Max Hurd suffered a broken neck, five fractures in his back, extensive bruising and brain damage after the accident on December 5, the day after his 17th birthday, onthe Deliverance Cove track, in Wairarapa.
A CT scan this month revealed a disc had collapsed and his neck was healing incorrectly.
Doctors removed the crushed disc, replacing it with a bone graft taken from a cadaver, and put a metal plate in front of the damaged vertebrae to hold them in place.
The young man will spend six more weeks recovering in a soft brace before he finds out if he can remove his neck collar for good.
