Cartilage icing and chondrocalcinosis on knee radiographs in the differentiation between gout and calcium pyrophosphate deposition

Abstract

Objective To determine if findings of "cartilage icing" and chondrocalcinosis on knee radiography can differentiate between gout and calcium pyrophosphate deposition (CPPD). Methods IRB-approval was obtained and informed consent was waived for this retrospective study. Electronic medical records from over 2.3 million patients were searched for keywords to identify subjects with knee aspiration-proven cases of gout or CPPD. Radiographs were reviewed by two fellowship-trained musculoskeletal radiologists in randomized order, blinded to the patients' diagnoses. Images were evaluated regarding the presence or absence of cartilage icing, chondrocalcinosis, tophi, gastrocnemius tendon calcification, and joint effusion. Descriptive statistics, sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. Results From 49 knee radiographic studies in 46 subjects (31 males and 15 females; mean age 66 ±13 years), 39% (19/49) showed gout and 61% (30/49) CPPD on aspiration. On knee radiographs, cartilage icing showed a higher sensitivity for CPPD than gout (53-67% and 26%, respectively). Chondrocalcinosis also showed a higher sensitivity for CPPD than gout (50-57% versus 5%), with 95% specificity and 94% positive predictive value for diagnosis of CPPD versus gout. Soft tissue tophus-like opacities were present in gout at the patellar tendon (5%, 1/19) and at the popliteus groove in CPPD (15%, 4/27). Gastrocnemius tendon calcification was present in 30% (8/27) of subjects with CPPD, and 5% (1/19) of gout.

Systematic literature review to inform the EULAR recommendations for the use of imaging in crystal-induced arthropathies in clinical practice

“…Regarding the specific differentiation of CPPD from gout, at the level of the knee, the highest reported sensitivity (95% CI) to was 84% (73% to 91%)93 for calcification of the menisci, while the lowest was 0% (0% to 18%)100 for patellar tophus-like opacity; the highest specificity to differentiate CPPD from gout was 100% (82% to 100%) for popliteal tophus-like opacity, while the lowest was 74% (54% to 93%) for cartilage icing (deposition of CPP crystals on the surface of the cartilage) in the same population 100. At the wrist, the highest sensitivity for making a diagnosis of CPPD was 86% (70% to 95%) for deposition at the triangular fibrocartilage complex90 and the lowest was 44% (36% to 52%) for scaphotrapeziotrapezoidal osteoarthritis (OA) 120.…”

“…44 studies were included (online supplemental table 11, figure 2), mostly presenting data on CR (23 studies)17 40 55 85–103 and US (24 studies),40 49 55 86–88 90–93 95 96 98 99 102–111 with only 6 studies on CT,37 95 112–115 3 on DECT37 40 116 and 2 on MRI 117 118. The reference standard for making a diagnosis of CPPD was histology in 3 studies,96 108 111 SFA in 13,40 55 85 86 92 97–100 106 107 119 McCarty criteria in 19,37 40 87–93 95 103 105 112–116 120 clinical diagnosis in 349 104 116 and evidence of CPPD on CR in 3 94 117 118. There were 4 SLRs,96 101 102 110 15 cross-sectional cohort studies,40 49 55 86 95 97–99 106 108 109 111 112 117 119 19 case–control studies37 85 87–94 100 103 107 113–116 118 120 and 2 longitudinal cohort studies 17 104.…”

“…The reference standard for making a diagnosis of CPPD was histology in 3 studies,96 108 111 SFA in 13,40 55 85 86 92 97–100 106 107 119 McCarty criteria in 19,37 40 87–93 95 103 105 112–116 120 clinical diagnosis in 349 104 116 and evidence of CPPD on CR in 3 94 117 118. There were 4 SLRs,96 101 102 110 15 cross-sectional cohort studies,40 49 55 86 95 97–99 106 108 109 111 112 117 119 19 case–control studies37 85 87–94 100 103 107 113–116 118 120 and 2 longitudinal cohort studies 17 104. The knee and the wrist were the most commonly investigated sites, with 1793–96 98–100 105–108 111 116–119 and 817 37 89–92 112 120 studies assessing exclusively these areas, respectively.…”

“…There were 4 SLRs,96 101 102 110 15 cross-sectional cohort studies,40 49 55 86 95 97–99 106 108 109 111 112 117 119 19 case–control studies37 85 87–94 100 103 107 113–116 118 120 and 2 longitudinal cohort studies 17 104. The knee and the wrist were the most commonly investigated sites, with 1793–96 98–100 105–108 111 116–119 and 817 37 89–92 112 120 studies assessing exclusively these areas, respectively.…”