Systematic Review Craniocervical posture and craniofacial morphology

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1 European Journal of Orthodontics 36 (2014) doi: /ejo/cjt004 Advance Access publication 23 April 2013 The Author Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please Systematic Review Craniocervical posture and craniofacial morphology Liliane de C. Rosas Gomes, Karla O. Carpio Horta, João Roberto Gonçalves and Ary dos Santos-Pinto Department of Orthodontics, Araraquara School of Dentistry, UNESP Univ Estadual Paulista, Araraquara, São Paulo, Brazil Correspondence to: Liliane de C. Rosas Gomes, Department of Orthodontics, Faculdade de Odontologia de Araraquara, UNESP Univ Estadual Paulista, Rua Humaitá, 1680, Araraquara, São Paulo, Brazil, CEP SUMMARY The purpose of this study was to investigate the published evidence regarding the association between head and cervical posture and craniofacial morphology. An electronic search was conducted in PubMed, Medline, Embase, Scopus, and Cochrane databases up to 23 March Abstracts that seemed to correspond with the goals of this review were selected by a consensus between two independent reviewers. The original articles were retrieved and evaluated to ensure they match the inclusion criteria. Only articles that directly compared head and/or cervical posture with craniofacial morphology were included. A total of 84 articles were found of which 12 matched all inclusion criteria. Detailed analysis of the methodology in selected articles revealed quality scores ranging from weak to moderate. Nine articles were cross-sectional studies, whereas only three were longitudinal studies. The findings of selected articles were linked together in order to clarify the evidence on sagittal and vertical craniofacial features as well as growth prediction regarding different postures of the head and neck. On the basis of the data obtained from the literature, significant associations were found between variables concerning head and cervical posture and craniofacial morphology. However, the results of this systematic review suggest that such associations should be carefully interpreted, considering that correlation coefficients found ranged from low to moderate. Moreover, conflicting results were observed regarding some postural variables. Further longitudinal studies are required to elucidate the relationship between the development of craniofacial morphology and functional aspects of head and cervical posture. Introduction Associations between craniofacial morphology and individual variation in head and cervical posture have been reported (Solow and, 1976; Marcotte, 1981; Solow, 1984; Solow and Siersbaek-Nielsen, 1986, 1992; Hellsing, 1987; Showfety, 1987; Ozbek and, 1993; Huggare and Cooke, 1994; Solow and Sandham, 2002; D Attilio, 2005), showing that functional principles of cervical spine are of special interest in orthodontics and orthopaedics. However, important issues remain unanswered. It is still unclear if the craniofacial development is influenced by the posture of the head and cervical column. If so, which sagittal and vertical morphological features would be directly connected with such different postures? Soft-tissue stretching hypothesis (Solow and Kreiborg, 1977) linked postural-induced stretching of soft-tissue facial layer, craniofacial morphology, and airway adequacy into a cycle of factors related to craniofacial morphogenesis. It stated that the soft-tissue layer of facial skin and muscles would be passively stretched when the head is extended in relation to the cervical column, which would increase the forces on skeletal structures. Such forces would restrict forward growth of maxilla and mandible and redirect it caudally (Solow and Kreiborg, 1977; Solow and Sandham, 2002). A study on lip pressure changes following extension and flexion of the head reported such forces in a more accurate way. Bonded strain gauge transducers on upper and lower central incisors revealed that mean differences between pressures obtained during natural head posture and 5, 10, and 20 degrees of extension showed continuous highly significant increase, whereas during 5, 10, and 20 degrees of flexion, upper lip pressure continuously decreased with highly significant values. However, the results were achieved under experimental conditions of short duration. It is still unclear whether the response would be maintained over time (Hellsing and L Estrange, 1987). It has been shown an association between head and cervical posture with functional factors such as breathing, considering that the maintenance of a sufficient nasopharyngeal space may require postural changes (Ricketts, 1968; Solow, 1984). Solow observed that obstructed nasopharyngeal airways were connected with extension of the head in

2 56 relation to the cervical column. Moreover, such a condition was linked to a specific craniofacial type characterized by mandibular retrognathism and high mandibular plane angle. Proper understanding of postural mechanism contribution on normal or abnormal craniofacial development is of fundamental importance for diagnosis and treatment planning of morphological and functional disorders of stomatognathic system. Therefore, a comprehensive systematic review may contribute to the knowledge of the complex relationship between head/cervical posture and craniofacial morphology, critically analysing whether available evidence is sufficient to support the hypothesis that posture influences growth and development of craniofacial structures. Materials and methods The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement was used to guide this study (Moher, 2009) (Supplementary Table 1). Inclusion/exclusion criteria Longitudinal, cohort, case control, cross-sectional and case series studies that directly compared craniofacial morphology with head and/or cervical posture were eligible to be part of this review. Case reports and literature reviews were not included. Searches were restricted to English publications involving only humans. The study population consisted of healthy child, adolescent or adult subjects of both genders. Patients with any congenital disorder or syndrome as well as those with history of previous head or neck surgery were not included. The sample must not have been constituted by patients with a single skeletal facial type, given the fact that different skeletal patterns are required to make it possible the correct analysis