Vertebral cavitation surgical tool

The instant invention describes a surgical tool for providing cavitations, or void spots, within the interior of body regions. The surgical tool is constructed and arranged to penetrate almost all interior body regions in which formation of a cavity or void space is necessary for diagnostic or treatment purposes. The surgical tool comprises an insertable member receiving structure sized and shaped to receive one or more insertable devices. The interior lumen of the insertable member receiving structure allows the insertable device to slide and/or rotate relative to the insertable member receiving structure and vice versa. At least one insertable member is a cavity forming device which has a plurality of cavity forming members constructed and arranged with spring-like characteristics for traversing between a cavity forming position and a non-cavity forming position. Upon traversal back to the cavity forming position, the displacement members retain their cavity forming structural configurations.

FIELD OF THE INVENTION

The invention relates to medical devices for creating cavities within body organs; and more particularly, to a device and system for creating cavities or voids in vertebral bodies.

BACKGROUND OF THE INVENTION

The central nervous system is a vital part of the human physiology that coordinates human activity. It is primarily made up of the brain and the spine. The spinal chord is made up of a bundle of nerve tissue which originates in the brain and branches out to various parts of the body, acting as a conduit to communicate neuronal signals from the brain to the rest of the body, including motor control and sensations. Protecting the spinal chord is the spinal, or vertebral, column. Anatomically, the spinal column is made up of several regions, including the cervical, thoracic, lumbar and sacral regions. The cervical spine is made up of seven vertebrae, and functions to support the weight of the head. The thoracic spine is made up of twelve vertebrae and functions to protect the organs located within the chest. Five vertebrae make up the lumber spine. The lumber spine contains the largest vertebra and functions as the main weight bearing portion of the spine. Located at the base of the spine is the five fused vertebrae known as the sacrum. The coccyx sits at the base of the spinal column and consists of four fused vertebrae.

Each of the vertebrae associated with the various spinal chord regions are made up of a vertebral body, a posterior arch, and transverse processes. The vertebral body, often described as having a drum-like shape, is designed to bear weight and withstand compression or loading. In between the vertebral bodies is the intervertebral disc. The intervertebral disc is filled with a soft, gelatinous-like substance which helps cushion the spine against various movements and can be the source of various diseases. The posterior arch of the vertebrae is made up of the lamina, pedicles and facet joints. Transverse processes extend outwardly from the vertebrae and provide the means for muscle and ligament attachment, which aid in movement and stabilization of the vertebra.

While most people have fully functional spinal chords, it is not uncommon for individuals to suffer some type of spinal ailment, including degenerative spine disease, spinal trauma, spinal tumors, or spinal chord/vertebral column abnormalities. Spinal fractures, or vertebra compression fractures, occur when one the bones of the spinal column fractures. Such an event is often accompanied by sudden onset of pain in the back which intensifies when sitting or standing and decreases when lying down. The pain associated with vertebra compression fractures can be strong enough to limit the activities a person can undertake, thereby reducing the overall quality of life of the individual. When the bone breaks, it often cracks and collapses, thereby becoming compressed. Typical bones in the skeleton system, such as long bones of the leg, which must be capable of handling rigorous movement, are more dense and rigid as compared to bones of the spinal system. The bones of the spinal chord, however, are less dense than other bones and contain spongy, soft bone areas, allowing the body to move in certain manners, such as bending and twisting. While these bones allow for such motions, they are more susceptible to fractures.

Vertebra compression fractures often result from physical injury or trauma. Various other conditions, such as osteoporosis and long term drug usage, including steroid usage, can make bones more fragile and therefore more prone to fractures. In addition, cancer, such as those that occur in the bone, i.e. multiple myeloma, and those that do not occur in the bone but metastasize and spread to the bone, i.e. breast or prostate cancer, weaken bone structure resulting in increased risk for vertebra compression fractures. Spinal fractures that are not properly treated can result in serious medical conditions, such as kyphosis (forward curvature of the spine) or dowager's hump. While the actual fracture may lessen in pain severity over time as the fracture heals, spinal fractures that are not treated, typically through surgical intervention, result in the bone healing in the fractured, collapsed position. A fracture that remains deformed, therefore, can shorten the spine and push it forward, thereby adversely affecting the alignment of the spine.

