WO2012003555A1

WO2012003555A1 - Nail device

Info

Publication number: WO2012003555A1
Application number: PCT/BE2011/000044
Authority: WO
Inventors: Norbert De Jonghe
Original assignee: Jeannor Bvba
Priority date: 2010-07-09
Filing date: 2011-07-11
Publication date: 2012-01-12

Abstract

The invention relates to a nail device (35, 50) for repairing bone defects, suitable to be attached to two main bone fragments (36, 37) and stretching out the bone defect, with the length of the device between the main bone fragments (34, 37) able to increase and/or decrease in a hydraulic progressive way, causing new bone tissue in the caused openings, the nail device (35) comprising: a proximal end part (40) provided with one or more proximal locking holes (4, 5) and a hydraulic active actuator (2), a distal end part (41) provided with a nail or bar (8) that can slide in and/or out; the nail (8) is provided with distal locking holes (9), and here between extends a double cylindrical housing (38) in which in the center the nail (8) is provided extendably and with a flexible supply pipe (1) for the supply of hydraulic fluid, removable attached to the hydraulic active actuator (2) with the flexible supply tube (1) preferably bolted to actuator (2).

Description

NAIL DEVICE

TECHNINAL FIELD The invention relates to a nail device for repairing bone defects. The nail device is suitable to be attached through a long bone in two main bone fragments and extending through the bone defect, whereby the length of the device between the bone fragments can progressively increase and / or decrease in a hydraulic manner causing spaces where bone tissue can be developed and grow to the bone. The nail device according to the invention can be performed for combined compression / extension, compression only, as a transport nail for transporting a intermediate bone segment or just for lengthening.

BACKGROUND AND PRIOR ART

In the prior art bone distractors, or also even in the English literature, lengthening nails are known. Nail devices that procure both compression and lengthening are only known in the external ring fixator of Gravriil A. Ilizarov US 4 615 338.

A known nail device from Folia Traumatologica Lovaniensia 2007, "The hydraulic lengthening nail for lengthening the lower limb. A prospective cohort trial of thirty-four nails" ISBN 90807978 p.74-82 comprises a proximal end provided with proximal locking holes, a hydraulic active actuator, and a distal end provided with an extendable nail or bar, the nail provided with distal locking holes. The locking apertures are suitable for lifting up the corresponding screws so that the proximal part of the device is attached to the proximal main bone fragment and according to the distal side of the nail to the distal main bone fragment. The nail is axially extendable contained in a cylindrical housing by means of a hydraulic system. After application of the device the pressure in the cylindrical housing is being increased once every day, through the connection of an external hand pump. This pressure increase pushes the lowest nail down. When this shift happens slowly (0.5 to 1.3 mm / 24 h), bone tissue is spontaneously grown in the distraction space, which makes it possible to extend the bone up to 8 cm. The disadvantages of this known nail are numerous. The supply of hydraulic fluid takes place by means of a rigid metal supply tube, which is connected radially sideways to the actuator. This provides sealing problems and increases the risk of infection. Moreover, there is also a short of rotation- and axial movement stability against the cylindrical housing. This known device is being fixed into a desired end position of the bar through many of the provided drilling operations, so that the mechanical strength is significantly weakened.

In addition, there are currently three systems globally applicable: a) the ring fixator of Gavriil A. Ilizarov US patent No. 4 615 338, b) the mechanical lengthening nail of J.M. Guichet (also referred to as Albizzia nail) WO 200404531, Grammont Paul CA 1335952, Alexander Bliskunov US patent No 7 530 981, J. Dean Cole (also referred to as ISKD nail) US patent No. 7 018 380 and 7 041 104 and c) the elektronical lengthening nail of A. Betz (also referred to as fitbone) from US patent No. 6 245 075.

With Ilizarov, no matter which device can be applied for compression and lengthening, the limb is being fixed by means of several rings connected to the bone with thin metal pens. To guarantee the stability of the construction, the pens are being put under pressure (100 kg). For each ring two metal pins need to be drilled through the member. The bone is being lengthened through external threaded rods. By replacing a few nuts on the threaded rod, the rings can be separated or brought closer. The advantage of this technique is its reproducibility and robustness. The main complications are a) pain during the lengthening because the metal pins cut through the skin to allow distraction between the rings, b) infections of the skin because of prolonged contact with the skin, c) bending of the bone because the newly formed bone is not always of good quality and inflection of the limb can be induced, d) psychological problems with long-term presence of an external metal frame on the arm or leg.

