Adjustable spinal implant

In one embodiment, a non-invasively adjustable spinal system for treatment of a subject having spondylolisthesis includes a first implantable actuator having at least one anchoring structure, the anchoring structure configured to facilitate securement of the first implantable actuator to a portion of the sacrum of the subject. The non-invasively adjustable spinal system can further include an adjustment element, configured to be coupled to the first implantable actuator, the adjustment element having an engagement structure configured to engage at least one transverse process of a lumbar vertebra of the subject. The non-invasively adjustable spinal system can further include a driving element, wherein remote activation of the driving element causes movement of the adjustment element in relation to the first implantable actuator.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claims is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND

Field of the Invention

The field of the invention generally relates to medical devices for treating deformities of the spine, including spondylolisthesis.

Description of the Related Art

Spondylolisthesis is a condition of the spine in which one vertebra is displaced in relation to another vertebra.

SUMMARY

In one embodiment, a non-invasively adjustable spinal system for treatment of a subject having spondylolisthesis is provided. The system includes a first implantable actuator having at least one anchoring structure, the anchoring structure configured to facilitate securement of the first implantable actuator to a portion of the sacrum of the subject. The non-invasively adjustable spinal system further includes an adjustment element, configured to be coupled to the first implantable actuator, the adjustment element having an engagement structure configured to engage at least one transverse process of a lumbar vertebra of the subject. The non-invasively adjustable spinal system further includes a driving element, wherein remote activation of the driving element causes movement of the adjustment element in relation to the first implantable actuator.

In another embodiment, a method for treating spondylolisthesis in a subject having a spine containing a sacrum and at least a portion of an L5 vertebra is provided. The method includes providing a non-invasively adjustable spinal implant having a first implantable actuator having at least one anchoring structure, the anchoring structure configured to facilitate securement of the first implantable actuator to a portion of the sacrum of the subject, an adjustment element, configured to be coupled to the first implantable actuator, the adjustment element comprising an engagement structure configured to engage at least one transverse process of a lumbar vertebra of the subject, and a driving element, wherein remote activation of the driving element causes movement of the adjustment element in relation to the first implantable actuator. The method for treating spondylolisthesis further includes making a first incision in the skin of the subject, placing the non-invasively adjustable spinal implant through the first incision, securing at least a portion of the non-invasively adjustable implant to a portion of the sacrum of the subject, coupling the engagement structure to at least one transverse process of the L5 vertebra, and causing or allowing the first incision to close.

DETAILED DESCRIPTION

InFIG. 1the lower spine100includes vertebrae L3102, L4104, L5106, and the sacrum108. Intervertebral discs110,112,114are also shown. In certain subjects, chronic or acute upward stresses on the sacrum108can create upward forces on the contacting spinous process116(in this case the spinous process116of L5106) and downward forces on the L5106vertebral body itself. This may culminate in a defect120, for example, a stress fracture, of the pars interarticularis118. The defect120, as seen inFIG. 1B, is known as spondylolysis, and may occur in as much as 6% of the population. Some risk factors which may lead to spondylolysis, often occurring in combination, include hereditary anatomic factors (thin spinal bone) and strenuous sports and activities, such as tennis, volleyball, soccer, and gymnastics. The hyperextension and heavy landings common to many strenuous sports have each been hypothesized as causes for spondylolysis. The L5106vertebra is the location of the defect120in the majority of spondylolysis cases, but it may also occur in other lumbar vertebrae, and even in non-lumbar vertebrae. Spondylolysis may on its own cause back pain, neck pain, or radiating limb pain, but it is often followed by related disc slippage known as spondylolisthesis, which is illustrated inFIG. 1C. The spondylolisthesis inFIG. 1Cis shown between the L5106vertebra and the sacrum108. This is thought to be the most common location for spondylolisthesis to occur, but again, it may occur between other vertebrae.

