Graham Laycock was subjected to a three-hour assault after he was left unsupervised on a hospital ward with his tormentors. Laycock, 17, was cut with razor blades and stabbed with a dirty hypodermic needle, Newcastle upon Tyne Crown Court was told.
The incident happened at Deerbolt young offenders' institution, in Barnard Castle, Co Durham, after staff had closed the ward for the night.
Laycock, of Doncaster, South Yorkshire, who was on the ward recovering after a suicide attempt, was held down by two youths while another tried to pull a vein out of his arm with a pencil. The attack went unnoticed despite prison authority claims that the ward was checked every 30 minutes.
Kris Lindsay, 17, of Spennymoor, and Gavin Taylor, 19, of Wingate, both Co Durham, were convicted of wounding with intent and sentenced to a further two years in a young offenders' institution. Alan Dugdale, 18, of Heaton, Newcastle, was sentenced to 12 months in a young offenders' institution for wounding, along with nine months for burglary.