Abstract:
A device for dimensioning a circumference of a cavity includes a body with a lumen and a distal aperture. The device also includes a longitudinal member extending through the lumen with a distal end and a proximal end. The longitudinal member is capable of slidable movement through the body between retracted and advanced positions. The device also includes a flexible member adapted to conform to a circumference of a cavity contained, e.g., in an intervertebral disc space. The flexible member is operatively connected to a longitudinal member such that upon retraction of the longitudinal member the flexible member retracts into the lumen. When the longitudinal member is moved toward the advanced position, the flexible member is advanced out of the lumen and expands to conform to a dimension which approximates the circumference of the cavity. An apparatus is provided which includes a device for dimensioning a circumference of a cavity and an access member for facilitating conduction of the device to a surgical site, the device adapted and configured to fit within the access member. A kit is provided which includes a working tube incorporating a vertebral distractor, a spreader for assisting and maintaining the vertebral distractor in a distracted configuration, a closing tube for maintaining the working tube in a closed configuration, and a cavity circumference measuring device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit and priority of provisional application Ser. No. 60/874,618 filed on Dec. 13, 2006 and titled APPARATUS FOR DIMENSIONING CIRCUMFERENCE OF CAVITY FOR INTRODUCTION OF A PROSTHETIC IMPLANT. The entire contents of Ser. No. 60/874,618 are hereby incorporated in its entirety herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure is directed to a device for determining a circumference of a cavity such as a spinal disc cavity post nucleotomy. More particularly, the present disclosure is directed to a device for determining whether the cavity is dimensionally sufficient to receive a prosthetic implant. 
     2. Description of the Related Art 
     Applications are known in the art which create interior disposed cavities of unknown dimensions associated with herniated discs. A device for determining parameters of blind voids is described in the art. See, e.g., U.S. Pat. No. 6,500,132 B1 to Li (hereinafter “Li”). 
     Although potentially useful, the Li device is deficient. For example, as described therein, the device includes a first flexible element that bulges outwardly to engage interior walls of the void. The device includes a second element that bulges outwardly in a configuration substantially duplicative of the first element bulge, the second element being outside of the void and subject to observation. Although, it may be possible for a surgeon to observe the second flexible element outside the void, the surgeon may also desire to use radiologic imaging to observe the device within the void. However, such imaging using Li&#39;s device may be negatively affected by the presence of other elements, e.g., actuator, engagement member, and/or plates, in addition to the first flexible element which obscure the image, i.e., the surgeon may have difficulty distinguishing between the flexible element, the plates, the actuator and the engagement member in determining the size of the blind void. 
     Additionally, Li&#39;s device has a relatively large profile, and a thick width which may prove cumbersome More importantly, the second flexible element would not function within the confines of a narrow cannula since it would be unable to bulge against the side walls of the cannula. If a nucleotomy is being conducted using, inter alia, a cannula, the surgeon would have to remove the cannula before introducing Li&#39;s device. The cannula would then be reintroduced for additional spinal procedures, which is inefficient. 
     Further, depending on the size of the disc space, one or more differently sized prosthetic implants can be introduced into the void during surgery once the void size is determined. Li&#39;s device is not well-suited for precisely determining the size the blind void for a pre-dimensioned prosthetic implant in an efficient manner. When using Li&#39;s device, the surgeon may visually observe the second flexible element&#39;s size. However, to precisely determine the size of the void for the prosthetic implant, the surgeon must measure the second flexible element and then match that measurement to a size of the prosthetic implant. The process may take extra time and requires multiple measurements. It would be advantageous for the surgeon to simply use the device and then automatically know the correct prosthetic implant size. 
     There is a need in the art for a device for quickly and efficiently determining whether the amount of the nucleus pulposus removed from the intervertebral disc space is sufficient to create a cavity to accommodate a predetermined spinal nucleus implant. Furthermore, there is a need for a device for measuring a cavity that is compact, and has a substantially narrow profile to be quickly introduced into the cavity for measurement through a cannula and then quickly removed from the cannula. There is also a need in the art for a device for measuring a cavity that can be used with imaging techniques and x-ray machines or other scanning devices without cumbersome elements that may obscure the view. There is also a need in the art for a device for measuring the circumferential dimension of a cavity that automatically indicates to the practitioner whether the circumferential dimension is sufficient to accommodate a predetermined implant size. Thereafter, the surgeon can quickly withdraw the instrument through a cannula. 
     SUMMARY 
     According to a first embodiment of the present disclosure, there is provided a device for determining sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension. The device has a body forming a lumen with a distal aperture. The device also has a longitudinal member extending through the lumen with a distal end and a proximal end. The longitudinal member is capable of slidable movement through the body. The device also has a flexible looped member operatively attached to the longitudinal member at the distal end. The flexible looped member is capable of going from a contracted configuration to an expanded configuration. The longitudinal member optionally contains one or more markings on a proximal end. In one embodiment, the looped member is radiopaque and configured for radiological imaging. 
     In one embodiment, the markings on the proximal end portion of the longitudinal member correspond to predetermined circumference amounts of the flexible looped member. In one embodiment, the proximal end portion of the longitudinal member extends past the end of the lumen so the markings can be observed at a suitable distance from the site of the surgical entry. 
     According to another aspect of the present disclosure, there is provided a device for determining sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension. The device has a body forming a lumen. The body includes a distal opening and a longitudinal member extending through the lumen with a distal end and a proximal end. The longitudinal member is capable of slidable movement through the body. The device also has a deformable member connected to the distal end. The deformable member has an expanded configuration when the deformable member extends outside the lumen and a collapsed configuration when the deformable member is housed in the lumen. In another embodiment, the deformable member is brought into close cooperative alignment with a distal nose outside the lumen in the collapsed configuration. 
     In the collapsed configuration, the deformable member fits within the confines of the lumen. In one embodiment, the deformable member has a width that is about the same width as the lumen. The deformable member is adjustable to a plurality of different intermediate widths measured across the deformable member when the longitudinal member moves distally. The longitudinal member moves the deformable member relative to the body from the collapsed configuration to the expanded configuration to increase the adjustable width of the deformable member. In one embodiment, the longitudinal member pushes the deformable member out of the lumen and causes the deformable member to expand as it exits the lumen. In one embodiment, the proximal end portion of the longitudinal member contains one or more markings which correspond to predetermined circumference amounts of the deformable member. The proximal end portion of the longitudinal member extends past the end of the lumen so the markings can be observed at a suitable distance from the site of the surgical entry. 
