Variation in natural head position and establishing corrected head position.

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Variation in natural head position and establishing corrected head position A.L. Barbera, W.J. Sampson ∗, G.C. Townsend School of Dentistry, University of Adelaide, SA 5005, Australia

a r t i c l e

i n f o

Article history: Received 3 October 2012 Accepted 5 March 2014 Available online xxx

a b s t r a c t Corrected head position (CHP) has been simulated by using the Frankfurt horizontal (FH) for over 100 years but FH varies between individuals. Because CHP is biologically relevant for orthodontic diagnosis and treatment planning, orthognathic surgical planning, and art, this study examined relationships between head position and selected cephalometric planes. Natural head position cephalograms of Aboriginal Australians and two contemporary samples from private orthodontic practices were analysed. Each sample comprised 40 individuals (20 males and 20 females). The Aboriginal Australian sample comprised longitudinal data (T1 early adolescent, T2 late adolescent, and T3 adult), enabling examination of natural head position (NHP) reproducibility over a period of approximately 8 years. Results of reproducibility differences revealed an absolute mean = 2.9◦ , range = −7.9◦ to 8.2◦ , and standard deviation = 3.6◦ . Stable basicranial line (SBL), neutral horizontal axis (NHA), FH, palatal plane (P plane), and Krogman–Walker plane (KW plane) demonstrated near parallelism and their mean angulations from the true horizontal (HOR) ranged between −4.6◦ and 2.4◦ . While NHP is not consistently reproducible at the individual level, the combined use of multiple planes such as SBL, P plane, and KW plane enables a more consistent CHP to be achieved. Crown Copyright © 2014 Published by Elsevier GmbH. All rights reserved.

∗ Corresponding author. Tel.: +61 8 83033293; fax: +61 8 83033444. E-mail address: [email protected] (W.J. Sampson). http://dx.doi.org/10.1016/j.jchb.2014.03.002 0018-442X/Crown Copyright © 2014 Published by Elsevier GmbH. All rights reserved.

Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002

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Introduction Natural head position (NHP) is the most balanced, natural position of the head when a person views an object at their eye level (Moorrees and Kean, 1958). In NHP, various craniofacial planes may be compared to the true horizontal (HOR) or true vertical (VER) derived from plumb-bobs or spirit levels which are usually transferred to photographs or radiographs for analysis. In this study, angles are described as being measured from HOR in accordance with the definition of Lundström (1982:82): “A forward-upward deviation from the true horizontal is denoted as a positive inclination and forward-downward as a negative inclination.” NHP is not a new concept and was used by artists such as Leonardo da Vinci and Albrecht Dürer in the late 15th and early 16th centuries. Their art work depicts subjects in apparent NHP, often with grid lines drawn on the images. It seems that prediction of NHP assisted these artists with depiction of human head position and face form. Grids which bear striking similarity to Da Vinci’s grid, such as those described by De Coster (1939), Thompson (1942) and Moorrees (1953) have been used for craniofacial evaluation. However, De Coster used Frankfurt horizontal (FH) whereas Moorrees used a constructed HOR to sella-nasion (SN) angle at 5◦ to establish head position. In orthodontics and oral and maxillofacial surgery it is useful to be able to predict the NHP of patients who have dental and facial skeleton deformity because their reconstruction relates to the most frequently adopted head orientation (i.e. NHP). Schmidt (1876) used the phrase “corrected head position” (CHP) to describe manipulation of a subject’s head position to a predicted natural head position. CHP is synonymous with “natural head orientation” (NHO) (Lundström and Lundström, 1995). Schmidt’s frame included an attached protractor and plumb-bob to determine the relation of Von Ihering’s line (a line joining the midpoint of the external acoustic meatus to orbitale) to VER and, therefore, to HOR. It was concluded that head position could be reproduced with less variation when head position corrections were made to Von Ihering’s line which displays a mean angle of 5.5–5.8◦ from HOR (Schmidt, 1876). Many studies have investigated the variability of cephalometric planes, such as FH and SN, from HOR with subjects in NHP (Bjerin, 1957; Downs, 1956; Moorrees and Kean, 1958; Schmidt, 1876; Solow and Tallgren, 1971). Various skull planes have been used to correct head position, including the Camper plane (Camper, 1768, cited by Bjerin, 1957), the FH (Broadbent, 1931; De Coster, 1939; Hofrath, 1931), and the vestibular axes (Delattre and Fenart, 1960). The problem with use of a single plane to correct head position is that its landmark locations and, therefore, its angulation vary between individuals. It has been suggested that NHP is appropriate for craniofacial evaluation because it is a physiological position determined by vision (Fjellvang and Solow, 1986), gravity and muscular proprioceptive stimuli (Delattre and Fenart, 1960; Fjellvang and Solow, 1986), airway patency (Behlfelt, 1990; Cuccia et al., 2008; Huggare and Rolling, 1986; Linder-Aronson and Woodside, 2000; Solow et al., 1993), ambient temperature (Huggare and Rolling, 1986), personality, mood, emotions, and intelligence (Schmidt, 1876). In fact, this multitude of factors might provide reason not to rely upon NHP because head position can vary in an individual at different points in time. It is not surprising that studies of NHP demonstrate a lack of reproducibility at the individual level (Barbera et al., 2009; Cooke and Wei, 1988a; Downs, 1956; Foster et al., 1981; Luyk et al., 1986; Madsen et al., 2008; Moorrees and Kean, 1958; Peng and Cooke, 1999; Schmidt, 1876; Siersbaek-Nielsen and Solow, 1982; Solow and Tallgren, 1971). Nevertheless, these studies also suggest that NHP appears to be somewhat reproducible when group averages are determined. Therefore, a reliable method to establish a correlated head position (CHP) would be helpful when natural head position is uncertain. In the authors’ previous study of head position, 40 Aboriginal Australians (17 years of age or older) were investigated (Barbera et al., 2009). A near parallelism of neutral horizontal axis (NHA), FH, palatal plane (P plane), and Krogman–Walker plane (KW plane) was found. The average inclination from HOR ranged between −2.5◦ and −0.2◦ . Although variation between individuals was also demonstrated, it was concluded that it might be more consistent to use the means of the angles of multiple planes from HOR, rather than one plane, to correct for head position ambiguity. In addition to the planes measured in the authors’ previous study, stable cranial base plane (SBL) was measured in the current study. Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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Sassouni (1955) noted that there are two contours of the anterior cranial base to consider: the upper is the roofing of the orbit, including the lesser wing of the sphenoid; the lower is the spheno-ethmoid area posteriorly and the cribriform plate anteriorly. The lower anterior cranial base was of particular interest due to its parallel relationship with the maxillary hard palate, described previously in most detail by Delaire and co-workers in their cephalometric analysis (Delaire, 1978; Delaire et al., 1981) and in broader terms by Enlow his co-workers in their equivalent-balance concept or counterpart analysis (Enlow et al., 1969; Enlow, 1982). The angle of the hard palate relative to HOR has been investigated (Barbera et al., 2009; Cooke and Wei, 1988b; Foster et al., 1981; Leitao and Nanda, 2000; Madsen et al., 2008; Solow and Siersbaek-Nielsen, 1986; Solow and Tallgren, 1971; Sonnesen and Bakke, 2005; Tecco et al., 2005), but it appears that lower anterior cranial base plane angles relative to HOR or VER with subjects in NHP have not been measured in previous studies. Enlow and McNamara (1974) measured a lower anterior cranial base plane (cribriform plate plane) angle, relative to another craniofacial plane (midfacial plane) using lateral headfilms of 147 adults and found that 97% of the sample was within an 87.5◦ to 92.0◦ range. The cribriform plate plane was not measured in relation to HOR/VER with individuals in NHP. The current study measured a lower anterior cranial base plane, the stable basicranial line (SBL), angle from HOR. There were two main aims of this study. One was to examine NHP reproducibility in Aboriginal Australians over an 8-year period and compare/contrast the findings with those of previous studies. A second aim was to examine SBL, NHA, FH, P plane, and KW plane variability and develop a simple method to correct head position in contemporary orthodontic practice where subjects are predominantly adolescent and of European ancestry. The hypotheses tested in this study are that: 1. Natural head position is not always reproducible at the individual level. 2. Use of multiple planes to adjust head position is more reliable than use of a single skull plane. Materials and methods Sample 1 Lateral cephalographs of Aboriginal subjects from Yuendumu, Central Australia were obtained between 1961 and 1972 (Brown and Townsend, 2001). The roentgenographic method followed closely that of Björk (1950). NHP was systematically obtained by asking subjects to look at a point on a wall at their eye level while the head was stabilised and orientated with ear rods and a nose rest (Brown and Barrett, 1964). Forty subjects (20 males and 20 females) were randomly chosen from the Yuendumu sample. Each subject had a lateral cephalograph obtained between age 9 and 12 years (T1, mean age = 9.9 years), 13 and 16 years (T2, mean age = 13.2 years), and at 17 years or greater (T3, mean age = 17.6 years), providing 120 lateral cephalographs in total. The lateral cephalographs were scanned into a computer using an ‘Epson Perfection 4990 Photo’ scanner at 350 dpi resolution. ‘Adobe Photoshop CS’ (Adobe Systems Inc., San Jose, CA, USA) was used to adjust lighting and contrast levels of the images. Measurements were made with the ‘Mona Lisa’ computer software program (Tidbinbilla, Pty Ltd., Canberra, Australia). HOR was determined by construction of a perpendicular line from the vertical edge of the lateral cephalograph film. Landmarks were digitised from the computer screen to record the reference planes and calculate the angular measurements. The landmarks and planes are shown in Fig. 1 and their descriptions are in Table 1. The angles examined were: HOR–StN, HOR–SBL, HOR–NHA, HOR–FH, HOR–P plane, and HOR–KW plane. The reliability of the method was determined by randomly re-digitising 20% of the cephalographs after at least 1 week. Paired t-tests, Dahlberg’s (1940) statistic, and error % were calculated to assess systematic and random errors. The cephalographs obtained at T1 were compared with those at T3 to test the reproducibility of NHP by comparing StN – HOR angles. The StN line was chosen due to the consistency and ease of locating Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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Fig. 1. The lines and planes used to construct the angular variables examined in this study shown on a tracing of one of the Aboriginal Australian female subjects from our previous study (Barbera et al., 2009). See Table 1 for definitions/descriptions of landmarks and planes.

