Outcomes of the conservative hip preservation treatment in patients with osteonecrosis of the femoral head: With 4-year follow-up

Table 6 Success rate of hip preservation

Items	Number of hips	Conversion to THA	Conversion to HPS	Success rate	χ2	P value
ARCO stage (hips)
Stage I, II	43	1	0	97.67%	8.736	0.011
Stage IIIa	59	2	3	91.53%
Stage IIIb	17	4	1	70.59%
JIC classification (hips)
Type A, B	38	0	1	97.37%	6.521	0.031
Type C1	54	2	2	92.59%
Type C2	27	5	1	77.78%
Lesion size (hips)
< 15%	26	2	1	88.46%	0.798	0.771
15%-30%	37	2	2	89.19%
> 30%	56	3	1	92.86%
Collapse degree (hips)
≤ 2 mm	102	3	3	94.12%	9.616	0.009
> 2 mm	17	4	1	70.59%

THA: Total hip arthroplasty; HPS: Hip preservation surgery; ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.