referring more particularly to the drawings , fig1 shows device 10 which is a preferred embodiment of the present invention and may be used for three - dimensional distraction osteogenesis having a left arm 20 , a right arm 30 , a central joint 80 , a left bone - pin clamp 40 and a right bone - pin clamp 60 . fig2 a and fig3 a show the left arm 20 and the right arm 30 , respectively . arms 20 , 30 are l - shaped , each arm having a head segment 22 , 32 which is perpendicular to shaft 28 , 38 . each shaft 28 , 38 is d - shaped in cross - section and has threaded segments 24 , 34 along its partially cylindrical surface and a flat - keyed segment 26 , 36 , both extending the length of the shaft 28 , 38 . the arms 20 , 30 are substantially identical except for the orientation of flat - keyed segments 26 , 36 with respect to head segments 22 , 32 . whereas , the flat - keyed segment 26 faces the same direction as the head segment 22 of the left arm 20 as shown in fig2 a , the flat - keyed - segment 36 faces 90 ° clockwise from the head segment 32 of the right arm 30 as shown in fig3 a . the central joint 80 as shown in fig4 has a housing 81 , two gears 84 , 94 , and two angular - adjustment screws 88 , 98 . the central joint 80 adjusts the angular relation between the arms 20 , 30 . housing 81 has two u - shaped supports 83 , 93 having respective sets of paired holes 82 , 92 which receive and support respective head segments 22 , 32 of the arms 20 , 30 . the u - shaped supports define axes of rotation for the arms 20 , 30 and are oriented such that the axes of rotation define differently oriented planes , and preferably , are in perpendicular relation to one another . the angular - adjustment screws 88 , 98 have threads 89 , 99 and are housed within the housing member 81 adjacent to the respective gears 84 , 94 as shown in the cross - sectional view of the central joint 80 in fig5 . the screw 98 fits within the bore 72 of the housing member 81 . the head 96 of screw 98 is the same size as the minimum screw diameter such that the peaks of the threads 99 are of larger diameter than the head 96 of the screw 98 . axial movement of the screw 98 is restricted by threads 99 being retained by the lip 73 of the housing 81 and by the other screw 88 which also fits within the larger bore 72 of the housing member 81 . the screw 88 has a circumferential groove 74 which is fitted with pin 75 to restrict axial movement of the screw 88 yet allowing for unrestricted rotational movement . each gear 84 , 94 has an arm hole 86 , 96 and a toothed segment 87 , 97 along at least part of its circumference . fig5 shows the central joint with the gear 84 fitted between the u - shaped supports 83 such that the arm hole 86 of gear 84 is aligned with the paired holes 82 of the u - shaped supports 83 . in a similar fashion , gear 94 is fitted between u - shaped supports 93 such that arm hole 96 of gear 94 is aligned with paired holes 92 of the u - shaped support 93 . the toothed segments 87 , 97 of the gears 84 , 94 mesh with the threads 89 , 99 of the angular - adjustment screws 88 , 98 both to retain angular - adjustment screws 88 , 98 within the housing 81 and so that the angular - adjustment screws 88 , 98 turn the gears 84 , 94 . in the preferred embodiment of fig4 and 5 , the housing 81 is configured such that the angular - adjustment screws 88 , 98 lie along the same axis such that both may be adjusted easily while the device is in use . in this embodiment , with the screws aligned back - to - back , the ends of the angular - adjustment screws 88 , 98 have radii 90 , 91 on their ends so that rotational motion is not transferred between them . in the preferred embodiment , the angular - adjustment screws 88 , 98 have standard machine threads 89 , 99 and the toothed segments 87 , 97 of the gears 84 , 94 have &# 34 ; v - shaped &# 34 ; grooves or teeth which have the same helix angle and pitch as the respective angular - adjustment screws 88 , 98 . in particular , the helix angle θ which is the angle in which the teeth are formed in the gear with respect to an axis parallel with its axis of rotation as shown in fig6 and the pitch p would be equal to the helix angle and pitch of the machine threads 89 , 99 of the angular - adjustment screws 88 , 98 . in addition , the profile of the &# 34 ; v - shaped &# 34 ; teeth would mate with the machine thread profile to insure proper alignment as the angular - adjustment screws 88 , 98 are turned and rotate the respective gears 84 , 94 . alternatively , the gears 84 , 94 may be standard gears with involute - shaped teeth such as are well - known in the art , in which case angular - adjustment screws 88 , 98 would be standard worm screws configured so as to mate with the teeth of the standard gears . the &# 34 ; v - shaped &# 34 ; teeth are preferred because they require less intricate machining to form the gears and mating worm screws and , in addition , the standard