Abstract:
A surgical device comprising a plate member ( 10 ) for mounting to a bone of a subject. The plate member ( 10 ) has a first end, a second end, a first face and a second face. At least one spacer member ( 20 ) is adapted to be mountable to at least a portion of the plate member ( 10 ) and relatively moveable towards and/or away from its first end ( 13 ). The spacer member ( 20 ) extends outwardly from the second face of the plate member ( 10 ) and is prevented from moving away from the first end ( 13 ) by a stop member ( 28 ) positioned between the first and second ends of the plate member ( 10 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method and an apparatus for surgical reconstruction and intervention in orthopaedic surgery. The invention further relates to preferred constructions of surgical procedures especially high tibial osteotomies, femoral osteotomies, mandibular reconstruction, skull reconstruction and other such orthopaedic procedures.  
         BACKGROUND ART  
         [0002]    Correction of skeletal deformities and abnormalities, both inherent and from trauma can be performed using surgical procedures and devices. Distraction techniques whereby bone, which is of the incorrect length and/or alignment, is drawn out to the correct length are often used in conjunction with surgical devices.  
           [0003]    In the case of reconstruction of skull bone, techniques and devices exist whereby the use of wires and scaffolding provides a reinforced structure to which bone can grow through and over.  
           [0004]    High tibial osteotomy is a surgical procedure that is commonly used in the correction of “bowed legs” and in some circumstances “knock knees”. In the event of either of these disorders, abnormal load distribution and transfer is generated in and across the tibio-femoral joint. Abnormal load transfer causes increased load distribution on the medial tibial and femoral condyles in the case of “bow legs”, resulting in increased stresses, wear and patient pain. Increased loading on the medial condyles has a positive feedback effect on wear, resulting in exacerbated wear unless there is surgical intervention.  
           [0005]    Conventionally, patients with such conditions are treated by several surgical techniques. Aged patients are usually treated with a total knee replacement, or in latter years with a Unicompartmental Knee replacement, when the medial articular surfaces of the knee are worn and the patient is suffering pain and lack of mobility. Younger subjects are more often treated by use of a high tibial osteotomy. The preferred approach for this procedure is a lateral approach of the proximal tibia. The procedure involves either removing a wedge of bone (referred to as a closing wedge) or by making a dome shaped cut, rotating the tibia and reducing the tibial plateau to the tibia. In either of the above procedures, the reduced “fracture” requires fixation such that fracture reunion can occur. Fixation is most commonly achieved by the use of plaster, staples, staple plates, fracture plates, fracture hardware and screws.  
           [0006]    Another approach for the procedure is an approach from the worn side of the tibia, often the medial side, and to provide an opening wedge. In this case, a transverse cut is made across the tibia and the worn side is elevated such that the tibial plateau is more favourably aligned.  
           [0007]    There are a number of complications associated with traditional high tibial osteotomy. The aim of the procedure is to realign the tibia with an over correction of typically about 3° such that, in the case of “bowed legs”, the loading is transferred from the medial side of the joint to the lateral side of the joint, allowing the medial side of the joint to recover.  
           [0008]    Intraoperatively, it is difficult to effect the correct angle of adjustment. In the closing wedge procedure, a wedge of the correct thickness must be removed from the tibia. It has been found that if the second cut is not such that the correct size of wedge is removed, a third cut is a difficult action for correction. In the case of the domed osteotomy, the precise angle of shift for the tibia is difficult to determine accurately and difficult to adequately fix. Clinically it has been found that it is difficult to reliably to set the angle within 2° of the required angle. It has been found clinically that the opening wedge procedure is an easier procedure in so far as determining the correct angle, however, this procedure has substantial difficulties as will be discussed below.  
