Liquid nitrogen (LN) has been used as an adjuvant cryotherapy for bone tumors including giant cell tumor of the bone (GCTB) to remove residual tumor cells after curettage. This study evaluated variables related to the efficacy of LN-based cryoablation in the context of adjuvant treatment of GCTB using porcine femur bone model.
A porcine femur bone model was adopted to simulate intralesional cryotherapy. A LN-holding cavity (point 1, nadir) in the medial epicondyle, 4 holes (points 2-5) in the shaft situated 5, 10, 15, and 20 mm away from the proximal edge of the cavity, and 2 more holes (points 6 and 7) in the condyle cartilage (10 and 20 mm away from the distal edge of the cavity) were made. The cooling rate was compared between the 5 points. The cellular morphological changes and DNA damage in the GCTB tissue attributable to LN-based cryotherapy were determined by H&E stain and TUNEL assay. Cartilage tissue at points 6 and 7 was examined for the extent of tissue injury after cryotherapy.
The temperature kinetics at points 1, 2 reached the reference target and were found to be significantly better than the reference (both p<0.05). The target temperature kinetics were not achieved at points 4 and 5, which showed a significantly lower cooling rate than the reference (both p<0.001) without reaching the -60℃ target. Compare to untreated samples, significantly higher proportion of shrunken or apoptotic cells were found at points 1-3; very small proportion were observed at points 4, 5. Significantly increased chondrocyte degeneration was observed at point 6, and was absent at point 7.
The cryotherapy effective range was within 5 mm from nadir. Complications were restricted to within this distance. The cooling rate was unchanged after three repeated cycles of cryotherapy.