Transdermal intraosseous device

A transdermal intraosseous device includes a transdermal adapter for an external prosthetic device for a bone of a patient and a bone fixator including a distal portion coupled to the transdermal adapter and a proximal portion for anchoring into the bone. The transdermal adapter includes a dome-shaped portion for transcutaneous implantation and an external shaft extending from the dome-shaped portion. A dermal transition structure is configured to include a controlled roughness gradient from the external shaft to the dome-shaped portion and configured for use in infection control at a dermis layer of the patient.

INTRODUCTION

Various known external fixation devices for amputation or trauma include compliant mechanisms for supporting a prosthetic device to a bone. In devices of this type, the compliant fixation mechanism provides a compressive stress at the bone interface for preventing bone resorption over time. Typically, a metal portion of the fixation device may extend beyond the cut surface of the bone, such that soft tissue is attached to the metal, rather than the bone.

The interface between the prosthetic device and soft tissue can be a source of infection. The present teachings provide devices and surface treatments associated with the transcutaneous portion of an external prosthesis adapter.

SUMMARY

The present teachings provide a transdermal intraosseous device that includes a transdermal adapter for an external prosthetic device for a bone of a patient and a bone fixator including a distal portion coupled to the transdermal adapter and a proximal portion for anchoring into the bone. The transdermal adapter includes a dome-shaped portion for transcutaneous implantation and an external shaft extending from the dome-shaped portion. A dermal transition structure is configured to include a controlled roughness gradient from the external shaft to the dome-shaped portion and configured for use in infection control at a dermis layer of the patient. The bone fixator can be a compliant bone fixator or a static, non-compliant bone fixator.

In some embodiments, the dermal transition structure includes a porous metal dome-shaped structure surrounding and overlaying the dome-shaped portion of the transdermal adapter, and first and second transitional surface treatment layers between the external shaft and the porous metal dome-shaped structure along the longitudinal axis of the transdermal adapter. The first transitional surface treatment layer is roughened by blasting for contact with the dermis and the second transitional surface treatment layer is roughened by a combination of blasting treatment and acid-etching treatment for contact with the dermis.

The present teachings also disclose a method for providing a controlled roughness gradient transition between an external prosthetic device for a bone of a patient and the corresponding dermis of the patient. The method includes positioning a porous metal dome-shaped structure around a metal dome-shaped portion of a transdermal adapter. An external shaft extends from the dome-shaped portion of the transdermal adapter and a first portion of the external shaft is roughened by blasting. A second portion of the external shaft is roughened by blasting and acid etching. The first portion extends above the porous metal dome-shaped structure along a longitudinal axis of the external shaft and the second portion extends above the first portion along the longitudinal axis of the external shaft. The porous meal dome-shaped portion and the first and second portions of the external shaft are configured to contact the dermis for infection control.

Further areas of applicability of the present teachings will become apparent from the description provided hereinafter. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings.

DESCRIPTION OF VARIOUS EMBODIMENTS

The following description is merely exemplary in nature and is in no way intended to limit the present teachings, applications, or uses. The present teachings can be used for attaching any external prosthetic device to a bone through skin via a transdermal intraosseous device. The transdermal intraosseous device can include a transdermal adapter and an intraosseous fixator. In some embodiments, the intraosseous fixator can optionally include a compliant fixator, such as, for example, the Compress® Pre-Stress Implant, which is commercially available from Biomet, Inc. Warsaw, Ind., or a compliant fixator according to the present teachings and described herein. Compliance, as used herein, is a measurement of softness as opposed to stiffness of a material. Compliance of a structural member is generally the reciprocal of Young's modulus (one dimension) or the inverse of the stiffness matrix (more than one dimensions). Accordingly, a compliant member is generally a structural member that has enhanced compliance, such as an elastic spring, bellows, Belleville washers and other elastically biasing members. The compliant fixator of the present teachings, as well as the Compress® Compliant Pre-Stress Implant, allows osseointegration at the bone/implant interface and can provide a stable, high-pressure/implant interface. The compliant fixator can also assist in the prevention of stress shielding and any concomitant bone loss.

