Coronoid process: cone beam computed tomography (CBCT) evaluation and proposal of radiographic classification

Abstract

Objective

The objective of the study was to investigate the cone beam computed tomography (CBCT) features of coronoid processes in patients without mouth opening limitations and to develop a functional classification of coronoid process considering its relationship with the zygomatic bone.

Study Design

This cross-sectional retrospective study analyzed CBCTs of 204 patients (408 coronoid processes). CBCTs were acquired in a closed-mouth position, capturing the coronoid process and the temporomandibular joint. The scans with temporomandibular joint abnormalities, orofacial trauma or syndromes, and artifacts were excluded. Volume renderings and axial images were evaluated for the shape, surface configuration, coronoid length, condylar length, coronoid/condyle ratio, distance of the coronoid process from the posteromedial surface of the zygoma and its vertical level. The coronoid process was considered hyperplastic when coronoid/condyle ratio was greater than 1.

Results

Most coronoid processes (221) had a triangular shape. The mean length of the coronoids and condyles was 13.85 mm and 16.77 mm, respectively. The mean coronoid/condyle ratio was 0.84. A total of 87 coronoid processes were hyperplastic. The mean distance from the coronoid process to posteromedial surface of zygoma was 15.99 mm, ranging from 5.8 to 27.9 mm. The mean vertical level of coronoid processes in the study sample was 9.6 mm. A novel working classification was developed using the results of this study. The coronoid process was classified as either type I, II, III (a,b,c) and type IV (a,b,c). Type IIIa was the most common (45.83%); followed by type II (29.6%); type I (16.17%); type IIIc (4.41%); type IIIb (3.18%); type IVa (0.49%); and type IV b (0.24%).

Conclusions

The coronoid process can present a wide variety of shapes, sizes, and positions. On the basis of the results, we also propose a working radiographic classification of coronoid process that can help oral and maxillofacial radiologists to identify any abnormalities associated with the coronoid process.