Experimental Study On Anatomic Reduction Of Lateral Pterygoid Muscle And Condylar Free Reduction For Condylar Fracture

Objective: In this study,the animal model of mandibular condylar neck fracture model was constructed by New Zealand white rabbits,and the anatomic reduction lateral pterygoid muscle and the free reduction of the condyle were performed respectively.By measuring the gross specimens of mandibular condyle,observing the condylar surface proliferating layer,analyzing the number of microvessels and analyzing the parameters of bone tissue,a comparative study was conducted on the healing of the two reduction methods,which provided a theoretical basis for clinical work.Methods: Twenty-four New Zealand white rabbits were randomly divided into two groups with 12 rabbits in each group,and the anatomic reduction lateral pterygoid muscle and the free reduction of the condyle were performed respectively.After 2,4,6 and 8 weeks,3animals in each group were put to death by ink infusion through neck vessels.The bilateral anteroposterior and mediolateral condylar diameters of each animal were measured.The changes of condylar proliferation layer,number of microvessels and bone parameters were observed and analyzed after operation side condyle.The experimental data were analyzed by SPSS 24.0 software.Results: 1.The anteroposterior and mediolateral condylar diameters were compared between the operation side and health side: in the condylar free reduction group,the mediolateral condylar diameters of operation side at 4,6 and 8 weeks were significantly smaller than health side(P<0.05),and there was no statistically significant difference of the anteroposterior condylar diameters(P>0.05);in the anatomic reduction lateral pterygoid muscle group,there was no statistically significant difference between the operative side and the healthy side in the time points of the anteroposterior and mediolateral condylar diameters(P>0.05).2.The observation of the proliferative layer of condylar surface on the operative side showed that the change of the proliferative layer in the anatomic reduction lateral pterygoid muscle group was faster and was earlier than that the condylar free reduction group.3.Comparison of the number of microvessels: the number of microvessels in the condylar free reduction group at each time point was smaller than that in the anatomic reduction lateral pterygoid muscle group(P<0.05).4.Comparison of bone tissue parameters: at each time point of BV/TV and Tb.Th,the condylar free reduction group was smaller than that the anatomic reduction lateral pterygoid muscle group(P<0.05);Tb.N was smaller in the condylar free reduction group than theanatomic reduction lateral pterygoid muscle group at all time points except 2 weeks(P<0.05);Tb.Sp at each time point the anatomic reduction lateral pterygoid muscle group was smaller than the condylar free reduction group(P<0.05).Conclusion: After condyle fracture,the anatomic reduction lateral pterygoid muscle can restore some blood supply and start the reconstruction of the temporomandibular joint at an early stage compared withthe condylar free reduction.The reconstruction of blood supply is required after condylar free reduction.Because the reconstruction of fracture healing is closely related to the number of microvessels,so in the slower healing rate of the fracture after the condylar free reduction compared with the anatomic reduction lateral pterygoid muscle,and more obvious bone absorption.When the condyle is fractured it should keep lateral pterygoid muscle as possible,which is important in the fracture healing and temporal bone joint functional recovery in the clinical work.