DESCRIPTION OF THE PRIOR ART

Numerous devices have been developed in an effort to treat spinal injuries. For example, U.S. Pat. No. 5,928,239 discloses a device and method for percutaneous surgical cavitation. The device includes an elongated shaft and cutting tip interconnected by a freely-rotating hinge. Upon rotation of the shaft to a sufficient velocity, the cutting tip will be deflected toward a position that is angularly offset from the shaft's access of rotation. The length of the cutting tip will determine the radius of the cavity being formed, which may be several times the radius of the shaft. The method of the present invention provides for formation of a cavity within a body through a small percutaneous access opening such that an enlarged cavity may be formed without an invasive access opening. The '239 patent also describes s a method of percutaneous prophylactic replacement of osteoporotic bone wherein weakened bone material is removed from a cavity using only a needle-sized access opening. Strengthening bone replacement material, such as bone cement, can be injected into the cavity to provide reinforcement of weakened bone without invasive surgical access.

U.S. Pat. No. 6,425,887 discloses a needle assembly including an infusion needle that includes a plurality of needle cannulae made of a superelastic material such as nitinol. The needle cannulae are cold-worked or heat annealed to produce preformed bends that can be straightened within passageway of a coaxial outer cannula for introduction into the body of a patient. Upon deployment from the outer cannula, the needle cannulae substantially return to their preformed configurations for the introduction or extraction of materials at areas lateral to the entry path of the needle assembly. The plurality of needle cannulae can be variably arranged or configured for their distal tip portions to attain a desired infusion pattern such as an umbrella shaped array, and/or be staggered axially.

U.S. Pat. No. 6,592,559 discloses a needle assembly including a needle that includes a needle cannula made of a superelastic material such as Nitinol. The needle cannula is cold-worked or heat annealed to produce a preformed bend that can be straightened within passageway of a coaxial outer cannula for introduction into the body of a patient. Upon deployment from the outer cannula, the needle cannula substantially returns to the preformed configuration for the introduction or extraction of materials at areas lateral to the entry path of the needle assembly. The needle assembly can comprise a plurality of needle cannulae that can be variably arranged or configured for attaining a desired infusion pattern.

U.S. Pat. No. 6,746,451 discloses a percutaneous surgical device and method for creating a cavity within tissue during a minimally invasive procedure. A cavitation device includes a shaft interconnected to a flexible cutting element. A flexible cutting element has a first shape suitable for minimally invasive passage into tissue. The flexible cutting element has a means to move toward a second shape suitable for forming a cavity in tissue. When used in bone, the resulting cavity is usually filled with bone cement or suitable bone replacement material that is injectable and hardens in situ. The disclosed cavitation device and methods can be used for the following applications: treatment or prevention of bone fracture, joint fusion, implant fixation, tissue harvesting (especially bone), removal of diseased tissue (hard or soft tissue), and general tissue removal.

U.S. Pat. No. 6,923,813 discloses several embodiments of cutting tips for tools for creating voids in interior body regions. The cutting tips provide for rotational and translational cutting. An actuator mechanism for deploying a cutting tip converts the rotational movement of a wheel into translational movement of a plunger rod. The actuator mechanism provides positive cutting action as the cutting tip is moved from a first, non-deployed position to a second, deployed position and from the second, deployed position to the first, non-deployed position. Methods of creating a void in bone provide one or more mechanical cutting tools that may be used in combination with one or more expandable void-creating structures to form a void of a desired size and configuration.

U.S. Publication No. 2007/0168041 discloses a method of replacing a nucleus pulposus in an intervertebral disc by filling the disc with a flowable augmentation material through a through bore in a pedicle. The device includes a tubular member constructed of a shape memory alloy that is used to create a throughbore from a pedicle of a first vertebra. Once in place, the distal end of the shape memory tube curves toward one of the end plates. The curved tube thereby creates a passage for the flexible drill and conduit for both disc tissue removal and augmentation material filling.

