Indexed tri-planar osteotomy guide and method

Methods and devices for performing an osteotomy produce a bone cut producing a multi-planar change in the alignment of a bone portion by rotating it relative to another bone portion.

FIELD OF THE INVENTION

The invention relates to methods, implants, and instruments for performing an osteotomy.

BACKGROUND

Various conditions may affect skeletal joints such as the deterioration, elongation, shortening, or rupture of soft tissues, cartilage, and/or bone associated with the joint and consequent laxity, pain, and/or deformity. It is often desirable to change the angular alignment of a bone or a portion of a bone to restore function and/or reduce pain. To this end, various osteotomy procedures and instruments have been proposed. For example, osteotomies have been performed throughout the body to make various angular adjustments such as in a tibia, fibula, femur, pelvis, humerus, ulna, radius, metacarpal, metatarsal, and other bones.

SUMMARY

The present invention provides methods, implants, and instruments for performing an osteotomy.

In one example of the invention, methods and devices for performing an osteotomy produce a bone cut allowing multi-planar correction of the alignment of a bone portion by rotating it relative to another bone portion.

In another example of the invention, an osteotomy system operable to guide the formation of a tri-planar rotational osteotomy between a proximal portion of a metatarsal bone and a distal portion of the metatarsal bone, includes at least one cutter guide and a cutter. The cutter guide includes reference features operable to align the cutter guide with the metatarsal bone in a predetermined position and one or more cutter guiding features each defining an osteotomy plane or rotation axis relative to the metatarsal bone and corresponding to a coupled change in at least two of intermetatarsal angle, pronation, and plantar flexion of the distal portion of the metatarsal bone, at least one of the change in intermetatarsal angle, pronation, and plantar flexion being user selectable among a plurality of values at the time of surgery. The cutter is operable to selectively reference one of the one or more cutter guiding features to cut the metatarsal bone to mobilize the proximal portion of the metatarsal bone and the distal portion of the metatarsal bone relative to one another and produce cut surfaces on which the distal metatarsal bone portion and proximal metatarsal bone portion are relatively rotatable.

In another example of the invention, a method of performing an osteotomy on a metatarsal bone having a proximal portion and a distal portion, the proximal and distal portions defining a first relative position between them, includes determining a desired positional change between the proximal portion of the metatarsal bone and the distal portion of the metatarsal bone in at least two anatomic reference planes; mounting a guide on the metatarsal bone; establishing an osteotomy plane or rotational axis with the guide; guiding a cutter in the osteotomy plane or about the rotational axis to mobilize the proximal portion of the metatarsal bone and the distal portion of the metatarsal bone relative to one another and produce cut surfaces on which the distal portion of the metatarsal bone and proximal portion of the metatarsal bone are relatively rotatable, the cut surfaces being oriented to incorporate the desired positional change in the at least two anatomic reference planes; rotating the distal portion of the metatarsal bone relative to the proximal portion of the metatarsal bone to a second relative position different from the first relative position; and fixing the distal portion of the metatarsal bone and the proximal portion of the metatarsal bone relative to one another in the second relative position with the cut surfaces of the proximal portion of the metatarsal bone and the distal portion of the metatarsal bone abutting one another.

DESCRIPTION OF THE ILLUSTRATIVE EXAMPLES

The following illustrative examples describe implants, instruments and techniques for performing an osteotomy. The present invention may be used to perform osteotomies on any bone including but not limited to a tibia, fibula, femur, pelvis, humerus, ulna, radius, metacarpal, and metatarsal.

While instruments and techniques according to the present invention may be used in conjunction with any bone or joint, the illustrative examples are shown in a size and form most suitable for the joints of the hand and foot. The hand and foot have a similar structure. Each has a volar aspect. In the hand the volar, or palmar, aspect includes the palm of the hand and is the gripping side of the hand. In the foot the volar, or plantar, aspect is the sole of the foot and is the ground contacting surface during normal walking. Both the hand and foot have a dorsal aspect opposite the volar aspect. Both the hand and foot include long bones generically described as metapodial bones. In the hand, the metapodial bones are referred to as metacarpal bones. In the foot, the metapodial bones are referred to as metatarsal bones. Both the hand and foot include a plurality of phalanges that are the bones of the digits, i.e. the fingers and toes. In both the hand and foot, each of the most proximal phalanges forms a joint with a corresponding metapodial bone. For convenience, the invention will be illustrated with reference to a metatarsus of the first ray of a human foot.

FIG. 1illustrates the orientation of anatomic planes and relative directional terms that are used for reference in this application. The coronal plane10extends from medial12(toward the midline of the body) to lateral (away from the midline of the body) and from dorsal14(toward the top of the foot) to plantar16(toward the sole of the foot). The sagittal plane18extends from anterior20(toward the front of the body) to posterior22(toward the back of the body) and from dorsal14to plantar16. The transverse plane24extends anterior20to posterior22and medial to lateral parallel to the floor26. Relative positions are also described as being proximal or distal where proximal is along the lower extremity toward the knee and distal is along the lower extremity toward the toes. The following examples serve to demonstrate the relative directions. The great toe is medial of the lesser toes and the fifth toe is lateral of the great toe. The toes are distal to the heel and the ankle is proximal to the toes. The instep is dorsal and the arch is plantar. The toenails are dorsal and distal on the toes.

