Patent Publication Number: US-2003225327-A1

Title: Compressible foot plate to monitor pressure

Description:
DESCRIPTION  
       [0001] 1. Technical Field  
       [0002] The present invention relates to a device comprising a compressible footplate having an indicator means and a display unit suitable to be used in a device for complementary examination of the lumbar region at computer tomography and magnetic resonance tomography.  
       [0003] The object of the present invention is to obtain a footplate for monitoring pressure, the indication of said footplate being independent from of where and how the pressure is applied, which footplate is suitable to be used in a device with the help of which a careful and reproducible examination of the lumbar region in connection with computer tomography and magnetic resonance tomography can be carried out, in particular for the diagnosis of changes of the spinal cord and its nerve structures (spinal stenosis).  
       BACKGROUND OF THE INVENTION  
       [0004] Traditionally, patients have been examined in a relaxed position on their backs at computer tomography and magnetic resonance tomography, which means that structures in connection with the spinal cord channel, which are variable, e.g., intervertebral discs, ligaments, and small joints, are subject to a minimal load. At load i.a., the pressure in the intervertebral disc will increase, which results in a protuberance, which in turn reduces the space in the spinal cord channel where nerve and vessel structures available are present. At the examination of the spinal cord channel of the lumbar region using computer tomography or magnetic resonance tomography suspecting spinal stenosis there is a demand for being able to load the lumbar region in the same way as takes place when standing right up, simultaneously as the patient is placed in horizontal position.  
       [0005] In U.S. Pat. No. 3,629,581 a device is disclosed for positioning a patient&#39;s shoulders in connection with an X-ray examination of a patient&#39;s spine, whereby the upper vertebral column is pressed down towards the examination table and facilitates a good X-ray imaging of the upper vertebras. Hereby a pressure is applied over the vertebral column of the lying patient by means of two flexible traction lines provided with handles for the patient, which traction lines are arranged around a footplate.  
       [0006] In EP-A-0 714 265 a device for the compression of the lumbar region for medicinal imaging is disclosed, comprising a resting plane to which a foot support is applied containing pressure sensors arranged to register the pressure from the respective foot on said footplate, a waistcoat arranged to be placed around the body of a patient, traction lines being arranged between said footplate and said waistcoat, as well as a straining device to said traction lines, which device is arranged to be strained to a predetermined value.  
       [0007] The design of the footplate can be directly connected to lack of carefulness of the determination result, whereby there is a problem present at the design of a compressible footplate which indicates a pressure thereon independent of where and how the pressure is applied onto the footplate, which can used in a device which can be utilised at the examination of the spinal cord channel of the lumbar region.  
       [0008] 2. Description of the Present Invention  
       [0009] The present invention encompasses a pressure footplate suitable for reproducible indication in a device for the compression of the lumbar region for the medical imaging. Besides waistcoat, traction lines and a resting plane a footplate is to be included which to a considerably degree contributes to the carefulness of said device for the compression of the lumbar region.  
       [0010] The compressible footplate comprises a footplate, a compressible device, an indicator means, and an outer house and the Cupertino thembetween, i.e., both the constructions of the same, and wherein the fitting and the mounting of the compressible footplate determine the carefulness of the final determination result.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0011] The present invention relates to a compressible footplate of a device used at complementary examination of the lumbar region at computer tomography, whereby it comprises a resting plane being part of a patient table, a foot support arranged to said resting plane said support comprising at least one compressible footplate, whereby the compressible footplate comprises a footplate, a compressible device, an indicator means and a contra support, preferably in the form of an outer house, which is characterized in that the compressible device comprises at least four plates having a higher hardness and at least two plates having lower hardness than the first mentioned plates, and at least two distance means, whereby said plates and distance means are arranged in such a way in relation to each other that the two parallel plates having a lower hardness contributes to said device being compressible.  
       [0012] According to a preferred embodiment of the invention the distance means have sides provide with semi-circular recesses with a substantially circular or oval cross-section or the similar, which are turned inward towards each other in a mounted position of the compressible device in order to create better compression properties and a higher resistance.  