of differences related to posture and morphologic facial features. Measurements used to analyse both postural and morphological variables must have been obtained from cephalometric radiographs performed in natural head position (NHP). Articles that presented any questionable information regarding cephalometric measurement were not included. Articles were excluded if they did not match the inclusion criteria. Search strategy This systematic review was performed using the following electronic databases: PubMed, Medline, Embase, Scopus, and Cochrane (from 1966 to 2012). For our search query, medical subject headings (MeSH) terms and free text were used in combination to restrict the search. Some of the keywords used in the search were growth and development, craniocervical posture, facial morphology, head position, and craniofacial type. Supplementary Table 2 shows detailed information regarding specific search terms and combinations. Two independent reviewers screened the publications found in the databases. After excluding repetitions, a first L.C.R. Gomes selection based on title was performed. Manual search of the references was conducted to find other relevant articles. Another selection on the basis of abstracts was conducted to find potentially useful articles. When divergences occurred in articles selection, reasons were clearly identified, and a consensus achieved. Subsequently, full-text articles were obtained for those references that appeared to match our inclusion criteria. The search was updated on 23 March Critical appraisal Articles were assessed for the quality of their methodology by two examiners. Critical appraisal was performed regarding nine criteria (Supplementary Table 3). Each study was graded as weak (0 to <13 points), moderate ( 13 to 15 points), high moderate (>15 to 18 points), and strong (>18 points). The kappa (κ) coefficient was used to assess agreement between the reviewers. Results The initial search yielded 155 PubMed citations, 77 Medline citations, 345 Embase citations, 112 Scopus citations, and 0 Cochrane citations. After excluding repetitions, completely off-topic titles were excluded, which returned 73 articles. Manual search of references revealed 11 additional articles. After abstract reading, 27 off-topic articles and 9 non-english publications were excluded, which resulted in 48 references achieved by a consensus. Subsequently, full-text articles were obtained for those references that appeared to match our inclusion criteria. Out of the 48 topic-related articles selected, 36 did not fit the inclusion criteria. The remaining 12 articles were found relevant for the purpose of the study. The search was summarized in Figure 1. Table 1 shows detailed information about each one of the included articles. Methodological quality of included studies At the end of the critical appraisal phase, there was an agreement of κ = (P < 0.001) between reviewers. Among the studies, six presented moderate quality level and the other six were considered weak. The following were the main methodological shortcomings: only one article presented detailed information about including representatives of the three different facial types in selection description; none of the articles reported sample size calculation; just three articles were longitudinal studies and none reported measurement blinding when assessing craniofacial morphology and head/ cervical posture (Table 2). Head and cervical posture versus craniofacial morphology Variables used for head and cervical posture cephalometric analysis are shown in Figure 2 and Supplementary Table 4. Figure 3 illustrates the cephalometric points and

3 Craniocervical Posture and Craniofacial Morphology 57 Figure 1 Flow chart. reference lines used for craniofacial morphology assessment. Considering that a majority of the selected articles used correlation coefficients for assessing the comparison between postural and craniofacial morphology variables, such coefficients were grouped together to make the quantitative analysis of results feasible. Data were summarized considering the minimum and maximum correlation coefficients found among the selected articles, regarding sagittal (Table 3) and vertical diagnostic features (Table 4). Sagittal assessment On the basis of significant correlation coefficients between postural and morphological variables, as well as significant differences among skeletal class I, class II, and class III groups, it was observed that greater craniocervical and craniovertical were related to lower lengths of the maxilla (Solow and, 1976) and mandible (Solow and, 1976; Showfety, 1987), greater maxillary (Solow and, 1976; Marcotte, 1981; Showfety, 1987; Ozbek and, 1993) and mandibular retrognathism (Solow and, 1976; Marcotte, 1981; Solow, 1984,, Showfety, 1987; Ozbek and, 1993; Leitao and Nanda, 2000), and a skeletal class II pattern (Solow and, 1976; Solow, 1984; Ozbek and, 1993; Leitao and Nanda, 2000; D Attilio, 2005). Lower cervicohorizontal were related to maxillary and mandibular protrusion regarding measurements that considered extracranial reference lines (Ozbek and, 1993) and large sagittal interjaw discrepancy (Solow, 1984; Ozbek and, 1993). One article reported facial prognathism (Hellsing, 1987) in association with increased cervicovertical. Cervical spine was significantly straighter in skeletal class III patients (P 0.001) and markedly curved in skeletal class II patients regarding the angle formed by the intersection of the cervical vertebra tangent and the lower segment of the cervical vertebra (CVT/EVT) (P 0.01) (D Attilio, 2005). Subjects with lower maxillary length (PNS-vpOK) were associated with a more lordotic cervical curve (Tecco and Festa, 2007). Other authors did not find significant correlations between cervical lordosis (OPT/CVT, CVT/EVT) and craniofacial morphology considering sagittal analysis (Solow and, 1976; Hellsing, 1987; Ozbek and, 1993). Vertical assessment Greater craniocervical and craniovertical were related to large anterior face height (Solow and, 1976; Showfety, 1987; Leitao and Nanda, 2000), small posterior face height (Solow and, 1976; Solow, 1984) and thereby reduced face height ratio (S-Go/N-Me;

