HK1194960B - Percutaneous osseointegrated prosthetic implant system - Google Patents

Description

Percutaneous osseointegrated prosthetic implant system

Cross-referencing of related files

Priority claims are also filed for U.S. provisional patent application No. 61/493,914 filed 6/2011, for U.S. provisional patent application No. 61/594,815 filed 2/3/2012, and for U.S. provisional patent application No. 61/622,783 filed 4/11/2012, the entire contents of all three of which are incorporated herein by reference.

Technical Field

The present invention relates generally to implant systems for securing a prosthesis to a selected bone of a patient (subject), and more particularly to implant systems for securing a prosthesis to a selected bone of a patient in a modular, osseointegrative manner.

Statement of government support

The invention is made with the support of the U.S. government and obtains the batch text (Grant) PR054520 granted by the department of defense, the batch text R01HD061014 granted by the national institutes of health, the batch text 1RC1AR058356 granted by the national institute of health, the batch text # RX000262-01 granted by the department of affairs of refuge military personnel, the batch text # A5-4159RA granted by the department of affairs of refuge military personnel, the batch text #10091004 granted by the department of commander of medical research equipment, and the batch text # W81XWH-05-1-0628 granted by the center of remote medical and advanced technology research of the military amputation research project of the U.S. military. The united states government has certain rights in this invention.

Background

Amputation may occur due to injury or surgical treatment. Currently, despite its limitations, socket technology remains a standard of care for attaching or interfacing external prosthetic devices to residual amputations of patients.

Recent clinical studies of amputees with socket prostheses have shown that 8% to 50% of amputees with socket prostheses encounter one or more skin conditions that require temporary disablement of the prosthesis. The inability of these amputees to consistently use prosthetic limbs severely degrades their quality of life. In lower limb amputees, this limitation of use of the prosthesis increases the susceptibility of these amputees to other complications. Many of the conditions associated with current socket prosthesis designs are inherently biochemical and biomechanical in relation.

High infection rates remain a major limitation of current prosthetic systems. High infection rates are often associated with a lack of skin seal at the skin-implant interface, which provides an ideal direct path for opportunistic bacterial invasion of the stoma tissue and often leads to sinus formation. This in turn can lead to deep infection, bone loss and implant removal. Due to the rapid evolution of antibiotic-resistant pathogens and the high incidence of methicillin-resistant staphylococcus aureus (MRSA) cases, these infections may not be adequately treated with conventional antibiotic therapy. Often, the result of this is removal of the prosthetic device and also loss of limb tissue.

What is needed in the art, therefore, is an internally adaptable, modular, percutaneous, osseointegrated prosthetic implant system that allows for the formation of a seal at the implant-skin interface, reduces the dermatological complications associated with a socketed prosthesis, improves proprioception, extends the time of use of an external prosthesis, and reduces energy expenditure in amputees with prostheses, thereby improving the overall quality of life of the amputees.

Disclosure of Invention

Embodiments of the present invention relate to an implant system for securing a prosthesis to a prepared site in a selected bone of a tissue region of a patient. The implant system may include a stem and an abutment. The shank may include an elongate shaft portion and a collar portion. The elongate shaft portion of the stem defines an insertable end of the stem that is received in the prepared portion of the selected bone. The elongate shaft portion may have a porous region having a selected length along the longitudinal axis of the shaft that facilitates bone ingrowth and interdigitation with host bone tissue, i.e., "osseointegration". The collar portion of the shank defines a second end of the shank and a shoulder surface extending radially outward from an outer surface of the elongate shaft portion. Optionally, the shoulder surface may have a porous region that promotes osseointegration. The collar portion and the elongate shaft portion collectively define a central bore of the shank. The ratio between the longitudinal length of the shank and the selected length of the porous region of the elongate shaft portion may range from about 3:1 to about 10: 1. At least a portion of an outer surface of the collar portion may be configured to inhibit bio-adhesion.

The abutment includes an attachment element, a post, and a fixation element. The attachment element may be securely attached to the stem such that the abutment is operably coupled to the stem. The post may have an insertable first end, an opposite second end, and a middle portion between the first and second ends. The insertable first end may be operably positioned relative to the handle when the attachment element is attached to the handle, and the opposing second end may be configured to be selectively securely attached to a prosthesis. At least a portion of the outer surface of the post may be configured to inhibit bioadhesion. The securing element may be secured to the outer surface of the post at selected locations along the longitudinal axis of the abutment. The fixation elements may extend radially outward relative to an outer surface of an adjacent portion of the post, thereby defining a fixation surface configured to abut patient tissue located adjacent a prepared site in the selected bone. Alternatively, the fixing element may be formed of a porous material.

Drawings

The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects, and together with the description serve to explain the principles of the invention. Like numbers refer to like elements throughout.

Fig. 1 shows an exemplary stem (stem) for use with the implant system described herein.

Fig. 2 illustrates an exemplary abutment for use with the implant systems described herein.

Fig. 3 illustrates an exemplary implant system having a stem and an abutment as described herein.

Fig. 4-5 show close-up views of exemplary tapered surfaces of posts (posts) of an abutment as described herein. Fig. 4 illustrates an exemplary configuration of a tapered surface in connection with the fixation elements described herein. FIG. 5 illustrates respective orientation angles of exemplary first and second tapered surfaces described herein.

Fig. 6A-6C illustrate an exemplary collar (collar) portion of the shanks described herein. Fig. 6A and 6B illustrate an exemplary collar portion having a tapered elongated portion, while fig. 6C illustrates an exemplary collar portion having an elongated portion of substantially constant size.

Fig. 7A-7C illustrate exemplary handles described herein. Fig. 7A-7B show an exemplary shank having a selectively attachable collar portion and an elongate shaft portion, while fig. 7C shows an exemplary shank having only a collar portion.

Fig. 8 shows Kaplan-Meier survival curves for smooth (n = 8) and porous coating groups (n = 14) as described in the experimental examples section below. The log rank sum test (logrank) showed a significant difference between the two groups (p = 0.018), which indicates that the porous coated subcutaneous barrier described herein avoids infection compared to a smooth subcutaneous barrier.

Detailed Description

The present invention may be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed or described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

The following description of the invention is provided as a best mode presently known of carrying out the invention in its broadest sense. To this end, those skilled in the art will recognize and appreciate that many modifications are possible in the various aspects of the present invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without using other features. Thus, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof.

As used throughout this application, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a porous region" can include two or more such prostheses unless the context clearly indicates otherwise.

The word "or" herein means any one member of a particular list and also includes any combination of members of that list.

Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently.

As used herein, the terms "optional" or "optionally" mean that the subsequently described event or condition may or may not occur, and that the description includes instances where said event or condition occurs and instances where it does not.

By "patient" is meant an individual. The term "patient" may include humans, as well as small or laboratory animals and primates. "laboratory animals" include, but are not limited to, rodents such as mice or rats. The term "laboratory animal" is also used interchangeably with "animal", "small laboratory animal" or "patient", including, for example, mice, rats, cats, dogs, fish, rabbits, guinea pigs, rodents, and the like. The term "laboratory animal" does not denote a particular age or sex. Thus, the term includes adult or newborn animals as well as fetuses (including embryos), whether male or female.

As used herein, the term "insertable" refers to an end of a first element that is configured to be inserted into a second element. For example, as used herein, the "insertable" end of an element may be configured as a handle to be inserted into a prepared site in bone or to insert an implant.