St and N. The average time between T1 and T3 was approximately eight years and comparisons were made using paired t-tests. Descriptive statistics were produced for all variables. Statistical analyses were performed for data from males and females combined because there were no statistically significant sex differences (Barbera et al., 2009; Madsen et al., 2008). Five skeletal planes, SBL, NHA, FH, P plane, and KW plane were focussed upon due to their observed near parallelism and apparently horizontal orientation. A one-way analysis of variance (ANOVA) was performed using data for these planes to compare variation within and between samples. Sample 2 A sample of 40 adolescents (20 males and 20 females, mean age = 13.4 years, age range = 9–17 years), each having a lateral cephalograph carefully obtained in NHP, was compiled from a private orthodontic practice in Canberra, Australia. HOR was determined by construction of a perpendicular line from a plumb-bob visible in the cephalometric image. The lateral cephalographs were analysed in exactly the same manner as for Sample 1 using the ‘Mona Lisa’ software. Method error was assessed in the same manner as for Sample 1. Sample 3 A sample of 40 adolescents (20 males and 20 females, mean age = 12.2 years, age range = 8–15 years), each having a lateral cephalograph taken in NHP by an experienced radiographer, was sourced from a private orthodontic practice in Perth, Western Australia. The cephalographs, including assessment of method error, were analysed in the same manner as for Sample 1. Both the Canberra and Perth practices employ strict protocols to record cephalograms in NHP. The lateral cephalostat machines of all samples were carefully positioned so that the vertical edge of the film holder was parallel with the earth’s gravity (this was confirmed by plumb-bob comparison). Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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Table 1 Definitions/descriptions of landmarks and planes. Definition/description Landmarks ANS = anterior nasal spine Max = maxillon

N = nasion Occ = occipitale OM = orbital margin point Or = orbitale PNS = posterior nasal spine Po = porion St = sella tangent

T = tuberculum sellae Ti = tuberculum sellae inferior Planes HOR = true horizontal plane NHA = neutral horizontal axis = OM–Ti StN = St–N

SBL = stable basicranial line

“The tip of the median, sharp bony process of the maxilla at the lower margin of the anterior nasal opening.” (Riolo et al., 1974) “. . .a point just below (occasionally above) the Key Ridge, midway between the upper and lower border of the palate.” (Walker, 1967; Rothstein and Yoon-Tarlie, 2000) “The junction of the frontonasal suture at the most posterior point on the curve at the bridge of the nose.” (Riolo et al., 1974) “. . .the lowest point on the occipital bone.” (Walker, 1967; Rothstein and Yoon-Tarlie, 2000) “. . .the superoinferior midpoint between the lower and upper orbital rims.” (McCarthy and Lieberman, 2001) “The lowest point on the average of the right and left borders of the bony orbit.” (Riolo et al., 1974) “The most posterior point at the sagittal plane on the bony hard palate.” (Riolo et al., 1974) A point on the superior edge of the external auditory canal. (Broadbent, 1931) Consider a line passing through N and tangent to the inferior border of sella turcica. St is the point at which this line touches the inferior border of sella turcica. (Barbera et al., 2009) “The most superior point of the anterior wall of sella turcica at the junction with tuberculum sella.” (Viazis, 1991) A point on the anterior wall of sella turcica approximately 2 mm inferior from tuberculum sellae. (Barbera et al., 2009) A plane determined as being perpendicular to earth’s gravity.