In many people, the defect120is created during adolescence, but it often goes unnoticed at that time. Typical disc degeneration occurring during adulthood may then produce the spondylolisthesis, which can be accompanied by other symptoms. Sometimes, adult degenerative disc disease may even lead to spondylolisthesis without the defect120(spondylolysis) occurring.FIG. 2Aillustrates the L4104and L5106of the lumbar vertebrae and S1122, S2124, and S3126vertebrae of the sacrum108of a subject having L5-51 segment128which is normal.FIGS. 2B through 2Fshow L5-S1 segments128having increasing grades of spondylolisthesis. These figures are intended to show the orientation of the L5106to the S1122, and not their overall orientation in relation to anything else, for example, the ground while the subject is standing. A commonly used method of grading spondylolisthesis divides the sacrum108into four equal sectors (i.e., 1, 2, 3, and 4), as seen inFIG. 2A. A subject has a grade 1 spondylolisthesis (FIG. 2B) when the edge130of the slipped vertebra (in this case L5106) is within sector 1. InFIG. 2Cthe spondylolisthesis is grade 2 because the edge130of the slipped L5106is within sector 2. InFIG. 2Dthe spondylolisthesis is grade 3 because the edge130of the slipped L5106is within sector 3. InFIG. 2Ethe spondylolisthesis is grade 4 because the edge130of the slipped L5106is within sector 4. InFIG. 2Fthe edge130of the slipped L5106has slipped past the four sectors and is therefore considered a grade 5; the condition of grade 5 spondylolisthesis is also known as spondyloptosis. In the higher grades of spondylolisthesis, subjects may either remain asymptomatic, or may present with back pain and/or leg pain. Subjects having higher grade spondylolisthesis may also experience secondary changes to the natural sagittal curve of their spine (sagittal deformity). It may be desirable to treat an adult who has experienced chronic pain symptoms that may be medically attributed to a spondylolisthesis grade of about 4 or higher by implantation of an embodiment of devices as described and illustrated herein. Such treatment may be used to either minimize the risk of progression to a higher spondylolisthesis grade, to lower the spondylolisthesis grade, or both minimize the risk of progression and lower the grade of spondylolisthesis.

Adolescents with higher grade spondylolisthesis may be at a heightened risk for progression in the severity of their condition than adults, and for this reason, surgery is often recommended. While adults with spondylolisthesis may have less risk of progression, they often have back pain or leg pain symptoms that warrant surgery. In order to reduce the risk of progression to a higher grade spondylolisthesis it may be desirable to treat an adolescent having grade 1 spondylolisthesis that is at risk of progressing/worsening by implantation of an embodiment of devices as described and illustrated herein.

FIGS. 3A and 3Billustrate several sagittal pelvic parameters which may be calculated from x-rays (taken while the subject is standing) in subjects having L5-S1 spondylolisthesis, or at risk of progression of L5-S1 spondylolisthesis. The purpose of these parameters is to describe the location and orientation of the sacrum108in relation to the ground and to the entire spinal column144and pelvis. Lumbar lordosis (LL)132is defined as the angle measured between the superior (upper) endplate of the L1 vertebra134and the superior endplate of the S1 vertebra122. Thoracic vertebra T12136is also shown inFIG. 3A, for reference. Pelvic tilt (PT)138is defined as the angle between vertical146(a line perpendicular to the ground on which the subject stands) and the line148which leads to the middle150of the sacral plate152at the superior end of the sacrum108(chosen midline between the two hip/femur joints). Sacral slope (SS)140is defined as the angle between the horizontal154and a line156drawn along the sacral plate152at the superior end of the sacrum108. Pelvic Incidence (PI)142is equal to the sum of the pelvic tilt (PT)138and the sacral slope (SS)140. Some studies have concluded that an increased pelvic incidence (PI)142may be a risk factor for the development and progression of spondylolisthesis.

Surgery typically includes of partial or complete reduction (restoration to correct alignment) followed by fusion, or, in many cases, fusion alone without reduction. Fusion without reduction (in situ fusions) can be successful in subjects in whom symptoms have occurred mainly because of motion of the segment. However, in a large number of subjects, some amount of reduction prior to fusion can advantageously decompress the nerve root. Reduction of higher grade spondylolisthesis may be difficult due to both increased rigidity of the deformity and stiffness across the junction between the L5106and S1122. This is especially true in adults who have secondary degenerative changes as the entire deformity is frequently less mobile. In some studies, a significant percentage of subjects experienced further slip progression, even after fusion surgery, a phenomenon that some attribute to incomplete correction of the angular deformity (e.g., bringing the lumbar lordosis (LL)132back towards its normal desired value). Fusion without reduction may also be associated with higher rates of non-union than reduction followed by fusion, which many have attributed to the higher stresses on the junction between the L5106and S1122, and also to the decreased surface area for fusion because of the incomplete alignment of the L5106and S1122.

FIGS. 4 and 5depict the lower spine100of a normal subject (FIG. 4) and a subject with spondylolisthesis (FIG. 5). InFIGS. 4 and 5, the lower spine100is shown without the surrounding soft tissue in order to better illustrate a treatment plan using an embodiment of devices as described and illustrated herein. An adjustable spinal implant200(FIG. 7) according to an embodiment of devices as described and illustrated herein will be coupled at least partially to a medial-dorsal portion158of the sacrum108following removal of a dorsal portion160of the L5106, for example, a dorsal portion160that previously had been severed from the L5106during the creation of the defect120in spondylolysis.FIG. 6illustrates the anatomy of a dorsal portion of the sacrum108, indicating the medial-dorsal portion158within a dashed box. Within this medial-dorsal portion158is the sacral crest162which covers the sacral canal174and extends towards the sacral hiatus170. The sacral crest162comprises a plurality of tubercles172. Several dorsal sacral foramina164(also called posterior sacral foramina) are arrayed along the sacrum108and provide openings in the sacrum108for the transmission of the posterior divisions of the sacral nerves (not shown). Two alas166extend laterally and two sacral horns168(also called superior auricular processes) reside at the superior portion of the sacrum108. A medial surface176(within the dashed oval marking) at the edge of each ala166extends substantially towards each sacral horn168. The adjustable spinal implant200ofFIG. 7may also be configured to at least partially contact a portion of the medial surface176.

