US 20080108996 A1
Deployment systems for deploying a bone fixation device are disclosed herein. One embodiment of a deployment system includes a syringe-shaped body configured to provide proximal traction to a bone fixation device in response to a compressive force between a finger grip and a plunger adapted to be engaged by the heel of a clinician's hand. The device may include a collet for gripping a proximal pin of a fixation device. The deployment device may also include a tool that includes an elongate body with a distal tip adapted to rotationally engage a bone fixation device in order to axially rotate the fixation device. A further deployment device embodiment includes a cauterizing tip for heat-cutting an excess portion of a pin of a bone fixation device.
1. A method of securing a first bone fragment to a second bone fragment, comprising the steps of:
forming a bore through the first bone fragment in the direction of the second bone fragment;
advancing a fixation device comprising an elongate body, having a proximal end and a distal end, a helical anchor on the distal end of the elongate body and a proximal anchor, moveably carried by the elongate body, the elongate body and the proximal anchor having complementary retention structures configured to resist proximal movement of the proximal anchor with respect to the elongate body;
rotating the fixation device to engage bone in the second bone fragment; and
using a deployment device to apply a distal force to proximally withdraw the elongate body with respect to the proximal anchor.
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3. A method of securing a first bone fragment to a second bone fragment as in
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7. A method of securing a first bone fragment to a second bone fragment as in
8. A method of securing a first bone fragment to a second bone fragment as in
9. A method of securing a first bone fragment to a second bone fragment as in
10. A method of securing a first bone fragment to a second bone fragment as in
The present application is a divisional of U.S. patent application Ser. No. 10/790,671, filed Mar. 1, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 09/991,367, filed Nov. 13, 2001, now U.S. Pat. No. 6,890,333, which is a continuation-in-part of U.S. patent application Ser. No. 09/934,467, filed Aug. 23, 2001, now U.S. Pat. No. 6,551,481, and claims priority and benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/464,398, filed Apr. 21, 2003, and claims priority and benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/451,296, filed Feb. 28, 2003, the entireties of the disclosures of each of which are incorporated herein by reference.
1. Field of the Invention
The invention relates in general to the field of bone anchors, and specifically to a deployment device for a bone anchor.
2. Description of the Related Art
The femur, otherwise known as the thigh bone, generally comprises an elongate shaft extending from the hip to the knee. The proximal end of the shaft includes a head, a neck, a greater trochanter and a lesser trochanter. The head of the femur fits into the acetabular cup of the hip bone to form a ball and socket joint at the hip. The distal end of the femur includes a medial condyle and a lateral condyle. The condyles engage an upper end of the tibia to form the knee joint. Overall, the femur is the longest and strongest bone in the skeleton. However, portions of the femur are extremely susceptible to fracturing.
Pertrochanteric fractures among geriatric patients are the most frequent in connection with those of the region of the neck of the bone. The advanced age and the pathologies which are encountered in these patients make a timely stabilization of skeletal injuries necessary in order to reduce to a minimum the bed confinement and the rehabilitation times. Preferably, devices and procedures are utilized which minimize complications brought about by the so-called immobilization syndrome, which may be lethal for patients in delicate metabolical circumstances. It is also preferable to reduce to a minimum blood losses related to surgical intervention. At the same time, the syntheses means utilized must be stable in order to allow the patient to very timely assume a seated position and, two or three days following the intervention, to reassume an erect posture with progressive bearing of weight.
Internal fixation of femoral fractures in general is one of the most common orthopedic surgical procedures. Fractures of the femur occur in both the proximal portion of the femur and the distal portion of the femur. Fractures of the proximal portion of the femur (hip fractures) are generally classified as femoral neck fractures, intertrochanteric fractures and subtrochanteric fractures. Fractures of the distal portion of the femur (knee fractures) are referred to as supracondylar fractures. Supracondylar fractures generally extend vertically between the condyles at the lower end of the femur to separate the distal portion of the femur into two main bone fragments. A fracture line may be further comminuted to create a plurality of smaller bone fragments. Fractures of the femur which extend into the neck of the bone are generally more difficult to treat than fractures restricted to the shaft of the femur.
Operative treatment of the fractures requires that the fractures be internally fixed and possibly compressed. Fractures of the neck, head or trochanters of the femur have been treated with a variety of compression screw assemblies which include generally a compression plate having a barrel member, a lag screw and a compressing screw. The compression plate is secured to the exterior of the femur and the barrel member is inserted into a predrilled hole in the direction of the femoral head. The lag screw which has a threaded end and a smooth portion is inserted through the barrel member so that it extends across the break and into the femoral head. The threaded portion engages the femoral head. The compressing screw connects the lag screw to the plate. By adjusting the tension of the compressing screw the compression (reduction) of the fracture can be adjusted.
