Implantable bone adjustment devices

A reconfigurable bone adjustment device (1, 101, 201) includes a first member (10,110, 210, 1010) configured for attachment to a first bone fragment, a second member (20, 130, 230, 1030) configured for attachment to a second bone fragment and a reconfiguration assembly (2, 102, 401, 501, 601, 701, 801, 901, 1020) configured to move the second member relative to the first member. The reconfiguration assembly includes a drive mechanism (50, 150, 250, 440, 540, 640, 740, 840, 940, 1050) and a threaded rod (70, 170, 245, 470, 570, 670, 770, 870, 970, 1070, 1170) operatively coupled to the drive mechanism so that rotation of the drive mechanism rotates the threaded rod. The reconfiguration assembly operates to reduces stresses, forces, bending moments and/or eccentric moments on a junction and/or by configuring the junction in a manner whereby one of more of the forces, is isolated away from the junction.

TECHNICAL FIELD

The present disclosure generally relates to implantable reconfigurable bone adjustment devices, and more particularly, but not exclusively, relates to implantable reconfigurable bone adjustment devices that include a reconfiguration assembly including a threaded rod rigidly coupled to a driver.

BACKGROUND

Implantable reconfigurable bone adjustment devices are occasionally used in orthopedic procedures to gradually adjust the position, orientation, geometry and/or length of a bone, such as, for example, by distraction, compression, realignment or bone transport. One form of an implantable reconfigurable bone adjustment device is a limb lengthening nail (LLN) configured for implantation in the medullary canal of a long bone and subsequently manipulated to adjust the length of the bone. Another form of an implantable reconfigurable bone adjustment device is a bone transport nail configured for implantation in the medullary canal of a long bone and subsequently manipulated to move a middle bone fragment across a gap between proximal and distal bone fragments to induce bone regeneration in the gap. Still other forms of implantable reconfigurable bone adjustment devices include spinal adjustment implants and implants configured to achieve other gradual adjustments to the shape, position or length of skeletal structures.

Implantable reconfigurable bone adjustment devices may include internal magnets that are configured to rotate upon actuation by an external actuating device, thereby driving a threaded rod that engages other device components to achieve a dimensional modification of the device or other relational modification between components of the device. Such dimensional modification or relational modification of the device operate on bone segments, portions or fragments to which the device is affixed to exert pressures on the bone segments, portions or fragments to which the device is affixed, thereby gradually moving the bone segments, portions or fragments relative to one another. Such devices may include a first member configured to be affixed to a first bone segment, portion or fragment; a second member configured to be affixed to another bone segment, portion or fragment; a rod with at least one thread, the rotation of which causes displacement of the second member relative to the first member, and a mechanism for controlling the rotation of the threaded rod. In the case of certain LLN devices, for example, the second member may be assembled telescopically relative to the first member and rotation of the threaded rod operates to telescopically displace the second member relative to the first member, thereby increasing the distance between the bone segments, portions or fragments to which the first member and the second member are respectively affixed. In the case of certain bone transport nails, the first member may have a first end configured to be affixed to a first bone fragment, a second end configured to be affixed to a second bone fragment, and a carriage configured to be affixed to a middle bone fragment positioned within a gap between the first and second bone fragments. Rotation of the threaded rod in such a device operates to axially transport the carriage relative to the first member to thereby facilitate formation of regenerate bone between the first and second bone fragments.

In such implantable reconfigurable bone adjustment devices, rotation of the threaded rod may be driven by a component, referred to herein as a “drive mechanism,” whose actuation is controlled to achieve a desired amount of rotation over time and at a desired rate, thereby to achieve a desired amount of bone adjustment at a desired rate. In certain devices, the drive mechanism includes a magnet hermetically sealed in a housing, although other types of drive mechanisms, such as electric motors, are contemplated. A common feature of such drive mechanisms, which may also include gear reducers, is that the threaded rod is rigidly affixed to a structure of the drive mechanism to achieve controlled rotation of the threaded rod. This structure is referred to herein as a “driver.”

The threaded rod in such devices necessarily engages at least one component of the device (other than the driver) such that rotation of the threaded rod changes the relative positions of different device components. The rotation of the threaded rod imposes forces on the threaded rod, which may differ in different regions of the threaded rod, such as axial loads (compressive and/or tensile), bending moments and the like. For example, in some such devices, the junction at which the threaded rod is connected to the driver carries a tensile load when the device is in normal use. Moreover, the torque required to rotate the rod is sometimes substantial, which places substantial forces on the point of connection between the threaded rod and the driver. As a result of these loads, together with potential bending moments and eccentric loading, stresses are localized at the junction of the threaded rod and the driver when such a device is loaded.

While currently-available bone adjustment systems have produced excellent results, many of these devices exhibit one or more shortcomings or disadvantages that render the device susceptible to failure. For example, a problem has been encountered where the stress concentrations at the point where the threaded rod is affixed to the driver can cause failure of the device at this junction. Failures of a device at this junction results in the inability of the device to perform its intended bone adjustment action. For these reasons among others, a need remains for further improvements in this technological field. The present disclosure addresses this need.

SUMMARY

The present disclosure provides implantable reconfigurable bone adjustment devices, kits, systems and methods for moving first and second members of the device, and hence first and second bone segments, portions or fragments coupled thereto, with respect to one another.

There is provided a reconfigurable bone adjustment device including a first member configured for attachment to a first bone fragment, a second member configured for attachment to a second bone fragment, and a reconfiguration assembly configured to move the second member relative to the first member. The reconfiguration assembly including a drive mechanism including a driver, the drive mechanism operable to controllably rotate the driver, and a threaded rod having a proximal end operatively coupled to the driver at a junction so that rotation of the drive mechanism rotates the driver, which rotates the threaded rod. The reconfigurable bone adjustment device further including means for reducing applied stresses at the junction.

In some embodiments, the driver has a first axis of rotation and the threaded rod has a second axis of rotation, the first and second axes of rotation being offset with respect to one another.

In some embodiments, the threaded rod includes a helical channel formed therein, the helical channel being formed in a proximal portion of the threaded rod adjacent to the proximal end of the threaded rod adjacent to the junction.

In some embodiments, the junction includes a dynamic joint selected from one of a pin joint, a ball joint, or a universal joint for connecting the proximal end of the threaded rod to the driver.

In some embodiments, the driver includes first and second projections having first and second apertures, respectively, the first and second projections being configured to receive the proximal end of the threaded rod therebetween, the threaded rod including an aperture near the proximal end thereof so that, when aligned, a pin is inserted through the first and second projections of the driver and the aperture of the threaded rod to secure the threaded rod to the driver.

In some embodiments, the reconfigurable bone adjustment device includes a collar positioned between the driver and the second member such that rotation of the threaded rod in a first direction exerts a compressive force between a distal surface of the driver and a proximal surface of the collar, and between a distal surface of the collar and a proximal end of the second member.

In some embodiments, the distal surface of the collar includes a convex surface for contacting a complementary concave surface formed on the proximal end of the second member, the complementary convex and concave surfaces forming an interface for transmitting the compressive force.

In some embodiments, the threaded rod includes a first distal segment having a first diameter and a second proximal segment adjacent the proximal end of the threaded rod, the second proximal segment having a second diameter, the second diameter being greater than the first diameter.

In some embodiments, the second proximal segment includes a tapered surface extending from the proximal end of the threaded rod to the first distal segment, rotation of the threaded rod causes the tapered surface of the second proximal segment to contact a proximal end of the second member.

In some embodiments, the threaded rod includes a third segment having a third diameter, the third diameter being greater than the first diameter and the second diameter.

In some embodiments, the third segment is located in-between the first and second segments.

In some embodiments, the third segment includes an enlarged spherical segment.

In some embodiments, the enlarged spherical segment includes an articulating surface for contacting a proximal end of the second member.

In some embodiments, the articulating surface of the enlarged spherical segment and the proximal end of the second member include corresponding concave and convex articulating surfaces.

In some embodiments, the articulating surface of the enlarged spherical segment and the proximal end of the second member include corresponding spherical articulating surfaces.

In some embodiments, the driver is operatively coupled to a proximal end of the second member via a ball joint type connection.

In some embodiments, the junction includes a stop component coupled to the threaded rod adjacent to the proximal end of the threaded rod and a spacer component. The spacer component including (i) a bore dimensioned to permit passage of the threaded rod therethrough, (ii) a distal surface configured to contact a proximal end of the second member, and (iii) a cavity extending from a proximal side of the spacer component, the cavity dimensioned to receive the stop component therein.

In some embodiments, the cavity formed in the spacer component and the stop component have complementary surfaces so that rotation of the spacer component rotates the stop component.

In some embodiments, the stop component includes a body having an aperture and the threaded rod includes an aperture, the aperture formed in the body and the aperture formed in the threaded rod being aligned with one another for receiving a pin therethrough. The pin includes a first end, a second end, and a length defined by the first and second ends, the length of the pin being greater than an outer dimension of the body so that the first and second ends of the pin extend beyond the body of the stop component. The spacer component including a channel for receiving the first and second ends of the pin when the stop component is received within the cavity of the spacer component, wherein the first and second ends of the pin contact one or more side surfaces of the channel when the driver is rotated so that torque is transferred from the spacer component to the threaded rod.

In some embodiments, the stop component includes a radially extending flange, the cavity formed in the spacer component including a shoulder dimensioned to contact the flange when the stop component is received within the cavity.

