Cartilage Thickness Measurements Research Articles

Molecular imaging of cartilage damage of finger joints in early rheumatoid arthritis with delayed gadolinium‐enhanced magnetic resonance imaging

To assess cartilage glycosaminoglycan content and cartilage thickness in the metacarpophalangeal (MCP) joints of patients with early rheumatoid arthritis (RA) and healthy volunteers. After review board approval and informed consent were obtained, 22 subjects were prospectively enrolled (9 patients with early RA [7 women and 2 men with a mean ± SD age of 49 ± 13 years; range 25-68 years] and 13 healthy volunteers [10 women and 3 men with a mean ± SD age of 51 ± 12 years; range 25-66 years). In a total of 44 MCP joints of the index and middle fingers, measurements of cartilage thickness and delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) index (T1 [msec]) were obtained using the variable flip-angle method and a 3T MR scanner. MRIs were evaluated for bone edema, erosions, and synovitis (using the RA MRI Scoring criteria). Student's t-test was used to test the significance of differences between groups. The mean ± SD dGEMRIC index was 497 ± 86 msec in healthy volunteers and was significantly lower in the early RA group (421 ± 76 msec) (P = 0.042). There was no joint space narrowing seen on standard radiographs. No significant difference was found between cartilage thickness in patients with early RA and that in controls (index finger mean ± SD 1.27 ± 0.23 mm in RA patients versus 1.46 ± 0.34 mm in controls [P = 0.16] and middle finger 1.26 ± 0.23 mm in RA patients versus 0.97 ± 0.47 mm in controls [P = 0.10]). No significant correlation was noted between cartilage thickness and dGEMRIC index (R = 0.36, P = 0.88 in RA patients; R = 0.156, P = 0.445 in controls). Our findings indicate that cartilage damage is present in the MCP joints of patients with early RA despite the absence of joint space narrowing on standard radiographs and MRI. Cartilage damage in RA can be imaged with dGEMRIC.

Measurement of Articular Cartilage Thickness Using a Three-Dimensional Image Reconstructed from B-Mode Ultrasonography Mechanical Scans Feasibility Study by Comparison with MRI-Derived Data

The present study aimed to develop a method to measure three-dimensional (3-D) thickness of cartilage (Tc) at the femoral condyle using B-mode ultrasonography (US) and to clarify the feasibility of US in clinical evaluations of articular cartilage by comparing the results with 3-D measurement values using magnetic resonance imaging (MRI) and assessing repeatability. The medial surface of the right knees of two healthy male volunteers (age, 37 and 59 years) and the knees on affected side of three male patients with osteoarthritis (OA) (age, 73, 81 and 83 years) were scanned using B-mode US with the knee flexed at 120°. The range of the angle of probe rotation for the arm was 0-80° and B-mode images (total, 101 images) were acquired every 0.8°. MRI of the knees was also performed using the double echo steady-state sequence. Both US and MRI images were used to create 3-D models of medial femoral condyle articular cartilage. Tc was determined at points 1 mm apart from one another in the US model (Tc-US) and MRI model (Tc-MRI). Tc-US was compared with Tc-MRI and the repeatability of Tc-US was assessed by mean Tc in the specific region of interest of the femoral condyle. Tc-US correlated significantly with Tc-MRI both in volunteers and in OA patients (p < 0.0001 each) and coefficients of correlation were 0.976 and 0.964 for volunteers and OA patients, respectively. The coefficient of variance for mean Tc-US was 4.90%. Our results show that 3-D US measurements of femoral cartilage are reproducible and correlate strongly with MRI measurements.

