the revision devices and methods of this invention may be used with a variety of spinal implants , such as arthroplasty implants . fig1 shows an exemplary spinal arthroplasty device attached to adjacent vertebrae 14 and 14 ′. the spinal arthroplasty device includes a crossbar 105 , a pair of cephalad arms 120 , 120 ′ and a pair of caudal cups 150 , 150 ′. heads 110 and 115 at opposing ends of crossbar 105 interact with bearing surfaces inside caudal cups 150 and 150 ′ to replace the articulating action of the patient &# 39 ; s natural facet joints , which have been removed , when the patient flexes and extends his or her back . in this example , each cephalad arm 120 , 120 ′ attaches to the pedicle of the superior vertebra 14 as shown , via , e . g ., a stem ( not shown ) inserted into the pedicle . the other ends of the cephalad arms attach to crossbar 105 via crossbar mounts 175 and 175 ′. the caudal cups 150 and 150 ′ attach to the inferior vertebra 14 ′ via , e . g ., stems ( not shown ) inserted into the pedicles . further details of this exemplary spinal arthroplasty device may be found in u . s . ser . no . 11 / 206 , 676 . fig2 shows an implanted spinal arthroplasty device that has been revised by a revision device . in this example , the revision device alters the biomechanics of the implanted device by substantially eliminating movement between the cephalad and caudal members and , thereby , between the adjacent vertebrae . the caudal cups that had been attached to inferior vertebra 14 ′ have been removed from their stems , which remain implanted . the caudal cups may be removed , e . g ., by grasping them with a grasping tool and / or through the application of energy ( heat , vibration , ultrasound , etc .). in place of the caudal cups , attachment devices 180 and 180 ′ are attached to the exposed portions of the caudal stems . caudal attachment devices , such as rods 182 and 182 ′, extend medially from attachment devices 180 and 180 ′. alternatively , a single rod extending between attachment devices 180 and 180 ′ may be used in place of shorter rods 182 and 182 ′. as shown in fig2 , instead of attaching to a movable crossbar , cephalad arms 120 and 120 ′ are now attached to the immovable caudal attachment devices via mounts 175 and 175 ′ or other connectors or housings . addition of the revision device therefore substantially eliminates movement between the remaining cephalad and caudal components of the implanted arthroplasty device and between vertebrae 14 and 14 ′. a crossbar 184 may be added between the cephalad arms for additional stability . the crossbar may have an adjustable length , as shown . alternatively , the crossbar may have a fixed length and may possibly provide multiple cephalad arm attachment points selectable along its length , as shown , e . g ., in fig7 or fig8 . fig3 and 4 show a revision device according to another embodiment of the invention . as in the fig2 embodiment , the caudal cups of the implanted arthroplasty device have been removed and replaced with attachment devices 180 and 180 ′ attached to the implanted caudal stems 165 and 165 ′. caudal attachment rods 182 and 182 ′ extend from attachment devices 180 and 180 ′. in this embodiment , however , portions of the cephalad arms of the implanted arthroplasty device have been removed , e . g ., to provide access to otherwise inaccessible portions of the spinal anatomy . removal of such portions ( or other components of the arthroplasty device ) may be desirous to allow surgical access to selected anatomy ( such as the intervertebral disk and / or other posterior anatomy for disc replacement and / or augmentation , and / or installation of fusion cages ), removal of damaged , dislodged and / or loose portions or components , as well as those portions or components that may be causing undesirable anatomical effects ( i . e ., impinging upon nerves or other structures ). the remaining portions 121 and 121 ′ of the cephalad arms provide attachment points for the revision device . specifically , cephalad attachment devices 190 and 190 ′ attach to the cephalad arm portions by , e . g ., set screws 191 and 191 ′. two new cephalad arms 194 and 194 ′ are attached to the cephalad attachment devices via attachment mounts or housings 192 and 192 ′. the new cephalad arms 194 and 194 ′ attach to the caudal attachment rods 182 and 182 ′ via mounts or connector housings 196 and 196 ′. as in the fig2 embodiment , the revision device shown in fig3 and 4 alters the biomechanics of the implanted device by substantially eliminating movement between the cephalad and caudal members and , thereby , between the adjacent vertebrae . a crossbar ( such as the crossbar shown in fig2 or 8 ) may be attached to the new cephalad arms to provide additional stability for the entire construct and / or for individual components relative to the construct ( such as a loose cephalad arm ). fig5 and 6 show alternative connector housings for attaching the new cephalad arm to the remaining portion of the implanted cephalad arm . in fig5 , as in fig3 , the axis of the new cephalad arm is offset with respect to the axis of the remaining portion 121 ′ of the implanted cephalad arm . in fig6 , the new cephalad arm 194 ′ is substantially uniaxial with the remaining portion 121 ′ of the implanted cephalad arm . fig7 is an embodiment similar to that of fig2 and shows an