External mounting device, particularly for extension of a distance between clamping elements

An external fixation device for the extension of the distance between two clamping members of an external fixator has a central internal rod and an outer hollow housing. The internal rod is movable axially. One end of the internal rod projects over the one end of the housing, and serves to fix the one clamping member. An adjusting member is provided disposed at the other end of the housing and is connected with internal rod and/or the outer hollow housing, whereby the axial position of the interior shaft can be adjusted in relation to the housing by means of rotation of the adjusting member. Furthermore, an adjusting knob is provided that can be detachably attached to the adjusting member with an essentially positive fit.

FIELD OF THE INVENTION

The invention relates to an external fixation device, particularly for the extension of the distance between two clamping members. It further relates to such a fixation device for osteosynthesis and, for example, to the use thereof for an external fixator.

More particularly, it relates to an external fixation device for the extension of the distance between two clamping elements for an external fixator having a central internal rod, with an outer hollow housing, in which internal rod is movable axially. One end of internal rod projects over the one end of the housing, and with an adjusting or drive member, that is disposed at the other end of the housing and that is connected with internal rod and/or the outer hollow housing, whereby the axial position of internal rod can be adjusted in relation to the housing by means of rotation of the adjusting member.

BACKGROUND OF THE INVENTION

A similar device is known from FR 2,557,933. It is used particularly in the context of an external fixator. It comprises a rectangular internal rod and a hollow tube surrounding the same, which are thus movable in one another in a torsion-resistant manner. The adjustment is to be made by means of a nut and an adjusting screw, disposed at the free end of the hollow tube. At the two ends of the device, a clamping member is or will be attached that is connected to the bone fragments by means of rods or pins. A clamping member is attached to the hollow tube by means of a bracket that is thus resistant to torsion in relation to the axis of the rectangular tube. At the free end of the interior shaft, an additional clamping member is attached through a longitudinal screw that can be screwed into internal rod, which is thus freely rotatable in relation to the axis of the rectangular internal rod. Non-metallic materials are used as the material for disposable use. After fixation of two facing bone fragments with two clamping members, it is possible, by means of actuation of the adjustment device, i.e., the nut and adjusting screw, to extend the distance between the attachment points of the fixator to the bone, i.e., to extend the length of the bone overall.

Another such device is known from U.S. Pat. No. 5,454,810. This publication targets the problem of the use of a rotationally-symmetrical inner rod and outer tube in relation to rotatory stability. In U.S. Pat. No. 5,454,810, a round outer tube with a bore of continuous square cross-section is used so that an internal rod with a square cross-section can be used in the outer tube. The outer tube is composed of two aluminum halves while the inner rod is made of steel. To avoid jamming, the prior art uses polymeric material strips in the bore.

The free end of the inner rod ends in a larger diameter part projecting out from the outer tube. This end serves to fix the one clamping member. The other end of the inner rod in the telescoping version of the device according to U.S. Pat. No. 5,454,810, shown with members inFIG. 8therein, connects with a slide that is axially movable by means of a screw thread.

Other such devices are shown in U.S. Pat. Nos. 5,275,599 and 4,475,546.

These devices present the disadvantage that they are difficult to adjust because both publications refer to the operating surgeon effecting adjustments. The fixation knobs at the free ends, in contrast to this, can also be actuated unintentionally by the patients both in the hospital and under outpatient treatment and can thus be misadjusted.

One disadvantage of existing devices of this type therefore lies particularly in the fact that they are not simple to use. They should, advantageously, be changeable to a defined extent by the user as well, e.g., a patient should be able to extend said distance, i.e., said bone length, him/herself, in the simplest manner. At the same time, the device should be protected against unintentional actuation.

SUMMARY OF THE INVENTION

One aspect of the invention therefore relates to the task of improving a device of the above-mentioned type such that the device is simple to adjust to a defined extent, particularly by the patient him/herself. At the same time, it should be better protected against unintentional misadjustments.

The task is solved, according to the invention, by an adjusting knob that can be detachably attached to the adjusting member with an essentially positive fit. The attached adjusting knob can be placed in contact with at least one area of the housing. Adjusting knob and housing each have at least one complementary stop member so that a stop position with an altered length can be reached through the number and arrangement of the complementary stop members according to a predefined angle of rotation of adjusting knob.

A “stop” here is not an absolute halt in the sense of a lock on the device, but rather a location preventing rotation that can be overcome by minimal force, which facilitates a tactile experience for the user executing the rotation. The one end of internal rod projects beyond the one end of the housing and thus serves to fix a clamping member, while the housing serves to fix the other clamping member. A rotation in the one direction leads to an extension of the changed length while a rotation in the other direction leads to a retraction. Both changes are possible.