       [0013] According to another preferred embodiment of the invention an indicator means comprises at least two rolls, an adjustable slide, an elastic band, and a wire, which are arranged to counteract each other, a pointing means, whereby said indicator means is arranged to influence an outer movement/force and to transform the outer movement/force to a value via a display unit. 
     
    
    
     DESCRIPTION OF THE FIGURES  
     [0014]FIG. 1 a  shows a side view of an embodiment of a complete device for compression of the lumbar region for medical imaging and with the footplate seen in its environment.  
     [0015]FIG. 1 b  shows a side view of an enlargement of the footplate with its ingoing details.  
     [0016]FIG. 2 shows a view of the footplate seen from above.  
     [0017]FIG. 3 shows a side view of the compressible device.  
     [0018]FIG. 4 shows an indicator means seen in a cross-section from above and from the side.  
     [0019]FIG. 5 a  shows the outer house seen from above.  
     [0020]FIG. 5 b  shows the outer house seen from below. 
    
    
     PREFERRED EMBODIMENT  
     [0021] The compressible footplate seen in its environment is a complete device for the compression of the lumbar region for a medical imaging, cf. FIG. 1 a.    
     [0022] The device, i.e., the compressible footplate comprises a footplate  1 , a compressible means  2 , an indication means  3  and an outer house  4 , cf. FIG. 1 b.    
     [0023] The footplate  1  has a substantially rectangular form having rounded short ends, cf. FIG. 2. The front side of the footplate  1  is a contact surface of a patient&#39;s foot. On the rear side of the footplate  1  the compressible means  2  is arranged, which in a mounted condition is covered by the outer house  4  of the device, cf. FIG. 1 b.    
     [0024] On the outmost end of one of the rounded short sides of the footplate  1  there is a protrusion  5  and screw hole  6  arranged for an adjustable screw, cf. FIG. 1 b , which will be described more in detail in the following.  
     [0025] In a preferred embodiment the compressible means  2  encompasses four hard discs  41 ,  42 ,  43 ,  44 , two bendable discs  45 ,  46 , two distance means  47 ,  48 , one stability washer  38  and a number of fastening elements, cf. FIG. 3.  
     [0026] Further in a preferred embodiment all four hard discs  41 ,  42 ,  43 ,  44  have a substantially right-angled triangular form and are preferably of the same size. One of the right sides of the triangularly shaped, hard discs, i.e., one cathetus, s about 4 times longer than the other right side, i.e., than the other cathetus. A somewhat convex protuberance is arranged longitudinally along the edges of the right sides of the lower and upper hard discs  41 ,  42 ,  43 ,  44 . This creates a better fitting when mounting when the somewhat convex edges will be pressed out rectilinearly when they are fixed to the footplate  1  and the outer house  4 .  
     [0027] The two bendable plates  45 ,  46  have a substantially oblong, rectangular form and are of the same size.  
     [0028] The two distance washers  47 ,  48  have both a designs as right block. In a particularly preferred embodiment the two distance washers  47 ,  48  are provided with each their side with a semi circular recess with a circular or oval cross-section or the similar to create a better strength at compression of the compressible means  2 , FIG. 3.  
     [0029] At the mounting of the compressible means  2  onto the footplate  1  two  41 ,  42  of the four hard discs  41 ,  42 ,  43 ,  44  are arranged on their ends having the longer right sides as contact surface with the footplate  1 , and are arranged on a distance from each other, and substantially parallel to each other.  
     [0030] A fixation of the two hard discs  41 ,  42  on the footplate  1  is carried out by means of two protrusions  7 ,  8 . The protrusions  7 , 8  are arranged on the footplate  1  in such away that they are arranged on either side of the said hard discs  41 ,  42  when these are arranged on end on the footplate  1 . In a lateral view the protrusion  7 ,  8  have a substantially triangular, right-angled form.  
