Patent Publication Number: US-2017367847-A1

Title: System and method for monitoring by-impaction assembly between a prosthetic component and a support member, and surgical kits including such a system

Description:
The present invention relates to a system and method for monitoring by-impaction assembly between a prosthetic component and a support member. 
     In the field of human joint replacement surgery, surgeons often have to assemble a prosthetic component with a bone or with another prosthetic component. A common surgical technique is to impact the prosthetic component so as to block or jam a feature of the prosthetic component with a matched feature of the bone or of the other prosthetic component, in particular when no cement is used or when a thin cement layer is interposed between the aforesaid features. As the force to apply to the prosthetic component is high, the surgeon uses an impact application device to impact the prosthetic component so as to engage the aforesaid features with each other: the impact application device typically includes a hammer, which is manipulated by hand by the surgeon, and an impactor, which is a surgical tool designed to be interposed between the hammer and the prosthetic component so as to transmit force of the hit of the hammer thereon to the prosthetic component. 
     In practice, several impacts are necessary in order to fully assembly the prosthetic component with the bone or with the other prosthetic component and thus to be sure that the assembly is fully seated and therefor stable. A fully seated assembly is also expected in order to promote osseointegration when the prosthetic component is assembled with a bone. The prosthetic component is considered as being partially or not fully assembled with a bone or with another prosthetic component when in use, the prosthetic component is likely to move or even to disassemble with respect to the bone or the other prosthetic component. Such a partial or not fully seated assembly may occur for example when a gap remains between the aforesaid features or between at least respective parts of these features, which are intended to be in full contact. Another example of such a partial assembly is when assembly force between the aforesaid features is not sufficient even if no gap remains between them, which may typically the case for a Morse taper assembly between two prosthetic components. 
     However, the specific number of impacts that is necessary for the fully seated assembly is not predetermined and may depend on factors such as the force of each of the successive impacts, implant type, patient anatomy and the surgeon&#39;s ability. In order to be sure that the assembly is fully seated, the surgeons tend to strike the prosthetic component with the impact application device a number of times which is much higher than what is necessary. Thus, the total number of the impacts that can be given is twice or three times what is necessary. This excess of impacts may lead to weaken or even break the prosthetic component and/or the support member, i.e., bone or another component, with which the prosthetic component is assembled by impaction. For example, in the case of an acetabular cup to be assembled cementless and by-impaction into the acetabulum of the pelvis of a patient, continuing to strike the cup whereas this cup is already fully assembled into the acetabulum risks of fracturing the pelvis. According to another example, in the case of a prosthetic humeral head, especially in pyrocarbon, to be assembled cementless and by-impaction with a prosthetic humeral stem that is already or not yet implanted in the humerus of a patient, continuing to strike the head whereas this head is already fully assembled with the stem risks of damaging the head. Other examples can be considered for prosthetic components to be assembled with a support member, either osseous or prosthetic, by impaction and, if appropriate, without cement. In any case, the number of impaction impacts should be reduced at the minimum for having a fully seated assembly without damaging the prosthetic component and/or the support member. 
     In practice, the surgeons have difficulties to evaluate whether the prosthetic component is fully impacted. Some prosthetic components have a back side hole through which the surgeon can check the assembly, but using such a back side hole may be difficult in case of minimally invasive surgical techniques and is even not possible for numerous prosthetic components which are not provided with such a back side hole. Otherwise, the surgeon can ask intraoperative radiographic images, but that increases the operating time and radiation to the patient. Thus, the surgeon often stops to strike the prosthetic component only when he or she has the manual feeling that the assembly is fully seated. Of course, such a manual feeling is different between surgeons and is not the same depending on the prosthesis, the impact application device, and the bone quality. 
     This issue has already been considered in US  7   879   043 . This document discloses a system and method for preventing intraoperative fracture in cementless hip arthroplasty. This system uses damage identification techniques based on vibration characteristics associated with femoral component impaction to determine when a femoral prosthetic stem is fully assembled into the femur of a patient. More precisely, the system comprises accelerometers that are attached to a large neck of the femoral stem: each time a hammer impacts the upper end of the femoral stem, the femoral stem is moved into the femur and the accelerometers provide a signal representative of acceleration of the femoral stem. A temporal analysis of the acceleration signals, which are provided for successive impacts, enables to warn the surgeon that the full assembly is reached. In practice, this system is quite difficult to use because the accelerometers thereof need to be attached to the femoral stem: the accelerometers need to be sterilized before being placed on the femoral stem in the sterile surgical field and they risk being damaged by the hammer. Besides, unlike a femoral stem that includes a large neck, numerous prosthetic components cannot be equipped with such attached accelerometers. 
