Method and apparatus for the external fixation and correction of bone

An external fixation device includes a frame assembly having a first arc segment and a second arc segment. The first arc segment is for interconnection to a first bone portion. The second arc segment is for interconnection to a second bone portion. The first arc segment is coupled to the second arc segment for relative rotation. The external fixation assembly additionally includes an articulating module. The articulating module includes a central member, a first pivot segment and a second pivot segment. The first pivot segment is coupled to the central member for driven rotation about a first pivot axis. The second pivot segment is coupled to the central member for driven rotation about a second pivot axis. The second pivot axis is substantially perpendicular to the first pivot axis.

FIELD OF THE INVENTION

The present invention relates to the external fixation of bones during orthopedic surgical applications, such as the repair of bone fractures and the correction of bone defects. More particularly, the present invention relates to a method and apparatus which allow for gradual and controlled correction of bone deformities and malunions. The various applications of the present invention involve gradual angular, translational and rotational correction of bone deformities and malunions.

BACKGROUND OF THE INVENTION

In various orthopedic surgical procedures, it is necessary to secure two bone portions in a relatively fixed relationship to each other. For example, the need for establishing such a secured relationship is often a result of a fracture which has occurred to the bone. This secured relationship is also employed to correct deformities and malunions. To ensure that the bone can regenerate in the proper orientation and fuse the fracture, it is important that the bone portions be fixed and in the desired position during bone regeneration.

Various external fixation devices for the repair of traumatized bone are known. For example, commonly assigned U.S. Pat. No. 5,662,650 to Bailey et al. discloses an apparatus for the external fixation of large bones. The apparatus is illustrated to include a main body as well as a first and second bone screw clamps. The main body serves to allow the apparatus to axially rotate, thereby providing a proper longitudinal rotational location of the bone screws with respect to a bone. The first bone screw clamp is used to secure a first bone screw to the apparatus while permitting the first bone screw to be axially displaced from the main body. In a similar fashion, the second bone screw clamp functions to secure a second bone screw to the apparatus and to allow the second bone screw to be axially displaced with respect to the main body. U.S. Pat. No. 5,662,650 is incorporated by reference as if fully set forth herein.

In certain orthopedic surgical procedures, it is necessary to engage two bone portions in a fixed relationship and to angulate, rotate and/or translate the two bone portions relative to each other. The need for making such an adjustment is frequently the result of bone deformity. Such bone deformities may result from congenital defects including but not limited to Blount's Disease, Tibia Vara, and Hypophosphatemic Rickets. Adjustment of bone portions may also be required as a result of post-traumatic applications, such as the correction of bone malunions.

Other known devices are available for the correction of bone deformities and malunions. For example, commonly assigned U.S. Pat. No. 5,941,879 discloses an external fixator for adjustably securing a first bone portion in a position relative to a second bone portion. The fixator includes a first clamping assembly for receiving a first bone screw connected to the first bone portion and a second clamping assembly for receiving a second bone screw connected to the second bone portion. The first and second clamping assemblies are interconnected by a connection member. The external fixator also includes a drive unit for controlling angular adjustment of the second clamping assembly relative to the first clamping assembly.

While the fixators specifically for correcting bone deformities and malunions of the type described above may have proven acceptable for certain applications, such fixators are nevertheless susceptible to improvements that may enhance the performance of the fixator for particular applications.

SUMMARY OF THE INVENTION

In general, the present invention relates to the external fixation of bones. More specifically, the present invention relates to an external fixator which is operable to adjustably secure a first bone portion in a particular position with respect to a second bone portion.

An advantage of the present invention is the provision of a method and apparatus for the external fixation of bone which allows the rate of angular, rotational and/or translational correction of bone deformities and malunions to be easily and more accurately controlled.

In one particular form, the present invention provides a frame assembly for an external fixation device. The frame assembly includes a first arc segment and a second arc segment. The first arc segment is for interconnection to a first bone portion. The second arc segment is for interconnection to a second bone portion. The first arc segment is coupled to the second arc segment for controlled relative rotation.