     In one embodiment, the markings include at least a first marking corresponding to a first prosthetic implant circumference amount. The first prosthetic implant circumference amount corresponds to a first adjustable circumference of the deformable member and is complementary to the first prosthetic implant size so that the first prosthetic implant having the first prosthetic implant size fits in the cavity at that predetermined adjustable width of the deformable member. The markings also include at least a second marking that corresponds to a second prosthetic implant circumference amount different than the first prosthetic implant circumference amount. The second prosthetic implant circumference amount corresponds to a second adjustable circumference of the deformable member and is complementary so that a second differently sized prosthetic implant fits in the cavity at that second adjustable circumference of the deformable member. 
     According to another embodiment of the present disclosure, there is provided device for dimensioning a circumference of a cavity. The device includes a body forming a lumen having a distal aperture and a longitudinal member extending through the lumen with a distal end and a proximal end. The longitudinal member is capable of slidable movement through the body between retracted and advanced positions. The device also has a flexible member adapted to conform to a circumference of an intervertebral disc space. The flexible member is operatively connected to the longitudinal member such that upon retraction of the longitudinal member, the flexible member retracts into the lumen. When the longitudinal member is moved toward the advanced position the flexible member is advanced out of the lumen and expands to conform to a dimension which is limited by and approximates the circumference of the intervertebral disc space. The device also has the longitudinal member with a proximal end with at least one marking. The marking corresponds to a predetermined circumference of a prosthetic implant. When the longitudinal member is advanced from the retracted configuration to the expanded configuration, a flexible member circumference expands to contact a lateral side wall of the cavity. The flexible member circumference upon contacting the lateral side wall of the cavity may correspond to the marking on the proximal end of the longitudinal member. The marking corresponds to the predetermined prosthetic implant circumference when the predetermined prosthetic implant is at its maximum diameter, e.g., when hydrated. Visualization of the marking indicates that the circumferential dimension of the cavity is sufficient to accommodate the circumferential dimension of the prosthetic implant and thus provide a proper fit within the cavity. 
     According to another embodiment of the invention, a device for dimensioning a circumference of a cavity adapted to fit within the confines of an access member in combination with an access member is provided. The device includes i) a tubular body adapted and configured to fit within an access member, said tubular body having a lumen extending therethrough, the tubular body having distal and proximate ends, ii) a longitudinal member slidably disposed within the lumen, the longitudinal member having distal and proximate end portions, iii) a deformable member operatively attached to the distal portion of the longitudinal member, the deformable member adapted to fit within said lumen when drawn into said lumen by said longitudinal member and further adapted to expand into an expanded configuration when pushed out of said lumen by said longitudinal member, said expanded configuration corresponding to an approximation of the circumference of a cavity. In one embodiment, the cavity is a cavity formed in a spinal disc space by removal of all or a portion of the nucleus pulposus. In one embodiment, the proximate end portion of said longitudinal member contains one or more markings which respectively correspond to predetermined circumference amounts of the deformable member, said proximal end portion adapted to extend out past the proximal end of said tubular body such that said one or more markings are visible outside said tubular body. In one embodiment, said proximate end portion further includes a handle for grasping and slidably manipulating said longitudinal member. The access member provides access to a surgical site and has a tubular shape which is adapted to receive the device and allow it to be conducted to the surgical site. Examples of access members are cannulas, trocars and distractors which include portions which approximate to form a tubular member having a lumen extending through its length. 
     According to another embodiment of the present disclosure, there is provided a kit for use in implanting a prosthetic implant. The kit includes an access member referred to herein as a working tube. The working tube has a first member and a second member which are pivotally attached to each other. In one embodiment, the first and second members are pivotally attached to one another by a first pivot and a second pivot. The first member and second member have first and second respective distraction ends which cooperate by virtue of the pivotal attachment to form a vertebral distractor. The first member is brought into approximation with the second member for distracting a disc space at the distraction end. The first member and the second member form a lumen therebetween when brought into approximation. The kit also includes a spreader configured to be inserted into the lumen. The spreader has a distal end configured to assist in maintaining the distracted disc space. The kit further includes a closing tube configured to be introduced in coaxial alignment over the working tube. The closing tube prevents the opening of the working tube and confines movement of the first member and the second member to the approximated position. The spreader may be removed when the closing tube is disposed in coaxial alignment with the working tube. 
     The kit also includes a cavity circumference measuring device adapted and configured to fit within the confines of the lumen formed by approximation of the first and second members of the working tube. The measuring device includes a tubular member which is adapted and configured to slidably receive a longitudinal member having a flexible member disposed at one end thereof. The flexible member is adapted to conform to a circumference of the intervertebral disc space. The flexible member is operatively connected to the longitudinal member at one end such that upon retraction of the longitudinal member the flexible member retracts at least partially into the tubular member. When the longitudinal member is moved toward an advanced position, the flexible member is advanced out of the tubular member and expands to conform to a dimension which approximates the circumference of the intervertebral disc space. One or more circumference indicating marks on the longitudinal member are visible to the operator of the cavity circumference measuring device, said marks corresponding to predetermined circumference amounts of the flexible member, to inform the operator of the circumferential size of the cavity and automatically indicate which pre-sized implant is of suitable size for implantation. The pre-sized implant is inserted into the disc space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a device for determining a sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of predetermined dimension; 
         FIG. 2  is a cross sectional view of the device along line  2 - 2  of  FIG. 1  showing an end effector connected to a push rod; 
         FIG. 3  is another perspective view of the device of  FIG. 1  with the end effector withdrawn into the body of the device; 
         FIG. 4  is a another perspective view of the device of  FIG. 1  with the end effector partially extended from the body of the device; 
         FIG. 5  is a close up view of the end effector of  FIG. 4  in a relatively more extended and expanded configuration; 
         FIG. 6  is a schematic illustration of an access member which functions as a distractor for distraction of adjacent vertebrae and which is capable of forming a working tube having a lumen to introduce the device for determining a sufficiency of a cavity to a surgical site; 
         FIG. 7  is side view of a spreader for assisting and supporting the distractor function of the access member illustrated in  FIG. 6 . 