A line which passes through nasion and is a tangent to the inferior border of sella turcica. Sassouni (1955) used the Lower anterior cranial base Plane or Basal Plane (OS ) which is “A plane parallel to the axis of the upper contour of the lower anterior cranial base and tangent to the inferior border of sella turcica.” O is the point where most of Sassouni’s planes intersected. The reasons for changing S to St were that: St is in a different part of the inferior border of sella turcica when compared to S because it is associated with a different line. The stable basicranial line passes “. . .through the most superior point of the anterior wall of the sella turcica at the junction with tuberculum sellae (point T) and tangent to lamina cribrosa of the ethmoid.” (Tollaro et al., 1995)

FH = Frankfurt horizontal = Po–Or KW plane = Krogman–Walker plane = Occ–Max P plane = palatal plane = ANS–PNS

Method error Method error results include any significant systematic (p < 0.05) and random errors (error % > 10%). Sample 1 T1 showed significant error % for the variables HOR–SBL = 25.5% and HOR–P plane = 14.7%. No method error significance was shown in Sample 1 T2, Sample 1 T3 or Sample 2. Sample 3 showed a p value = 0.00 for HOR–NHA. Sample 3 also demonstrated significant error % for the variables HOR–SBL = 22.6%, HOR–NHA = 17.3% and HOR–P plane = 26.6%. HOR was a common plane of all angular measurements. The ability to consistently locate HOR may have lowered the error %. Overall, larger errors were found with measurements involving points that are notoriously difficult to identify, but most errors were small in absolute terms and unlikely to bias the results. Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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Table 2 NHP reproducibility, measuring HOR–StN, between T1 and T3. Subject number

HOR–StN T3

T1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Sum Mean MADa SEDb Range SD

d

5.7 8.5 5.8 2.4 6.2 12.3 7.5 7.0 7.4 14.1 6.6 11.4 10.9 14.9 10.4 10.5 13.0 3.5 9.6 5.8 10.0 10.7 10.8 2.4 10.4 13.3 3.8 13.4 8.1 7.3 12.7 15.2 6.6 15.8 8.2 4.9 7.1 3.7 3.7 7.7

8.2 6.5 5.5 3.6 4.8 8.8 15.7 2.9 4.9 10.5 5.7 11.1 8.0 16.6 3.8 8.6 5.1 3.2 7.1 3.8 11.7 9.9 16.1 2.5 15.1 10.0 3.6 12.4 12.8 11.7 14.6 10.8 11.1 9.6 14.9 8.3 8.8 3.1 5.3 9.7

349.4 8.7

346.4 8.7

2.4–15.8 3.69

2.5–16.6 4.14

2.5 −2.0 −0.3 1.2 −1.4 −3.5 8.2 −4.1 −2.5 −3.6 −0.9 −0.3 −2.9 1.7 −6.6 −1.9 −7.9 −0.3 −2.5 −2.0 1.7 −0.8 5.3 0.1 4.7 −3.3 −0.2 −1.0 4.7 4.4 1.9 −4.4 4.5 −6.2 6.7 3.4 1.7 −0.6 1.6 2.0 −3.0 −0.1 2.9 0.6 −7.9 to 8.2 3.64

t = 0.13, p = 0.90 (paired t-test). a Mean absolute difference. b Standard error of the differences of means.