     One of the goals of the present invention is to propose a system for monitoring impaction of a prosthetic component, which is easy and convenient to use, for any type of prosthetic component. 
     To this end, one object of the invention is a system for monitoring by-impaction assembly between a prosthetic component and a support member, comprising:
         at least one vibrational sensor which is operable to produce data each time an impact application device applies an impact from a user to the prosthetic component during assembly between the prosthetic component and with the support member, the produced data representing acoustic vibrations generated in the air and/or material vibrations generated in the impact application device,   an analysis unit which is configured both to calculate a frequency characterization of the vibrations for each impact applied by the impact application device to the prosthetic component, from the corresponding data produced by the at least one vibrational sensor, and to compare the frequency characterizations that are respectively calculated for successive impacts so as to provide at each of the successive impacts either a first indication when the assembly between the prosthetic component and the support member is not fully seated or a second indication when the assembly between the prosthetic component and the support member is fully seated, and   a user interface which provides feedback to the user based on the first and second indications.       

     According to additional advantageous features of this system:
         The at least one vibrational sensor includes a microphone operable to produce data representing the acoustic vibrations generated in the air, the microphone being separate from the prosthetic component.   The microphone is also separate from the impact application device.   The microphone, the analysis unit and the user interface are integrated into a portable device, such as a laptop, a smartphone or a pad.   The microphone is integrated into the impact application device.   The at least one vibrational sensor includes a piezoelectric sensor which is operable to produce data representing the material vibrations generated in the impact application device, the piezoelectric sensor being integrated into the impact application device.   The analysis unit and the user interface are also integrated into the impact application device.   The frequency characterization calculated by the analysis unit is a natural frequency of the acoustic vibrations generated in the air.   The frequency characterization calculated by the analysis unit is a wave frequency of the material vibrations generated in the impact application device.   At each of the successive impacts, the analysis unit is configured to compare the frequency characterization resulting from the last impact or an average of the frequency characterizations respectively resulting from the N last impacts, N being a number between two and four, with the frequency characterization resulting from the second last impact or with an average of the frequency characterizations respectively resulting from the M impacts just preceding the last impact, M being a number between two and four.   At each of the successive impacts, the analysis unit is configured to compare the frequency characterization resulting from the last impact or an average of the frequency characterizations respectively resulting from the N last impacts, N being a number between two and four, with a threshold.       

     Another object of the invention is a surgical kit comprising:
         a prosthetic component to be assembled with a bone by impaction,   an impact application device for applying successive impacts to the prosthetic component during assembly between the prosthetic component and the bone, and   a system for monitoring assembly between the prosthetic component and the bone, the system being as described above.       

     According to additional advantageous features of this surgical kit:
         The prosthetic component is an acetabular cup of a hip prosthesis, intended to be assembled into an acetabulum of a human pelvis without cement.   The prosthetic component is a humeral stem of a shoulder prosthesis, intended to be assembled into a medullary canal of a human humerus without cement.   The prosthetic component is a glenoid plate of a shoulder prosthesis, intended to be assembled into a glenoid cavity of a human scapula without cement.       

     Another object of the invention is a surgical kit comprising:
         a first prosthetic component and a second prosthetic component, which are to be assembled together by impaction,   an impact application device for applying successive impacts to the first prosthetic component during assembly between the first prosthetic component and the second prosthetic component, and   a system for monitoring assembly between the first prosthetic component and the second prosthetic component, the system being as described above.       

     Another object of the invention is a method for monitoring by-impaction assembly between a first prosthetic component and a second prosthetic component, comprising:
         each time an impact application device applies an impact from a user to the first prosthetic component during assembly between the first prosthetic component and the second prosthetic component, producing data representing acoustic vibrations generated in the air and/or material vibrations generated in the impact application device, from at least one vibrational sensor,   calculating a frequency characterization of the vibrations for each impact applied by the impact application device to the first prosthetic component, from the corresponding data produced by the at least one vibrational sensor,   comparing the frequency characterizations that are respectively calculated for successive impacts so as to provide at each of the successive impacts a first indication when the assembly between the first prosthetic component and the second prosthetic component is not fully seated then a second indication when the assembly between the first prosthetic component and the second prosthetic component is fully seated, and   providing feedback to the user based on the first and second indications.       

