gms | German Medical Science

German Congress of Orthopaedics and Traumatology (DKOU 2022)

25. - 28.10.2022, Berlin

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

Meeting Abstract

  • presenting/speaker Maximilian Menger - Abteilung für Unfall- und Wiederherstellungschirurgie, BG Unfallklinik Tübingen, Eberhard Karls Universität Tübingen, Tübingen, Germany
  • Christina Körbel - Institut für Klinisch-Experimentelle Chirurgie, Universität des Saarlandes, Homburg, Germany
  • David Bauer - Institut für Klinisch-Experimentelle Chirurgie, Universität des Saarlandes, Homburg, Germany
  • Michelle Bleimehl - Institut für Klinisch-Experimentelle Chirurgie, Universität des Saarlandes, Homburg, Germany
  • Mika Rollmann - Abteilung für Unfall- und Wiederherstellungschirurgie, BG Unfallklinik Tübingen, Eberhard Karls Universität Tübingen, Tübingen, Germany
  • Benedikt Braun - Abteilung für Unfall- und Wiederherstellungschirurgie, BG Unfallklinik Tübingen, Eberhard Karls Universität Tübingen, Tübingen, Germany
  • Steven Herath - BG Klinik Tübingen, Klinik für Unfall-, Hand- und Wiederherstellungschirurgie, Tübingen, Germany
  • Matthias W. Laschke - Institut für Klinisch-Experimentelle Chirurgie, Universität des Saarlandes, Homburg, Germany
  • Michael Menger - Institut für Klinisch-Experimentelle Chirurgie, Universitätsklinikum des Saarlandes, Homburg, Germany
  • Tina Histing - Abteilung für Unfall- und Wiederherstellungschirurgie, BG Unfallklinik Tübingen, Eberhard Karls Universität Tübingen, Tübingen, Germany

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2022). Berlin, 25.-28.10.2022. Düsseldorf: German Medical Science GMS Publishing House; 2022. DocAB21-526

doi: 10.3205/22dkou093, urn:nbn:de:0183-22dkou0935

Published: October 25, 2022

© 2022 Menger et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Objectives: Non-union formation represents a major complication in trauma and orthopedic surgery. Adequate vascularization has been recognized as vital for successful bone healing. However, the role of vascularization in the pathophysiology of non-union formation still remains elusive. This is mainly due to difficulties in studying bone microcirculation in vivo. Because photoacoustic imaging provides structural and functional data on vascular perfusion and tissue oxygenation, we herein studied in a murine osteotomy model whether this technique may be used to analyze vascularization in bone healing and non-union formation.

Methods: CD-1 mice with an age of 12- 16 weeks were used. In the non-union group, a distally flattened pin was implanted through the intramedullary canal. Afterwards the femur was exposed by a second lateral approach to implant a 6 mm clip ventro-dorsally into the femur. Then, an osteotomy with a gap size of 1.8 mm was created using size-standardized spherical trephines. In the union group the femur was exposed and stabilized accordingly. Then, a gigy saw was used to create a osteotomy with a gap size of 0.25 mm. The femora were analyzed at 2, 5 and 10 weeks after surgery by radiology, biomechanics, photoacoustic imaging, µCT and histology. Values are expressed as mean ± SEM. Statistical significance: P < 0.05.

Results and conclusion: The radiological and biomechanical analyses showed a succesful bone healing in the union group 10 weeks after surgery. In the non-union group our analyses demonstrated failed fracture healing without osseous bridging 10 weeks after surgery. This was associated with a significantly higher ratio of bone volume

(54.8 ± 4.4 vs 6.0 ± 1.1 %) and an increased bending stiffness (47.7 ± 3-1 vs. 0.4 ± 0.06 N/mm) in unions when compared to non-unions. Moreover, we found that during early healing, oxygen saturation within the callus tissue is significantly lower in non-unions compared to unions (44.9 ± 1.0 vs. 35.3 ± 2.8 %) and further declines over time. Moreover, the amount of total hemoglobin (HbT) within the callus tissue was markedly reduced in non-unions at 2 and 5 weeks after osteotomy. This was associated with a lower microvessel density and a lower number of alpha-smooth muscle actin (SMA)-positive microvessels within the callus tissue of non-unions. Additional correlation analyses showed a strong positive correlation between microvessel density and HbT, indicating that photoacoustically determined HbT is a valid in vivo parameter to assess vascularization during bone healing. In summary, photoacoustic imaging is a promising non-invasive in vivo approach to study vascular function and tissue oxygenation in bone defects, and may, therefore, be a helpful tool in future preclinical and clinical studies which focus on the pathophysiology, prevention and treatment of non-union formation.