Knee arthroplasty prosthesis method
A knee arthroplasty prosthesis includes a femoral component having multiple pieces with engagement means provided for engaging various pieces of the femoral component to one another following their insertion in the incised area of the femur. A tibial component includes multiple pieces designed for assembly following positioning in the incision. The tibial component includes a Morse taper cavity on one piece of the tibial component and a Morse taper extension on another member of the component for receipt therein.
1. A method of performing knee arthroplasty comprising the steps of:
(a) providing a multi-piece tibial component, the tibial component including
(i) a tibial base having an inferior surface for engagement with a prepared surface at the proximal end of a tibia and a passageway extending through the base, the passageway including an open proximal end, an open distal end, and a portion which tapers inwardly in a distal direction, the tibial base further including an enlarged threaded aperture adjacent said superior surface and defining a shoulder extending outwardly from the portion which tapers inwardly, and
(ii) a tibial stem including a tapered extension shaped to snugly engage the tapered portion of the passageway and a threaded flange portion shaped to threadably engage the enlarged threaded aperture of the tibial base, the threaded flange positioned proximal of the tapered extension;
(b) preparing the proximal end of a tibia including forming a cavity along the intramedullary canal of the tibia;
(c) positioning the tibial base on the prepared tibia proximal end;
(d) thereafter positioning the tibial stem through the passageway in the tibial base, wherein a portion of the tibial stem is retained within the passageway and a portion of the tibial stem extends distally from the open distal end of the passageway and into the prepared cavity; and
(e) securing the tibial base and the tibial stem together by threadably engaging the threaded flange portion of the tibial stem with the threaded aperture of the tibial base, such that the tapered extension of the tibial stem is lockingly engaged with the passageway of the tibial base,
said step of securing the tibial base including leaving a gap between a distal side of the threaded flange and a proximal surface of the shoulder to ensure that the threadably engaging step effects locking engagement of the tapered extension and tibial base.
2. The method of claim 1 wherein the tibial base has inwardly facing threads and the tibial stem has outwardly facing threads proximally of the tapered extension and further including the step of engaging the outwardly facing threads to the inwardly facing threads.
3. The method of claim 2 wherein the tibial component further includes an insert engageable with the base, the insert having a passageway and the tibial stem extension having a threaded cavity and further extending a screw through the insert passageway and engaging it in the extension threaded cavity.
4. A method for anchoring a tibial implant to a proximal tibia, the method comprising the steps of:
seating a tibial plate on the proximal tibia, the tibial plate having a passageway extending therethrough, the passageway having an open proximal end and an open distal end, the open proximal end having a threaded aperture formed therein, the threaded aperture defining a shoulder extending outwardly from the passageway;
extending an elongated member through the tibial plate and into the tibia after the step of seating a tibial plate on the proximal tibia, the elongated member having a proximal end with a threaded flange portion and a distal end, wherein the proximal end of the elongated member is positioned within the passageway and the distal end of the elongated member extends distally from the open distal end of the passageway;
securing the elongated member to the tibial plate by threadably engaging the threaded flange portion of the elongated member with the threaded aperture of the tibial plate, said step of securing effecting a taper lock between a tapered portion of the elongated member and a correspondingly tapered portion of the passageway, such that a gap remains between a distal side of the threaded flange and a proximal surface of the shoulder, whereby firm locking engagement of the tapered extension and tibial base is ensured by said threadably engaging step;
mounting a tibio-femoral insert to the tibial plate; and
inserting a screw through the tibio-femoral insert and into threaded engagement with a socket formed in the elongated member to retain the tibio-femoral insert on the tibial plate.
5. The method of claim 4 , wherein extending an elongated member through the tibial plate includes threadably engaging the elongated member with the tibial plate.