Evaluating Long-Term Retention of Fresh-Frozen Costal Cartilage Allograft in An Animal Model

BACKGROUND: Data is limited regarding the in-vivo behavior of fresh-frozen costal cartilage allografts (CCA). This study aims to evaluate retention and biological behavior of CCA in an immunocompetent mouse model. METHODS: Clinical-grade fresh-frozen CCA (MTF Profile ®) from 4 donors, subcutaneously implanted into 9 SKH-1 mice. Cartilage size and volume were evaluated at 2 and 6 weeks, and 3, 6, and 9 months, using clinical assessment, digital-caliper measures, and micro-CT scan volumetric analysis. Linear measurements, total volume, and volume of calcification were compared across time-points. After sacrifice, H&E staining was performed for comparison at 3, 6, and 9 months. RESULTS: There were no significant changes in cartilage implant length (p = 0.16), width (p = 0.21), or total volume (p = 0.9) across timepoints. Average volume of calcified cartilage increased from 1.1% to 10% of total volume (p<.001). Clinical assessment did not show evident change. Clinical assessment did not show overt changes in implant appearance. Histology demonstrated capsule formation without evidence of undue inflammatory response or resorption. CONCLUSIONS: This study evaluated the in-vivo behavior of new forms of CCA currently used in practice, with implications for clinical use in facial reconstruction. We found no significant resorption or morphologic changes in fresh-frozen CCA when implanted in an immunocompetent murine model at 9 months. Although reassuring for continued use and stability long-term, further work is needed to understand the impact of cartilage calcification.Clinical Relevance: Fresh-frozen CCA demonstrated structural stability and detail preservation with minimal to no resorption, when implanted in our immunocompetent mouse model over our 9-month study period. However, progressive calcification of the graft was also observed, which may impact superficial applications.