Abstract:
A patient head clamp is provided with two pairs of interconnected arms arranged so that the sleeves carrying skull penetrating pins will maintain the pins in alignment with the limits of the spatial separation of the arms of clamp.

Description:
FIELD OF THE INVENTION 
     This invention relates to head or skull clamping and holding devices used in surgery on the head of a patient and, more specifically, to an improved design for such devices that facilitates placement of the head in the clamp so as to more securely hold the head in position during a surgical procedure and allow adjustment of the head during an operation. 
     BACKGROUND OF THE INVENTION 
     It has long been the practice in neurosurgery to employ a three point clamp on the head of a patient to securely locate and hold the head in place during surgery. In the prior art devices, pins mounted on one or more adjustable arms are forced into the skull of the patient to positively grip the skull so that subsequent movement is not possible. This is important in neurosurgery since, in many procedures, the patient is not fully sedated but remains conscious to enable responses to probes to be evaluated by the medical staff. 
     The use of three arms to support three penetrating pins introduces a complication that has proved unnecessary in the installation of the prior art skull clamps. This is the case primarily because such clamps could not provide accurate alignment of two of the skull engaging pins for all head sizes. In many arrangements, there was no possibility of aligning two oppositely disposed pins. In other systems, the ability to align two of the pins relied on the use of complicated structure that occupied an unacceptable amount of space in the vicinity of the patient&#39;s skull and was difficult to both put in place and to adjust during a surgical procedure. It is well recognized that surgical staff must have the maximum space available to move about a patient during surgery particularly in the event of unforeseen complications arising. With several available clamping apparatus, freedom of movement about the patient was curtailed due to the obstructions caused by the skull clamping apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention provides a surgical head clamp that is much easier to install in a secure manner. Also, while providing three point contact, the clamp of the present invention utilizes a much simpler support structure which will maximize the maneuvering space in the vicinity of the patient&#39;s head available to the surgeon and support staff. 
     The foregoing objects are attained by providing two pairs of articulatable arms with each pair having one end pivotally mounted on a single yoke. The opposite or free ends of each pair on one side of the yoke carries a pivot mount for a pin carrier which is typically a threaded bore and which receives a skull engaging pin. Each articulatable arm is provided with a plurality of threaded bores for accommodating a third pin. Structure is provided to ensure that the pins carried by the pivot mount on the arms are maintained in substantially perfect alignment whatever the separation of the free ends of the arms. This is accomplished without compromising the simplicity of the clamping structure so that a maximum maneuvering space will be afforded the surgeon and medical staff during a surgical procedure. Also, installation of clamp will be much simpler than the three arm clamps of the prior art while allowing the clamp to accommodate the same or a much greater range of skull sizes. 
     These advantages as well as others will become apparent as consideration is given to the following description and accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of one side of the clamp; 
     FIG. 2 is a view similar to FIG. 1 but showing the opposite side of the clamp; 
     FIG. 3 is a sectional view taken along lines  3 — 3  of FIG. 1; and 
     FIG. 4 is an exploded view of the yoke and attachment ends of the arms. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, there is shown in FIGS. 1 and 3, an elevational view of one face of the clamp  10  of the present invention and a sectional view along lines  3 — 3  FIG.  1 . The clamp  10  includes a yoke or base member  11  which, as is shown more clearly in FIG. 3, is provided with two spaced apart arms  14  and  16  which extend substantially parallel to one another. The bottom surface of the base  11  is provided with a rigid post  12  which is typically provided to permit insertion into a support arm extending from the operating table which may be of the type disclosed in U.S. Pat. Nos. 4,964,748 or 5,560,728. 
