Abstract: PURPOSE: To investigate the effect of surgical treatment of sagittal fractures of mandibular condyle (SFMC) with biocortical resorbable pins and compare the difference between unstable and rigid fixation with resorbabale pins. METHODS: Sixteen sheep were used to creat SFMC models on right temporamadibular joints (TMJ) through osteotomy, and divided into 4 groups randomly (n=4). The control group was treated with closed treatment. Group 1 was treated by open reduction and internal fixation (ORIF) with lateral titanium screws. Group 2 was treated by unstable ORIF with lateral resorbable pins. Group 3 was treated by open reduction and rigid fixation with lateral resorbable pins. Computed tomograms (CT) of TMJ were obtained for the control group after osteotomy and 3 months later. For group 1, 2 and 3, CT films were obtained after osteotomy immediately and 3 months later after open reduction and internal fixation (ORIF). CT taken 3 months after osteotomy was scored according to the criteria for assessing osteoarthrotic changes and ankylosis of right TMJ. Three months later after treatment, the sheep were killed and TMJs were dissected, observed, measured and histologically examined. The data were analyzed using SPSS 18.0 software package. RESULTS: CT images of right TMJ in control group and group 2 3 months after treatment were obviously abnormal. The radiological scores that indicated the degree of osteoarthrotic changes and ankylosis of right TMJ in group 1 and 3 were significantly lower than those in control group and group 2. Anatomical observation showed severely deformed condyles, worm-eaten erosion of the temporal surface, and the discs partially adherent to the condyle, and fragile articular cartilage of the right TMJ in control group and group 2. Histological examination showed myxoid degeneration of discs and articular cartilage in the right TMJ in control group and group 2. In contrast, the right TMJ in group1 and 3, and the left TMJ in all groups were closed to normal. CONCLUSIONS: The study demonstrates that appropriate reduction and rigid fixation are essential for SFMC to reconstruct anatomical shape. If conducted properly, fixation of SFMC with resorbable pins is rigid as titanium screws and yields good results. There are advantages in using resorbable pins to fix SFMC, because they obviate the need for removal. Closed treatment or unstable ORIF for SFMC can lead to severely pathological changes in TMJ.

Key words: Mandibular fractures, Sagittal fractures of mandibular condyle, Resorbable pins, Open reduction and internal fixation