Abstract:
A composite instrument is provided comprising a first functional instrument and a second functional instrument when the first functional instrument is coupled with the second functional instrument. A composite handle for the composite instrument is provided comprising a first handle and a second handle when the first handle is coupled with the second handle. The handle makes possible the reliable transmission, with increased mechanical advantage, of both torsional and longitudinal loads by the physician to the composite instrument, while resisting relative rotation between the first and second instruments.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of copending U.S. patent application Ser. No. 09/421,635, filed Oct. 19, 1999, and entitled “Hand-Held Instruments that Access Interior Body Regions,” which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention generally relates to hand-held tools and instruments and to procedures that deploy these instruments through tissue to access interior regions of the body. 
     BACKGROUND OF THE INVENTION 
     There are many different types and styles of hand-held surgical instruments that physicians use to gain access into interior body regions. These instruments are intended to penetrate tissue by the application of pushing forces, twisting forces, or both in combination. 
     Often, a single surgical procedure will require the physician to employ different surgical instruments, each possessing a different shape, size, and function. Often, the procedure will require the physician to deploy these instruments in both soft and hard tissue to meet the diagnostic or therapeutic objectives of the procedure. The physician will often need an enhanced mechanical advantage to advance an instrument through tissue, particularly through dense or hard tissue, such as bone. 
     The common need to use different instruments in a given procedure, coupled with the need to accurately and reliably deploy each of these different instruments through both soft and hard tissue, often with an enhanced mechanical advantage, complicate the physician&#39;s already difficult task. The need to handle different instruments in different ways for different purposes can distract the physician and lead to wasted effort, which can lengthen the overall time of the procedure. 
     SUMMARY OF THE INVENTION 
     The invention provides a surgical instrument with a handle design that allows initial placement of both a cannula and a trocar into interior body regions, and allows for later withdrawal of the trocar while leaving the cannula in place. The invention obviates the need for several instruments during surgical procedures, and simplifies interior access protocol. At the same time, the handle of the surgical instrument makes possible the reliable transmission, with increased mechanical advantage, of both torsional and longitudinal loads by the physician to the selected instrument. 
     One aspect of the invention provides a tool comprising a first functional instrument having a first handle and a second functional instrument having a second handle. The first functional instrument engages the second functional instrument, forming a composite instrument. The first handle mates with the second handle, forming a composite handle for the composite instrument. The composite handle includes a latching mechanism to resist disengagement of the first and second functional instruments. 
     Features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first functional instrument engaging a second functional instrument to form a composite tool having a composite handle that the handles of the first and second instruments form; 
     FIG. 2 is a perspective view of the first instrument separated from the second instrument; 
     FIG. 3 is a perspective view of a hand engaging the composite handle of the tool shown in FIG. 1; 
     FIG. 4 is a perspective view of a hand engaging the handle of the second functional instrument when separated from the first functional instrument; 
     FIG. 5 is an enlarged perspective view of the handles of the first and second functional instruments, when separated, showing a coupling system than resists relative rotation between the functional instrument when the composite tool is formed; 
     FIG. 6A is an enlarged side view of the handles shown in FIG. 5, when separated; 
     FIG. 6B is an enlarged side view of the handles shown in FIG. 5, when mated together to form the composite handle; 
     FIG. 6C is a side view of a trocar suited for use with the composite handle of FIG. 6B; 
     FIG. 6D is a side view of a cannula suited for use with the composite handle of FIG. 6B; 
     FIG. 7A is a lateral view of a human spinal column; 
     FIG. 7B is a coronal view, with portions broken away and in section, of a human vertebral body, which is part of the spinal column; 
     FIG. 8 is a lateral view, with portions broken away and in section, of several vertebral bodies, which are part of the spinal column; 
     FIG. 9 is a perspective view showing advancement of the composite instrument through tissue, by using the composite handle to supply a twisting and/or pushing force; 
     FIG. 10 is a top view showing deployment of the composite instrument in a vertebral body, by using the composite handle to apply an axial and/or torsional force; 
     FIG. 11 is a top view of the vertebral body, showing deployment of a drill bit through a cannula instrument, which forms a part of the composite tool shown in FIG. 9; 
     FIG. 12 is a top view of the vertebral body showing deployment of an expandable structure in a collapsed condition through the cannula instrument that forms a part of the composite tool shown in FIG. 9; 
     FIG. 13 is a top view of the vertebral body after the structure shown in FIG. 12 is expanded to compact cancellous bone and form a cavity; 
     FIG. 14 is a top view of a syringe and attached nozzle in use to inject material into the cannula instrument for passage into the cavity shown in FIG. 13; 
     FIG. 15 is a side view showing advancement of a tamping instrument in the cannula instrument to displace and distribute material from the cannula instrument into the cavity shown in FIG. 13; 
     FIG. 16 is a side view of a syringe attached to the cannula instrument that forms a part of the composite tool shown in FIG. 9, for the purpose of conveying material through the cannula instrument into bone; 
     FIGS. 17A and 17B are perspective views showing material deformation that occurs in each handle as a result of heat sterilization, to prevent subsequent formation of the composite handle; 
     FIG. 18 a perspective view of an alternative embodiment of a composite tool like that shown in FIG. 1, with an interior lumen to accommodate passage of a spinal needle assembly to aid deployment; 
     FIG. 19 is a front perspective view of another embodiment of a composite tool formed by a first functional instrument engaging a second functional instrument, and also having a composite handle that the handles of the first and second instruments form; 
     FIG. 20 is a rear elevation view of the composite tool shown in FIG. 19; 
     FIG. 21 is a perspective view of the composite tool shown in FIG. 10, as the first and second instruments are being separated; 
     FIG. 22 is a perspective view of the first instrument separated from the second instrument; 
     FIG. 23 is a section view of the latching mechanism for the composite tool, taken generally along line  23 — 23  in FIG. 20; and 
     FIG. 24 is a section view of the latching mechanism shown in FIG. 23, with the associated latch finger moved out of its normal latching position by the application of an external force. 
