Abstract:
The invention relates generally to apparatus and devices for stereotactic surgery, computer aided surgery and other similar medical procedures. More particularly, a clamping device for firm attachment to a body part during surgery and for firmly and precisely positioning and orienting medical instruments attached to the clamping device is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Application No. 61/252,003 filed on Oct. 15, 2009, hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates generally to apparatus and devices for stereotactic surgery, computer aided surgery and other similar medical procedures. More particularly, a clamping device for firm attachment to a head and for firmly and precisely positioning and orienting medical instruments attached to the clamping device is disclosed. 
       BACKGROUND OF INVENTION 
       [0003]    During stereotactic surgery, intracranial operations, computer aided tomography imaging, or similar medical procedures, it is generally desirable to precisely position and orient various instruments relative to a patient&#39;s skull or other anatomy and to hold the patient&#39;s head or other anatomy immobilized relative to a support surface, such as an operating table, an operating chair or such other patient support structures. 
         [0004]    For example, U.S. Pat. No. 6,117,143 describes an apparatus comprising a head clamp that includes three fixation pins to firmly secure the clamp to a patient&#39;s skull, a connector to firmly secure the clamp to a surgical table or like structures, and an articulated arm, including clampable joints, secured to the clamp for attachment of medical or imaging devices. 
         [0005]    It is desirable that various parts of a head clamp, once a registration to a neuronavigation system has been completed, do not permit any movement relative to each other, so that registration may be maintained during the medical procedure, such as stereotactic surgery. It is also desirable that the head clamp permits its positioning relative to a patient&#39;s head differently to accommodate different procedures to be performed on the patient and that any interference with the performed procedure caused by any attached accessories is minimized. 
         [0006]    The forgoing creates challenges and constraints for a clamping device for firm attachment to a head or other body parts and for firmly and precisely positioning and orienting medical instruments attached to the clamping device. There is therefore a need for a clamping device as compared to the existing art. It is an object of the present invention to mitigate or obviate at least one of the above mentioned disadvantages. 
       SUMMARY OF INVENTION 
       [0007]    The present invention relates to a clamping device for firm attachment to a patient&#39;s body during medical procedures and for firmly and precisely positioning and orienting instruments attached to the clamping device. One aspect of the present invention involves a clamping device for firm attachment to a patient&#39;s head or other location of the patient&#39;s body during surgery or other medical procedures and for firmly and precisely positioning and orienting medical instruments attached to the clamping device. In one embodiment, a clamping device such as a head clamp may generally have a support member such as a clamp arc, body anchoring members such as fixation pins carried by the clamp arc, one or more mounting blocks for attachment of instruments, and securing arrangement to releasably and repositionably secure the one or more mounting blocks to the clamp arc. 
         [0008]    In a first aspect of the invention, a clamping device is provided for firm attachment to a body part of a person. The clamping device includes a support member, body anchoring members carried by the support member, and a mounting block releasably secured to the support member. The support member is shaped to accommodate said body part and includes a plurality of connection sites, each connection site having opposed mounting surfaces that are converging toward a narrower side. The body anchoring members engage the body part to secure the support member on the body part such as head in outwardly spaced position therefrom. The mounting block has one or more connection surfaces for attaching medical instruments to the clamping device or for releasably securing said clamping device to a support surface. The mounting block has converging mounting surfaces complementary with the mounting surfaces of the support member for mating therewith, and securing arrangement releasably and repositionably securing the one or more mounting blocks to the support member. 
         [0009]    According to one feature of this aspect of the invention, the securing arrangement of the clamping device includes a connector, the connector securing the mounting block to the support member at least one of the plurality of connection sites by applying a force urging relative movement of the mounting block and the support member in a direction for tighter mating between the mounting surfaces of the mounting block and the mounting surfaces of the support member. 
         [0010]    According to another feature of this aspect of the invention, at least one of the body anchoring members is a skull fixation pin, the skull fixation pin having a threaded external cylindrical body, and the support member has one or more threaded throughbores to receive the threaded external cylindrical body. 
         [0011]    According to a further feature of this aspect of the invention, the clamping device further includes an accessory mounting block and an elevation block releasably secured to the accessory mounting block, the accessory mounting block having converging mounting surfaces to be mated with the outer converging surfaces of the support member. 