gears would have to be larger than the &# 34 ; v - shaped &# 34 ; teeth gears , but then they would not be able to perform the same precise , gradual and controlled angular - adjustments to the arms of the device . the head segments 22 , 32 of the arms 20 , 30 fit through the respective paired holes 82 , 92 of the central joint 80 and arm holes 86 , 96 of gears 84 , 94 . each respective arm 20 , 30 is properly oriented and then secured to the gears 84 , 94 by any of a number of ways . in this embodiment , pin - holes 85 , 95 are drilled into gears 84 , 94 and head segments 22 , 32 of arms 20 , 30 and pins 7 , 17 are inserted therein . in operation , the angular - adjustment screw 88 turns the gear 84 which ultimately pivots or rotates the arm 20 in a plane . likewise , the angular - adjustment screw 98 turns the gear 94 which ultimately pivots or rotates the arm 30 in a plane . the plane in which the arm 20 rotates is differently oriented from , and in this embodiment , is perpendicular to , the plane in which the arm 30 rotates . the configuration of the central joint 80 as shown in fig4 allows the two independent centers of rotation of the arms 20 , 30 to be located in close proximity to each other and within the central portion of the device . fig7 shows the left bone - pin clamp 40 which has a rider 42 , a cap 50 , a screw 56 and a wheel 46 . the left bone - pin clamp 40 fits around and rides along left arm 20 . the rider 42 has two cylindrical extensions 45 , a bore 48 ( which cannot be seen in fig7 but which is shown in fig9 shown in fig9 ), an extended portion 44 having a recessed surface 41 extending the width of the rider 42 , a screw - hole 49 piercing the recessed surface 41 and two diametrical grooves 43 of a semi - cylindrical shape spaced in parallel extending the entire width of the recessed surface 41 . the two cylindrical extensions 45 have d - shaped bores 47 which are configured to fit around the left arm 20 . the d - shaped bores 47 are oriented in the cylindrical extensions 45 such that the bone - pins held by the left bone - pin clamp 40 will remain perpendicular to the face of the flat - keyed segment 26 of the left arm 20 as the left bone - pin clamp 40 rides along the left arm 20 . in addition , the d - shaped bores 47 are oriented in the cylindrical extensions 45 such that the extended portion 44 of the rider 42 is directed toward the central joint 80 when the left bone - pin clamp 40 is assembled onto the left arm 20 . the cap 50 has a screw - hole 58 throughout its thickness and a bottom surface 52 having two parallel diametrical grooves 54 along the entire width of the bottom surface 52 of a partial semi - cylindrical shape . the cap 50 is screwed to the rider 42 with the screw 56 which fits in the screw - hole 58 of the cap 50 and the screw - hole 49 of the rider 42 such that the diametrical grooves 43 of the rider 42 oppose the diametrical grooves 54 of the cap 50 , thereby forming holes adapted to receive and retain bone - pins ( not shown ). the bone - pins are secured to the bone - pin clamp 40 by tightening the screw 56 . as shown in fig8 the cap 50 is preferably connected to rider 42 by a web 53 . as seen in fig7 - 8 , the wheel 46 fits between the two cylindrical extensions 45 of the rider 42 such that the left arm 20 may fit through the cylindrical extensions 45 and the wheel 46 . the wheel 46 is threaded along its inner circumference to mate with the threaded segments 24 , 34 of the arms 20 , 30 . the left bone - pin clamp 40 moves along the left arm 20 as the wheel 46 is turned . to facilitate rotation of wheel 46 , grooves or threads may be provided along its outer circumference . as the wheel 46 is rotated in one direction , the left bone - pin clamp 40 moves away from the central joint 80 ( see fig1 ), and conversely , as the wheel 46 is rotated in the opposite direction , the left bone - pin clamp 40 moves toward the central joint 80 . due to the mating of the left arm 20 with the d - shaped bores 47 of the cylindrical extensions 45 , the left bone - pin clamp 40 is prevented from rotating about the left arm 20 . fig9 shows the right bone - pin clamp 60 which is substantially identical to the left bone - pin clamp 40 except that the d - shaped bores 47 of the cylindrical extensions 45 are oriented differently ( as shown ) such that the extended portion 44 of the rider 42 of the right bone - pin clamp 60 is directed toward the central joint 80 when the right bone - pin clamp 60 is assembled onto the right arm 30 . the device of the present invention preferably has an indexing feature such that the bone - pin clamps can be moved along the arms in predetermined increments . one manner of providing this indexing feature is to provide a small bore 48 as shown in fig9 in between the two cylindrical extensions 45 of the rider 42 which is fitted with a spring 55 and a small ball 58 . the wheel 46 is provided with a number of indentations