Title of Invention

A TWO PART TELESCOPIC INTRAMEDULLARY ORTHOPEDIC DEVICE.

Abstract THE PRESENT INVENTION PROVIDES A TWO-PART TELESCOPIC INTRAMEDULLARY ORTHOPEDIC DEVICE CAPABLE OF CONNECTING TWO ADJACENT FRACTURED OR SEVERED BONE ENDS, CHARACTERIZED IN THAT SAID DEVICE COMPRISES A FIRST SECSTION INSERTED INTO THE MEDULLARY CAVITY OF ONE OF THE FRACTURED OR SEVERED BONE ENDS, AND SECURED THERETO, AND A SECOND SECTION INSERTED INTO THE MEDULLARY CAVITY OF THE OTHER FRACTURED OR SEVERED BONE END AND SECURED THERETO, WHEREIN SAID SECOND SECTION COMPRISES AN INTERNAL SPACE COMMUNICATING WITH AN EXTERNAL OPENING, AND WHEREIN SAID FIRST SECTION IS MORE OR LESS STELESCOPED WITHIN SAID INTERNAL SPACE OF SAID SECOND SECTION, AND WHEREIN ONE OF SAID SECTIONS COMPRISES A FERROMAGNETIC MATERIAL AND THE OTHER SECTION IS EITHER CONSTRUCTED ENTIRELY OF A NON-MAGNETIC MATERIAL OR COMPRISES A FERROMAGNETIC MATERIAL, WHEREIN THE FERROMAGNETIC SECSTION(S) ARE ACTUABLE BY AN EXTERNAL MAGNETIC FIELD, SUCH THAT ONE SECTION MAY BE CAUSED TO MOVE AXIALLY IN RELATION TO THE OTHER SECSTION, AND WHEREIN SAID AXIAL MOVEMENT MAY BE EITHER BIDIRECTIONAL OR ESSENTIALLY UNIDIRECTIONAL. IN ADDITION, THE INVENTION ENCOMPASSES A METHOD FOR CHANGING BONE LENGTH AS WELL AS A METHOD FOR ENHANCING BONE FRACTURE HEALING.
Full Text Field of the Invention
The present invention relates generally to a magnetically-
actuated orthopedic implant for use in promoting the healing
of bone fractures and in manipulating bone length. More
particularly, the present invention relates to an
intramedullary device capable of changing its length in a
cyclic manner under the influence of an electromagnetic field,
said device being particularly suitable for the treatment of
cases in which there is non-union of the fractured bone ends,
as well" as for the primary treatment of long bone fractures.
Background of the Invention
The use of implant devices in the management of many
orthopedic conditions is well known in the art. In some cases,
the use of such internally-fitted devices may be the only
effective way of stabilizing fractured bones. However, this
approach suffers from the drawback that, once in place, the
length and/or position of the implant cannot be physically
manipulated without further surgical intervention. This is a
particular drawback when implants are used in order to achieve
one or both of the following clinical goals:
a) increase or decrease in bone length, and
b) accelerated healing of bone fractures.
It is known in orthopedic surgery to sever a bone, such as a
tibia or femur, in order to increase its overall length and
thereby correct a skeletal or other defect. One common
procedure for this purpose makes use of a special nail that is
implanted in an intramedullary fashion into the bone to be
lengthened. A longitudinally-adjustable frame external to the
appendage containing the bone to be lengthened is secured at
one end of the bone and it is attached at its other end to the
nail as well as to the other end of the bone.
The bone is then osteotomized by the surgeon and the
adjustable frame is periodically lengthened, thereby causing
the bone, while the break therein is knitting, to assume a
desired overall length. The implant is then embedded in the
lengthened bone.
As pointed out in U.S. Patent 5,704,938 to Staehlin et al.
(1998) the external frame fixation system used in this known
bone lengthening procedure is difficult to securely locate on
the patient and not only gives rise to discomfort, but it also
presents an unattractive appearance. Moreover, pins anchored
in the bone and protruding through the skin to join the frame
increases the risk of infection and nerve injury, either
immediate or delayed, during the lengthening procedure.
To overcome these drawbacks, Staehlin provides a bone-
lengthening device which is wholly implantable, except for a
tube extending from the device and passing through the skin to
supply a hydraulic fluid to the implant which is hydraulically
adjustable in length.
Staehlin"s two-part implant is mechanically complicated, for
it includes a drive bolt located in one part that extends into
the other part, which bolt, when rotated by a drive mechanism
is activated by a hydraulically-operated plunger making it
necessary to supply through a tube leading into the implant a
pressurized hydraulic fluid.
In their least complicated forms, bone fractures may be
treated by simple immobilization of the relevant body part.
In many case, particularly when the fracture occurs in a long
bone, this type of management may be sufficient to permit the
body"s natural processes to completely close the fracture and
to lead to complete healing of the affected bone. In other
cases, the distance between the mating surfaces of a fractured
bone may be so great as to result in non-union of the
fracture. Clinically, non-union of fractures is often defined
as failure of the fracture fragments to unite after 8 months.
Typically, such a situation can arise from excessive movement
at the fracture site, soft tissue interposition, infection, or
trauma. In such cases, the normal process of calcification
fails to take place and the fracture gap remains occupied by
fibrocartilage and/or fibrous tissue. Ingrowth of new blood
vessels cannot take place, and normal healing will be
prevented.
It has been found that application of cyclic compressive
forces to the fracture (in imitation of the normal weight
bearing forces) accelerates this process by up to one third of
the normal healing time. This effect will be discussed in more
detail hereinbelow.
Currently, long bone fractures are preferably treated by the
use of intramedullary nails or rods. The stability of these
implant devices, and the reduced soft tissue damage caused
thereby, render this approach preferable over open reduction
techniques. However, although these implants permit weight
bearing forces to be exerted thereon, they often isolate the
fracture from compression forces due to the presence of
locking screws, whose primary purpose is to prevent rotation.
Also, as a result of the fixed distance between the fracture
ends imposed on the fracture by virtue of their rigid
structure, intramedullary nails can actually cause cases of
fracture of non-union. Various studies have estimated that
the incidence of non-unions that result directly from the use
of intramedullary nails may reach up to 5% of all fracture
cases treated with these devices.
Various other techniques for managing non-union fractures have
been used and reported in the art. For example, different
forms of electrical stimulation have been investigated. These
basic studies have in turn led to a number of proposals for
promoting the healing of bone fractures, including invasive
treatments involving the use of implanted electrodes as well
as non-invasive techniques utilizing electrostatic and
electromagnetic fields.
U.S. 3,745,995, for example, describes metal splints that are
affixed to fractured bone by means of screws. The device
further comprises pickup coils having terminals connected both
to said splints and to electrodes invasively inserted into the
bone. A coil surrounding the limb having the fracture induces
in the pickup coils an alternating current signal. In this
way, the electrical signals are transmitted to the fracture
ends.
In another approach, the use of mechanical stimuli to promote
healing of non-union fractures has been described. For
example, in one study [J. Kenwright & A.E. Goodship, Clin.
Ortho. & Rel. Res. (1989) 241: 36-47] the effects of
mechanical stimulation on midshaft tibial breaks were
investigated in experimental animals. The applied stimulation
had frequencies approximating that of the walking frequency of
the animal used. Cyclic loading of the fracture region for 17
minutes per day was used. Although useful results were
obtained in these experimental studies, it was found that it
was critical to accurately control the displacements of the
fractured bones, as high displacements were noted to lead to
mechanical failure of the wound healing process.
US 6,022,349 describes a method and system for treating bone
fractures and osteoporosis that is based on the mechanical
stimulation described in the aforementioned study by Kenwright
and Goodship. However, it would appear that the apparatus
described therein is not capable of producing the controlled,
axially-directed oscillatory movements that imitate normal
force-loading on the affected limb (e.g. the cyclic
compression that occurs during walking), that have been shown
to be useful in accelerating fracture healing.
US 6,032,677 discloses a method and apparatus for stimulating
the healing of medical implants, particularly those used in
dental surgery. The apparatus described therein uses an
internally-placed permanent magnet and externally applied
electromagnetic field to cause oscillation of the implant
within a tooth socket or medullary cavity of a fractured bone.
It is a purpose of the present invention to provide a reliable
implant device and method for the alteration of bone length.
It is another purpose of the present invention to provide the
aforementioned implant device in a form suitable for the
management of bone fractures, particularly long bone
fractures, and more particularly, cases of non-union of said
long bone fractures.

