Instrumentarium for repositioning and fixing petrochanterous and subtrochanterous fractures

An insert member of use in an impact hole leading into a medullary canal of a bone for treating a fracture by insertion of at least one bone nail into the medullary canal is disclosed. The insert member has a guide channel for receiving the proximal end of the bone nail, lateral openings and a pin for fixing the insert member in the impact hole, and a closure member for the proximal end of the guide channel. The closure member includes an abutment for the proximal end of the bone nail which allows limited reverse movement of the proximal end of the bone nail within the guide channel. The abutment may be a separate member attached to the closure member by a spring or the abutment may be a shaped projection extending forwardly from the closure member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an instrumentarium for repositioning and fixing of 
pertrochanterous and subtrochanterous fractures, comprising at least one 
bone nail of resilient material, which nail is bent at least at its 
proximal end portion and which is insertable into the medullary canal of a 
bone through an impact hole formed in the bone and which abuts under 
tension with its apex of curvature the wall of the medullary canal 
opposing the impact hole, the distal end of the bone nail being provided 
with a coupling member allowing a non-rotatable connection with an impact 
tool, an insert member insertable into the impact hole having a guiding 
channel for the bone nail to be driven in and for the at least partial 
accommodation of the coupling member of the bone nail, the insert member 
further being provided with a fixing means preventing its shifting in the 
impact hole and with a closure member for closing the guiding channel. 
2. Description of the Prior Art 
It is known to reposition and to fix pertrochanterous and subtrochanterous 
fractures by opening the medullary canal of the bone through an impact 
hole and by introducing into this impact hole at least one bone nail, 
conveniently several bone nails consisting of elastic material and being 
bent at least in its (their) proximal area. When introducing such bone 
nails into the medullary canal, the nails, under tension due to their 
elasticity, contact the wall of the medullary canal opposing the impact 
hole, so that on the proximal point of each nail arriving at the site of 
the fracture, the nail passes beyond this fracture into the condyle of the 
bone and fixes the fracture. By rotating the individual nails, the bone 
portions can be reduced so that they assume the correct relative position 
at the site of the fracture. For this purpose, the distal end of each nail 
is provided with a coupling member allowing a wholly non-rotatable 
connection with an impact tool. It is known to give this coupling member 
the shape of a small plate-like flattening U.S. Pat. No. 4,055,172), 
although other embodiments of the coupling member are possible. When the 
known nails are correctly positioned in the medullary canal, the nail ends 
protrude from the impact hole and the coupling member abuts under tension 
the outer surface of the bone distally of the impact hole, so that there 
exists the danger, particularly for older persons having porous bones, 
that the bone may collapse at the abutment site and moreover the sinews 
and muscles extending above the impact hole will be irritated by the 
protruding distal nail ends. 
As a rule, the impact hole is made such that the bone is first punctured 
and subsequently the small hole thus formed is widended by means of a 
three- or four-edged reamer, enlarged by means of a chisel or by means of 
a drill. In all these cases, parts of the bone can be split off, thus 
enlarging the impact hole in an undesired manner. But also when forcibly 
driving the nails, a cortical wedge can be split off the proximal cortex 
by tangential shearing stress, which results in an undesired enlargement 
of the impact hole so that the edge of the impact hole can also collapse 
on its front side. Both cases result in the nails protruding in an 
uncontrolled manner and if the fracture extends into the bone, a torsional 
fracture of the femur may be produced by the surgeon. 
It can also occur that the bone nails are driven too far into the impact 
hole so that the coupling member no longer abuts the outer surface of the 
bone or that the coupling member abutting the outer surface of the bone 
shifts towards the medullary canal because part of the edge of the hole 
has been broken off. 
If the coupling member enters the interior of the medullary canal and thus 
disappears within the bone, this invariably results in the drawback that 
the required tension stress of the nails is reduced and the desired effect 
is thus no longer assured. If the whole nail is located within the 
medullary canal, it may be caught by the spongiosa bubbles present in the 
medullary canal and thereby prevented from sliding distally. If in such a 
case the bone is loaded so that the bone portions are brought closer 
together at the fracture site, the nail tip may perforate the condyle of 
the bone and penetrate into the socket of the hip joint (acetabulum). If 
nails having wholly entered the medullary canal are not caught by the 
spongiosa bubbles, the nails slide in distal direction and can then be 
removed only with great difficulty. For removing such nails, the impact 
hole must be enlarged to such an extent that the distal end of the nail 
located within the medullary canal can be seized. 
