TECHNICAL FIELD

The present invention relates to an adjustment tool for an external fixator adapted for securing a first bone portion in a position relative to a second bone portion, wherein the adjustment can comprise a compression or a distraction.

PRIOR ART

An external fixator in use with a patient is usually a device comprising at least two clamping assemblies for receiving at least one bone pin each, wherein, in a preferred embodiment, each clamping assembly comprises a second clamp for receiving a rod of an external fixator which extends over the fracture. If a compression or a distraction is to be applied, at least one clamping assembly has to loosened with the risk that the angular orientation of the corresponding bone pin engaging the bone from one side of the fracture looses it's orientation.

US 5,304,177 discloses an integrated adjustable fixator having two clamping assemblies within which each receives a bone pin to be entered into a bone of a patient of on each side of a fracture. Between the two clamping assembling holding the bone pins there is provided a main body having a worm in order to allow varying the distance between the two clamping assemblies. The device allows adjusting the distance between such two bone pins and therefore can be considered as a compression and/or distraction tool itself.

US 7,261,713 discloses another bone fixator which is adjustable, wherein two multipin clamping assemblies are attached to a longitudinal main body. Said main body allows different orientations of the clamping bodies and comprises a longitudinal translation element which allows shifting the positions of the two multipin clamping assemblies.

The prior art allows an easier adaptation of the distance between the clamping assemblies providing bone pins on each side of a fracture in a bone of a patient but they fail to provide a rigid frame. The existence of pivoting joints between the clamping assemblies necessitates some forces to block the universal joints.

SUMMARY OF THE INVENTION

Based on this prior art it is an object of the present invention to provide a compression and distraction tool allowing a more secure and easy variation of the distance of such two bone pins of an external fixator. It is a further object of the invention to provide a compression and distraction tool which can be used with a variety of clamping assemblies.

A further object of the invention is to provide a compression and distraction tool which is not part of the external fixator, i.e. which is only used when the length variation is to be adjusted but is not part of the external fixator which is, e.g. worn by a person having a broken limb.

The object of the invention is achieved with a tool having the features of claim 1. The adjustment tool is to be used for an external fixator for exerting a compression or distraction on a broken bone fixed by bone pins spanned over such a fracture. Therefore the adjustment tool comprises

a fitting element for holding fast a clamping assembly of the external fixator, a positioning clamp for fixing the adjustment tool on a rod of the external fixator near said clamping assembly, and

a connecting element attached to the fitting element and the positioning clamp, adapted to move the fitting element towards to or away from the positioning clamp. Thereby the fitting element comprises a blocking sleeve adapted to push the uppermost jaw of the clamping assembly of the external fixator in the direction of the longitudinal axis of the clamping assembly to block the second upper most jaw against an abutment portion of the fitting element and an actuation element within the blocking sleeve to actuate the locking element of the clamping assembly for releasing the rod of the external fixator within the clamping assembly without releasing the bone pin.

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows a perspective view of the device according to the invention in connection with one clamping assembly, one rod and one bone pin,

Fig. 2 shows a partial prosecution of Fig. 1 along the middle axis of the extension element,

Fig. 3 shows an exploded view of the compression tool according to Fig I,

Fig 4 shows a section of the compression tool according to Fig. 3, and

Fig 5 shows a view from above on the compression tool according to Fig. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a partial explanatory view of the compression tool 10 used with an external fixator and shows some parts of such an external fixator. Throughout the following specification tool 10 is always mentioned as compression tool, since compression of a fracture is the most common adjustment of the distance between two bone pins over a fracture, but the tool is also usable an distraction tool, since the distance between such bone pins can also be enlarged. The tool is therefore in fact a combined compression and distraction tool, an adjustment tool.

