Patent Publication Number: US-2021177386-A1

Title: Bone biopsy device and related methods

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/946,830, filed Dec. 11, 2019, and titled BONE BIOPSY DEVICE AND RELATED METHODS, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to devices used to perform a biopsy procedure, specifically a bone biopsy procedure. More specifically, the present disclosure relates to devices used to drill into a bone to obtain a core tissue sample of a bone lesion and/or bone marrow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments disclosed herein will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. These drawings depict only typical embodiments, which will be described with additional specificity and detail through use of the accompanying drawings in which: 
         FIG. 1  is a perspective view of an embodiment of a bone biopsy device. 
         FIG. 2  is a perspective exploded view of the bone biopsy device of  FIG. 1 . 
         FIG. 3A  is a perspective view of the bone biopsy device of  FIG. 1  with a portion of a handle housing removed in a trocar extended configuration. 
         FIG. 3B  is a side view of the bone biopsy device of  FIG. 1  with a portion of the handle housing removed in a trocar retracted configuration. 
         FIG. 4  is a perspective view of a transmission of the bone biopsy device of  FIG. 1 . 
         FIG. 5A  is a perspective view of an outer coax cannula assembly of the bone biopsy device of  FIG. 1 . 
         FIG. 5B  is a detailed view of a cutting tip of the outer coax cannula assembly of  FIG. 5A . 
         FIG. 6A  is a perspective view of an embodiment of a trocar of the bone biopsy device of  FIG. 1 . 
         FIG. 6B  is a perspective view of another embodiment of a trocar of the bone biopsy device of  FIG. 1 . 
         FIG. 6C  is a cut-away perspective view of a part-off tab of an inner cannula of the bone biopsy device of  FIG. 1 . 
         FIG. 7A  is a side view of the bone biopsy device of  FIG. 1  inserted into skin over a guidewire. 
         FIG. 7B  is a side view of the bone biopsy device of  FIG. 1  inserted in a bone. 
         FIG. 7C  is a side view of the bone biopsy device of  FIG. 1  drilled through a cortical bone layer. 
         FIG. 7D  is a side view of the bone biopsy device of  FIG. 1  drilled into a bone lesion and/or bone marrow. 
         FIG. 7E  is a side view of the bone biopsy device of  FIG. 1  with the inner cannula removed from an outer coax cannula. 
         FIG. 7F  is a side view of the bone biopsy device of  FIG. 1  with a tissue sample ejected from the inner cannula. 
         FIG. 7G  is a side view of the bone biopsy device of  FIG. 1  with the inner cannula removed from an outer coax cannula and an aspiration needle inserted through the coax cannula. 
         FIG. 8  is a perspective view of another embodiment of a bone biopsy device. 
         FIG. 9  is a side cut-away view of the bone biopsy device of  FIG. 8 . 
         FIG. 10  is an exploded view of a transmission of the bone biopsy device of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     A bone biopsy device may include a handle assembly, a coax assembly, and a power pack. The handle assembly may include a housing configured to hold an inner cannula. The inner cannula may extend distally from the housing and may be configured to receive a core tissue sample. A trocar with a penetrating tip may be slidably disposed within a lumen of the inner cannula. The housing may include a slider member that is configured to displace the trocar relative to the inner cannula from a retracted configuration to an extended configuration where the trocar can drill into a bone. A motor and a transmission may rotate the inner cannula and the trocar. In certain instances, the transmission may include a worm drive. In other instances, the transmission may include a plurality of spur gears. The inner cannula and trocar may be configured to remain part of the handle assembly (e.g., coupled to the housing) before, during, and after a biopsy procedure. The coax assembly may be selectively detachable from the handle assembly. The coax assembly may include an outer coax cannula extending distally from a coax connector. The inner cannula may be partially disposed within a lumen of the outer coax cannula. The outer coax cannula can be rotated by the motor. A tip of the outer coax cannula may be a cutting tip (e.g., a trephine tip) and be configured to saw into a bone lesion and/or bone marrow. The power pack may be selectively removable from the handle assembly such that the power pack may be a reusable component. The power pack may comprise a power source, a controller, and a connector. The power pack and/or controller may also comprise a printed circuit board. In some instances, the motor may also be selectively removable from the handle assembly such that the motor may also be a reusable component (for instance, the motor may be selectively removable with the power pack). 
