sexing the human skull through the mastoid … · sexing the human skull through the mastoid...

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REV. HOSP. CLÍN. FAC. MED. S. PAULO 58(1):15-20, 2003

From the Department of Legal Medicine,Medical Ethics, Social and OccupationalMedicine, Hospital das Clínicas, Faculty ofMedicine, University of São Paulo.

Received for publication onFebruary 28, 2002.

SEXING THE HUMAN SKULL THROUGH THEMASTOID PROCESS

Luiz Airton Saavedra de Paiva and Marco Segre

PAIVA LAS et al. – Sexing the human skull through the mastoid process. Rev. Hosp. Clín. Fac. Med. S. Paulo 58(1):15-20,2003.

OBJECTIVE: The purpose of this study was to evaluate the significance for sex determination of the measurement ofthe area formed by the xerographic projection of 3 craniometric points related to the mastoid process: the porion, asterion,and mastoidale points.

METHOD: Sixty skulls, 30 male and 30 female, were analyzed. A xerographic copy of each side of the skull wasobtained. On each xerographic copy, the craniometric points were marked to demarcate a triangle. The area (mm2) of thedemarcated triangle for each side of the skull (right (D) and left (E) sides) was determined, and the total value of thesemeasures (T) was calculated.

RESULTS: Concerning the right area of the male and female skulls, 60% of the values overlapped; for the left area,51.67% overlapped, and for the total area, 36.67% overlapped. The analysis of the differences between the sexes in the areasstudied was significant for the 3 areas. Regarding the total area, which is the preferred measurement because of the asymmetrybetween the sides of the skull, the value of the mean was 1505.32 mm2 for male skulls, which was greater than the maximumvalue obtained in the female skulls. The value of the mean for female skulls was 1221.24 mm2, less than the minimum valueobtained for the male skulls.

CONCLUSIONS: This study demonstrates a significant result in the 3 studied areas, (D), (E), and (T). The total areavalues show less overlapping of values between the sexes, and therefore can be used for sexing human skulls. For thepopulation studied, values of the total area that were greater than or equal to 1447.40 mm2 belonged to male crania (95%confidence). Values for this area that were less than or equal to 1260.36 mm2 belonged to female crania (95% confidence).

DESCRIPTORS: Forensic medicine. Forensic anthropology. Anthropometry. Mastoid. Sexual characteristics.

INTRODUCTION

Historically, human identificationis one of the most challenging subjectsthat man has confronted. The conceptof identity, with few significant varia-tions, is the same as the assertion ofAlves1 that identity is a set of physi-cal characteristics, functional or psy-chic, normal or pathological, that de-fine an individual.

Nowadays, human identification isa universal process based on scientificprinciples, mainly involving finger-printing, the objective of which is toidentify and register individuals for

both civil and criminal identificationpurposes. According to Arbenz2, theapplication of the knowledge of physi-cal anthropology for the purpose of fo-rensic medicine constitutes forensicanthropology.

The identification of human re-mains, when it is not possible to applythe scientific method of fingerprintidentification, demands a forensic medi-

cine investigation. This skillful process,carried out by a coroner using knowl-edge of other professional areas, char-acterizes the medico-legal identifica-tion and is based on the application ofknowledge of forensic anthropology.

The protocols of application ofthis knowledge by the authors in thisarea are not very different. The deter-mination of the sex of skeletons rep-resents an important stage in the ex-ecution of the forensic anthropologi-cal examination. The studies for sexdetermination are based on the dimor-phism between the sexes that is presentin the majority of human bones.

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Sexing the human skull through the mastoid processPaiva LAS et al.


Reichs3 stated that the applicationof some existing methods of study oc-curs through two main approaches: bycomment and description of the mor-phology of the bones in question, andby the values obtained using mor-phometry, or in other words, the meas-urement of these bones. A summary ofthe main differences in bones thatpresent dimorphism between the sexesis presented by Bass4, Ubelaker5,Stewart6, Rathbum and Buikstra7, andKrogman and Íscan8.

