Abstract:
Apparatus for controlling the deformation of an implant during deployment thereof, comprising: a force application mechanism for applying deformation force to the implant, by motion of a force applicator against the implant; and a restraint element positioning mechanism that positions a restraining element such that the deformation of the implant is controlled by restraint of the restraining element on allowable deformation; and a synchronizer that synchronizes the motion of the restraining element and the force applicator, to achieve a desired deformation of the implanted.

Description:
RELATED APPLICATIONS 
     This application is a U.S. national filing of PCT Application No. PCT/IL00/00056, filed Jan. 27, 2000. This application is also related to PCT Application Nos. PCT/IL00/00055 and PCT/IL00/00058, the disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to delivery systems for expandable implants, and especially to delivery systems for a spinal prosthesis. 
     BACKGROUND OF THE INVENTION 
     A common medical situation is that of a ruptured spinal disc. Material that exits the disc may press against the spinal cord, causing severe pain. A ruptured disc is typically treated by a surgical procedure, in which the damaged disc is partially or completely removed, and spinal fusion, in which at least the two vertebrae adjacent the removed disc are fused. 
     Disk removal may be performed percutaneously, for example via a tube through which tissue removal devices and/or an endoscope are provided. 
     Several approaches exist for spinal fusion. In one approach, the two vertebrae are connected using a plate and/or screws. In another approach, a spacer (also called a “cage device”) is inserted between the two vertebrae, so that bone growth into the space will fuse the adjacent vertebra. Typically, the axis of the spacer is perpendicular to the axis of the spine and to the plane of the body. Sometimes the spacer includes a plurality of holes, to encourage bone growth into the spacer. PCT publication WO 98/38918, the disclosure of which is incorporated herein by reference, describes a spacer that is inserted in a collapsed condition and expanded to fill the inter-vertebral space. Another type of spacer, exemplified by U.S. Pat. 5,123,926 (and others) to Pisharodi, the disclosure of which is incorporated herein by reference, functions like a concrete anchoring screw, in that a portion of the spacer, usually a center portion-thereof, expands by a relatively small amount to engage the adjacent vertebrae. 
     U.S. Pat. 5,800,549, the disclosure of which is incorporated herein by reference, describes a flexible disc replacement that is inserted using a syringe. However, this replacement does not fuse adjacent vertebrae, rather, it is designed to replace the form and function of a removed inter-vertebral disc. 
     One disadvantage of some of known fusion devices is that a relatively large entry hole in the body is required to insert the device. In some, a regular-sized surgical incision is required. In others, a minimally invasive laproscope-size hole is required, which is still quite large. Often, the spinal processes and/or other spinal structures are damaged by the insertion of the fusion device. 
     Another disadvantage of some known fusion devices is lies in a relative complexity of procedures for delivering the devices. 
     Another disadvantage of some known fusion devices is a requirement to trade/off the invasiveness of the procedure (e.g., do the spinal processes need to be cut or the abdomen opened) and the surface contact area between the fusion device and the bone. Generally, if the contact surface is small, the fusion device embeds itself in the bone and the spine slowly shrinks. 
     SUMMARY OF THE INVENTION 
     An aspect of some preferred embodiments of the invention relates to a method of controlling the deformation of an implant. In a preferred embodiment of the invention, a force is applied to the implant while the expansion of the implant is constrained by an element external to the implant. The expansion force is preferably applied externally to the implant by may be applied by the implant itself, for example if the implant is super-elastically or elastically deformed or is formed of a shape memory material. In a preferred embodiment of the invention, the force is an axially applied fore that axially contacts the implant, causing it to expand or extend elements radially. In a preferred embodiment of the invention, the constraint element is external to the implant and is moved between or during application of the deformation force, to modify the deformation behavior of the implant. In a preferred embodiment of the invention, the external constrained is retracted as the implant is axially contracted. The axial force may be applied by pushing an element towards the implant and/or by pulling the implant towards an element. 
     An aspect of some preferred embodiments of the invention relates to a device for controlling the deformation of an implant, in which an operator applies continuous motion to a knob or lever. and the device converts the continuous motion into at least two discrete motions. In an exemplary application, one motion is for applying force to the implant for deforming it and one motion is for moving a constraining element that affects the deformation of the implant under the force. 
     In a preferred embodiment of the invention, an alternating pin mechanism is provided for alternating the applied operator motion between a deformation force providing element and a constraint element. 
     In an alternative embodiment of the invention, an eccentric-wheel mechanism is provided, which wheel advances and retracts two arms, one arm which applies force to the deformation and one arm which moves the constraining element. Preferably, the two arms alternately active the constraining element and the deformation. In some embodiments, both arms move in phase and in other embodiments the two arms move out of phase or even unsynchronized with regard to cycles. 
     In a preferred embodiment of the invention, an apertured or nubbed plate is provided for controlling the motions. In a nubbed plate, the nubs are preferably one way nubs, which allow an arm to engage a nub when moving in one direction and slip over the nubs when moving in the other direction. In an apertured plate, a spring loaded pin is preferably provided, for locking into an aperture when a motion is completed and for sliding along the plate when the motion is in progress. 
     In a preferred embodiment of the invention, the deforming force is applied as axially as possibly with respect to the delivery system, to prevent twisting moments. 
     In an alternative embodiment, a two-phase apparatus is provided. The apparatus comprises two components, one for applying force to a spacer and one for retracting a collar that acts as a constraining element. In each component, an operator activates the component to apply the desired forces or motion and at the completion of the activation, the component locks. The operator then activates the other component until it locks. Repeats are achieved by unlocking the components and activating them again. In a particular implementation, the collar is advanced when force is applied to the spacer, so that the collar maintains a same position relative to the proximal end of the spacer. 
     An aspect of some preferred embodiment of the invention relates to a device for intra-vertebral measurement. In a preferred embodiment of the invention, the device comprises a shaft having two wings at its end. When the wings extend, the shaft advances or retracts, the amount of motion of the shaft being determined by the extend of extension of the wings. Various mechanisms may be used for extending the wings. In a preferred embodiment of the invention, the wings form a parallelogram, with the shaft attached to one vertex of the parallelogram and the opposite vertex constrained form moving. Advancing the shaft, extends the wings. One, two or more wings may be provided, thus enabling measurement to one side, a planar measurement or a volume measurement. Alternatively or additionally, a plurality of concentric shafts may be provided, each with its own set of wings. The wings of the different shafts may be perpendicular to each other, or at any other angle, for example parallel to each other. Possibly, the angle between the wings is controlled by rotating the shafts relative to each other. 
     In some mechanisms, the relation between shaft motion and wing extension is not linear. In a preferred embodiment of the invention, a mechanical display is coupled to the shaft and converts the shaft motion into a more readable scale, such as a linear or quasi linear scale of wing extension. 
