GB2302284A

GB2302284A - Tool for inserting an expander into an intramedullary nail

Info

Publication number: GB2302284A
Application number: GB9610113A
Authority: GB
Inventors: Erwin Ludwig Klinge
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-06-20
Filing date: 1996-05-15
Publication date: 1997-01-15
Also published as: DE19624295A1; GB9512534D0; GB9610113D0

Description

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"Insertion apparatus for an expander" 2302284 The present invention relates to an insertion apparatus for an expander designed to facilitate insertion of the expander into the medulla of a bone. This expander is designed for use in conjunction with an intramedullary nail. When conjoined, the expander and intramedullary nail form a composite expanding nail for the purpose of uniting bone fragments.

The present applicant has already disclosed an expanding nail in WO 94/12112. This teaches an intramedullary nail, selectively cross sectionally expandable along its entire length, and an expander which together, when the expander is inserted into nail, form a composite nail with a complete circumference.

The intramedullary nail placed inside the bone is configured to accommodate the insertion of an expander, the nail being in the form of an elongate tube provided with a longitudinal slit. Initially, the intramedullary nail is placed in the desired position along the axis of a bone in its unexpanded form and an expander is inserted therein such that the composite 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 is 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 expandable nail expands along its length. Insertion of the expander requires application of a degree of force to prise open the slit in the intramedullary nail.

It was anticipated that forcing means for expander insertion would be manual, comprising a substantially non-percussive mechanism. However, in practice this has proved difficult to achieve and so an alternative method of insertion has had to be devised.

According to the presentinvention there is provided an insertion apparatus for an expander for use in conjunction with an intramedullary nail, said insertion apparatus comprising a housing or frame, power supply means which supplies power in the form of a rotary motion, an axially movable member adapted to engage an expander to apply axial force thereto, driving means for driving said member to apply said force, and transmission means for transmitting power from said power supply means to said driving means.

The power supply means may be powered by pressurised gas, which may be air or oxygen or another gas. In a preferred embodiment the power supply means is a pneumatic drill. However it may be an electric motor.

Preferably the transmission means converts high speed low power rotary input of the power supply means to low speed high power axial output of the axially movable member.

In a preferred embodiment the transmission means comprises a rotary nut having an internal thread, while the driving means comprises a rod having an external thread, the rod being located within the rotary nut and constrained against rotation such that a rotation of 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 21 22 23 24 26 27 28 29 30 31 32 33 34 35 36 the rotary nut produces an axial movement of the rod.

The driving means may further comprise a thrust plate rotationally coupled to the rod.

The insertion apparatus may further comprise a first guide means for guiding the driving means, comprising a plurality of tie rods rigidly connected to the housing or frame, the tie rods passing through said thrust plate. The guide means may also include a cylindrical guide tube rigidly connected to the housing or frame such that the rod can slide in an axial direction within the guide tube.

In a preferred embodiment the transmission means further comprises a reduction gear which drives the rotary nut, and conical roller taper bearings which prevent both axial and radial movement of the rotary nut.

The insertion apparatus may further comprise a second guide means for guiding the axially movable member. This may be in the form of a sleeve rigidly connected to the housing or frame, one end of the sleeve being adapted to be fastened to an intramedullary nail.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:- Figure 1 is a cross sectional side view of a complete insertion apparatus for an expander in accordance with the present invention.

Figure 2 is a cross sectional side view of a first, rearward part of the apparatus of Figure 1.

4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Figure 3 shows a rear end view of the apparatus of Figure 2.

Figure 4 is a cross sectional side view of a second, forward part of the apparatus of Figure 1.

Figure 5 shows a front end view of the apparatus of Figure 4.

Figure 6 is a cross sectional side view of a clamp forming part of the apparatus of Figure 1.

Figure 7 shows a rear end view of the clamp of Figure 6.

Figure 8 is a cross sectional side view of a housing forming part of the apparatus of Figure 1.

Figure 9 shows a front view of the housing of the apparatus of Figure 8.

Figure 10 is a cross sectional side view of a mounting plate forming part of the apparatus of Figure 1.

Figure 11 shows a front view of the plate of Figure 10.

Figure 12 shows a cross sectional side view of a drive shaft forming part of the apparatus of Figure 1.

Figure 13 is a cross sectional side view of a disc forming part of the apparatus of Figure 1.

Figure 14 shows a cross sectional side view of a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 first gear wheel forming part of the apparatus of Figure 1.

Figure 15 shows a cross sectional side view of a second gear wheel forming part of the apparatus of Figure 1.

Figure 16 shows a cross sectional side view of a threaded nut forming part of the apparatus of Figure 1.

Figure 17 shows a cross sectional side view of a guide tube forming part of the apparatus of Figure 1 - Figure 18 shows a rear end view of the guide tube of Figure 17.