A variety of elongated implants (nail, screw, pin, etc.) have been developed, which are adapted to be positioned along the longitudinal axis of the femoral neck with a leading (distal) end portion in the femoral head so as to stabilize a fracture of the femoral neck. The elongated implant may be implanted by itself or connected to another implant such as a side plate or intramedullary rod. The leading end portion of the implant typically includes means to positively grip the femoral head bone (external threads, expanding arms, etc.), but the inclusion of such gripping means can introduce several significant problems. First, implants with sharp edges on the leading end portion, such as the externally threaded implants, exhibit a tendency to migrate proximally towards the hip joint weight bearing surface after implantation. This can occur when the proximal cortical bone has insufficient integrity to resist distal movement of the screw head. Such proximal migration under physiological loading, which is also referred to as femoral head cut-out, can lead to significant damage to the adjacent hip joint. Also, the externally threaded implants can generate large stress concentrations in the bone during implantation which can lead to stripping of the threads formed in the bone and thus a weakened grip. The movable arms of known expanding arm devices are usually free at one end and attached at the other end to the main body of the leading end portion of the implant. As a result, all fatigue loading is concentrated at the attached ends of the arms and undesirably large bending moments are realized at the points of attachment. In addition, conventional threaded implants generally exhibit insufficient holding power under tension, such that the threads can be stripped out of the femoral head either by over-tightening during the implantation procedure or during post operative loading by the patient's weight.
Thus, notwithstanding the variety of efforts in the prior art, there remains a need for a deployment device for an orthopedic fixation device with improved locking force such as within the femoral head in a femoral neck application.
In one embodiment, a method of securing a first bone fragment to a second bone fragment comprises forming a bore through the first bone fragment in the direction of the second bone fragment. A fixation device is advanced though the first bone fragment. The fixation device comprises an elongate body, having a proximal end and a distal end, a helical anchor on the distal end of the elongate body and a proximal anchor, moveably carried by the elongate body. The elongate body and the proximal anchor have complementary retention structures configured to resist proximal movement of the proximal anchor with respect to the elongate body. The fixation device is rotated to engage bone in the second bone fragment. A deployment device is used to apply a distal force to proximally withdraw the elongate body with respect to the proximal anchor.
In one embodiment, a deployment device for use with a bone fixation device is provided. The deployment device generally includes an elongate body with proximal and distal ends. A housing is disposed at the distal end, and has a traction member slidably disposed therein. The device also includes a plunger disposed a the proximal end, and a central portion between the housing and the plunger. The elements are assembled such that distal movement of the plunger relative to the central portion results in proximal motion of the traction member relative to the housing.
According to another embodiment, a deployment device includes an elongate proximal housing having a proximal end and a distal end, and an elongate distal housing extending distally from the distal end of the proximal housing. The device further includes a finger grip movably disposed along the proximal housing, a plunger attached to the proximal end of the proximal housing, and a tensioner extending through the distal and proximal housings. The tensioner is adapted to grip a proximal end of a bone fixation device. The elements are assembled such that a compressive force between the finger grip and the plunger portion causes proximal movement of the tensioner relative to the distal housing. In another embodiment, the tensioner comprises a pin adapted to engage a bone fixation device.
In another embodiment, a syringe-shaped deployment device for use with a bone fixation device is provided. The deployment device comprises a plunger disposed at a proximal end and a finger engagement portion disposed distally from the plunger. The finger engagement portion is free to move axially relative to the plunger. Additionally, the device includes an elongate housing disposed distally from the finger engagement portion. The elongate housing is adapted to move with the plunger relative to the finger engagement portion. The device also includes a tensioner within the housing adapted to move with the finger engagement portion relative to the plunger and the housing. The tensioner is adapted to grip a proximal pin of a bone fixation device. In another embodiment, the tensioner and a proximal pin form an integral body to engage a bone fixation device.
In still another embodiment, a bone anchor deployment device includes an elongate body having a handle at a proximal end and a distal tip. The distal tip is configured to engage a proximal flange of a proximal bone anchor such that rotation of the deployment device results in rotation of the bone anchor. In this embodiment, distal tip comprises a hexagonal shape with a central hole configured to receive a proximal pin of a bone anchor. The pin may be received in the central hole until it abuts a stop at a pre-determined depth within the hole.