The reason that reduction is sometimes avoided prior to fusion is traditionally because it is often associated with a high rate of neurological deficit. However, neurological deficit can also occur, though at a lower rate, in fusions done without reduction. Because of complications inherent to either excess reduction or insufficient reduction, a partial reduction prior to fusion may elicit the best result. However, it is frequently difficult to predict what will be the most appropriate amount of reduction prior to fusion. Additionally, a gradual reduction, such as several small steps spaced out by days, weeks or even months, may allow for a complete reduction prior to fusion: in some cases, it may even obviate fusion.

FIGS. 7 and 8illustrate an adjustable spinal implant200for implantation and subsequent non-invasive adjustment within a subject having spondylolisthesis. The adjustable spinal implant200comprises an implantable actuator204which is coupled to an adjustment element206. Between the implantable actuator204and the adjustment element206is a flexible tubular member218, which serves to protect the connecting elements and create a seal or barrier to prohibit body fluids from entering either the implantable actuator204or the adjustable element206. The implantable actuator204includes an anchoring structure208, for example, anchoring tabs210having holes212for passing bone screws to secure the implantable actuator to the sacrum108of a subject. The adjustment element206comprises a gear housing214which is fully enclosed by a gear housing cover216. The adjustment element206also includes an engagement structure220having a right transverse process hook222and a left transverse process hook224. The engagement structure220may be monolithic or may be an assembly of more than one part. The engagement structure220is adjustable with respect to the gear housing214. A moveable arm236of the engagement structure220extends into the gear housing214. A dynamic seal234is provided in an opening238of the gear housing214, which seals around the moveable arm236. The adjustment element206includes several feet226,228,230,232which aid in stabilizing the adjustment element206with respect to the sacrum108by, for example, providing opposing forces to traction created when the engagement structure220is adjusted.

FIGS. 9 through 15show additional internal and external detail of the adjustable spinal implant200.FIG. 9shows the adjustable spinal implant200with the flexible tubular member218and the gear housing214removed. A driving element or rotatable magnetic assembly242is rotationally mounted within a housing205of the implantable actuator204and comprises a radially-poled permanent magnet202which is held within a magnetic housing240, for example, with adhesive or epoxy, or by a mechanical fit. The magnetic housing240sealably encloses the radially-poled permanent magnet202by attachment of a magnetic housing cap244. The radially-poled permanent magnet may be a cylindrical or partially cylindrical rare earth magnet, for example, Neodymium-Iron-Boron, and may have two poles, four poles, or more. The rotatable magnetic assembly242is coupled to a planetary gear set246, and both the rotatable magnetic assembly242and the planetary gear set246are held between a radial bearing248and a thrust bearing250. The output shaft252of the planetary gear set246is joined to a rotational coupler254, for example, by welding or adhesive bonding. If, for example, the planetary gear set246is provided with a 4:1 gear ratio, then four rotations of the rotatable magnetic assembly242cause one rotation of the rotational coupler254. Additionally, given a 4:1 gear ratio, torque generated by the rotational coupler254can be up to four times greater than the torque applied to the radially-poled permanent magnet202(for example, by the application of a rotating magnetic field). An o-ring256is held within a circumferential groove258in the housing205, and seals around the diameter of the rotational coupler254.

