U.S. patent application number 11/979336 was filed with the patent office on 2008-06-05 for system to be used with an implanting tool.
This patent application is currently assigned to BIORETEC OY. Invention is credited to Timo Allinniemi, Harri Heino, Joonas Mikkonen, Pertti Tormala, Pertti Vesanen.
Application Number | 20080132959 11/979336 |
Document ID | / |
Family ID | 36540052 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080132959 |
Kind Code |
A1 |
Mikkonen; Joonas ; et
al. |
June 5, 2008 |
System to be used with an implanting tool
Abstract
A system to be used with an implanting tool having a tip part.
The system has a longitudinal axis and includes a polymeric screw
having a head and an adapter between the screw and the implanting
tool. The adapter includes a first part that fits the tip part of
the implanting tool.
Inventors: |
Mikkonen; Joonas; (Tampere,
FI) ; Heino; Harri; (Tampere, FI) ; Tormala;
Pertti; (Tampere, FI) ; Vesanen; Pertti;
(Toijala, FI) ; Allinniemi; Timo; (Lempaala,
FI) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
BIORETEC OY
Tampere
FI
|
Family ID: |
36540052 |
Appl. No.: |
11/979336 |
Filed: |
November 1, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11802692 |
May 24, 2007 |
|
|
|
11979336 |
|
|
|
|
Current U.S.
Class: |
606/308 ;
606/301 |
Current CPC
Class: |
A61B 17/8685 20130101;
A61B 17/685 20130101; A61B 2017/00004 20130101; A61B 17/8891
20130101; A61B 17/8883 20130101; A61B 17/862 20130101; A61B 17/866
20130101; A61B 2090/031 20160201 |
Class at
Publication: |
606/308 ;
606/301 |
International
Class: |
A61B 17/56 20060101
A61B017/56 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2006 |
FI |
20065349 |
Claims
1. A system to be used with a surgical implanting tool having a tip
part, the system having a longitudinal axis, the system comprising:
an adapter comprising a first part which fits the tip part of the
implanting tool, the first part being concentric with the
longitudinal axis of the system, the first part comprising a first
element which comprises fingers; a polymeric screw having a head,
the polymeric screw being concentric with the longitudinal axis of
the system, the head of the polymeric screw comprising a second
element, the second element comprising cutting-ins on the outer
periphery of the head of the polymeric screw; and the fingers and
the cutting-ins form counterparts.
2. The system according to claim 1, wherein the shape of the first
element and the second element is such that the maximum torque in
the screwing-in direction is substantially the same as in the
screwing-off direction.
3. The system according to claim 1, wherein the first part is
compatible with the implanting tool according to ISO 5835.
4. The system according to claim 1, wherein the head of the first
part comprises a recess which is hexagonal, cruciform, hexalobular,
quadratic, or the recess is a single slot.
5. The system according to claim 1, wherein the adapter comprises
metal.
6. The system according to claim 1, wherein the polymeric screw is
bioabsorbable.
7. The system according to claim 1, wherein the first part of the
adapter is connectable to the screw by either a female connection
or a male connection.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/802,692 filed 24 May 2007, which claims
priority to Finnish patent application 20065349 filed 24 May 2006,
the entire contents of both of which are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a system to be used with an
implanting tool. There is a special adapter between a polymeric
screw to be screwed and the implanting tool.
BACKGROUND
[0003] Metallic screws have been used for tissue fixation in
surgical procedures since the 1940's. Metallic screws preferably
made of stainless steel or titanium are still most commonly used in
surgery. Metallic materials, however, are significantly stiffer
than bone or other tissues in human body. This mechanical
incompatibility of the fixation device with the healing tissue
generates several problems, such as a stress shielding effect, the
loosening of the fixation due to micro motion on the implant tissue
interface, and the local necrosis of the tissue due to too high
local stresses in the tissue. Additionally, long term complications
due to the corrosion products of the fixation devices are not
uncommon.
[0004] Bioabsorbable fixation devices theoretically overcome all
the above mentioned problems related to metallic fixation devices.
The modulus of the polymer materials can be tailored to be nearly
equivalent with the tissues related to a specific application,
which leads to accelerated healing due to biomechanically optimised
stress transfer to the healing tissue. Bioabsorption, on the other
hand, diminishes the risk of long term complications.
