U.S. patent application number 11/604427 was filed with the patent office on 2007-04-26 for method of performing anterior cruciate ligament reconstruction using biodegradable interference screw.
Invention is credited to Lisa Donnelly, Yufu Li, Joan M. Sullivan, Gregory Whittaker, J. Jenny Yuan.
Application Number | 20070093895 11/604427 |
Document ID | / |
Family ID | 34194891 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070093895 |
Kind Code |
A1 |
Donnelly; Lisa ; et
al. |
April 26, 2007 |
Method of performing anterior cruciate ligament reconstruction
using biodegradable interference screw
Abstract
A method of replacing an ACL with a graft. The method provides
for the drilling bone tunnels in a femur and a tibia. A replacement
graft is provided having first and second ends. A biodegradable
composite screw is provided. The screw is made from a biodegradable
polymer and a bioceramic or a bioglass. At least one end of the
graft is secured in a bone tunnel using the biodegradable composite
screw.
Inventors: |
Donnelly; Lisa; (Wayland,
MA) ; Li; Yufu; (Bridgewater, NJ) ; Sullivan;
Joan M.; (Hanover, MA) ; Whittaker; Gregory;
(Stoneham, MA) ; Yuan; J. Jenny; (Neshanic
Station, NJ) |
Correspondence
Address: |
PHILIP S. JOHNSON;JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
34194891 |
Appl. No.: |
11/604427 |
Filed: |
November 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10673737 |
Sep 29, 2003 |
|
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11604427 |
Nov 27, 2006 |
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Current U.S.
Class: |
623/13.14 |
Current CPC
Class: |
A61F 2002/0882 20130101;
A61L 31/128 20130101; A61L 31/026 20130101; A61F 2002/0829
20130101; A61L 31/148 20130101; A61F 2002/087 20130101; A61F
2002/0823 20130101; A61F 2002/0841 20130101; A61F 2002/0858
20130101; A61F 2/08 20130101; A61L 2400/18 20130101; A61F 2/0811
20130101; A61L 31/127 20130101 |
Class at
Publication: |
623/013.14 |
International
Class: |
A61F 2/08 20060101
A61F002/08 |
Claims
1. A method of replacing an anterior cruciate ligament in a knee,
comprising: providing a graft having a first end and a second end;
drilling a bone tunnel in a tibia, said bone tunnel having an inner
wall; drilling a bone tunnel in a femur, said bone tunnel having an
inner wall; mounting the first end of the graft in the femoral bone
tunnel; mounting the second end of the graft in the tibial bone
tunnel; providing a biodegradable, composite interference screw,
said interference screw comprising: a biodegradable comprising a
copolymer of poly (lactic acid) and poly(glycolic acid); and, a
bioceramic; inserting the biodegradable screw into the femoral bone
tunnel between an interior surface of the femoral bone tunnel and
the first end of the graft; and, rotating the interference screw
such that the screw is substantially contained within the femoral
bone tunnel, and the first end of the graft is fixed in place
between the interference screw and a section of the interior
surface of the femoral bone tunnel.
2. The method of claim 1, additionally comprising the steps of:
inserting the second end of the graft into the tibial tunnel;
inserting the biodegradable screw into the tibial bone tunnel
between an interior surface of the tibial bone tunnel and the
second end of the graft; and, rotating the interference screw such
that the screw is substantially contained within the tibial bone
tunnel, and the second end of the graft is fixed in place between
the interference screw and a section of the interior surface of the
tibial bone tunnel.
3. The method of claim 1, wherein the bioceramic comprises a
bioceramic selected from the group consisting of mono-, di-, tri,
.alpha.-tri, .beta.-tri and tetra-calcium phosphate,
hydroxyapatite, calcium sulfates, calcium oxides, calcium
carbonate, and magnesium calcium phosphates.
4. The method of claim 4 wherein the bioceramic comprises
.beta.-tricalcium phosphate.
5. The method of claim 1 wherein the bioabsorbable polymer
comprises a copolymer of polylactic acid and poly (glycolic acid)
comprising about 85 mole percent to about 95 mole percent of poly
(lactic acid) and about 5 mole percent to about 15 mole percent of
poly (glycolic acid).
