Cortical heat generation using an irrigating/aspirating single-pass reaming vs conventional stepwise reaming

To compare the heat generation and pressure generation of a prototype irrigating aspirating intramedullary reaming system to traditional stepwise reaming.

This in vitro study used 8 pairs of fresh-frozen human cadaver tibias. Thermocouples were mounted in the mid-diaphysis and distal diaphysis. A pressure transducer was placed distally to assess intramedullary pressure, a load cell measured axial load was applied by the surgeon, and the entire construct was placed in a 37 degrees C saline bath. One specimen from each pair underwent single-pass reaming with the prototype reamer irrigator aspirator (RIA), and the contralateral limb underwent standard stepwise reaming. All variables were recorded.

There were no significant differences in pressure applied to the load cells during reaming. The maximum temperatures reached in the distal diaphysis in the RIA group (42.0 +/- 9.1 degrees C) were significantly lower (P = 0.025) than in the standard reaming group (58.7 +/- 15.9 degrees C). The maximum pressure generated in the distal tibia in the RIA group (32.7 +/- 39.4 kPa) was significantly higher (P = 0.019) than in the standard reaming group (17.0 +/- 32.6 kPa).

This study demonstrated substantially decreased temperatures with the RIA prototype when compared with standard stepwise reaming. It appears that the continuous flow of room temperature saline irrigant into the system manages to cool the cortical bone, despite the aggressive nature of a single-pass reaming method. However, in this model, contrary to the findings of other studies, the RIA system did generate higher pressures in the distal tibial metaphysis, perhaps as a result of congestion within the outflow of the RIA system. The results of this study confirm that cortical heat generation is not a problem but definitely indicate further development of this prototype aspirator function is warranted, followed by careful in vivo evaluation.