         FIG. 8  is a side view illustrating the working tube with a closing tube over the working tube with the spreader illustrated in  FIG. 7  in the lumen of the working tube to maintain the working tube in the distracted configuration at the surgical site; 
         FIG. 8A  is a side view of the closing tube and the working tube having the spreader removed; 
         FIG. 9  is side view illustrating the device for determining a sufficiency of a cavity introduced through the lumen formed by the working tube and closing tube of  FIG. 8A  with the end effector partially extended in the spinal disc space; 
         FIG. 9A  is schematic illustration of the device for determining a sufficiency of a cavity inserted into an access member in the form of a cannula to access a surgical site instead of the working tube and the closing tube; 
         FIG. 9B  is a side view of the device with the end effector introduced into the spinal disc space without an access member; 
         FIG. 10  is an enlarged side view of the end effector in an advanced position and disposed in the spinal disc space for measuring the circumference of a cavity therein; 
         FIG. 11  is an enlarged side view of the end effector in a partially retracted position in the intervertebral disc space; 
         FIG. 12  shows a number of prosthetic implants having a first width size or circumference, a second width size or circumference and a third width size or circumference; 
         FIG. 13  is a perspective view of another embodiment of the device for determining a sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension with the device having a distal nose assembly adapted to cooperate with and support the end effector; 
         FIG. 14  is a top view in partial cross-section of the end effector and nose assembly of  FIG. 13  showing one end of the end effector pivotally attached to the nose and the other end fixedly attached to a push rod; 
         FIG. 15  is a cross sectional view of a portion of the device along line  13 - 13  of  FIG. 13  showing the end effector having one end connected to a push rod; 
         FIG. 16  is another perspective view of the device of  FIG. 13  with the end effector partially retracted into the body of the device; 
         FIG. 17  is a close up perspective view of the end effector of  FIG. 13  in an advanced position with the push rod partially shown in phantom dotted lines to show the contents thereof; 
         FIG. 18  is still another perspective view of the device for determining a sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension with the device having the end effector in a retracted, collapsed configuration and in close cooperative alignment with the distal nose. Markings are shown at the proximal end of the push rod which correspond to predetermined circumference amounts of the end effector; 
         FIG. 19  is an enlarged view of the end effector of the device shown in  FIG. 13  disposed in the spinal disc space for measuring the circumference of a cavity therein; and 
         FIG. 20  is another enlarged view of the end effector shown in  FIG. 19  in a partially retracted position. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed device will be described herein below with reference to the accompanying drawing figures wherein like reference numerals identify similar or identical elements. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. It should be understood that, as used herein, the terms “circumference” and “circumferential” are used in their customary manner, e.g., referring to the boundary of a circle, but are also intended to encompass ellipsoid and rectangular configurations which may have regular or irregular topography. This broad reading of the terms “circumference” and “circumferential” is meant to take into account the fact that cavities which result from cavitation procedures or natural processes can have irregular shapes. The circumference of such cavities can be measured in accordance with the present disclosure. 
     Referring now to  FIG. 1 , there is shown a perspective view of the device  10 . The device  10  advantageously determines sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined circumferential dimension with the nucleus pulposus fully or partially removed. In operation, a distal end of the device  10  is inserted into the cavity for treatment purposes. The treatment may be the treatment of a herniated disc, or treatment of degenerative spinal disc disease without spinal fusion. 
     The device  10  may be used, e.g., with techniques to treat disc disease whereby a degenerated nucleus pulposus is replaced, in whole or in part, with a prosthetic implant instead of spinal fusion. The prosthetic implant restores disc function to the spine in a minimally invasive surgical technique. In one embodiment, different sized prosthetic implants may be used depending on the size of the disc space, the amount of the degenerated nucleus pulposus that is removed and the size of the annulus such as shown by way of example in  FIG. 12 . In one embodiment, the prosthetic implant may be introduced in a dry or xerogel state. The implant is inserted into the excised disc space, and then once properly positioned in the cavity, water, body fluid, or another suitable liquid flows into or is introduced into the cavity to hydrate the prosthetic implant and to increase a size of the prosthetic implant. In this embodiment, the prosthetic implant may have a number of different dry width sizes or circumferences. Each dry prosthetic implant may have a second hydrated width size that will correspond to the amount of the degenerated nucleus pulposus that is removed to provide support to the diseased or herniated disc. 
       FIG. 1  shows the device  10  that has a longitudinal body  12  and an actuator portion  14 . The device  10  determines sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension. The longitudinal body  12  has a lumen ( FIG. 2 ) formed therethrough. The longitudinal body  12  is a resilient member and is connected to a portion of the actuator  14  at the proximal end. In one embodiment, the longitudinal body  12  is a resilient metallic member such a nickel, titanium or stainless steel. However, in another embodiment, the longitudinal body  12  can be any surgically acceptable resilient plastic material, e.g.,a biocompatible thermoplastic material such as polyethylene and the like. The portion of the actuator  14  which is connected to the longitudinal body has a pair of finger loops  16   a ,  16   b  for helping grasp the device  10 . The actuator portion  14  also includes a loop member  18 . The loop member  18  is connected to a push rod  20  that is disposed through the lumen of the body  12  in concentric fashion, and the push rod  20  is intended to slide through the longitudinal body  12 . The loop member  18  may be moved proximally and distally to move the push rod  20  through the longitudinal body  12 . The actuator  14  is shown as having the loop member  18  and a pair of finger loops  16   a ,  16   b , however other handle configurations are envisioned and the arrangement shown is not limiting. 
     The device  10  also has an end effector  22 . The end effector  22  is a flexible looped member that is inserted into a cavity disposed within an intervertebral disc space to determine whether the circumference of the cavity can receive a spinal nucleus implant of a predetermined circumferential dimension. The end effector or flexible member  22  preferably can be manipulated distally and proximally by the push rod  20 . In one aspect, the end effector  22  can be withdrawn entirely into the device  10 , or in another aspect the end effector  22  can be extended completely out of the device  10  and in yet another aspect the end effector  22  can be manipulated at various intermediate positions therebetween. The end effector  22  preferably is sufficiently flexible so as to adjust a width  34  measured across the lateral sides or diameter (if the end effector  22  is circular) as shown in  FIG. 1  by manipulating the push rod via the loop member  18 . The end effector  22  is flexible and can be manipulated from a negligible or zero width when the end effector  22  is completely in the body  12  to a maximum width or circumference when the end effector  22  is completely advanced outside of the body  12  and adjustable to any other intermediate width therebetween to approximate a cavity. The body  12  has a window  15  on a lateral side. The push rod  20  has a pin  17  that will engage a lateral edge  19  of the window  15  to limit distal movement of the end effector  22 . 
     Referring now to  FIG. 2 , there is shown a cross sectional view of the end effector  22  connected to the push rod  20  that is disposed in the body  12 . As can be understood from the figure, the push rod  20  shown in cross sectional view along line  2 - 2  of  FIG. 1  and is shown in cross hatching for illustration purposes. The push rod  20  is connected to the end effector  22  by a first pin  24  and a second pin  26 . Although shown as being connected by pins  24 ,  26 , it is contemplated that the end effector  22  may be connected to the push rod  20  by other means including welding, adhesive, direct connection, ultrasonic welding or the end effector  22  may be die cast as one integral piece with the push rod  20 . Various configurations are possible and within the scope of the present disclosure and the operative connection is suitable such that the end effector  22  may be moved proximally and distally by the push rod  20  with ease and in a repeated manner. 
