Effects of gamma radiation and post-operative cisplatin injection on the incorporation of bone allografts in rats

Background. The reconstruction of long bone defects that occur after resection of tumors is a problem that requires constant study. Bone allografts are often used in this scenario. Unfortunately, while they are prepared, allografts partially lose their strength and osteoinductive properties; their survivability in oncological patients is only 40% after 10 years. This is why the search for superior allograft treatment methods and the study of allograft remodeling and incorporation in oncological patients, whose state has been affected by radiation or chemotherapy, is an area of interest. Purpose – study the structure of bone tissue in the distal metaphysis of a rat’s femur after bone allograft implantation (sterilized using gamma radiation or antibiotic saturation) and post-operative intraperitoneal cisplatin injection. Materials and Methods. Experiments were performed on 20 male white rats aged 5–6 months at the beginning of the experiment and weighed 365.8 ± 6.4g. All rats underwent a surgery that created a defect in the distal metaphysis of the femur which was filled with a bone allograft treated with gamma radiation (Control-1 and Experimental-1 groups) or saturated with an antibiotic (Control-2 and Experimental-2 groups). 14 days after allograft implantation, animals from the control groups received an intraperitoneal injection of 2.0–2.4 ml of 0.9% NaCl, while animals from the experimental groups received 2.5mg/kg of cisplatin. Histological analysis and histomorphometry were completed 30 days after the surgery. Results. 30 days after the operation, the smallest relative area of bone tissue (11.79%) was observed in rats from the Experimental-1 group, with gamma radiation treated allografts and post-operative intraperitoneal cisplatin injections. A somewhat higher value was found in the Experimental-2 group (antibiotic saturation + cisplatin) – 31.64%. In the control groups, (intraperitoneal injection 0.9% NaCl), the relative area of bone tissue was 16.7% (Control-1, gamma radiation treatment) and 58.09% (Control-2, antibiotic saturation). The relative area of fibrous tissue was the largest in the Experimental-1 group – 31.55% and the smallest in the Control-2 group – 12.79%. Conclusions. Allograft remodeling occurs along with the formation of bone and fibrous tissue when allografts are used to fill defects in the distal femoral metaphysis of rats, However, the relative percentages of those tissues depend on the allograft sterilization method and the use of cytostatic agents. The largest relative percentage of bone tissue (58.09%) was obtained using an allograft saturated with antibiotics and without the administration of cisplatin. The smallest (11.79%), on the other hand, occurred in gamma radiation treated allografts with cisplatin injected intraperitoneally after the operation