fig1 a , 1 b and 2 schematically illustrate a system 10 for use with a hollow intramedullary nail 11 when implanted into a intramedullary canal of a bone b . the nail has a proximal end 11 a , a distal end 11 b and two transverse distal holes 13 formed in the nail walls adjacent the distal end 11 b , each having hole axis h ( not shown ), and is designed for determining the location of the holes 13 . the system 10 comprises a first member in the form of a jig 12 ( fig1 a and 2 ) adapted for use externally relative to the bone b , and a disposable member 22 ( fig2 ), adapted for insertion in the nail 11 , when inserted in the bone b . the jig 12 has a jig proximal end 12 a and a jig distal end 12 b , and it comprises a proximal support portion 16 and a distal support portion 18 , respectively . the jig 12 is adapted to be attached at its proximal end to the proximal end 11 a of the nail 11 by a handle 14 , with both the proximal and distal support portions 16 and 18 being attached to the bone , as shown . adjacent to its distal end 12 b , the jig 12 further comprises a positioning head 15 with a ball joint 17 ( fig1 b ) having a passage 17 a extending along and co - axial with a guiding axis g oriented generally perpendicular to the nail 11 . the jig 12 further comprises guiding joints and screws as follows : a proximal joint 19 a which is adjacent to the proximal support portion 16 , a universal joint 19 b , which is positioned between the proximal end 12 a of the jig 12 and the positioning head 15 , and positioning screws 15 a and 15 b ( not shown ), which are part of the positioning head 15 . the positioning screws 15 a and 15 d allow the ball joint 17 to move in any of the x or y directions ( shown by arrows in fig1 a ) so as to bring its guiding axis g into different spatial positions with respect to the hole axis h and to the positioning head 15 . in operation , the jig 12 together with the handle 14 creates a rigid bridge between a distal end b 2 of the bone b and the proximal end 11 a of the nail 11 , which facilitates a procedure of positioning of the positioning head 15 and then drilling of the holes , by the limitation of mutual movement of the nail 11 with respect to the bone b . the proximal support portion 16 and the distal support portion 18 ( shown only partly ) of the jig 12 contribute to the stability of the created bridge . the second disposable member 22 of the system 10 has a laser source 21 , a stem ( laser stick ) 23 , two locking bosses 25 , a spring 27 and an unlocking frame 29 . this disposable member is designed in a way that allows the member 22 with it &# 39 ; s locking bosses 25 to be disposed exactly at the distal hole 13 axis and to allow either locking the laser source 21 inside the nail having the laser beam directed through the opening in the center of the locking boss 25 , or unlocking the stem 23 with the laser source 21 from the bosses 25 at the end of the initial pre - adjustment of the system . the laser source 21 may be of any appropriate type and it may emit radiation of a wavelength of 550 nm to 2 . 2 μm . as shown in fig3 , in operation , the disposable member 22 is inserted into the nail 11 so that a laser beam 24 , emitted by the laser source 21 , projects through the distal hole 13 of the nail 11 and is coaxial with its axis h , thereby creating an illuminated spot 26 on the outer surface of the bone b . with reference to fig3 and 4 , the system also comprises an alignment pin 41 receivable within the passage 17 a of the ball joint 17 within the positioning head 15 . as shown in fig4 , the alignment pin 41 has a proximal end 41 a , a distal and 41 b and a pin axis p . the alignment pin 41 comprises reference marks 43 on its outer surface , which are visible in x - ray images . the alignment pin 41 may further comprise a laser pointer 45 at its proximal end 41 a . the system may further comprise a viewing optics 81 , such as aiming telescope with a tv camera , shown in fig8 a , and a penetrating trocar ( not shown ), both receivable within the 17 a of the ball joint 17 of the positioning head 15 , whose use will be further described in more detail . fig5 illustrates the system 10 mounted on the bone b and positioned in the radiation field of a c - arm x - ray machine 50 , having an x - ray source 53 and an x - ray receiver 51 having an emitting face 57 , to which a mirror 54 may be attached as shown . the bone b has the nail 11 inserted therein ( not seen ) and the jig 12 is attached to the bone b , as previously described . the c - arm 50 is rotatable about the longitudinal axis 59 around the bone b , so that x - ray images may be taken by the c - arm from different angles . there is further provided an image processing software and hardware 55 , which may be connected directly or indirectly to the system 10 , for processing x - ray images taken by the c - arm 50 . the use of the system 10 for the determination of the location of the distal hole 13 comprises the following stages : 1 . pre - adjustment of the positioning head 15 prior to the insertion of the nail 11 into the bone b ; 2 . insertion of the nail 11 into the bone b and attaching the jig 12 3 . initial adjustment of the c - arm 50 and calculation of the parameters of initial position of the guiding axis g of the system relative to the hole axis h . 