Note: Descriptions are shown in the official language in which they were submitted.
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INTRAMEDULLARY NAIL
This invention relates to surgical intramedullary nails for stabilising
condylar and supracondylar fractures, particularly of the distal femur or
humerus.
The use of inert metal rods or tubes inserted into the intrameduIlarv caviri~
of long bones in order to stabilise fractures is well established in
orthopaedic and
veterinary practice. These rods or tubes are usually referred to as "nails".
Fractures in the middle third of a long bone may be effectively stabilised
with a simple intramedullary nail.
The effectiveness of this method may be increased by the use of cross
bolts or screws passing through pre-drilled holes in the nail, so as to
achieve better
hold on the proximal and distal bone fragments.
Nails with cross bolts have become known as "locking" or "locked" nails.
These nails have broadened the use of the method to fractures extending well
into
the proximal or distal ends.
The insertion of the cross boltslscrews may be facilitated by the use of a
guide jig which attaches temporarily to the end of the intramedullary nail,
but this
is not invariable and many systems require at least some of the cross
bolts/screws
to be inserted freehand.
In cases where the fracture is in the vicinity of the condylar region of the
femur or humerus, difficulties may be encountered in stabilising the distal
condylar fragments in relation to the shaft of the bone.
The present invention comprises an intramedullary surgical nail designed
for retrograde or reversed insertion into the distal end of the femur or
humerus. It
incorporates a unique staggered/crossed or "Cruciate" configuration of holes,
so
that two distal locking bolts may be inserted. This arrangement permits the
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locking bolts to cross and overlap so that each condyle may be gripped by an
individual bolt
Both condyles are thereby stabilised in relation to the shaft of the bone,
along which the
intramedullary nail passes.
The nails may also incorporate further pre-formed holes at their proximal ends
so that
S further cross bolts may be inserted to improve the fixation of the nail with
respect to the
more proximal femoral or humeral shaft. Such further holes are usually
arranged so that
when cross bolts are inserted, they extend at right angles to the nail.
The invention thus provides according to an aspect, for a surgical
intramedullary nail
and locking bolt assembly for stabilizing fractures of the condyles and
supracondylar region
of a femur or humerus. The assembly comprises a nail in the form of a rod or
tube having a
longitudinal axis and adapted for insertion into an intramedullary canal
through a distal end
of the femur or humerus, the nail having first and second distal locking
holes. The assembly
also comprises first and second distal locking bolts for insertion into the
first and second
distal locking holes. The first and second distal locking holes are staggered
and angled with
respect to the longitudinal axis such that the distal locking bolts when
inserted into the holes
extend in a divergent manner from the nail and permit each condyle to be
gripped by a
respective one of the first and second locking bolts so as to stabilize the
condyles with
respect to the nail.
According to another aspect, the invention provides for a jig for facilitating
the retro-
grade insertion of a surgical intramedullary nail into a femur or humerus from
distal to
proximal, the nail having a longitudinal axis, a proximal end and a distal
end, the distal end
having preformed holes which are staggered and angled with respect to the
longitudinal axis
such that distal locking bolts inserted into the holes extend in a divergent
manner from the
nail and permit each condyle to be gripped by a respective bolt. The jig
comprises a frame
having guide arms adapted to extend on either side of a knee or elbow. The
frame includes
means for attachment to the distal end of the nail in a predetermined angular
relationship
therewith. And the guide arms have guide means for guiding the introduction of
the locking
bolts into the condyles and into the preformed holes.
According to yet another aspect, the invention provides for a surgical
intramedullary
nail for stabilising fractures of the condyles or supracondylar region of a
femur, the nail
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comprising a rod or tube adapted for insertion into a distal end of the femur,
the nail having
first and second distal locking holes which are so positioned and angled with
respect to the
nail, that cross bolts inserted into the distal holes extend into and grip the
condyles. The
distal locking bolts are positioned with respect to the nail so that a distal
end of the nail is
recessed beneath an articular surface of a femoral intercondylar groove,
whereby the distal
end of the nail is kept clear of the patella.
The invention also provides for the use of the surgical intramedullary nail
and Iock-
ing bolt assembly in the stabilisation of condylar or supracondylar fracture,
the nail being
further adapted for insertion of the locking bolts through non articular
surfaces of the con-
dyles and into the holes in the nail.
Features of the femoral and humeral nails in accordance with the invention and
a jig
for introducing the nails and locking bolts are illustrated in the
accompanying drawings:-
Figure 1 is a perspective view of the nail 10, showing its location in the
distal end of
a femur after insertion, and with locking bolts 21, 26 in position passing
through pre-drilled
holes 20, 25. Free holes 30, 35 for insertion of proximal locking bolts are
also shown.
Figure 2 is a similar view of the nail shown in Figure 1, but without the
femur shown.
Alternative patterns of distal locking bolts are shown in Figures 1 and 2.
In Figure 1, locking bolts are shown with smooth shanks 212, 262 which are an
easy
sliding fit in predrilled holes in the nail 20, 25. These locking bolts have
coarse threads 211,
261 which grip the bone of the femoral condyles.
