Surg Radiol Anat DOI 10.1007/s00276-014-1279-5
ORIGINAL ARTICLE
Morphometric study of mandibular foramen in macerated skulls to contribute to the development of sagittal split ramus osteotomy (SSRO) technique Nilton Alves · Naira Figueiredo Deana
Received: 8 December 2013 / Accepted: 21 February 2014 © Springer-Verlag France 2014
Abstract Purpose The aim of this study was to provide morphometric data, obtained from macerated mandibles, which might facilitate the topographic location of the mandibular foramen, considering aspects such as gender, age and ethnicity. Materials and methods One hundred and eighty-five macerated mandibles of adult black and white individuals of both sexes were analyzed. Initially, 5 points were established: MF, the lowest point of the mandibular foramen; S, greatest concavity of the mandibular notch; A, anterior margin of the ramus of mandible; P, posterior margin of the ramus of mandible; and Go, gonion. Then the following measurements were performed bilaterally: MF-S, MF-A, MF-P and MF-Go. Results The following mean values were found: MFS: 21.02 mm for white females (WF) and 22.00 mm for black females (BF); 24.40 mm for white males (WM) and 24.35 mm for black males (BM); MF-A: 17.05 mm for WF and 18.09 mm for BF; 17.18 mm for WM and 18.11 mm for BM; MF-P: 11.11 mm for WF and 12.24 mm for BF; 13.10 mm for WM and 14.15 mm for BM; MF-Go: 19.00 mm for WF and 19.44 mm for BF; 23.13 mm for WM and 22.12 mm for BM. Conclusions The values found in this study, considering gender, age and ethnic group, can be used as a parameter to carry out the sagittal split ramus osteotomy N. Alves (*) CIMA Research Group, Faculty of Dentistry, Universidad de La Frontera, Avenue Manuel Montt, 112. Casilla 54-D., Temuco, Chile e-mail:
[email protected] N. F. Deana Private Physical Therapist, Martín Lutero, 02145 Temuco, Chile
technique, making it more predictable and with less risk of complications. Keywords Mandibular foramen · Ramus of mandible · Sagittal split ramus osteotomy · Morphometry
Introduction The sagittal split ramus osteotomy (SSRO) is a technique suitable for the correction of mandibular dentofacial deformities, as prognathism and retrognathia. The SSRO was introduced by Schuchardt, but it was through Trauner and Obwegeser [26] that this technique was popularized being widely used until the present day with or without modifications [7]. The SSRO has the advantage that it is an intraoral approach, with rapid healing and early reestablishment of mandibular function [30]. Furthermore, the large area of bone contact favors the repair not requiring interpositional bone grafts, and provides greater stability for most malformations such as excess or sagittal mandibular deficiency and facial asymmetry [19]. However, some complications may occur during the performance of this technique, as an undesirable fracture, which can be caused when the SSRO is performed at a too high place, where the mandibular ramus is thin or where there is fusion of the medial and lateral cortical plates with no cancellous bone [16]. Injury to the inferior alveolar nerve (IAN) is a complication which determines a neurosensory disturbance that persists after 1 year in 15 % of patients [29]. The inferior alveolar neurovascular bundle penetrates into the MF, which is the opening on the medial surface of the ramus of mandible that leads into the mandibular canal [2].
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The correct identification of MF is important in performing functional and aesthetic surgeries, where the knowledge of the anatomical characteristics of this structure supports mandibular osteotomy procedure, preventing accidents and avoiding surgical complications [8]. Many authors have proposed anatomical reference points to guide surgeons in locating the inferior alveolar nerve; however, very few researchers have analyzed variables such as gender, ethnicity and age. The aim of this study was to provide morphometric data, obtained from macerated mandibles, which might facilitate the topographic location of the mandibular foramen, considering aspects such as gender, age and ethnicity. Thus, we intend to contribute to the guidance of maxillofacial surgeons by the development of a safe and accurate surgical technique.
