Systems and methods for distraction

A system for moving a portion of a patient's body including a housing having a first cavity extending along a longitudinal axis, a first distraction rod having a proximal end and a distal end, the first distraction rod and the housing being telescopically displaceable with respect to each other along the longitudinal axis, the first distraction rod having a cavity extending along the longitudinal axis, a second distraction rod having a proximal end and a distal end and configured to be telescopically displaceable from within the second cavity along the longitudinal axis, and a drive system configured to move the first distraction rod in relation to the housing and to move the second distraction rod in relation to the first distraction rod.

BACKGROUND

Scoliosis is a general term for the sideways (lateral) curving of the spine, usually in the thoracic or thoracolumbar region. Scoliosis is commonly broken up into different treatment groups, Adolescent Idiopathic Scoliosis, Early Onset Scoliosis and Adult Scoliosis.

Adolescent Idiopathic Scoliosis (AIS) typically affects children between ages 10 and 16, and becomes most severe during growth spurts that occur as the body is developing. One to two percent of children between ages 10 and 16 have some amount of scoliosis. Of every 1000 children, two to five develop curves that are serious enough to require treatment. The degree of scoliosis is typically described by the Cobb angle, which is determined, usually from x-ray images, by taking the most tilted vertebrae above and below the apex of the curved portion and measuring the angle between intersecting lines drawn perpendicular to the top of the top vertebrae and the bottom of the bottom. The term idiopathic refers to the fact that the exact cause of this curvature is unknown. Some have speculated that scoliosis occurs when, during rapid growth phases, the ligamentum flavum of the spine is too tight and hinders symmetric growth of the spine. For example, as the anterior portion of the spine elongates faster than the posterior portion, the thoracic spine begins to straighten, until it curves laterally, often with an accompanying rotation. In more severe cases, this rotation may actually create a noticeable deformity, wherein one shoulder is lower than the other. Currently, many school districts perform external visual assessment of spines, for example in all fifth grade students. For those students in whom an “S” shape or “C” shape is identified, instead of an “I” shape, a recommendation is given to have the spine examined by a physician, and commonly followed-up with periodic spinal x-rays.

Typically, patients with a Cobb angle of 20° or less are not treated, but are continually monitored, often with subsequent x-rays. Patients with a Cobb angle of 40° or greater are frequently candidates for fusion surgery. It should be noted that many patients do not receive such a spinal assessment, for numerous possible reasons. Many school districts do not perform this simple assessment, and many children do not regularly visit a physician. Therefore, the curve often progresses rapidly and severely. There is a large population of grown adults with untreated scoliosis, some having extreme cases exhibiting Cobb angles of 90° or greater. Many adults having untreated scoliosis, though, do not have pain associated with their deformity and live relatively normal lives, though oftentimes with restricted mobility and motion. In AIS, the ratio of females to males having Cobb angles under 10° is about one to one. However, at Cobb angles above 30°, females outnumber males by as much as eight to one. Fusion surgery can be performed on the AIS patients or on adult scoliosis patients. In a typical posterior fusion surgery, an incision is made down the length of the back and Titanium or stainless steel straightening rods are placed along the curved portion. These rods are typically secured to the vertebral bodies, for example with hooks or bone screws, or more specifically pedicle screws, in a manner that allows the spine to be straightened. Usually, at the section selected for fusion, the intervertebral disks are removed and bone graft material is placed to create the fusion. If autologous graft material is used, the bone is generally harvested from a hip via a separate incision.

Alternatively, fusion surgery may be performed anteriorly. A lateral and anterior incision is made for access. Usually, one of the lungs is deflated in order to allow access to the spine from this anterior approach. In a less-invasive version of the anterior procedure, instead of the single long incision, approximately five incisions, each about three to four cm long are made in several of the intercostal spaces (between the ribs) on one side of the patient. In one version of this minimally invasive surgery, tethers and bone screws are placed and secured to the vertebra on the anterior convex portion of the curve. Currently, clinical trials are being performed in which staples are used instead of the tether/screw combination. One advantage of this surgery in comparison with the posterior approach is that scars resulting from the several smaller incisions are not as dramatic, though they are still located in a visible area, when a bathing suit, for example, is worn. Staple-based techniques have experienced some difficulty in clinical trials. The staples tend to pull out of the bone when a critical stress level is reached.

In some cases, after surgery, the patient will wear a protective brace for a few months as the fusing process occurs. Once the patient reaches spinal maturity, it may be difficult to remove the rods and associated hardware in a subsequent surgery because the fusion of the vertebra usually incorporates the rods themselves. Therefore, standard practice is to leave this implant in for life. With either of these two surgical methods, after fusion the patient's spine is rendered straight, but, depending on the number of vertebrae that were fused, limitations in the degree of flexibility, both in bending and twisting, are often observed. As fused patients mature, the fused section of the spine can impart significant stresses on the adjacent non-fused vertebrae, and often, other problems including pain can occur in these areas, sometimes necessitating further surgery. This tends to be in the lumbar portion of the spine that is prone to problems in aging patients. Many physicians are now interested in fusionless surgery for scoliosis, which may be able to eliminate, or at least reduce, one or more of the drawbacks of fusion.

One group of patients in which the spine is especially dynamic is the subset known as Early Onset Scoliosis (EOS), which typically occurs in children before the age of five, and more often in boys than in girls. EOS is a more rare condition than AIS, occurring in only about one or two out of 10,000 children, but can be severe, sometimes affecting the normal development of organs. Because the spines of these children will generally grow a large amount after treatment, non-fusion distraction devices known as growing rods and a device known as the VEPTR—Vertical Expandable Prosthetic Titanium Rib (“Titanium Rib”) have been developed. These devices are typically adjusted approximately every six months, or as required to match the child's growth, until the child is at least eight years old, and sometimes until they are 15 years old. Each adjustment requires a surgical incision to access the adjustable portion of the device. Because the patients may receive the device at an age as early as six months old, this treatment may require a large number of surgeries. Because of the multiple surgeries, these patients have a rather high incidence of infection.

