That they are done . First, that they are done for the wrong reason and by physicians who may not be really spine trained. Most discs that they are indicated for this procedure would have resolved without surgery. The risks are the same as a standard disc surgery including infection, nerve injury, injury to other organs or structures, spinal fluid leakage/dural tear and failure to fix the problem!
Infection. The procedure is designed to cause less operative trauma to your back. Smaller holes will heal faster. You still risk getting an infection but precautions are taken. Bad response to anesthesia is another risk. Not getting better after the surgery is another risk. Results re back pain getting better are much less promising.