As there is a deterministic correspondence between the points of the predicted (as the source) and the post-surgery PCL (as the target) for each patient, the evaluation metric can be defined by the Euclidean point-wise distance (p2p). Denoted in Equation (3), the point-wise distance evaluates the performance of the regression model, since it measures the amount of displacement of each pair of points regardless of the total PCL displacements. Less distance means the regression model predicted the coordinate of each point closer to its expected location.