4 58 L.C.R. Gomes Table 1 Characteristics of studies on head posture and facial morphology. Study/year Type of study Methods Results Sample characteristics Method used to perform measurements Sample size (n) Gender distribution Other relevant features Mean age range (years)* Cephalometric radiographs obtained in NHP (specific method) Mean period of observation**, range (years) Associations found; correlation coefficients range***/other statistical method; significance 1. Solow and Cross sectional male Self-balance and mirror position Not applicable Craniocervical, craniovertical, cervicohorizontal, and cervical lordosis related to facial morphology; r = ; significance at 5 and 1% 2.Marcotte (1981) Cross sectional 136 Not reported Mirror position Not applicable Craniovertical angle (TVH) related to facial morphology; r = ; significance at 0.1% 3. Solow 4. Solow and Siersbaek-Nielsen (1986) 5. Hellsing (1987) 6. Showfety (1987) 7. Solow and Siersbaek-Nielsen (1992) 8. Ozbek and 9. Huggare and Cooke (1994) 10. Leitao and Nanda (2000) Cross sectional boys, 12 girls Longitudinal girls, 23 boys Cross sectional boys, 62 girls 12 class I, 25 class II Div 1, 06 class II Div 2 Calculations based on EVT line were limited to 112 subjects Cross sectional females Look into the far distance (fluid-level device)**** Longitudinal girls, 18 boys Cross sectional female, 49 male Longitudinal boys, 16 girls 12 class I, 18 class II Div 1, 04 class II Div 2 21 class I, 12 class II Div 1, 03 class III 8.6 ( ) Mirror position Not applicable Craniocervical, craniovertical, and cervicohorizontal related to facial morphology; r = ; significance at 5, 1, and 0.1% 9.5 ( ) Mirror position 2.7 (1 4) Craniocervical and cervicohorizontal related to true growth rotation of the mandible; r = ; significance at 5, 1, and 0.1% 8 15 Mirror position Not applicable Cervicovertical and cervical lordosis (CVT/EVT) related to facial morphology; r = ; significance at 5, 1, and 0.1% Not applicable Craniovertical angle (SN/V) related to facial morphology; r = ; significance at 5 and 0.1% 9.9 (SD 1.4) Mirror position 2.8 (2 3.6) Craniocervical, craniovertical, and cervicohorizontal related to facial growth; r = ; significance at 5, 1, and 0.1% No external references (fluid-level device)**** 12 Self-balance and mirror position Cross sectional male 22.6 (18 25) Self-balance and mirror position Not applicable Craniocervical, craniovertical, and cervicohorizontal related to facial morphology; r = ; significance at 5, 1, and 0.1% 2 5 Craniovertical related to mandibular growth direction in boys; r = 0.59; significance at 1% Not applicable Craniovertical related to facial morphology; r = ; significance at 5, 1, and 0.1% (Continued )

5 Craniocervical Posture and Craniofacial Morphology 59 Table 1 Continued Study/year Type of study Methods Results Associations found; correlation coefficients range***/other statistical method; significance Mean period of observation**, range (years) Sample characteristics Method used to perform measurements Cephalometric radiographs obtained in NHP (specific method) Mean age range (years)* Other relevant features Sample size (n) Gender distribution 9.5 (SD 0.5) Mirror position Not applicable Craniocervical, cervicovertical, and cervical lordosis related to facial morphology; Kruskal Wallis one-way analysis of variance; significance at 5, 1, and 0.1% 40 Skelatal class I, 40 Skeletal class II, 40 Skelatal class III Cross sectional girls, 60 boys 11. D Attilio (2005) 31.5 (18 51) Mirror position Not applicable Cervical curvature related to facial morphology; r 2 = 0.24; significance at 5% Cross sectional males, 42 females 12. Tecco and Festa (2007) *Mean age at the first observation in case of longitudinal studies. **Just for longitudinal studies. ***It was only shown the magnitude of correlations found regarding variables of interest for the purpose of this review. ****A fluid-level device was used to transfer the NHP to the cephalostat r 0.51; P 0.001) and S-Go/ANS-Me proportion (0.38 r 0.41; P 0.001; Ozbek and, 1993). It was also associated with high mandibular plane angle (Solow and, 1976; Marcotte, 1981; Solow, 1984; Showfety, 1987; Ozbek and, 1993; Leitao and Nanda, 2000), large inclination of the maxilla to anterior cranial base (Solow and, 1976; Solow, 1984; Ozbek and, 1993), and high occlusal plane angle (r = 0.32; P 0.05) (Marcotte, 1981). Lower cervicohorizontal were linked to large anterior face height (Solow and, 1976), small posterior face height (Solow, 1984) as well as high mandibular plane angle (Solow and, 1976; Ozbek and, 1993). Articles reported decreased lower and total face height and also small inclination of the mandible to anterior cranial base (Hellsing, 1987) in association with increased cervicovertical. Straightened cervical lordosis assessed by CVT/EVT or OPT/CVT was related to high mandibular plane angle and large anterior face height (Solow and, 1976; Hellsing, 1987). Head posture and growth prediction Three longitudinal studies found a clear pattern of associations between head and cervical posture with craniofacial growth determined by structural superimposition method (Solow and Siersbaek-Nielsen, 1986, 1992; Huggare and Cooke, 1994; Table 5). Subjects with greater cervicohorizontal and small craniocervical were associated with a horizontal facial growth pattern characterized by reduced backward displacement of the temporomandibular joint (TMJ), increased growth in length of the maxilla (Solow and Siersbaek-Nielsen, 1992), increase in maxillary and mandibular prognathism (Solow and Siersbaek-Nielsen, 1992), and larger than average forward true rotation of the mandible (Solow and Siersbaek-Nielsen, 1986, 1992). Subjects with lower cervicohorizontal and large craniocervical were associated with a vertical facial development and are likely to exhibit large backward displacement of the TMJ, reduced growth in length of the maxilla (Solow and Siersbaek- Nielsen, 1992), reduction of maxillary and mandibular prognathism (Solow and Siersbaek-Nielsen, 1992), and less than average forward true rotation of the mandible (Solow and Siersbaek-Nielsen, 1986, 1992). Craniovertical angle significantly correlated with mandibular growth direction. The larger the angulation, the more vertical the facial growth pattern in boys (Huggare and Cooke, 1994). One article developed a prediction model from which it was suggested that children with the angle between the nasion-sella reference line and the odontoid process tangent (NSL/OPT) larger than 113 degrees may exhibit a vertical growth pattern of the lower face, whereas children with NSL/OPT smaller than 79 degrees may exhibit a horizontal growth pattern (Solow and Siersbaek-Nielsen, 1992).

