Background Total knee joint replacement (TKR) is a cost-effective procedure with good long-term outcomes. However, there is no clear consensus on indications for TKR. Subchondral bone marrow lesions (BMLs), have been identifiied as important disease features relevant for not only clinical disease manifestations such as pain but also for structural progression. Thus, BMLs are promising biomarkers for structural progression to important clinical outcomes such as TKR.
Objectives The aims of this study were therefore to test whether presence and size of BMLs were associated with increased odds of TKR, and if worsening of BMLs over time is also associated with TKR.
Methods We studied 121 knees from OAI participants (age 45-78 years) that underwent TKR before the 48 month visit for the time point prior to TKR, i.e. “T0” (i.e. for a TKR reported at the 48 month (M) visit, T0 =36M and T-1 =24M) and 121 control knees that did not undergo TKR that were matched for radiographic disease stage, gender, and age and were assessed at the same T0 and T-1 follow-up visit. Images were acquired at four OAI clinical centers using dedicated 3 T scanners. MRIs were read for subchondral BMLs in 14 articular subregions using the semiquantitative MOAKS system. Only BML size, which is scored from 0-3, was considered in the analyses. Analyses were performed on a plate (medial tibia, medial femur, lateral tibia, lateral femur, trochlea, patella) and compartmental level (medial tibio-femoral joint [TFJ], lateral TFJ and patello-femoral joint – [PFJ]). Conditional logistic regression was applied to assess the risk of TKR in regard to maximum BML size per plate at T0. In addition, the number of subregions per compartment showing BML worsening from the time point prior T0 (=T-1) to T0 was analyzed in regard to risk for TKR following T0.
Results Subjects were on average 65.3 years old (SD ± 8.6), predominantly female (58.1%) and overweight (mean BMI 29.6 SD ± 4.9). The odds for TKR were significantly increased for the group exhibiting large (i.e. grade 3) BMLs in the medial compartment when compared to the knees without BMLs at T0 as the reference (unadjusted OR 2.62, 95% confidence interval [CI] 1.16-5.91 for medial tibia, and 2.35, 95% CI 1.10-5.00 for medial femur, respectively). Further, the odds for TKR were significantly increased for knees with ≥3 subregions exhibiting increase in BML size in the medial TF compartment from T-1 to T0 compared to knees with no subregions showing worsening (OR 3.35, 95%CI 1.14-9.82). No significant associations were found for the lateral TFJ and PFJ and respective plates cross-sectionally or longitudinally.
Conclusions On a plate-level analysis, presence of large BMLs in the medial femur and/or tibia at the time point prior to TKR suggests increased risk of TKR, while presence of large BMLs in the lateral TFJ or in the PFJ does not. Worsening of BML size in ≥3 subregions in the medial TF compartment from T-1 to T0 also indicates increased risk for TKR when compared to knees without worsening in any subregion in the same compartment.
Disclosure of Interest F. Roemer Shareholder of: Boston Imaging Core Lab (BICL),LLC., Consultant for: Merck Serono, NIH, C. Kwoh Consultant for: Novartis, D. Hunter Grant/Research support from: Australia Research Council Future Fellowship, Consultant for: DonJoy, NIH, Stryker, R. Boudreau: None Declared, M. Hannon: None Declared, F. Eckstein Shareholder of: Chondrometrics, Z. Wang: None Declared, M. John Employee of: Novartis, A. Guermazi Shareholder of: Boston Imaging Core Lab (BICL),LLC., Consultant for: Astra Zeneca, Genzyme, Novartis, Stryker,Merck Serono
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