    
    
     The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This Specification describes new instruments for penetrating tissue. This specification also describes systems and methods to treat bones using expandable bodies in conjunction with new instruments for penetrating tissue. 
     The use of expandable bodies to treat bones is generally disclosed in U.S. Pat. Nos. 4,969,888 and 5,108,404, which are incorporated herein by reference. Improvements in this regard are disclosed in U.S. patent application Ser. No. 08/188,224, filed Jan. 26, 1994; U.S. patent application Ser. No. 08/485,394, filed Jun. 7, 1995; and U.S. patent application Ser. No. 08/659,678, filed Jun. 5, 1996, which are each incorporated herein by reference. 
     The new instruments, systems and methods will be described with regard to the treatment of vertebral bodies. It should be appreciated, however, that the handle configuration, instruments, systems and methods so described are not limited in their application to vertebrae. The systems and methods are applicable to the treatment of diverse bone types. Additionally, the handle configuration could be used with instruments other than a trocar and a cannula. 
     I. The Instruments 
     FIG. 1 shows a composite instrument  10  for penetrating tissue. The composite instrument  10  includes a first functional instrument  20  and a second functional instrument  40 , and a composite handle  12  comprising a first handle  22  and a second handle  42 . The composite handle  12  aids a physician in manipulating the composite instrument  10 , but a physician can also desirably use the first handle  22  to independently manipulate the first instrument  20  or the second handle  42  to independently manipulate the second instrument  40  during use. 
     The number and type of instruments  20  and  40  can vary. FIG. 1 shows two representative instruments  20  and  40 , each having a different size and function. In a preferred embodiment, the first functional instrument  20  is a trocar instrument, and the second functional instrument  40  is a cannula instrument. 
     A. The Trocar Instrument 
     Referring to FIGS. 1-4, the first instrument  20  functions as a trocar instrument to penetrate tissue. A trocar  30  has a proximal end  32  and a distal end  34 . The distal end  34  is tapered to present a penetrating surface  35 . In use, the penetrating surface  35  is intended to penetrate soft tissue and/or bone in response to pushing and/or twisting forces applied by the physician at the first handle  22 , or the composite handle  12 . 
     The first handle  22  is coupled to the trocar  30  at the proximal end of the trocar  32 . As best seen in FIG. 6C, the proximal end  32  of the trocar  30  can be formed in a T-shape, with the first handle  22  being molded around the T-shaped end. This arrangement significantly increases the mechanical strength of the bond between the handle  22  and the trocar  30 , and allows significant longitudinal and torsional forces to be transmitted from the handle  22  to the trocar  30  without bond failure. Alternatively, with or without a T-shaped end, the proximal end  32  of the trocar  30  can be scored (indicated by scored region  33  in FIG. 6C) to increase the mechanical strength of the bond between the trocar  30  and the handle  22 , or various bonding adhesives could be used, with varying results. 
     The first handle  22  desirably includes a viewing window  24 , an alignment ridge receiver  26 , a handle bore receiver  28 , and a handle key  36 , the uses of which are described later. 
     In an alternative embodiment (see FIG.  18 ), the trocar  30  includes an interior lumen  21 , which passes through the handle  22  and the body of the trocar  30 . The interior lumen  21  accommodates passage of a stylet and/or conventional spinal needle assembly  23 , to guide the deployment of the first instrument  20 , by itself or nested with the second instrument  40  (as FIG. 18 shows), through soft tissue to a targeted bone treatment site. 
     B. The Cannula Instrument 
     The second instrument  40  functions as a cannula instrument or guide sheath, and includes a cannula  50 . The cannula  50  of the second instrument  40  is desirably somewhat larger in diameter than and not as long as the trocar  30  of the first instrument  20 . As best shown in FIGS. 1 and 2, the second instrument  40  includes an interior lumen  44  that extends through the instrument from its distal end  54  to its proximal end  52 . The interior lumen  44  is sized to accept the trocar  30 . The size of the interior lumen  44  desirably allows the second instrument  40  to slide and/or rotate relative to the first instrument  20 , and vice versa, as will be described in greater detail later. 
     The distal end  54  of the second instrument  40  presents an end surface  60 . In use, the end surface  60  of the second instrument  40  desirably presents a low-profile surface, which can penetrate soft tissue surrounding the first instrument  20  in response to pushing and/or twisting forces applied at the composite handle  12  or the second handle  42 . 
     The proximal end  52  is coupled with the second handle  42 . As best seen in FIG. 6D, the proximal end  52  of the cannula  50  desirably incorporates a flared and notched end “A” and a textured surface “B”, around which the second handle  42  is molded. The flared and notched end “A” and textured surface “B” serve to increase the mechanical strength of the bond between the cannula  50  and the second handle  42 , allowing significant longitudinal and torsional forces to be transmitted between the second handle  42  and cannula  50  without bond failure. As with the trocar  30 , however, alternative bonding methods such as scoring of the cannula  50  and/or the use of various adhesives could be employed, with varying results. 
     Extending from the interior lumen  44  at the proximal end  52  of the cannula  50 , the second handle  42  desirably includes a handle bore  48 , preferably co-circumferential with the cannula  50 . The second handle  42  includes an alignment ridge  46 , and a handle groove  56 , the uses of which are described later. 
