TABLE I.

Reliability of Classification Systems for Osteonecrosis of the Femoral Head

Study	Classification System*	Measure of Reliability	Result†
Schmitt-Sody et al.38 (2008)	Ficat	Interobserver reliability	0.37 (0.23-0.70)
		Intraobserver reliability	0.50 (0.29-0.71)
	ARCO	Interobserver reliability	0.35 (0.06-0.56)
		Intraobserver reliability	0.44 (0.26-0.56)
Smith et al.39 (1996)	Ficat	Interobserver reliability	0.46 (0.30-0.67)
		Intraobserver reliability	0.59 (0.44-0.73)
Kay et al.40 (1994)	Ficat	Interobserver variability	0.56 ± 0.01
		Intraobserver variability	0.82 ± 0.16

^*ARCO = Association Research Circulation Osseous.

^†Data are presented as the mean kappa value (range) or mean kappa value and standard deviation. According to the guidelines of Svanholm et al.¹⁸⁷, kappa values for reliability of <0.5 indicate poor agreement, those between 0.5 and 0.75 indicate fair agreement, and values of >0.75 indicate excellent agreement.