Evaluation of the Accuracy of Articular Cartilage Thickness Measurement by B-Mode Ultrasonography with Conventional Imaging and Real-Time Spatial Compound Ultrasonography Imaging

The present study aimed to quantify the thickness of articular cartilage (Tc) in vitro using both conventional and real-time spatial compound B-mode ultrasonography (US) with a clinically used transducer and to evaluate the accuracy of measurement by comparing the results with values obtained microscopically. Femoral condyle samples were obtained from a 6-month-old pig and a 3-year-old pig. B-mode US images with conventional imaging and real-time spatial compound imaging (RTSCI) of osteochondral blocks were acquired. Tc determined using US (Tc-US) was measured from line data parallel to US beam direction acquired from B-mode images with an objective method for determining cartilage surface and bone-cartilage interfaces at the peak brightness values. Tc was also determined under microscopy (Tc-optical) using the corresponding points from US measurement. Tc-US was compared with Tc-optical to assess accuracy. Tc-US correlated significantly with Tc in both conventional imaging and RTSCI (r = 0.961, 0.976, respectively). Bland-Altman plots showed mean differences between Tc-optical and Tc-US were −0.0073 mm and 0.0139 mm with standard deviations of 0.171 mm and 0.131 mm for conventional imaging and RTSCI, respectively. Our results show that Tc-US measurement using B-mode US allows accurate measurement of Tc. Considering correlation coefficients between Tc-US and Tc-optical, RTSCI US may offer higher accuracy for measuring Tc than conventional methods when an objective tissue border determination algorithm is used, even though both showed good accuracy in our study.

Ultrasonographic Measurement of the Femoral Cartilage Thickness in Patients with Juvenile Idiopathic Arthritis

Objective: To evaluate the femoral cartilage thicknesses of oligoarticular JIA patients (affected vs unaffected) by using ultrasonography (US), and to find out whether those US measurements were related with the clinical parameters of the patients. Methods: Twenty-six children (12 boys, 14 girls) with mono-articular (knee involvement) juvenile idiopathic arthritis ( JIA), with a mean age of 8.84±4.06 years were enrolled. Demographic and clinical features of the subjects including age, sex, body mass index, disease duration, age at onset, medical treatment, laboratory evaluations and presence of uveitis were all noted. The femoral cartilage thicknesses of both knees were measured with a 7-12 MHz linear probe while subjects’ knees were held in maximum flexion. Three mid-point measurements were taken from both knees (lateral condyle, intercondylar area and medial condyle) and the values relating to the unaffected knees were taken as controls. Results: Femoral cartilage thickness values were found to be similar (affected vs. non-affected sides) for all the three measurement sites (p values >0.05) and cartilage thickness values did not correlate with the clinical features of the patients.

Normal Epiphyseal Cartilage Measurements in the Knee in Children

The purpose of this study was to validate previously reported distal femoral cartilage measurements in healthy children of different ages using an alternative sonographic imaging plane and patient position than previously reported and to provide preliminary proximal tibial epiphyseal cartilage measurements in healthy children. Distal femoral and proximal tibial epiphyseal cartilage thickness was measured using sonography in a cohort of healthy children based on a coronal image at the medial aspect of the femorotibial joint with the knee in 30° of flexion. The average of 3 measurements of femoral and tibial epiphyseal cartilage was obtained and correlated with age and sex. Femoral epiphyseal cartilage measurements were compared to recently reported measurements at the patellofemoral joint. Sixty children (31 boys and 29 girls; newborn to 21 years; mean, 9 years; median, 7 years 11 months) were imaged. Seventy-four percent of distal femoral cartilage epiphyseal measurements fell into the 95% confidence intervals predicted by previously published reports. At age ranges outside those previously reported, there was less concordance between measured cartilage thickness values and those predicted. Values of distal femoral epiphyseal cartilage thickness measured by sonography of the femorotibial joint are similar to those reported at the patellofemoral joint. We propose that femoral epiphyseal cartilage thickness be measured on the basis of a coronal image at the medial femorotibial joint. This technique requires less knee flexion, which may prove advantageous when evaluating cartilage in patients with joint inflammation and a limited range of motion. It also allows concurrent measurement of tibial epiphyseal cartilage and thus provides another parameter for assessing cartilage loss.

Quantitative cartilage degeneration associated with spontaneous osteoarthritis in a guinea pig model

To determine (i) the feasibility and intra- and inter-scan reproducibility of T(1ρ) MRI in assessing cartilage degeneration in a guinea pig model with naturally occurring joint disease that closely mimics human osteoarthritis (OA), (ii) demonstrate the sensitivity of T(1ρ) MRI in assessing the age dependent cartilage degeneration in OA progression as compared to histopathological changes. Duncan-Hartley guinea pigs were obtained at various ages and maintained under an IACUC approved protocol. The left hind stifle joint was imaged using T(1ρ) MRI on a 9.4 Tesla Varian horizontal 20 cm bore scanner using a custom surface coil. Reproducibility of T(1ρ) MRI was assessed using 4-month-old guinea pigs (N = 3). Three age cohorts; 3 month (N = 8), 5 month (N = 6), and 9 month (N = 5), were used to determine the age-dependent osteoarthritic changes as measured by T(1ρ) MRI. Validation of age-dependent cartilage degeneration was confirmed by histology and Safranin-O staining. T(1ρ) values obtained in the cartilage of the stifle joint in guinea pigs were highly reproducible with an inter-scan mean coefficient of variation (CV) of 6.57% and a maximum intra-scan CV of 9.29%. Mean cartilage T(1ρ) values in animals with late stage cartilage degeneration were 56.3-56.9 ms (5-9 month cohorts) were both significantly (P < 0.01) higher than that obtained from 3-month-old cohort (44 ms) demonstrating an age-dependent variation. T(1ρ) was shown to be significantly greater than T(2) . T(1ρ) dispersion was observed in this animal model for the first time showing an increase of 45% between 500 Hz and 1500 Hz spin-locking frequency. Cartilage thickness measurements were calculated from single mid-coronal histology sections from same animals used for T(1ρ) MRI. Thickness calculations showed insignificant differences between 3- and 5-month cohorts and was significantly decreased by 9 months of age (P < 0.01). A moderate correlation (R(2) = 0.45) existed between T(1ρ) values and signal intensity of Safranin-O stain. The data presented demonstrate that T(1ρ) MRI is highly reproducible in this spontaneous model of OA and may serve as a noninvasive tool to characterize joint cartilage degeneration during OA. Age-dependent changes, verified with histological measurements of proteoglycan loss, correlated with T(1ρ) across different age groups. T(1ρ) has adequate dynamic range and is sensitive to detect and track the progression of cartilage degeneration in the guinea pig model before gross anatomical changes such as cartilage thinning has occurred. This study presents a technological advancement that would permit longitudinal studies of evaluating disease-modifying therapies useful for treating human OA.

Ultrasonographic measurement of the femoral cartilage thickness in patients with polycystic ovary syndrome

To compare the femoral cartilage thickness values of polycystic ovary syndrome (PCOS) patients with those of age-matched, healthy women and to find out whether cartilage thickness changes with the clinical parameters. A cross-sectional controlled study. A secondary care center and a tertiary care center. Thirty-three women with PCOS (mean age: 23.7 ± 3.5 years; 66 knees) and 30 healthy control women matched for age and body mass index (mean age: 24.8 ± 4.2 years; 60 knees). Measurement of knee cartage thickness of infertile PCOS patients. The thickness of femoral articular cartilage measured with an ultrasound with a linear probe (7-12 MHz) as well as three midpoint measurements taken from each knee: the lateral condyle, intercondylar area, and medial condyle. The demographic and clinical features of the PCOS patients, the laboratory evaluations, and the endometrial thickness values were recorded, and the three midpoint measurements were taken from each knee. The PCOS patients had thicker cartilage values than the control group at all measurement sites. There was no correlation between the clinical parameters and the cartilage thickness values of PCOS patients. Our findings support the possible favorable effects of estrogen and androgens in PCOS patients. However, our data cannot determine whether PCOS patients have less risk of developing osteoarthritis later in life because they also have higher BMI values. The possible long-term changes in cartilage thickness in PCOS patients require further study.

An analysis algorithm for accurate determination of articular cartilage thickness of hip joint from MR images

To test the accuracy of the most widely used technique based on edge detection for thickness measurement of the hip joint cartilage in MR images, and to improve the measurement accuracy by developing a new measurement method based on a model of the MRI process. MRI was performed in 3 normal cadaver hips, 25 hips of normal volunteers, and 25 hips of patients with osteoarthritis. In general, thickness was defined as the distance between the two sides of the hip cartilage along the normal directions of the cartilage surfaces. In this article this is referred to as the "edge detection method." A theoretical simulation analysis revealed that the edge detection method considerably underestimated the cartilage thickness of the hip joint. A new measurement method based on a model of the MR imaging process was accordingly proposed for correcting the measurement errors. In the experiment using the cadaver hips, anatomical measurement of cartilage thickness was used as reference standard. For measurements at 35 sites, the proposed model-based method gave results similar to those presented from anatomic section, while the edge detection method gave underestimation compared with the anatomic thickness. The underestimation biases for the edge detection method were consistent with the biases predicted by theoretical simulation. In the experiment using the hips of volunteers and patients, the edge detection result was an underestimation compared with the result generated by using the model-based method. The edge detection method underestimated the hip cartilage thickness in MR images. The proposed model-based method was more accurate than the edge detection method for thickness measurement of the hip cartilage.

MR imaging and anatomic study of articular cartilage of the knee joint

Objective To compare corpse sampling and MR imaging with 3D-FS-SPGR sequences in measurement of the articular cartilage thickness and to investigate knee cartilage topography. Methods Two fresh specimens of the knee joint were obtained from 2 normal young adult male corpses of medium stature. MR1 scanning was carried on the 2 specimens in sagittal 3D-FS-SPGR MR sequences. After defrosted,the knee specimens were dissected longitudinally, and the cartilage thicknesses were measured at different locations of the knee joint. Paraffin sections of the knee cartilage were observed following compound staining with victoria blue and ponceau red. Results The average cartilage thicknesses measured by dissection and MR imaging sequence were respectively: 2. 25 mm and 2. 25 mm at the anterior weight-loading surface of the femoral lateral condyle, 2. 70 mm and 2. 75 mm at the posterior weight-loading surface of the femoral lateral condyle, 2. 00 mm and 2. 10 mm at the anterior weight-loading surface of the tibial lateral condyle,2. 35 mm and 2. 25 mm at the posterior weight-loading surface of the tibial lateral condyle, 2. 20 mm and 2. 20mm at the anterior weight-loading surface of the femoral medial condyle, 2. 15 mm and 2. 30 mm al the posterior weight-loading surface of the femoral medial condyle, 2. 20 mm and 2.45 mm at the anterior weight-loading surface of the tibial medial condyle, 2. 70 mm and 2. 95 mm at the posterior weight-loading surface of the tibial medial condyle and 3. 08 mm and 3. 15 mm at patella cartilage surface. Collagen fibers were rich at the periphery of the articular cartilage with sparse chondrocytes and matrixes, while the opposite was observed at the center of the articular cartilage. Conclusions MR imaging with 3D-FS-SPGR sequences can display the actual knee cartilage topography. Collagen fibers mainly concentrate at the periphery of the articular cartilage, which accounts for the function of the articular cartilage. Key words: Knee joint; Cartilage, articular; Magnetic resonance imaging; Anatomy, cross section

Reliability and validity of ultrasound imaging of features of knee osteoarthritis in the community