It is a further aim of the present invention to provide a
device for managing bone fractures that will act to prevent
the occurrence of fracture non-union, by permitting movement
of the fractured bone ends towards each other.
Yet a further purpose of the invention is to provide a device
and method for managing fractures that will reduce the time
required for complete healing.
It is another purpose of the invention to provide a device and
method that may be applied during the initial stages of the
treatment of bone fractures.
It is a further purpose of the invention to provide a method
for managing non-union fractures or for elongating or
shortening bones that does not require the complete
immobilization of the patient, or the use of uncomfortable and
unaesthetic externally-placed devices such as external
fixation frames.
It is yet another purpose of the present invention to provide
a device for the management of non-union fractures that
overcomes the problems and disadvantages of prior art devices.
It is yet another purpose of the present invention to provide
a device for elongating or shortening bones that overcomes the
problems and disadvantages of prior art devices.
Further objects and advantages of the present invention will
become apparent as the description proceeds.

Summary of the Invention
The present invention is primarily directed to a two-part
telescopic intramedullary orthopedic device capable of
connecting two adjacent fractured or severed bone ends,
characterized in that said device comprises
a first section inserted into the medullary cavity of one
of the fractured or severed bone ends, and secured thereto,
and
a second section inserted into the medullary cavity of
the other fractured or severed bone end and secured thereto,
wherein said second section comprises an internal space
communicating with an external opening, and wherein said first
section is more or less telescoped within said internal space
of said second section, and
wherein one of said sections comprises a ferromagnetic
material and the other section is either constructed entirely
of a non-magnetic material or comprises a ferromagnetic
material, wherein the ferromagnetic section(s) are actuable by
an external magnetic field, such that one section may be
caused to move axially in relation to the other section, and
wherein said axial movement may be either bidirectional or
essentially unidirectional.
The "move axially" and "axial movement" as used herein refer
to movement of the ferromagnetic section or sections of the
device in a direction parallel to the long axis thereof. Said
axial movement may occur either bidirectionally (that is, in
an oscillatory manner) or essentially unidirectionally, as
will be described in the following sections.
It has now been unexpectedly found that the above-defined two-
part telescopic device may be used both to promote the
accelerated healing of bone fractures, as well as to change

bone length. It is to be emphasized that the accelerated
healing effect may be obtained either in conjunction with
bone-length alteration, or as a separate effect, in the
absence of changes in bone length. It was further found that
the accelerated healing effect occurs when the axial movement
of the telescopic device is bidirectional (that is,
oscillatory) , while bone lengthening or shortening is obtained
when said axial movement is unidirectional. It has further
been found that by alternating the mode of axial movement
between unidirectional and bidirectional, it is possible to
promote healing of the severed bone fragments in addition to
inducing changes in the final length of the severed bone.
The term "severed" bone ends, as used hereinabove and
throughout this application is used to indicate the situation
where the bone to be treated was intentionally severed into
two portions by a surgeon as part of a procedure for changing
the length of said bone. The term "fractured" bone ends,
however, is used to indicate the more common situation,
wherein a patient presents with a bone fracture that was
caused by means other than planned surgical intervention.
Thus in one aspect, the present invention is directed to a
device as disclosed hereinabove, wherein the axial movement of
one section of said device in relation to the other section is
essentially unidirectional such that the first section of said
device may be caused to shift progressively in one direction
with respect to the second section, thereby changing the
separation between the fractured or severed bone sections.
It is to be noted that the term "essentially unidirectional",
as used hereinabove, is employed to indicate that although the
main mode of axial movement is in one direction only, the
device of the invention will also permit low-amplitude
bidirectional, oscillatory, movement for the purposes of
promoting accelerated bone healing.
In one embodiment of the device, the direction of the
essentially unidirectional axial movement is such that the
relative movement of the two sections of said device causes an
increase in the length of the bone.
In another embodiment of the device of the invention, the
direction of the essentially unidirectional axial movement is
such that the relative movement of the two sections of said
device causes a decrease in the length of the bone.
In one preferred embodiment of the invention, the
ferromagnetic material used in the construction of the
section(s) comprising such material is a hard ferromagnetic
material. Although any suitable hard ferromagnetic material
may be used, this is preferably either Alnico or ferrite.
In one preferred embodiment of the device of the invention,
the non-magnetic section (if used) is a synthetic plastic
material. In another preferred embodiment, the non-magnetic
material is titanium.
In one preferred arrangement of the device, the first section
of said device is formed by a core of ferromagnetic material,
and the second implant section is formed by a tubular socket
into which the first section is telescoped.
In one particularly preferred embodiment of the device of the
invention, the first section has a non-circular cross section
and the internal space of the second section has a

corresponding cross section whereby said first section cannot
be rotated within said second section.
In one preferred embodiment of the device, telescopic
advancement of the first section within the second section by
incremental steps is achieved by a series of annular grooves
formed along the first section, said grooves defining ratchet
teeth that are detented by a pawl mounted on the second
section. Preferably, said pawl is a flat spring having a
tongue extending into a groove in the series thereof. In
another embodiment, a pair of pawls is mounted on opposite
sides of the second section. In a particularly preferred
embodiment, the aforementioned grooves have a triangular cross
section and a groove height with permits the first section
ratcheted by the pawl to vibrate.
The device of the present invention may also be constructed
such the second implant section includes a reservoir loaded
with a flowable healing agent and provided with an orifice
from which is emitted a charge of the agent each time the
first implant section is advanced an incremental step. This
embodiment of the device may further comprise means to subject
the agent in the reservoir to a pressure pulse each time the
first implant section is advanced to force the agent out of
the orifice. Many different healing agents may be used in
conjunction with the device, including but not limited to,
growth factors which promotes the bone healing process and
antibiotics.
In another preferred embodiment, the first section of the
device of the invention has a square cross section and the
second section which is channel-shaped includes parallel
sidewalls banking a cross section area matching the cross

section of the first section whereby the first section can be
telescopically received in the second section. In an even
more preferred embodiment of the device, the first section has
a top wall that is notched to define ratchet teeth that are
detented by a pawl mounted on the second section whereby the
first section can be incrementally advanced beyond the second
section.
The present invention is also directed to an orthopedic
implant assembly adapted to manipulate the length of a
skeletal bone to attain a predetermined length in a procedure
in which a canal may be reamed through the bone to accommodate
an implant and the bone severed to define complementary bone
sections each having a cavity therein to receive a respective
section of the implant, said assembly comprising:
A. a two-part telescopic device, as disclosed
hereinabove, and
B. means external to said device to apply magnetic
forces thereto to cause the one or more ferromagnetic sections
of said device to shift progressively in one direction with
respect to the other section of said device to change the
separation therebetween until the severed bone attains said
predetermined length.
In one preferred embodiment of the aforementioned assembly,
the magnetic forces are constituted by successive impulses
each of which causes the first section to advance an
incremental step. In a more preferred embodiment of this
aspect of the invention, the impulses of magnetic force are
produced by applying direct current power pulses to a magnetic
field coil adjacent to the bone whose length is to be changed.

In one preferred arrangement of the aforementioned assembly,
the bone to be manipulated is embedded in a body appendage and
the field coil surrounds the appendage.
The present invention also provides an assembly as disclosed
hereinabove that further comprises means for applying an
alternating magnetic force to the device after the first
section of said device has been incrementally advanced to
cause said first section to vibrate to promote the healing
process. In one preferred embodiment, the alternating
magnetic force is produced by a field coil adjacent to the
device to which an alternating voltage is applied. In a
particularly preferred embodiment said alternating voltage is
generated by an oscillator whose frequency is such as to
promote the healing process.
In another aspect, the present invention is directed to a
method of lengthening or shortening a skeletal bone to attain
a predetermined length comprising the steps of:
A. reaming the marrow of the bone to be lengthened or
shortened to create a canal to accommodate a two-part
telescopic intramedullary orthopedic device having a first
section more or less telescoped within a second section,
wherein one of said sections comprises a ferromagnetic
material and the other section is either constructed of a non-
magnetic material or comprises a ferromagnetic material;
B. severing the bone to define complementary bone
sections, each having a cavity therein;
C. inserting the first section of the device into the
cavity in one section of the bone and securing it thereto;
D. inserting the second section of the device into the
cavity of the other bone section and securing it thereto,
whereby the degree to which the bone sections are separated

and the severed bone is lengthened or shortened depends on the
extent to which the first section projects beyond the second
section; and
E. applying successive magnetic force impulses to the
first section to cause it to advance an incremental step per
impulse until the severed bone has attained said predetermined
length.
In addition to the use of the aforementioned magnetic force
impulses, the method also provides the use of ratchet and/or
spring components within the telescopic device to cause the
first section of the device to advance an incremental step.
In one embodiment of the above-disclosed method, successive
incremental steps in the advance of the first section are
separated by time intervals of sufficient duration to permit
effective healing of the severed bone. Preferably, the
duration of each of said time intervals is at least one full
day.
In another preferred embodiment, the method further comprises
the step of monitoring the change of length of the implant by
use of an imaging technique. In one preferred embodiment, the
imaging technique is ultrasonic imaging. In another preferred
embodiment, the imaging technique is based on the use of a
magnetic sensor.
In a preferred embodiment of the method of the invention, the
parameters of the magnetic force lie in the range of 100 to
1000 newtons. In another preferred embodiment of the method,
the implant is extended in increments of 0.1 to 1 mm per day.
Preferably, 1-6 incremental steps per day are used in order to
achieve the desired change in length. More preferably, 4