implanted spinal arthroplasty device that has been revised by a revision device . as in the fig2 embodiment , the revision device alters the biomechanics of the implanted device by substantially eliminating movement between the cephalad and caudal members and between the adjacent vertebrae . the caudal cups that had been attached to inferior vertebra 14 ′ have been removed from their stems , which remain implanted . in place of the caudal cups , attachment devices 180 and 180 ′ are attached to the exposed portions of the caudal sterns . caudal attachment devices , such as rods 182 and 182 ′, extend medially from attachment devices 180 and 180 ′. cephalad arms 120 and 120 ′ are attached to the immovable caudal attachment rods via mounts 175 and 175 ′ or other connectors or housings . addition of the revision device therefore substantially eliminates movement between the remaining cephalad and caudal components of the implanted arthroplasty device and between vertebrae 14 and 14 ′. crossbar 184 has been added between the cephalad arms for additional stability . in this embodiment , the point at which crossbar 184 attaches to cephalad arm 120 may be adjusted through the interaction of attachment screw 188 and crossbar slot 189 . fig8 shows an alternative adjustable cephalad arm crossbar 184 for use in a spinal arthroplasty revision device . the effective length of crossbar 184 can be adjusted through the interaction of adjustment screw 188 and crossbar slot 189 . fig9 shows yet another embodiment of a revision device attached to remaining portions 121 and 121 ′ of removed cephalad arms of an implanted spinal arthroplasty device . as in other embodiments , the caudal cups of the implanted arthroplasty device have been removed and replaced with attachment devices 180 and 180 ′ attached to the implanted caudal stems , and caudal attachment rods 182 and 182 ′ extend from attachment devices 180 and 180 ′. as in the fig3 embodiment , portions of the cephalad arms of the implanted arthroplasty device have been removed , e . g ., to provide access to otherwise inaccessible portions of the spinal anatomy , and the remaining portions 121 and 121 ′ of the cephalad arms provide attachment points for the revision device . cephalad attachment devices 190 and 190 ′ attach to the cephalad arm portions by , e . g ., set screws 191 and 191 ′. two new cephalad arms 194 and 194 ′ are attached to the cephalad attachment devices via attachment mounts or housings 192 and 192 ′. unlike the fig3 embodiment in which the new cephalad arms are disposed lateral to the remaining portions of the implanted cephalad arms , in this embodiment the new cephalad arms 194 and 194 ′ are medial to the remaining portions 121 and 121 ′ of the implanted cephalad arms . also , the new cephalad arms 194 and 194 ′ attach to the caudal attachment rods 182 and 182 ′ via mounts or connector housings 196 and 196 ′ at locations medial to caudal attachment devices 180 and 180 ′. a crossbar 184 is attached to the new cephalad arms to provide additional stability . the revision device shown in fig9 alters the biomechanics of the implanted device by substantially eliminating movement between the cephalad and caudal members and , thereby , between the adjacent vertebrae . fig1 shows still another embodiment of a spinal arthroplasty revision device ( including cephalad attachment device 190 ′, new cephalad arm 194 ′ and attachment housings 192 ′ and 196 ′) attached to only one side of the spine and lateral to both the implanted cephalad arm 121 ′ and the caudal attachment device 180 ′. the remaining portion 121 of the other implanted cephalad arm and the other caudal stem 165 are not being used as part of the revision ( although such portions could be utilized for the revision , if desired , or as anchoring points for other spinal hardware ). use of a lateral location for the revision device may be useful in cases where the patient &# 39 ; s anatomy does not permit a medial position for the revision device due , e . g ., to the size of the patient or to the limited amount of bone that had previously been removed and / or the location of the spinal cord / nerves and other anatomical structures . fig1 a illustrates a revision or securing device for use in connection with an arthroplasty device to revise and / or modify , control , or limit motion of the arthroplasty device . the securing device has a body 520 with a distal surface 521 having pair of prongs 522 , 522 ′. when installed , the prongs 522 , 522 ′ form a base and are positioned below the crossbar member and the indenture 524 of the securing device engages the anchors on three sides . when used with a device of fig1 , the prongs can be positioned below the caudal cup which receives an end of the crossbar member , while the top sits above the crossbar end ( 110 , 115 ) to secure the end in place within the caudal cup 150 . the prongs 522 , 522 ′ engage a wall 526 of the securing device on one side . the wall 526 mates with a top or roof 528 that fits above the cross - bar member . the top 528 has an aperture 529 . the aperture 529 can function as a detent , catch or plunger to snap fit over the ball end 110 of the crossbar member in an arthroplasty device . alternatively , the securing device can be a securing mechanism , such as a set screw 530 . fig1 b is a top view of the securing device 520 . from this perspective , it is apparent that the top 528 can be positioned off a central axis of the device to the two prongs 522 , 522 ′, thus also potentially positioning the aperture 529 off the central axis as well . fig1 c is a side view of the securing device , illustrating the angled configurations of the sides 531 , 531 ′ back wall 526 . the angled configuration positions the top 528 , which can have a smaller dimension in at least one direction ( e . g ., length or width ) than the length or width formed by the prongs and the wall . fig1 d is a bottom view of the securing device 520 . fig1 e is a cross - sectional view of the securing device taken through an axis parallel to the prongs 522 , 522 ′. fig1 a illustrates a side view of the securing device of fig1 in combination with a portion of an arthroplasty device , such as the arthroplasty device of fig1 . the prongs 522 , 522 ′ sit below the caudal cup 150 , holding the caudal cup in a fixed position . the top 528 of the securing device 520 sits above an end of the cross - member 110 , which fits within the caudal cup 150 . an anchoring device 530 ( see fig1 a ) can be fed through the aperture to engage the end of the cross - member and hold it in position within the caudal cup 150 . as illustrated , the caudal cup 150 is tilted t toward an axial plane 52 , enabling the caudal cup to secure the cross - member at a location . adjustment of the position of the caudal cup relative to the cross - member end can affect the position of the device . fig1 b illustrates a perspective view of the securing device in combination with a portion of the arthroplasty device . from this perspective , a set screw 530 located within the aperture 529 on the top of the securing device can be seen . fig1 c is a perspective view from a partially anterior view of the securing device again in combination with a portion of the arthroplasty device . fig1 d is a top view of the securing device 520 with a portion of the arthroplasty device . as evident from this perspective , the caudal cup extends on one side past the prong 522 ′. the set screw 530 is positioned off - center relative to the length of the securing device , but the top of the securing device is positioned over the end of the cross - member . fig1 e is a bottom view of the securing device engaging an arthroplasty device . from this view , it is illustrated that the prongs 522 , 522 ′ are seated beneath , for example , the caudal cup of the arthroplasty device . thus , the implanted arthroplasty device can be revised to incorporate locks or “ fusion caps ” that desirably convert the device from an articulating joint replacement construct to a non - articulating ( or controlled and / or limited articulation ) spinal fusion construct . in this embodiment , the fusion cap can be installed on or into the caudal cups to desirably immobilize the cephalad bearings within the cups . in various embodiments , the fusion caps could immobilize the cephalad bearings by direct compression or contact , through use of a set screw or other device to secure the cephalad bearing relative to the cup , or the fusion cap could contain or cover an encapsulating material , such as bone cement , which could fill the caudal cup and immobilize the cephalad bearing . various techniques could be used in conjunction with the installation of such fusion caps , and the cap could be installed prior to , during , or after the completion of a concurrent spinal fusion procedure , including the removal of intervertebral disc material , installation of fusion cages , and / or introduction of material ( such as bone graft material ) that desirably promotes spinal fusion . if desired , the bearing surface could be textured and / or knurled to increase friction between the ball , bearing surface and / or the fusion construct . alternative embodiments could incorporate bearings of different shapes or sizes ( not shown ), including square or non - spherical bearings and / or bearings shaped to that fit snugly into and accommodate most or all of the interior of the caudal cup ( not shown ), that can be secured within the cup in a similar manner . turning now to fig1 a , a perspective view of an implanted arthroplasty device 600 with the securing device of fig1 is illustrated . the arthroplasty device 600 features a pair of caudal cups 150 engaging a cross - member 110 . the cephalad arms have been removed , but it has been determined desirable to keep the caudal cups and cross - bar in place . the use of the securing device enables the caudal cup and crossbar member to be retained in position even without one or more of the cephalad arms to anchor the cross - member . additionally , as will be appreciated by those of skill in the art , one of the two cephalad arms could be removed with the use of one or two of the securing devices to provide a three - point secured device ( i . e ., rigidly connecting two caudal cups to a single cephalad arm ). the securing device engages the caudal cup and an end of the cross - member in the manner described above . fig1 b is a perspective view of another implanted spinal arthroplasty device 602 having a pair of caudal cups 150 , 150 ′ engaging a cross - member 110 and a pair of cephalad arms 120 , 120 ′ extending vertically toward the adjacent vertebra 12 along with the securing device of fig1 . fig1 c is a perspective view of yet another