In yet another embodiment, a bone fixation device and deployment system is described. The system includes a bone fixation device comprising an elongate body having a proximal end and a distal end and comprising a first portion and a second portion which are detachably coupled to each other at a junction. The fixation device further includes a helical anchor on the distal end, a retention structure on the body proximal to the anchor, and an anti-rotational structure on the first portion of the body. The fixation device also includes a proximal anchor, movably carried by the body and comprising a tubular sleeve that in a first position extends distally past the junction between the first portion the second portion. The proximal anchor also has a rotational coupling. The proximal anchor is movable in the distal direction with respect to the body, the retention structure resists proximal movement of the proximal anchor with respect to the body and the anti-rotational structure prevents rotational movement of the first portion of the body with respect to the proximal anchor. The system further includes a deployment device comprising an elongate body having a distal end configured to engage the rotational coupling of the proximal anchor.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the present invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.
Having thus summarized the general nature of the invention, certain preferred embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which:
FIGS. 6A-C illustrate a procedure for using of the fixation device of
Although the fixation devices of the present invention will be disclosed primarily in the context of fractures of the proximal femur, the methods and structures disclosed herein are intended for application in any of a wide variety of bones and fractures, as will be apparent to those of skill in the art in view of the disclosure herein. For example, the bone fixation device of the present invention is applicable in a wide variety of fractures and osteotomies in the hand, such as interphalangeal and metacarpophalangeal arthrodesis, transverse phalangeal and metacarpal fracture fixation, spiral phalangeal and metacarpal fracture fixation, oblique phalangeal and metacarpal fracture fixation, intercondylar phalangeal and metacarpal fracture fixation, phalangeal and metacarpal osteotomy fixation as well as others known in the art. A wide variety of phalangeal and metatarsal osteotomies and fractures of the foot may also be stabilized using the bone fixation device of the present invention. These include, among others, distal metaphyseal osteotomies such as those described by Austin and Reverdin-Laird, base wedge osteotomies, oblique diaphyseal, digital arthrodesis as well as a wide variety of others that will be known to those of skill in the art. The bone fixation device may be used with or without plate(s) or washer(s), all of which can be either permanent, absorbable, or combinations.
Fractures of the fibular and tibial malleoli, pilon fractures and other fractures of the bones of the leg may be fixated and stabilized with the present invention with or without the use of plates, both absorbable or non-absorbing types, and with alternate embodiments of the current invention. Fractures and osteotomies of the mid and hind foot, tarsal arthrodesis and osteotomy, or others as are known to those with skill in the art. One example is the fixation of the medial malleolar avulsion fragment.
The fixation device of the present invention may also be used to attach tissue or structure to the bone, such as in ligament reattachment and other soft tissue attachment procedures. Plates and washers, with or without tissue spikes for soft tissue attachment, and other implants may also be attached to bone, using either resorbable or nonresorbable fixation devices depending upon the implant and procedure. The fixation device may also be used to attach sutures to the bone, such as in any of a variety of tissue suspension procedures.
For example, peripheral applications for the fixation devices include utilization of the device for fastening soft tissue such as capsule, tendon or ligament to bone. It may also be used to attach a synthetic material such as marlex mesh, to bone or allograft material such as tensor fascia lata, to bone. In the process of doing so, retention of the material to bone may be accomplished with the collar as shown, or the pin and or collar may be modified to accept a suture or other material for facilitation of this attachment.
Specific examples include attachment of the posterior tibial tendon to the navicular bone in the Kidner operation. This application may be accomplished using an appropriately sized implant of the present invention along with a washer with distally extending soft tissue spikes. Navicular-cuneiform arthrodesis may be performed utilizing the device and concurrent attachment of the tendon may be accomplished. Attachment of the tendon may be accomplished in the absence of arthrodesis by altering the placement of the implant in the adjacent bone.
Ligament or capsule reattachment after rupture, avulsion or detachment, such as in the ankle, shoulder or knee can also be accomplished using the devices disclosed herein.
The fixation devices may be used in combination with semi tubular, one-third tubular and dynamic compression plates, both of metallic and absorbable composition, if the collar is modified to match the opening on the plate.
The canulated design disclosed below can be fashioned to accept an antibiotic impregnated rod for the slow adsorption of medication locally. This may be beneficial for prophylaxis, especially in open wounds, or when osteomyelitis is present and stabilization of fracture fragments is indicated.
A kit may be assembled for field use by military or sport medical or paramedical personnel. This kit contains an implanting tool, and a variety of implant device size and types. The kit may include additional components such as sterilization or disinfectant materials, a skin stapler, bandages, gloves, and basic tools for emergent wound and fracture treatment. Antibiotic rods may be included for wound prophylaxis during transport.