FIG. 2illustrates dorsiflexion23in which the toes are moved dorsally, or closer to the shin, by decreasing the angle between the dorsum of the foot and the leg and plantar flexion25in which the toes are moved plantar, or further away from the shin, by increasing the angle between the dorsum of the foot and the leg. For example when one walks on their heels, the ankle is dorsiflexed and when one walks on their toes, the ankle is plantar flexed.

FIG. 3illustrates inversion27in which the sole of the foot is tilted toward the sagittal plane or midline of the body and eversion29in which the sole of the foot is tilted away from the sagittal plane.

FIGS. 4-10illustrate the arrangement of the bones within the foot30. A right foot is illustrated. Beginning at the proximal aspect of the foot, the heel bone or calcaneus32projects plantar. The talus34is dorsal to the calcaneus32and articulates with it at the talocalcaneal or subtalar joint. Dorsally, the talus articulates medially with the tibia36and laterally with the fibula38at the ankle joint. Distal to the ankle are the navicular bone40medially and the cuboid bone42laterally which articulate with the talus and calcaneus respectively. The navicular bone40and cuboid bone42may also articulate with one another at the lateral side of the navicular bone and the medial side of the cuboid bone. Three cuneiform bones lie distal to the navicular bone and articulate with the navicular bone and one another. The first, or medial, cuneiform44is located on the medial side of the foot30. The second, or intermediate, cuneiform46is located lateral of the first cuneiform44. The third, or lateral, cuneiform48is located lateral of the second cuneiform46. The third cuneiform48also articulates with the cuboid bone42. Five metatarsals50,52,54,56,58extend distally from and articulate with the cuneiform and cuboid bones. The metatarsals are numbered from 1 to 5 starting with the first metatarsal50on the medial side of the foot and ending with the fifth metatarsal58on the lateral side of the foot30. The first metatarsal50articulates with the first cuneiform44at a metatarsocuneiform (MTC) joint51. The second metatarsal52articulates with the first, second and third cuneiforms44,46,48and may articulate with the first metatarsal as well. Five proximal phalanges60,62,64,66,68extend distally from and articulate with the five metatarsals respectively. The first proximal phalanx60articulates with the first metatarsal50at a metatarsophalangeal (MTP) joint61. One or more distal phalanges70,72,74,76,78extend distally from the proximal phalanges. The first metatarsal50, first proximal phalanx60, and, first distal phalanx70together are referred to as the first ray of the foot. Similarly, the metatarsal, proximal phalanx, and distal phalanges corresponding to the lesser digits are referred to as the second through fifth rays respectively.

FIG. 4is a dorsal view illustrating bones, tendons and ligaments of the foot. Plantar structures illustrated inFIG. 5are omitted fromFIG. 4for clarity. The extensor hallucis longus muscle originates in the anterior portion of the leg, the extensor hallucis longus tendon80extends distally across the ankle and along the first ray to insert into the base of the distal phalanx70. The tibialis anterior muscle originates in the lateral portion of the leg and the tibialis anterior tendon82extends distally across the ankle and inserts into the first cuneiform44and first metatarsus50at the first MTC joint51where it contributes to the MTC capsular structure84(FIGS. 9 and 10). A transverse intermetatarsal ligament83inserts into the capsule of the MTP joint such that it connects the heads of the first through fifth metatarsal bones. InFIGS. 4 and 5, only the connection between the first and second metatarsal bones50,52is shown.

FIG. 5is a plantar view illustrating bones, tendons, and ligaments of the foot. Dorsal structures shown inFIG. 4are omitted fromFIG. 5for clarity. The peroneus longus muscle originates at the head of the fibula and its tendon86passes posteriorly around the lateral malleolus88of the ankle, around the cuboid notch90on the lateral side of the cuboid bone42, along the peroneal sulcus92on the plantar surface of the cuboid bone42, and inserts into the first metatarsal50. The flexor hallucis brevis muscle94originates from the cuboid42and third cuneiform48and divides distally where it inserts into the base of the proximal phalanx60. Medial and lateral sesamoid bones96,98are present in each portion of the divided tendon at the MTP joint61. The sesamoids96,98articulate with the plantar surface of the metatarsal head in two grooves100,102separated by a rounded ridge, or crista104(FIG. 8). The flexor hallucis longus muscle originates from the posterior portion of the fibula38. The flexor hallucis longus tendon106crosses the posterior surface of the lower end of the tibia, the posterior surface of the talus, runs forward between the two heads of the flexor hallucis brevis94, and is inserted into the base of the distal phalanx70of the great toe.

FIG. 7is a medial view of tendons at the MTP joint61of the first ray. A medial collateral ligament108originates from the head of the first metatarsus50and inserts into the proximal phalanx60. A medial metatarsosesamoid ligament110originates from the head of the first metatarsus50and inserts into the medial sesamoid bone96. Similar collateral and metatarsosesamoid ligaments are found on the lateral side of the first MTP joint. The flexor hallucis brevis94is shown inserting into the sesamoids96,98. Ligamentous fibers extend further distally in the form of a phalangealsesamoid ligament112from the sesamoids to the proximal phalanx60.

FIG. 8is a sectional view taken along line8-8ofFIG. 7showing the metatarsal head50, the tendon of the extensor hallucis longus80, the medial and lateral sesamoid bones96,98, the grooves100,102in which the sesamoids articulate, the crista104separating the grooves, the flexor hallucis longus106, the abductor hallucis114, and the adductor hallucis116.

