Isometric Reflection Analysis of Mandible Symmetry in JIA Patients: Semi-Automatic Novel 3D Approach

This study introduces a novel semi-automated 3D approach using isometric reflection for evaluating craniofacial symmetry in patients with juvenile idiopathic arthritis. The defects caused in growing patients were analysed either bilaterally or unilaterally at the condyle head, condylar area and the whole hemimandible.

Patients were recruited according to inclusion and exclusion criteria, subsequently divided into three groups: unilateral, bilateral and healthy controls. The cone beam of each patient was segmented into three different sections for each hemimandible. The isometric reflection method was applied to each segment, allowing three-dimensional superimposition along with all the volumes.

Seventy-two patients aged 16-23 showed a mean reduction of 34.5% in condyle body volume, 34.6% in condyle head and 10.6% in the whole hemi-mandible of unilateral cases. Bilateral cases exhibited more symmetrical patterns compared to unilateral cases (5.1%-14.3%) while healthy controls showed near-perfect symmetry (2.2%-3.8%). Root mean square (RMS) and mean distance across all three mandibular sections confirmed significantly greater deviations in unilateral cases.

The new approach allowed for the visual analysis of the 3D asymmetry between the affected side and the normal side and to quantify them numerically. The unilateral involvement might inhibit growth up to the mandibular body, while bilateral involvement showed values similar to healthy controls.