[0005] Bioabsorbable fixation devices have not replaced the
metallic fixation devices used in surgery as was expected already
years ago. There are several reasons for that, such as the lack of
confidence on the bioabsorbable products among the clinicians used
to perform the operations with metallic devices, and in some cases,
the more demanding surgical technique related to the use of the
bioabsorbable fixation device. In the case of bioabsorbable
fixation screws, the screw head design is strongly limited by the
mechanical properties of the bioabsorbable polymer materials. The
material properties of bioabsorbable polymers do not allow the
usage of standardised bone fixation screw heads, e.g. hexagonal or
torx heads.
[0006] Most surgical screws have been made of metallic materials,
e.g. titanium or stainless steel. These screws have multiple thread
and head configurations to be used with different kinds of
instrumentation. To ease the work of the orthopaedic surgeons,
AO/ASIF (Arbeitsgemeinschaft fur Osteosynthesefragen/Association
for the Study of Internal Fixation) has published proposed
configurations of general surgical screws to unify the instruments
used in surgery. The surgeons could then use the same
instrumentation, drills, taps etc. with implants of different
manufacturers, if the implants have been made according to the
AO/ASIF proposal. The proposal has also been turned to the ISO
standards ISO 5835, ISO 6475 and ISO 9268 and to the ASTM standards
ASTM F116-00 and ASTM F543-02.
[0007] The AO/ASIF proposal comprises multiple different shapes for
the slot of the screw head, such as cruciform, square and
hexagonal. The most used one is the hexagonal head. There are also
holding sleeves to be attached to the screwdriver, which holds the
screw in the driver during the implantation. The AO/ASIF
screwdrivers with the holding sleeves have been designed to be used
with standard screws.
[0008] There are also bioabsorbable screws in use, which are
absorbed in the human body after the implantation so that a removal
operation is not needed. The problem with AO/ASIF compatible
instruments and bioabsorbable screws is that the instruments have
been designed to be used with metallic implants. The mechanical
properties of the bioabsorbable screws are not adequate to be able
to use the AO/ASIF instruments with them. Usually, the
bioabsorbable screws have to be implanted with appropriate
instrumentation that increases the costs of the operations.
Adapters which have been attached to the screw but which only fit
the appropriate instruments, have been invented in several cases,
see for example U.S. Pat. No. 5,971,987 and EP 0276153. Also, an
adapter that fits between the screw and the AO/ASIF instrument has
been invented, see U.S. Pat. No. 5,868,749, but the invention has
not included the holding sleeve that should also fit the adapter,
to be used with it. Moreover, the adapter in question is intended
to be used only with screws made of bone substance.
[0009] The other problem with the use of bioabsorbable screws is
the breaking off of the screw when twisted with the screwdriver.
Because surgeons are used to applying metallic screws that can
withstand much more torque, the shift to bioabsorbable screws often
results in using excessive torque with them. There are
torque-limiters invented to be used with both metallic and
bioabsorbable screws. Some of them are mechanisms built in the
screwdrivers so that the driver gives in when twisted with too much
torque (see U.S. Pat. No. 6,132,435). The forces of such
torque-limiters have been adjusted to metallic screws and cannot be
used with bioabsorbable ones. In many cases, they have also been
designed to be used with electrical screwdrivers, which are not
appropriate for bioabsorbable screws because it is important to use
manual drivers to maintain a better response when tightening
bioabsorbable screws. There are also torque-limiters for metallic
and bioabsorbable screws that are integrated in the screw (see EP
0276153 and U.S. Pat. No. 6,471,707). They function so that there
is a weaker score in the screw head for the purpose that the head
will break off when excessive torque is applied. The screw has to
be tightened with a secondary instrument, if the screw has not been
tightened enough until the head breaks off. Also, if the screw has
been stuck, the secondary instrument has to be used to remove the
screw.
SUMMARY OF THE INVENTION
[0010] According the current invention, the screw can be inserted
into the bone with the novel adapter design which enables the use
of standard bone screw instruments with holding sleeves and still
allows the use of the screw head design best suitable for the
polymeric screw. The adapter can comprise one part or several
parts. The uppermost part has the standard screw head design and is
preferably made of metal. The lowest side of the adapter will fit
to a screw head design that is not standardised but optimized for a
polymeric bone fixation screw. The lower part may be made of metal
and/or plastics. Between the upper and lower parts there is a
special junction which limits the maximum torque and which can be
transferred from the uppermost part to the lower part in order to
avoid breaking of the bioabsorbable polymer screw breakage during
the surgical procedure, if a surgeon, who is used to inserting
stronger metallic screws, uses too high a torque during the
installation. The design of the junction is such that it enables
the removing of the screw from the bone even if the torque-limit
has been exceeded during the tightening of the screw. The adapter
can be attached to the screw head with a mechanical quick coupling
so that it holds the screw firmly during the insertion, but after
the screw has been tightened enough, the adapter can be easily
detached with the screwdriver.