The greater trochanter 18 extends outwardly above the junction of the neck 16 and the body 17 of the femur 10. On the medial side of the greater trochanter 18 is the trochanteric fossa 20. This depression accommodates the insertion of the obturator externus muscle. The lesser trochanter 21 is located posteromedially at the junction of the neck 16 and the body 17 of the femur 10. Both the greater trochanter 18 and the lesser trochanter 21 serve for the attachment of muscles. On the posterior surface of the femur 10 at about the same axial level as the lesser trochanter 21 is the gluteal tuberosity 22, for the insertion of the gluteus maximus muscle. Additional details of the femur are well understood in the art and not discussed in further detail herein.
In one embodiment, the body 28 comprises titanium. However, as will be described in more detail below, other metals or bioabsorbable or nonabsorbable polymeric materials may be utilized, depending upon the dimensions and desired structural integrity of the finished fixation device 12.
The distal end 32 of the body 28 is provided with a cancellous bone anchor or distal cortical bone anchor 34. Additional details of the distal bone anchor are described below. In general, in a femoral neck application, distal bone anchor 34 is adapted to be rotationally inserted into the cancellous bone within the head 14 of the femur 10, to retain the fixation device 12 within the femoral head.
In a modified arrangement, the second portion 38 can comprise any of a variety of tensioning elements for permitting proximal tension to be placed on the distal anchor 34 while the proximal anchor is advanced distally to compress the fracture. For example, any of a variety of tubes or wires can be removably attached to the first portion 36 and extend proximally to the proximal handpiece. In one such arrangement, the first portion 36 can include a releasable connector in the form of a latching element, such as an eye or hook. The second portion 38 can include a complementary releasable connector (e.g., a complementary hook) for engaging the first portion 36. In this manner, the second portion 38 can be detachably coupled to the first portion 36 such proximal traction can be applied to the first portion 36 through the second portion as will be explained below. Alternatively, the second portion 48 may be provided with an eye or hook, or transverse bar, around which or through which a suture or wire may be advanced, both ends of which are retained at the proximal end of the device. Following proximal tension on the tensioning element during the compression step, one end of the suture or wire is released, and the other end may be pulled free of the device. Alternate releasable proximal tensioning structures may be devised by those of skill in the art in view of the disclosure herein.
The proximal end 30 of the fixation device is provided with a proximal anchor 50. Proximal anchor 50 is axially distally moveable along the body 28, to permit compression of the fracture 24 as will be apparent from
In the illustrated embodiment, proximal anchor 50 comprises a housing 52 such as a tubular body, for coaxial movement along the body 28. As best seen in
For example, as best seen in
Retention structures 58 are spaced axially apart along the body 28, between a proximal limit 62 and a distal limit 64. The axial distance between proximal limit 62 and distal limit 64 is related to the desired axial working range of the proximal anchor 50, and thus the range of functional sizes of the fixation device 12. Thus, the present invention provides a bone fixation device which can provide compression across a fracture throughout a range of motion following the placement of the distal anchor. The distal anchor may be positioned within the cancellous and/or distal cortical bone, and the proximal anchor may be distally advanced throughout a range to provide compression across the fracture without needing to relocate the distal anchor and without needing to initially locate the distal anchor in a precise position with respect to the proximal side of the bone. Providing a working range throughout which tensioning of the proximal anchor is independent from setting the distal anchor allows a single device to be useful for a wide variety of fractures, as well as eliminates the need for accurate device measurement and accurate placement of the distal anchor. In many applications, the working range is at least about 10% of the overall length of the device, and may be as much as 20% or 30% or more of the overall device length. In the context of a femoral application, working ranges of up to about 10 mm or more may be provided, since estimates within that range can normally be readily accomplished within the clinical setting. In other applications, such as a metatarsal fracture, a working range in the area of from about 1 mm to about 2 mm may be all that is necessary. The embodiments disclosed herein can be scaled to have a greater or a lesser working range, as will be apparent to those of skill in the art in view of the disclosure herein. Additional embodiments of the proximal anchor are disclosed in U.S. Pat. No. 6,685,706, issued Feb. 3, 2004, entitled “PROXIMAL ANCHORS FOR BONE FIXATION SYSTEM”, which is hereby incorporated by reference in its entirety herein.
The proximal anchor 50 includes a flange 66 that seats against the outer surface of the femur or tissue adjacent the femur. The flange 66 is preferably an annular flange, to optimize the footprint or contact surface area between the flange 66 and the femur. Circular or polygonal shaped flanges for use in femoral head fixation will generally have a diameter of at least about 4 mm greater than the adjacent body 28 and often within the range of from about 4 mm to about 20 mm or more greater than the adjacent body 28.