FIG. 9is a dorsal view showing the dorsal capsular structure84of the MTC joint51of the first ray including the insertion of the tibialis anterior tendon82.

FIG. 10is a medial view of the MTC joint51of the first ray showing the medial capsular structure118including the insertion of the tibialis anterior tendon82.

FIGS. 11-13illustrate deformities of the first ray. In a dorsal view, as shown inFIG. 11, an intermetatarsal angle (IMA)120may be measured between the longitudinal axes of the first and second metatarsal bones50,52. The angle is considered abnormal when it is 9 degrees or greater and the condition is known as metatarsus primus varus (MPV) deformity. A mild deformity is less than 12 degrees, a moderate deformity is 12-15 degrees, and a severe deformity is greater than 15 degrees. Similarly, a hallux valgus angle (HVA)122may be measured between the longitudinal axes of the first metatarsus50and the first proximal phalanx60at the MTP joint61. The angle is considered abnormal when it is 15 degrees or greater and the condition is known as a hallux valgus (HV) deformity. A mild deformity is less than 20 degrees, a moderate deformity is 20 to 40 degrees, and a severe deformity is greater than 40 degrees.

MPV and HVA often occur together as shown inFIGS. 11-12. As the deformities progress several changes may occur in and around the MTC and MTP joints. Referring to FIG.13, as the IMA and HVA increase, the extensors80, flexors106, abductors114, and adductors116of the first ray (along with the sesamoids96,98) are shifted laterally relative to the MTP joint. The tendons exert tension lateral to the MTP joint creating a bow string effect (as best seen inFIGS. 11 and 12) that tends to cause the deformities to increase. The relative shift of the sesamoids96,98is often accompanied by erosion of the crista104. The abnormal muscle forces cause the metatarsus50to pronate, or in other words, rotate so that the dorsal aspect of the bone moves medially and the plantar aspect moves laterally. Rotation in the opposite direction is referred to as supination. Soft tissues on the medial side of the MTP joint and lateral side of the MTC joint attenuate, through lengthening and thinning, thus weakening the capsule and permitting the deformities to progress. Soft tissues on the opposite sides of the capsule tend to shorten, thicken and form contractures making it difficult to reduce the joints to their normal angular alignment.

More generally, deformities of the first ray may include metatarsus primus varus, hallux valgus, abnormal pronation, abnormal supination, abnormal dorsiflexion, and/or abnormal plantar flexion. These deformities correspond to three different planar rotations. Metatarsus primus varus and hallux valgus result from rotations in the transverse plane24. Pronation and supination are rotation in the coronal plane10. Dorsiflexion and plantar flexion are rotation in the sagittal plane.

The terms “suture” and “suture strand” are used herein to mean any strand or flexible member, natural or synthetic, able to be passed through material and useful in a surgical procedure. The term “transverse” is used herein to mean crossing as in non-parallel.

The present invention provides methods and devices for performing an osteotomy. In a method according to the present invention, a desired positional change between two bone portions is predetermined and then the bone is cut to allow the bone portions to be repositioned in the new position. By way of illustrative example,FIGS. 14 and 15illustrate the medial cuneiform200, first metatarsus202, and proximal phalanx204of the first ray of a human foot with overlying coordinate axes.FIG. 14is a dorsal view, looking down, on the first ray.FIG. 15is a medial view, looking from the medial side, of the first ray. The Z-axis is positive plantar, the X-axis is positive medial, and the Y-axis is positive distal. The Y-axis is parallel to the anatomic axis of the first metatarsus. The Y-Z plane is a local, first metatarsal sagittal plane and in a healthy foot is rotated slightly medial about the Z-axis relative to the sagittal plane of the body. The X-Y plane is a local, first metatarsal transverse plane and in a healthy foot is rotated slightly dorsal about the X-axis relative to the transverse plane of the body due to the natural angle of the foot. The X-Z plane is a local, first metatarsal coronal plane and in a healthy foot is rotated slightly anterior about the X-axis relative to the coronal plane of the body due to the natural angle of the foot.

FIGS. 16-18illustrate the metatarsus202alone with the coordinate axes ofFIGS. 14 and 15. Rotation about each of the axes is shown. Referring toFIG. 16, rotation in the X-Y plane about the Z-axis results in a change in the IMA. Referring toFIG. 17, rotation in the Y-Z plane about the X-axis results in a change in dorsiflexion/plantarflexion. Referring toFIG. 18, rotation in the X-Z plane about the Y-axis results in a change in pronation/supination. In the case of an osteotomy, a cut is made in a bone to change the position of one portion of the bone relative to another portion. For example, in a metatarsus202, it may be desirable to change the position of the distal metatarsal head206relative to the proximal portion of the bone. As shown inFIG. 16, a cylindrical cut208, also referred to as a crescentic cut, concentric with the Z-axis allows a change in IMA by rotating the cut surfaces relative to one another about the Z-axis. Likewise, as shown inFIG. 17, a cylindrical cut210concentric with the X-axis allows a change in flexion angle by rotating the cut surfaces relative to one another about the X-axis. Similarly, a planar cut212parallel to the X-Z plane (FIGS. 16 and 17) allows a change in pronation/supination by rotating the cut surfaces about the Y-axis (FIG. 18).

