Abstract:
The invention relates to a joint for movably connecting two stabilizing elements. The joint includes at least two joint segments, which can be rotated relative to each other. Each joint segment is connected to a respective stabilizing element. The joint can be releasably locked by locking means, and the locking means can be locked and/or unlocked by a fluid that is supplied and/or discharged via conduits.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This is a continuation of International Patent Application No. PCT/CH2002/000676, filed Dec. 9, 2002, the entire contents of which are incorporated herein by reference thereto.  
       TECHNICAL FIELD OF THE INVENTION  
       [0002]     The invention relates to a joint for movably connecting two stabilizing elements to each other and/or to a holding arm that can be used for surgical purposes and/or to a holding device for bones, particularly bone fragments.  
       BACKGROUND OF THE INVENTION  
       [0003]     The correct alignment of bone fragments is an important surgical step in osteosynthesis. In repositioning bone fragments, and in particular, for example, long bones, the pelvis, or bone joints, relatively large forces may act on the bone fragments, so that a holding device for bone fragments can be very advantageous for the surgeon. Using such a device, one of the main bone fragments can be held in place after it has been at least approximately aligned, so that its position remains constant, particularly during long procedures.  
         [0004]     A holding device for use during surgical procedures is known. This known device comprises two stabilizing elements that can be pivoted relative to one another. Each element has a joint at its end, in addition to a joint between the stabilizing elements. All three joints can be locked in place by locking means, which can be activated by means of a single operating instrument. The functioning of the locking means as well as their activation is purely mechanical. The joint, disposed between the relatively long stabilizing elements, is locked by a friction lock via the manual tightening of a screw connection. A disadvantage of this known holding device is that it is restricted to relatively small locking forces and therefore to relatively short stabilizing elements.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention is directed to a releasably lockable joint between two stabilizing elements of a holding device. The invention advantageously permits stable locking of the joint between the stabilizing elements even when large forces act on the stabilizing elements.  
         [0006]     The invention is also directed to a holding arm for surgical purposes and to a holding device for bone fragments.  
         [0007]     One of the advantageous features of the invention includes a fluid-driven locking means that allows a high locking force to be exerted on the joint. Thus, when high torques are exerted on the joint, the stabilizing elements of a holding arm can be held in an exact position, and precise positioning of a bone or bone fragment attached to a stabilizing element, for example, is possible even during a lengthy repositioning procedure.  
         [0008]     The fluid for locking the joint or joints is preferably compressed air. Instead of compressed air, the locking means can also be operated by means of a vacuum.  
         [0009]     In a preferred embodiment, the inventive joint has only a single axis of rotation. In comparison with ball joints having several axes of rotation, this embodiment enables the releasably lockable joint to be configured in a simple manner, for example, by means of a single pneumatic cylinder.  
         [0010]     In another embodiment, a first joint segment of the joint has a cavity coaxial to the axis of rotation, while the locking means comprises a piston that is displaceable in the cavity, parallel to the axis of rotation. The piston can be pressed against a second joint segment by means of supplying and/or discharging the fluid. In this manner, a pneumatic cylinder operated with compressed air, for example, can be integrated into the joint parts, thereby making it possible to achieve a compact construction of the joint. The piston is preferably guided by a coaxial axle and at least one second axle disposed eccentrically in the cavity, whereby both axles are secured to the first joint segment. In this way, an exact coaxial displaceability of the piston is ensured, while a rotation of the piston relative to the first joint segment is prevented by the eccentric axle.  
         [0011]     Preferably, the piston has a front face that stands crosswise to the axis of rotation and that can be pressed against the second joint segment. The piston also has a rear face that stands crosswise to the axis of rotation. If the fluid has pressure applied to it, the fluid is preferably guided into the cavity delimited and sealed by the rear face of the piston via one or more supply/discharge lines. In an embodiment in which the locking means is operated by means of a vacuum, a cavity between the front face of the piston and the second joint segment, for example, can be evacuated.  
         [0012]     In another embodiment, the contact surface of the second joint segment, which stands crosswise to the axis of rotation and is directed against the first joint segment, and the front face of the piston are provided with toothed gear wheels that can be brought into engagement with one another. By means of these toothed gear wheels, which can be brought into a positive-lock engagement, the holding force that prevents a relative rotation of the two joint segments about the axis of rotation in the locked state can be significantly increased. The toothed gear wheels are structured in such a manner that the joint can be locked in steps, at a specific angle of rotation. The size of the steps is dependent on the size of the joint.  
         [0013]     In another embodiment of the invention, the toothed gear wheels are structured such that the joint can be locked in 2° steps of angular rotation.  
         [0014]     In yet another embodiment, the second joint segment comprises elastic deformable means that can be elastically compressed parallel to the axis of rotation in response to a displacement of the piston against the second joint segment. Preferably, the elastic means are structured as pressure springs that are disposed between the second joint segment and the piston. In this way, locking of the joint by means of the locking means is merely performed by means of a fluid to which pressure or vacuum is applied, while unlocking takes place by means of the spring force of the elastic deformable means.  