In another particular form, the present invention provides an articulating module for an external fixation device. The articulating module includes a central member, a first pivot segment and a second pivot segment. The first pivot segment is coupled to the central member for driven rotation about a first pivot axis. The second pivot segment is coupled to the central member for driven rotation about a second pivot axis. The second pivot axis is substantially parallel to the first pivot axis.

In yet another particular form, the present invention provides a method of correcting a rotational deformity or malunion of a bone having a longitudinal axis. The method includes the step of providing an external fixation device including a frame assembly with a first arc segment coupled to a second arc segment. The method additionally includes the steps of interconnecting the first arc segment to a first bone portion and interconnecting the second arc segment to a second bone portion. The method further includes the step of rotating the first arc segment relative to the second arc segment to correct the rotational deformity or malunion of the bone.

Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With general reference toFIGS. 1 through 17of the drawings, an apparatus for the external fixation and correction of a bone constructed in accordance with the teachings of a preferred embodiment of the present invention is illustrated and generally identified at reference character10. With particular reference to the environmental view ofFIG. 1, the apparatus10is shown connected to a bone12through a plurality of bone screws14which serve to secure a first bone portion12arelative to a second bone portion12b.

In the exemplary application illustrated, the first and second bone portions12aand12bsecured by the apparatus10are of a single bone12. The bone12shown in the drawings represents a human tibia. It is to be understood, however, that the apparatus10may be operatively attached to a variety of other types of bones and used to correct bone deformities, correct malunions, or repair fractures. As will become apparent below, by securing the first and second bone portions12aand12bwith the apparatus10of the present invention, the orientation of the first portion12arelative to the second portion12bmay be angularly, rotationally, and translationally adjusted.

In the particular construct shown, the apparatus10is illustrated to generally include first and second frame assemblies16and18interconnected by an articulating module or adjustable module20. The particular construct shown is further illustrated to include a bone screw clamping assembly24. The second frame assembly is secured to the first bone portion12a. The bone screw clamping assembly24is secured to the second bone portion12b. The bone screw clamping assembly24is coupled to the first frame assembly16. The first and second frame assemblies16and18are adjustably interconnected by the module20.

As will become apparent to those of ordinary skill in the art, the teachings of the present invention may be employed in many different constructs for external fixation depending on the particular surgical application and further depending on surgeon preferences. The construct shown in the drawings will be understood to be merely exemplary. The various components of the apparatus10of the present invention may be alternatively utilized in different constructs involving some or all of the illustrated components. Additionally, the various components of the present invention may be used in connection with other components, some of which are commercially available from the assignee of the subject application under the registered trademark DynaFix®.

The first frame assembly16defines an arc segment. In the embodiment illustrated, the first frame assembly16is shown to only partially circumscribe the bone12. As shown most clearly inFIGS. 2 and 2A, the first frame assembly16defines approximately one-third of a complete circle. Alternatively, the first frame assembly16can be configured to define more or define less of an incomplete circle or configured as a complete ring to fully circumscribe the bone12. The first frame assembly16is formed to include tabs21to facilitate attachment to additional segments (not shown). This arrangement and manner of attachment is more fully described in commonly assigned U.S. Pat. No. 5,997,537 which is hereby incorporated by reference as if fully set forth herein.

The first frame assembly16is formed to include a plurality of apertures22to facilitate attachment of the module20in a manner to be more fully addressed below. The first frame assembly16is further shown to define a groove26in an outer peripheral face to facilitate attachment of clamping elements. In the application illustrated, no clamping elements are employed for directly connecting the first frame assembly16to the bone12.

With particular reference toFIGS. 11,11A and12, the bone screw clamping assembly24is shown to include a main body having a base portion30and a cover portion32. The base portion30serves to receive a bone screw14in one of a plurality of grooves34. The cover portion32serves to secure the bone screw14within the groove34.

