Although it had been used in the 1850s for the management of locally advanced carcinoma of the cervix, the applicability of cryoablation in the management of bone tumors was not assessed until more than a century later, in the classic 1966 animal study by Gage et al¹³ in which the femora of living mongrel dogs were frozen by perfusing liquid nitrogen through encircling latex coils. Liquid nitrogen, which has a boiling temperature of -196 °C, allowed rapid freezing of a 2-cm rim of bone around these coils. Using histopathologic studies and plain radiographs, the authors documented the occurrence of tissue necrosis and bone resorption that was associated with mechanical weakening and spontaneous fractures.¹³ These changes, however, were followed by new bone formation that developed slowly, starting from the vital bone at the periphery: It was first observed at 2 months and reached its peak at 6 months after freezing.¹³

Although only normal bone was investigated in their experiment, Gage et al¹³ speculated that cold allows for nonspecific cell destruction and may induce tumor kill as well. They further suggested the use of intralesional cryoablation in lieu of tumor resection or amputation. The use of this technique in the management of human bone tumors was first reported in 1969.³³ Following curettage of a metastatic bone lesion, those authors poured liquid nitrogen into the tumor cavity with the intent of inducing tumor necrosis and avoiding the need for extensive resection and reported having achieved both goals.

Further studies confirmed and refined the initial findings of Gage et al¹³ and showed that temperatures between -21 °C and -60 °C are needed to obtain cell necrosis, whereas temperatures below -60 °C exerted no further lethality.¹⁸,²⁸,³³

It also emerged that a number of mechanisms are responsible for the tissue necrosis induced by cryoablation.¹²,¹⁵,²²,²⁶,²⁸,⁴¹,⁴² These mechanisms can be grouped into two categories: immediate and delayed.

During cryoablation, ice crystals first occur in the extracellular spaces. The withdrawal of water from the system into these crystals creates a hyperosmotic extracellular environment, which, in turn, draws water from the cells. As the process continues, these crystals grow, the cells shrink and dehydrate, electrolyte concentration is increased, and membranes and cell constituents are damaged.¹²,¹⁷,⁴¹ Rapid freezing, such as that achieved by direct pour of liquid nitrogen, does not allow sufficient time for the withdrawal of water from the cells and so intracellular ice crystals are formed simultaneously. Conversely, a slow thaw will cause intracellular recrystallization of the already formed crystals and membrane disruption, whereas a rapid thaw will not.²,⁷,⁴¹,⁴⁸ Repeated freeze-thaw cycles will also increase the extent of tissue necrosis because of the improved cold conductivity following the first cycle.¹¹,¹²,¹⁵ Therefore, repeated cycles of rapid freezing and spontaneous thaw will achieve the maximal effect of cell necrosis.

Histologically, the most dramatic effect of cryoablation is on the appearance of the bone marrow: a rim of 1 to 2 cm of extensive necrosis with minimal inflammatory response appears, following direct pour of liquid nitrogen.¹³,²⁹,³⁹,⁴¹ This is followed by liquefaction and progressive fibrosis. Large, thickened, and thrombosed vessels are occasionally seen as well.