1. D.Bruni, MD; L.Bragonzoni, PhD; M.Gagliardi, MD; M.Bontempi, PhD; Akkawi I, MD; G.Raspugli,MD, Tedi M, MD; S.Patella, MD; Prof. M.Marcacci, MD. Rizzoli Orthopaedic Institute – Bologna, Italy

2. The RSA system - background What is RSA? Roentgen Stereophotogrammetric Analysis

3.  What it is used for? The RSA system - background

4.  how it works? The RSA system - background

5. Materials and Methods  15 patients treated with UKA- allpoly tibial component, marked with tantalum beads.  Average age at surgery: 71 years  Average Follow Up: 10 years (range 4- 15)

6. Evaluation mode: 1. Clinical evaluation:Knee Society Score (KSS) system [1] 2. Radiographic evaluation: RSA acquisition and software processing of data Materials and Methods Maximum Total Point Motion (MTPM) [1] Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res. 1989 Nov;(248):13-4.

7. Results: RSA evaluation

8. Absolute values within 1° year:  MTPM > 2mm in 3/4 revised patients  MTPM < 2mm in 11/11 non revised patients MTPM differences between 1°-2° year:  >0,2 mm in 4/4 revised patients  <0,2mm in 11/11 non revised patients

9. Clinical results

10. Results: Clinical-radiographic correlation

11. Conclusions– Take Home Message 1. Even in the long-term static RSA is an efficient tool for the predictive evaluation of the state of fixation of an all-poly UKA 2. MTPM can be used as an early indicator of aseptic loosening: Absolute values > 2mm within 1°year MPTM differences between 1°-2° year > 0,2mm High risk of Aseptic loosening