With the mechanical lengthening nails, the limb has to be turned 54 times a day, to activate the double gear system in the nail. With the Albizzia nail, the operated bone should be turned to 20° before the gear system is activated. With the ISKD nail, this torsion is reduced to 3°. An advantage of the mechanical systems is that the whole is built into the patient, which would reduce the risk of infection. A disadvantage of the Albizzia is the large turning angle required to activate the gear system. The latter reduces the patients comfort significantly. With the ISKD nail, the turning angle is smaller (3°), but gives a specific disadvantage that the preprogrammed nail may bolt, with the result of a sudden lengthening of several centimeters in one day. This sudden lengthening of the limb can cause paralysis, necrosis of tissue and delayed bone healing. Both nails have the same disadvantage: the nails are straight which make it more difficult to insert the nail in a, by nature, curved bone.

The electromotive nail (also referred to as fitbone) has the same advantage as the mechanical lengthening pen; they can be placed entirely internal. Noted as an important disadvantage: rust and withdrawal of the lengthening. In some cases pseudotumors were determined as consequence of this rusting.

Scientific and experimental implants were also described by Gotz & Schellmann however they were never put into practice in : "Continuous lengthening of the femur with intramedullary stabilisation". Archiv. Orthopadische Unfall-Chirurgie 82: 305-310, J.F. Bergmann Publishing. Munich (1975).

The invention aims to partially eliminate these disadvantages and provide therefore a device according to claim 1. In the subsequent claims the preferred forms are being explained.

The nail device according the invention can be employed for combined compression - lengthening, only for compression, as a transport nail, or as a nail extension.

SHORT DESCRIPTION OF THE ILLUSTRATIONS

The preferred embodiments of the nail devices according to the invention are shown in the picture. Cross sections along the length show:

Figure la en lb a lengthening nail device in a long bone and a lengthening nail device as such,

Figure 2 the proximal part of a nail device adjacent to a pressure chamber and a piston,

Figure 3 an anti-rotation system in the middle part of the device of Figure 1 where the rotation of the extendable nail is being obstructed with respect to the cylindrical housing,

Figure 4 the distal end of the device of Figure 1 provided with an extension piece,

Figure 5a, 5b and 5c the anti-return system of a lengthening nail which avoids collapse or withdrawal of the nail back upwards,

Figure 6a and 6b a transport nail device in a long bone and the transport nail device such as,

Figure 7a and 7b the device of Figure 6 after transport at At interval,

Figure 8 the middle of a distraction-lengthening or a transport nail device, Figure 9 the distal end of a distraction-compression or a transport nail device,

Figure 10a en 10b a compression-distraction nail device in a long bone and the compression-lengthening nail device such as,

Figure 11a en lib the device of Figure 10 after compression at At interval,

Figure 12 the detail of an actuator of a preferred embodiment of a nail device according to the invention,

Figure 13a en 13b a transport nail device in a long bone and a transport nail device such as single hulled housing,

Figure 14a and 14b the device of Figure 13 after transport at At interval. TERMS OF NUMBER INDICATION