     The bone biopsy device may be used by a practitioner to obtain a core tissue sample of a bone lesion and/or bone marrow. In other instances, the bone biopsy device may be used to obtain a core tissue sample of other tissues within a patient, such as a soft tissue sample. In use, the trocar, outer coax cannula, and inner cannula may be rotated by the motor and drilled into the cortical bone layer adjacent to a lesion and/or bone marrow. The trocar may be retracted, and the inner cannula and the outer coax cannula rotated to saw a core tissue sample of the lesion and/or bone marrow that is collected in the inner cannula. The outer coax cannula may be removed from the inner cannula and the trocar advanced within the inner cannula to eject the core tissue sample. A needle or aspiration needle can also be inserted into the outer coax cannula to collect or aspirate bone marrow, blood, and/or tissue cells. A needle could also be inserted into the outer coax cannula to infuse or inject a substance (such as a medicament) into the patient. 
     Embodiments may be understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood by one of ordinary skill in the art having the benefit of this disclosure that the components of the embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated. 
     It will be appreciated that various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. Many of these features may be used alone and/or in combination with one another. 
     The phrase “coupled to” refers to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be coupled to each other even though they are not in direct contact with each other. For example, two components may be coupled to each other through an intermediate component. 
     The directional terms “distal” and “proximal” are given their ordinary meaning in the art. That is, the distal end of a medical device means the end of the device furthest from the practitioner during use. The proximal end refers to the opposite end, or the end nearest the practitioner during use. As specifically applied to the bone biopsy device, the proximal end of the device refers to the end nearest the handle and the distal end refers to the opposite end, the end nearest the end of the outer coax cannula. Thus, if at one or more points in a procedure a physician changes the orientation of the device, as used herein, the term “proximal end” always refers to the handle end of the device (even if the distal end is temporarily closer to the physician). 
       FIGS. 1-10  illustrate different views of bone biopsy devices and related components. In certain views each device may be coupled to, or shown with, additional components not included in every view. Further, in some views only selected components are illustrated, to provide detail into the relationship of the components. Some components may be shown in multiple views, but not discussed in connection with every view. Disclosure provided in connection with any figure is relevant and applicable to disclosure provided in connection with any other figure or embodiment. 
       FIGS. 1-7G  depict one embodiment of a bone biopsy device  100 . The bone biopsy device  100  includes three general groups of components; each group may have numerous subcomponents and parts. The three general component groups are: a handle assembly  110 , a coax assembly  170 , and a power pack  180  as illustrated in  FIG. 1 . 
     As depicted in  FIG. 2 , the handle assembly  110  may at least partially include a handle housing  111 , a motor  122 , a motor activation switch  124 , a transmission  125 , an inner cannula  150 , and a penetrating member or trocar  160 . The handle housing  111  can include an upper portion  112  and a grip portion  113 . The grip portion  113  may be configured to be grasped by a hand of a practitioner during use of the bone biopsy device  100 . The motor activation switch  124  may be disposed adjacent a distally facing surface of the grip portion  113  such that the motor activation switch  124  may be engageable by a finger of the practitioner. In other embodiments, the motor activation switch  124  may be disposed on any other suitable surface of the handle housing  111 . The handle housing  111  may be formed of two separate halves that may be coupled using any suitable technique. For example, the separate halves may be coupled using a snap fit, welding, gluing, fasteners, pins, etc. The handle housing  111  may include any suitable polymeric and/or metallic material, such as polycarbonate, acrylonitrile butadiene styrene, polycarbonate/acrylonitrile butadiene styrene copolymer, nylon, acetal, polyethylene (e.g., such as high density polyethylene and/or low density polyethylene), silicone, thermoplastic elastomers, steel, stainless steel, aluminum, ceramic, and combinations thereof. The polymers may also be reinforced with other materials, such as glass or aramid fibers. The handle housing  111  may be formed using any suitable technique, such as injection molding, thermoforming, machining, 3D printing, etc. 
