Objective·To evaluate the relationships between disc-condyle distance and anterior disc displacement,as well as between disc-condyle distance and disc morphology,in patients with temporomandibular disorders(TMD)using magnetic resonance imaging(MRI)of the temporomandibular joint(TMJ).Methods·From September 2023 to March 2024,90 patients(180 TMJs)who visited the TMJ clinic of Department of Stomatology,The Second Affiliated Hospital of Anhui Medical University,with clinical symptoms of TMD and were diagnosed via MRI with either anterior disc displacement or no significant displacement,were included.Clinical data were collected,and MRI images were used to measure the angle of disc displacement,disc-condyle distance,disc length,and thickness.The degree of disc deformation was assessed.The relationships between clinical symptoms and anterior disc displacement,between anterior disc displacement and both disc morphology and disc-condyle distance,and between disc-condyle distance and disc morphology were analyzed.Results·Among the 90 patients,there were 16 males and 74 females,with a mean age of(28.1±14.5)years.Among the 180 TMJs,175 had clinical symptoms and 5 were asymptomatic.There were 40 joints with no displacement,78 with reducible anterior disc displacement,and 62 with irreducible anterior disc displacement.In the joints with irreducible anterior disc displacement,the proportion of those with two or more symptoms was slightly higher at 62.9%,but the difference was not statistically significant compared with the joints with no displacement or reducible anterior disc displacement.MRI assessment revealed that in the joints with irreducible anterior disc displacement,the proportion of disc deformation type Ⅲ or higher was significantly higher compared with the non-displaced joints(P<0.001).The disc length was significantly shorter(P<0.001),and the intermediate zone thickness was significantly greater(P<0.001)compared with the non-displaced joints.The disc displacement angles at centric closure and maximum opening were also significantly larger(P<0.001).The disc-condyle distance was 3.10(2.70,3.70)mm for non-displaced joints,3.40(3.00,4.00)mm for joints with reducible anterior disc displacement,and 6.60(4.78,7.90)mm for joints with irreducible anterior disc displacement,with significant differences(P<0.001).The disc-condyle distance was 3.10(2.80,3.60)mm for type Ⅰ discs,3.70(3.10,4.60)mm for type Ⅱ discs,5.10(4.00,7.30)mm for type Ⅲ discs,and 6.80(4.98,8.20)mm for type Ⅳ/Ⅴ discs,with significant differences(P<0.001).The disc-condyle distance was negatively correlated with disc length(rs=-0.469,P<0.001),positively correlated with intermediate zone thickness(rs=0.319,P<0.001),and positively correlated with disc displacement angle at centric closure(rs=0.626,P<0.001).Conclusion·With increasing severity of disc deformation,intermediate zone thickness,and disc displacement angle at centric closure,as well as decreasing disc length,the disc-condyle distance increases.The disc-condyle distance is an important indicator for MRI assessment of pathological changes in TMD.

Objective·To evaluate the relationships between disc-condyle distance and anterior disc displacement,as well as between disc-condyle distance and disc morphology,in patients with temporomandibular disorders(TMD)using magnetic resonance imaging(MRI)of the temporomandibular joint(TMJ).Methods·From September 2023 to March 2024,90 patients(180 TMJs)who visited the TMJ clinic of Department of Stomatology,The Second Affiliated Hospital of Anhui Medical University,with clinical symptoms of TMD and were diagnosed via MRI with either anterior disc displacement or no significant displacement,were included.Clinical data were collected,and MRI images were used to measure the angle of disc displacement,disc-condyle distance,disc length,and thickness.The degree of disc deformation was assessed.The relationships between clinical symptoms and anterior disc displacement,between anterior disc displacement and both disc morphology and disc-condyle distance,and between disc-condyle distance and disc morphology were analyzed.Results·Among the 90 patients,there were 16 males and 74 females,with a mean age of(28.1±14.5)years.Among the 180 TMJs,175 had clinical symptoms and 5 were asymptomatic.There were 40 joints with no displacement,78 with reducible anterior disc displacement,and 62 with irreducible anterior disc displacement.In the joints with irreducible anterior disc displacement,the proportion of those with two or more symptoms was slightly higher at 62.9%,but the difference was not statistically significant compared with the joints with no displacement or reducible anterior disc displacement.MRI assessment revealed that in the joints with irreducible anterior disc displacement,the proportion of disc deformation type Ⅲ or higher was significantly higher compared with the non-displaced joints(P<0.001).The disc length was significantly shorter(P<0.001),and the intermediate zone thickness was significantly greater(P<0.001)compared with the non-displaced joints.The disc displacement angles at centric closure and maximum opening were also significantly larger(P<0.001).The disc-condyle distance was 3.10(2.70,3.70)mm for non-displaced joints,3.40(3.00,4.00)mm for joints with reducible anterior disc displacement,and 6.60(4.78,7.90)mm for joints with irreducible anterior disc displacement,with significant differences(P<0.001).The disc-condyle distance was 3.10(2.80,3.60)mm for type Ⅰ discs,3.70(3.10,4.60)mm for type Ⅱ discs,5.10(4.00,7.30)mm for type Ⅲ discs,and 6.80(4.98,8.20)mm for type Ⅳ/Ⅴ discs,with significant differences(P<0.001).The disc-condyle distance was negatively correlated with disc length(rs=-0.469,P<0.001),positively correlated with intermediate zone thickness(rs=0.319,P<0.001),and positively correlated with disc displacement angle at centric closure(rs=0.626,P<0.001).Conclusion·With increasing severity of disc deformation,intermediate zone thickness,and disc displacement angle at centric closure,as well as decreasing disc length,the disc-condyle distance increases.The disc-condyle distance is an important indicator for MRI assessment of pathological changes in TMD.