Patent Publication Number: US-8114036-B2

Title: Apparatus and method for therapeutically treating damaged tissues, bone fractures, osteopenia or osteoporosis

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 11/448,201 (1429-11 CON 2) filed on Jun. 7, 2006, now U.S. Pat. No. 7,207,955, which is a continuation of U.S. patent application Ser. No. 11/073,978 filed on Mar. 7, 2005, now U.S. Pat. No. 7,094,211 (1429-11 CON), which is a continuation of U.S. patent application Ser. No. 10/290,839, filed on Nov. 8, 2002, now U.S. Pat. No. 6,884,227 (1429-11). The priority of these prior applications is expressly claimed and the entire contents of these disclosures are hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to the field of stimulating tissue growth and healing, and more particularly to apparatuses and methods for therapeutically treating damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions. 
     2. Description of Related Art 
     When damaged, tissues in a human body such as connective tissues, ligaments, bones, etc. all require time to heal. Some tissues, such as a bone fracture in a human body, require relatively longer periods of time to heal. Typically, a fractured bone must be set and then the bone can be stabilized within a cast, splint or similar type of device. This type of treatment allows the natural healing process to begin. However, the healing process for a bone fracture in the human body may take several weeks and may vary depending upon the location of the bone fracture, the age of the patient, the overall general health of the patient, and other factors that are patient-dependent. Depending upon the location of the fracture, the area of the bone fracture or even the patient may have to be immobilized to encourage complete healing of the bone fracture. Immobilization of the patient and/or bone fracture may decrease the number of physical activities the patient is able to perform, which may have other adverse health consequences. 
     Osteopenia, which is a loss of bone mass, can arise from a decrease in muscle activity, which may occur as the result of a bone fracture, bed rest, fracture immobilization, joint reconstruction, arthritis, and the like. However, this effect can be slowed, stopped, and even reversed by reproducing some of the effects of muscle use on the bone. This typically involves some application or simulation of the effects of mechanical stress on the bone. 
     Promoting bone growth is also important in treating bone fractures, and in the successful implantation of medical prostheses, such as those commonly known as “artificial” hips, knees, vertebral discs, and the like, where it is desired to promote bony ingrowth into the surface of the prosthesis to stabilize and secure it. 
     Numerous different techniques have been developed to reduce the loss of bone mass. For example, it has been proposed to treat bone fractures by application of electrical voltage or current signals (e.g., U.S. Pat. No. 4,105,017; 4,266,532; 4,266,533, or 4,315,503). It has also been proposed to apply magnetic fields to stimulate healing of bone fractures (e.g., U.S. Pat. No. 3,890,953). Application of ultrasound to promoting tissue growth has also been disclosed (e.g., U.S. Pat. No. 4,530,360). 
     While many suggested techniques for applying or simulating mechanical loads on bone to promote growth involve the use of low frequency, high magnitude loads to the bone, this has been found to be unnecessary, and possibly also detrimental to bone maintenance. For instance, high impact loading, which is sometimes suggested to achieve a desired high peak strain, can result in fracture, defeating the purpose of the treatment. 
     It is also known in the art that low level, high frequency stress can be applied to the bone, and that this will result in advantageous promotion of bone growth. One technique for achieving this type of stress is disclosed, e.g., in U.S. Pat. Nos. 5,103,806; 5,191,880; 5,273,028; 5,376,065; 5,997,490, and 6,234,975, the entire contents of each of which are incorporated herein by reference. In this technique, the patient is supported by a platform that can be actuated to oscillate vertically, so that the oscillation of the platform, together with acceleration brought about by the body weight of the patient, provides stress levels in a frequency range sufficient to prevent or reduce bone loss and enhance new bone formation. The peak-to-peak vertical displacement of the platform oscillation may be as little as 2 mm. 
     However, these systems and associated methods often depend on an arrangement of multiple springs supporting the platform, with the result that precise positioning of the patient on the platform becomes important. Moreover, even a properly positioned patient standing naturally will exert more force on some portions of the platform than others, with the result that obtaining true vertical motion of the patient becomes difficult or impossible. 
     There remains a need in the art for an oscillating platform apparatus that is highly stable, and relatively insensitive to positioning of the patient on the platform, while providing low displacement, high frequency mechanical loading of bone tissue sufficient to promote healing and/or growth of damaged tissues, bone tissue, reduce or prevent osteopenia or osteoporosis, or other tissue conditions. 
     Furthermore, there remains a need for apparatuses and methods for therapeutically treating damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions. 