6. The method of claim 5 wherein the bioabsorbable polymer
comprises a co-polymer of about 85 mole percent poly (lactic acid)
and about 15 mole percent poly (glycolic acid).
7. The method of claim 1 wherein the composite screw comprises
about 2.0 Volume percent to about 25.0 Volume percent of
bioceramic.
8. The method of claim 1, wherein the composite screw comprises
about 15.0 Volume percent of bioceramic.
9. The method of claim 1, wherein the graft has a bone block
attached to one end.
10. The method of claim 1, wherein each end of the graft has a bone
block attached thereto.
11. The method of claim 1 comprising the additional step of tapping
the inner surface of the bone tunnels and the bone blocks to create
a threaded space therebetween.
Description
TECHNICAL FIELD
[0001] The field of art to which this invention relates is surgical
procedures for the repair of an anterior cruciate ligament, more
specifically, a surgical procedure for affixing an anterior
cruciate ligament graft into a bone using a biodegradable
interference screw.
BACKGROUND OF THE INVENTION
[0002] The knee joint is one of the strongest joints in the body
because of the powerful ligaments that bind the femur and tibia
together. Although the structure of the knee provides one of the
strongest joints of the body, the knee may be one of the most
frequently injured joints, e.g., athletes frequently stress and
tear knee ligaments. The large number of ligament injuries has
given rise to considerable innovative surgical procedures and
devices for replacing and reconstructing torn or dislocated
ligaments, typically involving grafting autografts, allografts, or
a synthetic construct, to the site of a torn or dislocated
ligament. For example, the replacement of an anterior cruciate
ligament (ACL) may involve transplanting a portion of the patellar
tendon, looped together portions of semitendinosus-gracilis
(hamstring) tendons, or donor Achilles tendons, to attachment sites
in the region of the knee joint.
[0003] Tears or ruptures of an anterior cruciate ligament of a knee
(ACL) typically require a major surgical intervention wherein a
replacement graft is mounted to the ends of the bones surrounding
the knee in order to reconstruct the knee. A ruptured or damaged
ACL typically results in serious symptoms such as knee instability
resulting in diminished ability to perform high level or
recreational sports, or in some cases daily activities relating to
motility. Although the use of knee braces may alleviate some of
these symptoms, the potential long term effects of a damaged ACL
include meniscal damage and articular cartilage damage.
[0004] The basic steps in a conventional ACL reconstruction
procedure include: harvesting a graft made from a portion of the
patellar tendon with attached bone blocks; preparing the graft
attachment site (e.g., drilling holes in opposing bones of the
joint in which the graft will be placed); placing the graft in the
graft attachment site; and rigidly fixing the bone blocks in place
within the graft site, i.e., the holes or "bone tunnels". The
screws used to fix the graft in place are called "interference
screws" because they are wedged between the bone block and the wall
of the bone tunnel into which the bone block fits. Typically, there
is very little space between the bone block and the inner wall of
the bone tunnel in the bone at the fixation site.
[0005] Several types of surgical procedures have been developed to
replace the ACL. Although repair would be a preferred procedure, it
is not typically possible since the end of the torn ACL is
typically not of sufficient length to reattach successfully.
However, reconstructions can be made to a damaged ACL.
[0006] There are several types of conventional replacement grafts
that may be used in these replacement procedures. In all procedures
tibial and femoral tunnels are drilled by the surgeon using
conventional techniques. Known, conventional drill guides and
drills are used. In one type of procedure known as a
bone-tendon-bone procedure, an autograft tendon is harvested from
the patellar tendon along with an attached bone block on one end
harvested from the patella and a harvested bone block on the other
end harvested from the tibia. In order to secure the graft in the
knee, one end is mounted into the tibial tunnel and other end is
mounted into the femoral tunnel. This is done by mounting the
opposed bone blocks in the tibial and femoral tunnels,
respectively, in the following manner. A guide pin is passed
through the tibial tunnel, into the fermoral tunnel and out through
the lateral femoral cortex. Suture is used to attach the graft to
the proximal end of the guide pin. The distal end of the guide pin
is then pulled out of the lateral cortex of the femur and the graft
is pulled into the knee (femoral and tibial tunnels). Once the bone
blocks are emplaced in the respective tibial and femoral tunnels,
the blocks are secured in place in the following manner. One method
of securing or fixing the ends of the graft in the tunnels is to
use a conventional metallic interference screw. The screw is
inserted into the opening of a tunnel and placed in between the
graft and the interior surface of the bone tunnel. It is then
turned and screwed into the tunnels, thereby forcing the end of the
graft against an interior surface of the bone tunnel. The ends of
graft are secured and maintained in place in the tunnel by means of
a force fit provided by the interference screw.
