News Column

Patent Issued for Mobile Bearing Assembly Having a Closed Track

July 16, 2014



By a News Reporter-Staff News Editor at Biotech Week -- A patent by the inventors Wyss, Joseph G. (Fort Wayne, IN); Lee, Jordan S. (Warsaw, IN), filed on March 17, 2008, was published online on July 1, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also DePuy Synthes Products, LLC).

Patent number 8764841 is assigned to DePuy Synthes Products, LLC (Raynham, MA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. For example, many knee replacement surgeries are performed each year. Total knee replacement or arthroplasty may involve replacement of the mid-shaft portion of the femur, proximal, distal, and/or total femur, and proximal tibia. Unicompartmental knee replacement or arthroplasty involves unicondylar resurfacing. Unicompartmental knee arthroplasty provides an alternative to total knee arthroplasty for rehabilitating knees when only one condyle has been damaged as a result of trauma or disease such as noninflammatory degenerate joint disease or its composite diagnosis of osteoarthritis or post-traumatic arthritis. As such, unicompartmental knee arthroplasty may be indicated for use in patients undergoing surgery for a severely painful and/or disabled joint damaged as a result of osteoarthritis, traumatic arthritis, rheumatoid arthritis, or a failed previous implant when only one condyle of the knee (medial or lateral) is affected. Further, unicompartmental knee replacements may be 'multi-piece' replacements in which a unicompartmental tibial insert is used to replace each of the medial and lateral condyles of the patient. A single, total femoral component or two partial femoral components may be used to cooperate with the two unicompartmental inserts.

"In addition, in some knee replacement procedures, a total knee tibial tray may used with a unicompartmental tibial insert. For example, a total knee tibial tray may be used with a single unicompartmental tibial insert to replace either the medial or lateral condyle of the patient's knee. Alternatively, a total knee tibial tray may be used with two unicompartmental tibial inserts, each replacing one of the medial and lateral condyles of the patient's knee. In such applications, the medial and lateral unicompartmental tibial inserts may have different characteristics and be selected based on the orthopaedic considerations associated with the respective condyle of the patient's knee.

"Unicompartmental knee replacements are intended to provide increased patient mobility and reduce pain by replacing the damaged knee joint articulation in patients where there is evidence of sufficient sound bone to seat and support the components. Age and activity level factor into all reconstructive procedures and the state of the arthritis determines the treatment. With the advancement of minimally invasive techniques that support unicompartmental knee reconstruction, a growing number of patients are offered this alternative for relief from the disabling pain of arthritis and for the potential benefits of a rapid recovery.

"A tibial assembly of a unicompartmental knee prosthesis typically includes a tibial tray configured to be coupled to the patient's tibia and a polymer tibial bearing or insert adjacent the tibial tray. As discussed above, the tibial tray may be a total or unicompartmental tibial tray. The tibial insert includes an upper bearing surface configured to engage a corresponding articulating condylar surface of a femoral component coupled to the patient's femur. A mobile tibial assembly generally refers to a tibial assembly wherein the tibial insert is movable relative to the tibial tray. In other words, the tibial insert may rotate relative to the tray and/or the tibial insert may move medially, laterally, anteriorly, and/or posteriorly relative to the tibial tray. This motion of the tibial insert relative to the tray may be constrained in any number of ways in order to limit the type of motion of the tibial insert. For example, the tibial insert may be limited to anterior/posterior motion relative to the tibial tray and/or rotation of the tibial insert relative to the tibial tray may be limited to something less than 360 degree rotation. A fixed tibial assembly generally refers to a tibial assembly wherein the tibial insert is not movable relative to the tibial tray and remains in a fixed location thereon. Surgeons may choose between fixed and mobile tibial assemblies depending upon the particular needs of the patient.

"Typical mobile tibial assemblies fall into one of two classifications with respect to the insert-to-tray interface: unconstrained and constrained. In an unconstrained mobile tibial assembly, the tibial insert is free to move in all directions relative to the tibial tray. In a constrained mobile tibial assembly, the tibial insert is typically restricted from movement relative to the tibial tray in all but one or more directions and/or movements (e.g., translations and/or rotations)."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "According to one aspect, a mobile tibial assembly may include a tibial tray and a tibial insert. The tibial tray may be configured to be coupled to a surgically-prepared surface of the proximal end of a tibia. Additionally, the tibial tray may include a closed track defined in an upper surface. The tibial insert may include a stem configured to be inserted into the closed track. Additionally, the tibial insert may be configured to move along the closed track while being retained therein.