     An aspect of some preferred embodiments of the invention relates to kits for implant procedures, comprising two or more of a delivery system (which may be sterilized or be disposable), an implant, a collar, a bolt, an access tube, a trephine, a guide wire, a vertebra puncher and/or an obturator. Preferably, the kit parts are adapted for a size and access direction of a spacer. In some spacers, the spacer axis when the spacer is expanded is not parallel to the spacer insertion direction. This can be achieved by providing different length spike son either side of the space. Thus, a rectangular spacer, parallel to the abdomen and back can be inserted at an oblique angle to the spine. 
     There is thus provided in accordance with a preferred embodiment of the invention, apparatus for controlling the deformation of an implant during deployment thereof, comprising: 
     a force application mechanism for applying deforming force to the implant, by motion of a force applicator against the implant; and 
     a restraint element positioning mechanism that positions a restraining element such that the deformation of the implant is controlled by restraint of the restraining element on allowable deformation; and 
     a synchronizer that synchronizers the motion of the restraining element and the force applicator, to achieve a desired deformation of the implant. 
     Preferably, the apparatus comprises a force input which receives continuous motion and couples it to the force application mechanism and to the restraint element positioning mechanism. Preferably, said continuous motion is reciprocating motion. Preferably, said restraint positioning mechanism moves said restraint element during one stroke of said reciprocating motion. Preferably, said one stroke comprises a retraction of said restraint mechanism from said implant. 
     In a preferred embodiment of the invention, said force application mechanism moves said force applicator during one stroke of said reciprocating motion. Preferably, said one stroke comprises a retraction of said force applicator from said implant. Alternatively, said one stroke comprises an advance of said force applicator towards said implant. 
     In a preferred embodiment of the invention, said force application mechanism comprises a selective coupler that selectively couples said input motion to said force applicator. Alternatively or additionally, said element positioning mechanism comprises a selective coupler that selectively couples said input motion to said restraining element. Alternatively or additionally, said synchronized motion is repetitive, comprises a plurality of cycles of positioning said restraining element and applying said force. Alternatively or additionally, said motion is applied simultaneously to said restraint element positioning mechanism and to said force application mechanism. 
     In a preferred embodiment of the invention, said motion is applied alternately to said restraint element positioning mechanism and to said force application mechanism. Preferably, the apparatus comprises an alternating locking mechanism that alternately couples the motion form the force input to the restraint element positioning mechanism and to the force application mechanism. 
     In a preferred embodiment of the invention, said force input comprises a manual force input. 
     In a preferred embodiment of the invention, said force input comprises a motorized force input. 
     In a preferred embodiment of the invention, said synchronizer is integrated with said mechanisms. Alternatively or additionally, said synchronizer is manual, providing an indication to an operator to switch between the mechanisms. Alternatively, said synchronizer is automatic, switching by itself between the mechanisms. 
     In a preferred embodiment of the invention, said synchronizer comprises a pin extractor for decoupling a pin from one mechanism and coupling the pin to another mechanism. Preferably, said synchronizer comprises a spring for urging said pin towards one of said mechanisms and an inclined plane for withdrawing said pin from said one mechanism and urging said pin towards said other mechanism. 
     In a preferred embodiment of the invention, said synchronizer blocks the motion of one of said mechanisms when a desired motion effect of said mechanism is. achieved. Preferably, the apparatus comprises a pin that engages an aperture to effect said locking. 
     In a preferred embodiment of the invention, said restraint mechanism comprises an unevenly surfaced element for coupling said motion to said restraint element. 
     In a preferred embodiment of the invention, said force application mechanism comprises an unevenly surfaced element for coupling said motion to said force applicator. Alternatively or additionally, said unevenly surfaced element comprises a nubbed plate. Preferably, said nubs are one-way nubs that allow an arm element of said mechanisms to slip over them when the arm travels in one direction relative to the nubs and engages the arm when the arm travels in the opposite relative direction. 
     In a preferred embodiment of the invention, said unevenly surfaced element comprises an apertured plate. 
     In a preferred embodiment of the invention, said uneven surface comprises even surface portions separated, by uneven surface portions, a plurality of separation distances defined by said separation of surface portions. Preferably, said separation distances determine the deformation of said implant. Alternatively or additionally, said separation distances take into account a plastic deformation of said implant. Alternatively or additionally, said separation distances take into account an. elastic deformation of said implant. Alternatively or additionally, wherein said separation distances take into account a spring-back of said implant. 
     In a preferred embodiment of the invention, said force applicator and said force application mechanism are substantially restricted to a straight, narrow, elongate volume, thereby reducing moments on the force application mechanism. Alternatively or additionally, said force applicator pushes against said implant. 
     In a preferred embodiment of the invention, said force applicator pulls a base against a far side of said implant. 
     In a preferred embodiment of the invention, said force applicator exhibits axial motion, along an axis connecting the force applicator and the implant. Alternatively, said force applicator exhibits rotational motion, around an axis connecting the force applicator and the implant. Alternatively, said force applicator exhibits only axial motion, along an axis connecting the force applicator and the implant. 
     In a preferred embodiment of the invention, said restraint element exhibits axial motion, along an axis connecting the force applicator and the implant. 
     In a preferred embodiment of the invention, said restraint element exhibits rotational motion, around an axis connecting the force applicator and the implant. Alternatively, said force applicator exhibits only axial motion, during times when force is applied by it to the implant, along an axis connecting the force applicator and the implant. 
     In a preferred embodiment of the invention, said force applicator applies at least 20 Kg to said implant. Alternatively or additionally, said force applicator applies at least 40 Kg to said implant. Alternatively or additionally, said force applicator applies at least 60 Kg to said implant. Alternatively or additionally, said force applicator applies at least 100 Kg to said implant. 
     In a preferred embodiment of the invention, said restraint element and said force applicator are elongate elements. Preferably, said restraint element and said force applicator are cylindrical elements. 
     In a preferred embodiment of the invention, said cylindrical elements are tubes. 
     In a preferred embodiment of the invention, said force applicator comprises two concentric elements, an outer element which applies force away from said apparatus towards said implant and an inner counter force element that applies force from said implant towards said apparatus. Preferably, said inner element is mechanically coupled to said implant. Alternatively said outer element is mechanically coupled to said implant. 
     In a preferred embodiment of the invention, said motion of said force applicator comprises motion of only one of said concentric elements relative to said apparatus. Preferably, said inner element retracts towards said apparatus during said motion of said force applicator. Alternatively, said outer element advances away from said apparatus during said motion of said force applicator. 
     In a preferred embodiment of the invention, said inner element is decoupled from said implant by unscrewing it. Preferably, said inner element extends substantially all the way through said apparatus. 
     In a preferred embodiment of the invention, the apparatus comprises a handle for holding said apparatus by an operator. 
     In a preferred embodiment of the invention, the apparatus comprises means for fixing said apparatus to said patient. 