It is possible to create an oblique cut, i.e. a cut angled relative to two or three axes, that results in simultaneous angular changes in 2 or 3 anatomic planes. For example, referring toFIG. 19A, an initial position214of a bone portion axis can be changed by rotating the bone portion about two axes to a new position216. Using the illustrative example ofFIGS. 14-18, this would correspond to plantar flexing the metatarsus by an angular amount218corresponding to a plantar displacement220of the distal head206and decreasing the IMA an angular amount222corresponding to a lateral displacement224of the distal head206. These two motions to move to the new position216can be resolved to a bi-planar rotation plane226having a bi-planar rotation axis228normal to the bi-planar rotation plane226. In other words, cutting the bone and relatively rotating the resulting bone portions in the bi-planar rotation plane226, e.g. such as about the bi-planar rotation axis228, will simultaneously change the relative plantar flexion and IMA of the bone portions. For any given combination of predetermined plantar displacement220and change in IMA222, rotating the cut bone portions to achieve one of the changes will necessarily produce the other change due to the coupled motion about the bi-planar rotation axis228. For example, repositioning the bone portions to reduce the IMA by the predetermined amount222will also result in the predetermined plantar displacement220. For many combinations of correction, the bone cut may be a crescentic cut coaxial with the bi-planar rotation axis228or a planar cut normal to the bi-planar rotation axis228. For other combinations, the angle of the bi-planar rotation axis228may make either a crescentic cut or a planar cut more practical.

Referring toFIGS. 19A and 19B, an additional rotation about the bone axis from the initial position214to the new position216may be included and when combined with the other two motions results in a tri-planar rotation axis230about which a rotation will result in a tri-planar correction. In the illustrative example ofFIGS. 14-18, this additional rotation corresponds to a change in pronation/supination of the metatarsus about its anatomic axis. InFIG. 19B, a first plane may be constructed containing the bi-planar rotation axis228and the initial position214of the bone portion axis. A second plane may be constructed containing the bi-planar rotation axis228and the new position216of the bone portion axis. A bisector plane215contains the bi-planar rotation axis228, the tri-planar rotation axis230and is angularly spaced half-way between the initial and new positions214,216.

FIG. 19Cillustrates the motion of the end of the metatarsus202in a motion plane217(FIG. 19B) perpendicular to the bisector plane215for the case of rotation about the bi-planar rotation axis228. A reference mark219is included to illustrate the pronation/supination of the bone. With rotation about the bi-planar rotation axis228, the end of the metatarsus translates from the initial position214to the new position216resulting in a medial/lateral displacement221and a dorsal/plantar displacement223but without any change in pronation/supination; i.e. without any rotation about the anatomic longitudinal axis.

FIG. 19Dillustrates the motion of the end of the metatarsus202in the motion plane217for the case of rotation about the tri-planar rotation axis230. With rotation about the tri-planar rotation axis230, the end of the metatarsus translates medial/lateral221, translates dorsal/plantar223and rotates225in pronation/supination from the initial position214to the new position216.

Referring toFIG. 19B, the bi-planar rotation axis228lies in the X-Z plane at an angle θ227relative to the Z-axis. The tri-planar rotation axis230lies in the bisector plane215at an angle Φ229from the bi-planar rotation axis228. Letting α=the change in IMA222, ω=the change in pronation/supination225, L=the metatarsal axis length from the rotation axis to the joint line of the MTP joint, C=the dorsal/plantar displacement220of the metatarsal head, and R=the ratio C/L, then θ=fn(R, α) and Φ=fn(α, ω) using vector transformations as is known in the art.

By determining the current position of an abnormally positioned metatarsus and the desired final position, a desired positional change in each plane may be determined. The current and desired positions may be determined by medical imaging, computer modeling, manual measurement, or other techniques as is known in the art. The desired positional change may be expressed as an angular change or, for a given position relative to the osteotomy location, it may be expressed as a displacement. For example, in the illustrative example of an osteotomy of the first metatarsus, it may be desirable to express one or more of the positional changes in terms of a displacement of the distal metatarsal head206such as, e.g., the plantar displacement220ofFIG. 19A. As long as the distance from the metatarsal head to the rotation axis of the osteotomy is known, the positional change may be expressed as either an angle or a displacement. In the following examples, for example, plantar flexion is expressed as an amount of plantar displacement of the distal head of the metatarsus, based either a gauged metatarsal axis length L or an estimated metatarsal axis length L determined as the difference between an average metatarsus overall length and a gauged distance from the proximal end of the metatarsus to the osteotomy.

