A patient previously had a TMA and I had to go back and resect more bone at the TMT area for each ray is this now a CPT 28800 Chopart amp?

I billed 28800, Chopart amputation, because I resected the 1st metatarsal all way back to medial cuneiform cartilage and then remodified the 2nd-5th metatarsal resections to re-establish a better parabola. I had billed this as a CPT 28800, but now the insurance reviewed my operative report and denied the claim, why?