     SUMMARY OF THE INVENTION 
     The invention described herein satisfies the needs described above. More particularly, apparatuses and methods according to various embodiments of the invention are for therapeutically treating damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions. Furthermore, apparatuses and methods according to various embodiments of the invention can be an oscillating platform apparatus that is highly stable and relatively insensitive to positioning of the patient on the platform, while providing low displacement, high frequency mechanical loading of bone, muscle, tissue, etc. sufficient to promote healing and/or growth of bone tissue, or reduce, reverse, or prevent osteopenia or osteoportosis, or other tissue conditions. Note that a platform according to the invention can be referred to as an “oscillating platform” or as a “mechanical stress platform.” 
     One aspect of apparatuses and methods according to various embodiments of the invention focuses on a platform for therapeutically treating bone fractures, osteopenia, osteoporosis, or other tissue conditions. The platform supports a body. The platform includes an upper plate; a lower plate; a drive lever supported from the lower plate; a spring in contact with the drive lever; and a distributing lever arm in contact with the upper plate. The drive lever is actuated at a first predetermined frequency. Next, the damping member creates an oscillating force at a second predetermined frequency on the drive lever. A portion of the oscillating force transfers to the distributing lever arm. Then a portion of the oscillating force from the distributing lever arm transfers to the platform so that the body on the platform receives an oscillation. 
     A particular method for therapeutically treating a tissue in a body having a mass includes supporting a body with a platform. The method includes actuating the platform at a first frequency, and then oscillating the platform to create an oscillating force with a second frequency associated with a resonance frequency of the mass of the body. Finally, the method includes distributing the oscillating force to the mass of the body on the platform. 
     Another particular method for therapeutically treating tissue in a body includes supporting a body with a mass on a platform. The platform includes an upper plate; a lower plate; a drive lever supported by the lower plate; a damping member in contact with the drive lever; and a distributing lever arm in contact with the upper plate. The method also includes actuating the drive lever at a first predetermined frequency; oscillating the damping member to create an oscillating force with a second predetermined frequency; transferring a portion of the oscillating force from the damping member to the distributing lever arm; and distributing a portion of the oscillating force from the distributing lever arm to the platform so that the body&#39;s mass on the platform receives an oscillation. 
     Objects, features and advantages of various apparatuses and methods according to various embodiments of the invention include: 
     (1) providing the ability to therapeutically treat damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions in a body; 
     (2) providing the ability to therapeutically treat tissues in a body to reduce or prevent osteopenia or osteoporosis; 
     (3) providing the ability to therapeutically treat damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions in a body at a frequency effective to promote tissue or bone healing, growth, and/or regeneration; and 
     (4) providing an apparatus adapted to therapeutically treat damaged tissues, bone fractures, osteopenia, osteoporosis, or other tissue conditions in a body. 
     Other objects, features and advantages of various aspects and embodiments of apparatuses and methods according to the invention are apparent from the other parts of this document. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of an oscillating platform according to various embodiments of the invention, viewed through the top plate, and showing the internal mechanism of the platform. 
         FIG. 2  is a side sectional view taken along line  1 - 1  in  FIG. 1 , and partially cut away to show details of the connection of the oscillating actuator to the drive lever. 
         FIG. 3  is an exploded perspective view of the oscillating platform shown in  FIG. 1 , and partially cut away to show the internal mechanism of the platform. 
         FIG. 4  is a top plan view of another oscillating platform according to various embodiments of the invention, viewed through the top plate, and showing the internal mechanism of the platform. 
         FIG. 5  is a side sectional view along line A-A in  FIG. 4 , showing the oscillating platform in an up-position. 
         FIG. 6  is a side sectional view along line A-A in  FIG. 4 , showing the oscillating platform in a mid-position. 
         FIG. 7  is a side sectional view along line A-A in  FIG. 4 , showing the oscillating platform in a down-position. 
         FIG. 8  is a side sectional view along line B-B in  FIG. 4 . 
         FIG. 9  is a side sectional view along line A-A in  FIG. 4 . 
         FIG. 10  is a rear section view along line C-C in  FIG. 4 , showing the oscillating platform. 
         FIG. 11  is a side-sectional view of another oscillating platform according to various embodiments of the invention, showing the internal mechanism of the platform. 
         FIG. 12  is a side-sectional view of another oscillating platform according to various embodiments of the invention, showing the internal mechanism of the platform. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Apparatuses and methods in accordance with various embodiments of the invention are for therapeutically treating tissue damage, bone fractures, osteopenia, osteoporosis, or other tissue conditions. Furthermore, apparatuses and methods in accordance with various embodiments of the invention provide an oscillating platform apparatus that is highly stable, and relatively insensitive to positioning of the patient on the platform, while providing low displacement, high frequency mechanical loading of bone tissue sufficient to promote healing and/or growth of tissue damage, bone tissue, or reduce, reverse, or prevent osteopenia and osteoporosis, and other tissue conditions. 