     In a preferred embodiment of the invention, the apparatus comprises means for fixing said apparatus to a bed on which said patient lies. 
     In a preferred embodiment of the invention, said synchronizer adapts said apparatus for deforming a particular implant from a set of same types of implants having different geometries. 
     In a preferred embodiment of the invention, said synchronizer synchronizes said force applicator to apply force to said implant after said implant is completely expanded. 
     In a preferred embodiment of the invention, said restraint element has an outer diameter of less than 7 mm. Alternatively or additionally, said restraint element has an outer diameter of less than 6 mm. Alternatively or additionally, said restraint element has an outer diameter of less than 5 mm. Alternatively or additionally, said restraint element has an outer diameter of less than 4 mm. 
     In a preferred embodiment of the invention, said implant is a spinal implant for fusing adjacent vertebrae. Alternatively or additionally, said implant is an axially contracting and radially expanding implant. Alternatively or additionally, said implant comprises a slotted tube, which as it contracts, radially extends a plurality of spikes and wherein said restraining element encloses said tube and prevents the extension of at least one of said spikes. 
     In a preferred embodiment of the invention, said implant comprises a slotted tube, to which force is applied against an end of said tube, to deform the tube. Alternatively or additionally, said implant radially expands by said deforming at least by a ratio of two. Alternatively or additionally, said implant radially expands by said deforming at least by a ratio of four. 
     There is also provided in accordance with a preferred embodiment of the invention, a method of controlling the deformation of an implant, comprising: 
     providing a medical implant; 
     positioning a restraining element relative to said implant, which restraining element prevents deformation of at least some of said implant; 
     applying a deformation force to said implant using at least one tube; 
     controlling the deformation of the implant using the restraining element; 
     moving said restraining element to a new position; and 
     repeating said applying, said controlling and said moving, a plurality of times. Preferably, said deformation comprises radial expansion. Alternatively or additionally, said restraining element is inside said implant. 
     Alternatively, said restraining element is outside said implant. 
     In a preferred embodiment of the invention, said motion of said restraining element is controlled using a mechanism external to the implant. Preferably, said external mechanism receives a continuous motion input from an operator. Preferably, the method comprises converting said continuous motion into discrete motion of said restraining element. 
     Alternatively or additionally, the method comprises converting said continuous motion into discrete application of force to said implant. 
     In a preferred embodiment of the invention, said motion and said force application do not overlap in time. 
     In a preferred embodiment of the invention, said motion and said force application do overlap in time. 
     There is also provided in accordance with a preferred embodiment of the invention, a method of controlling the deformation of an implant, composing: 
     providing an axial implant having a plurality of spikes extending radially thereto, arranged along the implant&#39;s axis, which implant is in a collapsed state where said spikes do not extend; 
     enclosing said implant with a collar that restrains the extension of said spikes; 
     inserting said implant into a desired location; 
     retracting said collar to allow at least one spike to extend; and 
     repeating said retracting until substantially all of said spikes are extended. Preferably, said spikes extend as a result of forces stored within said implant. Preferably, said implant is formed of a super-elastic material. Alternatively, said implant is formed of a shape-memory material. 
     In a preferred embodiment of the invention, said spikes extend as a result of forces applied externally to said implant. Preferably, said forces are axially applied to said implant. Preferably, the method comprises applying an axial force to said implant after all of said spikes are extended. 
     There is also provided in accordance with a preferred embodiment of the invention, a measurement apparatus for taking measurements inside the body, comprising: 
     a hollow tube, defining at least one slot at its end; 
     a shaft disposed within said tube; and 
     at least one wing coupled to said shaft and adapted to extend through said slot, wherein an extension position of said wing determines an axial motion of said shaft in said tube, 
     wherein said apparatus is adapted to come in contact with body fluids and wherein said apparatus is sterile. Preferably, said apparatus is sterilizable. Alternatively or additionally, said tube comprises defines at least two slots and wherein said at least one wing comprises at least two wings. 
     In a preferred embodiment of the invention, extension of said wings retracts said shaft towards said wings. 
     In a preferred embodiment of the invention, extension of said shaft away from said wings extends said wings. 
     In a preferred embodiment of the invention, said wings are molded from a single piece of plastic. 
     In a preferred embodiment of the invention, said at least one wing, defines a parallelogram, with the shaft attached to one vertex of the parallelogram and the two neighboring vertexes of the parallelogram comprises the extended parts of two wings. 
     In a preferred embodiment of the invention, the apparatus comprises a dial coupled to said shaft and displaying an extension of said wings as a function of a relative displacement between said shaft and said tube. Preferably, said dial comprises a scale converter that converts a non-linear coupling of said wing motion to said shaft motion into a linear scale display. 
     In a preferred embodiment of the invention, the apparatus comprises an axial position control for controlling an axial position of said tube relative to a body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more clearly understood from the following detailed description of the preferred embodiments of the invention and from the attached drawings, in which: 
         FIG. 1A  shows a flat projection of an expandable spacer, in an un-expanded configuration thereof, in accordance with a preferred embodiment of the invention; 
         FIG. 1B  shows a perspective view of the spacer of  FIG. 1A ; 
         FIG. 1C  shows both an axial flat projection and a front flat projection of the spacer of  FIG. 1A , in an expanded configuration thereof; 
         FIG. 1D  shows a perspective view of the spacer of  FIG. 1A , in an expanded configuration thereof; 
         FIGS. 2A-2D  illustrate a process of inserting and expanding a spacer, in accordance with a preferred embodiment of the invention; 
         FIGS. 3A-3F  illustrate a method of providing a guide tube into an intra-vertebral space, in accordance with a preferred embodiment of the invention; 
         FIGS. 4A-4F  illustrate an exemplary set of tools for performing the method of FIGS.  3 A- 3 F,in accordance with a preferred embodiment of the invention; 
         FIGS. 5A-5C  illustrate an intra-vertebral measurement device, in accordance with a preferred embodiment of the invention; 
         FIG. 6  illustrates a trigger and display mechanism for the measurement device of  FIGS. 5A-5C , in accordance with a preferred embodiment of the invention; 
         FIGS. 7A-7F  illustrate, schematically, a method of deploying the spacer of  FIGS. 1A-1D , in accordance with a preferred embodiment of the invention; 
         FIGS. 8A-8D  illustrate. a delivery control system for affecting the process shown in  FIGS. 7A-7F , in accordance with a preferred embodiment of the invention; 
         FIGS. 9A-9B  illustrate a delivery control systems utilizing an alternating pin, in accordance with a preferred embodiment of the invention; 
         FIGS. 10A-10B  illustrate an eccentric-rotation based delivery system, in accordance with a preferred embodiment of the invention; and 
         FIG. 11  illustrates an alternative eccentric-rotation based delivery system, in accordance with another preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Basic Spacer (Cage) Description 
       FIG. 1A  shows a flat projection of an expandable spacer  20 , in an un-expanded configuration thereof, in accordance with a preferred embodiment of the invention.  FIG. 1B  is a perspective view of spacer  20 . Spacer  20  comprises an elongate hollow object  22 , such as a tube, having a plurality of spikes  24  defined thereon (in a flattened form), each spike being defined by a pair of slots  26 . In a preferred embodiment of the invention, the cross-section of tube  22  is a circle, as shown in an axial projection  36  of the spacer. In the embodiment shown in  FIG. 1A , tube  22  includes alternating spike segments  28  and non-spike segments  30 . At one end of the tube, an end-cap  34  is preferably defined. In a preferred embodiment of the invention, end-cap  34  is hollow. Alternatively, end-cap  34  is solid, but preferably comprising a porous material or including holes, to enhance bone ingrowth. Alternatively or additionally to end-cap  34 , spacer  20  is attached to the end of a tube, such that only a portion of the tube, preferably an end portion, has slits defined therein. 
