MRI-based Morphometrics of hand+wrist Joint Spacing in a Patient with Juvenile Idiopathic Arthritis

Background: Juvenile idiopathic arthritis (JIA) is a subtype of rheumatic polyarthritis. Pathophysiology of JIA is defined by the abnormal activation of both the cell-mediated and humoral immune response, leading to the degradation of joint synovium, cartilaginous structures, and bone. MRI can be utilized to visualize joint morphology changes from the effects of JIA. The full efficacy of MRI to evaluate bone erosion in the early stages of JIA is unknown; thus, our case report aims to understand this potential.

Methods: A 23-year-old Caucasian female with an 11-year history of JIA autonomously participated in our study. We utilized T1 weighted MRI to retrieve images of the patient’s right hand. Software programs Horos and Slicer allowed for analysis and full 3D volume rendering of series coronal and sagittal plane images. Then, bone morphology and distance evaluation between articular surfaces of variable carpal joints were examined. Joints analyzed included radiocarpal, ulnocarpal, and distal radioulnar. Joint spaces between radius-scaphoid, radius-lunate, ulnar-lunate, and ulnar-triquetrum were also measured. Lastly, individual phalangeal joint spaces were captured of digits I-V (metacarpophalangeal, proximal interphalangeal, distal interphalangeal). We approximated mean distances by averaging six transects with equivalent spacing between them within each joint.

Results: The smallest measurement in both the sagittal and coronal planes was 0.778 mm in the fifth digit DIP joint in the coronal plane, followed by the first digit MCP joint in the sagittal plane at an average spacing of 0.787 mm. Several other spaces measured under 1 millimeter. In the coronal plane, the PIP joint on the third digit measured 0.973 mm, the PIP on the fourth digit 0.839 mm, and the DIP on the fourth digit 0.954 mm. In the sagittal plane, the PIP on the second digit 0.862 mm, the DIP on the third digit 0.993 mm, the DIP on the fourth digit 0.819 mm, the PIP on the fifth digit 0.881 mm, and the DIP on the fifth digit 0.830 mm. The greatest spacing between bones occurred in the coronal view between the ulna and triquetrum bones at 8.831 mm, followed by the ulna and lunate joint space at 5.536 mm. Other carpal bone spacings in the coronal view were 2.727 mm for the radius and scaphoid joint space, 2.478 mm for the radius and lunate joint space, and 2.253 mm for the distal radioulnar joint space.

Conclusion: This case demonstrates the potential for routine joint imaging in patients with JIA to monitor for treatment efficacy and changes in morphology secondary to inflammatory processes. Early detection of bone erosion through MRI can determine dosage variability, the type of treatment course, and a better prognosis in preventing further joint damage. Extensive research in inflammatory polyarthritis is currently underway with novel studies focusing more on improving comprehensive treatment for future cases of pediatric rheumatic disease. Further imaging from our ongoing research may provide better insight into the progression of JIA and its transition into other fulminant, inflammatory arthritic conditions.