Knee chondrocalcinosis: an ultrasonographic study of the hyalin cartilage

Which are the most frequently involved peripheral joints in calcium pyrophosphate crystal deposition at imaging? A systematic literature review and meta-analysis by the OMERACT ultrasound – CPPD subgroup

Objectives

To identify the prevalence of calcium pyrophosphate crystal deposition (CPPD) using ultrasound and conventional radiology at peripheral joints in patients with suspected or definite CPPD.

Methods

A systematic literature search was performed in PubMed and Embase using pre-defined search strategies from inception to April 2021 to identify studies that evaluated conventional radiology and ultrasound in detecting CPPD at peripheral joints, including definite or suspected CPPD [Research question 1 (RQ1) and Research Question 2 (RQ2), respectively]. For the meta-analysis, the first, second, and third sub-analysis included studies with the knee, and knee or wrist as the index joint for CPPD (without restrictions on the reference standard) and synovial fluid analysis or histology as a reference standard (without restrictions on the index joint), respectively.

Results

One-thousand eight hundred and twenty-seven manuscripts were identified, of which 94 articles were finally included. Twenty-two and seventy-two papers were included in RQ1 and RQ2, respectively. The knee had the highest prevalence for RQ1 and RQ2 by both conventional radiology and ultrasound, followed by the wrist with the highest prevalence for RQ1. The hand had the lowest CPPD prevalence. The third sub-analysis showed a higher CPPD prevalence on ultrasound than conventional radiology at the knee (only data available).

Conclusion

Among all peripheral joints, the knees and wrists could be regarded as the target joints for CPPD detection by imaging. Furthermore, ultrasound seems to detect a higher number of calcium pyrophosphate deposits than conventional radiology, even when using a more restrictive reference standard.

The role of Interleukin-1 receptor antagonist as a treatment option in calcium pyrophosphate crystal deposition disease

Calcium Pyrophosphate Crystal Deposition (CPPD) disease is characterized by the deposition of calcium pyrophosphate crystals in the cartilage. In most cases, it can manifest as a subclinical condition named chondrocalcinosis, often revealed by joint x-ray examination. In other cases, deposition can cause flares of arthritis, known as acute CPP crystal arthritis. In the last few years, many pathogenic pathways have been discovered. Interleukin-1 (IL-1) plays a key role in the pathogenesis of CPPD disease, both as a mediator of inflammatory response to crystals and as a promoter of damage to articular cartilage. In this review, we investigated the role of IL-1R inhibitor, such as Anakinra, as an alternative to the various therapeutic strategies for CPPD disease, especially among patients resistant to traditional treatment with NSAIDs, corticosteroids and colchicine.

The diagnostic value of conventional radiography and musculoskeletal ultrasonography in calcium pyrophosphate deposition disease: a systematic literature review and meta-analysis

OBJECTIVE

To examine and compare the accuracy of conventional radiography (CR) and musculoskeletal ultrasonography (US) in the diagnosis of calcium pyrophosphate (CPP) crystals deposition disease (CPPD).

DESIGN

A systematic search of electronic databases (PubMed, Embase, and Cochrane), conference abstracts and reference lists was undertaken. Studies which evaluated the accuracy of CR and/or US in the diagnosis of CPPD, using synovial fluid analysis (SFA), histology or classification criteria as reference tests were included. Subgroup analyses by anatomic site and by reference test were performed.

RESULTS

Twenty-six studies were included. Using SFA/histology as reference test, CR and US showed an excellent (CR AUC = 0.889, 95%CI = 0.811-0.967) and an outstanding (US AUC = 0.954, 95%CI = 0.907-1.0) diagnostic accuracy (p < 0.01), respectively. Furthermore, US showed a higher sensitivity (0.85, 95%CI = 0.79-0.90 vs 0.47, 95%CI = 0.40-0.55) and only a little lower specificity (0.87, 95%CI = 0.83-0.91 vs 0.95, 95%CI = 0.92-0.97) than CR. A considerable heterogeneity between the studies was found, with adopted reference test being the main source of heterogeneity. In fact, subgroup analysis showed a significant change in the diagnostic accuracy of CR, but not of US, using Ryan and McCarty criteria or SFA/histology as reference test (CR: AUC = 0.956, 95%CI = 0.925-1.0 vs AUC = 0.889, 95%CI = 0.828-0.950, respectively, p < 0.01) (US: AUC = 0.922, 95%CI = 0.842-1.0 vs AUC = 0.957, 95%CI = 0.865-1.0, respectively, p = 0.08) CONCLUSIONS: Although US is more sensitive and a little less specific than CR for identifying CPP crystals, both these two techniques showed a great diagnostic accuracy and should be regarded as complementary to each other in the diagnostic work-up of patients with CPPD.