6 60 L.C.R. Gomes Table 2 Critical appraisal scores of included studies. Study/year Critical appraisal scores Total score Rating Solow and Moderate 2. Marcotte (1981) Weak 3. Solow Weak 4. Solow and Siersbaek-Nielsen (1986) Moderate 5. Hellsing (1987) Moderate 6. Showfety (1987) Weak 7. Solow and Siersbaek-Nielsen (1992) Moderate 8. Ozbek and Weak 9. Huggare and Cooke (1994) Weak 10. Leitao and Nanda (2000) Moderate 11. D Attilio (2005) Moderate 12. Tecco and Festa (2007) Weak 1, Proposition; 2, study design; 3, sample size; 4, selection description (4.1, different facial types; 4.2, gender/age features); 5, method for obtaining NHP; 6, cephalometric analysis; 7, method error analysis; 8, statistical analysis; 9, blind measurement. Discussion The term extension of the head has been used to denote a raised position of the head in relation to the cervical column or the true vertical (Solow and, 1976; Hellsing, 1987; Showfety, 1987; Leitao and Nanda, 2000; Solow and Sandham, 2002). Thus, it was associated with increased craniocervical (Solow and, 1976; Solow, 1984; Solow and Siersbaek-Nielsen, 1986, 1992; D Attilio, 2005) and increased craniovertical ones (when considering the downward opening formed in front of the true vertical) (Solow and, 1976; Solow, 1984; Showfety, 1987; Solow and Siersbaek-Nielsen, 1992; Leitao and Nanda, 2000). An extended head position was also related to cervical spine sloping forward (Solow and, 1976; Ozbek and, 1993; Solow and Sandham, 2002). Therefore, it was linked to decreased cervicohorizontal (Solow and, 1976; Solow, 1984; Solow and Siersbaek-Nielsen, 1986, 1992; Ozbek and, 1993) and increased cervicovertical ones (when considering the magnitude of downward opening formed behind the Figure 2 Cephalometric postural variables. The convention employed for related to the true vertical was that downward opening formed behind the true vertical (VER) were taken as negative, whereas formed in front were positive.

7 Craniocervical Posture and Craniofacial Morphology 61 Figure 3 Cephalometric points and reference lines used for craniofacial morphology assessment. true vertical; Hellsing, 1987; D Attilio, 2005). On the other hand, the term flexion of the head denotes a forward bent position of the head (Solow and, 1976; Showfety, 1987) and is generally associated with backward slope of the cervical column (Solow and, 1976; Solow and Sandham, 2002), i.e. a vertical cervical posture (Ozbek and, 1993). It was observed that, in general, correlations obtained for cervicohorizontal showed opposite signs when compared with those obtained for craniocervical and craniovertical, which means that an extended head position is actually related to forward cervical posture (Solow and, 1976; Solow and Sandham, 2002). However, care must be taken when interpreting the results of correlations regarding cervicovertical. Conventionally, the downward opening formed behind the true vertical were taken as negative, whereas those formed in front were considered positive. Thus, increased cervicovertical mean backward inclination of the cervical column. Authors believe that the craniofacial morphology is often visually masked by the posture of the head and cervical column (Bjork, 1951; Brodie, 1971). Investigators stated that the convex facial profile is masked somewhat by the extension of the head relative to the true vertical, which tends to reduce the facial convexity by increasing the prominence of the chin. Conversely, in those individuals with prognathic facial profiles, the mandible protrusion tends to be masked by the forward posturing of the forehead. The results of correlation coefficients analysis regarding craniovertical seem to support this hypothesis (Solow and, 1976; Marcotte, 1981; Solow, 1984; Showfety, 1987; Leitao and Nanda, 2000). In general, the results of selected articles statistical analysis in this systematic review corroborate the softtissue stretching hypothesis (Solow and Kreiborg, 1977). Therefore, an extended head posture and/or forward inclination of the cervical column were related to individuals with high mandibular plane angle and long-face morphology as well as retrognathic profile (Solow and, 1976; Marcotte, 1981; Solow, 1984; Solow and Siersbaek- Nielsen, 1986; Hellsing, 1987; Showfety, 1987; Solow and Siersbaek-Nielsen, 1992; Ozbek and, 1993; Huggare and Cooke, 1994; Leitao and Nanda, 2000; Solow and Sandham, 2002; D Attilio, 2005). On the other hand, subjects with short-face morphology and lower mandibular plane angle, as well as those with mandibular prognathism often carry their heads somewhat lowered and/ or presented a backward inclination of the cervical column (Solow and, 1976; Marcotte, 1981; Solow, 1984; Solow and Siersbaek-Nielsen, 1986; Hellsing, 1987; Showfety, 1987; Solow and Siersbaek-Nielsen, 1992; Ozbek and, 1993; Huggare and Cooke, 1994; Leitao and Nanda, 2000; Solow and Sandham, 2002).