implanted arthroplasty device 604 with the securing device of fig1 . fig1 - 18 show still other embodiments of a spinal arthroplasty revision system according to the invention . fig1 - 16 show an implanted spinal arthroplasty system ( such as that shown in fig1 ) with cephalad arms 120 and 120 ′, cephalad heads ( such as head 110 shown in fig1 ) at either end of a cephalad crossbar 105 and caudal cups 150 and 150 ′. the cephalad arms connect to crossbar 105 via crossbar mounts 175 and 175 ′. revision devices 200 and 200 ′ have been added to the implanted arthroplasty prosthesis to substantially eliminate movement between the cephalad heads and the caudal cups and , thereby , between adjacent vertebrae 14 and 14 ′. as shown in detail in fig1 and 16 , the revision device includes a securing section 202 ′ similar to that of fig1 extending from one side of the caudal cup 150 ′ to an opposing side of the cephalad head 110 . securing sections 202 and 202 ′ lock the cephalad heads against the caudal cups with screws and 203 and 203 ′. cephalad arm hook plates and connectors 204 and 204 ′ are attached to the securing section 202 ′ ( via screw 203 or 203 ′) and to cephalad arms 120 and 120 ′ ( via set screw 205 or 205 ′) to provide additional stability . the upper surfaces of the securing sections 202 and 202 ′ s and the lower surfaces of hook plates 204 and 204 ′ may have complementary shapes ( e . g ., spherical ) and roughened surface texture to form a more secure connection between them . revision devices 200 and 200 ′ alter the biomechanics of the implanted device by substantially eliminating movement between the cephalad and caudal members and between the adjacent vertebrae , thereby transforming the implanted spinal arthroplasty device into a fusion device . fig1 and 18 show an alternative design to the revision devices 200 or 200 ′ of fig1 - 16 . 100671 the first step of adding a revision system , such as one of those shown above in fig1 - 18 , to an implanted spinal arthroplasty device , is to expose the existing device . bone and / or soft tissue may be removed from under the caudal cup to make room for the securing device , such as securing device 202 or 202 ′ in fig1 - 18 . after placing the securing devices 202 and 202 ′ around caudal cups 150 and 150 ′ and the cephalad heads at either end of crossbar 105 , screws 203 and 203 ′ are tightened ( to , e . g ., 70 in - lbf ) to hold the cephalad and caudal components together . the cephalad heads are preferably in the “ home ” position within their respective caudal cups . the vertebrae can be compressed prior to final assembly of the revision device , if desired . a hook plate of suitable size and dimensions is selected ( from , e . g ., a kit containing multiple hook plates of various sizes ) and placed over a portion of the securing device screw 203 or 203 ′ extending above the securing device 202 or 202 ′. the hook plate is attached to its corresponding cephalad arm via set screw 205 or 205 ′. bone graft material may be added to facilitate fusion . the incision may then be irrigated and closed in a standard fashion . the revision devices of this invention may be provided in kits containing components of various sizes so that the revision device can be tailored to the patient &# 39 ; s anatomy . in addition , the kits may contain the removal , sizing and implantation tools needed to perform the revision procedure . fig1 shows an implanted spinal arthroplasty device similar to that shown in fig1 . as in the fig1 embodiment , cephalad arms 120 and 120 ′ connect via crossbar mounts 175 and 175 ′ to a cephalad crossbar 105 having heads 110 and 115 at either end . in this device , however , the caudal cups 150 and 150 ′ are connected with a crossbar 212 as well . in addition , cephalad crossbar 105 has an opening 210 that lines up with an opening ( not shown ) in caudal crossbar 212 . the two openings may be used to secure a revision device , e . g ., to secure the cephalad and caudal components together during installation or to limit or eliminate the range of motion between the cephalad and caudal components . while the various embodiments of the invention have been described in the context of a spinal arthroplasty device revision that substantially eliminates motion between the cephalad and caudal device components ( i . e ., fusion ), it should be understood that the revision device may alter but still permit motion between the cephalad and caudal components .
the present method includes the following steps : removing a portion of a previously implanted spinal arthroplasty device ; and attaching a revision component to a remaining portion of the previously implanted spinal arthroplasty device to alter a biomechanical characteristic of the implanted arthroplasty device . another aspect of the invention provides a method of limiting motion between adjacent vertebrae including the steps of accessing an implanted spinal arthroplasty device comprising a cephalad component fixed to a first vertebra and a caudal component fixed to a second vertebra inferior to the first vertebra , the cephalad and caudal components having a range of motion between them , and attaching a revision component to the cephalad and caudal components to reduce the range of motion . the invention also includes revision devices for revising the biomechanics of implanted spinal arthroplasty devices .