       FIGS. 1-3  illustrate an oscillating platform according to various embodiments of the invention.  FIG. 1  shows a top plan view of the platform  100 , which is housed within a housing  102 . The platform  100  can also be referred to as an oscillating platform or a mechanical stress platform. The housing  102  includes an upper plate  104  (best seen in  FIGS. 2 and 3 ), lower plate  106 , and side walls  108 . Note that the upper plate  104  is generally rectangular or square-shaped, but can otherwise be geometrically configured for supporting a body in an upright position on top of the upper plate  104 , or in a position otherwise relative to the platform  100 . Other configurations or structures can be also used to support a body in an upright position above, or otherwise relative to the platform. FIG.  1  shows the platform  100  through top plate  104 , so that the internal mechanism can be illustrated. Oscillating actuator  110  mounts to lower plate  106  by oscillator mounting plate  112 , and connects to drive lever  114  by one or more connectors  116 . 
     Oscillating actuator  110  causes drive lever  114  to rotate a fixed distance around drive lever pivot point  118  on drive lever mounting block  120 . The oscillating actuator  110  actuates the drive lever at a first predetermined frequency. The motion of the drive lever  114  around the drive lever pivot point  118  is damped by a damping member such as a spring  122 , best seen in  FIGS. 2 and 3 . The damping member or spring  122  creates an oscillation force at a second predetermined frequency. One end of spring  122  is connected to spring mounting post  124 , which is supported by mounting block  126 , while the other end of spring  122  is connected to distributing lever support platform  128 . Distributing lever support platform  128  is connected to drive lever  114  by connecting plate  130 . Distributing lever support platform  128  supports primary distributing levers  132 , which rotate about primary distributing lever pivot points  134 , which may be formed by the surface of the primary distributing lever  132  bearing against the end of a notch  136  in a support  138  extending from lower plate  106 . Secondary distributing levers  140  are connected to primary distributing levers  132  by linkages  142 , which may be simply mutually engaging slots. Secondary distributing levers  132  rotate about pivot points  144  in a manner similar to that described above for the primary distributing levers  132 . 
     Upper plate  104  is supported by a plurality of contact points  146 , which can be adjustably secured to the underside of the upper plate  104 , and which contact the upper surfaces of primary distributing levers  132 , secondary distributing levers  140 , or some combination thereof. 
     In operation, a patient (not shown) sits or stands on the upper plate  104 , which is in turn supported by a combination of the primary distributing levers  132  and secondary distributing levers  140 . When the apparatus is operating, oscillating actuator  110  moves up and down in a reciprocal motion, causing drive lever  114  to oscillate about its pivot point  118  at a first predetermined frequency. The rigid connection between the drive lever  114  and distributing lever support platform  128  results in this oscillation being damped by the force created or exerted by the spring  122 , which can desirably be driven at a second predetermined frequency, in some embodiments its resonance frequency and/or harmonic or sub-harmonics of the resonance frequency. The oscillatory displacement is transmitted from the distributing lever support platform  128  to primary distributing levers  132  and thus to secondary distributing levers  140 . One or more of the primary distributing levers  132  and/or secondary distributing levers  140  distribute the motion imparted by the oscillation to the free-floating upper plate  104  by virtue of contact points  146 . The oscillatory displacement is then transmitted to the patient supported by the upper plate  104 , thereby imparting high frequency, low displacement mechanical loads to the patient&#39;s tissues, such as the bone structure of the patient supported by the platform  100 . 
     In this particular embodiment, the oscillating actuator  110  can be a piezoelectric or electromagnetic transducer configured to generate a vibration. Other conventional types of transducers may be suitable for use with the invention. For example, if small ranges of displacements are contemplated, e.g. approximately 0.002 inches (0.05 mm) or less, then a piezoelectric transducer, a motor with a cam, or a hydraulic-driven cylinder can be employed. Alternatively, if relatively larger ranges of displacements are contemplated, then an electromagnetic transducer can be employed. Suitable electromagnetic transducers, such as a cylindrically configured moving coil high performance linear actuator may be obtained from BEI Motion Systems Company, Kimchee Magnetic Division of San Marcos, Calif. Such a electromagnetic transducer may deliver a linear force, without hysteresis, for coil excitation in the range of 10-100 Hz, and short-stroke action in ranges as low as 0.8 inches (2 mm) or less. 
     Furthermore, the spring  122  can be a conventional type spring configured to resonate at a predetermined frequency, or resonance frequency. The resonance frequency of the spring can be determined from the equation:
 
Resonance Frequency(Hz)=[Spring Constant(k)/Mass(lbs)] 1/2  
 
     For example, if the oscillating platform is to be designed for treatment of humans, the spring  122  can be sized to resonate at a frequency between approximately 30-36 Hz. If the oscillating platform is to be designed for the treatment of animals, the spring  122  can be sized to resonate at a frequency up to 120 Hz. An oscillating platform configured to oscillate at approximately 30-36 Hz utilizes a compression spring with a spring constant (k) of approximately 9 pounds (lbs.) per inch in the embodiment shown. In other configurations of an oscillating platform, oscillations of a similar range and frequency can be generated by one or more springs, or by other devices or mechanisms designed to create or otherwise dampen an oscillation force to a desired range or frequency. 