or depressions 51 , in this embodiment , four , which are equally spaced along its outer circumferential surface which engage the ball 58 to provide a noticeable feel and / or sound such that turning the wheel 46 from one indentation 51 to the next produces a known linear adjustment along the length of the arms 20 , 30 . in addition , the flat - keyed segments 26 of each arm 20 , 30 may be marked in the manner shown in order that the linear distance which the bone - pin clamps 40 , 60 travel along the arms 20 , 30 may be measured . the device of the present invention also preferably is provided with a means to retain the bone - pin clamps on the arms . it is understood that many ways can be used to accomplish this feature such as altering the threaded segment at a point on the free end of the arms 20 , 30 so that the threads on the wheel do not properly mesh with the threads on the arms 20 , 30 . another means would be to provide a cap or other similar locking mechanism which is well - known in the art which would mate with the threads on the arms and act as a stop . the preferred means of retaining the clamps on the device of the present invention is to flare the ends of the arms 20 , 30 so as to disrupt and damage the threads on the arms . the central joint 80 also can be configured , as shown in fig1 to retain bone - pins , for example , by having bores 71 for receiving the bone - pins and set screws 76 to retain the bone - pins in the bores 71 thereby fixing them to the central joint 80 . it is to be understood that other ways can be used to retain the housing to the bone - pin such as , for example , using two plates with opposed diametrical grooves and clamping them together as described in reference to bone - pin clamps 40 , 60 . by configuring the central joint 80 to retain bone - pins , more than one distraction can occur , such as a distraction between the central joint 80 and arm 20 as well as the central joint 80 and arm 30 . in addition , arms 20 , 30 can be fitted with more than one bone - pin clamp each , such that multiple linear distractions , such as bone transport , can occur . with no limitation intended and for illustrative purposes only , the central joint may be configured such that the center of rotation for each arm is within 5 mm of each other . the bone - pin clamps may be configured to retain either two 2 mm pins or one 3 mm pin and the diametrical grooves of the bone - pin clamps may be 10 mm apart . the device may allow for linear expansion of up to 20 mm along each arm and angular movement of up to 120 °. it is contemplated that the device will be made from stainless steel with the angular - adjustment screws being formed of 455 h . t ., the housing , arms , rider and cap formed of 17 - 4 and the gears and wheels formed of &# 34 ; gall - tough ™&# 34 ; stainless steel made by carpenter technology corporation for its wear resistance and self - lubricating characteristics . while the device in its preferred form has been described with two arms , it is to be understood that the use of a single arm or multiple arms , i . e ., more than two , is contemplated also . for example , the alternative embodiment of fig1 illustrates an angular distraction device having a single arm . fig1 shows device 110 which may be used to perform angular and linear distraction osteogenesis having an arm 120 , a left bone - pin clamp 140 , and a right bone - pin clamp 160 which has an angular - adjustment assembly 180 . the arm 120 has a core member 122 , a cylindrically - shaped telescoping member 124 which slides along core member 122 and a length - adjustment screw 126 . the core member 122 has an internally threaded screw - hole 161 into which the length - adjustment screw 126 is fitted and mates . a collar 125 on the telescoping member maintains the length - adjustment screw 126 on the telescoping member so that it cannot move axially but allows the screw 126 to rotate freely . the length - adjustment screw is rotated in order to adjust the length of the arm 120 . as shown in fig1 , the external shape of the core member 122 is non - circular in cross - sectional shape , and may be axisymetrical , and mates with the internal shape of the telescoping member 124 to prevent rotation of the telescoping member 124 about core member 122 . the left bone - pin clamp 140 has two plates 145 , 155 each having a central hole 146 , 156 and two diametrical grooves 143 , 153 spaced in parallel and extending the entire width of plates 145 , 155 . the plates 145 , 155 are configured on the arm so that the diametrical grooves 143 oppose diametrical grooves 153 to form holes adapted to receive and retain bone - pins ( not shown ). the left bone - pin clamp 140 is fixed to the arm 120 so that it does not rotate or translate linearly along the length of the arm 120 . the manner of fixing the left bone - pin clamp 140 to the arm 120 in fig1 is by providing threads 127 along the end