GENERAL DESCRIPTION OF THE INVENTION
[0011] The system is to be used with fixation screws, such as
bioabsorbable fixation screws. The system is intended to be used
with an implanting tool having a tip part. The system comprises an
adapter comprising a first part, and a polymeric screw. The adapter
may comprise a second part. The system is elongated and has a
longitudinal axis. The head of the first part fits the tip part of
the implanting tool, e.g. a special screwdriver. The second part of
the adapter is compatible with the head of the polymeric screw.
[0012] When the adapter comprises the second part, the first and
the second parts of the adapter are connected to each other with a
torque limiting junction. The torque limiting junction allows the
first part to rotate with respect to the second part and the
polymeric screw when the predetermined maximum torque has been
exceeded during the screwing of the polymeric screw. However, when
the polymeric screw is screwed off, i.e. when the tensioning of the
polymeric screw is loosened, the first and the second parts do not
rotate with respect to each other. Therefore, the polymeric screw
can be screwed off although it cannot be tightened any further.
[0013] The first part of the adapter comprises a head and a shaft
which axis is concentric to the longitudinal axis of the system.
The head usually has a larger diameter than the shaft. The head
comprises a spot which is compatible with the implanting tool. The
spot can be a suitably shaped recess, for example a hexagonal,
cruciform, hexalobular, or quadratic recess, or the recess is a
single slot. In the end of the shaft there is an end part which
forms a connection to the second part.
[0014] On the surface of its periphery the shaft comprises a first
element which counteracts with a second element in the second part.
The first element and the second element together form a body which
allows the rotation when the maximum torque is exceeded during the
screwing and prevents rotating when the screw is screwed off. The
first element may comprise suitably shaped ridges which are
provided around the periphery of the shaft. The ridges are shaped
so that they can operate in above-described manner in connection
with the first element. The number of the ridges or teeth can vary.
The ridges can be teeth of a pinion.
[0015] The second part is concentric with the longitudinal axis of
the system. The second part comprises the second element which
forms a counterpart to the first element. The second element may be
a cavity whose shape corresponds to that of the first element. In
the bottom of the cavity there may be a recess which is compatible
with the end portion of the shaft of the first part of the
adapter.
[0016] The cavity is surrounded by walls which are separated from
each other by at least one slot. The slot makes it possible that
the walls can bend outwards when the first element has to rotate
with respect to the second element. There are usually more than one
slot, for example four slots.
[0017] On the opposite side of the second part (in the length
direction) there is a slot for fastening the polymeric screw. The
slot is surrounded by forks which support the head of the screw
from their side. The forks may comprise tabs on their inner
surface.
[0018] The polymeric screw is concentric with the longitudinal axis
of the system and it is attached to the second part. The head of
the polymeric screw is shaped so that it fits the slot of the
second part. The head of the screw may comprise flutes which are
compatible with the tabs.
[0019] According to another modification, the first element
comprises a pinion. The pinion comprises blades which extend
towards the periphery of the pinion. The pinion is fastened to an
end of a shaft which is compatible with a hole in the second
part.
[0020] The second element comprises walls whose upper side is
bevelled in the screwing direction. The walls are placed radially
and their height becomes smaller towards the center of the second
part. The underside of each blade is stepped so that the walls will
grip the steps of the blades when the screw is screwed off.
[0021] The materials, the dimensions and the shapes which are used
in the adapter are selected so that the desired torque forces can
be achieved. The materials are normally selected amongst metals or
plastics.
[0022] When the adapter does not comprise the second part, the
second element is formed on the head of the polymeric screw. The
head of the polymeric screw may comprise on its periphery
cutting-ins which are compatible with the first element of the
first part of the adapter. The first element may comprise fingers
which grip the cutting-ins. The cutting-ins and the fingers are
shaped so that when the maximum torque in the screwing-in direction
is exceeded, it is possible to rotate the screw in the screwing off
direction.