Returning to the AIS patients, the treatment methodology for those with a Cobb angle between 20° and 40° is quite controversial. Many physicians prescribe a brace (for example, the Boston Brace) for a patient to wear on his body, under the clothes, 18 to 23 hours a day until the patient become skeletally mature (e.g., age 16). Because these patients are all passing through their socially demanding adolescent years, it is a quite serious prospect to choose between wearing a somewhat bulky brace that covers most of the upper body, having fusion surgery that may leave large scars and limit motion, and doing nothing and risking becoming disfigured and possibly disabled. It is common knowledge that many patients have, at times, hidden their braces, for example, in a bush outside of school, in order to escape embarrassment associated with the brace(s). The patient compliance with brace wearing has been so problematic that special braces have been constructed that sense the body of the patient and keep track of the amount of time per day that the brace is worn. Even such special braces have problems with patient compliance: patients have been known to place objects into unworn braces of this type in order to fool the sensor. Coupled with the inconsistent patient compliance with brace usage, is a feeling by many physicians that braces, even if used properly, are not at all effective at curing scoliosis. Physicians may agree that bracing can possibly slow down or even temporarily arrest curve (Cobb angle) progression, but they have noted that as soon as the treatment period ends and the brace is no longer worn, often the scoliosis progresses rapidly to a Cobb angle even more severe than it was at the beginning of treatment. Some say the reason for the supposed ineffectiveness of the brace is that it braces only on a portion of the torso, and not on the entire spine. Currently a prospective, randomized, 500-patient, clinical trial known as BrAIST (Bracing in Adolescent Idiopathic Scoliosis Trial) is enrolling patients, 50% of whom will be treated with the brace and 50% of who will simply be watched. Cobb angle data from these patients will be measured continually up until they reach skeletal maturity, or until a Cobb angle of 50° is reached, at which time the patient will likely undergo surgery. Many physicians feel that the BrAIST trial will show that braces are completely ineffective. If this is the case, the quandary about what to do with AIS patients who have a Cobb angle of between 20° and 40° will only become more pronounced. It should be noted that the patient population having a Cobb angle of 20-40° is as much as ten times larger than the population having a Cobb angle of 40° and greater.

Distraction osteogenesis, also known as distraction callotasis and osteodistraction has been used successfully to lengthen various bones of the body (e.g., long bones). Typically, the bone, if not already fractured, is purposely fractured by means of a corticotomy, and the resulting two segments of bone are gradually distracted apart, thereby allowing new bone to form in the gap. If the distraction rate is too high, there is a risk of nonunion. If the rate is too low, there is a risk that the two segments will prematurely, fuse to each other more than desired before the distraction period is complete. Once the desired length of the bone is achieved using this process, the bone is allowed to consolidate. Distraction osteogenesis applications are mainly focused on the growth of the femur or tibia, but may also include the humerus, the jaw bone (micrognathia), or other bones. There are many reasons for lengthening or growing bones which may be desirable. The applications including, but not limited to: post osteosarcoma bone cancer, cosmetic lengthening (both legs-femur and/or tibia) in short stature or dwarfism/achondroplasia; lengthening of one limb to match the other (congenital, post-trauma, post-skeletal disorder, prosthetic knee joint), nonunions.

Distraction osteogenesis using external fixators has been done for many years, but the external fixator can be unwieldy and painful for the patient. It can also subject the patient to the risk of pin track infections, joint stiffness, loss of appetite, depression, cartilage damage and other side effects. An external fixator, e.g., around the patient/patient's limb, can also delay the beginning of rehabilitation.

In response to the shortcomings of external fixator distraction, intramedullary distraction nails which may be contained entirely within the bone have been surgically implanted. Some such nails may be automatically lengthened via repeated rotation of the patient's limb, which can sometimes be painful to the patient, and can often proceed in an uncontrolled fashion. This therefore makes it difficult to follow the strict daily or weekly lengthening regime that avoids nonunion (if too fast) or early consolidation (if too slow). Lower limb distraction rates are generally on the order of about one mm per day. Other intramedullary nails which have an implanted motor and may be remotely controlled by an antenna have also been developed. These devices are designed to be lengthened or distracted in a controlled manner, but, due to their complexity, may not be manufacturable as an affordable product. Others have proposed intramedullary distractors containing an implanted magnet, which allows the distraction to be driven electromagnetically by an external stator. Because of the complexity and size of the external stator, this technology has not been reduced to a simple and/or cost-effective device, which can be taken home to allow patients to do daily lengthenings. Non-invasively adjustable implantable distraction devices, at least one embodiment of which is magnetically non-invasively adjustable, have been developed and used clinically in both scoliosis and limb lengthening patients.

Knee osteoarthritis is a degenerative disease of the knee joint that affects a large number of patients, particularly over the age of 40. The prevalence of this disease has increased significantly over the last several decades, attributed partially, but not completely, to the rising age of the population as well as the increase in obesity. The increase may also be due to an increase in highly active people within the population. Knee osteoarthritis is caused mainly by long term stresses on the knee that degrade the cartilage covering the articulating surfaces of the bones in the knee joint. Oftentimes, the problem becomes worse after a particular trauma event, but it can also be a hereditary process. Symptoms include, but are not limited to, pain, stiffness, reduced range of motion, swelling, deformity, and muscle weakness. Osteoarthritis may include one or more of the three compartments of the knee: the medial compartment of the tibiofemoral joint, the lateral compartment of the tibiofemoral joint, and the patellofemoral joint. In severe cases, partial or total replacement of the knee is performed in order to replace the diseased portions with new weight bearing surfaces for the knee, typically made from implant grade plastics or metals. These operations may involve significant post-operative pain and require substantial physical therapy. The recovery period may last weeks or months. Several potential complications of this surgery exist, including deep venous thrombosis, loss of motion, infection, and bone fracture. After recovery, surgical patients who have received uni-compartmental or total knee replacement must significantly reduce their activity, removing running and high energy sports completely from their lifestyle.

