Exeter Stem Design THR

 Mention type of Cemented Stem Designs 

1. Charnley stem Design

2. Exeter Stem Design

https://holycrossleonecenter.com/exeter-hip-stem-still-gold-standard-industry

Write Characteristics of Exeter system. 

    Exeter is polished, double tapered stem.

What is the design philosophy of Exeter stem  ?

        Taper slip (force close ) principle    

        Stability - achieved by allowing micromotion at prosthesis-cement mantle 

        Collarless geometry , polished surface finish (< 0.01 Pa )

        Polish surface - allow tapered stems subside within cement mantle ,generate radial stress at bone cement and prosthesis interface in turn stabilizing bone cement prosthesis composite. 

    viscoelastic property of cement (creep and stress relaxation ) are key factors in this process.

How do they fail ? 

       Polish tapered design - mechanically stable , mechanism of wear not well understood. 

                                            rotation in axial plane may be the cause based on RSA analysis.

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