These authors emphasize the di-morphism of the pelvis and the skull.Krogman and Íscan8 state that determi-nation of sex, age, and race in a col-lection of 750 skeletons was possible,with levels of reliability of 100% whenall the skeleton was present, with 95%reliability when using the pelvisalone, 92% using the skull alone, and98% using the pelvis and the skull.This clearly demonstrates the impor-tance of these regions—the skeleton,pelvis, and skull—for sex determina-tion in forensic anthropological ex-aminations.

Bass4 says that the skull is prob-ably the second best region of the skel-eton to determine the sex. Broca(1875), and Hoshi9 have already sug-gested that when skulls were placedon flat surface, the male skulls rest onthe mastoid processes, while the fe-male skulls rest on the occipitalcondyles or other portions of the skull.A great many researchers have studiedthe dimorphism of the mastoid proc-ess between the sexes through the useof its measurements, in isolated formor through the product between its val-ues, emphasizing in a general way thatthe mastoid process is larger in themale.

Many authors, cited by Wahl andHenke10, have highlighted the impor-tance of the petrous portion of the tem-poral bone and its general preservationin the case of burning. This preserva-tion occurs for two reasons: the com-

pact structure of the petrous portionand its protected position at the baseof the skull. Thus, this anatomical re-gion is favorable for sex determinationdue to its craniometric characteristics.Upon careful examination of the avail-able literature, we can recognize thefollowing:1 - the importance of the skull for sex

determination;2 - the importance of the temporal

bone for anthropological studiesdue to its robustness and its loca-tion, usually making it possible toexamine it in fragmented or burnedskulls;

3 - the interest demonstrated by au-thors, since the last century, in thestudy of the mastoid process for thesex determination, both throughits morphological traits (descriptivemanner) and its measurement (mor-phometry);

4 - the search for related mathematicalvalues to the mastoid process ob-tained by craniometric techniquesthat better demonstrate dimorphismbetween the sexes;

5 - the superior results demonstratedin studies that make use of multi-ple measurements rather than anisolated measurement of the mas-toid process to determine the sexof skeleton;

6 - the significant results demon-strated in studies that make use ofthe dimorphism between the sexesof the correlation between the sur-face of the mastoid process and therobustness of the mastoid process;

7 - the scarcity of Brazilian nationalstudies utilizing material of ourethnic and biological make up.Thus, the present study, which was

carried out using resources generallyavailable to the majority of medicalexaminer’s offices, is founded on aneasily applied methodology and isbased on our anthropologic archives.

METHODS

This study involved the use of 60skulls that were housed in the collec-tion of the Forensic AnthropologyLaboratory of the “Setor de PeríciasMédico-Legais” of Guarulhos duringthe period of January to July of 1997.In this study, the skulls (30 males and30 females) had been obtainedthrough the exhumation of identifiedcadavers that had anthropologicaldata, including the date of death, sex,age, and color, which is registered inthe archives of the Municipal Cem-etery Necropolis of Campo Santo,Guarulhos, São Paulo.

Adult skulls of mature individuals,18 or more years old, that had no de-struction of the mastoid region or ab-sence of metopic bone in the region ofthe craniometric points were chosenfor the study. A xerographic copy ofeach side of the skull was obtainedthrough a standardized technique, asdemonstrated in figure 1. The skullunder study was kept on the copyingsurface supported by 2 points:a) the lateral surface of the mastoid

process;b) the zygomatic arc.

The objective of the techniqueproposed was to obtain a xerographiccopy with as little distortion as possi-ble. This was achieved by resting themastoid process on the surface of thecopier.

After the copies were made, eachxerographic copy was identified withthe identification number of the skull.

The device used to obtain thexerographic copies was a XEROXmodel 5334.

On each xerographic copy, wemarked these craniometric points:1 - Porion – the uppermost lateral

point of the external auditorymeatus;

2 - Asterion – the meeting point of thelambdoid, occipitomastoid, andparietomastoid sutures;

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3 - Mastoidale – the lowest point ofthe mastoid process.We then drew a triangle linking

these three points. The resulting trian-gle was our object of study (Figure 2).