A universal joint258(FIG. 9) provides a flexible connection between the rotational coupler254and a worm260.FIG. 15illustrates the releasable connection between the implantable actuator204and the adjustable element206. A first member262of the universal joint258having a square end264can be snapped into and snapped out of a square cavity266. The universal joint258and the surrounding flexible tubular member218allow for the securement of both the implantable actuator204and the adjustable element206in a number of different orientations, to match varying anatomy of the subject, while still allowing operation. The worm260engages a worm gear portion268of a gear270so that rotation of the worm260causes rotation of the gear270. As visible also inFIGS. 13 and 14, the gear may also include a pinion272configured to engage with an arcuate rack274that extends from the movable arm236of the engagement structure220. As the gear270is caused to turn in a first rotational direction by the worm260the arcuate rack274moves in an arcuate path276. By providing an engagement structure220capable of holding the L5 vertebra106without any rotational slippage, the L5 vertebra106may not only be translated (reduced) in relation to the sacrum108, but also, the L5 vertebra106may be rotated (or derotated) in relation to the sacrum108. An example is shown by the decrease of angle A fromFIG. 13toFIG. 14, which happens in conjunction with the displacement of right transverse process hook222. Such angle change can lower the pelvic incidence (PI)142in a subject, and thus potentially lower their risk of progressive spondylolisthesis. Angle change can also directly improve lumbar lordosis (LL)132. One way of achieving this change in angle of the L5 vertebra106is shown inFIG. 9. A cross bar278extends between the right transverse process hook222the left transverse process hook224, and is configured to provide a pushing force in the proximity of a dorsal portion of the L5 vertebra106while the right transverse process hook222the left transverse process hook224are providing traction. Because these opposing forces are applied at different heights on the L5 vertebra106(one inferior to the other), a rotational moment is applied to the L5 vertebra106. The gear270and the worm260are held within both the gear housing214and the gear housing cover216by standard stops, pins, bosses and the like. Additionally first bar290and second bar292extend within the gear housing214and/or the gear housing cover216in order to act as guides for the arcuate rack274as it is moved. At least the second bar292can act as a stop to prevent overextension of the arcuate rack274.

The housing205of the implantable actuator204may also contain a maintenance tube280(illustrated inFIG. 12). The maintenance tube280is constructed from a structurally rigid material that is also relatively magnetic, for example, 400 series stainless steel. Open elongated holes282in the wall of the maintenance tube280cause circumferential magnetic discontinuities. The north and south poles of the radially-poled permanent magnet202will be attracted to the extending wall ribs284, but not to the open elongated holes282. While implanted within a subject, the adjustable spinal implant200maintains its configuration (dimension, etc.) due to this attraction. Adjusting the adjustable spinal implant200with the use of a sufficient strong externally applied moving magnetic field can overcome this attraction and allow the radially-poled permanent magnet202to be turned. The maintenance tube280is secured within the housing205of the implantable actuator and can provide one end of an axial stop for the thrust bearing250. Another axial stop for the thrust bearing250can be provided by a ledge286within the housing205. In some embodiments, the thrust bearing250is not held completely tight, and may have a finite amount of axial play. In other embodiments, the thrust bearing250is held with substantially no axial play. An actuator housing cap288may be permanently or removably attached to the housing205of the implantable actuator204to enclose and protect the contents of the housing205from body fluids.

In use, the adjustable spinal implant200can be coupled to the L5 vertebra106and the sacrum108by a surgeon during a surgical implantation procedure. The adjustable spinal implant200is shown inFIG. 16, as implanted, on the L5 vertebra106and sacrum108. The right transverse process hook222of the engagement structure220has been hooked around a right transverse process178of the L5 vertebra106. The left transverse process hook224of the engagement structure220has been hooked around a left transverse process180of the L5 vertebra106. A foot226has been trimmed and/or bent (or otherwise shaped) so that it rests against medial surface176of the right ala166and a foot228has been trimmed and/or bent (or otherwise shaped) so that it rests against medial surface176of the left ala166. The implantable actuator204has been secured to the sacrum108by placing bone anchors294through the holes212in the anchoring tabs210(shown inFIG. 7). The bone anchors294may comprise a screw having a threaded shank and a tapered threaded head. The holes212may have matching tapered internal threads to interface with the tapered head of the bone anchors294. The adjustable element206has been coupled to the implantable actuator204via the square end264and square cavity266, and the flexible tubular member218has been slid into place over the end of the housing205of the implantable actuator204and over a cylindrical extension (not shown) of the gear housing214. It can be appreciated fromFIG. 17that legs230,232may also be trimmed and/or bent (or otherwise shaped) to contact medial-dorsal portion158of the sacrum108. Prior to the implantation of the adjustable spinal implant200, portions of the sacral crest162and other bone material within the medial-distal portion158may be cut or ground away, or even partially hollowed out. As can be seen inFIGS. 16 and 17, the implantable actuator204may reside partially within this hollowed out area.

InFIGS. 16 and 17, the L5 vertebra106is in a slipped position approximating grade 3 spondylolisthesis in relation to the sacrum108.FIG. 17shows the lower spine100after a dorsal portion160of the L5 vertebra106has been removed through an incision in the skin. Subsequently, the adjustable spinal implant200is implanted as described above and the incision is allowed or caused to close, for example, by suturing or using an adhesive sealant, and the overall healing is allowed to progress. In one or more subsequent procedures, a medical care professional or a member of the family of the subject applies a remote moving magnetic field, thereby causing the moveable arm236to be retracted into the gear housing214via the rack274and pinion272.FIG. 18shows the lower spine100after one or more adjustment procedures. The L5 vertebra106has been reduced to a position approximating grade 1 spondylolisthesis. In addition, the angular orientation between the L5 vertebra106and the sacrum108has been changed. Specifically, the kyphotic condition has been improved, returning more of the natural lordosis. Because the lumbar vertebrae are connected to each other, the reduction of the L5 vertebra106may cause the lower spine100, particularly the adjacent L4 vertebra104and L3 vertebra102, to reform to its preferred conformation. It should be noted that inFIGS. 17 and 18, the foot226has purposely not been depicted to better show the positioning of feet230and232.