         [0012]    In another aspect of the invention, a clamping device is provided for firm attachment to a head. The clamping device includes an arc-like support member, a plurality of skull anchoring members carried by said support member for engaging said head to secure said support member on said head in outwardly spaced position therefrom, and a mounting block releasably secured to the support member. The support member has a plurality of threaded throughbores and opposed outer surfaces that are converging toward a narrower side formed at each of the plurality of threaded throughbores. Each of the skull anchoring members has an external threaded cylindrical body sized to be threaded into said threaded throughbores. The mounting block has one or more mounting surfaces for attaching medical instruments to the clamping device or for releasably securing said clamping device to a support surface. The mounting block has inner surfaces to be mated with the outer surfaces of the support member and a thread bore. A shoulder bolt received in one of the threaded througbores of the support member and the threaded bore of the mounting block tightly secures the mounting block to the support member. 
         [0013]    According to one feature of this aspect of the invention, the clamping device also has a removal tool, the removal tool having a handle portion, a front portion sized to pass through the threaded throughbores and a threaded body between the handle portion and the front portion, sized to be threaded into the threaded througbores of the support member. 
         [0014]    According to another feature of this aspect of the invention, the clamping device has a connection block releasably secured to the support member for securing said clamping device to a support surface, the connection block having converging mounting surfaces to be mated with the converging surfaces of the support member. 
         [0015]    In other aspects the invention provides various combinations and subsets of the aspects described above. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]    For the purposes of description, but not of limitation, the foregoing and other aspects of the invention are explained in greater detail with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  shows in a perspective view a clamping device, such as a head clamp, secured to a patient&#39;s head; also shown mounted to the head clamp is an articulated, surgical arm for carrying a medical device; 
           [0018]      FIG. 2  shows in another perspective view a head clamp with the articulated arm removed for better illustration; 
           [0019]      FIG. 3  shows in a cross-sectional view the connection between a mounting block and the head clamp arc; 
           [0020]      FIG. 4  shows a mounting block in a perspective view; 
           [0021]      FIG. 5  shows in a perspective view an accessory mounting block and an elevation block secured to the accessory mounting block; 
           [0022]      FIG. 6  shows in a perspective view an accessory mounting block; 
           [0023]      FIG. 7  shows in a perspective view an installation/removal tool for installing and removing a mounting block; 
           [0024]      FIGS. 8A ,  8 B and  8 C show in cross-sectional views alternative configurations for attaching a mounting block to a head clamp arc; and 
           [0025]      FIG. 9  shows in a perspective view a head clamp with a differently constructed accessory mounting block and an elevation post. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0026]    The description which follows and the embodiments described therein are provided by way of illustration of an example, or examples, of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not limitation, of those principles and of the invention. In the description which follows, like parts are marked throughout the specification and the drawings with the same respective reference numerals. 
         [0027]    In the description reference may be made to the general environment of a clamping device. By way of a general overview,  FIG. 1  shows in a perspective view a clamping device such as head clamp  20  firmly attached to a patient&#39;s head  10 . Mounted to the head clamp is an articulated, surgical arm  12  for carrying a medical device, such as probe  14 .  FIG. 2  shows in another perspective view a head clamp  20  like that shown in  FIG. 1 , with the articulated arm  12  removed for better illustration. 
         [0028]    Head clamp  20  has a support member for carrying body anchoring members and mounting blocks. The support member is shaped to accommodate a patient&#39;s head (or an animal&#39;s head) or other parts of a patient&#39;s body (e.g., leg, arm or torso), and may be arc-like. Body anchoring members, such as fixation pins, fix the support member relative the patient&#39;s head, for example, and places the support member in spaced position outwardly from the head.  FIGS. 1 and 2  illustrate an arc-like support member, namely a head clamp arc  22 . Head clamp arc  22  can have a generally circular shape. The circular shape allows the arc to be oriented in any suitable position to suit the needs of performed procedure. Head clamp arc is suitably sized to fit human and/or animal skull sizes. It will be appreciated, however, that the support member may also take other shapes, such as a ring, a plate having an inner curved edge etc., to accommodate a head, a leg, an arm, among others. 
         [0029]    Head clamp arc  22  has a plurality of threaded throughbores, namely, threaded throughholes  24 , spaced from each other along the arc and formed generally along a radial direction, to accept skull fixation pins  26 . Each skull fixation pin  26  has an externally threaded cylindrical body  28  that can be threaded into one of the threaded throughholes  24  and a sharp pin tip  30  mounted to the cylindrical body for engaging skull  10 . Of course, for engaging other body parts, such as leg or torso, fixation pins may he replaced by fixation pads as body anchoring members, to reduce discomfort that might be caused by a pin but still effectively maintain the base support member in a fixed relationship to the engaged body part. 