"The closed track may include a first end and a second end. At least one of the first end and the second end is closed. In some embodiments, the closed track may include an elongated opening defined in the upper surface of the tibial tray. In such embodiments, the stem of the tibial insert may have a dimension greater than the width of the opening. Additionally, the closed track may include an access opening, such as an elliptical, circular, rectangular, or polygonal opening, defined in the upper surface of the tibial tray. The access opening may be connected to the elongated opening. For example, the access opening may be positioned at one end of the elongated opening. The elliptical opening may have a dimension greater than the dimension of the stem. The closed track may be defined by a bottom wall, a first side wall, a second side wall, a first lip extending from the first side wall over a portion of the bottom wall, and a second lip extending from the second wall over a portion of the bottom wall. The first and second lips may define an opening therebetween. In some embodiments, each of the first and second lip may include a bottom surface substantially parallel to the bottom wall of the track. In other embodiments, each of the first and second lips may include a bottom surface oblique to the bottom wall of the track.

"The stem of the tibial insert may be configured to be positioned in a first orientation that allows the stem to be inserted into the closed track and a second orientation that causes the stem to be retained in the closed track. The tibial insert may include a bottom surface and the stem may extend downwardly from the bottom surface. The stem may include a neck and a flange defined at an end of the neck. The flange may have dimension greater than a width of an opening of the closed track defined in the upper surface of the tibial tray. The flange may have an elliptical bottom profile, such as a circular bottom profile, when viewed in plan view. In some embodiments, the flange may also have a bottom surface substantially parallel to a the bottom surface of the tibial insert and an oblique top surface with respect to the bottom surface.

"In other embodiments, the flange may have any one of a number of different bottom profile shapes when viewed in plan view. For example, the flange may have a rectangular bottom profile, a triangular bottom profile, a hexagonal or other polygonal or substantially polygonal bottom profile, or the like. In embodiments wherein the flange has a rectangular bottom profile, the flange may have a length greater than a width of an elongated opening of the closed track and a width less than the width of the elongated opening. The flange may include a first end and a second end extending from the neck of the stem. The first and second end may be curved in some embodiments. The second end may extend from the neck farther than the first end in some embodiments. In such embodiments, the closed track may be defined by a bottom wall, a first side wall, a second side wall, a first lip extending from the first side wall a first distance, and a second lip extending from the second wall a second distance greater than the first distance. The first and second lips may define an opening therebetween. The first lip may establish a region thereunder configured to receive a portion of the first end and the second lip may establish a region thereunder configured to receive a portion of the second end of the flange.

"According to another aspect, a mobile tibial assembly may include a tibial tray and a tibial insert. The tibial tray may be configured to be coupled to a surgically-prepared surface of the proximal end of a tibia. Additionally, the tibial tray may include a closed track having an elongated opening defined in an upper surface. The tibial insert may include a bottom surface and a stem. The stem may extend downwardly from the bottom surface. The stem may include a flange defined at an end of a neck. The flange may have a dimension greater than a width of the elongated opening of the closed track.

"The closed track may include an elliptical opening defined in the upper surface of the tibial tray at one end of the elongated opening. The elliptical opening may have a dimension greater than the dimension of the stem. The stem may be configured to be positioned in a first orientation that allows the stem to be inserted into the closed track and a second orientation that causes the stem to be retained in the closed track. The flange may have a circular bottom profile when viewed in plan view in some embodiments. Alternatively, the flange may have a rectangular bottom profile when viewed in plan view. The flange may include a first end and a second end extending from the stem. The second end may extend from the stem farther than the first end.

"According to a further aspect, a method for implanting a tibial assembly may include securing a tibial tray to a surgically-prepared surface of the proximal end of a tibia. The tibial tray may include a closed track defined in an upper surface. The method may also include positioning a tibial insert in a first orientation. Additionally, the method may include inserting a stem of the tibial insert into the closed track while the tibial insert is in the first orientation. The method may also include moving the tibial insert to a second orientation to cause the tibial insert to be retrained in the closed track."

URL and more information on this patent, see: Wyss, Joseph G.; Lee, Jordan S.. Mobile Bearing Assembly Having a Closed Track. U.S. Patent Number 8764841, filed March 17, 2008, and published online on July 1, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8764841.PN.&OS=PN/8764841RS=PN/8764841

Keywords for this news article include: Biomedical Engineering, Biomedicine, Surgery, Arthritis, Bioengineering, Joint Diseases, Medical Devices, Knee Replacement, Knee Arthroplasty, Orthopedic Procedures, Musculoskeletal Diseases, DePuy Synthes Products LLC.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Biotech Week


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