8 62 L.C.R. Gomes Table 3 Correlation coefficients between postural variables and craniofacial morphology: Sagittal assessment. Lengths of the maxilla Lengths of the mandible Maxillary position Mandibular position Sagittal interjaw relationship A-PNS Pg-Go, Co-Gn SNA, A-Nperp, N-A(H)*, A-VER/N-VER** SNB, N-B(H)*, B-VER/N-VER** SNPog, SN.Sym, Pog-VER/N-VER** AN.Pog ANB, B-VER/A-VER** Minimun Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Craniocervical Craniovertical Cervicohorizontal Cervicovertical 0.25*** 0.25*** Solow and -0.20**** -0.20**** Solow and, **** -0.33**** Showfety, *** 0.38*** Solow and 0.37***** 0.40***** Ozbek and 0.48*** 0.48*** Solow and 0.29**** 0.29**** Showfety (1987) 0.54*****, 0.54*****, Ozbek and 0.58***** 0.58***** 0.27***** 0.27***** Marcotte (1981) 0.23**** 0.24**** Ozbek and 0.19**** 0.19**** Hellsing (1987) 0.45*** 0.49*** Solow and 0.43***** 0.46***** Ozbek and 0.54*** 0.54*** Solow and 0.62***** 0.62***** Showfety (1987) 0.62*****, 0.62*****, Ozbek and 0.50***** 0.50***** 0.45***** 0.45***** Marcotte (1981) 0.57***** 0.57***** Leitao and Nanda (2000) 0.29*** 0.31*** Ozbek and 0.18**** 0.18**** Hellsing (1987) 0.49*** 0.52*** Solow and 0.49**** 0.59**** Solow 0.47***** 0.51***** Ozbek and 0.54*** 0.54***** Solow and 0.42**** 0.67***** Solow 0.62***** 0.62***** Showfety (1987) 0.60*****, 0.60*****, Ozbek and 0.46***** 0.46***** 0.32***** 0.32*** Marcotte (1981) 0.56***** 0.56***** Leitao and Nanda (2000) 0.35***** 0.35***** Ozbek and 0.21**** 0.23**** Solow and 0.44**** 0.44**** Solow 0.18**** 0.18**** Solow and -0.43**** -0.43**** Solow 0.22**** 0.22**** Ozbek and 0.19***** 0.19***** Leitao and Nanda (2000) -0.23**** -0.24**** Ozbek and Topographic correlations are in bold; only correlation coefficients significant at the 5% level are shown. *Measurements parallel to the horizontal (H) constructed at a fixed angle of 7 below SN line. Only performed by Marcotte (1981). **Measurements that considered extracranial reference lines. Significant correlations were only found for craniovertical and cervicohorizontal in Ozbek and article. Articles that considered the downward opening formed behind the true vertical for craniovertical angle assessment had the sign of correlation coefficients corrected (Marcotte, 1981; Showfety, 1987; Leitao and Nanda, 2000). ***P < 0.01, ****P < 0.05, *****P <

9 Craniocervical Posture and Craniofacial Morphology 63 Table 4 Correlation coefficients between postural variables and craniofacial morphology: vertical assessment. Anterior face height Posterior face height Inclination of jaw bases N-A, N-ANS ANS-Gn, ANS-Me N-Gn, N-Me S-PNS Co-Go, Ar-Go S-Go SN.GoMe, NSL.ML, MP.H*, NSL.GoGn, NSL.MBL, FH.ML NSL.NL, ANS-PNS.NS Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum Maximum References Minimum MaximumReferences Minimum Maximum References Minimum Maximum References Craniocervical Craniovertical Cervicohorizontal Cervicovertical Cervical lordosis 0.42** 0.48** Solow and 0.23** 0.23** Solow and 0.34*** 0.34*** Showfety (1987) 0.24** 0.29** Solow and 0.19*** 0.19*** Solow and 0.24** 0.32** Solow and 0.20**** 0.263**** Leitao and Nanda (2000) 0.24** 0.30** Solow and, ** 0.27** Hellsing, *** 0.21*** Solow and, ** 0.37** Solow and 0.12*** 0.23**** Leitao and Nanda (2000) 0.25** 0.32** Solow and, ** 0.29**** Hellsing, *** 0.22*** Solow and, *** 0.19*** Hellsing, ** 0.25** Solow and 0.43*** 0.48*** Solow 0.33** 0.33** Solow and 0.46*** 0.47*** Solow 0.20*** 0.28** Solow and 0.42*** 0.47*** Solow 0.24** 0.34** Solow and 0.41*** 0.41*** Solow 0.42*** 0.42*** Solow 0.21*** 0.21*** Solow and 0.34** 0.34** Solow and 0.37** 0.57** Solow and 0.42*** 0.42*** Solow 0.46**** 0.50**** Ozbek and 0.30** 0.41** Solow and 0.31**** 0.31**** Marcotte (1981) 0.43*** 0.43*** Solow 0.33*** 0.33*** Showfety (1987) 0.39**** 0.52**** Ozbek and 0.16** 0.45**** Leitao and Nanda (2000) 0.24** 0.25** Solow and 0.32**** 0.33**** Ozbek and 0.32** 0.34**** Hellsing (1987) 0.23** 0.29** Solow and 0.25** 0.25** Hellsing (1987) 0.32** 0.33** Solow and 0.42*** 0.44*** Solow 0.23*** 0.26*** Ozbek and 0.36** 0.36** Solow and 0.51*** 0.51*** Solow 0.33**** 0.33**** Ozbek and Only correlation coefficients significant at the 5% level are shown. Topographic correlations are in bold. *Angle between mandibular plane (MP) and the horizontal (H) constructed at a fixed angle of 7 below SN line. Only performed by Marcotte (1981). Articles that considered the downward opening formed behind the true vertical for craniovertical angle assessment had the sign of correlation coefficients corrected (Marcotte, 1981; Showfety, 1987; Leitao and Nanda, 2000). **P < 0.01, ***P < 0.05, ****P <