As used herein, the term "ultra-low friction surface" refers to a surface that includes or is coated with one or more materials, the surface being configured to inhibit adhesion and/or adsorption between the surface and other materials. For example, the "ultra-low friction surface" described herein allows little if any ingrowth, bonding and/or adhesion of the surface to biological tissues, fluids and bacteria. It is contemplated that the reduced bio-adhesion allowed by the "ultra-low friction surface" described herein may allow improved wound healing, easy "at home" clean up throughout post-operative drainage, and reduced infection rates. Exemplary ultra-low friction surfaces include surfaces comprising or coated with a superhydrophobic material. Other exemplary ultra-low friction surfaces include, for example, but are not limited to, gold, ceramics, polymers (e.g., ultra-high molecular weight polyethylene), diamond-like carbon (DLC) coatings, zirconium oxide, titanium nitride, and the like. It is contemplated that the coefficient of friction of the exemplary "ultra-low friction surfaces" described herein may be less than or equal to about 0.6, and more preferably, less than or equal to about 0.01 (approaching super-lubrication).

Disclosed herein are implants, implant systems, and methods to secure a prosthesis to a limb of a patient. It is contemplated that the implants, implant systems, and methods may be used to allow integration of a patient's bone and skin into an implant to which a prosthesis is operatively attached. It is further contemplated that the implants, implant systems, and methods may allow for the formation of a seal between the patient's skin and the implant, thereby minimizing the possibility of infection at the interface between the implant and the patient's skin. It is still contemplated that the disclosed implants, systems and methods may minimize post-implantation migration of the patient's skin, thereby reducing the likelihood of formation of a pocket (pocket) between the patient's skin and the implant. In particular applications, it is contemplated that the implants, implant systems and methods may bring lower extremity amputees in the military, retired military and civilian back to pre-amputation/elevated activity levels. In general, it is contemplated that the above objectives may be achieved by optimal selection of various features of the implant, for example, optimal selection of features of the stem and/or abutment described herein, to achieve a desired placement and/or orientation of the implant relative to the patient's bone and surrounding tissue, and to achieve a desired attachment between the implant and the prosthesis.

Referring to fig. 1-5, an implant system 10 is provided for securing a prosthesis to a selected bone of a tissue region of a patient, such as a selected bone in an upper or lower limb of a patient. As used herein, the term "prepared site" refers to any location in a selected bone of a patient that is ready to receive an implant, such as a stem implant as described herein, using conventional surgical methods. In an exemplary aspect, the "prepared site" may be a medullary cavity of the selected bone. In other exemplary aspects, the selected bone may be a femur of a patient. However, it is contemplated that the disclosed methods, systems, steps, and components may be used with any bone in a tissue region of a patient, including, for example, any bone in an upper or lower limb of a patient. It is contemplated that implant system 10 may be used to secure a prosthesis to a prepared site in a selected bone. In an exemplary aspect, the implant system 10 can include a stem 20 and an abutment 50. In these aspects, the stem 20 can be configured to securely attach to a selected bone, and the abutment 50 can be configured to securely attach to the stem. Once the abutment 50 is attached to the stem 20, the abutment can be configured to securely attach to the prosthesis.

In one aspect, as shown in fig. 1 and 3, the shank 20 may have a longitudinal axis 22 and a longitudinal length 24. In this regard, it is contemplated that the longitudinal length 24 of the handle 20 can range from about 1 inch to about 10 inches. In femoral prosthetic applications, it is contemplated that the longitudinal length 24 of the stem 20 may range from about 2 inches to about 10 inches. In an exemplary femoral prosthetic application, it is contemplated that the longitudinal length 24 of the stem may range from about 6 inches to about 10 inches. In another aspect, the shank 20 may optionally include an elongate shaft portion 26, the elongate shaft portion 26 defining an insertion end 30 of the shank and having an outer surface 28 defining a diameter of the shank. In this regard, the insertion end 30 of the shank 20 may be configured to be received in a prepared site of a selected bone. It is contemplated that the shank 20 may be securely received in the prepared site such that the longitudinal axis 22 of the shank may be generally axially aligned with the longitudinal axis of the selected bone. In one aspect, the handle 20 may comprise one or more metallic materials including, for example, but not limited to, medical grade titanium, cobalt chrome, and the like. In an exemplary aspect, at least a portion of the outer surface 28 of the elongate shaft portion 26 of the shank 20 may be grit blasted using conventional methods to provide the elongate shaft portion with a desired surface roughness, thereby improving the attachment of the bone. Optionally, the outer surface 28 of the elongated shaft portion 26 of the handle 20 may include at least one channel (flute), at least one rib (rib), and/or at least one slot configured to promote fixation with a selected bone. In an exemplary aspect, it is contemplated that the outer surface 28 of the elongate shaft portion 26 can include a plurality of spaced apart ribs oriented generally perpendicular to the longitudinal axis 22 of the shank 20. It is contemplated that the outer diameter of the shank 20 may range from about 0.25 inches to about 1.00 inches, and more preferably, the outer diameter of the shank 20 may range from about 0.5 inches to about 0.75 inches.

Optionally, in exemplary aspects, the elongate shaft portion 26 of the stem 20 may be configured to have simulated physiologic properties of an anatomical arch in the body bone, thereby reducing and/or limiting torsional displacement of the stem after implantation and improving long term and short term performance of the stem. It is further contemplated that the elongate shaft portion 26 of the stem 20 may be configured to inhibit proximal implant adhesion and limit subsequent distal bone atrophy due to stress shielding. In an exemplary aspect, if the selected bone is a femur, it is contemplated that the selected bone may be configured to perform a intramedullary curvature with a radius of curvature in a range of about 100 mm to about 1400 mm and a cortical curvature with a radius of curvature in a range of about 100 mm to about 1700 mm. In these aspects, it is contemplated that the elongate shaft portion 26 of the shank 20 may be configured to bend at a radius of curvature in the range of about 600 millimeters to about 900 millimeters, and more preferably, in the range of about 700 millimeters to about 800 millimeters. It is further contemplated that the amount of curvature of the engagement/implantation device may depend on the overall length of the stem, and the optimal seating position of the stem after transection (transformation). In an exemplary femoral application, it is contemplated that the optimal seating position of the stem after transection may be within about 16 millimeters of the distance between the distal end of the transected femur and the knee joint connection space. In these applications, it is contemplated that the radius of curvature of the stem may be determined and/or calculated by assuming that the length of the stem initially corresponds at least generally to the length of the intact/entire femur. In exemplary aspects, it is contemplated that the amount of curvature of the engaged/implanted stem may be substantially equal to the amount of curvature (i.e., the curved arc length) in the remaining length of the shaft positioned below/inside the greater trochanter and above/over the distal end of the transection/bone cut. For non-femoral applications (the selected bone is not the femur), it is contemplated that a similar procedure may be followed to determine the desired bone marrow bending characteristics of the stem.

In another aspect, the elongate shaft portion 26 can include a porous region 32 of a selected length 34 along the longitudinal axis 22 of the shank. In exemplary aspects, the ratio of the longitudinal length 24 of the handle 20 to the selected length 34 of the porous (loose) region 32 can range from about 1.5:1 to about 20:1, and, more preferably, from about 4:1 to about 8: 1. Accordingly, it is contemplated that in exemplary aspects, the selected length 34 of the porous region 32 may range from about 0.1 inches to about 4 inches, and more preferably, from about 0.5 inches to about 3 inches.

In other respects, it is contemplated that the modular nature of the handle 20 may provide a platform to optimize the design of the handle without requiring extensive surgery. For example, it is contemplated that the limited size of the porous region may be configured to allow removal and/or revision of the stem with minimal residual bone loss or damage. It is further contemplated that once the bone is infected after implantation of the stem, the stem may be removed, the surgical revision site may allow drainage, and therapeutic treatment may be performed without substantial tissue loss or harm to the patient.

