Hello Mark,
Your Contorted Filbert is propagated by budding or grafting the "contorted" part onto a normally growing Filbert plant and later removing all the normal shoots. What you are seeing are shoots coming from the normal Filbert root system and should be removed as soon as you see them. This pruning should be done as close to the soil surface or slightly below. The contorted portion is slower growing and when the plant has "extra" food, it will spout new growth from the root system as a way to utilize that food. You would rather force that energy into new growing points on the contorted portion.
Sincerely, Richard Hentschel