Imaging tissue characteristics in osteoarthritis and rheumatoid arthritis

Introduction
Rheumatoid arthritis (RA) and osteoarthritis (OA) are diseases involving synovial joints. These diseases lead to joint degeneration, but each have their own specific clinical presentation and pathogenesis. The current state-of-the-art treatment of RA includes early and intensive intervention, which is important to retard progression of tissue damage. The challenge at present is to further optimize treatment, minimizing over-treatment with unnecessary side effects and costs. In contrast, treatment of osteoarthritis (OA) is necessarily limited to conservative treatment. Eventually, surgery is to be considered if conservative therapy does not suffice. As in RA, early detection of synovitis in hand joints of patients with (erosive) hand OA, and consecutively early therapeutic intervention might be important to retard or prevent long-term joint damage and function loss. In OA patients without synovitis, joint degeneration might be a more cartilage and bone driven process, probably initiated and perpetuated by biomechanical factors. In knee joint distraction, a temporary biomechanical intervention seems to provide an intra-articular environment for joint repair. The initial boost of cartilaginous tissue regeneration potentially provides long-term structural benefit, and is able to prevent or delay the need for joint replacement. The aim of this thesis was to identify and validate tools for non-invasive assessment of tissue characteristics, in patients with RA or OA. These would be of use to better monitor disease activity, disease progression, and treatment effects.
Methods
The first part of this thesis described the validation and application of optical spectral transmission (OST) as an imaging technique to assess synovitis in RA. Additionally, the potential relevance of synovitis in OA was discussed and a first OST model for imaging synovitis in (inflammatory) hand OA was developed. The second part of this thesis showed the implementation of imaging techniques to help characterize the regenerative process initiated by KJD.
Results
OST performed very well in the assessment of hand and wrist synovitis in RA patients. Consequently, a randomized clinical trial was designed to compare conventional clinically guided and novel OST guided treatment of early RA. The first OST model for (inflammatory) hand OA performed well in the assessment of synovitis in the proximal interphalangeal (PIP) joints of OA patients. Reliability of OST measurements was high in both RA and OA patients.
Structural improvement after KJD seemed to be caused by the increased medial compartment joint space, as seen on weight-bearing radiographs, i.e. an increase in cartilaginous tissue thickness. This increased joint space even led to an improvement in axial alignment. Cartilage quality as assessed by delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), was maintained after KJD.
Conclusion
OST might facilitate tight-control and treat-to-target treatment of rheumatoid arthritis. A first OST model for imaging synovitis in (inflammatory) hand OST in OA seems promising, but the performance needs to be improved before considering clinical applicability. Imaging techniques were used to characterize the regenerative process that is initiated by KJD. Maintenance of cartilage quality (dGEMRIC) and the observed increase in radiographic joint space width (JSW) suggested that KJD was able to modify the natural course of OA.