U.S. patent application number 12/552796 was filed with the patent office on 2009-12-24 for limb lengthener.
Invention is credited to Randolph C. Robinson.
Application Number | 20090318919 12/552796 |
Document ID | / |
Family ID | 27616560 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090318919 |
Kind Code |
A1 |
Robinson; Randolph C. |
December 24, 2009 |
LIMB LENGTHENER
Abstract
A bone distraction device and a method for installing and using
the bone distraction device are disclosed. Separated portions of a
bone may be coupled to two or more mounts of the bone distraction
device. Each portion of the bone may be coupled to at least one
mount. The mounts may be contoured in arcs of at least .pi./3
radians to accommodate the circumference of the bone. The bone
distraction device may include three or more guide rods coupled to
the mounts. A distractor may be used to move one mount relative to
one or more other mounts to distract the bone portions. In one
embodiment, one mount may be coupled to a transport segment of bone
for transport distraction between two bone segments. In some
embodiments, a hydraulic bone distractor may be used to distract
the bone portions.
Inventors: |
Robinson; Randolph C.;
(Centennial, CO) |
Correspondence
Address: |
COOLEY GODWARD KRONISH LLP;ATTN: Patent Group
Suite 1100, 777 - 6th Street, NW
WASHINGTON
DC
20001
US
|
Family ID: |
27616560 |
Appl. No.: |
12/552796 |
Filed: |
September 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10306857 |
Nov 27, 2002 |
7601156 |
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12552796 |
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60337580 |
Dec 5, 2001 |
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Current U.S.
Class: |
606/57 |
Current CPC
Class: |
A61B 2017/00539
20130101; A61B 17/66 20130101; A61B 17/8004 20130101; A61B 2090/037
20160201 |
Class at
Publication: |
606/57 |
International
Class: |
A61F 5/04 20060101
A61F005/04 |
Claims
1. A bone distraction device, comprising: a hydraulic housing
configured to be coupled to a first portion of a bone; a first
mount configured to be coupled to a second portion of the bone; and
a piston at least partially enclosed in the hydraulic housing,
wherein the piston is configured to be coupled to the mount, and
wherein the piston is further configured to move relative to the
hydraulic housing such that the second portion of the bone is
distracted from the first portion of the bone during use.
2. The device of claim 1, further comprising one or more seals
configured to substantially surround a portion of the piston
enclosed in the hydraulic housing, wherein the one or more seals
are configured to inhibit hydraulic fluid from escaping the
hydraulic housing during use.
3. The device of claim 2, wherein the one or more seals are
configured to stabilize the piston during use.
4. The device of claim 1, further comprising a second mount coupled
to the hydraulic housing, wherein the second mount is configured to
couple the hydraulic housing to the first portion of the bone.
5. The device of claim 1, further comprising a pump coupled to the
hydraulic housing, wherein the pump is configured to provide
hydraulic fluid into the hydraulic housing during use in order to
move the piston relative to the hydraulic housing.
6. The device of claim 5, further comprising a valve coupled to the
pump, wherein the valve is configured to inhibit backflow of
hydraulic fluid towards the pump during use.
7. The device of claim 6, wherein the valve is placed in the
hydraulic housing.
8. The device of claim 6, wherein the hydraulic fluid comprises
saline fluid.
9. The device of claim 6, wherein the pump is placed
subcutaneously.
10. The device of claim 1, further comprising a bleed valve coupled
to the hydraulic housing.
11. The device of claim 1, wherein the first mount is contoured in
an arc of at least .pi./3 radians to accommodate the circumference
of the bone.
12. The device of claim 1, wherein the hydraulic housing is
contoured in an arc of at least .pi./3 radians to accommodate the
circumference of the bone.
13. The device of claim 1, wherein the device comprises
bioabsorbable materials.
14. The device of claim 1, wherein the first mount comprises one or
more plates.
15. The device of claim 1, further comprising: two or more guide
rods, wherein a first end of each guide rod is coupled to the
hydraulic housing, and wherein each of the guide rods is coupled to
the first mount.
16. A bone distraction device, comprising: a hydraulic housing
configured to be coupled to a first portion of a bone; an
intermediate hydraulic cylinder at least partially enclosed in the
hydraulic housing, wherein the intermediate hydraulic cylinder is
configured to move relative to the hydraulic housing during use; a
first mount configured to be coupled to a second portion of bone;
and a piston at least partially enclosed in the intermediate
hydraulic cylinder, wherein the piston is configured to be coupled
to the first mount, and wherein the piston is further configured to
move relative to the intermediate hydraulic cylinder and the
hydraulic housing such that the second portion of the bone is
distracted from the first portion of the bone during use.
17. The device of claim 16, further comprising one or more seals
configured to substantially surround a portion of the piston
enclosed in the intermediate hydraulic cylinder, and one or more
seals configured to substantially surround a portion of the
intermediate hydraulic cylinder enclosed in the hydraulic
housing.
18. The device of claim 16, further comprising a second mount
coupled to the hydraulic housing, wherein the second mount is
configured to couple the hydraulic housing to the first portion of
the bone.
19. The device of claim 16, further comprising a pump coupled to
the hydraulic housing, wherein the pump is configured to provide
hydraulic fluid into the hydraulic housing during use.
20. The device of claim 16, wherein the hydraulic housing and the
first mount are contoured in an arc of at least .pi./3 radians to
accommodate the circumference of the bone.
21. The device of claim 16, further comprising: two or more guide
rods, wherein a first end of each guide rod is coupled to the
hydraulic housing, and wherein each of the guide rods is coupled to
the first mount.
22. A method of lengthening a bone, comprising: making an osteotomy
in a bone to form a first portion of the bone and a second portion
of the bone; and separating the second portion of the bone from the
first portion of the bone using a distraction device coupled to the
bone, the distraction device comprising a piston coupled to the
second portion of the bone configured to move relative to a
hydraulic housing coupled to the first portion of the bone.