     Referring to  FIG. 3 , there is shown the device  10  in a retracted or collapsed configuration with the end effector (not shown) of the device  10  being withdrawn or completely in the body  12  of the device  10  through the aperture  28  formed in the distal end  30  of the body  12 . In this aspect, the end effector has a substantially zero or negligible width. The device  10  can be arranged in the retracted configuration simply by pulling the looped handle  18  in a proximal direction as shown. This proximal movement causes the push rod  20  to be retracted in a proximal manner which also moves the end effector  22  in the proximal manner. In this manner, the end effector  22  does not extend out the aperture  28 , and the device  10  has a slim profile that is advantageous for manipulating the device  10  in a spinal surgical environment in a quick and easy manner such as through an access member such as a tube, a cannula or trocar. In this manner, the end effector  22  does not impede or increase a width or length of the device  10  and the device  10  can be manipulated in a compact and advantageous manner. 
     Referring now to  FIG. 4 , there is shown the device  10  in an expanded configuration with the end effector  22  of the device  10  partially expanded out of the body  12  of the device  10  and through the aperture  28  formed in the distal end  30  of the body  12 . The device  10  can be arranged in the expanded configuration simply by moving the looped handle  18  in a distal direction as shown by arrow A. This distal movement causes the push rod  20  to be advanced in a distal manner which also moves the end effector  22  in the distal manner. 
     In this manner, the end effector  22  extends out the aperture  28  where it circumferentially expands. When utilizing an access member such as a cannula, the distal end  30  of the device  10  extends past the end of the access member and is introduced into the cavity or in proximity to the cavity for approximation of the cavity. In this manner, the end effector  22  increases its circumference to approximate the circumference of the cavity within the disc space to determine the sufficiency of the cavity, i.e., to determine whether the circumference of the cavity is sufficient to receive a spinal nucleus implant of a predetermined circumferential dimension. The device  10  determines a dimension of the cavity when the end effector  22  contacts the lateral side walls of the cavity and can no longer expand without exertion of extraordinary pressure. Extraordinary pressure would cause the end effector  22  to deform, e.g., bow inwardly and away from the lateral side walls. In normal operation, however, when the end effector stops expanding, the push rod  20  and loop handle  18  are prevented from moving distally, and the surgeon will feel resistance. In one aspect, the dimension may be a length of the cavity. In another aspect, the dimension may be a width of the cavity. In yet a further aspect, the dimension may be a width and the length of the cavity or a circumference of the cavity. Preferably, the end effector  22  measures a “foot print” or a specific known predetermined circumference of a specific prosthetic implant that is desired to be introduced into the cavity to determine whether the specific prosthetic implant will fit into the cavity. In one embodiment, the end effector  22  is flexible enough to generally correspond to the circumference topography of the excised disc space when the end effector  22  is deployed in the cavity. 
     Referring now to  FIG. 5 , there is shown a close up view of the distal end  30  of the body  12 . The end effector  22  extends from the body  12  through aperture  28  in the distal end  30 . The end effector  22  is made from a flexible element such as a metal strip or a flexible polymeric material. In one aspect, shape memory alloys are particularly advantageous for such a material; e.g., nitinol (NiTi), CuZnAl, CuAlNi, and the like. Preferably, in each embodiment, the end effector  22  is made from a biocompatible material that can be used once and discarded. Alternatively, the device  10  with the end effector  22  can be reusable and can be sterilized for later use. Various configurations are possible and within the scope of the present disclosure. 
     In one embodiment, the end effector  22  is made from a metal. It is envisioned that the end effector  22  can be made from nitinol, nickel/titanium material or alloy that is biocompatible. When fully deployed, the end effector  22  preferably has a substantially “O”, circular or elliptical shape and is operatively connected to the push rod  20  as discussed above, and has a sufficient width or thickness so the end effector  22  will not bend back on itself once contacting the lateral side walls of the cavity in the absence of extraordinary force. It is envisioned that the end effector  22  in one embodiment is made from a metal ribbon, however in another embodiment; the end effector  22  may be made from a biocompatible polymer, e.g., a thermoplastic polymer. Other configurations of the end effector are suitable, e.g., a wire such as an elastic wire, a cable, a braided cable, a rope or a tape. Various configurations are possible and within the scope of the present disclosure. The end effector  22  may be made from any material that can assume a first shape and be sufficiently flexible and deformable to be withdrawn into the body  12  of the device  10 . The end effector  22  has a lateral side  32 , and a thickness. The thickness is preferably about 0.1 mm to about 0.25 mm. It should be understood, however, that one skilled in the art can vary the thickness to other values depending, e.g., on the material, the length of the end effector and the intended surgical environment. 
     In one embodiment, the proximal end of the push rod  20  has a plurality of markings  22   a ,  22   b , and  22   c  ( FIGS. 3 ,  9 ,  9 A and  9 B). In this embodiment, only three markings  22   a ,  22   b , and  22   c  are shown simply for illustration purposes; however it should be appreciated that the push rod  20  may have any number of markings or indicia to assist with the surgical spinal procedure. The push rod  20  may have length, width, or depth gradations to measure the cavity or one more dimensions of the cavity such as the sufficiency of the cavity in the intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension. It is envisioned that the push rod  20  may have several different types of marking to measure several parameters simultaneously. Various configurations are possible and within the present disclosure. 
     In this embodiment, the push rod  20  has markings  22   a ,  22   b , and  22   c  that correspond specifically to a first prosthetic implant width size, a second prosthetic implant width size, and a third prosthetic implant width size. The markings  22   a ,  22   b , and  22   c  preferably indicate the circumference of the cavity and the sufficiency of the cavity in the intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension. In particular, when the end effector  22  can no longer expand due to the resistance exerted by the walls of the cavity, the push rod will stop advancing. The surgeon can then observe the position of the push rod  20  and note where each specific marking  22   a ,  22   b , and  22   c  is relative to the the proximal end of the longitudinal tube  12  and then immediately know the size of the circumference of the cavity and which size specific prosthetic implant will best fit within the cavity. Since the markings are observable at a remote location outside the cavity or access member, the device  10  allows this measurement to be determined without having to look at the end effector  22  in the cavity, which cannot be seen by the surgeon. It is envisioned that the specific markings  22   a ,  22   b ,  22   c  may correspond to a size of the implant by a general category such as “A”, “B”, “C”, and “D” sized implants, or the markings may show the exact size of the implant in units. Various configurations are possible and the present disclosure is not limited to any specific marking arrangement. 