[0007] Another surgical procedure for the replacement of an
anterior cruciate ligament involves providing a graft ligament
without attached bone blocks. The graft can be an autograft or an
allograft. The autografts that are used may typically be harvested
from the hamstring tendons or the quadriceps tendons. The
allografts that are conventionally used are harvested from
cadaveric sources, and may include the hamstring tendons,
quadriceps tendons, Achilles tendon, and tibialus tendons. If
desired, and if readily available, it may possible to use synthetic
grafts or xenografts. Tibial and femoral tunnels are similarly
drilled in the tibia and femur respectively using-conventional
techniques, drill guides and drills. Once the tunnels have been
drilled, the surgeon then pulls the graft through the tibial and
femoral tunnels using conventional techniques such that one end of
the graft resides in the tibial tunnel and the other end of the
graft resides in the femoral tunnel. For example, one conventional
technique for pulling a graft through the tunnels is to attache the
graft to the proximal end of a guide pin using conventional
surgical suture. The guide pin is then passed through the tibial
tunnel, into the femoral tunnel, and out though the femoral cortex.
The distal end of the guide pin is then pulled out of the lateral
cortex of the femur and the graft is pulled into the knee (femoral
and tibial tunnels). After the surgeon has emplaced and positioned
the ends of the graft in the respective tunnels, the graft ends
need to be secured and fixed in place to complete the replacement
procedure. One method of securing or fixing the ends of the graft
in the tunnels is to use a conventional metallic interference
screw. The screw is inserted into the opening of a tunnel and
placed in between the graft and the interior surface of the bone
tunnel. It is then turned and screwed into the tunnels, thereby
forcing the end of the graft against an interior surface of the
bone tunnel. The ends of the graft are secured and maintained in
place in the tunnel by means of a force fit provided by the bone
screw.
[0008] Interference screws for anchoring ligaments to bone are
typically fabricated from medically approved metallic materials
that are not naturally degraded by the body. One potential
disadvantage of such screws is that once healing is complete, the
screw remains in the bone. An additional disadvantage of a metal
screw is that in the event of a subsequent rupture or tear of the
graft, it may be necessary to remove the metal screw from the bone
site. Metallic screws may include a threaded shank joined to an
enlarged head having a transverse slot or hexagonal socket formed
therein to engage, respectively, a similarly configured, single
blade or hexagonal rotatable driver for turning the screw into the
bone. The enlarged heads on such screws can protrude from the bone
tunnel and can cause chronic irritation and inflammation of
surrounding body tissue.
[0009] Permanent metallic medical screws in movable joints can, in
certain instances, cause abrading of ligaments during normal motion
of the joint. Screws occasionally back out after insertion,
protruding into surrounding tissue and causing discomfort.
Furthermore, permanent metallic screws and fixation devices may
shield the bone from beneficial stresses after healing. It has been
shown that moderate periodic stress on bone tissue, such as the
stress produced by exercise, helps to prevent decalcification of
the bone. Under some conditions, the stress shielding which results
from the long term use of metal bone fixation devices can lead to
osteoporosis.
[0010] Biodegradable interference screws have been proposed to
avoid the necessity of surgical removal after healing. Because the
degradation of a biodegradable screw occurs over a period of time,
support load is transferred gradually to the bone as it heals. This
reduces potential stress shielding effects.
[0011] In order to overcome the disadvantages that may be
associated with metal interference screws, interference screws made
from biodegradable polymers are known in this art. For example, it
is known to use an interference screw made from polylactic acid.
