Patent Description:
Various reconstruction implants have been developed over the years to salvage the healthy bone. However, such implants are typically not patient specific and therefore may leave the patient with awkward bone geometries and a longer or shorter limb than prior to their disease or injury. Additionally, such implants are often heavy as compared to bone and may be difficult to implant and assemble in-situ as the healthy bone segments can be distracted only so far. Thus, further improvements are desirable. Other examples of implants are disclosed in <CIT> and <CIT>.

According to the present invention, an intercalary prosthesis as defined in appended claim <NUM> and the corresponding dependent claims is provided. In one aspect of the present disclosure, an intercalary prosthesis for spanning portions of a long bone include an intramedullary component that has a first stem and a first connector disposed at one end of the first stem. The first stem is configured to be received within an intramedullary canal of a long bone. The prosthesis also includes a second intramedullary component that has second stem and a second connector disposed at one end of the second stem. The second stem is configured to be received within an intramedullary canal of the long bone. The prosthesis further includes a connector component that has a body. The body has opposing ends each with a connector configured to respectively connect to the connectors of the first and second intramedullary components. The body has an outer shell and an inner lattice structure disposed within and connected to the outer shell.

Additionally, the first and second intramedullary components may each include a modular collar and an integral collar. The modular collar may be connectable to the integral collar and may have an outer surface that comprises a porous structure. The integral collar of the first intramedullary component may be disposed between the first stem and first connector portion. The body of the connector component may also include a plurality of openings extending through the outer shell to the inner lattice structure. The lattice structure may be comprised of a plurality of interconnected struts forming interstices therebetween. The connector component may further include a plurality of flats circumferentially arrayed about a longitudinal axis of the connector for engagement by a torque applying tool.

Continuing with this aspect, the body may be bowed such that a longitudinal axis thereof is curved about a center of curvature. The body may include an anterior groove that is coplanar with the center of curvature. The first and second connectors may each be a female connector, and the connectors of the connector component may be male connectors extending from opposing ends of the body. The male connectors may be configured to be respectively received within the female connectors and locked thereto upon rotation of the connector component relative to the first and second intramedullary components. The first and second connectors may each be a male connector respectively extending from the first and second stems. The connectors of the connector component may be female connectors disposed at opposing ends of the body. The male connectors may be configured to be respectively received within the female connectors and locked thereto upon rotation of the connector component relative to the first and second intramedullary components.

In another aspect of the present disclosure, an intercalary prosthesis for spanning portions of a long bone includes a first intramedullary component that has a first stem and a first connector disposed at one end of the first stem. The first stem is configured to be received within an intramedullary canal of a long bone. The prosthesis also includes a second intramedullary component that has a second stem and a second connector disposed at one end of the second stem. The second stem is configured to be received within an intramedullary canal of the long bone. The prosthesis further includes a connector component that has a body and third and fourth connectors disposed at opposed ends of the body. The first and third connectors and second and fourth connectors are configured to be locked to each other upon rotation of the connector component relative to the first and second intramedullary components.

Additionally, the first and second connectors may each be a female connector, and the third and fourth connectors of the connector component may be male connectors extending from opposing ends of the body. The male connectors may be configured to be respectively received within the female connectors and locked thereto upon rotation of the connector component relative to the first and second intramedullary components. The male connectors may include a post and spline keys extending from the post, and the female connectors may include a spiraled recess configured to interfere with the spline keys when rotated within the spiraled recess for providing a locking connection. Alternatively, the male connectors may include a cam surface and a tooth, and the female connectors may include a recess with a leaf spring extending therein. The cam surface may be configured to move the leaf spring radially outwardly upon rotation of the male connectors in a first direction. The tooth may be configured to engage the leaf spring to prevent rotation of the male connectors in a second direction.

Continuing with this aspect, the first and second connectors may each be a male connector respectively extending from the first and second stem, and the third and fourth connectors of the connector component may be female connectors disposed at opposing ends of the body. The male connectors may be configured to be respectively received within the female connectors and locked thereto upon rotation of the connector component relative to the first and second intramedullary components. The male connectors may include a post and spline keys extending from the post, and the female connectors may include a spiraled recess configured to interfere with the spline keys when rotated within the spiraled recess. Alternatively, the male connectors may include cam surface and a tooth, and the female connectors may include a recess with a leaf spring extending therein. The cam surface may be configured to move the leaf spring radially outwardly upon rotation of the male connectors in a first direction. The tooth may be configured to engage the leaf spring to prevent rotation of the male connectors in a second direction. The body of the connector component may include a solid shell surrounding a lattice structure.