         [0015]     In another embodiment, the second joint segment comprises a cavity (referred to herein as the “second cavity”) that can be delimited relative to the first joint segment by the piston, instead of the elastically deformable means. A fluid to which pressure is applied can be supplied to the second cavity by way of a second line. In this embodiment, the locking means act as dual-action cylinders, such as, for example, compressed air cylinders.  
         [0016]     Preferably, at least one connection element for the lines is affixed to the housing of the first joint segment, so that fluid to be supplied and/or discharged in the lines can be supplied to or discharged from the cavity of the first joint segment by means of these connection elements.  
         [0017]     In a preferred embodiment of a holding arm, the arm comprises at least two stabilizing elements disposed between the two ends of the holding arm. The two stabilizing elements are movably connected to one another by a joint of the invention. Each of the two stabilizing elements connected to the joint is connected to a respective joint segment of the joint.  
         [0018]     The holding device serves to fix bones or bone fragments of a patient positioned on an object, such as, for example, an operating table or operating chair, that is preferably fixed in place relative to the patient. Positioning of the holding device on the ceiling of the operating room, or a free-standing set-up of the holding device on the floor of the operating room, or leaning against another object, is also possible. The holding device comprises a movable holding arm having a first end and a second end, whereby at least one first and one second stabilizing element, connected by means of a joint, are disposed on the holding arm between the first and the second ends. Attachment means for fixing the holding arm in place on an object fixed in place relative to the patient, for example the operating table, are disposed on the first end of the holding arm, while fixation means for releasable fixation of a bone or bone fragment of a patient are disposed on the second end of the holding arm.  
         [0019]     In a preferred embodiment of a holding device, the device comprises at least two, preferably three joints. The axes of rotation of the individual joints can run parallel, or be disposed at a slant, preferably perpendicular to one another, so that in the case of an embodiment having three joints, the second end of the holding arm can be moved in space relative to three coordinate axes that stand perpendicular to one another.  
         [0020]     In another embodiment of a holding device, the device comprises three stabilizing elements and four joints, whereby one joint is disposed between each of two stabilizing elements, one joint between the one end-position stabilizing element and the attachment means, and another joint between the second end-position stabilizing element and the fixation means. This embodiment permits a movement of the holding arm relative to the operating table, while the fixation means can be aligned relative to the holding arm. Therefore the holding arm can be positioned by the surgeon when the joints are unlocked, and locked in the desired position by means of a single switch, for example a foot switch, after the second end has been fixed in place on the bone or bone fragment to be held in place by means of the fixation means.  
         [0021]     Instead of simultaneous locking of all the joints disposed on the holding arm by means of activating a single switch, the control and/or the lines for supply or discharge of the fluid can be laid out such that the joints can be individually locked by means of activating one or more switches.  
         [0022]     In addition to Kirschner wires, the following can be alternatively used as fixation means: bone clamps, Schanz screws, plates, or endomedullar hooks or nails.  
         [0023]     The attachment means for fixing the holding arm in place on, for example, an operating table, can comprise one or more clamping jaws. Because of the weight of the holding arm, a carrier is preferably passed through below the operating table, between two side edges of the operating table, so that attachment takes place on both sides of the operating table, making it possible to better absorb the forces and torques that occur due to the weight of the holding arm. The weight of the holding arm can then be compensated by means of a gas pressure spring, for example. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The detailed description will be better understood in conjunction with the accompanying drawings, in which like reference characters represent like elements, as follows:  
         [0025]      FIG. 1  shows a section through an embodiment of a joint of the invention;  
         [0026]      FIG. 2  shows a perspective view of an embodiment of a holding device of the invention; and  
         [0027]      FIG. 3  shows a perspective view of an embodiment of a holding device of the invention, having three joints.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]      FIG. 1  shows an embodiment of a joint  4 , preferably operated with compressed air and having only a single axis of rotation between two stabilizing elements  2 ,  3 . Joint  4  comprises two joint segments  30 ,  31  that can rotate relative to one another about an axis of rotation  12 . Each joint segment is connected to a respective one of the stabilizing elements  2 ,  3 . Joint segments  30 ,  31  are held together axially by means of a bolt  21 , which is coaxial to axis of rotation  12 . Bolt  21  is accommodated in a bore  22  that passes coaxially through the two joint segments  30 ,  31 . Bolt  21  has a head  24  that is enlarged in diameter at an end of bolt  21 , accommodated in first joint segment  30 . A screw  23  that can be screwed in perpendicular to the axis of rotation  12  is disposed in the second joint segment  31 , by means of which bolt  21  is secured in bore  22  axially and rotationally, when