           [0009]    Successful fixation of the surgically created fracture is a problem faced in respect of all known methods of high tibial osteotomy. The wedge is constantly being forced closed by muscle, ligament and weight forces. To overcome this problem, bone harvested from other parts of the patient has been used to hold open the gap. Also plate and screw hardware has been used to hold open the gap created by the removal of the wedge. These methods have often failed due to collapse of the bone autograft prior to osteo-integration and bone union, and from failure of the plate/screw system. The plate/screw system offers limited resistance to torsional loads and axial rotation. This often results in screw pull-out or screw failure due to shear.  
           [0010]    In the case of surgical intervention on the lateral aspect, there are several complications including the anatomical location of a major nerve in the proposed site for the osteotomy, and that once the osteotomy has been performed, total knee replacement, should that option be required at a later date, is complicated. In addition, many incisions in this area pose increased risk of limiting vascularity, resulting in tissue failure. Also, a lateral approach requires shortening of the fibula and as well there is a reduction in overall leg length.  
           [0011]    Secondary alignment is often difficult to control with known methods of high tibial osteotomy. There should be no inadvertent posterior tilt or rotation. Such misalignments result in subsequent deformities and complications. The closing wedge procedure poses alignment problems as two separate cuts must be made, such that upon loading the faces of the cuts meet at the cortex and the cortex acts as a stabilising means for the procedure. There is not a uniform meeting of the proximal and distal cortices at the osteotomy site, leading to increased stress concentration and deformity.  
           [0012]    In order to overcome such complications, Puddu (U.S. Pat. No. 5,749,875) uses a system of plates and screws of varying sizes and geometries and a calibrated wedge tool for opening a resected tibial wedge to determine the size of the plate required. Again, excessive loads to screws and plates across osteotomy sites has resulted in failure due to the heads of the screws shearing off under load. Such failure results in further complications and restorative surgery.  
           [0013]    The present invention is directed to providing an alternative to the existing techniques and apparatus for use in the performance of surgical procedures, especially those requiring reconstructive orthopaedic intervention, such as high tibial osteotomies and mandibular or other skull bone reconstructions. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.  
         DISCLOSURE OF THE INVENTION  
         [0014]    Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.  
           [0015]    In a first aspect, the present invention is a surgical device comprising:  
           [0016]    a plate member that is mountable to a bone of a subject, the plate member having a first end, a second end, a first face, a second face, and a stop means between said first end and said second end; and  
           [0017]    at least one spacer member mountable to at least a portion of the plate member and relatively moveable towards and/or away from the first end, the spacer member, on mounting, extending outwardly from the second face of the plate member;  
           [0018]    wherein on abutment of the spacer member with the stop means, the spacer member is prevented from undergoing further movement in a direction away from the first end of the plate member.  
           [0019]    In one embodiment, the plate member further comprises a receiving means for a bone fixation device, the receiving means having an abutment surface wherein on engagement of a fixation device fixed in a bone with the abutment surface and relative movement between the plate member and the bone thereto leads to an alteration in the stress within the fixation device, the altered stress within the fixation member being such that further relative movement between the plate member and the bone is reduced.  
           [0020]    In another embodiment of the first aspect, the plate member has a first side and a second side. The at least one abutment surface can extend from the first side of the plate member to the second side of the plate member on at least a portion of the first face of the plate member. The at least one abutment surface can have a first side and a second side. Examples of fixation devices that can engage with the at least one abutment surface include bone screws and circumferential fixation devices including cable and block fasteners, screw-driven circumferential clamps and wedge/block mechanisms.  
           [0021]    In another embodiment of the first aspect, the plate member can have an orifice extending through the at least one abutment surface. The orifice can extend through the plate member and through the second face of the plate member. In one embodiment, the orifice can be ovoid or elongate. In another embodiment, the fixation device can have a first end to engage with the abutment surface of the plate member, a second end to engage with the subject&#39;s bone and an intermediate portion between the first and second ends which can pass through the ovoid or elongate orifice of the plate member. Examples of fixation devices that can engage with the at least one abutment surface and engage with the bone include screws, bolts, nails and pins.  