Infection is generally a common complication with known transdermal (transcutaneous) intraosseous devices. Aggressive apical epithelial migration, or epithelial downgrowth may be initiated as a normal wound healing process to foreign bodies. If not prevented, this process may result in deep pocket formation and subsequent marsupialization of the transdermal devices. In contrast, subepithelial connective tissue adhesion to a transdermal intraosseous device may prevent epithelial downgrowth and associated complications, such as infection.

As discussed below, the transdermal intraosseous device of the present teachings can include a transdermal adapter coupled to an intraosseous fixator, such as a compliant fixator or other intramedullary anchoring member. The transdermal adapter can include a porous titanium material, such as Regenerex® Porous Titanium Construct, commercially available from Biomet, Inc., Warsaw, Ind. Similarly to Regenerex®, the porous titanium material may have an average porosity of about 67 percent and pore size ranging from about 100 to about 600 microns (average of 300 microns), as well as high strength and flexibility

Referring toFIGS. 1A-7B, an exemplary transdermal intraosseous device10according to the present teachings can include a transdermal adapter100for connection to an external prosthetic device (not shown) and a bone fixator200for compliant or non-compliant fixation into an intramedullary bore84of a bone80, such as a femur, tibia, humerus, etc., that will receive the external prosthetic device. Accordingly, the bone fixator200can be a compliant fixator that can provide pre-stress to the bone or a non-compliant fixator in the form of a static (non-dynamic) anchoring member.

The bone fixator200can include a distal portion202and a proximal portion204. The distal portion202is configured for coupling with the transdermal adapter100outside the bone80in the subdermal soft tissue82under the epidermis and dermis layers (skin)86of the patient, such as, for example, with a taper connection, as discussed below. The proximal portion204is received into the bore84of the bone80for anchoring into the bone80as discussed below. The bone fixator200can also include an intermediate portion206between the distal portion202and the proximal portion204of the bone fixator200. The intermediate portion206can be a skirt-like collar and can be modularly or fixedly coupled to the distal portion202and the proximal portion204and can include a porous titanium plasma spray208(FIG. 3A) with a hydroxyapatite (HAS) coating or other similar treatment for increased biologic fixation. The intermediate portion206can be fixed to a resected distal surface88of the bone80with anti-rotation pins or other fasteners210through corresponding apertures212at an angle relative to a longitudinal axis A of the bone fixator200, as shown inFIG. 3B. As shown inFIG. 1A, the longitudinal axis A is also a center axis of the transdermal adapter100.

Referring toFIGS. 1A and 8, the transdermal intraosseous device10can include a centering sleeve300. The centering sleeve300can include an outer surface302engageable with the bone bore84and an inner surface304receiving and engaging the proximal portion204of the bone fixator200. In some embodiments, the centering sleeve300can be patient-specific (customized for an individual patient). For example, the outer surface302of the centering sleeve300can be patient-specific (customized for an individual patient) to conform to the surface of the bone bore84based on a three-dimensional image of the bone bore84. The a three-dimensional image of the bone bore84can be generated via MRI, CT or other imaging methods of the patient's anatomy during a pre-operative planning phase of the surgical procedure using computer modeling technology commercially available, for example, by Materialise USA, Plymouth, Mich. Accordingly, the outer surface302of the centering sleeve300can include, for example, patient-specific, cylindrical or piece-wise cylindrical, conical or other curved and closed surface portions. The inner surface304of the centering sleeve300can be configured to receive and engage the proximal portion204of standard (non-custom) bone fixators200of different standard sizes and can be, for example, tapered, cylindrical, piece-wise cylindrical or piece-wise tapered. In this regard, the centering sleeve300provides a transition from a patient-specific engagement with the bone80of the patient to a standard engagement with one of the standard size bone fixators200.