In the illustrated embodiment, the bone contacting surface 68 of the flange 44 is tapered and generally faces the shaft 17 of the femur 10. In other embodiments, the bone contacting surface 69 can resides in or approximately on a plane, which is perpendicular with respect to the longitudinal axis of the body 28. In other embodiments, other angular relationships between the bone contacting surface 68 of the flange 66 and the longitudinal axis of the body 28 and housing 52 may be utilized, depending upon the anticipated entrance angle of the body 28 and associated entrance point surface of the femur 10. In general, the longitudinal axis extending through the head 14 and neck 16 of the human femur is inclined at an angle of approximately 126° from the longitudinal axis of the long body 17 of the femur 10. Angles between the longitudinal axis of body 28 and tissue contacting surface 68 within the range of from about 90° to about 140° will generally be utilized.
In a modified embodiment, the housing 52 of the proximal anchor 50 can include one or more one or more barbs that extend radially outwardly from the tubular housing 52. Such barbs provide for self tightening after the device has been implanted in the patient as described in a co-pending U.S. patent application entitled “DISTAL BONE FOR BONE FIXATION WITH SECONDARY COMPRESSION”, application Ser. No. 10/012,687, filed Nov. 13, 2001, which is hereby expressly incorporated by reference herein. The barbs may be radially symmetrically distributed about the longitudinal axis of the housing 52. Each barb is provided with a transverse engagement surface, for anchoring the proximal anchor 50 in the bone. The transverse engagement surface may lie on a plane which is transverse to the longitudinal axis of the housing 50 or may be inclined with respect to the longitudinal axis of the tubular 50. In either arrangement, the transverse engagement surface 43 generally faces the bone contacting surface 68 of the flange 44. As such, the transverse engagement surface inhibits proximal movement of the proximal anchor with respect to the bone.
The clinician can be provided an array of proximal anchors 50 of varying angular relationships between the bone contacting surface 68 and the longitudinal axis of the body 28 and housing 52 (e.g., 90°, 100°, 110°, 120°, and 130°). A single body 28 can be associated with the array such as in a single sterile package. The clinician upon identifying the entrance angle of the body 28 and the associated entrance point surface orientation of the femur 10 can choose the anchor 50 from the array with the best fit angular relationship, for use with the body 28.
With particular reference to
In one embodiment, the rotational coupling 70 comprises a proximal projection of the body 28 having an axial recess with a polygonal cross section, such as a hexagonal cross section. The rotational coupling 70 is illustrated as a female component, machined or milled or attached to the proximal end 30 of the body 28. However, the rotational coupling may also be in the form of a male element, such as a hexagonal or other noncircular cross sectioned projection.
As illustrated, the body 28 is cannulated to accommodate installation over a placement wire as is understood in the art. The cross section of the illustrated central cannulation is circular but in other embodiments may be non circular, e.g., hexagonal, to accommodate a corresponding male tool for installation or removal of the second portion 38 of the body 28 as will be explained below. In other embodiments, the body 28 may partially or wholly solid.
In all of the embodiments illustrated herein, the distal anchor 34 comprises a helical locking structure 72 for engaging cancellous and/or distal cortical bone. In the illustrated embodiment, the locking structure 72 comprises a flange that is wrapped around the axial lumen. The flange extends through at least one and generally from about two to about 50 or more full revolutions depending upon the axial length of the distal anchor and intended application. For most femoral neck fixation devices, the flange will generally complete from about 2 to about 20 revolutions. The helical flange 72 is preferably provided with a pitch and an axial spacing to optimize the retention force within cancellous bone, to optimize compression of the fracture.
The helical flange 72 of the illustrated embodiment has a generally triangular cross-sectional shape (see
The distal end 32 and/or the outer edges of the helical flange 72 may be atraumatic (e.g., blunt or soft). This inhibits the tendency of the fixation device 12 to migrate anatomically proximally towards the hip joint bearing surface after implantation (i.e., femoral head cut-out). Distal migration is also inhibited by the dimensions and presence of the proximal anchor 50, which has a larger footprint than conventional screws.
A variety of other arrangements for the distal anchor 32 can also be used. For example, the various distal anchors described in U.S. Pat. No. 6,511,481, issued Jan. 29, 2003, co-pending U.S. patent application entitled “DISTAL BONE FOR BONE FIXATION WITH SECONDARY COMPRESSION”, application Ser. No. 10/012,687, filed Nov. 13, 2001 and co-pending U.S. patent application entitled “METHOD AND APPARATUS FOR BONE FIXATION WITH SECONDARY COMPRESSION”, application Ser. No. 10/195,832, filed Jul. 12, 2002 can be incorporated into the fixation device 12 described herein. The entire contents these applications are hereby expressly incorporated by reference. In particular, the distal anchor may comprise a single helical thread surrounding a central core, much as in a conventional screw, which has been cannulated to facilitate placement over a wire. Alternatively, a double helical thread may be utilized, with the distal end of the first thread rotationally offset from the distal end of the second thread. The use of a double helical thread can enable a greater axial travel for a given degree of rotation and greater retention force than a corresponding single helical thread. Specific distal anchor designs can be optimized for the intended use, taking into account desired performance characteristics, the integrity of the distal bone, and whether the distal anchor is intended to engage exclusively cancellous bone or will also engage cortical bone.