Results Table 2 shows NHP reproducibility between T1 and T3 in Sample 1. The mean of absolute differences equalled 2.9◦ , whereas the mean difference equalled −0.1◦ . The range of differences was from −7.9◦ to 8.2◦ , and the standard deviation of differences was 3.6◦ . The mean value for HOR–StN at T1 and at T3 equalled 8.7◦ but individuals were less consistent. Those individuals who were in the extremities of the Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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Table 3 Summary of the five planes in Sample 1 (T1, T2, T3), Sample 2, and Sample 3, including descriptions based on combinations of three and five planes. Sample

Angular variables (◦ )

n

Mean

Range

SD

Sample 1 T1

HOR–SBL HOR–NHA HOR–FH HOR–KW plane HOR–P plane 5 planes average 3 planes average

40 40 40 40 40 40 40

−0.1 −2.9 −3.5 0.4 −1.1 −1.4 −0.2

−4.8 to 7.4 −11.3 to 5.4 −10.0 to 5.4 −5.1 to 7.7 −7.6 to 7.9 −7.7 to 6.8 −5.7 to 7.7

2.59 3.49 3.15 2.91 3.63 2.72 2.74

Sample 1 T2


40 40 40 40 40 40 40

0.3 −2.7 −3.2 0.0 0.1 −1.1 0.1

−7.1 to 7.0 −13.6 to 6.4 −10.1 to 4.8 −6.6 to 7.3 −6.9 to 8.3 −8.0 to 6.0 −5.5 to 6.5

3.56 4.03 3.71 3.46 4.25 3.37 3.40

Sample 1 T3


40 40 40 40 40 40 40

−0.1 −3.6 −3.6 −1.1 −0.7 −1.8 −0.6

−5.9 to 7.7 −12.6 to 4.5 −10.0 to 3.4 −6.2 to 5.2 −7.5 to 5.5 −6.5 to 3.8 −5.7 to 5.6

3.02 4.08 3.23 2.95 3.44 2.93 2.82

Sample 2


40 40 40 40 40 40 40

2.4 −0.5 −1.3 0.9 2.1 0.7 1.8

−3.1 to 10.3 −8.1 to 12.6 −17.1 to 7.4 −13.1 to 11.1 −5.5 to 9.7 −7.7 to 10.2 −5.6 to 10.3

3.31 4.49 4.19 4.33 3.79 3.51 3.36

Sample 3


40 40 40 40 40 40 40

−1.0 −4.0 −4.6 −2.8 −1.3 −2.8 −1.7

−12.0 to 6.1 −11.1 to 8.2 −11.3 to 7.9 −10.6 to 10.2 −10.0 to 11.7 −9.6 to 8.4 −9.1 to 8.6

3.97 4.49 4.18 4.54 4.88 4.01 4.01

5 planes = SBL + NHA + FH + KW plane + P plane; 3 planes = SBL + KW plane + P plane.

range of differences were male subject 17 (d = −7.9◦ ) and male subject 7 (d = 8.2◦ ). Subject 17 had a T1 HOR–StN measurement of 13.0◦ and a T3 measurement of 5.1◦ . Subject 7’s T1 measurement was 7.5◦ and T3 HOR–StN equalled 15.7◦ . These examples illustrate the extent of intra-individual variability and the need for obtaining a corrected head position. Table 3 shows the descriptive statistics for the five planes, SBL, NHA, FH, P plane, and KW plane measured from HOR, with subjects in NHP. The five planes demonstrated near parallelism and the range of the averages was from −4.6◦ to 2.4◦ from HOR. The overall range was −13.6◦ to 12.6◦ and the SD was 3.7◦ . Additionally, the average of the five planes was determined for each individual, then an overall mean for all subjects was determined, as well as SD and range. The same process was undertaken for the three planes that demonstrated the lowest variation and are the easiest to visualise quickly; they are the SBL, P plane, and KW plane. Variation was generally less when multiple planes were combined in individuals when compared to variation of a single plane. NHA and FH generally demonstrated more variation than SBL, P plane, and KW plane, supporting the finding that there seemed to be minimal advantage in combining all five planes rather than three in order to decrease variation. On average, NHA and FH demonstrated slightly more negative inclination from HOR compared with the other planes. ANOVA revealed statistically significant differences in the angles Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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from HOR between samples. However, the angles were all very small, being approximately 1◦ to −3◦ from HOR. Only data from Sample 1 at T2 were used in the ANOVA because the ages of T2 Aboriginal adolescents more closely matched the ages of subjects of Samples 2 and 3.