[0023] According to another solution, the cutting-ins and the
fingers may be shaped so that the maximum torque to both directions
is substantially the same. In that case, the fingers and
cutting-ins have symmetrical halves with respect to a vertical
plane which divides the halves.
[0024] The number and the shape of the fingers and the cutting-ins
may vary but they always form counterparts. The fingers are adapted
to grip the cutting-ins on the outer periphery of the head of the
polymeric screw. The adapter is usually made of a metallic
material.
[0025] The adapter comprising the fingers has a large area which is
in contact with the head of the polymeric screw. This feature is
meaningful, for example, in connection with brittle bones, such as
osteoporotic bones.
[0026] Further, the system comprising the screw and the adapter
also has other advantages. The head of the adapter is compatible
with the tip part of the implanting tool. The head of the first
part of the adapter may comprise, for example, a recess which is
compatible with the tip part of the implanting tool. Thus, a tight
and stable joint is achieved. Furthermore, there is no need to
touch the system by hand so the aseptic conditions are well
maintained on the surface of the system comprising the adapter and
the polymeric screw.
[0027] As a common feature for all modifications described in this
application, there may be a canal for a guide wire. The canal is
concentric with the system of the invention and extends through the
system to the longitudinal direction of the system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 shows a perspective view of a first part of the
adapter,
[0029] FIG. 2 shows a perspective view of a second part of the
adapter,
[0030] FIG. 3 shows a perspective view of a bioabsorbable
screw,
[0031] FIG. 4 shows a perspective view of an exploded assembly
comprising parts of the system of the invention,
[0032] FIG. 5 shows a perspective view of the system of the
invention,
[0033] FIGS. 6-8 and 10 and 11 show cross-sectional views of a
torque limiting junction,
[0034] FIG. 9 shows a perspective view of an adapter (a partial
view),
[0035] FIG. 12 shows schematic views of possible modifications of
the system according to the invention,
[0036] FIG. 13 shows a perspective view of an adapter (a partial
view),
[0037] FIG. 14 shows a view of the adapter of FIG. 13 in extended
position,
[0038] FIG. 15 shows a perspective view of the system of the
invention,
[0039] FIG. 16 shows a view of the system of FIG. 15 in extended
position, and
[0040] FIG. 17 shows a top view of a head of a polymeric screw.
DETAILED DESCRIPTION
[0041] An example of the first part of the adapter is shown in FIG.
1. The head of the first part comprises a hexagonal slot 1 that
fits the AO/ASIF hexagonal screw driver. The first part 32 is also
formed in the shape of an AO/ASIF metallic screw head so that it
fits the screw holding sleeve 2. In the middle of the first part
32, there are ridges 3 that form part of the torque-limiting
element. The sequential ridges 3 are on the periphery of a shaft
34. The ridges 3 are shaped so that they allow torsion in the
clockwise direction when the maximum torque to the clockwise
direction is exceeded, but grip the counterpart when the first part
is turned in counterclockwise direction (in this case, the
polymeric screw is screwed to the clockwise direction and screwed
off in the counterclockwise direction). In this case, the ridges
incline in the counterclockwise direction, i.e. in the screwing-off
direction. The end portion 4 of the first part is formed so that it
attaches firmly to a recess 8 in the counterpart.
[0042] The counterpart of FIG. 1, i.e. the second part 33, is shown
in FIG. 2. There is a cavity 5 of the same form as in FIG. 1 so
that the ridges 3 fit inside the part. There are four bending walls
6 that allow the torque-limit to function with the clockwise
torsion. The four bending walls are separated with four slots 7.
The counterpart, i.e. the first part 32, fits the recess 8 in the
middle of the second part 33. The other end of the part has two
forks 9 that fit the bioabsorbable screw head. Small tabs 10 allow
the part to attach firmly to the screw so that the adapter only
comes off with a bending motion.
[0043] The polymeric screw 31 is shown if FIG. 3. The head 11 of
the screw is formed to fit the adapter by two cuts 12 in both sides
of the head. Flutes 13 that fit the tabs of the adapter attach the
screw to the adapter. The screw comprises threads 14 and a core 15
underneath the threads below the head 11.
[0044] There is an exploded assembly of the screw-adapter
combination in FIG. 4. The different parts are positioned in their
proper places before the assembly. The built up adapter-screw is
shown in FIG. 5.