       FIG. 2  is a side sectional view taken along line  1 - 1  in  FIG. 1 , and partially cut away to show details of the connection of the oscillating actuator  110  to the drive lever  114 . The drive lever  114  includes an elongate slot  148  (also shown in  FIGS. 1 and 3 ) for receiving connectors  116 . The elongate slot  148  permits the oscillating actuator  110  to be selectively positioned along a portion of the length of the drive lever  114 . The connectors  116  can be manually adjusted to position the oscillating actuator with respect to the drive lever  114 , and then readjusted when a desired position for the oscillating actuator  110  is selected along the length of the elongate slot  148 . By adjusting the position of the oscillating actuator  110 , the vertical movement or displacement of the drive lever  114  can be adjusted. For example, if the oscillating actuator  110  is positioned towards the drive lever pivot point  118 , then the vertical movement or displacement of the drive lever  114  at the opposing end near the spring  122  will be relatively greater than when the oscillating actuator  110  is positioned towards the spring. Conversely, as the oscillating actuator  110  is positioned towards the spring  122 , the vertical movement or displacement of the drive lever  114  at the opposing end near the spring  122  will be relatively less than when the oscillating actuator  110  is positioned towards the drive lever pivot point  118 . 
       FIG. 3  is an exploded perspective view of the oscillating platform  100  shown in  FIG. 1 , and partially cut away to show the internal mechanism of the platform  100 . In this embodiment as well as other embodiments, the invention is contained within a housing  102 . The housing  102  can be made from any material sufficiently strong for the purposes described herein, e.g. any material that can bear the weight of a patient on the upper plate. For example, suitable materials can be metals, e.g. steel, aluminum, iron, etc.; plastics, e.g. polycarbonates, polyvinylchloride, acrylics, polyolefins, etc.; or composites; or combinations of any of these materials. 
     Also shown in this embodiment is a series of holes  150  machined through the upper plate  104  of the platform  100 . The holes  150  are arranged parallel with each of the primary distributing levers  132  and secondary distributing levers  140 . These holes  150  (also shown in  FIG. 1 ) provide different points of connection or attachment for contact points  146 , thereby varying the points at which these contact points contact the distributing levers  132 ,  140 , and thus the amount of lever arm and mechanical advantage used in driving the upper plate  104  to vibrate. 
       FIGS. 4-10  illustrate another oscillating platform according to various embodiments of the invention.  FIG. 4  shows a top plan view of the platform  400 , which is housed within a housing  402 . The platform  400  can also be referred to as an “oscillating platform” or a “mechanical stress platform.” The housing  402  includes an upper plate  404  (best seen in  FIGS. 5-9 ), lower plate  406 , and side walls  408 . Note that the upper plate  404  is generally rectangular or square-shaped, but can otherwise be geometrically configured for supporting a body in an upright position on top of the upper plate  404 , or in a position otherwise relative to the platform. Other configurations or structures can be also used to support a body in an upright position above, or otherwise relative to the platform.  FIG. 4  shows the platform  400  through upper plate  404 , so that the internal mechanism can be illustrated. An oscillating actuator  410  mounts to lower plate  406 . The oscillating actuator  410  is an electromagnetic-type actuator that consists of a stationary coil  412  and armature  414 . The oscillating actuator  410  is configured so that when the stationary coil  412  is energized, the armature  414  can be actuated relative to the stationary coil  412 . The stationary coil  412  mounts to the lower plate  406 , while the armature  414  connects to a drive lever  416  by one or more connectors  418 . 
     Oscillating actuator  410  causes drive lever  416  to rotate a fixed distance around drive lever pivot point  420  on drive lever mounting block  422 . The oscillating actuator actuates the drive lever  416  at a first predetermined frequency. The drive lever mounting block mounts to the lower plate  406 . The motion of the drive lever  416  around the drive lever pivot point  420  is damped by a damping member such as a spring  424 , best seen in  FIGS. 5-8 . The damping member or spring  424  creates an oscillation force at a second predetermined frequency, such as its resonance frequency or a harmonic or sub-harmonic of the resonance frequency. The spring  424  fits around a damping member mounting post such as a spring mounting post  426  which extends between a damping member mounting block such as a spring mounting block  428  and the upper plate  404 . The spring mounting post  426  mounts to the lower plate  406 . 
