Twenty-three patients’ DECT results were selected for analysis in this study. All participants were male with mean and standard deviation age were 55.3 and 13.8 years. The mean and standard deviation of disease duration was 6.9 and 5.5 years, and the total subcutaneous tophus appeared in 20 patients (87%). There were 14 (60.9%) patients with gout disease duration longer than 3 years. Serum uric acid level in the population has the mean and standard deviation was 8.3 and 1.7 mg/dl. Furthermore, among these patients, the mean and standard deviation volume of overall urate deposition were 24.3 and 58.6 cm3.
There were 104 (56.5% (95% CI 49.3-63.7%)), 63 (34.2% (95% CI 27.4-41.1%)) joints with DECT urate deposition in lower and upper limbs respectively. sclerosis was the most commonly observed feature of structural joint damage 113 (61.4% (95% CI (54.4-68.5%)), 44 (23.9% (95% CI (17.7-30.1)), while space narrowing was the least observed feature 59 (32.1% (95% CI (25.3-38.8%)), 28 (15.2% (95% CI(10-20.4%)) in lower and upper limbs respectively (see Table 1).
Table 1. Distribution by the general area affected in lower extremities and upper extremities
|
Imaging feature
|
Monosodium urate crystals, n; % (95% CI)
|
Bone erosion, n; % (95% CI)
|
Periarticular Calcification, n; % (95% CI)
|
Joint space narrowing , n; % (95% CI)
|
Bone sclerosis , n; % (95% CI)
|
Lower extremities
|
Knee (n=46)
|
33; 71,7% (58,6-84,9)
|
15; 32,6% (18,9-46,3)
|
29; 63% (48,9-77,1)
|
17; 37% (22,9-51,1)
|
39; 84,8% (74,3-95,3)
|
Ankle Joints (n=46)
|
37; 80,4% (68,8-92)
|
20; 43,5% (29-58)
|
32; 69,6% (56,1-83)
|
13; 28,3% (15,1-41,4)
|
36; 78,3% (66,2-90,3)
|
MTP Joints (n=46)
|
21; 45,7% (31,1-60,2)
|
22; 47,8% (33,2-62,4)
|
21; 45,7% (31,1-60,2)
|
16; 34,8% (20,9-48,7)
|
22; 47,8% (33,2-62,4)
|
interphalangeal joint (n=46)
|
13; 28,3% (15,1-41,4)
|
15; 32,6% (18,9-46,3)
|
13; 28,3% (15,1-41,4)
|
13; 28,3% (15,1-41,4)
|
16; 34,8% (20,9-48,7)
|
Total affected joints
|
104; 56,5% (49,3-63,7)
|
72; 39,1% (25-53,3)
|
95; 51,6% (44,4-58,9)
|
59; 32,1% (25,3-38,8)
|
113; 61, 4% (54.4-68.5)
|
Patients affected lower extremities (%)
|
100
|
52,2
|
82,6
|
56,5
|
91,3
|
Upper extremities
|
Elbow (n=46)
|
27; 58,7% (44,3-73,1)
|
10; 21,7% (9,7-33,8)
|
13; 28,3% (15,1-41,4)
|
8; 17,4% (6,3-28,5)
|
8; 17,4% (6,3-28,5)
|
carpometacarpal joint (n=46)
|
16; 34,8% (20,9-48,7)
|
9; 19,6% (8-31,2)
|
10; 21,7% (9.7-33.8)
|
8; 17,4% (6,3-28,5)
|
21; 45,7% (31,1-60,2)
|
MCP joint (n=46)
|
11; 23,9% (11,5-36,4)
|
11; 23,9% (11,5-36,4)
|
9; 19,6% (8-31.2)
|
7; 15,2% (4,7-25,7)
|
10; 21,7% (9,7-33,8)
|
IP joint (n=46)
|
9; 19,6% (8-31,2)
|
4; 8,7% (0,5-16,9)
|
5; 10,9% (1.8-20)
|
5; 10,9% (1,8-20)
|
5; 10,9% (1,8-20)
|
Total affected joints
|
63; 34,2% (27,4-41,1)
|
34; 18,5% (12,9-24,1)
|
37; 20,1% (14,3-25,9)
|
28; 15,2% (10-20,4)
|
44; 23,9% (17,7-30,1)
|
Patients affected in upper extremities (%)
|
82,6
|
26,1
|
52,2
|
26,1
|
21,7
|
828 joints sites were assessed to determine the relationship of MSU deposition in DECT with structural joint damage on plain computed tomography. They are divided into 4 areas: upper limb, lower limb, MCP and MTP (see Table 2).