Materials and methods One hundred and eighty-five macerated mandibles of adult black and white individuals of both sexes, belonging to the Department of Morphology and Genetics—UNIFESP (São Paulo, Brazil) were analyzed. Excluded from this study were edentulous mandibles and/or those that did not contain information on sex, age and race. Wholly or partially dentate hemimandibles were included, totaling 339 hemimandibles, 105 females (aged 18–77 years old) and 234 males (aged 20–68 years old). Initially 5 points were established: MF, the lowest point of the mandibular foramen; S, point of greatest concavity of the mandibular notch; A, point located on the anterior margin of the ramus of mandible at the level of mandibular foramen; P, point located on the posterior margin of the ramus of mandible at the level of mandibular foramen; and Go, craniometric point: gonion. To analyze the anatomical landmarks of the ramus of the mandibles, the following measurements were performed bilaterally: superior distance of mandibular foramen (MFS) (Fig. 1); anterior distance of mandibular foramen (MFA) (Fig. 1); posterior distance of the mandibular foramen (MF-P) (Fig. 1); and inferior distance of the mandibular foramen (MF-Go) (Fig. 1). To perform these measurements we used a digital caliper. The data obtained were tabulated and analyzed using Mann–Whitney and Kruskal–Wallis tests, according to their relevance; p ≤ 0.05 was considered statistically significant. For analysis of variable age, the individuals were previously separated according to gender and then in four groups: 18–30 years old, 31–45 years old, 46–60 years old, and above 61 years old. For analysis of variable ethnicity, the individuals were previously separated according to gender and then into two groups, black and white.
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Fig. 1 Superior distance of mandibular foramen (MF-S); anterior distance of mandibular foramen (MF-A); posterior distance of the mandibular foramen (MF-P); inferior distance of the mandibular foramen (MF-Go)
Results Tables 1 and 2 show the mean, minimum, maximum values, standard deviation and p value found for ethnic groups. We analyzed 21 white female mandibles (WF), 39 black female mandibles (BF), 69 white male mandibles (WM) and 56 black male mandibles (BM). There was no statistically significant difference for the variable side in any case. Regarding the analysis of the variable age, the mean values and p value found for each age group are shown in Table 3. The results related to variables of gender and ethnic group are shown in Fig. 2, which shows the mean values of the distances found for black/white males and black/white females. We found statistically significant differences for the distances MF-S, MF-P and MF-Go. In our study, we found in two mandibles an anatomical variation, in both there was an accessory mandibular foramen, unilateral, large, and located in right hemimandible superiorly to the lingula (Fig. 3).
Discussion The position of the mandibular foramen is a useful parameter to perform a safe surgical intervention in the mandibular ramus region, reducing the risk of complications, such as injury to IAN [18].
Surg Radiol Anat Table 1 Mean values, minimum, maximum, standard deviation (SD) and p value, found for white (W) and black (B) females in millimeters
MF-S
Mean SD p value Minimum
* Statistical significance Table 2 Mean values, minimum, maximum, standard deviation (SD) and p value, found for white (W) and black (B) males in millimeters
* Statistical significance Table 3 Mean values (in millimeters) and p value for males (M) and females (F), found for the distances MF-S, MF-A, MF-P and MF-Go, according to age groups
Maximum
MF-P
MF-Go
W
B
W
B
W
B
W
B
21.02 ±3.31
22.00
17.05 ±2.34
18.09
11.11 ±2.02
12.24
19.00 ±3.09
19.44
15.42
17.52
12.51
13.20
7.37
8.02
13.54
12.59
27.20
28.34
23.10
23.76
15.06
17.75
23.90
29.05
0.03*
0.03*
MF-S
0.007*
MF-A
0.96
MF-P
MF-Go
W
B
W
B
W
B
W
B
24.35
17.18 ±2.54 0.007*
18.11
13.10 ±2.20 0.001*
14.15
23.13 ±3.69 0.05*
22.12
p value
24.40 ±2.98 0.85
Minimum
18.27
17.69
8.79
11.81
8.20
10.19
14.45
14.19
Maximum
31.83
30.75
22.45
23.71
18.55
18.89
33.19
33.22
Landmarks
Gender
18–30 years
31–45 years
46–60 years
Above 61 years
p value
MF-S
M F M F M F M
24.61 22.03 17.42 18.36* 13.14 12.28 21.60
24.11* 21.81 17.35 17.27 13.66 11.22 22.60*
24.04* 22.13 18.48 17.15 13.81 11.23 24.10*
26.34* 19.56 17.14 16.18* 13.83 12.03 23.35
0.02* 0.48 0.07 0.03* 0.15 0.24 0.01*
F
19.98*
18.25*
19.59*
17.71*
0.02*
Mean SD
MF-A MF-P MF-Go
* Statistical significance
MF-A