1. Supply tube

2. Actuator

3. Middle part liquid transit

4. Proximal locking hole - frontal sight

5. Proximal locking hole - sagittal sight

6. Outer cylinder

7. Inner cylinder

8. Extendable bar/nail

9. Distal locking hole

10. Positioning slots

11. Locknut

12. Conical coupling

13. Check valve with spring

14. Valve housing

15. Sealing

16. Transit canal

17. Pressure room

18. Piston/pestle

19. Slot

20. Locking plate or wedge

21. Long piston/pestle with guide

22. Extension bar/nail

23. Coupling of the bars

24. Recessed locking system

25. Locking bolt with locking bars

26. Expansion spring

27. Double-sided long slot

28. Middle transport screw

29. Distal transport boring

30. Lock screw

1. Anti- rotation screw

2. Double sided short slot

3. Transverse compression screw 4. Short piston/pestle with guide 35. Extension nail device

36. Proximal main bone fragment

37. Distal main bone fragment

38. Double cylindrical housing

39. Long bone

40. Proximal end part

41. Distal end part

42. Expansion slot

43. Steps in slot

44. Lateral boring for insertion of the nail

45. Double pressure springs

46. Anchor pin

47. Manual positioning for extension

48. Rotation/fixation locking screw

50. Compression-distraction/transport nail device

51. Single-hulled housing

DETAILLED DESCRIPTION OF THIS INVENTION

In one embodiment according the invention, the nail device is an extension nail device, for this reference is made to figures 1-5.

A nail extension device 35 according to the invention is suitable for repairing bone defects. The device 35 is normally installed in the long bone 39 and attached to two main bone fragments (proximal 36 and distal 37). The device stretches over the bone defect or the bone fracture. The length between the main bone fragments increases progressively, because the nail 8 is renounced hydraulically out of the housing. When this occurs gradually, it is possible for new bone tissue to form in the caused opening. The nail extension device 35 comprises of a proximal end part 40 with proximal locking holes 4, 5, a hydraulic employed actuator 2 in a liquid transit 3. The axial extendable nail or bar 8 is situated in the distal end part 41. The nail 8 is provided with distal locking holes 9. Between the distal 41 and the proximal 40 end part, a double cylindrical housing 38 reaches out in which the nail 8 is axially and centrally extendable partially included. A flexible supply tube 1 for supplying a hydraulic fluid is removable attached to the hydraulic employed actuator 2 in the proximal end part 40. Preferably, the flexible supply 1 is connected by screws with the actuator and this supply can be easily tightened with and screwed in the actuator 2.

A nail extension device 35 according to the invention aims to extend bone and soft tissue of a long bone 39 - usually in human applications - by dosed increase of fluid pressure in a pressure room 17 of a cylindrical housing 38. By externally or internally conducting a pressure increase in the device 35, the central nail is being pushed out of the double cylindrical housing 38. The pressure increase can occur continuously or preferably discontinuously. By a firm anchoring to the main bone fragments 36, 37, this will result in marrow extension and subsequently to an extension of the bone. The space formed between the main bone fragments is progressively filled with own bone tissue. Initially, the treating doctor takes out the soft marrow tissue in the defect bone by using cutters that can be installed on the flexible support rod system. The bone is taken through and the extension nail 35 is inserted. The extension nail device 35 is being connected proximally and distally to the main bone fragment 36, 37 with screws 31. Through an external flexible supply tube 1, for example made from synthetic material possibly reinforced with steel wire or a metal or a suitable alloy, the doctor will put sterile the hydraulic fluid (usually oil) under pressure in the extension nail device 35 to pressurize the pressure room via actuator 2. For this the doctor normally uses an external pump, which can insert hydraulic fluid, manually, electronically or by piezoelectric mechanisms, through a supply tube 1 in the extension nail device. Internally installed fluid reservoirs under pressure, which can in an autonomous way realize (not shown) a pressure increase in the pressure room 17, can also be used. A one-way valve made of synthetic material or metal seals the hydraulic chamber so that no fluid can escape or return from the hydraulic room. A supply tube 1 in metal or polymer makes a fluid connection with the hydraulic room. This supply can consist of a small flexible tube that can go out of the skin and connect with a reservoir which can also be installed internally or externally. When the tube 1 stretches through the skin, the end can be connected through a coupling with a mechanical hand pump or any other drive unit, either mechanical, electromechanical or by piezoelectric means. Preferably, the flexible supply tube 1 is bolted to the actuator 2; for example, by means of a lock nut 11 and a conical coupling 12. The cylindrical housing 38, in which the nail 8 is situated, comprises an outer cylinder 6 and an inner cylinder 7.

A mechanical system (24, 25, 26, figure 5a) provides additional locking of the nail 8 in the inner cylinder 7 so that the nail cannot retract. This anti-reverse mechanism may comprise a locking pin 25 mounted on a spring 26 which is installed, so that it can be dragged, in separate circular recesses 24. The anti- reverse mechanism can also comprise a serrated plate, which connects with its negative in the full part of the nail 8. This serrated plate can only move in one direction and prevents axial withdrawal or retraction of the nail 8.