incremental steps are used each day, each step representing a
change in length of 0.1 mm.
The present invention also encompasses a two-part telescopic
device, as disclosed hereinabove, wherein the axial movement
of one section of the device in relation to the other section
is essentially bidirectional such that the ferromagnetic
section(s) may be caused to oscillate axially, thereby causing
axial oscillatory motion of the fractured or severed bone
section(s) to which the device is attached, wherein the axial
movement in one direction is caused by the magnetic forces
induced by an external magnetic field on the ferromagnetic
section(s), and wherein the axial movement in the opposite
direction is caused either by magnetic forces having a
reversed polarity or by mechanical means.
This aspect of the invention is thus directed to a two-part
telescopic device for promoting the healing of bone fractures,
comprising
a first section inserted into the medullary cavity of one
of the fractured bone ends and secured thereto, and
a second section inserted into the medullary cavity of
the other fractured bone end and secured thereto,
wherein said second section comprises an internal space
communicating with an external opening, and wherein said first
section is more or less telescoped within said internal space
of said second section, and
wherein at least one of said sections comprises a
ferromagnetic material that is actuable by an external
magnetic field, such that the ferromagnetic section(s) may be
caused to oscillate axially,
wherein the axial movement in one direction is caused by
the magnetic forces induced by said magnetic field acting on

said ferromagnetic section(s), and wherein the axial movement
in the opposite direction is caused either by magnetic forces
having a reversed polarity or by mechanical means.
In one preferred embodiment of the device of the invention,
the magnetic forces are alternating magnetic forces having
forward and reverse directional components, each of the two
directions of axial movement being caused by one of said
directional components.
In another preferred embodiment of the device of the
invention, the magnetic forces are unidirectional magnetic
forces, and said device further comprises mechanical means for
causing axial movement in a direction opposite to that of said
magnetic forces.
In a preferred embodiment, the mechanical means comprise a
spring located within the internal space of the second section
of the telescopic device, such that said spring is positioned
between the base of said internal space and the free end of
the first section.
A variety of magnetic and non-magnetic materials may be used
in the construction of the device of the present invention.
In one preferred embodiment, the ferromagnetic section is at
least partially formed by a hard ferromagnetic material.
Examples of hard ferromagnetic materials that may be used in
the working of the present invention include, but are not
limited to, Alnico and ferrite. In a more preferred
embodiment of the device of the invention, the section
comprising the ferromagnetic material is constructed such that
the ferromagnetic material itself is in the form of a "core"
that is completely enclosed by a biocompatible material such

as titanium or biocompatible stainless steel alloy such as L-
316. This preferred two-layer structure obviates the health
hazards associated with direct contact of certain
ferromagnetic materials with living tissue.
In the event that one of the two sections of the
aforementioned device is entirely non-magnetic, said non-
magnetic section may be made of any non-magnetic material
possessing the required physical and mechanical properties.
These properties include sufficient mechanical strength and
rigidity to withstand the cyclical mechanical forces acting on
the device, as well as sufficient toughness in order to reduce
frictional wear. In addition, the materials need to be
biocompatible. In one preferred embodiment, the non-magnetic
section is formed of a synthetic plastic material. In another
preferred embodiment, the non-magnetic section is formed of
titanium.
In another aspect, the apparatus disclosed hereinabove further
comprises means for causing the local release of biologically-
active agents at the fracture site. Thus, in one preferred
embodiment, the second section of the two-part device includes
a reservoir loaded with a flowable healing agent and is
provided with an orifice from which said agent is emitted. In
another preferred embodiment, the apparatus further comprises
means for subjecting the agent in the reservoir to a pressure
pulse. Many different examples of biologically-active agents
that may be used to assist fracture healing are known in the
art. Thus, in one preferred embodiment of this aspect of the
invention, the healing agent is a growth factor which the
ability to promote bone healing. Examples of suitable growth
factors include, but are not limited to: bone morphogenetic
protein, transforming growth factor beta, osteogenic growth
peptide (OP-1), decalcified bone matrix and parathyroid
hormone (PTH).
In another preferred embodiment, the healing agent is an
antibiotic agent.
The healing agent may be provided in any suitable physical
form that is capable of flowing through the abovementioned
orifice. Suitable physical forms include, but are not limited
to, liquids, pastes, creams, granules and beads.
The present invention is also directed to a therapeutic system
for promoting the healing of bone fractures comprising a
device as disclosed hereinabove, together with means external
to said device for applying magnetic forces thereto.
In one preferred embodiment of the therapeutic system of the
invention, the means for applying magnetic forces comprises a
magnetic field coil situated adjacent to the telescopic
device.
In one preferred embodiment, the abovementioned magnetic field
coil generates alternating magnetic forces by means of the
application of an alternating voltage to said magnetic field
coil. Preferably, the alternating voltage is generated by an
oscillator.
The term "alternating magnetic forces" as used hereinabove and
hereinbelow refers to magnetic forces that are cyclic nature
such that the direction in which said forces are exerted is
reversed in a periodic manner.
In a further preferred embodiment, the magnetic field coil of
the therapeutic system generates direct magnetic forces by
means of the application of a direct voltage to said magnetic
field coil.
Although the therapeutic system disclosed hereinabove may be
used to treat fractures in any part of the body, according to
a preferred embodiment the fracture to be treated is located
in a limb bone, and the magnetic field coil surrounds said
limb.
The present invention also encompasses a method for promoting
the healing of bone fractures comprising the steps of:
A. reaming the medullary cavity of each of the
fractured bone ends to accommodate a two-part telescopic
device, wherein said device comprises a first section more or
less telescoped within a second section, wherein said second
section contains an internal space, and wherein at least one
of said sections is formed of a ferromagnetic material;
B. inserting said second section into the reamed
medullary cavity of one bone end and securing it thereto, such
that the external opening of said internal space faces towards
the other bone end;
C. inserting one end of said first section into the
internal space of said second section;
D. inserting the other end of said first section into
the reamed medullary cavity of the other bone end and securing
it thereto;
E. applying magnetic forces to the ferromagnetic
section (s), such that said section (s) is or are caused to
oscillate axially with respect to the other section.
Preferably, the magnetic force has a value in the range of 1
to 1000 newtons.
In one preferred embodiment of the method of the invention,
the magnetic forces are alternating magnetic forces that are
generated by means of an alternating voltage applied to a
magnetic field coil located adjacent to the telescopic device.
In another preferred embodiment, the magnetic forces are
unidirectional forces that are applied by means of a direct
voltage applied to a magnetic field coil located adjacent to
the telescopic device, and wherein a spring located within the
internal space of the second section of said device provides a
counter force to said unidirectional magnetic forces.
In another preferred embodiment, the method further comprises
the step of monitoring the position of the device of the
invention by use of an imaging technique. In one preferred
embodiment, the imaging technique is ultrasonic imaging. In
another preferred embodiment, the imaging technique is based
on the use of a magnetic sensor.
The method disclosed hereinabove may be used to treat many
different types of fracture. In one preferred embodiment, the
fracture to be treated is a long-bone fracture. In a more
preferred embodiment, the long-bone fracture is a non-union
fracture.
In a further aspect, the present invention also encompasses
the use of the two-part telescopic device disclosed
hereinabove for the primary treatment of long bone fractures.
All the above and other characteristics and advantages of the
present invention will be further understood from the
following illustrative and non-limitative examples of
preferred embodiments thereof.
Brief Description of the accompanying Drawings
Fig. 1 schematically illustrates the basic structure of the
two-part device of the invention, in which the telescopic
sections of the device are anchored in complementary sections
of fractured or severed bone ends.
Fig. 2 shows a preferred embodiment of the device which is
intended for use in altering bone length.
Fig. 3 is a detail of the ratchet mechanism included in the
implant shown in Fig. 2.
Fig. 4 shows another embodiment of the device.
Fig. 5 illustrates the system by which an implant installed in
a severed leg bone is magnetically actuated in order to
generate either unidirectional or bidirectional, oscillatory,
movement of the ferromagnetic section(s) of the telescopic
device.
Fig. 6 shows an implant in whose socket section is a reservoir
containing a healing agent which is discharged into the gap
region between the severed sections of the bone.
Fig. 7 shows an ultrasound imaging system on whose screen is
displayed the bone being lengthened by the implant.
Fig. 8 depicts one preferred embodiment of the device intended
for use in promoting the healing of fractures, in which a
helical spring is used in order to generate counter force to
unidirectional magnetic forces.
Detailed Description of Preferred Embodiments
The device, as disclosed hereinabove, consists essentially of
two sections: a core-like first section, and a socket-like
second section, said first section being capable of sliding in
and out of said second section in an essentially telescopic
manner. (For ease of description, the "first section" and
"second section" of the device, as disclosed hereinabove and
claimed hereinbelow, are referred to in the following
description of preferred embodiments as "core section" and
"socket section" (or readily-identifiable variants thereof)
respectively.) It will also be recalled that at least one of
these two sections comprises a ferromagnetic material. It is
to be noted that the ferromagnetic section (s) may be the core
section, the socket section or both sections. In a preferred
embodiment, however, both sections of the device are
ferromagnetic.
The term "ferromagnetic material" as used herein, refers to
magnetic materials having a magnetic constant Km that varies
with an applied electric field, but that is typically much
larger than unity. Such materials (which generally are based
on one of the five elements: Fe, Co, Ni, Gd or Dy) are
characterized by strong interactions between adjacent atomic
dipoles, such that even in the absence of an applied magnetic
field, there may be spontaneous dipole alignment. (In cases
wherein spontaneous dipole alignment occurs, or wherein some
ordered dipole alignment remains after removing an external
field, the material may be considered to be "magnetic" as well
as "ferromagnetic".) In any event, on application of an
external field, the ordering or alignment of the dipoles is
greatly enhanced, thus generating a large magnetic field.
As disclosed hereinabove, the telescopic device of the
invention is intended to be used in conjunction with an
externally applied magnetic field, the purpose of said
magnetic field being to induce axial movement of one or more
of the sections of said device. The magnetic field is
preferably generated by means of a solenoid or field coil
consisting of a copper winding enclosed within a plastic
cover. The internal diameter of the solenoid is designed to
appropriately match the external dimensions of the body part
to be treated, and is generally in the range of 20 to 30 cm.
The length of the solenoid is typically about 10% to 30%
greater than that of the telescopic device. The number of
turns in the winding, per centimeter length along the
solenoid, is adjusted such that an AT (ampere-turn) value in
the range of 20,000 to 40,000 may be reached upon using
suitable power supplies.
Preferably, the solenoid is provided in a modular form, to
allow an easy insertion thereof over the treated body part.
Optionally, the solenoid is coupled with means for removing
the heat produced thereby during operation. The heat removal
may be accomplished by a water-containing spiral like
structure, said spiral being in contact with the solenoid, or
by causing air to flow between the turns of the solenoid.