     C. The Drill Bit Instrument 
     As shown in FIG. 11, an optional third functional instrument  70  functions as a drill bit. The drill bit instrument  70 , having a distal end  72  and a proximal end  74 , typically is slightly longer than and has generally the same physical dimensions as, the trocar  30 . Like the trocar  30 , the drill bit instrument  70  is intended, in use, to fit for sliding and rotational movement within the interior lumen  44  of the second instrument  40 . 
     The distal end  72  of the drill bit instrument  70  desirably includes cutting edges  76 . In use, the cutting edges  76  are intended to penetrate hard tissue in response to rotation and longitudinal load forces applied at the proximal end  74  of the drill bit instrument  70 . 
     The drill bit instrument  70  can be of known construction, and could vary widely. Desirably. the diameter of the drill bit instrument  70  is smaller than the interior lumen  44  of the second instrument  40 , and the length is longer than the cannula  50 , such that the drill bit instrument  70  can access tissue deeper than the cannula  50  when the cannula  50  is installed in a patient. 
     II. The Instrument Handles 
     The first handle  22  and the second handle  42  are designed to comfortably accommodate a hand, to desirably interlock to form a composite handle  12  that resists relative rotation between the first handle  22  and the second handle  42 , and desirably to indicate whether the instruments have been reused and/or resterilized. 
     A. Hand Accommodation 
     As shown in FIGS. 1-4, the composite handle  12  is shaped to be comfortably and securely grasped by a normal human hand as shown in FIG.  3 . Preferably, the contours of the composite handle  12  are rounded to provide a comfortable grip and to minimize surgical glove tears. 
     As shown in FIG. 3, in the preferred embodiment, the first handle  22  is desirably equipped with two finger receivers  38 , intended to receive the index finger and the pinkie finger of a physician. 
     Shown in FIG. 4, in the preferred embodiment, the second handle  42  is desirably equipped with two finger receivers  58 , intended to receive the middle finger and the ring finger of a physician. 
     The shape and size of the first handle  22  and second handle  42 , of course, vary. In the embodiment shown in FIG. 1, the composite handle  12 , and in particular the first handle  22 , includes a striking plate  14 , elongated to fit comfortably across the palm of the hand. The striking plate  14  is also configured to receive a striking blow, described later. 
     B. Interlocking Configuration 
     In order to properly interact when applying striking, pushing and/or twisting forces to the composite handle  12 , the first handle  22  desirably will not rotate relative to the second handle  42 . Referring now to FIGS. 5,  6 A and  6 B, to avoid relative rotation, the first handle  22  preferably includes the alignment ridge receiver  26  to receive the alignment ridge  46  of the second handle  42 . Although described and pictured as a ridge, the alignment mechanism interaction between the first handle  22  and the second handle  42  could comprise any number of shapes other than an arcuate shape, for example a block shape or a star shape. 
     In use, when the trocar  30  of the first instrument  20  is slid through the cannula  50  of the second instrument  40 , the first handle  22  and second handle  44  can fit together to form the composite handle  12 . In addition to the alignment ridge  46  resisting rotation because of the alignment ridge receiver  26 , the first handle  22  can include a handle key  36  for coupling with the handle groove  56  of the second handle  42 . 
     If the handle groove  56  is not aligned with the handle key  36 , and thus the alignment ridge  46  not aligned with the alignment ridge receiver  26 , the handle bore  48  of the second handle  42  desirably will not fully insert into the handle bore receiver  28  of the first handle  22 . In this alignment, the viewing window  24  will display the trocar  30 , which preferably extends past the viewing window  24 . Also in this alignment, the first handle  22  is desirably able to rotate independently of the second handle  42 . 
     If, however, as shown in FIG. 6B, the handle groove  56  is aligned with the handle key  36 , and thus the alignment ridge  46  is aligned with the alignment ridge receiver  26 , the handle bore  48  of the second handle  42  can be fully inserted into the handle bore receiver  28  of the first handle  22 . 
     In this operational alignment, the viewing window  24  displays the handle bore  48 . Preferably, the handle bore  48  is a different color than the trocar  30  such that visualization would be simplified. Also in this alignment, the first handle  22  desirably does not rotate independently of the second handle  42 . In this alignment, the composite handle  10  is sized and shaped to accommodate four fingers, two fingers each on the first handle  22  and the second handle  42 . 
     Of course, its should be understood that the first and second handles  22  and  42  could be designed to engage in non-parallel orientations, such that the first and second handles  22  and  42  would not be parallel when properly engaged to form the composite handle  10 . For example, the first handle  22  could incorporate a star or hexagonal shaped opening, into which a corresponding star or hexagonal shaped second handle  42  could engage in a multiplicity of orientations. 
     In use, various forces resist relative motion between the first instrument  20  and the second instrument  40 . As shown in FIG. 3, when a hand grips the composite handle  10 , the upward force supplied by the fingers, coupled with the downward force supplied by the palm, will compress the first instrument  20  and the second instrument  40  together. As previously noted, when properly configured, relative rotation of the instruments is desirably constrained as well. 
     C. Handle Materials 
     1. Structural Integrity 
     The material chosen for the first handle  22  and the second handle  42  desirably provides sufficient structural integrity to withstand manual manipulation and forces expected from manual striking blows. The first handle  22  and the second handle  42  are made from a molded or cast rigid material sufficient in strength to withstand the striking, pushing and twisting forces without significant deformation. 
     Another preferable characteristic of the handle composition is that the first handle  22  and the second handle  42  can be roughened or otherwise textured to provide a secure gripping surfaces. 
     2. Reuse 
     To encourage single use and discourage reuse and/or resterilization, it is preferable to differentiate between new hand tools and hand tools that have been reused and/or resterilized. 
     Striking and exertion of manual pressure on any of the instruments and structures described herein during first use generates stress on the material or materials which make up the instruments and/or structure. The material stress created by operational loads during first use can significantly alter the molded morphology of the structure, making future performance of the structure unpredictable. 
