Can't a surgery be tag teamed?

Depends on the procedure. Like all other doctors, surgeons specialize and, over the course of their career, informally subspecialize into niches they become great at. As the surgery gets more complex, the number of surgeons capable of or have experience in that procedure shrink rapidly. Given that neurosurgery had ~5100 actively practicing doctors in the United States in 2014^[1] , making up 0.6% of all actively practicing doctors in the United States in 2014, the number of doctors licensed to operate in this general field is already small to begin with. It's hard to say for sure without knowing the exact procedure being performed, but it's not unheard of for only one qualified surgeon for a particularly nuanced or complex case in a very large area for something like neurosurgery. There very likely isn't anyone else that can tap in for him. You're right - the situation isn't ideal. That said, when there aren't enough qualified people to go around, what other option do you have?