Traumatic heterotopic ossification (HO) is the pathological formation of bone in soft tissue and is a debilitating sequela
following acute trauma involving blast-related extremity musculoskeletal injuries, severe burns, spinal cord injury, and
traumatic brain injury. Over 60% of combat related injuries and severe burns develop HO; often resulting in reduced
mobility, chronic pain, ulceration, tissue entrapment, and reduced ambulation. Detection and prognosis is limited by
current clinical imaging modalities (computed tomography, radiography, and ultrasound). This study identifies Raman
spectral signatures corresponding to histological changes in a combat-trauma induced rat HO model at early time points
prior to radiographic evidence of HO. HO was induced in Sprague-Dawley rats via blast over pressure injury, mid-femoral
fracture, soft tissue crush injury, and limb amputation through the zone of injury. Rats were euthanized, and
amputated limbs were formalin fixed and embedded in paraffin; 10 μm sections were placed on gold slides, and paraffin
was chemically removed. Tissues from sham-treated animals served as controls. Tissue maps consisting of Raman
spectra were generated using a Raman microprobe system with an 80-90 μm spot size and 785 nm excitation in regions
exhibiting histological evidence of early HO development according to adjacent HE sections. Factors were extracted
from mapping data using Band-Target Entropy Minimization algorithms. Areas of early HO were highlighted by a
Raman factor indicative of the presence of collagen. Identification of collagen as an early marker of HO prior to
radiographic detection in a clinically relevant animal model serves to inform future clinical work.
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