Impact of Bone Marrow Edema-Like Signals on Outcomes Following Cartilage Repair
Overview
This five-year follow-up study evaluated bone marrow edema-like signals (BMELS) in 45 patients after knee cartilage repair using microfracturing (MFX) or matrix-induced autologous chondrocyte implantation (MACI). BMELS were categorized by their progression and correlated with clinical outcomes and cartilage tissue composition using MRI and T2 mapping.
Background
Cartilage lesions pose a significant treatment challenge, commonly addressed by MFX and MACI procedures. BMELS are frequently observed postoperatively, but their clinical significance remains debated. Some evidence suggests BMELS may represent normal healing early on, while persistent or atypical BMELS could predict poorer outcomes such as osteophyte or cyst formation. This study aimed to clarify the role of BMELS over a long-term follow-up and their association with clinical and morphological outcomes.
Data Highlights
Parameter
Time Points
Assessment Method
Findings
BMELS Presence and Size
3, 12, 60 months
Fat-suppressed PD MRI, size measured longitudinally and transversely
BMELS classified as minor (<50% repair tissue diameter) or severe (>50%) with excellent interrater reliability (kappa=1, ICC>0.99)
T2 Mapping Ratios
3, 12, 60 months
T2 values of repair tissue vs. reference femoral cartilage
Used to assess compositional changes in cartilage repair tissue
Clinical Scores
Multiple postoperative points
KOOS and subjective IKDC scores
Correlated with BMELS categories and morphological scores
Key Findings
BMELS were observed in a subset of patients post cartilage repair, with three distinct progression patterns: no edema, typical diminishing edema, and atypical edema (including new or increasing lesions).
Typical BMELS tended to decrease in size over time, whereas atypical BMELS showed variable or worsening patterns.
Persistent or atypical BMELS were associated with poorer morphological outcomes on MOCART 2.0 scoring and potential compositional cartilage changes indicated by T2 mapping.
Clinical outcome scores (KOOS and IKDC) correlated with BMELS progression, with atypical edema linked to less favorable patient-reported outcomes.
Interrater reliability for BMELS detection and size measurement was excellent, supporting the robustness of MRI assessment methods used.
Clinical Implications
Monitoring BMELS via MRI and T2 mapping after cartilage repair can provide valuable prognostic information. Typical diminishing BMELS may reflect normal healing, whereas persistent or atypical BMELS warrant closer clinical attention due to their association with poorer morphological and clinical outcomes. These findings support integrating BMELS assessment into postoperative evaluation protocols to guide patient management and rehabilitation.
Conclusion
This study demonstrates that the presence and progression pattern of BMELS after cartilage repair significantly influence morphological and clinical outcomes over five years. Differentiating typical from atypical BMELS can aid in predicting long-term success of cartilage repair procedures.
References
Magnetic Resonance Observation of Cartilage Repair Tissue Scoring System (MOCART) 2.0 -- 6
Knee Injury and Osteoarthritis Outcome Score (KOOS) and IKDC Scores -- 7,8
by Felix R. M. Koenig, Marcus Raudner, Vladimir Juras, Pavol Szomolanyi, Veronika Vetchy, Jakob Kittinger, Ehsan Safai Zadeh, Martin L. Watzenböck, Siegfried Trattnig
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