The external fixator for which the tool 10 is intended to be used with comprises a first clamping assembly, which is not shown in the drawings. Said first clamping assembly to attach a bone pin on one side of the fracture of a limb is then connected with rod 1 to span over the fracture. On the other side of the fracture a second clamping assembly 3 is attached to rod 1 and comprises a second bone pin 2 which is intended to be entered into the bone on the other side of the fracture in view of the above mentioned bone pin in connection with the first clamping assembly of the external fixator, which is not shown in the drawings. Clamping assembly 3 has several elements which are shown in the cross- section of Fig. 2. The second clamping assembly 3 is a clamping assembly according to copending US application 12/780.231 for applicant. It can also be a clamping assembly according to EP 0 700 664. In any case it has two pairs of jaw, a lower pair of jaws 30 and 31 providing receptions 36 to accommodate rods 1 and pins 2. A further upper pair of jaws 32 and 33 also comprises reception 36 to accommodate rods 1 and pins 2. The pairs of jaws 30, 31, 32 and 33 are connected with a connection screw 34 which is actuated through head 35. Said screw 34 extends along the longitudinal axis of the second clamping assembly 3. Such a clamping assembly 3 is also known from EP 700 664 having a similar design. In this context it is only important that said clamping assembly has at least two pairs of jaws 30, 31, 32, 33 allowing accommodating a rod 1 and a bone pin 2 at the same time. They are embodiments on the market within which the middle jaws 31 and 32 can be replaced by one single jaw. It is preferred that there are different receptions 36 or inserts to adapt the receptions 36 at different levels in height in view of the rods 1 and pins 2 which should not be positioned at the same level.

The outer form of such a clamping assembly 3 is usually cylindrical or nearly cylindrical. However in a view from above it can also have a square or rectangular cross-section. As mentioned above first and second clamping assemblies are used to fix two or more bone pins 2 on two sides of a fracture, wherein a rod 1 is used to establish a rigid frame and a defined distance, position and orientation of the bone pins 2. During the use of such an external fixator it is now contemplated that the two fractured bone parts have to be displaced one in the direction of the other (i.e. a compression movement) or they have to be displaced in the opposite direction (i.e. a distraction). According to prior art solutions a worm bridging the clamping assemblies has to be actuated to vary the distance.

In the present context having a rigid and fixed rod 1 giving a higher strength to the external fixator, such a compression or distraction would not be possible without loosening the actuator screw 34 through turning the head 35. However, this not only enables gliding of the lower jaws 30 and 31 along the rod 1 but also opens the clamping jaws 32 and 33 holding the bone pin 2.

According to the invention it is suggested to use compression tool 10 as follows: As it can be seen in Fig. 1 to 5 compression tool 10 comprises a positioning clamp 11, adapted to be clamped on rod 1, a connection element 13, connecting the positioning clamp 11 with the fitting element 12 which is adapted to hold fast the clamping assembly 3.

The positioning clamp 11 comprises a lower jaw 110 and an upper jaw 111 providing receptions 114. In the embodiment shown in the figures there are three receptions 114 of different sizes. It is important that one reception 114 is adapted to accommodate rod 1. Through actuating the longitudinal screw 112 against the washer 116 jaws 110 and 111 are closed and clamp rod 1. Screw 112 extends beyond jaw 111 into the connection body 132 of the connecting element 13.

In a simple embodiment it would be possible to combine jaw 111 and connecting body 132 in one single element. However it is preferred to have two different elements to have a lower structured surface 113 on jaw 111 and a complementary structured surface on the complementary connecting body 132. This enables turning the jaws 110 and 111 around the longitudinal axis of screw 112, thus choosing the reception 114 of corresponding size to accommodate rod 1.

The connecting body 132 has a through bore having an inner thread 133 which is orientated perpendicular to the axis of the above mentioned fixing screw 112 of positioning clamp 11. The connection body 132 also has an upper opening 135 in the vicinity of the longitudinal axis of screw 112. The connecting element 13 comprises a worm 130 having an outer thread adapted to be rotated in the bore of the connecting body 132 comprising an inner thread 133. The worm 130 has a flange 137 and a turning knob 134 at one end. It is not necessary that the bore of the connecting body 132 separated into two parts on both sides of upper opening 135 has a complementary inner thread 133. In the embodiment shown in Fig. 2 it can be seen that the bore adjacent to flange 137 has no inner thread.

