in the syringe, the volumetric flow Q being then given by Q=V.sub.pist..r.sup.2.

9. The method according to claim 1, wherein the controlling e8) of the active heat exchanger realizes the cooling or heating of the bone cement as a function of .sub.T throughout a temperature regulation scheme composed of two nested closed loops, where: a temperature controller C.sub.T uses the difference .sub.T between the previously determined set point temperature T(*)t and the effective temperature T to compute the current reference I* of the active heat exchanger, the current reference I* being limited by a current saturation block, a current controller C.sub.I uses the difference .sub.I between the current reference I* and the effective input current I to compute the input voltage U of a power supply H driving the active heat exchanger.

10. The method according to claim 4, wherein the intravertebral pressure P.sub.vertebra is computed according to formula (1): $\begin{array}{cc}{P}_{\mathrm{vertebra}}=P_o\left(1-\frac{L_{\mathrm{vertebra}}}{L_{\mathrm{sensor}}}\right)+\frac{L_{\mathrm{vertebra}}}{L_{\mathrm{sensor}}}.Math.P_i& \left(1\right)\end{array}$ with: L.sub.vertebra being the length comprised between the outlet of the syringe and the outlet of the needle.

11. The method according to claim 2, wherein the step e2) of computing the pressure drop P is realized between the outlet of the syringe and the outlet of the needle.

12. The method according to claim 2, wherein the step e2) of computing the pressure drop P is realized between the outlet of the syringe and the outlet of the active heat exchanger.

13. The method according to claim 2, wherein the instant viscosity (t,T,{dot over ()}.sub.p), if the flow rate is nonzero, is calculated according to modified Power Law as defined by formula (2) in the case of a pipe having a cylindrical geometry of radius r: $\begin{array}{cc}\left(t,T,{\stackrel{.}{}}_p\right)=a_{T_0}\left(T\right).Math.K\left(t\right).Math.{\left(a_{T_0}\left(T\right).Math.{\stackrel{.}{}}_p\right)}^{n\left(t\right)-1}.Math..Math.\mathrm{with}.Math..Math.a_{T_0}\left(T\right)=\exp \left(\frac{-E_a}{R}.Math.\left(\frac{1}{T}-\frac{1}{T_0}\right)\right)& \left(2\right)\end{array}$ with: E.sub.a being the activation energy in J.mol.sup.1, T being the effective temperature of the bone cement at the outlet of the active heat exchanger, T.sub.0 being a reference temperature at which the viscosity .sub. is known, R being the gas constant, n(t) being the flow index of the bone cement at the current time t, n is either a known constant or defined as a function of t.sub.0 and t. {dot over ()}.sub.p being the shear rate at the wall of the pipe being given by formula (3): $\begin{array}{cc}{\stackrel{.}{}}_p=\frac{Q}{.Math..Math.r^3}.Math.\frac{3.Math..Math.n\left(t\right)+1}{n\left(t\right)}& \left(3\right)\end{array}$ with r being the radius of the pipe. K(t) being given by formula (4): $\begin{array}{cc}Q={\left(\frac{.Math..Math.P}{L_{\mathrm{sensor}}}\right)}^{1/n\left(r\right)}.Math.{\left(\frac{r}{2.Math..Math.K\left(t\right)}\right)}^{1/n\left(t\right)}.Math.\left(\frac{.Math..Math.n\left(t\right).Math.r^3}{3.Math..Math.n\left(t\right)+1}\right)& \left(4\right)\end{array}$

14. The method according to claim 2, wherein the instant viscosity (t) is calculated according to the differential equation (5):
{dot over ()}(t,T,{dot over ()}.sub.p)=f((t,T,{dot over ()}.sub.p)) (5) wherein the time derivative of the viscosity is defined as a function the instant viscosity .

15. The method according to claim 3, wherein the instant viscosity (t) is calculated according to the differential equation (5):
{dot over ()}(t,T,{dot over ()}.sub.p)=f((t,T,{dot over ()}.sub.p)) wherein the time derivative 1) of the viscosity is defined as a function the instant viscosity .

16. The method according to claim 4, wherein the instant viscosity (t) is calculated according to the differential equation (5):
{dot over ()}(t,T,{dot over ()}.sub.p)=f((t,T,{dot over ()}.sub.p)) wherein the time derivative 3 of the viscosity is defined as a function the instant viscosity .