For these reasons, surgeons are attempting to intervene early in order to delay or even preclude knee replacement surgery. Osteotomy surgeries may be performed on the femur or tibia, in order to change the angle between the femur and tibia, and thus adjust the stresses on the different portions of the knee joint. In closed wedge or closing wedge osteotomy, an angled wedge of bone is removed, and the remaining surfaces are fused together, creating a new improved bone angle. In open wedge osteotomy, a cut is made in the bone and the edges of the cut are opened, creating a new angle. Bone graft is often used to fill in the newly-opened, wedge-shaped space, and, often, a plate is attached to the bone with bone screws. Obtaining the correct angle during either of these types of osteotomy is almost always difficult, and, even if the final result is close to what was desired, there can be a subsequent loss of the correction angle. Some other complications associated with this technique include nonunion and material failure.

Amputation of the arm or the leg can result in a residual limb, with a stump, having a shortened bone (e.g., a shortened femur, tibia, fibula, humerus, radius or ulna). A prosthetic limb or prosthetic limb attachment which may be attached to a residual limb may have problems fitting or functioning when attached to a residual limb having insufficient bone length. There may be poor energy transfer between the residual limb and the attached prosthesis, as short lever arms generate less torque for a given force. This functional deficit is compounded when the lever arm is encased in very compliant tissue, such as a residual femur that is surrounded by the soft tissues of the thigh. This may further impair prosthesis control. Individuals having short residual limbs may display gait asymmetries and gait changes. The wearer of a prosthetic limb who has a relatively short residual limb may exhibit compensatory changes that affect posture and cause discomfort or injury to the spine or other body structures. Amputation may occur or may be performed for several reasons including war-related injuries, motor vehicle accidents, including motorcycle accidents, other types of trauma or cancer of the bone or other adjacent tissue.

In addition to the many different types of implantable distraction devices that are configured to be non-invasively adjusted, implantable non-invasively adjustable non-distraction devices have also been envisioned, for example, adjustable restriction devices for gastrointestinal disorders such as GERD, obesity, or sphincter laxity (such as in fecal incontinence), or other disorders such as sphincter laxity in urinary incontinence. These devices, too, may incorporate magnets to enable non-invasive adjustment.

SUMMARY

The present disclosure provides for a system for moving a portion of a patient's body including a housing having a first cavity extending along a longitudinal axis, a first distraction rod having a proximal end and a distal end and configured to be telescopically displaceable from within the first cavity along the longitudinal axis, the first distraction rod having a second cavity extending along the longitudinal axis, a second distraction rod having a proximal end and a distal end and configured to be telescopically displaceable from within the second cavity along the longitudinal axis, and a drive system configured to move the first distraction rod in relation to the housing and to move the second distraction rod in relation to the first distraction rod.

The present disclosure further provides for a method of modifying a residual limb of a patient including the steps of providing a distraction device having a housing extending along a longitudinal axis, a first distraction rod having a proximal end and a distal end, the first distraction rod and the housing being telescopically displaceable with respect to each other along the longitudinal axis, the first distraction rod having a cavity extending along the longitudinal axis, a second distraction rod having a proximal end and a distal end and being configured to be telescopically displaceable from within the cavity along the longitudinal axis, and a drive system configured to move the first distraction rod in relation to the housing and to move the second distraction rod in relation to the first distraction rod, attaching the housing to a first portion of a bone within the residual limb, attaching the second distraction rod to a second portion of the bone within the residual limb, decoupling the first portion of the bone from the second portion of the bone, and wherein the distraction device is actuatable such that the first distraction rod is caused to move in relation to the housing and the second distraction rod is caused to move in relation to the first distraction rod, to increase at least one of a force or a distance between the first portion of the bone and the second portion of the bone.

The present disclosure further provides for a system for moving a portion of a patient's body including a housing having a first cavity extending along a longitudinal axis, a first distraction rod having a proximal end and a distal end, the first distraction rod and the housing being telescopically displaceable with respect to each other along the longitudinal axis, the first distraction rod having a cavity extending along the longitudinal axis, a second distraction rod having a proximal end and a distal end and configured to be telescopically displaceable from within the second cavity along the longitudinal axis, and a drive system configured to move the first distraction rod in relation to the housing and to move the second distraction rod in relation to the first distraction rod.

In one embodiment, a system for moving a portion of a patient's body is provided. The system for moving a portion of a patient's body includes: a housing having a first cavity extending along a longitudinal axis; a first distraction rod having a proximal end, a distal end, and a second cavity extending between the proximal end and the distal end, and being configured for telescopic displacement from within the first cavity; a second distraction rod having a proximal end and a distal end, and being configured for telescopic displacement from within the second cavity; and a drive system configured to move at least one of the first distraction rod and the second distraction rod.

In one embodiment, a method of modifying a residual limb is provided. The method of modifying a residual limb of a patient includes the steps of: providing a distraction device comprising: a housing extending along a longitudinal axis; a first distraction rod having a proximal end and a distal end, the first distraction rod and the housing being telescopically displaceable with respect to each other, the first distraction rod having a cavity extending along the longitudinal axis; a second distraction rod having a proximal end and a distal end and configured to be telescopically displaceable from within the cavity; and a drive system configured to move at least one of the first distraction rod in relation to the housing and the second distraction rod in relation to the first distraction rod; decoupling the first portion of the bone from the second portion of the bone; attaching the housing to a first portion of a bone within the residual limb; attaching the second distraction rod to a second portion of the bone within the residual limb, wherein the distraction device is actuatable such that the first distraction rod is caused to move in relation to the housing and the second distraction rod is caused to move in relation to the first distraction rod, to increase at least one of a force or a distance between the first portion of the bone and the second portion of the bone.