     For example, during advancement of the trocar and the cannula into the cancellous bone during a single use creates contact with surrounding cortical and cancellous bone. This contact can damage the structure, creating localized regions of weakness, which often can escape visual detection. The existence of localized regions of weakness can unpredictably cause structural failure during a subsequent use. Such contact can also cause flattening and/or curling of the end surface of the cannula, or dulling of the penetrating surface of the trocar. 
     In addition, exposure to blood and tissue during a single use can entrap biological components on or within the structure of the cannula or handles. Despite cleaning and subsequent sterilization, the presence of entrapped biological components can lead to unacceptable pyrogenic reactions. 
     As a result, following first use, the structure might not meet established performance and sterilization specifications. The effects of material stress and damage caused during a single use, coupled with the possibility of pyrogen reactions even after resterilization, reasonably justify and encourage single use for the instruments and handles that are deployed in tissue and bone. 
     To protect patients from the potential adverse consequences occasioned by multiple use, which include disease transmission, or material stress and instability, or decreased or unpredictable performance, various materials may be used to indicate and possibly prevent re-use and /or resterilization of the hand tools. 
     For example, a heat degradable material can be used to indicate, through deformation, whether a hand tool has been autoclaved. Additionally, chemical sensitive pigments, such as inks commercially available from Tempil, could be applied to the composite handle  12  to indicate, through a change of color, whether a hand tool has been chemically sterilized, for instance by use of ethylene oxide (ETO), as described in the requirements of ANSI/AAMI/ISO11135:1994 for sterilizing devices. In addition, various materials which change color and/or physical composition in the presence of other sterilization methods, such as radiation sterilization, can be incorporated into hand tools to indicate sterilization. 
     One material that provides sufficient structural rigidity and yet indicates whether an instrument has been exposed to heat common to sterilization is LUSTRAN™ material, which is commercially available from Bayer. As shown in FIGS. 17A and 17B, when this material is used in handle construction, the material will typically deform during heat sterilization, desirably preventing the handle groove  56  from aligning with the handle key  36 , and thus preventing the alignment ridge  46  from aligning with the alignment ridge receiver  26 . Additionally, following deformation, the handle bore  48  of the second handle  42  desirably cannot be fully inserted into the handle bore receiver  28  of the first handle  22 . 
     III. Illustrative Use of the System 
     The following describes use of the composite instrument  10 , instruments  20 ,  40 , and  70 , in conjunction with a catheter component  130 , a diagnostic or therapeutic element  132 , a syringe  136  and a tamping instrument  142  as shown in FIGS. 9-15 in the context of treating bones. This is because these items can be advantageously used for this purpose. Still, it should be appreciated that the composite instrument  10  is not limited to use in the treatment of bones, nor limited to instruments intended to contact tissue to perform a diagnostic or therapeutic function. The composite handle  12  configuration associating the first handle  22  and the second handle  42  can be used in association with various other hand-held instruments. 
     The composite instrument  10 , handles  12 ,  22 , and  42 , and instruments  20 ,  40 ,  64  and  70  will now be described with regard to the treatment of human vertebra. It should be appreciated, however, their use is not limited to human vertebrae. The handle  18  can be used in association with hand-held instruments in the treatment of diverse human or animal bone types. 
     A. Vertebral Anatomy 
     One use of the system is to treat vertebral bodies. As FIG. 7A shows, the spinal column  80  comprises a number of uniquely shaped bones, called the vertebrae  82 , a sacrum  84 , and a coccyx  86  (also called the tail bone). The number of vertebrae  82  that make up the spinal column  80  depends upon the species of animal. In a human (which FIG. 7A shows), there are twenty-four vertebrae  82 , comprising seven cervical vertebrae  88 , twelve thoracic vertebrae  90 , and five lumbar vertebrae  92 . 
     When viewed from the side, as FIG. 7A shows, the spinal column  80  forms an S-shaped curve. The curve serves to support the head, which is heavy. In four-footed animals, the curve of the spine is simpler. 
     As FIGS. 7A,  7 B and  8  show, each vertebra  82  includes a vertebral body  96 , which extends on the anterior (i.e., front or chest) side of the vertebra  82 . As FIGS. 7A,  7 B and  8  show, the vertebral body  96  is in the shape of an oval disk. As FIGS. 7B and 8 show, the vertebral body  96  includes an exterior formed from compact cortical bone  98 . The cortical bone  98  encloses an interior volume  100  of reticulated cancellous, or spongy, bone  102  (also called medullary bone or trabecular bone). A “cushion,” called an intervertebral disk  104 , is located between adjacent vertebral bodies  96 . 
     An opening, called the vertebral foramen  106 , is located on the posterior (i.e., back) side of each vertebra  82 . The spinal ganglion  109  pass through the foramen  106 . The spinal cord  108  passes through the spinal canal  107 . 
     The vertebral arch  110  surrounds the spinal canal  107 . The pedicles  112  of the vertebral arch  110  adjoin the vertebral body  96 . The spinous process  114  extends from the posterior of the vertebral arch  110 , as do the left and right transverse processes  116 . 
     B. Surgical Technique 
     In a typical procedure, a patient lies on an operating table, while the physician introduces the composite instrument  10  into soft tissue (designated S in FIG. 9) in the patient&#39;s back. The patient can lie face down on the table, or on either side, or at an oblique angle, depending upon the physician&#39;s preference. Moreover, the procedure can be performed through an open anterior procedure or an endoscopic anterior procedure. 
     1. Accessing Cancellous Bone 
     Under radiologic or CT monitoring, the physician advances the composite instrument  10  through soft tissue S down to and into the targeted vertebra  82 , as FIG. 9 shows. The physician will typically administer a local anesthetic, for example, lidocaine, to the targeted region. In some cases, the physician may prefer other forms of anesthesia, such as general anesthesia. 