17. The method according to claim 2, wherein the set point temperature T(*)t is calculated according to a chosen control strategy either via $\underset{T}{\mathrm{argmin}.Math.}.Math.\stackrel{.}{}$ or using the inverse solution of equation (5).

18. The method according to claim 3, wherein the set point temperature T(*)t is calculated according to a chosen control strategy either via $\underset{T}{\mathrm{argmin}.Math.}.Math.\stackrel{.}{}$ or using the inverse solution of equation (5).

19. The method according to claim 4, wherein the set point temperature T(*)t is calculated according to a chosen control strategy either via $\underset{T}{\mathrm{argmin}.Math.}.Math.\stackrel{.}{}$ or using the inverse solution of equation (5).

20. The method according to claim 5, wherein the set point temperature T(*)t is calculated according to a chosen control strategy either via $\underset{T}{\mathrm{argmin}.Math.}.Math.\stackrel{.}{}$ or using the inverse solution of equation (5).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0123] Other features and advantages of some embodiments will become more clearly apparent on reading the following description, given with reference to the appended figures, which illustrate non-limiting examples of possible or preferable realizations (FIGS. 1 and 2) and also non limiting examples of different realizations of an injection device that may be used in the method of some embodiments:

[0124] FIG. 1 represents schematically the viscosity regulation scheme composed of three nested closed-loops for realizing the controlling e8) of the active heat exchanger of an injection device, according to a possible embodiment of the method,

[0125] FIG. 2 represents schematically the thermal loop that is nested in the viscosity loop illustrated on FIG. 1,

[0126] FIG. 3 represents a tridimensional CAD general view of an injection device that is used in the method of some embodiments as a whole,

[0127] FIG. 4 represents a schematic diagram of the injection device illustrated on FIG. 3,

[0128] FIG. 5 represents a CAD view of a master device that remotely controls the injection,

[0129] FIG. 6A represents a tridimensional CAD view of a heat exchanger with a thermal block,

[0130] FIG. 6B represents its corresponding cross-sectional schematic view,

[0131] FIG. 7 represents a principle diagram of a deported active heat exchanger put on a closed fluid circuit with a fluid-to-cement heat exchanger, according to an embodiment of some embodiments,

[0132] FIG. 8 represents a detailed view of the deported active heat exchanger illustrated on FIG. 7,

[0133] FIG. 9 represents a detailed view of the water-to-cement heat exchanger illustrated on FIG. 7,

[0134] FIG. 10 represents an exploded view of a sheath surrounding the syringe, according to an realization of some embodiments,

[0135] FIG. 11 represents a detailed view of the syringe with sheath illustrated on FIG. 10,

[0136] FIG. 12 represents a cross-sectional schematic view of an embodiment of a pressure sensor (located on the cement pipe) with a water-filled channel,

[0137] FIG. 13 represents a cross-sectional schematic view of another embodiment of a pressure sensor with an elastomer-filled channel,

[0138] FIG. 14 represents a cross-sectional schematic view of another embodiment of a pressure sensor with both an elastomer-filled channel and an elastomeric membrane.

[0139] For the sake of clarity, identical or similar elements have been referenced with identical reference symbols in all or most of the figures.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0140] For purposes of understanding the principles of some embodiments, reference will now be made to the realizations illustrated in the drawings and the accompanying text.

[0141] An advantage of the method of some embodiments is to control the cement viscosity. A regulation scheme composed of three nested closed-loops may be used for realizing the controlling e8) of the active heat exchanger of an injection device, as shown by FIGS. 1 and 2:

[0142] A. after defining for the bone cement to be injected the target viscosity * to be reached or maintained, the target viscosity * being included in the range [.sub.min.sub.max], .sub.min being the minimal threshold viscosity of the cement which has to be reached for beginning the injection and .sub.max being the maximum threshold viscosity of the cement above which the injection is not possible anymore;

[0143] B. the set point temperature T*(t) associated to the target viscosity * is computed according to the method of some embodiments (step e6) in the temperature set point generation block in the viscosity loop of FIG. 1,

[0144] C. the value of the set point temperature T*(t) is injected in the temperature regulation loop that is illustrated on FIG. 2, in which a temperature controller C.sub.T uses the difference .sub.T between the previously determined set point temperature T*(t) and the effective measured temperature T to compute the current reference I* of the active heat exchanger (usually or always using electrical energy as input),

[0145] D. the current reference I* is limited by a current saturation block,

[0146] E. the current is also controlled in a closed loop control (current loop), in which a current controller C.sub.T uses the difference .sub.I between the current reference I* and the effective input current I to compute the input voltage U of a power supply H driving the active heat exchanger (current loop).

