Ms Spicer's injuries included puncture wounds to her neck/upper chest and back, a broken left wrist, lacerations to both hands with nerve damage and lacerations to both legs.
She also suffered a partial lung collapse and concussion with significant memory loss. She had two operations to repair the left wrist fracture and may need a third.
Ms Spicer needs ongoing physiotherapy to regain use of her hands, the court heard.
Crown prosecutor Hayley Sheridan argued a prison sentence of 11 to 12 years was warranted given the "extreme, prolonged violence" before any discount for his guilty plea.
The prisoner had attempted to shift blame for the attack to the victim and he had shown little remorse, she said.
Mrs Sheridan also submitted a minimum non-parole period of 50 to 60 per cent was needed as an added deterrent and to protect the community from Spicer.
Spicer's lawyer, Bruce Hesketh, argued a minimum non-parole period was not needed, given his client had no prior history of violence and was a first-time offender.
References from friends and others who had known him for 30 years spoke positively about Spicer's character and described him as "hard-working", he said.
"It's fair to say it appears emotions were running high at the reunion but, whatever the catalyst was, this man snapped on the day and pleaded guilty at the first opportunity."
Mr Hesketh said there were no winners in this case.
"Everyone lost from what happened," he said.
Sentencing Judge David Cameron told Spicer this was clearly "premeditated, sustained violence" against a woman who would have feared for her own safety.
"I'm satisfied a minimum non-parole period is necessary to hold you accountable for this despicable act and deter other like-minded individuals from this sort of offending."
Judge Cameron also granted a protection order in favour of Ms Spicer.
Family members seated in the public gallery began clapping when Judge Cameron imposed the jail sentence on Spicer, who appeared in court via audio-visual link from prison.
Outside court, Brenda Spicer told the Bay of Plenty Times Weekend that despite the vicious attack and the lasting impacts she does not want to be described as a victim.
"I'm a survivor and just want to focus on my recovery which is going to a very long road ahead, and I may never get back full use of my hands," she said.
Ms Spicer said she struggled to come to terms with her brother's attack.
"I still have no memory of the attack, but I knew instantly when I woke up it was Shane.
"When I woke up in hospital, my legs looked like someone had taken to them with an apple corer, and it was quite numbing when I was told the extent of all my injuries," she said.
"I was horrified and didn't think the doctors could put me back together again."
Ms Spicer said she only got the casts off her arms a couple of weeks ago. She returned to part-time work three weeks ago.
Ms Spicer said she was speaking to the newspaper because she wanted her brother to be held publicly accountable for his actions.
"It's very important as it does not appear to me that Shane is even sorry for what he has done. Shane is no longer part of our family."
Ms Spicer said her brother Shane was not safe to be around.
"I don't ever want to see him again."