It may be useful to perform the adjustment of spondylolisthesis using the adjustable spinal implant200on a conscious subject who is able to provide at least substantially real-time feedback related to pain and/or balance. Conscious subjects may be able to advantageously move into several different, positions, including those positions that are most likely to cause pain. This is to be contrasted with “wake up tests,” sometimes performed during surgery, in which subjects are neither in natural positions, nor do they have their standard senses and reflexes (due to the effects of drugs and anesthesia). Additionally, the amount of linear reduction to treat a patient is generally expected to be in the range of about 5-60 mm, about 7-50, and more specifically about 10-40 mm. Derotation of the L5 vertebra106in relation to the sacrum108versus the total amount of linear reduction can be controlled by producing a rack having varied radii. For example, a straight (linear) rack may be used if no derotation is desired. It is generally expected that derotation in the range of about 0-75 degrees is appropriate, and in many cases a derotation in the range of about 5-50 degrees. The amount of adjustment may be at least partially determined using feedback received from a conscious subject.

FIGS. 19 and 20depict a pair of adjustable spinal implants300,400according to another embodiment of the of devices as described and illustrated herein. A first adjustable spinal implant300comprises a first implantable actuator304coupled to a first adjustable element306, with a flexible tubular member318extending between them. The first implantable actuator304may be secured to the sacrum by a bone anchor294which passes through an anchoring tab310. In some embodiments, only one anchoring tab310is used, with the other removed, leaving a remnant311. In other embodiments, two anchoring tabs310are used. A right transverse process hook322is hooked around the right transverse process178. A stability element313is secured to the right transverse process hook322with a set screw315, in order to clamp onto the right transverse process178and substantially eliminate rotational slippage between the right transverse process hook322and the right transverse process178. The surface of the right transverse process178may be slightly ground flat in order to better accept the stability element313to further inhibit rotation between the two. The right transverse process hook322may be directly connected to a movable arm336which extends into a rack and pinion mechanism similar to that described in the embodiment depicted inFIGS. 7-18. Feet330,332for contacting and bracing against the sacrum108, are illustrated inFIG. 20. A second adjustable spinal implant400comprises a second implantable actuator404coupled to a second adjustable element406. A clamping bone anchor494holds outer diameter of the second implantable actuator404. A left transverse process hook424is hooked around the left transverse process180. In some embodiments, a stability element313may also be used with the left transverse process hook424(in the same manner as described with respect to the right transverse process hook322), though it is not shown inFIG. 19. The first adjustable spinal implant300and second adjustable spinal implant400have separate internal adjustment mechanisms, including radially-poled permanent magnets. Therefore, the two adjustable spinal implants300and400may be independently adjustable in relation to one another. This may aid in situations where the L5 vertebra106is rotated undesirably along the axis of the subject's torso. For example, the first adjustable spinal implant300may be adjusted differentially relative to the second adjustable spinal implant400in order to derotate a chosen amount. During implantation, the first adjustable spinal implant300and the second adjustable implant400may be implanted through the same incision or they may be implanted through different incisions.

FIG. 21illustrates an external adjustment device1180which may be used to non-invasively adjust devices and systems described herein. The external adjustment device1180comprises a magnetic handpiece1178, a control box1176and a power supply1174. The control box1176includes a control panel1182having one or more controls (buttons, switches or tactile, motion, audio or light sensors) and a display1184. The display1184may be visual, auditory, tactile, the like or some combination of the aforementioned features. The external adjustment device1180may contain software which allows programming by a physician, including the ability to lock a patient out from using the external adjustment device1180, limit the amount of possible adjustment per day, per hour, etc.

FIG. 22shows an exploded view of the magnetic handpiece1178of the external adjustment device1180. There are two magnets1186that can have a cylindrical shape. The magnets1186may be made from rare earth magnets. The magnets1186may be bonded or otherwise secured within magnetic cups1187. The magnetic cups1187can include shafts1198attached to a first magnet gear1212and second magnet gear1214. The orientation of the poles of each the two magnets1186are substantially fixed with respect to each other through a gearing system including, for example, center gear1210, which meshes with both first magnet gear1212and second magnet gear1214).