In a further aspect of the present disclosure, a method of connecting first and second portions of a long bone includes: inserting a first stem of a first intramedullary component into a first portion of a long bone and a second stem of a second intramedullary component into a second portion of the long bone. After the inserting step, the method includes connecting a first end of a connector component to an end of the first intramedullary component and a second end of the connector component to an end of the second intramedullary component.

Additionally, the connecting step may include rotating the connector to lock the first and second intramedullary components to the connector component. The connecting step may also include inserting male connectors each extending from opposing ends of a body of the connector component into respective female connectors of the first and second intramedullary components. Alternatively, the connecting step may include inserting male connectors each extending from a respective end of the first and second intramedullary components into respective female connectors of the connector component. The female connectors may be disposed at opposing ends of a body of the connector component.

The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings in which:.

When referring to specific directions in the following discussion of certain implantable devices, it should be understood that such directions are described with regard to the implantable device's orientation and position during exemplary application to the human body. Thus, as used herein, the term "proximal" means close to the heart and the term "distal" means more distant from the heart. The term "inferior" means toward the feet and the term "superior" means toward the head. The term "anterior" means toward the front of the body or the face, and the term "posterior" means toward the back of the body. The term "medial" means toward the midline of the body, and the term "lateral" means away from the midline of the body. Also, as used herein, the terms "about," "generally" and "substantially" are intended to mean that slight deviations from absolute are included within the scope of the term so modified.

<FIG> depict an intercalary prosthesis <NUM> according to an embodiment of the present disclosure. The intercalary prosthesis <NUM> generally includes a first intramedullary component 30a, a second intramedullary component 30b, and a connector component <NUM>.

The connector component <NUM> generally includes a body <NUM> and connectors disposed <NUM> at opposing ends of the body <NUM>. The body <NUM> has an outer shell <NUM> and an inner lattice structure <NUM>. The outer shell <NUM> is a solid metal material with a generally continuous outer surface. The outer shell <NUM> defines a hollow cavity <NUM> therein which is occupied by the lattice structure <NUM>. The lattice structure <NUM> is connected to the outer shell <NUM> and provides structural support to the connector component <NUM> while also providing reduced weight as compared to a connector component that is completely solid through its entire thickness. The lattice structure <NUM> is formed of a plurality of interconnected struts <NUM> which defined interstices <NUM> therebetween.

The body <NUM> includes a plurality of openings <NUM> extending through the outer shell and into the inner cavity <NUM> so as to communicate with the lattice structure <NUM>. This facilitates the removal of metallic powder from the cavity <NUM> after manufacturing via an additive manufacturing process, as described below. The body <NUM> also includes a plurality of flats <NUM> circumferentially arrayed about a longitudinal axis thereof. These flats <NUM> are angled relative to each other so that they can be engaged by a torque applying tool, such as a wrench, to facilitate the rotation of the connector component in-situ. In the particular embodiment depicted, the openings <NUM> in the body <NUM> each extend through a corresponding flat <NUM>. However, in other embodiments, the openings <NUM> may extend through other regions of the body <NUM>.

In addition, the body <NUM> may have a patient specific curvature or bow. For example, femurs typically have an anterior curvature or bow. The body <NUM> may be manufactured such that it matches the curvature or bow of the patient's particular anatomy. In this regard, connector component <NUM> may have a longitudinal axis that is curved about a center of curvature which would be positioned posterior to the body <NUM>. An anterior groove 21a, as shown in <FIG>, may be aligned with this curvature so as to provide the surgeon the appropriate orientation. In this regard, the anterior groove <NUM> may have an axis that is coplanar with the center of curvature.

As shown, the connectors <NUM> extend from opposing ends of the body <NUM> and are male connectors. More particularly, these male connectors <NUM> are comprised of a post 22a and one or more spline keys 22b extending radially outwardly from the post 22a. As best shown in <FIG> and <FIG>, a through-opening <NUM> extends through the entire length of connector component <NUM> and through the center of each of the connectors <NUM>. Such through-opening <NUM> communicates with the lattice structure <NUM> and provides an additional egress route for powder removal.

The connector component <NUM> is formed layer-by-layer using additive layer manufacturing (ALM), i.e., 3D printing, process so no separate connection mechanism is necessary to bring together any of the multiple features of the implant, such as the connectors, shell and lattice structure. In some examples, ALM processes are powder-bed based and involve one or more of selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM), as disclosed in <CIT>;<CIT>; <CIT>; and <CIT>.