     [0031] In the highest points of said protrusions  7 ,  8  there are through-going holes  9 ,  10  being arranged. The two hard discs  41 ,  42  are arranged with fitting holes  49 ,  50  for the arrangement of a through-going fixation joint, i.e., to fixedly secure the two said hard discs  41 ,  42  onto said footplate  1 .  
     [0032] The compressible means  2  further comprises two distance washer  47 ,  48 . The first one  47  is arranged by means of a joint between two of the vertical side surfaces of the distance  47  to the two pointed upper, inner situated corners of the two first hard discs  41 ,  42 , when these are arranged on end, cf. FIG. 3.  
     [0033] On the underneath side of the distance  47  there is a surface of an end of the first bendable plate  45  being arranged, which then is situated above the first bendable plate  45  and the footplate  1 , and is substantially parallel to both the first bendable plate  45  and the footplate  1 . A second distance  48  is arranged vertically in a corresponding manner by means of a joint between the upper and lower sides respectively, of opposite ends of the two bendable plates  45 ,  46 , cf. FIG. 3. The third and forth hard discs  43 ,  44  are arranged on end, however, in such away that they are reversed in relation to the first and second hard discs  41 ,  42 . The vertical side surfaces of the distance  48  are joined to the pointed lower, inner corners of the hard discs  43 ,  44  when they are arranged on end in accordance with above, cf. FIG. 3.  
     [0034] A stabilization washer  38  is arranged in an oblong rounded through-going hole  55 , 56  in the upper part of each of the two upper hard discs  43 ,  44  to create further stability of the compressible means  2 . In the centre of the stability washer  38  a screw hole  39  is arranged for a fixed mounting to the outer house  4  at the mounting thereof, which will be described more in detail in the following.  
     [0035] Hard discs, bendable discs and distances are preferably fixedly arranged and joined to each other by means of an adhesive which is then temperature hardened. The edges between distance and hard disc, and between distance and bendable disc, respectively, are bevelled for the purpose of obtaining a better strength when sharp fillet joints are avoided. The sides of the distances  47 ,  48  having semi-circular recesses are turned inward towards each other in a mounted position of the compressible means  2  to create better compression properties and to obtain a better strength, cf. FIG. 3.  
     [0036] In two through-going holes  51 ,  52 , and  53 ,  54 , preferably arranged in the same manner of the two hard discs  41 ,  42 , and  43 ,  44 , respectively, and in accordance with the holes of the respectively distance  47 ,  48  there is shaft, screw or the similar used as a further fastening element besides the adhesive.  
     [0037] When the footplate  1  is pressed in a preferred embodiment this leads to that the first bendable plate  45  is bent in such away that it will come closer to the rear side of the footplate  1  at the compression. The second bendable plate  46  is then bent in a similar way so that it will come closer to the bendable plate  45  and the footplate  1 . Thus it is substantially the bendable plates  45 ,  46  which are bent at the compression, which leads to that it is primarily the bendable plates  45 ,  46 , the second distance  48 , and the upper two hard discs  43 ,  44  which are moved out of their starting positions and closer to the rear side of the footplate  1 . Accordingly, the third and fourth hard discs  43 ,  44  are brought closer to the first and second hard, rigid discs  41 ,  42  at the compression, so that the gap present at a non-compressed condition is reduced during compression.  
     [0038] In a particularly preferred embodiment the four vertical, triangular discs  41 ,  42 ,  43 ,  44  are suitably made of glass fibre reinforced, hardened polymer, and the two horizontal, rectangular plates  45 ,  46  are preferably made of a carbon fibre reinforced polymer, such as KEVLAR®.  
     [0039] The distances  47 ,  48  are preferably made of a hardened polymer.  
     [0040] Concerning the footplate  1  it is arranged with two further oblong angular protrusions  11 ,  12 , which are arranged perpendicular to the first protrusions  7 ,  8 . The two shorter protrusions  11 ,  12  contributes to that a perfect fitting is obtained between the footplate  1  and the outer house  4  of a mounted device, which will be discussed more in detail in the following.  
     [0041] The footplate  1  is preferably made of hardened polymer, such as polyurethane.  
