Osteomyelitis S/P hypophysectomy

I had a transphendoidal hypophysectomy 26 years ago.  Three years ago a petrified fungal mass was found in the sella (thought to have been there since the former surgery. This had been 'assumed' to have been anatomical surgical changes when former ENT surgeons and ER docs/radiologists looked at subsequent CT scans and MRI scans. The mass was partially removed in 2005. Sphenoid sinusitis persisted. The fungal mass in the sella was completely removed, then successfully in Nov. 2006. Immediate acute bouts with sinusitis, bronchitis and uncontrolled asthma followed repeatedly over the course of the next 6 months. In June 2007, I was returned to surgery where the neurosurgeon removed/debrided and irrigated osteomyelitis in sella/sphenoid (being told that a piece of the residual debris from the Nov. 2005 surgery embedded in that area). After posting a question on this forum, I did follow the recommedations and was referred to an Infectious Disease specialist. Whereas I thought I had understood the osteomyelitis to have been removed, the ID suggests that the organism can be deeper seated and kind of like in remission? (or waxes/wanes in other words), and that the 2 organisms that were cultured from my sphenoid Dec. 2007 (same as in the cultures from the surgery--one Staph Aureus, other a fungus found in immunocompromised people) may in fact not be able to be treated if they are determined to be 'chronic' (and given my multiple allergies to antibiotics). The SA is sensitive to antibiotics to which I am allergic but resistant to those I can take.
My question: What tests are most appropriate to determine if there is osteo that has not caused bone erosion? And are neurosurgeons able to get a biopsy from there if needed? I thought I understood my ENT surgeon to explain that that area is rather 'thin' and could not be probed very deeply (in a safe manner). Also if they can not treat this, what is the prognosis--can this spread to the brain, skull, spine, (joints i.e. would it prevent me from being able to get a knee replacement in future years)? I continue these episodes with these infections that have now damaged my lungs from the bronchitis. I am only 52 years old and would appreciate any information. Thank you so much.