Fig. 2 Mean values of the distances found for black/white males and females, in millimeters
Analyzing Table 4 we can observe that in the literature there is a discrepancy in the values found for the distances MF-S, MF-A, MF-P and MF-Go, which leads us to conclude that there is great variety on the position of
the mandibular foramen, a fact already reported by other authors [9, 27]. Strini et al. [24] found more than 80 % of the mandibular foramen in the middle third of the ramus of edentulous mandible. da Fontoura et al. [6] observed that the mandibular foramen is almost entirely located in the middle third of the ramus of mandible, considering the anteroposterior distance. Ennes and Medeiros [9] have localized the mandibular foramen, posterior and inferiorly to the middle point of the ramus of the mandible in majority of cases. Trost et al. [27] affirm that the posterior and superior thirds of the ramus of mandible constitute a “safety zone”, where the mandibular foramen is improbable to be found. Reitzik et al. [20] affirm that in the surgical technique where the ramus of the mandible is sectioned, the horizontal cut must be made high enough to avoid the inferior alveolar neurovascular bundle and low enough to avoid an undesirable fracture through the mandibular notch, and the vertical cut must be made far enough posteriorly to avoid the bundle, but as far forward as possible to avoid the undesirable fracture through the posterior margin of the ramus of the mandible.
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Fig. 3 Two cases of accessory mandibular foramen (arrowheads) located in right hemimandible superiorly to the lingula (1); the arrows indicate the mandibular foramen
The formation of mandibular foramen and canal occurs due to the fact that the intramembranous ossification of the body and of the ramus of mandible develops it in the presence of inferior alveolar neurovascular bundle. In the 24th week of intrauterine life, the IAN is not a single branch, there is no single mandibular foramen, there is only one open groove that contains nerves and blood vessels. The mandibular nerve supply in the region of the body consists of at least three nerve branches which subsequently will suffer fusion [14]. In some situations, incomplete fusion of IAN can occur determining the presence of double or accessory foraminas [3]. Freire et al. [10] studying Brazilian mandibles found at least one mandibular accessory
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foramina in 27.93 % of cases, 5.85 % were present bilaterally and in 43.24 % of cases were positioned above the mandibular foramen. In our study we found two cases of accessory mandibular foramen, both unilateral, located in the right hemimandible, superiorly to the lingula. Chrcanovic et al. [4] studying morphometric variations in human mandibles of Brazilians did not find any case of double mandibular foramen. Other types of anatomical variations may also occur, such as described by Cvetko [5], who reported a mandibular foramen located in upper region, near the mandibular notch. Such variations are not common, but result in increased risk of complications involving the IAN. Lima et al. [15] affirm that the distance MF-S is particularly useful in clinical practice, since it allows predicting the location of the mandibular foramen from the mandibular notch. In our study the value of the distance MF-S in black females was slightly higher than in white females, presenting a significant statistical difference. While in males, the mean values for black and white were similar and much higher than those found for females. We found in the literature great diversity of values for this distance; Lima et al. [15] found a mean value of 27.70 mm, higher than ours, while lower averages were reported by Gutierrez-Ventura and Tataje-Vivanco [11], with 17.40 mm. Yu and Wong [30] analyzing gender differences found, for females, slightly lower values than those that we found for white females, and for males they found lower values than ours. This difference in results may be associated with race, since the research of Yu and Wong [30] was performed in Asian, whereas our study was carried out in European and Brazilian. Other authors found mean values close to those found in our work but were not specified gender and age groups [9, 12, 13, 17, 23, 25, 28] (Table 4). In the analysis of age groups, we observed that for the distance MF-S in males, the younger groups had similar mean values to each other and lower than the group of 61 years old and above; statistically significant difference was observed between the groups 