Some tour players I can think of that have/had back trouble are...
George Archer
Paul Azinger
Michael Bradley
Fred Couples
Ernie Els
Hale Irwin
Peter Jacobsen
Davis Love
Jack Nicklaus
Frank Nobilo
Payne Stewart
Lee Trevino
Fuzzy Zoeller
Some that have played/playing for many years with little or no injury that I have heard of...
Sam Snead
Gary Player
Craig Stadler
Nick Price
Miller Barber
Jay Haas
Raymond Floyd
Chi Chi Rodriguez
Dana Quigley
Do you think the difference is technique, genetics, posture, conditioning... or other factors?
Well ...you got Stads and Gary Player in the healthy column...so I think the "conditioning theory" is out the window...but I could believe genetics and perhaps style....
BTW...I know the only conditioning Stads enjoys is Duck Hunting in South America and working out with 12 ounce curls...