Patent Application
20110077560
The present invention relates to medical devices. More particularly the present invention relates to a passive motion machine with integrated mechanical deep vein thrombosis (DVT) prophylactic therapy.
It is estimated that more than a million joint replacement surgeries are performed each year worldwide. It is further estimated that that number will double in the next ten or twenty years. While joint replacement surgeries are common and generally very successful, they are not without risk. Frequent complications include loosening of the implant, infection and deep vein thrombosis (DVT).
DVT affects millions of people each year. DVT occurs when blood cells coagulate within a deep vein. Once a DVT occurs, portions of the clot can break free and move through the bloodstream to the lungs or brain. A clot that lodges in the lungs may block blood flow within the lungs, causing a potentially fatal pulmonary embolism. A blood clot that reaches the brain may cause a stroke. As many as 200,000 people die each year as the result of complications from DVT.
A post-operative joint replacement patient is at the highest risk of developing a DVT approximately ten to twelve days after surgery. At that point, the large majority of patients are being cared for on an outpatient basis. To prevent the formation of DVT, and avoid the risks associated with DVT, doctors generally prescribe one or more forms of DVT prophylaxis, which include primarily chemical and mechanical DVT prophylactic therapies. While each of these therapies is beneficial in some respect, each suffers significant shortcomings.
Common types of chemical DVT prophylaxis include drugs such as warfarin and heparin, which are used to prevent the patient's blood cells from adhering and forming clots. These drugs work by effectively preventing the formation of certain proteins that are needed for blood to clot. While they are effective, they are also very dangerous. The treatment leaves patients at high risk for various potentially fatal bleeding problems including, but not limited to, gastrointestinal bleeding and brain hemorrhage. Further, a number of patients are advised not to use anticoagulants due to various other conditions that create increased risk of fatality. Hence, there is a need for effective non-chemical DVT prophylaxis.
The most common mechanical DVT prophylactic therapy, device is a pneumatic sleeve, which consists primarily of a flexible plastic envelope that encloses a portion of a limb—generally a lower limb. The envelope is periodically inflated to create pressure against the tissues of the limb. The periodic compression and release of the tissues serves to facilitate blood and fluid exchange. When the pneumatic pressure within the envelope increases, the tissues are compressed and a portion of blood and other fluids in the limb are forced out through the circulatory and lymphatic pathways. When the envelope is deflated the limb is free to fill with fluid unimpeded. This method of providing mechanical compression increases the overall velocity of venous flow. Additional means of providing mechanical compression include stockings, compression straps, massage and vibrations, each of which is also designed to increase circulation and fluid exchange.
Mechanical DVT prophylaxis is beneficial in that it physically aides movement of blood and other fluids. Additionally, it is believed to have a wider systemic effect, likely due to the release of various anti-clotting factors during endothelial compression. However, existing means of mechanical compression are enormously imperfect. Circulation in the lower limbs is predicated on the function of one-way valves in the large veins. Currently used devices, such as compression stockings and pneumatic sleeves, attempt to cause movement of fluid in the limb by creating non-directional mechanical compression of the tissues. However, because this compression is non-directional, it simply creates pressure against which blood must be pumped on its way from the distal end of the extremity back towards the torso. This type of non-directional mechanical compression is very inefficient. Accordingly, there is a need for a device that causes directional mechanical compression of the lower limb, oriented such that the compression pushes blood up the limb and back towards the heart, effectively aiding the one-way valves of the leg.
In addition to being an inferior method for increasing venous flow, existing methods of providing mechanical DVT prophylaxis are cumbersome and difficult to maneuver. For example, pneumatic compression sleeves consist of various fasteners, tubes, electrical cords and a machine. Post-operative patients are generally taking significant pain medications, experiencing very limited mobility, and are often elderly. The equipment for providing mechanical DVT prophylaxis creates an additional hazard for these patients, and as such, doctors hesitate to send patients home with such a device. Accordingly, patients often do not receive adequate DVT prophylaxis during the critical ten to twelve day period. Hence, there is an additional need for a system that is simple and portable such that it is practical for use both in a treatment facility and at home.
In addition to preventing formation of DVT and other risks associated with joint replacement, doctors generally prescribe a physical therapy regimen to aide the patient's functional recovery.
Continuous passive motion (CPM) machines are used regularly in orthopedics and physical therapy. These machines are most often used after surgical procedures, such as joint replacement. The machine moves a patient's limb through a predetermined range of motion without physical exertion by the patient. The passive movement of the affected limb has several positive effects. First, CPM helps to prevent the adhesion of superficial tissues to deeper tissues during healing. These adhesions, if developed, can limit the range of motion of the joint and therefore limit the functional recovery of the patient. Second, CPM serves to stretch the tissues around the joint to maximize flexibility and prevent healing of tissues with stiff fibrous connections that further limit mobility.