     A hole  430  near one end of the drive lever  416  permits the spring mounting post  426  to extend upward from the spring mounting block  428 , through the drive lever  416 , and to the bottom side of the top plate  404 . One end of the spring  424  is connected to a spring mounting block  428  while the other end of the spring  424  is connected to a lever bearing surface  432  which mounts to the bottom side of the drive lever  416  and around the hole  430  through the drive lever  416 . Lever bearing surface  430  is connected to drive lever  416  by a threaded connector  434  that fits within the hole  430 . Thus the spring  424  extends between the bottom side of the drive lever  416  and the spring mounting block  428 . 
     A crossover bar  436  mounts to the bottom side of the drive lever  416  with connector  438 , and extends in a direction substantially perpendicular to the length of the drive lever  416 . At each end of the crossover bar  436 , side distributing levers  440  mount to the crossover bar  436  with connectors  442  at one end of each side distributing lever  440 . Each side distributing lever  440  then extends substantially perpendicular from the length of the crossover bar  436  and substantially parallel to a respective sidewall  408  of the platform  400 . Each side distributing lever  440  rotates about side distributing lever pivot points  444  located near the opposing ends of the side distributing levers  440 . A lift pin  446  adjacent to the side distributing lever pivot point  444  and extending substantially perpendicular from the side distributing lever arm  440  bears against the end of a notch  448  in a support  450  extending from upper plate  404 . 
     Upper plate  404  is supported by a plurality of contact points  452  which result from the bearing contact between the upper surface of the lift pin  446  and a portion of the notch  448  in the support  450 . 
     A printed circuit board (PCB)  454  mounts to the lower plate  406  by connectors  456 . The PCB  454  provides control circuitry and associated executable commands or instructions for operating the oscillating actuator  410 . 
     An access panel  458  in the upper plate  404  provides maintenance access to the internal mechanism of the platform  400 . 
     In operation, a patient (not shown) sits or stands on the upper plate  404 , which is in turn supported by the lift pins  446 . When the apparatus is operating, oscillating actuator  410  moves up and down in a reciprocal motion, causing drive lever  416  to oscillate about its pivot point  420  at a first predetermined frequency. The rigid connection between the drive lever  416  and drive lever mounting block  422  results in this oscillation being damped by the force exerted by the spring  424 , which can be driven at a second predetermined frequency, in some embodiments its resonance frequency, or a harmonic or sub-harmonic of the resonance frequency. The damped oscillatory displacement is transmitted from the drive lever  416  to crossover bar  436  and thus to side distributing lever arms  440 . One or more of the side distributing lever arms  440  distribute the motion imparted by the oscillation to the free-floating upper plate  404  by virtue of the lift pins  446  and contact points  452 . The oscillatory displacement is then transmitted to the patient supported by the upper plate  404 , thereby imparting high frequency, low displacement mechanical loads to the patient&#39;s tissues, such as a bone structure of the patient supported by the platform  400 . 
     It is desired that a high frequency, low displacement mechanical load be imparted to the bone structure of the patient supported by the platform. To achieve this load, in some embodiments the horizontal centerline distance between the damping member or spring  424  and the drive lever pivot point  420  is approximately 12 inches (304.8 mm); and the horizontal centerline distance between the oscillating actuator  410  and the drive lever pivot point  420  is approximately 3 inches (76.2 mm). The ratio of the distance from the damping member or spring  424  to the drive lever pivot point  420 , and from the oscillating actuator  410  to the drive lever pivot point  420  may be about 4 to 1, and is also called the drive ratio. Furthermore, in this embodiment, the horizontal centerline distance between the side distributing lever pivot point  444  near the drive lever pivot point  420  and the side distributing lever pivot point  444  near the damping member or spring  424  should be approximately 12 inches (304.8 mm); and the horizontal centerline distance between each side distributing lever pivot point  444  and the respective lift pin may be approximately ¾ inch (19 mm). The ratio of the distance from the side distributing lever pivot point  444  near the drive lever pivot point  420  to the side distributing lever pivot point  444  near the spring  424 , and from each side distributing lever pivot point  444  and the respective lift pin is about 16 to 1 in some embodiments, and is also called the lifting ratio. In the configuration shown and described, the oscillating platform  400  provides a specific drive ratio and lifting ratio. Other combinations of drive ratios and lifting ratios may be used with varying results in accordance with various embodiments of the invention. 
     Moreover, in this particular embodiment, the oscillating actuator  410  is an electromagnetic-type actuator configured to actuate or generate a vibration, such as a combination coil and armature or a solenoid. Other conventional types of actuators may be suitable for use with the invention. In the configuration shown and described, the oscillating actuator may be configured to actuate at approximately 30-36 Hz. 