     This method is implemented by using the system as defined above. In practice, this method can be carried out whereas the second prosthetic component is already or not yet implanted in a bone. 
     Another object of the invention is a method for monitoring by-impaction assembly between a prosthetic component and a bone, comprising:
         each time an impact application device applies an impact from a user to the prosthetic component during assembly between the prosthetic component and the bone, producing data representing acoustic vibrations generated in the air and/or material vibrations generated in the impact application device, from at least one vibrational sensor,   calculating a frequency characterization of the vibrations for each impact applied by the impact application device to the prosthetic component, from the corresponding data produced by the at least one vibrational sensor,   comparing the frequency characterizations that are respectively calculated for successive impacts so as to provide at each of the successive impacts a first indication when the assembly between the prosthetic component and the bone is not fully seated then a second indication when the assembly between the prosthetic component and the bone is fully seated, and   providing feedback to the user based on the first and second indications.       

     One of the ideas underlying the invention is to exploit not the vibrations generated in the prosthetic component each time the latter is hit by an impact application device in order to be assembled with the support member, but the vibrations that are generated in the air and/or in the impact application device. For this purpose, one or more vibrational sensors are used to detect the acoustic vibrations in the air and/or the material vibrations in the impact application device. In practice, this or these vibration sensors may not necessarily be attached to the prosthetic component. Thus, the invention can be used for any type of prosthetic components and simplifies or even avoids sterilization issue of these vibrational sensors. 
     Insofar as the data provided by the vibrational sensors are not directly representative of the displacement of the prosthetic component during the assembly between the prosthetic component and the support member, the invention proposes to analyze the frequency of the vibrations detected by the vibrational sensors: by calculating a frequency characterization of the vibrations generated for each impact applied by the impact application device and by comparing the respective frequency characterizations of the successive impacts of the impact application device, the invention enables to provide relevant information about the degree of impaction of the prosthetic component. In practice, various types of frequency characterization can be considered, such as a natural frequency for the acoustic vibrations in the air or a wave frequency for the material vibrations in the impact application device. Similarly, the type of feedback provided to the surgeon is not !imitative for the invention, sound or light feedback being possible. In any case, as soon as an appropriate indication is given by the system of the invention utilizing methods described herein, and/or by the method of the invention, the surgeon can stop to strike the prosthetic component, while being sure that the assembly between the prosthetic component and the support member is fully seated and thus stable. 
    
    
     
       Embodiments of the invention will be better understood from reading the description which will follow, which is given solely by way of example and with reference to the drawings in which: 
         FIG. 1  is a schematic view of a system for monitoring assembly between a hip prosthetic component and a pelvis; 
         FIGS. 2 and 3  are views similar to  FIG. 1 , which respectfully illustrate a partial assembly of the hip component and a fully seated assembly of the hip component; 
         FIG. 4  is a diagram of a temporal acoustic signal produced during assembly of the hip component; 
         FIG. 5  is a diagram of frequency characterizations calculated from the temporal signal of  FIG. 4 ; 
         FIGS. 6, 7 and 8  are schematic views of various exemplary embodiments for the monitoring system of  FIG. 1 ; 
         FIG. 9  is a perspective view of humeral prosthetic components; 
         FIGS. 10 and 11  are schematic views of another monitoring system, which illustrate the use of this system for monitoring assembly between a first humeral component amongst those of  FIG. 9  and a humerus, this assembly being partial in  FIG. 10  and being fully seated in  FIG. 11 ; and 
         FIGS. 12 and 13  are schematic views of another monitoring system, which illustrate the use of this system for monitoring assembly between the second and third humeral components of  FIG. 9  and the first humeral component. 
     
    
    
       FIG. 1  shows a human pelvis P having two acetabula A. Each of the acetabula is a cavity in the pelvis P, which articulates with the head of a (not shown) femur. Total hip arthroplasty replaces the joint between the pelvis and the femur with prosthetic components of a hip prosthesis, which articulates with each one other for replicating the natural hip joint and which are respectively assembled with the pelvis P and the femur. These prosthetic components typically include an acetabular cup  1 . During surgery, the cup  1  is assembled with the pelvis P, within one of the acetabula thereof. As depicted on  FIG. 1 , the assembly of the cup  1  into the acetabulum A of the pelvis P is performed by impaction by using an impact application device  10  detailed here-after. This assembly is usually achieved without cement, that is to say without interposing surgical cement between the cup  1  and the acetabulum A. The cup  1  is known per se and is for example DYNACUP sold by TORNIER, France. 