           [0022]    In a second aspect, the present invention is a surgical device comprising:  
           [0023]    a plate member that is mountable to a bone of a subject, the plate member having a first end, a second end, a first face and a second face; and  
           [0024]    at least one spacer member extending outwardly from the second face of the plate member and positionable between two bone surfaces formed in the bone of the subject;  
           [0025]    wherein the plate member has at least one abutment surface engageable with a fixation device used to affix the plate member to the bone, such that relative movement between the plate member and the bone induces an altered stress within the fixation device, the altered stress within the fixation device being such that further relative movement between the plate member and the bone is substantially prevented or at least reduced.  
           [0026]    In a first embodiment of the second aspect, the spacer member can be formed integrally with the plate member.  
           [0027]    In an embodiment of the first and second aspects, the at least one abutment surface is at an angle of inclination to the first face of the plate member. The inclination of the abutment surface can be upwardly from the first end of the plate member toward the second end of the plate member, or from the second end of the plate member to the first end of the plate member. In a further embodiment, the plate member can have a first side and a second side. The at least one abutment surface can extend from the first side of the plate member to the second side of the plate member on at least a portion of the first face of the plate member. The at least one abutment surface can itself have a first side and a second side. The at least one abutment surface can extend outwardly from the first surface of the plate.  
           [0028]    In another embodiment of the first and second aspects, the abutment surface can be recessed within the body of the plate member. Examples of fixation devices that can engage with the at least one abutment surface include bone screws, and circumferential fixation devices including cable and block fasteners, screw-driven circumferential clamps and wedge/block mechanisms.  
           [0029]    In another embodiment of the second aspect, the plate member can have an ovoid or elongate orifice extending from the abutment surface through the plate member, to the second face of the plate member. The ovoid or elongate orifice preferably extends along at least a portion of the abutment surface. The ovoid or elongate orifice can have a short axis and a long axis. The long axis can be in alignment with the longitudinal axis extending between a first end of the plate member and a second end of the plate member.  
           [0030]    In the second aspect, a fixation device can have a first end to engage with the abutment surface of the plate member, a second end to engage with the subject&#39;s bone and an intermediate portion which can pass through the orifice of the plate member, can be used to affix the plate member to the bone. Examples of fixation devices that can engage with the at least one abutment surface and engage with the bone include screws, bolts, nails and pins.  
           [0031]    In yet another embodiment of the first and second aspects, the plate member preferably has at least one abutment surface between the first end of the plate member and the at least one spacer member, or between the second end of the plate member and the at least one spacer member. More preferably, the plate member has at least one abutment surface between the first end of the plate member and the at least one spacer member and at least one abutment surface between the second end of the plate member and the at least one spacer member. Still more preferably, the plate member has a plurality of abutment surfaces between the second end of the plate member and the at least one spacer member and at least one abutment surface between the first end of the plate member and the at least one spacer member. More preferably still, at least one of the abutment surfaces can have an orifice extending from the abutment surface through the plate member, to the second face of the plate member. The at least one orifice can be circular or ovoid or elongate.  
           [0032]    In a further embodiment of the first and second aspects, the plate member and the at least one spacer member can be made of a biocompatible material, preferably of a biocompatible metal or metal alloy. Examples of metals and metal alloys include stainless steel, titanium, titanium alloys and cobalt-chrome alloys. In another embodiment, the at least one spacer member and/or the plate member can be formed from a biologically active material. For example, the spacer member can be formed from a block of calcium phosphate.  
           [0033]    In a still further embodiment of the first and second aspects, the spacer member can include a built-in substance delivery system. The built-in delivery system can be used for the delivery of at least one drug and/or therapeutic agent to a site within the patient&#39;s body. Examples of drugs or therapeutic agents include prophylactic antibiotic or steroids, hydroxyapatite, calcium phosphate, bone morphogenic proteins and growth factors.  