U.S. Publication No. 2009/0138043 discloses medical devices and methods for accessing a biological body. In one embodiment, a method includes inserting a cannula at least partially into a vertebra such that a threaded portion of the cannula secures the cannula to a portion of a cortical bone of the vertebra and forms a channel within the cortical bone. A medical device is inserted at least partially through the cannula such that a distal end portion of the medical device is disposed within a portion of a cancellous bone of the vertebra. A medical procedure is performed within the cancellous bone using the medical device and then the cannula and the medical device are removed from the vertebra, leaving a channel in the vertebra having at least partially threaded interior walls. A bone screw that has threads configured to matingly engage the threaded channel is then inserted into the threaded channel.

U.S. Publication No. 2010/0174267 discloses a needle assembly compromising an infusion needle that includes a needle cannula made of a superelastic material such as Nitinol. The needle cannula is cold-worked or heat annealed to produce a preformed bend that can be straightened within passageway of a coaxial outer cannula for introduction into the body of a patient. Upon deployment from the outer cannula, the needle cannula substantially returns to the preformed configuration for the introduction or extraction of materials at areas lateral to the entry path of the needle assembly. The needle assembly can compromise a plurality of needle cannulae that can be variably arranged or configured for attaining a desired infusion pattern.

U.S. Publication No. 2010/0185161 discloses a system and methods for channeling a path into bone. The system includes a trocar having a proximal end, distal end and a central channel disposed along a central axis of the trocar. The trocar includes a radial opening at or near the distal end of the trocar. The system includes a curveable cannula sized to be received in the central channel, the curveable cannula comprising a curveable distal end configured to be extended laterally outward from the radial opening in a curved path extending away from the trocar. The curveable cannula has a central passageway having a diameter configured to allow a probe to be delivered through the central passageway to a location beyond the curved path.

SUMMARY OF THE INVENTION

The instant invention describes a surgical tool for providing cavitations, or void spots, within the interior of body regions. The surgical tool is constructed and arranged to penetrate almost all interior body regions in which formation of a cavity or void space is necessary for diagnostic or treatment purposes. The surgical tool comprises an insertable member receiving structure sized and shaped to receive one or more insertable devices. The interior lumen of the insertable member receiving structure allows the insertable device to slide and/or rotate relative to the insertable member receiving structure and vice versa. At least one insertable member is a cavity forming device which has a plurality of cavity forming members constructed and arranged with spring-like characteristics for traversing between a cavity forming position and a non-cavity forming position. Upon traversal back to the cavity forming position, the displacement members retain their cavity-forming structural configurations.

Accordingly, it is an objective of the instant invention to teach an improved surgical tool for providing cavitations, or void spots, within the interior of the body regions.

It is a further objective of the instant invention to teach an improved surgical tool which can be used for providing cavitations in vertebral bodies.

It is yet another objective of the instant invention to teach an improved surgical tool which minimizes damage to vertebral body compact bone while forming cavities in soft, spongy bone.

It is a still further objective of the invention to teach an improved surgical device which minimizes the long-term affects associated with vertebral fractures.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention describes a Jamshidi-style surgical tool with one or more insertable parts, illustrated generally as10(seeFIG. 1), for providing cavitations, or void spots, within the interior of body regions, including tissues or organs. The surgical tool10is constructed and arranged to penetrate almost all interior body regions in which formation of a cavity or void space is necessary for diagnostic or treatment purposes. Referring toFIG. 2, an illustrative embodiment of the surgical tool10with one or more insertable parts is illustrated. The surgical tool10generally contains an insertable member receiving structure, such as a cannula,12, one or more insertable devices, illustrated herein as a first insertable device14, and a traversing member16.