     The surgeon may introduce the distal end of the device  10  into the cavity in the retracted or collapsed configuration or where the end effector  22  is disposed in the body  12  of the device  10  as shown. Using the actuator  14 , the surgeon can then carefully move the end effector  22  from the collapsed configuration to the expanded configuration thereby causing the diameter  34  of the end effector  22  to increase or decrease to approximate the cavity and determine which marking  22   a ,  22   b , and  22   c  is visible on the push rod  20 . 
       FIG. 5  illustrates that the distal end  30  has a pin  31 . Pin  31  extends perpendicularly through a lumen (not shown) of the longitudinal body  12  at the distal end  30 . Pin  31  assists with spreading the end effector  22  from the collapsed configuration and into the expanded configuration shown in  FIG. 5 . In  FIG. 5 , the pin  31  is seated between the two sides of the end effector  22 . In this manner, the end effector  22  can quickly move between expanded and contracted configurations so the surgeon can efficiently use the device. In addition, the pin  31  serves as a stop which prevents the end effector  22  from being drawn too far within the device. 
       FIGS. 6 through 12  illustrate the device  10  and other instruments which may be utilized in operation in a surgical environment. Referring now to  FIG. 6 , there is shown an access member in the form of a working tube  100  having a first member  102  and a second member  104 . The working tube  100  is made from a biocompatible material such as titanium, or stainless steel, or a resilient polymer such as polyethylene or polyethylene terephthalate. The working tube  100  is placed in a predetermined location or between vertebrae as shown in proximity to a cavity  200  in the disc space. For purposes of clarity, the annulus of the spinal disc is not shown in the drawings. It should be understood that the cavity  200  in the disc space resides within the bounds of the annulus and may or may not encompass the entire disc space. The cavity may be created artificially, e.g., by any denucleation procedures known in the art, or by a natural disease process. Accordingly, the cavity  200  may only encompass a portion of the entire disc space or it may substantially encompass the entire disc space. The working tube  100  preferably assists with the introduction of the distal end  30  of the device  10  into the cavity  200  where the surgical conditions require disc space distraction. 
     In certain instances, the disc space may be collapsed or partially collapsed and may require a disc space distraction. The working tube  100  preferably assists with the disc space distraction and increases the distance between vertebrae using a lever type action. The first and the second members  102 ,  104  are connected by a pivot  106  near a distal end  107  which is near or in proximity to the cavity  200 . The first and the second members  102 ,  104  preferably are intended to be used in connection with a collapsed disc space to distract the disc space. First member  102  has a jaw  108  at its distal end. Second member  104  has a jaw  109  at its distal end. A first distraction pin and a second opposite distraction pin (not shown) are disposed on the opposite sides of the pivot  106  to permit the first member  102  to pivot in relation to the second member  104  without blocking any interior space therebetween which is used to form a lumen to introduce the distal end  30  of the device  10  into the disc space  200 . The jaws  108  and  109  of the first member  102  and the second member  104  are inserted into an opening or surgical incision and are positioned in proximity to the collapsed disc space for disc space distraction. The distraction also may be aided by aligning the patient in a bent manner over a surgical table to further assist with distraction of the intervertebral disc space. The first member  102  and the second member  104  are brought into approximation with one another to push the jaws  108  and  109  apart and act as a lever to push apart adjacent vertebrae and raise a collapsed disc space at the distal end  107 . In one embodiment, the collapsed disc space that is raised may include a distraction distance of about 4.7 mm to 8.4 mm. 
     Referring now to  FIG. 8 , a closing tube  110  is shown concentrically disposed over first and second members  102  and  104  after the members  102  and  104  have been brought into approximation and jaws  108  and  109  distract the adjacent vertebrae. The closing tube  110  prevents the first and second members  102  and  104  from spreading apart, thus maintaining the jaws  108  and  109  in spaced apart relation. The closing tube  110  is preferably shorter than the working tube  100  to allow access to the proximal end of the working tube and to avoid interfering with the distal end  107  of the working tube  100 . A spreader  112  is shown in  FIG. 7  which can be used to assist and support the spreading action of the jaws  108  and  109 . The distal end  114  of the spreader  112  is configured to exert cam pressure against the jaws  108  and  109  and abut the interior of the distal end of the working tube  100  to help counter any opposing force exerted by the distracted vertebrae. A disc-shaped handle  115  is located at the proximal end of the spreader  112 . The handle  115  aids in grasping the spreader  112  and has a diameter which is preferably equal to or greater than the outside diameter of the working tube  100 . In this manner, the handle prevents the spreader  112  from being completely inserted into the lumen  116  formed in the working tube  100  when first and second members  102  and  104  are brought into approximation. The distal and proximal ends of the spreader are shown disposed in the lumen created by approximation of members  102  and  104  in  FIG. 8 . 
     Referring now to  FIGS. 8 and 8A , the working tube  100  is closed and the spreader  112  ( FIG. 7 ) is placed through the working tube  100  to support the working tube  100  at its distal end  107 . The spreader  112  may be brought through the working tube  100  to the distal end  107 . The distal end of the spreader  114  is introduced into the lumen  116  and the distal end of the spreader  114  helps maintains the distraction space that is formed by the working tube  100  as discussed above. Alternatively, the spreader  112  is placed between members  102  and  104  before they are brought into approximation, and then the members  102  and  104  are brought into approximation around the spreader. 
     Thereafter, the closing tube  110  is placed over the first working tube  100  to keep the first working tube  100  closed, and prevent the first member  102  and the second member  104  from moving opposite one another as shown in  FIG. 6 . The closing tube  110  has a unitary cylindrical configuration and is placed over the working tube  100 . The closing tube  110  placed over the first working tube  100  keeps the distraction distance fixed as the first working tube  100  abuts the interior space of the closing tube  110  and cannot move to the opened position. As shown in  FIG. 8 , once the position of the jaws and distraction space is maintained by the closing tube  110 , the spreader  112  can be withdrawn from the lumen  116 . The spreader  112  is then removed and the lumen  116  is formed within the first working tube  100  and the closing tube  110  (See  FIG. 8A ). The lumen  116  provides access to the operative site and access to the distracted space. An optional nut (not shown) may be threaded to the proximal end of the closing tube  110 . This ensures that the closing tube  110  remains connected and closed over the working tube  100  to maintain the distraction disc space. 
