Tibial Stem



- Discussion:
    - tibial component fixation requires a stem to prevent sinking of the implant due to compressive failure of prox 
            tibial cancellous bone, & shear stresses are high enough in knee to require fixation of tibial tray with
             peripheral pegs;
    - tibial stem reduces shear forces at the prosthesis bone interface, as well as distributing angulatory load 
            through upper tibia;
    - stemmed component is utilized for pts with severe osteoporosis or in cases where large bone defects are encountered or bone grafts have been used;
    - stem length > than 5 cm is probably minimally beneficial in terms of stability;
            - in additon longer stem is not necessarily better since some degree of stress shielding of tibial cortex along length will occur;
    - tibial plateau may lose its support due to development of fibrous membrane, osteolysis from wear debris, or resorption of grafts;
            - in these cases, stem support of the tibial plateau is crucial to prevent fatigue failure of the cantilever plateau;

- Role of Polyethylene:
    - tibial prosthesis made of ultra-high molecular weight polyethylene should have a stem to help reduce lift-off, and the stem should be
            designed to prevent flexion, extension, varus & valgus angulation, & rotation;
    - due to the mechanical properties of ultra-high molecular weight polyethylene, a stem length of more than five centimeters is probably minimally
             beneficial in terms of the stability

 
The anatomy of the tibial intramedullary canal.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, May 10, 2012 8:31 am