Discussion Natural head position does not appear to be reproducible enough at an individual level to be used with confidence for craniofacial analysis. Likewise, the use of only one hard tissue plane in isolation, such as FH, is inadequate for establishing a corrected head position. It appears to be more reliable to use the averaged angles of several planes related to HOR to help correct ambiguous head position. Head position correction based on averages may not be applicable for all individuals due to their anatomical variation, but it is suggested that use of multiple planes to correct head position is less prone to variability than using a single plane or NHP alone. Use of two to three of the selected planes is thought to be reasonable without being onerous. This study focussed on the planes SBL, NHA, FH, P plane, and KW plane which were found to demonstrate near parallelism with their averages ranging from −4.6◦ to 2.4◦ from HOR. Although there were generally large ranges and standard deviations associated with each variable, less variation was demonstrated when multiple planes were combined (Table 3). The reason for focussing on the selected planes was their apparent horizontal orientation. The practical aspect of re-orientating head position using planes of generally horizontal orientation (Barbera et al., 2009) is that visualisation of head position is immediately clear. It is suspected that FH was constructed and changed from Von Ihering’s line for this same reason. Other studies which have investigated some of these planes in relation to HOR or VER with subjects in NHP are detailed in Table 4 (Barbera et al., 2009; Bjerin, 1957; Cooke and Wei, 1988b; Downs, 1956; Foster et al., 1981; Leitao and Nanda, 2000; Lundström and Lundström, 1992, 1995; Madsen et al., 2008; Moorrees and Kean, 1958; Schmidt, 1876; Solow and Tallgren, 1971; Solow and SiersbaekNielsen, 1986; Sonnesen and Bakke, 2005; Tecco et al., 2005). Most commonly, the HOR–FH and/or HOR–P plane has been measured. In the studies using VER, values have been converted to HOR for comparative purposes. Variations in means, standard deviations, and ranges are evident between the different studies. When comparing four of the angles from this study which have been considered by other studies, there are some differences but, if averaged, the mean angles generally demonstrate slight negative inclination from HOR. For example, the mean value of HOR–FH from all studies combined is −1.0◦ and that of HOR–P plane equals −2.0◦ . A clearly discernable rectangular shape of the nasal airway region was observed between SBL and P plane which may have evolutionary and functional associations (Delaire, 1978; Delaire et al., 1981; Enlow, 1982; Enlow and Azuma, 1975). Therefore, a good method for correction of head position would be to orientate the nasal airway region to the horizontal [Fig. 2(a) and (b)]. This should be done with consideration of the orientation of KW plane. The orientation of FH and NHA could also be considered but their immediate landmark detection on lateral cephalographs can be problematic. It is suggested that SBL, P plane, and KW plane are measured in relation to the horizontal edge of the radiograph (radHOR). Then, the average of SBL, P plane, and KW plane angles can be used to represent the corrected horizontal (cHOR) line [Fig. 2(b)]. This then represents the reference plane for corrected head position (CHP). The suggested method of correcting head position should be applicable to long-faced or short-faced individuals. In the case of long faces, Sassouni and Nanda (1964), Richardson (1969), Nahoum (1971), and Frost et al. (1980) have demonstrated that the long face effect on the facial planes appears to occur below the hard palate. The hard palate appears to maintain a horizontal angulation in relation to other structures such as the PM vertical and the lower anterior cranial base with growth (Björk, 1977; Broadbent, 1937; Brodie, 1940; Enlow, 1982; Frost et al., 1980; Nanda and Merrill, 1994; Riolo et al., 1974). Selection criteria based on the corrected horizontal would help standardise facial patterns when group comparisons are made. For example, clinical trials have often used selection criteria such as ANB angle to discriminate treatment outcome groupings when this is known to be misleading and poorly representative of many dento-facial patterns (Darendeliler, 2006). Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002

m/f, n

HOR–NHA Mean

SD

Range

Study features

m/f, n

HOR–FH Mean

SD

Range

Study features

m/f, n

Schmidt (1876)

Mean

SD

Range

5.5 5.8 100

1.3

5.00

Bjerin (1957)

35 35 f 66

−1.8 −0.1 −2.2

4.55 4.26 4.02

f 61

−1.7

3.68

Foster et al. (1981) Solow and SiersbaekNielsen (1986)

90

−2.3

5.91

43

0.9

43

1.1

Cooke and Wei (1988a,b)

m 120

3.4

6.90

m 40 m 27

−2.3 −5.1

5.20 5.30

f 25 m 39

−4.8 −1.6

4.70 5.20

f 40 m 39 f 40 m 284

−2.0 1.0 2.1 0.7

4.00 3.60 3.00 5.02

−30.7 to 13.7

57

−4.8

4.63

−17.1 to 5.9

Solow and Tallgren (1971)

Lundström and Lundström (1992) Lundström and Lundström (1995)

Leitao and Nanda (2000) Sonnesen and Bakke (2005) Tecco et al. (2005) Madsen et al. (2008)

57

−5.4

5.36

−23.1 to 6.0

−18.0 to 13.0 Approx. 9.5 years old

Approx. 12 years old Chinese Caucasian

NHP

NHP CHP CHP

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Von Ihering’s line Von Ihering’s line Soft tissue palpation of FH Standing Sitting Condylion replacing Po, NHP CHP

Downs (1956)

Moorrees and Kean (1958)

Study features

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JCHB-25341; No. of Pages 14

Authors (date)



Table 4 Comparison of HOR–SBL, HOR–NHA, HOR–FH, HOR–KW plane, and HOR–P plane with other studies.

