BACKGROUND

The present invention relates to retraction assemblies used in surgery, For retracting soft tissue particularly though not exclusively in spinal surgery. The invention further relates to a retracting blade having a geometry which enables more convenient engagement of the blade to an anchor. The invention further provides a retraction blade having a formation which enables engagement of an anchorage fastener, before or after the fastener has been set in bone. The invention further- relates to a retractor plate which has an open channel which enables the blade to detachably receive an anchorage fastener once the fastener has been set in vertebral bone.

The invention further relates to a retractor blade usable with an anchor and including at least one cannulated region each capable of engagement with an anchor pin before or after insertion of the pin in bone, the blade allowing retraction of veins and arteries during surgery. Although the , invention is described below in relation to the anterior lumbar spine, the principles and geometry embodied in the retractor blade have applications throughout the spine and wherever bone is available to provide support.

PRIOR ART

There are in existence a number of assemblies used in retraction of soft tissues and which include retractor blades which engage bone during such retraction. In particular, - there are known retractor blades which retract soft tissue during, spinal surgery. Such retractor blades are maintained at a setting to allow a surgeon access to a spinal disc space and vertebrae in cervical and lumbar spinal disc surgery. Retractors are sometimes used in conjunction with distraction assemblies. The process of separating bones is termed distraction. This involves insertion of a spreading type instrument into an excised disc space which engages the upper and lower vertebral bodies and when applied, separates them. This is known as intervertebral distraction. Alternatively, in the cervical spine in a procedure known as non - intervertebral distraction may be used in which long screws are inserted into the upper and lower vertebral bodies. Surrounding soft tissues must be held apart by retractors. Once retracted, there is a natural elastic recoil of the stretched tissues so it is essential to employ retractors which effectively restrain soft tissues and without loosing the requisite retraction.

It is important to reduce trauma to soft tissues which may occur from contact with parts of retractor blades so that the surgical procedure is as minimally invasive as possible and thus minimally interferes with and minimally traumatizes the organs, tissues and vasculature being displaced to allow access to the vertebral region being treated. Various types of retractors arc known each having means to enable retention, by a support member.

Anterior, lumbar surgery can be performed for a number of reasons, but most commonly this is for excision of degenerate intervertebral disc after which a fusion procedure or lumbar disc arthroplasty is performed. Amongst spinal surgeons it is recognized that the most difficult and dangerous part of the surgery on the anterior lumbar disc spaces is dissection, mobilization and maintenance of retraction of the vessels, and in particular the left common iliac vein. In the usual left retroperitoneal approach to the spine, this vein has to be retracted from left to right and inferiorly to expose the inferior right hand corner of the 45 disc space. Whatever level of surgery is being performed, there is an initial approach requiring some degree of vascular dissection. The approach and surgery generally requires the use of handheld retractors, at least initially, which may then be replaced with fixed retractors to maintain retraction for the rest of the procedure. Fixed retractors require either internal fixation to spinal vertebra or external fixation using a table mounted system. Retractors are usually positioned to hold tissues away from the surgical field both laterally (side to side) and longitudinally (up and down) relative to a spine.

Existing retractors may be internally or externally fixed. Internal fixation of retractors is utilized to hold the left common iliac vein or other tissues in a retracted position. There is a danger that veins may be punctured or squeezed. Due to. the difficulty and dangers of moving and keeping the blood vessels retracted during anterior lumbar surgery, stability of the retractors is particularly important. The most stable retractors are those embedded in the bone e.g. Steinmaπ pins and Hohmann retractors. Steinman pins are long pins impacted into the bone while Hohmann retractors are conventional retractor blades with a curved pointed end which can be impacted into the bone for stability. Some limited movement of the Hohmann blade is possible by bending. Also known arc standard retractor blades that have a through passage which allows separate introduction of sharp pins through the passage into the vertebral body thus securing the blade to the spine. It is lateral as distinct from longitudinal retraction that represents the greatest difficulty as the soft tissues naturally want to return to their normal anatomical location. Typically the soft tissues when displaced or retracted by a retractor blade, will attempt to locate to their normal position by migrating under a distal end of the blade which would normally be in engagement with vertebral bone.