Articular and periarticular spinal calcifications in relation to synovial fluid findings in patients with calcium pyrophosphate dihydrate deposition disease (CPPD)

Background

Calcium pyrophosphate dihydrate deposition disease (CPPD) is the second most common form of the crystal-associated arthritis. Diagnosis is achieved by detection of crystals by polarized light microscopy and/or detection of hyaline cartilage or fibrocartilage calcifications characteristic of CPPD deposition by musculoskeletal ultrasound (MSUS). Axial involvement with intervertebral disc calcification, sacroiliac erosions, and sub-chondral cysts of the facet joints occurs with CPPD deposition.

Aim

To assess the presence and relation between calcification of intervertebral discs, other articular and periarticular spinal structures, and synovial fluid analysis (SFA) and MSUS calcifications in patients with CPPD deposition disease.

Methods

One hundred patients with CPPD disease diagnosed according to the modified proposed diagnostic criteria by McCarty 1994 were included. Plain radiography on the spines, pelvis, and affected joints, MSUS on affected joints, and synovial fluid analysis (SFA) were done.

Results

Spinal calcification was present in 55% of patients. The commonest site was anterior longitudinal ligament (43%). Characteristic CPPD calcifications by plain radiography on the knee and wrist joints were present in 38% and 16% respectively. Characteristic CPPD calcifications by MSUS on the knee and wrist joints presented in 93% and 27% respectively. CPPD crystal detection by SFA was 97%. The accuracy of MSUS to diagnose CPPD deposition disease is more than double that of plain radiography, and it is comparable to that of synovial fluid analysis. The result of intra-rater analysis between SFA by polarized light microscopy and MSUS was kappa 0.767 (p < 0.001); this indicates substantial level of agreement between SFA and MSUS; between plain radiography and MSUS, it was kappa 0.188 (p = 0.32) which indicates slight agreement, and between plain radiography and SFA, it was kappa 0.037 (p = 0.1) which fails to reach a significant level of agreement. There was a significant positive relation between spinal calcification and wrist joint calcification by plain radiography.

Conclusion

Considerable spinal affection by CPPD deposition disease can be detected. Although the most definitive, reliable direct approach for CPPD deposition disease diagnosis is SFA using polarized light microscopy, MSUS is considered a useful non-invasive diagnostic tool in this situation. In CPPD deposition disease, MSUS has proven to be an excellent technique for detecting calcification in the articular tissue disease compared to conventional radiography.

Reliability of a new scoring system for intraarticular mineralization of the knee: Boston University Calcium Knee Score (BUCKS)

BACKGROUND

The role of intra-articular mineralization in osteoarthritis (OA) is unclear. Its understanding may potentially advance our knowledge of knee OA pathogenesis. We describe and assess the reliability of a novel computed tomography (CT) scoring system, the Boston University Calcium Knee Score (BUCKS) for evaluating intra-articular mineralization.

METHODS

We included subjects from the most recent study visit of the Multicenter Osteoarthritis Study (MOST) Study, a NIH-funded longitudinal cohort of community-dwelling older adults with or at risk of knee OA. All subjects underwent CT of bilateral knees. Each knee was scored at 28 scored locations (14 for cartilage, 6 for menisci, 6 for ligaments, 1 for joint capsule, and 1 popliteal-tibial vessels). A single musculoskeletal radiologist scored cartilage and meniscus subregions, as well as vascular calcifications assigning to each a score ranging from 0 to 3. The joint capsule, medial and lateral posterior meniscal roots, anterior cruciate ligament (ACL)/posterior cruciate ligament (PCL) and 2 collateral ligaments [medial collateral ligament (MCL)/lateral collateral ligament (LCL)] were each scored 0 or 1 for absence or presence of mineralization. To assess reliability, 31 subject CTs were reread 12 weeks later by the same reader and by a second reader and agreement was evaluated using a weighted kappa.

