Table 1.

Accuracy of model-based and marker-based RSA (phantom model)

RSA method	Translation (mm)	Translation (mm)	Translation (mm)	Rotation (degrees)
	x axis	y axis	z axis	y axis
Model-based RSA
Mean difference	−0.01	−0.01	0.02	−0.23
95% CI	(−0.02 to −0.01)	(−0.03–0.00)	(−0.04–0.07)	(−0.41 to −0.06)
Accuracy	0.02	0.03	0.13	0.39
Marker-based RSA
Mean difference	0.00	−0.02	−0.02	−0.15
95% CI	(−0.01–0.01)	(−0.04–0.01)	(−0.03 to −0.01)	(−0.23 to −0.07)
Accuracy	0.02	0.06	0.03	0.18
Marker-based RSA (UmRSA®)
Mean difference	−0.01	−0.01	−0.02	−0.04
95% CI	(−0.02–0.00)	(−0.01–0.00)	(−0.04–0.00)	(−0.17–0.10)
Accuracy	0.02	0.01	0.04	0.30

Mean difference = paired difference between micrometer-measured actual displacements and RSA-measured values; accuracy = t × SD/√2.