     As shown in FIG. 10, the physician directs the composite instrument  10  such that the trocar  30  of the first instrument  20  and the cannula  50  of the second instrument  40  penetrate the cortical bone  98  and the cancellous bone  102  of the targeted vertebra  82 . If desired, the physician twists the composite handle  10  while applying longitudinal force to the handle  10 . In response, the penetrating surface  35  of the trocar  30 , and the end surface  60  of the cannula  50  rotate and penetrate soft tissue and/or bone. 
     Preferably the depth of penetration of the distal end  34  of the trocar  30  and the end surface  60  of the cannula  50  are through a first wall of the cortical bone  98  and into the cancellous bone  102 . However, if the penetration through the first wall of the cortical bone  98  and into the cancellous bone  102  is not achievable by manual advancement of the composite instrument  10 , a physician can continue penetration by gently striking the striking plate  14  with a blunt instrument such as a surgical hammer (not shown), or otherwise applying appropriate additional longitudinal force to the composite handle  12 , to advance the distal end  34  of the trocar  30  and the end surface  60  of the cannula  50 . 
     If desired, the physician can utilize a spinal needle assembly and stylet to initially access the vertebral body  82 , and then utilize the alternative embodiment shown in FIG. 18 to complete the access procedure. The embodiment shown in FIG. 18 allows the physician to place a stylet  23  into the targeted vertebral body  82 , and then guide the composite instrument  10  through soft tissue and into the targeted vertebra body  82  along the stylet  23 , which passes through the trocar lumen  21  as the composite instrument  10  is advanced through soft tissue and into the vertebral body  82 . Once the trocar  30  has sufficiently penetrated cortical bone, the physician can withdraw the spinal needle assembly  23 . 
     After penetrating the cortical bone  98 , if desired, the physician may continue advancing the composite instrument  10  through the cancellous bone  102  of the vertebral body  96 , thereby forming a passage through the cancellous bone  102 . Preferably this passage will extend no more than 95% across the vertebral body. The physician may then withdraw the instrument  10 , such that the cannula  50  remains within the cortical bone  98  and/or extends only part-way into the cancellous bone  102 . The trocar  30  may then be withdrawn from the cannula  50 , allowing access to the passage formed in the interior of the vertebral body  82  through the cannula  50 . 
     Alternatively, after penetrating the cortical bone  98 , the physician may choose to withdraw the trocar  30  from the cannula  50  and form a passage in the cancellous bone  102  using a drill bit  70 . In such a case, the physician removes the first functional instrument  20  by holding the second instrument  40  in place and manually withdrawing the first instrument  20 . 
     Next, as shown in FIG. 11, the physician advances the drill bit  70  through the cannula  50 . Under X-ray control (or using another external visualizing system), the physician applies appropriate twisting and longitudinal forces to the drill bit  70 , to rotate and advance the cutting edge  76  of the drill bit  70  to open a passage through the bone tissue and completely into the cancellous bone  102 . The drilled passage preferably extends no more than 95% across the vertebral body  96 . 
     At this point in the procedure, access to the cancellous bone  102  has been accomplished and the end surface  60  of the cannula  50  extends into the interior volume  100 , leaving only the cannula instrument  50  in place. 
     2. Bone Treatment 
     As shown in FIG. 12, the physician can now acquire the catheter component  130 . The physician can advance the diagnostic or therapeutic element  132  carried by the catheter component  130  through the handle bore  48  and cannula  50  and into the interior volume  100  of the vertebral body  96 . 
     The distal diagnostic or therapeutic element  132  of the catheter component  130  can be configured to perform various functions. For example, the element  132  can comprise a biopsy instrument, to obtain samples of cancellous bone or to harvest bone marrow. Alternatively, the distal element  132  can be a stylet to introduce a medication or the like into cancellous bone. Still alternatively (as shown in FIG.  13 ), the distal element  132  can comprise an expandable body to compact cancellous bone  102  and form a cavity  134  in the vertebral body  96 , in the manner disclosed in U.S. Pat. Nos. 4,969,888, 5,108,404, and 5,827,289, which are incorporated herein by reference. 
     Upon compaction of cancellous bone  102 , the distal element  132  can also include a nozzle  140  to inject a material into the formed cavity. 
     Upon formation of the cavity  134 , the physician acquires a syringe  136  and injection nozzle  140 . As FIG. 14 shows, the nozzle  140  is sized to pass through the cannula  50 , to thereby pass into the cavity  134 . The nozzle  140  connects by a threaded connector  186  to a syringe  136 . The nozzle  140  can be formed from a rigid metal material, e.g., stainless steel. 
     As FIG. 14 shows, the physician fills the syringe  136  with the desired volume of filling material  138 . The physician attaches the nozzle  140  to the filled syringe  136 . The physician inserts the nozzle  140  a selected distance beyond the distal end  54  of the cannula  50  and into the cavity, guided by markings  166  on the nozzle  140 . Next, the physician operates the syringe  136  to expel the material  138  through the nozzle  140  into the cavity  134 . 
     Desirably, the physician first introduces the material  138  into the region of the cavity  134  farthest from the distal end  54  of the cannula  54 . The physician successively draws the nozzle  140  toward the distal end  54  of the cannula  50 , while injecting the material  138 , to fill the remainder of the cavity  54 . 
     At this stage, the nozzle  180  is unthreaded from the syringe  104 . As FIG. 15 shows, the physician next advances a tamping instrument  142  through the nozzle  140 . The distal end of the tamping instrument  142  contacts the residual volume of material  138  in the nozzle  140 . Advancement of the tamping instrument  142  displaces the residual material  138  from the nozzle  140 , forcing it into the cavity  134 . The flow of material  138  into the cavity  134 , propelled by the advancement of the tamping instrument  142  in the nozzle  140  serves to uniformly distribute and compact the material  138  inside the cavity  134 , without the application of undue pressure. 
