Capsular contracture remains the most common reason for women having a revisionary breast surgery.
Even when a surgeon does everything perfectly, employing all we know about avoiding contractures, it can still happen.
It is normal to form a capsule - a thin membrane - around the implant. It should stay thin and pliable. But if there is inflammation around the implant, it can thicken, stiffen, and tighten.
The key is to avoid the inflammation. Many things can cause it, such as trauma at the time of surgery and bacteria. Studies today demonstrate that bacterial contamination may be the most profound avoidable cause of contracture.
Your surgeon should employ a method that minimizes trauma to your tissue, lessening the duration of your mobility and inflammation, thereby allowing you easier motion earlier on. He or she should also give you approriate antibiotics as well as antibiotic irrigation of the implant and pocket during surgery.
And one more thing --your quesiton implied a difference between saline and silicone with regards to capsular contracture. While that may have been true with implants in years gone by, that has not been found to be true with the current generation of silicone implants.
Find a surgeon that is well-versed in the issues of contraction and can explain to you why they believe it occurs and how they avoid it. But be careful of those that say "i never get it!" That's impossible! You want your surgeon to demonstrate both a healthy respect for this problem as well as a thoughtful strategy for how they deal with it.