The solenoid may be constructed of any suitable ferromagnetic
metals, but is preferably constructed of one of one or more of
the following materials: iron, stainless 430, PH174.
The device of the invention may be used in the following two
essentially different ways, in accordance with the desired
clinical effect:
a) Essentially unidirectional movement of the ferromagnetic
section(s), for use in situations where the desired clinical
effect is an increase or decrease in bone length.
b) Bidirectional movement of the ferromagnetic section(s), for
use in situations where the clinician wishes to promote and
assist the healing of bone fractures.
A. UNIDIRECTIONAL MODE
The Basic Implant Structure: A telescopic orthopedic device in
accordance with the invention, as shown schematically in Fig.
1, is adapted to lengthen a skeletal bone such as a leg or arm
bone. To prepare the bone for lengthening, it is necessary
for an orthopedic surgeon to perform an osteotomy in which the
bone is severed to create complementary sections 10 and 11.
The degree to which these bone sections are forced to separate
by an implant anchored in the sections ultimately determines
the extent to which the bone has been lengthened.
And to prepare the bone for installation of the implant, it is
possible for the surgeon before or after severing the bone to
ream a canal through the marrow of the bone so that bone
section 10 is then provided with an intramedullary cavity 10c
and bone section 11 with an intramedullary cavity 11c.
The implant includes a ferromagnetic magnet section 12 in the
form of a core telescoped within a tubular non-magnetic
section 13. Magnetic section 12 of the implant is received
within cavity 11c of bone section 11 of the severed bone and
is secured thereto by a screw 14 or other fastener means. The
non-magnetic section 13 is received in cavity 10c of bone
section 10 and is secured thereto by a screw 15. Hence the
respective implant sections are anchored in the complementary
bone sections.
In practice, the core section 12 of the implant, instead of
being cylindrical may have an elliptical cross section so that
it cannot be rotated within socket section 13 which has a like
cross section. But the core can be axially displaced so that
it can be advanced axially to lengthen the implant.
Alternatively, the cross section could be a circle having a
flat segment, again for the purpose of preventing rotation but
not axial movement. One is able for the same purpose to
provide other core and socket section shapes.
Core section 12 is preferably fabricated by a "hard"
ferromagnetic material which is polarized to form a permanent
magnet having a North Pole at one end and a South Pole at the
opposite end. A suitable metallic material for core 12 is
Alnico or other alloy having a high coercive force so that
even though the core is small it acts as a powerful permanent
magnet. Alternatively, a non-metallic "hard" ferromagnetic
material such as a ceramic ferrite may be used for the core.
The advantage of using a ferrite to fabricate core section 12
rather than a metal which must be machined to assume the
corrugated formation of the core, is that a ferrite can easily
be molded to assume the desired configuration.

It is not essential to the invention that the magnetic core
section 12 of the implant be composed entirely of "hard"
permanent magnet material, but only that it include a
sufficient amount of such material as to be able to react to
an impulse of magnetic force to effect a positive stepping
action.
Thus core section 12 may be constituted by a hollow cylinder
of "hard" ferromagnetic material filled with a non-magnetic
synthetic plastic composition. Or core section 12 may be
formed by a solid plug of non-magnetic material having a head
or cap of hard magnetic material functioning as a permanent
magnet.
The socket section 13 of the implant may, in one embodiment,
be made entirely of non-magnetic plastic or metal material. A
preferred material for this purpose is one commonly employed
in prosthetic implants, such as titanium or a steel alloy. Or
socket 13 may be molded of high-strength synthetic plastic
material such as polypropylene or polyethylene. It is
essential that the material from which the implant is composed
be biologically compatible with the tissue in which it is
embedded. In another embodiment, socket section 13 may
comprise a ferromagnetic material, such as one of the
ferromagnetic materials listed hereinabove.
When the implant is installed so that its socket section is
held within cavity 10c of bone section 10 and its core section
is held within cavity 11c of bone section 11, the implant then
bridges the separated complementary bone section.
The implant can be pre-constructed so that both components are
integrated and placed in either a retrograde or antegrade
fashion into the medullary canal under fluoroscopic guidance.
In the course of a stepwise bone lengthening procedure, the
length of the bridge is incrementally increased until the
overall length of the severed bone attains a predetermined
value. Typically, the incremental length may be from 2 to 20
centimeters.
To allow adequate time for the severed bone sections to knit
together and heal and to permit the soft tissues surrounding
the bone to adjust thereto in the course of the incremental
bone-lengthening procedure there should be a time interval
between successive lengthening steps of sufficient duration
for this purpose, such as at least one day per step.
It is necessary that the implant, in the course of a
lengthening procedure, maintain the bone sections bridged
thereby in a proper alignment so that when the severed bone is
healed, it is properly formed and not crooked. Because the
implant is formed by a core telescoped in a socket and is
coaxial therewith, the linearity of the implant is maintained
as it is being lengthened.
The circumferential surface of core section 12 of the implant,
as shown in Fig. 2 is corrugated to form a series of equi-
spaced annular grooves G1, G2, G3 etc. which define ratchet
teeth. These teeth are detented by a pair of pawls 16A and
16B mounted at diametrically opposed positions on the upper
end of socket section 13, the pawls falling into successive
grooves when the core is being pulled out of the socket in
which it is telescoped. The pawls are preferably in the form
of flat metal springs having tongues that fit into the
grooves, the: spring flexing when the core is advanced so that
the pawls can then snap into the next groove.