         [0030]    Head clamp arc  22  has opposed outer surfaces  32 , formed at connection sites  34  surrounding each threaded throughholes (more clearly shown in  FIG. 3 ). As can be seen more clearly in  FIG. 3 , a radial outward portion of head clamp arc  22  has a cross-sectional shape that is essentially trapezoidal in a radial plane, with outer surfaces of the trapezoidal arc converging radially outwardly. In other words, a portion of the outer, surfaces  32 , namely the portion forming the trapezoidal shape, converge radially outwardly. It will be understood, however, that the cross section of the head clamp arc may not always be trapezoidal. It may take a different shape. In general, the cross section includes a portion of converging outer surfaces. While the trapezoidal shape shown in  FIG. 3  has outer surfaces converging radially outwardly, the converging surfaces may also converge inwardly. Further, conveniently, the outer surfaces may extend over the entire length of the arc, such as shown in  FIG. 2 . 
         [0031]    Referring to  FIGS. 2 ,  3  and  4 , head clamp  20  includes one or more mounting blocks  36  for mounting to the head clamp arc  22  at connection sites  34 . Mounting block  36  has opposing inner surfaces  38  to be mated with the outer surfaces of the head clamp arc  22  at a connection site. Inner mounting surfaces  38  have at least a converging portion matching the converging portion of the outer mounting surfaces  32 .  FIG. 3  shows a mounting block  36  that has a trapezoidal slot  40  matching the trapezoidal cross-sectional shape  42  of the head arc clamp, with matching and complementary mounting surfaces. These matching mounting surfaces, i.e., the complementary, converging outer surfaces  32  of head clamp arc  22  and inner surfaces  38  of the trapezoidal slot  40  of mounting block  36  allow the mounting block  36  to be firmly attached to the head clamp arc  22 , as will be further described now. As can be seen in  FIG. 3 , both trapezoidal cross sections have narrower end located further outwardly of the center. This allows the mounting block to be located on the outside of the head clamp arc  22 . A securing arrangement is provided to force the mounting block toward the head clamp arc, or more generally, to force the mounting block and the head clamp arc toward each other, so that the mounting block is releasably secured to the head clamp arc when needed. A shoulder bolt  44 , for example, may be used for pulling the mounting block toward the head clamp arc. A threaded hole  46  is formed in the mounting block  36 . The shoulder bolt  44  is sized smaller than the threaded throughhole  24  of the head clamp arc so it can pass through the threaded throughhole  24  unhindered and threaded into the threaded hole  46  of the mounting block to pull the mounting block toward the head clamp arc. The shoulder bolt  44  pulls the mounting block toward the head clamp arc  22  until the mounting block  36  cannot be pulled any closer to the head clamp arc  22  and will lock the mounting block onto the head clamp arc. Any translational movement of the mounting block  36  is restricted by the shoulder bolt  44  and the matching converging surfaces. Any rotational movement of the mounting block rotate relative to the head clamp arc is restricted by tight engagement of matching converging surfaces of the mounting block with those of head clamp arc. As will be understood and as will be illustrated in some examples to be provided later, a variety of methods may be employed to force the mounting block and the head clamp arc toward each other. Such securing arrangement also is not limited to mechanical configurations. For example, the mounting block or head clamp arc  22  may be magnetized (or selectively magnetized by electricity) for pulling the mounting block toward the head clamp arc. 
         [0032]    Referring to  FIGS. 2 and 4 , mounting block  36  has one or more outer connection surfaces formed thereon for connection of medical instrument or accessories to the head clamp. Mounting block  36  may be a starburst connection block with toothed connection surfaces  48  and a central hole as shown in  FIG. 4 . The starburst connection block may be used to mount a variety of devices with mating toothed connection surfaces. A central hole  50  is formed near the center of the toothed connection surfaces  48 . The central hole  50  may be threaded, in which may be threaded a bolt or screw, or a throughhole for a bolt to pass therethrough, to securely attach a device to the starburst connection block. The cooperating toothed connection surfaces of the mounting block and the mounted devices also encourage precisely locating the connected device at one of the angular positions defined by the toothed connection surfaces. One such mating device or attachment may be an articulated surgical arm  12  to be attached to support instruments used in surgical procedures. Another such attachment may be a marker for providing a reference point during neurovavigation. The starburst connection block also allow mounting of other attachments, such as an attachment to hold the mounting block in a fixed position relative to an operating table, operating chair, desk or other mounting support structure or surface. This would hold a patient&#39;s head immobilized for surgery or other procedures. 
