Three-Dimensional Measurement of the Temporomandibular Joint in Pruzansky-Kaban Type IIa Hemifacial Microsomia

Objective: This observational retrospective cross-sectional study aimed to investigate the morphological characteristics of the temporomandibular joint (TMJ) in type IIa hemifacial microsomia (HFM). Methods: We recruited 88 patients with unilateral type IIa HFM. Data relating to the length, distance, and angle of the TMJ, were measured on 3-dimensional models created by the analysis of computed tomography data. Normality analysis was performed by using the Shapiro-Wilk test. Data were compared with the paired t test and Wilcoxon signed-rank test. Results: The height, long axis, and short axis of the affected condyle were significantly shorter than the unaffected side ( P <0.001); the ratios were 0.41±0.15, 0.75±0.20, and 0.95±0.24, respectively. The spaces between the condyle and the glenoid fossa were significantly larger in affected TMJs ( P <0.001). The ratio between the ipsilateral and contralateral anterior space in the sagittal plane was 4.62±2.59; this was significantly different than the ratio of inner space (1.50±1.70), superior space (1.70±0.97), and lateral space (1.28±0.62) in the coronal plane ( P <0.001) and the ratio of superior space (1.43±1.05) and posterior space (1.47±0.98) in the sagittal plane ( P <0.001); there were no statistical differences between the 5 spaces ( P >0.05). The breadth and depth of the glenoid fossa were significantly shorter in affected TMJs ( P <0.001), the ratio of the breadth in the affected and unaffected glenoid fossa was between 0.5 and 1 and the depth of the affected glenoid fossa was almost half of that on the unaffected side. The ratio between the ipsilateral and contralateral height of the condyle was significantly different when compared with the length of the mandibular ramus ( P <0.001). The ratio between the ipsilateral height of the condyle and the length of the mandibular ramus was significantly different when compared with that of the contralateral side ( P <0.001). The height of the affected condyle were significantly different ( P =0.005) among different ages. Conclusions: We found that hypoplasia was more severe in terms of the height of the condyle than the long axis and short axis of the condyle. The degree of condyle deformity was more severe than the mandible. And the affected condyle still had growth potential in the vertical direction with age.