Photoacoustic imaging for the study of oxygen saturation and total hemoglobin in bone healing and non-union formation

Non-union formation represents a major complication in trauma surgery. Adequate vascularization has been recognized as vital for bone healing. However, the role of vascularization in the pathophysiology of non-union formation remains elusive. This is due to difficulties in studying bone microcirculation in vivo. Therefore, we herein studied in a murine osteotomy model whether photoacoustic imaging may be used to analyze vascularization in bone healing and non-union formation. We found that oxygen saturation within the callus tissue is significantly lower in non-unions compared to unions and further declines over time. Moreover, the amount of total hemoglobin (HbT) within the callus tissue was markedly reduced in non-unions. Correlation analyses showed a strong positive correlation between microvessel density and HbT, indicating that photoacoustically determined HbT is a valid parameter to assess vascularization during bone healing. In summary, photoacoustic imaging is a promising approach to study vascular function and tissue oxygenation in bone regeneration.