     Furthermore, the damping member or spring  424  can be a conventional type coil spring configured to resonate in a range of predetermined frequencies. For example, if the oscillating platform is to be designed for treatment of humans, the damping member or spring is sized to resonate at a frequency between approximately 30 and 36 Hz. If the oscillating platform is to be designed for the treatment of vertebrae animals, the damping member or spring is sized to resonate at a frequency range between approximately 30 Hz and 120 Hz. In the configuration shown, the damping member or spring is a compression spring with a spring constant of approximately 9 pounds (lbs.) per inch. In other configurations of an oscillating platform, oscillations of a similar range and frequency can be generated by one or more damping members or springs, or by other devices or mechanisms designed to create or otherwise dampen an oscillation force to a desired range or frequency. 
       FIGS. 5-7  illustrate the platform  400  of  FIG. 4  in operation.  FIG. 5  is a side sectional view along line A-A in  FIG. 4 , showing the platform  400  in an up-position.  FIG. 6  is a side sectional view along line A-A in  FIG. 4 , showing the platform  400  in a mid-position.  FIG. 7  is a side sectional view along line A-A in  FIG. 4 , showing the platform  400  in a down-position. In  FIGS. 5-7 , the internal mechanism of the platform  400  is shown in operation with respect to a load (not shown) placed on the upper plate  404 . These views illustrate the relative positions of the drive lever  416 , side distribution lever arms  440 , and the spring  424  while various loads are placed on the upper plate  404 . 
     As shown in  FIGS. 5-7 , when a specific load is placed on the upper plate  404 , the side distributing lever arms  440  respond to the respective load on the upper plate  404 . In all instances, the load creates a downward force on the upper plate  404  that is transferred from the supports  450  to a respective lift pin  446  and further transferred to the side distributing lever arms  440 , the crossover bar  436 , and then to the drive lever  416  and spring  424 . For example, in  FIG. 5 , when a load weighing approximately fifty pounds (22.5 kilograms) is placed on the upper plate  404 , a side distributing lever arm  440  nearest to and adjacent to the drive lever pivot point  420  is displaced upward towards the crossover bar  436 , whereas the side distributing lever arm  440  nearest to and adjacent to the spring  424  is displaced downward from the crossover bar  436 . The drive lever  416  is displaced generally upward from the drive lever pivot point  420  with the spring  424  in a relatively extended position. 
     In  FIG. 6 , when a load weighing approximately 140 pounds (63 kilograms) is placed on the upper plate  404 , the side distributing lever arm  440  nearest to and adjacent to the drive lever pivot point  420  is displaced to a substantially parallel orientation with the front side distributing lever arm  440  nearest to and adjacent to the spring  424 . The drive lever  416  is displaced generally horizontal from the drive lever pivot point  420  with the spring  424  in a relatively compressed position compared to  FIG. 5 . 
     Finally, in  FIG. 7 , when a relatively large load of approximately 300 pounds (135 kilograms) is placed on the upper plate  404 , the side distributing lever arm  440  nearest to and adjacent to the drive lever pivot point  420  is displaced downward towards the crossover bar  436 , whereas the side distributing lever arm  440  nearest to and adjacent to the spring  424  is displaced upward from the crossover bar  436 . The drive lever  416  is displaced generally downward from the drive lever pivot point  420  with the spring  424  in a relatively compressed position compared to  FIGS. 5 and 6 . 
       FIG. 8  is a side sectional view of the platform  400  along line B-B in  FIG. 4 . This view illustrates the platform  400  in a no-load position, and details the relative positions of the upper plate  404 , side distribution lever arms  440 , and crossover bar  436  in a no-load position. 
       FIG. 9  is a side sectional view of the platform  400  along line A-A in  FIG. 4 . This view further illustrates the platform  400  in a no-load position, and details the relative positions of the drive lever  416 , crossover bar  436 , spring  424 , and oscillating actuator  410  in a no load position. 
       FIG. 10  is a rear section view of the platform  400  along line C-C in  FIG. 4 , showing the platform  400  in a no-load position, and details the relative positions of the drive lever  416 , oscillating actuator  410 , crossover bar  436 , side distribution lever arms  440 , and upper plate  404 . 
       FIG. 11  illustrates another oscillating platform  1100  according to various embodiments of the invention. In  FIG. 11 , a cross-sectional view of the internal mechanism of an oscillating platform  1100 . This embodiment is shown with a housing  1102  including an upper plate  1104 , lower plate  1106 , and side walls  1108 . Note that the upper plate  1104  is generally rectangular or square-shaped, but can otherwise be geometrically configured for supporting a body in an upright position on top of the upper plate  1104 , or in a position otherwise relative to the platform. Other configurations or structures can be also used to support a body in an upright position above, or otherwise relative to the platform. Oscillating actuator  1110  mounts to lower plate  1106  by oscillator mounting plate  1112 , and connects to drive lever  1114  by one or more connectors (not shown). 
