<s>
Roentgen	B-Algorithm
stereophotogrammetry	I-Algorithm
(	O
RSA	O
)	O
is	O
a	O
highly	O
accurate	O
technique	O
for	O
the	O
assessment	O
of	O
three-dimensional	O
migration	O
and	O
micromotion	O
of	O
a	O
joint	O
replacement	O
prosthesis	O
relative	O
to	O
the	O
bone	O
it	O
is	O
attached	O
to	O
.	O
</s>
<s>
Two	O
synchronised	O
x-ray	B-Library
foci	O
are	O
used	O
to	O
obtain	O
a	O
stereo	O
image	O
of	O
the	O
bone	O
and	O
the	O
prosthesis	O
.	O
</s>
<s>
The	O
change	O
in	O
the	O
position	O
(	O
translation	B-Algorithm
and	O
rotation	B-General_Concept
)	O
of	O
the	O
prosthesis	O
markers	O
relative	O
to	O
the	O
bone	O
markers	O
is	O
then	O
determined	O
.	O
</s>