portion of the left end of the arm 120 and having a nut 142 to clamp the plates 145 , 155 in place . in particular , nut 142 is fitted on the threaded portion 128 of the arm 120 and the plates 145 , 155 are placed on arm 120 by fitting the threaded portion 128 through central holes 146 , 156 . the threaded portion 128 of arm 120 is non - circular in cross - section and has a smooth portion which does not have threads which prevent the plates from rotating . after the nut 142 and plates 145 , 155 are placed on the arm 120 , a stop 129 is provided at the left distal end of the arm 120 to prevent the plates 145 , 155 from becoming detached from the arm 120 . in operation , the bone - pins are placed in the holes formed by diametrical grooves 143 , 153 and nut 142 is rotated to clamp and fix the bone - pins in the plates 145 , 155 and the plates 145 , 155 to the arm 120 . the right bone - pin clamp 160 in fig1 and 12 has two support members 165 and a cylindrically - shaped hole 167 formed between the support members 165 which receives the telescoping member 124 of arm 120 so that it can slide along the telescoping member 124 . a threaded hole 127 extends through both support members 165 and receives a screw 128 which can be tightened to fix the bone - pin clamp 160 on the telescoping member 124 . loosening the screw 128 allows bone - pin clamp 160 to be positioned along the length of the telescoping member 124 . the right bone - pin clamp 160 also contains an angular - adjustment assembly 180 . the angular - adjustment assembly 180 has an angular - adjustment screw 198 and two pin - clamp plates 162 , 172 . the angular - adjustment screw 198 is similar and may be identical to the angular - adjustment screw 88 described in fig4 - 5 . the two pin - clamp plates 162 , 172 have a circular shape along a portion of their perimeters 163 , 173 and are formed with &# 34 ; v - shaped &# 34 ; teeth 185 , 195 similar to those described in fig4 - 6 . the angular - adjustment screw 198 and &# 34 ; v - shaped &# 34 ; teeth 185 , 195 are configured to cooperate and mesh with each other as described earlier in reference to angular - adjustment screw 88 and gear 84 in fig4 - 6 such that rotating screw 198 angularly adjusts plates 162 , 172 . the pin - clamp plates 162 , 172 adjust angularly in unison . pin - clamp plates 162 , 172 are also formed with two diametrical grooves 166 , 176 each set spaced in parallel and extending the entire width of the pin - clamp plates 162 , 172 . each pin - clamp plate 162 , 172 also is provided with a screw - hole 167 extending throughout its thickness and adapted to receive a threaded pin 168 . the pin - clamp plates 162 , 172 are arranged on threaded pin 168 so that diametrical grooves 166 oppose diametrical grooves 176 to form holes to hold bone - pins . a nut 169 is threaded on threaded pin 168 to press the plates 162 , 172 together to hold the bone - pins . the threaded pin 168 , however , allows the plates 162 , 172 to angularly adjust about the pin 168 when the plates are tightened together by nut 196 . the alternative embodiment shown in fig1 can be used to perform two distractions and has two arms 220 , a central joint 270 and bone - pin clamps 240 , 260 . the arms 220 are identical and each has a core member , a telescoping member which slides along the core member and a length - adjustment screw as described above in reference to fig1 and 11 . each bone - pin clamp 240 , 260 also is the same as bone - pin clamp 160 described in fig1 and 12 . both arms 220 are connected to central joint 270 via angular - adjustment support piece 275 as shown in fig1 . the central joint 270 has two bone - pin holes 207 to receive bone - pins and two set screws 208 to hold the bone - pins within the holes 207 and fix them to the central joint 270 . the angular - adjustment support piece 275 has two u - shaped support extensions 276 with circular holes 277 configured to receive axle 280 and a u - shaped gear section 271 having a portion which is of circular perimeter . the gear section 271 has a hole 273 and &# 34 ; v - shaped &# 34 ; teeth 272 , as previously described with reference to fig4 - 6 , formed along its circular perimeter . the angular - adjustment support piece 275 has a bore 284 which receives angular - adjustment screw 285 . a pin and groove similar to that described in reference to fig4 - 6 is used to retain the screw 285 in the angular - adjustment support piece while allowing it to rotate . the arms 220 are provided with ends which have a disk - like circular perimeter 283 with &# 34 ; v - shaped &# 34 ; teeth 282 formed therein similar to gear section 271 of the angular support piece 275 . the arm 220 is provided with a bore 284 ( not shown ) configured to receive axle 280 . the circular perimeter 283 of arm 220 is inserted in between the u - shaped support extensions 276 of the angular - adjustment piece 275 so that bore 284 is aligned with circular