Ideally, the biodegradable interference screw will rapidly absorb
or break down and be replaced by bone. However, it is known that
screws made from polylactic acid tend to maintain their structural
integrity for very long periods of time thereby preventing the
desired bone in growth. Attempts have been made to improve the bone
regeneration process by using other biodegradable polymers and
copolymers of lactic acid that resorb or absorb more quickly. The
problem often associated with these quicker absorbing polymers or
copolymers is that the bone regeneration may proceed at a much
slower rate than the rate of resorption, resulting in premature
mechanical failure of the screw and a resulting pull out of the
graft end from the femoral tunnel. Some of the absorbable
interference screws of the prior art may take several years to
absorb, and may result in a fibrous tissue mass or cyst being left
behind, not bone. This lack of bone in-growth may create fixation
problems if the ACL is torn again, necessitating a new graft
replacement. In addition, if the screw absorbs too slowly, the
screw will need to be removed in the event of a subsequent failure
of the graft.
[0012] Accordingly, what is needed in this art is a novel method of
performing an ACL replacement graft procedure using a novel
interference screw made from a biodegradable material which rapidly
absorbs or degrades and promotes bone in-growth.
SUMMARY OF THE INVENTION
[0013] Therefore, it is an object of the present invention to
provide a novel method of replacing a ruptured or injured anterior
cruciate ligament with a graft using a novel biodegradable
interference screw consisting of a composite of a biodegradable
polymer and a biodegradable ceramic or bioglass.
[0014] Accordingly, a novel method of repairing an anterior
cruciate ligament in the knee is disclosed. A replacement graft is
provided having a first end and a second end. A bone tunnel is
drilled in the tibia. A bone tunnel is also drilled in the tibia.
The first end of the graft is mounted in the femoral bone tunnel.
The second end of the graft is mounted in the tibial bone tunnel. A
biodegradable, composite interference screw is provided. The
interference screw is made from a copolymer of poly (lactic acid)
and poly(glycolic acid) and a bioceramic. The biodegradable screw
is inserted into the femoral bone tunnel between an interior
surface of the femoral bone tunnel and the first end of the graft.
The interference screw is rotated such that the screw is
substantially contained within the femoral bone tunnel, and the
first end of the graft is fixed in place between the interference
screw and a section of the interior surface of the femoral bone
tunnel.
[0015] These and other features, aspects and advantages of the
present invention will become more apparent from the following
description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1A is a side view of a biodegradable interference bone
screw useful in the method of the present invention.
[0017] FIG. 1B is an end view of the interference bone screw of
FIG. 1A.
[0018] FIG. 1C is a cross-sectional view of the inference bone
screw of FIG. 1B taken along view line A-A.
[0019] FIG. 2 is a side view of a driver device useful for
emplacing the bone screw of FIG. 1 in a bone tunnel.
[0020] FIG. 3 illustrates a bone-tendon-bone graft prior to
emplacement in a knee for an ACL reconstruction.
[0021] FIG. 4 shows a guide wire placed into the femoral tunnel
between the tunnel wall and the bone block.
[0022] FIG. 5 illustrates a conventional tap being used to tap a
hole between the wall and the bone block.
[0023] FIG. 6 shows a biodegradable interference screw being
inserted into the femoral tunnel between the tunnel wall and the
bone block.
[0024] FIG. 7 illustrates a guide wire placed into the tibial
tunnel between the tunnel wall and the bone block.
[0025] FIG. 8 illustrates a conventional tap device being used to
tap a hole between the tunnel wall and the bone block.
[0026] FIG. 9 illustrates the screw being inserted into the tibial
tunnel between the tunnel wall and the bone block.
[0027] FIG. 10 is a side view of the knee after the ACL replacement
procedure has been completed.
[0028] FIG. 11A is a histological section of a PLA/PGA bone pin
containing .beta.-tricalcium phosphate and surrounding tissue.
[0029] FIG. 11B is a histological section of a PLA bone pin and
surrounding tissue.
[0030] FIG. 11C is a histological section of a PLA bone pin and
surrounding tissue.
[0031] FIG. 11D is a histological section of a PLA bone pin
containing .beta.-tricalcium phosphate and surrounding tissue.
[0032] FIG. 11E is a histological section of a PLA/PGA bone pin
containing .beta.-tricalcium phosphate and surrounding tissue.
DETAILED DESCRIPTION OF THE INVENTION
[0033] The novel interference screws of the present invention are a
composite of a biodegradable polymer or copolymer and a bioceramic.
The term biodegradable as used herein is defined to mean materials
that degrade in the body and then are either absorbed into or
excreted from the body. The term bioceramic as defined herein is
defined to mean ceramic and glass materials that are compatible
with body tissue. The bioceramics are preferably biodegradable.