Referring toFIG. 3A, the insertable member receiving structure12is illustrated as a generally tubular structure containing a distal end18, a proximal end20, and an insertable member receiving structure main body22. The main body contains a longitudinal bore or inner lumen23, seeFIG. 3B, which is sized and shaped to allow one or more insertable devices to be inserted therein. The inner lumen23is also constructed and arranged to allow the insertable devices to move in a longitudinal direction, i.e. from the proximal end to the distal end, and to rotate within. The distal end18contains a tissue engaging tip24. The tissue engaging tip24may be any shape, such as square shaped or rounded. Alternatively, the tissue engaging tip24may be a multi-faceted, triple crown cannulated tip. The insertable member receiving structure main body22may contain a pair of stabilizing wings25A,25B for stabilizing the device during rotation or for preventing the device from being inserted too deep into the bone. The proximal end20preferably contains a handle26for providing a user gripping and maneuvering ability. While the handle26is illustrated as a T-shaped handle, other handle configurations can be used as well. The handle26is ergonomically designed for comfortable use and can be made of any material known to one of skill in surgical tools art, such as rigid polymers or metals. The T-shaped handle26contains a cut out portion28which is sized and shaped to receive one or more insertable devices. Within the cut out area, insertable member receiving structure12contains an engaging member30, illustrated herein as threading.

Fluidly coupled to the inner lumen23is a fluid delivering/aspirating member32. The fluid delivering/aspirating member32contains an aperture34which is sized and shaped, and may be flared, to allow the insertable devices to be inserted therein and enter the inner lumen23. Additionally, the fluid delivering/aspirating member32may be sized, shaped, and adapted to attach to the distal portion of a syringe. Accordingly, the fluid delivering/aspirating member32may contain male/female threading corresponding to the female/male threading of a syringe or snap-fit type fasteners. Preferably, the fluid delivering/aspirating member32is constructed as one portion of a luer lock system, such as a luer lock tip or luer slip tip of luer locking syringes, or other male/female luer adapters, known to one of skill in the art, and is sized and shaped to receive the corresponding member of the luer lock system. In this manner, fluids, such as bone cement or bone growth compositions, may be inserted into the lumen and dispensed to the cavity or void space, or aspirated from the cavity to the syringe.

Referring toFIG. 4, a first insertable device14is shown. The first insertable device14is illustrated as a cavity forming device36, comprising a distal end38, a proximal end40, and a cavity forming device main body42traversing between the distal end38and the proximal end40. The distal end38contains a cavity forming tip44which is preferably coupled to the cavity forming device main body42as a single unitary piece. In this manner, the cavity forming device main body42and the cavity forming tip44is made of the same material. Alternatively, the cavity forming tip can be made as a separate unit and subsequently attached to the cavity forming device main body42. The cavity forming tip44is preferably made of independent displacement members46and48, which when inserted into a tissue and rotated, act in unison to provide a cavity. While the cavity forming tip44may be adapted for use in any body region, it is preferably adapted for use in vertebral bodies. The unique aspect of the instant invention is that the cavity forming tip44and displacement members46and48, are designed to easily form cavities within the cancellous (soft, sponge-like portion) while not damaging any compact bone which comes in contact with the cavity forming tip44. In this manner, the user can be assured that a cavity is formed in the desired place without the increased risk of damaging the harder, external portions, thereby causing unintended medical problems.

FIG. 5Aillustrates a partial perspective view of an illustrative example of the first insertable device14, illustrating the cavity forming tip44. The displacement members46and48can be sized and shaped according to the size and shape of the cavity desired. For example, the displacement members46and48illustrated inFIG. 5Acontain curved portions35and37with generally rounded terminal ends39and41. Each of the displacement members46and48are adapted to traverse from a first position to a second position. Preferably, the displacement members46and48are made of a material that has spring-like action, traversing between multiple positions. In this manner, the spring-like action allows the displacement members46and48to move relative to each other when a predetermined force is applied and assume the their original position when the force is removed. Preferably, the displacement members are made of nickel titanium (Nitinol, NiTi). Alternatively, they can be made of other superelastic alloys which can be constrained into a first shape and then deployed to a second shape without experiencing plastic deformity. As illustrated, the displacement members46and48are shown in the cavity forming position. In this position, they are arranged in an overlap alignment in which displacement member46rests partially on top of displacement member48, similar to the arrangement of scissors when in the open position. Since each of the displacement members has spring-like properties, upon contact with a surface having certain hardness or resistance, the displacement member46and/or48traverse to a second non-cavity forming position. In this position, the displacement member46is in a parallel arrangement with and resting above or on top of the displacement member48, see for example,FIG. 17. In an alternative embodiment, a spring mechanism may be used to provide traversal between the two positions.