     In some embodiments as the one shown in  FIG. 1 , the impaction application device  10  comprises an impactor  11  and a hammer  12 . The hammer  12  is manipulated by hand by a surgeon and is consequently provided with a handle  13 . The hammer  12  is also provided with a head  14  arranged at an end of the handle  13 . The head  14  is designed to hit the impactor  11  and thus to apply an impaction force thereto from the surgeon. The impactor  11  is a surgical tool which is mainly intended to transmit impaction force from the hammer  12  to the acetabular cup  1 . In some embodiments as the one shown in  FIG. 1 , the impactor  11  comprises a rod  15  having a proximal end  16  designed to be hit by the head  14  of the hammer  12  whereas a distal end  17  of the rod  15  is coupled to the cup  1 . 
     The type of the coupling between the distal end  17  of the impactor  11  and the acetabular cup  1  is not limitative for the invention: in any case, this coupling is provided for driving the cup  1  into the acetabulum A by the rod  15  when the impactor  11  is hit by the hammer  12 . In summary, the impaction application device allows the surgeon to apply an impact to the acetabular cup  1  in order to assemble this acetabular cup with the pelvis P. 
     In practice, as explained in the introductive part of the present document, several impacts or hits are necessary so that the assembly between the acetabular cup  1  and the pelvis P is fully seated, or in other words full or complete or completely seated or properly positioned and assembled.  FIG. 2  depicts a not fully seated, or partial assembly, in which the acetabular cup  1  is not sufficiently engaged into the acetabulum A, whereas  FIG. 3  depicts the assembly when it is fully seated or in other words completely assembled. Passing the assembly from the partial state, or in other words partially seated state, of  FIG. 2  to the full state, or in other words fully seated state, of  FIG. 3  requires applying several impacts to the acetabular cup by the impact application device  10  operated by the surgeon. 
     Referring back to  FIG. 1 , a monitoring system  20  is provided to allow the surgeon to monitor the assembly between the acetabular cup  1  and the pelvis P. The monitoring system  20  comprises a microphone  21 , that is to say a vibrational sensor which both measures acoustic vibrations and produces data, typically an electronic signal, representing these acoustic vibrations. The microphone  21  is designed to be sensitive to the acoustic vibrations V A  which are generated in the air when an impact is applied by the impact application device  10  to the acetabular cup  1 . In practice, microphone  21  is chosen to be sensitive to these acoustic vibrations V A  or is set to be sensitive to such acoustic vibrations. In some embodiments, the data which are produced by the microphone  21  are an acoustic signal as the one shown for example in  FIG. 4 . The signal of  FIG. 4  corresponds to the sounds which are produced during surgery when successive impacts are applied to the cup  1  by the impact application device  10 : in this specific and not limitative example, this temporal acoustic signal includes nineteen sound traces ST 1 , ST 2 , . . . , ST 19 , which are temporally successive and which respectively correspond to nineteen successive impacts applied to the cup  1 . The time between two successive sound traces is not constant amongst the sound traces ST 1  to ST 19  because this time depends on the speed with which the surgeon manipulates the hammer  12  to hit the impactor  11 . In the same way, the sound intensity of each of the sound traces is not necessarily constant amongst the sound traces ST 1  to ST 19  because the surgeon does not hit exactly with the same force. 
