Does mechanical filtration of intraoperative cell salvage effectively remove titanium debris generated during instrumented spinal surgery? An in vitro analysis

Abstract Background context Instrumented fusion of the spine is a surgery commonly performed to stabilize vertebrae causing pain and to correct anatomic deformities. Such surgery can create substantial blood loss. Autotransfusion is a means to limit homologous blood transfusion in this setting. However, a dilemma is created when the high-speed drill used for bone removal comes in contact with implanted titanium spinal hardware. A clinician at this point is forced to decide between two options: to discontinue autotransfusion to avoid the potential transfusion of titanium fragments while risking blood loss and the need for homologous transfusion or to continue autotransfusion while risking transfusion of titanium fragments back into circulation. Purpose To conclusively identify whether titanium fragments created by a high-speed drill are able to pass through standard autotransfusion microaggregate blood filters. Study design A positive and negatively controlled experiment with blinded sample analysis. Outcomes measures The presence or absence of titanium alloy on a filter with detection by energy-dispersive X-ray spectroscopy (EDX). Methods A mock autotransfusion setup was devised for in vitro filtering. Six investigational and two control experiments were conducted. Titanium fragments generated by a high-speed drill were aspirated with saline and filtered with standard autotransfusion reservoirs and microaggregate blood filters. A final filter with a 1-μm pore size was placed distal to the blood filters. After filtration was complete, this final filter was analyzed using EDX. Results The presence of titanium was confirmed by EDX on five of six investigational filters. The positive and negative control filters were analyzed by EDX and tested positive and negative, respectively, for titanium. Conclusions Standard 40 μm reservoir and blood microaggregate filters do not eliminate the smallest fragments of titanium generated by contact between a high-speed drill and a titanium hardware. The mass of titanium able to elude filtration is very small. The impact of transfusing blood contaminated with such a small mass of titanium is not known.