           [0034]    In a preferred embodiment of the second aspect, the present invention has a plate member having at least one spacer member mountable to at least a first portion of the plate member, the spacer member being relatively moveable to the plate member from the first end of the plate member toward and away from the first end of the plate member. The plate member has a stop means for preventing the further relative motion of the spacer member toward the second end of the plate member. The plate member has at least one abutment surface between the stop means and the first end of the plate member, and at least one abutment surface between the stop means and the second end of the plate member. The respective abutment surfaces are recessed below the first surface of the plate member. Ovoid or elongate orifices extend through the plate member, passing through the at least one abutment surfaces. The ovoid or elongate orifices can be co-linear or offset.  
           [0035]    In a third aspect, the present invention is a method of carrying out an osteotomy on a bone of a patient to align the bone or correct a deformity comprising the steps of:  
           [0036]    (a) forming a saw cut in the bone of a patient;  
           [0037]    (b) causing the cut to be widened on at least one side so as to align or correct the deformity of the bone;  
           [0038]    (c) placing the at least one spacer member of the surgical device according to the first aspect within the widened cut such that the at least one spacer member is in contact with cortical bone on each side of the cut; and  
           [0039]    (d) securing the plate member to the bone of the patient.  
           [0040]    In an embodiment of the third aspect, the method can comprise a further step of engaging the plate member to the at least one spacer member. Preferably, the further step of engaging the plate member with the at least one spacer member is performed between step (c) and step (d).  
           [0041]    In a preferred embodiment of the third aspect, the present invention relates to a process for carrying out a high tibial osteotomy, where the saw cut is performed through a tibia of a patient substantially in the medio-lateral plane adjacent to the head of the fibula.  
           [0042]    Many combinations of fixation devices can be used to secure the plate member of the devices of the first, second and third aspects to the bone of a subject. Such fixation devices include screws, bolts, nails, pins, screw driven circumferential clamps, cable and block fasteners and a combination of one or more of these devices. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]    By way of example only, preferred embodiments of the invention are described with reference to the accompanying drawings, in which:  
         [0044]    [0044]FIG. 1 is a perspective view of one embodiment of a plate member according to the present invention having two protruding abutment surfaces;  
         [0045]    [0045]FIG. 2 is a perspective view of another embodiment of a plate member according to the present invention having two recessed abutment surfaces;  
         [0046]    [0046]FIG. 3 is a perspective view of another embodiment of a plate member according to the present invention having a protruding abutment surface and an elongate orifice;  
         [0047]    [0047]FIG. 4 is a perspective view of another embodiment of a plate member according to the present invention having a recessed abutment surface and an elongate orifice;  
         [0048]    [0048]FIG. 5 is a perspective view of another embodiment of a plate member according to the present invention having a recessed abutment surface and an elongate orifice;  
         [0049]    [0049]FIG. 6 is a longitudinal cross sectional view of the plate member of FIG. 5;  
         [0050]    [0050]FIG. 7 is a perspective view of another embodiment of a plate member according to the present invention having a protruding abutment surface and an elongate orifice;  
         [0051]    [0051]FIGS. 8 a  and  8   b  are cross-sectional and perspective views of a plate member having a recessed and chamfered abutment surface for engagement with the head of a bone screw, respectively;  
         [0052]    [0052]FIG. 9 is a cross sectional view of one embodiment of a plate member and spacer member in situ in bone of a subject;  
         [0053]    FIGS.  10 ( a ),  10 ( b ) and  10 ( c ) are views of another embodiment of a plate member and spacer member according to the present invention; and  
         [0054]    [0054]FIG. 11 is a perspective view of the plate member and spacer member of FIG. 10 in an assembled configuration.  
         [0055]    [0055]FIG. 12 is a perspective view of the plate member mounted to the bone of a subject by fixation means. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0056]    As an example only, a configuration of the abutment surface  15  of a plate member for one embodiment of a surgical device according to the present invention is depicted in FIG. 1. In this example, the abutment surface  15  extends upwardly from the first face  11  of the plate member  10 , and extends across the width of the first face of the plate member from a first side  16  of the plate member  10  to a second side  17  of the plate member  10 . Circumferential fixation devices including cable and block fasteners, screw-driven circumferential clamps and wedge/block mechanisms can be used to engage with the abutment surface  15  to secure the depicted plate member  10  to the bone of a subject.  