The grooves G1 etc. along core 12 have a triangular cross
section which as best seen in Fig. 3 is defined by a
horizontal upper wall and an angled lower wall inclined
downwardly with respect to the upper wall. Hence when the
tongue of the flat spring is within a groove and one then
seeks to displace the core downwardly, this movement is
arrested by the horizontal wall of the groove which then abuts
the tongue. But when one seeks to displace the core upwardly,
the tongue then slides down the inclined wall of the groove to
permit this advance.
Hence the pawl and ratchet teeth mechanism associated with the
core and socket make it possible to jack up the implant
bridging the bone sections of the bone to be lengthened
incrementally in a stepwise manner to progressively increase
the length of the bridge until the overall length of the
severed bone attains its predetermined desired value.
In the implant shown in Fig. 2, the means which prevents the
core from advancing backwards into the socket and thereby
reducing the length of the bridge are the detents which engage
the ratchet teeth. To resist retrograde movement in the
implant arrangement shown in Fig. 2, one may to this end place
underlying the core section 12 a helical spring 31 which urges
the core upwardly and therefore resists downward movement of
the core into the socket. The spring therefore acts to
maintain the core at its advanced position.
Other known means may be included in the implant to permit the
required axial movement in one direction and to prevent
retrograde movement.
Second Embodiment:
The invention does not require cylindrical or tubular implant
sections but only that the first section telescope into the
second section regardless of their cross sectional geometry.
What is essential to the invention is that the first section
functions as a permanent magnet and that the second section be
non-magnetic so that when the implant installed in the
complementary sections of the severed bone is subjected to an
impulse of magnetic force, this will induce the first section
to incrementally lengthen the implant and thereby lengthen by
one step the severed bone.
Thus the implant shown in Fig. 4 includes a non-magnetic
section 17 which is channel-shaped and therefore has a
rectangular cross section. Formed in the parallel sidewalls
of this section are longitudinally extending grooves 17A and
17B.
Telescopically received in section 17 is a magnetic core
section 18 having a square cross section that matches the
cross sectional area between the sidewalls of section 17.
Ribs 18A and 18B formed on opposing sides of section 18 slide
into grooves 17A and 17B of the walls.
Thus the magnetic cross section 18 can more or less telescope
within the non-magnetic section 17. The top wall of section
18 is provided with a row of transverse grooves defining
ratcheted teeth 19 which cooperate with a pawl or detent (not
shown) to limit the advance of this section to one step per
impulse, as in the embodiment shown in Fig. 2.
Advance of the Implant:

An implant, in accordance with the invention, must be capable
of being advanced incrementally. But it may also be made
capable, when at any one ratcheted step, of causing the core
of the implant to vibrate in order to promote the bone-healing
process.
The core ratchet can be designed so that its operation is
limited to incremental advances or so that it can also vibrate
at each step. A core whose operation is to be limited to
incremental steps, may be provided with annular grooves G1,
G2, G3 etc. as shown in Fig. 2 having an optimal height in the
range of 0.1 to 1.5 millimeters. A core which can also
vibrate at each step without causing it to advance to the next
step is then provided with grooves of greater height in the
range of 0.15 to 0.4 mm, thereby giving the pawl more freedom.
Incremental advance of the permanent magnet core section 12 is
effected by means external to leg L which as shown in Fig. 5
has the implant 12-13 installed between the complementary bone
sections of the severed bone to be lengthened and healed.
These external means are constituted by a magnetic field coil
20 surrounding leg L adjacent to the region of the implant
therein and a DC power source 21 connected to the coil through
a control switch 27. Source 21 is provided with a voltage
control potentiometer 23 so that the strength of the field may
be raised or lowered to a required degree.
Each time switch 27 is momentarily closed, as surge of current
flows unidirectionally through coil 20 to produce an
electromagnetic field whose lines of flux penetrate the leg
and are intercepted by magnet core section 12 of the implant.
The direction of current flow in the coil is such as to

