The purpose of this retrospective cross-sectional study was to investigate the association between cartilage lesions assessed with 3T-MRI and remodeling of the subchondral bone detected by (99m)Tc-DPD-SPECT/CT.
(99m)Tc-DPD-SPECT/CT and MRI of 27 knees of 25 patients with chronic knee pain and risk factors for osteoarthritis (OA) were evaluated by one nuclear physician and one radiologist. Six regions of the knee (in total 162 regions in 27 knees) were assessed according to structural joint lesions graded with a modified Whole Organ MR imaging score (WORMS) and according to subchondral (99m)Tc-DPD-SPECT uptake. Relationships between regional WORMS scores and uptake were quantified using general estimating equations. In a secondary analysis the uptake sum with the WORMS sum per joint was compared using Spearman correlations.
Elevated subchondral uptake was significantly associated with the grade of cartilage lesions (P < 0.0001). Mean uptake was significantly higher subjacent to full thickness cartilage lesions compared to partial thickness lesions (P < 0.0001). A similar association was observed between bone marrow edema pattern (BMEP) and cartilage lesions. The sum of uptakes per joint was positively correlated to the WORMS sum (rs = 0.42) and to the sum of cartilage lesions per joint (rs = 0.50).
Both functional and structural changes of the subchondral bone in terms of scintigraphic osseous activity and the presence and degree of BMEP were significantly associated with cartilage lesions in patients with OA of the knee. This association was pronounced with full thickness lesions, indicating a possible protective effect of the cartilage layer for the subjacent bone.