Description
PRIORITY CLAIM
[0001] This is a continuation application of U.S. application Ser.
No. 10/306,857 entitled "Limb Lengthener", filed Nov. 27, 2002,
Attorney Docket No. RARO-001/00US 310250-2001 which claims priority
to U.S. Provisional Application No. 60/337,580 entitled "Limb
Lengthener," filed Dec. 5, 2001. The above-referenced
non-provisional application and provisional application are hereby
incorporated by reference as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to devices and
procedures used during orthopedic surgery. An embodiment relates to
bone lengthening by distraction osteogenesis.
DESCRIPTION OF RELATED ART
[0003] Some people may have one or more shortened limbs due to
short bone length in the affected limbs. Short bone lengths may be
due to birth defects, disease, and/or injury. Distraction
osteogenesis may be used to elongate a short bone. Distraction
osteogenesis may involve a separation phase, an activation phase,
and a consolidation phase. During the separation phase, a bone that
is to be elongated may be cut at a selected location to separate
the bone into two pieces. The bone pieces may be stabilized
relative to each other with a separation mechanism. A callus may
form between the ends of the two bone pieces. During the activation
phase, the bone pieces may be gradually separated using a
separation mechanism. The separation mechanism may separate the
bone pieces at a rate of approximately 1 millimeter (mm) per day.
Gradual separation of the bone pieces may result in slow stretching
of the callus. Slow stretching of the callus may result in the
formation of additional callus at an interface between the bone
pieces. In addition, gradual stretching of the callus may allow
neurovascular bundles and muscles to adjust in position and/or
length. After a desired length of the bone is obtained, separation
of the bone pieces may be stopped. A consolidation phase may ensue.
During the consolidation phase, the separation mechanism may be
left in position to provide support to the forming bone and
remaining portions of callus.
[0004] Distraction osteogenesis was pioneered by the Soviet
orthopedic surgeon Dr. Gavriel Ilizarov. Ilizarov lengthened the
limbs of dwarfs up to eighteen inches using bicycle sprockets and
spokes to form extendable cages fitting externally over the
patient's limbs. The distal end of the cage was incrementally
extended from the proximal portion mechanically. A plurality of
pins was inserted through the muscle of the limb, and into both
portions of the bone. With the proximal portion of the limb
"anchored" by the pins in the cage, force was transmitted through
the pins to pull the distal portion away from the anchored portion.
This type of device required numerous incisions in a limb for the
pins. The incisions were susceptible to infection and the pins were
continually pulling on flesh. Furthermore, wearing a cage over a
period of months severely limited the mobility of the patient.
[0005] Various distracting means have been developed, such as
external fixators, in which each segment of bone is transfixed by
pins or wires coupled to clamps, which are then distracted.
Examples of external fixator systems include: (i) bilateral frames,
for which fixator bodies or rods arc located one on each side of
the bone being transfixed, (ii) unilateral frames, for which only a
single fixator body or rod is located to one side of the bone, and
(iii) ring fixators, for which a series of rings are spatially
arranged around the limbs so as to form a cylinder, the rings being
interconnected by struts.
[0006] The applications of lengthening procedures using external
fixators have been limited due to a high rate of complications,
including wire site infection, bone infection, pain, scarring,
patient discomfort, and restricted joint motion due to the
transfixation of tendons and muscles.
[0007] Many of the associative complications with external
distraction devices, such as external fixators, were eliminated
when internal distraction devices were introduced. Schollner
reported using a distraction device implanted adjacent to the bone
being lengthened. (Schollner, D., New ways of operating to lengthen
the femur, Z. Orthop. 110:971-974 (1972) citing Anderson, W. V.,
Leg lengthening, J. Bone Joint Surg. [Br] 34-b: 150 (1952)). Gotz
and Schellmann described studies on a hydraulic distractor placed
in a modified interlocking nail. (Gotz, J., Schellmann, W. D.,
Continuous lengthening of the femur with intramedullary
stabilization, Arch. Orthop. Unfall-Chir. 82:305-310 (1975)).
According to Gotz and Schellmann, a cylinder external to the bone
supplied hydraulic pressure to an internal nail. Baumann and Harms
reported using a telescoping nail driven by a threaded spindle
transcutaneously attached to the nail. (Baumann, F., Harms, J., The
extension nail. A new method for lengthening of the femur and
tibia, Arch. Orthop. Unfall-Chir. 90:139-146 (1977)).
[0008] Witt et al. were the first to report human clinical results
from a completely implantable femur distractor. (Witt, A. N.,
Jager, M., Bruns, H., Kusswetter, W., Hildebrant, J. J., Die
operative Oberschenkelverlangerung mit einem vollimplantierbaren
Distraktionsgerat, Arch. Orthop. Traumat. Surg. 92:291-296 (1978)).
Witt et al. reported implanting a device in the soft tissue
adjacent to the bone and screwing the device into the femur
proximally and distally. Witt et al. used an electric motor housed
in the device to generate a distraction force. The motor is
controlled by telemetry from outside the body, providing for both
forward and backward motion.
[0009] Betz et al. disclosed a fully implantable intramedullary
system for lengthening bones, using telemetry to control an
electric motor in U.S. Pat. No. 6,245,075. Betz et al. developed
two variants of an intramedullary nail, one with implanted energy
and control units, and one with external energy and control units.
The first device utilizes a battery pack and a telemetry receiver,
which are both implanted subcutaneously, with an automatic
controller. The second device uses only a receiver that is
implanted and connected to the driving motor, allowing for a much
smaller subcutaneous packet. The patient attaches a telemetry
sender to his leg during the night, which activates the device and
transmits the energy to the motor. According to the teachings of
Betz et al., both devices use an electric motor to provide a
distraction force.