Often, when a post-operative joint replacement patient is discharged from the hospital, the doctor prescribes a CPM regimen, to be performed on an outpatient basis. A CPM machine is generally purchased or rented from one of a variety of companies. Medicare covers the cost of renting a CPM machine for the prescribed period of time following some joint replacement surgeries.
In view of the foregoing, there is a need to provide a more effective system for providing mechanical DVT prophylaxis, both within the treatment facility and at home, particularly ten to twelve days after surgery. An ideal device would be portable and simple to use such that it can be used safely on an outpatient basis. The system should provide directional compression such that it effectively aides movement of the blood from a distal position back towards the heart. Further, the mechanical DVT prophylactic therapy is preferably provided in combination with CPM therapy because the simultaneous provision of CPM and mechanical DVT prophylaxis is likely to provide enhanced synergistic effects such as enhanced venous flow during CPM that likely serves to further reduce the risk of DVT formation, and increased blood supply to the damaged tissue during DVT prophylaxis that may serve to increase the rate of healing and enhance the ability to fight infection. Finally, the therapies are ideally provided in combination because such an arrangement is cost effective for the large number of patients on Medicare. The present invention addresses one or more of these needs.
In accordance with one aspect of the present invention, and by way of example only, there is provided a passive motion machine with integrated deep vein thrombosis prophylactic therapy for use by or on a human patient. The passive motion machine may include a base, one or more motors, one or more hinged frame rails for imparting passive motion, a roller assembly, and a suspension structure or support structure for positioning the roller assembly in proximity to the hinged frame rails for contact with a patient's limb. The one or more motors provide the passive motion to the limb and rotate the roller assembly against the limb.
In one embodiment the suspension structure positions the roller assembly in proximity to the hinged frame rails for contact with a patient's limb by suspending the roller assembly from the hinged frame rails. In another embodiment of the invention, the support structure, which is affixed to the base of the machine, positions the roller assembly in proximity to the hinged frame rails for contact with a patient's limb by supporting the roller assembly from the base.
According to one embodiment of the present invention, the roller assembly has a single roller. According to another embodiment, the roller assembly is a multiple roller unit. In a further embodiment, the roller assembly is a belt and roller apparatus. The roller assembly preferably includes one or more hubs supporting the roller or rollers for rotation.
As the one or more rollers of the roller assembly contact the patient's limb, both the roller assembly and the one or more rollers roll on the patient's limb. The one or more rollers apply a mechanical DVT prophylaxis therapy to the patient's limb, reducing the risk of blood clotting. Each roller may have a symmetrical or asymmetrical contour along its length. Further, each individual roller may have surface structures, such as bumps, ridges and the like.
Preferably, rotation is imparted to the roller assembly so that the roller assembly rotates in a direction that presses fluid from the distal end of the limb towards the torso. Rotation may be imparted to the roller assembly by a motor driven gear drive, belt drive, direct drive or transmission. The motor may be the same motor that drives the passive motion machine or it may be a separate motor driving just the roller assembly.
The CPM machine may include one or more limb supports for supporting the affected limb from the hinged frame rails for CPM. The limb supports may include a sling and/or a foot rest.
In one embodiment of the invention a vascular monitor system is employed in a feedback loop supplying vascular flow information to a controller for the motor driving the roller assembly.
Other independent features and advantages of the continuous passive motion device will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention. Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring initially to
Referring to
Alternatively, as depicted in
According to the embodiment shown in
Less desirable, but still within the inventive concept, is an embodiment wherein the single roller 41 is positioned at the center of rotation of the single roller roller assembly 26A. In this embodiment, the roller 41 is preferably free to rotate with respect to the one or more suspension structures 30. During use, this embodiment provides constant contact between the roller 41 and the limb.
