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

Table 1 Patient demographic characteristics

Demographics	Value
Gender (male/female)	45/28
Age (years)	39.10 ± 11.22 (21-67)
BMI (kg/m2)	23.00 ± 3.48
Follow up time (month)	53.58 ± 26.80 (18-129)
THA (hips)	7
Hip preservation surgery (hips)	4
Etiology (hips)
Steroid	59
Alcohol	22
Trauma	13
Idiopathic	25
ARCO stage (hips)
Stage I	2
Stage II	41
Stage IIIa	59
Stage IIIb	17
JIC classification (hips)
Type A	12
Type B	26
Type C1	54
Type C2	27
Lesion size (hips)
< 15%	26
15%-30%	37
> 30%	56
Collapse degree (hips)
≤ 2 mm	102
> 2 mm	17

BMI: Body mass index; THA: Total hip arthroplasty; ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Table 2 Kappa consistency coefficients for radiological data assessment at the initial visit

Items	Intra-observer kappa		Inter-observer
	Observer 1	Observer 2	Kappa	P value
AROC stage	0.431	0.590	0.403	< 0.001
JIC classification	0.706	0.771	0.796	< 0.001
Lesion size	0.813	0.802	0.656	< 0.001
Collapse degree	0.627	0.804	0.525	< 0.001

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Table 3 Kappa consistency coefficients for radiological data at the final follow-up

Items	Intra-observer kappa		Inter-observer
	Observer 1	Observer 2	Kappa	P value
AROC stage	0.942	0.454	0.504	< 0.001
JIC classification	0.928	0.374	0.348	< 0.001
Lesion size	0.959	0.492	0.430	< 0.001
Collapse degree	0.895	0.638	0.666	< 0.001

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

Table 4 Results of Harris Hip Score, international Hip Outcome Tool 12, visual analogue scale, and Western Ontario and McMaster Universities Arthritis Index before treatment and at the last follow-up

Items	Pre-treatment	Post-treatment	Z	P value
HHS	61.00 (77.00, 51.00)	75.00 (93.00, 67.00)	-9.389	< 0.001
iHOT-12	72.00 (80.00, 63.00)	102.00 (110.00, 94.00)	-9.472	< 0.001
WOMAC	90.00 (99.00, 75.00)	45.00 (63.00, 29.00)	-9.472	< 0.001
VAS	7.00 (7.00, 6.00)	3.00 (4.00, 2.00)	-9.326	< 0.001

HHS: Harris Hip Score; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Table 5 Overall distribution of clinical scores in patients pre-treatment and at the last follow-up

Items	Pre-treatment	Post-treatment	χ2	P value
ARCO stage (hips)
Stage I	2	2	31.966	< 0.0011
Stage II	41	31
Stage IIIa	59	34
Stage IIIb	17	39
Stage IV	0	13
JIC classification (hips)
Type A	12	15	7.071	0.070
Type B	26	21
Type C1	54	51
Type C2	27	32
Lesion size (hips)
< 15%	26	28	5.485	0.140
15%-30%	37	30
> 30%	56	61
Collapse degree (hips)
≤ 2 mm	102	67	25.002	< 0.001
> 2 mm	17	52

¹Indicates Fisher’s exact test.

ARCO: Association Research Circulation Osseous; JIC: Japanese Investigation Committee.

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.

Table 7 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on Association Research Circulation Osseous stages

Items	ARCO I, II	ARCO IIIa, b	Z	P value
Harris	81.00 (93.00, 67.00)	75.00 (86.50, 66.25)	-1.133	0.257
iHOT-12	106.00 (114.00, 96.00)	101.00 (109.50, 91.00)	-1.877	0.060
WOMAC	43.00 (62.00, 20.00)	46.00 (63.00, 33.00)	-1.822	0.069
VAS	3.00 (3.00, 0.00)	3.00 (6.00, 3.00)	-2.286	0.007

ARCO: Association Research Circulation Osseous; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Table 8 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on Japanese Investigation Committee classification

Items	JIC A, B	JIC C1	JIC C2	F/H	P value
Harris	75.50 (93.00, 65.00)	75.00 (93.00, 63.00)	77.00 (95.00, 67.00)	0.714	0.7001
iHOT-12	104.00 (112.00, 96.00)	101.00 (108.50, 93.75)	98.00 (110.00, 92.00)	2.077	0.3541
WOMAC	44.47 ± 24.55	49.07 ± 23.37	47.22 ± 22.95	0.422	0.657
VAS	3.00 (4.00, 0.75)	3.00 (4.00, 3.00)	3.00 (6.00, 2.00)	1.047	0.5921

¹Indicates Kruskal-Wallis H test.

JIC: Japanese Investigation Committee; iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Table 9 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on lesion size

Items	< 15%	15%-30%	> 30%	H	P value
Harris	82.50 (93.00, 67.00)	77.00 (93.00, 68.00)	72.00 (85.00, 60.25)	3.638	0.162
iHOT-12	111.00 (120.00, 98.00)	104.00 (110.00, 93.50)	98.00 (106.00, 91.25)	12.344	0.0021
WOMAC	30.00 (53.50, 18.00)	45.00 (61.50, 28.50)	46.00 (66.00, 36.00)	6.456	0.0401
VAS	2.00 (3.00, 0.00)	3.00 (4.50, 2.50)	3.00 (5.50, 3.00)	8.872	0.0121

¹Refers to a two-by-two comparison, where the results of the two-by-two comparison between the necrosis range > 30% group and the < 15% group were P (international Hip Outcome Tool 12) = 0.002, P (Western Ontario and McMaster Universities Arthritis Index) = 0.035, and P (visual analogue scale) = 0.009.

iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.

Table 10 Clinical scores after conservative hip preservation treatment for osteonecrosis of the femoral head based on collapse degree

Items	≤ 2 mm	> 2 mm	t/Z	P value
Harris	75.00 (93.00, 65.25)	82.00 (93.00, 71.50)	-1.096	0.2731
iHOT-12	99.82 ± 13.41	107.24 ± 10.24	-2.172	0.032
WOMAC	38.06 (64.75, 30.50)	38.06 ± 19.03	-1.592	0.1111
VAS	3.00 (4.00, 2.00)	3.00 (3.00, 0.00)	-1.267	0.2051

¹Refers to the Mann-Whitney U test.

iHOT-12: International Hip Outcome Tool 12; WOMAC: Western Ontario and McMaster Universities Arthritis Index; VAS: Visual analogue scale.