In another embodiment, a system for moving a portion of a patient's body is provided. The system for moving a portion of a patient's body includes: a housing having a first cavity extending along a longitudinal axis; a first distraction rod having a proximal end, a distal end, and a cavity extending along the longitudinal axis, the first distraction rod and the housing being telescopically displaceable with respect to each other along the longitudinal axis; a second distraction rod having a proximal end and a distal end, and configured to be telescopically displaceable from within the second cavity along the longitudinal axis; a drive system configured to move the first distraction rod in relation to the housing and to move the second distraction rod in relation to the first distraction rod.

In still another embodiment, a system for moving a portion of a patient's body is provided. The system for moving a portion of a patient's body includes: a housing having a first cavity; a first distraction rod having a proximal end, a distal end, and a second cavity, wherein the first distraction rod is configured for telescopic displacement relative to the first cavity; a second distraction rod having a proximal end and a distal end, wherein the second distraction rod is configured for telescopic displacement from within the second cavity; and a drive system configured to move at least one of the first distraction rod and the second distraction rod.

In one embodiment, a method of modifying a residual limb of a patient is provided. The method of modifying a residual limb includes the steps of: providing a distraction device comprising: a housing having a first cavity; a first distraction rod having a proximal end, a distal end, and a second cavity, wherein the first distraction rod is telescopically displaceable relative to the first cavity; a second distraction rod having a proximal end and a distal end, wherein the second distraction rod is telescopically displaceable from within the second cavity; and a drive system configured to move at least one of the first distraction rod and the second distraction rod with respect to the housing; then decoupling a first portion of a bone within the residual limb from a second portion of the bone; attaching the housing to one of the first portion and the second portion of the bone within the residual limb; and attaching the second distraction rod to the other of the first portion and the second portion of the bone within the residual limb, wherein the drive system is configured to be actuated so as to increase at least one of a force and a distance between the first portion and the second portion of the bone.

DETAILED DESCRIPTION

Embodiments of the adjustable devices for implanting into the body disclosed herein are capable of achieving a large (e.g., greater than 40%, greater than, greater than 60%, greater than 80%, greater than 100% and even greater than 120%) total amount of adjustment length in comparison to the total length of the adjustable portion of the device. Adjustable devices may include distraction devices, for example distraction devices for orthopedic applications, including, but not limited to scoliosis, limb lengthening, bone transport, spinous process distraction, tibial wedge osteotomy adjustment, and spondylolisthesis. Maintaining a small size an adjustable (e.g., distraction and/or retraction) implant to fit into a small, short space within the body, and achieving large amounts of adjustable length have historically been conflicting design goals.

FIGS. 1-3illustrate an embodiment of an implantable adjustable system100comprising a distraction device110. The distraction device110comprises a housing202, a first distraction rod204and a second distraction rod206. The second distraction rod206and the housing202are each configured for coupling to a patient. The second distraction rod206contains one or more holes208for passing an anchor with which to secure the distraction device110to a patient. One of the one or more holes208may be located between about 3 mm and 15 mm, or approximately 5 mm, from the distal end of the second distraction rod206. The housing202contains one or more holes210for passing an anchor with which to secure the distraction device110to the patient. One of the one or more holes210may be located between about 5 mm and about 20 mm, or approximately 10 mm, from the proximal end of the housing202. The housing202may have a diameter of between about 8.5 mm and about 16 mm, or between about 10.5 mm and about 14.5 mm, or about 14 mm. In some embodiments, the anchor is a bone anchor, for example, a bone screw224,226(FIG. 4). The bone screws224,226may be between about 3 mm and about 6 mm in diameter. In some embodiments, bone screw244is 4 mm in diameter and bone screw226is 5 mm in diameter. The bone screws may be between about 18 mm and about 80 mm in length, or between about 20 mm and about 75 mm in length. However, other types of anchoring and/or connection are contemplated for coupling the second distraction rod206and the housing202to the bone of the patient. As illustrated inFIG. 2, the second distraction rod206may be configured to be telescopically displaceable with respect to the housing202. As seen inFIG. 2, the second distraction rod206may be configured to also be telescopically displaceable with respect to the first distraction rod204. As illustrated inFIG. 3, the first distraction rod204may be configured to be telescopically displaceable with respect to the housing202. The first distraction rod204may be longitudinally displaceable from within a cavity212in the housing202that extends along longitudinal axis Z (FIG. 1). The first distraction rod204may be configured to be telescopically displaceable along the longitudinal axis Z. The first distraction rod204has a cavity214, with the second distraction rod206configured to telescopically displace from the cavity214along the longitudinal axis Z. In some embodiments, the first distraction rod204may have a diameter of between about 8 mm and about 13 mm, or about 11.5 mm. In some embodiments, the second distraction rod206may have a diameter of between about 5 mm and about 11 mm, or about 9 mm. In some embodiments it may be desired that there be no rotational motion (about the longitudinal axis Z) between at least one of the housing202, the first distraction rod204, and the second distraction rod206. In some embodiments, one or more first longitudinal grooves216extends along an exterior surface218of the first distraction rod204and is slidingly engaged by protrusions209(FIG. 4) which extend in an inward radial direction from the interior of a cap215, which is coupled to the housing202, thus allowing longitudinal displacement between the first distraction rod204and the housing202, but not allowing rotation between them. External ribs217on the cap215insert into grooves219in the housing202during assembly. The cap215may be snapped into place on the housing202or otherwise secured by adhesive, welding, soldering, brazing or other methods. One or more second longitudinal grooves220extending along an exterior surface222of the second distraction rod206are slidingly engaged by protrusions211(FIG. 4) which extend from the interior of the cavity214of the first distraction rod204in an inward radial direction, thus allowing longitudinal displacement between the second distraction rod206and the first distraction rod204, but not allowing rotation between them. If the distraction device110is used for the purpose of distracting two pieces of bone (e.g., move two bones or two pieces of a bone apart from each other), then the protrusions209,211and longitudinal grooves216,220make it possible to assure that there may be substantially no rotation between the two bone pieces. As seen inFIG. 3, the first longitudinal grooves216and the second longitudinal grooves220can be purposely configured to reside at different clock positions (in circumferential relation to the longitudinal axis Z (FIG. 1), in order to make enough room in the second distraction rod206, the first distraction rod204, and the housing202, so that wall thickness, and thus strength and durability, are not compromised.