Referring toFIGS. 1A,1B,2,7A and7B, the transdermal adapter100can include a body101having a substantially dome-shaped portion102received subcutaneously, and an external shaft104. The body101, including the dome-shaped portion102and the external shaft104can be made as a monolithic (single) piece from a biocompatible metal, such as polished titanium alloy (Ti-6-4). The dome-shaped portion102includes an internal bore or opening105. The internal bore105can be tapered and receive a tapered distal portion202of the bone fixator200for a taper connection therebetween. In some embodiments, an extension106can depend proximally from the dome-shaped portion102toward the bone of the patient defining a circumferential slot or groove108. A redundant connector350can be used to provide an additional secured connection between the intermediate portion206of the bone fixator200and the extension106of the transdermal adapter100. The redundant connector350can engage the groove108and can be, for example, a two-piece split locking nut or washer, as illustrated inFIG. 1A. The redundant connector350can be tightened against the intermediate portion with a connector element, such as a screw or other fastener (not shown) and can also provide a tapered engagement with a corresponding tapered portion of the outer surface of the intermediate portion206. Referring toFIGS. 7B and 6B, a plurality of tabs111can protrude from the internal bore105for engagement with corresponding slots211of the intermediate portion206of the bone fixator200.

Regarding infection control, and referring toFIGS. 1A,1B and2, the transdermal intraosseous device10of the present teachings can include a dermal transition structure400between the body101of the transdermal adapter100and the dermis and epidermis86of the patient. The dermal transition structure400can include a porous metal dome-shaped structure402surrounding and overlaying on the dome-shaped portion102of the transdermal adapter100. The material of the porous metal dome-shaped structure402can be, for example, the Regenerex® Porous Titanium Construct discussed above. The porous metal dome-shaped structure402can be attached to the dome-shaped structure402with laser welding, brazing, sintering, or other methods.

The dermal transition structure400can also provide a controlled roughness gradient from the smooth/polished external shaft104to the porous metal dome-shaped structure402. Accordingly, first and second transitional surface treatment layers404,406can be included at the interface between the transdermal adapter100and the dermis/epidermis86for providing a roughness gradient. A first transitional surface treatment layer404is positioned and extends directly above the porous metal dome-shaped structure402surrounding a contiguous portion of the external shaft104along the longitudinal axis A and contacting the dermis86. The first transitional surface treatment layer404can be a roughness treatment on the external shaft104formed by blasting, including ceramic bead blasting, sand blasting, grit blasting and similar treatments.

The second transitional surface treatment layer406is contiguous to the first transitional surface treatment layer404and includes a blasting treatment in combination with acid etching, such as an Osseotite®-treated surface. Osseotite® is a surface treatment commercially available from Biomet, Inc., Warsaw, Ind. Osseotite® treated surfaces may yield up to 110% increase in platelet adhesion and up to 54% increase in red blood cell (RBD) agglomeration over a smooth machined surface. RBD agglomeration is known to enhance blood clot permeability, which promotes wound healing. Increased platelet activity can also lead to enhanced wound healing through the release of cytokines and growth factors such as platelet derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1.

The dermal transition structure400provides a gradual transition from the polished outer surface of the external shaft104to the rough surface of the porous metal dome-shaped structure402through the first and second transitional surface treatment layers404,406. Thus, the first transitional surface treatment layer402, has greater roughness than the second transitional surface treatment layer404.

The dermal transition structure400may enhance dermal connective tissue adhesion, given that dermal tissue preferentially adheres to substrates with percentage porosity and pore size similar to porosity of the porous metal dome-shaped structure402and the Regenerex® material, as described above. The roughness gradient from the porous metal dome-shaped structure402to the polished shaft104through the first and second layers404,406described above may provide dermal tissue ingrowth as well epidermal adhesion, as described above.