Referring toFIGS. 5B-5D, an alternative embodiment of the cavity forming tip44is illustrated. The cavity forming tip44contains displacement members46and48, each having similar characteristics as described above. Each of the displacement members46and48have curved portions43and45respectively, forming hook or semi-hooked terminal ends47and49. While the terminal ends47and49are illustrated generally as being separated by 180 degrees, such arrangement is illustrative only. In any embodiment, the displacing members46and48function to displace cells, cellular debris, or tissue components from a body organ/tissue to form a void or cavity therein. The displacement members46and48illustrated inFIGS. 5B-5Dare shown forming a cavity within the soft bone area of a vertebral body inFIGS. 5E-5G. Referring specifically toFIG. 5E, the cavity forming tip44is shown in a first position inserted within the cancellous bone51of the vertebral body. As the cavity forming tip44is rotated, the displacing members46and48rotate as well. The displacing members46and48contact the cancellous bone51as they rotate, displacing the cancellous bone from its original position to a second position, seeFIG. 5F. The displacement of the bone from the first position to the second position forms a cavity53. Some of the cancellous bone51displaced by the displacing members may become compacted55.FIG. 5Gillustrates the displacing members46and48rotated about 90 degrees from their original position, thereby forming a larger portion of the cavity53.

Referring back toFIG. 4, the proximal end40contains a rotating member, illustrated as a knob50, for providing the user the ability to place the cavity forming device36into the outer sleeve member12and/or for rotation of the cavity forming device36. The rotating member further contains a traversing sleeve receiving member52constructed and arranged to couple and rotatably engage with a traversing sleeve54. Referring toFIG. 6, the traversing sleeve54is illustrated in a generally cylindrical shape having a first end56and a second end58. This shape, however, is not a limiting shape as other shapes may be employed. The outer surface60of the traversing sleeve54is threaded in a manner which couples to internal threading (not illustrated) of the traversing sleeve receiving member52. A lumen62is sized and shaped to provide passage of the cavity forming device main body42. Additionally, the traversing sleeve54contains an inner surface (not illustrated) having internal threading (not illustrated) at or near the second end. The internal threading is designed to engage the threading of the engaging member30of the insertable member receiving structure12. The first end56of the traversing sleeve54is secured to the traversing sleeve receiving member52and the second end58of the traversing sleeve54is secured to the insertable member receiving structure12. As the user turns the knob50, the traversing sleeve receiving member52screws into the traversing sleeve54, providing the cavity forming device36linear motion toward the distal end of the insertable member receiving structure12. As the knob50moves linearly from the proximal end toward the distal end, the displacement members rotate, thereby providing cavity forming function.

FIG. 7illustrates a second insertable device, illustrated herein as a trocar64. The trocar64has a distal end66, a proximal end68, and a main body70traversing between the distal end and the proximal end. The distal end66contains a sharp pointed end72, preferably three sided, for insertion into a hard surface. The main body70is sized and shaped to be insertable within the lumen23of the insertable member receiving structure12, seeFIGS. 8A and 8B. The proximal end68contains a handle73for aiding the user when inserting within the insertable member receiving structure12. The handle73may contain threading (not illustrated) along the internal surface74which is constructed and arranged to engage with the threading30of the insertable member receiving structure12.

FIGS. 9-15illustrate the features of the surgical tool10when used in a vertebral surgical procedure, such as treatment of a fractured spinal vertebra.FIG. 9illustrates a portion of a healthy spine76having vertebral bodies78,80,82, with spinous process84,86, and88respectively, and facet joint illustrated at90. Each of the vertebral bodies is separated by intervertebral discs,92and94.FIG. 10illustrates the spine76shown inFIG. 9having a vertebra compression fracture96in vertebral body80. The vertebra compression fracture96causes the vertebral body80to collapse, resulting in movement and misalignment of vertebral body78. In order to prevent complications associated with vertebra compression fractures, the patient typically undergoes a surgical procedure in which the surgeon inserts (using techniques known to surgeons performing spinal surgeries) the surgical tool10into the patient's spine at the damaged vertebral body. The insertable member receiving structure12of the surgical tool10contacts the vertebral body80(FIG. 11). With the aid of the trocar64inserted within and secured to the insertable member receiving structure12, the surgical tool10is inserted into the vertebral body to a location at or near the vertebra compression fracture96(seeFIG. 12). Once the surgical tool10reaches the desired place and is ready for formation of a cavity, the trocar64is removed from the insertable member receiving structure and replaced with the cavity forming device36, seeFIG. 13, to form a cavity102, seeFIG. 14, and restore the vertebral body80back to its original, or near original, shape, seeFIG. 15.