     [0042] The task of the indication means  3  is to indicate a compression of the compressible means  2  and to transfer that to a readable value. The indication means  3  comprises a bottom plate  20 , an upper spherical lid  21 , a slidable slide  22 , two rotating rolls  25 ,  26 , an elastic band  27 , a thread  28 , and a pointer  29 , cf. FIG. 4. In a preferred embodiment the bottom plate  20  abuts a side surface of the outer house  4  and the upper spherical lid  21  is arranged on top of the bottom plate  20 . A slide  22 , preferably in the form of a disc can slide along two tracks  23 ,  24 , which are formed inside the indication means  3  between the bottom plate  20  and the upper spherical lid  21 , and perpendicular to a surface  58  where a display unit  59  is arranged. On one of the edges of the slide  22  there is a protrusion  31 , as well, having a smooth side surface  32  arranged perpendicular to the sliding direction of the slide  22 , cf. FIG. 4.  
     [0043] The indication means  3  comprises in a mounted condition the two rolls  25 ,  26 , as well. The first roll  25  is made rotating around its axis and is arranged parallel to the slidable slide  22 , and perpendicular to the surface  58  of said display unit  59 . The second roll  26  is rotating around its axis, as well, and is arranged perpendicular to the first roll  25 , and parallel to the slidable slide  22 , cf. FIG. 4. Both rolls  25 ,  26  are rotating around their axis in both directions within the indication means  3 .  
     [0044] In a preferred embodiment a first end of an elastic band  27  is fixedly arranged in the end of the slide  22  facing the protrusion  31 , cf. FIG. 4. A second end of the elastic band  27  is fixedly arranged to the outer surface of the first roll  25  with an extension via the second roll  26 . When both rolls  25 ,  26  are rotating the elastic band  27  slides from the first roll  25 , via the second roll  26 , and towards the end position of the slidable slide  22 , and back to its starting position after compression.  
     [0045] The said elastic band consists, preferably, of a silicon rubber or the similar. Further, in said embodiment a first end of a thread  28 , substantially without elasticity, is fixedly arranged with its one end to a part of the smooth surface  32  of the slide and with a second end fixedly arranged to the outer surface of the first roll  25  with an extension via the second roll  26 . When the two rolls are rotating the thread  28  slides from the first roll  25 , via the second roll  26 , and to the second end position at the protrusion  31  of slidable slide  22  and back to its starting position after compression.  
     [0046] Both the elastic band  27  and the thread  28  are fixedly arranged to the envelope surface of the first roll  25 . They are, however, arranged in substantially opposite side to each other and in opposite directions to each other over the first  25  and second roll  26 . At a compression of the footplate  1  this leads to that the elastic band  27  and the thread  28  contracts each other.  
     [0047] In a preferred embodiment one of the sliding directions of the slide  22  is restricted by said protrusion  31 , and its second sliding direction is restricted by the smooth surface  32  of the slide  22  when the device has been mounted.  
     [0048] Further the indication means  3  comprises a pointer  29  which is fixedly arranged to the first roll  25  and is preferably fixedly surrounding its envelope surface. The pointer  29  is arranged parallel to and in close vicinity to the surface of the display unit in order to avoid parallax effect.  
     [0049] In a particularly preferred embodiment rotation of the roll  25  around its axis within the indication means  3  leads to a deflection of the pointer  29 . The deflection can be read on the display unit  59 , when the angle, as the pointer  29  moves, when the first roll  25  rotates corresponds to one scale deflection, cf. FIGS. 4 and 5 b . The pointer can also be connected to a monitoring unit for monitoring the value obtained. The components of the indication means are preferably made of hardened polymer.  
     [0050] The are also other embodiments of the indication means, which then can be applied in a different way in relation to the display units and pointers.  
     [0051] The outer surrounding house  4  of the device for compression of the lumbar region is arranged with a space  61  for applying the compressible means  2  and has a recess  62  for receiving the footplate  1 , cf. FIG. 5 b .  