     Referring now to  FIG. 9 , there is shown the device  10  with the distal end  30  of the device  10  introduced through the lumen  116  formed by the working tube  100  and the closing tube  110 . The lumen  116  provides access to cavity  200 . As can be understood, the body  12  of the device  10  is introduced through the lumen  116 , and once the distal end  30  of the body  12  reaches the operative site or cavity  200 , the end effector  22  can be introduced into the cavity  200  from inside the body  12 . In other words, the end effector  22 , once introduced in the cavity  200 , is manipulated from the collapsed configuration to the expanded configuration. This is advantageous since, the end effector  22  has a substantially zero width in the retracted position and can travel distally through the lumen  116  formed by tubes  100 ,  110  with ease. 
     It should be appreciated that the device  10  may be used with any access device such as a plain cannula  110 ′ as shown in  FIG. 9A  or may be used where no cannula  110 ′ or tubes  100 ,  110  are present, and where the end effector  22  of the device  10  is directly inserted into the cavity  200  as shown in  FIG. 9B . Various configurations and surgical environments are contemplated and within the scope of the present disclosure. It should be appreciated that the device  10  may be used in a number of different spinal surgical procedures for disc replacement and a number of different approaches to the spinal disc cavity. These approaches include a posterior disc approach, and anterior disc approach, a lateral approach, or an anterolateral transpsoatic approach. 
       FIG. 10  illustrates a close up view of the end effector  22  in the cavity  200 . As can be seen, the end effector  22  is introduced through the distal opening  30  and through aperture  28  to measure one or more dimensions of the cavity  200 . In one embodiment, the end effector  22  may measure whether enough tissue of the nucleus pulposus has been removed by a cavitation procedure such as a nucleotomy or discectomy to approximate the cavity  200  and to determine a sufficiency of the cavity  200  to receive a spinal nucleus implant of a predetermined dimension. 
     It is advantageous since the end effector  22  may be withdrawn into the body  12  of the device  10  so the device  10  can be inserted through the lumen  116  of the tube  100  for ease of entry to the cavity  200 . In this manner, the end effector diameter  34  is reduced. Thereafter, as shown in  FIGS. 10 and 11 , the end effector  22  can be adjusted to increase its width/circumference and contact either the lateral side walls of the cavity  200  or the amount of the nucleus pulposus that remains in the cavity  200 . Referring again to  FIG. 9 , the surgeon using the device  10  can then determine a sufficiency of a cavity in an intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension and whether a specific prosthetic implant having a predetermined circumference will fit into the cavity  200 . The surgeon will then manipulate the looped handle  18  to manipulate the end effector  22  in the cavity  200  so the end effector  22  contacts the lateral side walls of the cavity  200  to approximate the cavity  200 . Once the surgeon cannot manipulate the looped member  18  distally and the end effector  22  is contacting the lateral side walls of the cavity  200 , the surgeon can optionally confirm this condition by taking a radiological image. The surgeon can observe the markings  22   a ,  22   b ,  22   c  at the proximal end of the device  10  outside the cavity  200  on the push rod  20 . The surgeon can determine which marking  22   a ,  22   b ,  22   c  is visible on the push rod  20  at the approximated circumference of the end effector  22  to determine a circumference of the cavity and a sufficiency of a cavity to receive a spinal nucleus implant of a predetermined dimension. In one embodiment, alignment of a marking with the distal end of the tube  12  signifies that the circumference of the end effector  22  matches the value defined by the marking. 
     In yet another embodiment, the prosthetic implant may be a dried prosthetic implant that has a first size when dry and a second larger size when hydrated. The markings  22   a ,  22   b ,  22   c  on the push rod  20  may correspond to a hydrated size of the dried prosthetic implant so the surgeon can easily determine and fit the correct prosthetic implant into the cavity  200 . It is appreciated that the device  10  is useful since the hydrated size of the prosthetic implant may not be readily appreciated when observing the dry prosthetic implant. Thus, the markings  22   a ,  22   b , and  22   c  on the push rod  20  that correspond to the hydrated sizes of the prosthetic implant assists the surgeon with approximating the cavity  200 . 
     Referring now to  FIG. 12 , there is shown three prosthetic implants or a first prosthetic implant  300  having a first circumference (or diameter), a second prosthetic implant  302  having a second sized circumference (or diameter) and a third prosthetic implant  304  having a third sized circumference (or diameter) with each having a first dry size and a second larger hydrated size. In this embodiment, the marking  22   a  describes a hydrated size of the first prosthetic implant  300 , the marking  22   b  describes a hydrated size of the second prosthetic implant  302  and the third marking  22   c  describes a hydrated size of the third prosthetic implant  304 . It should be appreciated that although three sized circumferences are shown for the prosthetic implant (for illustration purposes only) it is envisioned that any number of prosthetic implant circumferences may be used in connection with the present disclosure such as five, six or ten different prosthetic implant circumferences. 
     In yet another embodiment, the markings  22   a ,  22   b ,  22   c  on the push rod  20  may simply describe a unit of measurement such as millimeters, centimeters, or inches, or a unit of volume. In one embodiment, there may be four different Implant sizes with the sizes being in terms of an implant diameter by a an implant height with the four different sizes being 20 mm by 30 mm, 22.5 mm by 30 mm, 22.5 mm by 32.5 mm, and 25 mm by 35 mm. Various configurations are possible and within the scope of the present disclosure. 
     Referring again to  FIG. 11 , the end effector  22  in one embodiment may be made from a radiopaque material, or a material that does not allow x-rays or radiation to pass through the end effector  22  for imaging purposes. It is envisioned that the surgeon in connection with the device  10  may take at least one image to assist with sizing of the cavity  200 . The end effector  22  may be made from a suitable radiopaque material such as a radiopaque metal, and be configured for imaging so the surgeon can readily distinguish in the amount of the tissue that has been already removed and/or an amount of tissue that needs to be removed. The images may be taken from several different locations such as from an anterior location, a posterior location, or a lateral location. It is envisioned that images from several different locations may be taken. 
     Such radiopaque materials may include gold, platinum, tantalum, tungsten, iridium, rhenium, or an alloy of two or more such materials, or a coating of such materials to increase radiopacity such as a radiopaque material layer on the end effector  22 . In another alternative embodiment, the end effector  22  may be made from a non-radiopaque material that is impregnated with a radiopaque material such as tantalum. The impregnated radiopaque material may include beads, bearings, wire, tape, or another radiopaque material that is dispersed along an array to render the device  10  radiopaque. 
