Can an intense back massage cause damage to silicone implants?

You most definitely could have caused the implant capsule to be torn (closed capsulotomy) which will cause pain which may last 6 weeks, or may have even caused an implant rupture, although that is less likely.

Back massage should not cause any damage to silicone implants. As a general rule it is preferred to sleep on your back, but time spent with a massage, even deep tissue should have no impact.

Thanks for sharing your concerns with us.In my practice, after performing a breast surgery I recommend to my patients to limit the movement of the arms for two weeks. After that, you can move your arms taking care and always with common sense. In this regard, it's not advisable to carry heavy weights to prevent the implant out of position, and allow the formation of the physiological capsule around the implant, also to avoid pain and breast swelling. Respesctfully,Dr. Emmanuel Mallol.-

In general, massage won't cause an issue with breast implants. Many masseuses will have special breast "pillows" to offload pressure from the breasts during a massage and this can make it more comfortable. If an implant does have a small hole, even minimal pressure can turn that into a larger tear in the implant - massage or no massage. However, pain is not a typical symptom from an acute rupture of an implant, but rather an indication that your chest wall or muscles are sore from the massage. If you are concerned, an MRI is the imaging of choice to verify whether the implants are ruptured or not. 

Rare reason but anything is possible! Best to see your PS asap. Or seek other in person examinations from boarded PS in your area... 

Anything could happen but injury to your implant itself,unless it is very old, is unlikely.  More likely you injured soft tissues and or ribs.  Follow up with your plastic surgeon for the benefit of an examination.  Might consider not having folks walk on your back.  Best wishes