Viva · IR system
Musculoskeletal Viva Questions
Oral-exam style questions and answers on musculoskeletal for MD, DNB and super-specialty practical examinations. Each answer links back to the playbook or Library entry it was written from.
- Why is CT preferred for RFA of osteoid osteoma?
- CT best depicts the small nidus, central mineralization and surrounding cortical sclerosis and permits precise coaxial targeting. MRI is valuable for edema, cartilage and neurovascular relationships but can obscure the nidus within extensive reactive change.
- What is the classic RFA protocol for osteoid osteoma?
- The commonly cited temperature-controlled protocol is **90 °C for 6 minutes** with the active tip centered in the nidus. The actual cycle must match the validated electrode-generator system because impedance-controlled and other platforms differ.
- Why must the introducer cannula be retracted before ablation?
- The metallic cannula can conduct heat toward the skin and soft tissues and can electrically interact with the active electrode. Retracting it exposes the active tip within the nidus and reduces tract and skin burns.
- Is biopsy mandatory before RFA?
- Tissue sampling is strongly indicated when the clinical or imaging features are atypical or an alternative diagnosis is possible. In a classic lesion, practice varies, and a nondiagnostic specimen does not invalidate a concordant clinical and CT diagnosis.
- How do you protect a nerve close to the nidus?
- Create separation with hydrodissection or carbon dioxide, use thermal monitoring and consider neurophysiologic monitoring. If a safe buffer and temperature cannot be maintained, stop and choose another modality or surgery.
- Are prophylactic antibiotics routinely required?
- No. SIR classifies osteoid osteoma ablation as a clean procedure with low infection risk and does not routinely recommend prophylaxis; antibiotics are reserved for specific patient or institutional indications.
- What is the difference between technical and clinical success?
- Technical success is correct intranidal electrode placement and completion of the planned ablation cycle. Clinical success is durable resolution or major reduction of the characteristic pain without continued analgesic requirement.
- How do you manage recurrent pain after RFA?
- Exclude infection, fracture, neural injury and another pain source, then obtain symptom-directed MRI and thin-section CT if residual nidus is suspected. Repeat RFA is usually effective when a residual or recurrent target is demonstrated.