4 . insertion of the viewing optics 81 into the positioning head 15 ; 5 . insertion of the disposable member 22 into the nail 11 and determination of an entry point at which in future a drilling bit will be located for drilling the bone b ; 6 . insertion the alignment pin 41 into the ball joint 17 , taking x - ray images and calculation of the parameters of the updated position of the guiding axis g relative to the hole axis h . 7 . moving the ball joint 17 to adjust the position of the guiding axis g based on the updated parameters ; 8 . adjusting the c - arm 50 according to the new position of the ball joint 17 and taking an additional , control x - ray image . each of the above stages will now be described in more detail . 1 . pre - adjustment of the positioning head 15 prior to the insertion of the nail 11 into the bone b the disposable member 22 is inserted into the nail 11 when the nail 11 is still outside the bone , and the position of the laser source 21 therein is adjusted by the locking bosses 25 so that the laser source is aligned with the axis h of the distal hole 13 . since the adjustment is performed when the nail 11 is outside the bone , the distal hole 13 and the laser source aligned therewith are clearly seen . therefore , activation of the laser is not necessarily needed for the adjustment and it may be activated just for check - up purposes . the jig 12 is attached to the nail 11 at its proximal end 12 a by means of the handle 14 and the universal joint 19 b using an aligning conductor ( not shown ) or by any other appropriate way known in the art . the positioning head 15 is adjusted to align the axis g thereof with the distal hole axis h . the y axis of the positioning head 15 is made parallel to the axis of the nail , while the g axis is initially made parallel to the z axis of the jig 12 by setting the ball joint 17 in the pre - defined 90 ° position . the x - y plane of the positioning head should be normal to the g axis . after the adjustment of the positioning head 15 , the proximal joint 19 a , the universal joint 19 b , the positioning screws 15 a and 15 b , and the ball joint 17 are locked and the jig 12 together with the handle 14 is dismantled from the nail 11 and put aside . this pre - adjustment is performed only once , matching the jig set - up to the specific nail chosen for the operation , and allowing relatively large displacements of the positioning head 15 in x or y directions . therefore , in further steps only fine adjustment of the ball joint 17 will be needed , which may be achieved by unlocking only the ball joint 17 and by using the positioning screws 15 a and 15 b . the joints 19 a and 19 b will remain locked till the end of the procedure . the purpose of this stage is to bring the positioning head 15 together with the ball joint 17 to a position as accurate as possible relative to the distal hole 13 and to align the axis g with the axis h , thereby facilitating the adjustment thereof after the nail 11 is inserted into the bone b . 2 . insertion of the nail 11 into the bone b and attaching the jig 12 the nail 11 is inserted into the bone b using traditional techniques , and at the end of the implantation the proximal end of the jig 12 a together with the handle 14 is attached to the proximal end of the nail 11 a ( as shown in fig1 a ). the jig 12 may be further attached ( when improved stability is needed ) to the bone b by the proximal support 16 and / or the distal support portion 18 using standard clips and a schanz screw . when the jig 12 is attached , a penetrating trocar may be inserted through the passage 17 a of the ball joint of the positioning head 15 , which penetrates the flesh until it touches the bone cortex , in order to expose it and facilitate further steps of the method . the exposure of the bone cortex may be facilitated by other known techniques , e . g . using scalpel to make a small incision . 3 . initial adjustment of the c - arm 50 and calculation of the parameters of initial position of the guiding axis g of the system relative to the hole axis h the trocar is pulled out of the passage 17 a and replaced with the alignment pin 41 . the alignment pin 41 is inserted into the passage 17 a , as shown in fig4 , whereby its axis p is aligned with the guiding axis g ( not shown ) of the ball joint 17 . the alignment pin 41 is inserted so as to touch the bone at a point t thereon . with reference to fig5 , the laser pointer 45 at the proximal end 41 a of the alignment pin 41 is turned on to emit a laser beam 52 , which is aligned with the pin axis p , toward the center of the mirror 54 on the emitting face 57 of the x - ray emitter 53 ( or the receiving face of the receiver 51 ) so as to obtain a beam reflected from the mirror . the coincidence of such reflected beam with the incident laser beam 52 will indicate that the axis of the c - arm 50 is aligned with the axis of the alignment pin p , and , consequently , with the guiding axis g of the ball joint 17 . this coincidence is achieved by locating a