Referring toFIG. 16, the cavity forming device36is illustrated prior to insertion into the inner lumen23of the insertable member receiving structure12. Insertion is done by sliding the cavity forming tip44into the aperture34and moving the cavity forming device36towards the distal end18of the outer insertable member receiving structure12. As the cavity forming tip44is inserted into the aperture34, the spring-like nature of the displacement members46and48allows them to traverse from a cavity forming position, in which the plane of one displacement member diverges from the plane of the other displacement member, to a non-cavity forming position. In the non-cavity forming position, each displacement member46and48is arranged in a parallel fashion in which one displacement member rest on top of the other, i.e. they have converging planes, seeFIG. 17. The cavity forming tip44may be designed such that should one displacement member retract to the non-cavity forming position, the other displacement member retracts as well. Alternatively, the cavity forming tip44may be constructed such that should one displacement member retract to the non-cavity forming position, the other displacement member remains in the cavity forming position. The first end56of the traversing sleeve54may then be secured to the traversing sleeve receiving member52as described above. Once secured, the second end58of the traversing sleeve54is secured to the engaging member30of the insertable member receiving structure12as described previously. Alternatively, the surgeon may first attach the second end58of the traversing sleeve54to the engaging member30prior to attaching the first end to the traversing sleeve receiving member52.

Once the cavity forming tip44traverses the length of the lumen23and exits out, the spring-like characteristics allow the displacement members46and48to traverse back to the cavity forming position, seeFIG. 18. The degree of separation between the displacement members46and48can be controlled by limiting how far the cavity forming tip44travels through the lumen23. Once located at the correct position, the user rotates the knob50. Rotation of knob50causes the cavity forming device36to move in a linear direction towards the distal end of the insertable member receiving structure12as the traversing sleeve receiving member52rotatably engages the traversing sleeve. As the knob50gets rotated, the displacement members46and48move as well, forming a cavity as they undergo rotational movement.

FIGS. 19-23illustrate the formation of a cavity within the vertebral body80.FIG. 19is a cross sectional view of the vertebral body80showing compact bone98and cancellous, (soft, sponge) bone100. Once the cavity forming device36, with the displacement members46and48in the cavity forming position, is inserted into the vertebral body80and rotates, seeFIGS. 20 and 21, a cavity, or void space,102is formed. As the cavity102is expanded, should either of the displacement members46or48contact any portion of the compact bone98, they traverse from the cavity forming position to the non-cavity forming position, thereby preventing the compact bone from being damaged. Where the displacement member contacts the bone, there is no cavity formation, seeFIGS. 22-23. Once the displacement member moves away from the compact bone, the member springs back to the cavity forming position.

FIGS. 24-29illustrate alternative embodiments of the cavity forming tip44. Referring specifically toFIG. 24, the cavity forming tip44is shown extending from the insertable member receiving structure12. The cavity forming tip44contains a first displacement member104and a second displacement member106arranged around a center member108. Both displacement members104and106comprise a first surface110and112respectively, and a second surface114and116, respectively. The first surfaces110and112contain curved portions118and120which provide a generally S-shaped configuration in cross section or when viewed from the front end (FIG. 25). The first and second displacement members104and106are arranged to allow for each of the surfaces104and106to contact the bone material as the tip44rotates, thereby compressing the bone material as it rotates. The displacement members104and106have the same spring-like nature as described for displacement members46and48which allows them to traverse between a cavity forming position and a non-cavity forming position.FIG. 26illustrates an alternative embodiment of the displacement tip illustrated inFIG. 24. The cavity forming tip44illustrated inFIG. 26comprises displacement members104and106which have edge121and123which are angled to form a V-shape and the generally S-shaped cross section is not maintained throughout. While the tip44is shown with displacement members104and106, an alternative embodiment may include a single displacement member104or106, seeFIG. 27. In the non-cavity forming position, each of the members104and106can be configured around the center member108. This position is typically used when inserting the cavity forming tip44into the insertable member receiving structure12, allowing the tip44to traverse the length of the insertable member receiving structure without expanding. As soon as the tip44reaches the distal end, the first displacement member104unwinds. At a certain point, the second displacement member106unwinds until both members expand to the cavity forming position, seeFIGS. 28 and 29. Alternatively, each displacement member104and106can be designed to expand into the cavity forming position instantaneously.

Referring toFIGS. 30-32, the cavity forming tip44illustrated inFIGS. 24-26is shown with a tip member122arranged on the distal end of the center member108. In this configuration, the displacement members104and106, when in the cavity forming position, are positioned between the tip member122and the distal end of the insertable member receiving structure12. The tip member122may include, but is not limited to, a trocar tip, a beveled tip, a pencil tip, a blunt tip, a screw tip, or a drill tip. Referring toFIGS. 31-32, the tip member122may be designed such that as the tip member122contacts a surface or object at a pre-determined force, the tip member122retracts in an inwardly direction, i.e. toward the insertable member receiving structure12. A displacement member124is coupled to the cavity forming tip44and is arranged in such a manner, that in the non-cavity forming position, it can traverse the length of the insertable member receiving structure12without expanding or unwinding. As illustrated inFIG. 31, the displacement member124is shown in the non-cavity forming position and is wrapped around a portion of the displacement tip, such as the center member108, and/or a portion of tip member122. As the tip member122pushes against a surface, displacement member124expands into a cavity forming position.

FIGS. 33-35illustrate an alternative embodiment of the cavity forming tip44, illustrated herein as a plurality of individually formed displacement members126A-126E, collectively referred to as126. The displacement members126may be formed as single unit, such as a nitinol wire, that is split and shaped into a desired configuration. Alternatively, the displacement members126may be formed as individual components and coupled together. The displacement members126have the same spring-like nature as described for displacement members46and48, which allows them to traverse from a cavity forming position (fan-like configuration, open position) to a non-cavity forming position (closed position), seeFIG. 35, in which each of the individually formed displacement members align to form a single member. Preferably, each of the displacement members126A-126E are the same, or similarly, sized so that in the closed position, all the displacement members align forming an edge128that is generally linear.

FIGS. 36-39illustrate an alternative embodiment of the cavity forming tip44. The cavity forming tip44illustrated inFIGS. 36-39have the same features as described inFIG. 33. As illustrated inFIG. 36, cavity forming tip44has a plurality of individually formed displacement members126A-126E, collectively referred to as126. In addition to the displacement members126A-126E, the cavity forming tip44contains a pointed member130, illustrated as an attached trocar tip. The displacement members126A-126E are formed in the same manner as described above. Once the displacement members are formed, the trocar tip130can be coupled, through chemical fastening mechanisms or other known fastening mechanisms known to one of skill in the art, to at least one of the displacement members126A-126E. In the closed position, each of the displacement members126A-126E folds behind the trocar tip130, seeFIG. 38.FIGS. 40-43illustrate an alternative embodiment of the cavity forming tip44. The cavity forming tip44illustrated inFIGS. 40-43have the same features as described inFIGS. 36 and 38, but differ in that the trocar tip130is integrally formed as part of the cavity forming tip44. The displacement members are formed by splitting the cavity forming tip44with the trocar tip130and then shaping each of the displacement members. In this configuration, one of the displacement members,126C, contains a pointed end130, seeFIG. 40. Because the trocar tip130is integrally formed with the tip and the displacement members126A-126E are formed by splitting and shaping each member into a desired configuration, the resulting length of the displacement members126A-126E are not equal and contain partially rounded ends. As illustrated inFIG. 41, when in the closed position, the length of displacement member126C is larger than the displacement members126B and126A. The length of the displacement member126B is larger than the displacement member126A.