         [0033]    As noted, a surgeon may need to locate the head clamp  20  to different positions relative to the head or orient differently for different procedures while minimizing interference of the head clamp with the procedure performed. The medical instrument or devices attached to the head clamp may also need to be located differently relative to the head clamp arc  22  as required by different procedures. This can be accomplished by threading skull fixation pins  26  into different threaded throughholes  24 , or repositioning the mounting block or blocks to different connection sites, or connecting the instruments or devices to different toothed connection surfaces of the mounting block or blocks. To reposition a mounting block  36 , the shoulder bolt  44  is removed to allow separation of the mounting block from the header clamp arc. A special tool, as will be fully described below, may be provided for facilitating the separation of the mounting block form the header clamp arc. 
         [0034]    There may also be situations where a skull fixation pin  26  may still interfere with the procedure performed even when it is moved to a different threaded throughhole  24 . It is therefore desirable that skull fixation pins may be secured to head clamp arc  22  at a location generally spaced from the plan defined by head clamp arc. Similarly, attachments secured to a mounting block may interfere with performed procedures and moving attachments to a location spaced from the plan defined by head clamp arc may minimize the interference. 
         [0035]      FIG. 5  shows an accessory mounting block  52  and an elevation block  54  secured to the accessory mounting block. As can be more clearly seen in  FIG. 6 , accessory mounting block  52  has a front slot  56  that has front converging surfaces  58  for mating with the outer surfaces of head clamp arc  22 . Several threaded throughbores  60  are provided so that a shoulder bolt  44  inserted from the inside radius of the head clamp arc  22  can pass through a throughhole  24  and thread into one of the threaded throughbores  60  to secure the accessory mounting block to head clamp arc. Accessory mounting block also has a rear slot  62  that has opposing, rear converging surfaces  64  for accepting elevation block  54 . 
         [0036]    Referring to  FIG. 5 , elevation block  54  has an elongated body  66  sized to be partially received in the rear slot and slidable along the rear slot  62 . The elongated body has opposed outer converging surfaces  68  that converge toward its, front side  70 . The outer converging surfaces of the elevation block are to be mated with the rear converging surfaces  64  of the accessory mounting block  52  when a section of the elongated body is received in the rear slot. After the elevation block is suitably positioned relative to the accessory mounting block, a shoulder bolt  44  is passed through a slot  72  formed in the elongated body  66 , threaded into one of the threaded throughbores  60 , and tightened to pull the elevation block toward the accessory mounting block until they cannot be moved closer toward each other. The elevation block  54  is thus locked in place and immovably secured to the accessory mounting block  52 . Moving the elevation block to another location relative to the accessory mounting block is done by unscrewing the shoulder bolt securing the elevation block to the accessory mounting block and thereby allowing their separation and tightening the shoulder bolt again after the elevation block is appropriately repositioned. 
         [0037]    Elevation block has a mounting site  74  formed integral with the elongated body  66 . Mounting site  74  may be configured to accept a skull fixation pin, or for connection of attachment thereto. For example, a threaded throughhole  24  may be formed at the mounting site  74  for accepting a skull fixation pin. The threaded throughhole  24  may be oriented generally parallel to the plane defined by the head clamp arc  22  or angled with respect to the plane. The mounting site may also have one or more toothed connection surfaces  48  like that of mounting block  36 , formed on side surfaces at mounting site  74  or front side  70 , for attaching medical instrument or connection of attachment. 
         [0038]    Conveniently, a combined installation and removal tool  76  is provided for easy installation and removal of skull fixation pins.  FIG. 7  illustrates such a combined installation and removal tool  76 , which has an elongated cylindrical body  78 , which includes a front portion  80  and a threaded body portion  82 , and a handle portion  84  for fixing a handle  86  thereto. The threaded body portion  82  is sized to be threaded into a threaded throughhole  24  of the head clamp arc  22 . The front portion  80  is sized to pass through the threaded throughholes  24  unhindered. The front portion  80  does not need to be threaded and is sized for pushing starburst mounting block  36  away from the head clamp arc  22 . For example, the front portion may be sized larger than the threaded hole  46  of the mounting block. Alternatively, the front portion may be sized smaller than the threaded hole  46  but sufficiently long so that the front portion (or its tip  88 ) can reach the bottom of the threaded hole  46 . The tip of the front portion may have a non-cylindrical shape (such as a hex tip  88  or a tip of any other suitable shape) that fits into a complementarily shaped hole (such as a hex hole  90 ) formed on the bolt head  92  of the shoulder bolt  44 , so that the installation and removal tool can also be used for tightening or loosening the shoulder bolt. 
         [0039]    To removal a starburst mounting block or accessory mounting block, the shoulder bolt is first loosened and removed, using the combined installation and removal tool  76 , for example. It will be appreciated that when a mounting block is tightened onto the head clamp arc, the converging surfaces tend to lock the mounting block onto the arc and it may be difficult to separate the starburst mounting block from the head clamp arc. Conveniently, the installation and removal tool can be threaded into the threaded throughhole until the front portion  80  is in contact with the bottom of the threaded hole  46  of the starburst mounting block  36  and pushes the starburst mounting block  36  off of the head clamp arc. 