In another exemplary aspect, the porous region 32 of the elongate shaft portion 26 may be recessed relative to the outer surface 28 of the bonded portion of the elongate shaft portion. Optionally, in this aspect, the porous region 32 may comprise a recessed portion of the outer surface 28 of the elongate shaft portion 26 that is coated with a porous material using known methods of coating substrates. It is contemplated that porous region 32 may alternatively comprise a continuous circumferential layer of porous material. Alternatively, it is contemplated that the porous region 32 may alternatively comprise a plurality of porous segments spaced about the working circumference of the porous region. Alternatively, the outer surface 28 of the elongate shaft portion 26 may define the outer boundary of each of the spaced porous segments of the porous region 32. For example, it is contemplated that the outer surface 28 of the elongate shaft portion 26 may include one or more narrowed regions extending continuously along the longitudinal axis 22 of the shank 20 throughout the porous region 32, each of the one or more narrowed regions forming a boundary between adjacent porous segments. Alternatively, in another aspect, the portion of the elongate shaft portion 26 corresponding to the porous region 32 may comprise a separate structure having at least one outer surface made of a porous material such that the outer surface 28 of the elongate shaft portion is discontinuous at the location of the porous region, the elongate shaft portion is segmented into different segments on opposite sides of the porous region, and the porous region 32 connects the segments of the elongate shaft portion. It is contemplated that the porous region 32 of the elongate shaft portion 26 may be formed using known grinding techniques.

In one aspect, the porous region 32 may comprise porous titanium. In this regard, it is contemplated that the porous region 32 may comprise substantially pure porous titanium, thereby enhancing the effectiveness of osseointegration by allowing bone ingrowth and interdigitation along the length of the porous region. However, it is contemplated that other medical grade porous materials as well as porous polymers and ceramics may be used as described herein. In exemplary aspects, the porous region 32 of the elongate shaft portion 26 can have a thickness ranging from about 0.5 millimeters to about 2.0 millimeters. In another exemplary aspect, the porosity of the porous region 32 of the elongate shaft portion 26 can range from about 40% to about 80%, and, more preferably, from about 50% to about 70%. In these aspects, it is contemplated that the size of the pores of the porous region 32 may range from about 25 microns to about 1000 microns, and, more preferably, from about 20 microns to about 400 microns. However, as one will appreciate, it is contemplated that the desired porosity and pore size of the porous region 32 may be selectively varied depending on factors such as, but not limited to, host bone mass/condition, amputation cause, patient age, residual limb length, time from initial initiation to surgery, post-amputation time, patient vascular health, and other factors.

It is contemplated that the porous region 32 of the handle may be configured to promote the incorporation and ingrowth of the selected bone of the patient into the handle when the handle 20 is securely received into the prepared site. It is further contemplated that this osseointegration (between the selected bone and the porous region 32 of the stem 20) may improve the quality of life of the patient after surgery by improving patient experience (i.e., load experience of the active external prosthesis) and gait efficiency (i.e., improved physiological energy expenditure).

In other aspects, the shank 20 may include a collar portion 36 having an outer surface 46 and defining a second end 38 of the shank. In this regard, the second end 38 of the shank 20 is spaced from the insertion end 30 of the shank along the longitudinal axis 22 of the shank. In one aspect, the collar portion 36 may have at least a portion with an outer diameter that is larger than the outer diameter of the elongate shaft portion 26. In this regard, it is contemplated that the collar portion 36 may define a shoulder surface 40 extending radially outward from the outer surface 28 of the elongate shaft portion 26. It is contemplated that the shoulder surface 40 may be configured to form a flush interface and/or seal with the selected bone. It is further contemplated that the flush interface and/or seal formed between the shoulder surface 40 and the selected bone may allow for substantially direct transfer of ground reaction forces to the patient's skeletal system, thereby avoiding bone atrophy. In an exemplary aspect, the shoulder surface 40 may be generally flat and extend in a generally perpendicular direction relative to the longitudinal axis 22 of the shank 20. However, it is contemplated that the shoulder surface 40 may be beveled or have other surface shapes if the shoulder surface 40 allows for a flush interface with the selected bone. It is further contemplated that the shoulder surface may be shaped to generally conform to the shape of the patient's adjacent tissue. In an exemplary aspect, the shoulder surface 40 can have a generally circular cross-section about the longitudinal axis 22 of the shank 20. However, it is also contemplated that the profile is an oval or other cross-section that allows for a flush interface with the selected bone and provides the desired support for the selected bone. Optionally, at least a portion of the outer surface 46 of the collar portion 36 may include a porous material as described herein.

Alternatively, the outer surface 46 of the collar portion 36 may taper, slope and/or curve outwardly along the longitudinal axis 22 of the shank 20 from the second end 38 of the shank to the shoulder surface 40. In this regard, it is contemplated that the taper, slope, and/or curvature of the outer surface 46 of the collar portion 36 may be configured to generally conform to the shape of adjacent tissue structures within the patient.

In an exemplary aspect, the shoulder surface 40 may include at least one porous region 44. In these aspects, the at least one porous region 44 of the shoulder surface 20 (note: plain error, should be 40) may comprise a medical grade porous metal, polymer, ceramic, or the like. In one aspect, the at least one porous region 44 of the shoulder surface 40 may include, for example, but not limited to, porous titanium. It is contemplated that the at least one porous region 44 of the shoulder surface 40 may be in the form of a porous coating applied to the shoulder surface using known painting methods. Alternatively, it is contemplated that the at least one porous region 44 of the shoulder surface 40 is formed using known milling techniques. In exemplary aspects, the thickness of the at least one porous region 44 of the shoulder surface 40 may range from about 0.5 millimeters to about 2.0 millimeters. In other exemplary aspects, the porosity of the at least one porous region 44 of the shoulder surface 40 may range from about 40% to about 70%, and more preferably, from about 50% to about 80%. In these aspects, it is contemplated that the size of each of the pores of the at least one porous region 44 of the shoulder surface 40 can range from about 25 microns to about 1000 microns, and, more preferably, from about 30 microns to about 400 microns. It is contemplated that the at least one porous region 44 of the shoulder surface 30 (note: plain text, should be 40) of the collar portion 36 may be configured to facilitate and increase the effectiveness of osseointegration, thereby ensuring continuous load transfer between the implant system 10 and the distal end of the selected bone. It is further contemplated that moderate load transfer at this interface may avoid bone resorption due to stress shielding at the distal bone end of the transected bone, and may promote hypertrophy of the bone more proximally.

Optionally, in various aspects, the porous region 32 of the elongate shaft portion 26 of the shank 20 is spaced from the shoulder surface 40 of the collar portion 36 along the longitudinal axis 22 of the shank. In these aspects, it is contemplated that the space between the porous region 32 of the elongate shaft portion 26 of the stem 20 and the shoulder surface 40 can define a resection cut plane at the most distal portion of the residual limb. It is further contemplated that making cuts at the extreme distal end of the residual bone will help avoid losing other residual limb lengths if re-resection is required. It is still further contemplated that once the circumferential cut is made and tension is applied to the second end 38 of the shank 20, the engagement at the bone-recessed porous region interaction plane is substantially weakened so that the shank 20 may be released from the bone. It is still further contemplated that a split along the bone-porous region interface may allow the stem to be exposed smoothly without damaging the remaining cortical bone.

In another aspect, at least a portion of the outer surface 46 of the collar portion 36 may be configured to inhibit bio-adhesion. In this regard, the portion of the outer surface 46 of the collar portion 36 configured to inhibit bioadhesion may comprise an ultra-low friction surface as defined above. It is contemplated that the portion of the outer surface 46 of the collar portion 36 that includes the ultra-low friction surface may include the second end 38 of the shank 20. In another aspect, the portion of the outer surface 46 of the collar portion 36 configured to inhibit bioadhesion may comprise a highly polished surface having a low coefficient of friction. In this regard, it is contemplated that the portion of the outer surface 46 of the collar portion 36 that includes the highly polished surface may comprise the second end 38 of the shank 20.