RESULTS

The intra-reader reliability ranged from 0.92 for ligaments to 1.0 for joint capsule. The inter-reader reliability ranged from 0.94 for cartilage and ligaments, to 1.0 for joint capsule.

CONCLUSION

BUCKS demonstrated excellent reliability and is a potentially useful CT-based tool for studying the role of calcium crystals in knee OA.

Differential Diagnosis of Inflammatory Arthropathies by Musculoskeletal Ultrasonography: A Systematic Literature Review

Background: Differential diagnosis in early arthritis is challenging, especially early after symptom onset. Several studies applied musculoskeletal ultrasound in this setting, however, its role in helping diagnosis has yet to be clearly defined. The purpose of this work is to systematically assess the diagnostic applications of ultrasonography in early arthritis in order to summarize the available evidence and highlight possible gaps in knowledge. Methods: In December 2017, existing systematic literature reviews (SLR) on rheumatoid arthritis (RA), osteoarthritis (OA), psoriatic arthritis (PsA), polymyalgia rheumatica (PMR), calcium pyrophosphate deposition disease (CPPD), and gout were retrieved. Studies on ultrasound to diagnose the target conditions and detecting elementary lesions (such as synovitis, tenosynovitis, enthesitis, bone erosions, osteophytes) were extracted from the SLRs. The searches of the previous reviews were updated and data from new studies fulfilling the inclusion criteria extracted. Groups of reviewers worked separately for each disease, when possible diagnostic accuracy (sensitivities, specificities) was calculated from primary studies. When available, the reliability of ultrasound to detect elementary lesions was extracted. Results: For all the examined disease, recent SLRs were available. The new searches identified 27 eligible articles, with 87 articles included from the previous SLRs. The diagnostic performance of ultrasound in identifying diseases was addressed by 75 studies; in most of them, a single elementary lesion was used to define diagnosis, except for PMR. Only studies on RA included consecutive patients with new onset of arthritis, while studies on gout and CPPD often focused on subjects with mono-arthritis. Most of the remaining studies enrolled patients with a defined diagnosis. Synovitis was the most frequently detected lesion; clinical diagnosis was the most common reference standard. The diagnostic performance of ultrasound across different conditions was extremely variable. Ultrasound to identify elementary lesions was assessed in 38 studies in OA, gout and CPPD. Its performance in OA was very variable, with better results in CPPD and gout. The reliability of ultrasound was moderate to good for most lesions. Conclusions: Although a consistent amount of literature investigated the diagnostic application of ultrasound, in only a minority of cases its additional value over clinical diagnosis was tested. This SLR underlines the need for studies with a pragmatic design to identify the placement of ultrasound in the diagnostic pathway of new-onset arthritis.

High-Resolution US of Rheumatologic Diseases

For the past 15 years, high-resolution ultrasonography (US) is being routinely and increasingly used for initial evaluation and treatment follow-up of rheumatologic diseases. This imaging technique is performed by using high-frequency linear transducers and has proved to be a powerful diagnostic tool in evaluation of articular erosions, simple and complex joint and bursal effusions, tendon sheath effusions, and synovitis, with results comparable to those of magnetic resonance imaging, excluding detection of bone marrow edema. Crystal deposition diseases including gouty arthropathy and calcium pyrophosphate deposition disease (CPPD) have characteristic appearances at US, enabling differentiation between these two diseases and from inflammatory arthropathies. Enthesopathy, which frequently accompanies psoriatic and reactive arthritis, also has a characteristic appearance at high-resolution US, distinguishing these two entities from other inflammatory and metabolic arthropathies. The presence of Doppler signal in examined joints, bursae, and tendon sheaths indicates active synovitis. Microbubble echo contrast agents augment detection of tissue vascularity and may act in the future as a drug delivery vehicle. Frequently, joint, tendon sheath, and bursal fluid aspirations and therapeutic injections are performed under US guidance. The authors describe the high-resolution US technique including gray-scale, color or power Doppler, and contrast agent-enhanced US that is used in evaluation of rheumatologic diseases of the wrist and hand and the ankle and foot in their routine clinical practice. This article demonstrates imaging findings of normal joints, rheumatoid arthritis, gouty arthritis, CPPD, psoriatic and reactive arthritis, and osteoarthritis.