Figure 19 shows a cross sectional side view of a gripping strip forming part of the apparatus of Figure 1.

Referring to the drawings the present invention relates to an insertion apparatus for inserting an expander 1 into a hollow intramedullary nail 2 which is already in place within the medulla of a bone, to form a composite nail. The purpose of the composite nail is to unite bone fragments.

A pressurised gas source provides power to a rotor such as a pneumatic drill 3 which produces high speed rotation at low power. Pressurised gas, for example compressed air or oxygen, is generally provided in operating theatres or is at least readily available therein. Alternatively the insertion apparatus can use pressurised gas from any convenient source. It is 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 possible to use an electric motor as the power supply, when pressurised gas is not available.

The drill 3 has a collar 4 which is secured by a clamp 5. The purpose of clamping the drill 3 is to prevent it from rotating relative to the rest of the insertion apparatus thereby maximising power output.

The clamp 5 is attached to a housing 6 which is itself attached to a mounting plate 7. This arrangement keeps the drill 3 in its desired position relative to the rest of the insertion apparatus and provides a casing for the drive mechanism of the apparatus. Attached to the drill 3 is a driveshaft 10 which sits within a disc 33 and is supported between two bearings 8.

The driveshaft 10 is driven by the drill 3 to rotate at high speed. It is secured by means of a transverse pin 9 to a first gear wheel 11, and the purpose of the shaft 10 is the transmission of drive from the drill 3 to the first gear wheel 11.

The first gear wheel 11 is part of a reduction gearing mechanism in which it meshes with a second, larger, gear wheel 12. In this example, the first gear wheel 11 has 14 teeth and the second gear wheel 12 has 35 teeth.

The second gear wheel 12 is fastened to an internally threaded nut 13 which is locked to the second gear wheel 12 and is concentric with it. The nut 13 is in parallel with the driveshaft 10 and is mounted on conical roller taper bearings 29. It is constrained such that when it is turned by the gearing mechanism it is only able to do so in one plane. That is it is able 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 to rotate but, being constrained end-to-end, has no forward movement and cannot move up or down.

This nut 13 is used to drive a threaded spindle or rod 14 which is able to move only axially. The threaded spindle 14 is enclosed within a guide tube 15 which aligns and stabilises it. The guide tube 15 also acts to prevent the threaded spindle 14 from wobbling.

The threaded spindle 14 has provision for attachment to an expander 1, by means of a push member 21 and locking device 22. When the drill 3 is operated, the driveshaft 10 rotates. Rotary motion is transmitted to the threaded nut 13 which causes the threaded spindle 14 to move forwards, and this forward movement of the threaded spindle 14 acts to push the push member 21, which then pushes the expander 1 into the medulla of a bone as described in greater detail below.

This nut 13 and threaded spindle 14 arrangement can be used to vary the mechanical advantage developed by the insertion apparatus. The advantage developed is dependent on the number of threads per unit length of the spindle 14.

This threaded spindle 14 extends from the mounting plate 7 towards a front end plate 16, which is rigidly connected by tie rods 17, 18 to the mounting plate 7. To the front end plate 16 is also connected a gripping strip or rail 30, to which may be fastened a handle. In use the apparatus may thus be guided by holding the handle attached to the rail 30 in one hand, while holding the drill or other power supply means 3 in the other hand. Preferably the gripping rail 30 is provided with several holes, so that the handle may be connected in the most appropriate position for the task 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 being carried out.

A thrust plate 19 is provided which can move along the tie rods 17,18 in a substantially straight line between the mounting plate 7 and the front end plate 16. The forward end of the threaded spindle 14 engages the thrust plate 7 which moves forward with the movement of the spindle 14. Rotation of the thrust plate 19 is prevented by the tie rods 17. 18 which pass through holes in the thrust plate. The spindle 14 may be hollow or solid and is rotationally coupled to the thrust plate 19, for example by means of a pin 25, so that the threaded spindle or rod 14 is also constrained against rotation.

On the opposite side of the thrust plate 19 to the threaded rod 14 is a projecting portion 20. The projecting portion 20 is attached to a push member 21, configured to engage and apply a pushing force to an expander, by a locking device 22 which provides a first pin 23 which passes through the projecting portion 20 and a second pin 24 which passes through the push member 21. In this way the threaded spindle 14 is connected securely to both the thrust plate 19 and the push member 21 during insertion of the expander 1. The push member may be secured to the expander 1 by a pin (not shown).

