T1ρ/T2 mapping and histopathology of degenerative cartilage in advanced knee osteoarthritis

AIM To investigate whether normal thickness cartilage in osteoarthritic knees demonstrate depletion of proteoglycan or collagen content compared to healthy knees.METHODS Magnetic resonance(MR) images were acquired from5 subjects scheduled for total knee arthroplasty(TKA)(mean age 70 years) and 20 young healthy control subjects without knee pain(mean age 28.9 years). MR images of T1ρ mapping, T2 mapping, and fat suppressed proton-density weighted sequences were obtained.Following TKA each condyle was divided into 4 parts(distal medial, posterior medial, distal lateral, posterior lateral) for cartilage analysis. Twenty specimens(bone and cartilage blocks) were examined. For each joint,the degree and extent of cartilage destruction was determined using the Osteoarthritis Research Society International cartilage histopathology assessment system.In magnetic resonance imaging(MRI) analysis, 2 readers performed cartilage segmentation for T1ρ/T2 values and cartilage thickness measurement.RESULTS Eleven areas in MRI including normal or near normal cartilage thickness were selected. The corresponding histopathological sections demonstrated mild to moderate osteoarthritis(OA). There was no significant difference in cartilage thickness in MRI between control and advanced OA samples [medial distal condyle, P = 0.461;medial posterior condyle(MPC), P = 0.352; lateral distal condyle, P = 0.654; lateral posterior condyle, P = 0.550],suggesting arthritic specimens were morphologically similar to normal or early staged degenerative cartilage.Cartilage T2 and T1ρ values from the MPC were significantly higher among the patients with advanced OA(P= 0.043). For remaining condylar samples there was no statistical difference in T2 and T1ρ values between cases and controls but there was a trend towards higher values in advanced OA patients. CONCLUSION Though cartilage is morphologically normal or near normal, degenerative changes exist in advanced OA patients. These changes can be detected with T2 and T1ρ MRI techniques.     

Detection of early cartilage deterioration associated with meniscal tear using T1ρ mapping magnetic resonance imaging

Background

In patients with degenerative meniscal tears, subclinical cartilage degeneration may be present even if gross morphological changes are not evident. The aim of this study was to detect occult cartilage degeneration using T1ρ MRI mapping in patients with meniscal tears without obvious radiographic osteoarthritis (OA).

Methods

A total of 22 subjects with degenerative meniscal tears in the early stages of osteoarthritis [Kellgren-Lawrence (KL) grade of 0–2] and 19 healthy subjects as the control group were examined. The femoral condyle was divided into four 30° wedges (−30°–0° anteriorly, 0°–30°, 30°–60° and 60°–90° posteriorly), and each area of cartilage was further divided into superficial and deep layers of equal thickness. The tibial side was divided into anterior and posterior areas with superficial and deep layers in each. The mean T1ρ values (ms) in each area were calculated.

Results

On the femoral side, T1ρ values of the superficial and deep regions (−30°–0°, 0°–30° and 30°–60°) in the meniscal tear group were significantly higher than those in the control group [superficial (−30°–0°): 49.0 ± 4.0 (meniscal tear group) vs 45.1 ± 2.1 (control group), deep (−30°–0°): 45.2 ± 3.3 vs 39.5 ± 5.0, superficial (0°–30°): 54.5 ± 5.3 vs 47.4 ± 5.7, deep (0°–30°): 46.8 ± 4.0 vs 40.7 ± 6.3, superficial (30°–60°): 50.5 ± 3.1 vs 47.1 ± 5.7]. On the tibial side, the meniscal tear group had significantly higher T1ρ values superficially in both anterior and posterior regions compared with the control group [superficial (anterior): 52.0 ± 4.3 vs 46.7 ± 5.4, superficial (posterior): 53.1 ± 5.1 vs 46.0 ± 4.9]. Moreover, these significant differences were observed when comparing patients in the meniscal tear group with KL grades of 0 or 1 and the control group.

Conclusions

Our study suggested that early biochemical changes in cartilage associated with degenerative meniscal tears occur first in the superficial zones in areas of contact during slight flexion. Characterising the early relationship between cartilage degeneration and degenerative meniscal tears using T1ρ MRI mapping may be of clinical benefit and provide further evidence linking meniscal injury to OA.     

Human cartilage glycoprotein 39—biomarker of joint damage in knee osteoarthritis

Human glycoprotein of cartilage (YKL-40) synthesises chondrocytes and synovial cells in inflammatory conditions or remodels the outer cell matrix in osteoarthritis. The aim of this study was to conduct a parallel analysis between thickness of cartilage and length of osteophytes, ultrasound indicators of joint destruction, with levels of YKL-40 in serum in patients with primary osteoarthritis. Ultrasound findings and concentration of YKL-40(ng/ml) were examined in 88 patients. The average value cartilage thickness measured on medial condyles of the femur was 1.30 ± 0.23 mm and on lateral was 1.39 ± 0.27 mm. Median YKL-40 in patients with shorter osteophytes was 62.0 (44.5–90) ng/ml, and with longer osteophytes was 119 (range 80–171) ng/ml (p = 0.000). YKL-40 can be a marker for the appearance of longer osteophytes (sensitivity = 79.1%; specificity = 61.9%;cut off = 75.0 ng/ml). The duration of illness is very much connected to values of YKL-40 (r = 0.651, p = 0.000). After an illness duration of five years, the concentration of YKL-40 was 83.68 ± 33.65 ng/ml, after ten years it was 138.22 ± 48.88 ng/ml, and after 15 and 20 years it was 209.30 ± 79.36 ng/ml and 218.50 ± 106.51 ng/ml, respectively. Higher concentrations of YKL-40 indicate the level of cartilage destruction and can be used for assessment of destruction.

---

Résumé  La glycoprotéine YKL-40 est synthétisée par les chondrocytes des cellules synoviales lorsqu’il existe une d’inflammation et un remodelage dans l’arthrose du genou. Le but de cette étude est de faire, en parallèle, une analyse entre l’épaisseur du cartilage et la dimension des ostéophytes, les lésions constatées par échographie ainsi que le taux sérique de YKL-40 dans l’arthrose primaire du genou. L’échographie et la concentration de YKL-40 (ng/ml) ont été examinées chez 88 patients. L’épaisseur moyenne du cartilage a été mesurée au niveau du condyle interne du fémur. Elle était de 1,30 +/–  0,233 mm, au niveau du condyle externe elle était de 1,39 +/– 0,27 mm. Le taux moyen de YKL-40 des patients porteurs d’ostéophytes relativement brefs était de 62,0 (44,5–90)ng/ml, pour des ostéophytes plus longs de 119 (80–171)ng/ml (p = 0,000). Le taux sérique de YKL-40 peut donc être un marqueur de la dimension des ostéophytes avec une sensitivité de 79,1% , une spécificité de 61,9%, et un taux limite de 75,0 ng/ml. La durée de l’évolution de la pathologie est également en relation directe avec les valeurs de YKL-40 (r = 0,651 p = 0,000). Après une durée d’évaluation des lésions de moins de 5 ans la concentration d’YKL-40 est de 83,68 +/– 33,65 ng/ml, après 10 ans de 138,22 +/– 48,88 ng/ml et après 15 et 20 ans de 209,30 +/– 79,36 ng/ml et 218,50 +/– 106,51 ng/ml. Une concentration élevée de YKL-40 est donc un indicateur permettant d’évaluer le niveau de destruction du cartilage.