Alternatively, the single roller 41 may be attached to one or more support structures 35 that are further attached to or supported upon the base 21, as shown by way of example in
Another embodiment of the roller assembly 26 is the multiple roller unit 26B, as shown best in
Depicted in
It is desired that the rollers 41 and not a surface of the belt 61 or 61′ be brought into contact with a patient. Thus as shown in
The belt 61 moves the rollers 41 from a distal position to a relatively proximal position on the patient's limb. As each roller 41 rolls against the patient's limb it creates directional pressure, thereby moving blood and fluid from the distal end of the limb towards the torso. The belt and roller apparatus 26C is oblong or elliptical in profile with dimensions further selected such that the belt and roller apparatus 26C does not interfere with movement of the one or more hinged frame rails 23 during movement of the patient's limb. To enable passage of the rollers, the rolling end pieces 63 can be individual spaced apart wheel-like pieces arranged at edge of the belt with enough space between them to allow passage of the rollers 41, or as shown in
With respect to each of the above described embodiments, a rotational motion may be imparted to the roller assembly 26 during use. Such rotational motion is advantageous in that it moves the one or more rollers 41 against the area to be treated thereby imparting directional mechanical DVT prophylaxis. In a preferred embodiment, rotation is imparted to the roller assembly 26 such that the entire assembly rotates in a direction that presses fluid from the distal end of the limb towards the torso. As shown in
Each of the above described embodiments includes one or more rollers 41. Although the rollers 41 may be of any material, they are preferably of material that is soft enough to be comfortable to the patient, but firm enough to cause the desired tissue compression. Further, the profile or contour of each roller 41 may take a variety of shapes. In one embodiment, the roller 41 has a symmetric contour, wherein a mid portion 43 of the roller 41 is smaller in diameter than the ends, 44 and 45, as illustrated in
It is further noted that each roller 41, whatever its contour, may also be configured so as to have structures 52 on its surface such as bumps, ridges, or other configurations. The roller of
According to a further embodiment, the device 20 includes a vascular monitoring system forming a feedback loop in control or partial control of the motor. One such monitoring system is a commercially available Doppler ultrasound monitor 56 shown schematically in
In yet a further embodiment, the one or more limb supports 25 comprise the sling 43 shown in
The CPM machine with integrated DVT prophylactic therapy 20 operates to provide simultaneous continuous passive motion and mechanical DVT prophylaxis to a patient. A typical patient, such as an individual recovering from a total knee replacement, lies on a floor, bed or other surface in a supine position. The machine 20 is positioned with respect to the patient, such that the patient's limb rests atop the one or more limb supports 25. The device 20 is adjusted or otherwise manipulated so as to bring roller assembly 26 into contact with a patient's leg. The patient's leg can be secured to the one or more hinged frame rails 23 of the device 20. Operation of the device causes passive motion of the patient's limb and joint through a predetermined range of motion. Further, operation imparts a turning motion to the roller assembly 26, such that one or more rollers 41 move across the patient's limb. The rollers 41 partially compress the patient's tissues and assist in moving blood through the tissues, and particularly the deep veins. The roller assembly 26 may be positioned and manipulated so as to rotate in either a clockwise or a counterclockwise direction. The preferred direction or rotation causes the rollers 41 to translate from a distal position to a relatively proximal position, in order to encourage movement of blood and fluid from the distal end of the extremity towards the torso.
The above described embodiments provide significant advantages over the devices, methods and therapies found in the prior art. First, the present invention provides more effective mechanical DVT prophylaxis than is provided by the devices and methods found in the prior art. Specifically, the above-described device provides directional compression, which effectively aides the movement of blood and other fluids from the distal end of the limb towards the torso. Second, the present invention is portable and simple to use in the same ways that prior art CPM devices are known to be portable and simple to use. Accordingly, doctors will likely use and prescribe the present invention in the same manner that they have long prescribed inpatient and outpatient use of a CPM machine for post-operative therapy. Further, doctors will enjoy enhanced peace-of-mind knowing that patients are undergoing safe and effective DVT prophylaxis during the period of highest risk for DVT formation. Third, the present invention is practical and cost effective for a majority of patients, as Medicare covers the at-home use of a CPM device.
Finally, this combination of two therapies is significantly more than the sum of its parts. The simultaneous provision of CPM and DVT prophylaxis will likely provide enhanced and synergistic effects. For example, it has been shown that CPM of the lower limb alone creates enhanced venous flow which serves to decrease risk of DVT formation. It follows logically that the simultaneous provision of CPM and mechanical DVT prophylaxis maximizes venous flow and further minimizes risk of DVT formation in an otherwise sedentary post-operative patient. Further, it is likely that maximum venous flow will have the additional effect of reducing swelling in the limb, as enhanced circulation draws excess fluid from the soft tissue by osmosis. Conversely, healing damaged tissue and fighting infection at the site of an incision, such as that made during joint replacement surgery, involves a complex cellular inflammatory response that includes white blood cells, platelets, and a variety of other cells and proteins that travel in the blood. Accordingly, increased blood flow to the damaged tissues further promotes wound healing and fighting infection. Moreover, increased blood supply may help prevent formation of excess scar tissue.
While the invention has been described with reference to a preferred embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to a particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