Turning toFIG. 4, bone screws224,226are depicted having unicortical threads228,230and unthreaded shafts232,234, however, any type of bone screw, for example a fully-threaded bone screw, may be used for placement through the holes208,210. The holes208,210may be perpendicular to the longitudinal axis Z, or may be at various angles, depending upon the configuration through which they are to be coupled to the bone. With further reference toFIGS. 4-6, the distraction device110comprises a driving element242configured to be activated by a remotely applied source. A nut236may be secured within a cavity238in the second distraction rod206. The nut236may have external threads240, which are engaged or bonded into an internal thread244of the cavity238. The nut236also contains an internal thread246. A magnetic assembly248may be held between a radial bearing250and a thrust bearing252(FIG. 6), and comprises a radially-poled permanent magnet338which is rotationally coupled to one or more gear modules256(e.g., planetary gearing). The thrust bearing252and radial bearing250may be restrained at their longitudinal extents in relation to the housing202, in order to maintain the magnetic assembly248within the housing202, while allowing it and its components to rotate freely. In some embodiments, the permanent magnet338may be carried within one or more cylindrical housings or cups. The one or more gear modules256output (through the interior of the thrust bearing252) to a coupler258, which may be rotationally coupled to a first lead screw260via a pin262, which passes through a hole261in the coupler258and a hole263at a proximal end264of the first lead screw260. The first lead screw260also has an abutment270at its distal end266, and comprises an external thread268. In some embodiments, the gear modules256may provide a gear ratio of 4:1, 16:1, 64:1, 256:1 between the magnet338and the first lead screw260, or another ratio. In some embodiments, the first lead screw260may be directly coupled to the magnet338, and thus provide 1:1 rotation. The first lead screw260may be threadingly engaged with an internal thread272of a second lead screw274. The majority of the length of the second lead screw274may be an internal bore271with a diameter that is equal to or greater than the major diameter of the internal thread272. The internal thread272may be located only at the proximal end275of the second lead screw274. In some embodiments, the length of the internal thread272along the longitudinal axis Z may be about 3 mm to about 7 mm, or about 5.5 mm. The external thread276of the second lead screw274may be threadingly engaged with the internal thread246of the nut236which may be secured within the second distraction rod. An exemplary external thread specification for each of the lead screws260,274may be 80 threads per inch.

The interior contents of the distraction device110, including the interior portions of cavities212,214,238, which contain the magnetic assembly248and the lead screws260,274, are protected from external fluids and materials by dynamic seals278,280. A first dynamic seal278includes an o-ring282, which resides within a circumferential groove284at a proximal end286of the first distraction rod204. The o-ring282seals along an inner cylindrical surface288of the housing202, and maintains the dynamic seal278throughout the longitudinal displacement of the first distraction rod204with the housing202. A second dynamic seal280includes an o-ring290, which resides within a circumferential groove292at a proximal end294of the second distraction rod206. The o-ring290seals along an inner cylindrical surface296of the first distraction rod204, and maintains the dynamic seal280throughout the longitudinal displacement of the second distraction rod206with the first distraction rod204.

FIG. 6illustrates the distraction device110in a fully undistracted (or retracted) condition, wherein the distal end287of the first distraction rod204and the distal end295of the second distraction rod206are located near the distal end203of the housing202. In use, when the magnet338is rotated (e.g., by an externally-applied moving magnetic field) (and caused to rotate in a first rotational direction) the first lead screw260may be turned (through the gear ratios of gear modules256A,256B,256C). The turning of the external thread268of the first lead screw260in relation to the internal thread272of the second lead screw274, thus causes both the second distraction rod206and the second lead screw274to longitudinally extend from the housing202. As described, in at least some embodiments, the second distraction rod206is prevented from rotation with respect to the first distraction rod204and the housing202. In some embodiments, the second lead screw274does not turn as it longitudinally extends with the second distraction rod206, thus the first distraction rod204does not longitudinally extend in relation to the housing202.FIG. 12, which will be referred to later when describing the procedure for lengthening a bone in a residual limb, shows the distraction rod110after the second distraction rod206has been longitudinally extended in relation to both the housing202and the first distraction rod204. For this first stage of distraction to occur as described, the frictional torque between the external thread268of the first lead screw260and the internal thread272of the second lead screw274is less than the frictional torque between the external thread276of the second lead screw274and the internal thread246of the nut236. This tends to be the case, however, other assembly steps and materials may additionally be provided in order to assure this. For example, in some embodiments, a silicone lubricant or a Krytox® lubricant may be applied to the external thread268of the first lead screw260and/or the internal thread272of the second lead screw274, but not to the external thread276of the second lead screw274and the internal thread246of the nut236. In some embodiments, the lubricant may be applied more liberally to the external thread268of the first lead screw260and/or the internal thread272of the second lead screw274than to the external thread276of the second lead screw274and/or the internal thread246of the nut236. In some embodiments, a more lubricious lubricant may be applied to the external thread268of the first lead screw260and/or the internal thread272of the second lead screw274while a less lubricious lubricant is applied to the external thread276of the second lead screw274and/or the internal thread246of the nut236.

