RADIOGRAPHIC ASSESSMENT OF STRUCTURAL DEFECTS IN BJORK-SHILEY CONVEXO-CONCAVE PROSTHESES

Following the implantation of Bjork Shiley 60 degrees convexo-concave (BS-CC) prostheses, outlet strut fracture rates up to 2.5% per year ha ve been reported, According to experimental results and clinical obser vations, single leg separations are regarded as the primary mechanisms leading to complete outlet strut fracture after a certain interval, I n an experimental study the question was addressed, whether single leg separation can be identified by especially developed radiographic mea ns, before outlet strut fracture occurs, Five BS-CC mitral prostheses (29-31 mm) with intentionally made single leg separations of defined g ap sizes (0-75 mu m) and one intact mitral prostheses were implanted i n sheep in a double-blind study design, Repeat non-invasive investigat ions were then performed applying a recently developed fluoroscopy ima ging technique with direct radiographic magnification (DIMA COR C22), Single leg separations with gap sizes of more than 25 mu m were proper ly detected using DIMA COR C22. Separations 25 mu m or less could not be detected with certainty but were evaluated as probable or possible as a result of multiple investigations. The intact prosthesis was corr ectly identified, but was investigated on only one occasion, Non-invas ive control of Bjork-Shiley CC mitral prostheses applying especially d eveloped direct radiographic magnification may allow for a reliable as sessment of single leg separtion with gap sizes of more than 25 mu m i n sheep, Using this technique of non-invasive serial investigations on particular patients with high probability of outlet strut fracture ap pears feasible, anticipating single leg separation detectability in hu mans, This has to be assessed in a second step, Thus, elective reopera tion may be scheduled according to the detection of single leg separat ion rather than solely on epidemiologically defined risk-benefit ratio s in these patients.