In order to prevent these difficulties, it has been proposed to provide an 
insert member insertable into the impact hole and provided with a guiding 
channel for the bone nail to be driven in and for the at least partial 
accommodation of the coupling member of the bone nail and fixed to the 
bone by a fixing means, for instance a screw. After insertion of the bond 
nail(s), the insert member is closed by means of a lid-shaped closure 
member preventing the shifting of the distal nail ends out of the insert 
member (U.S. Pat. No. 4,467,793). The disadvantage of this known 
embodiment resides in the fact that the bone nails shift in the medullary 
canal until their distal ends abut the side of the closure member facing 
the guiding channel where the position of the bone nails is fixed. On 
loading the bone, however, the bone fragments are brought close together 
at the fracture site and it is then convenient to shift the bone nails in 
a distal direction in order to prevent the nail tip from perforating the 
condyle, although the shifting must not be so great as to disturb the 
function of the bone nails. 
BRIEF SUMMARY OF THE INVENTION 
It is thus the object of the invention to improve an instrumentarium of the 
type initially mentioned by assuring a defined and limited shift of the 
bone nails inserted into the medullary canal in particular on subjecting 
the leg to stress, so that when the distal end of a bone nail is located 
at a larger distance from the side of the closure member facing the 
guiding channel, a comparatively unhindered movement of this nail in its 
longitudinal direction is possible, while when the distal end of the nail 
approaches the side of the closure member facing the guiding channel, this 
movement encounters increased resistance until it is finally completely 
inhibited.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a bone 1 having a fracture 2. For repositioning and fixing the 
fracture 2, three bone nails 4 consisting of elastic material and bent in 
their proximal end portion are inserted into the medullary canal 3 of the 
bone 1. To this end, the medullary canal is opened by puncturing at the 
knee joint area of the bone and an impact hole is then milled or bored by 
means of a milling cutter or a drill, the axis of the hole being so 
selected that the nails 4 can be driven in the required direction. 
Subsequently, an insert member 5 is inserted into the impact hole, ten the 
bone nails are driven in and rotated for reducing the fracture site. For 
this purpose, the bone nails are provided at their respective distal ends 
with a coupling member (not shown) permitting a wholly non-rotatable 
connection with an impact tool. The insert member 5 is provided with a 
guiding channel (see FIGS. 2 to 5) which is arranged so that the nails 
driven in arrive in the medullary canal 3 in the desired manner. The nails 
4 are driven in so far that their distal end provided with the coupling 
member is received by the guiding channel, thus does not protrude to the 
outside and does not irritate the sinews and muscles positioned above the 
impact hole. 
The insert member 5 is closed by means of a closure member 7. The insert 
member 5 and the closure member 7 are fixed by means of a screw 8 screwed 
into the bone and extending essentially perpendicularly to the axis of the 
guiding channel 6 and penetrating an opening 9 in the closure member 7 as 
well as an opening 10 aligned therewith in the insert member. A screw 8 
like this is usually required for fixing the insert member, so that a 
single screw serves for attaching the insert member 5 as well as the 
closure member 7 to the bone. 
The side 11 of the closure member 7 facing the guiding channel is provided 
with means limiting a shifting of the bone nails 4 present in the 
medullary canal 3 as a function of the position of the distal ends of the 
nails in the insert member. 
In the embodiment according to FIG. 1, a supporting body 12 connected to 
the closure member 7 by a helical spring 13 is provided for supporting the 
distal nail ends. When the nails 4 shift in the direction of the closure 
member 7, the helical spring is compressed via the distal nail ends and 
the shifting is opposed by increased resistance. 
In the embodiment according to FIG. 3, the closure member 7 is provided on 
its side 11 facing the guiding channel with an inclined surface 14 facing 
upwards on which the distal nail ends are supported. If these distal nail 
ends slide along the inclined surface 14 due to a shifting of the nails, 
the curvature of the bone nails 4 consisting of elastic material and thus 
also the tension with which the bone nails abut the wall of the medullary 
canal 3 changes, so that the friction on the wall of the medullary canal 
is increased and the shifting is thus opposed by increased resistance. 
The embodiment according to FIG. 5, the side of the closure member 7 facing 
the guiding channel 6 is provided with a projection 15 formed rotationally 
symmetrical in relation to the axis of the guiding channel and provided 
with inclined surfaces 16 on all sides along which the distal nail ends 
slide during their shifting in the direction to the closure member 7, the 
curvature of the bone nails consisting of elastic material and thus the 
resistance to a shifting changing independent of the position which said 
distal nail ends occupy in the guiding channel 6.