The device is smaller overall due to the fact that adjusting knob can be removed. This makes it easier for the patient to use the device to extend the distance between the bones, particularly on a daily basis.

Provision of a hanging device on the device, particularly in the form of a loop, is advantageous.

The problem is solved, in relation to the solution of the device as a whole according to the invention by an adjusting member having a rod with an external thread, an internal rod that is at least partially hollow and has an internal thread at its hollow end into which the external thread penetrates. The internal rod and housing have a torsion-resistant cross-section complementary to each other, and the adjusting member and the housing have a complementary conforming stop member to lock the adjusting member connected with internal rod and the housing against direct axial displacement.

“Lock” here is defined as the immobilization of the device that avoids a shortening of the distance between the clamping members.

A method for the use of the device according to the invention is presented.

Various aspects of the invention are provided by an extendable external fixation device which has a housing with an internal bore and a bone pin holder fixably mounted on an external surface of the housing. A telescoping member having a threaded inner bore and a bone pin holder fixably mounted thereon is slidably received within the bore of the housing. The bone pin holder is attached at a first end of the telescoping member opposite the end inserted into the housing. An anti-rotation element which may be in the form of polygonal cross-sections for the housing and telescoping member is utilized to prevent the relative rotation between the two. A drive member is rotatably mounted on a second end of the housing, which drive member has a threaded outer surface threadably received within the inner bore of the telescoping member whereby rotation of the drive member causes relative movement between the telescoping member and the housing. The drive member has an end spaced from the second end of the housing which includes a removable drive knob. Thus, the knob can be selectively engaged and disengaged from the drive head of the drive member. The housing has an outwardly facing circumferential recess for engaging at least one spring loaded detent element mounted on the drive knob. Preferably, the spring loaded detent elements are mounted in an external groove on the drive knob and extend through bores in the knob into engagement with the recesses in the housing. An O-ring or other spring element is mounted in or adjacent the groove and acts on the detent elements to provide the spring loading. Preferably, the telescoping member includes indicia such as a calibrated scale indicating the length of the external fixator as it expands and contracts via rotation of the knob when it is engaged on the drive head. Preferably, the drive head has four sides with coated indicia such as dots on each of the four sides. The indicia are visible when the drive knob is removed from the drive head.

DESCRIPTION

Referring toFIG. 1there is shown a perspective view of an external fixation device1according to a preferred embodiment of the invention with an external second clamping member12attached thereto. A rod-like member such as a bone-pin (not shown) is attached to this external second clamping member12by the use of the device, which rod-like member is attached to a bone fragment. Reference number11designates a first clamping member disposed essentially in extension of the device1, to which first clamping member11, an additional rod-like member can be attached as well. This additional rod-like member is attached to another bone fragment by the use of the device, for example such that between the above-mentioned bone fragment and this bone fragment there is a gap whose length can be extended with this device.

Such an external fixation device1for extension of a distance between the bone fragments attached to clamping members11,12has, for an external fixator, a central internal rod4, that is first properly visible inFIG. 3, since it is disposed in an outer hollow housing5of device1. In this housing5, internal rod4is movable axially indirectly by means of a first adjusting member10, shown first inFIG. 3. Here, one end of internal rod4projects beyond the one end of housing5and is connected in the embodiment shown with a bracket6to which first clamping member11is rotatably fixed. Device1also has an adjusting member10, shown inFIG. 7, which can be attached to the other end of housing5, wherein an engagement knob36, square in cross-section, is disposed, whose function is described in the following drawings in greater detail. The axial position of internal rod4can be adjusted in relation to housing5by means of the adjusting member.

First clamping member11, in the embodiment shown, belongs entirely to device1and is rotatably connected with device1by means of an axle3. InFIG. 2, a partial cross-section of the device according toFIG. 1is shown. The same characteristics bear the same reference numbers in all drawings. First clamping member11can swivel around axle3, for example for more than 90°, for example by 115° as here, until it reaches the position13shown by the dotted line inFIG. 2. A hollow body14is attached to the axle3, in which a bore15is disposed in the radial direction thereof, into which first clamping member11can be inserted and clamped. A screw16can be used in the bore15for this purpose. Hollow body14has lateral stop edges17, which, with the corresponding stop edges18of the bracket6, limit the rotational movement of the clamping member11around the axle3. Hollow body14is attached in a defined angular position by means of a clamping member19, for example, a screw, which penetrates into the bracket6.

In another embodiment not shown in the drawings, the extension of internal rod4can have a cylindrical member with the cross-section of housing5. It is thus possible to use an additional second clamping member12as the “first” clamping member instead of the integrated first clamping member11, as described below.