[0010] Pursley disclosed two embodiments of an intramedullary
telescoping distractor in U.S. Pat. No. 5,156,605. Like the device
of Betz et al., both embodiments require a distraction force be
provided using an electric motor and controller to drive a lead
screw. According to the first embodiment, the motor is housed
outside the body and connected to the internal tube by means of a
flexible shaft. In the second embodiment, the motor and control
units are internally mounted and controlled by a communication
assembly from outside the body.
[0011] Other limited reports of work on internal lengthening
devices include Herzenberg, J. E., Hensinger, R. N., Goldstein, S.
A., Michigan intramedullary leg lengthening nail, in: Biomechanics,
Trauma and Sports Medicine Laboratory Annual Report, University of
Michigan (1989); Vcrkerke, G. J., Koops, H. S., Verb, R. P. H.,
Nielsen, H. K. L., Design of a load cell for the Wagner distractor,
Proc. Instn. Mech. Engrs. 203:91-96 (1989); Fisher, C., personal
communication., Feb. 12, 1992; and Hellend, P., Femoral elongation
by use of an elongable intramedullary device, Acta Orthop. Scand.
63(Suppl. 247):16 (1992).
[0012] An implantable distraction device designed for a long bone
may provide the capability of: (1) a low profile around the bone,
(2) structural stability when attached to the bone to prevent
bending movement, (3) an economical construction, and (4)
distraction without the risk of infection by percutaneous wounds or
significant scarring.
SUMMARY OF THE INVENTION
[0013] In an embodiment, a hydraulic bone distractor may be used to
distract bone segments. In certain embodiments, the hydraulic bone
distractor may be contoured in an arc to accommodate the
circumference of the bone to be distracted. A hydraulic bone
distractor may include a hydraulic housing. The hydraulic housing
may be coupled to a first portion of a bone. In certain
embodiments, the hydraulic housing may be coupled to a first
portion of a bone using a second mount. A piston may be at least
partially enclosed in the hydraulic housing. The piston may be
coupled to a second portion of the bone. The piston may be coupled
to a second portion of the bone using a first mount. In an
embodiment, the piston may move relative to the hydraulic housing
to distract the second portion of the bone from the first portion
of the bone. A hydraulic fluid may be provided into the hydraulic
housing to move the piston relative to the hydraulic housing. In an
embodiment, the hydraulic fluid may be provided from a pump coupled
to the hydraulic housing. In certain embodiments, a valve may be
used to inhibit backflow of hydraulic fluid towards the pump. In
some embodiments, the hydraulic bone distractor may include
bioabsorbable materials. In an embodiment, the hydraulic housing
and/or the first/second mount can be contoured in an arc of at
least .pi./3 radians to accommodate the circumference of the bone.
In some embodiments, the bone distractor may further include two or
more guide rods coupled to the hydraulic housing and the first
mount.
[0014] In one embodiment, the hydraulic bone distractor may include
an intermediate hydraulic cylinder. The intermediate hydraulic
cylinder may enclose a portion of the piston. Hydraulic fluid
provided to the hydraulic housing may cause the intermediate
hydraulic cylinder to move relative to the hydraulic housing. The
piston may move relative to the intermediate hydraulic cylinder and
the hydraulic housing. Using an intermediate hydraulic cylinder may
increase the distraction distance for a hydraulic bone
distractor.
[0015] In one embodiment, the present invention could include a
method of lengthening a bone, comprising making an osteotomy in a
bone to form a first portion of the bone and a second portion of
the bone and separating the second portion of the bone from the
first portion of the bone using a distraction device coupled to the
bone, the distraction device comprising a piston coupled to the
second portion of the bone configured to move relative to a
hydraulic housing coupled to the first portion of the bone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Advantages of the present invention will become apparent to
those skilled in the art with the benefit of the following detailed
description of the preferred embodiments and upon reference to the
accompanying drawings in which:
[0017] FIG. 1 depicts a representation of an embodiment of a limb
lengthener coupled to a bone.
[0018] FIG. 2 depicts an end-on representation of an embodiment of
a mount of a limb lengthener coupled to a bone segment.
[0019] FIG. 3 depicts an end-on representation of another
embodiment of a mount of a limb lengthener coupled to a bone
segment.
[0020] FIG. 4 depicts a representation of another embodiment of a
limb lengthener coupled to a bone for transport distraction.
[0021] FIG. 5 depicts a representation of an embodiment of a limb
lengthener in a mid-distraction position.
[0022] FIG. 6 depicts a side, top, and bottom view of an embodiment
of an input shaft.
[0023] FIG. 7A depicts a side, top, and bottom view of a
bushing.
[0024] FIG. 7B depicts a cross sectional view of a bushing.
[0025] FIG. 8 depicts a side, top, and bottom view of an embodiment
of an output shaft.
[0026] FIG. 9 depicts a side, top, and bottom view of a
bushing.
[0027] FIG. 10 depicts a representation of an alternate embodiment
of a limb lengthener.
[0028] FIG. 11 depicts a representation of an embodiment of a limb
lengthener in a post-distraction position.
[0029] FIG. 12 depicts a representation of an embodiment of a limb
lengthener.
[0030] FIG. 13 depicts a cross-sectional representation of an
embodiment of a hydraulic bone distractor.
[0031] FIG. 14 depicts a cross-sectional representation of an
embodiment of a hydraulic bone distractor.