Internally fixed retractors have limitations. Although very stable once in place they arc not adjustable and insertion does produce bone injury. Insertion and removal can also be hazardous to vessels or other soft tissues.

External fixation of retractors is achieved by the use of table mounted retractors.

Various table mounted retractor systems are available e.g. Thomson, Omnitract, Bookwalter, Synframe etc. The table based systems, offer a variety of retractor blades for holding back the tissues connected to a table mounted ring or support frame. Various shapes of blade are available. In order to improve on these and in particular to improve stability of these non internally- fixed blades a new shape of retractor blade, called The Brau Blade, was developed. This blade is described in US patent number 6,416,465 and is incorporated by reference herein.

The known externally fixed retractor blades have significant limitations.

5 Contact and pressure on the blade against the bone improves stability of retractor blades. Most conventional blades however rely only on their external fixation for stability. If there is contact with the bone it lies at the side of the vertebral body usually at or above the equator of the vertebrae where the bone is curving postero- laterally. The lip of the Brau blades and all other conventional blades when used for

I O lateral retraction are in contact with the bone along the side of the body i.e. in contact with the spine along a superior inferior plane. To remain stable they rely on a solid immobile connection to the operating table through various linkages and if in contact with the bone, a force is directed along the edge of the blade (the lip) parallel to this radius of the body. Many conventional blades just sit beside the bone with a

15 lip curving away from the bone.

In practice, once in position all table mounted retractor blades hold reasonably still relative to the table but not necessarily the spine. This is because they do not fix to the patient and when the patient's spine moves e.g. during impaction or positioning of implants, or other vigorous work, the lateral retractors tend to bounce and slip. In0 that case, soft tissues including vessels can slip under or around the retractor blades-

Contact with the bone by providing an additional point of stability helps reduce this, but it remains a problem. If a constant force is applied from the frame along the line of the blade, pushing the blade against the spine helps stability, but this can easily lead to the blade slipping or sliding posteriorly and causing tissue injury when' the5 spine moves. Inadvertent downward pressure by surgeons or their assistants on these blades also is a problem as it leads to posterior displacement, because there is usually little or no support for the blade from the pone relying as it dies essentially on friction grip. This can lead to soft tissue injury. By comparison when retracting longitudinally using retractor blades, the edge of the blades can be pushed down onto the anterior surface of the vertebral bodies where they are lying across llie spine and perpendicular to the main radius. This gives them much greater relative stability. The stability is also enhanced because the anterior surface of the spine is less curved anteriorly than laterally.

In addition to instability leading to tissue injury, it is also preferable to improve stability as this reduces the operating time lost spent adjusting retractors. In general terms the morbidity of surgery tends to increase with increasing length of procedure.

One of the limitations of many existing retraction systems is I he tendency for the vessels, in particular the left common iliac vein, to bulge around the retractor, which can expose the vein to injury and impede the surgeon. Various techniques can be employed to keep the vein safe, either by placing the lateral retractors as far laterally as possible displacing the vein laterally while retracting the vein infcriorly away from the disc space with another retractor. This technique risks over stretching the vein Another technique is to fill the 'difficult corner' between the side to side and inferior blades with a swab or other protective material. Another approach is to displace the vein away with hand held retractors and insert a Steinman pin at the apex of the corner to maintain retraction. All of these techniques have the disadvantage that excessive retraction can lead to direct vessel injury, bleeding or thrombosis, and irregular retraction e.g. with pins produces angular distortion i.e. indenting the vein predisposing the patient to increased turbulent flow, and thereby thrombosis within the vessel. It is preferable to minimize the amount of retraction used and to use smooth retraction over an area, particularly when retracting blood vessels in order to reduce turbulence and thereby the potential for thrombosis within the vessel.