The insertion device includes two pins 26 which, in use, engage apertures in a hollow intramedullary nail 2 in order to secure the device to the nail 2. The pins 26 are attached to a sleeve member 27 which serves to guide the push member 21 and which is securely fastened to the front end plate 16. The sleeve member 27 fits around and engages the outside of the nail 2, facilitating insertion of the pins 26 into the 9 1 2 3 4 6 7 8 9 10 11 12 13 14 15 16 17 18 19 apertures wherein they are secured by a circlip 28. This circlip 28 can be slid over the pins to prevent the pins from disengaging during the insertion procedure. The circlip 28 can also serve to hold the several parts of the sleeve member 27 together in the case where the sleeve member 27 is formed of more than one part.

Once the expander 1 is inserted in the intramedullary nail 2, the insertion apparatus may be disconnected from the expander 1.

The expander 1 itself is now part of a composite nail and will remain in position until it is required that the intramedullary nail be contracted for its repositioning or removal. The above insertion process may thus be reversed to remove the expander 1 and allow the intramedullary nail to revert to its unexpanded state.

21 For this purpose the push member 21 may be replaced by a pull member configured to engage and apply a pulling force to an expander 1.

22 23 24 25 26 27 28 29 31 32 33 34 35 36 Previous apparatus for insertion were found to suffer badly from the effects of friction. Thus, with this method of insertion, conical taper roller bearings 29 were introduced. Such bearings 29 take axial load in addition to radial load, and in so doing increase efficiency and decrease wear.

It is expected that this means of insertion of an expander 1 for an intramedullary nail 2 will make employment of such nails 2, which are valuable medical aids, much more widespread. The insertion means is designed to facilitate both initial insertion of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 expander 1 and construction of the complete expanded nail, and to allow removal or repositioning of the nail with comparative ease when necessary. The insertion apparatus requires only low power, so it can make use of simple power supply means such as compressed gas, which is readily available in operating theatres. The guide tube 15, guided thrust plate 19 and sleeve member 27 ensure that the expander is inserted in a straight line at a constant angle, without fluctuations in alignment. The use of a rotary nut 13 and threaded rod 14 in the transmission means ensures that insertion of the expander 1 takes place smoothly, at a constant rate and in a controlled manner.

Modifications and variations of the above described embodiments can be adapted without departing from the scope of the invention.

Claims

1 CLAIMS 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25

26 27 28 29 30 31 32 33 34 35 36

11 1. An insertion apparatus for an expander for use in conjunction with an intramedullary nail, said insertion apparatus comprising - a housing or frame, - power supply means which supplies power in the form of a rotary motion, - an axially movable member adapted to engage an expander to apply axial force thereto, - driving means for driving said member to apply said force, and - transmission means for transmitting power from said power supply means to said driving means.

2. An apparatus as claimed in Claim 1 wherein said power supply means is powered by pressurised gas.

3. An apparatus as claimed in Claim 2 wherein said pressurised gas is air or oxygen

4. An apparatus as claimed in one of Claims 1 to 3 wherein said power supply means is a pneumatic drill

5. An apparatus as claimed in Claim 1 wherein said power supply means is an electric motor.

6. An apparatus as claimed in one of Claims 1 to 5 wherein said transmission means converts high speed low power rotary input of said power supply means to low speed high power axial output of said axially movable member.

7. An apparatus as claimed in one of Claims 1 to 6 wherein said transmission means comprises a rotary 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 nut having an internal thread and said driving means comprises a rod having an external thread, said rod being located within said rotary nut and constrained against rotation such that a rotation of said rotary nut produces an axial movement of said rod.

8. An apparatus as claimed in Claim 7 wherein said driving means further comprises a thrust plate rotationally coupled to said rod.

9. An apparatus as claimed in Claim 8 wherein said insertion apparatus further comprises a first guide means for guiding said driving means, said first guide means comprising a plurality of tie rods rigidly connected to said housing or frame, said tie rods passing through said thrust plate.

10. An apparatus as claimed in Claim 9 wherein said first guide means further comprises a cylindrical guide tube rigidly connected to said housing or frame such that said rod can slide in an axial direction within said guide tube.

11. An apparatus as claimed in one of Claims 7 to 10 wherein said transmission means further comprises a reduction gear which drives said rotary nut.

12. An apparatus as claimed in one of Claims 7 to 11 wherein said transmission means includes conical roller taper bearings which prevent both axial and radial movement of said rotary nut.

13. An apparatus as claimed in one of Claims 1 to 12 wherein said insertion apparatus further comprises a second guide means for guiding said axially 1 2 3 4 5 6 7 8 9 11 12 13 14 15 13 movable member.

14. An apparatus as claimed in Claim 13 wherein said second guide means comprises a sleeve rigidly connected to said housing or frame, one end of said sleeve being adapted to be fastened to an intramedullary nail.

15. The use of an apparatus as claimed in one of Claims 1 to 14 to insert an expander into an intramedullary nail.

16. An insertion apparatus as hereinbefore described with reference to the accompanying description and drawings.