Patent Description:
There are medical treatments that include transversely displacing structures in the body. For example, kyphoplasty is a procedure used to treat painful vertebral compression fractures in the spinal column, which are a common result of osteoporosis. Doctors displace portions of the fractured bone to create a space and then fill the space with cement or another filler.

<CIT> describes self-expanding stabilization devices for repairing bone may include one or more bone screw attachment regions for attaching a bone screw after or before inserting the device into a subject. The stabilization devices may be attached using an inserter. The stabilization devices may be used with bone screws having multiple parts or components.

<CIT> describes a fracture reduction instrument for an osseous body, extending between a distal end and a proximal end, the distal end comprising at least one deformable element suitable for passing from a relaxed position for positioning of the distal end inside the osseous body, to a deformed position for forming a cavity inside the osseous body, the deformable element being stressed by a shift mechanism so that the deformable element may pass from one position to another and vice versa.

According to the invention, a device for creating a cavity during spinal surgery comprises an inner body with a first end and a second end;.

Embodiments of these devices can include one or more of the following features.

In some embodiments, the second end of the inner body defines a cavity that is aligned with the first strip of resilient material when the outer sleeve is in its retracted position. In some cases, the second end of the first resilient strip is outside the cavity when the outer sleeve is in its retracted position. In some cases, the cavity extends from a first opening oriented towards the first resilient strip to a second opening oriented away from the resilient strip. In some cases, a central portion of the first resilient strip is spaced apart from the inner body when the outer sleeve is in its extended position and the second end of the strip of resilient material is disposed in the cavity. In some cases, the second end of the first strip of resilient material has a tapered shape.

In some embodiments, devices also include a handle with a trigger, the trigger mechanically connected to the outer sleeve such that operation of the trigger moves the outer sleeve relative to the handle. In some cases, the second end of the inner body is fixed in position relative to the handle.

In some embodiments, a portion of the inner body defines a slot positioned within the outer sleeve. In some cases, devices also include a connector extending through the slot, the connector attached to the outer sleeve and the first strip of resilient material and fixed in position relative to the outer sleeve and the strip of resilient material.

In some embodiments, the second end of the inner body comprises threading on a surface adjacent the second opening. In some cases, devices also include a pointed tip screwed onto the second end of the inner body.

In some embodiments, a central portion of the resilient strip is spaced apart from the inner body when the outer sleeve is in its extended position and the second end of the strip of resilient material is disposed in the cavity.

In some embodiments, the outer sleeve has a hollow cylindrical shape. In some cases, devices also include a brace disposed between the inner body and the outer sleeve, the brace fixed in position relative to the outer sleeve, the brace having a generally semi-cylindrical shape with a rounded end extending outside the outer sleeve. In some cases, devices also include a connector extending through the slot, the connector fixed in position relative to the outer sleeve and abutting the strip of resilient material.

In some embodiments, the strip of resilient material comprises implant grade material.

In some embodiments, the strip of resilient material is a first strip of resilient material and the device further comprises a second strip of resilient material having a first end and a second end, the first end of the second strip of resilient material fixed in position relative to the outer sleeve; wherein the second end of the second strip of resilient material is engaged with the inner body when the outer sleeve is in its extended position and disengaged from the inner body when the outer sleeve is in its retracted position.

Some embodiments of these surgical instrumentation can provide some or all of the following advantages. A non-attached tip can provide a fail-safe disengage/reengage mechanism for the strips of resilient material that reduces the likelihood that the instrument will jam inside vertebra. A low friction hinge for low stress expansion of strips of resilient material can reduce the likelihood of requiring excessive force for activation. A slip fit of a proximal section of strips of resilient material for low friction free, manual activation can reduce the likelihood of requiring excessive force for activation. A body that is stationary with respect to the handle can reduce the risk of patient injury while providing higher security and comfort for the surgeon. A distal tip design can allow for two strips of resilient material within a small cannula size (e.g., ø < <NUM>) that allows the use of the instrument through a pedicle. A manual, direct force, squeeze handle activation with low friction can provide direct, tactile feedback for distal resilient blade expansion and allows for the assessment of tissue quality. A locking nut for locking instrument in active, expanded position can enable x-ray imaging with surgeon out of x-ray field. The device can include stressrelieving braces for the strips of resilient material that can reduce the likelihood the strips break. This approach can increase the fatigue strength of the strips, allowing for use of the instrument bi-pedicularly (e.g., the instrument can be inserted through one pedicle of a vertebrae, activated, de-activated, withdrawn, inserted through the other pedicle of the same vertebrae, activated, de-activated, and withdrawn) and on multiple levels (e.g., the instrument can be inserted into one vertebrae, activated, de-activated, withdrawn, inserted into another vertebrae, activated, de-activated, and withdrawn) without strip breakage. In contrast, once a balloon-based device is activated and the balloon deployed, it is difficult or impossible to recover the balloon back into its initial position to reset the device. This approach also allows for easy replacement of the strips of resilient material.