[0045] The FIG. 6. shows one modification of the torque-limiting
part of the adapter. The shaped pinion 16 allows rotation in the
clockwise direction and prevents it in counterclockwise direction
(in this case, the polymeric screw is screwed to the clockwise
direction and screwed off in the counterclockwise direction). The
teeth of the pinion incline in the counterclockwise direction, i.e.
in the screwing-off direction. The walls 17 around the pinion 16
restrict the rotation. The slots 18 allow the walls 17 to bend, and
with the proper torque, allow the pinion 16 to turn.
[0046] In FIG. 7. there is another modification of the
torque-limiting part of the adapter. The shaped pinion 20 is shaped
so it can bend walls 21 around it. The slots 22 allow bending of
the walls 21 with the proper torque. The counterclockwise rotation
is prevented by the blades 24 of the pinion 20 and the walls 21.
The blade 24 have a rounded edge and a rectangular edge. The
rounded edges of the blades 24 allow the rotation when necessary
but the rectangular edges prevents the rotation.
[0047] FIG. 8 shows still another modification of the
torque-limiting part of the adapter. On the shaft 34 of the first
part of the adapter there are blades 36 which have rounded edges
and incline in the screwing-off direction. The shape of the blades
allows the rotation in the clockwise direction and prevents it in
the counterclockwise direction (in this case, the polymeric screw
is screwed in the clockwise direction and screwed off in the
counterclockwise direction). In this case, the blades have rounded
edges. Walls 35 keep the blades 36 in their position but when the
torsional force is high enough the walls 35 bend and allow the
rotation. In the current modification, the walls 35 are individual
columns as shown in FIG. 9.
[0048] FIG. 10 shows blades 37 which are formed on the shaft 34 and
walls 36. The blades comprise a rounded edge and a rectangular
edge. The function of the adapter is the same as described also in
connection with the other figures.
[0049] FIG. 11 shows blades 38 which are formed on the shaft 34 and
walls 39. The blades have rounded edges and incline in the
screwing-off direction. The function of the adapter is the same as
described also in connection with the other figures.
[0050] FIG. 12 shows different modifications of the
instrument-adapter-screw junctions. The screw 25 can be attached to
the adapter 26 with a male or female connection. Simultaneously the
instrument 27 can be attached to the adapter 26 with a male or
female connection.
[0051] FIGS. 13 and 14 show still another modification of the
torque-limiting part of the adapter. The first element comprises a
laterally rotating pinion 40. The pinion 40 comprises blades 41
which become larger towards the periphery of the pinion 40.
[0052] The second element comprises walls 42 whose upper side is
bevelled in the screwing direction. The walls 42 are placed
radially and their height becomes smaller towards the center of the
second part. The underside of each blade is stepped so that the
walls will grip the steps 43 of the blades 41 when the screw is
screwed off.
[0053] The first element also comprises a shaft 44 which is
compatible with a hole 45 in the second element. When the shaft 44
is placed in the hole 45 the torque-limiting junction is
accomplished.
[0054] FIGS. 15 and 16 show a modification of the system of the
invention. The system comprises the first part 32 of the adapter
but the second part is omitted. The first element of the first part
32 comprises fingers 50. The head of the polymeric screw 11 has
cutting-ins 51 which serve as the second element. The fingers 50
and the cutting-ins 51 form counterparts. The fingers 50 bend
outwards when the maximum torque in the screwing-in direction is
exceeded. However, the screw 31 may still be screwed off if
desired.
[0055] FIG. 17 shows the head of the polymeric screw 31 shown in
FIGS. 15 and 16. The periphery of the head comprises the
cutting-ins 51 so that teeth 52 are formed therebetween. The teeth
52 incline in the screwing off direction.
[0056] It is also possible that the fingers 50 and the cutting-ins
51 are shaped so that the maximum torque in both directions is
substantially the same. For example, the teeth 52 illustrated in
FIG. 17 may be modified so that they are straight.
[0057] The number and the shape of the fingers and the cutting-ins
may vary. However, the fingers and the cutting-ins always form
counterparts.
[0058] A skilled person can readily construct other modifications
in addition to those shown in FIGS. 1-17 after seeing the principle
of this invention. Further, it is possible to use both left-handed
screws or right-handed screws and a skilled person will understand
how to modify the adapter according to the screw to be used.
* * * * *