Fluorescence-guided bone resection: A histological analysis in medication-related osteonecrosis of the jaw

Surgical treatment of medication-related osteonecrosis of the jaw (MRONJ) consists of necrotic bone removal followed by dense mucosal closure. Fluorescence-guided surgery has become a promising tool to intraoperatively distinguish between healthy and necrotic bone. Until now, there has been a lack of histopathological studies correlating the intraoperative fluorescence situation to histopathological analyses of the respective bone areas in order to further validate this method. Histopathological sections from intraoperatively detected fluorescence- and non−fluorescence-labeled bone were analyzed detecting osteocyte and collagen content, RANK(L) and TRAP expression as well as proportion of immature bone regeneration. Samples were compared with viable-looking bone areas according to the intraoperative clinical situation. Staining revealed a significant decrease of osteocytes and collagen type-I fibers in necrotic, non-fluorescing areas compared to fluorescing bone (R/RGB [%]: 0.56 ± 0.38 (fluorescence positive) vs. 3.18 ± 2.22 (fluorescence negative), p = 0.041). Furthermore, the number of osteocytes was higher in fluorescing, clinically viable bone samples (cell/mm2: 151.26 ± 95.77 (fluorescence positive) vs. 0.56 ± 0.38 (fluorescence negative), p = 0.028). Additionally, the amount of immature bone was substantially increased in luminescent jaw bone (proportion of red [%]: 6.78 ± 7.00 (fluorescence positive) vs. 2.24 ± 1.36 (fluorescence negative), p = 0.442). RANK(L) and TRAP expression did not differ between the investigated areas, resembling a generalized decrease in osteocyte−osteoclast function all over the jaw (RANK(L) −positive cells per mm2: 8.97 ± 7.85 (fluorescence positive) vs. 7.76 ± 6.41 (fluorescence negative), p = 0.793; TRAP-positive cells per mm2: 0.36 ± 0.38 (fluorescence positive) vs. 0.33 ± 0.41 (fluorescence negative), p = 0.887). Intraoperative fluorescence-guided surgery might be more precise in identifying and resecting the necrotic bone compared to previous indicators like bone bleeding, which could be useful to further improve surgical therapy in MRONJ patients.