Natural head position

Natural head position is a reproducible position of a head when it is in an upright position, with eyes looking straight at a mark.[1] The concept was introduced into the field of orthodontics in the late 1950s by Moorrees and Kean.[2] A horizontal line related to the natural head position has been recommended as the most reliable plane to study cephalometric analysis.[3]

History

Anthropologists and craniologists when studying skulls faced a dilemma which was related to the head position of the skulls relative to the head position of the living human beings. In order to take care of this problem a horizontal axis line outside the skull was used to approximate a natural head position of the skull. However, a linkage between an outside horizontal plane and a horizontal plane on the skull still had to be done. Thus, after several meetings, in 1882 at a craniometric conference in Frankfort, Germany a plane known as the Frankfort horizontal plane was proposed through left and right porion and left orbitale as a horizontal plane that can be used to study skulls. In the meeting of 1884, this plane was finally accepted.[4]

Drawbacks of other planes

Planes such as the Frankfort horizontal plane or sella-nasion plane have their own drawbacks. The anatomical points that these planes are based on are not known to be stable over time, which may lead to variability and error in studying the cephalometric analysis of a patient. For example, the nasion-sella line which part of our anterior skull is used as a reference line for lateral cephalometric radiographs. The nasion point is known to be move anteriorly and inferiorly over time and thus can lead to an error in the values that are used to study the maxillo-mandibular relationship to the cranial base in lateral cephalometrics.[5]

Frankfurt Horizontal plane itself has been known to show an error of anywhere between +9 and -7 degrees. This plane is compromised by two points: Porion and Orbitale. Identifying the porion by itself is shown high variability, especially due to the point machine porion sometimes overlapping the anatomical porion.[3]

Registration

Registration of natural head position was defined by Solow and Tallgren in 1970s.[6] They used the term 'orthoposition' in which a person is asked to stand in front of a mirror and look into their own eyes after a set of neck exercises. Other ways of registering natural head position have been described by Lundstrom[7] who used an operator-based natural head position. Other methods such as use of inclinometer,[8] fluid device[9] or looking at a small light[10] have also been described.

Reproducibility

Ideally, a cephalometric plane should have good reliability, good individual reproducibility, and be as close to true horizontal plane and true vertical plane as possible. Many studies over time have discussed the reproducibility of the natural head position in patients.[11] Cooenrad and Morees in 1958, performed a study where they looked at two groups of 20-year-old female students at the Forsyth School for Dental Hygienists were radiographed in their natural head position. They showed in their short-term study that the reproducibility error was 2.05 degrees.[2] In a long-term study done by Cooke et al.,[12] they showed 1.9 degree error at 5-year mark and 2.23 degree of error at 15 year mark.

See also

References
  1. "Radiographic Cephalometry: From Basics to 3-D Imaging, Second Edition (Book/CD-ROM set)". www.quintpub.com. Retrieved 2017-11-21.
  2. "Natural head position, a basic consideration in the interpretation of cephalometric radiographs: By Coenraad F. A. Moorrees and Martin R. Kean. Am. J. Phys. Anthropol.16: 213–234, June 1958". American Journal of Orthodontics. 45 (10): 785–791. 1959-10-01. doi:10.1016/0002-9416(59)90124-1.
  3. Lundström, Anders; Lundström, Fredrik (May 1, 1995). "The Frankfort horizontal as a basis for cephalometric analysis". American Journal of Orthodontics and Dentofacial Orthopedics. 107 (5): 537–540. doi:10.1016/S0889-5406(95)70121-4.
  4. Meiyappan, N.; Tamizharasi, S.; Senthilkumar, K. P.; Janardhanan, K. (August 2015). "Natural head position: An overview". Journal of Pharmacy & Bioallied Sciences. 7 (Suppl 2): S424–S427. doi:10.4103/0975-7406.163488. ISSN 0976-4879. PMC 4606633. PMID 26538891.
  5. Houston, W. J. (1991). "Bases for the analysis of cephalometric radiographs: intracranial reference structures or natural head position". Proceedings of the Finnish Dental Society. Suomen Hammaslaakariseuran Toimituksia. 87 (1): 43–49. PMID 2057489.
  6. Solow, B.; Tallgren, A. (November 1971). "Natural head position in standing subjects". Acta Odontologica Scandinavica. 29 (5): 591–607. doi:10.3109/00016357109026337. ISSN 0001-6357. PMID 5290983.
  7. Lundström, A.; Lundström, F.; Lebret, L. M.; Moorrees, C. F. (April 1995). "Natural head position and natural head orientation: basic considerations in cephalometric analysis and research". European Journal of Orthodontics. 17 (2): 111–120. doi:10.1093/ejo/17.2.111. ISSN 0141-5387. PMID 7781719.
  8. Preston, C. B.; Evans, W. G.; Todres, J. I. (March 1997). "The relationship between ortho head posture and head posture measured during walking". American Journal of Orthodontics and Dentofacial Orthopedics. 111 (3): 283–287. doi:10.1016/s0889-5406(97)70186-0. ISSN 0889-5406. PMID 9082850.
  9. Showfety, K. J.; Vig, P. S.; Matteson, S. (June 1983). "A simple method for taking natural-head-position cephalograms". American Journal of Orthodontics. 83 (6): 495–500. doi:10.1016/s0002-9416(83)90248-8. ISSN 0002-9416. PMID 6574706.
  10. Cleall, J. F. (August 1965). "DEGLUTITION: A STUDY OF FORM AND FUNCTION". American Journal of Orthodontics. 51 (8): 566–594. doi:10.1016/0002-9416(65)90028-x. ISSN 0002-9416. PMID 14331958.
  11. Madsen, D. P.; Sampson, W. J.; Townsend, G. C. (2008-10-01). "Craniofacial reference plane variation and natural head position". The European Journal of Orthodontics. 30 (5): 532–540. doi:10.1093/ejo/cjn031. ISSN 0141-5387. PMID 18632837.
  12. Cooke, Michael S.; Orth, D. (1990-06-01). "Five-year reproducibility of natural head posture: A longitudinal study". American Journal of Orthodontics and Dentofacial Orthopedics. 97 (6): 489–494. doi:10.1016/S0889-5406(05)80029-0. PMID 2353678.
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