The longitudinal length of distraction possible for the second distraction rod206on its own may be between about 20 mm and about 90 mm, or between about 40 mm and about 70 mm, or about 50 mm. When the second distraction rod206has been fully distracted in relation to the first distraction rod204, the first lead screw260will rotationally engage with the second lead screw274, and thus the rotation of the first lead screw260will begin to turn the second lead screw274(e.g., in a one-to-one manner). In some embodiments, this occurs when the abutment270at the distal end266of the first lead screw260contacts a ledge273adjacent the internal thread272at the proximal end275of the second lead screw274. As the first lead screw260continues to turn the second lead screw274, the external thread276of the second lead screw274turns inside the internal thread246of the nut236of the second distraction rod206, causing the second distraction rod206to longitudinally extend further in relation to the housing202, but now, while also dragging the first distraction rod204along with it. The longitudinal length of distraction possible for the first distraction rod204, after full distraction of the second distraction rod206, may be between about 20 mm and about 90 mm, or between about 40 mm and about 70 mm, or about 50 mm.FIG. 13shows the distraction rod110after the first distraction rod204and the second distraction rod206have been longitudinally extended in this manner in relation to the housing202. Using this two-stage approach to distraction, a total distraction length of 100 mm, or even greater than 100 mm, may be possible with a housing202having a cavity212length of only 97 mm; thus the distraction length provided can be 102% of the housing cavity length. In some embodiments, the length of the distraction device110is 130 mm in a fully retracted state and 230 mm in a fully distracted state. Prior art devices that use only a single distraction rod generally provide distraction lengths of only 40% to 50% of the housing cavity length. The distraction device110may be also capable of retracting, by applying a moving magnetic field in an opposite direction, and causing the components to turn in opposite directions.

In some embodiments, the distraction device110(FIG. 4) may include features to limit the extent of distraction of the second distraction rod206in relation to the first distraction rod204, and in the first distraction rod204in relation to the housing202. For example, an abutment289, or stop, may be located at the end of the longitudinal groove216, or at another location at the proximal end286of the first distraction rod204. An abutment291, or stop, may be located at a distal, internal portion of the housing202, For example, wherein the abutment291is a protrusion carried on the internal wall of the housing202, or wherein it is a one end of the protrusion209of the cap215. The abutment291may be configured to abut/engage the abutment289at a maximum degree of extension of the first distraction rod204in relation to the housing202. Furthermore, an abutment293, or stop, may be located at the end of the longitudinal groove220, or at another location at the proximal end294of the second distraction rod206. An abutment297, or stop, may be located at a distal, internal portion of the first distraction rod204, for example, wherein the abutment297is a protrusion carried on the internal wall of the first distraction rod204. The abutment297may be configured to abut/engage the abutment293at a maximum degree of extension of the second distraction rod206in relation to the first distraction rod204. Each of the abutments289,291,293,297may be configured so that the second distraction rod206, the first distraction rod204, and the housing202do not get stuck or jammed against each other when the longitudinal extents are reached, thus allowing for retraction or shortening of the distraction device110, if desired. The shortening of the distraction device110may be desired in certain situations in which compression of bone pieces is needed. This includes situations in which it is desired to form, reform, or improve a callus for osteogenesis. In some embodiments, the protrusions209,211themselves may serve as the abutments291,297.

The implantable adjustable system100incorporating a distraction device110, as disclosed herein, may utilize an External Remote Controller (ERC).FIG. 10illustrates an example of an External Remote Controller (ERC)180which may be used to non-invasively control the distraction device110by means of a magnetic coupling of torque. ERC180comprises a magnetic handpiece178, a control box176(containing a processor) which may be integrated with the handpiece178and a power supply174such as a battery or external plug for connection to a standard power outlet. The control box176includes a control panel182having one or more controls (buttons, switches or tactile, motion, audio or light sensors) and a display184. The display184may be visual, auditory, tactile, the like, or some combination of the aforementioned features, or any other display/UI described in this disclosure. The control box176may further contain a transceiver for communication with a transceiver in the implant and/or other external devices.

FIG. 11illustrates an internal assembly478of the magnetic handpiece178configured for applying a moving magnetic field to allow for non-invasive adjustment of the distraction device110by turning the magnet338within the distraction device110. The magnet338of the distraction device110includes a north pole406and a south pole408. A motor480with a gear box482outputs to a motor gear484. The motor gear484engages and turns a central (idler) gear486, which has the appropriate number of teeth to turn first and second magnet gears488,490at identical rotational speeds. First and second magnets492,494turn in unison with the first and second magnet gears488,490, respectively. Each magnet492,494may be held within a respective magnet cup496(shown partially). An exemplary rotational speed may be 60 RPM or less. This speed range may be desired in order to limit the amount of current density included in the body tissue and fluids, to meet international guidelines or standards. As seen inFIG. 11, the south pole498of the first magnet492may be oriented the same as the north pole404of the second magnet494, and likewise, the first magnet492has its north pole400oriented the same and the south pole402of the second magnet494. As these two magnets492,494turn synchronously together, they apply a complementary and additive moving magnetic field to the radially-poled, magnet338. Magnets having multiple north poles (for example, two) and multiple south poles (for example, two) are also contemplated in each of the devices. Alternatively, a single magnet (e.g., a magnet with a larger diameter) may be used in place of the two magnets. As the two magnets492,494turn in a first rotational direction410(e.g., counter-clockwise), the magnetic coupling causes the magnet338to turn in a second, opposite rotational direction412(e.g., clockwise). The rotational direction of the motor480may be controlled by buttons414,416. One or more circuit boards418contain control circuitry for both sensing rotation of the magnets492,494and controlling the rotation of the magnets492,494.