10 64 L.C.R. Gomes Table 5 Correlation coefficients regarding postural and craniofacial growth variables. Solow and Siersbaek-Nielsen (1986) Solow and Siersbaek-Nielsen (1992) Huggare and Cooke (1994) SN-Pgn NSL/REFml* (degrees/year) REFcrb/REFml* (degrees/year) REFcrb/REFml* NSL/REFml* A-Pm (mm/year) SNA (degrees/year) SNB (degrees/year) SNPog (degrees/yearr) Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum 0.55*** 0.58*** 0.48**** 0.48** 0.43**** 0.46** 0.52** 0.55*** 0.40**** 0.40**** 0.36**** 0.37**** 0.41** 0.45*** 0.54*** 0.47** 0.51*** 0.55*** Craniocervical 0.50*** 0.52*** 0.42** 0.44** 0.49** 0.52** 0.48** 0.51** 0.52**** 0.52**** 0.59*** 0.59*** 0.35**** 0.35**** Cervicohorizontal 0.35* 0.35* 0.59** 0.59** Craniovertical Only correlation coefficients significant at the 5% level are shown. Topographic correlations are in bold. *True rotation of the mandible is determined as growth change in REFcrb/REFmI and NSL/REFml. REFcrb is the reference line through the fiducial points in the cranial base. On film 1, REFcrb coincides with NSL; REFml is the reference line through the fiducial points in the mandible. (Fiducial points are transferred from film 1 to film 2 after superimposition of films on stable structures in anterior cranial base and/or in the mandible). **P < 0.01, ***P < 0.001, ****P < However, it is important to consider that the vast majority of correlations found were low. Moderate correlations were found regarding variables related to mandibular position (sagittal assessment) and mandibular base inclination (vertical assessment). Moreover, associations between variables that are topographically related, i.e. having a reference line in common, should be distinguished from those between variables that have nothing in common. Topographically related variables may be correlated even if all reference points vary independently. On the other hand, non-topographical correlations are assumed to reflect biological coordinating mechanism (Solow and, 1976). The present review showed that although topographic associations were widely found, non-topographic correlations were also observed for almost all morphologic variables studied. Considering only non-topographical associations, the correlation coefficients ranged from r = 0.35 (P 0.05) to r = 0.59 (P 0.001) in longitudinal studies and from r = 0.18 (P 0.05) to r = 0.58 (P 0.001) in cross-sectional ones. Craniovertical and craniocervical posture are often determined by nasion-sella reference line (NSL). However, the inclination of such a line seems to show wide individual variations (Bjork, 1951; Moorrees and Kean, 1958; Lundstrom, 1982; Ozbek and, 1993). Ozbek and stated in NHP, the inclination of NSL was found to be associated with the vertical localization of Sella turcica point, rather than the extension or flexion of the entire head. Thus, they concluded that associations between posture and structure of the head would be merely caused by the functional factors related to forward cervical posture and vertical cervical posture. Corroborating these findings, D Attilio (2005) found significant differences among three different skeletal types regarding the values of the inclination of the lower segment of the spinal column (EVT) to a true vertical (VER). EVT/ VER angle was smaller (as absolute value) in class III than in skeletal class I and class II subjects (P < 0.001). Moreover, no significant differences in craniovertical were observed among the three groups. Regarding craniocervical formed by the upper section of the spinal column (NSL/OPT), no significant differences were also observed among the three groups. However, the angle created between the head and the midsection of the spinal column (NSL/ CVT) showed significant differences among the three groups. Subjects in skeletal class II showed a significantly more extended head upon the spinal column than subjects in skeletal Classes I and III (P < and P < 0.01, respectively). The evaluation of craniofacial structure by means of intracranial reference lines has been criticized considering that the individual variations in the slope of intracranial reference lines may result in different interpretation of the craniofacial structure of subjects with similar profiles (Bjork, 1951; Moorrees and Kean, 1958; Ozbek and, 1993). However, only one article assessed craniofacial morphology also considering measurements that involved extracranial

11 Craniocervical Posture and Craniofacial Morphology 65 reference lines (Ozbek and, 1993). Authors stated that when the facial prognathism was assessed by traditional (SNA, SNB, and SNPog), which are topographically correlated with craniovertical and craniocervical postural parameters (NSL/VER, NSL/OPT, and NSL/CVT), significant negative correlations were obtained, which may falsely lead to a conclusion that facial prognathism decreases with the extension of the head. On the other hand, when the facial prognathism was assessed in the NHP with parameters that were based on the extracranial reference lines (A-VER/N- VER, B-VER/NVER, and Pog-VER/N-VER), they showed positive correlations with NSL/VER and negative correlations with cervicohorizontal (OPT/HOR and CVT/ HOR) (Ozbek and, 1993). However, the positive correlations found with NSL/ VER may probably be related to the fact that the greater the inclination of the SN line during head extension, the more anteriorly positioned the points A, B, and Pog, in relation to nasion (N). Conversely, the negative correlations obtained for cervicohorizontal follows the same line of reasoning, regarding the fact that an extended head position