In some embodiments, the stop component includes a distal side having a geometric shape defined by a plurality of distal contact surfaces, and the cavity formed in the proximal side of the spacer component includes a plurality of complementary contact surfaces so that, when the stop component is received within the cavity, the contact surfaces of the cavity contact the distal surfaces of the stop component.

In some embodiments, the junction includes a welded joint between the proximal end of the threaded rod and the driver.

In some embodiments, the reconfigurable bone adjustment device is an intramedullary limb lengthening nail.

In some embodiments, the reconfigurable bone adjustment device is an intramedullary bone transport nail.

In some embodiments, the drive mechanism is an internal magnetic adapted for rotation via an external magnetic actuator.

Embodiments of the present disclosure provide numerous advantages. For example, incorporation of the reconfiguration assembly operates to reduce applied stresses, such as axial forces, torsional forces, bending moments and/or eccentric moments on the junction and/or by configuring the junction in a manner whereby one of more of the forces, torsional forces, bending moments and/or eccentric moments is isolated away from the junction.

Further features and advantages of at least some of the embodiments of the present disclosure, as well as the structure and operation of various embodiments of the present disclosure, are described in detail below with reference to the accompanying drawings.

It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and devices or which render other details difficult to perceive may have been omitted. It should be further understood that this disclosure is not limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the figures and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the present disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates.

Various implantable reconfigurable bone adjustment devices are disclosed herein. In one embodiment, the implantable reconfigurable bone adjustment device may include a first member, body portion or component (used interchangeably herein without the intent to limit), a second member, and a rotatable threaded rod that engages at least one component affixed to the first member and at least one component operable to axially move the second member relative to the first member. The implantable reconfigurable bone adjustment device may also include a drive mechanism to controllably actuate rotation of the threaded rod. In certain embodiments, the drive mechanism may be an internal magnet coupled to the threaded rod such that rotation of the internal magnet drives rotation of the threaded rod. This can be achieved, for example, by fixing the threaded rod directly to the internal magnet or a casing in which the internal magnet is contained, or can be achieved by connecting the threaded rod indirectly to the internal magnet, such as through a gear mechanism or other structure positioned therebetween. As described further herein, torque may be applied to the internal magnet by applying a rotating magnetic field across the internal magnet from an external source. In other implantable reconfigurable bone adjustment device embodiments, rotation of the threaded rod may be controlled or driven by a drive mechanism other than an internal magnet. Alternative drive mechanisms for driving the threaded rod may include any other now known or hereafter developed drive mechanisms known to a person of ordinary skill in the art, including, for example, an electric motor with or without gear reducer, a current source inside or outside the patient's body, a permanent magnet with a gear reducer and a rotating magnetic field source external to the patient, etc. In alternate embodiments, the drive mechanism can be configured to drive the threaded rod in one direction only, or in both directions, according to requirements.

The first and second body portions are dimensioned such that the body portions can move in at least one axial direction with respect to one another upon rotation of the threaded rod. In one representative embodiment, depicted schematically inFIG. 1, the implantable reconfigurable bone adjustment device1may include a first body10and a second body20at least partially received within first body10. The first body10may also house a reconfiguration assembly2which, in this embodiment, includes an internal magnet50, which is affixed to a threaded rod70. As described in further detail below, the internal magnet50may be rotated about an axis90of the device1by application of an external rotating magnetic field, which may be applied, for example, using an external magnetic actuator, as discussed further below.

One representative, but non-limiting, example, of an implantable reconfigurable bone adjustment device contemplated by the present disclosure is an intramedullary limb lengthening nail, such as intramedullary (“IM”) limb lengthening nail101depicted inFIGS. 3-5. Further details regarding representative IM limb lengthening nails are available in U.S. Pat. No. 8,777,947, which is hereby incorporated herein by reference in its entirety. Referring toFIGS. 3-5, the IM limb lengthening nail101may include a proximal body portion110, a distal body portion130, and a threaded rod170operatively associated with the proximal body portion110and the distal body portion130. In use, rotation of the threaded rod170causes the proximal body portion110and the distal body portion130to move with respect to one another. In one embodiment, as will be described in greater detail, the proximal body portion110may be configured as an outer body and the distal body portion130may be configured as an inner body so that at least a portion of the distal body portion130may be received with the proximal body portion. Alternatively, it is envisioned that the proximal body portion may be configured as the inner body and the distal body portion may be configured as the outer body. In one embodiment, the threaded rod170may be mounted in and coupled to the distal body portion130.

Each of the proximal body portion110, distal body portion130, and threaded rod170has a proximal end111,131,171and a distal end114,134,174, respectively. The IM limb lengthening nail101may also include a reconfiguration assembly102, which may include an inner magnet150(also referred to herein as “internal magnet”) seated in the proximal body portion110and coupled to the proximal end171of the threaded rod170, a distal block136coupled to the distal body portion130and a distal end174of the threaded rod170, and a threaded block119coupled to the proximal body portion110and engaged with the threaded rod170. The term “inner” or “internal” is used herein in reference to the magnet150to distinguish this magnet from a different magnet or multiple different magnets employed by an external actuator as described in greater detail below, which magnet or magnets of an external actuator, are referred to as “outer magnets.” While neodymium magnets are suggested, other magnets may be employed as will be apparent to those skilled in the art.

The proximal body portion110may be at least partially hollow, having an inner wall120that defines an internal cylindrical chamber, for accommodating a portion of the distal body portion130, which extends through the distal end114of the proximal body portion110. The proximal and distal body portions110,130are dimensioned such that the proximal and distal body portions110,130can move in both axial directions with respect to one another. The proximal body portion110may also house the inner magnet150, which may be mounted in a casing or carrier to facilitate the coupling of the inner magnet150to the threaded rod170. The inner magnet150may include at least one permanent magnet, one of the poles of which is directed in one radial direction relative to a longitudinal axis190of the IM limb lengthening nail101and the other pole directed in an opposite radial direction relative to the longitudinal axis190. As described in further detail below, the inner magnet150may be rotated about the longitudinal axis190of the IM limb lengthening nail101by application of an externally applied rotating magnetic field. The IM limb lengthening nail101may also include a first locking portion112and a second locking portion132, each of which includes a plurality of fastener openings113,133structured to receive fasteners for coupling the respective ends of the IM limb lengthening nail101to the patient's bone.

The inner magnet150is coupled to the threaded rod170, which extends through the proximal end131of the distal body portion130. The threaded rod170may also extend through a bearing (not shown) which engages the inner wall120of the proximal body portion110. Similarly, a bearing may be coupled to a proximal end of the inner magnet150to facilitate rotation of the inner magnet150within the proximal body portion110. The distal end174of the threaded rod170is engaged with the distal block136, which is coupled to the distal body portion130. In use, the distal block136permits rotation of the threaded rod170with respect to the distal body portion130, and couples the distal body portion130and the threaded rod170for joint movement along the longitudinal axis190. For example, the distal block136may be coupled or affixed to the distal body portion130such that the threaded rod170can rotate freely without altering the position of the distal end174of the threaded rod170with respect to the distal body portion130. The threaded rod170also extends through the threaded block119, which is coupled to the proximal body portion110.

The threaded rod170may include a set of external threads176which are engaged with a set of internal threads formed in a threaded bore (not shown) of the threaded block119. As noted above, the threaded rod170is axially coupled to the distal body portion130and is axially and rotationally coupled to the inner magnet150, and the threaded block119is engaged with the threaded rod170and axially and rotationally coupled to the proximal body portion110. As a result, rotation of the inner magnet150causes relative movement of the proximal and distal body portions110,130along the longitudinal axis190.

FIG. 3illustrates the IM limb lengthening nail101in a retracted or contracted state, andFIGS. 4 and 5illustrate the IM limb lengthening nail101in an extended or distracted state. The IM limb lengthening nail101may be moved between the contracted and distracted states by rotating the inner magnet150by application of an externally applied rotating magnetic field. More specifically, rotation of the inner magnet150may cause rotation of the threaded rod170and movement of the threaded block119and the proximal body portion110relative to the distal body portion130along the longitudinal axis190, thereby adjusting the length of the IM limb lengthening nail101. As is evident from a comparison ofFIGS. 3 and 4, the longitudinal positions of the distal block136and the distal end174of the threaded rod170with respect to the distal body portion130remain unchanged. That is, the distal body portion130may include an elongated slot140which enables the threaded block119to slide along the distal body portion130during relative movement of the proximal and distal body portions110,130along the longitudinal axis190.

In use, the IM limb lengthening nail101is configured for implantation in a bone having a medullary canal. Typically, the IM limb lengthening nail is implanted such that the first locking portion112is affixed to a first bone portion and the second locking portion132is affixed to a second bone portion, and a gap separates the first and second bone portions. The gap may be formed, for example, during an osteotomy procedure in which the bone is severed for purposes of lengthening the bone over time. The IM limb lengthening nail101is implanted into the medullary canal of the bone and is surgically coupled to the bone. For example, the proximal body portion110is coupled to the first bone portion and the distal body portion130is coupled to the second bone portion by fasteners such as screws or pins, which may be received in or otherwise engaged with the openings113,133.