     [0052] The space  61  is arranged with tracks  63 ,  64  for receiving the edges of the upper hard discs  43 ,  44  of the compressible device  4  and with tracks  65 ,  66  for the said shorter protrusions  11 ,  12  of the footplate  1 . All said tracks of the outer house  4  creates a substantially perfect fitting in a mounted condition of the device, which thereby leads to that the device for compression of the lumbar region carries out very careful measurements.  
     [0053] In connection to the space  61  and the recess  62  two further tracks  67 ,  68  are arranged to be fit in with the two protrusions  7 ,  8  of the footplate  1 .  
     [0054] There is a suitable clearance between the outer side edges of the footplate  1 , and its rear side and the inner edges of the space  61  and the recess  62  of the outer house  4  so that these parts can move freely at a compression of the footplate  1  and the compressible means  2 . In a preferred embodiment a distance remains of about 4 mm between the footplate  1  and the surface of the recess  62  of the outer house  4  at a complete compression.  
     [0055] There are other embodiments of the outer house  4 , which, however, preferably has a function as a counter holder-on to the footplate  1  and the compressible means  2 . Fixation between the footplate  1  and the compressible means  2  has been discussed previously. The outer house  4  and the compressible means  2  are, in turn, fixedly arranged by means of fastening elements through a through-going screw hole of the lower space  61  of the outer house  4  and through a screw hole  39  of the stability washer  38  of the compressible means  2 . There is then a good fitting between the upper hard discs  43 ,  44  and the inner tracks  63 ,  64 , and the protrusions  11 ,  12  of the footplate  1  and the tracks  65 ,  66  of the outer house  4 .  
     [0056] On a side surface  57  of the outer house  4  the indication means  3  is arranged by means of fastening element and is arranged perpendicular to a surface  58  where a display unit  59  is applied, which is previously mentioned. A suitable gap can be arranged between the inner side of the spherical lid  21  and the surface  58 , as well, where the display unit  59  is arranged.  
     [0057] A hole is furthermore arranged in the outer house  4  for the movement of the slidable slide  22  and the protrusion  31 , and to create a firm abutment between the protrusion  31  of the slide  22  and the protrusion  5  of the footplate  1 .  
     [0058] The said protrusions  31 ,  5  are surrounded by an O-ring at the mounting for a substantially exact abutment surface without any clearance between the footplate  1 , the compression means  2 , the indication means  3  and the outer house  4 , which is required for a careful calibration.  
     [0059] The material of the outer house  4  is preferably hardened polymer. The O-ring is preferably of an elastic rubber material.  
     [0060] In a particularly preferred embodiment adjustment and calibration are carried out by means of an adjustment screw, which is arranged in the screw hole  6  of the footplate  1 , as previously mentioned. The adjustment screw is arranged with its point against the said smooth surface  32  of the slidable slide  22 . When the pointer  29  is adjusted to a zero-position on the display unit  59  the point of the adjustment screw is brought into contact with the smooth surface  32  of the slide  22 , however, without forcing this out of its position. The smooth surface  32  then functions as a calibration and stop surface.  
     [0061] The function of the compressible footplate will now be described more in detail. When the footplate  1  is compressed and the compressible means subsequently is compressed, then the adjustment screw of the footplate  1  is pressed against the smooth surface  32  of the slide  22 . Then the slidable slide  22  is pressed further into the tracks  23 ,  24 . The slide  22  forces by means of the elastic band  27  the first roll  25  via the second roll  26 . Then the first roll  25  rotates a certain angle around its axis whereby the pointer  29  provides an angle deflection, which can be read on the display unit  59 .  
     [0062] When a patient&#39;s foot still no longer compresses the footplate  1  the O-ring contributes to returning the slide  22  to its starting position. The thread co-operates with the second roll  26 , when it slides and drives thereby the first roll  25 , which rotates to its starting position, whereby the pointer  29  is returned to its starting position.  
     [0063] One may also consider embodiments of the invention both with regard to the footplate  1 , the compressible means  2 , the indication means  3  and the outer house  4 .  
     [0064] Finally, it is noted that the invention can be utilized for other compressible discs in connection with other applications.