is generally associated with forward inclination of the cervical column. Therefore, such postural influence on craniofacial proportions assessed by those variables may generate misunderstandings. On the other hand, when analysing extreme skeletal patterns, such postural changes may not produce significant craniofacial proportions changes. However, the article did not mention sample morphological features. Controversial results were found regarding cervical lordosis. Authors associated extension of the head with straighter cervical lordosis when considering OPT/CVT angle (Solow and, 1976), whereas other studies reported high cervical lordosis (CVT/EVT) related to head extenders (D Attilio, 2005). Those divergent results may probably be associated with different angle analysis. Through a correlation study, Solow and observed a tendency towards reduced cervical lordosis in head extenders regarding measurements obtained from the upper and middle segments of the cervical column. Such tendency was observed considering the opposite sign correlations found when comparing the results obtained for cervical lordosis (OPT/CVT) with those for craniocervical (NSL/OPT, NSL/CVT) and craniovertical (NSL/VER). Authors also evaluated mean facial diagrams of the 10 subjects with the largest extension of the head and the most marked flexion of the head in relation to the cervical column (NSL/OPT), which characterized the two extreme types proposed by them. Through direct comparisons, Hellsing (1987) found negative correlations between CVT/EVT and upper segment craniocervical (NSL/OPT, NSL/CVT) and positive correlations regarding the lower cervical segment (NSL/ EVT; P < 0.001), which means that a straight cervical lordosis was related to head extension only when considering the second cervical vertebra. Moreover, positive correlations were found regarding craniovertical, which means that extension of the head to a true vertical was related to increased cervical lordosis. This observation seems to show evidence of different behaviours of the upper/middle and lower segments of the cervical column, which corroborates the natural physiology of cervical column regarding protrusion and retraction movements, i.e. the lower cervical flexion moves the head forward and extension moves it backward, whereas the upper and middle cervical segments respond in a compensatory mechanism to maintain the face-forward position and keep the visual axis unaltered (Ordway, 1999). Craniocervical of the upper and middle segments (NSL/OPT, NSL/CVT) seem to diminish with lordosis increase (Solow and, 1976; Hellsing, 1987), whereas craniocervical angle of the lower segment (NSL/ EVT) seems to increase (Hellsing, 1987). Thus, when evaluating only the upper/middle segment it is not possible to establish conclusions about the overall cervical posture. D Attilio (2005) evaluating differences among skeletal class I, class II, and class III subjects reported that cervical spine was significantly straighter in skeletal class III subjects (P 0.001). This study also revealed that a more lordotic curve of the spine was related to greater extension of the head and, additionally, to a skeletal class II (P 0.01). Smaller CVT/EVT angle observed in subjects in skeletal class III was probably associated with the significant backward slope of the lower part of the spinal column (EVT/ VER), and not to any difference in the inclination of the upper (OPT) or middle (CVT) part of the cervical spine. No significant differences among the three groups were observed in the inclination of the middle (CVT/VER) or upper segment (OPT/VER) of the spinal column. On the other hand, straighter cervical lordosis assessed by CVT/EVT or OPT/CVT was related to high mandibular plane angle, and large anterior face height (Solow and, 1976; Hellsing, 1987), features usually found in head extenders. However, very low correlation coefficients explained such associations. Thus, it is still unclear the relationship between cervical lordosis and craniofacial morphology. Tecco and Festa (2007) stated that the cervical column curvature was highly variable between individuals, and only showed weak influence on craniofacial morphological variables. Subjects with lower maxillary length were associated with a more lordotic cervical curve in the sagittal plane. Through regression analysis, they found that this cephalometric variable explained only 24% of the total variance of cervical curvature. Cross-sectional studies have indicated the presence of some biologic mechanisms coordinating changes in posture and lower facial development. However, considerable caution must be exerted when interpreting findings obtained