         [0040]    As will be appreciated, the converging nature of the converging surfaces of the mounting block and the head clamp arc assists the tight engagement of the mounting block with the head clamp arc and prevents their relative movement once the mounting block is tightened and locked in place. The converging angle, namely the angle a between the converging surfaces, is generally in the range of 5 to 40 degrees. Depending or materials used and whether the contacting surfaces of the mounting block and the clamp arc are formed using the same material, the converging angle may be outside this range. However, to obtain satisfactory results, the converging angle should not be significantly larger than 60 degrees or much smaller than 2 degrees. As will also be appreciated, the converging angle may be evenly or unevenly divided between the pair of converging surfaces of the slot or arc.  FIG. 3  shows the converging angle to be evenly divided, but that is not necessary. It is found that a converging angle of about 10 degrees, divided evenly between the pair of converging surfaces, tends to provide satisfactory results with mounting block and head clamp both made of steel. 
         [0041]    As noted earlier, there are different ways of configuring the converging surfaces and the engagement arrangement to tighten the mounting block, other than that is shown in  FIG. 3 . For example,  FIG. 8A  is a cross-sectional view of a mounting block  36  and a head clamp arc  22  at a connection site  34  (see  FIG. 2 ) illustrating one such alternative configuration. The mounting block has a trapezoidal slot  40  that matches the trapezoidal cross-sectional shape  42  of the head clamp arc. The converging surfaces  94  converge outwardly along a radial direction. Unlike that shown in  FIG. 3 , the shoulder bolt passes through a throughhole of the mounting block and is threaded into the threaded hole of the head clamp arc. Tightening the shoulder bolt  44  pulls the head clamp arc  22  towards the mounting block  36  to lock the mounting block onto the head clamp arc.  FIG. 8B  shows in a cross-sectional view another alternative configuration. The converging surfaces  94  converge inwardly along a radial direction. A shoulder bolt  44  is threaded into a threaded throughhole of the head clamp arc  22  and pushes the mounting block  36  away from the head clamp arc to tightly lock the mounting block on the head clamp arc. Similarly,  FIG. 8C  shows in a cross-sectional view yet another alternative configuration. The converging surfaces  94  converge inwardly along a radial direction, as in  FIG. 8B . The shoulder bolt  44  is threaded through a threaded throughhole of the mounting block  36  and pushes the head clamp arc  22  away from the mounting block, in order to lock the mounting block tightly onto the head clamp arc. These are but a few examples to illustrate different configurations of engagement arrangement, for tightly locking the mounting block onto the head clamp arc. The same configurations may be applied to accessory mounting blocks, too. Other configurations are also possible. For example, it is not necessary to use a threaded shoulder bolt. Magnetic force can be utilized to force a mounting block towards or away from a head clamp arc. Such magnetic force also can be selectively applied, for example, by utilizing electromagnet. 
         [0042]      FIG. 9  shows in a perspective view a head clamp  20 ′ with a differently constructed accessory mounting block  52 ′ and elevation block  54 ′. Unlike accessory mounting block  52  shown in  FIG. 6 , which provides an open rear slot  62  for receiving an elongated body  66  of elevation block  54 , the differently constructed accessory mounting block has a throughhole  96  defined therein. Elevation block  54  has the form of a post. Elevation post  54 ′ is slidably received in throughhole  96 . Elevation post  54 ′ and its matching throughhole may have a cylindrical shape as shown in  FIG. 9  or any other suitable shape. A skull fixation pin  26  is threaded in a threaded throughhole  24  provided on elevation post  54 ′, to carry the pin  26  with the elevation post  54 ′ as the elevation post slides along the throughhole  96 . A locking nut  98 . such as a wing nut or a thumbnut, may be provided to releasably lock pin  26  relative to the elevation post  54 ′. A locking thumbscrew  94 , or any other suitable locking screw, is provided to releasably secure the elevation post relative to the accessory mounting block  52 ′. To minimize damages to the elevation block  52 ′, the tip of the locking thumbscrew may be made from a plastic material. 
         [0043]    Various embodiments of the invention have now been described in detail. Those skilled in the art will appreciate that numerous modifications, adaptations and variations may be made to the embodiments without departing from the scope of the invention. Since changes in and or additions to the above-described best mode may be made without departing from the scope of the invention, the invention is not to be limited to those details but only by the appended claims.