Abstract:
A patient lateral positioning device for pelvic treatments suitable to support a patient in a defined lateral position includes a vacuum mattress. The vacuum mattress includes an upper body support attachable to an upper body portion of the patient, and a lower body support attachable to a lower body portion of the patient. A region between said upper and lower body support is formed such that when the vacuum mattress is attached to the patient, both a front pelvic side and an upper pelvic side of the patient are exposed.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims priority of U.S. Provisional Application No. 60/917,097 filed on May 10, 2007, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a patient lateral positioning device for pelvic treatments. 
       BACKGROUND OF THE INVENTION 
       [0003]    In pelvic treatments, in particular hip replacement operations, patients typically are operated on while lying on their side, and this requires the patient to be fixed such that their pelvis is positioned at rest. This is conventionally achieved using patient positioners, which comprise supporting means for the lower region of the patient&#39;s body. In this position, however, it is often difficult to ascertain navigation information by tapping body landmarks (ASIS and pubic points) within the framework of medical navigation, because these characteristic pelvic landmarks are in most cases difficult to access, at least in the lower region. X-ray or fluoroscopic registration is therefore often employed. 
         [0004]    Many conventional patient positioners use pads or poles that are fixed to an arm system of the operating table or to similar fixed means. Such a mechanical positioner is known, for example, from U.S. Pat. No. 6,311,349. 
         [0005]    In addition to mechanical positioners, there are also positioners that comprise navigation reference means for medical navigation; such a positioner is known, for example, from WO 2004/089192 A2. The reference means are used to indirectly localize the ASIS and pubic points, which can be used to register the front pelvic plane. 
         [0006]    When registering the ASIS points and pubic points by manually tapping the points and access to these points is impeded by the presence of a positioning means, it is necessary to fall back on fluoroscopic registration. There are positioning means for this purpose that are made of a material that is as radiolucent as possible and comprise the supporting devices already mentioned above, e.g., poles and pads, which are fixed to a carrier system (on a guiding rail) of the operating table. A problem with these existing positioning means for navigation software arises when both fluoroscopic images are to be recorded for registration and image-free registration is to be performed (e.g., by moving a navigation pointer to said points). Despite the at least largely radiolucent material used in the positioning means, it still can cause shadows and edges on the images. On the x-ray recording  60  in  FIG. 7 , for example, a region  61  is marked that shows the shadow of a patient positioner, which is hiding the left-hand os pubis structure.  FIG. 8  shows a fluoroscopic recording  62  obtained using a “radiolucent” positioner, which also shows how the shadow  63  of a part of the positioner hides the content of the image and weakens the contrast. 
         [0007]    Another problem with the known positioning devices for lateral positioning arises when adipose patient tissue overlaps the pelvic rim marks. This makes it difficult or impossible to tap these points with a navigation pointer. Moving a pointer to the pelvic landmarks in this way also is often obstructed by the poles and pads. For this reason, the patient is initially positioned supine, registration is performed and the patient is then repositioned laterally. This is not only time-consuming but also critical with regard to sterility, which may be lost as result of repositioning. 
         [0008]    All the aforementioned disruptions to the registration procedure, e.g., a lack of or incorrect image-free tapping with a pointer or a misinterpretation of fluoroscopic images due to shadows or a lack of contrast, can lead to incorrect registration and therefore errors in navigation, which can in turn have a negative effect on the treatment result. 
       SUMMARY OF THE INVENTION 
       [0009]    A patient lateral positioning device in accordance with the invention for pelvic treatments, by means of which the patient is supported in a defined lateral position, comprises a vacuum mattress that includes an upper body supporting part and a lower body supporting part, and substantially omits the pelvic region on the front side and on the upper side of the positioned patient. In other words, the positioning device in accordance with the invention provides a lateral positioning device comprising a vacuum mattress that allows access to and/or substantially leaves free the locations on the patient that are to be freely accessible for the treatment and for fluoroscopic registration or image-free registration. 
         [0010]    Reference markers or arrays can be attached to the positioning device and detected by a medical tracking or navigation system so as to enable image guided surgery. For example, the medical tracking or navigation system may include infrared cameras or the like that can detect three-dimensional spatial positions of the reference markers attached to the positioning device as well as to markers attached to medical instruments. This position data can be used in conjunction with previously obtained image data, which can be stored in the navigation system, so as to provide guidance to the surgeon. 
         [0011]    It should be noted here that using the lateral positioning device in accordance with the invention, it is already possible to perform optimum image-free registration, e.g., tapping landmark points on the pelvis with a navigation pointer, if the vacuum mattress in the pelvic region omits the front side and upper side of the patient. For said image-free registration, the vacuum mattress still can be easily provided on the rear side of the patient, in order to exercise an additional supporting function. 
         [0012]    In one embodiment in accordance with the invention, the vacuum mattress also substantially omits the pelvic region on the rear side of the patient. In this embodiment, the radiation path for fluoroscopic registration is then completely free of any supporting means, and the images obtained contain high-contrast representations that enable landmarks to be unambiguously assigned in a computer-assisted way. It is thus possible to optimally perform both an image-free registration and an image-assisted registration. 