[0147] Now concerning the injection device 1 that may be used in the method of some embodiments, FIG. 3 represents a tridimensional (3D) CAD general view of the entire injection device 1 of some embodiments as a whole. It is based on a quite straightforward design, using a ball screw linear axis to transform the rotation of the rotor of a high torque servo-motor 2 into a linear translation, in order to push on a high-pressure syringe 7. Two separated mobile carts are placed on the axis, with the first one (3) being motorized by the screw while the second one (4) is capable of moving along the axis freely. The two carts 3 and 4 are linked together through a force sensor 5 in order to measure the linear force running through the assembly 1. A hand maneuvered clamping device 6 has been placed on the free cart 4. It is used to grip a specific syringe piston rod 8 and has been equipped with a low force limit switch to provide an automatic approach during the setup phase. An incremental encoder has also been added between the free cart 4 and the base in order to provide a direct reading of the cart position without being affected by the potential backlash and the flexibility of the kinematic chain.

[0148] On the fixed part of the device, a mounting base has also been designed to support the syringe. The syringe itself is fixed to the mounting base by using a specific sheath that will be more precisely illustrated and detailed below (see FIGS. 6 and 7 and the corresponding accompanying paragraphs of the text). The syringe 7 is disposable because of the medical nature of its use.

[0149] FIG. 3 also shows a percutaneous needle 14 connected to the syringe 7 via a pipe 17. An active heat exchanger 13 such as a thermal block (see also FIGS. 4A and 4B) is located on the pipe 17) (surrounding the pipe 17) for the dynamic controlled heating and/or cooling of the cement 12 during the injection.

[0150] FIG. 4 represents a schematic diagram of the injection device shown on FIG. 3. The motor input 2 provide the displacement of the piston 8 that pushes the cement 12 in the cement channel 17. As shown of the diagram, both the position and force signal are provided by the system.

[0151] The overall dimensions of the injection device 1 as a whole are approximately 500100100 mm for a mass of approximately 5.5 kg. It can provide a service load of 2 kN. This can generate a pressure of about 100 bar on the cement 12 in the syringe 7, and will allow to inject a fluid with a viscosity up to 2000 Pa.Math.s at a flow rate of 33 mm.sup.3/s considering the pressure drop of a 1500 2.5 mm cylinder (equivalent to a typical cement near the end of its solidification injected in a typical large section injection needle plugged into a short channel).

[0152] A master device 11, illustrated on FIG. 5, controls the injection remotely. In order to give to the physician the same feedback as he would have in a manual injection, the master device 11 can provide the force feedback of the pressure applied to the cement 12. Concerning the control of the injection itself, it is a flow rate control, which is more precise and practical than a volumetric control, generally provided by the current known manual systems. It then adds a design constraint to the master device 11 that should return to neutral position when the physician releases the interface because of safety issues. Besides that, the remote control also allows some flexibility as it may have some scaling or non-linear fitting both on the force-feedback and on the control signals, giving the possibility to customize easily both features with the experienced feedback of the practitioner.

[0153] The control of the injection is done via a rotating knob 111 located on the master device that returns the pressure information in the form of a force feedback. Should the physician release the knob during the injection, an integrated spring returns the interface in a neutral position.