Ultrasound in the diagnosis of calcium pyrophosphate dihydrate deposition disease. A systematic literature review and a meta-analysis

OBJECTIVE

Ultrasonography (US) demonstrated to be a promising tool for the diagnosis of calcium pyrophosphate dihydrate deposition disease (CPPD). The aim of this systematic literature review (SLR) was to collect the definitions for the US elementary lesions and to summarize the available data about US diagnostic accuracy in CPPD.

METHODS

We systematically reviewed all the studies that considered US as the index test for CPPD diagnosis without restrictions about the reference test or that provided definitions about US identification of CPPD. Sensitivity and specificity were calculated for each study and definitions were extrapolated. Subgroup analyses were planned by anatomical site included in the index text and different reference standards.

RESULTS

Thirty-seven studies were included in this review. All the studies were eligible for the collection of US findings and all definitions were summarized. US description of elementary lesions appeared heterogeneous among the studies. Regarding US accuracy, 13 articles entered in the meta-analysis. Considering each joint structure, the sensitivity ranged between 0.77 (0.63-0.87) and 0.34 (0.16-0.58) while the specificity varies between 1.00 (0.89-1.00) and 0.92 (0.16-1.00). Considering the reference standards used, the sensibility ranged between 0.34 (0.02-0.65) and 0.87 (0.76-0.99) while specificity ranged between 0.84 (0.52-1.00) and 1.00 (0.99-1.00).

CONCLUSION

US is potentially a useful tool for the diagnosis of CPPD but universally accepted definitions and further testing are necessary in order to assess the role of the technique in the diagnostic process.

Diagnostic value of ultrasound in calcium pyrophosphate deposition disease: a systematic review and meta-analysis

OBJECTIVE

A systematic review and meta-analysis of data from cohort studies to analyse the diagnostic performances (ie, sensitivity and specificity) of ultrasound (US) for diagnosis of calcium pyrophosphate deposition (CPPD) disease with microscopic crystal detection used as a gold standard.

METHODS

We performed a systematic review of articles published up to December 2014 using EMBASE, MEDLINE and Cochrane databases and abstracts from the past two EULAR and ACR annual meetings. Only studies reporting the performance of US for diagnosis of CPPD disease were selected. A meta-analysis involved the inverse variance method to evaluate global sensitivity and specificity of US. Statistical heterogeneity was assessed by the Cochran Q-test and I(2) values.

RESULTS

The search resulted in 85 articles and 11 abstracts; 17 and 4, respectively, were selected for the systematic review. A total of 262 patients with CPPD disease and 335 controls from 4 original articles and 4 abstracts were included in the meta-analysis. The US diagnostic patterns most frequently recorded were thin hyperechoic bands in the hyaline cartilage (8 articles); hyperechoic spots in fibrous cartilage or in tendons (7 articles); and homogeneous hyperechoic nodules localised in bursa or articular recesses (4 articles). The meta-analysis revealed a heterogeneity of the data, with a sensitivity of 87.9% (95% CI 80.9% to 94.9%) and specificity of 91.5% (95% CI 85.5% to 97.5%) using a random model.

CONCLUSIONS

This meta-analysis confirmed that US has high sensitivity and specificity for the diagnosis of CPPD and may be a promising tool for the diagnosis and management of CPPD.

Sensitivity and Reproducibility of Ultrasonography in Calcium Pyrophosphate Crystal Deposition in Knee Cartilage: A Cross-sectional Study

Objective.

To compare the ability to detect calcium pyrophosphate (CPP) crystals deposition (CPPD) in knee cartilage by ultrasonography (US) and radiography.

Methods.

Patients with knee effusion were consecutively included and underwent radiography and US evaluation of knees. Diagnosis of CPPD was made by the identification of CPP crystals. Two blinded rheumatologists performed US assessment.

Results.

We included 51 patients (25 with CPPD). US revealed hyperechoic spots in all 25 patients with CPPD (sensitivity 100%, specificity 92.3%), whereas radiography revealed CPPD in 16 (sensitivity 64%, specificity 100%; p < 0.0001).

Conclusion.

US of knees is more sensitive than radiography for CPPD diagnosis.

CT imaging for evaluation of calcium crystal deposition in the knee: initial experience from the Multicenter Osteoarthritis (MOST) study

OBJECTIVE

Role of intra-articular calcium crystals in osteoarthritis (OA) is unclear. Imaging modalities used to date for its evaluation have limitations in their ability to fully characterize intra-articular crystal deposition. Since Computed Tomography (CT) imaging provides excellent visualization of bones and calcified tissue, in this pilot project we evaluated the utility of CT scan in describing intra-articular calcium crystal deposition in the knees.