The stripes of resilient material disengage and automatically reengage during surgical use, therefore reducing the risk of instrument breakage or instrument jamming with tissue. This feature reduces the likelihood of excessive rotational force breaking strips of resilient material; of tissue jamming between strips of resilient material preventing removal of the instrument out of surgical site; of excessive manual force being required to expand/deform stripes of resilient material; and of material stress points in strips of resilient material.

The details of one or more embodiments of these devices are set forth in the accompanying drawings and the description below. Other features and advantages of these devices will be apparent from the description and drawings, and from the claims.

This specification describes systems and methods for transversely displacing structures in the body. These systems and methods can be used for restoring bone, particularly for performing bone alignment and displacement in the spine of a human or other animal. Only devices are claimed.

Some devices include an instrument with an elongated body that is connected or affixed to a handle of the instrument. The elongated body is partially positioned within a sleeve that is movable relative to the body. One or more substantially planar or flat strips of resilient material are positioned partially within the sleeve and are fixed in position relative to the sleeve. In operation, the strips of resilient material releasably engage the end of the elongated body that is away from the handle of the instrument.

In its fully relaxed position when the instrument is not activated, the strip(s) of resilient material can freely move away from and towards the planar surface of the elongated body. While displacing tissue, in its expanded state, the strips of resilient material can disengage from the end of the elongated body when encountering excess forces or when tissue pieces get lodged between the resilient blade and the planar surface of the stationary body, in order to prevent breaking of the resilient blade or to allow removal of the instrument through the access cannula. When the instrument is in its fully relaxed position, automatic reengagement of strip(s) of resilient material can occur after safety disengagement due to excessive forces or jamming with debris of strip(s) of resilient material during surgical use.

<FIG> show a device <NUM> for displacing structures in a patient's body. The device <NUM> has an inner body <NUM>, an outer sleeve <NUM>, and two strips <NUM> of resilient material. The inner body <NUM> and the outer sleeve <NUM> are coaxial and part of the inner body <NUM> is positioned within the outer sleeve <NUM>. The inner body has a first end <NUM> (shown in <FIG>) and a second end <NUM>. The inner body <NUM> extends out of the outer sleeve <NUM> on both the distal and proximal ends. The outer sleeve <NUM> is movable relative to the inner body <NUM> between a retracted position (shown in <FIG>) and an extended position (shown in <FIG>).

The strips <NUM> of resilient material each have a first end <NUM> (shown in <FIG>) and a second end <NUM>. The first end <NUM> of each strip <NUM> of resilient material is fixed in position relative to the outer sleeve <NUM> such that movement of the outer sleeve <NUM> and movement of the first end <NUM> of the strip of resilient material are coupled. In the device <NUM>, a pin <NUM> (also shown in <FIG>) extends through the outer sleeve and the strips <NUM> of resilient material. The second end <NUM> of each of the strips <NUM> of resilient material is releasably engaged with the inner body <NUM> when the outer sleeve <NUM> is in its extended position and disengaged from the inner body <NUM> when the outer sleeve <NUM> is in its retracted position. <FIG> shows the strip of resilient material in the non-activated state, arranged flat against the inner body <NUM>.

Some devices only have a single strip <NUM> of resilient material and some devices have more than two strips <NUM> of resilient material. The device <NUM> has strips <NUM> of resilient material made of implant grade material such as, for example, Nitinol, Poly Ether Ether Ketone (PEEK), Poly Ether Ketone Ketone (PEKK). Use implant grade material allows the strips <NUM> to be left in the body if they break off during use. The material can have elastic modulus between approximately <NUM> MPa and <NUM> MPa (e.g., approximately <NUM> MPa, a yield strength between approximately <NUM> MPa and <NUM> MPa, an ultimate tensile strength between approximately <NUM> MPa to <NUM> MPa.

The device <NUM> also includes a handle <NUM> (best seen in <FIG>). The handle <NUM> has a trigger <NUM> attached to a base <NUM>. The base <NUM> of the handle is fixed in position relative to the inner body <NUM>. The trigger <NUM> is mechanically connected to the outer sleeve <NUM>, such that the outer sleeve <NUM> moves from the retracted position to the extended position when the trigger <NUM> is activated. In <FIG>, the trigger <NUM> is not activated and the outer sleeve <NUM> is in its retracted position. In <FIG>, the trigger is activated.

Two factors help the trigger to return to its retracted position when the trigger is released. The resilient strips automatically return to their flat, planar position and therefore exert a force back through the outer sleeve onto the trigger. In addition, a torsion spring (see <FIG>) around pin <NUM> helps to bias the trigger to its retracted position.

In the device <NUM>, the trigger <NUM> is attached to the base <NUM> by a pin <NUM>. Another pin <NUM> connects the trigger <NUM> to the outer sleeve <NUM>. Rotation of the trigger <NUM> about the pin <NUM> moves the pin <NUM> within a slot <NUM> defined in the base <NUM> and a slot <NUM> (see <FIG>) defined in the inner body <NUM>. As the pin <NUM> moves in the slot of the trigger, the slot in the trigger translates the rotational movement from the trigger into a linear movement of pin <NUM>. The proximal connector pin <NUM> slides freely up and down in the slot <NUM> of the trigger <NUM> on both the left and right side portions of the trigger. The connector pin <NUM> is coupled, securely fixed to the proximal end of the outer sleeve through the hole <NUM> and also freely moves within the slot of the handle and the proximal slot of the inner body.

For example, activation of the trigger <NUM> by pulling a grip portion of the trigger <NUM> towards the base <NUM> rotates the trigger <NUM> about the pin <NUM>. The rotation causes the pin <NUM> to move forward (to the right in <FIG>) and the outer sleeve to move to its extended position. Some devices use other approaches to coupling the trigger <NUM> to the outer sleeve <NUM>. However, this approach's direct mechanical connection provides tactile feedback to medical personnel performing procedures using the device <NUM>. For example, a surgeon performing a kyphoplasty using the device <NUM> can gauge the stage of fracture healing, the consistency of the bone (e.g., hard bone or soft bone), or the stage of osteoporosis within the vertebral body. In case of soft (i.e., highly osteoporotic) bone, the surgeon will likely decide to insert more material / PMMA / allograft implant to better stabilize the fracture or even possibly proactively treat adjacent levels.

The second end <NUM> of the inner body <NUM> also comprises threading <NUM> on a surface adjacent the second opening. A tip (e.g., a trocar tip) can be screwed onto the second end <NUM> of the inner body <NUM> using threading <NUM>. Some devices use other approaches to attaching the tip to the second end <NUM> of the inner body <NUM> (e.g., a press fit, a shrink fit, gluing, pinning, or snapping). The tip may be pointed. The pointed tip allows the device <NUM> to create a channel into the body of a patient. This eliminates the need of a separate drill that is currently used when the surgeon creates the cavity with a balloon.

The second end <NUM> of the inner body <NUM> is chamfered to provide a symmetrical sloping edge. The chamfered second end of <NUM> of the inner body <NUM> allows for the second end of the inner body <NUM> to be pushed into the tissue. During tests, the chamfered second end <NUM> of the inner body <NUM> was sufficient for the instrument to be pushed into the vertebral body without having a sharper tip attached to the second end <NUM> of the inner body <NUM>.

The handle also has a locking nut <NUM> operable to lock the outer sleeve <NUM> in position (e.g., in its extended position, in its retracted position, or in a position between its extended and retracted positions). The locking nut <NUM> may be threaded so that it can be rotated to lock the outer sleeve <NUM>. Alternatively, the locking nut may be pressed into a locking position by the user to lock the outer sleeve <NUM>. Locking the outer sleeve <NUM> also locks the trigger <NUM>.

The outer sleeve <NUM> has a substantially hollow cylindrical shape. Two braces <NUM> are positioned within the outer sleeve <NUM> between the outer sleeve <NUM> and the strips <NUM> of resilient material. The braces <NUM> have a generally semi-cylindrical shape with a rounded end and are disposed between the inner body <NUM> and the outer sleeve <NUM>. The braces <NUM> are fixed in position relative to the outer sleeve <NUM> by the pin <NUM>. In some devices, the braces are welded or glued to the outer sleeve. The braces <NUM> partially extend outside the outer sleeve <NUM> and relieve stress on the strips <NUM> of resilient material when the strips <NUM> are flexed or bowed. The braces <NUM> are configured to reduce breakage of the strips <NUM> of resilient material. During multiple activations of the instrument <NUM>, the braces increase the fatigue strength/resistance of the strips to allow for bi-pedicular and multi-level or even multi-patient use. The first ends <NUM> of the strips <NUM> of resilient material are disposed between the inner body <NUM> and the braces <NUM>. A hole on the proximal side of the strips <NUM> of resilient material receives the pin <NUM>. With this approach, the strip cannot be replaced but is secured in place and will not be able to fall out accidentally during surgery. In some devices, the strips <NUM> of resilient material abut to the pin <NUM>. With this approach, strips <NUM> of resilient material can easily be replaced,.

<FIG> shows one of the braces <NUM>. The brace <NUM> includes a rounded tip <NUM>. The brace <NUM> defines an opening <NUM> for receiving the pin <NUM> (shown in <FIG>) that couples the outer sleeve <NUM> with the strips <NUM> of resilient material and the braces <NUM>. The braces <NUM> are made of stainless steel. In some devices, the braces are made of other materials such as, for example, plastic or aluminum. In addition to reducing the material stress on the strip and increasing the fatigue life of the strips, the braces <NUM> also provide a planar surface for the proximal end of the strips <NUM> on one side. The other planar surface on the other side is provided by the recessed portion <NUM> of the inner body <NUM>. The planar surfaces are spaced apart to allow for a friction free movement of the strips along the recessed portion <NUM> of the inner body. The space between the two planar surfaces is slightly larger than the thickness of the strip.

<FIG> is a side view of the outer sleeve <NUM>. The outer sleeve <NUM> defines an opening <NUM> sized to receive the pin <NUM> that couples the outer sleeve <NUM> with the trigger <NUM> (shown in <FIG>). The outer sleeve <NUM> also defines an opening <NUM> sized to receive the pin <NUM> that couples the outer sleeve <NUM> with the strips <NUM> of resilient material and the braces <NUM> (shown in <FIG>). The outer sleeve <NUM> is hollow and is sized to receive the first ends <NUM> of the strips <NUM> of resilient material, the braces <NUM>, and the inner body <NUM>. In a prototype, the outer diameter of the outer sleeve is ø <NUM> (less than ø <NUM>) and the inner diameter of the outer sleeve at the distal tip is ø <NUM> for a length of <NUM>. The rest of the inner diameter of the outer sleeve is ø <NUM>. The outer sleeve <NUM> of the device <NUM> is generally cylindrical but some devices have other cross-sections (e.g., a triangular cross section or a square cross section).

<FIG> is a side view of the inner body <NUM>. The first end <NUM> of the inner body <NUM> defines an opening <NUM> and a slot <NUM>. The opening <NUM> is sized to receive a pin (not shown) that fixes the inner body <NUM> to the base <NUM> of the handle <NUM> such that the second end <NUM> of the inner body <NUM> is fixed in position relative to the base <NUM> of the handle <NUM>. When the device <NUM> is assembled, the slot <NUM> of the inner body <NUM> is aligned with the slot <NUM> in the base <NUM> of the handle <NUM>. The slot <NUM> is sized to receive the pin <NUM> that connects the trigger <NUM> to the outer sleeve <NUM>. The slot <NUM> has a length that is equal to or greater than the displacement of the outer sleeve <NUM> during operation of the device <NUM>. When the trigger <NUM> is not activated, the pin <NUM> is positioned at the end of the slot <NUM> towards the first end <NUM> of the inner body <NUM>. When the trigger is fully activated, the pin <NUM> is positioned at the end of the slot <NUM> towards the second end <NUM> of the inner body <NUM>. This configuration allows the pin <NUM> to move within the slot <NUM> without applying substantial pressure to the inner body <NUM>.