joint segments  30 ,  31  rest against one another. Joint  4  can be locked and unlocked by locking means  8 . Locking means  8  can have compressed air applied to it by way of a supply/discharge line  11 , where in one embodiment, locking means  8  can be locked by supplying compressed air, and unlocked by discharging compressed air. The first joint segment  30  includes a housing  14  having a hollow-cylinder journal  15  concentric to the axis of rotation  12 . First joint segment  30  also has a cavity  32  coaxial to the axis of rotation  12 . Here, locking means  8  for locking joint  4  includes a piston  33  that is displaceable in cavity  32 , parallel to the axis of rotation  12 , which can be pressed against the second joint segment  31  by means of supplying or discharging compressed air. Piston  33  comprises a front face  35  that stands crosswise to the axis of rotation  12  and can be pressed against the second joint segment  31 . Piston  33  also comprises a rear face  36  that stands crosswise to the axis of rotation  12 . The compressed air can be supplied to cavity  32  delimited by a second face  36  of the piston  33  by way of line  11 . Piston  33  is also structured as a hollow cylinder and mounted on journal  15 , displaceable parallel to the axis of rotation  12 . Here, the second joint segment  31  includes two parts  16 ,  17  disposed axially one behind the other and rigidly connected with one another by means of four screws  18 . The first part  16  of the second joint segment  31  has a contact surface  34  that stands crosswise to the axis of rotation  12 , directed against the first joint segment  30 . This contact surface  34  as well as the front face  35  of piston  33  are provided with ring-shaped toothed gear wheels  38  that can be brought into engagement with one another and are concentric to the axis of rotation  12 . The ring-shaped toothed gear wheels  38  form the periphery of a second coaxial cavity  19 , which penetrates into the first part  16  of the second joint segment  31  from the contact surface  34 , on the one hand, and penetrates into the piston  33  from the front face  35 , on the other hand. The elastically deformable means  37 , which are configured as pressure spring  13 , are disposed in the second cavity  19 . The three pressure springs  13  are uniformly distributed on the circumference and have ends that rest against the first part  16  of the second joint segment  31  and on the piston  33 . These pressure springs  13  are elastically compressed, parallel to the axis of rotation  12 , in the case of a displacement of the piston  33  against the second joint segment  31 , so that in the case of a discharge of the compressed air in the cavity  32 , the piston  33  is pushed back into its starting position when joint  4  is unlocked, by means of the recovery force of the pressure springs  13 . Piston  33  is secured against rotation about the axis of rotation  12  by means of a rotation-securing device  20 , in the first joint segment  30 . Here, this rotation-securing device  20  comprises a cylindrical rod  25  that is accommodated, eccentrically with reference to the axis of rotation  12 , in a notch  26  recessed into the periphery of the journal  15 , on the one hand, and in a groove  27  made in the bore  28  in the piston  33 , on the other hand. Furthermore, the cylindrical rod  25  is attached in the housing  14  at one of its ends.  
         [0029]      FIG. 2  shows an embodiment of the inventive holding device, having a holding arm  1  comprising a first stabilizing element  2  and a second stabilizing element  3 . The holding device essentially comprises a movable holding arm  1  having a first end  5  and a second end  6 . The stabilizing elements  2 ,  3  are disposed between the two ends  5 ,  6 , and are connected with one another by means of a joint  4 , so as to rotate about the axis of rotation  12 . Furthermore, the holding device comprises attachment means  7  at the first end  5  of the holding arm  1 , which means are structured here as a rod that is attached to the operating table  29 , and serve to fix the holding arm  1  in place on the operating table  29 . Here, attachment means  7  are connected to the first stabilizing element  2  so as to rotate. Fixation means  9 , such as, for example, Kirschner wires for releasable fixation of free end  6  to a bone  10  of a bone fragment of a patient, are disposed on the second end  6  of the holding arm  1 .  
         [0030]      FIG. 3  shows an embodiment of the inventive holding device, having three stabilizing elements  2 ,  3 ,  40 , of which two stabilizing elements  2 ,  3 ,  40 , in each instance, are connected with one another by a joint  4 , in each instance. The stabilizing element  2  that is in the end position on the first end  5  of the holding arm  1  is attached to a fixed object  41 , by means of another joint  4 , with the attachment means  7  configured as a clamp. Here, the axes of rotation  12  of the three joints  4  are parallel. Furthermore, the accommodations  42  for the fixation means  9  ( FIG. 2 ) are connected with the end-position stabilizing element  40  on the second end  6  of the holding arm  1 , to rotate about a second axis of rotation  39  that stands perpendicular to the axes of rotation  12 . Connection elements  45  are affixed to the housings  14  of the joint segments  30 , to which the lines  11  ( FIGS. 1 and 2 ) can be connected. In this connection, the lines  11  can be run in series or parallel, as needed. The control for the compressed air feed can, on the one hand, be configured such that joints  4  can be locked individually, in any desired sequence, or one after the other, or, on the other hand, in such a manner that the joints  4  can be locked simultaneously.  
         [0031]     While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Various features and structures can be used singularly or in combination with other features and structures. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the invention.