         [0057]    [0057]FIG. 2 depicts an example of the abutment surface  15  when recessed within the plate member  10 , and extending across the width of first face  11  of the plate member  10  from the first side  16  to the second side  17 . Circumferential fixation devices including cable and block fasteners, screw-driven circumferential clamps and wedge/block mechanisms can again be used to engage with the abutment surface  15  to secure the plate member  10  to the bone of a subject.  
         [0058]    A further example of a protruding abutment surface  15  of a plate member  10  is depicted in FIG. 3. The abutment surface  15  extends across the width of the first face of the plate member  11  from the first side  16  of the plate member  10  to the second side  17  of the plate member  10 . An elongate orifice  18  passes through the abutment surface  15 , through the plate member  10  and out through the second face  12  of the plate member  10 . Fixation devices that can engage with the abutment surface  15  of this example and secure the plate member  10  to the bone of a patient include screws, bolts, nails, pins, screw-driven circumferential clamps, cable and block fasteners and a combination of one or more of these devices.  
         [0059]    [0059]FIG. 4 depicts an example of a plate member  10  having a recessed abutment surface  15  extending across the width of the first face of the plate member  11  from the first side  16  of the plate member  10  to the second side  17  of the plate member  10 . An elongate orifice  18  passes through the abutment surface  15 , through the plate member  10  and out through the second face  12  of the plate member  10 . Fixation devices that can engage with the abutment surface  15  of this example and secure the plate member  10  to the bone of a subject include screws, bolts, nails, pins, screw driven circumferential clamps, cable and block fasteners and a combination of one or more of these devices.  
         [0060]    [0060]FIG. 5 depicts an example of the abutment surface  15  recessed within the plate member  10 . In this embodiment, the abutment surface extends across only a portion of the width of the first face  11  of the plate member  10 . An elongate orifice  18  passes through the abutment surface  15 , through the plate member  10  and out through the second face  12  of the plate member  10 . Fixation devices that can engage with the abutment surface  15  of this example and secure the plate member  10  to the bone of a patient include screws, bolts, nails and pins.  
         [0061]    [0061]FIG. 6 depicts a longitudinal cross sectional view of a portion of the plate  10  of FIG. 5 through the elongate orifice  18 . The head  19  of a screw  21  engages with the abutment surface  15  to secure the plate member  10  to the bone of a subject. The gradient of the abutment surface  15  is such that relative motion between the plate member in the direction A and the screw member  21  in the direction of B, is opposed due to the abutment surface increasing the stress in the screw member  17  by virtue of a wedge-type action.  
         [0062]    Where there a plurality of abutment surfaces  15 , stress due to relative motion can be distributed between a plurality of fastening means.  
         [0063]    The gradient of the abutment surface  15  is such that as the head of the screw member  17 , in the event of relative motion along the abutment surface in the direction of B, does not fail due to increased stress.  
         [0064]    [0064]FIG. 7 depicts a further example of a plate member  10  where the abutment surface  15  is protruding from the first face  11 . In this embodiment, the abutment surface  15  extends across a portion of the width of the first face of the plate member  10  and has a first face  22  and a second face  23 . An elongate orifice  18  passes through the abutment surface  15 , through the plate member  10  and out through the second face  12  of the plate member  10 . Fixation devices that can engage with the abutment surface  15  of this example and secure the plate member  10  to the bone of a subject include screws, bolts, nails, pins, screw driven circumferential clamps, cable and block fasteners and a combination of one or more of these devices.  