         [0013]    The vacuum mattress can be embodied as a single piece and comprise a narrow connecting part between the upper body supporting part and the lower body supporting part, wherein when the patient is in the lateral position, the connecting part comes to rest substantially beneath the patient. In accordance with such an embodiment, the vacuum mattress can have a wide upper body supporting part, a narrower lower body supporting part and an even narrower connecting part between the upper and lower parts. In particular, the upper body supporting part is the widest part of the vacuum mattress so as to support the patient&#39;s upper body from beneath while in the lateral position and from both sides over a substantial part of the upper body. The lower body supporting part is narrower than the upper body supporting part so as to at least partly encompass at least one of the patient&#39;s legs, wherein the connecting part is the narrowest part and is narrower than the lower body supporting part. 
         [0014]    In another embodiment in accordance with the invention, the vacuum mattress can be embodied in two parts and individually comprise an upper body supporting part and a lower body supporting part, respectively. 
         [0015]    In accordance with another embodiment in accordance with the invention, the device also comprises a support base for the vacuum mattress or its parts, which can be tilted into predefined angular positions. The support base can be formed from a rigid material as a plate, and it is possible to provide a support base for the upper body supporting part and the lower body supporting part that is in particular formed in two parts, e.g., comprises one support base part for the upper body supporting part and one support base part of the lower body supporting part. 
         [0016]    In accordance with another embodiment, the support base or its parts have two plate portions that are at a predefined angle to each other and can be tilted via a tilting edge in their connecting region. In this case, an angle of about 45 degrees can be selected. It is advantageous if a tilting aid is provided in the region of the tilting edge, in particular a tilting roller along the tilting edge. In order to make tilting easier for the user, a manipulating device for lifting or tilting the support base can be provided on the support base and can comprise grip portions on the plate rims and/or supporting portions beneath the plate portions. 
         [0017]    The patient positioning device (lateral positioning device) in accordance with the invention is capable of fixing the patient in a lateral position on the treatment table, for example during a hip joint replacement operation and while recording fluoroscopic images, without creating shadows or edges in the fluoroscopic image. In addition to the fact that the radiation of the fluoroscopic image is not obstructed, it is also advantageously possible to reposition the patient from a lateral position into a position tilted by about 45 degrees (and vice versa), in order to be able to register the anatomical structures, such as for example pelvic landmarks (ASIS and pubic points) with a navigation pointer. The specially shaped vacuum mattress covers the entire body except for the main part of the pelvic region to be treated (pelvic joint region) and provides a stable fixation for the patient. Important anatomical structures, such as the os pubis, for example, are not covered by fixation material. This is advantageous because such structures of the pelvis are required in order to automatically detect the position of the patient&#39;s pelvis via software. The operating environment is also freely accessible for the surgeon. The fluoroscopic images will not exhibit any disrupting shadows and edges, which could lead to incorrect registrations when using the software. 
         [0018]      FIG. 9  shows an exemplary fluoroscopic image  64  that has been produced using the lateral positioning device in accordance with the invention. The image does not exhibit any disrupting shadows and edges, and the contrast is strong enough to enable image-assisted registration. 
         [0019]    A second advantage of the device in accordance with the invention as compared to known positioning devices is provided by the repositioning mechanism (tilting mechanism). Using this integrated mechanism, it is possible to move a patient from the lateral position into a position tilted by about 45 degrees. This feature enables the surgeon to move the patient in a simple and defined way into a 45 degree tilted lateral position, before or after the sterile environment is created. When the patient is positioned in this way, it is easier to register the anatomical landmarks because any adipose tissue that may be present does not overlap the regions that the pointing apparatus (navigation pointer) is positioned. After registration, the patient can be quickly and easily repositioned, without any loss of sterility. 
         [0020]    The device in accordance with the invention is flexible and can be adapted to any human build and any operating table environment. It is suitable for slim and adipose patients, and the soft material of the vacuum mattress avoids injuries or bedsores on the patient&#39;s body. 
         [0021]    The positioning device in accordance with the invention is explained below in more detail on the basis of an example embodiment and by referring to the enclosed drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The forgoing and other features of the invention are hereinafter discussed with reference to the drawings. 
           [0023]      FIG. 1  is an outline of an exemplary vacuum mattress for a lateral positioning device in accordance with the invention. 
           [0024]      FIGS. 2 and 3  illustrate a patient positioned on an operating table with the aid of the lateral positioning device in accordance with the invention from the front and rear sides. 
           [0025]      FIGS. 4 and 5  illustrate an exemplary repositioning and/or tilting mechanism for laterally positioning a patient in accordance with the invention. 
           [0026]      FIG. 6  illustrates a positioned patient in the tilted position. 
           [0027]      FIGS. 7 and 8  illustrate unsuitable fluoroscopic images of the pelvic region, as created using lateral positioning in accordance with the prior art. 