The ALM process used to form the connector component <NUM> allows the creation of the lattice structure <NUM> which is completely surrounded by the outer shell <NUM>. This allows the connector component <NUM> to be lighter weight than a connector component made from traditional manufacturing processes, such as machining, forging and casting, without sacrificing strength. The openings <NUM> in the body <NUM> and through-opening <NUM> facilitate the removal of loose powder from within the lattice structure after the connector component has been made. In addition, the use of ALM allows for a custom or semi-custom design. In preparing such an implant, the patient's anatomy around at least the region for treatment may be scanned, such as by a CT scan or other use of x-rays or by magnetic resonance imaging (MRI) or other known imaging device. The scanned image may then be converted to virtual patient-specific bone image using computer-aided modeling and segmentation software. Such software may be but is not limited to ImorphicsTM, which is wholly owned by Imorphics Limited, a subsidiary of Stryker® Corporation, Stryker® Orthopaedics Modeling and Analytics (SOMA) by Stryker® Corporation, GeoMagic® by 3D Systems, Inc. , and 3D Slicer software developed by the Massachusetts Institute of Technology. A manual segmentation or an automatic segmentation process, such as either of the processes described in <CIT> and <CIT>, may be used. A virtual connector component <NUM> would then be manipulated in the virtual space to match certain aspects of the patient's anatomy, such as an anterior curvature of the patient's femur, also known as an anterior bow, which is discussed above. The virtual component <NUM> could then be printed with those same features using ALM.

The first and second stem assemblies 30a-b each generally include a stem component <NUM> and a modular collar <NUM>. The stem component <NUM> includes an intramedullary stem <NUM>, integral collar <NUM>, and a connector <NUM>. The stem <NUM> may have flutes (not shown) for anti-rotation or indented elongate grooves for strength. The integral collar <NUM> is positioned between the stem <NUM> and connector <NUM>. The integral collar <NUM> has a larger cross-sectional dimension than the stem <NUM> and may have a tapered outer surface. For embodiments in which collar <NUM> is a separate component that couples with stem <NUM>, collar <NUM> may have a tapered inner diameter to facilitate a taper-lock connection to the stem <NUM>.

The connector <NUM> may have a larger cross-sectional dimension than the integral collar <NUM> so as to form a shoulder <NUM> which acts as a stop for the modular collar <NUM>. The connector <NUM> also has a plurality of notches <NUM> on its exterior for receipt of the tabs <NUM> of the modular collar, as discussed below. The connector <NUM>, as best shown in <FIG>, is a female connector. As a female connector, it has an opening <NUM> for receipt of the male connector <NUM> of the connector component <NUM>. Such opening <NUM> has notches <NUM> configured to receive the splines 22b of the male connector <NUM> in one orientation, as best shown in <FIG>. Within opening <NUM> is a spiraled groove <NUM> which has one or more surfaces, depending on the number of splines 22b, which each have a progressively smaller radius so as to interfere with a corresponding spline 22b in order lock the male and female connectors <NUM>, <NUM> together, as best shown in <FIG>.

The modular collar <NUM> has a body <NUM> with a porous outer surface <NUM> and an opening extending <NUM> entirely through the body <NUM> along a length of the modular collar <NUM>. The through-opening <NUM> may be tapered so as to facilitate a taper lock between the integral collar <NUM> and modular collar <NUM>. Tabs <NUM> extend from one end of the body <NUM> and may be received within the notches <NUM> in the connector <NUM> so as to prohibit rotation of the modular collar <NUM> relative to the stem component <NUM>.

As assembled, the connector component <NUM> is positioned between the first and second intramedullary components 30a, 30b and locked thereto via the corresponding connectors <NUM>, <NUM>, as shown in <FIG>. The modular collars <NUM> are positioned over the respective integral collars <NUM> of the stem components 30a, 30b.

In a method of implantation, the connector component <NUM> facilitates the assembly of the endoprosthesis in-situ. In this regard, the first and second intramedullary components 30a-b are implanted into respective bone portions. For example, a femur may include a first or proximal bone portion and a second or distal bone portion. The stem <NUM> of the first intramedullary component 30a may be inserted into the intramedullary canal of the first bone portion, such as in a press-fit or cemented manner. Similarly, the stem <NUM> of the second intramedullary component 30b may be inserted into the intramedullary canal of the second bone portion, also in a press-fit or cemented manner. The first and second intramedullary components 30a-b may be implanted such that the modular collars <NUM>, which are assembled to the stem components 30a-b prior to implantation, abut the ends of the respective bone portions. The bone may grow into the porous structures <NUM> of the modular collars <NUM>.