In Figure 2, Locking bolts of an alternative design are shown which have fully
threaded shanks 214, 264. The threaded shanks are received in correspondingly
threaded
holes in the nail 10.
The head of all bolts 211, 261 and 213, 263 incorporate slots or sockets to
accom-
modate an appropriate insertion wrench or screwdriver.
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Figure 3- is an axial view of the nail 10 and distal locking bolts
21,26 of Figure 1 showing how the cross bolts are-insezted to pass through the
non-articular surfaces of the condyles (shown cross-hatched), while gripping
the
~ major mass of oancellous bone in each condyle 60,65.
Figures d and 5 show lateral views of the nail 10 and distal locking bolts
21,6.
Figure 5 shows how the nail is to be positioned in the femur so that the
distal end of the nail lies recessed below the articular surface of the
intercondviar
groove 61 of the femur so that it does not foul the tracking of the patella.
In this
position, due to the obliquity of the cross bolts, these pass through the
major mass
of the cancellous bone of each condyle 60,65.
Intramedullary surgical nails in accordance with the invention are
introduced into the femur through the knee. After surgically exposing the
distal
femur, an entry point is made in the intercondylar groove in line with the
axis of
the intramedulIary canal. A guide wire or rod may be passed into the femoral
intramedullary canal in order to assist the introduction of the nail into the
canal.
The nail may be of hollow section or "cannulated" so that it may be passed
over
the guide wire.
It is intended that insertion of the locking bolts will be facilitated by the
use of a removable jig. This will be attached to the distal end of the nail
which
incorporates guide slots and a threaded axial hole I I, shown in Figures 1, 2,
4 and
5, for secure attachment to the jig, in the appropriate position to align the
cross
bolts with respect to the preformed holes in the nail. Typically, the
attachment
~ of the jig to the distal end of the nail will also be cannulated so that the
jig may
~ also pass over any guide wire used to introduce the nail into the femur.
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Figure 6 shows a perspective view of a typical jig for facilitating
introduction of the nail and locking screws. The jig comprises parts 51, 52
and
53, securing bolt 50 and guide tubes 54, 55, 56 atld 57.
The jig is employed as follows:
An extension piece 51 is attached to the distal end of the nail fitting
rigidly
to slots and threaded axial hole 11 in the nail 10. The distaff locking guide
5?
attaches rigidly to the extension piece 51. This may be achieved using a jig
securing bolt 50 which may be cannulated and engages in threads in extension
piece 51. The distal locking guide 52 has predrilled guide. holes through
which
guide tubes 54 and 55 may be passed. When the nail 10, extension piece 5l and
distal locking guide 52 are rigidly coupled in this manner, the guide tubes
54,55
line up precisely with the predrilled distal holes in the nail 20,25. This
permits
drilling through the guide tubes to form holes through the femoral condyles in
the
correct position to pass through the existing predrilled distal holes 20,35 in
the
nail 10, and for subsequent insertion of the distal locking bolts 21 and 26.
The proximal locking guide arm 53 may be similarly attached to the
extension piece 51. This incorporates predrilled guide holes through which
guide
tubes 56,57 may similarly be passed to align with the proximal predrilled
holes
30,35 in the nail. Appropriately placed holes in the femoral shaft may be
drilled
and the proximal locking bolts inserted. The proximal locking guide arm 53 may
be mounted either to the right as shown in Figure 6 or to the left, so that
the
proximal cross bolts can be introduced from the lateral side for left and
right
femurs respectively.
Following insertion of the nail and all locking bolts, all components of the
jig as above are disconnected and removed.
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Typically, the nails may be manufactwed in varying lengths and diameters
from a biologically inert material which is steriiisable and has appropriate
mechanical strength and stiffness, such as stainless steel. For the femoral
nail,
typical lengths are 250 to 360 mm. The section of the nail is typically
tubular
with an outer diameter of approximately 12 to 16 mm. The nail may be slightly
bent to suit the curvature of the long bone. Distal cross bolts may be
typically 6 to
I I mm outer diameter and approximately 75 to 85 mm long. Cross bolts may be
part or fully threaded.
Typical approximate linear dimensions (mm) and angular configuration
(degrees) of the distal locking bolts in relation to a 14 mm diameter femoral
nail
are shown in Figures 7a-d.
Figure 7a shows an axial view of a femoral nail similar to that shown in
Figwe 3.
Figure 76 is a lateral view of the distal end of the femoral nail and distal
locking bolts and in a similar projection to that shown in Figwes 4 and 5.
Figwes 7c and 7d are projections taken on the lines A-A and B-B, as
shown in Figwe 7a, showing distal locking bolts 21 and 26 respectively.
Figure 8 is a perspective view of a humeral nail 100, showing its position
in the distal end of the humerus with distal locking bolts 210,260 in
position,
passing through predrilled holes 200,250. Free holes 300,350 are provided for
insertion of proximal locking bolts.
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