The components of the magnetic handpiece1178may be held together between a magnet plate1190and a front plate1192. Most of the components are protected by cover1216. The magnets1186rotate within a static magnet cover1188, so that the magnetic handpiece1178may be rested directly on the patient while not causing motion to the external surfaces of the patient. Prior to distraction of the adjustable spinal implant200using the external adjustment device1180, the operator places the magnetic handpiece1178over the patient near the location of the radially-poled permanent magnet202, for example, on the skin covering the dorsal portion of the sacrum108. A magnet standoff1194interposed between the two magnets1186can contain a viewing window1196, that may aid in placement. For instance, a mark made on the patient's skin at the appropriate location with an indelible marker may be viewed through the viewing window1196. To use the external adjustment device1180to perform a distraction, an operator generally holds the magnetic handpiece1178by its handles1200and causes motor1202to drive in a first direction. The motor1202may have a gear box1206which can cause the rotational speed of an output gear1204to be different from the rotational speed of the motor1202(for example, a slower speed). The output gear1204can then turn a reduction gear1208meshing with center gear1210, which can cause center gear1210to turn at a different rotational speed than the reduction gear1208. The center gear1210can mesh with both the first magnet gear1212and the second magnet gear1214thereby turning them at the same rate. Depending on the portion of the body where the magnets1186of the external adjustment device1180are located, it may be desired that the rate of rotation of the magnets be controlled to minimize the resulting induced current density imparted by magnet1186and cylindrical magnet1134though the tissues and fluids of the body. In some embodiments, a magnet rotational speed of about 60 RPM or less is contemplated. In other embodiments, a magnet rotational speed of about 35 RPM or less may be used. At any time, the distraction may be lessened by causing the magnets to rotate in the opposite direction (e.g., by depressing retract switch1230). If the patient feels significant pain, or numbness in the area holding the device, the magnitude of distraction may be decreased. The magnets1186of the magnetic handpiece can comprise one or more permanent magnets or one or more electromagnets. For example, one or more electromagnets can be configured to provide a rotating magnetic field capable of causing rotation of the radially-poled permanent magnet202.

FIGS. 23A through 23Cillustrate a magnetic actuator504which may be used with any of the embodiments of the of devices as described and illustrated herein, and which allows for temporary or permanent removal of a rotatable magnetic assembly542. Patients undergoing magnetic resonance imaging (MRI) may benefit from the removal of radially-poled permanent magnet502prior to MM in order to avoid a large imaging artifact caused by the radially-poled permanent magnet502. Additionally, there is a risk that in implanted radially-poled permanent magnet502may be demagnetized upon entering an MM scanner. An actuator housing cap588has a male thread599which engages with a female thread597of the housing505of the magnetic actuator504. Alternatively, a snap/unsnap interface may be used. A smooth diameter portion595of the actuator housing cap588is sealed with an o-ring593, which is held within a circumferential groove on the inner surface of the housing505. If, at a time subsequent to the implantation of the magnetic actuator504, it is desirable to remove the rotatable magnetic assembly542while leaving the rest of the implant intact, a small incision may be made in the skin of a subject in proximity to the actuator housing cap588, and the actuator housing cap588may be unscrewed. The rotatable magnetic assembly542may then be removed through the incision, as shown inFIG. 23A.FIGS. 23B and 23Cshow the subsequent steps of replacing the actuator housing cap588onto the housing505again sealing it against the o-ring593. The incision may then be closed, and the subject may undergo typical MRI scanning. If desired, the rotatable magnetic assembly542may be replaced by following a reverse method.

FIGS. 24A through 24Dillustrate a magnetic actuator604which may be used with any of the embodiments of the of devices as described and illustrated herein, and which allows for temporary or permanent removal of a radially-poled permanent magnet602. An actuator housing cap688attaches to and detaches from the magnetic actuator604in the same manner as in the magnetic actuator504ofFIGS. 23A through 23C. The radially-poled permanent magnet602has two radial portions687and two flat portions685. The two flat portions685fit within flat walls683of a magnetic housing640, which allows rotation of the radially-poled permanent magnet602to directly impart rotation on the magnetic housing640without the need for any adhesive or epoxy. A magnetic housing cap681having an o-ring679is attachable to and removable from the magnetic housing640. If an MM of the subject is desired and it has been determined that the radially-poled permanent magnet602should be removed, a small incision may be made in the skin of the subject in close proximity to the actuator housing cap688through which the actuator housing cap688may be removed. The incision may be substantially at or near the location of an incision made during the implantation surgery, for example, adjacent or over the location of an incision made during the initial implantation surgery. Alternatively, the incision instead may be made in a separate location, as skin may be moved to access the magnetic actuator604. Then magnetic housing cap681may then be removed from the magnetic housing640. A pull rod677extends through a longitudinal hole (not shown) in the radially-poled permanent magnet602, extending at one end such that it may be gripped, for example, by forceps or hemostats. The pull rod677has a flat base675at its opposite end so that, when pulled, it drags the radially-poled permanent magnet602with it. The radially-poled permanent magnet602may be removed, as shown inFIG. 24B(either permanently or temporarily) and the magnetic housing cap replaced (FIG. 24C). The actuator housing cap688may then be replaced (FIG. 24D). The incision may then be closed or allowed to close, and the subject may undergo typical MRI scanning. If desired, the radially-poled permanent magnet602may be replaced by following a reverse method. Alternatively, the magnetic housing cap681or the actuator housing cap688may be replaced by an alternatively shaped cap which will guide into a keyed structure within the magnet actuator604(not shown), thus keeping the internal mechanisms from turning, and keeping the subject's particular amount of adjustment from changing as the subject walks, runs and/or stretches.