     As shown in FIG. 16, as an alternative to attaching the nozzle  140  to the syringe  136 , the physician can attach the syringe  136  directly to the handle bore  48  of the second instrument  40 . As shown in the alternate embodiment in FIG. 16, the syringe  136  can have threads  137  or other fasteners, such as snap-sit fasteners or luer-lock fasteners. The threads  137  would match with bore threads  49  contained in the handle bore  48 . Next, the physician operates the syringe  136  to expel the material  138  through the handle bore  48  and the cannula  50  and directly into the cavity  134 . In this arrangement, the physician disconnects the syringe  136  and advances the tamping instrument  142  through the handle bore  48  and the cannula  50  to displace the residual material  138  from the cannula  50 , forcing it into the cavity  134 . 
     The use of the syringe  136  with or without nozzle  140 , and the tamping instrument  142  allows the physician to exert precise control when filling the cavity  134  with material  138 . The physician can immediately adjust the volume and rate of delivery according to the particular local physiological conditions encountered. The application of low pressure (i.e., desirably no greater than 360 psi at the distal end of the cannula, more desirably no greater that 190 psi at the distal end of the cannula, and most desirably no greater than 100 psi at the distal end of the cannula), which is uniformly applied by the tamping instrument  142 , allows the physician to respond to fill volume, flow resistance, and flow path conditions quickly. The chance of overfilling and leakage of material  138  outside the cavity portion is thereby significantly reduced. 
     When the physician is satisfied that the material  138  has been amply distributed inside the cavity portion, the physician withdraws the tamping instrument  142  from the cannula  50  and handle bore  48 . The physician preferably first twists the tamping instrument  142  to cleanly break contact with the material  138 . 
     Of course, this procedure could be repeated to access and treat one vertebral body multiple times in multiple orientations to create multiple cavities that may or may not interconnect. After a cavity has been filled and tamped in the above described manner, the instruments can be withdrawn and the incision sites sutured closed. The bone treatment procedure is concluded. 
     C. Suggested Materials 
     Desirably, the material  138  will provide sufficient support within the vertebral body to prevent further fracture of the body. The capability of the vertebral bodies to withstand loads will have thereby been improved. The material may also facilitate healing of the vertebral body. 
     The selected material  138  can be a bone cement, or autograft or allograft bone graft tissue collected in conventional ways, e.g., in paste form (see Dick, “A Use of the Acetabular Reamer to Harvest Autogenic Bone Graft Material: A Simple Method for Producing Bone Paste,”  Archives of Orthooaedic and Traumatic Surgery  (1986), 105: 235-238), or in pellet form (see Bhan et al, “A Percutaneous Bone Grafting for Nonunion and Delayed Union of Fractures of the Tibial Shaft,”@  International Orthopaedics  ( SICOT ) (1993)  17: 310-312 ). Alternatively, the bone graft tissue can be obtained using a Bone Graft Harvester, which is commercially available from SpineTech. Using a funnel, the paste or pellet graft tissue material is loaded into the cannula  50 . The tamping instrument  142  is then advanced into the cannula  50  in the manner previously described, to displace the paste or pellet graft tissue material out of the cannula  50  and into the cavity  134 . 
     The selected material  138  can also comprise a granular bone material harvested from coral, e.g., ProOsteon™ calcium carbonate granules, available from Interpore. The granules are loaded into the cannula  50  using a funnel and advanced into the cavity using the tamping instrument  142 . 
     The selected material  138  can also comprise demineralized bone matrix suspended in glycerol (e.g., Grafton™ allograft material available from Osteotech), or SRS™ calcium phosphate cement available from Novian. These viscous materials, like the bone cement previously described, can be loaded into the syringe  136  and injected into the cavity directly or using the nozzle  140 , which is inserted through the cannula  50  into the cavity  134 . The tamping instrument  142  is used to displace residual material from the cannula  50  into the cavity  134 , as before described. 
     The selected material  138  can also be in sheet form, e.g. Collagraft™ material made from calcium carbonate powder and collagen from bovine bone. The sheet can be rolled into a tube and loaded by hand into the cannula  50 . The tamping instrument  142  is then advanced through the cannula  50 , to push and compact the material in the cavity  134 . 
     IV. Interlocking Hand Held Instruments 
     FIGS. 19 and 20 show an alternative embodiment for a composite instrument  210  for penetrating tissue, which shares many of the features of the composite instrument  10 , previously described. As FIG. 22 shows, when disassembled, the composite instrument  210 , like the composite instrument  10  previously described, includes a first functional instrument  220  and a second functional instrument  240 . A composite handle  212  joins the two instruments  220  and  240 , when assembled (as FIGS. 19 and 20 show). The composite handle  212  comprises a first handle  222  (associated with the first instrument  220 ) and a second handle  242  (associated with the second instrument  240 ) (as FIG. 22 also shows). Like the composite handle  12  for the composite instrument  10 , the composite handle  212  for the instrument  210  aids a physician in manipulating the composite instrument  210 , but a physician can also desirably use the first handle  222  to independently manipulate the first instrument  220  or the second handle  242  to independently manipulate the second instrument  240  during use. 
     As previously explained, the number and type of instruments  220  and  240  can, of course, vary. In the illustrated embodiment, each instrument  220  and  240  has a different size and function. In a preferred embodiment, the first functional instrument  220  is a trocar instrument, and the second functional instrument  240  is a cannula instrument. 