[0154] As regards the active thermal regulation, which is realized in the method some embodiments by an active heat exchanger 13, FIGS. 6A and 6B show a first embodiment of an active heat exchanger 13 including or consisting of a unique thermal block 130. A thermal insulation (not shown on these figures) wraps the central part of the block 130. The thermal block is composed of [0155] a central regulated block 131 that is crossed by the cement pipe 17. [0156] two stacks 132, disposed symmetrically to the regulated block which include: [0157] two Peltier modules 1321, [0158] two heat sinks 1322, [0159] two fans 1323, [0160] a thermal insulation (not shown on FIGS. 4A and 4B) wrapping the central block 131, which reduces the thermal exchanges between the regulated volume and the ambient air, [0161] three temperature sensors (not shown on FIGS. 6A and 6B) placed respectively on the central block 131 and on both heat sinks 1322 to measure the temperature of the regulated part and to control both Peltier modules, and [0162] two Luer-lock connections at the extremity of the channel 17 to plug the thermal block 130 to the syringe 7 on one side and to the needle 14 on the other side

[0163] The active thermal regulation may also be alternatively realized by a deported active heating/cooling heat exchanger 15 put on a closed water circuit 16 with a water-to-cement heat exchanger 13 located on the pipe 17 of the injection device 1, according to a second realization of some embodiments. Such a deported device allows a remote control of the viscosity of the cement during the intervention, thus protecting the radiologist during the cement injection phase by keeping her/him outside the radiation area.

[0164] FIG. 7 represents a schematic diagram of this closed water circuit 16 including the deported heat exchanger 15 and the water-to-cement heat exchanger 13 of the injection device 1. The water circulation is powered by a tanking/pumping device 18 placed on the closed loop 16. The advantage of this thermal regulation, in comparison with the thermal block of the first realization, is the possibility of doing the same regulation at a remote location, as the thermal block 130 of the first embodiment is both fragile, heavy and space consuming in a critical place such as the surgical area.

[0165] The deported heat exchanger 15 of FIGS. 7 and 8 (detailed section of FIG. 7) includes: [0166] a heat transfer block 150 being crossed by a water circuit 16 connected to the water-to-cement heat exchanger 13, [0167] Peltier cells 152 [0168] heat sinks 153, and [0169] fans 154. [0170] temperature sensors 155 placed on the water circuit 16.

[0171] As the orientation of the fan/sink couple has an impact on the performance on the heat sinks dissipation in free airflow, the fans 154 have been placed in a geometry designed to provide a more efficient forced airflow.

[0172] The water circuit 16 shown on FIG. 8 also includes a pumping system 18 that is able to work in reverse direction in order to purge the circuit 16 and thus, to avoid water leakage when the physician unplugs the exchanger 13 from the circuit 16.

[0173] The water-to-cement heat exchanger 13 shown on FIG. 9 is built around a finned block 130 whose task is to ensure a proper heat transfer between the cement pipe 17 and the water circuit 16. In this realization, it replaces the thermal block 13 presented in FIG. 1 on the cement pipe 17.

[0174] Now concerning the passive thermal exchange, FIGS. 10 and 11 represent a sheath 71 surrounding the syringe 7, according to a realization of some embodiments. In order to design this sheath, several constraints were taken in account: [0175] it has to resist the service load that may rise up to 2 kN, [0176] it should be able to passively exchange thermal energy as to maintain the cement stored within the syringe 7 with the lowest viscosity possible throughout the injection, [0177] it has to be easily interfaced to the injection device 1 by having a dedicated interface 9 and by allowing a fast and easy locking of the syringe piston 8 to the free cart 4.

[0178] As such, the sheath 71 has been machined out of a 316L stainless steel in order to provide a high mechanical resistance and to resist to various chemical products, including biologic fluids and asepsis solutions. The sheath 71 provides some space around the syringe that may filled with an eutectic mixture known for its ability to exchange heat at constant temperatures, thus ensuring that the syringe 71 is kept cool during most of the injection.

[0179] The assembly (sheath) is also equipped with a fixation 9 at the back that interfaces with the mounting base 10 on the injector. A nut 72 and screw system is used to put in and extract the disposable syringe that contains the cement.

[0180] FIG. 10 shows the syringe 71, the syringe sheath 71 (partly disassembled) and the high-pressure piston 8, while

[0181] FIG. 11 shows a more detailed cutout of the sheath with the syringe 7 in it, where the room 73 for the eutectic gel is visible.

[0182] Now concerning pressure measurements of the cement along the cement pipe 17, FIGS. 12 to 14 are cross-sectional schematic views of different embodiments of pressure sensors 19, 20, 21 located on the pipe 17. In order to have a better control on and understanding of the injection procedure, it may be helpful to estimate the intravertebral pressure. This pressure may be used intraoperatively to detect failure during the procedure, such as pressure spikes or drops that may be symptomatic of clogging or leakage.

