The O-arm is essentially an intra-operative CT scanner with the capacity for navigation.
We use this technology as follows:
1. A reference frame is attached to the bone during surgery.
2. The O-arm scan is obtained.
3. The instruments are registered. Wherever the instrument tip is placed in the patient will now show up on the CT scan, allowing us to know its precise location.
4. The registered instruments are used to place the hardware.
5. A second O-arm scan is obtained prior to closure.
Using the O-arm, we can safely and accurately place screws just about anywhere we need to in the spine. We can confirm before leaving the OR that everything is properly positioned.
I have not had to go back to the OR yet in my practice for misplaced hardware.