Second exterior clamping member12is attached to housing5of device1by means of a bracket22. The shanks of the bracket encompassing housing5are tensioned against the housing by a clamping screw29. Rod4runs in housing5. Internal rod4can be moved longitudinally in relation to housing5by members2,10described below so that the first clamping member11can move in relation to the second clamping member12. Here, the clamping members11and12perform a translational movement in relation to each other, even if the axles of the bone pins or rods clamped by clamping members11,12need not be aligned parallel to each other. With the clamping members11and12shown here as examples, the rods are each used in the openings20and fastened by the clamping screws21.

FIG. 3shows a partial cross-section view of the device1according toFIG. 1, without an external clamping member12. The clamping member21is fixed in position with the screw16of the clamping member11. The function of the clamping screw19is very easy to describe, since it compresses bracket6and thus clamps and fixes hollow body14.

The following description is to be viewed in connection withFIG. 4, which shows an enlarged sectional view of the one end of housing5, withFIG. 5, which shows a perspective view of internal rod4, withFIG. 6, which shows a cross-section view of internal rod4according to Lines VI-VI ofFIG. 5, and withFIG. 7, which shows a side view of the adjusting member10.

Housing5has an essentially square bore that is designed to be complementary to outer shell23of internal rod4. The outer shell23is provided, on its flat side, with a readable scale. Here, the value of the scale mark above housing5is to be read. Interior rod4is formed at its end into a cylinder24so that it can be attached in bracket6. The section shown inFIG. 3corresponds to a top view of a rectangular side of internal rod4.

Interior rod4is designed to be hollow. The cylindrical interior bore25is preferably continuous, but can also end as a blind hole in the area of reduced cylinder24. At the end facing the cylinder24, internal rod4is designed internally with an internal thread26whose exterior diameter is at least not larger than the internal diameter of the interior bore25, so that the adjusting member10can be inserted into rod4by means of thread26.

The adjusting member10has a threaded rod30of sufficient length, where the length, together with the dimensions of housing5and internal rod4, determine the total travel of the telescoping function. The thread26and the complementarily threaded rod30are advantageously designed with a very fine thread so that a number of rotations are necessary to reach a given translational travel.

A conical expansion31element connects to this threaded rod30after a short unthreaded section, which expansion element evolves into a cylindrical section32of a larger diameter, in which a circumferential circular groove is provided. Broadening out like a flange, an additional cylindrical section34of a larger diameter is connected, in which an additional groove35is provided. Finally, the engagement knob36connects to section34, which knob preferably has a square cross-section in the top view along axis7. Each side of the knob36has a coding of holes, like spots on dice, in a number from one to four. Thus, a flat wrench can be used and the further rotation of the spots is each counted as a quarter-turn. The user can also recognize the direction of rotation for the extension function from the increasing number of spots.

FIG. 3shows that a retaining ring41is inserted into the groove33, which ring is inserted into the internal groove38of housing5through the sliding edges37. The additional lines inFIG. 4belong to the square receptacle4. After insertion of the retaining ring41into the groove38in the housing, the shoulder also comes into contact between sections32and34, near housing5. The first O-ring42is inserted into the groove35in section34. One the outside of housing5, at a regular angular pitch of 90°, a groove39is chamfered on the running surface, which is also a rounded recess in the direction of the circumference of housing5, whose function will be made clear in connection with the stop member8. The retaining ring41can, for example, be a steel spring that holds members5and10apart at a fixed distance. Thus, only internal rod4is moved axially by the rotation of member36.

FIG. 8shows a perspective view of adjusting knob2.FIG. 9shows a partial cross-section of the device according toFIG. 1with adjusting knob2according toFIG. 8.FIG. 10shows an exploded view of the rotary groove50of adjusting knob2.FIGS. 11 and 12show two perspective views of the stop member8of adjusting knob2. In connection with the description of these figures, the method of functioning of the device will also be explained.

On the left side of the drawing inFIG. 9, housing5can be seen, in which internal rod4and the adjusting member10run.

Adjusting knob2has an engagement area51for the user. At its end on the engagement side, it has a two-stage internal bore54and an internal square shaft55for acceptance of the first O-ring42or the engagement knob36. Essentially, the O-ring42is intended to hold the clamping device12, which can thus be disposed on housing5and cannot be lost when the device is being handled.