31–45 years old, 46–60 years old and 61 years old and above, which suggests that in younger individuals the mandibular foramen is located in a slightly higher region of the ramus of the mandible. The distance MF-A showed similar values for males and females; however, we found statistically significant difference when analyzing ethnic group, the mean values in black individuals were higher than those obtained for white individuals. Analyzing age groups, we found that in females there was a reduction of mean values in the group of 61 years old or above. The values found in this work for the distance MF-A were similar to those found by Yu and Wong [30] and by Kilarkage et al. [13] for the adults. Other authors found lower values than ours [11, 13, 17, 28]. The highest average was reported by Afsar et al. [1], with
Surg Radiol Anat Table 4 Mean values (in millimeters) found in the literature for the distances MF-S, MF-A, MF-P and MF-Go Authors
References
Afsar et al. Ennes and Medeiros
[1] [9]
Gutierrez-Ventura and Tataje-Vivanco
Total of mandibles
Population
Side
MF-S
MF-A
MF-P
MF-Go
79 74
Mixed Brazil
– R
19.90 24.30
20.20 –
12.60 –
28.30 –
[11]
53
–
L R
24.40 17.70
– 17.20
– 14.00
– –
Kaffe et al.
[12]
100
Israel
L –
17.40 21.89
16.08 –
13.90 –
– –
Kilarkaje et al.
[13]
124
–
Adults R
21.60
18.50
–
25.10
L
21.60
18.50
–
24.70
Olds R L R L R
21.50 21.50 27.70 27.32 22.37
16.80 16.70 19.48 14.56 16.90
– – – – 14.09
24.20 23.90 24.20 24.97 –
Lima et al.
[15]
38
–
Oguz et al.
[17]
34
Turkey
L
22.17
16.78
14.37
–
Shenoy et al.
[23]
50
–
R L
23.52 22.84
– –
– –
– –
Thangavelu et al.
[25]
93
India
R L
20.80 20.54
– –
– –
– –
Valente et al.
[28]
35
Brazil
R L
24.12 23.65
Yu and Wong
[30]
40
Taiwan
–
20.50a 22.70b
16.94 17.32 18.00a 19.30b
14.24 14.03 –
– – –
a
Female
b
Male
20.20 mm (Table 4). Regarding distance MF-A, Lima et al. [15] reported important difference between the right and left sides, a situation not found in our study in any case. For the distance MF-P we found higher mean values in male mandibles. Black individuals showed higher mean values than white individuals. In the analysis of the age groups we found no statistically significant difference for that distance in any case. Many authors reported mean values similar to those that we found for black males [11, 17, 28]; however, Afsar et al. [1] reported values close to those that we found for black females (Table 4). For the distance MF-Go, we found similar values for black and white females; however, the values obtained for white males were higher than those found for black males (p = 0.05). Furthermore, the mean values obtained for males were much higher than those found for females. Regarding the analysis by age groups we found statistically significant difference in both sexes. In females, this distance becomes smaller in individuals aged 61 or above and the opposite occurs in males, being the distance greater in subjects with increasing age. The mean values found by
Lima et al. [15], Kilarkaje et al. [13] and Afsar et al. [1] for the distance MF-Go were higher than ours (Table 4). Afsar et al. [1], analyzing the same distances that we used in our study, but in panoramic radiographs, affirm that they found no statistically significant difference between men and women. The result obtained by these authors is different from that found in our study, because, except in the distance MF-A, our results showed a marked gender difference; males showed higher values than females, especially in the distance MF-Go. From the literature, it is evident that various repair points are adopted in the location of the IAN. The lingula, medially limits the mandibular foramen [2], thus, many authors consider this structure as an ideal reference point [21], indicating that the horizontal osteotomy should be just above the lingula [7, 19]. However, we must emphasize that the lingula is a structure that varies in size and shape, and the assimilated type can be found in some cases [22], a fact that can hamper the use of this structure as a parameter for the surgeon. In this study we used as a parameter the inferior margin of the mandibular foramen, because
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we consider it a stable and accurate repair point to assist in locating the IAN. We note that there is wide variation in the results reported in the literature, even in studies that use the same methodology. Such differences should be related to the fact that different populations are analyzed in these studies; in addition, there are few studies that consider gender, age and ethnicity of the sample.
