Table 3.

Modified Anderson’s MRI-based classification was checked at initial and 24-month visit

Stage	Characteristics	Initial MRI	Follow-up MRI (24-month visit)
Stage I	Marrow oedema	4 (11 %)	2 (6 %)
Stage IIA	Irregular subchondral bone plate	8 (21 %)	28 (80 %)
Stage IIB	Formation of subchondral cyst	6 (16 %)	3 (9 %)
Stage IIC	Incomplete separation of fragment	11 (29 %)	1 (3 %)
Stage III	Unattached, undisplaced fragment with synovial fluid around fragment	3 (8 %)	1 (3 %)
Stage IV	Displaced fragment	6 (16 %)	0 (0 %)
Total number		38	35

Most MRI findings were improved to a higher stage. However, irregular subchondral bone plate, stage IIA observed in 28 ankles, may have been caused by drilling for delamination after implantation. On the follow-up MRI, 10 cases of irregular bone marrow oedema and three subchondral cysts were observed. The three subchondral cysts spontaneously healed