Separate interchangeable distal ends of extension 22 (straight or curved) can be connected to the distal end of the nail 8 to adapt the nail to different lengths and eventually different shapes of bone. These ends are provided with locking holes 9 for receiving screw 31, which can be anchored to the bone. These openings or bore holes can be provided with (not shown) expanding plugs in a suitable material, for example a plastic material to improve the screw anchoring in the device 35. The proposed extension pins are designed for the femur and the lower leg, but the principle can be used for the extension of any other long bone.

Figure la and lb show an extension nail 35 which is provided at its proximal end 40 with a flexible, foldable and thin supply hose or supply tube 1 for supplying the hydraulic fluid. The supply tube 1 is detachable connected to a central lumen of the actuator 2. This supply tube can be made from of or another suitable biocompatible material such as synthetic material.

In an embodiment according to the invention, the supply tube 1 is made of synthetic material, for example polyamide. Preferably, the flexible supply tube is screwably connected to the actuator. This screwable connection assures no leakage of the hydraulic fluid in the long bone. In this embodiment, it is easy to screw the flexible supply tube 1 loose from the actuator 2. This can be done by turning the supply tube; there are no additional tools necessary. Furthermore, this embodiment has to its advantage that the supply is flexible as from its connection point with the nail. This increases the ease of use and comfort of the patient. The flexible supply tube can be easily worn partly on the body.

There is a valve 13, in the actuator 2 and under the connection of the supply tube, provided in the middle part 3 where proximal locking holes or boring holes 4 for anchoring are installed, in the coronal side and 5 in the sagittal side. These locking holes are used for receiving and the fixation of osteosynthesis screws 31 for attachment to the proximal main bone fragment 36. 6 shows the outer cylinder or tube segment and 7 shows the inner cylinder or tube segment, provided with the extendable bar or nail 8. At the distal end of the extendable bar/nail 8, distal locking holes or boring holes 9 are provided, through which screws can be placed to the distal main bone fragment 37. These openings or boring holes can be provided with a blocking system (e.g. by means of an expanding plug) which fixes the screws. These expanding plugs can be resorbable, made of a metal or a non-resorbable polymer.

The flexible supply tube 1 can be made with every biocompatible material, either synthetic material or metal. This tube 1 leads hydraulic fluid from an internal reservoir or is connected with an (not shown) external coupling. This coupling can be provided with an external pump. The flexible tube 1 (figure 2) is connected in the valve housing 14 central the actuator 2, through a conical coupling with a lock nut 11. The actuator 2 is provided with two or more, for example four, positioning notches 10 to place the weft device correctly in the nail 8. The valve with coil spring 13 is located in the lower part of the valve housing 14. The valve housing 14 is screwed into the actuator 2. Through a small hole the valve housing is connected with the actuator with a welding point. To avoid loss of pressure, a seal 15, of biocompatible elastomer that does not tear when turning in the valve housing, is installed between the valve housing and its recipient.

A channel 16 connects the valve housing with the pressure room 17. The connection channel 16 is located through the middle part 3 where the proximal locking holes 4 and 5 are situated. The pressure chamber (fluid chamber) 17 is located in the double hulled cylinder 6 and 7 where the piston/pestle (figure 3) are located. This piston/pestle 18 is pushed axially down (in the direction of the upper distal part) by the fluid pressure built up. This piston/pestle 18 has a double system of circular elastomeric shock absorbers that provide a good sealing between the piston/pestle 18 and the inner cylinder 7. This perfect sealing is necessary to retain the pressure between the non-return valve 13 and the piston/pestle 18.

Figure 3 is a detailed view of the central part of the extension nail device 35. The bar or nail 8 is in a double hulled cylindrical housing, with an outer cylinder 6 and an inner cylinder 7. This nail 8 is lengthwise provided with a shallow wedge-slot 19 in which fits an oval security plate or a wedge 20. This oval security plate 20 is fixed in a corresponding oval opening in the inner cylinder 7. The full bar 8 with the longitudinal wedge-slot can move along the security plate 20 which gives sufficient rotation stability to the extension nail 8, during the sliding out.

