Thats ACC record keeping for you..
At least ACC have a record of your original accident (good start).. The unfortunate part being that only the major damage.. ie primary treatment showing surgery for liver is recorded.
Accident date of 1981 also means there (should) have been lump sum payment & presumably assessments for lump sum so maybe your back was assessed then too.
A complete copy of your ACC file is a first ask.. Including schedule of claim expenses..
It is quite possible that the hospital you were treated at has a copy of your records in their archives.. You are well within your rights to ask for a copy.
Again ask other treatment providers you have seen over the years ie physios etc. They may also have records.
So at present the main task is information gathering.. Possibly your own medical records have old treatment payments from ACC.
Yes its a daunting task especially when your unable to function normally because of pain/meds..
Small steps at time..
Also there are some very good orthopaedic specialists that don't tolerate the ACC bullshit..
If you'd care to share your location.. (off board via
personal Message) if you wish we may well be able to point you to proper experts not the noddies ACC use.