Both distraction and compaction of the proximal and distal body portions110,130with respect to each other is possible. Thus, with the IM limb lengthening nail101implanted in the bone, the segmented portions of the bone may be distracted or compacted as necessary by rotation of the threaded rod170and the inner magnet150in a first direction or a second direction, respectively, thereby enabling lengthening or shortening of the bone. In other words, the telescoping ability allows the IM limb lengthening nail101to both distract and contract the bone portions, to which the proximal and distal body portions110,130are coupled. During lengthening, the IM limb lengthening nail101may be transitioned from the retracted state (FIG. 3) to the expanded state (FIG. 4), thereby lengthening the bone. The IM limb lengthening nail may be transitioned from the retracted state to the expanded state gradually over a given period of time, such that an ossified region forms as the bone lengthens and heals. It should be understood that the principles and features of the present disclosure are not limited to use with the IM limb lengthening nail illustrated and described in connection withFIGS. 3-5and that the principles and features may be used in combination with other IM limb lengthening nails.

In another embodiment, an implantable reconfigurable bone adjustment device contemplated by the present disclosure is an IM bone transport nail, such as the IM bone transport nail201depicted inFIGS. 6-9. IM bone transport nails typically are employed in situations where regeneration of bone across a gap between two bone fragments is indicated. For example, typically a gap of 3 cm or more may be formed such as, for example, as a result of a surgical resection. In an example bone transport procedure, two bone fragments, a distal end fragment and a proximal end fragment, are held in a displaced relationship to each other by, for example, a medullary pin or nail fixed in the medullary canal of each bone fragment. A middle bone segment, which also originates from the same original bone tissue as the two bone fragments, is positioned adjacent a first one of the two bone fragments. At a contact site between the middle bone segment and the first one of the end bone fragments, bone tissue grows as a result of normal physiological bone healing processes. Regenerate bone thereafter continues to form in a longitudinal direction relative to the medullary canal by displacement of the middle bone segment toward the second one of the two bone fragments at a prescribed rate of translation of the middle segment, i.e., a rate that is sufficiently slow to allow bone regeneration to take place.

Referring toFIGS. 6-9, the IM bone transport nail201may include a proximal locking portion212configured for fixation to a first bone fragment295, a distal locking portion215configured for fixation to a second bone fragment296, and a nail body210extending between the proximal locking portion212and the distal locking portion215. The IM bone transport nail201is configured for use, for example, where the gap in which bone is to be regenerated is located in a proximal femoral or distal tibial location. Each of proximal locking portion212and distal locking portion215may include a plurality of fastener openings positioned roughly perpendicular to a longitudinal axis290of IM bone transport nail201and structured to receive fasteners, also referred to as fixation elements, such as, for example, locking screws or bolts (not shown) for anchoring each of the proximal locking portion212and distal locking portion215to respective first and second bone fragments of a patient. In the embodiment shown, proximal and distal locking portions212,215define first openings213and second openings216, respectively.

The nail body210of the IM bone transport nail201may be roughly cylindrical and may include at least a partially hollow cavity to accommodate a transport carriage assembly230. For example, the nail body210may include an internal chamber217configured to receive and retain the transport carriage assembly230in an axially slidable arrangement. The internal chamber217of the nail body210and the transport carriage assembly230are dimensioned such that the transport carriage assembly230can translate axially within the nail body210. That is, the nail body210may include an elongated longitudinal opening or slot218that opens diametrically out on opposite sides of the nail body210at an axial position corresponding to the axial range of motion desired for movement of a transport bone segment screw236that is affixed to a middle bone segment297during normal use of the IM bone transport nail201. That is, the middle bone segment297is situated between a first bone fragment295, which typically is a first end of a long bone, and a second bone fragment296, which typically is a second end of a long bone. Movement of the middle bone segment297from its initial position shown inFIG. 6to its final position shown inFIG. 7produces regenerate bone298between the first bone fragment295and the middle bone segment297. In alternate embodiments, the first bone fragment295can be a proximal bone fragment or a distal bone fragment. For example, the IM bone transport nail201is well suited for a bone transport procedure to regenerate bone for repair of a proximal femoral or distal tibial defect. When the IM bone transport nail201is used for repair of a proximal femoral defect, the first bone fragment295is a distal end fragment of a femur and the second bone fragment296is a proximal end fragment of the femur. When the IM bone transport nail201is used for repair of a distal tibial defect, the first bone fragment295is a proximal end fragment of a tibia and the second bone fragment296is a distal end fragment of the tibia.

The transport carriage assembly230may include a carriage body231, a threaded rod245and a magnetic driver250. The threaded rod245may be coupled to the magnetic driver250in axial alignment. Together, the threaded rod245, the magnetic driver250and their respective components are referred to in this embodiment as a “magnet housing assembly.” The magnetic driver250includes an inner magnet251, which may be accommodated in a casing or carrier to facilitate coupling of the inner magnet251to the threaded rod245. In one embodiment, the inner magnet251is hermetically sealed in a housing as described further below. The term “inner” is used herein in reference to the magnet of the magnetic driver250to distinguish this magnet from a different magnet or multiple different magnets employed by an external actuator as described in greater detail below, which magnet or magnets of an external actuator, are referred to as “outer magnets.” The magnet housing assembly of the embodiment shown includes the inner magnet251, a magnet housing252, a first magnet housing cap254and a second magnet housing cap255. In the embodiment shown, the inner magnet251, the magnet housing252, the first magnet housing cap254, the second magnet housing cap255and the threaded rod245are assembled and coupled together such that rotation of the inner magnet251rotates the remaining elements. In one manner of assembly, for example, these components are welded together to achieve rotation of these elements together. In one embodiment, the inner magnet251is hermetically sealed within the magnet housing252, which prevents contact of the inner magnet251with the patient's body. As shown, the carriage body231and the magnet housing252may be roughly cylindrical in this embodiment and have outer diameters that are roughly equal to the inner diameter of the internal chamber217of the nail body210. In the embodiment shown, the inner magnet251includes a permanent magnet with diametrical magnetization. In other words, the poles of the inner magnet251are perpendicular to the rotational axis of the internal magnet251. While neodymium magnets are suggested, other magnets may be employed as will be apparent to those skilled in the art.

The Carriage body231of the transport carriage assembly230may include a radially oriented aperture235in which a transport bone segment screw236is positionable during use of the IM transport nail201. In use, the transport bone segment screw236fixes the middle bone segment297to the carriage body231. The carriage body231may also include an axial bore233and an elongated longitudinal opening or slot234.

The axial bore233is configured to accommodate or receive at least a portion of the threaded rod245within the carriage body231without restricting free rotation of the threaded rod245relative to the carriage body231. The axial bore233therefore may include a radial dimension greater than the largest diameter of the threaded rod245and an axial dimension sufficient to accommodate the full length of the threaded rod245when the transport carriage assembly230is fully assembled for use. Upon assembly of the transport carriage assembly230by insertion of the threaded rod245into the axial bore233, a bearing ring260may be positioned between the second magnet housing cap255and the proximal end232of carriage body231to reduce frictional forces of the assembly and enable the magnet housing assembly240to rotate freely within the nail body210relative to the carriage body231. The magnet housing assembly240in the embodiment shown also includes an optional bearing ring265adjacent to the first magnet housing cap254to facilitate rotation of the magnetic driver250within the nail body210. For example, incorporation of the optional bearing ring265may operate to reduce frictional forces within the IM bone transport nail201should the proximal end of the magnet housing assembly240come into contact with other surfaces within the internal chamber217.

The elongated slot234formed in the carriage body231may be configured to accommodate a threaded block219, and to provide clearance relative to the threaded block219when the transport carriage assembly230moves axially relative to the nail body210(to which the threaded block219is affixed) during normal operation of the IM bone transport nail201following implantation into a patient. While the elongated slot234in this embodiment passes entirely through the carriage body231, which enables the threaded block219to extend diametrically to both opposing sides of the nail body210, in alternative embodiments (not shown) the elongated slot234can be formed as a groove on one side of the carriage body231that extends only part way through the carriage body231and opens radially out on only one side of the carriage body231. In this alternate embodiment, the threaded block219may be affixed to the nail body210only on one side of the nail body210.

The magnetic driver250in this embodiment may be rigidly coupled to the proximal end247of the threaded rod245. In this embodiment, the magnetic driver250and the threaded rod245are rotationally fixed relative to one another. Fixation of the magnetic driver250to the threaded rod245can be achieved by any mechanism now known or hereafter developed including, for example, welding the proximal end247of the threaded rod245to the second magnet housing cap255, which is in turn welded to the distal end of the magnet housing252. In this embodiment, welding of the threaded rod245to the magnetic driver250eliminates any degrees of rotational freedom between the threaded rod245and the magnetic driver250. Therefore, axial rotation of the magnetic driver250directly drives axial rotation of the threaded rod245. Other embodiments are contemplated, however, where components comprising gears or other mechanisms are incorporated into the transport carriage assembly230between the inner magnet251and the threaded rod245to modify the relative rate of rotation between these two components. This may be desired, for example, to increase torque applied to the threaded rod245or for other reasons. In such embodiments, rotation of the inner magnet251drives rotation of the threaded rod245.

