The Influence Of Unilateral Disc Displacement Without Reduction Of Temporomandibular Joint On Condylar Height In Juvenile:MRI Evaluation

Purpose:To evaluate the occurrence and severity of condylar resorption in the juvenile patientswith unilateral disc displacement without reduction of temporomandibular jointbased on magnetic resonance imaging(MRI), and observe the influence of discdisplacement without reduction on condylar height during its natural course, so as toprovide reference for making treatment protocol for disc displacement withoutreduction and exploring the relationship between disc displacement and maxillofacialabnormalities.Patients and Methods:The study retrospected all the juvenile patients with unilateral disc displacementwithout reduction referred from January2010to June2013. Severity of condylarresorption in affected side was evaluated, comparing with the unaffected side. After atleast6months’ follow-up, progression of condylar resorption was evaluated, and thelength/distance of the displaced disc and the condylar height before and afterfollow-up were measured quantitatively. According to the age on the first visit, thepatients were grouped and analyzed. All the data were statistically analyzed viaSoftware SAS9.13.Result:One hundred and twenty-four patients were collected, with the mean age of16.4years old. On the first visit, none/mild/moderate/severe condylar resorption was foundin on49/47/23/5patients, respectively. After a mean interval of13.6months, the data above became36/44/34/8, and condylar resorption aggravated(P<0.05). On the firstvisit, the mean condylar height and disc length of the healthy side were26.07mm and12.48mm, while the condylar height, disc length and distance of displacement of theaffected side were24.22mm,9.06mm and5.45mm, respectively. After the follow-up,the mean condylar height and disc length of the healthy side were26.82mmand12.98mm, while the condylar height, disc length and distance of displacement ofthe affected side were23.81mm,8.12mm and6.83mm, respectively. The difference ofthe condylar height between the healthy side and affected side increased from1.85mmto3.00mm. The difference between the affected and healthy side, between before andafter follow-up were all significant (P<0.05). As to3groups divided according to theage on the first visit, the mean age were12.97y,16.02y and18.98y. The discs of3groups were more anteriorly displaced by1.19mm,1.81mm, and1.01mm,respectively. The discs were shortend by0.85mm,1.26mm, and0.65mm. Thedifference of condylar height between the affected and healthy side increased by1.71mm,0.99mm, and0.98mm after follow up. But all the comparison among groupsshowed no significant difference (P>0.05).Conclusion:Condylar resorption was found in about60%juvenile patients with unilateral discdisplacement without reduction. During its natural course, condylar resorptionaggravated. The disc become more shortened and more anterior displaced. Theunaffected condyle grows on, while the condylar height of the affected side reduces.The difference of condylar height between the affected and healthy side becomesgreater, which could finally contribute to maxillofacial abnormalities. Therefore, wesuggest to treat disc displacement as early as possible.