FIGS. 7-9 and 12-13illustrate the implantable adjustable system100incorporating a distraction device110and an External Remote Controller (ERC)180being used in a surgery and subsequent adjustment procedures to increase the length of a bone502in a residual limb500. In some cases, the residual limb is a femur of an above-the-knee amputee. As seen inFIG. 7, the bone502may have an amputated end504, and the residual limb500may have a stump surface506. A prosthetic limb or prosthetic limb attachment which may be attached to a residual limb500may have problems fitting or functioning when attached to a residual limb500having insufficient bone502length. The medullary canal514of the bone502may be drilled or reamed to a diameter about equal or slightly larger than that of the distraction device110to be utilized. The bone502may be divided into a first bone portion508and a second bone portion510by creating an osteotomy512. InFIG. 8, the distraction device110may be placed within the medullary canal514so that the one or more holes210are within the first portion508and the one or more holes208are within the second portion510. During pre-operative planning, members of the surgical team will often assess both the condition and the coverage of soft tissues. The stump surface506may be modified, by stretching the skin or tissue, or by adding skin graft material, or performing plastic surgery, in order to create enough future available room for the bone502to increase in length inside the residual limb500in the area adjacent the stump surface506. In addition, infection prevention measures are commonly performed. During pre-operative planning, several other factors are determined including: the amount of limb length discrepancy, the diameter of the medullary canal, the required length of distraction device110to be used, or the location of the planned osteotomy. In some cases, the distraction device may be implanted in an antegrade manner and in some cases in a retrograde manner. When implanted in an antegrade manner the distraction device110may be implanted via piriformis fossa entry. A retrograde approach may instead be chosen, for example, in patients with a severely abducted hip. InFIG. 9, bone screws226,224are secured to the bone502through the holes210,208in order to secure the distraction device110to the first and second bone portions508,510. The patient may be allowed to recover and at a later time, for example, about two to about ten days or about five days, the first distraction procedure may be performed. The ERC180may be placed on the residual limb500at a location adjacent the magnet338, and is operated to distract the first bone portion508and the second bone portion510apart. The procedure may be repeated several times and may be performed by medical personnel, or the patient's family and friends, or even the patient themself. Exemplary distraction protocol may include distraction of about 0.50 mm to about 1.50 mm in longitudinal distraction per day. In some cases, it may include distraction of about 0.75 mm to about 1.25 mm in longitudinal distraction per day. In some cases, the distraction may be about 1.00 mm per day. This may be broken up into several distraction procedures per day, for example, about 0.33 mm, three times a day.

FIG. 12illustrates the distraction device110in the bone502after the second distraction rod206has approximately been fully distracted in relation to the first distraction rod204. Over the several weeks and/or months that the distraction procedures take place, a new bone growth section516of bone begins to form between the first portion508and the second portion510.FIG. 13illustrates the distraction device110in the bone502after the first distraction rod204has approximately been fully distracted in relation to the housing202. After the desired final distraction length is reached, distraction procedures are discontinued, and the new bone growth section516may be allowed time to fully consolidate. The distraction device110can continue to provide stability to the bone502of the residual limb500while the bone502is allowed to consolidate and after the bone has consolidated. After consolidation, the distraction device110may then be removed from the patient, though in some cases, the distraction device110may be left in place within the bone502.

FIG. 14illustrates one embodiment of a distraction device600placed next to a prior art distraction device602. The distraction device600may be capable of distracting about 50 mm, as is the prior art distraction device602, however the length L1of the housing portion of the distraction device600is over 25% percent shorter than the length L2of the housing portion of the prior art distraction device602. The treatment of early onset scoliosis or adolescent idiopathic scoliosis is generally performed on small, thin patients having little space in their surgical sites to implant large device housings. Therefore, high efficiency adjustable distraction devices (total distraction length to housing length ratio) may allow more patients to be treated. Turning toFIG. 15, the distraction device600includes a housing604which may be connected to a rod606by welding or other bonding methods. In some embodiments, the rod606and the housing604may be formed from the same monolithic material. Within the housing604, a driving element including a magnetic assembly608(containing a radially-poled magnet630) may be held longitudinally stationary between a thrust bearing610and a radial bearing612. Though gear modules may be incorporated, as in the embodiment ofFIG. 1, inFIG. 15the distraction device is depicted in an embodiment wherein the magnetic assembly608may be directly connected to a first lead screw614by a pin616. In the distraction device600embodiment ofFIG. 15, a first distraction rod618is telescopically carried on the outside of the housing604, and is longitudinally displaceable along a longitudinal axis Z. A second distraction rod620may be telescopically carried within a cavity622within the housing604, and is longitudinally displaceable along the longitudinal axis Z. The second distraction rod620has a cavity632which allows space for the first lead screw614. A second lead screw624having an internal thread626at its proximal end628may be carried annularly between the first lead screw614and the second distraction rod620. Rotation of the magnetic assembly608by a remotely-applied moving magnetic field causes the first lead screw614to rotate within the internal thread626of the second lead screw624, thus causing the second lead screw624and the second distraction rod620to longitudinally displace in relation to the housing604and the first distraction rod618. The distraction device600with the second distraction rod620fully displaced in relation to the first distraction rod618is illustrated inFIGS. 16-17. At this fully displaced condition, an abutment634at the distal end636of the first lead screw614abuts a ledge638at the proximal end640of the second lead screw624. As the first lead screw614continues to turn, this causes the second lead screw624to turn in unison with the first lead screw614, thus turning of the second lead screw624within an inner thread642within the cavity632of the second distraction rod620. This causes the second distraction rod620to longitudinally displace further from the housing604, dragging the first distraction rod618along with it. The distraction device600with the first distraction rod618fully displaced in relation to the housing604is illustrated inFIGS. 18-19. A first o-ring644held in a circumferential groove in the first distraction rod618forms a dynamic seal between the first distraction rod618and the housing604. A second o-ring646held in a circumferential groove in the first distraction rod618forms a dynamic seal between the first distraction rod618and the second distraction rod620. The distraction device600may be capable of retracting, by applying a moving magnetic field in an opposite direction, and causing the components to turn in opposite directions.