     The handle housing  111  can include a plurality of pockets or recesses configured to hold or retain at least some of the components of the handle assembly  110 . For example, the handle housing  111  may include a power pack pocket  114  to retain the power pack  180 , a motor pocket  115  to retain the motor  122 , a transmission pocket  116  to retain the transmission  125 , and an inner cannula pocket  121  to retain the inner cannula  150  and the trocar  160 . In other embodiments, the handle housing  111  may include other pockets or recesses to hold or retain other components of the handle assembly  110 . 
     In the depicted embodiment, the motor  122  may be disposed within the motor pocket  115  of the handle housing  111 . The motor  122  may be any suitable type of rotatory motor. For example, the motor  122  may be a DC brushed motor, a DC brushless motor, a stepper motor, a servo motor, a pneumatic motor, or an AC powered motor, etc. The motor  122  may also be bi-directional. The motor  122  can include a drive shaft  123  extending from the motor  122 . The motor  122  may rotate the drive shaft  123  at a speed ranging from about 0 rpm to about 50,000 rpm, or from about 15 rpm to about 20,000 rpm. The motor  122  can be electrically coupled to the power pack  180  and to the motor activation switch  124 . 
     As illustrated in  FIGS. 2-4 , the transmission  125  can be disposed within the transmission pocket  116  of the handle housing  111 . The transmission  125  can be operably coupled to the motor  122 . In the illustrated embodiment, the transmission  125  includes a worm drive  133 . The worm drive  133  may include a worm screw  126 , a first worm gear  127 , and a second worm gear  128 . The worm screw  126  can be fixedly coupled to the drive shaft  123  and rotated by the motor  122 . The worm screw  126  can include a spiral or helical thread  130  extending radially outward from the worm screw  126 . The worm screw  126  may be oriented within a central vertical plane of the handle housing  111  and directed outwardly from a central vertical axis. The worm screw  126  may be formed from any suitable rigid or semi-rigid material, such as polycarbonate, acrylonitrile butadiene styrene, polycarbonate/acrylonitrile butadiene styrene copolymer, nylon, acetal, polyethylene (e.g., high density polyethylene and/or low density polyethylene), silicone, thermoplastic elastomer, steel, stainless steel, aluminum, ceramic, and combinations thereof. The polymers may be reinforced with other materials, such as glass or aramid fibers. 
     The worm screw  126  may operably couple with the first and second worm gears  127 ,  128 . The first and second worm gears  127 ,  128  may be generally disk-shaped and include teeth  131  disposed around a periphery. The first and second worm gears  127 ,  128  may be oriented vertical to and may rotate about a horizontal axis of the bone biopsy device  100 . The teeth  131  may be double beveled and may mesh with the helical thread  130  of the worm screw  126  such that when the motor  122  rotates the worm screw  126  the first and second worm gears  127 ,  128  rotate about the horizontal axis. The first and second worm gears  127 ,  128  may include a plurality of teeth  131  ranging in number from about 10 to about 100, from about 30 to about 80, or from about 25 to about 50. A gear reduction ratio of the transmission  125  may range from about 50:1 to about 20:1, or from about 40:1 to about 30:1. In other words, a speed of rotation of the first and second worm gears  127 ,  128  may range from about 0 rpm to about 4000 rpm, from about 0 rpm to about 1000 rpm, from about 0 rpm to about 500 rpm, and from about 200 rpm to about 300 rpm. A delivered torque force may range from about 0.01 Nm to about 2 Nm, from about 0.5 Nm to about 1 Nm, and from about 0.5 Nm to about 0.75 Nm. 
     The first worm gear  127  can be rotatably coupled to the worm screw  126  and also continuously engaged with the worm screw  126  before, during, and after use. The first worm gear  127  may be fixedly coupled to the inner cannula  150  such that a proximal portion  151  extends proximally from the first worm gear  127  and a distal portion  152  extends distally from the first worm gear  127 . The first worm gear  127  can rotate the inner cannula  150  about a longitudinal axis of the inner cannula  150  at the same speed as the first worm gear  127  is rotated about the horizontal axis. The second worm gear  128  may be fixedly coupled to an outer coax cannula  173  as will be described below. 