     A. The Trocar Instrument 
     Referring to FIG. 22, the first instrument  220  functions as a trocar instrument  230  to penetrate tissue. The trocar  230  has a proximal end  232  and a distal end  234 . The distal end  234  is intended to penetrate soft tissue and/or bone in response to pushing and/or twisting forces applied by the physician at the first handle  222 , or the composite handle  212 . If desired, the distal end  234  can terminate in a substantially blunt and/or cannulated tip, or alternatively terminate in a sharpened tip for cutting through tissue, as known in the art. 
     The first handle  222  is coupled to proximal end  232  of the trocar  230 . Similar to that shown in FIG. 6C for the trocar  30 , the proximal end  232  of the trocar  230  can likewise be formed in a T-shape, with the first handle  222  being molded around the T-shaped end. As earlier described with reference to the trocar  30 , this arrangement significantly increases the mechanical strength of the bond between the handle  222  and the trocar  230 , and allows significant longitudinal and torsional forces to be transmitted from the handle  222  to the trocar  230  without bond failure. Alternatively, with or without a T-shaped end, the proximal end  232  of the trocar  230  can be scored (as shown, in relation to the trocar  32 , by scored region  33  in FIG. 6C) to increase the mechanical strength of the bond between the trocar  230  and the handle  222 , or various bonding adhesives could be used, with varying results. 
     The first handle  222  desirably includes a receiving channel  226  with a viewing window  224  and a latch mechanism  236  (also shown in FIGS.  23  and  24 ), the structure and function of which are described later. 
     Like the trocar  30 , the trocar  230  may include an interior lumen (not shown), which passes through the handle  222  and the body of the trocar  230 , to accommodate passage of a stylet and/or conventional spinal needle assembly, to guide the deployment of the first instrument  220 , by itself or nested with the second instrument  240  (as FIG. 18 shows with respect to the first described embodiment) , through soft tissue to a targeted bone treatment site. 
     B. The Cannula Instrument 
     Still referring principally to FIG. 22, the second instrument  240  functions as a cannula instrument or guide sheath, and includes a cannula  250 . The cannula  250  of the second instrument  240  is desirably somewhat larger in diameter than and not as long as the trocar  230  of the first instrument  220 . As best shown in FIG. 21, the second instrument  240  includes an interior lumen  244  that extends through the instrument from its distal end  254  to its proximal end  252 . The interior lumen  244  is sized to accept the trocar  230  (as FIG. 21 shows). The size of the interior lumen  244  desirably allows the second instrument  240  to slide and/or rotate relative to the first instrument  220 , and vice versa, unless the two handles  222  and  242  are locked together, as will be described later. 
     The distal end  254  of the second instrument  240  presents an end surface that desirably presents a low-profile surface, which can penetrate soft tissue surrounding the first instrument  220  in response to pushing and/or twisting forces applied at the composite handle  212  or the second handle  242 . 
     The proximal end  252  is coupled with the second handle  242 . As shown in FIG. 6D with respect to the cannula  50 , the proximal end  252  of the cannula  250  can desirably incorporate a flared and notched end “A” and/or a textured surface “B”, around which the second handle  242  is molded. The flared and notched end “A” and/or textured surface “B” serve to increase the mechanical strength of the bond between the cannula  250  and the second handle  242 , allowing significant longitudinal and torsional forces to be transmitted between the second handle  242  and cannula  250  without bond failure. As with the trocar  230 , however, other bonding methods such as scoring of the cannula  250  and/or the use of various adhesives could be employed, with varying results. 
     Extending from the interior lumen  244  at the proximal end  252  of the cannula  250 , the second handle  242  desirably includes a handle bore  248 , preferably co-circumferential with the cannula  250 . The second handle  242  includes a transverse shoulder  246  and at least one latch notch  256  on the shoulder  246 , the structure and function of which are described later. 
     C. The Handles 
     The first handle  222  and the second handle  242  are designed to comfortably accommodate a hand, to desirably interlock to form a composite handle  212  that resists relative rotation between the first handle  222  and the second handle  242 . 
     D. Hand Accommodation 
     Like the composite handle  12 , the composite handle  212  is shaped to be comfortably and securely grasped by a normal human hand, as generally shown in FIG.  21 . Preferably, the contours of the composite handle  212  are likewise rounded to provide a comfortable grip and to minimize surgical glove tears. The first handle  222  is desirably equipped with two finger receivers  238 , intended to receive the index finger and the pinkie finger of a physician, in the same fashion shown for the handle  12  in FIG.  3 . 
     The second handle  242  is desirably equipped with two finger receivers  258 , intended to receive the middle finger and the ring finger of a physician, in the same fashion shown for the handle  42  in FIG.  4 . 
     The shape and size of the first handle  222  and second handle  242 , of course, vary. In the embodiment shown in FIGS. 19 to  21 , the composite handle  212 , and in particular the first handle  222 , includes a striking plate  214 , elongated to fit comfortably across the palm of the hand. The striking plate  214  is also configured to receive a striking blow, for the purposes described above. 
     The material chosen for the first handle  222  and the second handle  242  desirably provides sufficient structural integrity to withstand manual manipulation and forces expected from manual striking blows. The first handle  222  and the second handle  242  are made from a molded or cast rigid material sufficient in strength to withstand the striking, pushing and twisting forces without significant deformation. Representative materials for the first and second handles  222  and  242  can include various plastics, metals, and/or ceramics well known in the art. In one disclosed embodiment, the first and second handles  222  and  242  are formed from Lustran® ABS (acrylonitrile-butadiene-styrene) plastic, available commercially from Bayer Corporation. 
     Another preferable characteristic of the handle composition is that the first handle  222  and the second handle  242  can be roughened or otherwise textured to provide a secure gripping surfaces. 