The distraction device600may comprise features to limit or stop rotation between the first distraction rod618and the housing604, and/or between the second distraction rod620and the first distraction rod618. For example, the longitudinal grooves,216,220and protrusions209,211of the embodiment ofFIGS. 1-6may be incorporated into the design of the distraction device600, so that there may be substantially no rotation possible between the second distraction rod620and the housing604. For example, if the second distraction rod620is rigidly coupled to a first vertebra (e.g., via a screw or hook) and the housing604(e.g., via rod606) is coupled to a second vertebra (e.g., via a screw or hook), rotation may be substantially limited between the first vertebra and the second vertebra, so that no unwanted movement between them can occur. Furthermore, the abutments289,291,293,297of the embodiment ofFIGS. 1-6may be incorporated into the design of the distraction device600in order to control the extent of lengthening of the first distraction rod618in relation to the housing604, and/or the second distraction rod620in relation to the first distraction rod618.

FIGS. 20-23illustrate embodiments of alternate sources to the rotatable magnetic assembly as the driving element242of a non-invasively adjustable implant.FIG. 20illustrates a non-invasively adjustable 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 portion1302may be secured to a first bone portion197and the second implant portion1304may be secured to a second bone portion199within a patient191. A motor1308may be operable to cause the first implant portion1302and the second implant portion1304to displace relative to one another. An external remote controller (ERC)1310has 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. 21illustrates a non-invasively adjustable 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 portion1402may be secured to a first bone portion197and the second implant portion1404may be secured to a second bone portion199within a patient191. An ultrasonic motor1408may be operable to cause the first implant portion1402and the second implant portion1404to displace relative to one another. An external remote controller (ERC)1410has a control panel1412for input by an operator, a display1414and an ultrasonic transducer1416, which may be coupled to the skin195of the patient191. The ultrasonic transducer1416produces ultrasonic waves1418which pass through the skin195of the patient191and operate the ultrasonic motor1408.

FIG. 22illustrates a non-invasively adjustable 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 portion1702may be secured to a first bone portion197and the second implant portion1704may be secured to a second bone portion199within a patient191. A shape memory actuator1708may be operable to cause the first implant portion1702and the second implant portion1704to displace relative to one another. An external remote controller (ERC)1710has 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. 23illustrates a non-invasively adjustable 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 portion1802may be secured to a first bone portion197and the second implant portion1804may be secured to a second bone portion199within a patient191. A hydraulic pump1808may be operable to cause the first implant portion1802and the second implant portion1804to displace relative to one another. An external remote controller (ERC)1810has 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.

Though not illustrated, another driving element242may include a magnetorestrictive element. A number of materials may be used to produce the components like the housing, first distraction rod, second distraction rod, first lead screw, and second lead screw, including but not limited to titanium, titanium alloys, titanium 6-4, cobalt-chromium alloys, and stainless steel.

FIG. 24illustrates a sterilizable kit700of instruments for use with embodiments of the distraction device described herein. A sterilizable tray702includes holes704which may allow gas or steam to enter the tray702when the tray702is covered by a cover (not shown). One or more dividers706may be constructed of a pliable material (such as silicone) and provide cavities, holes or slits therebetween for securing the one or more instruments. A drill bushing708and a guide tube710may be used for guiding one or more drills or reamers, for example, while drilling holes within the medullary canal of a bone. Prior to this, a hole may be made in the skin, soft tissue, and/or bone using a piercing rod730. Vent holes may be made in the bone prior to reaming in order to avoid high intramedullary pressures which may cause fat embolism, or other complications, The medullary canal may in some cases be reamed to a slightly larger diameter than the diameter of the distraction device110, for example 0.5 mm larger, or may be reamed 1 mm larger or 2 mm larger. A guide arm712may be connected at a distal end713of its guide tube725to a the housing202of the distraction device110ofFIG. 6, for example an engagement portion213at the proximal end221of the housing202. The engagement portion213may include a cavity, for example, a threaded cavity, and may be engageable via a distal end723of a locking rod722. The locking rod722may be inserted through the guide tube725of the guide arm712. The locking rod722may be tightened (or untightened) by turning a handle727, or by placing a tommy bar718through a transverse hole729at or near the handle727of the locking rod722. The drill bushing708and a guide tube710may be placed through transverse holes735in the guide arm, or a guide extension724may be secured to the end737of the guide arm712. One or more additional transverse holes735may be within the guide extension for placement of the drill bushing708and a guide tube710. During the manipulation of the distraction device110with the instruments, soft tissue of the patient may be protected with a soft tissue protector714. Some or all of the cylindrical instrument components may be rotated with increased torque by attaching a T-handle716. If the distraction device110and the guide arm712need to be removed, for example from a reamed medullary canal in the bone, a mallet720may be placed so that a slit731in the head733of the mallet720is around the guide tube725of the guide arm712. The mallet720may be then caused to impact against the handle727of the guide arm712to aid in the removal of the distraction device110and guide arm712. After implantation of the distraction device110and its securement to the bone by one or more bone screws, the guide arm112may be removed, by unscrewing the locking rod722from the engagement portion213of the distraction device110.

If the distraction device110is to be removed from the bone (for example after the bone has been lengthened and allowed to consolidate), after the bone screws are removed, an extractor726may be attached to the engagement portion213of the distraction device110and the distraction device may be pulled out of the medullary canal by hand, or may be hammered out using the mallet731. The distal end of the extractor726may have a male or female thread that can be engaged with the proximal end221of the housing202of the distraction device110. An additional removal rod728may be used. Further instruments that may be used include a locking key732, a short impactor734, a hexagon headed river736and a locking driver738. Bone screws740may be secured with a screw capture rod740. Other instruments and uses of instruments are described in U.S. Pat. No. 8,449,543, which is incorporated herein by reference in its entirety.

Similarly, this method of disclosure, is not to be interpreted as reflecting an intention that any claim require more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment.