MDL = minimum deco limits.
Taught in GUE's DIRF (a more conservative ascent than that taught by open water agencies) The OP has presumably taken GUE's DIRF and would know this if he's working on their Tech1.
I kinda doubt the OP will be able to continue with GUE Tech2 given the medical history. They are very conservative with any kind of prior injuries and deco. You should check into this with GUE HQ.
Got it....not being totally privy to GUE's terminology it stumped me. So just how conservative are they talking...sorry for off-topic MattL...but had to ask.?