When a desired magnitude of reduction has been reached—for example, lowering or maintaining the spondylolisthesis grade over a particular amount of time—any of the embodiments of the adjustable spinal implant disclosed herein may be removed from a patient. Alternatively, they may be left in place within a patient.

FIGS. 25 and 26illustrate an adjustable spinal implant700according to another embodiment of the of devices as described and illustrated herein. The adjustable spinal implant700comprises an implantable actuator704having a transition section701which transitions to an adjustable element706. Two feet726and728extending from the adjustable element706are configured to contact the medial surfaces176of the alas166of the sacrum108. The implantable actuator704may have anchoring tabs710through which bone anchors294can be placed to secure the implantable actuator704to the sacrum108. The adjustable element706features a tethering system for creating traction on the T5 vertebra106. A right tether line703may be coupled to the right transverse process178of the L5 vertebra106, and a left tether line705may be coupled to the left transverse process180of the L5 vertebra106. The right tether line703and left tether line705are wrapped around each respective transverse process178,180and secured to themselves via a crimp or clamp723and725. This crimp or clamp723and725may be created using an appropriate tool during implantation, or may be pre-formed. In some embodiments, a durable surface727is wrapped around the transverse processes178and180first, in order to distribute contact stresses on the transverse processes178and180.

The right tether line703and left tether line705enter the adjustable element706through a seal734(for example, an o-ring) which protects the inner contents of the adjustable element706from body fluids. The right and left tether lines703and705can wind first around first pulleys751and753and then around second pulleys755and757(which may be in an orthogonal plane to the first pulleys751and753). The pulleys751,753,755, and757may serve to guide the right and left tether lines703,705towards the center of a cavity717in the adjustable spinal implant700. In some embodiments, the right and left tether lines703and705bifurcate from single tether line707which extends over a main pulley759and is wound around a spool709. In other embodiments, the right and left tether lines703and705themselves extend over a main pulley759and are then wound around a spool709. The main pulley759can be held by post763. The spool709can be rotationally held by a stepped post721having a large diameter portion715and a smaller diameter portion713. The stepped post721is secured inside the adjustable spinal implant within the transition section701at a connection point761. A radially-poled permanent magnet702is held within a magnetic housing740having a magnetic housing cap744. The magnetic housing744cap and magnetic housing740are rotatable within a radial bearing748. This portion of the assembly is enclosed by an actuator housing cap788and o-ring765. The radially-poled permanent magnet702and thus magnetic housing740are coupled to a first planetary gear stage746, which is in turn coupled to a second planetary gear stage747. The second planetary gear stage747may be coupled to the spool709by pin711. A thrust bearing750axially engages the spool709at the opposite end of the rotatable components from the radial bearing748. A guide loop719assures that the single tether line707is smoothly wound around the spool709. When a moving magnetic field is applied to the radially-poled permanent magnet702(for example, by use of the external adjustment device1180), the radially-poled permanent magnet702and magnetic housing740can be caused to rotate, making the first and second planetary gear stages746and747rotate (at different rotational speeds as determined by the respective gear ratios) and thereby rotating the spool and taking up some of the single tether line707. As the right and left tether lines703and705are pulled, traction (by the changing of tension and/or length of one or more of the tether lines707,703,705) may be applied to the right and left transverse processes178,180, reducing the L5 vertebra106with respect to the sacrum108. Alternatively, each of the tether lines703,705may be wound on its own spool/magnet assembly and thus be independently adjustable. For example, the right tether line703may extend from a first actuator and the left tether line705may extend form a second actuator, with the first actuator independently adjustable from the second actuator.

