A three-dimensional study of hemimandibular hyperplasia, hemimandibular elongation, solitary condylar hyperplasia, simple mandibular asymmetry and condylar osteoma or osteochondroma.

PURPOSE

To investigate the morphological features of hemimandibular hyperplasia (HH) in comparison to other condylar hyperplasia-associated asymmetries, including hemimandibular elongation (HE), solitary condylar hyperplasia (SCH), simple mandibular asymmetry (SMA) and condylar osteoma or osteochondroma (COS).

MATERIALS AND METHODS

A total of 31 HH, 9 HE, 6 SCH, 10 SMA and 10 COS patients were included in this study. Clinical documentation, panoramic radiography and computed tomography data were retrospectively reviewed. The three-dimensional measurements were performed on multi-planar reformation images and volume rendering images. The accuracy of the subjective radiological signs was evaluated using sensitivity, specificity and receiver operating curve analysis. Discriminant analysis was performed to generate predictive formulas using quantitative data.

RESULTS

The condyles in HH were regularly or irregularly enlarged, with significantly enlarged anterior-posterior length [16.2/5.29 (mean/SD, mm) P < 0.001] and volume [5.3/2.9(mean/SD, cm) P < 0.001] compared to the normal values. The condyles in HE and SMA were normally shaped, and the quantitative measurements were within the normal range. The ramus heights in the HH patients [55.7/5.4(mean/SD, mm)] were enlarged in comparison to the contralateral side (P < 0.001) and normal values (P < 0.001). The ramus heights in the HE [52.4/7.1 (mean/SD, mm), P < 0.001] and SMA [50.3/5.0(mean/SD, mm), P = 0.002] patients were enlarged in the contralateral side comparison but were within the normal range. The mandibular body heights in HH were enlarged in the premolar [16.6/1.3 (mean/SD, mm), P < 0.001] and molar [24.8/1.4 (mean/SD, mm), P < 0.001] regions. The inferior convexity of the lower mandibular border and inferiorly displaced mandibular canal produced high specificity, sensitivity and area under the curve for the diagnosis of HH. Discriminant analysis could predict the diagnoses with a cross-validation accuracy rate of 85.7%.

CONCLUSIONS

HH is a distinct clinical entity characterized by enlargement of the condyle, ramus and mandibular body. The inferior convexity of the lower mandibular border and inferiorly displaced mandibular canal is accurate and specific for the diagnosis of HH. The condyles in HE are not hyperplastic. The term "condylar hyperplasia" alone cannot be used to refer to HH or HE.