In exemplary aspects, it is contemplated that the highly polished surfaces described herein can have Rt values or maximum peak-to-valley values (P-V) that are less than about 20 microns, more preferably less than about 5 microns, and, most preferably, less than about 3 microns as measured by profilometry and/or white light interferometry. In other exemplary aspects, the highly polished surfaces described herein can have Rt values or maximum peak-to-valley values (P-V) of less than about 2 microns as measured by profilometry and/or white light interferometry. It is further contemplated that these values may be predetermined or designed by appropriate combinations of milling bits and/or surface coatings. Suitable profilometry analysis can be performed by sweeping and/or sliding a probe with a dedicated gauge over the highly polished surface to determine the relative roughness of the surface material. White light interferometry, an optical technique that utilizes the principles of light refraction and optics (and/or physics) to determine the relative roughness of the given surface material, can be used. It is contemplated that profilometry and white light interferometry, as well as other known equivalent techniques, may be used in combination to determine the surface characteristics of the various components of the implant system disclosed in this application. Alternatively, in exemplary aspects, it is contemplated that the ultra-low friction surfaces described herein can also have Rt values or maximum peak-to-valley (P-V) values, as determined by profilometry and/or white light interferometry analysis, of less than about 20 microns, more preferably, less than about 5 microns, and, most preferably, less than about 3 microns. In other exemplary aspects, the ultra-low friction surfaces described herein can have an Rt value or a maximum peak-to-valley value (P-V) of less than about 2 microns as determined by profilometry and/or white light interferometry.

In another aspect, the collar portion 36 and the elongate shaft portion 26 may collectively define a central bore 42 extending along at least a portion of the longitudinal length 24 of the shank 20. In this regard, it is contemplated that the collar portion 36 may define an inner surface 48 extending from the second end 38 of the shank 20 along at least a portion of the longitudinal length 24 of the shank. As shown in FIG. 3, it is also contemplated that the inner surface 48 may terminate generally at the central aperture. In an exemplary aspect, the inner surface 48 of the collar portion 36 may taper inwardly from the second end 38 of the shank 20 along the longitudinal axis 22 of the shank 20. In these aspects, the inner surface 48 of the collar portion 36 may include a conventional morse taper. It is contemplated that the inner surface 48 of the collar portion 36 may taper inwardly at an angle of about 3 degrees to about 7 degrees, preferably about 4 degrees to about 6 degrees, relative to the longitudinal axis 22 of the shank 20. In an exemplary aspect, the taper angle of the inner surface 48 of the collar portion 36 substantially corresponds to the respective partial taper angle of the abutment portion 50 described herein. It is contemplated that the inner surface 48 of the collar portion 36 may be configured to receive a "female" taper of a portion of the abutment 50 as further described herein. In an exemplary aspect, the central bore of the shank can be a threaded bore. However, it is contemplated that the central bore may have any shape and/or geometric configuration that allows for secure attachment to the abutment as described herein.

In an exemplary aspect, as shown in fig. 2-3, the abutment 50 can include a longitudinal axis 52, an attachment element 54, a post 56, and a fixation element 66. In these aspects, the attachment element 54 may be configured to be securely attached to the stem 20. In one aspect, the attachment element 54 may comprise a bolt configured to be received in the central bore 42 of the shank 20. However, it is contemplated that the attachment element 54 may have any shape and/or geometric configuration that allows for secure, complementary receipt of the attachment element in the central bore 42 of the shank 20. In an exemplary aspect, the abutment 50 can define a central bore 55 extending along the entire longitudinal length of the abutment. In this regard, it is contemplated that the attachment element 54 may be positioned in the central bore 55 of the abutment 50 so that when securely attached between the stem 20 and the abutment 50, the attachment element is securely positioned in both the central bore of the stem and the central bore of the abutment, thereby providing stability to the abutment. It is contemplated that the attachment element 54 may be securely positioned in the central bore 42 of the shank 20 such that the longitudinal axis 52 of the abutment 50 is generally aligned with the longitudinal axis 22 of the shank.

In other aspects, the post 56 of the abutment 50 can have an outer surface 58, an insertable first end 60, an opposing second end 62, and a middle 64 positioned between the first and second ends. In this regard, it is contemplated that the insertable first end portion 60 can include an insertable first end 61 and the second end portion 62 can include a second end 63 opposite the insertable first end along the longitudinal axis 52 of the abutment 50. It is further contemplated that the post 56 may be generally cylindrical. In another aspect, the post 56 can be operatively coupled to the attachment element 54 such that when the attachment element is securely attached to the stem 20, the insertable first end 60 of the abutment 50 is configured to be operatively positioned relative to the stem 20 and the opposing second end 62 of the abutment 50 is configured to be selectively securely attached to the prosthesis.

In another aspect, the outer surface 58 of the post 56 of the abutment 50 can include one or more tapered surface portions. In this regard, it is contemplated that one or more of the tapered surface portions may be generally uniformly tapered. Alternatively, it is further contemplated that the one or more tapered surface portions may have different tapers, such as, but not limited to, a gradually increasing, a gradually decreasing, or a varying taper. Optionally, the one or more tapered surface portions may be spaced apart along the longitudinal axis 52 of the abutment 50. In an exemplary aspect, the insertable first end 60 of the abutment 50 can include a first tapered surface 70 that tapers inwardly along the longitudinal axis 52 of the abutment 50, the first tapered surface 70 moving away from the central portion 64 of the post 56 and toward the insertable end 61 of the post. In these aspects, it is contemplated that the first tapered surface 70 of the insertable first end 60 of the abutment 50 may be a "male" taper configured to be complementarily received within the inner surface 48 of the collar portion 36 of the shank 20. It is further contemplated that the first tapered surface 70 may be oriented at an angle 71 relative to the longitudinal axis 52 of the abutment 50, the angle 71 ranging from about 0.25 degrees to about 3 degrees, and more preferably, from about 1 degree to about 3 degrees.

In other aspects, as shown in fig. 4-5, the outer surface 58 of the post 56 can define a second tapered surface 72 positioned near the interface between the insertable first end portion 60 of the post and the middle portion 64 of the post. In exemplary aspects, the second tapered surface 72 can taper inwardly along the longitudinal axis 52 of the abutment 50 from the central portion 64 of the post 56 toward the insertion end 61 of the post. In these aspects, the second tapered surface 72 may be oriented at an angle 73 relative to the longitudinal axis of the abutment, the angle 73 ranging from about 1.5 degrees to about 5 degrees. Thus, as shown in fig. 5, it is contemplated that the second tapered surface 72 may have an orientation angle 73 relative to the longitudinal axis of the abutment, the angle 73 being about 1 degree to about 1.5 degrees greater than the orientation angle 71 of the first tapered surface 70 relative to the longitudinal axis 52 of the abutment 50. In another exemplary aspect, the second tapered surface 72 may be configured to engage a fixation surface of a fixation element described herein (as shown in fig. 4). Alternatively, the first and second tapered surfaces 70, 72 may be spaced apart along the longitudinal axis 52 of the abutment 50 (as shown in fig. 4). Alternatively, the first and second tapered surfaces 70, 72 may be generally continuous along the longitudinal axis 52 of the abutment 50.

In exemplary aspects, at least a portion of the outer surface 58 of the strut 56 can be configured to inhibit bio-adhesion. In one aspect, the portion of the outer surface 58 of the strut 56 configured to inhibit bioadhesion can be an ultra-low friction surface as defined above. In this regard, it is contemplated that the middle portion 64 of the post 56 may be an ultra-low friction surface. In the construction of the post 56 with the second tapered surface 72 spaced from the first tapered surface 70, it is also contemplated that the portion of the outer surface of the post positioned between the first and second tapered surfaces may be an ultra-low friction surface.