The threaded rod245, at a location between the proximal end247of the threaded rod245that is coupled to the magnetic driver250and the distal end246of the threaded rod245that may be accommodated within the access slot237, engages the threaded block219. The threaded block219may include a threaded bore (not shown) extending through the threaded block219along the longitudinal axis290. The threaded rod245includes a set of external threads that are engaged with a set of internal threads formed in the threaded bore of the threaded block219. Stated alternatively, the external threads of the threaded rod245include diameter and pitch features complementary to those of the internal threads of the threaded bore such that outward facing threads on the threaded rod245properly engage inward facing threads in the threaded bore of the threaded block219. The threaded block219may be fixed to the nail body210so that the position of the threaded block219is fixed with respect to the nail body210. The threaded block219permits rotation of the threaded rod245relative to the nail body210, and rotatably couples the nail body210and the threaded rod245to drive axial movement of the transport carriage assembly230along the longitudinal axis290. In the embodiment shown, the threaded block219is coupled to diametrically opposite sides of the nail body210in an orientation whereby the threaded block219passes through the elongated slot234of the carriage body231, which is positioned within the internal chamber217of the nail body210. In this orientation, rotation of the magnetic driver250results in rotation of the threaded rod245within the threaded bore of the threaded block219and, because the threaded block219is fixed to the nail body210, rotation of the magnetic driver250and the threaded rod245results in axial movement of the transport carriage assembly230relative to the nail body210along the longitudinal axis290of the IM bone transport nail201.

FIG. 6illustrates the IM bone transport nail201with the transport carriage assembly230located at a first position, andFIG. 7illustrates the IM bone transport nail201with transport carriage assembly230located at a second position. The transport carriage assembly230may be moved between the first and second positions by rotating the inner magnet251with an externally actuated rotating magnetic field, as described more fully below. In use, rotation of the inner magnet251causes rotation of the threaded rod245and movement of the transport carriage assembly230along the longitudinal axis290, thereby axially adjusting the position of the transport carriage assembly230within the IM bone transport nail201. As is evident from a comparison ofFIGS. 6 and 7, the axial position of the threaded block219with respect to the nail body210remains unchanged and the axial positions of the magnetic driver250, the threaded rod245and the carriage body231translate relative to the nail body210, but remain unchanged relative to one another. The elongated longitudinal opening218of the nail body210enables the transport carriage assembly230to move axially relative to the nail body210with the transport bone segment screw236affixed to the middle bone segment297passing through the elongated longitudinal opening218.

Displacement of the transport carriage assembly230as described above is achieved by rotation of the threaded rod245, which may be achieved by rotation of the inner magnet251. In the IM bone transport nail201, the threaded rod245is under tension during axial loading conditions resulting from rotation of the threaded rod245. More specifically, during rotation of the threaded rod245and displacement of the transport carriage assembly230, the load-bearing points of contact between the nail body210and the magnetic driver250are at (i) the threaded rod245/threaded block219interface, (ii) the abutment of the proximal end of the carriage body231with the second magnet housing cap255(through bearing260), and (iii) at the junction between the threaded rod245and the second magnet housing cap255.

For example, when the transport carriage assembly230is moved in a direction represented by the arrow onFIG. 6as a result of rotation of the threaded rod245, the transport bone segment screw236transmits a tensile force on the transport bone segment297to which the transport bone segment screw236is affixed, relative to the first bone fragment295. The transport bone segment screw236thereby exerts a compressive load on the carriage body231via the engagement of the transport bone segment screw236in radially oriented aperture235. This compressive force is transmitted by the carriage body231to the second magnet housing cap255, thereby causing tension in the portion of the threaded rod245that extends from the second magnet housing cap255to the threaded block219, which is fixed to the nail body210. Thus, the axial load on the threaded rod245is between the threaded block219(affixed to the nail body210) and the proximal end247of the threaded rod245at its junction with the second magnet housing cap255. When the IM bone transport nail201is under a compressive axial load, which it is during use, the axial load on the threaded rod245is tensile. In other words, when the transport carriage assembly230is under compression, it imparts this load to the magnetic driver250, for example, the second magnet housing cap255, which in turn puts a tensile load on the threaded rod245between the second magnet housing cap255(where it is coupled) and where it is threaded into the locking block219. As the carriage distracts, the length of the threaded rod245under load decreases.

Rotation of the threaded rod245is achieved by applying a rotational force on the inner magnet251that overcomes opposing forces to rotate the inner magnet251. Because the inner magnet251is fixedly contained within the magnet housing252and the second magnet housing cap255is fixedly coupled to the magnet housing252and the threaded rod245, rotation of the inner magnet251drives rotation of the threaded rod245. Rotation of the inner magnet251is achieved by applying an appropriately positioned and oriented rotating magnetic field (also referred to herein as a magnetic driving field) of sufficient strength across the inner magnet251.

It should be understood that the principles and features of the present disclosure are not limited to use with the IM bone transport nail illustrated and described in connection withFIGS. 6-9and that the principles and features may be used in combination with other IM bone transport nails. In addition, while the IM limb lengthening nail101and IM bone transport nail201are described as representative implantable reconfigurable bone adjustment devices, it is to be understood that the present disclosure in not limited to use with an IM limb lengthening nail or an IM bone transport nail, it being understood that the principles and features of the present disclosure find advantageous use with a variety of other implantable reconfigurable bone adjustment devices that include a drive mechanism operable to controllably rotate a driver that is coupled to a threaded rod to drive rotation of the threaded rod to move first and second members of the device relative to one another.

As indicated above, to rotate the rotatable portion of an implanted medical device that employs a drive mechanism including an internal magnet, such as, for example, a rotatable internal magnet50,150,251that is coupled to a threaded rod70,170and245of the devices described above, a rotating magnetic field is applied to the device to apply torque to the internal magnet. In one embodiment, this torque is applied by magnetically coupling an external magnetic actuator with the rotatable internal magnet50,150,251.

The creation of a magnetic driving field for rotating internal magnets50,150,251and threaded rods70,170,245coupled coaxially therewith can be accomplished by a wide variety of mechanism. In one manner of actuating rotation of internal magnets50,150,251following implantation of an implantable reconfigurable bone adjustment device1,101,201in a skeletal position of a patient, an external magnetic actuator, also referred to herein as an actuation unit may be used. In one embodiment, the external magnetic actuator is operable to position a driving magnet, also referred to herein as an outer magnet, near the implanted device, but external to the patient, at the height of the internal magnet50,150,251. The external magnetic actuators are designed and positioned to maximize torque to the internal magnets50,150,251and the threaded rod70,170,245and, in any event, to provide sufficient torque to rotate the internal magnets50,150,251despite the distance between the internal magnets50,150,251and the one or more outer magnets in the external magnetic actuator and applied resisting forces on the device1,101,201. In this regard, rotation of the internal magnet50,150,251must overcome any compressive load imparted between the components of the device1,101,201by bone tissue and other tissues of the patient, together with internal frictional forces of the device.

In the presence of a magnetic driving field perpendicular to the rotational axis of the internal magnet50,150,251(which lies on the longitudinal axis90,190,290in the respective embodiments) and rotating around this axis, the internal magnet50,150,251tends to become oriented in the magnetic driving field, which applies a torque to the internal magnet50,150,251and causes the internal magnet50,150,251to rotate in the same rotational direction of the magnetic driving field, together with threaded rod70,170,245that is coupled coaxially with internal magnet50,150,251, if the applied torque is greater than the load torque on threaded rod70,170,245under the load applied to it at the time when the magnetic driving field is activated.

In one embodiment, the driving magnet comprises at least one permanent magnet, one of the poles of which is directed towards longitudinal axis90,190,290. In another embodiment, an even greater torque can be applied to the internal magnet50,150,251by using two permanent driving magnets positioned such that the south pole of one is facing the north pole of the other, and such that the implanted device and the part of the patient's body that surrounds the implanted device are positioned between the two permanent magnets.

In one embodiment, depicted inFIGS. 23-25, the actuation unit300may include a pair of housings310, an arcuate body320connecting the pair of housings310, and a pair of outer magnets340mounted in the pair of housings310, respectively. InFIGS. 23-25, the actuation unit300is illustrated in a position in which it partially surrounds the reconfigurable bone adjustment device1,101,201, such that the outer magnets340are positioned on opposite sides of the internal magnet50,150,251of the reconfigurable bone adjustment device1,101,201. The outer magnets340may, for example, be neodymium magnets, although other magnets may be employed as will be apparent to those skilled in the art. With the outer magnets340positioned on opposite sides of the internal magnet50,150,251, and with each of the outer magnets340having an inward-facing side of one polarity aligned with a side of the inner magnet having the opposite polarity, the internal magnet50,150,251is magnetically coupled to the actuation unit300. Thus, rotation of the actuation unit300about the longitudinal axis90,190,290of the reconfigurable bone adjustment device1,101,201results in a torque being applied to the internal magnet50,150,251. As a result of the torque, the internal magnet50,150,251rotates about the longitudinal axis90,190,290, thereby causing rotation of the threaded rod70,170,245.

In certain forms, the arcuate body320may include an adjustment device which permits relative movement of the housings310in a direction transverse to the longitudinal axis90,190,290of the reconfigurable bone adjustment device1,101,201. In such embodiments, the distance392(FIG. 25) between the center of the internal magnet50,150,251of the reconfigurable bone adjustment device1,101,201and the center of the outer magnets340of the actuation unit300may be adjustable in order to accommodate limbs of varying diameters. For example, the housings310may be moved further apart from one another to accommodate a limb having a larger diameter, and may be moved toward one another to increase the strength of the magnetic coupling when the limb has a smaller diameter.