BackgroundRadiographs are the main outcome measure in epidemiological studies of osteoarthritis (OA). Ultrasound imaging has unique advantages in that it involves no ionising radiation, is easy to use and visualises soft tissue structures. Our objective was to measure the inter-rater reliability and validity of ultrasound imaging in the detection of features of knee OA.MethodsEighteen participants from a community cohort, had both knees scanned by two trained musculoskeletal sonographers, up to six weeks apart. Inter-rater reliability for osteophytes, effusion size and cartilage thickness was calculated by estimating Kappa (κ) and Intraclass correlation coefficients (ICC), as appropriate. A measure of construct validity was determined by estimating κ between the two imaging modalities in the detection of osteophytes.ResultsReliability: κ for osteophyte presence was 0.77(right femur), 0.65(left femur) and 0.88 for both tibia. ICCs for effusion size were 0.70(right) and 0.85(left). Moderate to substantial agreement was found in cartilage thickness measurements. Validity: For osteophytes, κ was moderate to excellent at 0.52(right) and 0.75(left).ConclusionSubstantial to excellent agreement was found between ultrasound observers for the presence of osteophytes and measurement of effusion size; it was moderate to substantial for femoral cartilage thickness. Moderate to substantial agreement was observed between ultrasound and radiographs for osteophyte presence.

Toward Standardized Ultrasound Measurements of Cartilage Thickness in Children: Figure 1.

In the past decade, musculoskeletal ultrasound (US) has become well established as a diagnostic method in adult rheumatology. B-mode (or greyscale) US has been shown to be an excellent tool, equally as effective as magnetic resonance imaging (MRI), to assess joint effusions and synovial thickening1. Power Doppler US detects slow flow in small vessels, which is part of the pathological process in synovitis2. In addition, cartilage thickness can be assessed with US3. As one of the cardinal features of inflammatory arthritis is cartilage loss, and joint space narrowing is increasingly recognized as a factor in work disability and poor quality of life4, US might play an important role in the monitoring of patients with chronic arthritis. The clinical utility of musculoskeletal US is likely to be at least as important in pediatric rheumatology as it is in adult rheumatology. The longterm consequences of insufficiently treated and therefore persistently active juvenile arthritis are enormous given the young age of the patients5, and a recent review has outlined the impact on health related quality of life, physical function, and visual outcome6. The exact assessment of joint disease activity as well as the assessment of joint damage in the form of cartilage loss is therefore very important and has become ever more crucial with improvements in treatment. The induction of permanent remission is now possible for an increasing percentage of children but cannot always be reliably demonstrated on clinical examination alone7 … Address correspondence to Dr. Larché. E-mail: mlarche{at}mcmaster.ca

Ultrasonographic evaluation of degenerative changes in the distal radioulnar joint: Correlation of findings with gross anatomy and MR arthrography in cadavers

Objective To determine the accuracy of ultrasonography (US) in the evaluation of degenerative changes in the distal radioulnar joint (DRUJ). Methods and materials Ten cadaveric specimens were obtained. US evaluation of cartilage degeneration and thickness was performed by two independent and blinded readers (R1 and R2). Gross anatomy and MR arthrography evaluated by two readers in consensus served as the reference standard. The joint surface not accessible to US was measured. Results US interreader agreement was non-existent for cartilage thickness measurements and moderate for cartilage degeneration grading (weighted kappa = 0.41). Comparing US and MR imaging evaluation, there was no correlation between US R1 and MR imaging (Pearson correlation coefficient [PCC] = 0.352) and a moderate correlation between US R2 and MR imaging (PCC = 0.570) concerning cartilage thickness measurements. Concerning cartilage degeneration grading, there was a moderate to strong (R1 Spearman correlation coefficient [SCC] = 0.729)/R2 SCC = 0.767) correlation concerning cartilage degeneration grading. Comparing US and gross anatomic evaluation, there was no correlation for US R1 (PCC = 0.220) and a strong correlation for US R2 (PCC = 0.922) concerning cartilage thickness measurements, and a strong to moderate correlation (R1 SCC = 0.808/R2 SCC = 0.597) concerning cartilage degeneration grading. The mean sector of the articular surface of the ulna head not accessible to US was 13°. Conclusion In conclusion the DRUJ is accessible to US except in the central 13° sector of the joint surface. US was approved to be sufficient in demonstrating advanced stages of cartilage degeneration. Thus, US of the DRUJ is recommended in patients suffering from ulnar-sided wrist pain.