An illustrative method according to the present invention produces an osteotomy between a first bone portion and a second bone portion. The bone portions define a first relative position between them. The method includes defining a rotation axis or a corresponding rotation plane in fixed relationship to the bone, referencing a cutter to the rotational axis or plane, cutting the bone to mobilize the first and second bone portions relative to one another, and rotating the first bone portion relative to the second bone portion within the rotation plane and/or about the rotational axis. The rotational axis and plane incorporate a desired positional change in one or more planes, preferably in two or three anatomic planes. For example, to reposition a first portion of a bone relative to a second portion of the bone, an axis guide may be provided that defines one or more rotational axes. Each rotational axis may incorporate an angular change in one or more anatomic reference planes. Each rotational axis may be incorporated into the axis guide by, e.g., calculating angles θ227and Φ229as described above for a particular combination of corrections. The axis guide may then be modeled along with features operable to orient the guide relative to anatomic reference planes. Each rotational axis may then be superimposed on the model relative to the same anatomic reference planes and be used to define a feature such as a hole, pin, slot, groove, intersecting surfaces, or other suitable features corresponding to the rotational axis or corresponding rotational plane. A cutter may be referenced to one of the rotation axes or rotational planes and guided to mobilize the first and second bone portions relative to one another. The bone portions may then be relatively rotated within the rotational plane and/or about the rotation axis, to realize the angular change in the one or more reference planes. In one example, the cutter may be linked directly to the axis guide. In another example, the axis guide may be used to provide a feature such as a hole or pin in the bone defining the rotation axis which is referenced by the cutter. The axis guide may be removed prior to referencing the cutter to the rotation axis. For example, the axis guide may include a guide hole corresponding to each rotation axis and the guide hole may be used to place a pin in the bone aligned with a desired rotation axis and the axis guide may then be removed. A cutter may then engage the pin for rotation about the pin to create a cylindrical cut in the bone about which the bone portions may be relatively rotated. Alternatively, a cut guide defining a cut plane may be referenced to the pin. A cutter may then be guided in the cut plane to create a planar cut between the bone portions. The bone portions may then be rotated about the rotation axis. Alternatively, a cut guide defining one or more rotation planes corresponding to one or more predetermined multi-planar corrections may be provided. The cut guide may be referenced to the bone and used to guide a cutter to create a planar cut between the bone portions without first creating a rotation axis in or on the bone. In this case, the rotation plane or planes corresponding to the rotation axes are defined by the guide and the guide is positioned on the bone by aligning reference features of the guide with the bone to orient the guide to correctly position the one or more rotation planes. The guide may then be used to guide a cutter directly to create a planar cut in the bone corresponding the to the desired rotation plane. The freed bone portions may then be rotated in the rotation plane to achieve the multi-planar correction.

FIGS. 20-22depict an illustrative crescentic blade250. The blade250has a thin wall252forming a portion of a cylinder curved about a blade axis254and extending from a proximal end256to a distal end258. Teeth260are formed on the distal end258. The proximal end256is attached to a shaft262coaxial with the blade axis254. The shaft262may be attached to a powered handpiece to rotate the blade about the blade axis and form a cylindrical cut in a bone. By using an oscillating motion, a cut transcribing an arc of a cylinder can be made. The shaft262may include an axial bore264coaxial with the blade axis254able to receive a pin in rotational engagement for guiding the blade in rotation about the pin.

FIGS. 23-28depict an illustrative cut block270. The cut block270has a bore272defining a rotation axis274. The bore272is able to receive a pin in axial sliding and rotational relationship. The cut block includes a curved surface276defining at least a portion of a cylinder parallel to the rotation axis274. The cut block270may be pinned to a bone by placing a pin through the bore272and into the bone. A second pin may be placed through a second bore278and into the bone to prevent the cut block from rotating about the first pin. A cutter, such as the crescentic blade250ofFIGS. 20-22, may be guided to form a cut about the rotation axis274of the cut block by pressing the curved blade against the curved surface276.

FIGS. 29-34depict an illustrative blade guide280. The blade guide280includes a shaft282having a bore284defining an axis286extending between a proximal end288and a distal end290. A set screw291is contained in a hole transverse to the bore284. The set screw291may be tightened to lock the blade guide280to a pin received in the bore284. The blade guide280defines a plane281, normal to the bore axis286, for guiding a cutter, e.g. a saw blade, to make a planar cut in a bone. In the illustrative example ofFIGS. 29-34, a surface292formed near the distal end290defines the plane. More particularly in the illustrative example ofFIGS. 29-34, a pair of opposing surfaces defines a slot294between them able to receive a saw blade and constrain it to motion in a plane. The blade guide280is narrow proximally and wide distally to provide clearance for soft tissues while providing a wide slot294allowing the blade to be swept from side to side within the slot294. The distal end290is offset296from the axis286so that the bore284can be placed on a pin in a bone and the distal end290be placed beside the bone. The distal end290is curved as seen inFIGS. 29 and 34to accommodate the particular anatomy of the illustrative example for use on a metatarsus of a human foot.

FIGS. 35-41depict an illustrative axis guide310. The axis guide310is used to establish a rotation axis on a bone for guiding an osteotomy cut. The axis guide310includes at least one guide hole able to define a rotation axis on a bone. For example, the guide hole may be referenced directly. Alternatively, it may be used to guide a drill to form a hole in a bone such that the hole may be referenced to guide a cutter. Similarly, the guide hole may guide the placement of a pin that may be referenced to guide a cutter. When the guide is aligned with a bone, the guide hole defines a rotation axis corresponding to a positional change that may be produced by an osteotomy in which a cutter is referenced to the rotation axis. The position change may include changes in one or more anatomic planes. In the illustrative example ofFIGS. 35-41, the axis guide310includes multiple guide holes, each guide hole defining a rotational axis corresponding to a different positional change between first and second bone portions in at least two anatomic reference planes. For example, the illustrative axis guide310ofFIGS. 35-41is configured for establishing rotational axes for a metatarsal osteotomy to produce a positional change in IMA, pronation, and plantar flexion. In the illustrative example ofFIGS. 35-41, the plantar flexion is expressed on the guide as a change in plantar displacement of the distal head of the metatarsus. The axis guide310includes rows312and columns314of guide holes in which each guide hole corresponds to a unique combination of change in IMA, pronation, and plantarflexion. Indicia may be provided on the axis guide310to indicate the amount of change produced in one or more of IMA, pronation, and plantarflexion, using each guide hole. In the illustrative example ofFIGS. 35-41, the guide holes define axes that are angled relative to one another in at least two rotational degrees of freedom.

