Interobserver and intraobserver agreement for Letournel acetabular fracture classification system using 3-dimensional printed solid models

Table 1 Inter-observer agreement on classification, based on computed tomography or 3-dimensional printed models

Fx classification
		CT			3-D model
#Surgeon	Match pairs	Mean kappa	SE min	SE max	Mean kappa	SE min	SE max
Mean	153	0.44	0.00	0.24	0.55	0.00	0.22
1	17	0.06	0.06	0.20	0.54	0.17	0.21
10	17	0.22	0.04	0.23	0.41	0.15	0.20
7	17	0.24	0.04	0.20	0.65	0.15	0.22
4	17	0.35	0.06	0.21	0.58	0.15	0.20
12	17	0.36	0.17	0.22	0.26	0.14	0.22
16	17	0.40	0.13	0.22	0.61	0.15	0.20
17	17	0.41	0.11	0.22	0.68	0.15	0.21
14	17	0.42	0.11	0.24	0.60	0.14	0.21
8	17	0.45	0.14	0.22	0.56	0.16	0.20
9	17	0.48	0.10	0.24	0.69	0.00	0.21
6	17	0.50	0.11	0.24	0.54	0.17	0.21
15	17	0.52	0.14	0.22	0.51	0.16	0.21
3	17	0.56	0.11	0.24	0.55	0.15	0.21
11	17	0.57	0.00	0.22	0.69	0.00	0.21
18	17	0.57	0.00	0.22	0.40	0.16	0.21
2	17	0.60	0.00	0.24	0.69	0.00	0.21
5	17	0.60	0.00	0.24	0.44	0.14	0.21
13	17	0.66	0.00	0.24	0.58	0.15	0.20

CT: Computed tomography; 3-D: Three-dimensional; Fx: Fracture.

Table 2 Inter-observer agreement on surgical approach, based on computed tomography or 3-dimensional printed models

Surgical approach
		CT			3-D Model
#Surgeon	Match pairs	Mean kappa	SE min	SE max	Mean kappa	SE min	SE max
Mean	153	0.35	0.00	0.39	0.30	0.00	0.39
17	17	0.18	0.17	0.32	0.43	0.00	0.39
12	17	0.18	0.16	0.31	0.09	0.11	0.24
9	17	0.25	0.19	0.31	0.34	0.16	0.36
14	17	0.28	0.16	0.39	0.29	0.15	0.36
15	17	0.31	0.18	0.27	0.25	0.13	0.23
16	17	0.31	0.00	0.36	0.43	0.15	0.35
18	17	0.31	0.00	0.36	0.20	0.17	0.29
10	17	0.32	0.19	0.28	0.19	0.16	0.29
8	17	0.33	0.21	0.30	0.33	0.18	0.24
3	17	0.36	0.18	0.36	0.29	0.17	0.26
2	17	0.36	0.20	0.28	0.35	0.15	0.30
11	17	0.39	0.20	0.27	0.26	0.16	0.28
6	17	0.41	0.18	0.32	0.21	0.19	0.32
1	17	0.41	0.00	0.30	0.43	0.00	0.39
4	17	0.41	0.00	0.30	0.35	0.11	0.26
7	17	0.44	0.20	0.32	0.37	0.19	0.30
5	17	0.50	0.00	0.39	0.24	0.14	0.36
13	17	0.50	0.00	0.39	0.30	0.13	0.39

CT: Computed tomography; 3-D: Three-dimensional.

Table 3 Intra-observer agreement on classification and surgical approach, between computed tomography and 3-dimensional printed models

#Surgeon		Fx classification					Surgical approach
1	1	-0.02					0.70
2	1	0.50					0.18
3	1	0.50					0.32
4	1	0.50					0.55
5	1	0.83					0.36
6	1	0.48					0.28
7	1	0.32					0.77
8	1	0.66					0.34
9	1	0.67					0.22
10	1	0.22					0.40
11	1	0.50					0.58
12	1	0.49					0.25
13	1	0.66					1.00
14	1	0.50					0.70
15	1	0.64					0.15
16	1	0.48					0.19
17	1	0.32					0.16
18	1	0.35					0.19
		Mean	Median	Min	Max	P value	Mean	Median	Min	Max	P value
Total	18	0.48	0.50	-0.02	0.83	0.592	0.41	0.33	0.15	1.00	0.331
Pelvis	9	0.45	0.50	-0.02	0.83		0.37	0.25	0.15	1.00
Trauma	9	0.50	0.50	0.22	0.67		0.45	0.36	0.18	0.77

Table 4 Reviewers' change of decision (computed tomography vs 3-dimensional model)

#Surgeon	Total decisions	Fracture classification		Surgical approach
		Number of decisions changed	% of decisions changed	Number of decisions changed	% of decisions changed
1	7	6	86	1	14
2	7	3	43	4	57
3	7	3	43	3	43
4	7	3	43	2	29
5	7	1	14	2	29
6	7	3	43	3	43
7	7	4	57	1	14
8	7	2	29	3	43
9	7	2	29	3	43
10	7	5	71	3	43
11	7	3	43	2	29
12	7	3	43	3	43
13	7	2	29	0	0
14	7	3	43	1	14
15	7	2	29	4	57
16	7	3	43	3	43
17	7	4	57	3	43
18	7	4	57	3	43
Total	126	56	44	44	35
Pelvis	63	29	46	20	32
Trauma	63	27	43	24	38