       FIGS. 13 through 20  illustrate another embodiment of the present device  10  generally represented by reference numeral  410 .  FIG. 13  shows a perspective view of the device  410  with a longitudinal body  412  and actuator portion  414  similar in function to the previously described embodiment. The device  410  determines sufficiency of the cavity in the intervertebral disc space to receive a spinal nucleus implant of a predetermined dimension generally similar to the embodiment of  FIG. 1 , however in this embodiment, the device  410  has a distal nose  416 . 
     The distal nose  416  is located near the distal end of the longitudinal body  412  opposite the actuator portion  414 . The distal nose  416  is formed in a cap like structure that covers and projects out of the distal opening of the longitudinal body  412 . The distal nose  416  extends out of the longitudinal body  412  a fixed amount, but the distal nose  416  preferably does not extend or widen an overall width or diameter of the longitudinal body  412 . This slim width permits the longitudinal body  412  to move freely and traverse through a cannula, tube or similar structure without any obstruction to permit the distal end of the device  410  to be readily delivered easily to a cavity for approximation purposes. 
     The distal nose  416  preferably may be made of a different or similar material than the remainder of the device  410 . In one embodiment, the distal nose  416  may be made from a thermoplastic polymer or a biocompatible metal material such as titanium or stainless steel, and may be disposable. In another alternative embodiment, the distal nose  416  may be removed or separable from the device  410 , e.g., a snap fit connection, by itself or together with the end effector  422 . In this manner, at least one or both the distal nose  416  and the end effector  422  may be sterilized and reused while the remainder of the device  410  is discarded. Various configurations are possible and within the scope of the present disclosure. 
     The distal nose  416  has a curved surface  416 ′. The curved surface  416 ′ is on the same side generally as the centermost portion of the longitudinal body  412 . The opposite side or the side away from the centermost portion of the body  412  on the distal nose  416  is generally orthogonal shaped and is arranged to be substantially flush with the lateral side of the longitudinal body  412 . The curved surface  416 ′ is intended to permit the retraction and advancement of the end effector  422  without any obstruction or impairment of the movement of the end effector  422  during movement to the collapsed configuration or the expanded configuration. In a preferred embodiment, the distal nose  416  and surface  416 ′ are adapted to receive the end effector  422  when the end effector  422  is in the retracted position. The curved shape of the surface  416 ′ is configured to prevent the end effector  422  from kinking when it is retracted while keeping the effector  422  tightly bound within the dimensional confines of the diameter of the longitudinal body  412 . The distal nose  416  may have other shapes, and is not limited to any particular shape, but in one embodiment, is configured to substantially seal the body  412  and permit the advancement and retraction of the end effector  422  in a quick and easy manner. Accordingly, the nose  416  may be configured to prevent or to impede bodily fluids from entering the device  410  that can interfere with movement of one or more components of the device  410  such as the push rod  420 . An example of such a seal is discussed below with respect to  FIG. 14 . 
     Referring now to  FIG. 15 , there is shown a cross sectional view of the device  410  having the longitudinal body  412  shown with a lumen formed therethrough along line  13 - 13  of  FIG. 12 . In this embodiment, the device  410  has the end effector  422  which is a flexible looped ribbon-shaped member. In an alternative embodiment, the end effector  422  may be a braided cable or rope or have another configuration as described above. However, referring again to  FIG. 13 , the end effector or flexible member  422  is fixedly connected at one end  422 ′ to the distal nose  416 . The other end  422 ″ of the flexible member  422  is connected to a push rod  420  ( FIG. 14 ) by pins  417 ,  419 . Alternatively, the end of the flexible member  422 ″ may contain different numbers of pins, or be welded, adhered to, or friction fit to the push-rod  420 . In this embodiment, the flexible end effector  422  is advantageously connected to the push rod  420  at one end  422 ″ only for ease of operation. In this embodiment, the surgeon can easily manipulate the end effector  422  by manipulating the end effector  422  only at the end  422 ″ using actuator  414  that is connected to the push rod  420 . In an alternate embodiment, illustrated in  FIG. 14 , the effector  422 A is attached to the nose  416 A at one end  422 A′ via a cylinder  430  in socket  432  connection and is fixedly connected to the push rod  420  at the other end  422 A″. The end  422 A″ may be attached to the push-rod  420  by one or more pins  417 A and  417 B, by welding, adhesive, friction fit or any other suitable attachment means. The nose  416 A is connected to the longitudinal body  412  by a snap fit connection which is preferably fluid-tight. Alternatively, the nose may be screwed into the distal end of the longitudinal body  412 . The nose  416 A includes a conduit  434  for slidably receiving and routing portions of the end effector  422 A in or out of the distal end of the longitudinal body  412 . The end of the end effector  422 A is fixedly mounted to the push rod by pins  417 A and  419 A. A stop  436  is mounted within the lumen of the longitudinal body  412  to prevent the push rod  420  from impacting the nose  416 A. The cylinder  430  and socket  432  connection allows the end  422 A′ to pivot as the end effector  422 A is advanced or retracted and thus provide a greater degree of flexibility than a rigidly mounted end. Other pivotable connections are contemplated such as ball and socket and the like. 
     In the embodiments of  FIGS. 13-20 , the flexible end effector  422  or  422 A can be manipulated distally and proximally by the push rod  420  simply by virtue of the connection at end  422 ″ or  422 A″ while the end  422 ′ or  422 A′ is connected to the distal nose  416  or  416 A. Unless otherwise mentioned, the two embodiments relating to attachment of the end effector  422  or  422 A discussed above, will be discussed interchangeably with respect to functionality of the embodiments while referring to the element numbers of the end effctor  422  embodiment for convenience. Referring now to  FIG. 16 , the end effector  422  can be manipulated at various intermediate positions therebetween by manipulating the actuator  414 . The end effector  422  can be partially withdrawn in the device  410  and brought into close cooperative alignment with curved surface  416 ′ of the distal nose  416 , or in another position of operation the end effector  422  can be extended completely out of the device  410 . In all arrangements, the end effector  422  can easily move from the collapsed configuration where the end effector  422  is in close cooperative alignment with the curved surface  416 ′ of the distal nose  416  to the expanded configuration in continuous fashion. 
       FIG. 17  illustrates a distal view of the end effector  422  connected to the push rod  420  which is rendered partially in phantom lines for illustration purposes. The end effector  422  is made of similar materials as discussed above and is sufficiently flexible so as to adjust a width  434  measured across the lateral sides or diameter (if the end effector  422  is circular) as shown in  FIG. 17  simply by manipulating the actuator  414  ( FIG. 13 ). 