     The monitoring system  20  further includes an analysis unit  22  which is in communication with the microphone  21  and which receives the data produced by the microphone  21 . The analysis unit  22  is configured to calculate a frequency characterization of the acoustic vibrations V A  for each impact applied by the impact application device  10  to the acetabular cup  1 , from the corresponding data provided by the microphone  21 . For this purpose, the analysis unit includes an appropriate calculator, for example a microprocessor or an electronic device which accepts as input the data coming from the microphone  21 . In some embodiments, calculation performed by the analysis unit  22  corresponds to an FFT (fast Fourier transform) spectrum analysis which leads to calculate a natural frequency, as frequency characterization, for the acoustic vibrations V A  resulting from each impact. For example,  FIG. 5  shows the result of such an FFT spectrum analysis for the temporal acoustic signal of  FIG. 4 : the natural frequency, also called fundamental frequency, of each of the nineteen sound traces ST 1  to ST 19  of  FIG. 4  is calculated by the analysis unit  22 , each of the calculated natural frequencies being represented as a point NF 1 , NF 2 , . . . , NF 19  in  FIG. 5 . In this  FIG. 5 , the nineteen impacts, of which the respective acoustic vibrations V A  are measured by the microphone  21 , are successively indicated along the abscissa of the diagram of  FIG. 5 , whereas the natural frequency associated to each of these nineteen impacts, as calculated by the analysis unit  22 , is plotted on the ordinate of this diagram. 
     According to optional aspects, the analysis unit  22  can filter out the data coming from the microphone  21  before calculating the respective frequency characterizations of the acoustic vibrations V A  of the impacts. For example, the analysis unit  22  can include a background noise filter and/or a bandpass filter. 
     The analysis unit  22  is also configured to compare the frequency characterizations that are respectively calculated for the successive impacts applied to the acetabular cup  1  by the impact application device  10 , so as to provide at each of these successive impacts either a first indication when the assembly between the acetabular cup  1  and the pelvis P is not full or a second indication when the assembly between the cup  1  and the pelvis P is fully seated. This comparison implemented by the analysis unit  12  is intended to indicate a substantial difference between the successive calculated frequency characterizations. 
     In some embodiments, this comparison is made, at each of the successive impacts, between the frequency characterization of the acoustic vibrations V A  measured by the microphone  21  at the last impact with the frequency characterization of the acoustic vibrations V A  measured by the microphone  21  at the second last impact: in the case in which the frequency characterizations are the natural frequencies of the acoustic vibrations as illustrated by  FIG. 5 , this comparison involves comparing, at the nth impact of the nineteen successive impacts, the natural frequency NFn with the natural frequency NF(n-1). 
     In some embodiments, rather to be the frequency characterization resulting from the last impact, the first member of the comparison implemented by the analysis unit  22  is an average of the frequency characterizations respectively resulting from the N last impacts, N being a number between two and ten, preferably between two and eight, preferably between two and six, and preferably between two and four. In some embodiments, rather to be the frequency characterization resulting from the second last impact, the second member of the comparison implemented by the analysis unit  22  is an average of the frequency characterizations respectively resulting from the M impacts just preceding the last impact, M being a number between two and ten, preferably two and eight, preferably two and six, and preferably two and four. Using one and/or the other of these averages in the comparison implemented by the analysis unit  22  can avoid distorting the result, for example due to one incorrect measurement or processing. 
     Also in some embodiments, rather to be the frequency characterization resulting from the second last impact or an average of the impacts just preceding the last impact, the second member of the comparison implemented by the analysis unit  22  is a threshold: this threshold can be predetermined, for example by calibration, or can be calculated, for example as a predetermined percent of the frequency characterization resulting from the first impact or an average of the frequency characterizations resulting from the several first impacts, for example the four first impacts, preferably the three first impacts and preferably the two first impacts. 
     Whatever the two members of the comparison implemented by the analysis unit  22 , as long as, at each new impact amongst the successive impacts, these two members remain substantially equal to each other, for example equal to each other to about 25% or about 20% or about 15% or about 10% or about 5%, it means that the respective frequency characterizations resulting from the successive impacts applied so far are representative of the partial assembly between the acetabular cup and the pelvis P. 
     However, as soon as, for an additional impact, the two compared members are considered by the analysis unit  22  as being different, it means that the assembly between the cup  1  and the pelvis P is now in its fully seated state and no more successive impacts are required. More generally, as long as the result of comparison implemented by the analysis unit corresponds to an unchanged value, to about 25% or about 20% or about 15% or about 10% or about 5%, for the frequency characterizations respectively associated to the impacts applied so far, the analysis unit  22  provides the first indication, that is to say the indication according to which the assembly between the cup  1  and the pelvis P is not fully seated; however, as soon as an additional impact implies a modification for the results of this comparison, the analysis unit  22  provides the second indication, that is to say the indication according to which the assembly between the cup  1  and the pelvis P is fully seated and therefor no additional impacts are necessary to fully seat the cup  1  with the pelvis P. 
