Recurrent bone tumours are a common complication post curettage or resection.
Radiographs taken pre- and postoperatively are sufficient for evaluation of recurrence based on the following features:
- osteolytic changes
- cortical changes
- matrix mineralisation (characteristic of a particular tumour)
- curetted cavities
- soft tissue mass
Recurrent bone tumours will also appear as lytic areas and hence comparison with previous x-rays is essential to determine if complete excision was carried out or not.
Cortical reactions, such as thickening or expansile changes, are seen in recurrent tumours.
A pattern-based approach to detect the type of tumour:
- fluffy or cloud-like pattern in osteosarcoma
- ring and arc pattern in chondrosarcoma or
- no matrix mineralisation as in giant cell tumour (GCT)
Postcurettage cavities are filled with bone cement (polymethyl methacrylate) or bone graft. Bone cement will appear denser and sharply delineates the borders of the cavity since resorption of cement does not occur.
Bone graft may get incorporated into the cavity blurring the outline of cavity or may undergo resorption and the entire area of cavity appears radiolucent
Soft tissue mass
An associated soft tissue mass gives a strong indication of recurrence warranting a further evaluation with MRI. On MRI the extent of soft tissue can be assessed. Also, bone cement gives low signal intensity on all sequences due to its lack of protons.
A combination of radiographic signs, such as osteolysis and cortical expansion, can be invaluable for distinguishing between graft resorption and tumour recurrence.