There have been many others before you who have made it through medical school with various disabilities. Schools are required to make accomodations - if that means you only scrub into cases where you can sit, so be it.
But, off the topic...I always thought Prev Med was at least 3+ years (ie, programs are either 2 years, not including an internship year [usually Prelim Med or FP], 3 years, some are combined IM/Prev Med in 4 years, and others require that you complete a full PC residency [ie, 3 years in FP, IM, etc.) before applying to their 2 year program in Prev Med.
While it does sound like those programs that are 2 years in length only consist of 1 clinical year (the first year is dedicated to research, getting your MPh), you will still have general medical training and all its physical requirements before getting into a Prev Med program.