(12) Free Fibular Flap Neomandible Density Changes in a Previously Irradiated Tissue Bed

Abstract: Microvascular fibula free flaps have become the gold standard for mandibular reconstruction. Various indications for maxillofacial reconstruction via microvascular fibula free flaps include benign tumors/cysts (ameloblastomas, odontogenic keratocysts, dentigerous cysts), osteoradionecrosis, and trauma. Our study set out to analyze the bone density of a microvascular fibula free flap neomandible reconstruction. Previous studies have evaluated these bone density changes; however, no study has compared the density changes of fibula reconstructions due to benign indications versus previously irradiated tissue beds. Our study set out to analyze if there was a significant difference in bone density changes in fibula free flap neomandible reconstruction due to benign indications versus previously irradiated tissue beds.
A retrospective chart review was performed on 10 patients who underwent mandibular resection with microvascular fibula free flap reconstruction between 2021 and current performed at Lenox Hill Hospital (New York, NY) and Long Island Jewish Medical Center (New Hyde Park, NY). Our data analysis focused on fibula density prior to resection in comparison to fibula free flap density in the reconstructed neomandible. After analyzing the pre-operative CT scans, 5 separate Hounsfield unit measurements 2 centimeters apart were taken along the fibula preserving 6 centimeters of the proximal and distal fibula. At each of these 5 respective measurement points, 5 separate measurements were taken. These measurements were then averaged. The same measurement technique was then applied to the post-operative neomandible CT. A percent change analysis was then performed. Comparisons were made between fibula flap density in patients with non-irradiated tissue beds versus patients with previously irradiated tissue beds prior to resection and reconstruction.
A total of 10 (6 female, 4 male) patients were evaluated after undergoing mandibular resection with microvascular fibula free flap reconstruction. 5 patients (F=3, M=2) had no previous history of radiation therapy in the resected region. 5 (F=3, M=2) patients had radiation therapy to the tissue bed prior to resection. The indications for surgery were ameloblastoma (n=3), gunshot wound (n=1), osteoradionecrosis (n=5), medication-related osteonecrosis of the jaw (n=1). The average age of the patients was 50.6 years (range 14-78) with no significant difference between irradiated and non-irradiated groups (p=0.33). The average weight of patients was 63.6 Kg (range 47.2-76.2) with no significant difference between irradiated and non-irradiated groups (p=0.99). The average length of follow up imaging and evaluation was 249.5 days. The average density change in the non-irradiated group was -6.49% ± 3.52%. The average density change in the irradiated group was –21.78% ± 5.16%. This change in density difference between the groups proved to be statistically significant (p=0.04); with the prior irradiated tissues beds showing a significantly higher decrease in density.
Overall, it can be seen that there is a significantly higher decrease in density of a fibula neomandible in patients with previously irradiated tissue beds. This leads to the assumption that the surrounding tissue bed contributes to flap characteristics more than previously thought. Consideration should be given to patients who have previously undergone radiation therapy to the mandible prior to resection. Restorative considerations for these patients include possible delayed loading of implants and an increased number of implants to compensate for the decrease in density.

Baron S, Salvan D, Cloutier L, Gharzouli I, Le Clerc N. Fibula free flap in the treatment of mandibular osteoradionecrosis. Eur Ann Otorhinolaryngol Head Neck Dis. 2016 Feb;133(1):7-11. doi: 10.1016/j.anorl.2015.09.010. Epub 2015 Oct 26. PMID: 26515530.

Zheng K, Yoda N, Chen J, Liao Z, Zhong J, Wu C, Wan B, Koyama S, Sasaki K, Peck C, Swain M, Li Q. Bone remodeling following mandibular reconstruction using fibula free flap. J Biomech. 2022 Mar;133:110968. doi: 10.1016/j.jbiomech.2022.110968. Epub 2022 Jan 22. PMID: 35139441.

Patient Demographics

Density Changes Between Fibula and Free Fibula Flap Neomandible

Neomandible Density Percent Change Comparison Between Irradiated and Non-irradiated Tissue Beds