holes 277 and axle 280 is inserted therein . the arm 220 can be fixed to the axle 280 in a number of ways and in this embodiment , is fixed thereto by drilling a hole through the circular perimeter 283 and axle 280 and using a pin similar to that used in the preferred embodiment described in fig1 - 6 . the &# 34 ; v - shaped &# 34 ; teeth 282 on the arm 220 mesh and cooperate with the threads on angular - adjustment screw 285 so that turning screw 285 angularly adjusts or rotates the arm 220 with respect to the angular - adjustment piece 275 . the central joint 270 has two sets of u - shaped supports 265 , one set on each end which is used to connect the annular adjustment support piece 275 to the central joint 270 in the same manner in which arm 220 is connected to the angular - adjustment support piece 275 . in particular , the u - shaped supports 265 are provided with circular holes 267 configured to receive cylindrical axle 290 . the gear section 271 of the angular - adjustment support piece 275 is received in the central joint 270 between the set of u - shaped supports 265 . axle 290 is inserted through hole 267 in the central joint 270 and hole 273 in the angular - adjustment support piece 275 . a pin , similar to pin 7 in fig4 is used to secure the angular - adjustment support piece 275 to the central joint 270 . in addition , the central joint 270 has two bores 274 formed on its ends and in proximity of the u - shaped supports 265 for receiving angular - adjustment screws 295 . the angular - adjustment screws are received in bores 274 and retained therein by a pin and groove as described with reference to fig4 - 5 . the threads on angular - adjustment screw 295 cooperate and mesh with the &# 34 ; v - shaped &# 34 ; grooves 272 on the angular - adjustment support piece 275 so that rotating the screw 295 angularly adjusts the angular - adjustment support piece 275 . it is to be understood that fig1 has been described with reference to a double angular - adjustment mechanism but that a single angular - adjustment mechanism can be provided by attaching the arm with its disk - like circular perimeter and &# 34 ; v - shaped &# 34 ; teeth on its end directly in between the u - shaped extensions 265 on the central joint 270 with an axle . it is understood also that only one arm 220 can be used with either the single or double angular - adjustment mechanism and / or with or without the angular - adjustment mechanism incorporated in the bone - pin clamps 240 , 260 . in the alternative embodiment in fig1 , the device 310 is substantially the same as the device 10 except for minor differences to be described . in the embodiment of fig1 , the arms 320 are fixed to supports 387 . each support 387 contains and retains angular - adjustment screws 388 , 389 in the manner described with reference to fig4 - 5 . gears 384 , 385 ( not shown ) are provided and are both semicircular in shape and fixed to each other . supports 387 are retained on gears 384 , 385 by cylindrical axles 317 , 327 ( not shown ) which allow the supports 387 and arms 320 to rotate about their respective gears 384 , 385 . the gears are oriented in different planes and in the embodiment of fig1 are perpendicular to each other so that the arms 320 rotate in perpendicular planes . the gears 384 , 385 are provided with &# 34 ; v - shaped &# 34 ; teeth as shown and described in reference to fig4 - 6 which mate with the standard machine threads on respective angular - adjustment screws 388 , 398 such that rotating the screws angularly adjusts arms 320 about the respective gears 384 , 385 . the bone - pin clamps 340 , 360 are similar to the bone - pin clamps 40 , 60 in the preferred embodiment . however , the bone - pin clamps 340 , 360 in fig1 have u - shaped clip locks 370 to prevent the wheel 346 from spinning and thereby maintain the bone - pin clamps 340 , 360 in a fixed position relative to the arms 320 , 330 . as shown in fig1 , each u - shaped clip lock 370 is attached at one end to the cylindrical extension 345 and extends across and in contact with the wheel 346 . the shape and configuration of the u - shaped clip lock is such that it is biased toward the wheel 346 . the wheel 346 is provided with grooves 347 and the u - shaped clip lock has an extension 375 where it contacts the wheel 346 in order to mate with a groove 347 and hold the wheel in place . the biasing force between the free end of each u - shaped clip lock 370 and the wheel 346 is such that the wheel 346 will be held firmly in place , but may be overcome if sufficient force were applied to the wheel 346 . in addition , the portion of the bone - pin clamps 340 , 360 which hold the bone - pins is slightly different in the embodiment of fig1 from the embodiment of fig7 - 9 . the recessed surface 341 extends throughout the rider 342 and the cap 350 covers the entire top of the rider 342 . the screw 356 is off - set from bone - pin grooves 378 and secures