Table 2.

Evolution and comparison of different classification and staging systems for ON

	Marcus and Enneking (Florida)	Ficat and Arlet (French)	Modified Ficat and Arlet (French)	Steinberg (Philadelphia)	ARCO (International)
Year of introduction	1973	1977	1985	1984	1993
Pathology
			0 (asymptomatic, XR−)
Clinically at risk and symptomatic		I (symptomatic, XR−, biopsy+)	I (symptomatic, XR−, biopsy+)	0 (normal or nondiagnostic XR, bone scan, and MRI)	0 (all imaging studies negative)
Infarct/hyperemic marrow border	I (XR+/−)	II	II	I (XR−, bone scan+, MRI+), [A: mild <15 %, B: moderate 15–30 %, C: severe >30 %]	I (XR−, CT−, scintigraph+, MRI+), {a: medial, b: central, c: lateral}, [area involvement: minimal A: <15 %, moderate B: 15–30 %, extensive C: >30 %]
Granulation tissue repair, lucent, sclerosis, cysts, calcified marrow	II (XR+)			II (XR+), [A,B,C]	II (XR+, CT+, scintigraph+, MRI+), {a,b,c}, [A,B,C]
Subchondral fracture (crescent sign)	III		Transitional stage	III (XR+: crescent sign without collapse), [A,B,C]	Early III, (XR+, CT+), {a,b,c}, [A,B,C]
Collapse	IV	III	III	IV (XR+: flattening), [A,B,C]	Late III, (XR+, CT+), {a,b,c}, [A,B,C]
Early arthritis	V	IV	IV	V	IV (XR+)
Advanced arthritis	VI			VI	IV (XR+)
Contribution	Initial staging system	Acknowledged the need for a biopsy to confirm functional changes in bone	Acknowledged presence of ONFH with negative XR	Added MRI criteria and lesion size and category for subchondral fracture with no collapse	Added location of lesion

Modified from Cheng EY, from Oxford Textbook of Orthopaedics and Trauma, Volume 2, edited by Bulstrode, et al. (2002), by permission of Oxford University Press

− negative, + positive