produce a magnetic field whose polarity repels the polarized
core and hence acts as an impulse of magnetic force to advance
the core of one step.
The implant, which functions dynamically, behaves like a
dynamic loudspeaker. In a speaker of this type, a field coil
mounted on a cone is displaced axially with respect to a fixed
permanent magnet, the displacement of the coil being in
accordance with variations in current flowing through the
coil. In a dynamic implant in accordance with the invention,
the coil is at a fixed position whereas the permanent magnet
core anchored in a bone section is movable and is displaced to
an extent and in a direction in accordance with variations in
current flowing through the coil.
When one wishes to vibrate the core at each step before the
core is advanced to the next step, then coil 20 is connected
to an A-C generator 24 through a switch 25. When switch 25 is
closed, the resultant A-C electromagnetic field causes the
core to oscillate. The frequency of oscillation is such as to
promote the healing process.
Ideally, coil 20 comprises helical windings that encircle the
appendage enclosing the bone to be lengthened such the when
the coil is energized momentarily, the resultant surge or
impulse of magnetic force is applied in the axial direction to
maximize the pull exerted by the impulse on the magnetic
section of the implant. And instead of a helical coil, a
ring-shaped toroidal coil may be designed so as to slip over
the appendage.
When the location of the bone to be lengthened is such that it
cannot be surrounded by a magnetic field coil, then use may be
made of a pair of planar or pancake coils which flan opposing
sides of the bone location and are connected in series to a
power source to produce combined magnetic fields which exert
an axial force on the implant.
As a practical matter, it is difficult in each bone
lengthening procedure to predetermine the magnitude of the
magnetic force impulse necessary to cause the implant to
advance a single step per implant and no more. Clearly an
excessive force may cause the core section of the implant to
jump several steps, whereas a weak force may be insufficient
to cause this section to advance even one step.
The magnitude of the magnetic force impulse appropriate to a
given implant installation is best determined empirically by
means of a voltage supply for the field coil having a control
potentiometer. The potentiometer is operated to slowly raise
the voltage applied to the coil until a point is reached where
a stepping action takes place, as indicated by the clicking
sound of the ratchet mechanism. This clicking sound can best
be heard by means of a stethoscope. Having determined the
magnitude of voltage that brings about a stepping action, the
same magnitude is applied in successive steps.
Healing:
The healing process by which the bone sections knit together
in the course of a bone-lengthening procedure can be promoted
by discharging into the gap region between the bone section in
which healing transpires a growth factor, such as a bone
morphogenetic protein or a decalcified bone matrix in granular
or paste form. Other growth factors are useable, such as
transforming growth factor beta or osteogenic growth peptide
or OP-1.
To this end, in the embodiment of the implant shown in accompany Fig. 6
socket 13 includes at its base a well or reservoir filled with
a growth factor borne by a carrier to create a gel 27, the
well being confined by a disc 28. At the bottom of this well
and slideable thereon is a piston 29 operated by a piston rod
30 attached to core section 12 telescoped in socket 13. Hence
each time the core section is advanced, the piston is then
raised thereby to apply a pressure pulse to the growth factor
gel, causing it to extrude into the gap region between the
bone sections through orifices 31 in the wall of socket
section 13 of the implant.
Instead of a growth factor, the gel or cream may be an
antibiotic such as penicillin or cephalosporin, or any other
suitable antibiotic to reduce the risk of infection in the
course of the healing process, or to treat bone infected in
the course of being lengthened.
Also useful for healing is a sub-dermal reservoir adapted to
cause infusion into the bone lengthening area of mesenchymal
cells. This is of particular value when treating the limbs of
a cancer patient who has been exposed to irradiation giving
rise to a lack of mesenchymal cells.
Imaging:
When in a bone lengthening procedure an external adjustable
frame is used which is mechanically coupled to an internal
implant, then one observing the frame can determine, by means
of a scale on the frame, the extent to which the bone has been
lengthened.
But in a bone lengthening procedure in accordance with the
invention in which there is no mechanical linkage between an
internal implant and an external frame, one is unable to tell
the extent to which the bone has been lengthened, if indeed it
has been lengthened at all. Thus while one knows the degree
to which the implant is lengthened, per step, one cannot be
sure that with each application of a magnetic force, the core
has actually stepped, particularly since the resistance
offered by the leg to each step in a bone lengthening
procedure often varies from step to step.
Should one depend on hearing a clicking sound to determine how
many steps the implant has advanced incrementally, one must be
careful to correctly count the clicks. Yet one cannot be sure
that with each click, there has been an actual stepwise
advance.
In order therefore to be able to actually see the operation of
the implant and the extent to which it is lengthening the
bone, use may be made of an ultrasound imaging system, as
shown in Fig. 7. The piezoelectric transducer 32 of this
system generates periodic ultrasonic pulses that are
propagated through the leg tissue and are reflected by the
bone. This transducer is placed on leg L at a position
overlying the implant therein. Coil 20 surrounding the leg is
configured to create an opening therein to accommodate the
transducer, so that the transducer operates in the region of
the magnetic field emanating from the coil.
One therefore sees on the monitor screen 22 of the ultrasound
imaging system, a full scale image of the implant (12-13)
interposed between the bone sections (10-11) . And one can
measure on the screen the adjusted distance between the
severed sections of the bone. As an alternative to the use of
an ultrasound imaging technique, the present invention also
makes provision for imaging techniques based on the use of
magnetic sensors.
In a procedure in accordance with the invention the proximity
of coil 20 to the implant depends on the dimensions of the
appendage and the locations of the implant therein. Hence the
power required to produce a magnetic force sufficiently strong
to step the core depends on how close the coil is to the core
and the strength of the magnet. But with imaging, one can see
whether the magnetic force acting on the core does in fact
step the core, and if it does not, one can then increase the
power applied to the coil to bring about the desired action.
This imaging system is a useful adjunct to the implant
procedure but not a prerequisite thereto. Other systems such
as an oscilloscope connected to a microphone can be used to
detect the click sound generated by advancement of the ratchet
mechanism. Also X-ray imaging can be used to visualize
lengthening of the implant. However, this entails multiple
exposures to ionizing radiation and may have adverse side
effects.
The implant functions not only to lengthen (or shorten) the
bone, but also when the bone is lengthened (or shortened) and
healed, to reinforce the bone. The dimensions of the implant
must be appropriate to those of the bone in which it is
implanted. Hence a bone which has a large cross sectional
area and when severed offers a relatively high resistance to
being lengthened, demands an implant whose dimensions are
appropriate to the bone. The same implant may be unsuitable
for a bone having a smaller cross sectional area.
A preferred material for forming the non-magnetic section of
the implant is titanium. The reason for the use of titanium
rather than any other material is that it is known from the
use of titanium in a dental implant in which a titanium post
is screwed into a hole drilled in a jaw bone, that the bone
then literally proceeds to fuse with the titanium. Such
fusion does not take place with other materials.
Third Embodiment:
Instead of using the implant to lengthen a bone, it can be
adapted to shorten a bone to a desired extent. To this end, a
short piece of bone to be shortened is excised to provide a
relatively large gap between the ends of the complementary
bone sections. The ferromagnetic core section of the implant
is then lodged in one of these bone sections and the non-
magnetic socket section in which the core is telescoped is
lodged in the other bone section.
Then by applying an external magnetic force thereto, the core
section of the implant is caused to advance an incremental
step further into the socket section, thereby reducing the gap
between the bone sections. This action is repeated until the
shortened distance between the ends of the bone section
provides a bone of the desired shortened length.
When the implant is adapted to shorten a bone, the detenting
of the core section must be such as to permit its stepwise
advance into the socket section and prevent retrograde
movement.
Fourth Embodiment:
An orthopedic implant adapted to transport a bone fragment
requires a ferromagnetic core the opposite ends of which are
telescoped within respective non-magnetic sockets. These
sockets are lodged in the complementary ends of the severed
bone sections.
When a magnetic force is applied to the implant, the core is
then advanced to step further into one socket and at the same
time to step further out of the other socket without changing
the length of the bone, for the distance between the ends of
the complementary bone section remains unchanged.
In this way, a bone fragment may be transported from one bone
section to the other in a direction that depends on the
polarity of the magnetic force applied to the core.
While there have been disclosed preferred embodiments of the
invention, it is to be understood that many changes may be
made therein without departing from the spirit of the
invention. Thus the implant may be used not to lengthen a
bone but as a splint to maintain a fractured bone in proper
alignment as the bone undergoes a natural healing process. In
this situation, a canal is reamed through the marrow of the
fractured bone to receive the implant. One section of the
implant is anchored in a section of the bone on one side of
the fractured region, and the other section is anchored in the
bone section on the opposite side of this region. In this
case the implant is not magnetically actuated unless in order
to straighten out the fractured bone it is necessary to
lengthen the implant.
B. BIDIRECTIONAL (OSCILLATORY) MODE
In the case of a long-bone fracture, the core section is
preferably attached to the distal section of the fractured
bone, the socket section being fixed into the cavity of the
proximal part of the fracture. The present invention,
however, also encompassed the possibility of the reverse
situation, that is, wherein the core section is fixed to the
proximal bone segment, while the socket section is attached to
the distal segment.
In many cases, it will be highly advantageous to install the
device of the invention such that the core section is inserted
deep inside the socket section. In such cases, one end of
each of the two sections of the device will be fixed into the
medullary cavity of one of the bone segments, while the other,
free, extremity of each section will extend into the medullary
cavity of the other segment (without being attached thereto).
The free end of the core section, in such cases, will not be
in direct contact with living tissue within the medullary
cavity, but rather enclosed within the inner space of the
socket section.
In other cases, rather less overlap between the two sections
will be required, with only one of the sections (either the
socket section or the core section) having both of its
extremities situated within the bounds of the medullary
cavities of both of the fractured bone segments. In still
other cases, the overlap will be minimal, the region of
insertion of the core section into the socket section being
confined to the space between the fractured bone segments.
A preferred embodiment of a two-part telescopic device for use
in promoting the healing of bone fractures in accordance with
the present invention is shown schematically in Fig. 1. In
this figure, the two sections of a fractured long bone are
represented by numerals 10 and 11. By way of preparation
before installing the device of the invention, the surgeon may
ream a canal through the bone marrow of each of the fractured
bone ends to from intramedullary cavities 10C and 11C.
The embodiment of the two-part device depicted in Fig. 1
includes a ferromagnetic section 12 in the form of a core
telescoped within a tubular non-magnetic section 13. Said
ferromagnetic section 12 of the device is received within
cavity 11C of bone section 11 of the fractured bone, and is
secured thereto by means of one or more locking screws 14 or
by the use of any other suitable bio-compatible fastener
means. Non-magnetic section 13 is inserted into cavity 10C of
bone section 10 and is secured thereto by means of one or more
locking screws 15. In one embodiment of the invention, said
locking screws 14 and 15 are each inserted into, and anchored
within, the bone cortex on one side of the medullary cavity.
In a more preferred embodiment, said locking screws are
inserted into, and anchored within, the bone cortex on both
sides of the medullary cavity. It may thus be seen that the
two sections of the device of the invention are anchored in
the medullary cavities of the two fractured bone ends.
Core section 12 is preferably fabricated of a "hard"
ferromagnetic magnetic material which is polarized to form a
permanent magnet having a North Pole at one end and a South
Pole at the opposite end. A suitable metallic material for
core 12 is Alnico or any other alloy having a high coercive
force so that even though the core is small, it acts as a
powerful permanent magnet. Alternatively, a non-metallic
"hard" ferromagnetic material such as a ceramic ferrite may be
used for the core. The advantage of using a ferrite to
fabricate core section 12 rather than a metal which must be
machined to assume the corrugate formation of the core is that
a ferrite can easily be molded to assume the desired
configuration.
It is not essential to the invention that the magnetic core
section 12 of the device be composed entirely of a "hard"
permanent material, but only that it include a sufficient
amount of such a material as to be able to react to an impulse
of magnetic force to effect the desired electromechanical
oscillation of the device.
The non-magnetic socket section 13 of the device may be made
entirely of a non-magnetic plastic or metal material. A
preferred material for this purpose is one commonly employed
in prosthetic implants, such as titanium or a steel alloy.
The reason for the preferred use of titanium is that it is
known from the use of this material in dental implants in
which a titanium post is screwed into a hole drilled into a
jaw bone, that the bone then literally proceeds to fuse with
the titanium. Such fusion does not appear to take place with
other materials.
Preferably, the magnetic core section 12 is fitted with a
small projection (not shown in the figures) on its external
surface, in close proximity to its free end. This projection
engages a longitudinal slot in a corresponding portion of the
socket section 13, the end of said slot that is closest to the
free end of said socket section forming a stop, beyond which
the projection on core section 12 cannot travel. The purpose
of this arrcingement is to prevent said magnetic core section
12 from moving outwards from socket section 13 further than a
preset value, or from completely separating therefrom. In one
preferred embodiment, the abovementioned projection has a
triangular, fin-like, outline shape.
When the device is installed such that its magnetic section is
held within cavity 10C of fractured bone section 10 and its
non-magnetic section is held within cavity 11C of bone section
11, these two sections of said device then bridge the
fractured and separated bone sections. Thus, in addition to
the use of the device (in conjunction with the externally-
placed magnetic field as disclosed hereinabove and described
hereinbelow) , the two-part device of the invention may be used
as a static stabilizing device for use in the very first
stages of the management of fractured bones. A further
advantage of the device of the invention is that its use from
the earliest stage of hospital management through to complete
healing ensures that the fractured sections are maintained in
their correct alignment, in view of the co-axial, rigid nature
of said device. Yet another advantage offered by the device
of the invention is that it may be used in place of an
earlier-inserted intramedullary nail, without the need for
further preparation of the fractured bone segments.
In order for the apparatus of the invention to function
optimally, both as an oscillatory two-part device and as a
static bridging device, it is necessary to construct said
apparatus such that its dimensions are appropriate to those of
the bone in which it will be installed. Thus, a bone which
has a large cross-sectional area requires a device having
dimensions appropriate for said bone. The same device,
however, may be unsuitable for a bone having a smaller cross-
sectional area.
The device of the invention may be pre-joined so that the
integrated device is placed in either a retrograde or
antegrade manner into the medullary canal under fluoroscopic
guidance.
Although the device of the invention may be constructed with a
circular cross-sectional shape, as shown in Fig. 8, any other
cross-sectional form that permits the magnetic and non-
magnetic sections to oscillate freely in relation to each
other may be used. Such cross-sectional forms include but are
not limited to square, rectangular, square or rectangular with
rounded corners or elliptical or ellipsoid.
In one preferred embodiment of the invention, the core section
12 and the socket section 13 are caused to oscillate in
relation to each other by the application of an external
magnetic field. The range of movement of one of said sections
in relation to said other section is 10 ┬Ám to 2 mm, with a
periodicity of oscillation of 0.1-1000 Hz. Thus, in the case
of the embodiment illustrated in Fig. 1, said external
magnetic field is an alternating field, such that alternating