           [0028]      FIG. 9  illustrate an optimum fluoroscopic image recording of the pelvic region, as created using a lateral positioning device in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  shows a view from above (outline) onto an exemplary vacuum mattress  10  for a patient lateral positioning device in accordance with the invention. The exemplary mattress  10  has the basic shape of a Roman numeral I and includes an upper body supporting part  11 , a lower body supporting part  13  and a connecting part  12  between said two parts  11  and  13 . The patient is laterally positioned onto the central longitudinal axis  10   a  of the vacuum mattress  10 , such that the two wings  11   a  and  11   b  of the upper body supporting part  11  can be bent upwards around the upper body, and the two wings  13   a  and  13   b  of the lower body supporting part  13  can partly encompass the lower leg from beneath. The air is then removed from the vacuum mattress, and a filler material  11   c , such as polystyrene balls, contained in the mattress adapt to the shape of the patient&#39;s body and fix the body. The patient is then lying laterally on the operating table as shown in  FIGS. 2 and 3 .  FIG. 2  shows the patient from the front side,  FIG. 3  shows the patient from the rear side. The patient  20  is fixed in the mattress  10 , such that the two parts  11  and  13  protrude upwards in the region of the upper body and at the leg, respectively, and fix the body and the leg. The connecting part  12  lies flat beneath the patient&#39;s pelvis. 
         [0030]    The patient is laterally positioned on an operating table  40 , namely on its upper plate  41 . In the embodiment shown, a tilting mechanism  30  is also provided between the vacuum mattress  10  and the table plate  41 , and includes a support base including two separate angled plates  31  and  32 , as well as grips  34 ,  35 ,  36  and straps  33 ,  37  ( FIGS. 2-4 ). The function of the tilting mechanism is explained below in more detail on the basis of  FIGS. 4 and 5 . It also follows from  FIGS. 2 and 3  that when the patient is laterally positioned via the positioning device in accordance with the invention, the operating area  21  is completely accessible to the surgeon. Further, no parts of the patient fixation device are provided on the front side or rear side of the pelvis, which would obstruct fluoroscopic recordings or the tapping of registration points (pelvic landmarks) using navigation pointers. 
         [0031]    Referring now to  FIG. 4 , the patient  20  is lying in the linear lateral position in which the operation can be performed. The position in  FIG. 5  is the position tilted by 45 degrees, which is also shown as a whole in  FIG. 6 , wherein the front side of the patient points obliquely upwards. The plane of intersection runs centrally through the grip  33  on the upper body (see  FIG. 2 ). 
         [0032]    The tilting mechanism lies on top of the table plate  41  and comprises an angled plate  32  made of a rigid material and comprising two plate portions  32   a ,  32   b , which are connected to each other such that they form an angle of 135 degrees (interior angle) with respect to each other. Straps  37  run beneath the plate portions  32   a ,  32   b  and end in grips  34 ,  35 ,  36  at the rims of the plate portions. A tilting roller  38  runs along the tilting edge and comprises attaching appendages (not indicated) for the straps  33  and  37 . The lower end of the upper body supporting part  11  lies flat and conformed on the plate  32 . 
         [0033]    If one then wishes to move the patient  20  from the position shown in  FIG. 2  into the position shown in  FIG. 6 , such that he is lying inclined by 45 degrees and his front side points obliquely upwards, the support base  30 , i.e., the plates  31  and  32 , respectively, can very easily be tilted with the aid of the grips  34 ,  35 ,  36 , wherein an angle between plates  31  and  32  can be altered via the tilting roller  38  and can easily be moved into the position shown in  FIG. 5  and  FIG. 6 , respectively. The support base part  31  ( FIG. 2 ) is simultaneously tilted accordingly, wherein the patient is still fixedly positioned, because the conformed vacuum mattress rests on the plate portion  32   b.    
         [0034]    When the patient has then been moved by the tilting procedure just described into the position shown in  FIGS. 5 and 6 , the pelvic landmark points (ASIS and pubic points  51 ,  52 ,  53  and  54 ) are easily accessible and can easily be tapped using a navigated pointer. Image-free registration thus can be performed unobstructed and reliably. After registration, the patient  20  can easily be returned again to his original position (90 degree lateral position) with the aid of the tilting mechanism, without creating any sterility problems. Because the support base (the two plates  31 ,  32  of the tilting mechanism) are attached next to the hip region, they also do not obstruct the fluoroscopic image recordings. 
         [0035]    One possible workflow using the patient lateral positioning device in accordance with the invention is as follows: 
         [0036]    1. positioning the patient in the lateral position in the vacuum mattress; 
         [0037]    2. repositioning the patient into the position tilted by 45 degrees; 
         [0038]    3. creating the sterile environment; 
         [0039]    4. attaching reference arrays to the patient; 
         [0040]    5. registering the anatomical landmarks using a navigation pointer; 
         [0041]    6. repositioning the patient back into the lateral position; 
         [0042]    7. beginning the operation. 
         [0043]    Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.