Why is spine surgery so expensive?

Spine surgery shouldn't be expensive but large out of pocket gap payments exist for reasons that are not really under our control. Firstly, most spine surgery these days involves a number of small operations, using different incisions, performed under the same anaesthetic or on different days. Most patients do not know this but whenever a surgeon performs a second incision / surgery the rebate from Medicare drops to 50% and sometimes 25%. Surgeons are simply not able to work for 25% of a government rebate fee. Secondly the recent freeze on rebate fees for 4 years or more has led to a complete inability to not charge a gap payment.