Decomposition of higher-order Wright convex functions revisited

In 2009, Maksa and P'ales established an extension of the decomposition theorem of Ng in the context of higher-order convexity notions. They proved that a real function is Wright convex of order $n$ if and only if it can be decomposed as the sum of a convex function of order $n$ and a polynomial function of order at most $n$. Their proof was based on transfinite tools in the background. The main purpose of this paper is to adopt the methods of a paper of P'ales published in 2020 and establish a new and elementary proof for the theorem of Maksa and P'ales.