     Oscillating actuator  1110  causes drive lever  1114  to rotate a fixed distance at a first predetermined frequency around drive lever pivot point  1116  on drive lever mounting block  1118 . The motion of the drive lever  1114  around the drive lever pivot point  1116  is damped by a damping member such as a cantilever spring  1120 . The cantilever spring  1120  then creates an oscillation force at a second predetermined frequency, such as its resonance frequency or a harmonic or sub-harmonic of the resonance frequency. One end of the cantilever spring mounts to a spring mounting block  1122 , while the other end of cantilever spring  1120  is in contact with the drive lever  1114  or spring contact point  1124 . The spring contact point  1124  may be an extension piece mounted to the underside of the drive lever  1114  and configured for contact with the cantilever spring  1120 . 
     One or more lift pins  1126  extend from a lateral side of the drive lever  1114 . The lift pins  1126  engage a respective notch  1128  in one or more corresponding supports  1130  mounted to the underside of the upper plate  1104 . The free-floating upper plate  1104  is supported by one or more contact points  1132  between the lift pins  1126  and the supports  1130 . 
     The second predetermined frequency, such as the resonance frequency or a harmonic or sub-harmonic of the resonance frequency, of the cantilever spring  1120  can be adjusted by a node point  1134 . The node point  1134  consists of a dual set of rollers  1136 , a roller mounting block  1138 , connectors  1140  and an external knob  1142 . The cantilever spring  1120  mounts between the dual set of rollers  1136  so that the rollers  1136  can be positioned along the length of the cantilever spring  1120 . The dual set of rollers  1136  mount to the roller mounting block  1138  via connectors  1140 . The position of the roller mounting block  1138  can be adjusted along the length of the cantilever spring  1120  by an external knob  1142  that slides along a track  1144  parallel with the length of the cantilever spring  1120 . 
     The position of the node point  1134  can be manually or automatically adjusted, or otherwise pre-set along the length of the cantilever spring  1120 . When the node point  1134  is adjusted to a specific position along the cantilever spring  1120 , the node point  1120  acts as a fixed point or fulcrum for the cantilever spring  1120  so that a resonant length of the cantilever spring  1120  can be set to a specific amount. Note that the resonant length of the cantilever spring  1120  depends upon the mass of the load placed on the upper plate  1104  and the mass of the combined drive lever  1114  and cantilever spring  1120 . The end of the cantilever spring  1120  in contact with the drive lever  1114  or spring contact point  1124  can then resonate when the oscillating actuator  1110  is activated. For example, with a fixed mass placed on the upper plate  1104 , as the node point  1134  is positioned towards the drive lever  1114  or spring contact point  1124 , the resonant length of the cantilever spring  1120  becomes relatively lesser. Alternatively, as the node point  1134  is positioned towards the spring mounting block  1122 , the resonant length of the cantilever spring  1120  becomes relatively greater. 
       FIG. 12  is a side-sectional view of another oscillating platform  1200  according to various embodiments of the invention, showing the internal mechanism of the platform. The view of this embodiment details another configuration of the internal mechanism of the oscillating platform  1200  with a cantilever spring with a sliding node. Other configurations or structures can be also used to perform the disclosed functions of the oscillating platform. 
     Generally, a housing (not shown) houses the internal mechanism. The housing includes a lower plate  1202  or base. An upper plate (not shown) for supporting a body or a mass opposes the lower plate  1202 . An oscillating actuator (not shown), such as those disclosed in previous embodiments, mounts to lower plate  1202 , and contacts the drive lever  1204  in a manner similar to that shown in  FIG. 11 . Generally, the drive lever  1204  is positioned adjacent to the upper plate to transfer oscillation movement from the drive lever to the upper plate and then to a body supported by or in contact with the upper plate. 
     A node mounting block  1206  and an associated servo stepper motor  1208  mount to the lower plate  1202 . The node mounting block  1206  and servo stepper motor  1208  connect to each other via a connector  1210 . When adjusted, the node mounting block  1206  can move with respect to the lower plate  1202  via a slot  1212  machined in the lower plate  1202 . The node mounting block  1206  includes a first roller  1214  mounted to and extending from the upper portion of the node mounting block  1206 . 
     A damping member such as a cantilever spring  1216  mounts to the lower plate  1202  with a fixed mounting  1218 . The cantilever spring  1216  extends from the fixed mounting  1218  towards the proximity of the node mounting block  1206 . The first roller  1214  mounted to the node mounting block  1206  contacts a lower portion of the extended cantilever spring  1216 . As the node mounting block  1206  is moved within the slot  1212 , the first roller  1214  moves with respect to the cantilever spring  1216 . Similar to the configuration shown in  FIG. 11 , this type of configuration is called a “sliding node.” A sliding node-type configuration causes the damping member such as a cantilever spring  1216  to change its frequency response as the node mounting block  1206  changes its position with respect to the damping member such as the cantilever spring  1216 . 