       FIGS. 1C-1D  show spacer  20  in an expanded configuration,  FIG. 1C  using a flat projection (side and axial) and  FIG. 1D  using a perspective view. When expanded, spikes  28  extend outwards and tube  22  is axially compressed. Non-spike segments  30  and end-cap(s)  34  preferably do not distort. As can be seen in the figures, a considerable expansion in diameter is achieved, for example a five fold expansion. In addition, a considerable axial contraction is achieved, as evidenced by comparing the thickness of a spike  24  in  FIG. 1C  ( 38 ) with  FIG. 1A  ( 28 ). 
     In a preferred embodiment of the invention, spacer  20  is maintained in an expanded configuration using a bolt  42 . A base  44  of bolt  42  engages one end-cap of spacer  20  and a flared lip  46  (flared for example by an advancing pole element after the spacer is expanded) engages end-cap  34 . 
     Although spacer  20  has been described as including non-spike portions, it should be appreciated that in some preferred embodiments of the invention no such non-spike portions are defined, for example, if the slits are interleaved, as shown by the example of a dotted line  35  in FIG.  1 A. 
     In a preferred embodiment of the invention, tube slits  26  include round holes, for example holes  32 , at their ends. Preferably, these holes are defined to reduce the propagation of stress and/or mechanical failure in tube  22 . Alternatively or additionally, these holes are defined to weaken the end of the slit so that when spacer  20  is axially collapsed, spikes  28  will preferentially fold out at the ends of the slits (at holes  33 ). Alternatively or additionally, slits  26  may include holes  33  at their center (the apex of spikes  28 ), to encourage folding of the spike at the location of the hole. 
     The above is a description of a limited subset of spacers, further variations are defined in a PCT application filed on even date with the present application in the Israel receiving office and titled “Expandable Element”, attorney docket 100/01325, the disclosure of which is incorporated herein by reference. 
     Basic Delivery Method 
       FIGS. 2A-D  illustrate a process of inserting and expanding spacer  20 . In  FIG. 2A , a damaged disc  54  is located in an inter-vertebral space  55 , between a vertebra  50  and a vertebra  52 . Typically, but not necessarily, before inserting a spacer between the two vertebra, disc  54  is partially or completely removed. Preferably, disc  54  is removed using a minimally invasive technique, illustrated by a thin needle  56 , for example a laproscopic approach, such as described in WO 98/38918. 
     In  FIG. 2B , the disc has been removed and a spacer  20  is inserted into inter-vertebral space  55 , in an un-expanded configuration. In a preferred embodiment of the invention, spacer  20  is mounted on- or formed at- the end of an elongate member  60 . Preferably, spacer  20  is inserted via a syringe or in an “over-tube” which may be retrieved, once the spacer is inserted. Alternatively or additionally, spacer  20  is inserted using X-Ray guidance, to avoid damaging the spinal cord and/or nearby blood vessels. 
     In  FIG. 2C , spacer  20  is in the process of being radially expanded (and axially shortened). A portion  62  of spacer  20  is expanded, while a portion  64  of spacer  62  is not yet expanded. 
     In  FIG. 2D , spacer  20  is expanded over its entire length and it fills inter-vertebral space  55 . In a preferred embodiment of the invention, a fixing material, such as a bone slurry or a setting fixing compound is provided into inter-vertebral space  55 , in order to encourage fusion between vertebra  50  and vertebra  52 . In the case of a bone slurry, bone chips or bone powder, such setting may require a week or so of bed rest. Preferably, spacer  20  is stiff enough to maintain its shape until the bone sets, so that little or no bed rest is required. Alternatively or additionally, at least some of the required stiffness is provided by the fixing material. Possibly, the fixing material degraded after a while and/or is a foam, to allow bone ingrowth. Alternatively or additionally, to injecting a fixing material or as part of the fixing material, growth hormones, enzymes, anti-bacterial pharmaceuticals, anti-inflammatory compounds and/or other bio-active materials may be injected into space  55 , to encourage fusion and/or another desired effect. 
     Spacer Delivery Direction 
     In a preferred embodiment of the invention, the surgical approach is from the back of the patient. Alternatively, a lateral or a posto-lateral approach may be used. It is noted that the implanted spacer may be very narrow during implantation, so it is easier to plan and execute an approach, even through the abdomen. Alternatively or additionally, it is noted that the spacer, in some preferred embodiments of the invention, may be made flexible along its main axis, at least in its un-expanded configuration and especially as a result of the slits formed therein. Thus, the spacer can be provided at inter-vertebral space  55  using a curved guide, possibly a bendable guide, such as an endoscope. Alternatively, if the spacer is formed of a shape-memory material, the spacer may be cooled below the temperature at which it turns ductile, so that it can be easily bent. Alternatively or additionally, and especially if the spacer is elastic or super-elastic, the spacer may be maintained in a curved configuration during insertion using a curved stylet inserted through the spacer, alternatively or additionally to using a curved outer tube. 
     Guide Tube Insertion And Removal of Disc-Tissue Material 
     In a preferred embodiment of the invention, the spacer implantation process is performed through a guide tube, which connects intra-vertebral space  55  with the outside of the body. In general, provision of guide tubes to the spine is known in the art, for example for minimally invasive disk removal. 
       FIGS. 3A-3F  illustrate a method of providing a sleeve  102 , for use as a guide tube, into an intra-vertebral space, in accordance with a preferred embodiment of the invention. 
       FIG. 3A  illustrates a guide wire  100  inserted into space  55 . Such insertion is typically, but not necessarily performed using X-ray imaging guidance. 