Once the intramedullary components 30a-b are implanted, the connector component <NUM> is positioned between the intramedullary components 30a-b. The connectors <NUM> of the connector component <NUM> are then inserted into the connectors <NUM> of the respective intramedullary components 30a-b, as best shown in <FIG>. In this regard, splines 22b pass through notches <NUM>. Once splines 22b are inserted passed notches <NUM>, the connector component <NUM> may be rotated such as via a wrench or the like which causes the splines 22b to engage the spiral grooves <NUM> thereby locking the connector component <NUM> to the intramedullary components 30a-b, as best shown in <FIG>. It is noted that the connector component <NUM> and intramedullary components 30a-b are oriented prior to rotation in a way that once the connector component <NUM> is rotated into the locked position, the anterior groove <NUM> faces anterior so that the bow of the connector component <NUM> aligns with the bow of the patient's femur.

<FIG> depict a connector component <NUM> and intramedullary component 130a according to another embodiment of the disclosure. Like elements are accorded like reference numerals to that of connector component <NUM> and intramedullary components 130a-b but within the <NUM> series of numbers. In this configuration, the connector component <NUM> and first and second intramedullary components 130a-b respectively include male and female connectors <NUM>, <NUM> at their ends. <FIG> only depicts the first intramedullary components 130a which is representative of the second intramedullary component 130b (not shown). The male connectors <NUM> at the ends of the connector component <NUM> is in the form of a snail cam defined by a spiral post 122a that has a reducing radius cam surface that terminates at a tooth 122b. The female connectors <NUM> at the ends of the intramedullary components 130a-b have a grooved opening <NUM> with a leaf spring <NUM> that extends into the opening <NUM>, as shown in <FIG>.

In use, the connectors <NUM> of the connector component <NUM> are inserted into corresponding female connectors <NUM> of the intramedullary components 130a-b, as illustrated in <FIG>. Once the male connectors <NUM> are received within the corresponding female connectors <NUM>, the connector component <NUM> is rotated about its axis in the same manner described above. This causes the cam surfaces to push the leaf spring <NUM> radially outwardly. Once the tooth 122b passes the leaf spring <NUM>, the leaf spring <NUM> snaps back into its original position. The tooth 122b now extends further radially outwardly than the leaf spring <NUM> which prohibits rotation of the connector component <NUM> in the opposite direction thereby locking the connector component <NUM> to the intramedullary components 130a-b.

Other connector configurations are also contemplated but not shown. For example, the male connector of connector component <NUM> may instead be located at the ends of intramedullary components 30a-b, while the female connectors of components 30a-b may be located at the ends of connector component <NUM>. In other words, the connection is functionally the same as that of components <NUM> and 30a-b but with the male/female connectors <NUM>, <NUM> being swapped between components <NUM> and 30a-b. Such reverse configuration of male/female connectors is also contemplated for connector component <NUM> and intramedullary components 130a-b.

Claim 1:
An intercalary prosthesis (<NUM>) for spanning portions of a long bone, comprising:
a first intramedullary component (30a, 130a) having a first stem (<NUM>, <NUM>) and a first connector (<NUM>, <NUM>) disposed at one end of the first stem (<NUM>, <NUM>), the first stem (<NUM>, <NUM>) being configured to be received within an intramedullary canal of a long bone;
a second intramedullary component (30b) having a second stem (<NUM>) and a second connector (<NUM>) disposed at one end of the second stem (<NUM>), the second stem (<NUM>) being configured to be received within an intramedullary canal of the long bone; and
a connector component (<NUM>, <NUM>) having a body (<NUM>, <NUM>), the body (<NUM>, <NUM>) having opposing ends each having a connector (<NUM>, <NUM>) configured to respectively connect to the connectors (<NUM>, <NUM>) of the first and second intramedullary components (30a, 130a, 30b), the body (<NUM>, <NUM>) also having an outer shell (<NUM>) and defining a through-opening (<NUM>) extending through the connector component (<NUM>, <NUM>) and through each of the connectors (<NUM>, <NUM>),
the prosthesis (<NUM>) being characterized in that
the body (<NUM>, <NUM>) of the connector component (<NUM>, <NUM>) has an inner lattice structure (<NUM>) disposed within and connected to the outer shell (<NUM>) and in that
the lattice structure (<NUM>) is in communication with the through-opening (<NUM>).