In another aspect, the portion of the outer surface 58 of the struts 56 configured to inhibit bioadhesion can be a highly polished surface. In this regard, it is contemplated that the central portion 64 of the post 56 may be a highly polished surface. In the construction of the post 56 with the second tapered surface 72 spaced from the first tapered surface 70, it is also contemplated that the portion of the outer surface 58 of the post positioned between the first and second tapered surfaces may be a highly polished surface.

In other aspects, the abutment 50 can include a securing element 66, the securing element 66 being secured to the outer surface 58 of the post 56 at selected locations along the longitudinal axis 52 of the abutment 50. In this regard, it is contemplated that the securing element 66 may extend radially outwardly relative to the outer surface 58 of the adjacent portion of the post 56. It is further contemplated that a portion of the fixation element 66 extending radially outward relative to the outer surface 58 of the post 56 may define a fixation surface 68. In an exemplary aspect, the fixation surface 68 may be generally planar and extend in a direction generally perpendicular to the longitudinal axis 52 of the abutment 50. However, it is contemplated that fixation surface 68 may be beveled, curved, or may have other surface shapes if fixation surface 68 is configured to interface with at least a portion of the patient's soft tissue proximate a prepared site within a selected bone. It is still contemplated that fixation surfaces 68 defined by fixation elements 66 may be configured to abut soft tissue of the patient adjacent a prepared site within the selected bone. It is still contemplated that fixation elements 66 may be configured to promote fixation and inhibit rotation/movement of soft tissue adjacent the prepared site, such that inflammation is reduced and healing is accelerated. In an exemplary aspect, a surface of the securing element 66 may be welded to the outer surface 58 of the post 56 at selected locations. In these aspects, it is contemplated that the securing element 66 may be cold welded to the outer surface 58 of the post 56 using known methods. It is further contemplated that the selected position of the fixation element 66 may vary depending on the particular location and configuration of the stem 20 and prosthesis to which the abutment 50 is to be attached.

It is contemplated that attachment elements 54 and posts 56 may comprise conventional surgical quality metallic materials including, for example, but not limited to, titanium, cobalt chrome, and the like. It is contemplated that the fixation element 66 may comprise any metal, polymer, or ceramic material having a desired porosity. In exemplary aspects, the desired porosity of the fixation element 66 may range from about 40% to about 70%. In these aspects, it is contemplated that the size of each aperture of the securing element 66 ranges from about 25 microns to about 1000 microns, and more preferably, from about 30 microns to about 400 microns. In other aspects, it is contemplated that the fixation element 66 can include a porous material, for example, a porous metal material different from the metal material forming the struts 56. For example, it is contemplated that the fixation element 66 may comprise porous titanium and the post 56 may comprise cobalt chrome. It is contemplated that the use of a fixation element 66 and post 56 comprising two different metallic materials, such as cobalt chrome and titanium, may result in favorable surface electrostatic interactions that may enhance the bonding of the design elements. It is further contemplated that the porosity of fixation element 66 may enhance the effectiveness of soft tissue by reducing relative motion between implant system 10 and the surrounding soft tissue, thereby reducing the inflammatory response of the patient, and reduce or avoid infection by improving soft tissue uptake, thereby helping to maintain a biological barrier to the external environment.

Optionally, in other aspects, the implant system 10 can further include an overload protection mechanism 80. In this regard, it is contemplated that overload protection mechanism 80 can comprise any conventional means for isolating a bone-engaging component, such as a stem, from the external environment such that a selected bone of a patient is protected from catastrophic loading experienced by portions of the patient's external implant system, such as a prosthesis. As shown in fig. 2-3, it is further contemplated that an overload protection mechanism 80 is operatively coupled to the second end 62 of the mast 56.

Alternatively, it is contemplated that the collar portion 36 may be integrally formed with the elongate shaft portion 26 of the shank 20. Alternatively, in other alternative aspects, the collar portion 36 may be configured for selective, detachable engagement with the elongate shaft portion 26 of the shank. For example, in these aspects, it is contemplated that the collar portion 36 may define a cavity configured to receive at least a portion of the elongate shaft portion 26 of the shank 20. It is further contemplated that the elongate shaft portion 26 of the shank 20 may be configured to be positioned within the cavity of the collar portion 36 in a snap-fit, press-fit, or other friction fit.

In an exemplary aspect, as shown in fig. 6A-7C, if the collar portion 36 is not integrally formed with the elongate shaft portion 26 of the shank 20, the collar portion 36 may have a longitudinal axis 37, and may include an elongate portion 39 that extends from a shoulder surface 40 of the collar portion 36 along the longitudinal axis of the collar portion in the direction of insertion (away from the second end 38 of the shank 20). In these aspects, it is contemplated that the elongate portion 39 of the collar portion 36 can define at least a portion of a collar portion cavity configured to receive at least a portion of the elongate shaft portion 26 of the shank 20. Optionally, in these aspects, it is further contemplated that at least a portion of the elongate portion 39 of the collar portion 36 can comprise a porous material as described herein. In some exemplary alternative aspects, it is contemplated that the elongate shaft portion 26 of the shank 20 may be non-porous, while the elongate portion 39 of the collar portion 36 may include a porous region, the porous region of the elongate portion of the collar portion being positioned relative to the shoulder surface 40 in substantially the same manner as the porous region 32 (described above) of the elongate shaft portion is positioned. Alternatively, in other aspects, both the elongate shaft portion 26 of the shank 20 and the elongate portion 39 of the collar portion 36 may include at least one porous region. In other aspects, it is contemplated that at least a portion of the elongate portion 39 of the collar portion 36 may be grit blasted to impart a desired surface roughness to the shank 20 and thereby increase the strength of the attachment between the shank and the selected bone of the patient. Alternatively, it is contemplated that at least a portion of the elongate portion 39 of the collar portion 36 may be channeled, ribbed, and/or slotted to improve fixation between the stem 20 and the selected bone of the patient.

In other alternative aspects, the elongate portion 39 of the collar portion 36 may have a generally uniform diameter, and thus may be generally cylindrical. Alternatively, in other optional aspects, the elongate portion 39 of the collar portion 36 may have a varying diameter along the longitudinal axis 37 of the collar portion 36, and thus, may be tapered. In these respects, it is contemplated that the elongate portion 39 of the collar portion 36 may taper inwardly along the longitudinal axis 37 of the collar portion 36 in the direction of insertion (away from the second end 38 of the shank 20). It is further contemplated that the elongated portion 39 of the collar portion 36 tapers inwardly at an angle of about 1 degree to about 30 degrees relative to the longitudinal axis of the collar portion 36. In one aspect, it is contemplated that the taper of the elongate portion 39 of the collar portion 36 may be generally uniform along the longitudinal axis 37 of the collar portion. However, in other aspects, it is contemplated that the taper of the elongated portion 39 of the collar portion 36 may be compound, such as, but not limited to, a taper that includes two or more steps of uniform, increasing, decreasing, or varying tapers.

It is contemplated that at least one of the longitudinal length (a) of the elongated shaft portion 26 of the shank 20, the longitudinal length (b) of the elongated portion 39 of the collar portion 36 of the shank, the taper (c) of the elongated portion of the collar portion of the shank, the diameter (d) of the elongated shaft portion of the shank, and the diameter (e) of the elongated portion of the collar portion of the shank may be selectively varied depending on the selected bone and the characteristics of the prepared site, including, for example, but not limited to, the degree of amputation. It is further contemplated that the diameter of the elongated shaft portion 26 and the elongated portion 39 of the collar portion 36 will generally be smaller the higher the degree of amputation.