     The inner cannula  150 , as depicted in the illustrated embodiment of  FIG. 2 , includes the proximal portion  151 , the distal portion  152 , and a lumen  153 . The proximal portion  151  extends to a proximal end of and is rotatably coupled to the handle housing  111 . The inner cannula  150  may be formed from any suitable material, such as stainless steel, titanium, titanium-nickel alloy, etc. A longitudinal slot  154  through a wall of the inner cannula  150  is disposed adjacent the proximal portion  151 . In some embodiments, the longitudinal slot  154  may be reinforced. For example, a sleeve or tube including a slot may be disposed over the inner cannula  150  such that the slot of the sleeve aligns with the longitudinal slot  154 . In another example, the first worm gear  127  may include a proximally extending member (e.g., sleeve or tube) that includes a slot such that the slot of the proximally extending member aligns with the longitudinal slot  154 . In yet another embodiment, a distal end of the inner cannula  150  is fixedly coupled to the handle housing  111  distal to the first worm gear  127 . The first worm gear  127  may include a proximally extending member (e.g., sleeve or tube) that includes a slot. The trocar  160  can be slidably disposed within the proximally extending member. The first worm gear eccentric shaft portion  127  may rotate the trocar  160  while the inner cannula  150  is rotationally stationary. 
     In some embodiments, the inner cannula  150  may include a part-off tab  155  disposed within the lumen  153  adjacent the distal portion  152  as depicted in  FIG. 6B . The part-off tab  155  may be actuatable from a non-actuated configuration where it is axially aligned with a longitudinal axis of the inner cannula  150  to an actuated configuration, as shown in  FIG. 6B , where a portion of the part-off tab  155  extends radially inward into the lumen  153 . The part-off tab  155  may be configured to sever a core tissue sample disposed within the lumen  153  from a bone lesion and/or bone marrow. A distal end of the part-off tab  155  may be fixedly coupled to a distal portion of the inner cannula  150 . A proximal portion of the part-off tab  155  may be longitudinally translated such that a portion of the part-off tab is deflected inwardly. In other embodiments, other sampling/cutting mechanisms can also be used. 
     Referring again to  FIGS. 2 and 6A-6B , the trocar  160 , is slidingly disposed within the lumen  153  of the inner cannula  150 . The trocar  160  may be an elongate rod having a penetrating tip  161 . The penetrating tip  161  may include a plurality of facets  164  with cutting edges  165 . The cutting edges  165  may be angled to allow for drilling of the trocar  160  into a bone. A laterally extending protrusion  162  may be disposed adjacent a proximal end of the trocar  160 . In some embodiments the laterally extending protrusion  162  may be a pin as depicted in  FIG. 6A . In other embodiments, a proximal end of the trocar  160  is bent at approximately a 90-degree angle relative to a longitudinal axis of the trocar  160  to form the lateral protrusion  162  as shown in  FIG. 6B . The protrusion may be configured to extend through the longitudinal slot  154  of the inner cannula  150 . The protrusion  162  may also be configured to engage with a slider member  117  to displace the trocar  160  relative to the inner cannula  150  from a retracted configuration to an extended configuration as depicted in  FIGS. 3A and 3B . In the extended configuration the penetrating tip  161  extends distally beyond the inner cannula  150 , and in the retracted position the penetrating tip  161  is disposed within the inner cannula  150 . In certain embodiments, the trocar  160  may include a longitudinally extending groove or trough  163 . The groove  163  may have a substantially V-shape and be configured for passage of a guidewire through the lumen  153  of the inner cannula  150 . 
     As illustrated in  FIGS. 2-4 , the slider member  117  may be slidingly coupled to the handle housing  111 . The slider member  117  may also be sliding coupled to the inner cannula  150 . The protrusion  162  is shown to extend through the slot  154  and is disposed distal to the slider member  117 . When the slider member  117  is displaced from a proximal position to a distal position, as shown in  FIG. 3 , the slider member  117  engages the protrusion  162  to displace the trocar  160  from the retracted configuration to the extended configuration. The slider member  117  may be locked in the distal position when engaged with a locking member  135  of the handle housing  111 . When the slider member  117  is locked in the distal position, the trocar  160  is also locked in the extended configuration. A resilient member or compression spring  134  may be disposed distal to the protrusion  162  and the slider member  117 . The resilient member  134  can be compressed when the slider member  117  is displaced to the distal position. When the slider member  117  is unlocked from the distal position, the resilient member  134  may decompress and apply a proximally directed force to the protrusion  162  and the slider member  117  to displace the slider member  117  to the proximal position and the trocar  160  to the retracted configuration. The resilient member  134  may bias the slider member  117  to the proximal position. 
