Patent Application
20150216683
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This document generally relates to the field of prosthetic liners and sockets having information systems for managing the comfort level of the user.
A lower limb prosthetic liner provides optimum functionality when the distribution of patient's weight in a prosthetic socket is one third distal and two thirds proximal. Currently there is no feasible way for a prosthetist to measure weight distribution during the fitting of a new socket to an amputee. The prosthetist relies on experience to make an approximate evaluation of weight distribution. An inappropriate distribution of weight may result in discomfort, poor gait, and damage to the limb. Many of the lower limb amputees are vascular with poor circulation in the residual limb and poor sensory perception. Excessive pressure points are likely to go unnoticed by the amputees which result in wounds that are difficult to heal. Even if the initial socket is properly made and allows an optimal distribution of weight therein, with the maturing of the residual limb over time, the size of the limb shrinks and the pressure of the distal end of the residual limb against the distal end surface of the socket increases. Vascular patients are subjected to positive and negative volume fluctuations more than healthy individuals and such fluctuations affect the distribution of weight in the socket. This problem is addressed by the prosthetist by training the patient to use additional prosthetic socks or a different ply sock for the management of the volume fluctuations of the residual limb. This solution is only partially effective with many older amputees who are not able to assess how many prosthetic socks or what ply of sock to use.
As a solution to this problem, prosthetic sockets and/or liners now on the market have been designed to have residual limb monitoring systems built into them. For example, Published Patent Application No. US 2012/0226197 to Sanders, et al. disclose a prosthetic liner having sensors built into the liner for monitoring various activities of the amputee that effect the volume of an amputee's residual limb. The sensors on the liner further includes a transmitters for transmitting the collected data to a remote computer system of the user, a doctor or prosthetist for developing a sock monitoring strategy. Such data is useful in determining what adjustments must be made to the interface between the residual limb and socket, such as adding or eliminating extra socks, or using sock of a different ply thickness.
However, to date, such prior art systems either have the sensors built into the liner or into the socket. Such liners and sockets are complicated to manufacture and expensive not to mention the fact that costs rise dramatically if they have to be replaced. Thus, the present invention provides another and simpler solution to this problem without having to mount the sensors in the liner and/or socket. The present invention provides a simple resilient insert having force sensing and transmitting electronics for continuous and accurate measurement of the distal contact of an amputee's residual limb against the inside distal surface of a prosthetic socket.
The present invention relates generally to a pressure measurement device that is inserted into a prosthetic socket at the distal end and located between the socket and a socket liner. The device comprises a molded replaceable cushion insert made of resilient silicone or polymeric material shaped to have a lower surface to complementally fit firmly against the interior distal end surface of the socket and an upper concave surface that is contiguous with the concave surface of the distal interior of the socket. The insert is removable from the socket and therefore replaceable. The insert further includes at least one force sensor and electronic receiving and transmitting circuitry associated therewith either embedded or removably mounted therein. In the embodiment where the force sensor and circuitry are embedded therein such as during the molding process, the entire device would be replaceable. In the embodiment where the force sensor and circuitry are removably mounted therein, only the force sensor and/or the transmitting circuitry would have to be replaced. Each force sensor is disposed in the insert and adapted to detect downward pressure caused by a distal end of an amputee's residual limb against the distal end of the socket. Throughout the day, an amputee's residual limb may change in volume such as by swelling or contraction of the residual limb for various reasons. Such volumetric changes will affect the fit of the residual limb within the socket which in turn affects the downward pressure of the residual limb against the distal end of the socket. The present invention is designed to measure these pressure variations and provide feedback to the user, rehabilitation doctor, and/or a CPO (Certified Prosthetist/Orthotist). The electronic circuitry transmits the pressure measurements wirelessly to a personal computer or mobile computing device throughout the day. This invention is designed to systematically inform the user, rehabilitation doctor, and/or a CPO (Certified Prosthetist/Orthotist) of the degree of force or pressure that the distal end of the residual limb is exerting against the distal end of the prosthetic socket throughout the time of use. Accordingly, such information is useful in determining whether a new socket, a new sock, additional socks or elimination of socks may be needed.
In a first embodiment, the insert is molded of a resilient silicone or polymeric material to have a concave-convex shape with the convex side molded to match the interior concave surface of a distal end of a socket. This embodiment could be molded to have at least one force sensor and transmitter circuitry embedded therein or molded to have a cavity in the convex side in which the at least one force sensor and transmitting circuitry can be removably secured.