     An illustration of the forgoing can be considered referring back to  FIG. 5 : in the case illustrated by  FIG. 5 , the six first natural frequencies NF 1  to NF 6  have approximately the same value whereas the seventh natural frequency NF 7  and the following natural frequencies NF 8  to NF 19  have approximately the same value which is substantially lower than the value of the first six natural frequencies NF 1  to NF 6 , which means that during surgery, the acetabular cup  1  is not fully assembled with the pelvis P after the six first impacts (corresponding to NF 1 -NF 6 ) but the cup is fully assembled at the seventh impact (corresponding to NF 7 ) and remains fully assembled for the following impacts (corresponding to NF 8 -NF 19 ). The example of  FIG. 5  also helps to understand that in the context of this example, the analysis unit  22  provides the first indication at least for the six first impacts and provides the second indication at the seventh impact or at an impact that closely follows the seventh impact depending on the specificities of the comparison implemented by the analysis unit. More generally, whatever the type of the comparison implemented by the analysis unit  22 , this unit provides the second indication either at the “just enough” impact, that is to say the impact that ends up moving the cup  1  into the fully seated assembly with the pelvis P, or at an impact that closely follows the “just enough” impact, depending on the specificities of the comparison implemented by the analysis unit. Applying one or a few additional impacts beyond the “just enough” impact may confirm stabilization or the fully seated assembly. 
     In practice, calculation and comparison, which are implemented by the analysis unit  22 , are processed in real-time and result from appropriate instructions which are stored in the analysis unit  22  or stored on a medium readable by this analysis unit. 
     Referring back to  FIG. 1 , the monitoring system  20  further comprises a user interface  23 . The user interface  23  is in communication with the analysis unit  22  and receives from the analysis unit  22  a signal representative of the first and second indications which are provided by the analysis unit. The user interface  23  is designed to provide feedback based on these first and second indications: when the user interface  23  receives the first indication from the analysis unit  22 , the user interface provides a first feedback element whereas when the user interface  23  receives the second indication, the user interface provides a second feedback element that is different from the first feedback element. In practice, the types of feedback provided by the user interface are not !imitative so long as the various types of feedback are communicated to and understood by the surgeon. In some embodiments, feedback provided by the user interface  23  is visual: for example, the user interface  23  changes its color or its pattern. In this context, as illustrated by the  FIGS. 2 and 3 , it can be considered that the user interface  23  remains blank when receiving the first indication from the analysis unit whereas the user interface  23  displays an exclamation mark “!” when receiving the second indication. In some embodiments, in addition to being visual or instead of being visual, the feedback provided by the user interface may be audible. Whatever the type of feedback provided by the user interface  23 , this feedback gives the surgeon the information that the assembly between the acetabular cup  1  and the pelvis P is first partially seated, and then fully seated. 
     In use, the monitoring system  20  allows the surgeon to monitor the assembly between the acetabular cup  1  and the pelvis P. Indeed, each time the surgeon uses the impact application device  10  to apply an impact to the cup  1  in view of assembly thereof with the pelvis, the microphone  21  measures the acoustic vibrations V A  generated in the air by the impact and produces data representing these acoustic vibrations V A . For each impact, these data are processed by the analysis unit  22  in real-time so as to calculate a frequency characterization of the corresponding acoustic vibrations V A . By comparing the frequency characterizations that are respectively calculated for the successive impacts, the analysis unit  22  provides at each of the successive impacts the first indication then the second indication. As long as the surgeon has feedback from the user interface  23 , which corresponds to the first indication, the surgeon continues to apply new impacts, but when the surgeon has feedback corresponding to the second indication, the surgeon can stop to apply any new impact while having the assurance that the assembly between the cup  1  and the pelvis P is fully seated. 
     Thus, unnecessary additional impacts are avoided. It can be noted that in the example given in the  FIGS. 4 and 5 , the 8th impact and the following impacts are unnecessary so that all of them or at least a majority of them could have been avoided if the surgeon had reacted to the corresponding feedback (e.g., stopping impaction or impact hits), shown in  FIG. 3 , given by the monitoring system  20 . 
     As the monitoring system  20  exploits the acoustic vibrations V A  in the air, this system, especially the microphone  21  thereof, can be separate from the acetabular cup  1 , that is to say can be not attached completely and rigidly to the cup  1 , insofar as the data provided by the microphone  21  are not directly representative of the displacement of the cup  1  during the assembly thereof. 