METHOD

We included 12 subjects with and four subjects without radiographic chondrocalcinosis in the most recent visit from the Multicenter Osteoarthritis (MOST) study, which is a longitudinal cohort of community-dwelling older adults with or at risk for knee OA. All subjects underwent CT scans of bilateral knees. Each knee was divided into 25 subregions and each subregion was read for presence of calcium crystals by a musculoskeletal radiologist. To assess reliability, readings were repeated 4 weeks later.

RESULTS

CT images permitted visualization of 25 subregions with calcification within and around the tibio-femoral and patello-femoral joints in all 24 knees with radiographic chondrocalcinosis. Intra-articular calcification was seen universally including meniscal cartilage (most common site involved in 21/24 knees), hyaline cartilage, cruciate ligaments, medial collateral ligament and joint capsule. Readings showed good agreement for specific tissues involved with calcium deposition (kappa: 0.70, 95% CI 0.62-0.80).

CONCLUSION

We found CT scan to be a useful and reliable tool for describing calcium crystal deposition in the knee and therefore potentially for studying role of calcium crystals in OA. We also confirmed that "chondrocalcinosis" is a misnomer because calcification is present ubiquitously.

The structural consequences of calcium crystal deposition

Calcium pyrophosphate dihydrate and basic calcium phosphate (BCP) crystals are the most common calcium-containing crystals associated with rheumatic disease. Clinical manifestations of calcium crystal deposition include acute or chronic inflammatory and degenerative arthritides and certain forms of periarthritis. The intra-articular presence of BCP crystals correlates with the degree of radiographic degeneration. Calcium crystal deposition contributes directly to joint degeneration. Vascular calcification is caused by the deposition of calcium hydroxyapatite crystals in the arterial intima. These deposits may contribute to local inflammation and promote further calcification, thus aggravating the atherosclerotic process. Calcium crystal deposition results in substantial structural consequence in humans.

Do not hallow until you are out of the wood! Ultrasonographic detection of CPP crystal deposits in menisci: facts and pitfalls

PURPOSE

Ultrasonography (US) has been demonstrated to be an important tool in the diagnosis of calcium pyrophosphate (CPP) crystal deposition disease. The aim of our study was to individuate and describe possible pitfalls in US detection of such deposits in menisci.

PATIENTS AND METHODS

We enrolled all patients waiting to undergo knee replacement surgery due to osteoarthritis, for one-month period. Each patient underwent US examination of the knee, focusing on the menisci. After surgery, the menisci were examined by US, macroscopically and microscopically, using the microscopic analysis as the gold standard for CPP deposition.

RESULTS

11 menisci of 6 patients have been studied. Ex vivo examination of menisci performed better in CPP identification than in vivo examination. The possible reasons of misinterpretation or misdiagnosis of the in vivo exam were identified and are extensively described in the paper. Also a new sign of CPP crystal deposits was found.

CONCLUSIONS

This study permitted to highlight some difficulties in CPP crystal detection by US in menisci. Further studies are needed to define completely US CPP crystal aspect and to improve the sensibility and specificity of US in CPP deposition diagnosis.

Ultrasonographic diagnosis of articular chondrocalcinosis

To investigate the role of high-frequency ultrasonography in the diagnosis of calcium pyrophosphate dihydrate (CPPD) calcifications, in the most commonly affected joints in CPPD disease. Sixty patients with knee effusion were included in the study. All patients underwent musculoskeletal ultrasonography (on the shoulder, elbow, wrist, and knee joints), radiological examination of the sites examined by US, and synovial fluid analysis (using polarized light microscopy). Out of 60 patients with knee effusion, ultrasonographic calcifications (knees, shoulders, and wrists) were present in 38 patients (63.3%) and out of those patients; 32 had calcification characteristic of CPPD crystals deposition (hyperechoic deposits) in the knee and wrist joints. Pattern II (punctate pattern) was the most common pattern of calcification. It was present in all patients who had wrist calcification (18 patients) and in the knee in either alone (21 patients) or in association with pattern I (hyperechoic band) and/or pattern III (hyperechoic nodular or oval deposits) (9 patients). The sensitivity of ultrasonography for the detection of calcification was 84.2% while that of plain radiography was 13.2%, the specificity of both ultrasonography and plain radiography for the detection of calcification was 100%, and ultrasonography is valuable for diagnosing articular chondrocalcinosis via the detection of calcifications within the joint cartilage and fibrocartilage. Both sensitivity and specificity are high for detecting CPPD deposits.