Numerous retractor blades exist for use in surgery of various shapes and geometry. One retractor blade is known with two surfaces at right angles to each other over the length of the blade. This is a handheld retractor for use posteriorly in the lumbar spine to retract muscle to aid in implantation of pedicle screws. This does not have any function to retract blood vessels. The end is shaped for bone contact on or close to the transverse processes of the spine or the sacrum without adapting to the anatomical shape of the bones and the bone contact is in one plane only.

Although there are a wide variety of retractor blades currently in use, in view of the disadvantages inherent in those blades, there remains room for improvement in the geometry of the blades with the objective of providing a blade which is easy to use, adaptable to existing support frames, efficiently maintains retraction of soft tissue and does not obstruct the surgeons path to the operating site and does not compromise retraction in the event of unwanted loading such as inadvertent bumping during surgery.

US patent number 6,692,434 discloses a method and device for retractor for microsurgical intermuscular lumbar arthrodesis An instrument useful in performing lumbar arthrodesis with a minimal approach which spares the lumbar muscles from surgical disruption .and includes one of two retractor designs having blades angled approximately 90-degrecs with respect to each respective retractor handle.

In operations on the anterior lumbar spine, retraction of vessels and abdominal contents is critical and stability of retractors is vital to safe performance.

Known retractors without bone fixation are employed but they all tend to move under load or bounce during bone surgery. This instability can expose vessels to injury. Soft tissue injury can also occur, due to retractor repositioning.

One solution that has been provided to this problem is a co operating cannulated retractor blade which receives an anchor pin or screw, which is screwed into bone during surgery. These pins apply a downward force and secure the blade against the bone by means of mutual engagement between the cannulation in the blade and the anchor pin. This provides good anchorage but there are dangers ^■ inherent in finding the optimal pin position and holding the blade in a position near the optimal pin anchorage position until the pin is passed through the blade. There is a danger when the pin is moved around to find the optimal anchorage position could snag vital structures such as blood vessels. There is another disadvantage of the prior art assemblies in that the surgeon must hold the retractor blade perfectly still in the critical selected position while sliding a sharp potentially dangerous pin through the cannulation in the blade and into engagement with the spine. Moving the retractor blade while the pin is on the bone incurs the risk of dragging the point- of the pin over a difficult to see compressed vein which could be inadvertently impaled during pin insertion. An error of this kind can have fatal consequences. Correct or optimal placement oF the retractor blade is critical to. its performance. The angle at which the blade sits relative to the spine is critical to its performance as is the angle of entry of the pin. Correct angle of entry is critical to avoid insertion through the end plates of the vertebral body. The lenglh of the pin is also critical to avoid over insertion and penetration of critical structures on the opposition side of the bone and also to prevent under penetration which could lead to pin breakage. Maintaining the optimal blade and pin angles to optimize retraction against soft tissue forces while at the same time trying to locate a safe entry point for safe insertion of the pin can be difficult and hazardous.

There is a need to provide a more convenient and safer means of installation of retractors and also a more efficient means for engagement between an anchor and retractor blade during installation, which ameliorates or eliminates the aforesaid disadvantages of the prior art.

INVENTION

The present invention addresses the problems associated with the known retraction blades and seeks to eliminate the aforesaid disadvantages of existing prior art retractor systems by providing a retractor blade having an open recess which receives an anchor before or after insertion of the anchor in bone.

The present invention provides retraction assemblies used in surgery, for retracting soft tissue particularly though not exclusively in spinal surgery, and comprising a retracting blade which has an open channel which enables the blade to dctachably receive an anchorage fastener once the fastener has been set in vertebral bone. The invention further provides a retraction blade having a formation which enables engagement of an anchorage fastener before or after the fastener has been set in bone. The invention further provides a retractor blade usable with an anchor and including at least one cannulated region each capable of engagement with an anchor pin before or after insertion of the pin in bone, the blade providing retraction of soft tissues including veins and arteries during surgery. Although the invention is described below in relation Io the anterior lumbar spine, the principles and geometry embodied in the retractor blade have applications throughout the spine and wherever bone is available to provide support.

Preferably the retractor blade in addition to the cannulation includes a distal end geometry which conforms at least in part to vertebral bone contours to facilitate stability and more effective and efficient soft tissue retraction during blade insertion.

This retractor according to the invention seeks to improve the installation and stability of an anchor blade and pin assembly during an operation such as anterior lumbar surgery. The invention provides an alternative blade shape and configuration including a recess which allows an alternative means of coupling of the blade and anchor to avoid the dangers described earlier of selecting positioning for the anchor point. Although designed to aid retraction during surgery on the anterior lumbar spine the principles of the invention have application throughout the spine and elsewhere where bone is available for load distribution.

The anterior surface of all the vertebral bodies forms an approximate arc of a circle which is .slightly flattened in the middle. The vertebral body diameter however varies. It is narrowest in the mid body and then expands circumferentially adjacent to the disc spaces between adjacent vertebra. When viewed in coronal section this produces a modest, hour glass shape. In the axial plane the anterior oval vertebral shape is relatively constant with the discs and the endplatcs forming slightly larger diameter circles than in the mid body.

In its broadest form the present invention comprises; a retractor blade for retracting soft tissues during surgery, ihe blade comprising: a blade body having first and second ends, the first end providing means to allow connection of the blade body to a support member, the second end having a contour adapted to engage bone; and located between said first and second ends a generally elongated open longitudinal channel defining a recess, the channel extending at least part of the distance between said first and second ends and enabling the blade to be coupled and uncoupled to an anchor member before or after the anchor member is engaged to bone.

In another broad form the present invention comprises: a retractor blade for retracting soft tissues during surgery, the blade comprising: a blade body having first and second ends, the first end providing means to allow connection of the blade body to a support member, the second end having a contour adapted to engage bone; and located between said first and second ^' ends a generally elongated open channel defining a longitudinal recess, the channel extending at least part of the distance between said first and second ends and enabling the blade to be coupled to an anchor member while the anchor member is engaged to bone.

According to one embodiment the blade comprises a first part disposed in a first plane and a second part disposed in a second plane normal to the first plane forming an L shape. Preferably the open channel is disposed at or near the junction of the first and second parts. Preferably, the blade includes a formation at an edge at least part of which is capable of transmission of load applied Io the retractor to spinal vertebrae to resist unwanted movement of the retractor. Although the ideal form of recess is a generally circular channel having a longitudinal opening, it will be appreciated by persons skilled in the art that alternative channel configurations arc feasible provided they accept an anchor by at least lateral, rotational or lateral and rotational engagement

In another broad form the present invention comprises:

a retractor blade comprising; a blade body having first and second ends, a first part disposed in a first plane and a second part disposed in a second plane, wherein at least one of said first and second parts terminates in an edge at least part of which includes a contour which generally conforms to a contour of a spinal vertebrae; at or near a junction of the first and second parts an open channel defining a longitudinal recess which follows the channel; the recess allowing the blade to be coupled to a corresponding anchor body even where the anchor is in engagement with bone.

Preferably the blade is V or L shaped and the channel is located along the iunction of the legs of the L or V. The channel according to one embodiment passes along the full length of the blade. According to an alternative embodiment, the channel comprises channel sections which pass at least part way along the length of the blade. The channel or channel section is arranged so that the blade can be urged towards a shaft body of an anchor so that when the blade is coupled the anchor is engage with bone.

In another broad form the present invention comprises:

a retractor blade for retraction of soft tissue, the blade comprising: a generally elongated blade body having first and second ends, the first end providing means for connection of the blade body to a support member, the second end comprising a first part disposed in a first plane and a second part connected to the first part and disposed in a second plane, wherein at least one of said first and second parts terminates in an edge at least part of which includes a contour which transmits load to a contour of a spinal vertebrae; characterised in that the blade includes an open longitudinal channel which passes along at least part of the length of the blade so that the blade allows mutual engagement with an anchorage in addition to axially, from a direction at angle to a longitudinal axis of the channel.