     In some embodiments as the one shown in  FIG. 6 , the monitoring system  20  is integrated into the impactor  11  of the impact application device  10 : in the example of  FIG. 6 , the microphone  21 , the analysis unit  22  and the user interface  23  are integrated into the grip  18  of the impactor  11 . A not shown variant is to integrate the monitoring system  20  into the hammer  12  of the impact application device  10 . In both cases, sterilization requirements are less than for the acetabular cup  1  or for the distal end  17  of the impactor  14 , which is coupled with the cup  1 . 
     In some embodiments as the ones shown in the  FIGS. 7 and 8 , the monitoring system  20  is also separate from the impact application device  10 . In that case, the monitoring system  20  can be placed outside the sterile field of surgery. As depicted on  FIG. 7 , the monitoring system  20  can be integrated into a personal computer  30 : the central unit of the computer  30  incorporates the analysis unit  22 , the microphone  21  is formed by an appropriate peripheral of the computer  30 , and at least a part of the screen of the computer  30  forms the user interface  23 . As depicted on  FIG. 8 , the monitoring system  20  can be incorporated into a smartphone  40  as an example of any portable device that can integrate the monitoring system. Other examples of such portable devices are a laptop, a pad, etc. In the case of the smartphone  40 , the microphone, the microprocessor and the screen of this smartphone respectively form or incorporate the microphone  21 , the analysis unit  22  and the user interface  23  of the monitoring system  20 . 
       FIG. 9  shows three humeral prosthetic components of a shoulder prosthesis which are respectively a humeral stem  101 , a humeral head  102  and a humeral plate  103 . As known per se and as depicted on the lower part of the  FIGS. 10 and 11 , the humeral stem  101  is provided to be assembled with a human humerus H, by being introduced into a medullary canal C of the humerus H and assembled with this canal by impaction and with or without cement. The humeral head  102  and the humeral plate  103  are designed to be assembled with the humeral stem  101  by impaction: for example, as known per se and as shown in  FIG. 9 , the stem  101  is provided with an upper female feature  104  of a Morse connection, and the humeral head  102  and the plate  103  are each provided with a lower male feature  105 ,  106  of the Morse connection. The components  101 ,  102  and  103  are for example part of AEQUALIS shoulder prosthesis, sold by TORNIER, France. In some embodiments, the humeral head can be at least partly made of pyrocarbon. 
     Turning to the  FIGS. 10 and 11 , an impact application device  110  and a monitoring system  120  will now be discussed in connection with the humeral stem  101 . 
     The impact application device  110  allows the surgeon to apply successive impacts to the humeral stem  101  so as to assemble this humeral stem with the humerus H and thus move the corresponding assembly from a partial state (or partially seated), as shown in  FIG. 10 , to a full state (or fully seated), as shown in  FIG. 11 . For this purpose, the impact application device  110  includes an impactor  111  and a hammer  112 . As explained above for the hammer  12  of the impact application device  10 , the hammer  112  comprises a handle  113  and a head  114 . As also explained above for the impactor  11  of the impact application device  10 , the impactor  111  comprises a rod  115  having a proximal end  116 , on which the head  114  of the hammer  112  can be hit, and a distal end  117 , which is, in use, coupled to the humeral stem  101  so as to drive this stem at each hit of the hammer  112  on the impactor  111 . 
     The monitoring system  120  allows the surgeon to monitor the assembly between the humeral stem  101  and the humerus H. Like the monitoring system  20 , the monitoring system  120  comprises a vibrational sensor  121 , an analysis unit  122  and a user interface  123 . 
     Unlike the vibrational sensor  21  that is sensitive to acoustic vibrations in the air, the vibrational sensor  121  is sensitive to material vibrations V M  that are generated in the impact application device  110  at each impact applied by the impact application device  110  to the humeral stem  101 . The sensor  121 , which is a piezoelectric sensor in some embodiments, is integrated into the impact application device  110  and is operable to produce data representing the material vibrations V M . As depicted on the  FIGS. 10 and 11 , such a piezoelectric sensor is for example integrated into the head  114  of the hammer  112 . 
     The analysis unit  122  is similar to the analysis unit  22 , except that the analysis unit is configured to process the data coming from the sensor  121 . In some embodiments, the frequency characterization, that is calculated by the analysis unit  122  for each impact applied by the impact application device  110  to the humeral stem  101 , is a wave frequency of the corresponding material vibrations V M  generated in the impact application device. 
