Table 1.

Summary of measurement errors comparing computed tomography (CT) to biplanar radiography for hip angles

Measure	Observer 1 Cup inclination (°)	Observer 2 Cup inclination (°)	Observer 1 Cup anteversion (°)	Observer 2 Cup anteversion (°)	Observer 1 Femoral anteversion (°)	Observer 2 Femoral anteversion (°)
Mean absolute difference	0.24	0.65	− 0.13	− 1.72	3.67	2.47
Standard deviation	1.97	2.01	3.43	4.04	3.65	5.28
Range	4.6 − 4.0	3.7 − 4.4	7.3 − 7.8	5.8 − 9.8	11.3 − 1.3	13.6 − 14.8
95% confidence interval range	1.10 − 0.63	1.53 − 0.23	1.37 − 1.63	0.05 − 3.49	5.27 2.07	4.79 0.16
Pearson correlation coefficient*	r = 0.87, p < 0.01	r = 0.89, p < 0.01	r = 0.85, p < 0.01	r = 0.78, p < 0.01	r = 0.91, p < 0.01	r = 0.88, p < 0.01

*Reliability of biplanar radiography measurements compared to reference CT measurements