LAUSR

OBJECTIVE To evaluate the contact area of the radio-capitellar joint with forearm pronation and supination under axial loading. MATERIALS AND METHODS Six healthy volunteers (2 males and 4 females, mean age 44.6 years) were included in the study. CT scan of the extended elbow joints was obtained at four positions of forearm: full pronation with or without load, and full supination with or without load. Mimics, 3-matic Medical, Geomagic, and Photoshop were used to reconstruct 3-dimensional models. The contact area of radio-capitellar joint was measured. Shifting of the center of the contact area of radio-capitellar joint was measured. RESULTS The axial load added 8.6% and 10.5% contact area to pronation and supination without load, respectively. From pronation without load, the center of contact area significantly shifted 2.4±1.1mm anteromedially to supination without load and shifted by 1.0±0.5mm to the center of the radial head compared with the pronation with load. The center of the contact area significantly shifted 2.4±1.5mm anteromedially from the pronation to the supination under loading. The contact area of the tuberosity anterior in radial head significantly increased 14% (without load) and 8% (with load) from pronation to supination. CONCLUSION Axial loading increases the contact area of the radio-capitellar joint. The center of the contact area of the radio-capitellar joint changed according to loading and shifted to the anterior tuberosity of the radial head from forearm pronation to supination. LEVEL OF EVIDENCE Basic Science Study; Kinematics.