spot created by the reflected beam on a plane , e . g . a sheet of paper , positioned close to the laser pointer 45 , and adjusting the c - arm 50 so that the spot is located exactly on the laser pointer 45 . once the c - arm 50 is adjusted , two x - ray images of the system with the bone b are taken , examples of which are shown in fig6 a and 6b . the first image is taken along the y - axis ( fig6 a ) and the second image is taken along the z - axis ( fig6 b ). based on these images it is determined whether bending and / or twisting of the nail 11 has been occurred during the implantation of the nail 11 into the bone b . moreover , since in both of these cases the center of the distal hole 13 and its axis h will not be located at the same place as it was before the implantation , at this stage the location of the center of the distal hole 13 is determined and , in case the twisting occurred , a distance is calculated between the orientation of the hole axis h determined at stage 1 and its new orientation due to the twisting . this distance is designated as sx 1 in fig7 . these and other parameters can be determined using the x - ray images as follows : ( a ) the center c of the hole 13 is determined visually or using software based on the x - ray image taken along the z - axis , as shown in fig6 b . ( b ) the twisting of the nail 11 is determined based on the same x - ray image as used in step ( a ) above , where non - circularity of the hole 13 indicates to the twisting of the nail . the image further shows the reference marks 43 , which appear circular due to the c - arm 50 adjustment . the fact that the marks are not concentric with the hole 13 , as shown in fig6 b , will indicate the bending of the nail 11 . ( c ) based on non - circularity of the distal hole 13 and non - concentricity of the reference marks on the x - ray image taken along the z - axis with the hole 13 , a distance sx 0 ( not shown ) is calculated , which is actually the distance that the guiding axis g of the ball joint should be moved along the x - axis parallel to itself , for the hole axis 13 to meet with the axis g at the bone outer surface . at this stage , the distance sx 0 can be only calculated and not actually measured , since the hole 13 is inside the bone and not on the outer surface thereof . the actual measurement of this distance will be performed during further steps . the x - ray image taken along the y - axis ( fig6 a ) allows calculating other distances such as a distance r between the center c of the distal hole 13 and the point t and a distance l — distance between the point t and the center of the ball joint 17 , as also schematically shown in fig7 in addition , the size of screws length to be used for fixing the distal end 11 b of the nail 11 may be calculated . it should be noted , that this stage may be optional , and actually may be performed as a part of stage 5 and 6 ( see below ), which will speed up the operation and reduce the number of x - ray images taken . the final decision in this respect will be made after sufficient experience with the described procedures is acquired . 4 . insertion of the viewing optics 81 into the positioning head 15 with reference to fig8 a , the alignment pin 41 is replaced with the viewing optics 81 ( fig8 a , which is inserted into the passage 17 , whereby optical axis of the viewing optics is aligned with the guiding axis g . 5 . insertion of the disposable member 22 into the nail 11 and determination of an entry point at which in future a drilling bit will be located for drilling the bone b the disposable member 22 is inserted into the nail 11 and adjusted as described in stage 1 . the laser is then activated and as a result of the laser beam 24 projected though the distal hole 13 and the surrounding tissue of the bone , whereby a spot 26 is created on the outer surface of the bone b , as shown in fig3 . the spot 26 is viewed by the viewing optics and the center of the spot is determined visually or by using software , indicating the intersection of the distal hole axis h with the outer surface of the bone b . the center of the spot in fact constitutes an entry point e at which a drilling bit will enter the bone . the viewing optics 81 within the ball joint 17 may be moved manually using the positioning screws 15 a and 15 b , until it is aligned with the center of the spot 26 . the values of this displacement are stored for future use . this displacement ( being a sum of distance sx 1 and sx 0 ) is measured and compared to its value calculated in stage 3 based on the x - ray images , so as to assure that the measurement is correct and actual sx 1 may be calculated being a result of the nail twisting and not bending . as it may be appreciated from the explanations above , the value of the distance sx 1 depends on the extent of the nail distortions which could take place during the insertion process , namely bending and twisting of the nail 11 . the results of these distortions may add to or subtract from one another . however , it is important to distinguish between them , and such distinction can be done by using data acquired from x - ray images and entry point determination . it should be noted , that bending of the nail results in displacement of the hole axis h being parallel to itself , while twisting results in “ turning ” of the said axis and non - circularity of the hole 13 image in the x - ray images taken along the x - axis . both movements result in displacement of the laser spot 26 created at the outer surface of the bone . 