Abstract: BACKGROUND:  Gutta-percha has low yield strength and shows hard and tough mechanical properties. On this basis, a sports protective gear that can be freely shaped according to the body shape has been developed, and it has been preliminarily confirmed that this performance can reduce the damage to athletes caused by external impact forces.
OBJECTIVE: To evaluate the effect of gutta-percha splint on fracture fixation.
METHODS: Thirty-five adult male New Zealand rabbits were used to establish closed fracture models of the left tibia by the modified three-point stress method. Totally 30 successful models were randomly divided into two groups (n=15) and fixed with gutta-percha splint and gypsum, respectively. The effects of the two external fixation methods were compared by X-ray imaging and fracture healing was observed at 2 hours, 4 and 6 weeks after fixation. After 6 weeks of fixation, the tibia specimens were observed for gross and histological morphology.
RESULTS AND CONCLUSION: (1) X-ray films: Clear fracture line was seen 2 hours after fixation, without obvious periosteal reaction. After 4 weeks, the fracture line became blurred, and a large area of spindle low-density callus shadow was seen at the broken end. After 6 weeks, the fracture line nearly disappeared; the callus connected together to form a cortical bone bridge, and the bone marrow cavity was partially canalized, and partially close to recanalization. After 6 weeks, gray value at the fracture site was higher in the gutta-percha splint group than that in the gypsum group (P < 0.05). (2) General observation: In the gutta-percha splint group, except for three rabbits with malunion, the fracture line of the rest of the rabbits basically disappeared; part of the outer callus was absorbed, and the cortical bone density was close to the normal level. In the gypsum group, except for four rabbits with malunion, the fracture line of the rest of the rabbits disappeared, a small part of the outer callus was absorbed, and the cortical bone density was close to the normal level. (3) Histological morphology: In the gutta-percha splint group, new bone trabeculae were thick; the trabecular space was reduced and fused to form lamellar bone, and the medullary cavity had been partially recanalized. In the gypsum group, new bone trabeculae were reticular, forming a woven bone, and a large number of transected small arteries, veins and capillaries could be seen in the medullary cavity. (4) Complications: Within 6 weeks of fixation, the extremity swelling, purple darkening, displacement and malunion, and the number of local pressure ulcers in the gutta-percha splint group tended to be less than those in the gypsum group, but there was no significant difference in statistical analysis (P > 0.05). (5) The results showed that gutta-percha splint could play a similar fixation effect to plaster on the rabbit model of closed tibial fracture. 

Key words: gutta-percha, gypsum, splint, closed fracture, histopathology, complication, New Zealand rabbit