In an exemplary aspect, and with reference to fig. 6A, the stem 20 is used for a 35% degree of amputation, it is contemplated that the diameter of the elongated portion of the collar portion near the shoulder surface 40 may be about 18 millimeters, while the diameter of the elongated portion of the collar portion near the opposite insertable end may be about 14 millimeters. In this regard, it is contemplated that the diameter of the elongate shaft portion of the shank may be about 12 millimeters. In another exemplary aspect, referring to FIG. 6B, if the stem 20 is used for a 50% degree of amputation, it is contemplated that the diameter of the elongated portion of the collar portion near the shoulder surface 40 may be about 14 millimeters, while the diameter of the elongated portion of the collar portion near the opposite insertable end may be about 12 millimeters. In this regard, it is contemplated that the diameter of the elongate shaft portion of the shank may be about 10 millimeters. In yet another exemplary aspect, and referring to FIG. 6C, if the stem 20 is used for a 65% degree of amputation, it is contemplated that the diameter of the elongated portion of the collar portion may be generally uniform, approximately 12 millimeters, along the longitudinal length of the elongated portion. In this regard, it is contemplated that the diameter of the elongate shaft portion of the shank may be about 12 millimeters.

In an exemplary aspect, in a femoral application, the longitudinal length of the elongate shaft portion 26 of the stem 20 ranges from about 40 millimeters to about 150 millimeters, and more preferably, from about 75 millimeters to about 125 millimeters.

In other exemplary aspects, it is contemplated that the diameter of the shoulder surface 40 of the collar portion 36 may be about 25 millimeters and the longitudinal length of the elongated portion 39 of the collar portion may be about 40 millimeters.

In various modified aspects, it is contemplated that the elongate shaft portion 26 may be configured to extend through the lumen of the collar portion 36 beyond the second end 38 of the shank 20 when positioned within the lumen of the collar portion as described herein. In these aspects, it is contemplated that an end of the elongate shaft portion 26 can be configured to engage with an abutment and/or prosthesis as described herein such that the elongate shaft portion can effectively serve as an attachment element as described herein.

Alternatively, in one aspect, as shown in FIG. 7C, the shank 20 may include a collar portion 36 without the elongate shaft portion 26. In this regard, the elongate portion 39 of the collar portion 36 may be configured to be securely received into a prepared portion of a selected bone.

In use, the implant system of the present disclosure may be used by securing a prosthesis to a selected bone of a limb of a patient. In one aspect, a method of securing a prosthesis may include preparing a selected bone to receive an implant. In this regard, it is contemplated that the step of pre-defining the selected bone may include preparing a medullary cavity of the selected bone to receive the implant. In another aspect, a method of securing a prosthesis may include positioning the stem to a prepared site of a selected bone. Optionally, if the stem comprises a collar portion that is selectively detachable from the elongate shaft portion of the stem, the method of securing the prosthesis further comprises securing a portion of the elongate shaft portion of the stem into a cavity of the collar portion. In other aspects, optionally, the method of securing the prosthesis may include securing the abutment to the implant such that a longitudinal axis of the abutment is generally axially aligned with a longitudinal axis of the stem. In another aspect, a method of securing the prosthesis can include attaching the prosthesis to at least a portion of the abutment.

The stem may be configured to promote the bonding of the selected bone of the patient and the skin of the patient to the stem when the stem is securely received into the prepared site such that the longitudinal axis of the stem is substantially axially aligned with the longitudinal axis of the selected bone. More particularly, it is contemplated that the porous material coating of the handle may promote the bonding effect of the patient's bone and skin to the handle, such that a seal is formed between the patient's skin and the implant. It is further contemplated that the seal formed between the patient's skin and the handle may reduce the likelihood of infection to the patient and minimize the likelihood of voids forming between the patient's skin and the handle.

While the exemplary stems and abutments described herein are configured to be operably secured to one another, it is contemplated that the stems described herein may be configured to be operably secured to other conventional abutment designs. It is further contemplated that the abutments described herein can be configured to be operably secured to other conventional stem designs.

It is contemplated that one or more of the individual components described herein may be provided in kit form. It is further contemplated that each component of the implant systems described herein may include a label, color chart, or other indicia that indicates the particular size and/or attachment characteristics of the component that enables a physician or other practitioner to determine whether the component is suitable for use in a particular procedure and/or whether the component is complementary in size and function to other components of the implant system.

Experimental examples

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of the manner in which the compounds, compositions, articles, devices, and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the present disclosure. Efforts have been made to ensure accuracy with respect to numbers (i.e., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless otherwise indicated, parts are parts by weight, temperature is in degrees celsius or at room temperature, and pressure is at or near atmospheric pressure.

Images of the third metacarpal bone obtained from 20 adult hybrid sheep carcasses were taken using a clinical-based Computed Tomography (CT) scanner (universal electrical and medical group, milwaukee, wi) with a tube voltage of 100kVp and auto-corrected varying milliamp current, and digitally stored as a digital image and communications in medicine (DICOM) standard file. These captured images were reconstructed using commercially available software (MIMICS, princes, michigan) and then passed to a custom analysis program (MatLab, nattok, Math Works, ma) for analysis to provide AP and ML dimensions of the medullary canal at 1 mm increments for the entire length of each bone. From these data, three implant sizes and surgical holes (intelligent implant systems, llc) corresponding to the 25 th, 50 th, and 75 th percentiles were designed and made from medical Ti-6a1-4V alloy (IMDS, luo gen, utah).

The control and experimental groups were geometrically similar. The intramedullary portion is grit blasted to facilitate direct attachment to the bone and to achieve bone-implant bonding. Both sets of implants have a central rib to improve the initial fixation. For the control group, the Ti subcutaneous surface was polished smooth (surface roughness (Ra) 1.7 ± 0.1 microns) mimicking the human implant design pattern. For the experimental group, the subcutaneous barrier structure was coated with pure Ti porous paint type P2 (manufactured by Thortex corporation, Portland, Oregon, porosity 52. + -. 12%, surface roughness (Ra) 113. + -.25 μm). Both groups have a porous coating structure at the bottom in the prosthesis to promote bone attachment. The coating was made from the same type P2 paint. All implants were passivated and sterilized using ASTM standard B600-91.

Initially, 23 skeleton-matured, 2-to 3-year-old, mixed-breed sheep were divided into two groups by using a random number generator: g1-experimental group (n =14, porous coated implant) and G2-control group (n =9, smooth implant). Each sheep underwent a single stage "amputation and transplant surgery". All work was conducted under institutionally approved animal care and use committee (IACUC) protocols at animal protection facilities approved by the international animal assessment and accreditation committee (AAALAC) (IMDS research and development center, luo gen, utah).

A pre-operative radiograph is taken at a standard distance from the limb, with reference to a three-dimensional object for size calibration. A template is used to determine the most appropriate implant size. After induction (attraction) of general anesthetics (tranquilizer (0.1-0.5 mg/kg) and ketamine hydrochloride (4.4-7.5 mg/kg)), sheep were maintained under inhaled anesthetic (isoflurane in oxygen 0.5-5%), and the hair of the right forelimb was shaved and scrubbed with iodophor soap, prepared with iodophors and alcohol, and then covered with sterile drape. When making skin incisions, temporary rubber tourniquets were used near the wrist-palm joint, and then hemostasis was achieved by electrocautery. A transverse anterior incision was then made immediately above the hoof and dissected near and along the coronal midline of the limb to above the upper paw. The posterior cross cut is connected to allow for the final amputation to remove the upper jaw. Careful dissection established a pre-basal flap lacking subcutaneous fat and with an intact blood supply. The flap was protected in a saline soaked gauze sponge. The flexor and extensor tendons were fixed in the middle joint position in the tendon sheaths using #0 fiber cord and then transected at the distal segment. The metacarpal-phalangeal joint is disarticulated and the metacarpal is transected with a bone saw at a location immediately above the junction of the condylar bone and metaphyseal flash.

