Establishing a best practice for the freeze-thaw cycle of cryopreservation to approximate living muscle, joint, and associated soft tissue properties in cadaveric upper limbs.

Introduction: Fresh-frozen cadavers are useful for surgical simulation and experimentation since they preserve many properties of live specimens, but achieving realistic physiological properties requires thawing that risks tissue damage. Methods: Ten fresh-frozen cadaveric upper limbs were frozen at -17 °C, refrigerated at 4 °C for 48 h, then thawed at room temperature for 8 h. The core temperature of the limbs was measured hourly. Joint flexibility, durometric hardness, and shore hardness were measured every two hours. Four limbs had muscle biopsies acquired every 2 h. Results: The limbs were above freezing after about 1 h of thawing. The upper limbs achieved a flexibility score of 3/5 after 2 h of thawing, mimicking healthy live limbs. The limbs became softer and more pliable with more time thawing. Muscle biopsies showed no tissue damage in any samples taken at h 2 and 4 of thawing. Three limbs showed no tissue damage at h 6 or 8, either. One limb had biopsies at 6 and 8 h demonstrating moderate to severe tissue damage. Conclusions: It was concluded that for ideal thawing, fresh-frozen cadaveric upper limbs should be thawed for 2 h after 48 h of refrigeration, permitting surgical simulation for 4 h after thawing, though potentially for 6 h.