Figure 4 illustrates the distal aspect of the cylinder 6 and 7 with the possibility of longitudinal movement (see: arrow) of the bar/nail 8. Various attachments or extensions 22, which can extend the length of a full bar 8, are provided as well. This extension 22 is fixed in advance on the fixed bar 8 with locking screw 23. These extensions can be provided with openings or slots 9. In these openings or slots 9, multiple screws 31, which provide the extension pieces 22 the necessary stability, can be inserted. These parts for extension or attachment 22 are straight or slightly bent to be able to follow the flection of the bone.

Figure 5a, 5b and 5c illustrate a magnified view of the part of the inner cylinder 7. Its inner wall is provided with asymmetric recesses 24. A mechanic blocking mechanism, comprising of one or two round bars 25, is pushed apart by spring 26 in the recesses 24. This coil spring, acting as lock pin, is provided through the nail 8 and slides over the serrated wall 24 of the inner cylinder 7 in downward direction. In an embodiment according the invention, the recesses 24 define a regular fringe pattern, preferably a fringe shark fin pattern. Every time this security pin ends up in a recess 24, this avoids the reverse of the fixed bar 8 in the upward direction.

In a preferred embodiment according to the invention the mechanical blocking system comprises a wedge 20 in contact with double pressure springs 45 (figure 5c), which are provided with anchor pins 46. This anchor pins 46 are installed in the steps 43 in the slots, so that they the can be dragged. The wedge 20 can only move in one direction and prevents axial withdrawal or retraction of the nail 8 and prevents rotation of the nail 8 in the inner cylinder 7. Figure 12 shows the detail of an actuator 2. This actuator includes positioning slots 10 at the upper edge. Such slots are suitable to hold a bracket (not shown) in its position during the installation of a nail device into a patient. The raised edges of the positioning slots show an inclination.

In an embodiment according to the invention, the nail device is a compression- distraction or a transport nail device, referred to in figures 6-11 and 13-14.

A compression-distraction nail device 50 (figure 10a and 10b) according to the invention is suitable for repairing bone defects. Normally the device is installed in a long bone 39 and attached to two main bone fragments (proximal 36 and distal 37). The device stretches out of the bone defect or fracture. At first the length between the two main bone fragments decreases progressively, because the nail 8 is being hydraulically brought back in the housing 38 by means of fixing it on a temporary - during the compression installed screw, the compression screw 33. The compression screw 33 is situated in the bone fragment and through the nail device 50. The compression screw 33 is situated in a slot 32 in the length of the device. The length of the slot 32 determines the maximal length of the compression. After the compression, the compression screw 33 is removed and the extension can take place between the screws 31. When this occurs gradually, new bone tissue can be formed in the caused spaces. It is obvious that the compression and the extension can take place on different planes of fractures. Sometimes it is advantageous to apply a new plane of fracture (for example: in a healthy bone segment) before the distraction or the extension takes place.

Extension after compression/distraction is possible through the expansion slot 42 (see figure 9). The slot 42 has an opening at the bottom and comes up to a narrower width upwards. In this slot, a screw can be placed with a diameter smaller than the width of this slot 42. This allows the nail 8 to shift axially over said screw under hydraulic pressure. When the desired length is reached, a screw 31 is installed in the opening at the bottom and through the bone fragment, so that the nail 8 is fixed again. The length of the slot 42 determines the maximal length of the extension.

The compression - distraction nail device 50 comprises a proximal end 40 provided with proximal locking holes 4, 5, a hydraulic active actuator 2 in the fluid transit 3. In the distal end part 41 the axially extendable nail or bar 8 stretches out. The nail 8 is provided with distal locking holes 9. Between the distal 41 and the proximal end 40, a double cylindrical housing 38, in which axially and centrally the nail 8 that can slide is installed, stretches out. A flexible supply tube 1 for supplying a hydraulic fluid is detachably connected to a hydraulic active actuator 2 in the proximal end 40. Preferably, the flexible supply tube 1 is screwably connected to the actuator and this tube 1 can easily be screwed tighter and into the actuator 2.

