What makes an operation "minimally invasive"? The doctor says my spinal fusion will be minimally invasive. Seems like any time a person goes under the knife it should be considered invasive.
We have to keep in mind the orthopedic surgeon's point of view. Cutting someone open with a 12-inch incision and using retractors to pull the soft tissue apart is invasive. The muscles are completely cut through. Sometimes the surgeon saws a bone in half to remove diseased bone. That is invasive.
Making a two or three inch incision and using tiny instruments to perform the operation is much less invasive. The surgeon uses special X-ray guidance. There's much less blood loss and shorter operating times. Often the patient goes home the same (or next) day.
These days spinal fusion can be done with a much smaller incision and less damage to the muscles, ligaments, and nerves. The term "invasive" is really relative compared to the past ways of doing this operation.