     E. Interlocking Configuration 
     In order to properly interact when applying striking, pushing and/or twisting forces to the composite handle  212 , the first handle  222  desirably will not rotate relative to the second handle  242  when the two handles  222  and  242  are secured together. To avoid relative rotation, the first handle  222  preferably includes the receiving channel  226  into which the shoulder  246  of the second handle  242  is advanced and nests (see FIGS. 23 and 24) 
     In use, when the trocar  230  of the first instrument  220  is slid through the cannula  250  of the second instrument  240  (see FIG.  21 ), the first handle  222  and second handle  244  fit together to form the composite handle  212  (as FIG. 19 shows). The shoulder  246  nests within the locking channel  226 , resisting rotation of the first instrument  220  relative to the second instrument  240 . 
     Furthermore, when the locking shoulder  246  is advanced a desired distance through the channel  226 , the latch mechanism  236  on the first handle  222  engages the latch notch  256  on the second handle  242 , to resist separation of the two instruments  220  and  240 . 
     The latch mechanism  236  can be constructed in various ways. As shown in FIGS. 23 and 24, the latch mechanism  236  includes a latch finger  260  situated to engage the latch notch  256  on the second handle  242 . The latch finger  260  is carried on a hinge  262  in the first handle  222 . The hinge  262  is desirably made from resilient plastic material and possesses plastic memory, forming a so-called “living hinge.” 
     The latch finger  260  is cantilevered on the hinge  262  for pivoting movement within the first handle  222 . The plastic memory of the hinge  262  normally biases the finger  260  toward a normal position, shown in FIG. 23, in which the finger  260  will rest within the notch  256 , provided that the two parts are in alignment. The latch finger  260  can be displaced out of its normal position (as shown in FIG. 24) in response to an applied force F. Upon removal of the force F, the hinge  262  returns the finger  260  to its normal position. 
     In the illustrated embodiment, the force F is applied in at least two different ways. One works in response to advancement of the shoulder  246  through the channel  226  toward the latch mechanism  236 . This serves to secure the two instruments  220  and  240  together, for use as a composite instrument  210 . The other works in response to manual pressure exerted by an operator upon the latch mechanism  236 . This serves to separate the two instruments  220  and  240 , for use of the instruments  220  and  240  individually. 
     Regarding the first mechanism, the latch finger  260  includes a cam surface  264  (best shown in FIG.  24 ). The leading edge  266  of the locking shoulder  246  slides or rides along the cam surface  264  as the shoulder  246  progresses through the channel  226 . Progressive advancement of the leading edge  266  of the shoulder  246  along the cam surface  264  will apply the force F, to cause the latch finger  260  to pivot on the hinge  262 . When the locking notch  256  on the shoulder  246  is in mutual alignment with the latch finger  260 , the force F is relieved, and the latch finger  260  resiliently returns toward its normal position. This moves the latch finger  260  into the notch  256 , in a snap-fit. The plastic memory of the hinge resists movement of the notch  256  out of engagement with the latch finger  260 , effectively locking the two handles  222  and  242  together as the composite handle  212 . 
     The shoulder  246  desirably includes a locking notch  256  on reverse facing, opposite sides of the shoulder  246 . In this way, the fitment of the shoulder  246  into the channel  226  is not sensitive to mutual orientation of the two handles  222  and  242 . 
     The viewing window  224  on the first handle  222  reveals the advancement of the shoulder  246  through the channel  226  and into engagement with the latching mechanism  236 . This provides visual confirmation of the locking fit. Preferably, the shoulder  246  is a different color than first handle  220 , such that visualization would be further simplified. 
     When formed, the composite handle  210  is sized and shaped to accommodate four fingers, two fingers each on the first handle  222  and the second handle  242 , in the same fashion shown for the composite handle  10  in FIG.  3 . 
     Regarding the second mechanism for applying the force F to the latch finger  260 , the latch mechanism  236  also includes a detent surface  268 . Pressing against the detent surface  268  applies the force F to the latch finger  260 , causing the finger  260  to pivot on the hinge  262 . The latch mechanism  236  also desirably incorporates a stop  280 , which limits the displacement of the latch mechanism during release. The force F frees the finger  260  from the notch  256 , to allow the shoulder  246  to be withdrawn from the channel  226 . The operator can thereby separate the two handles  222  and  224  (as FIG. 21 shows). 
     The composite instrument  210  and the instruments  220  and  240  can be used in conjunction with a catheter element  130 , a diagnostic or therapeutic element  132 , and other instruments in the same fashion as the composite instrument  10 , previously described. 
     The disclosed composite instrument  210  also greatly facilitates manipulation and use of the instrument by a physician wearing leaded and/or lead-lined gloves during the surgical procedure. Because many procedures are performed under fluoroscopic visualization, physicians repeatedly performing these procedures often wear leaded gloves to minimize exposure of their hands to harmful radiation. Such gloves are often thick, uncomfortable, and incorporate radiopaque materials, such as lead, and typically negatively impact the ability of the surgeon to manipulate small objects or to “feel” the surgical instruments during the procedure. With the disclosed composite instrument  210 , the physician can hold the instrument in a single hand, and can use a single finger to depress the detent surface  268  to separate the two handles  222  and  242 . The detent surface  268  is desirably sized such that it can be easily felt and manipulated, even through leaded gloves. 
     Moreover, because the stop  280  desirably limits the displacement of the latch mechanism  236  during release, the latch mechanism  236  can withstand a significant amount of force F without damage to the hinge  262 . This is especially important where the physician is wearing leaded gloves, because the physician may not be able to accurately gage the amount of force he or she is imparting to a given tool. Even where the physician uses an excessive amount of force to release the instrument, therefore, the disclosed composite instrument  210  is less likely to fail during the surgical procedure. 
     The features of the invention are set forth in the following claims.