     The faces  14  and  16  of the base  11  are provided with aligned apertures as at  18 ,  20  and  22  for receiving pivot pins such as shown at  24 ,  26  and  28 . Mounted on pivot pins  24  and  26  are the inner ends of a first pair of articulated arms  30  and  32 . The opposite ends of the arms  30  and  32  may be bifurcated as shown in FIG. 3 to provide a secure mount for a pin support body  42 . Also, the ends are formed as enlarged portions  34  and  36  which are apertured as at  38  to receive a pivot pin  40  which supports the pin support body  42 . The support body  42  adjustably carries a skull engaging or anchor pin  44  in the threaded bore  47  of the body  42 . 
     Intermediate their respective ends, each of the arms  30  and  32  is provided with an integral platform  46  which carries a threaded sleeve  48  for cooperation with the threaded portions of a spacer bar  50 . Rotation of the bar  50  will effect and regulate the pivoting movement of the arms  30  and  32  about the axis  24  of the base  11 . A separate tool will be provided to effect rotation of the bar  50 . Preferably, the sleeves  48  are rotatable on the platforms to maintain alignment with the bar  50  during movement of the arms  30  and  32 . In an alternate arrangement, the bar  50  can be replaced by internally threaded sleeve which has one end pivotally mounted on one sleeve  48  of arm  30  and a threaded rod which has one end mounted in the sleeve  48  on the other arm  32 . The rod will be threaded into and out of the internally threaded sleeve to move the arms  30  and  32  towards and away from each other. A spring detent may be installed in the internally threaded sleeve to provide resistance to threading as a safety measure. 
     Each pin supporting body  42  is formed with a depending extension  52  which are each pivotally connected by a respective pin  54  to the bifurcated end  56 ,  58  of a respective, second articulated arm  60 , 62 . The depending extension of each body  42  is selected so as to position and, as explained below, maintain the axis of each sleeve  42  aligned. With this arrangement, the points of each skull engaging pin  44  will always be in axial alignment, that is, opposite one another, for all spacings of the arms  30 ,  32  and  60 , 62 . To accomplish this, in addition to the spatial displacement between the axis of pins  40  and  54 , the pivot pin  28  on which the opposite ends  64  and  66  of arms  60 , 62  are attached is spaced a distance from the pivot pin  24  of arms  30 ,  32 . The magnitude of these distances must be selected with the view to maintaining the axis of each sleeve  42  in alignment with axis  70  which passes through each point of pins  44 . With such a disposition, the points of pins  44  will be substantially or exactly opposite each other when inserted into the skull of a patient for all positions of the respective arms. 
     Preferably, to reduce the protrusion of members into or adjacent the operation site, the arms  60  and  62  are configured to closely underlie the arms  30 ,  32  as shown more clearly in FIGS. 2 and 4. This disposition will require that the inner ends  64 ,  66  of the arms  60  and  62  depart from the smooth arcuate curvature of the major portion of each arm at a point adjacent to the faces  14 ,  16  of the base  11  and to assume a second curvature to the ends that are mounted on the pivot pin  28 . 
     A limit pin  26  is provided between pins  22  and  24  and which extends through an elongated slot  78  formed in each of the faces  14  and  16  in the base  11 . Each arm  30 ,  32  at its inner end is formed with pivot bore  80  through which extends the pivot pin  24 . An extension arm  76 ,  77  is provided on the inner end of each arm  30 , 32  and each arm  76 , 77  is formed with an angled slots  82  through which limit pin  26  extends and is moved in its slots  74 . The axial extent of the slot  74  limits the spreading of the pairs of arms  30 , 32  in which the pin  26  is free to move. Limiting movement of the arms  30 , 32  and by virtue of their interconnection, of the arms  60 , 62 , is effected by the positioning of the slots  74  in the extension arms  76 ,  77  provided at the inner ends of arms  30 , 32 . 
     For assured stability of the patient&#39;s head, a plurality of threaded bores, one of which is indicated at  68 , are formed in arms  30 ,  32  for the purpose of receiving a third skull pin  72 . The surgeon will select the appropriate bore  68  to use and this will depend on the size of the patient&#39;s skull. 
     Having described the invention, it will be apparent that various modifications can be made therein without departing from the spirit and scope of the invention.