9

HOR–SBL m/f, n

HOR–NHA Mean

SD

Range

Study features

Barbera et al. (2009)

2.59

−4.8 to 7.4

40

0.3

3.56

−7.1 to 7.0

40

−0.1

3.02

−5.9 to 7.7

40

2.4

3.31

40

−1.0

3.97

Aboriginal 9–12 years Aboriginal 13–16 years Aboriginal >17 years Sample 2, Australian Sample 3, Australian

−3.1 to 10.3 −12.0 to 6.1

SD

Range

Study features

m/f, n

Mean

SD

Range

Study features

40

−1.8

5.41

−13.5 to 10.0

Rest position (R) In occlusion (O) Aboriginal 9–12 years Aboriginal 13–16 years Aboriginal >17 years Sample 2, Australian Sample 3, Australian

40

−2.5

5.27

−13.5 to 9.0

R

40

−1.6

4.85

−12.0 to 8.0

O

40

−3.5

3.15

−10.0 to 5.4

Aboriginal 9–12 years Aboriginal 13–16 years Aboriginal >17 years Sample 2, Australian Sample 3, Australian

40

−0.9

5.40

−11.5 to 10.0

40

−2.9

3.49

−11.3 to 5.4

40

−2.7

4.03

−13.6 to 6.4

40

−3.6

4.08

−12.6 to 4.5

40

−0.5

4.49

40

−4.0

4.49

HOR–KW plane

−8.1 to 12.6 −11.1 to 8.2

40

−3.2

3.71

−10.1 to 4.8

40

−3.6

3.23

−10.0 to 3.4

40

−1.3

4.19

−17.1 to 7.4

40

−4.6

4.18

−11.3 to 7.9

HOR–P plane

m/f, n

Mean

SD

f 66

−3.3

3.55

f 61

−2.8

3.57

Range

Study features

m/f, n

Mean

SD

Range

Study features

m 120

−8.5

5.02

−22.0 to 9.3

m 120 90

−5.5 −2.6

4.69 6.38

−16.5 to 9.5 −17.0 to 16.0

Self-balance position Mirror position

43

−1.0

Schmidt (1876) Downs (1956) Bjerin (1957) Moorrees and Kean (1958)

Solow and Tallgren (1971) Foster et al. (1981) Solow and SiersbaekNielsen (1986)

Cooke and Wei (1988a,b) Lundström and Lundström (1992) Lundström and Lundström (1995)

Not really HOR–KW plane, was HOR–HIS

Approx. 9.5 years old

43

−0.3

m 120

−0.3

4.50

Approx. 12 years old Chinese

m 40

−2.6

5.50

Caucasian

ARTICLE IN PRESS

Authors (date)

−0.1

40

Mean


Barbera et al. (current study)

HOR–FH

m/f, n

G Model

Authors (date)


10


Table 4 (Continued)

HOR–P plane Mean

SD

Range

Study features

Leitao and Nanda (2000) Sonnesen and Bakke (2005) Tecco et al. (2005) Madsen et al. (2008) Barbera et al. (2009) Barbera et al. (current study)

m/f, n

Mean

SD

Range

m 284

−0.5

4.38

−15.1 to 10.1

0.8

5.75

88

57

−3.1

4.67

−17.2 to 6.1

40

−1.0

5.41

−11.5 to 9.0

40 40

−0.2 0.4

5.22 2.91

−8.5 to 10.0 −5.1 to 7.7

40

0.0

3.46

−6.6 to 7.3

40

−1.1

2.95

−6.2 to 5.2

40

0.9

4.33

−13.1 to 11.1

40

−2.8

4.54

−10.6 to 10.2

Study features

f 23 f 23 57

−8.8 −3.8 −1.0

11.11 9.65 5.04

−28.0 to 9.0 −18.0 to 10.0 −13.4 to 9.8

Prior to RME Tx. After RME Tx.