     In the illustrated embodiment of  FIG. 2 , the handle housing  111  also includes a core tissue sample length scale  118  disposed adjacent the slider member  117 . The scale  118  may include a plurality of indices, e.g., lines, spaced equidistance apart. In some embodiments, a distance between the lines may be 0.5 mm, one millimeter, two millimeters, five millimeters, 10 millimeters, etc. The scale  118 , in cooperation with the slider member  117 , may be used to determine a length of a core tissue sample that is contained within the lumen  153  of the inner cannula  150 . For example, the slider member  117  and the trocar  160  may be displaced distally until the penetrating tip  161  engages with the core tissue sample and the practitioner feels increased resistance to displace the slider member  117 . A portion of the slider member  117  may be adjacent to one line of the scale  118  that correlates with a length of the core tissue sample. 
     As depicted in the illustrated embodiment of  FIGS. 2 and 5A , the coax assembly  170  may be selectively coupled to the handle assembly  110 . The coax assembly  170  may include the second worm gear  128 , a coax connector  171 , and an outer coax cannula  173 . The coax connector  171  may include a coupling member  172  configured to mate with a receiving member  120  of the handle assembly  110 . For example, coax connector  171  and the handle assembly  171  may be coupled together using a bayonet mount. The coupling member  172  may be a laterally extended protrusion sized to be received by a channel of the receiving member  120 . The channel of the receiving member  120  may be substantially L-shaped such that the protrusion is proximally inserted into the channel and then rotated to lock the handle assembly  110  and the coax assembly  170  together. When the coax assembly  170  is selectively removed from the handle assembly  110 , the coax connector  171  and coupling member  172  are rotated in an opposite direction than when locking and displaced distally. Other types of coupling mechanisms may be contemplated and are within the scope of this disclosure. 
     The outer coax cannula  173  extends distally from the worm gear  128  and is rotatably coupled to the coax connector  171 . In other words, the outer coax cannula  173  is rotatable relative to the coax connector  171 . The coax connector  171  can also be coupled such that it does not translate longitudinally (e.g., distally and/or proximally) on the outer coax cannula  173 . The inner cannula  150  is coaxially disposed within a lumen  176  of the outer coax cannula  173 . The inner cannula  150  may not extend distally beyond the outer coax cannula  173 . The outer coax cannula  173  may include a cutting tip, such as a trephine tip  174  having a plurality of teeth  175  configured to rotate and saw a hole into a bone lesion and/or bone marrow when the outer coax cannula  173  is rotated. In some embodiments, the teeth  175  may be in alignment with a longitudinal axis of the outer coax cannula  173 . In other embodiments, the teeth  175  may be alternatingly biased inward and outward relative to the longitudinal axis. In the illustrated embodiment, a depth limiting member  177  is slidably coupled to the outer coax cannula  173 . The depth limiting member  177  may be used to indicate an insertion depth of the outer coax cannula  173  into the patient that may correlate to a core tissue sample length. In some embodiments, the outer coax cannula  173  may be rotatable relative to the depth limiting member  177 . In this embodiment, the depth limiting member  177  may be held by a user while the outer coax cannula  173  is rotating to guide the outer coax cannula  173  into the patient. 
     A proximal end of the outer coax cannula  173  can extend proximally from the coax connector  171 . The second worm gear  128  may be fixedly coupled to the proximal end. When the coax assembly  170  is coupled to the handle assembly  110 , the second worm gear  128  engages with the worm screw  126  such that the motor  122  rotates the second worm gear  128  and the outer coax cannula  173  at the same speed as the inner cannula  150  and the trocar  160  are rotated. In other embodiments, the rotation speed of the outer coax cannula  173  may be different, e.g., either faster or slower, than the rotation speed of the inner cannula  150  and the trocar  160 . In still other embodiments, the rotation direction of the outer coax cannula pin passages  173  may be different than the rotation direction of the inner cannula  150  and the trocar  160 . 