The distal cancellous bone surface is drilled axially into a tube, which is dug and drilled to receive the implant. Saline irrigation is used to minimize overheating. By surgery, each sheep of group G1 was implanted with a porous-coated subcutaneous barrier-synthesized (barrier-implanted) percutaneous OI device; each sheep of group G2 was implanted with a similar device, but the device was a smooth subcutaneous barrier OI implant. A surgical hammer is used to press the device into the tube. The flap was then modified and a sagittal stab wound was made in the center of the flap slightly smaller than the morse taper and the porous collar portion of the implant. The skin is then stretched around the conical and porous collar shaped portion, establishing a tight attachment and seal. The subcutaneous tissue was closed with 3-0 Biosyn sutures that were interrupted, and the skin was closed by manipulating 2-0 Biosyn subcutaneous sutures. The surgical site was bandaged with a Silvasorbl hydrogel clean pack for two weeks with a moderate compression pack. The external prosthesis "hoof" was fastened to the morse taper of the OI implant.

Naxcel (1.1 mg/kg IV) was provided during surgery for 7 daysAntibiotic prophylaxis after a course of antibiotic treatment (6.6 mg/kg). Ketoprofen (4.4 mg/kg) and fentanyl patch (100 μ g/h) were used for 5-7 days to control pain. By training sheep to sit down, use Pure(chlorophenylethylamine) disinfection spray to clean the skin-implant interface weekly. With retention of the stoma on the right forelimb, with infusion of PureA sponge of 4X4 disinfectant spray gently mechanically cleanses the stoma. After removal of any loose debris, a final spray treatment is performed directly on the skin-implant interface. Radiographs are taken every three months to assess bone-implant binding and to check for early laxity and possible osteomyelitis.

These sheep were rejected if clinical or radiographic symptoms of the fracture occurred during or after surgery. Sheep were euthanized if they developed clinical symptoms of infection and the site of infection was assessed as three levels by the Checketts scale (level 1 symptoms were a slightly reddened insertion with slight swelling; level 2 symptoms were swelling around the site of the implant exit, purulent discharge and sensitive and painful; level 3 symptoms were pus discharge in the right limb with amputation level 2 and unable to bear weight).

At the time of the autopsy, culture swabs were collected from the site remote from the implant, at the skin-implant interface, and near the metacarpal medullary canal, indicating normal skin flora, to examine the condition of prosthesis infection and deep bone infection.

At necropsy, the right forelimb (implanted) and left forelimb (not implanted) were harvested, processed and histologically analyzed. At least two coronal sections were prepared from each sample of the skin-implant interface. The coronary sections were ground into approximately-50 mm segments, stained with hematoxylin and eosin or Sanderson quick bone stain, and examined for symptoms of the association of inflammatory cells, living epithelial cells, and skin and epithelial tissue in the coronary sections.

The infection conditions were: (i) symptoms of clinical infection, (ii) positive culture results of tissue and/or bone marrow samples, or (iii) histological evidence. If the above 2-3 conditions are met, the animal is considered infected. Statistical analysis between the two groups was performed using a pre-defined survival analysis method allowing irregular follow-up times and using the log-rank test, and reported in detail using a Kaplan-Meier survival probability map. Statistical data was calculated using Stata version 11 statistical software (StataCorp LP, koricstation, texas). Considering the small sample size, the "exact" version of the log rank test can also be calculated using statxcact version 8 software (Cytel, inc., cambridge, ma). p-values only varied from p =0.018 to p =0.018, thus reporting a normal log rank test. A two-sided comparative test method was used, where p <0.05 indicates its significance.

The number of animals between the two groups was not consistent because the data here was part of a larger study with 86 sheep. In the larger study, 77 sheep were implanted with porous coated implants and 9 sheep were implanted with smooth percutaneous OI prostheses. Porous coated sheep were contributed at time points 0, 3, 6, 9 and 12 months to investigate the progress of bone and skin binding, wherein half of the sheep (n-7 per time point) in the porous coated group were subjected to biomechanical testing and the remaining sheep (n-7 per time point) were subjected to histological analysis. These results will be published in other publications. The multi-well and smooth groups from the larger study included 20% additional animals to exclude some animals in case of complications. In the current study, one animal in group G2 underwent spiral fracture after surgery. Thus 8 sheep were left in group G2. However, histological analysis was performed on 7 animals in group G1 and 8 animals in group G2.

After surgery and recovery from anesthesia, the sheep could be walked with minimal lameness within one hour. The lameness disappeared after one week of surgery. In the larger study described above, a Force plate analysis (Force plate analysis) was performed on sheep at 12 months time point; these data show that sheep carried the implanted limb for up to 80% of the pre-amputation load over 1 month.

One animal of group G2 received euthanasia at day 23 due to infection (grade 3); the second animal showed severe fluid drainage of superficial infection (grade 2), but survived to the end of the study (table 1). Skin tissue samples showed histopathological evidence of bacterial growth and infection. Two sheep in the G1 group had severe drainage, but had no symptoms of clinical infection at euthanasia. When infection occurred, a significantly larger infection occurred in G2 animals (log rank test, p =0.018, as shown in fig. 8).

TABLE 1

Although all skin-implant interfaces (100%) were full of general skin flora and/or environmental organisms, bone marrow samples did not grow positively due to the culture of potentially pathogenic microorganisms (table 2). However, 2 skin samples collected at the time of necropsy of group G2 infected animals yielded positive results due to coagulase-negative staphylococci, incoming bacteria and bacillus organisms. Both animals were confirmed to be infected with clinical and histopathological findings. The skin-implant interface showed a broken epithelial seal, with more inflammatory cells penetrating into the tissue in the prosthetic area. All skin-implant interfaces of the smooth group had a high density cell population of large fibroblasts and some lymphocytes, indicating that the tissue is under repair, possibly with low levels of infection. Although immunohistochemical experiments would verify this indication, it is not possible to do this on a Polymethylmethacrylate (PMMA) embedded sample.

Table 2:

although most of the animals in group G2 (6/8, 75%) survived without infection, the animals in group G2 were found to have higher proximal skin migration when the skin stoma was different between the two groups compared to group G1. The group G1 migrated at 0.6. + -. 0.1 mm/month, while the group G2 migrated at 2.1. + -. 0.3 mm/month.

It will be appreciated that the angles and dimensions shown in the figures may have been exaggerated for clarity of illustration and thus may not be drawn to scale.

Although a few embodiments of the present invention have been disclosed in the foregoing specification, it should be understood by those skilled in the art that many modifications and other embodiments of the invention will come to mind to which the invention pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments of the invention are intended to be included within the scope of the invention. In addition, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (35)

1. An implant system for securing a prosthesis within a medullary cavity of a selected bone of a tissue region of a patient, the implant system comprising:

a handle having a longitudinal axis and a longitudinal length, the handle comprising:

an elongate shaft portion having an outer surface and defining an insertable end of the stem, the insertion end of the stem configured to be received in the intramedullary cavity, the elongate shaft portion including a porous region of a selected length along a longitudinal axis of the stem; and

a collar portion defining a second end of the shank spaced from the insertable end of the shank along a longitudinal axis of the shank, the collar portion defining a shoulder surface extending radially outward from an outer surface of the elongate shaft portion,

wherein the collar portion and the elongate shaft portion cooperate to define a central bore extending along at least a portion of a longitudinal length of the shank, and a ratio between the longitudinal length of the shank and a selected length of the porous region of the elongate shaft portion ranges from 3:1 to 10: 1; and

an abutment having a longitudinal axis, an attachment element, and a post having an outer surface and being operably coupled to the attachment element, the attachment element of the abutment being configured to be complementarily received in the central bore of the stem such that the longitudinal axis of the abutment is substantially aligned with the longitudinal axis of the stem, at least a portion of the post being configured to be selectively fixedly attached to the prosthesis,

wherein, when the stem is securely received within the intramedullary canal, the porous region of the stem is configured to promote bonding of an interior of the selected bone of the patient to the stem, and the shoulder surface is configured to abut the selected bone, and at least a portion of an outer surface of the post of the abutment is configured to inhibit bio-adhesion.

