Morphologische und funktionelle Knorpeldiagnostik

[Osteochondral fractures in childhood and adolescence]

BACKGROUND

Osteochondral fractures (OCF) are traumatic shearing injuries to portions of cartilage and bone. The most common cause is patellar dislocation, with the main localisation being the medial patellar facet and the lateral femoral condyle. They can occur in all age groups.

DIAGNOSIS

Clinically, there is a painful knee joint effusion (haemarthrosis) with a "dancing patella". This is usually accompanied by restricted movement and/or a locking phenomenon. In addition to the standard X‑ray of the knee in three planes (lateral, anterior-posterior and tangential patella), an MRI should be performed promptly in the case of haemarthrosis and suspicious symptoms, as concomitant injuries are present in up to 70% of cases.

TREATMENT

The aim of treatment is to restore joint congruence in order to prevent the risk of secondary osteoarthritis. Small chondral and stable osteochondral fractures can be treated conservatively. Surgery is indicated for all other OCFs. In addition to refixation with various materials (bioresorbable screws, bone plugs, suture material and Kirschner wires), cartilage regeneration procedures (AMIC, MACI, OAT, etc.) are available for late diagnosed or non-refixable fragments. However, the number of cases is small.

CONCLUSION

Osteochondral fractures are rare injuries in children and adolescents. Prompt MRI is recommended for diagnosis in cases of suspected OCF. Refixation is the preferred treatment method, with bioresorbable implants showing promising results in reducing the need for additional surgery. The risk of secondary osteoarthritis can be reduced with regular treatment.

[Chondral and osteochondral defects : Representation by imaging methods]

Morphological imaging of cartilage at high resolution allows the differentiation of chondral and osteochondral lesions. Nowadays, magnetic resonance imaging is the principal diagnostic tool in the assessment of cartilage structure and composition. Conventional radiography, computed tomography, ultrasound or optical coherence tomography are adjunct diagnostic modalities in the assessment of cartilage pathologies. The present article discusses the up-to-date diagnostic practice of cartilage imaging in terms of its scientific basis and current clinical status, requirements, techniques and image interpretation. Innovations in the field such as functional MRI are discussed as well due to their mid- to long-term clinical perspective.

Glycosaminoglycan chemical exchange saturation transfer at 3T MRI in asymptomatic knee joints

BACKGROUND

Biochemical alterations such as glycosaminoglycan (GAG) depletion occur early in the course of osteoarthritis, but cannot be detected with standard magnetic resonance techniques. With glycosaminoglycan chemical exchange saturation transfer (gagCEST), a biochemical imaging technique, it is feasible to detect biochemical components in knee joint cartilage.

PURPOSE

To establish baseline values for gagCEST magnetic resonance imaging (MRI) in knee joint cartilage at 3 Tesla (T).

MATERIAL AND METHODS

Twenty volunteers (8 women, 12 men; mean age, 24.55 ± 2.35 years;age range, 21-29 years) with no history or clinical findings indicative of knee joint pathologies underwent MRI at 3T. The imaging protocol included three-dimensional (3D) double-echo steady-state sequence for morphological cartilage assessment and a prototype 3D CEST pulse sequence to evaluate the CEST effects in six cartilage regions of the knee joint: (i) lateral femoral condyle; (ii) medial femoral condyle; (iii) lateral tibial plateau; (iv) medial tibial plateau; (v) patella; and (vi) trochlea. We used the asymmetry of the magnetization transfer ratio (MTRasym) parameter to quantify the gagCEST effects in these regions.

RESULTS

Regional differences revealed high MTRasym values in the patellar (1.62% ± 1.19%) and the trochlear (1.17% ± 1.29%) cartilages, and low MTRasym values in the medial femoral condyle (0.41% ± 0.58%) and the lateral tibial plateau (0.52% ± 0.53%) cartilages.

CONCLUSION

Regional differences in the gagCEST values must be considered when conducting gagCEST imaging of knee joint cartilage. In the future gagCEST imaging may be an additional feature in the evaluation of the biochemical composition of knee joint cartilage.