     A combination sleeve-obturator is then inserted over guide wire  100 , possibly requiring a small incision on the skin. A sleeve  102  preferably has a head  106  to which a head  112  of an obturator  110  can be fixed. A locking mechanism  114 , for example using rotationally interlocking element, in which, for example, a half turn locks or unlocks the two heads, is preferably provided for locking the two head together. Obturator  110  also includes an inclined tip  108 , preferably situated at its proximal end to aid in forcing the device through the tissue. A body stopper  104  is preferably provided, which can be positioned along the axis of sleeve  102 , to prevent the sleeve from advancing too far into the body. Typically, an initial estimate for the body stop position can be determined from the X-ray images and a more exact position can be determined once the sleeve is inserted, for example from fluoroscopic images. Preferably, but not necessarily, the sleeve diameter is large enough such that the sleeve itself cannot enter all the way into space  55 . Preferably, different sleeve sizes are used for different parts of the spine. Optionally, the sleeve size and/or geometry (e.g., barbs) is such that once the sleeve is inserted it is fixed in place and cannot be inadvertently retracted, except by application of significant force. Alternatively, The sleeve tip may include an extending barb or an expanding ring, to hold it in place. 
       FIG. 3C  is a perspective view of FIG.  3 B. 
     In  FIG. 3D , obturator  110  is retracted, leaving sleeve  102  in place. 
     In  FIG. 3E  a trephine  116  is provided through sleeve  102 , to perforate an annulus fibrosus capsule of space  55 , using a cutting tip  118  of the trephine. Preferably, a head  120  of trephine  116  includes a slipping mechanism  122 , so that it can freely rotate on head  106 , and not lock as obturator  110  does. 
     In  FIG. 3F , both trephine  116  and guide wire  100  are retracted, leaving sleeve  102  in place. 
     At this point the disc material is preferably removed. Optionally, the end-plates of the vertebrae are also removed. 
     Optionally, a plurality of holes are formed in the end-plates and/or the vertebrae, which holes may promote bone growth. Such holes may be formed using many tools, for example, a bent guide wire, a bent-tip trephine, a rotoblator or a punching device. Preferably, a bendabletip endoscope is used, to guide the hole cutting tool to a desired location. 
     Exemplary Guide Set 
       FIGS. 4A-4F  illustrate an exemplary set of tools for performing the method of  FIGS. 3A-3F . 
       FIG. 4A  illustrates an exemplary sleeve  102 , having a slot  101  formed near one end, for attaching head  106  to the sleeve. In the exemplary embodiment shown, the inner diameter is 6 mm; the outer diameter at the head end is 8 mm and the outer diameter at the tip end is 6.5 mm. An exemplary length is 149 mm sleeve length, between the head and the tip. 
       FIG. 4B  illustrates an exemplary obturator  110 , having a slot  111  formed near one end, for attaching head  112  thereto. In the exemplary embodiment shown, a bore of 1.3 mm is formed for guide wire  100 , from tip  108  to the head end of obturator  110 . Optionally, about 30 mm from tip  108 , the bore widens to a 3.0 mm diameter. Tip  108  is 7.84 mm long, with a minimum tip diameter of 1.8 mm. The length of obturator  110  is preferably 180 mm long, including a part that is inside head  112 . The outer diameter of obturator  110  is preferably  6 mm or slightly less. 
       FIG. 4C  is a perspective view of an exemplary head  106  for sleeve  102 , showing a part of locking mechanism  114  that is formed in head  106 . A bore of 1.3 mm is preferably formed in the head for guide wire  100 . 
       FIG. 4D  is a perspective view of an exemplary head  112  for obturator  110 , showing. the rest of locking mechanism  114 . A bore of 1.3 mm is preferably formed in the head for guide wire  100 . 
       FIG. 4E  illustrates a detail of a tip  118  of an exemplary trephine  116 , in accordance with a preferred embodiment of the invention. In general, form, such as length, diameter, slot and bore, trephine  116  can be the same as obturator  110 . Tip  118  includes a 5 mm section that has an inner diameter of 4.7 mm and is preferably serrated or sharpened (not shown) at its distal end, so that it can be easily rotated. 
       FIG. 4F  illustrates a head  120  for trephine  116 , also illustrating a hollow inside portion for completing free-turning mechanism  122 . A bore of 1.3 mm is preferably formed in the head for guide wire  100 . 
     Space Measurement Apparatus 
       FIGS. 5A-5C  illustrate an exemplary intra-vertebral measurement device  200 , in accordance with a preferred embodiment of the invention. Device  200  is preferably used to measure the distance between vertebrae  50  and  52  and/or other dimensions of space  55 , to better select a spacer to fit and/or for exerting control over the spacer expansion, so that it matches the physical geometry of the patient. 
     In some cases, it is sufficient to make one measurement in space  55 . In others, the measurement is repeated in several. locations in space  55 . 
     As shown in  FIG. 5A , exemplary device  200  comprises a slotted tube  202  having a cap  204  and a bore. A shaft  206  is inserted into the bore of tube  202 . A plurality of wings  208  are preferably connected on one end to shaft  206  and abut cap  204  at their other end, so that when shaft  206  is advanced, wings  208  extend. When wings  208  meet physical opposition (such as bone), they stop extending, so the advance of shaft  206  is stopped. The amount of movement of shaft  206  can be used as an indication of the measured dimension. Shaft  206  and tube  202  are preferably, but not necessarily flexible, so that they can be centered by wings  208  in space  55 . 
     Length of space  55  can be measured by detecting the extreme locations along the width of the space where wings  208  do not extend freely, as being the edges of space  55 . 
     Width and height of space  55  can be determined by rotating device  200  to an orientation at which they extend axially to the spine and taking a measurement. These measurements may be repeated at several points along space  55 , by axially retracting and advancing tube  202 . In some embodiments, tube  202  is bent or bendable, so that non-axial measurements can be taken. 
     In the exemplary embodiment shown, the outer diameter of tube  202  is 4.8 mm and wings  208  can extend to a maximum diameter of 18 mm. However, in other implementations, other sizes may be provided. For example, if device  200  is used for measurement of intramedullar channels, a smaller diameter device may be provided, for example having a diameter of 3 or 2 mm. A larger range of radii may also be required, for example, between 2 and 40 mm. Alternatively, a smaller range of radii may be provided, for example between 4 and 8 mm. 
       FIG. 5B  shows device  200  (with shaft  206  hidden) with wings  208  closed. 
       FIG. 5C  shows device  200  (with shaft  206  hidden) with wings open. Wings  208  are preferably attached to a head  210 , which head may molded onto shaft  206 . Shaft  206  is preferably metal, while head  210  and wings  208  are preferably a single piece of plastic. Alternatively, shaft  206  may be plastic, possibly a single unit with wings  208 . 
     In the exemplary embodiment shown, wings  208  form a parallelogram or a diamond, such that compressing an axial (of the shaft) axis of the parallelogram increases the other (transaxial of the shaft) axis, thereby extending wings  208 . When the shaft is retracted, for example using a spring, the transaxial axis is decreased, so the wings retract. In some embodiments, the spring-back of wings  208  themselves is used for retracting the wings. In an alternative embodiment, the shaft comprises at its end a cone, which, when retracted, pushes the wings out of the slots. Many other alternate mechanisms may be used. 