In the illustrated embodiment, the outer magnets340are fixedly mounted in the housings310, and rotation of the internal magnet50,150,251is achieved by rotating the actuating device300about the longitudinal axis90,190,290of the reconfigurable bone adjustment device1,101,201. In other embodiments, the outer magnets340may be rotatably mounted in the housings310of the actuation unit300. In such forms, rotation of the internal magnet50,150,251may be achieved by rotating the outer magnets while the actuation unit300remains stationary, as described, for example, in U.S. Pat. No. 8,777,947 to Zahrly et al, which is hereby incorporated herein by reference in its entirety. Alternatively, another embodiment of an external magnetic actuator is described in PCT Application No.: PCT/US17/68394, filed on Dec. 26, 2017, entitled Actuation System and Method for Orthopedic Implants with a Rotatable Internal Magnet, which is hereby incorporated herein by reference in its entirety.

After implantation of the reconfigurable bone adjustment device1,101,201in a patient, the external actuation unit300may be used at various times, per physician instructions, to non-invasively rotate the internal magnet50,150,251and the threaded rod70,170,245of the implanted reconfigurable bone adjustment device, as described herein. As will be appreciated, the ability of the actuation unit300to rotate the internal magnet50,150,251and the threaded rod70,170,245of the implanted reconfigurable bone adjustment device against the resistive forces of the bone callus and soft tissue is determined in part by the strength of the magnetic coupling between the internal magnet50,150,251of the reconfigurable bone adjustment device1,101,201and the outer magnets340of the external actuation unit300. For patients with a large limb diameter, the distance392between the internal magnet50,150,251and the outer magnets340reduces the strength of the magnetic coupling, which limits the amount of torque that can be applied to the threaded rod70,170,245and the internal magnet50,150,251by the actuation unit300. The ability of the actuation unit300to rotate the threaded rod70,170,245also depends in part upon the resistive frictional forces internal to the reconfigurable bone adjustment device1,101,201, such as friction between the engaged threads of the threaded rod170,245and the threaded block119,219in the reconfigurable bone adjustment devices1,101,201.

To address the risk of failure of the reconfigurable bone adjustment devices such as the devices described above, a variety of reconfiguration assembly embodiments are disclosed. The reconfiguration assembly embodiments are described in the context of a reconfigurable bone adjustment device that includes a first member configured for attachment to a first bone fragment, a second member configured for attachment to a second bone fragment, and a reconfiguration assembly configured to move the second member relative to the first member. The first member may be, for example and without limitation, the proximal body portion110of the IM limb lengthening nail101or the nail body210of the IM bone transport nail201. The second member may be, for example and without limitation, the distal body portion130of the IM limb lengthening nail101or the carriage body231of the IM bone transport nail201. The reconfiguration assembly may include a drive mechanism including a driver, wherein the drive mechanism is operable to controllably rotate the driver about a first axis of rotation, and a threaded rod having a proximal end coupled to the driver at a junction such that rotation of the driver causes rotation of the threaded rod about a second axis of rotation. As indicated above, the combination of the drive mechanism and the threaded rod is referred to herein as a “reconfiguration assembly,” representative examples of which include, without limitation, the internal magnet50and the threaded rod70of the reconfigurable bone adjustment device1; the internal magnet150and the threaded rod170of the IM limb lengthening nail101; or the magnet housing assembly240and the threaded rod245of the IM bone transport nail201. With reference to the IM bone transport nail201, the second magnet housing cap255represents the driver of the reconfiguration assembly of the IM bone transport nail201to which the threaded rod245is affixed.

In one embodiment, the reconfiguration assembly may be configured to withstand bending or eccentric loads that may be placed on the junction of the driver and the threaded rod of such a device. In another embodiment, the reconfiguration assembly may be configured to allow a degree of variation between the first axis of rotation and the second axis of rotation when the reconfiguration assembly is subjected to a bending or eccentric load. For example,FIG. 10illustrates one variation of a reconfiguration assembly401that may be used in a reconfigurable bone adjustment device, in which a junction405at which a proximal end471of a threaded rod470is coupled to a driver455of a drive mechanism440. The junction405can be any now known or hereafter developed junction including, for example, a welded joint. In some embodiments, the welded joint includes a threaded recess (not shown) in the driver455in which the proximal end471of the threaded rod470is advanced in threaded engagement, and then the threaded interface between the threaded recess and the portion of the threaded rod470at the interface are welded, such as by laser welding. In other embodiments, a segment of threaded rod470adjacent to the proximal end471is devoid of threads and is inserted into a smooth sided recess formed in the driver455and then welded in place. In yet other embodiments, the proximal end471of the threaded rod470may be welded in an abutting relationship with the driver455, such as by friction welding. Other manners of affixing the proximal end471of the threaded rod470to the driver455are also contemplated. In the reconfiguration assembly401, a proximal portion472of the threaded rod470, which is located adjacent to the proximal end471of the threaded rod470, includes a helical channel473formed therein. The incorporation of the helical channel473results in a decrease or elimination of bending stresses on or at the junction405, which may occur, for example, when the rotational axis491of drive mechanism440(e.g., a first axis of rotation) is not in exact alignment with rotational axis492of threaded rod470(e.g., a second axis of rotation).

Referring toFIG. 11, an alternate embodiment of a reconfiguration assembly for allowing a degree of variation between a first axis of rotation and a second axis of rotation is provided. In the reconfiguration assembly501, illustrated inFIG. 11, the proximal end571of the threaded rod570may be coupled to the driver555of the drive mechanism540via a dynamic joint505. In the embodiment shown, the dynamic joint505may be a pinned joint including the driver555. As shown, the driver555may include first and second projections556,557spaced sufficiently apart to provide clearance for the proximal end571of the threaded rod570. The threaded rod571includes a radial aperture573near the proximal end571thereof to receive a pin574. The pin574may include first and second ends576,577. In use, the pin574may be inserted into the radial aperture573formed in the threaded rod570such that the first and second ends576,577of the pin574extend from the radial aperture573and into engagement with the first and second projections556,557, respectively. In this manner, during use, the threaded rod570does not transfer moments to the driver555. This arrangement therefore also results in a decrease or elimination of bending stresses on the drive mechanism540, which may otherwise occur, for example, when the rotational axis591of the drive mechanism540(e.g., a first axis of rotation) is not in exact alignment with the rotational axis592of the threaded rod570(e.g., a second axis of rotation). In alternate embodiments (not shown), the dynamic joint505can take the form of a ball joint or a universal joint rather than a pinned joint.

In another manner of addressing the risk of failure of reconfigurable bone adjustment devices such as the reconfigurable bone adjustment devices1,101,201described above, bending moments and stresses on a junction between the driver and the threaded rod may be lessened or eliminated by positioning a collar between the driver and the second body portion or member of the reconfigurable bone adjustment device such that rotation of the threaded rod in a first direction exerts a compressive force between a distal surface of the collar and a proximal end of the second body portion or member to move the second body portion or member relative to the first body portion or member.

For example,FIG. 12illustrates one variation of a reconfiguration assembly601for use in a reconfigurable bone adjustment device in which a collar680is positioned between a driver655and a second body portion630of the reconfigurable bone adjustment device. For context,FIG. 12also depicts the first body portion610of the reconfigurable bone adjustment device. While the driver655, the collar680and the second body portion630are shown inFIG. 12with spaces therebetween, it is to be understood that in normal operation, rotation of the threaded rod670in a first direction will cause the driver655to exert a compressive force on the collar680, which in turn exerts a compressive force on the second body portion630. Thus, in normal use, a distal surface656of the driver655will be in contact with a proximal surface681of collar680and a distal surface682of the collar680will be in contact with a proximal surface631of the second body portion630. In one embodiment, each of surfaces656,681,682,631may be generally flat. In another embodiment, a bearing or bushing (not shown) may be positioned between the distal surface656of the driver655and the proximal surface681of collar680. In another embodiment, a bearing or bushing may be positioned between the distal surface682of the collar680and the proximal surface631of the second body portion630. In still another embodiment, two bearings or bushings may be present (or one of each), one positioned between the distal surface656of the driver655and the proximal surface681of collar680and another positioned between the distal surface682of the collar680and the proximal surface631of the second body portion630. In yet another embodiment, one or more of the surfaces656,681,682,631may include a contour that is not flat. In embodiments in which one or more of the surfaces656,681,682,631has a contour that is not flat, it is preferred for the contacting surfaces, that is, the distal surface656of the driver655and the proximal surface681of collar680, or the distal surface682of the collar680and the proximal surface631of the second body portion630(which can be referred to as “surface pairs”) to have complementary shapes, it being understood that at least one of the surface pairs must be configured to allow relative rotation between the driver655and the collar680, or between the collar680and the second body portion630, or both.

In the embodiment shown, the collar680may include a convex distal surface682(also referred to as a “domed surface”) and the second body portion630may include a complementary concave proximal surface631. The interface of the convex distal surface682and the concave proximal surface631is capable of transmitting a compressive force substantially in the direction of a longitudinal axis of the threaded rod670from the collar680to the second body portion630during normal use of the reconfigurable bone adjustment device that includes the reconfiguration assembly601. It is, of course, understood that the convex distal surface682and the concave proximal surface631can be symmetrical, but in some embodiments, are not symmetrical.

In another manner of addressing the risk of failure of reconfigurable bone adjustment devices such as the reconfigurable bone adjustment devices1,101,201described above, bending moments and stresses on a junction between the driver and the threaded rod may be lessened or eliminated by utilizing a threaded rod that has a first diameter along a major portion of its length and a second or proximal segment having a second diameter that is greater than the first diameter. The larger diameter, second or proximal segment of the threaded rod may be integrally formed with the smaller diameter portion of the threaded rod. In one embodiment, the larger diameter, second or proximal segment may include a tapered segment located between the major portion of the first diameter and the proximal end of the threaded rod. That is, with reference toFIG. 13, the threaded rod770of the reconfiguration assembly701may include a first segment770ahaving a first diameter D1along a threaded portion. The threaded rod770may also include a second segment772, located at a proximal end of the threaded rod adjacent to the driver755. The second or proximal segment772may include a second diameter D2, where the second diameter D2is greater than the first diameter D1. In one embodiment, the first segment770aincludes threads and constitutes a majority of the overall length of the threaded rod770. In the embodiment shown, the second or proximal segment772may include a tapered section that tapers from the first diameter D1, where the second or proximal segment772meets the first segment770aof the threaded rod770, to a second diameter D2at a proximal end771of the second or proximal segment772. For context,FIG. 13also depicts the first body portion710and the second body portion730. In use, rotation of the threaded rod770in a first direction causes the second or proximal tapered segment772to exert a compressive force on the proximal end731of the second body portion730. Because normal operation of the reconfigurable bone adjustment device requires relative rotation between the second or proximal tapered segment772and the second body portion730, a bearing or bushing (not shown) may be positioned between an outer surface773of the second or proximal tapered segment772and an outer surface732at the proximal end731of the second body portion730.

Because rotation of the threaded rod770in the first direction exerts a tensile load on a load bearing portion of the threaded rod770only at the location where the second body portion730contacts the second or proximal tapered segment772to the axial location where the threaded rod770engages a threaded mating component of the first body portion710(such as, for example, the threaded block119of the IM limb lengthening nail101), loading of the reconfigurable bone adjustment device that includes the reconfiguration assembly701does not place an axial load on the junction of the proximal end771of the second or proximal tapered segment772and the distal surface756of the driver755.

The proximal end771of the second or proximal tapered segment772can be coupled to the driver755in any desirable manner. In one embodiment, the proximal end771of the second or proximal tapered segment772may be coupled to the driver755by friction welding. In the embodiment shown, both of these surfaces are generally circular and have generally the same diameter; however, the surfaces can have different sizes and different shapes, if desired. Friction welding of the surfaces will provide a strong joint able to withstand the torque transmitted from the drive mechanism740to the threaded rod770through the joint.

FIG. 14illustrates another embodiment of a reconfiguration assembly that utilizes a threaded rod having different diameters to lessened or eliminate bending moments and stresses on a junction between the driver and the threaded rod. As illustrated, and as previously described, the implantable reconfigurable bone adjustment device may include a first body1010and a second body1030at least partially received within first body1010. For example, as illustrated, the implantable reconfigurable bone adjustment device may be an IM limb lengthening nail having a proximal outer body portion1010, a distal inner body portion1030, and a threaded rod1070operatively associated with the proximal outer body portion1010and the distal inner body portion1030. In use, rotation of the threaded rod1070causes the proximal outer body portion1010and the distal inner body portion1030to move with respect to one another. However, it is envisioned that the implantable reconfigurable bone adjustment device may be provided in other forms including, for example, IM bone transport nail.

As previously mentioned, the proximal outer body portion1010may house a drive mechanism (e.g., an internal magnet)1050operatively coupled to the threaded rod1070via a reconfiguration assembly1020. In use, the drive mechanism (e.g., internal magnet)1050may include or be operatively associated with a driver1055, which may be in the form of a magnetic housing cap. The driver1055may be coupled to the threaded rod1070by any suitable means. As illustrated, the driver1055may be coupled to the threaded rod1070(e.g., to a second or proximal segment1072of the threaded rod1070) via a pin connection1002.

As previously mentioned, rotation of the drive mechanism (e.g., an internal magnet)1050via, for example, an external rotating magnetic field, which may be applied, for example, using an external magnetic actuator (as described further below), results in rotation of the threaded rod1070, which causes the distal inner body1030to move with respect to the proximal outer body1010.

The threaded rod1070includes a first segment1071extending along a major portion of its length. The first segment1071may have a first diameter D1. In addition, the first segment1071may include external threads along all or a majority of its length for directly or indirectly engaging an inner surface of the distal inner body1030. In addition, the threaded rod1070may include a second or proximal segment1072having a second diameter D2that is greater than the first diameter D1. The larger diameter, second or proximal segment1072of the threaded rod1070may be integrally formed with the smaller diameter first segment1071of the threaded rod1070. In one embodiment, the threaded rod1070may also include a third segment1073having an enlarged spherical or bulbed segment having a third diameter D3. The third diameter D3being larger than the first diameter D1and the second diameter D2. As illustrated, the third segment1073may be located in-between the first and second segments1071,1072. The second and third segments1072,1073may be devoid of any external threading. That is, the threads preferably cease prior to the corresponding contacting surfaces between the enlarged spherical or bulbed segment1073and the proximal end1032of the distal inner body1030(as will be described in greater detail below).

By providing an enlarged spherical or bulbed segment1073having a third diameter D3where the third diameter D3is larger than the first diameter D1and the second diameter D2enables the second segment D2to be made smaller than otherwise possible if the enlarged spherical or bulbed segment1073was omitted. That is, for example, by providing the enlarged spherical or bulbed segment1073, allows for a smaller second segment1072, which enables the driver1055to have thicker walls.

In use, rotation of the drive mechanism (e.g., internal magnet)1050rotates the driver1055, which in turn, rotates the threaded rod1070. Rotation of the threaded rod1070in a first direction causes an outer contacting surface1074of the enlarged spherical or bulbed segment1073to contact and exert a compressive force on a proximal end1032of the distal inner body1030.

The contacting surfaces between the enlarged spherical or bulbed segment1073and the proximal end1032of the distal inner body1030preferably include corresponding concave and convex articulating surfaces. In one embodiment, the articulating, contact surfaces between the enlarged spherical or bulbed segment1073and the proximal end1032of the distal inner body1030are essentially spherical.

As a result, the axial load passes through the articulating surface. Moreover, as a result of the corresponding concave and convex articulating surfaces, a ball-joint type connection may be formed. In use, the articulating, contacting surfaces enable some rotation between the enlarged spherical or bulbed segment1073and the proximal end1032of the distal inner body1030. This connection leads to improved articulation, weight bearing, and improved distraction.

In one embodiment, clearances may be provided between the threaded rod1070and the driver1055(e.g., the distal magnet housing cap). As such, the threaded rod1070is no longer rigidly fixed to the driver1055(e.g., the distal magnet housing cap). That is, as illustrated, by incorporating a pin connection, gaps or spaces1057,159may be incorporated between the second or proximal segment1072of the threaded rod1070and the driver1055, allowing for some movement of the threaded rod1070about the pin axis and around the pin1002. By enabling some movement of the threaded rod1070allows for easier bending of the nail.

As illustrated, the reconfigurable bone adjustment device1020may also include a bushing1043, as previously mentioned. The busing1043may be positioned at a distal end of the driver1055. The bushing1043positioned between the driver1055and the inner surface of the proximal outer body1010, thus facilitating rotation of the driver1055within the proximal outer body1010.

In one embodiment, the threads formed on the threaded rod1070may include a surface treatment. In addition, the corresponding articulating, contact surfaces between the enlarged spherical or bulbed segment1073and the proximal end1032of the distal inner body1030may include a surface treatment. The surface treatment could be any suitable treatment that increases lubricity, for example, an amorphous diamond-like carbon (DLC), plasma immersion ion implantation, PA-CVD, PVD, etc.

FIG. 15illustrates another embodiment of a reconfiguration assembly that utilizes a threaded rod having different diameters to lessened or eliminate bending moments and stresses on a junction between the driver and the threaded rod. The embodiment illustrated inFIG. 15is substantially similar to the embodiment described and illustrated above in connection withFIG. 14, except as described herein.

Referring toFIG. 15, the threaded rod1170includes a first segment1171extending along a major portion of its length. The first segment1171may have a first diameter D1. In addition, the first segment1171may include external threads along all or a majority of its length for directly or indirectly engaging an inner surface of the distal inner body1030. In addition, the threaded rod1170may include a second or proximal segment1172having a second diameter D2that is greater than the first diameter D1. The larger diameter, second or proximal segment1172of the threaded rod1170may be integrally formed with the smaller diameter first segment1171of the threaded rod1170. The second segment1172may be devoid of any external threading. That is, the threads preferably cease prior to the corresponding contacting surfaces between the enlarged second segment1172and the proximal end1032of the distal inner body1030.

In use, rotation of the drive mechanism (e.g., internal magnet)1050rotates the driver1055, which in turn, rotates the threaded rod1170. Rotation of the threaded rod1170in a first direction causes an outer contacting surface1174of the enlarged second segment1172to contact and exert a compressive force on a proximal end1032of the distal inner body1030.

The contacting surfaces between the enlarged second segment1172and the proximal end1032of the distal inner body1030preferably include corresponding concave and convex articulating surfaces. In one embodiment, the articulating, contact surfaces between the enlarged second segment1172and the proximal end1032of the distal inner body1030are essentially spherical.

As a result, the axial load passes through the articulating surface. Moreover, as a result of the corresponding concave and convex articulating surfaces, a ball joint type connection may be formed. In use, the articulating, contacting surfaces enable some rotation between the enlarged second segment1172and the proximal end1032of the distal inner body1030. This connection leads to improved articulation, weight bearing, and improved distraction.

In one embodiment, clearances may be provided between the threaded rod1170and the driver1055(e.g., the distal magnet housing cap). As such, the threaded rod1070is no longer rigidly fixed to the driver1055(e.g., the distal magnet housing cap). That is, as illustrated, by incorporating a pin connection, gaps or spaces1057,159may be incorporated between the second or proximal segment1172of the threaded rod1170and the driver1055, allowing for some movement of the threaded rod1170about the pin axis and around the pin1002. By enabling some movement of the threaded rod1170allows for easier bending of the nail.

As will be described by one of ordinary skill in the art, threaded rod1170allows for easier manufacturability as compared to threaded rod1070. However, as a consequence, the driver1055may have thinner walls when used in combination with threaded rod1170as compared to threaded rod1060.

In still another manner of addressing the risk of failure of reconfigurable bone adjustment devices such as the reconfigurable bone adjustment devices1,101,201described above, there is provided a reconfigurable bone adjustment device in which the junction of the driver and the threaded rod includes a spacer component that is configured to receive the proximal end of the threaded rod, capture the proximal end of the threaded rod, drive rotation of the threaded rod and localize the tensile axial load on the threaded rod. In one embodiment, the junction may also include a stop component that is coupled to the threaded rod adjacent to the proximal end of the threaded rod and is dimensioned to be captured in a cavity in the spacer component. The stop component may be co-rotationally coupled to the threaded rod and the spacer component may be co-rotationally affixed to the drive mechanism. The stop component and the spacer component are configured such that torque applied by the drive mechanism transfers through one or more interfacing surfaces between the spacer component and the stop component to transfer torque to the threaded rod, thereby rotating the threaded rod. In use, rotation of the threaded rod in a first direction exerts a compressive force at an interface between a distal surface of the spacer component and the proximal end of the second body portion to move the second body portion relative to the first body portion.

FIGS. 16-19illustrate one embodiment of a reconfiguration assembly that includes a spacer component and a stop component. In the reconfiguration assembly801, a spacer component860includes a bore861that is dimensioned for passage of a threaded rod870therethrough. The spacer component860may also include a cavity863that opens, for example, towards a proximal end or side862of the spacer component860. The cavity863may be dimensioned to capture a stop component880, which is coupled to the threaded rod870adjacent to a proximal end871thereof. In the embodiment shown, the stop component880may include a body881defining an axial bore882having internal threads complementary to the external threading of the threaded rod870and dimensioned to threadingly engage the threaded rod870at a position adjacent the proximal end871of the threaded rod870. It is to be understood, however, that the internal threading of the axial bore882is optional, and other means can be used to affix the stop component880to the threaded rod870at a position adjacent the proximal end871of the threaded rod870as long as the other means for affixing the stop component880to the threaded rod870is operable to bear an axial load between the stop component880and the threaded rod870under loads encountered during use of an implantable reconfigurable bone adjustment device that includes the reconfiguration assembly801. In one embodiment, the stop component880may be coupled to the threaded rod870by welding.

The stop component880may also include a flange883, for example, at a proximal end thereof, that extends laterally beyond the body881, i.e., has a radial dimension greater than a radial dimension of the body881. In use, the cavity863formed in the spacer component860may be dimensioned to receive the stop component880and the spacer component860may include a shoulder surface864dimensioned to contact a distal surface884of the proximal flange883when the stop component880is received in the cavity863.

The body881of the stop component880may include a first radial aperture885and the threaded rod870may include a second radial aperture872near the proximal end871of the threaded rod870. The first and second radial apertures885,872are positioned such that they can be aligned to receive a pin875to couple the stop component880to the threaded rod870and limit relative rotational movement between the threaded rod870and the stop component880. In this embodiment, the spacer component860may also include a radial channel865(FIG. 19) configured to receive and retain the respective ends of the pin875. That is, in use, the pin875may have a length greater than the outer dimension of the body881of the stop component880and in the assembled device, the pin875may be positioned such that each end876,877of the pin875extends beyond the body881of the stop component880on each side of the body881. As is seen most clearly inFIG. 18, the radial channel865of the spacer component860has sufficient depth, relative to the position of the radial apertures885,872, such that the pin875does not contact a distal surface866of the radial channel865when the stop component880is received in the cavity863of the spacer component860. Therefore, the pin875does not bear an axial load when an implantable reconfigurable bone adjustment device that includes the reconfiguration assembly801is in use and under loads encountered during normal use. The pin875does, however, contact one or more side surfaces867a,867b,868a,868bof the radial channel865when the reconfiguration assembly801is rotated by the drive mechanism840, thereby transferring torque from the spacer component860to the threaded rod870.

In an alternative embodiment, depicted inFIGS. 20 and 21, a spacer component961and a stop component980of a reconfiguration assembly901may be configured such that a distal side983of the stop component980has a geometric shape and defines a plurality of distal surfaces984. The stop component980may include an axial bore982having internal threads complementary to the threading of the threaded rod970and dimensioned to threadingly engage the threaded rod970at a position adjacent a proximal end971of the threaded rod970. It is to be understood, however, that internal threading of the axial bore982is optional, and other means can be used to affix the stop component980to the threaded rod970at a position adjacent the proximal end971of the threaded rod970as long as the other means for affixing the stop component980to the threaded rod970is operable to bear an axial load between the stop component980and the threaded rod970under loads encountered during use of an implantable reconfigurable bone adjustment device that includes the reconfiguration assembly901. In one embodiment, the stop component980may be coupled to the threaded rod970by welding.

In the illustrated embodiment, the stop component980may include a first radial aperture985and the threaded rod970may include a second radial aperture972near the proximal end971of the threaded rod970. As with the embodiments described above, the first and second radial apertures985,972are positioned such that they can be aligned to receive a pin975to couple the stop component980to the threaded rod970and limit relative rotational movement between the threaded rod970and the stop component980. In the reconfiguration assembly901, however, the pin975need not extend past the outer dimension of the stop component980because torque is transmitted from the spacer component960to the stop component980by way of the complementary surfaces thereof, which form interfaces capable of transmitting torque. As an alternative to placing the pin975, or in addition to placing the pin975, as described above, the body981of the stop component980optionally can be welded to the threaded rod970after the stop component980is advanced onto the threaded rod970to a desired position adjacent the proximal end971of the threaded rod970.

The spacer component960may include a cavity963with a plurality of contact surfaces964dimensioned to complement the plurality of distal surfaces984of the stop component980such that, when the stop component980is received within the cavity963, the contact surfaces964of the cavity963contact the distal surfaces984of the stop component980and permit torque that is applied to the spacer component960to be transferred to the stop component980to thereby rotate the threaded rod970. In one embodiment, the spacer component960may have a pyramidal shape in which the proximal side986of the stop component980represents the base of the pyramid. It is, of course, understood that the pyramidal shape will be a partial pyramidal shape because the sides of the pyramidal shape will not come to a point due to the presence of the axial bore982through the stop component980. In the embodiment depicted inFIGS. 20 and 21, the proximal side986of the stop component980has a square shape, giving the stop component980a four-sided pyramidal shape, and the cavity963formed in the spacer component960has four contact surfaces964that complement the converging distal sides984of the pyramidal stop component980.

FIG. 22depicts a spacer component960aof another embodiment configured to receive a stop component for whose proximal side has a generally hexagonal shape and which stop component has a six-sided pyramidal shape. Thus, the spacer component960adefines a cavity with six contact surfaces964athat complement the six converging distal sides of the pyramidal stop component. As will be appreciated by a person of ordinary skill in the art, the square and hexagonal embodiments are provided only as examples, it being understood that a wide variety of geometric shapes, such as, for example, three-sided pyramids or five-sided pyramids, pyramids having bases with trapezoidal shapes and also non-geometric shapes, can be used to form alternative stop component embodiments having interfacing surfaces that complement contact surfaces of spacer component embodiments that are operable to exert torsional forces from spacer component to stop component and threaded rod.

Orthopedic implants and prosthetics such as reconfigurable bone adjustment devices described herein typically are formed of a biocompatible metal. Medical grade cobalt-chromium (CoCr) alloys such as cobalt-chromium-molybdenum (CoCrMo) and cobalt-chromium-iron (CoCrFe) are among the most suitable metallic biomaterials, particularly for weight-bearing implants. These alloys typically exhibit high mechanical properties, adequate corrosion resistance, and acceptable biocompatibility. In one embodiment, a reconfigurable bone adjustment device according to the present disclosure is formed of a cobalt-chromium-iron (CoCrFe) alloy. In another embodiment, the alloy comprises a 40Co-20Cr-16Fe-15Ni-7Mo alloy. It should be appreciated however that the reconfigurable bone adjustment devices may be manufactured from any suitable material.

As will be appreciated from the descriptions herein and the associated Figures, a wide variety of embodiments are contemplated by the present disclosure, examples of which include, without limitation, the following:

The present disclosure provides a reconfigurable bone adjustment device, and associated kits, systems and methods. In one embodiment, the reconfigurable bone adjustment device may include a first body portion or member configured for attachment to a first bone fragment, a second body portion or member configured for attachment to a second bone fragment, and a reconfiguration assembly configured to move the second body portion or member relative to the first body portion or member. The reconfiguration assembly may include a drive mechanism including a driver and a threaded rod having a proximal end coupled to the driver at a junction. In use, the drive mechanism is operable to controllably rotate the driver. In addition, rotation of the driver causes rotation of the threaded rod.