The inner body <NUM> has a recessed portion <NUM> which receive the strips <NUM> of resilient material when the device <NUM> is assembled and the outer sleeve <NUM> is in its retracted position. The second end <NUM> of the inner body <NUM> defines a cavity <NUM> that is aligned with the recessed portion <NUM> (see also <FIG>). In the inner body <NUM>, the cavity <NUM> extends through the second end <NUM>. These features of the inner body can be formed by machining a blank for the inner body to form the recessed portion <NUM> and then drilling from the distal end until the cavity <NUM> intersects the recessed portion <NUM>. The cavity <NUM> interacts with the strips <NUM> of resilient material to act as a low friction or friction free hinge when the outer sleeve <NUM> is moved from its retracted position to its extended position during operation.

<FIG> show the relationship between the inner body <NUM> and the strips <NUM> of resilient material that provides this hinge functionality in additional detail. <FIG> show a portion of the device <NUM> with the outer sleeve <NUM> in its retracted position (i.e., device <NUM> is not activated). When the outer sleeve <NUM> is in its retracted position, the second ends <NUM> of the strips <NUM> of resilient material are flush with or slightly outside the cavity <NUM>. This positioning allows the strips <NUM> of resilient material to move outward and, more importantly, inward with little or no contact with the portion of the second end <NUM> of the inner body <NUM> that defines the cavity <NUM>. The significance of this feature is discussed in more detail in the description of <FIG>.

<FIG> show the relationship between the strips <NUM> of resilient material and the inner body <NUM> just after the trigger <NUM> is activated. As the outer sleeve <NUM> starts to move from its retracted position to its extended position, the strips <NUM> of resilient material move towards the second end <NUM> of the inner body. The second ends <NUM> of the strips <NUM> of resilient material are shaped such that a portion of each of the second ends <NUM> enters the cavity <NUM> before the strips <NUM> of resilient material contact the second end <NUM> of the inner body <NUM>. Contact between angled faces of the tapered end <NUM> and the walls <NUM> of the second end <NUM> of the inner body <NUM> holds the second ends <NUM> of the strips <NUM> of resilient material in place relative to the inner body <NUM> as the outer sleeve <NUM> and the first ends <NUM> of the strips <NUM> of resilient material continue to move toward the second end <NUM> of the inner body <NUM>.

In the device <NUM>, the second end <NUM> of each of the strips <NUM> of resilient material has a tapered shape as shown in <FIG>. In some devices, the second ends <NUM> of the strips <NUM> of resilient material have different shapes such as, for example, a rectangular tab sized to enter the cavity <NUM>. In some devices, the second end <NUM> of each of the strips <NUM> is flat. With this approach, the strips <NUM> do not enter the cavity <NUM> but rather push against the wall <NUM>. With this option, lower rotational forces disengage the second ends <NUM> of the strips <NUM> from the inner body <NUM>.

<FIG> illustrate the operation of the device <NUM> with a focus on the tip of the device that would be inserted into a patient. In <FIG>, the device is not activated. The outer sleeve <NUM> is in its retracted position relative to the inner body <NUM>. As previously discussed, the pin <NUM> fixes the position of the strips <NUM> of resilient material and the braces <NUM> with respect to the outer sleeve <NUM> so the strips <NUM> of resilient material and the braces <NUM> are also in their retracted positions. The second ends <NUM> of the strips <NUM> of resilient material are outside the cavity <NUM> defined by the second end <NUM> of the inner body <NUM>.

<FIG> and <FIG> are, respectively, a perspective view and a cross-sectional view of one end of the device in <FIG> in an activated state. The device is activated by moving the outer sleeve <NUM> towards the second end <NUM> of the inner body <NUM>. As shown in <FIG>, the pin <NUM> extends through the outer sleeve <NUM>, the braces <NUM>, and the strips <NUM> of resilient material so they are fixed in position relative to each other. The pin <NUM> extends through a distal slot (i.e., the slot <NUM>) in the inner body <NUM>. The slot <NUM> limits the distance that the pin <NUM>, the outer sleeve <NUM>, the braces <NUM>, and the strips <NUM> of resilient material can move relative to the inner body <NUM>. Movement of the outer sleeve <NUM> moves the pin <NUM> within the slot <NUM> defined by the inner body <NUM> between the retracted position indicated by the dashed rectangle and the extended position. Moving the outer sleeve <NUM> and the pin <NUM> towards the second end <NUM> of the inner body <NUM> also moves the braces <NUM> and the strips <NUM> of resilient material towards the second end <NUM> of the inner body <NUM>.