     Trigger and Display Mechanism 
       FIG. 6  illustrates a trigger and display mechanism  220  for the measurement device of  FIGS. 5A-5C . Mechanism  220  comprises a trigger  222  attached to an axis  234 . One end  228  of trigger  222  can serve as a dial indicator  228  for indicating a position on dial  230 . An optional dial extension  232  may be provided. A spring  224  coupled to a base  226  and trigger  222  is preferably provided to return trigger  222  to a resting position and to retract shaft  206 . 
     A bent arm  242  interconnects tube  202 , shaft  202  (at point  244 ) and trigger  222 , (using a pin  236 ). Pin  236  is free to slide in a slot  240  in the body (not shown) of the measurement system) and a slot  238  of trigger  222 . This mechanism provides both spring back of the shaft and converts the motion of the shaft into a scale that linearly shows the wing extension. 
     Other conversion mechanisms, such as using non-linear gears and eccentrically moving gears, may be used instead. 
     An axial stopper  246  is preferably provided to control the axial position of the measurement system relative to the patient, allowing measurements in different parts of space  55 . Other mechanisms, such as a screw-connection to sleeve  102  may also be used. 
     In a preferred embodiment of the invention, system  200  is held with one hand, freeing the other hand to do other operations. 
     General Spacer Expansion Control 
       FIGS. 7A-7C  illustrate an exemplary method of spacer expansion, in accordance with a preferred embodiment of the invention. A spacer  402  is provided as a tube having an inner bolt  408 , which bolt is preferably configured to prevent the advance of the end of spacer  402 , past the end of the bolt. An outer collar  404  is provided for shaping the expansion of the spacer. A laproscopy tube  406  is also shown. In this embodiment, both bolt  408  and tube  406  are fixed to a base  410  outside the body. This base may be, for example, fixed to the patient and/or his bed or it may be prevented from advancing towards the body by other means. Thus, the base of the spacer does not advance into the body. In other embodiments described below, the bolt may be retracted, requiring the base  410  to advance or to move relative to bolt  408 , if the spacer is to maintain its place in the body during expansion. 
       FIG. 7A  shows a starting position, with bolt  408  and spacer  402  (in its unexpanded state) extending between two vertebrae (not shown). 
     Both spacer  402  and collar  404  are advanced. However, as the spacer is prevented from advancing by bolt  408 , it expands, at the areas where expansion is not prevented by collar  404 , forming one or more spikes  412 . This result is shown in FIG.  7 B. 
     Collar  404  is then retracted (FIG.  7 C), so that both the collar and the spacer can be advanced again. 
     In some embodiments, the spike size is different for different spikes, requiring a different amount of motion for expanding each spike. Different amounts of motions can be required for other reasons as well, for example to allow better control over the spike expansion. In some cases, the spacer exhibits a spring-back effect, in that the spikes, after being extended, spring back and axially extend the spacer. The amounts of motion preferably take the spring-back, as well as the plastic deformation, into account. In  FIG. 7D , collar  404  and spacer  402  are advanced by a different amount than in  FIG. 7A , to create a second spike  414 . 
     In  FIG. 7E , collar  404  is retracted by a different amount from  FIG. 7B , allowing a third spike  416  to expand out (FIG.  7 F). 
     Deployment System 
       FIGS. 8A-11  show several devices suitable for expanding a spacer in ways similar to that shown in  FIGS. 7A-7F . These devices may also be used for controlled deployment of other implants in the body, where the relative positions and/or orientations of several elements are modified to effect or allow a certain deformation of an implant. 
     In the following devices, linear motion of the spacer, bolt and/or collar is provided. However, in some embodiments, rotational motion, alternatively or additionally to linear motion, may be acceptable or desirable. For example, spiral motion of collar  404  is generally acceptable. Rotational motion of spacer  402  is generally not acceptable, however, a slip-ring may be provided between a pusher tube that exhibits a spiral motion and a spacer that does not. In some embodiments, collar  404  is not rotationally symmetric, for example including slits for expansion of spikes therethrough, in which case rotational control of the collar angle may be advantageous. 
     Also, although discrete motion of the elements is generally preferred, in some embodiments, simultaneous, continuous motion of elements (such as a bolt and a collar), even during spike expansion, are provided. 
     In the embodiments below, collar  404  is outside of spacer  402 . However, collar  404  can be inside spacer  402 , if it engages the inside of the spacer and prevent expansion at the engaged areas, for example using a threading. 
     Manual Deployment Device Embodiment 
       FIGS. 8A-8D  illustrate a delivery control system  500  for effecting the process shown in  FIGS. 7A-7F , in accordance with a preferred embodiment of the invention. 
     In general, system  500  includes two sub-systems, a collar retraction subsystem and a spacer advancement sub-system. Bolt  408  is fixed to a handle  502  of system  500 . 
     Each of the subsystems includes a knob for effecting the motion, means for converting rotational motion of the knob into linear motion of the moved element and a lock for stopping the motion once the required extent of motion, for a particular spike expansion, has be performed. In a preferred embodiment of the invention, the lock comprises a plate having a plurality of holes formed in it and a pin, which slides along the plate and is elastically urged into a hole. The distance between the holes corresponds to the amount of motion desired in each expansion step. 
     In operation, a user advances collar  404  and spacer  402  using the spacer advancing subsystem, until a pin fits in a spacer location plate (corresponding to FIGS.  7 A- 7 B). Then, the user retracts collar  404  using the collar retraction subsystem, until a pin fits in a collar location plate (corresponding to FIGS.  7 B- 7 C). The user then frees the pin from the spacer location plate and advances the spacer and collar again (corresponding to FIGS.  7 C- 7 D). Then the user frees the pin from the collar location plate and retracts the collar (corresponding to FIGS.  7 D- 7 E). This process is repeated until the spacer is properly deployed. A pole element that holds bolt  408  is released from the bolt and system  500  is retracted. In an exemplary embodiment, the pole is threaded on the bolt, so system  500  is rotated around its axis to free the bolt. Preferably, a screw fixing system  500  to its handle  502  is released, allowing easier rotation of system  500  and/or of the pole element. In some embodiments, the spacer is locked to the bolt by advancing the pole-element by screwing it in tighter. 
     In a preferred embodiment of the invention, at the end of the spacer expansion, an optional additional spacer advancing step is performed, to compensate for the spring-back of the spacer and allow the cap-locking mechanism of the spacer to be deployed. 
     Although a particular implementation of the above described device is shown, other implementations may be provided instead, while maintaining the general scheme of operation described above. 
       FIG. 8A  is a side perspective view of device  500 , showing a knob  504  that is part of the spacer advancement subsystem. Spacer location plate  506  can be seen in side profile. A button  508  for freeing the pin (not shown in this figure) from spacer location plate  506 . A button  510  frees the rest of system  500  to rotate relative to handle  502 . As the spacer advancement generally requires great force, knob  504  preferably includes a significant lever and/or gear-reduction. Preferably, button  510  is used after the spacer is locked to its bolt and/or the pole-element has been at least partly unscrewed, however, this is not essential. 