     As depicted in the illustrated embodiment of  FIG. 2 , the power pack  180  is selectively removably disposed within a power pack pocket  114  of the grip portion  113  of the handle housing  111 . A removable cap  119  may retain the power pack  180  within the handle housing  111 . The power pack  180  may include a case  181  containing a power source  182 , a controller  183 , and a connector  184 . The power source  182  may include a single battery or a plurality of batteries. The battery or batteries may be replaceable or rechargeable. The controller  183  may include a printed circuit board that is electrically coupled to the power source  182 , the motor  122 , and the motor activation switch  124 . The controller  183  can be configured to control activation and speed of the motor  122  when the motor activation switch  124  is actuated by the practitioner. The connector  184  may selectively electrically couple the power pack  180  to the handle assembly  110 . Following a bone biopsy procedure, the power pack  180  may be selectively removed from the bone biopsy device  100 . The handle assembly  110  and outer coax assembly  170  can be disposed of. As previously mentioned, the motor  122  can also be selectively removed from the handle assembly  110  if desired. When removed, the power pack  180  and/or motor  122  may be refurbished for use in a subsequent procedure. Refurbishment may include cleaning, sterilizing, recharging or replacing the power source  182  and/or motor  122 , etc. Alternatively, the power pack  180  (and/or motor  122 ) may be disposed of in an environmentally friendly manner. The bone biopsy device  100  may be disposed of following standard procedures for disposal of a medical device. 
     In use, the bone biopsy device  100  can be used to obtain a core tissue sample from a bone lesion and/or bone marrow. The power pack  180  can be inserted into the handle assembly  110 . The cap  119  can be coupled to the handle assembly  110  to retain the power pack  180  within the handle assembly  110  and to prevent contamination of the power pack  180  with body fluids. The coax assembly  170  may be coupled to the handle assembly  110 . The slider member  117  can be displaced distally and locked in the distal position such that the trocar  160  is displaced from the retracted configuration to the extended configuration. In the extended configuration, the penetrating tip  161  extends distally beyond the outer coax cannula  173 . 
     As depicted in  FIG. 7A , in certain instances, the trocar  160  may be optionally inserted into the patient over a guidewire  106  that passes through the inner cannula  150  via the trocar groove  163 . The guidewire  106  can then be removed prior to rotating the outer coax cannula  173 , the inner cannula  150 , and trocar  160 . In other instances, rotation of the outer coax cannula  173 , the inner cannula  150 , and the trocar  160  can begin prior to removal of the guidewire  106 . For example, rotation of the outer coax cannula  173 , the inner cannula  150 , and the trocar  160  and engagement into the bone can be initiated, after which the guidewire  106  can be removed. 
     As depicted in  FIG. 7B , the trocar  160 , the inner cannula  150 , and the outer coax cannula  173  can be inserted through the patient&#39;s skin  101  as a unit until the penetrating tip  161  is adjacent a bone  102  (optionally with a guide wire if desired). The trocar  160  is in the extended configuration and the slider member  117  is locked in the distal position. 
       FIG. 7C  illustrates the trocar  160  drilled through the cortical layer  103  of the bone  102 . To drill the trocar  160  through the cortical layer  103  of the bone  102 , the motor  122  can be activated when the motor activation switch  124  is actuated by the practitioner. In some embodiments, the practitioner can control the motor speed through the motor activation switch  124 . For example, the practitioner may partially actuate the motor activation switch  124  to run the motor  122  at a first speed and fully actuate the motor activation switch  124  to run the motor  122  at a second speed, third speed, fourth speed. etc. The motor  122  can rotate the transmission  125  to rotate the trocar  160  to drill through the cortical layer  103  of the bone  102  until the cutting tip  174  of the outer coax cannula  173  is adjacent a bone lesion and/or bone marrow  104 . In certain embodiments, the depth limiting member  177  may be positioned on the outer coax cannula  173  to limit an insertion depth to a desired core tissue sample length. 
