title: Does head posture have a significant effect on the hyoid bone position and sternocleidomastoid electromyographic activity in young adults?
abstract: The aim of this study was to evaluate the associations between head posture (head extension, normal head posture, and head flexion) and anteroposterior head position, hyoid bone position, and the sternocleidomastoid integrated electromyographic (IEMG) activity in a sample of young adults. The study included 50 individuals with natural dentition and bilateral molar support. A lateral craniocervical radiograph was taken for each subject and a cephalometric analysis was performed. Head posture was measured by means of the craniovertebral angle formed by the MacGregor plane and the odontoid plane. According to the value of this angle, the sample was divided into the following three groups: head extension (less than 95 degrees); normal head posture (between 95 degrees and 106 degrees); and head flexion (more than 106 degrees). The following cephalometric measurements were taken to compare the three groups: anteroposterior head position (true vertical plane/pterygoid distance), anteroposterior hyoid bone position (true vertical plane-Ha distance), vertical hyoid bone position (H-H' distance in the hyoid triangle), and CO-C2 distance. In the three groups, IEMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. In addition, the condition with/without craniomandibular dysfunction (CMD) in each group was also assessed. Head posture showed no significant association with anteroposterior head position, anteroposterior hyoid bone position, vertical hyoid bone position, or sternocleidomastoid IEMG activity. There was no association to head posture with/without the condition of CMD. Clinical relevance of the results is discussed.
authors.affiliation: Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile, Santiago.
authors.forename: Saúl
authors.initials: S
authors.lastname: Valenzuela
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Miralles
authors.forename: María José
authors.initials: MJ
authors.lastname: Ravera
authors.forename: Claudia
authors.initials: C
authors.lastname: Zúñiga
authors.forename: Hugo
authors.initials: H
authors.lastname: Santander
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ferrer
authors.forename: Jorge
authors.initials: J
authors.lastname: Nakouzi
mesh_terms: D000328:Adult; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology; D002508:Cephalometry; D001270:Cervical Atlas / Q000033:anatomy & histology; D002574:Cervical Vertebrae / Q000033:anatomy & histology; D017271:Craniomandibular Disorders / Q000473:pathology / Q000503:physiopathology; D003679:Deglutition / Q000502:physiology; D004576:Electromyography; D005260:Female; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D006928:Hyoid Bone / Q000033:anatomy & histology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology*; D009777:Occipital Bone / Q000033:anatomy & histology; D009809:Odontoid Process / Q000033:anatomy & histology; D011187:Posture; D012815:Signal Processing, Computer-Assisted; D013100:Sphenoid Bone / Q000033:anatomy & histology