After a short distance, the second ends <NUM> of the strips <NUM> of resilient material enter the cavity <NUM> and engage the second end <NUM> of the inner body <NUM> as shown in <FIG>. As movement of the outer sleeve <NUM> towards the second end <NUM> of the inner body <NUM> continues, contact between the angled faces <NUM> of the tapered end <NUM> and the walls <NUM> of the second end <NUM> of the inner body <NUM> stops axial movement of the second ends <NUM> of the strips <NUM> of resilient material relative to the inner body <NUM>. The second ends <NUM> of the strips <NUM> of resilient material pivot within the cavity <NUM> as shown in <FIG>. In effect, the interaction between the second ends <NUM> of the strips <NUM> of resilient material and the second end <NUM> of the inner body <NUM> provides a low- or no-friction hinge while the strips <NUM> of resilient material flex outwards.

As movement of the outer sleeve <NUM> towards the second end <NUM> of the inner body <NUM> continues after contact stops axial movement of the second ends <NUM> of the strips <NUM> of resilient material relative to the inner body <NUM>, the axial distance between the first ends <NUM> and the second ends <NUM> of the strips <NUM> of resilient material decreases. The center portions of the strips <NUM> of resilient material flex away from the inner body <NUM>. The flexing of the center portions of the strips <NUM> of resilient material is used to displace structures in the patient's body transversely. Typically, the instrument is slightly rotated after activation and activated. This process can be repeated though a <NUM> degrees of rotation to create a cylindrical cavity.

The first ends <NUM> of the strips <NUM> of resilient material are positioned between the inner body <NUM> and the braces <NUM>. As the strips <NUM> of resilient material flex away from the inner body <NUM>, the rounded tips <NUM> of the braces <NUM> bias the bend of the strips <NUM> of resilient material towards a curved configuration that is lower stress than sharper angled configurations. The reduced stress on the strips <NUM> of resilient material at this point is anticipated reduce the likelihood that the strips <NUM> will break during multiple uses, therefore increasing the fatigue resistance/life of the strips <NUM>.

During use, debris or material lodging between the strips <NUM> of resilient material and the inner body <NUM> can apply an outward force on the flexed strips <NUM> as indicated by arrow A in <FIG>. The second ends <NUM> of the strips <NUM> of resilient material are not fixed to the inner body <NUM> so such an outward force can disengage the strips <NUM> of resilient material from the cavity <NUM>. When this occurs, the disengaged strip <NUM> of resilient material is biased towards the shape and position indicated by the dashed lines. Debris or material typically is dislodged from the strip <NUM> as this occurs. In the unlikely event that debris or material within the space being created by use of the device <NUM> or the bone defining the boundaries of the space keep the disengaged strip <NUM> of resilient material from reaching this shape and position, the instrument can be activated and deactivated as necessary to dislodge the debris or material. The feature of the second ends <NUM> of the strips <NUM> of resilient being separable from the cavity <NUM> is anticipated reduce the likelihood that debris or material will remain lodged between the strips <NUM> and recessed portion <NUM> and that the strips <NUM> will break during use so that the instrument can be safely removed from the patient without jamming. Typically, the instrument is inserted into the patient through a separate access cannula/tube.

After this disengagement occurs, the device can be returned to an operational state by deactivating the device (e.g., by releasing the trigger <NUM>). As the outer sleeve <NUM> returns to its retracted position, the braces <NUM> and the first ends <NUM> of the strips <NUM> of resilient material move away from the second end <NUM> of the inner body <NUM>. As the second end <NUM> of the disengaged strip <NUM> reaches the position where it is flush with or slightly away from the second end <NUM> of the inner body <NUM>, the disengaged strip <NUM> will tend to resume its position in the recessed portion <NUM> of the inner body <NUM>. During this step, debris or material tends to be dislodged or freed from the instrument therefore allowing the free/simple removal of the instrument from the patient. In some instances, this reset can be performed without removing the tip of the device <NUM> from the patient's body. Debris or material stuck between the disengaged strip <NUM> and the inner body can prevent the disengaged strip <NUM> from resuming its position in the recessed portion <NUM> of the inner body <NUM>. If this occurs, it may be necessary to remove the tip of the device <NUM> from the patient's body to clear away the debris or material and perform the reset.

