Unveiling MRI-based structural phenotypes in temporomandibular joint osteoarthritis: implications for clinical practice and research

Abstract

Introduction: Osteoarthritis (OA) is a progressive degenerative disease characterized by the gradual degradation of cartilage, remodeling of subchondral bone, synovitis, and chronic pain. This condition impacts various large and small joints, including the temporomandibular joint (TMJ). However, addressing OA, particularly in impeding or reducing disease progression, is challenging due to its clinical and imaging heterogeneity. Authors are increasingly suggesting that this heterogeneity involves different phenotypes or subpopulations, discernible by variations in the disease's pathophysiology and structural manifestations. Even within the TMJ, these phenotypes may display distinct clinical features, laboratory parameters, biochemical markers, and imaging criteria. Recent research has proposed MRI as a reference standard for TMJ OA, highlighting its substantial agreement with histopathological changes. MRI-based phenotypes offer a promising avenue for understanding disease progression and treatment response, potentially providing valuable insights for prognosis and treatment planning.

Objective: This article introduces the ROAMES-TMJ (Rapid OsteoArthritis MRI Eligibility Score for TMJ) to assess the structural eligibility of individuals for inclusion in TMJ OA clinical trials.

Figure 1:. Cartilage erosive phenotype: a loss of continuity of the articular cortex of the condyle can be observed. A) Referential temporomandibular joint MRI sagittal T1-weighted image. B) Temporomandibular joint scheme. Adapted from ROAMES - Rapid OsteoArthritis MRI Eligibility Score (Source: Roemer et al., 2020).

Figure 2:. Hypertrophic phenotype: a marginal hypertrophy with sclerotic borders and exophytic angular formation of osseous tissue arising from the surface of the condyle (osteophyte) can be observed. A) Referential temporomandibular joint MRI sagittal proton density image. B) Temporomandibular joint scheme. Adapted from ROAMES - Rapid OsteoArthritis MRI Eligibility Score (Source: Roemer et al., 2020).

Figure 3:. Bone phenotype: a bone marrow lesion in the condyle, and an irregularly condylar head and/or articular fossa contour. A) Referential temporomandibular joint MRI sagittal T2-weighted image. B) Temporomandibular joint scheme. Adapted from ROAMES - Rapid OsteoArthritis MRI Eligibility Score (Source: Roemer et al., 2020).

Figure 4:. Inflammatory phenotype: a bright signal inside the joint spaces that has a convex configuration in the anterior and/or posterior recesses, and an irregularly condylar head and/or articular fossa contour. A) Referential temporomandibular joint MRI sagittal T2-weighted image. B) Temporomandibular joint scheme. Adapted from ROAMES - Rapid OsteoArthritis MRI Eligibility Score (Source: Roemer et al., 2020).

Figure 5:. Proposed flow chart for intra-articular injection therapy: Once TMJ OA diagnosis is confirmed, through patient history, physical examination, and MRI images, the presence or absence of joint effusion will determine the need for lavage and anti-inflammatory medications. In cases where joint effusion is absent, an assessment of the TMJ OA stage of progress should be conducted. If only cartilage erosion or both cartilage and bone erosion are observed, hyaluronic acid or injectable platelet-rich fibrin should be selected, respectively. If joint effusion is present, the location of the signal on MRI (i.e., in the superior or inferior joint spaces) will determine the space subjected to joint lavage under arthrocentesis. Following superior joint space arthrocentesis, the selection of intra-articular injection therapy will depend on the presence of primary inflammatory effusion (inflammatory phenotype) or secondary inflammatory effusion (other phenotypes), with corticosteroid or hyaluronic acid being chosen, respectively. In cases where joint effusion is observed in the inferior joint spaces of the TMJ, after arthrocentesis, intra-articular therapy should be selected based on the TMJ OA stage of progress, as previously described.