[0032] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and will herein be described in
detail. The drawings may not be to scale. It should be understood,
however, that the drawings and detailed description thereto are not
intended to limit the invention to the particular form disclosed,
but on the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope
of the present invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] FIG. 1 depicts a representation of an embodiment of limb
lengthener 20. Limb lengthener 20 may be used to extend the length
of long bone 22. FIG. 1 depicts limb lengthener 20 in an initial
position prior to distraction. Limb lengthener 20 may be coupled
(e.g., attached or secured) to long bone 22 by fasteners 24, as
depicted in FIGS. 2 and 3. Fasteners 24 may be bone screws, nuts
and bolts, nails, rivets, trocars, cables, adhesives, or
combinations thereof. Fasteners 24 may be received by openings 38
in limb lengthener 20. After coupling limb lengthener 20 to bone
22, the bone may be cut into bone segments 26 and 28. The procedure
used to cut bone 22 may be, for example, an osteotomy, surgical
corticotomy, or other surgical procedure used to separate a bone
into two or more pieces. Bone 22 may be cut such that nerves
adjacent to the bone segments are not damaged. In some embodiments,
limb lengthener 20 may be coupled to pre-separated bone segments 26
and 28. Bone segments 26, 28 may be pre-separated by a surgical
procedure (e.g., before coupling limb lengthener 20 to bone 22, the
bone may be cut into first segment 26 and second segment 28.) or by
a trauma.
[0034] In some embodiments, bone 22 may be partially cut to allow
the uncut bone to maintain stability and alignment of first segment
26 relative to second segment 28 during fixation of limb lengthener
20 to the bone. The partially cut bone may serve as a guide for
correct placement of limb lengthener 20. After limb lengthener 20
is coupled to bone 22, the bone may be separated into first segment
26 and second segment 28.
[0035] After limb lengthener 20 is implanted and bone segments 26,
28 have been separated, the patient's skin may be closed so that an
input shaft and/or an input bushing of the limb lengthener extends
through the skin. Limb lengthener 20 may be activated without
having to reopen the skin to begin distraction of bone 22.
[0036] A callus may be allowed to form between bone segments 26,
28. A distractor of the limb lengthener may be activated after
formation of the callus to move bone segment 28 in the direction of
distraction vector 30. Limb lengthener 20 may be used to gradually
distract bone segments 26, 28. Gradual distraction may promote
development of the callus between bone segments 26, 28. As bone
segments 26, 28 are distracted, the callus may continue to develop
between the bone segments. The callus may, after a period of time,
be converted to bone by the human body.
[0037] As depicted in FIG. 1, limb lengthener 20 may include first
mount 34 and second mount 36. First mount 34 and second mount 36
may include openings 38. Openings 38 may receive fasteners 24 to
couple first mount 34 and second mount 36 to segments of bone 22.
In some embodiments, openings 38 may be threaded to receive
fasteners 24. Fasteners 24 may be locking fasteners (e.g., locking
screws). In one embodiment, openings 38 are threaded and receive
locking fasteners 24. Locking fasteners 24 may secure first mount
34 and second mount 36 to bone segments 26, 28. Threads of locking
fasteners 24 may engage first mount 34 and second mount 36 to lock
the mounts to limb lengthener 20. In an embodiment, fasteners 24
couple first mount 34 to first bone segment 26 and second mount 36
to second bone segment 28. In one embodiment, first mount 34 and
second mount 36 may include five openings 38 each. In another
embodiment, first mount 34 and second mount 36 may include nine
openings 38 each, as shown in FIG. 1. Fewer or more openings and
fasteners may be used in alternate embodiments of mounts 34 and 36
to couple the mounts to bone segments 26 and 28, respectively. In
certain embodiments, first mount 34 may have a different number of
openings than second mount 36. Bone 22 may be drilled and/or tapped
beneath openings 38 before or during an installation procedure.
Drilling and/or tapping bone 22 may facilitate coupling of limb
lengthener 20 to the bone with fasteners 24. In some embodiments,
one or more additional openings 38 and fasteners 24 may be placed
at other locations on either first mount 34 and/or second mount 36.
These additional openings and fasteners may be used to further
secure the first mount and/or the second mount to bone
segments.
[0038] In an embodiment, limb lengthener 20 includes three or more
guide rods 40. Limb lengthener 20 in FIGS. 1-3 shows three guide
rods 40 encircling a portion of bone 22. Guide rods 40 may maintain
alignment between first mount 34 and second mount 36 as the spacing
between the mounts is adjusted during distraction. In some
embodiments, fewer or more than three guide rods may be used in a
limb lengthener (e.g., a limb lengthener may have 2, 4, 5 or more
guide rods).
[0039] Openings in first mount 34 may receive first ends 44 of
guide rods 40. In certain embodiments, guide rods 40 may be fixedly
coupled to first mount 34. The openings in first mount 34 may have
a diameter smaller than the diameter of guide rods 40. A tool
(e.g., a hammer or similar device) may be used to force guide rods
40 into the openings of first mount 34 to press fit the guide rods
into the openings.
[0040] Guide rods 40 may be positioned in guides 42 in second mount
36. Guides 42 may have a minimum length based on a relationship
between a distance between guide rods 40 and output shaft 50, and
the coefficient of friction between the guide rods and the guides.
In certain embodiments, a length of guide 42 may be greater than
about two times the coefficient of friction times a distance
between a center axis of guide rod 40 and a center axis of output
shaft 50 as defined in the equation:
L>2.times.u.times.D; (1)
where L is the length of a guide; u is the coefficient of friction
between a guide rod and a guide; and, D is distance between a guide
rod and an output shaft.
[0041] In certain embodiments, second ends 46 of guide rods 40 may
be slidably received in guides 42 of second mount 36 so that the
second mount is capable of slidable movement along the guide rods.
Guide rods 40 may couple first mount 34 to second mount 36 such
that the second mount may move along the path of the guide rods and
relative to the first mount. Ends of guide rods 40, or the end of
one guide rod, may be re-shaped (e.g., peened) after the guide rods
40 are positioned in guides 42 to inhibit uncoupling of the mounts.