Ultrasonography in chondrocalcinosis

Ultrasonography can visualize calcific deposits within soft tissues. The appearance and location of the deposits distinguishes articular chondrocalcinosis from other crystal deposition diseases. The most common findings are hyperechoic dots or lines running parallel to the joint surface, hyperechoic images within fibrous cartilage (menisci and triangular fibrocartilage complex), and deposits within tendons (Achilles tendon). Studies found that ultrasonography was highly sensitive and specific for detecting calcifications, using calcium pyrophosphate dihydrate crystal detection in joint fluid as the reference standard. Good agreement has been demonstrated between radiographs and ultrasonography for the detection of calcifications. Thus, ultrasonography is valuable for diagnosing articular chondrocalcinosis via the detection of calcifications within the joint cartilage, fibrocartilage, and tendons. In addition, ultrasonography is a noninvasive, widely available, inexpensive investigation that requires no radiation exposure.

Hyaline cartilage involvement in patients with gout and calcium pyrophosphate deposition disease. An ultrasound study

OBJECTIVE

The main aim of the present study was to determine the sensitivity, specificity and accuracy of ultrasonography (US) in detecting monosodium urate and calcium pyrophosphate dihydrate crystals deposits at knee cartilage level using clinical definite diagnosis as standard reference.

DESIGN

A total of 32 patients with a diagnosis of gout and 48 patients with pyrophosphate arthropathy were included in the study. Fifty-two patients with rheumatoid arthritis (RA), psoriatic arthritis or osteoarthritis (OA) were recruited as disease controls. All diagnoses were made using an international clinical criterion. US examinations were performed by an experienced sonographer, blind to clinical and laboratory data. Hyaline cartilage was assessed to detect two US findings recently indicated as indicative of crystal deposits: hyperechoic enhancement of the superficial margin of the hyaline cartilage and hyperechoic spots within the cartilage layer not generating a posterior acoustic shadow.

RESULTS

Hyperechoic enhancement of the chondrosynovial margin was found in at least one knee of 14 out of 32 (43.7%) patients with gout and in a single knee of only one patient affected by pyrophosphate arthropathy (specificity=99%). Intra-cartilaginous hyperechoic spots were detected in at least one knee of 33 out of 48 (68.7%) patients with pyrophosphate arthropathy and in two disease controls one with OA and the second with RA (specificity=97.6%).

CONCLUSIONS

The results of the present study indicate that US may play a relevant role in distinguishing cartilage involvement in patients with crystal-related arthropathy. The selected US findings were found to be highly specific.

Calcium pyrophosphate dihydrate crystal deposition disease: sonographic findings

High-resolution sonography is a rapidly evolving technique that is gaining an increasing success in the assessment of crystalline arthropathies. In calcium pyrophosphate dihydrate crystal deposition disease, the sonographic features of crystal deposition include hyperchoic spots within hyaline cartilage and/or fibrocartilage and soft tissue calcifications. The aim of this pictorial essay was to present the main findings evocative of crystal deposition in patients with pyrophosphate arthropathy.

“Crystal Clear”—Sonographic Assessment of Gout and Calcium Pyrophosphate Deposition Disease

OBJECTIVES

To date, high-resolution ultrasound (US) has not been fully exploited in the field of crystalline arthropathy. Both gout and calcium pyrophosphate deposition (CPPD) disease are significant diseases within the purview of the rheumatologist. The aim of this pictorial review was to present the principal findings in patients with crystal deposition in gout and CPPD.

METHODS

US pictures were obtained from 60 consecutive patients, 34 with CPPD disease and 26 with gout, whose diagnosis was confirmed by synovial fluid analysis. The US examinations were performed using the following US systems: Diasus (Dynamic Imaging, Livingstone, UK) and Logiq 9 (General Electric Medical Systems, Milwaukee, WI).

