Morphological observation of the medial pterygoid muscle by the superimposition of images obtained by lateral cephalogram and MRI.
OBJECTIVE
To observe the morphological relationship between the maxillofacial skeleton and medial pterygoid muscle by superimposing images constructed by MRI on a cephalogram.


METHODS
Cross-sectional study.


METHODS
The Departments of Maxillofacial Orthognathics and Orthodontics, Tokyo Medical and Dental University.


METHODS
Sixteen patients (5 males and 11 females, aged between 13.5 and 27.5 years) with various craniofacial skeletal patterns, who were about to start orthodontic treatment.


METHODS
Lateral cephalometric radiographs and MRI scans were obtained and their images uploaded to a computer using a digitizer. The area of the medial pterygoid muscle was selected by binarization from the MRI. The mid-sagittal-plane MRI with a complete superimposed sagittal image of the medial pterygoid muscle was superimposed on the cephalogram using anatomical structures situated in the mid-sagittal plane of the head and shapes that could be identified from both the radiograph and the MRI image.


RESULTS
These combined images showed various shapes of the medial pterygoid muscle. The inclination axis of the medial pterygoid muscle was correlated with various cephalometric variables including SNB (r=0.658), Facial angle (r=0.601), ramus inclination (r=0.676) and Ba-Po% (r=0.585). The volume of the medial pterygoid muscle was also correlated with cephalometric variables such as ramus inclination (r=0.453), Ba-Nmm (r=0.676), Ba-Po% (depth) (r=0.447), Ar-Go% (depth) (r=0.444) and Ar-Go% (actual length) (r=0.532).


CONCLUSIONS
Morphometric analysis using a superimposed image of the medial pterygoid muscle produced from a cephalogram and MRI may help explain the influence of the medial pterygoid muscle inclination axis and volume on the shape of the mandibular bone, especially the shape of the ramus.
Kusumah
Shinta Wirahadi
SW
Maxillofacial, Orthognathics, Graduate School, Tokyo Medical and Dental, University, Tokyo, Japan.
Suzuki
Shoichi
S
Itoh
Kouichi
K
Higashino
Ryoji
R
Ohbayashi
Naoto
N
Kurabayashi
Tohru
T
Moriyama
Keiji
K
D000293:Adolescent; D000328:Adult; D019412:Anatomy, Cross-Sectional; D002508:Cephalometry / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008334:Mandible / Q000033:anatomy & histology; D008437:Maxilla / Q000033:anatomy & histology; D009295:Nasal Bone / Q000033:anatomy & histology; D011626:Pterygoid Muscles / Q000033:anatomy & histology*; D012658:Sella Turcica / Q000033:anatomy & histology; D013100:Sphenoid Bone / Q000033:anatomy & histology; D055815:Young Adult