On the other side of the worm 130 it has a central bore 138 and a thread-free cylindrical sleeve 139 of smaller diameter intended to be introduced and to make the connection with the casing 120 of the fitting element 12. The casing 120 of the fitting element 12 has - in a view form above - the form of the letter C, wherein the closed portion of the fitting element is oriented towards the connecting body 132. The casing 120 has a bore to accommodate the complementary sleeve 139 of worm 130. The worm 130 is fixed within said bore with the counter screw 136 to allow rotation of worm 130. Counter screw 136 has a larger head than the bore within casing 120. It is thus clear that rotation of worm 130 changes the position of connection body 132 between the casing 120 and the flange 137 of worm 130. The fixed relationship between counter screw 136 and worm 130 can be especially achieved through gluing or it can be blocked by using a pin or welding etc. .

The fitting element 12 comprises beside casing 120 which is in a fixed rotational relationship with worm 130 a blocking sleeve 122 having an outer thread 125 being complementary to an inner thread 121 of casing 120 which is located near the top of the casing 120. Within blocking sleeve 122 there is provided an actuation screw 123 having a hollow cylinder 152 with a reception hole 124 at its lower end. Said hollow cylinder 152 is complementary for a positive fit to accommodate head 35 of the clamping assembly for which it is the adjustment tool.

Casing 120 further comprises a transverse slit 127 being at right angles to the longitudinal axis of blocking sleeve 122. The port of the transverse slit 127 is on the side of the open end of the "C" in the lower portion of the connecting casing 120 below inner thread 121. Below the transverse slit 127 - on both sides of the open "C" - there is provided a lower shoulder 129 protruding into the lower reception opening 154 and providing a flange on the lower end of the casing 120. As mentioned above the C-form of the sleeve comprises a lower reception opening 154 opposite to the inner thread 121. On the other side of the lower shoulder 129 near the inner thread there is provided a further reception shoulder 128 protruding into the opening partially filled by the blocking sleeve 122 from above.

The function of the device is therefore as follows. Two bone pins from which only one bone pin 2 is shown in Fig. 1 or 2 are lodged in the bone of a patient on both sides of a fracture. The rod 1 spans the fracture and is connected to the bone pins 2 on said both sides through two clamping assemblies 3. In order to move one bone pin 3 in the direction of the longitudinal axis of the underlying rod 1, either compressing or distracting the fracture region, one of the clamping assemblies 3 is to be moved and there the use of the adjustment tool 10 is shown in Fig. 1 and 2. The two jaws 30 and 31 of the clamping assembly 3 of the external fixator clamp the rod and the two jaws 32 and 33 of the clamping assembly 3 hold the bone pin 2.

The adjustment tool 10 is presented with the open "C", i.e. from the lateral opening 150 towards the upper two jaws 32 and 33 of the clamping assembly 3. The fitting element 12 is pushed over the upper two jaws 32 and 33 so that these are located between the upper and lower shoulders 128, 129. The bone pin 2 is therewith lodged within the lateral slit 127, wherein the length of the slit permits different orientations of the bone pin 2 in the horizontal axis; it is not necessary that the bone pin 2 is perpendicular to rod 1 as shown in Fig. 1. The orientation of bone pin 1 depends on the position of the upper jaws 32, 33 (more particularly the reception 36 receiving the bone pin 2) in relationship to the position of the lower jaws 30, 31 (more particularly the reception 36 receiving the rod 1).

When the upper portion of the clamping assembly 3 is within the casing 120 of the fitting element 12, then the blocking sleeve 122 is rotated through action of the threads 121, 125 down onto the head 135 of the clamping assembly 3. This allows introducing the head 35 into the reception hole 124 of the blocking sleeve 122. When there is a positive fit through pushing the blocking sleeve 122 down on the upper jaw 33, where the underside 126 of the blocking sleeve 122 contacts said upper jaw 33, then the fitting element 12 is fixed to the clamping assembly 3 of the external fixator.

Then, subsequently, the positioning clamp 11 is also attached to rod 1 through jaws 110, 111 by actuation of screw 112. Then positioning clamp 11 and fitting element 12 with the clamping assembly 3 are securely fixed to the rod 1. When said fitted clamping assembly 3 and positioning assembly 11 are now fixed on the rod 1, then the head of worm 134 is turned until a force would be exercised on positioning clamp 11 and fitting element 12 by worm 130 which can be detected by the user of the adjustment tool.

