[The value of panoramic radiograph, CT and MRI for the diagnosis of condylar fracture].

OBJECTIVE: To retrospectively analyze the advantages and disadvantages of radiographic methods commonly used for diagnostic of condylar fractures.

METHODS: From Jan 2002 to Nov 2013, 290 patients (405 condylars) in the temporomandibular joint (TMJ) division of Ninth People's Hospital Shanghai Jiao Tong University School of Medicine were diagnosed as condylar fractures. Panoramic films and CT were taken in all patients to check and count the amount of condylar fractures, including intracapsular condyle fracture (type A, B, C and M), condylar neck fracture and subcondylar fracture. MRI was also taken in 119 patients with 174 condylar fractures to check the position of TMJ disc. The data were analyzed and compared among the three examinations in the diagnosis of the condylar fractures.

RESULTS: Panoramic films showed 79.8% (323/405) condylar fractures. Among condylar fractures, intracapsular condylar fractures, condylar neck fractures and subcondylar fractures accounted for 48.9% (198/405), 20.3% (82/405) and 10.6% (43/405) respectively. CT showed 64.0% (259/405) intracapsular condylar fractures, 24.0% (97/405) condylar neck fractures and 12.1% (49/405) subcondylar fractures. Among intracapsular condylar fractures, Type A fracture was the most common type of ICF, which accounted for 48.7% (126/259), followed by Type B fracture, which accounted for 30.9% (80/259) and Type M fracture, 12.4% (32/259). Type C fracture was the least type which accounted for 8.1% (21/259). According to the diagnostic criteria of CT, there were 10 condylar neck fractures misdiagnosed with intracapsular condylar fractures. MRI showed 94.9% (129/136) TMJ disc displacement in intracapsular condylar fractures, 53.6% (15/28) in condylar neck fractures and 60.0% (6/10) in subcondylar fractures. Among intracapsular condylar fractures, there were 95.3% (61/64) TMJ disc displacement in type A, 95.2% (40/42) in type B, 89.0% (8/9) in type C, and 95.2% (20/21) in type M. There was significant difference of TMJ disc displacement between intracapsular condylar fractures and condylar neck fractures or subcondylar fractures (P < 0.05), and no significant difference between condylar neck fractures and subcondylar fractures (P < 0.05). There was also no significant difference among various type of intracapsular condylar fractures.

CONCLUSIONS: Panoramic films can initially diagnose condylar fractures but with the high misdiagnosis rate for intracapsular fractures, minor fractures and fractures without fragment displacement. CT, especially coronal CT, should be considered for positioning fracture lines and confirming the displacement angle of fragment. MRI should also be used to determine the position of TMJ disc in intracapsular condylar fractures.