12 66 from such studies. Only indirect inference can be made about the presence of growth-coordinating mechanism (Solow and Siersbaek-Nielsen, 1986). Direct inferences about form/function relationship and the possibility of predicting growth behaviour of facial dimensions require longitudinal assessment (Solow and Siersbaek-Nielsen, 1986, 1992; Ozbek and, 1993). The three longitudinal studies included in this review found a clear pattern of associations between head posture and subsequent craniofacial growth (Solow and Siersbaek- Nielsen, 1986, 1992; Huggare and Cooke, 1994), which also agreed with soft-tissue stretching hypothesis (Solow and Kreiborg, 1977). Although such associations were found for both genders in two articles, one article found significant associations only in boys (Huggare and Cooke, 1994). However, the authors assumed that the girls included in the study had already passed their peak height velocity that must have contributed to observed differences in strength of associations. The observation of an extremely large or extremely small craniocervical angle in a child appears to offer some prognostic value regarding facial developmental trends. However, the low to moderate correlations mean that although posture seems to influence facial development, many other factors must also affect this mechanism. Moreover, the determination of causal factors and of the detailed nature of the mechanism at work requires further studies (Solow and Siersbaek-Nielsen, 1992). Conclusions On the basis of the data available from literature, significant associations were found between variables concerning head posture and craniofacial morphology. However, our results suggest that such associations should be carefully interpreted, considering that correlation coefficients found ranged from low to moderate. The association between cervical lordosis and the head extension mechanism regarding craniofacial morphology is still unclear. Further longitudinal studies are needed in order to elucidate the relationship between craniofacial development and functional aspects of head and cervical posture. The evidence found is not enough to support any definite conclusion about the future mandibular growth in an individual case. Supplementary material Supplementary material is available at European Journal of Orthodontics online. Funding São Paulo Research Foundation (FAPESP) (2012/ ). L.C.R. Gomes References Bjork A 1951 Some biological aspects of prognathism and occlusion of the teeth. The Angle Orthodontist 21: 3 27 Brodie A G 1971 Emerging concepts of facial growth. Angle Orthodontist 41: D Attilio M, Caputi S, Epifania E, Festa F, Tecco S 2005 Evaluation of cervical posture of children in skeletal class I, II, and III. Cranio 23: Hellsing E, L Estrange 1987 Changes in lip pressure following extension and flexion of the head and at changed mode of breathing. American Journal of Orthodontics and Dentofacial Orthopedics 91: Hellsing E, McWilliam J, Reigo T, Spangfort E 1987 The relationship between craniofacial morphology, head posture and spinal curvature in 8, 11 and 15-year-old children. European Journal of Orthodontics 9: Huggare J A, Cooke M S 1994 Head posture and cervicovertebral anatomy as mandibular growth predictors. European Journal of Orthodontics 16: Leitao P, Nanda R S 2000 Relationship of natural head position to craniofacial morphology. American Journal of Orthodontics and Dentofacial Orthopedics 117: Lundstrom A 1982 Head posture in relation to slope of the sella-nasion line. Angle Orthodontist 52: Marcotte M R Head posture and dentofacial proportions. Angle Orthodontist 51: Moher D, Liberati A, Tetzlaff J, Altman D G 2009 Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Journal of Clinical Epidemiology 62: Moorrees C F A, Kean M R 1958 Natural head position, a basic consideration in the interpretation of cephalometric radiographs. American Journal of Physical Anthropology 16: Ordway N R, Seymour R J, Donelson R G, Hojnowski L S, Edwards W T Cervical flexion, extension, protrusion, and retraction. A radiographic segmental analysis. Spine 24: Ozbek M M, A Natural cervical inclination and craniofacial structure. American Journal of Orthodontics and Dentofacial Orthopedics 104: Ricketts R M Respiratory obstruction syndrome. American Journal of Orthodontics 54: Showfety K J, Vig P S, Matteson S, Phillips C 1987 Associations between the postural orientation of sella-nasion and skeletodental morphology. Angle Orthodontist 57: Solow B, Kreiborg S Soft-tissue stretching: a possible control factor in craniofacial morphogenesis. Scandinavian Journal of Dental Research 85: Solow B, Sandham A 2002 Cranio-cervical posture: a factor in the development and function of the dentofacial structures. European Journal of Orthodontics 24: Solow B, Siersbaek-Nielsen S Growth changes in head posture related to craniofacial development. American Journal of Orthodontics 89: Solow B, Siersbaek-Nielsen S Cervical and craniocervical posture as predictors of craniofacial growth. American Journal of Orthodontics and Dentofacial Orthopedics 101: Solow B, Siersbaek-Nielsen S, Greve E Airway adequacy, head posture, and craniofacial morphology. American Journal of Orthodontics 86: Solow B, A Natural head position in standing subjects. Acta Odontologica Scandinavica 29: Solow B, A Head posture and craniofacial morphology. American Journal of Physical Anthropology 44: Tecco S, Festa F 2007 Cervical spine curvature and craniofacial morphology in an adult Caucasian group: a multiple regression analysis. European Journal of Orthodontics 29: