fig1 depicts one embodiment of the mount 10 with a first collar arm 11 and a second collar arm 12 rotatable around hinge axis 13 . collar arms 11 and 12 are rotatably connected to each other at forward hinge point 14 and rearward hinge point 15 , and connected to frame 19 at first hinge 49 and second hinge 50 . specifically , first collar arm 11 is connected to frame 19 at first hinge 49 by a first hinge pin 52 that extends through a first slot 56 in frame 19 . similarly , second collar arm 12 is connected to frame 19 at second hinge 50 by a second hinge pin 54 that extends through a second slot 57 in frame 19 . hinge points 14 and 15 , as well as hinges 49 and 50 , allow for the rotational movement of collar arms 11 and 12 . additionally , slots 56 and 58 on frame 19 accommodate hinges 49 and 50 , respectively , and allow for the horizontal translation of hinges 49 and 50 with respect to frame 19 . actuator 17 is oriented on frame 19 such that its rotational actuation causes it to translate distally ( identified as dt in fig7 ). thus , as actuator 17 translates distally , it acts upon collar arms 11 and 12 causing the rotation of collar arms 11 and 12 around hinge axis 13 , and causing hinge axis 13 , itself , to translate distally . rotation around hinge axis 13 is facilitated and accompanied by rotation of collar arms 11 and 12 around hinges 49 and 50 , respectively , as well as translation of hinges 49 and 50 toward the center of frame 19 along slots 56 and 58 , respectfully . all this motion , in turn , causes the expansion of the apparatus . other actuating mechanisms for expanding and contracting the retractor 1 are also envisioned . mount channel 18 is oval in shape and located centrally between first and second collar arms 11 and 12 . mount channel 18 facilitates movement of instruments and other materials into and out of the surgical cavity created by the present invention . mount channel 18 further comprises mount connection points 20 , 21 , 22 , and 23 that allow for the connection between collar arms 11 and 12 and blades 24 and 25 ( fig2 , and 4 ). fig2 - 5 show views of first blade 24 , which is a mirror image of second blade 25 ( shown in fig6 , for example ). first blade 24 has a proximal end 26 , a distal end 36 , an inner portion 68 and a peripheral portion 70 . blade 24 also has blade connection points 27 and 28 , hole 72 , rearward slit 64 and forward slit 66 . additionally , as seen in fig3 and 4 , the distal end 36 of blade 24 is tapered toward its periphery 70 to facilitate easier insertion through tissue . as shown in assembled form in fig1 and 14 , for example , proximal end 26 of blade 24 is connected at blade connection points 27 and 28 , as well as at hole 72 , to corresponding connection points 22 and 23 , as well as pin 76 , on first collar arm 11 . blade 24 gets connected to collar arm 11 by compressing proximal end 26 , therefore moving blade connection points 27 and 28 toward each other , so as to prepare for assembly with connection points 22 and 23 on collar arm 11 . slits 64 and 66 facilitate this compression . it is recognized that compression of points 27 and 28 may be achieved by other configurations , and / or in other ways as well . once proximal end 26 is released from compression , blade 24 regains its original shape and firmly attaches to collar arm 11 through connections 27 to 22 , 28 to 23 , and 72 to 76 . the male / female relationship of these connections , as well as the friction fit , allows the blade 24 to remain attached to the first collar arm 11 upon release of the compressive force that had been applied to the proximal end of blade 24 . since first blade 24 is a mirror image of second blade 25 , it is understood that the above description equally applies to the connection of second blade 25 to second collar arm 12 . it is further recognized that many other connection configurations from the ones described above are possible . such configurations may permit for interchangeability of blades 24 and 25 , or just the removability of the blades for sterilization or disposability . interchangeability allows a surgeon to readily change blades 24 and 25 depending upon , for example , the desired surgical cavity depth and / or cross - sectional area . thus a surgeon may be provided with a kit of variably sized and shaped blades from which desired blades may be selected for a particular surgery or technique . additionally , disposability of the blades allows for easier post - use handling techniques . fig5 shows a top view of first blade 24 where the blade &# 39 ; s curvature is readily apparent . when placed together , blades 24 and 25 form a tube that is open at both the proximal and distal ends , with an oval channel therebetween . as shown in fig6 , this is the case when actuator 17 has not been translated distally and collar arms 11 and 12 have , therefore , not been rotated around hinge axis 13 . actuator 17 comprises a screw 60 that is threadably assembled in housing 62 , which is part of frame 19 . as best seen in fig7 , in opening the retractor 1 , upon distal translation dt of screw 60 through housing 62 , collar arms 11 and 12 rotate around hinge axis 13 as hinge axis 13 is moved distally . in conjunction with this motion , first collar arm 11 rotates in direction r 1 around first hinge 49 as hinge 49 translates in direction t 1 in slot 56 ( fig1 ), and second collar arm 12 rotates in direction r 2 around second hinge 50 as hinge 50 translates in direction t 2 in slot 58 ( fig1 ). in this manner , blades 24 and 25 are displaced in respective retraction directions r 1 and r 2 , and retractor 1 is opened . the displacement of blades 24 and 25 spreads apart tissue within the original incision and creates a larger surgical cavity , allowing for a larger working space for a surgeon . additionally , as shown in fig3 and 6 , for example , the distal ends 36 of blades 24 and 25 are tapered so as to allow easier insertion into the body of a patient . it is recognized that the screw 60 may be engaged by a tool , such as screwdriver or an allan key , to cause it to turn . additionally , it is envisioned that multiple variations of the type of tool , interface with the screw , as well as screw types , or even the absence of a screw , are possible to accomplish moving the blades of the retractor towards and away from each other . the material used in the construction of blades 24 and 25 is generally of a rigid type to support the spreading of the body tissue , such as aluminum , for example . in a preferred embodiment , the material is radiolucent or semi - radiolucent thereby allowing for the improved visualization of the anatomy when viewed on an x - ray with the retractor 1 in place . in other embodiments , the material may be non - autoclavable or otherwise non - sterilizable , and disposable . this further allows for the interchangeability of blades 24 and 25 , to suit a particular surgical cavity . fig8 shows an embodiment of a sheath 29 of the present invention . sheath 29 is preferably made of a pliable , elastic , and translucent material , such as silicone rubber , and fits snugly around blades 24 and 25 . preferably , sheath 29 is assembled over blades 24 and 25 when the retractor 1 is in the unexpanded condition , such as in fig6 . upon distal translation dt of screw 60 of actuator 17 , and displacement r 1 and r 2 of blades 24 and 25 , sheath 29 stretches and forms an enclosure around blades 24 and 25 , as shown in fig9 . this enclosure allows for a more manageable surgical cavity by preventing tissue from entering the cavity . sheath 29 may also be made of a completely clear material , so that when in the expanded condition , a surgeon may see tissue and objects through sheath 29 when it is in the surgical cavity . preferably , to prevent sheath 29 from riding up on blades 24 and 25 during the opening of the retractor 1 , the sheath 29 is sized slightly shorter than the length of the longest vertical peripheral dimension of blades 24 and 25 , as seen in fig3 . in this configuration , when retractor 1 is opened , the distal end of sheath 29 stretches over and hooks onto the distal central edges of the blades 24 and 25 , thus preventing the sheath &# 39 ; s movement up the blades . upon the reverse translation of screw 60 and the return of blades 24 and 25 to their original state , sheath 29 returns to its original form as well . depending on the pliability of the material used to construct sheath 29 , the sheath may aid in bringing blades 24 and 25 back to their original , unexpanded condition . in any event , the tissue surrounding the blades 24 and 25 aids in compressing the blades back to their unexpanded condition . it should be noted that various materials with the above desirable properties for the sheath 29 may improve the cost - effectiveness of the sheath &# 39 ; s 29 disposability . additionally , the sheath 29 may be of any shape or size and may cover any area of the retractor 1 , thereby creating any portion of covered and non - covered areas of blades 24 and 25 . fig1 shows dilator assembly 30 . this assembly is utilized prior to the introduction of retractor 1 into the body of the patient . dilator assembly 30 includes guide 31 and increasingly sized dilators 32 , 33 , 34 , and 35 . each of these dilators is a tube with an outside cross - section and an inside cross - section . the inside cross - section of each dilator is slightly larger than the outside cross - section of the next smallest dilator , while the outside cross - section of each dilator is slightly smaller than the inside cross - section of the next largest dilator . this allows for successive dilators to be placed over one another . initially , guide 31 is inserted through an incision and secured within the body of a patient . dilator 32 is then slid over guide 31 into the incision , thereby spreading the incision , and creating a surgical cavity having an area corresponding to the size of the dilator &# 39 ; s outside cross - section . this step is repeated with successive dilators 33 , 34 , and 35 until the desired surgical cavity is achieved . it should be noted that any quantity of variously - sized dilators may be used to achieve this surgical cavity . additionally , the dilators may be of any size or shape as long as they interact with one another as described above and allow the surgical cavity to be created and enlarged . with reference to fig1 , subsequent to inserting all the desired dilators into the incision , retractor 1 is inserted over the largest dilator 35 in the cavity . this is done while blades 24 and 25 are together , whereby they form a passage extending distally from mount channel 18 . this passage is large enough to accommodate the largest dilator 35 within it . additionally , the tapered distal ends 36 of blades 24 and 25 facilitate easier insertion through the tissue . once retractor 1 is in place over the largest dilator 35 , the guide 31 and all dilators 32 - 35 are removed from the surgical cavity . this leaves an opening corresponding to the passage extending from the proximal ends 26 to the distal ends 36 of the blades 24 and 25 . blades 24 and 25 of retractor 1 may then be expanded , thus enlarging the surgical cavity . it is also contemplated that retractor 1 may be inserted into the body in an orientation allowing blades 24 and 25 to displace in the same direction in which the muscles run in the area of the surgical site . orienting retractor 1 in this fashion helps minimize muscle tissue damage and contributes to a faster recovery time from surgery for the patient . however , retractor 1 may be oriented in any fashion necessary to create a larger surgical cavity , in any area of the body . the introduction of retractor 1 into the body of a patient allows for the preservation of a small portal at the skin &# 39 ; s surface . fig1 - 14 show another preferred embodiment of a retractor 2 of the present invention . this retractor 2 features a different frame 80 and actuator arrangement 90 from frame 19 and actuator 17 of retractor 1 . here , actuator 90 comprises a screw 96 threadably engaged in an actuator housing 94 , and a ball 100 within the housing 94 . the ball 100 rides on a bearing element 106 that resides on hinge pin 102 . hinge pin 102 couples the first and second collar arms 11 and 12 together at rearward hinge point 15 , while hinge pin 104 couples collar arms 11 and 12 together at forward hinge point 14 . both hinge pins , 102 and 104 , are on the same hinge axis 13 . it is understood , however , that other variations are also possible . the housing 94 is part of frame 80 , but is oriented at an angle that is other than parallel to hinge axis 13 . additionally , the exterior 92 of housing 94 is shaped to serve the same function as retractor connection segment 16 of retractor 1 , which is to facilitate coupling the retractor to a support structure that aids in maintaining the position of the retractor in place relative to the patient . the proximal interior of housing 92 contains a stop ring 98 which serves as a restriction to retraction of screw 96 beyond the proximal end of housing 94 , to prevent screw 96 from being inadvertently removed from housing 94 during the closing of retractor 2 . further , collar arms 11 and 12 also have cutouts 82 and 84 , respectfully , which aid in attaching and removing blades 24 and 25 to collar arms 11 and 12 , by providing additional manipulation space for the proximal ends 26 of blades 24 and 25 . fig1 and 14 show a cut - away view of half of retractor 2 , where actuator 90 , frame 80 , first collar arm 11 , and first blade 24 are visible . fig1 shows retractor 2 in the closed position , while fig1 shows retractor 2 in the open position . beginning with the closed arrangement of retractor 2 in fig1 , to expand