     A knob  512  is provided as part of the collar retraction subsystem. A gear  516 , rotated by knob  514 , engages a linear gear  518 . A collar location plate  520  can be seen on edge. A pin locking mechanism  522 , will be described below. A button  514  on knob  512  is used to release mechanism  522  and the pin from collar location plate  520 . 
       FIG. 8B  is a perspective view of system  500  from its other side, showing locking mechanism  522  and collar location plate  520  in greater detail. In particular, a plurality of holes  530  in collar location plate  520  are shown. 
     Spacer advancement is achieved by the rotation of knob  504  advancing a free-turning (or counter-threaded) bolt (not shown in this figure) having a plurality of pins  528  extending trans-axially from it. These pins are engaged by slots  526  in a tube  524 , restricting the bolt (and the spacer advancing system) to linear motion. 
       FIG. 8C  is a cut-through view of  FIG. 8B , showing spacer location plate  506  in greater detail, especially a plurality of holes  532  for an elastically biased pin  534  to engage, when the pin is adjacent one of the holes. 
     Knob  504  turns a threaded axis  536 , having mounted on it a free-rotating, threaded or a counter threaded bolt  538  (from which pin  528  extends). 
     A pole element  540 , that engages bolt  408  (not shown) is fixed in place relative to handle  502 . A spacer pushing rod  542  is only affected by the motion of linear gear  518 . A collar  404  is advanced by the motion of linear gear  518  and retracted by the motion of a collar retraction assembly  544  coupled to gear  516 . 
     A solution for unthreading pole element  540  from bolt  408 , alternative to using button  510  ( FIG. 8A ) is to extend pole element  540  through threaded axis  536 , until knob  504 . A button (not shown) may be provided to couple the rotation of knob  504  to element  540  or a separate knob may be provided. Thus, when deployment of the spacer is completed, pole element  540  can be easily rotated. This solution may also be applied to the other embodiments described below. 
       FIG. 8D  illustrates the locking mechanism for the collar motion in greater detail. A pin  554  is urged by a spring  550  in knob  512  to engage collar location plate  520  (not shown). A rod  552  couples release button  514  and locking mechanism  522 , to retract pin  554  from the collar location plate, when needed. 
     Alternating Pin Embodiment 
       FIGS. 9A-9B  illustrate a delivery control system  600 , utilizing an alternating pin, in accordance with a preferred embodiment of the invention. 
     Unlike system  500  of  FIGS. 8A-8D , system  600  uses a continuous rotational motion of a gear  606  to retract a linear gear  604  and components attached to it (described below) through an opening  608  in a handle  602  of system  600 . 
     Another difference from system  500  is that in system  600 , as implemented, spacer  402  is not advanced, instead, both bolt  408  and collar  404  are retracted. 
       FIG. 9B  shows in detail an alternating pin mechanism for selectively retracting with linear gear  604  either collar. 404  or bolt  408 . 
     Pole element  540 , which retracts bolt  408  is fixed to a bolt-retractor  610 . A pin  612  is provided to prevent rotation of retractor  610  and/or prevent un-powered axial motion of retractor  610 . 
     A plurality of holes  614  are formed in retractor  610  for receiving a pin  618 . When pin  618  is in one of holes  614 , linear gear  604  is coupled to retractor  610 , by pin  618 , so that backwards motion of gear  604  causes retraction of bolt  408 . Pin  618  is urged towards retractor  610  by a spring  620 . However, a plurality of inclined planes  621 , which are preferably fixed relative to handle  602 , meet pin  618  as it moves backwards with linear gear  604  and urge pin  618  away from bolt retractor  610 , to a collar retractor  622 . Also collar retractor  622  preferably has a plurality of holes  624  formed in it for engaging pin  618 . Collar retractor  622  is preferably coupled to collar  404 , so that linear motion of gear  604  retracts collar  404 . As collar retractor  622  and pin  618  move backwards with linear gear  604 , pin  608  moves closer to a hole  614 , which, once reached, engages pin  618  and decouples collar retractor  622  from linear gear  604 . 
     Pull-Pull Embodiment 
       FIGS. 10A-10B  illustrate an eccentric-rotation based delivery system  700 , in accordance with a preferred embodiment of the invention. 
     In this embodiment, a knob  702  is used to rotate a wheel  704  (the reference number points to a covering of the wheel, as the rim of the wheel is hidden). Forward motion of the two arms are attached to the wheel, at off-axis positions, such that turning wheel  704  advances one arm and retracts the other arm, for one half of its rotation and retracts the one arm and advances the other arm on its other half of rotation. One arm is a bolt retraction arm  706  and the other arm is a collar retraction arm  708 . Each of the arm, when it retracts engages a nubbed bar that is coupled to either collar  404  or bolt  408 . When the arms advance, they slip forward, over one or more nubs to the next nub for retraction. 
     Collar retraction arm  708  engages a nubbed bar  710 , having a plurality of one-way nubs  712  formed thereon. Nubs  712  are flat on one side, to engage a flat aperture formed (or protrusion) in arm  708 . The nubs are inclined at their other side, to allow an inclined surface of arm  708  to slip over them, when the arm advances. 
     A similar mechanism is provided for arm  706  and its associated bar  714  and nubs  716 . 
     It is noted that in this and other embodiments, the distance between the nubs (or aperture sin other embodiments) is selected to achieve a desired amount of motion of the collar and/or bolt. Thus, also the retraction motion of the arms may include some slippage of the arm against the bar, rather than retraction. The off-axis assistance between the arm and the wheel axis, can also be used to control the force leveraging and the amount of retraction possible. 
     In the figures, the bolt, spacer and sleeve are shown extending directly from device  700 , however, in some embodiment, a pole element is used for retracting the bolt and/or a spacer pusher is used for coupling the spacer to device  700 . In device  700  as shown, the spacer does not move relative to device  700 , so device  700  advances as the spacer axially contracts. 
     Although arms  706  and  708  are shown to be 180° apart from each other, in some embodiment, a different angular difference is used, so that there is an overlap in their advancing and/or retracting motions. 
     Push-Pull Embodiment 
       FIG. 11  illustrates an alternative eccentric-rotation based delivery system  800 , in accordance with another preferred embodiment of the invention. 
     System  800  illustrates two features desirable in some preferred embodiments of the invention:
         (a) advancing spacer  402  while maintaining bolt  408  in place; and   (b) reduction of moments in the forces applied to spacer  402 .       

     These two features are substantially independent and one may be provided without the other. 
