Table 2 Distribution of erosions in different region of interest according to CT and US, and sensitivity, specificity, accuracy and k values for high-resolution US in detecting erosion (grading from 0 to 3) at different joint sites using CT as the reference method

Second metacarpal head

156

27 (17.3)

21 (13.5)

51.9

95.3

87.8

0.63 (0.43 to 0.83)

 Dorsal

52

16 (30.8)

13 (25.0)

56.3

88.9

78.8

0.51 (0.26 to 0.75)

 Lateral

52

11 (21.2)

8 (15.4)

54.5

95.1

86.5

0.77 (0.54 to 1.00)

 Volar

52

0

0

NC

NC

NC

NC

Third metacarpal head

104

15 (14.4)

4 (3.8)

20.0

98.9

87.5

0.26 (0.03 to 0.48)

 Dorsal

52

14 (21.2)

4 (15.4)

21.4

97.4

76.9

0.24 (0.02 to 0.46)

 Volar

52

1 (1.9)

0

0

100

98.1

0 (0.00 to 0.00)

Fourth metacarpal head

104

7 (6.7)

1 (0.9)

14.3

100

94.2

0.19 (-0.12 to 0.51)

 Dorsal

52

6 (11.5)

1 (1.9)

17.0

100

90.4

0.08 (-0.09 to 0.26)

 Volar

52

1 (1.9)

0

0

100

98.1

0 (0.00 to 0.00)

Fifth metacarpal head

156

8 (5.1)

6 (3.8)

50.0

100

96.3

0.77 (0.66 to 0.89)

 Dorsal

52

6 (11.5)

4 (7.7)

66.7

100

96.2

0.73 (0.56 to 0.90)

 Lateral

52

2 (3.8)

2 (3.8)

100

100

100

0.85 (0.74 to 0.97)

 Volar

52

0

0

NC

NC

NC

NC

Radiocarpal

104

18 (17.3)

6 (5.8)

33.0

100

88.5

0.57 (0.30 to 0.83)

 Dorsal

52

15 (28.8)

4 (7.7)

26.7

100

78.8

0.48 (0.16 to 0.80)

 Lateral

52

3 (5.7)

2 (3.8)

66.7

100

98.1

0.79 (0.39 to 1.0)

Ulnar head

104

17 (16.3)

5 (4.8)

23.5

98.9

86.5

0.29 (0.05 to 0.54)

 Dorsal

52

13 (25.0)

4 (7.7)

23.1

97.4

78.8

0.23 (-0.03 to 0.50)

 Lateral

52

4 (7.7)

1 (1.9)

25.0

100

94.2

0.38 (-0.15 to 0.91)

Total

728

92 (12.6)

43 (5.9)

35.9

98.7

90.8

0.50 (0.36 to 0.63)