With particular reference to
To rotate the proximal collar, the flange 66 is preferably provided with a gripping structure to permit an insertion tool to rotate the flange 66. Any of a variety of gripping structures may be provided, such as one or more slots, flats, bores or the like. In one embodiment, the flange 44 is provided with a polygonal, and, in particular, a pentagonal or hexagonal recess 84 such that a similarly shaped and sized may engage the recess for rotation. See
In use, the clinician first identifies a patient having a fracture to be treated, such as a femoral neck fracture, which is fixable by an internal fixation device. The clinician accesses the proximal femur, reduces the fracture if necessary and selects a bone drill and drills a hole 90 (see
A fixation device 12 having an axial length and outside diameter suitable for the hole 90 is selected. The distal end 32 of the fixation device 12 is advanced distally into the hole 90 until the distal anchor 34 reaches the distal end of the hole 90. The proximal anchor 50 may be carried by the fixation device 12 prior to advancing the body 28 into the hole 90, or may be attached following placement of the body 28 within the hole 90. Once the body 28 and proximal anchor 50 are in place, the clinician may use any of a variety of driving devices, such as electric drills or hand tools (e.g., the embodiments described below) to rotate the proximal anchor 50 and thus cancellous bone anchor 34 into the head of the femur.
Once the distal tip of the anchor 34 is in the desired location, proximal traction is applied to the proximal end 30 of body 28, such as by the deployment devices described below or conventional hemostats, pliers or a calibrated loading device, while distal force is applied to the proximal anchor 50. In this manner, the proximal anchor 50 is advanced distally until the anchor 50 fits snugly against the outer surface of the femur or tissue adjacent the femur and the fracture 24 is completely reduced as shown in
Following appropriate tensioning of the proximal anchor 50, the second portion 38 of the body 28 is preferably detached from the first portion 36 and removed. See
Following removal of the second portion 38 of each body 28, the access site may be closed and dressed in accordance with conventional wound closure techniques.
In a modified arrangement, the second portion 38 may form part of the driving device, which is used to rotate the proximal anchor 50 and thus cancellous bone anchor 34 into the head of the femur. The second portion 38 is used to apply proximal traction so as to compress the fracture. After appropriate tensioning, the second portion 38 can be de-coupled from the first portion 36 and removed with the driving device.
In the foregoing variation, the second portion 38 may be connected to a rotatable control such as a thumb wheel on the deployment device. A container may be opened at the clinical site exposing the proximal end of the implant, such that the distal end of the second portion 38 may be removably coupled thereto. Proximal retraction of the hand tool will pull the implant out of its packaging. The implant may then be positioned within the aperture in the bone, rotated to set the distal anchor, and the hand piece may be manipulated to place proximal traction on the second portion 38 while simultaneously distally advancing the proximal anchor. Following appropriate tensioning across the fracture, the second portion 38 may be disengaged from the implant, and removed from the patient. In the example of a threaded engagement, the second portion 38 may be disengaged from the implant by rotating a thumb wheel or other rotational control on the hand piece. In an alternate embodiment, such as where the second portion 38 comprises a pull wire, following appropriate tensioning across the fracture, a first end of the pull wire is released such that the pull wire may be removed from the implant by proximal retraction of the second end which may be attached to the hand piece.
Preferably, the clinician will have access to an array of fixation devices 12, having, for example, different diameters, axial lengths and, if applicable, angular relationships. These may be packaged one per package in sterile envelopes or peelable pouches, or in dispensing cartridges which may each hold a plurality of devices 12. Upon encountering a fracture for which the use of a fixation device is deemed appropriate, the clinician will assess the dimensions and load requirements, and select a fixation device from the array, which meets the desired specifications.
In some instances, a clinician may want to introduce two or more fixation devices 12 into the femoral head 14 to secure the fracture 24. This may be desirable if the clinician determines that, based upon the nature of the fracture 24, there is a possibility that the head 14 of the femur 10 could rotate about a single fixation device 12. Even minor rotation can inhibit the healing of the fracture. Significant rotation can result in failure of the fixation device or necrosis of the femoral head. Two or more fixation devices 12 may also be desirable where the direction of the fracture is generally parallel to the axis of implantation as is understood in the art.