     As will be seen from FIG.  11  and the following description, forces on spacer  402 , which are generally the highest forces applied during spacer deployment, are applied substantially axially, so that there is little or no twisting and/or bending moment. In some cases, forces of 30, 60 or even 100 Kg may be applied to the spacer, to expand it. 
     Like system  700  of  FIGS. 10A and 10B , eccentric motion of a wheel is used to alternate advancing and retraction of arms. However, unlike system  700 , in system  800 , one arm is active while advancing and the other while retracting. 
     A knob  802  is used to rotate a wheel  804  and a wheel  806 . In some embodiments, these wheels include a gear reduction mechanism for reducing motion while increasing force. 
     Wheel  806  is coupled to an arm  808  which engages a nubbed bar  810  when it retracts, thereby retracting collar  404 . As in system  700 , when arm  808  advances, it can slip over one or more one-way nubs  812 . It should be noted that arm  808  is preferably near the axis of device  800 . 
     Wheel  804  is coupled to an arm  814  which is, in turn, coupled to a cylinder  816  that is centered on the axis of device  800 . A nub engaging tip  818  is coupled to cylinder  816 , preferably using a leaf spring  824 , so that it can engage a nub  822  of a nubbed bar  820 , when it advances. When arm  814  retracts, also tip  818  retracts and slips over the one-way nubs, as in system  700 . 
     Although  FIG. 11  does not show a sheath. System  800  is preferably sheathed using a cylindrical sheath. 
     Spacer Removal 
     Although the spacers are generally permanently implanted, it is sometimes desirable to remove them. In a preferred embodiment of the invention, the same devices used for implanting the spacers are used for retrieving them, being activated backwards (the collar advancing and the spacer retracting or the bolt advancing). Using dedicated devices is useful for controlling the direction in which the spacer will axially grow and to ensure that the uncollapsed spikes do not scratch the surrounding tissue. In some cases, it is necessary to unlock the bolt from the spacer end, for example by cutting or by bending in a flange of the bolt. 
     Delivery System Fixation 
     In a preferred embodiment of the invention, the delivery system is hand-held, being fixed in two dimensions by a laproscopic tube used to access space  55 . The delivery system may also be fixed to the tube to prevent axial motion and/or rotation. Generally, it is desirable that the system needs to be held with at most one hand (or no hands), leaving a second hand for performing various activities. In some cases, the free hand is used to rotate the knows used to expand the spacer. 
     In some embodiments, the body of the delivery system is fixed to the patient&#39;s body (possibly via a framework) and/or to the bed on which the patient lies. Many fixing methods can be used, for example the delivery system being clamped to the bed. Alternatively, other fixing methods, for example as used in neurological procedures, may be used. 
     In some embodiments, the operator&#39;s hand is not mechanically coupled to the delivery system, for example the delivery system being controlled using a flexible tube or wire or using wireless means. 
     In any of the above embodiments, power for expanding the spacer may be provided by a motor, rather than from the operator. however, in many cases it is desirable to provide feedback, especially tactile feedback, to the operator regarding the expansion of the spacer. In a preferred embodiment of the invention, non-tactile feedback is provided by a sensor that measures the relative motion of the bolt and the spacer or a sensor that measures the forces applied top the spacer. In a preferred embodiment of the invention, if the forces exceed a threshold, do not match the motion and/or do not match an expected force pattern or if the motion is unusual, an alert is provided, for example an audio alert. 
     Location Control 
     In the embodiments described above, a rigid tube is used to control the trans-axial and/or axial location of the delivery system and the spacer and a body stopper is used to limit the axial motion of the spacer. However, in some embodiments, such control may not be suitable or sufficient. In a preferred embodiment of the invention, the implantation of tubes uses x-ray imaging or other external medical imaging techniques to prevent damage to nerves, blood vessels and other adjacent tissue. Alternatively, visual imaging, such as using an endoscope, is used. Alternatively or additionally, ultrasonic imaging is used. Alternatively or additionally, local MRI imaging, for example using a local coil (possibly inside the body) is used. Such imaging tool may be provided through the access tube and through the delivery system, beside the delivery system or instead of the delivery system. In some cases, a second tube with the imaging tool is provided. Alternatively or additionally, a position sensor may be coupled to the tools and using a reference coupled to the body, a position of the tool and/or proximity to various body structures can be determined. Such a display is known in the art and can be overlaid on a two or three dimensional image of the body. 
     A position sensor or an ultrasonic imager may be integrated with the bolt of the spacer. Alternatively, such a bolt is hollow or is not needed. Space  55  is generally free, so a simple ultrasonic distance sensor may be used to detect if a tool is nearing dangerous areas. Possibly, a Doppler signal is used to detect the proximity of blood vessels. Such a Doppler signal can be time gated. 
     Alternatively, a fixed framework to which all tools are coupled is used. The allowed motion of the tools relative to the framework can be fixed mechanically or a sensor can detect the motion and generate a signal if an allowed ball park is exceeded. 
     Although the above described sleeve  102  can serve as such a framework, it is useful if the delivery system is coupled to the sleeve end inside the body and that sleeve  102  can be fixed in place in the body, for example using an expanding tip or a barbed tip. In one embodiment, the collar is threaded to sleeve  102  and retracted by rotation of the collar. Alternatively or additionally, the delivery system may be so fixed to sleeve  102 . Alternatively or additionally, a tool that couples the end of the spacer to sleeve  102  is provided to limit or sense motion of the end of the spacer. As the spacer is not solid, this limiting tool can remain in the body while the spacer is being expanded. 
     The use of an internal reference is especially useful if one or more of the tools is bent or flexible. 
     Non-Axial Variations 
     As described above, the various tools are generally rigid and straight. However, in some embodiments of the invention, bent tools, such as tubes and delivery systems, may be used. Alternatively or additionally, flexible tools, tubes and delivery systems may be used. 
     It is noted that although the above described devices are preferably applied inside the body, at least for testing and training purposes, these devices may also be used to expand an implant outside of a living human body, for example in the air, in a model, in an animal or inside a cadaver. 
     It will be appreciated that the above described apparatus and methods for delivering expandable inserts may be varied in many ways. In addition, a multiplicity of various features, both of methods and of devices have been described. It should be appreciated that different features may be combined in different ways. In particular, not all the features shown above in a particular embodiment are necessary in every similar preferred embodiment of the invention. Further, combinations of the above features are also considered to be within the scope of some preferred embodiments of the invention. It should also be appreciated that many of the embodiments are described only as methods or only as apparatus, however the scope of the invention includes both methods for using apparatus and apparatus for applying the methods. The scope of the invention also covers machines for creating the apparatus described herein. In addition, the scope of the invention includes methods of using, constructing, calibrating and/or maintaining the apparatus described herein. Section headings where they appear are meant for clarity and ease of browsing the application and are not to be construed as limiting the applicability of subject matter described within. When used in the following claims or in the text above, the terms “comprises”, “comprising”, “includes”, “including” or the like mean “including but not limited to”.