The first part in the first plane is essentially parallel to a longitudinal axis of the spine. The second part in the second plane is normal to the first plane. The contour of said edge of the second part defines an arc which generally conforms to a mid body circumferential surface of a lumbar vertebrae. According to a preferred embodiment, said edges of the first and second parts engage vertebral bone when an axial load is applied to the retractor.

In another broad form the present invention comprises:

a surgical retractor blade for retraction of soft tissue during anterior approach spinal surgery, the blade comprising: a generally elongated blade body having first and second ends, the first end providing means for connection of the blade body to a support member, the second end comprising a first part disposed in a first plane and a second part connected norma] to the (list part and disposed in a second plane, wherein each of said first and second parts terminate in respective continuous edges at least part of which include a concave contour which generally conforms to at least part of a contour of a spinal vertebrae, the second part further providing a load bearing edge which transmits loads applied to the blade to said vertebrae; characterised in that tho blade includes an open longitudinal channel which passes along al least part of the length of the blade so that the blade allows mutual engagement with an anchorage in addition to axially, from a direction at angle to a longitudinal axis of the channel. The angle of engagement between blade and anchor can be normal to the longitudinal axis of the channel . This form of engagement is alternative to axial engagement by passing the anchor through a closed passage ( cannulated) once the blade is located on the bone at a location which will correctly position the anchor. The present invention provides an alternative to the known prior art and the shortcomings identified. The foregoing and other objects and advantages will appeal" from the description to follow. In the description reference is made Lo the accompanying representations, which forms a part hereof, and in which is

„ shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without ^' departing from the scope of the invention. In the accompanying illustrations, like reference characters designate the same or similar parts throughout the several views. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.

BRTEP DESCRIPTION OF THE DRAWINGS The present invention will now be described in more detail according to a preferred embodiment but noπ limiting embodiment and with reference Io the accompanying illustrations, wherein-

Figure 1 shows a perspective exploded view of a retraction blade including abbreviated channel formations according to one embodiment.

Figures 2 shows the blade of figure 1 with anchor pin inserted in channel formations.

Figure 3 shows a perspective view of a retraction blade including open abbreviated channels according to an alternative embodiment.

Figure 4 shows the blade of figure 3 with pin inserted in channel formations.

Figure 5 shows a perspective view of a retractor assembly with retractor blades of the type shown in figures I and 3 fitted

Figure 6 shows according to a preferred embodiment, a side elevation of the handle assembly of figure 5 supporting a cannulated blade. Figure 7 shows a rear perspective elevation of the support assembly of figure 6 engaged with blade.

Figure 8 shows an opposite perspective view of slide assembly detached from the support assembly of figure 7

Figure 9 shows an exploded perspective view of a retractor blade prior to engagement with an anchor pin at least partially inserted in a spinal vertebrae.

Figure 10 shows the retractor blade of figure 9 rotated into engagement with the anchor pin.

Figure 11 shows the retractor blade of figure 9 engaged with an anchor pin but prior to full insertion of the pm. Figure 12 shows the retractor blade of figure 9 with the anchor pin rotated into locking engagement with the pin. DETAILED DESCRIPTION

The design objective with retraction blades are primarily, optimal stability and safe and efficient retraction of soft tissue. Contact and pressure on the blade against the bone improves stability of a retractor blade. Most conventional blades however rely only on their external fixation for stability. These ^' blades effectively "float" with a free end. In the case of the Brau blades which contact bone, the contact is at the side of the vertebral body usually at or above the ^■ equator of the vertebrae where the bone is curving posterolateral Iy. To remain stable the blade relies primarily on a solid immobile connection to the operating table through various linkages.

The required stability can be easily achieved by manual engagement of the blade but to a lesser extent when attached to an external frame such as assembly I because of the long moment arm from the end of the retractor blade to anchorage. Such lateral retractors tend to move and slip causing soft tissues and blood vessels to slip under or around the retractor blades.

Although urging the retractor blade against the bone provides additional stability, the applied force can lead to slipping or sliding anteriorly or posteriorly when the spine moves during heavy disc or bone work. This loss of position can cause tissue injury and frequently requires time consuming adjustments.