In the illustrative example ofFIGS. 35-41, the axis guide310may be one of a set of axis guides in which each axis guide has a fixed plantarflexion positional change applied to each guide hole. In the illustrative example ofFIGS. 35-41, the particular axis guide310shown corresponds to a fixed plantarflexion positional change corresponding to 2.5 mm of plantar displacement of the distal head of the metatarsus for a rotational axis a predetermined distance from the distal head of the metatarsus. The setting of that predetermined distance is shown later in this disclosure. The positional change is expressed in terms of plantar displacement for convenience. For metatarsal osteotomies, a surgeon typically is interested in preserving the plantar position of the distal head of the metatarsus or offsetting it a fixed amount. Therefore, it is convenient to have guides with a fixed plantar change and variable IMA and pronation changes.

For the illustrative axis guide310ofFIGS. 35-41, the guide hole316in the row labeled 0 degrees of pronation and the column labeled 15 degrees of IMA will establish a rotational axis to guide an osteotomy that when rotated to decrease the IMA by 15 degrees will also result in 0 degrees of pronation correction and a 2.5 mm plantar shift of the distal head of the metatarsus. Similarly, the guide hole318in the row labeled 5 degrees of pronation and 10 degrees of IMA will establish a rotational axis to guide an osteotomy that when reduced to decrease the IMA by 10 degrees will also result in 5 degrees of pronation correction and a 2.5 mm plantar shift of the distal head of the metatarsus. Axis guides may be provided that incorporate IMA changes corresponding to any clinically expedient amount, e.g., with the goal of reducing the IMA to fall within a normal anatomic range. Preferably axis guides are provided that incorporate an IMA reduction ranging from 0 to 25 degrees; more preferably from 5 to 15 degrees. The guides may incorporate pronation correction corresponding to any clinically expedient amount, e.g., with the goal of correcting pronation to fall within a normal anatomic range. Preferably axis guides are provided that incorporate a pronation correction ranging from 0 to 15 degrees; more preferably from 0 to 10 degrees. The guides may incorporate plantarflexion changes corresponding to any clinically expedient amount. Preferably axis guides are provided that incorporate a plantar shift ranging from 0 to 5 mm; more preferably 0 to 2.5 mm.

An alignment reference is provided to align the axis guide310to anatomic features of the bone so that the positional changes are referenced to the anatomic planes. An alignment reference may include a mark, line, plane, projection, or other suitable reference. In the illustrative example ofFIGS. 35-41, a dorsal-plantar through hole330and a distal hole332are provided to receive dorsal and distal alignment rods334,336that are used to align the axis guide310. The dorsal-plantar hole330may extend through the axis guide310, as shown, to permit the dorsal alignment rod334to be driven through the axis guide310and into underlying bone to fix the axis guide310to the bone. It is advantageous to offset the holes330,332medial-laterally as shown inFIGS. 37 and 40so that the alignment rods334,336do not collide. The distal alignment rod336may include an optional plantar directed pointer338at its distal end as an alignment aid. For example, the distal end of the distal alignment rod336may be bent to create the pointer338. The plantar surface340of the axis guide310is concave medial-laterally to help stabilize it as it sits on the dorsal surface of a bone. An additional fixation hole342through the axis guide310may be used to provide additional fixation of the axis guide310to an underlying bone.

FIGS. 42-54depict an illustrative method according to the invention. In the Illustrative example ofFIGS. 42-54, the illustrative instruments ofFIGS. 20-41are shown in use to perform an osteotomy on a metatarsus of the first ray of a human foot for changing the alignment of the first ray.

InFIGS. 42 and 43, the illustrative axis guide310ofFIGS. 35-41has been placed on the metatarsus202. The dorsal alignment rod334is aligned with the local sagittal plane of the metatarsus202. The distal alignment rod336is aligned parallel to the metatarsal anatomic axis402. The optional pointer338may be aligned with e.g. the joint line of the MTP joint to position the axis guide310at a predetermined distance from the distal head206. With the axis guide310at a predetermined distance from the distal head206, angular changes in the position of the distal head206may optionally be expressed as displacements. For example, in the illustrative axis guide310ofFIGS. 35-41, the change in dorsiflexion is indicated on the axis guide310as a plantar displacement of the metatarsal head. The dorsal alignment rod334may be driven into the metatarsus to temporarily fix the axis guide310in the aligned position.

InFIG. 44, an additional pin344has been placed through the additional fixation hole342to further stabilize the axis guide310.

InFIG. 45, an axis pin346has been placed through the axis hole corresponding to a 15 degree change in IMA and a 5 degree change in pronation. The particular axis guide310also incorporates a 2.5 mm distal plantar displacement into each of the axis holes.

