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Background: Free vascularized bone transfers are a versatile technique for reconstructing large bone defects but come with significant risk of complications. Complications are reported to range from 21-43% with total flap loss rates are as high as 14%. It is therefore imperative that we establish techniques to effectively monitor viability of vascularized bone grafts to decrease flap failure. This study was designed to investigate the ability of Near Infrared fluorescence (NIR) imaging to assess perfusion and viability of bone flaps in real time.
Methods: Vascularized bone grafts were created (N=12) using well-established porcine models. Bone perfusion was studied intraoperatively by clinical observation and confirmed with doppler ultrasound. Perfusion was also assessed with NIR imaging. Animals were injected with indocyanine green and NIR fluorescence excitation (745-779 nm) performed with intermittent clamping of the vascular pedicle.
Results: Our composite flaps appear viable and well perfused on examination (Figure 1A.) While clamped, NIRFI indicates that our vascularized bone does not emit fluorescence with ICG injection. (Figure 1B) On clamp removal, bone emits fluorescence indicating perfusion along the periosteum. (Figure 1C and composite1D)
Conclusion: There are no established techniques to effectively monitor the viability of vascularized bone grafts. Our pilot study suggests that NIR imaging has the capability to assess intra- and postoperative bone perfusion and viability. This emergent technology shows promise and could prove invaluable to reconstruction of large bone defects.