     As described above, the drive lever  1204  mounts to or contacts the lower portion of the upper plate. A roller mount  1220  extends from the lower portion of the drive lever  1204  towards the cantilever spring  1216 . A second roller  1222  mounts to the roller mount  1220 , and contacts an upper portion of the extended cantilever spring  1216 . 
     In this configuration, the oscillating actuator (not shown) causes drive lever  1204  to rotate a fixed distance at a first predetermined frequency around a drive lever pivot point (not shown). The motion of the drive lever  1204  around the drive lever pivot point is damped by a damping member such as the cantilever spring  1216 . The cantilever spring  1216  then creates an oscillation force at a second predetermined frequency, such as its resonance frequency or a harmonic or sub-harmonic of the resonance frequency. 
     The second predetermined frequency, such as the resonance frequency or a harmonic or sub-harmonic of the resonance frequency, of the cantilever spring  1216  can be adjusted as the position of the node mounting block  1206  is changed with respect the to the cantilever spring, i.e. sliding node configuration. The position of the node mounting block  1206  can be manually or automatically adjusted, or otherwise pre-set along the length of the damped member or cantilever spring  1216 . Note that the resonant length of the damped member such as the cantilever spring  1216  depends upon the mass of the load placed on the upper plate and the mass of the combined drive lever  1204  and cantilever spring  1216 . The end of the cantilever spring  1216  in contact with the drive lever  1204  or a spring contact point can then resonate when the oscillating actuator is activated. 
     In the embodiments of an oscillating platform shown in  FIGS. 11 and 12 , and in other structures in accordance with various embodiments of the invention, the platform (also referred to as an “oscillating platform” or “mechanical stress platform”) may be configured to allow different users to selectively adjust the platform to compensate for different weights of each user. For example, in a physical rehabilitation environment, patients or users having different weights may want to utilize the same oscillating platform. Each patient or user could set-up the oscillating platform for an anticipated user weight on the upper plate so that the oscillating platform can apply an oscillation force of a desired resonance frequency or harmonic or sub-harmonic of the resonance frequency to the user when he or she sits or stands on the upper plate. An external knob may be provided on the oscillating platform to permit the user to selectively adjust the oscillating platform in accordance with the user&#39;s weight. 
     In some embodiments such as those shown in  FIGS. 11 and 12 , the external knob controls the position of the sliding node, effectively changing the resonant length of the damped member such as a cantilever spring. In other embodiments, the external knob would control the position of the oscillating actuator relative to the drive lever. This type of configuration would allow the user to adjust the “effective length” of the drive lever and increase or decrease the vertical displacement of the drive lever as needed. The “effective length” of the drive lever is the distance from the centerline of the oscillating actuator to the end of the drive lever nearest the damping member or spring. For example, a user may increase the “effective length” of the drive lever by positioning the oscillating actuator towards the drive lever pivot point so that the corresponding vertical displacement of the drive lever can be increased. Conversely, a user may decrease the “effective length” of the drive lever by positioning the oscillating actuator towards the damping member or spring so that the corresponding vertical displacement of the drive lever can be decreased. 
     Thus, by positioning the oscillating actuator to a predetermined position in accordance with the weight of the user, or by positioning the sliding node in accordance with the weight of the user, the oscillating platform can provide a therapeutic vibration within a specific resonance frequency, or harmonic or sub-harmonic of the resonance frequency, range that is optimal for stimulating tissue or bone growth for different users having a range of different weights. 
     In other embodiments of the invention, the oscillating actuator may be configured for a single position. For example, in a home environment, a single patient only may utilize the oscillating platform. To reduce the amount of time necessary to set-up and operate the oscillating platform, the oscillating actuator may have a pre-set position in accordance with the particular patient&#39;s weight. The patient can then utilize the oscillating platform without need for adjusting the position of the oscillating actuator. 
     Finally, the embodiments disclosed above can also be adapted with a “self-tuning” feature. For example, when a user steps onto an oscillating platform with a self-tuning feature, the user&#39;s mass may be first determined. Based upon the mass of the user, the oscillating platform automatically adjusts the various components of the oscillating platform so that the oscillating platform can apply an oscillation force of a desired resonance frequency or harmonic or sub-harmonic of the resonance frequency to the user when he or she sits or stands or is otherwise supported by the oscillating platform. In this manner, the oscillating platform can provide a therapeutic treatment in accordance with the various embodiments of the invention, without need for manually adjusting the oscillating platform according to the user&#39;s mass, and reducing the possibility of user error in adjusting or manually tuning the oscillating platform for the desired treatment frequency. 
     While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the invention, but merely as exemplifications of the disclosed embodiments. Those skilled in the art will envision many other possible variations that within the scope of the invention as defined by the claims appended hereto.