Conclusions Considering the results obtained in our study we can assert that in relation to ethnic groups there is difference in the studied distances, being higher for black individuals, except for the distance MF-Go in males. Regarding gender there is an important difference; the values found for males were much higher than those found for females, except for the distance MF-A. Regarding age there is also difference in the distances, the mandibular foramen was located more superiorly in younger men compared to older and more posteriorly in younger women than older ones. The values found in this study, considering gender, age and ethnic group, can be used as a parameter to carry out the SSRO technique, making it more predictable and with less risk of complications. Conflict of interest There was no financial support for this research. The authors declare that they have no conflict of interest. Ethical standard The authors declare that all procedures adopted for this research are in agreement with the Brazilian laws.
References 1. Afsar A, Haas DA, Rossouw PE, Wood RE (1998) Radiographic localization of mandibular anesthesia landmarks. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 86:234–241 2. Alves N, Cândido PL (2013) Anatomia para o cirurgião-dentista. Gen-Santos, São Paulo 3. Chávez-Lomeli ME, Mansilla Lory J, Pompa JA, Kjaer I (1996) The human mandibular canal arises from three separate canals innervating different tooth groups. J Dent Res 75:1540–1544 4. Chrcanovic BR, Abreu MHNG, Custódio ALN (2011) Morphological variation in dentate and edentulous human mandibles. Surg Radiol Anat 33:203–213 5. Cvetko E (2013) Bilateral anomalous high position of the mandibular foramen: a case report. Surg Radiol Anat. doi:10.1007/ s00276-013-1209-y 6. da Fontoura RA, Vasconcellos HA, Campos AES (2002) Morphologic basis for the intraoral vertical ramus osteotomy: anatomic and radiographic localization of the mandibular foramen. J Oral Maxillofac Surg 60:660–665 7. Dal Pont G (1961) Retromolar osteotomy for the correction of prognathism. J Oral Surg Anesth Hosp Dent Serv 19:42–47
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8. Daw JL Jr, de la Paz MG, Han H, Aitken ME, Patel PK (1999) The mandibular foramen: an anatomic study and its relevance to the sagittal ramus osteotomy. J Craniofac Surg 10:475–479 9. Ennes JP, Medeiros RM (2009) Localization of mandibular foramen and clinical implications. Int J Morphol 27:1305–1311 10. Freire AR, Rossi AC, Prado FB, Caria PHF, Botacin PR (2012) Incidence of the mandibular accessory foramina in brazilian population. Braz J Morphol Sci 29:171–173 11. Gutierrez-Ventura F, Tataje-Vivanco Y (2012) Posición del agujero dentario inferior en la rama ascendente en huesos mandibulares secos de adultos. Rev Estomatol Hered 22:152–157 12. Kaffe I, Ardekian L, Gelerenter I, Taicher S (1994) Location of the mandibular foramen in panoramic radiographs. Oral Surg Oral Med Oral Pathol 78:662–669 13. Kilarkaje N, Nayak SR, Narayan P, Prabhu LV (2005) The location of the mandibular foramen maintains absolute bilateral symmetry in mandibles of different age groups. Hong Kong Dent J 2:35–37 14. Kjaer I, Keeling JW, Hansen BF (1999) The prenatal human cranium: normal and pathologic