     The end effector  422  is flexible and can be manipulated from a position where the end effector  422  is in close cooperative alignment with the surface  416 ′ of the distal nose  416  ( FIG. 17 ) to a maximum width or circumference. This maximum is when the end effector  422  is completely advanced outside of the body  412  ( FIG. 13 ). The end effector  422  also can be adjustable to any other intermediate widths therebetween to approximate a cavity as discussed above.  FIG. 17  illustrates the push rod  420  in a segmented fashion for illustration purposes. The push rod  420  is adapted to receive the end effector  422  through a channel  420 ′ formed in the push rod  420 . However, the end effector  422  can be directly connected to the push rod  420  or be made together with the push rod  420  as a single unitary member. In this illustrated embodiment, the end effector  422  is connected at the end  422 ″ to the push rod  420  by pins  417 ,  419 . However, it should be appreciated that the end effector  422  may be connected to push rod  420  by ultrasonic welding, fasteners, adhesive, or any other suitable connection. 
     On the other end  422 ′ of the end effector  422 , the end effector  422  may be fixedly secured to, or alternatively, be disposed through the distal nose  416  to secure end  422 ′ to the distal nose  416 . In another embodiment, the end effector  422  at end  422 ′ may be fixedly connected alternatively to the longitudinal body  412 , and not the distal nose  416 . It should be appreciated that the end  422 ′ is fixed and the distal nose  416  has a sloping surface  416 ′ that allows the end effector  422  to be easily and quickly retracted into body  412  to a position where the end effector  422  is held substantially taught and pulled around curved surface  416 ′ of distal nose  416 . The pivotal connection ( FIG. 14 ) was discussed above. 
       FIG. 13  and  FIG. 18  show the device  410  in operation.  FIG. 13  shows the device  410  having the end effector  422  in an expanded configuration.  FIG. 13  illustrates that when the actuator  414  is manipulated to a distal position, the push rod  420  ( FIG. 15 ) also moves distally which manipulates the end effector  422  to the expanded configuration. In this configuration, the end effector  422  is brought to a maximum circumference which may approximate a circumference of a cavity. 
       FIG. 18  illustrates the end effector  422  of the device  420  in a collapsed configuration. Here, the actuator  414  is manipulated in a proximal manner by the surgeon. The actuator  414 , again, being connected to the push rod  420  draws the end effector  422  at end  422 ″ proximally ( FIGS. 15 and 17 ). The push rod  420  moves proximally to modulate or adjust the diameter  434  of the end effector  422  since end  422 ′ or  422 A′ is fixed ( FIGS. 14 ,  17 ). In the partially retracted position shown as  FIG. 18 , the end effector  422  or  422 A is manipulated to be partially inside the longitudinal body  412 . Moving in this configuration, the end effector  422  may approximate the circumference of a smaller sized cavity relative to  FIG. 13 , and the surgeon may read or observe which marking  426 ,  428 , and  430  is visible on the proximal side of the push rod  420  and easily determine which of the prosthetic implants ( FIG. 12 ) may fit in cavity  200  at this approximated circumference. 
       FIGS. 19 through 20  illustrate the device  410  in operation in a surgical environment. Referring now to  FIG. 19 , there is shown the working tube  100  having the first member  102  and the second member  104  in a closed or approximated configuration with the closing tube  112  disposed over the working tube  100  as discussed with reference to  FIGS. 6 through 11  above. The spreader  112  may be utilized as above. A lumen  114  is formed within the working tube  100  and the closing tube  112 . As discussed above, the lumen  114  provides access to the operative site or cavity  200  through opening (not shown) on a proximal side. On the distal side, the distraction space is preserved by the closing tube  112  being placed in a coaxial alignment with the working tube  100 . 
     The distal end of the device  410  is introduced through the lumen  114  as discussed previously. Once the distal end of the body  412  reaches the operative site or cavity  200 , the end effector  422  can be introduced into the cavity  200  from a position where the end effector  422  is in close cooperative alignment with the curved surface  416 ′ of the distal nose  416  to the expanded configuration. In other words, the end effector  422  once introduced in the cavity  200  goes from a configuration where the end effector  422  is in close cooperative alignment with the curved surface  416 ′ to the expanded configuration to approximate the cavity. 
     This is advantageous since the end effector  422  has a reduced width when the end effector  422  is in close cooperative alignment with the curved surface  416 ′ of the distal nose  416 . In this configuration, the end effector  422  can travel distally through the working and closing tubes  100 ,  112  with ease. Once the end effector  422  is located in the cavity  200  and driven distally by moving the actuator (not shown) distally, the end effector  422  will contact the remaining nucleus pulposus or the lateral walls of the cavity to approximate one or more dimensions of the cavity  200 . In a preferred embodiment, the end effector  422  measures whether enough tissue of the nucleus pulposus has been removed by a cavitation procedure to approximate the cavity. The device  410 , thus, determines a sufficiency of the cavity  200  to receive a spinal nucleus implant of a predetermined dimension. As mentioned, the end effector  422  may itself be radiopaque or may be impregnated with radiopaque material so the surgeon can take images of the cavity  200 . 
     The end effector  422  can then be selectively adjusted by the surgeon to increase its width/circumference and contact either the lateral side walls of the cavity  200  or the amount of the nucleus pulposus that remains in the cavity  200  (which is not shown for illustration purposes). The surgeon using the device  410  can then determine a sufficiency of a cavity  200  in an intervertebral disc space and whether the cavity  200  is sufficiently sized to receive a spinal nucleus implant of a predetermined dimension and whether a specific prosthetic implant having a predetermined circumference will fit into the cavity  200 . If no implant is approximated to fit, the surgeon can easily and quickly remove the device  410  and then remove an additional amount of the nucleus pulposus remaining in the cavity  200 . This is all accomplished advantageously by the surgeon without having a direct line of sight into the cavity  200 . 
       FIG. 20  illustrates the end effector  422  manipulated proximally or in a direction toward the collapsed or retracted configuration. This is advantageous since at the conclusion of the approximation, and at the conclusion of the imaging, the end effector  422  may be withdrawn and brought into close cooperative alignment with the curved surface  416 ′ of the distal nose  416  of the device  410 . In this manner, the end effector diameter  434  is reduced substantially (relative to  FIG. 19  showing the expanded configuration) without kinking the end effector  422  while keeping any exteriorly disposed portion of the end effector  422  secured to the nose  416 . In this manner, the distal end of the device  410  can be easily removed through the working and closing tubes  100 ,  112 , and then the correct prosthetic implant delivered to the excised disc space. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. For example, while the disclosure has generally been directed to cavities within the spinal disc space, it is contemplated that any cavity of unknown circumferential dimension may be measured in accordance with the principles described herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments.