Embodiments described herein relate to an orthopaedic implant.
Orthopaedic implants can be equipped with sensors, antenna(s) and microelectronics to form a wireless link for communicating data between the implant and a remote device. The data may include information concerning the condition of the implant and/or the surrounding environment (for example, the tissue in which the implant is located). As an example, the link may be used to report an increase in temperature or pressure in the vicinity of the implant, which could, respectively, indicate an infection or a problem with the original positioning of the implant. The wireless link can also be used to transmit data to the implant, in order to control various functions or cause the implant to adopt a different configuration, for example.
The human body comprises a heavily RF hostile environment; the amplitude of radio waves diminishes quickly due to the lossy nature of the human tissues. In order to maintain the performance of the communication link, the design and configuration of the antenna(s) is critical.
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
According to a first embodiment, there is provided an orthopaedic implant comprising:
In some embodiments, the first surface comprises an electrically conductive surface of the body portion.
In some embodiments, the slot antenna is a cavity backed slot antenna. The cavity of the cavity backed slot antenna may be located inside the body portion.
At least one of the walls of the cavity may be formed by a wall of the body portion. In the event that one or more of the walls of the cavity are formed from walls of the body portion, one or more of those walls of the body portion may be electrically conductive.
In some embodiments, the cavity backed slot antenna is insertable into the cavity in the body portion.
In some embodiments, the first surface is a ground plane of the cavity backed slot antenna.
In some embodiments, the first surface comprises part of the outer surface of the implant. The first surface may be shaped so as to match the contours of the outer surface of the body portion.
In some embodiments, the implant includes sensing means for sensing temperature and/or pressure in the environment surrounding the implant and the antenna is configured to transmit data reflecting the temperature and/or pressure to the external device.
According to a second embodiment, there is provided a method for placing a slot antenna in the body of an orthopaedic implant, the body of the orthopaedic implant having a cavity for receiving a broach handle for use in positioning the implant within the patient's body, the method comprising:
As described herein, an orthopedic implant can be understood to refer to a medical device that is manufactured to replace a missing joint or bone or to support a damaged bone. Such an implant may be provided for different parts of the body, including the hip, knee or shoulder, for example. Typically, such implants are fabricated using stainless steel and titanium alloys. A plastic coating may be provided in order to act as artificial cartilage.
A conventional implant 100 is shown in
The external device may be one of any known communication devices having a wireless receiver and/or transmitter, including for example a laptop computer, mobile telephone or tablet. The external device may be used by a physician to monitor the state of the patient's implant following surgery to set the implant in place. The antenna can be used to transmit information about the implant's environment once the implant has been positioned within the patient's body, and/or to receive information or instructions to reconfigure the implant (for example, to cause the head portion of the implant to adopt a different position relative to the stem portion).
In use, the power dissipated by the antenna can be calculated by integrating the ohmic losses in the near field, these losses being caused by the conductivity of the tissues. In this respect, a slot antenna (which is an example of a magnetic antenna) provides an advantage over electric antennas, in that the electric field in the near-field of the antenna is smaller. Consequently, the slot antenna will induce fewer currents in the surrounding tissue, thereby reducing the ohmic losses. In addition, since the slot antenna is exposed to the outside of the implant, the wireless communication signals will not be blocked by the body of the implant. Accordingly, the integrity of the wireless communication link can be maintained without sacrificing the physical strength or the size and the shape of the orthopaedic implant.
In the embodiment shown in
In the present embodiment, the cavity backed slot antenna 203 is received within a cavity 211 in the body portion. When the cavity backed slot antenna is received within the body portion, the cavity 209 extends from the surface 207 towards the inside of the body portion.
Implementing a cavity backed slot antenna may help to improve the strength of the wireless signal received from the antenna, as most of the radiation from the antenna will be transmitted in a single direction.
It will be understood that in some embodiments, the walls of the cavity 211 in the body portion may themselves provide the cavity for the cavity-backed slot antenna 203; that is, it may not be necessary to provide a separate walled cavity 209 for the antenna, but instead this cavity can be fashioned from the body portion itself. In such a case, the slot antenna may be provided as an additional piece of metal (for example, a planar sheet) that is placed at one end of the cavity 211 in the body portion.
In the example shown in
In some embodiments, the surface in which the slot is located may itself comprise a conducting (outer) surface of the implant; that is, the outside surface of the implant may form a wall of the cavity backing the slot antenna, or the ground plane of the slot antenna.
In some embodiments, the orthopaedic implant may be provided as a single unit, in which the slot antenna is incorporated (fixed) within the body portion; alternatively, the antenna may be provided as a separate component from the body of the implant, which can then be inserted into the body portion during surgery.
When positioned in the body portion, the slot antenna can be connected to other circuitry that is housed within the implant and which is used to monitor the implant's environment, for example. Such circuitry may include sensors for performing measurements of temperature and/or pressure, as well as standard components for converting those measurements into signals capable of being transmitted by slot antenna and/or for processing of signals being received by the antenna.
In some embodiments, the surface in which the slot is located is a flat surface. In some embodiments, the surface may be shaped so as match the contours of the body portion; that is, there may be a smooth transition between the first surface and the rest of the outer surface of the body portion. The surface in which the slot is located may itself comprise an outer surface of the implant, or be substantially flush with the outer surface of the implant. The antenna can, therefore, be positioned within the body portion without protruding from the structure and adversely affecting the mechanical strength.
In some embodiments, the slot antenna is configured to transmit at frequencies in one or more of the 2.4 GHz ISM band, 5.2 GHz ISM Band and Lower UWB (for example, in a frequency range from 3.1 GHz to 4.8 GHz).
While certain embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the invention. Indeed, the novel methods, devices and systems described herein may be embodied in a variety of forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Filing Document | Filing Date | Country | Kind |
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PCT/GB2015/050609 | 3/3/2015 | WO | 00 |