InFIG. 46, alignment rods334and336, the fixation pin344, and the axis guide310have been removed leaving just the axis pin346establishing the rotation axis for a 15 degree IMA, 5 degree pronation, and 2.5 mm distal plantar displacement corrective osteotomy. In the illustrative example ofFIG. 46, the cannulated crescentic saw blade250has been placed over the axis pin346and rotated about the rotational axis pin346to produce a cylindrical cut347through the metatarsus202. Alternatively, the cut block270may be placed over the rotational axis pin346. The crescentic blade250may be guided on the cut block270alone, without engaging the pin346, or the blade250may engage both the cut block270and the rotational axis pin346. After the bone is cut, the distal portion is reduced to the desired IMA which will simultaneously change the pronation angle and plantar position of the distal bone portion. The bone portions may then be fixed with pins, screws, plates or other suitable fixation elements.

InFIG. 47, as an alternative to using the cannulated crescentic blade250, the blade guide280has been placed over the rotational axis pin346and adjusted to align with a desired cut plane on the metatarsus202. The set screw291is tightened to lock the blade guide280in place on the axis pin346. A saw blade (not shown) is guided in the slot294to form a planar cut surface through the bone. After the bone is cut, the distal portion is reduced to the desired IMA which will simultaneously change the pronation angle and plantar position of the distal bone portion. The bone portions may then be fixed with pins, screws, plates or other suitable fixation elements.

Referring toFIGS. 48 and 49, the rotational axis pin346may preferably be advanced partway into the bone as shown inFIG. 48prior to cutting the bone so that the tip of the pin is dorsal to the slot294. The bone may then be cut partially through, including under the rotational axis pin346. The set screw291may be loosened and the rotational axis pin346driven plantar past the planar cut as shown inFIG. 49. The set screw291may be retightened and the remainder of the bone cut through. The bone cut350is shown inFIGS. 50 and 51. In this way, the rotational axis pin346captures the cut bone portions.

FIGS. 52-54shows the bone with the blade guide280removed and the rotational axis pin346capturing the cut bone portions. The bone portions have been rotated as indicated by arrow348about the rotational axis pin to the desired IMA (FIG. 52) simultaneously changing the pronation angle (FIG. 53) and plantar position (FIG. 54) of the distal bone portion.

FIGS. 55-61illustrate an alternative cut guide400. The cut guide may be used to directly guide a cutter, such as a planar saw blade, to create a rotation plane between bone portions corresponding to a multi-planar correction as described relative to the examples above. The cut guide400includes a cutter guiding feature defining a rotation plane and includes reference features that are alignable with a bone to place the guide in a predetermined orientation relative to the bone. For sake of clarity, the cutter guiding surface is normal to a rotation axis determined as described above. However, in the illustrative example ofFIGS. 55-61, the rotation axis is not discretely defined with a hole or pin but rather the corresponding plane is defined and referenced to the bony anatomy with the reference features.

In the illustrative example ofFIGS. 55-61, the guide400includes a guide body402having a proximal end404, a distal end406opposite the proximal end, a medial side408, a lateral side410opposite the medial side, a top surface412, and a bottom surface414opposite the top. The guide body402includes a fixation feature to temporarily secure the guide body402to a bone. The fixation features may include one or more roughened surface, spike, hole for receiving a pin or screw, strap, or other fixation feature known in the art. In the illustrative example ofFIGS. 55-61, the fixation feature include holes416,418extending through the guide body402from the top surface412to the bottom surface414and configured to receive a fixation member such as a pin or screw that extends though the guide body402and into the bone. Preferably the holes416and418are coplanar but not parallel. By being coplanar the hole axes define a reference plane that can be used to align the guide. By being non-parallel, smooth pins inserted through the holes and into an underlying bone will secure the guide body402to the bone and prevent it from lifting off of the bone. In the illustrative example ofFIGS. 55-61, the holes416,418define a plane including a guide body longitudinal axis420intersecting the hole axes422,424.

The guide body includes reference features for aligning the guide body with a metatarsus. In the illustrative example ofFIGS. 55-61, the reference features include the bottom surface414, the proximal end404, and the longitudinal axis420defined by the holes416,418.

The guide body402includes a plurality of cutter guiding features, each corresponding to a different multi-planar correction. The cutter guiding features may be, for example, planar surfaces, slots, or other features known in the art for guiding a cutter to form a planar surface on a bone. In the illustrative example ofFIGS. 55-61, the cutter guiding features are in the form of saw blade slots430,432,434. Each slot430,432,434is aligned relative to the reference features so that when bottom surface414is resting on the bone, the longitudinal axis420is aligned parallel with the metatarsal axis, the hole axes424,426are aligned within the sagittal plane, and the proximal end404is aligned with the MTC joint line, the slot will guide a saw blade to produce a rotation plane corresponding to a particular multi-planar correction. In the illustrative example ofFIGS. 55-61, each slot is configured to produce 3 degrees of IMA correction and 10, 20, or 30 degrees of pronation correction. In addition, a slight amount of plantar displacement of the distal metatarsal head is included in each correction to compensate for shortening of the metatarsus due to the bone removed by the saw blade, i.e. the saw blade kerf. The amount of plantar displacement is an estimate based on an osteotomy-to-distal metatarsal head distance determined as the difference between the overall length of an average human first metatarsus and the distance from the MTC joint line to the osteotomy plane. In the illustrative example ofFIGS. 55-61, the plantar displacement is designed to maintain the metatarsal head in the same plane it was in prior to the osteotomy to avoid changing the load balance between the five rays of the foot. Typical values of plantar displacement are in the range of 0.1 mm to 3 mm. In the illustrative example ofFIGS. 55-61, the slots430,432,434define planes that are angled relative to one another in at least two rotational degrees of freedom.