The cover portion32of the bone screw clamping assembly24is secured to the base portion30by two screws36. To accommodate these screws36, the cover portion32of the bone screw clamping assembly24includes two apertures38which mate with corresponding apertures40in the base portion30of the bone screw clamping assembly24. Accordingly, upon secured threaded engagement of the screws36within the apertures38and40, the cover portion32of the bone screw clamping assembly24may be secured to the base portion30of the bone screw clamping assembly24.

With additional reference toFIG. 13, to provide for translation of the bone screw clamping assembly24relative to the first frame assembly16, the bone screw clamping assembly24further includes a rail member42. The rail member42preferably includes a D-shaped extension48which is able to be received in a D-shaped bore50of the bone screw clamping assembly24. The D-shaped extension48includes an elongated slot51for receiving a set screw (not particularly shown) that extends through a threaded aperture52provided in the base portion30. Because of the cross-sectional shape of the D-shaped extension48, the base portion30of the bone screw clamping assembly24is able to slide on the extension48of the rail member42. However, the base portion30is unable to rotate with respect to the D-shaped extension48.

The rail member42has a generally circular end53defining a cylindrical aperture54. The cylindrical aperture54receives a cylindrical portion55of a mounting member56(shown specifically inFIG. 12). The cylindrical portion55defines a reduced diameter groove58that receives a set screw60extending through an aperture62of the end53.

A pair of threaded fasteners64extend through apertures22of the first frame assembly16and engage threaded apertures66of the mounting member56. Prior to complete tightening of the set screw60, the rail member42and thereby the clamp24are able to rotate about an axis parallel to the bone segment12b.

With particular reference now toFIGS. 1 and 14through17, the second frame assembly18of the apparatus10constructed in accordance with the teachings of a preferred embodiment of the present invention will be further described. It will become apparent to those skilled in the art that the second frame assembly is specifically intended for the treatment of rotational deformities of bone. In other applications, it may be desirable to alternative use a frame assembly substantially identical to the first frame assembly16in place of the second frame assembly18.

In the environmental view ofFIG. 1, the second frame assembly18is shown operatively associated with a plurality of clamp members70and associated bone screws14for securing the second frame assembly18to the bone12. The clamps70shown inFIG. 1of the drawings engage an outer peripheral groove (similar in geometry to the groove26of the first frame assembly16) of the second frame assembly18and illustrate one particular manner for attachment of the second frame assembly18to the bone12. It will be understood by those skilled in the art that the particular manner of attachment of the second frame assembly18to the bone12is beyond the scope of the present invention and may be accomplished in any well known manner. One suitable manner of attachment is shown and described in commonly assigned U.S. Pat. No. 5,997,537.

The second frame assembly18of the preferred embodiment of the present invention is generally illustrated to include a first arc segment or member72and a second arc segment or member74. The first and second arc segments72and74are coupled to one another for relative rotation. In the embodiment illustrated, the first and second arc segments72and74are concentrically arranged and the first arc segment72is illustrated as an inner arc segment. Similarly in this regard, the second arc segment74is illustrated as an outer arc segment.

As with the first frame assembly16, the first arc member72of the second frame assembly18is formed to include a plurality of apertures76to facilitate connection to the module20.

Further similar to the first frame assembly16, the first and second arc segments72and74extend through approximately one-third of a complete circle. Alternatively, the first and second arc segments can be configured to define more or less of an incomplete circle or configured as a complete ring to fully circumscribe the bone12.

As particularly shown in the cross-sectional view ofFIG. 15, the first arc segment72has a main portion78having a downwardly opening U-shape. A upper horizontal segment connects two downwardly extending legs and defines the apertures76. The first arc segment72further has a generally T-shaped extension80outwardly extending from the main portion78. The T-shaped extension80is slidably received within a cooperative recess82of the second arc segment72.