       FIG. 7D  illustrates the slider member  117  unlocked and displaced to the proximal position. The trocar  160  is displaced from the extended configuration to the retracted configuration. The motor  122  may be activated to rotate the outer coax cannula  173 , the inner cannula  150 , and the trocar  160 . The cutting tip  174  of the outer coax cannula  173  may saw a hole into the bone lesion and/or bone marrow  104 . A core tissue sample  106  may be disposed within the inner cannula  150  as the cutting tip  174  saws the hole into the bone lesion and/or bone marrow  104 . In certain embodiments, a part-off tab  155  or other sampling mechanism (not shown) may be actuated while the inner cannula  150  is rotating or stationary to sever the core tissue sample  106  from the bone lesion and/or bone marrow  104 . The direction of rotation can also be reversed to sever the core tissue sample  106 . In some embodiments, the core tissue sample length scale  118  may be used to determine a length of the core tissue sample  106  disposed within the inner cannula  150  by distally displacing the slider member  117  and the trocar  160  until the penetrating tip  161  engages with the core tissue sample  106  and resistance to distal movement of the slider member  117  is sensed by the practitioner. A portion of the slider member  117  may correspond to an indicium of the core tissue sample length scale  118  to indicate the length of the core tissue sample  106 . 
       FIG. 7E  depicts the coax assembly  170  decoupled from the handle assembly  110 . The inner cannula  150  and the trocar  160  are removed from the outer coax cannula  173 . The outer coax cannula  173  may be left in the patient for obtaining subsequent core tissue samples and or biopsy samples. In other embodiments, the coax assembly  170  may not be decoupled from the handle assembly  110  and the outer coax cannula  173  may be removed from the patient. 
       FIG. 7F  illustrates the core tissue sample  106  ejected from the inner cannula  150  when the slider member  117  is displaced from the proximal position to the distal position and the trocar  160  is displaced from the retracted configuration to the extended configuration. As the trocar  160  is displaced to the extended position, the penetrating tip  161  may push against the core tissue sample  106  to displace it distally from the inner cannula  150 . 
     In some instances, as depicted in  FIG. 7G , an aspiration needle  107  and aspiration device (e.g., syringe, vacuum sample collection tube, or pump, etc.)  108  may be used to obtain a core tissue sample  106  of the bone marrow  104 . For example, the needle may be inserted into the bone marrow  104  through the outer coax cannula  173  (which can be seated in the bone and/or patient after being decoupled from the handle assembly  110 ). The aspiration device  108  can then be used to aspirate a tissue sample of the bone marrow  104  through the needle. 
       FIGS. 8-10  depict an embodiment of a bone biopsy device  200  that resembles the bone biopsy device  100  described above in certain respects. Accordingly, like features are designated with like reference numerals, with the leading digit incremented to “2.” For example, the embodiment depicted in  FIGS. 8-10  includes a handle assembly  210  that may, in some respects, resemble the handle assembly  110  of  FIG. 1 . Relevant disclosure set forth above regarding similarly identified features thus may not be repeated hereafter. Moreover, specific features of the handle assembly  110  and related components shown in  FIGS. 1-7G  may not be shown or identified by a reference numeral in the drawings or specifically discussed in the written description that follows. However, such features may clearly be the same, or substantially the same, as features depicted in other embodiments and/or described with respect to such embodiments. Accordingly, the relevant descriptions of such features apply equally to the features of the bone biopsy device  200  and related components depicted in  FIGS. 8-10 . Any suitable combination of the features, and variations of the same, described with respect to the bone biopsy device  100  and related components illustrated in  FIGS. 1-7G  can be employed with the bone biopsy device  200  and related components of  FIGS. 8-10 , and vice versa. This pattern of disclosure applies equally to further embodiments depicted in subsequent figures and described hereafter, wherein the leading digits may be further incremented. 
       FIGS. 8-10  illustrate another embodiment of a bone biopsy device  200 . The bone biopsy device  200  can include a handle assembly  210 , a coax assembly  270 , and a power pack  280 . The handle assembly  210  may include a motor  222  and a transmission  225 . As depicted in  FIG. 9 , the motor  222  is oriented parallel to a horizontal axis of a handle housing  212 . The motor  222  includes a drive shaft  223  extending distally from the motor  222 . 