the cap 350 to the rider 342 to secure the bone - pin ( s ). in the alternative embodiment in fig1 , the device 410 is substantially the same as the preferred embodiment shown in fig1 except for minor differences in the left arm 420 and the central joint 480 to be described . the central joint 480 in fig1 is shown in cross - section to reveal the inner components . there is only one u - shaped support 493 in the central joint 480 which is configured such that angular adjustments may be made to the right arm 430 via the angular - adjustment screw 498 corresponding with gear 494 as substantially described in the description of the embodiment of fig1 . however , in lieu of the second u - shaped supports , the central joint 480 shown in fig1 has an extended sandwich support 483 which has a pivot corner 411 , an adjustment corner 413 and a distal corner 412 . the sandwich support 483 has an inner layer 414 and an outer layer 415 and houses the angular - adjustment screw 488 at the adjustment corner 413 and a v - gear 484 between the inner layer 414 and the outer layer 415 . the inner layer 414 is the mirror image of the outer layer 415 . the v - gear 484 has teeth or grooves 487 and is retained within the sandwich support by an axle 417 at the pivot corner 411 . the threads 489 of the screw 488 mate with the teeth 487 on the v - gear 484 . angular adjustments may be made to the left arm 420 by rotating the angular - adjustment screw 488 which rotates the v - gear 484 which is attached to the left arm 420 . as the v - gear 484 is rotated , it moves in and out of the sandwich support 483 . the configuration of the central joint 480 minimizes the distance between the pivoting points of the two arms and places the centers of rotation as close as possible . the alternative embodiment shown in fig1 is substantially the same as the device described in fig1 . however , the central joint 580 is structured such that the angular - adjustment screws 588 , 598 are perpendicular to one another . the bone - pin clamps 540 , 560 are similar to those shown in fig1 . the alternative embodiment shown in fig1 is substantially the same as the embodiment of fig1 . however , the central joint 680 is configured such that the angular - adjustment screw 688 fits within the central joint 680 on the other side of the gear 684 . this configuration makes the central joint 680 in fig1 more compact than the central joint 580 in fig1 . in the alternative embodiment in fig1 , the arms 720 , 730 are identical as shown in fig2 , wherein each head segment is connected directly to the gear 784 . the arms 720 , 730 rotate about axes of rotation such that the planes of rotation of each arm are perpendicular to each other . the central joint 780 is structured such that the screws 788 , 798 are located in a different position in relation to the gear and in particular , are perpendicular to one another . the bone - pin clamps 740 , 760 of fig1 are essentially similar to the bone - pin clamps 40 , 60 of fig1 in that the cylindrical extensions 745 , d - shaped bores 747 and wheel 746 are the same . however , because of the extended linear nature of the central joint 780 , the extended portions 744 of the bone - pin clamps 740 , 760 must extend further away from the cylindrical extensions 745 than the extended portions 44 of the bone - pin clamps 40 , 60 in order that the bone - pin clamps 740 , 760 may be fitted onto bone - pins which are placed close together , as at the onset of distraction . in addition , the recessed surface 741 of rider 742 has a &# 34 ; v - shaped &# 34 ; groove 743 , and the cap 750 has a semicircular groove 754 . it is to be understood that the cross - sectional shapes of grooves 743 , 754 may be reversed . the &# 34 ; v - shaped &# 34 ; groove 743 of the rider 742 opposes the semicircular groove 754 to form an adjustable bore 758 in the bone - pin clamps 740 , 760 to retain bone - pin ( s ) of varying size , such as either a 2 mm or 3 mm bone - pin . the bone - pin clamps 740 , 760 are secured to a bone - pin by aligning the bone - pin in adjustable bore 758 and tightening the screw 756 . fig2 shows the device of the present invention 10 on the left as compared to a known linear distraction device on the right as they would be used to perform distraction osteogenesis of a human mandible . the device of the present invention finds particular utility where angular distraction is necessary in order to bend bone or form curved bone such as in the mandible in order to round out the face and to provide a proper bite . the ability to angularly adjust the arms in relation to each other as provided by the device shown on the left side in fig2 allows the bone to be curved or bent into its proper shape . the advantage of the device of the present invention is that it can perform distraction osteogenesis both linearly and angularly , both independently and simultaneously , and depending upon the embodiment , can perform linear and angular distraction about two independent axes defining differently oriented planes thereby providing three - dimensional distraction . the device of the present invention is used by drilling at least one bone - pin hole on both sides of the segmented bone , or where an osteotomy is intended to be performed , in a manner known in the art . the bone - pins are inserted into the drilled bone - pin holes such that a portion of each bone - pin extends from the bone . in particular , bone - pins 5 are inserted and fixed in a first side of a segmented bone and bone - pins 5 are inserted and fixed in a second side of a segmented bore and the distraction device is attached . the bone - pin clamps are fitted onto the external segments of the bone - pins such that at least one bone - pin fits through each bone - pin clamp on the arm ( s ) of the device . a template can be used in order to adjust the device before mounting it onto the bone - pins . with reference to the distraction device 10 of fig1 the bone - pin clamps 40 , 60 are then tightened such that the device is firmly attached to the bone - pins . linear distraction is effected by gradually moving the bone - pin clamps 40 , 60 a distance along the arms 20 , 30 by turning wheel 46 . it is contemplated that linear distraction of approximately 1 millimeter per day will occur by undergoing half - millimeter distractions twice a day . it is contemplated further that these adjustments will be made by the patient , the parent or other person not necessarily having any medical experience . angular distraction is effected by making small angular adjustments to the arms 20 , 30 of the device by turning screws 88 , 98 . it is further contemplated that the patient , parent , or other individual , not necessarily having any medical experience , will angularly adjust the device according to the physician &# 39 ; s instructions . it is understood that pure angular distraction may occur without undergoing any linear distraction osteogenesis . the angular adjustment of the arm occurs gradually , incrementally , precisely and in a controlled predetermined manner over a period of time so that the bone remains healthy and the blood vessels and nerves remain intact . further , it is understood that linear and angular adjustments may occur concurrently or separately . the invention has been described herein in considerable detail , both as to the preferred embodiment and several alternative embodiments , in order to enable those skilled in the art to manufacture and use the device according to the present invention . however , it is understood that this invention may be carried out by different devices having various modifications to the embodiments described herein without departing from the scope of the invention itself .
a method of performing angular distraction osteogenesis by drilling bone - pin holes into the first and second sides of a segmented bone , inserting bone - pins into the bone - pin holes , attaching the bone - pins in each side of the segmented bone to a distraction device and adjusting the distraction devise so that the bone portion of the first side of the segmented bone angularly adjusts , rotates or pivots its position relative to the bone portion on the second side of the segmented bone in precise , gradual and predetermined incremental amounts over a period of time so that the bone tissue remains healthy and the blood vessels and nerve endings remain intact during the bending distraction process . a device for achieving angular distraction osteogenesis is provided having a support member extending across a segmented piece of bone , members for securing the first side of the segmented bone to the support member and the second side of the segmented bone to the support member , and a member for angularly adjusting the first section of segmented bone relative to the second section of segmented bone . the angular adjustment member includes a gear and a cooperating adjustment screw which rotates the gear when the screw is adjusted in order to easily angularly adjust or rotate the support member or the members for securing the segmented bone pieces to the support member in precise , small incremental predetermined amounts over a period of time . the members for securing the segmented bone pieces to the support member include bone - pin clamps which can be adjusted linearly or translated in precise , gradual and incremental distances along the length of the support member . in one embodiment , the device has two arms , a central joint for angularly adjusting the two arms and two bone - pin clamps for attaching at least one bone - pin on each side of the segmented bone to a respective arm . the arms are attached to the central joint and angularly adjust or rotate in planes that are oriented different from one another and perhaps perpendicularly and the bone - pin clamps linearly translate along each arm .