The fixation device 12 of the present invention may also be used in combination with intramedullary nails or rods, as will be understood by those of skill in the art.
The fixation device 12 of the present invention may be used in any of a wide variety of anatomical settings beside the proximal femur, as has been discussed. For example, lateral and medial malleolar fractures can be readily fixed using the device of the present invention. Referring to
A fixation device 12 in accordance with the present invention is illustrated in
The fixation devices of the present invention may be made from either conventional bioabsorbable materials or conventional non-absorbable materials, combinations thereof and equivalents thereof. In addition, natural materials such as allografts may be used. Examples of absorbable materials include homopolymers and copolymers of lactide, glycolide, trimethylene carbonate, caprolactone, and p-dioxanone and blends thereof. The following two blends may be useful: 1) the blend of poly(p-dioxanone) and a lactide/glycolide copolymer, as disclosed in U.S. Pat. No. 4,646,741 which is incorporated by reference and (2) the glycolide-rich blend of two or more polymers, one polymer being a high lactide content polymer, and the other being a high glycolide content disclosed in U.S. Pat. No. 4,889,119 which is incorporated by reference. Additional bioabsorbable materials are disclosed in copending application Ser. No. 09/558,057 filed Apr. 26, 2000, the disclosure of which is incorporated in its entirety herein by reference.
The fixation devices may also be made from conventional non-absorbable, biocompatible materials including stainless steel, titanium, alloys thereof, polymers, composites and the like and equivalents thereof. In one embodiment, the distal anchor comprises a metal helix, while the body and the proximal anchor comprise a bioabsorbable material. Alternatively, the distal anchor comprises a bioabsorbable material, and the body and proximal anchor comprise either a bioabsorbable material or a non-absorbable material. As a further alternative, each of the distal anchor and the body comprise a non-absorbable material, connected by an absorbable link. This may be accomplished by providing a concentric fit between the distal anchor and the body, with a transverse absorbable pin extending therethrough. This embodiment will enable removal of the body following dissipation of the pin, while leaving the distal anchor within the bone.
The components of the invention (or a bioabsorbable polymeric coating layer on part or all of the anchor surface), may contain one or more bioactive substances, such as antibiotics, chemotherapeutic substances, angiogenic growth factors, substances for accelerating the healing of the wound, growth hormones, antithrombogenic agents, bone growth accelerators or agents, and the like. Such bioactive implants may be desirable because they contribute to the healing of the injury in addition to providing mechanical support.
In addition, the components may be provided with any of a variety of structural modifications to accomplish various objectives, such as osteoincorporation, or more rapid or uniform absorption into the body. For example, osteoincorporation may be enhanced by providing a micropitted or otherwise textured surface on the components. Alternatively, capillary pathways may be provided throughout the body and collar, such as by manufacturing the anchor and body from an open cell foam material, which produces tortuous pathways through the device. This construction increases the surface area of the device which is exposed to body fluids, thereby generally increasing the absorption rate. Capillary pathways may alternatively be provided by laser drilling or other technique, which will be understood by those of skill in the art in view of the disclosure herein. In general, the extent to which the anchor can be permeated by capillary pathways or open cell foam passageways may be determined by balancing the desired structural integrity of the device with the desired reabsorption time, taking into account the particular strength and absorption characteristics of the desired polymer.
One open cell bioabsorbable material is described in U.S. Pat. No. 6,005,161 as a poly(hydroxy) acid in the form of an interconnecting, open-cell meshwork which duplicates the architecture of human cancellous bone from the iliac crest and possesses physical property (strength) values in excess of those demonstrated by human (mammalian) iliac crest cancellous bone. The gross structure is said to maintain physical property values at least equal to those of human, iliac crest, cancellous bone for a minimum of 90 days following implantation. The disclosure of U.S. Pat. No. 6,005,161 is incorporated by reference in its entirety herein.
One embodiment, as illustrated in
The distal end 206 of the deployment device 200 may include an axial hole 208 with a stop 210 at a depth sufficient to receive the distal end 32 of the body 28 of the bone anchor. In the illustrated embodiment, the outer portion of the distal end 206 is configured to engage the gripping structure of the proximal anchor 50. In the illustrated embodiment, the distal end is therefore hexagonal in shape and configured to be received by the hexagonal recess 84 of the proximal anchor 50. However, the distal end 206 can have any of a variety of different shapes for differently shaped gripping structures on the proximal anchor 50. For example, the distal end 206 can have a pentagonal shape or any other polygonal shape that is similar to the shape of the gripping structure (e.g., the recess 84) of the proximal anchor. In still other embodiments, the distal end may comprise a recess configured to engage a anti-rotational protrusion formed on the proximal anchor 50. In addition, the hole 208 preferably extends through the device 200 such that the device 200 may be used over a guidewire.