In some embodiments, a stop (e.g., a larger diameter end) may be
placed at an end of one or more guide rods 40 to inhibit uncoupling
of the mounts. Guide rods 40 may allow second mount 36 to move
relative to first mount 34 in a controlled path. In an alternate
embodiment, guide rods 40 may be fixedly coupled to second mount 36
and may be placed in guides in first mount 34.
[0042] In an embodiment, as shown in FIGS. 2 and 3, two guide rods
40 may be positioned adjacent to sides of bone 22 to be lengthened.
Another guide rod 40 may be placed adjacent to bone 22 between the
other guide rods.
[0043] In an embodiment, first mount 34 and second mount 36 move
relative to each other to distract separated bone segments 26 and
28. First ends 44 of guide rods 40 may remain in substantially the
same position relative to first mount 34 throughout a distraction
procedure (i.e., the first ends may be fixedly coupled to the first
mount). Second mount 36 may start in a first position (as shown in
FIG. 1) and move in the direction of distraction vector 30. Thus,
as osteotomized bone segments 26 and 28 are distracted, second
mount 36 may move closer to second ends 46 of guide rods 40
relative to its first position. The position of second mount 36 in
relation to a point on guide rods 40 changes as bone segments 26
and 28 are distracted.
[0044] Bone 22 may be a hand, foot, leg, arm, finger or other
suitable bone for use with limb lengthener 20. Lateral stability
may be critical for long bones, which are prone to bending and/or
twisting during a distraction process. Surrounding a large portion
of a circumference of bone 22 with guide rods 40 may enhance the
lateral stability of the bone during distraction, thereby
substantially decreasing bending moments applied to the bone.
Bending moments may be produced by activation of shafts or other
moving parts in the limb lengthener. These bending moments may
cause misalignment or bending of bone segments in the absence of
support such as provided by guide rods 40.
[0045] Guide rods 40, along with output shaft 50, may form an arc
around bone 22 such that first mount 34 and second mount 36 form an
arc around the bone. In certain embodiments, first mount 34 and
second mount 36 may form an arc of at least .pi./3 radians to
accommodate the bone circumference. In some embodiments, first
mount 34 and second mount 36 may form an arc of at least .pi.
radians, at least .pi./2 radians, at least .pi./4 radians, at least
.pi./6 radians, or at least .pi./8 radians. In alternate
embodiments, guide rods 40 and output shaft 50 may form a
semicircle around bone 22, or may substantially encircle the bone.
Encircling bone 22 may allow limb lengthener 20 to have a lower
profile and/or held more securely in place. In certain embodiments,
one or more of guide rods 40 may be hollow to reduce cost and/or
weight of limb lengthener 20.
[0046] Limb lengthener 20 may include a distractor. In an
embodiment, the distractor includes output shaft 50 and output gear
52. Output gear 52 of output shaft 50 may be turned by input gear
54. In an embodiment, turning input shaft 56 rotates input gear 54.
In certain embodiments, input shaft 56 may be transcutaneous. Input
gear 54 may drive output gear 52. Driving output gear 52 may rotate
output shaft 50. Output shaft 50 may pass through output bushing
68. Output bushing 68 may allow output shaft 50 to freely rotate in
first mount 34 while not allowing significant change in axial
position of the output shaft relative to the first mount. Output
shaft 50 may include an external thread that mates to a threaded
opening in second mount 36. Rotation of output shaft 50 may move
second mount 36 relative to first mount 34 as the external thread
of the output shaft drives along the threaded opening in the second
mount. FIG. 5 depicts a side-on view of an embodiment of limb
lengthener 20 with second mount 36 moved away from first mount
34.
[0047] FIG. 6 depicts an embodiment of input shaft 56. Input shaft
56 may include activation stem 58. Activation stem 58 may interact
with an activation device. The activation device may be a tool such
as a wrench, screwdriver, ratchet, or other similar tool.
Activation stem 58 may, in some embodiments, be a square tip to
receive a square head of a wrench, driver, or ratchet. Activation
stem 58 may also be shaped as, but not limited to, external or
internal polygons such as triangles, hexagons, octagons,
dodecagons, or slots, crossed slots, or star patterns. In an
embodiment, input shaft 56 may have a length that allows activation
stem 58 to extend through a patient's skin while input gear 54 is
engaged to an output gear of a limb lengthener. As such, a wrench
or other suitable tool may engage tip surface 60 to turn activation
stem 58. An activation device may engage activation stem 58 to turn
input shaft 56, which in turn activates the limb lengthener input
gear. In an embodiment, clockwise rotation of the input shaft
allows the second mount to move away from the first mount, and
counter clockwise rotation of the input shaft allows the second
mount to move towards the first mount.
[0048] First mount 34 of limb lengthener 20 may have a threaded
opening to receive input bushing 62. FIGS. 7A and 7B depict an
embodiment of bushing 62. Input shaft 56 of a limb lengthener may
extend through an internal cavity of input bushing 62 when the
bushing is coupled to the first mount. Input bushing 62 may inhibit
removal of the input shaft from an assembled limb lengthener.
[0049] FIG. 8 depicts an embodiment of output shaft 50 with output
gear 52. Output shaft 50 may include first end 64 and second end
66. First end 64 may contact and spin freely in first mount 34 of a
limb lengthener. Output shaft 50 may include external threading. An
internal opening in second mount 36 of the limb lengthener may
receive second end 66 of output shaft 50. The internal opening in
the second mount may include threading that mates with the external
threading on output shaft 50. When input shaft 56 of the limb
lengthener activates input gear 54 that rotates output gear 52 and
output shaft 50, the second mount threadably advances along output
shaft 50 in a desired direction (e.g., in the direction of
distraction vector 30 depicted in FIG. 1 for distraction or, for
compression, in the opposite direction of distraction vector 30).
The second mount may be displaced with respect to the first mount.