     As shown in  FIGS. 9-10 , the transmission  225  may include a plurality of spur gears configured to provide a plurality of gear reductions and to rotate an inner cannula  250 , a trocar  260 , and an outer coax cannula  273 .  FIGS. 9-10  depict a first spur gear  237  that is fixedly coupled to the drive shaft  223 . A second spur gear  238  is radially offset from and engages the first spur gear  237 . The second spur gear  238  may be configured to rotate freely around the inner cannula  250 . The engagement of the first spur gear  237  and the second spur gear  238  may provide a first gear reduction. 
     A third spur gear  239  may be fixedly coupled to the second spur gear  238  and be configured to rotate freely around the inner cannula  250  with the second spur gear  238 . A fourth spur gear  240  may be disposed adjacent the first spur gear  237  on the drive shaft  223  and be configured to engage with the third spur gear  239 . The fourth spur gear  240  may be configured to rotate freely around the drive shaft  223 . The engagement of the fourth spur gear  240  and the third spur gear  239  may provide a second gear reduction. A fifth spur gear  241  may be fixedly coupled to the fourth spur gear  240  and be configured to rotate freely around the drive shaft  223 . A length of the fifth spur gear  241  may be longer than a length of the first spur gear  237  such that the fifth spur gear  241  can engage with a sixth and a seventh spur gear  242 ,  243 . 
     The sixth spur gear  242  can be disposed adjacent the third spur gear  239  and can be fixedly coupled to the inner cannula  250  such that rotation of the sixth spur gear  242  causes rotation of the inner cannula  250  and the trocar  260 . The sixth spur gear  242  may be configured to engage with the fifth spur gear  241  and may provide a third gear reduction. The seventh spur gear  243  can be disposed adjacent the sixth spur gear  242  and can be fixedly coupled to the outer coax cannula  273  such that rotation of the seventh spur gear  243  causes rotation of the outer coax cannula  273 . The seventh spur gear  243  may be configured to engage with the fifth spur gear  241  and may provide a fourth gear reduction. 
     In certain embodiments, an overall gear reduction ratio from the first spur gear  237  to the sixth and seventh spur gears  242 ,  243  may range from about 50:1 to about 20:1, or from about 40:1 to about 30:1. Thus, a rotation speed of the inner cannula  250 , the trocar  260 , and the outer coax cannula  273  may range from about 0 rpm to about 4,000 rpm, from about 0 rpm to about 1000 rpm, from about 0 rpm to about 500 rpm and from about 200 rpm to about 300 rpm. 
     Use of the biopsy device  200  can be similar to the biopsy device  100  previously discussed. For example, a trocar can be extended to facilitate insertion of an outer coax cannula and inner cannula into the skin of a patient. The trocar may be rotated by a motor to drill through the cortical layer of the bone. The outer coax cannula and the inner cannula can be rotated by the motor to saw a hole into the bone lesion and/or bone marrow and collect a core tissue sample within the inner cannula. The inner cannula and the trocar may be removed from the outer coax cannula. The trocar can then be extended to eject the core tissue sample from the inner cannula. 
     Any methods disclosed herein comprise one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified. 
     References to approximations are made throughout this specification, such as by use of the term “substantially.” For each such reference, it is to be understood that, in some embodiments, the value, feature, or characteristic may be specified without approximation. For example, where qualifiers such as “about” and “substantially” are used, these terms include within their scope the qualified words in the absence of their qualifiers. For example, where the term “substantially perpendicular” is recited with respect to a feature, it is understood that in further embodiments, the feature can have a precisely perpendicular configuration. 
     Similarly, in the above description of embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. 
     The claims following this written disclosure are hereby expressly incorporated into the present written disclosure, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. Moreover, additional embodiments capable of derivation from the independent and dependent claims that follow are also expressly incorporated into the present written description. 
     Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the invention to its fullest extent. The claims and embodiments disclosed herein are to be construed as merely illustrative and exemplary, and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having ordinary skill in the art, with the aid of the present disclosure, that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the disclosure herein. In other words, various modifications and improvements of the embodiments specifically disclosed in the description above are within the scope of the appended claims. Moreover, the order of the steps or actions of the methods disclosed herein may be changed by those skilled in the art without departing from the scope of the present disclosure. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order or use of specific steps or actions may be modified. The scope of the invention is therefore defined by the following claims and their equivalents.