With reference to
As will be explained below, the tensioner member 240 is configured to move with the finger grip 230. The member 240 and grip 230, in turn, move together relative to the plunger 224 and distal housing 234. The tensioner member 240, in turn, is preferably configured to grip a proximal end of the body 28 of the bone fixation device 12. In a modified embodiment, the distal housing 234 and the plunger 224 may be adapted to move together relative to the finger grip 230 and tensioner 240.
The provision of a tensioner member 240 on the deployment device 220 will generally allow a clinician to provide proximal traction to the body 28 of the bone fixation device 12. In the illustrated embodiment, the syringe-shaped body 222 is generally adapted such that application of a compressive force between the plunger 224 and the finger grip 230 results in engagement of the device 220 on a proximal end of the pin 28 (e.g., the rotational coupling 70 of
As mentioned above, the plunger 224 is generally adapted to be engaged by the heel of a clinician's hand, thus providing a comfortable handle by which the deployment device may be gripped for axial rotation, or a comfortable surface for the compressive force involved in providing traction to a bone fixation device as described elsewhere herein. Those skilled in the art will recognize that numerous specific arrangements of a plunger (or heel-engagement portion) may be provided according to the particular needs of the clinician. Similarly, the finger grip portion shown and described herein is merely provided by way of example. Those skilled in the art will recognize that other shapes and arrangements are available for providing a finger grip portion.
With reference to
In the illustrated embodiment, the plunger 224 can be held generally stationary and the finger grip 230 can be can be pulled towards the plunger 224. The finger grip 230 and the traction member 240 can both move proximally relative the plunger 224 and the distal housing 234 as the traction member 240 slides smoothly along the distal housing 234. Of course, many other arrangements are possible for providing the desired motion of the traction member 240 relative to the distal housing 234 as a result of a compressive force. For example, as will be described below,
The traction member 240 may comprise a solid rod, a hollow tube, one or more cables, or any other appropriate structure such that it functions as described. The traction member 240 may be made of any suitable material known to those skilled in the art such that it has sufficient tensile strength that it will not stretch or otherwise deflect significantly during traction of the anchor. Suitable materials usable for the construction of a traction member include stainless steel, nylon, etc. and further materials (e.g., metals, plastic and the like) will be apparent to those skilled in the art.
As seen best in
In the illustrated embodiment, the collet 250 comprises a plurality of flexible fingers 252, each having a gripping head 254 on its distal end. The flexible fingers 252 preferably have sufficient tensile strength that the collet 250 will provide sufficient proximal traction force to a bone fixation device when the deployment device is operated as described herein. In one embodiment, the gripping heads 254 comprise a polygonal cross section wherein the gripping head 254 joins to the finger 252 at one of the sides of the polygon. For example, the gripping head 254 may comprise an octagonal, hexagonal, quadrilateral, or other cross-sectional shape such that it functions as described herein. The functioning of the collet 250 will be described in further detail below with reference to
As mentioned above, the distal cap 260 may be threaded or otherwise attached, such as by adhesives, welds, etc. to the distal housing 234. A removable distal cap, however, is preferred because it advantageously allows for greatly simplified cleaning of the deployment device tip. Many embodiments of a distal cap 260 may be provided depending on the particular application. A distal cap 260 such as that shown in
The one embodiment of use of the deployment device 220 will now be described with reference to
The member 240 and the pin 38 can be coupled to the fixation device as illustrated in
The components of the present invention may be sterilized by any of the well known sterilization techniques, depending on the type of material. Suitable sterilization techniques include heat sterilization, radiation sterilization, such as cobalt 60 irradiation or electron beams, ethylene oxide sterilization, and the like.
The methods which are described and illustrated herein is not limited to the exact sequence of acts described, nor is it necessarily limited to the practice of all of the acts set forth. Other sequences of events or acts, or less than all of the events, or simultaneous occurrence of the events, may be utilized in practicing the embodiments of the invention. The specific dimensions of any of the bone fixation devices of the disclosed embodiments can be readily varied depending upon the intended application, as will be apparent to those of skill in the art in view of the disclosure herein. Moreover, although the present invention has been described in terms of certain preferred embodiments, other embodiments of the invention including variations in dimensions, configuration and materials will be apparent to those of skill in the art in view of the disclosure herein. In addition, all features discussed in connection with any one embodiment herein can be readily adapted for use in other embodiments herein. The use of different terms or reference numerals for similar features in different embodiments does not imply differences other than those which may be expressly set forth. Accordingly, the present invention is intended to be described solely by reference to the appended claims, and not limited to the preferred embodiments disclosed herein.