Figure 1 shows a front perspective view of a retractor blade 1 according to a preferred embodiment. The blade to be described below according to its various embodiments, is capable of adaption to various retraction assemblies. Blade 1 comprises: a generally elongated blade body 2 having first end 3 and second end 4. First end 3 is coniiectable to a blade support assembly ( not shown). Body 2 comprises a first part 5 disposed in a first plane and a second part 6 connected to the first part 5 and disposed in a second plane, the first and second • parts generally forming an L shape. The first part 5 according to one embodiment, terminates in an edge 7 at least part of which includes a contour which generally conforms to a contour of a spinal vertebrae at a point of contact with the vertebra when in situ. First part 5 in the first plane is essentially parallel to a longitudinal axis ( not shown) of a spine. The second part 6 in the second plane is normal to the first plane and is preferably normal to the first part 5. The contour of an edge 8 of the second part 6 defines an arc which generally conforms to a mid vertebral body circumferential surface. The radius of this arc in the lumbar spine is approximately 45 mm +/- 10mm. Edges 7 & 8 engage vertebral bone during insertion and when an axial load is applied to the retractor. Preferably, the blade 1 is formed as one piece.

Retractor 1 is preferably configured to maximize contact with the surface of the vertebral bone with first and second edges 7 and 8 of retractor 1 contoured to approximate the curvature of the vertebra, provide stability and Io maximise point of contact. As earlier explained, during placement of retractor blades the and particularly placement using an anchor pin, there can be unwanted soft tissue migration under the blade and into the region of an anchorage point of contact. The greater the contact area of the blade the lower the risk but there still remains the risk ofthe surgeon inadvertently puncturing the vital soft tissue. To address this problem blade I includes formations 9 and 10. Formation 9 comprises an open channel 11 defined by a wall 12 . Formation IO comprises an open channel 13 defined by a wall 14. Formations 9 and 10 are shown as ^■ abbreviated in that they doe not travel the full length of the retractor blade I . In an alternative embodiment, the blade can include one abbreviated formation. In a further embodiment the formation can extend the full length or approximately the full length ofthe blade. Figure 1 also shows an anchor pin 15 which is exploded from formations 9 and 10. The open channels 1 1 and 13 allows the surgeon to engage the retractor blade 1 by an alternative to axial insertion of pin 15. Since channels 1 1 and 13 are open, pin 15 can be inserted into channels 1 1 and 13 laterally in the direction of arrow 16 or by mutual rotation of blade 1 and anchor pin 15 or by rotation of blade 1 relative to pin 15 or pin 15 relative to blade I . This allows pin 15 to be engaged at the anchor point before coupling with blade I . This avoids the danger of the prior art methodology in puncturing vital soft tissues while 'hunting' for the best anchor position of the anchor pin for optimal retraction. Lifting the pin while coupled 5 with the retractor blade according to the prior art methods risks the pin coming in contact with soft tissues migrating under the blade and punctured by the pin as the pin is moved to find the optimal retraction position for the blade. Blade 1 also includes graduated openings 17 which enable engagement of the blade with a retraction support assembly ( as shown in figure 5). Figures 2 shows the 10 blade 1 of figure 1 with anchor pin 15 inserted in open channels 1 1 and 13.

Figure 3 shows a perspective view of a retraction blade 20 according to an alternative embodiment including formations 21 and 22. Retractor 20 would typically be used at would extremities of a surgical wound. Blade 1 would •

15 normally be used at lateral margins of a surgical wound. Formation 21 comprises an open channel 23 defined by a wall 24 . Formation 22 comprises an open channel 25 defined by a wall 26. Formations 21 and 22 arc shown as abbreviated in that they do not travel the full length of the retractor blade 20. In an alternative embodiment, the blade can include one abbreviated formation.

20 In a further embodiment the formation can extend the full length or approximately the full length of the blade. Blade 20 also includes graduated openings 27 which enable engagement of the blade with a retraction support assembly ( as shown in figure 5).

