Osteochondral Abnormalities on Three-Dimensional Ultrashort Echo Time MRI Scans Are Associated with Knee Cartilage Degradation

Rheumatology and Immunology Orthopedics Medicine Medical Imaging
osteochondral abnormalities knee cartilage degradation three-dimensional ultrashort echo time MRI osteochondral junction abnormalities cartilage degradation grade

Osteochondral Abnormalities on Three-Dimensional Ultrashort Echo Time MRI Scans Are Associated with Knee Cartilage Degradation

Academic Background

Osteoarthritis (OA) is the most prevalent musculoskeletal disease, characterized by pain and disability. A hallmark of OA is the progressive loss of articular hyaline cartilage, which connects to the subchondral bone plate (SBP) through a calcified cartilage layer (CCL). These layers collectively form an osteochondral unit that transitions into the subchondral trabecular bone. Articular cartilage is avascular and nourished by diffusion from synovial fluid or blood vessels in the subchondral bone, making CCL permeability crucial for cell growth and tissue repair. Studies using animal models and cartilage specimens from patients with OA have shown that early stages of OA involve structural alterations in the CCL, beginning with vascular penetration in microcracks and fissures along the osteochondral junction (OCJ). Therefore, identifying changes at this junction could improve the general understanding of OA pathophysiology.

MRI is useful in evaluating articular cartilage. However, CCL has a short T2 due to its bound water and dense collagen structures that restrict proton mobility. Conventional MRI sequences cannot capture the short T2 signals from the CCL, making it difficult to detect pathologic changes within the CCL and distinguish them from the low signal intensity of the SBP. MRI with ultrashort echo-time (UTE) sequences has been used to overcome this limitation. UTE imaging of patellar cartilage–bone specimens has demonstrated that both the CCL and the deep layer of uncalcified cartilage exhibit a high signal, distinct from the low signal of the SBP. In another study involving in vivo normal patellar samples from volunteers, the normal OCJ exhibited a well-defined smooth high signal, representing the deep uncalcified cartilage and CCL. However, the OCJ in cadaveric knee joints and in patients with OA typically shows an ill-defined high signal in the CCL. Therefore, it is clinically important to investigate changes in the CCL and SBP with cartilage degradation observed at conventional MRI.

Research Objective

The purpose of this study was to compare abnormalities in the CCL and SBP, observed at 3D UTE MRI, with cartilage degradation and OCJ abnormalities depicted using proton-density fast spin-echo sequence with fat suppression (PDFS) MRI.

Research Team and Publication Information

This study was conducted by a research team from Hanyang University Hospital, Hanyang University Guri Hospital, Eunpyeong St Mary’s Hospital, and the University of California, Davis. The primary authors include Sunmin Lee, Yeo Ju Kim, Seunghun Lee, and others. The study was published in December 2024 in the journal Radiology.

Research Methods

Participant Selection and Study Design

This prospectively designed study was approved by the review board of Inha University Hospital. Between April 2018 and March 2019, 143 participants were enrolled and underwent routine knee MRI with an additional sagittal 3D UTE MRI examination for chronic knee pain. The MRI scans were retrospectively analyzed by two musculoskeletal radiologists independently and at consensus. Cartilage degradation grades and OCJ abnormalities were evaluated at PDFS MRI. Calcified cartilage and SBP abnormalities were assessed at 3D UTE MRI by considering the location of cartilage degradation.

Image Analysis

Two radiologists independently analyzed PDFS MRI images, grading cartilage degradation using the modified Noyes classification and assessing OCJ abnormalities, including subchondral bone marrow edema-like lesions, subchondral cysts, and central osteophytes. Subsequently, they evaluated CCL and SBP abnormalities on 3D UTE MRI images and compared them with PDFS MRI results.

Statistical Analysis

Spearman rank correlation analysis was used to assess the relationship between cartilage degradation grade and abnormalities of CCL and SBP. Logistic regression models were used to analyze the association between OCJ abnormalities on PDFS MRI scans and CCL and SBP abnormalities.

Research Results

Participant Characteristics

A total of 143 knees (71 right and 72 left knees) from 143 participants (mean age, 50.8 years ± 17.6 [SD]; 72 male and 71 female participants) were analyzed. On 3D UTE MRI scans, calcified cartilage defects showed a moderate positive correlation with the cartilage degradation grade (ρ = 0.49–0.52; p < .001). Calcified cartilage thinning (ρ = 0.2–0.3; p < .001), SBP irregular thickening (ρ = 0.3–0.35; p < .001), and defects (ρ = 0.34–0.42; p < .001) exhibited a weak positive correlation with the cartilage degradation grade. OCJ abnormalities depicted at PDFS MRI were associated with calcified cartilage and SBP abnormalities (p < .05).

Key Findings

  1. Association between CCL and SBP abnormalities and cartilage degradation: Calcified cartilage defects, thinning, and SBP irregular thickening and defects were positively correlated with cartilage degradation grades, indicating that these abnormalities play a significant role in the progression of OA.
  2. Association between OCJ abnormalities and CCL and SBP abnormalities: OCJ abnormalities depicted at PDFS MRI were significantly associated with CCL and SBP abnormalities on 3D UTE MRI, further supporting the critical role of CCL and SBP in OA.

Research Conclusion

This study demonstrated that CCL and SBP abnormalities on 3D UTE MRI were associated with cartilage degradation and OCJ abnormalities depicted at PDFS MRI. These findings provide new insights into the pathophysiology of OA and suggest that 3D UTE MRI can be an effective tool for evaluating CCL and SBP changes in OA.

Research Highlights

  1. Innovation: This study is the first to apply 3D UTE MRI to evaluate CCL and SBP, overcoming the limitations of conventional MRI in detecting these structures.
  2. Clinical significance: The results indicate that CCL and SBP abnormalities are closely related to the progression of OA, providing new directions for early diagnosis and treatment.
  3. Multidisciplinary collaboration: This study combines knowledge from radiology, orthopedics, and biostatistics, demonstrating the importance of multidisciplinary collaboration in medical research.

Research Value

The scientific value of this study lies in revealing the important role of CCL and SBP in OA and providing new directions for future research. Additionally, the application of 3D UTE MRI offers clinicians a new tool to more accurately assess the progression of OA, enabling more personalized treatment plans for patients.

Future Research Directions

Future studies could expand the sample size, include more knee subregions and different types of joints, and incorporate pathological analysis and longitudinal studies to validate the findings of this study and explore the specific mechanisms of CCL and SBP in OA.

Through this study, we have deepened our understanding of the pathophysiology of OA and provided new tools and methods for clinical diagnosis and treatment. The application of 3D UTE MRI is expected to become an important means of assessing OA in the future, bringing better treatment outcomes for patients.