         [0065]    FIGS.  8 ( a ) and  8 ( b ) depict an example of a plate member  10  where the abutment surface  15  is recessed within the plate member  10 . The abutment surface is chamfered such that a chamfered or substantially hemispherical head of a screw can engage with the abutment surface  15 . A transverse cross section of the plate member is shown in FIG. 8( a ). The abutment surface has a first face  22   a  and a second face  23   a , however as the abutment surface is recessed in FIG. 8, the first face  22   a  and the second face  23   a  are internal the plate member  10 . The first face  22   a  and the second face  23   a  of the abutment surface extend downwardly from the first face  11  of the plate member  10  toward the second face  12  of the plate member  10 . At the termination of the first face  22   a  and the second face  23   a  of the abutment surface, the respective portions of the abutment surface  15  slope downwardly and toward each other. An elongate orifice  18  passes through the abutment surface  15 , through the plate member  10  and out through the second face  12  of the plate member  10 . Fixation devices that can engage with the abutment surface  15  of this example and secure the plate member  10  to the bone of a patient include screws, bolts, nails and pins. FIG. 8( b ) shows that portion of the plate member having the chamfered abutment surface  15  with an elongate orifice passing through the plate member and out through the second face  12  of the plate member  10 .  
         [0066]    [0066]FIG. 9 depicts a preferred embodiment of the device according to the present invention in use. The invention is depicted being used in a tibial osteotomy. In this arrangement, the spacer member  20  is depicted positioned within the opening of an osteotomy  27 . The plate member  10  is engaged with the spacer member  20  in a manner such that the spacer member is stopped from moving from the first end  13  of the plate member  10  toward the second end of the plate member by a stop member  28  incorporated within the plate member. In FIG. 9, the abutment surfaces are recessed within the plate member. There is also only one abutment surface between the stop member of the plate member and the first end of the plate member, and at least one abutment surface between the stop member and the second end of the plate member. The abutment surfaces extend across a portion of the first face  11  of the plate member  10 . An elongate orifice passes through the abutment surface, through the plate member  10  and out through the second face  12  of the plate member  10 . The abutment surfaces are inclined such that relative motion of the plate member  10  in the direction of B is reduced or inhibited. Fixation devices that can be used to secure the plate member to the bone of the patient include screws, bolts, nails and pins.  
         [0067]    FIGS.  10 ( a ),  10 ( b ) and  10 (c) depict one embodiment of the plate member  10  and spacer member  20 . FIG. 10( a ) depicts the plate member  10  having a stop member  28  that is adapted to prevent relative sliding motion between the plate member  10  and the spacer member  20  in a direction away from the first end  13  once the spacer member  20  has come into abutment with the stop member  28 . In this example, the stop member  28  is a thickening or widening of the plate member. FIG. 10( b ) depicts the face of the spacer member  20  that slides against the second face of the plate member  10 . FIG. 10( c ) depicts an undercut  29  in the spacer member  20  through which the plate member  10  is adapted to be slidable.  
         [0068]    [0068]FIG. 11 depicts the plate member  10  and spacer member  20  of FIG. 10 in an assembled configuration. The spacer member  20  can slide from the first end  13  of the plate member  10  toward the second end of the plate member until it comes into abutment with the stop member  28  of the plate member. In this example, the stop member  28  consists of a widening of the plate member  10 .  
         [0069]    [0069]FIG. 12 depicts an example of the plate member  10  fixed to a bone  26  using several different types of fixation devices engaging with the abutment surface  15  of the plate member  10 . A cable  31  and block fastener  32  is shown as one example of fixation means suitable for fixing the plate member  10  to the bone  26 . Another example of a fixation means is a screw-driven clamp means  33 . A further example of a fixation means suitable for fixing the plate member  10  to the bone  26  is a bone screw  34 . Although not depicted in this figure, many further combinations of fixation devices can be used to secure the plate member of the devices of the first, second and third aspects to the bone of a subject. Such fixation devices include screws, bolts, nails, pins, screw driven circumferential clamps, cable and block fasteners and a combination of one or more of these devices.  
         [0070]    It will be appreciated that the first end  13  of the depicted plate member  10  could be mounted to the bone of a subject so as to face proximally or distally as circumstances dictate.  
         [0071]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.