As discussed above, the bone fixator200can be a compliant fixator configured to provide a bone biasing force to a portion of a bone. Any known compliant fixator can be used, including, but not limited to, the compliant fixators disclosed in commonly assigned U.S. Pat. Nos. 7,141,073, 6,712,855, 6,508,841, 6,197,065, all of which are assigned to common assignee Biomet Manufacturing Corp., and are incorporated herein by reference. The compliant fixator200is adapted to provide a compressive load on the bone, thereby reducing bone loss and promoting bone growth. The compliance of the bone fixator200can exceed that of native bone80, such that stress shielding does not occur. Additionally, the native bone80can experiences physiologic dynamic compressive loading biased by a preset spring compression. In this context, evidence of bone hypertrophy or lack of bone loss may occur near the resection level resulting in increased bone strength, possibly as a result of a phenomenon known as Wolf's Law.

Referring toFIGS. 3A-5, an exemplary compliant bone fixator200can include, for example, a compliant member226. The compliant member226can be include one or more compliant elements, such as one or more Belleville washers, as shown inFIG. 3Bor other spring washers or a single or double helical spring. Detailed descriptions of the structure and operation of various compliant fixators200and biasing mechanisms are provided in the above-referenced patents. According to the present teachings, the compliant member226can be contained within a longitudinal bore228of the distal portion202of the bone fixator. The longitudinal bore228is shaped and configured for accommodating the compliant member226, such that the longitudinal bore228may have a larger diameter for Belleville washers than for a helical spring. The compliant bone fixator200can be anchored to the bone80and pre-stressed via an anchoring member230. The anchoring member230can include an elongated shaft232attached to a plug234at a first end and having a threaded distal end238. The plug234, which can be enlarged relative to the shaft232, can include a plurality of apertures236for receiving transverse bone fixation pins. The anchoring member230can be inserted through a longitudinal bore224that passes through the bone fixator200and through the Belleville washers when used as a compliant member226. The compliant member226can be held temporarily secured using a removable tubular knob220having a bore222. In this regard, the compliant bone fixator200can be inserted through a hole/incision punched through the skin and anchored into the bone80via the anchoring member230while the compliant member226is held with the tubular knob220. A nut240can be threaded on to the distal threaded portion238of the shaft232and rotated to pre-stress the compliant member226to a desired amount. The knob220may then be removed. The transdermal adapter100can be impacted in position for locking the tapered connection between the dome-shaped portion102of the transdermal adapter100and the distal portion202of the bone fixator200. The transdermal adapter can also be locked with the redundant connector350. The skin flap around the incision can be sutured around the external shaft104.

The compliant bone fixator200can be designed to have a fatigue strength which is substantially greater than expected and/or estimated loads transmitted from an external prosthetic device to the bone-implant interface. Referring toFIGS. 1A and 12, as an added precaution, a torque limiter530can be installed in series with the exoprosthetic device10to prevent a large torsional load transmission to the compliant bone fixator200in the case of trauma or other unexpectedly high load. The torque limiter530can be, for example, a two piece stepped device including first and second tubular shafts534,536with a common through bore532receiving a portion of the external shaft104of the body101of the transdermal adapter100. The torque limiter530can be, for example, a torque limiter commercially available from R+W America, Bensenville, Ill. The torque limiter530can be coupled to the external shaft104with a quick release collar500. An exemplary collar500is illustrated inFIG. 9and includes a central aperture504and two end portions506defining a gap (slit in the collar). The collar500can be locked and unlocked with an actuating mechanism, such as a cammed lever510. An exemplary cammed lever is illustrated inFIG. 10and includes a coupling end512and a curved engagement surface514.

Referring toFIGS. 1A and 11, an exemplary output shaft520for the prosthetic device is illustrated. The output shaft520can include a notch522to control a failure mode and location in bending.

The foregoing discussion discloses and describes merely exemplary arrangements of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein, so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the present teachings.