Ultrasonographic Measurements of Joint Cartilage Thickness in Healthy Children: Age- and Sex-Related Standard Reference Values

Loss of joint cartilage may be an early feature of chronic inflammatory joint diseases like juvenile idiopathic arthritis (JIA). Conventional radiography usually detects only late changes such as joint space narrowing and bone erosion rather than early inflammatory changes. Joint cartilage is easily visualized with high-frequency ultrasonography (US), but age- and gender-related normal standard reference values should be established before US measurement of cartilage thickness becomes standard procedure in the clinic. A cross-sectional study of bilateral grey-scale US cartilage thickness of the knee, ankle, wrist, and second metacarpophalangeal (MCP) and second proximal interphalangeal (PIP) joints was performed in 394 (215 boys/179 girls) healthy Danish Caucasian children aged between 7 and 16 years. Cartilage thickness differed significantly between sexes (p < 0.001 for all joints), boys having thicker cartilage than girls. Cartilage thickness clearly decreased with increasing age in both sexes. A formula for calculating sex-specific cartilage thickness at different ages in childhood is suggested. No difference between the right and left side of the investigated joints was observed. Using US, we established age- and sex-related normal reference intervals for cartilage thickness of the knee, ankle, wrist, and MCP and PIP joints in 7- to 16-year-old children, and designed a formula for calculating hyaline cartilage thickness in all age groups throughout childhood.

Changes in articular cartilage after meniscectomy and meniscus replacement using a biodegradable porous polymer implant

PurposeTo evaluate the long-term effects of implantation of a biodegradable polymer meniscus implant on articular cartilage degeneration and compare this to articular cartilage degeneration after meniscectomy.MethodsPorous polymer polycaprolacton-based polyurethane meniscus implants were implanted for 6 or 24 months in the lateral compartment of Beagle dog knees. Contralateral knees were meniscectomized, or left intact and served as controls. Articular cartilage degeneration was evaluated in detail using India ink staining, routine histology, immunochemistry for denatured (Col2-¾M) and cleaved (Col2-¾Cshort) type II collagen, Mankin’s grading system, and cartilage thickness measurements.ResultsHistologically, fibrillation and substantial immunohistochemical staining for both denatured and cleaved type II collagen were found in all three treatment groups. The cartilage of the three groups showed identical degradation patterns. In the 24 months implant group, degradation appeared to be more severe when compared to the 6 months implant group and meniscectomy group. Significantly more cartilage damage (India ink staining, Mankin’s grading system, and cartilage thickness measurements) was found in the 24 months implant group compared to the 6 months implant group and meniscectomy group.ConclusionDegradation of the cartilage matrix was the result of both mechanical overloading as well as localized cell-mediated degradation. The degeneration patterns were highly variable between animals. Clinical application of a porous polymer implant for total meniscus replacement is not supported by this study.

Ultrasound-detected synovitis with power Doppler signal is associated with severe radiographic damage and reduced cartilage thickness in hand osteoarthritis

To examine ultrasound (US) features of synovitis in hand osteoarthritis (OA) joints, and to evaluate their relationship with radiological damage severity and US-detected cartilage thickness. US examination was carried out on 14 joints of both hands of 25 patients with symptomatic hand OA (HOA) and 10 age- and sex-matched control subjects. US-detected features were: synovial hypertrophy, effusion, power Doppler signal (PDS), cartilage thickness. Conventional hand radiographs were scored utilizing the Kellgren-Lawrence and Kallman systems. HOA patients were divided into two subsets: non-erosive and erosive. Among the three groups of subjects studied, erosive OA showed the highest values of radiological scores and the highest prevalence of US-detected synovitis. Joints positive for US synovitis features (above all PDS) had higher radiological scores and lower cartilage thickness, while joints with X-ray detected central erosions [the hallmark of erosive HOA were more likely to present PDS positivity. US measured cartilage thickness inversely correlated with radiological damage scores. US-detected synovitis is present in about 10% of HOA finger joints and is associated with more severe radiological damage and reduced cartilage thickness. PDS and cartilage thickness (mm) may represent two innovative additional information tools provided by ultrasonography in HOA evaluation.