magnetic forces are applied to ferromagnetic core section 12.
Said core section then moves in and out of socket section 13
in a way essentially similar to the motion of a piston within
a cylinder of an internal combustion engine. The use of the
device of the invention together with an external magnetic
coil is depicted in Fig. 5. The external means for applying
the magnetic field shown in this figure comprise a magnetic
field coil 20 surrounding the affected limb L in the region
adjacent to the location of the installed device, said coil
being placed such that its entire structure is placed distal
to the distal extremity of the magnetic core section 12. In
the case of the embodiment presently described, an alternating
magnetic field is applied by connecting coil 20 to an
alternating current (AC) generator 24 through a switch 25.
When switch 25 is closed, the resultant AC electromagnetic
field causes the ferromagnetic core section 12 to oscillate
within socket section 13, as described hereinabove.
Preferably the AC voltage used to generate the AC
electromagnetic field is between 1 and 1000 V, with a
frequency of between 0.1 and 1000 Hz.
In another preferred embodiment of the device, as shown in
Fig. 8, a helical spring 31 may be fitted beneath the core
section 12 in the internal space of socket section 13. Said
helical spring may be attached to either the end of core
section 12, the base of the internal space of socket section
13, to both of these structures. The purpose of spring 31 is
to provide counter force to a unidirectional magnetic force
which, in Fig. 8, is applied in a direction such that
ferromagnetic core 12 moves further inside socket section 13.
It should be noted that although the embodiment depicted in
Fig. 8 shows the use of a helical spring, any other suitable
type of spring device may be used in its place. In this
embodiment of the invention, the unidirectional magnetic force
is effected by means of a direct current (DC) power source, as
shown in Fig. 5. Said DC power source is fitted with a
voltage control potentiometer 23 so that the strength of the
field may be raised or lowered to the required value.
Preferably, the DC voltage is in the range of 1-1000 V. Each
time switch 27 is closed, a surge of current flows
unidirectionally through coil 20 to produce an electromagnetic
field whose lines of flux penetrate the leg and intercepted by
magnet core section 12 of the device. The direction of
current flow in the coil is such as to produce a magnetic
field whose polarity is such that said core section is
impelled towards the base of the internal space of core
section 13. As a consequence of this reduction of space
within the internal cavity of socket section 13, helical
spring 31 (Fig. 8) is compressed. When the potential energy
of said spring reaches a critical value (corresponding to the
point wherein the kinetic energy of the spring is at its
lowest value, and its potential energy at its highest value),
said spring is able to overcome the path of travel of core 12
and pushes said core in the opposite direction, and in so
doing, allows the spring 31 to relax, until said core reaches
a stop position that is defined by the furthest point of
travel of the above-described projection on the surface of
said core within the slot present in socket section 13. This
process then proceeds in a cyclical manner, thus causing core
12 to oscillate within socket section 13.
In an alternative preferred embodiment, the spring and the
magnetic coil are arranged such that the unidirectional
magnetic forces cause the ferromagnetic core section 12 to
travel outwards, away from the base of socket section 13, thus
extending the total effective length of the device. In this
case, the helical spring reaches its maximal extended state,
wherein the potential energy stored therein reaches a maximal
value, said potential energy serving to counter the
unidirectional magnetic forces and to drive the core section
12 back towards the base of socket section 13.
It is to be noted that although the field coil 20 depicted in
Fig. 5 is a helical coil, other suitable coils, such as ring-
shaped toroidal coils that may be readily slipped over the
appendage to be treated, may also be used. When the location
of the fracture to be treated is such that it cannot be
surrounded by a magnetic field coil, use may be made of a pair
of planar or pancake coils which flank opposite sides of the
bone location, and which are connected in series to a power
source to produce combined magnetic fields which exert an
axial force on the device of the invention.
Without wishing to be bound by any theory, it is believed that
it is the oscillation of the two fractured bone sections into
which the oscillating two-part device is attached, which is
responsible for the promotion of the healing process.
The device of the invention may be used to assist healing of
bone fractures by application of the electromagnetic field as
described above, thus causing the ferromagnetic section to
oscillate within the other, non-magnetic section. Preferably,
the device is caused to oscillate for periods of between one
minute and 120 minutes, up to three times per day.
Alternatively, the device may be used in a continuous
treatment regime.
The healing process by which fractured bone sections knit
together can be accelerated and assisted by use of the
apparatus and method of the present invention as described
hereinabove. This healing process may be further assisted by
discharging into the gap region between the fractured bone
ends a healing factor, such as a growth factor with healing
properties such as bone morphogenetic protein or a decalcified
bone matrix in granular or paste form. Other growth factors
may also be used, including (but not limited to) transforming
growth factor beta and osteogenic growth peptide (OP-1).
Although these growth factors have been in clinical use for
many years, the device of the present invention permits their
controlled, local, high-concentration release into the region
of the healing fracture.
To this end, the device of the invention may incorporate a
well or reservoir filled with a growth factor within the base
of socket section 13. Said growth factor may be borne by a
carrier to create a gel, the well being confined by a disc.
In one preferred embodiment, a piston arrangement (not
illustrated) attached to core section 12 is used to apply a
pressure pulse to the growth factor preparation within its
well. Hence, each time the core section is advanced, the
piston is raised thereby applying a pressure pulse to the
growth factor gel, causing it to extrude into the gap region
between the bone sections through orifices in the wall of
socket section 13 of the device.
Instead of a growth factor, the gel or cream may comprise an
antibiotic such as penicillin or cephalosporin, or any other
suitable antibiotic to reduce the risk of infection in the
course of the healing process. An additional benefit of the
use of a locally-released antibiotic in conjunction with the
device of the present invention is that it will permit the
wider use of said device, particularly in cases of fracture
associated with more severe soft tissue damage (such as
Gustilo classes IIIA and IIIB), might be more successfully
treated by intramedullary devices.
In one preferred embodiment, the antibiotic may be contained
within a well or reservoir and delivered by use of a
mechanical piston system that is linked to ferromagnetic core
section 12 (as described hereinabove). Alternatively,
according to another preferred embodiment, the external
surfaces of the core section 12 and the socket section 13 may
be coated with antibiotic-containing granules. Such a coating
will serve as a slow-release system, allowing delivery of the
antibiotic both to the region of the fracture (thus speeding
the healing process) and to the inside of the device of the
invention (thus preventing problems of bacterial contamination
thereof) .
Also useful for healing is a sub-dermal reservoir adapted to
cause infusion of mesenchymal cells into the healing bone
region.
The abovementioned healing factors, growth factors and
antibiotics may be released from the device of the invention
in various amounts, in either a continuous or controlled
manner. In the case of continuous release, the device of the
invention may be loaded with between 1 and 10 g of the
aforementioned healing factors, growth factors and
antibiotics. In the case of controlled release, the device
may be loaded with up to 1 mg of these substances. These doses
are given for the purpose of exemplification only, and are not
intended to limit the amounts of such substances that may be
used in combination with device of the present invention.
While specific embodiments of the invention have been
described for the purpose of illustration, it will be
understood that the invention may be carried out in practice
by skilled persons with many modifications, variations and
adaptations, without departing from its spirit or exceeding
the scope of the claims.
We Claim :
1. A two-part telescopic intramedullary orthopedic device capable of connecting two adjacent
fractured or severed bone ends (10,11), comprising a first section (12) which is suitable for being
inserted into the medullary cavity (11c) of one of the fractured or severed bone ends, and secured
thereto, and a second section (13) which is suitable for being inserted into the medullary cavity (10c)
of the other fractured or severed bone end and secured thereto, wherein said second section
comprises an internal space communicating with an external opening, and wherein said first section is
more or less telescoped within said internal space of said second section,
characterized in that one of said sections is either constructed entirely of a ferromagnetic
material or is constructed of a ferromagnetic core together with non-ferromagnetic material, and that
the other section is either constructed entirely of a non-magnetic material or comprises a
ferromagnetic material, wherein the ferromagnetic section(s) are directly actuable by an external
magnetic field, such that one section may be caused to move axially in relation to the other section,
the spatial arrangement between said first and second sections being such that said arrangement
permits both bidirectional and essentially unidirectional axial movement of one section in relation to
the other section.
2. The device according to claim 1, wherein the ferromagnetic material is a hard ferromagnetic
material.
3. The device according to claim 2, wherein the hard ferromagnetic material is Alnico.
4. The device according to claim 2 wherein the hard ferromagnetic material is a ferrite.
5. The device according to claim 1, wherein the non-magnetic material is a synthetic plastic material.
6. The device according to claim 1, wherein the non-magnetic material is titanium.
7. The device according to claim 1, wherein the first section of said device is formed by a core of
ferromagnetic material, and the second implant section is formed by a tubular socket into which the
first section is telescoped.
8. The device according to claim 1, wherein the first section has a non-circular cross section and the
internal space of the second section has a corresponding cross section whereby said first section
cannot be rotated within said second section.
9. The device according to claim 8, wherein telescopic advancement of the first section within the
second section by incremental steps is achieved by a series of annular grooves formed along the first
section, said grooves defining ratchet teeth that are detented by a pawl mounted on the second
section.
10. The device according to claim 9, wherein the pawl is a flat spring having a tongue extending into a
groove in the series thereof.
11. The device according to claim 10, wherein a pair of pawls is mounted on opposite sides of the
second section.
12. The device according to claim 11, wherein the grooves have a triangular cross section and a
groove height which permits the first section ratcheted by the pawl to vibrate.
13. The device according to claim 1, in which the second implant section includes a reservoir loaded
with a flowable healing agent and provided with an orifice from which is emitted a charge of the agent
each time the first implant section is advanced an incremental step.
14. The device according to claim 13, further comprising means to subject the agent in the reservoir
to a pressure pulse each time the first implant section is advanced to force the agent out of the
orifice.
15. The device according to claim 14, wherein the healing agent is a growth factor which promotes a
bone healing process.
16. The device according to claim 15, wherein the healing agent is an antibiotic substance.
17. The device according to claim 1, wherein the first section has a square cross section and the
second section which is channel-shaped includes parallel sidewalls banking a cross section area
matching the cross section of the first section whereby the first section can be telescopically received
in the second section.
18. The device according to claim 17, wherein the first section has a top wall that is notched to define
ratchet teeth that are detented by a pawl mounted on the second section whereby the first section
can be incrementally advanced beyond the second section.
19. An orthopedic implant assembly adapted to manipulate the length of a skeletal bone to attain a
predetermined length in a procedure in which a canal may be reamed through the bone to
accommodate an implant and the bone severed to define complementary bone sections each having a
cavity therein to receive a respective section of the implant, said assembly comprising:
a device according to claim 1, and
means external to said device to apply magnetic forces thereto to cause the one or more
ferromagnetic sections of said device to shift progressively in one direction with respect to the other
section of said device to change the separation therebetween until the severed bone attains said
predetermined length.
20. The assembly according to claim 19, wherein the magnetic forces are constituted by successive
impulses each of which causes the first section to advance an incremental step.
21. The assembly according to claim 20, wherein the impulses of magnetic force are produced by
applying direct current power pulses to a magnetic field coil adjacent to the bone to be lengthened or
shortened.
22. The assembly according to claim 21, wherein the bone to be manipulated is embedded in a body
appendage and the field coil surrounds the appendage.
23. The assembly according to claim 19, further including means to apply an alternating magnetic
force to the device after the first section of said device has been incrementally advanced to cause said
first section to vibrate to promote the healing process.
24. The assembly according to claim 23, wherein the alternating magnetic force is produced by a field
coil adjacent to the device to which an alternating voltage is applied.
25. The assembly according to claim 24, wherein the alternating voltage is generated by an oscillator
whose frequency is such as to promote the healing process.
26. The device according to claim 1, further comprising mechanical means for reversing the direction
of the axial movement of the ferromagnetic section(s), in order to allow bidirectional axial movement
of said section(s).
27. The device according to claim 26, wherein the mechanical means comprise a spring located in the
internal space of the second section, such that said spring is positioned between the base of said
internal space and the free end of the first section.
28. The device according to claim 27, wherein the one or more ferromagnetic sections are at least
partially formed by a hard ferromagnetic material.
29. The device according to claim 28, wherein the hard ferromagnetic material is Alnico.
30. The device according to claim 28, wherein the hard ferromagnetic material is a ferrite.
31. The device according to claim 27, wherein the non-magnetic section is formed by a synthetic
plastic material.
32. The device according to claim 27, wherein the non-magnetic section is formed of titanium.
33. The device according to claim 27, wherein the second section includes a reservoir loaded with a
flowable healing agent and provided with an orifice from which is emitted a charge of said agent.
34.The device according to claim 32, further comprising means to subject the agent in the reservoir to
a pressure pulse.
35.The device according to claim 32, wherein the healing agent is a growth factor which promotes
bone healing.
36.The device according to claim 32, wherein the healing agent is an antibiotic agent.
37. Therapeutic system for promoting the healing of bone fractures comprising a device according to
any one of claims 1 to 36 together with means external to said device for applying magnetic forces
thereto.
38. Therapeutic system according to claim 37, wherein the means for applying magnetic forces
comprises a magnetic field coil situated adjacent to the telescopic device.
39. Therapeutic system according to claim 38, wherein the magnetic field coil generates alternating
magnetic forces by means of the application of an alternating voltage to said magnetic field coil.
40. Therapeutic system according to claim 39, wherein the alternating voltage is generated by an
oscillator.
41. Therapeutic system according to claim 37, wherein the magnetic field coil generates direct
magnetic forces by means of the application of a direct voltage to said magnetic field coil.
42. Therapeutic system according to any one of claims 37 to 41, wherein the fracture to be treated is
located in a limb bone, and wherein the magnetic field coil surrounds said limb.
The present invention provides a two-part telescopic
intramedullary orthopedic device capable of connecting two
adjacent fractured or severed bone ends, characterized in that
said device comprises
a first section inserted into the medullary cavity of one
of the fractured or severed bone ends, and secured thereto,
and
a second section inserted into the medullary cavity of
the other fractured or severed bone end and secured thereto,
wherein said second section comprises an internal space
communicating with an external opening, and wherein said first
section is more or less telescoped within said internal space
of said second section, and
wherein one of said sections comprises a ferromagnetic
material and the other section is either constructed entirely
of a non-magnetic material or comprises a ferromagnetic
material, wherein the ferromagnetic section(s) are actuable by
an external magnetic field, such that one section may be
caused to move axially in relation to the other section, and
wherein said axial movement may be either bidirectional or
essentially unidirectional.
In addition, the invention encompasses a method for changing
bone length as well as a method for enhancing bone fracture
healing.