A compression - distraction nail device 50 according to the invention aims to - usually for human applications - shorten the bone and soft tissue and then lengthen a long bone 39 by dosed increase of fluid pressure in the pressure room 17 of the cylindrical housing 38. By external or internal pressure increase in the device 50, the central nail 8 is pushed out the double cylindrical housing 38. The pressure increase can occur continuously or preferably discontinuously. By a firm anchoring to the main bone fragments 36, 37, this will first lead to a compression, by fixing on the compression screw 33, and then lead, after removing the compression screw 33, to marrow extension and extension of the bone. The space formed between the bone fragments is progressively filled with own bone tissue. Initially, the treating doctor will remove the soft marrow tissue in the defect bone by using cutters that can be mounted on a flexible support rod system. The extension nail 50 is inserted. The compression - distraction nail device 50 is being connected proximally and distally with screws 31 to the main bone fragments 36, 37. Through an external supply tube 1, for example a synthetic material possibly reinforced with steel wire or a metal or a suitable alloy, the doctor will insert sterile the hydraulic fluid (usually oil) under pressure in the compression - extension nail device 50, so that he can put the pressure room under pressure through the actuator 2. For this the doctor normally uses an external pump, which inserts hydraulic fluid, either manually, electronically or through piezoelectric mechanisms, through an external connection through supply 1 in the compression - distraction nail device 50. Internally installed fluid reservoirs under pressure, which can build up a pressure increase in the pressure room 17 in an autonomous way (not shown), can also be used. A one-way valve made from synthetic material or metal seals the hydraulic room so that no fluid can escape from the hydraulic room and return. A supply tube 1 in metal or polymer makes a fluid connection with the hydraulic room. This supply can preferably comprise a small flexible tube which goes through the skin and connects with the reservoir which can also be installed internally or externally. When the tube 1 pulls through the skin, away from the incision for applying the compression - extension nail device, the end can be connected through a coupling with a mechanical hand pump or any other drive either mechanical or electromechanical or in a piezoelectric way. Preferably, the flexible supply tube 1 is screwed to the actuator 2, for example by means of a locking nut 11 and a conical coupling 12.

Figure 10a and 10b show a compression - distraction nail 50 that is provided at its proximal end with flexible, pliable and thin supply hose or supply tube 1 for the supply of a hydraulic fluid. The supply tube 1 a simple detachably connected with a central lumen of the actuator 2, and preferable bolted. This supply tube 1 can be made of metal or any other suitable biocompatible material, such as synthetic material. In an embodiment according to the invention, the supply tube 1 is made of synthetic material, for example polyamide. In the actuator 2 and under the connection of the supply tube, there is a check valve 13 provided in the middle part 3 in which proximal locking holes or boring holes are made, 4 in the coronal side and 5 in the sagittal side for anchoring. These locking holes are used for the installation and the fixation of the screws 31 and 33 for attachment to the proximal main bone fragment 36.

The screws 31 are used for a compression - distraction nail through the distal bone fragment and through the openings 9 before the compression takes place. The transverse compression screw 33 is placed through the proximal main bone fragment 36 so that it is positioned in the slot 32. It is after compression/distraction has taken place that the screws 31 are being placed in the openings 4, 5. This is shown in figures 11a and lib. In this figure, both bone fragments are put in contact with each other and the screws 31 are installed to ensure this position. If necessary, the bone can be lengthened in this stadium by shifting the nail 8 in the expansion slot 42.

6 shows the outer cylinder or tube segment and 7 shows the inner cylinder or tube segment provided with the extendable bar or nail 8. At the distal end of the extendable bar/nail 8 are distal locking holes or boring holes provided, through which screws can be inserted to the distal main bone fragment 37. These openings or boring holes can be provided of a blocking system (for example, by means of an expanding plug) which fixes screws. These expandable plugs can be made of resorbable, metal or a non resorbable polymer.