After this moment actuation head 123 is turned to loosening the clamping assembly 3. Since jaw 32 is pushed against the lower shoulder 129, said opening of screw 34 does not liberate the bone pin 2, which is still pinched through the pressure of the underside 126 on the upper jaw and the abutment action of the lower shoulder 129; but only opens the lower jaws 30 and 31 in order to release rod 1 allowing a movement of the clamping assembly 3 as a whole in the direction of the axis of rod 1.

This can be effected through turning the worm head 134 so that rotation of worm 130 in the connection body 132 pulls the fitting element 12 with the clamping assembly 3 being in a positive fit within the fitting element 12. This pulling action is acting in direction of the positioning clamp 11. Of course the head 134 can also be rotated in the opposite position thus pushing the fitting element 12 with the clamping assembly 3 away from the positioning clamp 11. The kind of motion, i.e. distraction or compression, depends on the side where the positioning clamp 11 is fixed on the rod, either between the two clamping assemblies 3 or on the opposite side.

The displacement of the one bone pin 2 in the direction of the longitudinal axis of the underlying rod 1 is equivalent to a movement of the worm 130 towards the head 134 of the worm 130.

The embodiment of the fitting element 12 shows the lateral opening 150 opposite to the positioning bore of the worm 130. In other embodiment it is possible to provide the opening in an 90 degree angle to the worm 130 thus allowing to open the "C" not in the direction of the distraction or compression movement. However then the pin 3 has to be accommodated at a different level, e.g. lower than the worm 130.

In a different motorized embodiment not shown in the drawings, the fitting element 12 and the connecting element 13 can be combined in one single servo-motor assembly providing the same longitudinal displacement as in the embodiment of the drawings. Such a servomotor assembly would have a fixed connection with the casing 120 and would provide or have a fix connection with the upper structured surface 115. In fact the servo-motor assembly replaces the worm in the embodiment shown in the drawings. In other words, the connecting element 13 comprises an extendable element connected to the fitting element 12 and being in a fixable connection with the positioning clamp 11 allowing thus a translatory movement between the fitting element 12 and the positioning clamp 11, acting as a. mechanical translation means. It is preferred that the positioning clamp 11 is in a fixable connection with the connecting element 13 and not in a fixed connection. A fixable connection allows e.g. a rotation of the positioning clamp 11 and their receptions 114 around an axis.

Pins 151 allow maintaining the hollow cylinder 152 inside and the actuation head 123 outside the blocking head 122. It would also be possible to use a different blocking means allowing a longitudinal movement of the hollow cylinder to come into engagement with the screw head 35. In principle ut could also be allowed that the element 123/152 can be dissociated from the blocking sleeve 122. It is clear for someone skillde in the art that the interior cross-section of the blocking sleeve 122 as well as the shoulders 129 as well as the reception 128 has to be adapted to the specific clamping assembly 3. However, it is also clear, that any clamping assembly intended to be used for a rod-to-rod or rod-to-pin coupling can be used in such a structure to to block the second upper most jaw of the clamp against an abutment portion of the fitting element, wherein the actuation element within the blocking sleeve is provided to actuate the locking element of the clamping assembly for releasing the rod of the external fixator within the clamping assembly without releasing the bone pin. LIST OF REFERENCE SIGNS rod 122 blocking sleeve bone pin 123 actuation head clamping assembly 124 reception hole compression tool 125 outer thread

positioning clamp 126 underside

fitting element 127 transverse slit connecting element 128 reception

lower jaw 129 lower shoulder lower middle jaw 130 worm

upper middle jaw 132 connection body upper jaw 133 inner thread

screw / blocking shaft 134 head of worm blocking element head 135 opening

reception 136 counter screw lower jaw 137 flange

upper jaw 138 central bore

screw / blocking shaft 139 sleeve

lower structured surface 150 lateral opening reception 151 pin

upper structured surface 152 hollow cylinder washer 153 lower opening casing 154 lower reception opening inner thread