The second frame assembly18preferably includes a drive unit84for gradual and controlled rotation of the second arc segment16relative to the first arc segment72. In the embodiment illustrated, the drive unit84includes a housing or cover86secured to the second arc segment74with a pair of fasteners88. The drive unit84further includes a worm or worm gear90. The worm gear90is rotatably carried by the second arc segment74and substantially disposed in the outer peripheral groove defined by the second arc segment74. The second arc segment74is generally I-shaped. A vertically extending portion92of the second arc segment74defines an opening94(seeFIG. 16A). The worm gear90includes a threaded portion96. The threads of the threaded portion96partially extend through the opening94and a plurality of teeth98provided on an arcuate exterior portion of the first arc segment72. In the embodiment illustrated, the plurality of teeth98are formed on an outer peripheral side of the T-shaped portion80and extend along the entire length of the first arc segment72to facilitate relative rotational movement between the first and second arc segments72and74. A pin100(seeFIG. 16) retains the worm gear90from translating relative to the second arc segment74.

The common centers of curvature of the first and second arc segments72and74of the second frame assembly define a rotational axis about which the first bone portion12acan be rotated relative to the second bone portion12b. Significantly, this rotational axis can be postioned generally coincident with a long axis of the bone12. Relative movement between the bone segments12and12bis gear driven and thereby controlled and gradual.

With particular reference toFIGS. 1 and 1AandFIGS. 3 through 10, the module20of the preferred embodiment of the present invention will now be further described. The module20is generally illustrated to include a pair of mounting portions102, a pair of translation segments104, a first pivot segment106, a second pivot segment108and a central member110. The term “central” used to describe the central member110will be understood to reference the central location of the member110between the first and second pivot segments106and108. The central member110need not be located centrally within the module20.

A first of the mounting portion102functions to connect the module20with the first frame assembly16. A second of the mounting portions102similarly functions to connect the module20with the second frame assembly18. In the embodiment illustrated, the mounting portions102will be understood to be identical. The mounting portions102are illustrated to generally include a plate portion112and a single post or mounting member114. The post114passes through one of the apertures of the respect frame assembly16or18and threadably engages an aperture116of the plate member112. Insofar as interconnection of the module20with the frame assemblies16or18is made by a single post114, relative rotation between the mounting members102and the remainder of the module20is not necessary. In this regard, the post114defines an axis about which the module20can rotate prior to complete tightening.

The translation segments104will be understood to be identical. As perhaps most clearly shown in the environmental view ofFIG. 5, the translation segments104defines a groove118for slidably receiving a portion of the associated plate member112. The translation segments104define a generally rectangular opening120and include a threaded worm122. In the embodiment illustrated, the plate members112of the mounting portions102include a rectangular extension or carriage124. These rectangular extensions124define the apertures116for receiving the posts114. The worm122threadably engages an aperture126of the rectangular extension124. The rectangular extension124is sized to be slidably received within the opening120. Rotation of the worm122in a first direction operates to linearly translate the mounting member102relative to the associated translation segment104along an axis parallel to an axis defined by the worm122.

The worms122provide two axes for relative translation between the first and second bone portions12aand12b. The worms122of the pair of translation segments104are preferably oriented generally perpendicular to one another. In this manner, the module20of the preferred embodiment of the present invention is able to provide gradual and controlled translation of the first bone portion12arelative to the second bone portion12balong two perpendicular axes.

The central member110is preferably unitarily constructed. As particularly shown inFIG. 6, the central member110includes a first end130having an arcuate flange132. The flange132defines a first plurality of teeth134. The central member110includes a second end136similarly including an arcuate flange138defining a second plurality of teeth140. In the embodiment illustrated, the first plurality of teeth134are disposed in a plane substantially perpendicular to the second plurality of teeth140.

The first pivot segment106downwardly extends from the upper translation segment104. The first pivot segment106is illustrated to include a pair of spaced apart flanges125and a worm126. The worm126threadably engages the first plurality of teeth134of the central member110. A pin142(shown inFIG. 5) connects the flanges125with the plate central member110and defines a secondary pivot axis between the first and second pivot segments106and108of the module20. The flanges125are cut-away to accommodate pivoting of the second pivot segment108about the pin142. A set screw143is provided for selectively preventing relative rotation between the first pivot segement106and the central member110.