The displacement of the second mount may distract bone segments
coupled to the first and second mounts of the limb lengthener.
[0050] FIG. 9 depicts an embodiment of output bushing 68. Output
bushing 68 may couple output shaft 50 of a limb lengthener to first
mount 34 of the limb lengthener, as shown in FIG. 1. Output bushing
68 may allow rotation of output shaft 50 without a substantial
change in position of the shaft relative to the first mount.
[0051] As depicted in FIG. 1, turning activation stem 58 of input
shaft 56 in an appropriate direction, depending on the direction of
the threading and the direction in which it is desired to move
second mount 36 relative to first mount 34, may turn input shaft
56. In an embodiment, turning input shaft 56 causes input gear 54
to engage output gear 52 and cause output shaft 50 to turn.
Rotating output shaft 50 may move second mount 36 relative to first
mount 34.
[0052] In other limb lengthener embodiments, other mechanisms may
be used to move the second mount relative to the first mount. For
example, FIG. 10 shows sheath 70 and flexible cable 72, which may
be used to activate output shaft 50. Cable 72 and sheath 70 may be
coupled to output shaft 50 or may be formed as an integral part of
the shaft. Cable 72 and sheath 70 may be flexible above first mount
34 to allow the cable and sheath to exit the body of the patient at
a desired location away from the first mount. A wrench or other
suitable tool may engage tip surface 60 to turn cable 72 to
initiate distraction. Sheath 70 may protect adjacent tissue during
activation of the device.
[0053] In some embodiments, a universal joint system may be used to
move a second mount relative to a first mount. A single or double
universal joint may engage an input shaft and an output shaft. In
certain embodiments, a universal joint may replace an input gear
and/or an output gear. Turning an input shaft may drive the
universal joint. Driving the universal joint may rotate output
shaft. Rotation of the output shaft may move a second mount
relative to a first mount as external threading of the output shaft
drives along a threaded opening in the second mount. In an
embodiment, the output shaft may pass through an output bushing.
The output bushing may allow the output shaft to freely rotate in
the first mount while not allowing a significant change in axial
position of the output shaft relative to the first mount. In an
embodiment, the input shaft may be transcutaneous. In some
embodiments, the universal joint may be transcutaneous. The
universal joint may inhibit removal of the input shaft from an
assembled limb lengthener. An input bushing coupled to the
universal joint may inhibit removal of the input shaft from an
assembled limb lengthener.
[0054] As shown in FIG. 1, turning output shaft 50 with respect to
second mount 36 may result in displacement of second mount 36 with
respect to first mount 34 in a direction parallel to distraction
vector 30. First mount 34 may, however, remain stationary relative
to distraction vector 30. The displacement of second mount 36
relative to first mount 34 may stretch the bone callus between
first osteotomized bone segment 26 and second osteotomized bone
segment 28. Stretching (i.e., distracting) the bone callus may
encourage generation or promote development of new bone callus. The
generation of new bone callus may occur at a faster rate than
experienced in normal bone healing. The faster rate may be due in
part to the stress applied to the bone by the limb lengthener.
[0055] After the desired distraction distance has been achieved,
input shaft 56 and input bushing 62 may be removed from the
patient. Removal may be accomplished by unscrewing input bushing 62
using a removal tool (e.g., a removal wrench). The removal tool may
engage removal slits 74, which are depicted in FIGS. 7A-7B at the
top of input bushing 62. For example, input bushing 62 may be
removed by turning the removal wrench in a counter-clockwise
direction. After input bushing 62 is removed, input shaft 56 may be
lifted out of position using pliers or another suitable tool.
[0056] After removal of input shaft 56 and/or input bushing 62, a
seal and/or a brake may be coupled to limb lengthener 20 to
establish, or maintain, the position of output shaft 50. A seal or
a brake may engage an input bushing, an input gear, an output gear,
and/or a universal joint to inhibit rotation of output shaft 50.
Using a seal and/or brake to maintain the position of output shaft
50, may stabilize a distractor after activation.
[0057] In an embodiment, after coupling a limb lengthener to bone
segments, activation stem 58 may be turned to cause distraction of
bone 22. The first turning of the activation stein may be done
between zero to about fourteen days after limb lengthener 20 is
coupled to the bone segments, or at a time determined by a
practitioner as acceptable to avoid complications. The activation
stem may be turned periodically (e.g., daily) until bone 22 has
been lengthened to a desired length. In an embodiment, one full
turn of the activation stem may result in approximately 1 mm of
distraction. In other embodiments, one full turn of the activation
stem may result in about 2 mm, 3 mm, 4 mm, or larger distances of
distraction. FIG. 5 shows an embodiment of limb lengthener 20 in a
mid-distraction phase. The practitioner determines the length of
distraction necessary based on a discrepancy between the limbs and
other factors. In certain embodiments, distraction distances may
range from about 0 mm to about 75.0 mm. At the end of distraction,
input shaft 56 and input bushing 62 may be removed, while the
remainder of limb lengthener 20 may remain in position during a
consolidation phase.
[0058] In an embodiment, limb lengthener 20 may include an
indicator. The indicator may monitor rotation (i.e., activation) of
output shaft 50 and/or activation stem. The indicator may include
an audible noise and/or a visual display indicating the amount of
rotation or activation. Incremental rotations of output shaft 50
and/or activation stem may con-elate to incremental changes in the
distance of distraction (e.g., one full rotation of an activation
stem may correlate to about 1 mm distraction or a partial rotation
may correlate to a different amount of distraction). In some
embodiments, an indicator may monitor (e.g., register) each
activation or partial rotation of output shaft 50 and/or the
activation stem (e.g., the indicator may monitor incremental
rotation of the output shaft). Indicators may include, but not be
limited to, a clicker, a ball spring, and/or a numerical
counter.