<FIG> illustrate a feature provided by the fixed position of the inner body <NUM> relative to the handle <NUM>. <FIG>, respectively, show the device <NUM> before and after the trigger <NUM> is activated. A reference line <NUM> is shown on both <FIG>. As the device <NUM> is activated the strips <NUM> of resilient material move from their non-activated position to their flexed position, but the second end <NUM> of the inner body <NUM> remains stationary. Most notably, the end of the inner body <NUM> does not move relative to the reference line <NUM> when in the extended position or the retracted position. This feature allows medical personnel to position the device <NUM> in a patient's body and operate the device without concern that the end of the device <NUM> will penetrate farther into the patient's body as long as the handle <NUM> is maintained in a fixed position. This can be clinically important in order to avoid tissue damage from the distal tip of the device. Specifically, the concern of anterior break-through of the vertebral body and accidental harm or damage to the anterior vessels (aorta and vena cava) is reduced. Damage to either vessel during such a surgery can easily lead to a patient's death due to rapid bleeding that cannot be stopped in time.

<FIG> shows the device in use to transversely displacing structures in the spine of a patient to perform a kyphoplasty. A trocar <NUM> is attached to the device using the threaded section on the second end <NUM> of the inner body <NUM>. The end of the device is inserted into the spine using the trocar to create a channel or pathway into the body. In some approaches, separate device is used to create a channel or pathway into the body. The trocar does not create the channel inside the vertebral body but rather is only long enough to create the channel through the pedicle. Surgeons currently use an additional drill to drill out the cancellous bone inside the vertebral body. In contrast, the trocar tip/chamfer of the current instrument allows the elimination of the drill. The device <NUM> is inserted with the outer sleeve <NUM> in its retracted position and the strips of resilient material in their non-active position. After insertion, activation of the trigger <NUM> (see <FIG>) moves the strips <NUM> into the flexed position to apply a force onto the tissue, bone, or other biologic material in a vertebra, to create a space in the vertebra. When the user releases the trigger <NUM>, the strips <NUM> return to their non-activated position. The user can repeat activating and deactivating the trigger to create a larger space in the body, for example by rotating the device <NUM> or inserting the device <NUM> further into the body.

The elimination of the drilling step is an advantage of the current instrument over balloon-based systems. In addition, the current device eliminates the need of a pressure pump and the use of saline to inflate the balloon, therefore eliminating multiple additional steps.

Since this device provides tactile feedback, the surgeon is able to assess the health of the bone and alter his treatment accordingly. For example, she may add more material within the vertebral body. In another example, he may proactively treat adjacent vertebral bodies if tactile feedback indicates that the bone is very soft/weak. Alternatively, if the surgeon diagnoses very hard bone or a very stable fracture, the surgeon may alter his treatment with the insertion of less material and no need for adjacent level proactive treatment. In contrast to balloon-based systems, the surgeon can use a single instrument on both sides (bi-pedicular) and on multiple levels, eliminating the need of unpacking and using multiple balloons.

Claim 1:
A device (<NUM>) for creating a cavity during spinal surgery, the device comprising:
an inner body (<NUM>) with a first end (<NUM>) and a second end (<NUM>);
an outer sleeve (<NUM>) coaxial with the inner body, the outer sleeve movable relative to the inner body between a retracted position and an extended position;
a trigger mechanism (<NUM>) mechanically connected to the outer sleeve (<NUM>) and configured to apply an axial force to the outer sleeve;
a first strip (<NUM>) of resilient material having a first end (<NUM>) and a second end (<NUM>), the first end of the first strip of resilient material fixed in position relative to the outer sleeve; and
a second strip (<NUM>) of resilient material having a first end (<NUM>) and a second end (<NUM>), the first end of the second strip of resilient material fixed in position relative to the outer sleeve (<NUM>);
wherein the second ends (<NUM>) of the first strip (<NUM>) of resilient material and the second strip (<NUM>) of resilient material are releasably engaged with the second end (<NUM>) of the inner body when the outer sleeve is in its extended position and disengaged from the inner body when the outer sleeve is in its retracted position.