[0034] The biodegradable polymers that can be used to manufacture
the composite screws used in the novel process of the present
invention include biodegradable polymers selected from the group
consisting of aliphatic polyesters, polyorthoesters,
polyanhydrides, polycarbonates, polyurethanes, polyamides and
polyalkylene oxides. Preferably, the biodegradable polymers are
aliphatic polyester polymers and copolymers, and blends thereof.
The aliphatic polyesters are typically synthesized in a ring
opening polymerization. Suitable monomers include but are not
limited to lactic acid, lactide (including L-, D-, meso and D,L
mixtures), glycolic acid, glycolide, .epsilon.-caprolactone,
p-dioxanone (1,4-dioxan-2-one), trimethylene carbonate
(1,3-dioxan-2-one), .delta.-valerolactone, and combinations
thereof. These monomers generally are polymerized in the presence
of an organometallic catalyst and an initiator at elevated
temperatures. The organometallic catalyst is preferably tin based,
e.g., stannous octoate, and is present in the monomer mixture at a
molar ratio of monomer to catalyst ranging from about 10,000/1 to
about 100,000/1. The initiator is typically an alkanol (including
diols and polyols), a glycol, a hydroxyacid, or an amine, and is
present in the monomer mixture at a molar ratio of monomer to
initiator ranging from about 100/1 to about 5000/1. The
polymerization typically is carried out at a temperature range from
about 80.degree. C. to about 240.degree. C., preferably from about
100.degree. C. to about 220.degree. C., until the desired molecular
weight and viscosity are achieved. It is particularly preferred to
use a copolymer of poly(lactic acid) and poly(glycolic acid). In
particular, a copolymer of about 85 mole percent poly(lactic acid)
and about 15 mole percent poly(glycolic acid).
[0035] The bioceramics that can be used in the composite screws
used in the novel process of the present invention include ceramics
comprising mono-, di-, tri-, .alpha.-tri-, .beta.-tri-, and
tetra-calcium phosphate, hydroxyapatite, calcium sulfates, calcium
oxides, calcium carbonates, magnesium calcium phosphates. It is
particularly preferred to use a .beta.-tritricalcium phosphate.
[0036] In addition to bioceramics, bioglasses may also be used in
the composite screws. The bioglasses may include phosphate glasses
and bioglasses.
[0037] The amount of the bioceramic or bioglass in the composite
interference screw will be sufficient to effectively promote bone
in-growth. Typically the amount will be about 2.0 Vol. % to about
25.0 Vol. %, and preferably about 15.0 Vol. %.
[0038] The composite, biodegradable interference screws useful in
the present invention are manufactured in conventional extrusion
and molding processes using conventional extruding and molding
equipment. In a typical process, dry biodegradable polymer pellets
and dry bioceramic or bioglass are metered into a conventional
heated screw extruder. The materials are heated and blended in the
extruder for a sufficiently effective residence time to provide a
viscous composite having a uniform distribution of the particles of
bioglass or bioceramic. Then the viscous composite is cooled and
chopped to form pellets of the homogenous composite. The
interference screws may be molded in a conventional injection
molder. In a typical injection molder, pellets of composite are fed
into a barrel, passed through a heating zone to melt the polymer,
then pushed forward through a nozzle and into the cavity of a
chilled mold. After cooling, the mold is opened, and the part is
ejected.
[0039] A biodegradable interference screw 5 of the present
invention is seen in FIGS. 1A-C. The screw 5 is seen to have an
elongate body 10 having a cannulated passage 20 therethrough, with
proximal socket opening. 22 and distal opening 26. The body 10 is
seen to have a plurality of thread flights 30 extending from the
outer surface 12. The body 10 is seen to have distal end 14 and
proximal end 16. A driver 50 for inserting or emplacing the crew 5
in a bone tunnel is seen in FIG. 2. The driver 50 has an elongated
rod member 60 having distal end 62 and proximal end 64. Distal end
62 is seen to have a driver 63 extending therefrom having a
hexagonal configuration for mating with socket 22. The screw 5 is
mounted to driver 50 by inserting the driver 63 of distal end 62
into the mating proximal socket end 22 of the passage 20.