[0059] FIG. 11 shows an embodiment of limb lengthener 20 in a
post-distraction phase. The lengths of output shaft 50 and guide
rods 40 may be determined by the size of the bone to be distracted
and/or the desired distraction distance. Output shaft 50 and guide
rods 40 may be provided in various lengths and may be selected and
used interchangeably as needed. Alternately, a shaft or rod may be
shortened as needed by a practitioner or other user by cutting,
sawing, or grinding.
[0060] In some embodiments, limb lengthener 20 may remain in place
after distraction for a period of from about two to about six
months to allow the callus to harden and mature into bone. After a
bone has been distracted to the desired length and the callus has
hardened satisfactorily, limb lengthener 20 may be removed by
removing fasteners 24 from openings 38 of first mount 34 and second
mount 36 to disengage the mounts from the bone.
[0061] FIG. 12 shows an embodiment of limb lengthener 20 that
includes third mount 76. Third mount 76 may couple to second ends
46 of guide rods 40 and output shaft 50. Third mount 76 may inhibit
relative movement between guide rods 40 and output shaft 50 to
improve stability and alignment of device 20. In an embodiment,
third mount 76 may be positioned and/or shaped (e.g., curved) so
that the third mount does not touch the bone that is being
distracted. In some embodiments, an activation mechanism (e.g., an
input shaft and/or an output shaft) may be placed in third mount
76. The activation mechanism in third mount 76 may be used either
in combination with another activation mechanism or in place of
another activation mechanism.
[0062] FIG. 4 depicts an alternate embodiment of limb lengthener 20
utilizing transport distraction. Transport distraction may be used
where a large initial gap exists in bone 22. The large gap may
exist, for example, due to trauma and subsequent surgery, infection
and subsequent surgery, or other causes. First mount 34 and second
mount 36 may stabilize bone 22. Segment mount 77 may be positioned
between first mount 34 and second mount 36 for transport
distraction. Segment mount 77 may include openings allowing guide
rods 40 and output shaft 50 to pass through the segment mount. An
opening in segment mount 77 for output shaft 50 may include threads
that mate with the threading on the output shaft. Activation of
output shaft 50 may move segment mount 77 relative to first mount
34 and second mount 36 along the path of guide rods 40 and the
output shaft.
[0063] Transport segment 32 may be coupled to segment mount 77.
Transport segment 32 may be a portion of a bone. In some
embodiments, transport segment 32 may be obtained by surgically
removing a portion of bone segment 26. Alternately, transport
segment 32 may be a piece of allograft bone or synthetic bone.
Segment mount 77 may be coupled to transport segment 32 between
first mount 34 and second mount 36. A callus may be allowed to form
between bone segment 26 and transport segment 32. Limb lengthener
20 is activated after formation of the callus to move transport
segment 32, coupled to segment mount 77, across the gap between
bone segment 26 and bone segment 28 in the direction of distraction
vector 30. Transport segment 32 may be distracted until pressed
against bone segment 28 to promote healing between the bone
segments.
[0064] FIG. 14 depicts a representation of an embodiment of
hydraulic bone distractor 110. Hydraulic bone distractor 110 may be
made of bioabsorbable materials. In certain embodiments, hydraulic
bone distractor 110 may include materials such as, but not limited
to, poly (D,L-lactide), poly (L-lactide), or other polygycolic
acids. For example, hydraulic bone distractor 110 may be made of
Lactosorb.RTM. obtained from Arthrotek, Inc. (Warsaw, Ind.). An
advantage of using a bioabsorbable material is that the patient's
body will break down and absorb portions of hydraulic bone
distractor 110, eliminating the need for removal of the bone
distractor after bone distraction. Hydraulic bone distractor 110
may include hydraulic housing 80. Hydraulic housing 80 may be
coupled to a first portion of a bone (e.g., bone segment 26 of bone
22 depicted in FIG. 1). Hydraulic housing 80 may be coupled to the
first portion of the bone using one or more plates 100. In an
embodiment, plates 100 are break-off plates. Break-off plates may
allow flexibility of fitting and coupling of hydraulic bone
distractor 110 to bone 22. For example, plates 100 may be broken
between the first and second, the second and third openings, and/or
any other number of openings away from hydraulic housing 80 and/or
piston 94 depending on the size of a bone or the size of the
portions of the bone to be distracted. In certain embodiments,
hydraulic housing 80 may be shaped to accommodate the circumference
of the bone. In alternate embodiments, hydraulic housing 80 may be
flexible such that the hydraulic housing may conform to the shape
of the bone upon coupling to the bone. In some embodiments,
hydraulic housing 80 may be coupled to first mount 34, which is
coupled to bone 22 (as depicted in FIG. 1).
[0065] Hydraulic bone distractor 110 may include piston 94. Piston
94 may be at least partially enclosed in hydraulic housing 80.
Piston 94 may be coupled to a second portion of the bone (e.g.,
bone segment 28 of bone 22 depicted in FIG. 1). Piston 94 may be
coupled to the second portion using plates 100. In some
embodiments, piston 94 may be coupled to second mount 36, which is
coupled to bone 22 (as depicted in FIG. 1).
[0066] Seals 102 may be used to enclose a portion of piston 94 in
hydraulic housing 80 to inhibit the escape of fluid from the
hydraulic housing. In an embodiment, seals 102 are o-ring seals
that surround the circumference of piston 94. During use, seals 102
may allow for movement of piston 94 relative to hydraulic housing
80 while stabilizing the piston in the hydraulic housing and
inhibiting the escape of fluid.
[0067] Pump 88 may be coupled to hydraulic housing 80. In some
embodiments, conduit 86 may couple pump 88 to hydraulic housing 80.