Table 2. Relationship of DECT MSU crystal deposition with structural joint damage on plain computer tomography: site-by-site analysis by general area
|
|
Erosion present
|
Erosion absent
|
Periarticular calcification present
|
Periarticular calcification absent
|
Joint space narrowing present
|
Joint space narrowing absent
|
Bone sclerosis present
|
Bone sclerosis absent
|
Upper extremities (n=184 joints)
|
DECT MSU CD present
|
33
|
30
|
34
|
29
|
28
|
35
|
37
|
26
|
DECT MSU CD absent
|
1
|
120
|
3
|
118
|
0
|
121
|
7
|
114
|
OR (95% CI)
|
132 (17,3-1004,3)
|
46,1 (13,2-160,7)
|
NA
|
23,2 (9,3-57,8)
|
Lower extremities (n=184 joints)
|
DECT MSU CD present
|
65
|
39
|
80
|
24
|
53
|
51
|
95
|
9
|
DECT MSU CD absent
|
7
|
73
|
15
|
65
|
6
|
74
|
18
|
62
|
OR (95% CI)
|
17,4 (7,3-41,5)
|
14,4 (7-29,8)
|
12,8 (5,1-32)
|
36,4 (15,4-86,1)
|
MCP (n=230 joints)
|
DECT MSU CD present
|
20
|
5
|
20
|
5
|
15
|
10
|
22
|
3
|
DECT MSU CD absent
|
5
|
200
|
8
|
197
|
0
|
205
|
11
|
194
|
OR (95% CI)
|
160 (42,7-600,2)
|
98,5 (29,4-329,8)
|
NA
|
129,3 (33,5-499,2)
|
MTP (n=230 joints)
|
DECT MSU CD present
|
62
|
16
|
41
|
37
|
40
|
38
|
70
|
8
|
DECT MSU CD absent
|
16
|
136
|
20
|
132
|
9
|
143
|
30
|
122
|
OR (95% CI)
|
32,9 (15,5-70,1)
|
7,3 (3,8-14)
|
16,7 (7,5-37,5)
|
35,6 (15,5-81,9)
|
*Abbreviation: CD = crystal deposition
|
Using linear regression analysis on patient-level data, correlations were found between DECT MSU crystal deposition and damage on all categories of structural joint damage (p
Contrarily, the opposite result is presented in the case of Serum urate concentration (mg/dL), which has no statistically significant relationship with any features of structural joint damage (p>0.05 for all categories). Positive correlations between DECT MSU crystal deposition and serum urate concentration in erosion, calcification, space narrowing of the joint was also observed during analysis (p<0.001, p<0.041, p
Table 3. Linear regression analysis showing the relationships between DECT MSU crystal deposition, serum urate with structural joint damage on plain CT: patient-level analysis (n=23)
|
Dependent variable
|
Predictors
|
B(SE)
|
Standardized B
|
P-value
|
Model (r, R2, F, p value)
|
Number of joints with erosion
|
Number of joints with DECT MSU crystal deposition
|
0,99 (0,1)
|
0,92
|
<0,001
|
r=0,91, R2=0,83, F=48,4, p<0,001
|
Serum urate concentration (mg/dL)
|
-0,09 (0,22)
|
-0,04
|
0,7
|
Number of joints with periarticular calcification
|
Number of joints with DECT MSU crystal deposition
|
0,48 (0,18)
|
0,53
|
0,01
|
r=0,52, R2=0,27, F=3,8, p<0,041
|
Serum urate concentration (mg/dL)
|
-0,09 (0,38)
|
-0,05
|
0,81
|
Number of joints with joint space narrowing
|
Number of joints with DECT MSU crystal deposition
|
0,67 (0,14)
|
0,76
|
<0,001
|
r=0,75, R2=0,56, F=12,6, p<0,001
|
Serum urate concentration (mg/dL)
|
-0,12 (0,29)
|
-0,07
|
0,67
|
Number of joints with sclerosis
|
Number of joints with DECT MSU crystal deposition
|
0,29 (0,27)
|
0,22
|
0,29
|
r=0,44, R2=0,19, F=2,4, p<0,12
|
Serum urate concentration (mg/dL)
|
1,2 (0,65)
|
0,37
|
0,08
|
Frequency of largest sites with Monosodium crystal deposit
For sites in the lower limbs, MTP is the site with the highest rate of large MSU deposition sites, with the second being quadriceps tendon and bursa then Achilles tendon (21.7%, 13%, 13%, 8.7% respectively). For sites in the lower limbs, the most common sites include elbow, MCP, Triceps tendon (30.4%, 13%, 8.7%, respectively). Other sites have a low frequency with large scarcity on MSU crystals deposition. (see Table 4).
Table 4. Largest sites of Monosodium urate crystals deposition
|
Sites
|
Number of sites (n=23)
|
Percentage of sites (n=23)
|
Lower limb
|
MTP
|
5
|
21,7
|
Quadriceps tendon
|
3
|
13
|
Bursa
|
3
|
13
|
Achilles tendon
|
2
|
8,7
|
Others
|
10
|
43,5
|
Total
|
23
|
100
|
Upper limb
|
Elbow
|
7
|
30,4
|
Triceps tendon
|
2
|
8,7
|
MCP
|
3
|
13
|
Intercarpal
|
4
|
17,4
|
Other sites/ Not presence/ Not defined
|
7
|
30,4
|
|
Total
|
23
|
100
|