Replacement of the Condyle and Ascending Ramus by a Modular Endoprosthesis in Macaca fascicularis—Part 4: Evaluation of the Temporomandibular Joints

To assess, using cone-beam computed tomography and histologic examination, whether the fixation of a condyle-ascending ramus mandibular modular endoprosthesis results in a physiologic condylar replacement in Macaca fascicularis. The right condyle and ascending ramus were resected in 8 adult monkeys and replaced with a modular endoprosthesis, fixed with polymethyl methacrylate bone cement (Palacos). Four monkeys were sacrificed at 3 months and another 4 at 6 months postoperatively. The reconstructed and contralateral temporomandibular joints were harvested en bloc and studied using cone-beam computed tomography and descriptive histologic examination. Heterotopic bone formation was quantified using a modified grading scale. The condyle cartilage thickness in the contralateral temporomandibular joint was measured using histomorphometric methods. The results were compared with those of the unoperated control monkeys. Bone resorption in the glenoid fossa and pathologic changes in the articular disc were noted on the reconstructed side in most specimens. Nevertheless, cone-beam computed tomography findings, histologic findings, and condyle cartilage thickness measurements of the contralateral temporomandibular joint were not significantly different from those of the control specimens. Replacement of the condyle and ascending ramus using a modular endoprosthesis in Macaca fascicularis resulted in adaptive remodeling of the glenoid fossa at up to 6 months postoperatively. Long-term studies are required to further assess the potential of this mode of reconstruction.

Ultrasound and MRI Measurements of Joint Cartilage in Healthy Children: a Validation Study

In juvenile idiopathic arthritis (JIA), proliferative changes in the synovium and synovial fluid accumulation are pathological findings responsible for damage to the cartilaginous tissue and periarticular bone, which are late radiographic findings in conventional radiography. Early detection of these joint changes would allow the clinicians to initiate relevant therapies as is essential for the long-term outcome of JIA. Ultrasonography (US) has shown great potential for this purpose but validation in a pediatric setting is needed. The objective of this study was to validate US measurements of cartilage thickness in target joints in healthy children by comparing them with MRI. Twenty-five healthy Caucasian children (17 boys/ 8 girls), mean age 11.33 years, were examined with MRI (1.5 T, fat-suppressed T 1-weighted 3D sequences) and US (real-time Hitachi EUB 6500 CFM, B-mode 6 - 14 MHz linear transducer) in the right knee, ankle, wrist, metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. US was obtained according to the EULAR standard scans. All differences in cartilage thickness measurements between MRI and US were less than 0.5 millimeters. The coefficient of variation (CV) was found to be good (16 %) except for in the case of the wrist joint (20 %). We found a good level of agreement and no significant systematic joint size-related differences in cartilage thickness measurements between MRI and US. US appears to be a feasible method for evaluating cartilage thickness in JIA target joints, especially when age and sex-related references are defined.

Articular Cartilage Thickness Measured with US is Not as Easy as It Appears: A Systematic Review of Measurement Techniques and Image Interpretation

Theoretically, the high spatial resolution of US makes it well suited to monitor the decrease in articular cartilage thickness in osteoarthritis. A requirement is, however, that the borders of the cartilage are correctly identified and that the cartilage is measured under orthogonal insonation. If US measurements are compared to measurements with other techniques, they should be corrected for the higher sound speed in cartilage. To study whether investigators correctly identify the articular cartilage, whether they insonate orthogonally, and whether they correct for sound speed. A literature search limited to the last 10 years of studies applying US to measure cartilage thickness. 15 studies were identified and they referred to another 8 studies describing methods of thickness measurement. 11 of the 15 studies identified the superficial cartilage border incorrectly, and 6 applied oblique insonation. 2 of the 15 studies corrected for sound speed. Of the further 8 studies, one might correctly identify the superficial cartilage border, 4 applied oblique insonation, and none corrected for sound speed. We found that the majority of studies over the last 10 years, evaluating articular cartilage thickness with US, underestimated the cartilage thickness by not including the leading interface as part of the cartilage. Since the cartilage is relatively thin, this error is substantial. Some investigators also overestimated cartilage thickness by using oblique insonation of the cartilage. By not correcting for the high sound speed in cartilage, most investigators underestimated the cartilage thickness.