25 Figure 4 shows the blade 1 of figure I and blade 20 of figure 3 with pins 15 and 28 respectively inserted in channel formations in each blade-

Figure 5 shows a perspective view of a retractor assembly 30 with retractor blades 1 and 20 of the type shown in figures 1 and 3 fitted. An additional blade

'30 31 is included which opposes blade 1 and has a mirror image geometry to blade

1. Assembly 30 includes a hoop 32 which receives supporting arms 33 and 34 via adjustable fasteners 35 and 36. Connectors 37 and 38 allow vertical adjustment of retractor blades 1 and 31. Once blades 1 and 20 are located in position with respective anchor pins 15, 28 and 39 the retraction assembly can be attached. 5

Figure 6 shows according to a preferred embodiment, a side elevation of the support assembly 50 of figure 5 which receives and retains cannulated blade 20. Support assembly 50 includes a detachable handle 51 and press button release 52 which allows quick release of handle 51 from sleeve 53. Sleeve 53 engages I O articulated coupling 54 which engages retractor blade 20. S.leeve 53 includes a press button release 55 which enables sleeve 53 to be released from shaft 56 ( see figure 7).

Figure 7 shows a rear perspective elevation of the support assembly 50 of 15 figure 6 engaged with blade 20. Shaft 56 is shown released from sleeve 53.

Coupling member 54 includes a slide assembly 57 which engages runner 58. ■ Slide assembly 57 is capable of sliding adjustment along runner 58. Figure 8 shows an opposite perspective view of slide assembly 57 detached from support assembly 50 which includes a substantially U shaped boss defining a channel 590 which receives and retains therein runner 58. Runner 58 includes a series of openings which receive a locking pin 60 which is actuated by lever 61.

Selective actuation of locking pin 60 enables adjustment of the position of the support assembly 50 along runner 58. ^v 5 Figure 9 shows an exploded perspective view of a retractor blade assembly 70 prior to engagement between retractor blade 71 and anchor pin 72. retractor blade 71 according to the embodiment shown is substantially L shaped and . includes a proximal end 73 and distal end 74. Al proximal end 73 there is provided an abbreviated channel portion or cannulation 89 in which walls 750 define an internal passage 76. Also included at proximal end 73 is a runner 77 which receives a sliding connector similar to that shown in figure 7. At distal end 74, is a second abbreviated cannulation 78 in which walls 79 define an internal passage 80. Blade 71 also comprises at distal end 74 a first curved region 81 relative to the plane of leg 82 and a second curved region 83 relative to the plane of leg 84. Curved regions 81 and 83 allow retractor blade 71 to conform to the general shape of spinal vertebra. Assembly 70 further comprises anchor pin 72 which has a threaded distal end 85 and a tool engaging formation 90 on its proximal end 86. Located intermediate ends 85 and 86 is a retaining boss 87 which holds blade 71 in position by engagement with internal passage 88. Figure 10 shows the retractor blade 71 of figure 9 rotated into engagement with the anchor pin 72. Upon engagement pin 72 locates in passages 80 and 88 respectively of cannulatioπs 89 and 78. Retaining boss 87 is shown sitting proud of passage 80 so in that state, blade 71 is free to rotate away from pin 72. Once blade 71 is in engagement with pin 71 , the surgeon using a suitable tool which engages tool engaging formation 90 completes final rotation of pin 72 sufficient to facilitate engagement between retaining boss 87 and passage or channel 88.

Figure 11 shows the assembly 70 with corresponding numbering with pin 72 rotated in the direction of arrow 91 and further advanced distally into vertebra! bone but prior to full insertion.

Figure 12 shows the pin 72 fully anchored into vertebra 92 with blade 71 attached. Pin 72 is advanced distally so that retaining boss 87 has engaged channel 88. This prevents release of blade 71 until anchor pin 72 is unscrewed to release boss 87 from channel 88. To remove blade 71 , pin 72 is unscrewed and axially displaced to release boss 87 from channel 88.

The blades described herein may be a combination of the features of the present invention in all its embodiments and features of known retractor blade assemblies. Thus a blade according to the invention described, may be detachable or malleable, rotating and other variable engagements are envisaged. Blades may also be attached without handle 51 to allow fixation of the blade at various angles. Various materials may be used for the retractor blade including metals and plastics and malleable and radiolucent materials. Various sizes and 5 shapes arc envisaged.

Variations in the retractor may be made to accommodate different variation in engagement to vertebrae. For instance the length, width and relative heights of horizontal and vertical sections, may vary to accommodate, different locations in the spine and different types of procedures. Also, corners of the device may I O be radiused and in the lumbar spine build up sections over the corners added in order to retract blood vessels.

This invention provides an improved method of inserting an anchor pin in exactly the correct position. The method and cannulated blades also provide5 greater visibility of the sharp point of the pin as it engages the bone or surface of the bone covered with ligament which improves blade position. As there are major vessels close to the anchor points of the cannulated blades and ability to engage anchor pins by rotation improves safety but without compromise to current blade and pin engagement techniques i.e. stability of position through0 pin fixation and downward pressure.

The invention achieves increased safety by allowing the pins to be initially engaged in the bone in an ideal position , without requiring initial perfect positioning of the blade. The pin itself can then be used to act as a lever5 helping to position the blade and pin and move the soft tissues away until the correct angle of pin entry and blade angulation is achieved. Having already engaged the bone the risk of unwanted soft tissue entrapment by the pin is reduced. The blade then engages accurately with the pin and after this initial engagement, as the pin is further inserted in into the bone it becomes securely0 engaged in the cannulated blade preventing disengagement and finally at a controlled distance is able to apply downward pressure to the blade further securing the blade and pin.

According to the method aspect typically an insertion ofthe cannulated blade in the anterior lumbar spine are as follows ^*

1 Conventional surgical exposure of the anterior lumbar spine.

2 Critical structures arc moved out of the way using the cannulated blade or other retractors to expose correct pin entry point. These are generally close to ihe disc space to be worked on. The angle of final position is approximately parallel to or away from the adjacent disc space. These critical entry points may be obscured by critical vessels or other soft tissues requiring dissection and additional retraction with other instruments. This can be difficult and require considerable skill to be done safely.

3 After exposure, the retractor blade should be positioned close to final position but outside allowing good exposure of the critical entry point so as to be available to engage the pin as mentioned below. 4 The retractor blade holds the tissues out the way allowing the surgeon a good view ofthe entry point.

5 The pin tip is positioned (on the inside of the blade) on- its correct entry point without the need to be inserted through the cannulation as in the prior art retractor blades. The pin may and need not be in contact with the blade at this point. This allows an easier angle for tip positioning without the pin being displaced by the tissue forces acting on the retractor blade.

6 Once the tip is perfectly positioned and tissues clearly separate, the tip is engaged in the bone with a small tap on the end. The angulation is not however necessarily correct at this point merely sufficient to safely penetrate the bony cortex. 7 Having engaged the bone the pin can now be rotated on its tip levering the retractor blade (if required )against the force of the surrounding tissues until the correct angulation is achieved. This aids in correct postioπing of the retractor blades . This final angulation will generally be from lateral io medial and parallel or slightly away from adjacent disc space to avoid endplate penetration.

8 The pin is then engaged through the open slot into the canullation of the blade and further advanced in to the bone by screwing or tapping.

9 The screw and the blade have matching configurations that allow this engagement and as the screw advances it becomes securely held by the slot preventing disengagement plus these configurations further allow a compressive force downwards to be applied to the blade as the screw reaches its correct depth in to the bone.

It will be further recognised by persons skilled in the art that numerous variations and modifications may be made to the invention without departing from the overall spirit and scope of the invention broadly described herein. Such modifications would allow adaptation of key concepts to provide locking of distraction devices for use in anterior or posterior spinal surgery throughout the length of a spine or in orthopaedics or other surgical disciplines where bony fixation is available.