Connector 84 may be used to couple conduit 86 to hydraulic housing
80. Pump 88 may be located subcutaneously or outside of the body.
Conduit 86 may have a length that varies depending on a location of
pump 88 relative to hydraulic housing 80. If pump 88 is located
subcutaneously, the pump, conduit 86, and connector 84 may be made
of bioabsorbable materials. In an embodiment, pump 88 is a syringe
type device, which may be operated either internally or externally.
In some embodiments, pump 88 may be battery powered. Pump 88 may be
used to provide a hydraulic fluid to hydraulic housing 80. The
hydraulic fluid may be any biocompatible fluid used to provide
pressure in hydraulic housing 80. In an embodiment, the hydraulic
fluid is saline fluid.
[0068] Pump 88 may provide hydraulic fluid into hydraulic housing
80 for distraction of bone portions. The provided hydraulic fluid
may provide a force against the portion of piston 94 enclosed in
hydraulic housing 80 so that the piston moves relative to the
hydraulic housing (i.e., the piston is pushed out of the hydraulic
housing in the direction of distraction vector 30). As more
hydraulic fluid is provided to hydraulic housing 80, piston 94 may
be further pushed out of the hydraulic housing. Moving piston 94
relative to hydraulic housing 80 causes distraction of the second
portion of the bone coupled to the piston relative to the first
portion of the bone coupled to the hydraulic housing.
[0069] Valve 90 may inhibit backflow of hydraulic fluid from
hydraulic housing 80 towards pump 88. In an embodiment, valve 90 is
a one-way valve. Valve 90 may be placed in hydraulic housing 80
and/or in connector 84, as shown in FIG. 14.
[0070] In an embodiment, pump 88 is charged (pre-loaded) with a
selected amount of hydraulic fluid. The amount of hydraulic fluid
may be selected to provide a desired distance of distraction
between the bone portions. Pump 88 may discharge hydraulic fluid in
an elastic or spring like manner, which provides a constant force
against piston 94 and, thus, a constant rate of distraction. The
rate of distraction may be controlled or selected to allow time for
regrowth of bone tissue during distraction. In certain embodiments,
the force required for distraction may be relatively small (e.g.,
between about 4 pounds and 10 pounds). In some embodiments, the
force required to achieve distraction may be less for a hydraulic
distractor than other mechanical types of distractors. In addition,
a hydraulic distractor may apply force substantially a direction of
distraction with relatively little or no torsional or bending
components.
[0071] In some embodiments, one or more bleed valves 92 may be
coupled to hydraulic housing 80, connector 84, conduit 86, and/or
pump 88. Bleed valves 92 may be used to relieve excess pressure in
hydraulic housing 80. Bleed valves 92 may remove excess fluid that
may cause unwanted distraction of the bone and/or compression of
the bone.
[0072] FIG. 13 depicts another embodiment of hydraulic bone
distractor 110. Hydraulic bone distractor 110 may include
intermediate hydraulic cylinder 104. Intermediate hydraulic
cylinder 104 may be at least partially enclosed in hydraulic
housing 80. Piston 94 may be partially enclosed in intermediate
hydraulic cylinder 104. Seals 102 may enclose a portion of
intermediate hydraulic cylinder 104 in hydraulic housing 80 and a
portion of piston 94 in the intermediate hydraulic cylinder.
[0073] In an embodiment, hydraulic fluid provided into hydraulic
housing 80 provides a force against the portion of piston 94 in the
hydraulic housing and intermediate hydraulic cylinder 104 to move
the piston relative to the intermediate hydraulic cylinder. Piston
94 may be continually pushed out of intermediate hydraulic cylinder
104 with the addition of more hydraulic fluid until the piston is
fully extended from the intermediate hydraulic cylinder. After full
extension of piston 94, the further addition of hydraulic fluid
provides a force against the piston and intermediate hydraulic
cylinder 104 so that the intermediate hydraulic cylinder moves
relative to hydraulic housing 80 (i.e., the intermediate hydraulic
cylinder is pushed out of the hydraulic housing). Movement of
piston 94 and intermediate hydraulic cylinder 104 relative to
hydraulic housing 80 may cause distraction of a bone segment
coupled to the piston from a bone segment coupled to the hydraulic
housing. Using intermediate hydraulic cylinder 104 in hydraulic
bone distractor 110 may allow for a smaller hydraulic bone
distractor to be used for a given distraction distance. The
telescoping effect of using intermediate hydraulic cylinder 104 and
piston 94 allows for increased distraction distance compared to a
similarly sized hydraulic bone distractor without the intermediate
hydraulic cylinder.
[0074] In certain embodiments, other structures may be employed as
a distractor. Some embodiments may contain distractors that allow
controllable, incremental movement of output shaft 50 through
second mount 36. An example of such a distractor may be a
ratcheting arrangement that includes one or more notches on an
output shaft that interact with a projection or tooth on a
ratcheting mechanism to control movement. In some embodiments, a
small solenoid type motor may be used to supply motive forces to a
distractor. The small motor may be placed internally and controlled
externally with conventional remote control technology.
[0075] In some embodiments, surfaces of a limb lengthener that
contact bone may be treated to promote osteointegration. The
treatment may include, but is not limited to, applying a titanium
plasma spray to selected surfaces, applying a hydroxypatite coating
to selected surfaces, and/or texturing selected surfaces. In an
embodiment, a limb lengthener may be formed of medical grade
stainless steel (e.g., 316L stainless steel) and/or a
titanium-aluminum alloy (e.g., Ti.sub.6Al.sub.4V-Eli).
[0076] Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as the
presently preferred embodiments. Elements and materials may be
substituted for those illustrated and described herein, parts and
processes may be reversed, and certain features of the invention
may be utilized independently, all as would be apparent to one
skilled in the art after having the benefit of this description of
the invention. Changes may be made in the elements described herein
without departing from the spirit and scope of the invention as
described in the following claims.
* * * * *