RESULTS

Pictorial evidence of the principal US findings in gout includes monosodium urate (MSU) deposition on the surface of articular cartilage, various patterns within synovial fluid ranging from completely anechoic fluid to collections filled with aggregates of variable shape and echogenicity, microdeposition within tendons, and tophus formation. In CPPD, the hallmark US features include crystal deposition within articular cartilage, calcification of fibrocartilage, together with focal crystal deposition within tendons.

CONCLUSION

US is an impressive imaging modality in crystalline arthropathy. The anatomical location of the crystal deposits, clearly depictable by US, allows differentiation between MSU and CPPD aggregates.

Calcium-containing crystals and osteoarthritis: implications for the clinician

The clinical implication of articular deposits of calcium-containing crystals (specifically of calcium pyrophosphate dihydrate and hydroxyapatite) in osteoarthritis is unknown. Recent longitudinal studies have suggested that in some instances calcium crystals are direct participants in cartilage damage, while in other situations they are merely markers of joint damage. Better understanding of the mechanisms of crystal formation, especially in relation to inorganic pyrophosphate regulation, has lead to potential avenues for therapeutic intervention. The current treatment of osteoarthritis associated with calcium-containing crystals should involve nonsteroidal anti-inflammatory drugs, intra-articular steroids, and in resistant cases, joint irrigation can be considered. While preliminary studies suggest the possibility of favorable benefits from colchicine and hydroxycholorquine in this osteoarthritis disease subset, more rigorous studies need to be conducted to establish their roles.

Calcium pyrophosphate dihydrate and basic calcium phosphate crystal-induced arthropathies: update on pathogenesis, clinical features, and therapy

Calcium-containing crystals are the most common class for the osteoarthritic joint. They are responsible for acute periarthritis and destructive arthropathies, and for tissue deposits mimicking tumor-like masses. These crystals encompassed mainly calcium pyrophosphate dihydrate and basic calcium phosphate crystals, with the latter being related to hydroxyapatite, carbonate-substituted apatite, and octacalcium phosphate. Calcification deposit mechanisms will be reviewed with respect to extracellular inorganic pyrophosphate dysregulation mainly caused by modulation of specific membrane channel disorders. Genetic defects have been extensively studied and identified mutation of specific genes such as ANKH and COL. Pathogenesis of crystal-induced inflammation is related to synovial tissue and direct cartilage activation. Besides classical knee or wrist pseudogout attacks or Milwaukee shoulder arthropathies, clinicians should be aware of other specific common presentations, such as erosive calcifications, spinal cord compression by intraspinal masses, ligamentum flavum calcification, or atypical calcified tophus. Promising clinical results for preventing calcium crystal deposits and cartilage degradation are lacking. Practical imaging tools are needed to monitor reduction of calcification of fibrocartilage and articular cartilage as markers of drug efficacy.

Calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint: new developments relevant to the clinician

The major types of crystals containing calcium, which causes arthropathy and periarticular disease, are calcium pyrophosphate dihydrate and basic calcium phosphates, including hydroxyapatite. Exciting advances include the identification of mutations in the gene ANKH associated with disordered inorganic pyrophosphate (PPi) transport in some kindred with familial chondrocalcinosis linked to chromosome 5p. In addition, central basic mechanisms governing cartilage calcification and their relationship to aging and osteoarthritis have now been elucidated. These include the role of plasma cell glycoprotein-1, the PPi-generating ecto-enzyme, in chondrocalcinosis and the linkage of low- grade inflammation to expression and activation of two cartilage-expressed transglutaminase isoenzymes with direct calcification-stimulating activity. This review discusses clinically pertinent new information on pathogenesis. The authors also address, in detail, current diagnostic and therapeutic issues pertaining to calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint, as well as possible therapeutic directions for the future.

Radiographic tools for assessment of pathologic cartilage calcification

Both hyaline cartilage and fibrocartilage can calcify in a variety of pathologic conditions. Traditionally, plain film radiographs have been used to diagnose such calcifications; however, only when the calcifications have adequately mineralized are they radiographically apparent. Cross-sectional imaging modalities such as computed tomography, magnetic resonance imaging, and ultrasonography can often demonstrate cartilage calcifications before they are radiographically apparent, thus yielding earlier detection of disease processes. Cartilage calcifications have a distinct appearance on each of these various imaging modalities. A working knowledge of the typical locations of cartilage calcific deposits as well as their appearance on various imaging modalities is necessary for accurate diagnosis.