In a second embodiment, the insert is also molded to have a concave-convex shape with the convex side molded to match the interior concave surface of a distal end of a socket. However, in this embodiment, the convex side of the insert includes an extension leading therefrom which is complementally shaped to fit inside a well or recess defined by a lower section of the socket depending from the distal end thereof. This embodiment could be molded to have at least one force sensor and transmitter circuitry embedded in the extension or molded to have a cavity in the extension in which the at least one force sensor and transmitting circuitry can be removably secured.
The above two embodiments are designed to function with a suction liner or a suspension liner, but could also be modified to function with a locking liner. When modified to function with a locking liner, each of the above define inserts could be molded to have a central opening that aligns with an opening in the distal end of the socket for receiving a locking pin therethrough. Such locking pins are conventionally mounted to the distal end of the liner and cooperate with a locking mechanism mounted to the distal end of the socket. In these modified embodiments, the electronic transmitting circuitry could also be modified to have an opening for the locking pin to pass through.
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b is an enlarged cross-sectional view of the encircled structure illustrated in
c is an enlarged cross-sectional view of the encircled structure illustrated in
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The present invention insert 4 is not limited for use with any particular prosthetic liner and socket arrangement. The embodiment of
The insert 4 is made of a thermoplastic elastomeric material, preferably gel materials, for example by injection molding techniques, such as silicone, copolymer Styrenic gels, polyurethane, block copolymers or other TPE elastomers. A wide variety of thermoplastic materials that could be used to manufacture the present invention are disclosed in U.S. Pat. No. 5,633,286, incorporated herein by reference.
The force sensor 5 is comprised of an ultra-thin flexible force sensing element used to measure a relative change in force or applied load. It may be used for measuring rate of change and identify force thresholds to trigger an appropriate action. The sensor may be also used as a means of switching a device on therefore detecting presence contact and/or touch. The device used in this design is a durable piezoresistive force sensor created in various shapes and sizes tailored to the gel apparatus. The resistance measured is inversely proportional to the applied force. One type of force sensor is the FlexiForce® sensor manufactured and patented by Tekscan, this type of sensor provides a linear force measurement ±3% and can withstand high temperature environments up to 400° F. (HT201). The FlexiForce® sensor can measure up to 100 lbs of force with <5 microseconds response time. The sensor 5 is connected through pins to a flexible conductive fabric, thread or elastic bonded wire 6 which carries the signal to a receiver/transmitter microcontroller 7. The force sensor cables may also contain a resistor or resistive device to provide a ground reference to the controller.
The receiver/transmitter microcontroller 7 receives data from the force sensor 5 and relays such data via Bluetooth technology 29 to an external electronic device such as a personal computer 30 or cell phone 31 as illustrated in
One of the main advantages of this RF module and other types are the ultra-low power sleep mode that provides efficient battery use while asleep. The module will maintain a heartbeat looking for a control signal to wake up and transmit data again. At the receiving data may be processed, saved, cataloged, and displayed to the end user. The EEDS may be a hand-held electronic device or software application, the software is designed to be compatible with Android, IOS, or other major smart-phone device operating systems. The software application is an integral component of the system. The software is necessary in order to record a historical trend of the patients fit as well as perform sensor calibration. The EEDS can be also used by the clinician to provide feedback on the socket fit. The software also allows the ability to set how many data-points per day, and will generate a report and send it through email. The EEDS also has the ability to alert the patient of low battery levels in the device.
The battery 9 is a power supply of the PSBL type and may be a lithium ion, lithium polymer, lithium iron phosphate, nickel-cadmium or any rechargeable energy source. A single supply is used with an on-board voltage regulator to power 1.8V, 3.3V, and 5V levels. The cells may be configured in a single or multiple parallel, series, or similar layout.
As a wearable device battery life, energy density, accessibility and rechargeable capabilities are essential. In the first embodiment, the force sensor, electronic circuitry and battery are adhered to each by adhesive layers 10a and 10b and fully embedded within the elastomeric material 4 during the molding process. Thus, the entire unit may be disposable or, if not, may include a conventional recharging circuit (not shown) by plugging in the apparatus through a charging port. In the second and third embodiments illustrated in
All of the embodiments disclosed herein could be molded in various sizes to fit different size sockets or could be custom fitted to the distal interior surface of a prosthetic socket that may be in use by the user.
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The invention has been described in terms of various embodiments. It will be appreciated by those skilled in the art that various changes and modifications may be made to the embodiments without departing from the spirit or scope of the invention. It is not intended that the invention be limited to the embodiments shown and described. It is intended that the invention include all foreseeable modifications to the embodiments shown and described. It is intended that the invention be limited in scope only by the claims appended hereto.