[0183] The best or better way to measure the intravertebral pressure would be to integrate a pressure sensor at the tip of the needle, but it would be very constraining in terms of design. Thus, in the frame of some embodiments, the value of this pressure is obtained indirectly, using a pressure measurement in the cement channel.

[0184] Considering the flow of a cement with varying rheological parameters K and n in a cylindrical pipe of length L.sub.vertebra and of radius r, and given the known sensor position distant from the pipe inlet by a distance L.sub.sensor, the Poiseuille flow leads to equation (6):

[00006]$\begin{array}{cc}Q={\left(\frac{.Math..Math.P}{L_{\mathrm{sensor}}}\right)}^{1/n\left(t\right)}.Math.{\left(\frac{r}{2.Math..Math.K\left(t\right)}\right)}^{1/n\left(t\right)}.Math.\left(\frac{.Math..Math.n\left(t\right).Math.r^3}{3.Math..Math.n\left(t\right)+1}\right)& \left(6\right)\end{array}$

[0185] Assuming that the flow rate is high enough, the cement viscosity at the sensor is substantially equal to the cement at the outlet of the pipe. This provide then equation (7):

[00007]$\begin{array}{cc}{P}_{\mathrm{vertebra}}=P_o\left(1-\frac{L_{\mathrm{vertebra}}}{L_{\mathrm{sensor}}}\right)+\frac{L_{\mathrm{vertebra}}}{L_{\mathrm{sensor}}}.Math.P_i& \left(7\right)\end{array}$

[0186] As shown by the equations, the knowledge of at least one pressure outside the injection pressure is mandatory. However, as pressure sensors are too expensive to be integrated as a disposable component, there is a need for a reusable pressure sensor that could be carried over several interventions. Also because of sterility issues, the sensor should not have any internal interface with the cement in order to be cleanable.

[0187] For this purpose, reusable pressure sensors have been developed in the frame of some embodiments, in which the sensing area of a standard pressure sensor is immersed in an incompressible fluid that would transfer the pressure.

[0188] According to a first advantageous embodiment of such a pressure sensor 19 (as shown on FIG. 10), it is based on a standard pressure sensor 190 whose channel 191 is filled with water. A flexible interface 192 separates the cement channel 17 and the sensor channel 191. The interface 192 can include or can consist of a cap made out of a flexible silicon compound, such a polydimethylsiloxane (PDMS).

[0189] According to a second advantageous embodiment of such a pressure sensor 20 (as shown on FIG. 11), it is based on a standard pressure sensor 200 whose channel is filled with an elastomeric compound 201 such as PDMS.

[0190] According to a third advantageous embodiment of such a pressure sensor 21 (as shown on FIG. 12), it is based on a standard pressure sensor 210 whose channel is filled with an elastomeric compound 211 such as PDMS. The cement pipe 17 is equipped with an elastomeric membrane 212, forming a measure point. The pressure sensor is mounted on a removable bracket 213 that may be plugged on the cement pipe 17, and then removed when the pipe 17 is disposed at the end of the intervention.

LIST OF THE CITED REFERENCES

[0191] [1] A. Gangi, S. Guth, J. Imbert, H. Marin, and J.-L. Dietemann, Percutaneous vertebroplasty: indications, technique, and results. Radiographics, vol. 23, March 2003. [0192] [2] US 2013/0190680 of Baroud: US patent application filed on Mar. 8, 2013 by the SOCPRA S.E.C and published on Jul. 25, 2013. [0193] [3] US 2009/0062808 of Wolf: US patent application filed on March 2008 by Wolf (as inventor and applicant) and claiming the priority of a provisional application dated Sep. 5, 2007, and published on Mar. 5, 2009. [0194] [4] U.S. Pat. No. 8,523,871 of Truckai et al.: US granted patent filed on Apr. 3, 2008 by Truckai et al. (as inventors and applicants) and claiming the priority of four provisional applications dated Apr. 3, 2007, and granted on Oct. 9, 2008. [0195] [5] N. Lepoutre, G. Bara, L. Meylheuc, et B. Bayle, Phase Space Identification Method for Modeling the Viscosity of Bone Cement, in Control Conference (ECC), 2016 European, Juin-Juillet 2016.