FIGS. 27-30illustrate embodiments of a driving element alternative that may be used instead of a rotatable magnetic assembly as the driving element242of a non-invasively adjustable spinal implant.FIG. 27illustrates a non-invasively adjustable spinal system1300comprising an implant1306having a first implant portion1302and a second implant portion1304, the second implant portion1304non-invasively displaceable with relation to the first implant portion1302. The first implant portion1302is secured to a first bone portion197and the second implant portion1304is secured to a second bone portion199within a patient191. A motor1308is operable to cause the first implant portion1302and the second implant portion1304to displace relative to one another. An external adjustment device1310has a control panel1312for input by an operator, a display1314and a transmitter1316. The transmitter1316sends a control signal1318through the skin195of the patient191to an implanted receiver1320. Implanted receiver1320communicates with the motor1308via a conductor1322. The motor1308may be powered by an implantable battery, or may be powered or charged by inductive coupling.

FIG. 28illustrates a non-invasively adjustable spinal system1400comprising an implant1406having a first implant portion1402and a second implant portion1404, the second implant portion1404non-invasively displaceable with relation to the first implant portion1402. The first implant portion1402is secured to a first bone portion197and the second implant portion1404is secured to a second bone portion199within a patient191. An ultrasonic motor1408is operable to cause the first implant portion1402and the second implant portion1404to displace relative to one another. An external adjustment device1410has a control panel1412for input by an operator, a display1414and an ultrasonic transducer1416, which is coupled to the skin195of the patient191. The ultrasonic transducer1416produces ultrasonic waves1418which pass through the skin195of the patient191and operate the ultrasonic motor1408.

FIG. 29illustrates a non-invasively adjustable spinal system1700comprising an implant1706having a first implant portion1702and a second implant portion1704, the second implant portion1704non-invasively displaceable with relation to the first implant portion1702. The first implant portion1702is secured to a first bone portion197and the second implant portion1704is secured to a second bone portion199within a patient191. A shape memory actuator1708is operable to cause the first implant portion1702and the second implant portion1704to displace relative to one another. An external adjustment device1710has a control panel1712for input by an operator, a display1714and a transmitter1716. The transmitter1716sends a control signal1718through the skin195of the patient191to an implanted receiver1720. Implanted receiver1720communicates with the shape memory actuator1708via a conductor1722. The shape memory actuator1708may be powered by an implantable battery, or may be powered or charged by inductive coupling.

FIG. 30illustrates a non-invasively adjustable spinal system1800comprising an implant1806having a first implant portion1802and a second implant portion1804, the second implant portion1804non-invasively displaceable with relation to the first implant portion1802. The first implant portion1802is secured to a first bone portion197and the second implant portion1804is secured to a second bone portion199within a patient191. A hydraulic pump1808is operable to cause the first implant portion1802and the second implant portion1804to displace relative to one another. An external adjustment device1810has a control panel1812for input by an operator, a display1814and a transmitter1816. The transmitter1816sends a control signal1818through the skin195of the patient191to an implanted receiver1820. Implanted receiver1820communicates with the hydraulic pump1808via a conductor1822. The hydraulic pump1808may be powered by an implantable battery, or may be powered or charged by inductive coupling. The hydraulic pump1808may alternatively be replaced by a pneumatic pump.

While embodiments of the present invention have been shown and described, various modifications may be made without departing from the scope of the present invention. Supplementation (graft) may be applied during the initial implantation of an embodiment of the adjustable spinal implant, and the adjustments may be made during the time period that the fusion is occurring, for example, less than six months, or more specifically, less than three months. This may, for example, include fusion being attempted between L5106and S1122. The treatment of the patient may be to reduce the grade of spondylolisthesis, as described, but in certain cases, the goal may be simply to maintain the grade of spondylolisthesis in an otherwise progressing patient; for example, to keep spondyloptosis from occurring. In subjects who have undersized transverse processes, some augmentation of the transverse processes may be done prior to securing one of the embodiments of the present invention. In some cases, pedicle screws may be used instead of or to augment the connection to the transverse processes. An additional fulcrum may be placed between the vertebrae being treated (e.g., a wedge implant) in order to aid the derotation. The embodiments of the present invention may also be used in conditions other than spondylolisthesis, for example, ankylosing spondylitis. The invention, therefore, should not be limited, except to the following claims, and their equivalents.

It is contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments disclosed above may be made and still fall within one or more of the inventions. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with an embodiment can be used in all other embodiments set forth herein. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above. Moreover, while the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the various embodiments described and the appended claims. Any methods disclosed herein need not be performed in the order recited. The methods disclosed herein include certain actions taken by a practitioner; however, they can also include any third-party instruction of those actions, either expressly or by implication. For example, actions such as “securing at least a portion of the non-invasively adjustable implant to a portion of the sacrum of the subject” include “instructing the securing at least a portion of the non-invasively adjustable implant to a portion of the sacrum of the subject.” The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” “less than,” “between,” and the like includes the number recited. Numbers preceded by a term such as “approximately”, “about”, and “substantially” as used herein include the recited numbers, and also represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount.