Performance of the Aptis distal radioulnar joint implant: kinematic and geometric analysis

This study reviews the performance of the Aptis distal radioulnar joint arthroplasty by comparing multiple kinematic and geometric measurements in the operated and contralateral healthy forearm to elucidate whether these are altered after arthroplasty. Forearm geometry and motion were captured using 3-D and 4-D computed tomography in 12 patients with unilateral Aptis arthroplasties. After segmentation and registration, the axis of forearm rotation, translation of the radius along the ulna and range of wrist flexion-extension were measured, and the Dice coefficient and Hausdorff distance were calculated. The forearm rotation axis in the corrected arm deviated 2.3° from the healthy contralateral rotation axis, radial translation along the ulna decreased by 45% and wrist flexion-extension also decreased significantly. Multiple intra-individual geometric differences were observed. The Aptis distal radioulnar joint arthroplasty considerably alters forearm kinematics, which can have clinical implications.<b>Level of evidence:</b> IV.