The second pivot segment108upwardly extends from the lower one of the translation segments104and similar includes a pair of spaced apart flanges144and a worm146. The worm146threadably engages the second plurality of teeth140of the central member110. A pin148passes through the flanges144of the second pivot segment108and connects the flanges144with the central member110. The pin148defines a primary pivot axis of the module20. A set screw149is provided for selectively preventing relative rotation between the second pivot segment108and the central member110.

In use, if the primary pivot defined by the pin148is exactly aligned with a pivot point of a bone deformity, no further adjustment of the module20is required. However, if the pivot axis defined by the pin148is not aligned exactly with the pivot point of the deformity, an angular deformity in a perpendicular plane and a translational deformity will be observed. The module20is adapted to correct the angle in a plane perpendicular to the primary pivot axis. In addition, the module20is adapted to correct translational deformities that may also result if the primary pivot axis is not exactly aligned with the pivot point of the deformity.

The module20defines two (2) perpendicular axes (i.e., along the pins142and148) about which the bone portions12aand12bmay be angulated relative to one another. This relative angulation is gear driven and gradual. Additionally, the module20includes two perpendicular translation axes (i.e., coincident with the worms122and146). Again, this translation is gear driven and gradual. Furthermore, rotational axes are defined at the interconnections between the module20and the frame assemblies16and18(i.e., along the axis of the posts114).

In another particular form, the present invention provides an articulating module for an external fixation device. The articulating module includes a central member, a first pivot segment and a second pivot segment. The first pivot segment is coupled to the central member for driven rotation about a first pivot axis. The second pivot segment is coupled to the central member for driven rotation about a second pivot axis. The second pivot axis is substantially perpendicular to the first pivot axis.

The common centers of curvature of the first and second arc segments72and74of the second frame assembly define a rotational axis about which the first bone portion12acan be rotated relative to the second bone portion12b. Significantly, this retational axis can be positioned generally coincident with a long axis of the bone12. Relative movement between the bone segments12and12bis gear driven and thereby controlled and gradual.

The translation segments104will be understood to be identical. As perhaps most clearly shown in the environmental view ofFIG. 5, the translation segments104defines a groove118for slidably receiving a portion of the associated plate member112. The translation segments104define a generally rectangular opening120and include a threaded worm122. In the embodiment illustrated, the plate members112of the mounting portions102include a rectangular extension or carriage124. These rectangular extensions124define the apertures116for receiving the posts114. The worm122threadably engages an aperture129of the rectangular extension124. The rectangular extension124is sized to be slidably received within the opening120. Rotation of the worm122in a first drection operates to linearly translate the mounting member102relative to the associated translation segment104along an axis parallel to an axis defined by the worm122.

The module20defines two (2) perpendicular axes (i.e., along the pins142and148) about which the bone portions12aand12bmay be angulated relative to one another. This relative angulation is gear driven and gradual. Additionally, the module20includes two perpendicular translation axes (i.e., coincident with the two worms122shown inFIG. 5). Again, this translation is gear driven and gradual. Furthermore, rotational axes are defined at the interconnections between the module20and the frame assemblies16and18(i.e., along the axis of the posts114).

The first pivot segment106downwardly extends from the upper translation segment104. The first pivot segment106is illustrated to include a pair of spaced apart flanges125and a worm126. The worm126threadably engages the first plurality of teeth134of the central member110. A pin142(shown inFIG. 5) connects the flanges125with the plate central member110and defines a secondary pivot axis “B” (shown inFIG. 6) between the first and second pivot segments106and108of the module20. The flanges125are cut-away to accommodate pivoting of the second pivot segment108about the pin142. A set screw143is provided for selectively preventing relative rotation between the first pivot segment106and the central member110.

The second pivot segment108upwardly extends from the lower one of the translation segments104and similar includes a pair of spaced apart flanges144and a worm146. The worm146threadably engages the second plurality of teeth140of the central member110. A pin148passes through the flanges144of the second pivot segment108and connects the flanges144with the central member110. The pin148defines a primary pivot axis “A” (shown inFIG. 6) of the module20. A set screw149is provided for selectively preventing relative rotation between the second pivot segment108and the central member110.