[0040] The biodegradable composite interference screws described
herein are used in the novel ACL reconstruction procedure of the
present invention in the following manner as illustrated if FIGS.
3-10. Prior to reconstructing the ACL using a bone-tendon-bone
graft, a patient is prepared for surgery in a conventional manner.
The patient's knee 100 is prepared for surgery in a conventional
manner including swabbing the skin around the knee with a
conventional antiseptic solution, and draping the knee. The knee
100 is then angulated by the surgeon in a conventional manner to
facilitate the surgical procedure. The patient is then anesthetized
in a conventional manner using conventional anesthetics, either
general or local at the discretion of the surgeon. As seen in FIG.
1, the knee 100 is seen to have a femur 150 having a distal end 160
and a tibia 130 having a proximal end 140. Proximal end 140 is seen
to have a tibial plateau 141. Extending from the distal end 160 of
femur 150 are the femoral condyles 170 separated by notch 175. For
the sake of illustration, the tendons, cartilage, fascia, soft
tissue and skin are not shown. The knee 100 is accessed by the
surgeon using a conventional arthroscope that is inserted though a
conventional cannula, that has been previously emplaced in the knee
100 in a conventional manner through an incision in the skin
covering the knee 100. A flow of sterile saline is initiated
through channels in the arthroscope into the knee 100. The stumps
of the ACL are removed from the surfaces of the tibial plateau 141
and the chondryl notch 175 using conventional shavers that are
inserted through the cannula. A bone-tendon-bone graft 200 is
harvested and prepared by the surgeon in a conventional manner. The
graft 200 is harvested by making an incision in the skin over the
knee 100 down the anterior patella to the tibial. A conventional
sagittal saw is then used to harvest the opposed bone plugs 220
that are connected by harvested patellar tendon segment 210. The
tendon segment 210 is cut from the patellar tendon in a
conventional manner using a scalpel. If desired, a graft without
bone blocks attached may also be used in the method of the present
invention.
[0041] The procedure continues by mounting a conventional tibial
drill guide (not shown) to the proximal end of the tibia 130. A
conventional guide pin 250 is inserted into the drill guide and
mounted to a conventional surgical drill. The guide pin 250 is seen
to have elongated body 252 having distal cutting end 254 and
proximal end 255 with suture mounting opening 257. The guide pin
250 is drilled into the front of the tibia 130 in a conventional
manner until the distal end 254 exits out from the tibial plateau
141. The drill guide is then removed from the tibia 130 and a
conventional surgical reamer is placed over the guide pin 250 and
turned to ream out a tibial tunnel 280 having a passage 282, an
inner tunnel wall 283, a top opening 284 out of the tibial plateau
141 and a bottom opening 286 out through the tibia 130. Then the
reamer and the guide pin 250 are removed from the tibial tunnel 280
and a conventional femoral aimer device (not shown) is inserted
into tibial tunnel 280 and manipulated until the distal end of the
femoral aimer engages the appropriate location on the femoral notch
175. Then the guide pin 250 is inserted through a passage in the
femoral aimer, and the guide pin 250 is mounted to a conventional
surgical drill and drilled into the femoral notch such that the
distal end exits out through the lateral side of the femur 150 and
through the skin overlying that section of the femur 150. Next, the
femoral aimer is removed from the knee 100 and a conventional
surgical bone reamer is placed over the guide pin 250 and moved
through the tibial tunnel 280, and a femoral tunnel 290 is drilled
though the femur having a passage 292, an inner tunnel wall 293, an
upper opening 294 out through the lateral side of the femur 130 and
a bottom opening 296 out of the femoral notch 175. The reamer is
then removed from the bone tunnel 290.
[0042] Referring to FIG. 3, the graft 200 is illustrated proximal
to the knee 100 having the tibial tunnel 280 and femoral tunnel 290
drilled and reamed in the tibia 130 and femur 150, respectively.