The rotary groove50is disposed in the adjusting knob2outside the internal bore54, which groove has a two-stage bore56and57running radially at two facing points. The first layer stage56expands and deepens the rotary groove50. The second stage57forms a through-bore into the internal bore54. A second O-ring53is inserted into the rotary groove50. Prior to this, however, stop members8are inserted into bores56,57. These stop members have, as shown inFIGS. 11 and 12, a cylindrical upper area58and a lower hemispherical projection52of small diameter. Here, the cylindrical upper area58fits in the first stage of bore56and projection52can penetrate into the second stage57of the bore. Stop members8are held in their receptacles by the O-ring53and are pressed against the shoulder between the sections56and57of differing diameter. Stop members8have a groove59for this purpose, through which the O-ring53runs. Instead of two stop members8, for example, three can be disposed with an angular pitch of 120° or even four at 90°. Other numbers and angular distributions are also possible.

Instead of the separate bolt-like stop members8held by the second O-ring53, adjusting knob2can also have bosses corresponding to the hemispherical projections52by means of tongues, which bosses penetrate into grooves39on the running surface, so that the user has a tactile experience. Otherwise, housing5can also be provided with one or a plurality of embossments that are pressed apart by the corresponding conforming hollow cylindrical segments of adjusting knob2, wherein grooves in adjusting knob2provide a palpable stoppage. It is also possible to use individual balls directly instead of the stop members8with the hemispherical projections52, which ball-shaped projections run in the retainer formed by the edges56.

The device is used in two steps. The operating physician fixes the external fixator in the broken bone with the corresponding fixations formed of rod-like members each as bone pins, either directly on the device1or indirectly to it. Here the surgeon attaches adjusting knob2to engagement knob36. While attaching adjusting knob2, the stop members8slip against the first O-ring42and over it. Thus, the knob2, after fixation, is secured against axial displacement and unintentional falling out. In other embodiments not shown in the drawings, this can be achieved if a circular flexible member on the inside54of engagement knob2, similar to the O-ring.42, is provided to form, together with the above-mentioned stop members (then on housing5), an axial protection against removal for the engagement knob2.

The engagement knob36, shaped like a die, then slides into the complementary square internal bore55, which has some play, so that a positive fit is achieved. The physician now adjusts the initial distance by rotating knob2to achieve the desired spatial relationship between the rods holding the bones. It should be emphasized that this adjustment is subsequently fixed. An unintentional rotation of device1is also precluded by the tubes4and5, placed one inside the other and torsion-resistant. By means of the three-stage longitudinal adjustment with members4,10, and5, a secure immobilization of the desired distance is ensured, which cannot be misadjusted unintentionally, particularly if the physician removes adjusting knob2. Adjusting knob2can be equipped with a hanging device9that has a hole to pass a cord through, for example.

The current adjustment can now be read off the scale marking on internal rod4. The travel, and therefore the change in distance between clamping members11and12is determined by the screw threads26/30, by the rotation or partial rotation of adjusting knob2. Thus, the patient can make the subsequent corresponding adjustments him/herself, at the doctor's orders. The patient receives an adjusting knob2for this purpose. If such knob is not attached, the device is secured against unintentional changes in the adjustment, as stated above. A marking assigned to stop member8is advantageously placed on adjusting knob2, which is attached to housing5opposite a groove39on the running surface. Thus, adjusting knob2can be permanently attached. After attachment of adjusting knob2, the patient can carry out a defined, simple, reproducible rotation of the knob2. With preferably two opposing stop members8and preferably four grooves39on the running surface, the patient feels a stop after completion of a 90° turn. With correspondingly fine threads, changes in the length of the bone can be adjusted at predefined intervals. For example, the patient can be instructed to make three full turns every second day, i.e., turning the knob until the patient feels a catch with members8and39twelve times.

With three stop members8and one single groove39on the running surface or three grooves39on the running surface set at a pitch of 120°, the angular resolution of one rotation is equal to 120°. If three stop elements8are assigned to two opposing grooves39in the running surface, the angular resolution comes to 60°. The same resolution is achievable with two stop members8as in the present embodiment and six grooves39on the running surface. The person skilled in the art can see additional possibilities as needed. After removal of adjusting knob2, there are no members projecting beyond the rod, so that an accidental adjustment is unlikely. To ensure the adjustment, a hollow cylindrical protective housing can be pushed on over adjusting knob2on housing5, which is held by the first O-ring42, whose rotation by means of the rotating of such a housing does not cause the adjusting member10to rotate. In control tests, the scale on internal rod4permits reading and thus a check on the number of rotations made, i.e., the change in length effectuated.

The material selected for the components of housing5and internal rod4, adjusting member10, and the other members can be steel such as stainless steel so that steel-to-steel contact surfaces can be formed.

The embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings, which embodiments fall within the framework of the scope of protection requested in the present claims.