development. Munksgaard, Copenhagen 15. Lima DSC, Figuerêdo AA, Rocha EA, Costa VHMV, Castro MP, Silva RCP, Chagas GL, Araújo LP, Mendonça VRR, Gravina PR, Meneses JVL (2011) Estudo anatômico do forame mandibular e suas relações com pontos de referência do ramo da mandíbula. Rev Bras Cir Craniomaxilofac 14:91–96 16. Muto T, Shigeo K, Yamamoto K, Kawakami J (2003) Computed tomography morphology of the mandibular ramus in prognathism: effect on the medial osteotomy of the sagittal split ramus osteotomy. J Oral Maxillofac Surg 61:89–93 17. Oguz O, Bozkir MG (2002) Evaluation of location of mandibular and mental foramina in dry, young, adult human male, dentulous mandibles. West Indian Med J 51:14–16 18. Prado FB, Groppo FC, Volpato MC, Caria PHF (2010) Morphological changes in the position of the mandibular foramen in dentate and edentate brazilian subjects. Clin Anat 23:394–398 19. Rajchel J, Ellis E 3rd, Fonseca RJ (1986) The anatomical location of the mandibular canal: its relationship to the sagittal ramus osteotomy. Int J Adult Orthodon Orthognath Surg 1:37–47 20. Reitzik M, Griffths RR, Mirels H (1976) Surgical anatomy of the ascending ramus of the mandible. Br J Oral Surg 14:150–155 21. Salgado AG, Inzunza HO, Cantín M, Fuentes R, Inostroza V, Errázuriz MJ, Pavez C (2012) Evaluación de la anatomía mandibular relacionada con la osteotomía sagital de la rama. Int J Morphol 30:30–39 22. Sekerci AE, Sisman Y (2013) Cone-beam computed tomography analysis of the shape, height, and location of the mandibular lingula. Surg Radiol Anat. doi:10.1007/s00276-013-1150-0 23. Shenoy V, Vijayalakshmi S, Saraswathi P (2012) Osteometric analysis of the mandibular foramen in dry human mandibles. J Clin Diagn Res 6:557–560 24. Strini PJSA, Silva Júnior W, Rodrigues DA, Strini PJSA, Guimarães EC, Bernardino Júnior R (2006) Avaliação topográfica do forame mandibular em peças anatômicas maceradas parcialmente dentadas e edêntulas. Rev Fac Odontol Univ Passo Fundo 11:11–15 25. Thangavelu K, Kannan R, Senthil Kumar N, Rethish E, Sabitha S, SayeeGanesh N (2012) Significance of localization of mandibular foramen in an inferior alveolar nerve block. J Nat Sci Biol Med 3:156–160 26. Trauner R, Obwegeser H (1957) The surgical correction of mandibular prognathism and retrognathia with consideration of genioplasty. I. Surgical procedures to correct mandibular prognathism and reshaping of the chin. Oral Surg Oral Med Oral Pathol 10:677–689 27. Trost O, Salignon V, Cheynel N, Malka G, Trouilloud P (2010) A simple method to locate mandibular foramen: preliminary radiological study. Surg Radiol Anat 32:927–931
Surg Radiol Anat 28. Valente VB, Arita WM, Gonçalves PCG, Campos JADB, Capote TSO (2012) Location of the mandibular foramen according to the amount of dental alveoli. Int J Morphol 30:77–81 29. Yoshida T, Nagamine T, Kobayashi T, Michimi N, Nakajima T, Sasakura H, Hanada K (1989) Impairment of the inferior alveolar
nerve after sagittal split osteotomy. J Craniomaxillofac Surg 17:271–277 30. Yu IH, Wong YK (2008) Evaluation of mandibular anatomy related to sagittal split ramus osteotomy using 3-dimensional computed tomography scan images. Int J Oral Maxillofac Surg 37:521–528
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