ObjectiveTo evaluate the quantitative analysis value of gemstone spectral CT for diagnosing urate deposition in the first metatarsophalangeal joint and periarticular soft tissue of patients with hyperuricemia.

MethodsThis work involved 84 patients with hyperuricemia who underwent foot gemstone spectral CT from October 2016 to June 2017. The patients were divided into three groups:36 patients (group A) with normal imaging, 23 patients(group B) with bone destruction, and 25 patients(group C) with bone destruction and uric acid crystallization. The basal concentrations of uric acid(calcium) in the first metatarsophalangeal joint cortical bone, cancellous bone and periarticular soft tissue were measured using gemstone spectral CT scanning. The age, serum uric acid value, and basal concentration of uric acid(calcium) were compared by univariate ANOVA among the three groups. In intra-group comparison, LSD method was used for the data with equal variance, and Tamhane's T2 test was used for the data with unequal variance.Correlation of serum uric acid value with the uric acid(calcium) level of the first metatarsophalangeal joint cortical bone, cancellous bone, and periarticular soft tissue in all hyperuricemia patients was analyzed by linear regression.

ResultsSignificant differences in age, serum uric acid value, and uric acid (calcium) concentration were found for periarticular soft tissues of the first metatarsophalangeal joints(P < 0.05). No differences were observed between the uric acid(calcium) concentration in the first metatarsophalangeal joint cortical bone and cancellous bone. The following values were obtained for age:group A(39.1±11.1) years old, group B (48.5±13.9) years old, and group C (43.2±12.5) years old (LSD, P=0.019); for serum uric acid value:group A(489.5±90.6) μmol/L, group B(494.7±77.2) μmol/L, and group C(581.3±69.2) μmol/L(LSD, P < 0.001); for the uric acid (calcium) concentration in the periarticular soft tissues of the first metatarsophalangeal joints:group A (1169.58±7.88) mg/cm³, group B (1193.13±16.35) mg/cm³, and group C (1308.20±85.89) mg/cm³(χ²=61.698, P < 0.001); for the uric acid(calcium) concentration in the first metatarsophalangeal joints:group A (1324.8±31.4) mg/cm³, group B (1335.6±37.3) mg/cm³, and group C (1320.4±43.5) (LSD, P=0.346); for the uric acid(calcium) concentration in the cancellous bone of the first metatarsophalangeal joints:group A (1134.3±13.3) mg/cm³, group B (1145.8±23.3) mg/cm³, and group C (1145.8±30.9) mg/cm³ (χ²=3.464, P=0.177). The serum uric acid value was linearly positively correlated with the uric acid(calcium) concentration in periarticular soft tissues of the first metatarsophalangeal joints, but not with the uric acid(calcium) concentration in cortical bone and cancellous bone of the first metatarsophalangeal joints.

ConclusionGemstone spectral CT can measure quantitatively the internal and external base material concentrations of joints and define the crystallization of uric acid salt, which can provide a basis for clinical judgment.