Documents:

1493-kolnp-2003-granted-abstract.pdf

1493-kolnp-2003-granted-claims.pdf

1493-kolnp-2003-granted-correspondence.pdf

1493-kolnp-2003-granted-description (complete).pdf

1493-kolnp-2003-granted-drawings.pdf

1493-kolnp-2003-granted-form 1.pdf

1493-kolnp-2003-granted-form 18.pdf

1493-kolnp-2003-granted-form 2.pdf

1493-kolnp-2003-granted-form 3.pdf

1493-kolnp-2003-granted-form 5.pdf

1493-kolnp-2003-granted-letter patent.pdf

1493-kolnp-2003-granted-pa.pdf

1493-kolnp-2003-granted-reply to examination report.pdf

1493-kolnp-2003-granted-specification.pdf


Patent Number 212697
Indian Patent Application Number 01493/KOLNP/2003
PG Journal Number 50/2007
Publication Date 14-Dec-2007
Grant Date 12-Dec-2007
Date of Filing 18-Nov-2003
Name of Patentee ORTHOGON TECHNOLOGIES 2003 LTD.
Applicant Address BETZALEL STREET, 7, 87516 OFAKIM, ISRAEL
Inventors:
# Inventor's Name Inventor's Address
1 KOSASHVILI, YONA NORDAU STREET, 77, 75319 RISHON LEZION
2 ROBINSON, DROR KFAR SHMUEL 100, D N SHIMSHON
PCT International Classification Number A 61B 17/66
PCT International Application Number PCT/IL02/00401
PCT International Filing date 2002-05-22
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 143334 2001-05-23 Israel