R

40

−1.7

4.96

−13.0 to 9.0

R

O Aboriginal 9–12 years Aboriginal 13–16 years Aboriginal >17 years Sample 2, Australian Sample 3, Australian

40 40

−0.5 −1.1

4.83 3.63

−11.0 to 9.0 −7.6 to 7.9

40

0.1

4.25

−6.9 to 8.3

O Aboriginal 9–-12 years Aboriginal 13–16 years Aboriginal >17 years Sample 2, Australian Sample 3, Australian

40

−0.7

3.44

−7.5 to 5.5

40

2.1

3.79

−5.5 to 9.7

40

−1.3

4.88

−10.0 to 11.7

ARTICLE IN PRESS

m/f, n

G Model

HOR–KW plane


Authors (date)

A.L. Barbera et al. / HOMO - Journal of Comparative Human Biology xxx (2014) xxx–xxx 11


Table 4 (Continued)


ARTICLE IN PRESS


Fig. 2. (a) Lateral cephalograph of long-faced subject 12 of Sample 3 prior to head position correction. (b) Corrected head position of long-faced subject 12 of Sample 3 by nasal airway orientation. The radiograph has been rotated such that the average of the angles formed by SBL plane, P plane and KW plane becomes the corrected horizontal (cHOR).

In asymmetry cases, the planes unaffected by asymmetry should be used to correct head position. For example, in a patient with hemifacial microsomia, it may be best to avoid using FH due to its landmarks being located laterally on the skull. NHA may also be misleading if an orbit is affected. Nasal airway orientation in combination with visualising the KW plane may be the best approach. When using computed tomography (CT) or cone beam computed tomography (CBCT) scans to assess lateral head position, often lateral layers are rendered over the midline layer to establish head position from FH. The combined use of SBL, P plane, and KW plane avoids the requirement for layer rendering in CT or CBCT scans because they are midline structures. However, these midline structures are not broad enough transversely to achieve corrected frontal head position and the reader is referred to the study by Zepa and Huggare (1998). The reasons for using a combination of planes to determine CHP is similar to the rationale for establishing FH that has been used for many years. The suggested method simply replaces FH with cHOR to adjust head position. Single planes other than FH have also been used for apical base analysis such as functional occlusal plane (FOP) in the pitchfork analysis (Johnston, 1996) and P plane (Nanda and Merrill, 1994). An example of cHOR application to the pitchfork analysis would be to include a cHOR–FOP angle measurement to gain some appreciation of the patient’s vertical face type. It is well known that head positioning can substantially influence the profile and perception of mandibular and maxillary position in relation to the calvaria and may influence surgical treatment objectives. An example of clinical application is in determination of maxillary central incisor positioning in maxillary osteotomy cases (Taylor, 1998). It is suggested that it would be more appropriate to use a perpendicular from cHOR after head position correction using multiple planes rather than from FH alone to determine maxillary incisor positioning. In all, the use of cHOR, rather than FH, SN or other single planes to achieve CHP is a novel, practical and more reliable method. Conclusions Natural head position (NHP) was not consistently reproducible in individuals in this and other studies. However, when group averages are formed, NHP does appear to be more reproducible. Use of only one plane to correct head position provides a generally unreliable estimate of true NHP due to anatomical variation between individuals. A practical approach is to use at least two horizontally trending planes in combination. The stable basicranial line (SBL), palatal plane (P plane), and Krogman–Walker plane (KW plane) appear to be suitable planes. Please cite this article in press as: Barbera, A.L., et al., Variation in natural head position and establishing corrected head position. HOMO - J. Comp. Hum. Biol. (2014), http://dx.doi.org/10.1016/j.jchb.2014.03.002


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13

Acknowledgements Our sincere thanks are extended to the Australian Society of Orthodontists Foundation for Research and Education for research support. We are grateful that Dr. John Fricker (Canberra, Australia) provided the ‘Mona Lisa’ software and Sample 2. We also thank Associate Prof. Mithran Goonewardene (Perth, Australia) for Sample 3.

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Comparison of natural head position in different anteroposterior malocclusions.

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Natural head position as a basis for cephalometric analysis.

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Ocular Causes of Abnormal Head Position: Strabismus Clinic Data.

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Both head extension and mouth opening impair the ability to swallow in the supine position.

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Physical and Psychological Effects of Head Treatment in the Supine Position Using Specialized Ayurveda-Based Techniques.