2. The implant system of claim 1, wherein the porous region of the elongate shaft portion of the stem comprises porous titanium.

3. The implant system of claim 1, wherein the shoulder surface of the collar portion of the stem includes a porous region configured to facilitate integration of the selected bone of the patient to the stem.

4. The implant system of claim 3, wherein the porous region of the shoulder surface of the collar portion of the stem comprises porous titanium.

5. The implant system of claim 1, wherein the collar portion of the stem includes an outer surface, and at least a portion of the outer surface of the collar portion is configured to inhibit bio-adhesion.

6. The implant system of claim 1, wherein the porous region of the elongate shaft portion of the stem is recessed relative to an outer surface of an adjacent portion of the elongate shaft portion.

7. The implant system of claim 1, wherein the portion of the outer surface of the post of the abutment configured to inhibit bioadhesion comprises an ultra-low friction surface.

8. The implant system of claim 1, wherein the portion of the outer surface of the post of the abutment configured to inhibit bioadhesion comprises a highly polished surface.

9. The implant system of claim 1, wherein the post of the abutment has an insertable first end, an opposing second end, and a middle portion positioned along a longitudinal axis of the abutment between the first end and the second end, wherein the post is operably coupled to the attachment element such that when the attachment element is operably received in the implant system, the insertable first end of the post is configured to be operably positioned relative to the stem and the opposing second end of the post is configured to be selectively fixedly attached to the prosthesis.

10. The implant system of claim 9, wherein the middle portion of the post of the abutment is configured to inhibit bio-adhesion.

11. The implant system of claim 1, wherein the abutment further comprises a fixation element secured to the outer surface of the post at a selected location along a longitudinal axis of the abutment such that the fixation element extends radially outward relative to the outer surface of an adjacent portion of the post, thereby defining a fixation surface configured to abut patient tissue located adjacent a prepared site in the selected bone.

12. An implant stem to secure an abutment in a working position relative to a medullary cavity of a selected bone of a tissue region of a patient, the implant stem having a longitudinal axis and a longitudinal length, the implant stem comprising:

an elongate shaft portion defining an insertable end of the implant stem and having an outer surface defining an outer diameter of the elongate shaft portion, the insertable end of the implant stem configured to be received in the intramedullary cavity, the elongate shaft portion including a porous region of a selected length along a longitudinal axis of the implant stem, the porous region of the elongate shaft portion being recessed relative to an outer surface of an adjacent portion of the elongate shaft portion; and

a collar portion having an outer surface and defining a second end of the implant stem, the second end of the implant stem being spaced apart from the insertable end of the implant stem along a longitudinal axis of the implant stem, the collar portion defining a shoulder surface extending radially outward relative to an outer surface of an adjacent portion of the elongate shaft portion, at least a portion of the outer surface of the collar portion being configured to inhibit bio-adhesion,

wherein the collar portion and the elongate shaft portion cooperate to define a central bore extending along at least a portion of a longitudinal length of the implant stem, and the central bore is configured to securely receive a complementary portion of the abutment,

wherein the ratio between the longitudinal length of the implant stem and the selected length of the porous region ranges from 3:1 to 10: 1; and

wherein the porous region of the elongate shaft portion is configured to facilitate integration of the interior of the selected bone of the patient to the implant stem.

13. The implant stem of claim 12, wherein the porous region of the elongate shaft portion comprises porous titanium.

14. The implant stem of claim 12, wherein the shoulder surface includes a porous region configured to promote integration of the selected bone of the patient to the implant stem.

15. The implant stem of claim 14, wherein the porous region of the shoulder surface comprises porous titanium.

16. The implant stem of claim 12, wherein the at least a portion of the outer surface of the collar portion configured to inhibit bio-adhesion comprises an ultra-low friction surface.

17. The implant stem of claim 12, wherein the at least a portion of the outer surface of the collar portion configured to inhibit bio-adhesion comprises a highly polished surface.

18. The implant stem of claim 12, wherein the elongate shaft portion is configured to mimic a body anatomical arch of the selected bone.

19. The implant stem of claim 12, wherein the collar portion defines a second end of the implant stem, wherein the collar portion defines an inner surface extending from the second end of the implant stem along at least a portion of a length of the implant stem, the inner surface of the collar portion tapering inwardly along a longitudinal axis of the implant stem from the second end of the implant stem toward the insertable end of the implant stem.

20. The implant stem of claim 19, wherein the inner surface of the collar portion is configured to receive a portion of the abutment.

21. The implant stem of claim 20, wherein the inner surface of the collar portion terminates substantially within a central bore of the implant stem.

22. An abutment having a longitudinal axis, the abutment configured to securely attach to a prosthesis and an implant stem positioned in a medullary cavity of a selected bone of a tissue region of a patient, the abutment comprising:

an attachment element configured to securely attach to the implant stem;

a post having an outer surface, an insertable first end, an opposing second end, and a middle portion positioned along a longitudinal axis of the abutment between the first end and the second end, the post being operably coupled to the attachment element such that the insertable first end of the abutment is configured to be operably positioned relative to the implant stem when the attachment element is securely attached to the implant stem, wherein the opposing second end of the abutment is configured to be selectively securely attached to the prosthesis, at least a portion of the outer surface of the post being configured to inhibit bio-adhesion; and

a fixation element secured to an outer surface of the post at a selected location along a longitudinal axis of the abutment such that the fixation element extends radially outward relative to the outer surface of an adjacent portion of the post, thereby defining a fixation surface configured to abut patient tissue located adjacent a bone marrow lumen, the fixation surface comprising a porous material.

23. The abutment of claim 22, wherein the post comprises a first metallic material and the fixation element comprises a second metallic material, and wherein the first metallic material is different from the second metallic material.

24. The abutment of claim 23, wherein the first metallic material comprises a cobalt chromium alloy, and wherein the second metallic material comprises porous titanium.

25. The abutment of claim 22, wherein the outer surface of the post includes one or more tapers.

26. The abutment of claim 25, wherein the insertable first end of the post includes a first tapered surface that tapers inwardly in a direction away from the middle portion of the post along a longitudinal axis of the abutment, and wherein the first tapered surface is configured to be complementarily received in the implant stem.

27. The abutment of claim 26, wherein the outer surface of the post defines a second tapered surface positioned near an interface between the insertable first end and the middle portion of the post, the second tapered surface tapering inwardly in a direction away from the middle portion of the post along a longitudinal axis of the abutment.

28. The abutment of claim 27, wherein the first and second tapered surfaces each have an orientation angle relative to a longitudinal axis of the abutment, wherein the orientation angle of the second tapered surface is from 1 degree to 1.5 degrees greater than the orientation angle of the first tapered surface.

29. The abutment of claim 27, wherein the second tapered surface is configured to engage the fixation surface defined by the fixation element.

30. The abutment of claim 27, wherein a middle portion of the post and a portion of the insertable first end of the post positioned between the first and second tapered surfaces are configured to inhibit bio-adhesion.

31. The abutment of claim 28, wherein the middle portion of the post and the portion of the insertable first end of the post positioned between the first tapered surface and the second tapered surface comprise ultra-low friction surfaces.

32. The abutment of claim 28, wherein the central portion of the post and the portion of the insertable first end of the post positioned between the first tapered surface and the second tapered surface comprise highly polished surfaces.

33. A kit, comprising:

the implant system of claim 1.

34. A kit, comprising:

the implant stem of claim 12.

35. A kit, comprising:

the abutment of claim 22.