In one embodiment, the reconfigurable bone adjustment device may be an intramedullary limb lengthening nail. In another embodiment, the reconfigurable bone adjustment device may be a bone transport nail. The reconfiguration assembly operates by reducing applied stresses, such as axial forces, torsional forces, bending moments and/or eccentric moments on the driver/threaded rod junction and/or by configuring the junction in a manner whereby one of more of the axial forces, torsional forces, bending moments and/or eccentric moments is isolated away from the junction.

In one embodiment, the driver has a first axis of rotation, the threaded rod has a second axis of rotation and the reconfiguration assembly is configured to allow a degree of variation between the first axis of rotation and the second axis of rotation when the reconfiguration assembly is subjected to a bending load (e.g., when a proximal portion of the threaded rod is under an axial load and the reconfiguration assembly is subjected to a bending or eccentric load). In one embodiment, this may be accomplished by providing a helical channel in a segment of the threaded rod adjacent to a proximal end of the threaded rod. That is, for example, the junction may include a welded joint between the proximal end of the threaded rod and the driver, and a proximal portion of the threaded rod adjacent the proximal end of the threaded rod may include a helical channel formed therein. In another embodiment, this may be accomplished by providing a dynamic joint connecting the threaded rod to the driver. Examples of dynamic joints include, but are not limited to, pinned joints, ball joints and universal joints.

In another embodiment, the reconfigurable bone adjustment device may be constructed such that the threaded rod engages a threaded mating component of the first member such that rotation of the threaded rod in a first direction causes the driver to exert a compressive force on a proximal end of the second member. Moreover, rotation of the threaded rod in the first direction exerts a tensile load on a load bearing portion of the threaded rod extending from the junction to the threaded mating component. A collar may be positioned between the driver and the second member such that rotation of the threaded rod in the first direction exerts a compressive force between a distal surface of the collar and a proximal end of the second member to move the second member relative to the first member.

In one embodiment, the collar may be in the form of a domed collar. That is, the collar may include a convex distal surface and the proximal end of the second member may include a complementary concave surface, the convex distal surface of the collar and the complementary concave surface of the second member forming an interface for transmitting a compressive force substantially in the direction of a longitudinal axis of the threaded rod from the collar to the second member.

In another embodiment, the threaded rod may have a first diameter along a major portion of its length. The threaded rod may also include a proximal segment having a second diameter greater than the first diameter. The proximal segment may be integrally formed with the threaded rod. The proximal segment may be axially located between the portion of the threaded rod that has the first diameter and the proximal end of the threaded rod. The reconfigurable bone adjustment device may be constructed such that the threaded rod engages a threaded mating component of the first member, rotation of the threaded rod in a first direction causes the proximal segment to exert a compressive force on a proximal end of the second member, and rotation of the threaded rod in the first direction exerts a tensile load on a load bearing portion of the threaded rod that extends from the proximal segment to the threaded mating component such that the axial load is not placed on the junction. In one embodiment, the proximal segment is a proximal tapered segment, wherein the threaded rod tapers from the first diameter at the major portion of the threaded rod to a second diameter at the proximal end of the threaded rod, the second diameter being greater than the first diameter. In another embodiment, the proximal segment forms a shoulder surface against which the proximal end of the second member rests.

In another embodiment, the junction may include a stop component coupled to the threaded rod adjacent to the proximal end of the threaded rod and a spacer component defining a bore dimensioned to permit passage of the threaded rod therethrough. The spacer component may include a distal surface configured to abut or contact a proximal end of the second member and a proximal side including a cavity dimensioned to receive and capture the stop component. The reconfigurable bone adjustment device may be constructed such that the threaded rod engages a threaded mating component of the first member, rotation of the driver in the first direction causes co-rotation of the spacer component and the threaded rod in the first direction to exert a compressive force at an interface between a distal surface of the spacer component and the proximal end of the second member to move the second member relative to the first member. In this embodiment, the axial load is isolated away from the interface between the driver and the spacer component. The stop component can have a wide variety of shapes. In one embodiment, the cavity formed in the proximal surface of the spacer component has a complementary surface and the reconfiguration assembly is operable to transfer torque from the spacer component to the stop component.

In one embodiment, the stop component may include a body defining an axial opening having internal threads complementary to the threading formed on the threaded rod and dimensioned to threadingly engage the threaded rod at a position adjacent the proximal end of the threaded rod. In another embodiment, the stop component may include a body defining an axial opening dimensioned to receive the proximal end of the threaded rod and the body may be welded to the threaded rod at a position adjacent the proximal end of the threaded rod. In yet another embodiment, the stop component may be integrally formed with the threaded rod and include a radial dimension greater than the diameter of the bore formed in the spacer component. In still yet another embodiment, the stop component may include a body defining an axial opening dimensioned to receive the proximal end of the threaded rod, the body including a first radial aperture and the threaded rod including a second radial aperture, and the junction further includes a pin positioned through the first and second apertures to limit relative rotational movement between the threaded rod and the stop component. In another embodiment, the body of the stop component may include an outer dimension, the pin may have a length greater than the outer dimension of the body, and the pin may be positioned such that each of the first and second ends of the pin extend beyond the body of the stop component on respective sides of the body.

In one variation of any of the above-disclosed embodiments, the stop component may further include a proximal flange having a radial dimension greater than the body of the stop component, the cavity formed in the spacer component may be dimensioned to receive the body of the stop component, the spacer component defines a shoulder surface dimensioned to contact the proximal flange and the spacer component defines a radial channel configured to contain the first and second ends of the pin.

In an alternate embodiment, the distal side of the stop component may include a geometric shape defining a plurality of distal surfaces, the cavity formed in the proximal side of the spacer component may include a plurality of contact surfaces dimensioned to complement the plurality of distal surfaces of the stop component such that, when the stop component is received within the cavity, the contact surfaces of the cavity contact the distal surfaces of the stop component and permit torque applied to the spacer to be transferred to the stop component to thereby rotate the threaded rod. In one variation of this embodiment, the distal side of the stop component may include three or more sides.

In another embodiment, the proximal surface of the stop component may be affixed to the driver in a manner whereby the stop component is restricted from separating from the spacer component upon rotation of the driver in a second direction opposite the first direction. In yet another embodiment, the distal surface of the spacer component may be a convex surface and the proximal end of the second member may include a complementary concave surface, wherein the interface is capable of transmitting a compressive force substantially in the direction of a longitudinal axis of the threaded rod from the spacer component to the second member.

As previously mentioned, the reconfigurable bone adjustment device of any of the above embodiments may be an intramedullary limb lengthening nail or an intramedullary bone transport nail. In one embodiment, the first member has a proximal end and a distal end and defines an internal chamber therein, the drive mechanism may be positioned in the internal chamber, the second member has a proximal end and a distal end and at least the proximal end of the second member may be positioned in the internal chamber between the drive mechanism and the distal end of the first member.

In another embodiment, for example, when the reconfigurable bone adjustment device is an intramedullary limb lengthening nail, the proximal end of the first member is configured to be coupled to a first end of a bone and the distal end of the second member is configured to be coupled to a second end of the bone, and rotation of the threaded rod moves the second end of the bone relative to the first end of the bone. The proximal end of the first member may include one or more proximal holes configured to receive one or more screws that pass through the bone and through the one or more proximal holes to attach the first member to the bone and the distal end of the second member may include one or more distal holes configured to receive one or more screws that pass through the bone and through the one or more distal holes to attach the second member to the bone.

In another embodiment, for example, when the reconfigurable bone adjustment device is an intramedullary bone transport nail, the proximal end of the first member is configured to be coupled to a first bone fragment and the distal end of the first member is configured to be coupled to a second bone fragment, the second member is configured to be coupled to a middle bone segment and rotation of the threaded rod moves the middle bone segment relative to the first bone fragment. The proximal end of the first member may include one or more proximal holes configured to receive one or more screws that pass through the first bone fragment and through the one or more proximal holes to attach the proximal end of the first member to the first bone fragment, the distal end of the first member may include one or more distal holes configured to receive one or more screws that pass through the second bone fragment and through the one or more distal holes to attached the distal end of the first member to the distal bone fragment and the second member may include one or more intermediate holes configured to receive one or more screws that pass through the middle bone segment and through the one or more intermediate holes to attach the second member to the middle bone segment.

The present disclosure also contemplates a reconfigurable bone adjustment device in accordance with any of the above embodiments wherein the drive mechanism includes a member selected from the group consisting of an internal rotatable magnet, a motor with induction drive, a battery powered motor and a motor powered through transcutaneous wires. A subset of these embodiments includes embodiments in which the drive mechanism includes an internal magnet configured to be rotated about a longitudinal axis of the threaded rod coupled to the drive mechanism by a magnetic force applied external of the reconfigurable bone adjustment device.

In one embodiment, a system is provided including an embodiment of the reconfigurable bone adjustment device including a drive mechanism having an inner magnet and an external magnetic actuator. The system may also include a transport container for the external magnetic actuator. Kits may also be provided that include any embodiment of the reconfigurable bone adjustment devices or systems disclosed herein and two or more bone screws configured to attach the first and second members to the first and second bone fragments; and kits that include any embodiment of the reconfigurable bone adjustment devices or systems or kits disclosed herein and further comprising one or both of an inserter configured to releasably couple to a proximal end of the reconfigurable bone adjustment device or to a distal end of the reconfigurable bone adjustment device and instrumentation for aligning bone screws, driving bone screws or both.

While the present disclosure has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the certain embodiments have been shown and described and that all changes, alternatives, modifications and equivalents that come within the spirit of the disclosure are desired to be protected.