the blades 24 and 25 of the retractor 2 , screw 96 is advanced distally in housing 94 . as screw 96 is advanced , it pushes on ball 100 , which , in turn , pushes on bearing element 106 . bearing element 106 is coupled to hinge pin 102 which is part of rearward hinge point 15 . hinge pin 102 rotatably joins collar arms 11 and 12 , and hinge point 15 is capable of moving distally . thus , as screw 96 is advanced , ball 100 pushes downwardly on bearing element 106 . bearing element 106 then moves downwardly together with hinge pin 102 , which causes hinge point 15 to move distally and , therefore , blades 24 and 25 to expand from the closed configuration in fig1 to the open configuration in fig1 . the amount of distal movement of hinge point 15 is the same as the vertical component of the movement of ball 100 from its position in fig1 to its position in fig1 . thus , in opening the retractor 2 , ball 100 moves from an elevated rearward position on bearing element 106 , as shown in fig1 , to a lowered forward position on bearing element 106 , as shown in fig1 . preferably , ball 100 is made of a ceramic material , and has a low - friction surface . the ceramic material is used for the resulting strength of the ball 100 , while the low - friction surface is to diminish the undesirable friction forces associated with the functioning of actuator 90 , which otherwise increase the effort required to open the retractor 2 . bearing element 106 and screw 96 may be made of any suitable material , and have any suitable surface finish , to compliment and improve the functionality and compatibility of the retractor 2 , given the above parameters . for example , the tip of screw 96 that contacts ball 100 , may have a low - friction surface to further diminish the frictional forces involved in advancing ball 100 along bearing element 106 . fig1 shows a typical configuration where one or more retractors are used in conjunction with a support assembly 47 . the support assembly 47 comprises a first bar 37 connected to a first retractor 43 through a first holder 38 . optionally , there is a second bar 44 connected to a second retractor 45 through a second holder 46 . the first and second bars are joined together at coupling 48 . the support assembly 47 is ultimately attached to a rigid structure that facilitates maintaining the retractors 43 and 45 in relative position with respect to the patient . an example of a support assembly of this type is the af400 spinetract system manufactured by omni - tract surgical , a division of minnesota scientific . however , different support assemblies can be used , including but not limited to single support assemblies , where only one retractor is utilized . it is further contemplated that the retractor of the present invention may be utilized on any part of the patient where a small incision but large subcutaneous operating area is desirable . it is also contemplated that objects including but not limited to surgical instruments , surgical implants , and connection devices can be introduced into the body of a patient through the retractor of the present invention . the methods of use , as described above , may be performed with one or more retractors , with or without support assemblies , and in sequences different from those described . additionally , the steps utilizing dilators may or may not be performed . alternatively , various quantities , sizes , or shapes of dilators may be utilized . finally , the present invention may be a kit encompassing the various elements disclosed above . this kit may include , but is not limited to , differently sized and shaped mounts 10 , blades 24 and 25 , and sheaths 29 . any or all of these different elements may be interchanged to suit the desired surgical cavity . depending upon the conditions , a surgeon may select different mounts 10 , blades 24 and 25 , and sheaths 29 for assembly and use . although the invention herein has been described with reference to particular embodiments , it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention . it is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims .
a retractor having interchangeable or replaceable blades facilitates the expansion of a surgical site below an incision in the skin , and establishes a work - through surgical space . the retractor includes a frame connected to two collar arms , a pair of blades connected to the collar arms , a sheath for encompassing the blades and providing a circumscribed working space , and a device for rotating the collar arms , thereby displacing the blades and any tissue surrounding them .