The guide pin 250 is seen to reside in the knee 100 with the
elongated body 252 of guide pin 250 substantially contained within
tibial tunnel 280 and femoral tunnel 290, with distal end 254
exiting out through opening 294 and proximal end 255 exiting out
from opening 286. Next, the surgeon threads sutures 230 through the
suture tunnels 222 in bone blocks 220. The suture through the top
bone block 220 is also threaded through opening 257 of guide pin
250. The surgeon then pulls guide pin 250 distally such that the
graft 200 is displaced into the knee 100 with upper bone graft 220
located in passage 292 of femoral tunnel 290 and lower bone block
220 located in passage 282 of tibial tunnel 280. An optional step
of tapping the bone block and boned tunnel is illustrated in FIGS.
4 and 5. A guide wire 300 is seen to be inserted into femoral bone
tunnel 290 between bone block 220 and inner tunnel wall 293. Then,
a conventional cannulated bone tap 310 is inserted over guide wire
300. The bone tap 310 has elongated cannulated member 310, having a
transverse handle 314 mounted to proximal end 312 and a
tapping/cutting end 318 mounted to distal end 316. The tapping
cutting end 318 is rotated by rotating handle 314, causing an
opening to be cut and threads to be tapped between inner wall 293
and bone block 220 in the femoral tunnel 290. Then, as seen in FIG.
6, a biodegradable interference screw 5 mounted to a driver 50 is
mounted to the guide wire 300 and threaded into the femoral tunnel
290 between the bone block 220 and the inner wall 293, thereby
securing the upper bone block 220 in the passage 292 of femoral
tunnel 290. The guide wire is then removed from the femoral tunnel
290 and inserted into opening 286 of and into passage 280 of tibial
tunnel 280 between the lower bone block 220 and the inner wall 183
as seen in FIG. 7. Then, the surgeon tensions the graft 200 by
pulling proximally on sutures 230 connected to lower bone block
220. Then, the bone tap 310 is inserted into tibial tunnel 280 over
the guide wire 300 and an opening and threads are cut and tapped
between inner wall 283, and bone block 220. Finally, the bone tap
310 is removed and as seen in FIG. 9, a biodegradable interference
screw 5 is mounted over the guide wire 300 and threaded into the
tibial tunnel 280 between inner wall 282 and lower bone block 220,
thereby securing the lower bone block 220 in tibial tunnel 280.
This completes the ACL reconstruction, and the graft 200 is now
secured in the knee 100. The complete reconstructed knee 100 is
seen in FIG. 10. The surgeon then checks the knee for proper
flexion and completes the procedure in a conventional manner by
removing the scope and portal, and conventionally closing and/or
suturing and bandaging all incisions.
[0043] The following examples are illustrative of the principles
and practice of the present invention although not limited
thereto.
EXAMPLE 1
[0044] Biodegradable composite bone pins 1 were prepared in a
conventional manner and into the femurs of mammalian laboratory
animals. The pins were of the following three compositions: A)
composites of 15/85% by volume .beta.-tricalcium phosphate and
(85/15)poly (lactide co-glycolide); B) poly(lactide); and C)
composite of 15%/85% by volume .beta.-tricalcium phosphate and
poly(lactide). About 24 months after implantation, the animals were
euthanized and histological sections were obtained. As seen in FIG.
11A, a bone pin 500 having a Composition (A) demonstrated a
significant degree of absorption when compared with the original
diameter indicated by arrows 505, and significant tissue (bone)
in-growth. In addition, minimal tissue reaction was observed. As
seen if FIGS. 11B and 11C, bone pins 510 and 520 having Composition
(B) exhibited minimal absorption compared with the original
diameters indicated by arrows 515 and 525, respectively. As seen in
FIG. 11D, a bone pin 530 having Composition C showed minimal
absorption compared with the original diameter indicated by arrows
535. And, as seen in FIG. 11E, a bone pin 540 having Composition A
demonstrated a significant degree of absorption compared with the
original diameter indicated by arrows 545, and significant tissue
(bone) in-growth. Minimal tissue reaction was observed.
[0045] The novel ACL graft replacement method of the present
invention using a composite interference screw made from a
bioaborbable polymer and a bioceramic or bioglass has many
advantages. The advantages include having improved bioabsorption
and bone replacement, improved tissue in-growth, and minimizing
tissue trauma. In addition, there is an optimal balance between
stiffness and elasticity of the screws.
[0046] Although this invention has been shown and described with
respect to detailed embodiments thereof, it will be understood by
those skilled in the art that various changes in form and detail
thereof may be made without departing from the spirit and scope of
the claimed invention.
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