     The interface user  123  is similar or even identical to the interface user  23  of the monitoring system  20 . 
     In some embodiments as the one shown in the  FIGS. 10 and 11 , the analysis unit  122  and the user interface  123  are integrated in the hammer  112 , for example in the handle  113  of the hammer. 
     In use of the monitoring system  120 , each time the surgeon uses the impact application device  110  to apply an impact to the stem  101  in view of assembly thereof with the humerus H, the sensor  121  measures the material vibrations V M  generated in the impact application device  110  by the impact and produces data representing these material vibrations V M . For each impact, these data are processed by the analysis unit  122  in real-time so as to calculate a frequency characterization of the corresponding material vibrations. By comparing the frequency characterizations that are respectively calculated for the successive impacts, the analysis unit  122  provides at each of the successive impacts the first indication then the second indication. As long as the surgeon has feedback from the user interface  123 , which corresponds to the first indication, the surgeon continues to apply new impacts, but when the surgeon has feedback corresponding to the second indication, the surgeon can stop to apply any new impact while having the assurance that the assembly between the stem  101  and the humerus H is fully seated or complete. 
     Turning to the  FIGS. 12 and 13 , an impact application device  210  and a monitoring system  220  will now be briefly discussed in connection with the humeral head  102  and the humeral plate  103 . 
     The impact application device  210  allows the surgeon to apply successive impacts selectively to the humeral head  102  and to the humeral plate  103  so as to assemble selectively this humeral head or this humeral plate with the humeral stem  101  and thus move the corresponding assembly, especially by the aforesaid Morse connection between the features  104  and  105  or between the features  104  and  106 , from a partial state to a full state. Similarly to what has been explained above for the impact application devices  10  and  110 , the impact application devices  210  includes an impactor  211  and a hammer  212 . The impactor  211  comprises a rod  215  having a proximal end  216 , on which can be hit the hammer  212 , and a distal end  117 , which is, in use, coupled selectively to the humeral head  102  or the humeral plate  103 , the shape of this distal end  217  being slightly modified depending on the humeral component between the head  102  and the plate  103  to which it is coupled. 
     The monitoring system  220  is similar to the monitoring system  120  and comprises a vibrational sensor  221 , an analysis unit  222  and a user interface  223  which are respectively similar to the sensor  121 , the unit  122  and the interface  123 . 
     In some embodiments as the one shown in the  FIGS. 12 and 13 , the monitoring system  220  is integrated into the impactor  211 , especially into a grip  218  of this impactor. In use of the monitoring system  220 , each time the surgeon uses the impact application device  210  to apply an impact to the head  102  in view of assembly thereof with the stem  101 , the sensor  221  measures the material vibrations V M  generated in the impact application device  210  by the impact and produces data representing these material vibrations V M . For each impact, these data are processed by the analysis unit  222  in real-time so as to calculate a frequency characterization of the corresponding material vibrations. By comparing the frequency characterizations that are respectively calculated for the successive impacts, the analysis unit  222  provides at each of the successive impacts the first indication then the second indication. As long as the surgeon has feedback from the user interface  223 , which corresponds to the first indication, the surgeon continues to apply new impacts, but when the surgeon has feedback corresponding to the second indication, the surgeon can stop to apply any new impact while having the assurance that the assembly between the head  102  and the stem  101  is fully seated or complete. Same considerations apply when the monitoring system  220  is used during assembly between the humeral plate  103  and the stem  101 . In both cases, during the assemblies, the stem  1  can be held in an impaction table T, known per se. 
     The various embodiments and examples given so far show that the invention can be used to monitor by-impaction assembly between any type of prosthetic components and a support member that is either a bone or another prosthetic component. Thus, in addition to the examples already given above, the invention can be used to monitor by-impaction assembly between a glenoid baseplate and glenoid bone of a human scapula, or between a femoral hip stem and medullary canal of a human femur. In addition to the examples already given above, the invention can also be used to monitor by-impaction assembly between a prosthetic insert and a prosthetic stem, or between a glenosphere and a glenoid baseplate, or between an acetabular ceramic insert and an acetabular cup, or between a humeral head, potentially comprising pyrocarbon, and a humeral anchorage. 
     Each feature of the monitoring systems  20 ,  120  and  220  may be implemented for any of the above-disclosed embodiments, when technically possible.