The flexible supply tube 1 can be made with every biocompatible material, either synthetic material or metal. This tube 1 leads a hydraulic fluid from an internal reservoir or is in connection with an external coupling (not shown). This coupling may be provided with an external pump. The flexible tube 1 (figure 2) is connected by a conical coupling 12 with a lock nut 11 in the valve housing 14 central in the actuator 2. The actuator 2 is provided with two or more, for example four positioning openings 10 to correctly perform the positioning appliance to the device 50. The valve with coil spring 13 is at the bottom part of the valve housing 14. The valve housing 14 is tightened into the actuator 2. Through a small hole the valve housing is connected with the actuator through a welding point. To avoid pressure loss, a sealing, made of biocompatible elastomer that does not tear during the turning of the valve housing 14, is provided between the valve housing and its recipient.

A canal 16 connects the valve housing with the pressure room 17. The transit canal 16 is situated through the middle part 3 where the proximal locking holes 4 and 5 are located. The pressure room (fluid room) 17 is situated in the double hulled cylinder 6 and 7 where the piston/pestle 18 is located. This piston/pestle 21 is being pushed downwards (in a direction of the upper distal part) by the pressure built up. This piston/pestle 21 is provided with a double system of circular elastomeric shock absorbers that provide a good sealing between the piston/pestle and the inner cylinder 7. This perfect sealing is necessary to retain the pressure between the check valve 13 and the piston/pestle 21.

Figure 6a and figure 6b show a transport nail 50 before the transport takes place. For this, screws 31 are installed in the proximal 36 and the distal 37 main bone fragment. The bone is broken in an additional place so that an intermediate bone is obtained. In this intermediate bone fragment, the transport screw 28 is placed through the housing 38. The direction of movement of the intermediate bone fragment is visualized with an arrow. In the middle part 38, a longitudinally-oriented longer slot 27 is situated. In this slot, the transport screw 28 is placed, against the long piston/pestle 21 with guide 21. Just below the slot a transverse opening 29 is situated. At the end of the procedure (bone transport) the shifted bone segment is additionally fixed by an osteosynthesis screw 30. This screw is placed subcutaneously in the transverse opening 29 and prevents the retraction of the bone segment.

Figure 7a and 7b show the transport nail from figure 6, after transport has occurred of the intermediate bone fragment at an interval t+At. The movement of the intermediate bone fragment occurs at a speed which allows the growth of new bone tissue in the caused openings. Once the intermediate bone fragment is against the distal bone piece, the locking screw 30 is installed in the distal transport boring hole 26. This ensures the position of the bone fragments.

Figure 8 is a detailed view of the middle part of the transport nail, with an illustration of the long piston (pestle) with conduction. The long piston (pestle) 21 with guidance is being pushed downwards under pressure in the double- sided slot 27 and consequently moves the transport screw 28, which is situated in the bone segment, and this transport screw moves the bone segments downwards. Just below the slot, there is a distal transport boring hole 29, where the osteosysthesis fixation screw 30 is placed, at the end of the distraction.

After the compression, bone extension is possible, by removing the compression screw 33 (figure 10b). This allows the long piston/pestle 21 to be pushed further against the distraction bar or nail, which is pushed further downwards. The movement of the compression screw provides a movement of the most proximal bone segment until it makes contact with the lowest bone segment. This allows a pressure to build up progressively in the fracture, which accelerates the recovery process.

After the transport, bone extension is possible, by removing the transport screw 28 (figure 8). This allows the long piston/pestle 21 to be pushed further against the distraction bar or nail, which is also being pushed further downwards.

Then, when the transport screw or the compression screw is removed, an extension of the bone can be done, when the actuator is activated again. In this case, the bone extension has to be done before the complete bone healing at the level of the fracture is visible. For this the nail 8 is moved over the screw which is installed at the expansion slot 42.

The bar or nail 8 is located in the double hulled cylinder housing, with an outer cylinder 6 and an inner cylinder 7.

Figure 9 shows the distal aspect of a compression/distraction nail or a transport nail. The nail 8 can, before the device in installed in the patient, be shifted in or out the housing 38 in a certain number of fixed positions 47. In the housing, a lateral boring hole 44 is provided for shifting the nail in. Once the nail is positioned in the correct position in respect to the housing, the locking screw 48 can be secured. This screw 48 also prevents further rotation of the nail 8.