Indicia436,438printed on the guide body402indicate the IMA correction associated with all of the saw slots on the guide400and the different pronation correction associated with each of the saw slots. Additional indicia440printed on the guide body402indicates that the guide400is configured for a right foot.

A handle may be provided to aid in manipulating the guide400. In the illustrative example ofFIGS. 55-61, a handle interface442is formed on the medial side to engage a modular, removable handle (not shown). The handle interface may include a slot, tab, dovetail, or other feature as is known in the art for coupling to a modular handle.

FIG. 62depicts an exemplary kit450having a tray452for housing the guide400ofFIG. 55along with additional guides offering a variety of configurations. In the illustrative example ofFIG. 62, a plurality of guides400,454,456configured for a right foot is provided on one side of the tray452and a plurality of guides458,460,462configured for a left foot is provided on another side of the tray. In the illustrative example ofFIGS. 55-61, each guide provides for either 3, 6, or 9 degrees of IMA correction and the choice of 10, 20, or 30 degrees of pronation correction. All of the guides provide a fixed additional plantar displacement. The kit allows a surgeon to select a guide corresponding to a left or right foot and having a desired amount of IMA correction. After selecting the appropriate guide, the surgeon may then select the amount of pronation correction by choosing the corresponding saw slot. The tray may include other items useful in the osteotomy procedure such as fixation pins464.

FIGS. 63-65illustrate an osteotomy procedure using the kit450.FIG. 63is a dorsal view of the first and second rays470,472of a right foot having an IMA of approximately 19 degrees. A guide456is selected from the kit450corresponding to a 9 degree IMA correction. The guide456is mounted on the metatarsus474with the bottom of the guide456resting on the longitudinal axis420of the guide, the longitudinal axis420parallel to the metatarsal longitudinal axis, the plane containing the fixation hole axes426,424aligned parallel to the sagittal plane, and the proximal end aligned with the MTC joint. In the illustrative example ofFIGS. 63-65, the surgeon selects the saw slot corresponding to a 10 degree pronation correction and uses it to guide a saw blade476to form a cut478defining a rotation plane479between proximal and distal portions480,482of the metatarsus.

InFIG. 65, the distal portion of the metatarsus along with the phalanges484,486have been rotated within the plane479defined by the cut478to reduce the IMA by 9 degrees as well as correct the pronation by 10 degrees and produce a compensating plantar displacement of the metatarsal head. If desired, the surgeon may fine tune the position of the distal portion of the first ray by sliding the cut surfaces in addition to rotating them. The osteotomy may be fixed using pins, screws, plates, or other devices and methods as is known in the art.

Various illustrative examples of devices and methods of producing a multi-planar osteotomy on a bone have been provided. Examples of guides have been provided that can be used to define a rotation axis and/or corresponding rotation plane in three rotational degrees of freedom relative to a bone to perform a tri-planar rotational osteotomy. While such a guide may be used to perform a tri-planar rotational osteotomy on any bone, it has been illustrated for example to produce a tri-planar rotational osteotomy on a first metatarsus of a human foot to correct angular alignment of the first ray of the foot. The illustrative examples are particularly useful to a surgeon inasmuch as they provide the surgeon with the ability to intraoperatively select at least one of the correction angles. For example, an exemplary guide has been disclosed that allows the surgeon to vary the value of one of the three angular degrees of freedom simply by choosing one of a plurality of guiding features such as a hole defining a rotation axis or a surface or slot defining a rotation plane. An exemplary guide has been disclosed that allows the surgeon to vary the value of two of the three angular degrees of freedom by selecting one of a plurality of guiding features arranged in a matrix. Sets of guides have been disclosed that allow the surgeon to intraoperatively vary a third angular degree of freedom. It has been shown that the angular degrees of freedom may be stated in terms of rotational degrees or as displacements if additional information is provided regarding the size and shape of the bone and the location of the osteotomy. Examples have been disclosed in which the angular degrees of freedom may be related to a metatarsus of a foot so that they correspond to, for example, IMA, pronation, and plantar flexion. Guides have been disclosed that may be configured to allow user selectability of any one of IMA, pronation, and plantar flexion. Guides have been disclosed that may be configured to allow user selectability of any two of IMA, pronation, and plantar flexion. Guides have been disclosed as sets of guides that may be configured to allow user selectability of IMA, pronation, and plantar flexion. Guides have been disclosed having a plurality of cutter guiding features differing in the amount of angular correction. It is within the scope of the invention to provide a single cutter guiding feature with an adjustable position to permit varying the value of one or more angular corrections. It will be understood that substitutions among the various examples and variations are within the scope of the invention. For example, more or fewer options with regard to correction angles may be provided, alternative fixation of the guide to the bone may be incorporated, and different corrections may be coupled on a particular guide. For example, a particular guide may have a fixed pronation correction and variable IMA correction or a particular guide or set of guides may have variable plantar displacement. Many combinations are possible and the present inventors have demonstrated multiple, but not a comprehensive listing of, examples illustrating some of the possible combinations of features within the scope of the invention.