6 . insertion of the alignment pin 41 into the ball joint 17 , taking x - ray images and calculation of the parameters of the updated position of the guiding axis g relative to the hole axis h the viewing optics 81 is replaced with the alignment pin 41 , and it is positioned within the passage 17 a as described in stage 3 . the disposable member 22 is taken out of the nail 11 and two additional x - ray images are made along the x and z axes . the distances r , l and sx 1 are measured once again based on the x - ray images , to avoid any inaccuracy . the final sx 1 distance is then calculated being only the result of twisting ( if any ) and not of parallel displacement of the hole axis . the distal end of the alignment pin 41 b is fixed at the entry point e by any suitable means , even hold by hand . 7 . moving the ball joint 17 to adjust the position of the guiding axis g based on the updated parameters once the alignment pin 41 is fixed at the entry point e , the adjustment of its axis p ( and consequently the guiding axis g ) should be made , so that it will be aligned with the axis of the hole h . for this purpose a distance sx 2 is calculated ( fig7 ), based on the distances previously calculated . the ball joint 17 is then unlocked , and the positioning screws 15 a and 15 b are used to move the ball joint 17 with the alignment pin through the distance sx 2 along the x - axis ( and similarly sy 2 along y axis ), while its distal end 41 b is held fixed at the entry point e . this displacement is allowed due to the unlocked state of the ball joint 17 , in which the axis of the passage in the ball joint 17 may be at different angular positions with respect to the axis of the nail . it should be noted that the displacements shown in fig7 are for the purpose of explanation only , and the value and direction of actual displacement has to be determined in each case . 8 . adjusting the c - arm 50 according to the new position of the ball joint 17 and taking an additional , control x - ray image the c - arm 50 is adjusted based on the updated position of the alignment pin 41 using the laser pointer 45 , similar to the adjustment performed as explained in stage 3 . an additional x - ray image is then taken along the z - axis to assure that the guiding axis g is aligned with the distal hole axis h . if the alignment pin 41 distal end marker is positioned in the center of hole 13 at the x - ray image , and the hole 13 image is circular while the circular markers of the alignment pin 41 are concentric with the hole 13 — that means that the positioning is made correctly . any of the above stages may be repeated if the surgeon is not satisfied with the results and he feels that an additional adjustment is needed along both x - axis and y - axis . once the location and the axis of the distal hole 13 are determined and the guiding axis g is aligned with the distal hole axis h , the ball joint 17 is locked , the alignment pin 41 is removed out of the positioning head 15 and replaced with a drilling guide 83 ( fig8 b ) through which a drill bit is inserted and a hole is drilled through the bone b . the nail 11 is then secured in place within the bone by a transversely extending screw or bolt which is inserted through the drilled hole and the nail distal hole 13 . since the location of one distal hole 13 is already determined and the ball joint 17 is already adjusted such that its guiding axis g is aligned with the distal hole axis h , a guiding plate ( not shown ) is affixed to the positioning head 15 and drilling of a second distal hole may be performed . each of the previously mentioned stages may be repeated for final adjustment of the positioning head 15 with respect to the second distal hole . the second distal hole is then drilled through the bone and the second screw is inserted . after the distal screws are inserted and affixed , proximal holes , the locations of which are known , are drilled using drill guiding holes usually made in the handle 14 and proximal screws are inserted and affixed .
the present invention relates to alignment systems and methods for detecting a distal hole of an intramedullary nail . a jig is attached to the proximal end of the nail and also mounted on the bone . the jig has an adjustable positioning head that includes a drill axis hole along with an alignment pin . the alignment pin includes reference marks that are visible in x - ray images and helps to align the positioning head drill axis with the distal hole of the intramedullary nail . a light source is insertable into the nail in order to shine light out of the distal hole to illuminate a spot on the bone surface as an alignment aid . viewing optics are mountable on the positioning head for viewing the illuminated spot created by the light source in the intramedullary nail .