Figure 13a and 13b show a preferred embodiment of a transport nail 50 before the transport takes place. In this embodiment, the cylindrical housing 51, which extends between the proximal end part 40 and the distal end part 41, is single hulled. This embodiment has the advantage that the axial powers, which are transferred to the side walls, can be absorbed better. Because there is only one housing, it has a thicker wall and it is also stronger.

Figure 14a and 14 b show the transport nail in figure 13, after transport has taken place of the intermediate bone fragment at an interval t+At.

In this preferred embodiment (figures 13 and 14), the manual positioning for extension elements 47 and 48 are also provided on the distal part of the transport nail.

Claims

1. A nail device (35, 50) for repairing bone defects, suitable to be attached to two main bone fragments (36, 37) and stretching over the bone defect, whereby the length of the device between the main bone fragments (34, 37) is able to increase and/or decrease in a hydraulic progressive way, so that new bone tissue in the caused openings can be formed, the nail device (35) comprising : a proximal end part (40) provided with one or more proximal locking holes (4, 5) and a hydraulic active actuator (2), a distal end part (41) provided with a nail or bar (8) that can slide in and/or out; said nail (8) is provided with distal locking holes (9), and here between extends a double cylindrical housing (38) in which the nail (8) is generally provided extendable and whereby a flexible supply tube (1) for the supply of hydraulic fluid is removable attached to the hydraulic active actuator (2) whereby the flexible supply tube (1) is preferably bolted to the actuator (2).

2. A nail device (50) according to claim 1, characterized in that through the cylindrical housing (38) a nail or screw (28, 33) can be stretched out in a slot (32).

3. A nail device (35, 50) according to claim 1 or 2, characterized in that the flexible supply pipe (1) is provided with a locking nut (11) and a conical coupling (12).

4. A nail device (35, 50) according to any of the claims 1-3 characterized in that the hydraulic active actuator (2) is provided with a preferably spring-employed check valve (13), and provided between the connection of the flexible supply pipe (1) and the cylindrical housing (38).

5. A nail device (35, 50) according to any of the claims 1-4, characterized in that the cylindrical double housing (38) is provided with an inner cylinder (7) in which a pressure room (17) is sealed by a piston/pestle (18, 21).

6. A nail device (35, 50) according to claim 5, characterized in that the piston/pestle is provided with sealing rings.

7. A nail device (35, 50) according to any of the claims 1-6, characterized in that the nail (8) is provided with means to improve the position stability, with the result that freedom of rotation and axial retraction can be avoided.

8. A nail device (35, 50) according to claim 7, whereby the nail is provided with a slot (19) and the inner cylinder (7) is also provided with a corresponding slot (19) in which a slidingly journalled locking plate or wedge (20) is provided .

9. A nail device (35, 50) according to any of the claims 7 or 8, characterized in that the inner wall of the inner cylinder (7) is provided with recesses and the nail is provided with a corresponding mechanical active locking pin (25) so that the nail (8) is one-way slidingly journalled in the cylindrical housing.

10. A nail device (35, 50) according to claim 9, whereby the locking pin (25) grips spring-employed (through spring 26) in the recesses (24).

11. A nail device (35, 50) according to claim 9 or 10, whereby the recesses (24) describe a regular fringe pattern, preferably a fringy shark fin pattern.

12. A nail device (35, 50) according any of the claims 1-11, characterized in that the distal end of the nail (8) is suitable for being extended with an extension piece (22), said extension piece (22) can be connected to the nail (8) by means of transverse openings (23) and corresponding screws.

13. A nail device (35, 50) according to any of the conclusions 1-12, characterized in that the device is provided with an external hydraulic drive system.

14. A nail device (35, 50) according to any of the claims 1-13, characterized in that the device is provided with an external mechanic, electromagnetic or piezoelectric drive system.

15. A nail device (50) according to any of the claims 1-14, provided with a slot (32) in the longitudinal direction for receiving a compression screw (33).

16. A nail device (50) according to any of the claims 1-15, as compression nail, transport nail or as compression/distraction nail.

17. A nail device (50) according to any of the claims 1-16, whereby the cylindrical housing (51), which stretches out between the proximal end part (41) and the distal end part (40, is single hulled.

18. A nail device (35) according to any of the claims 1-14 as extension nail.