Acetabular cartilage thickness: accuracy of three-dimensional reconstructions from multidetector CT arthrograms in a cadaver study.

To prospectively quantify the accuracy of hip cartilage thickness estimated from three-dimensional (3D) surfaces, generated by segmenting multidetector computed tomographic (CT) arthrograms by using direct physical measurements of cartilage thickness as the reference standard. Four fresh-frozen cadaver hip joints from two male donors, ages 43 and 46 years, were obtained; institutional review board approval for cadaver research was also obtained. Sixteen holes were drilled perpendicular to the cartilage of four cadaveric acetabula (two specimens). Hip capsules were surgically closed, injected with contrast material, and scanned by using multidetector CT. After scanning, 5.3-mmcores were harvested concentrically at each drill hole and cartilage thickness was measured with a microscope. Cartilage was reconstructed in 3D by using commercial software. Segmentations were repeated by two authors. Reconstructed cartilage thickness was determined by using a published algorithm. Bland-Altman plots and linear regression were used to assess accuracy. Repeatability was quantified by using the coefficient of variation, intraclass correlation coefficient (ICC), repeatability coefficient, and percentage variability. Cartilage was reconstructed to a bias of -0.13 mm and a repeatability coefficient of + or - 0.46 mm. Regression of the scatterplots indicated a tendency for multidetector CT to overestimate thickness. Intra- and interobserver repeatability were very good. For intraobserver correlation, the coefficient of variation was 14.80%, the ICC was 0.88, the repeatability coefficient was 0.55 mm, and the percentage variability was 11.77%. For interobserver correlation, the coefficient of variation was 13.47%, the ICC was 0.90, the repeatability coefficient was 0.52 mm, and the percentage variability was 11.63%. Assuming that an accuracy of approximately + or - 0.5 mm is sufficient, reconstructions of cartilage geometry from multidetector CT arthrographic data could be used as a preoperative surgical planning tool.

Validation of Cartilage Thickness Calculations Using Indentation Analysis

Different methods have been used to cross-validate cartilage thickness measurements from magnetic resonance images (MRIs); however, a majority of these methods rely on interpolated data points, regional mean and/or maximal thickness, or surface mean thickness for data analysis. Furthermore, the accuracy of MRI cartilage thickness measurements from commercially available software packages has not necessarily been validated and may lead to an under- or overestimation of cartilage thickness. The goal of this study was to perform a matching point-to-point validation of indirect cartilage thickness calculations using a magnetic resonance (MR) image data set with direct cartilage thickness measurements using biomechanical indentation testing at the same anatomical locations. Seven bovine distal femoral condyles were prepared and a novel phantom filled with dilute gadolinium solution was rigidly attached to each specimen. High resolution MR images were acquired, and thickness indentation analysis of the cartilage was performed immediately after scanning. Segmentation of the MR data and cartilage thickness calculation was performed using semi-automated software. Registration of MR and indentation data was performed using the fluid filled phantom. The inter- and intra-examiner differences of the measurements were also determined. A total of 105 paired MRI-indentation thickness data points were analyzed, and a significant correlation between them was found (r=0.88, p<0.0001). The mean difference (+/-std. dev.) between measurement techniques was 0.00+/-0.23 mm, with Bland-Altman limits of agreement of 0.45 mm and -0.46 mm. The intra- and inter-examiner measurement differences were 0.03+/-0.22 mm and 0.05+/-0.24 mm, respectively. This study validated cartilage thickness measurements from MR images with thickness measurements from indentation by using a novel phantom to register the image-based and laboratory-based data sets. The accuracy of the measurements was comparable to previous cartilage thickness validation studies in literature. The results of this study will aid in validating a tool for clinical evaluation of in-vivo cartilage thickness.