Once demarcated the triangle wastransferred to tracing paper and its areacalculated.

The values used for the presentstudy, in mm2, were obtained through

the calculation of the area of the de-marcated triangle on each side of theskull, right and left, called right area(D) and left area (E), respectively, andthe value of the total of these 2 meas-urements, the total area (T).

The decision to use the value ofthe total area in the study was basedon the evidence obtained byHelmuth11, Schmitt and Saternus12 andDemoulin13 of the asymmetry of themastoid process between the sides ofthe skull.

RESULTS

In the group of male skulls, wefound the values in Table 1.

In the group of the female skulls,we found the values in Table 2.

The overlapping of the values ofthe right area (D) between the maleand female skulls was 60%. The over-lapping of the values of the left area(E) between the male and female skullswas 51.67%. The overlapping of thevalues of the total area (T) between themale and female skulls was 36.67%.The analysis of the difference betweenthe male and female skulls, using Stu-dent’s t test, is presented in Table 3.The values of the mean, the standarderror mean and the 95% confidence in-terval for the mean are presented inFigure 3.

DISCUSSION

The objective of this study was todemonstrate that through a practical,easily applied methodology, it is fea-sible for the majority of the medicalexaminer’s offices to determine the sexof skulls. This can be done using read-ily available resources. Based on asample of our anthropological ar-chives, we show that the triangle areameasurement demarcated through thexerographic projection of cranio-

Figure 1 - The standardized technique for obtaining a xerographic copy of the skull.

Figure 2 - The area of the demarcated triangle used for the study.

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metrical points related to the mastoidprocess is useful in the sexing of skulls.

Since this study was based on an-thropometric techniques, it surpasses inimportance the older studies such asthose of Broca14, and Martin15 apudHoshi9. It also improves on the crite-ria reported by Bass4, which werebased only on descriptive anatomical

aspects, as emphasized by Krogmanand Íscan8 .

By using a measurement of surfacearea, or in other words, by using the re-sult of a product between 2 values, ourresults improve on those of studies bySchultz16 apud Helmuth11, Schäefer17

apud Helmuth11, and Keen18 (1950),which used only a single measurement.

Thus, this study is in agreement withthe conclusions of Helmuth11, Schmittand Saternus12, and Demoulin13. Themastoid region used in this study, be-ing a part of the temporal bone, is rec-ognized as being the most protectedand resistant to damage, due to its ana-tomical position at the base of theskull. This has been demonstrated byKloiber (1953), Wells (1960), Schäefer(1961), Gejval (1963), and Spence(1967), as cited by Wahl and Henke10.

Therefore, compared with the mostimportant historical studies dealingwith sex determination of skulls, thepresent study shows important im-proved results. These results are basedon anthroposcopics and anthropomet-ric techniques, and they open paths forfurther studies based on statistics,which could be of considerable aid tomedico-legal investigations.

The required equipment for the ex-ecution of this technique is readilyavailable to the majority of medicalexaminer’s offices. Any model of pho-tocopy device can be used.

This technique is easy to execute,offers quick results, and dispenses withany type of special training for themedical examiner.

The technique for sexing skullspresented in this study offers a practi-cal alternative to other methods. Thistechnique meets the needs and reali-ties of the forensic investigation in ourcountry today.

ACKNOWLEDGMENT

To Doctor Wilmes GonçalvesTeixeira, Professor of Forensic Medi-cine at the University of Braz Cubas,for suggesting the subject for thisstudy and to Professor Günter WilhelmUhlmann, from the Human and SocialSciences Center of the University ofGuarulhos, for his assistance in thetranslation of German language texts,essential for this study.

Table 3 - Analysis of difference of the areas studied using the Student t test.

AREA t Gl SIGNIFICANT at P <.05

RIGTH (D) 6.40 58*

LEFT (E) 7.78 58*

TOTAL (T) 7.92 58*

α = 0.05

Table 2 - Reference values for the study in female skulls.

RIGHT AREA LEFT AREA TOTAL AREA(D) (mm2) (E) (mm2) (T) (mm2)

MINIMUM 471.50 462.00 942.00MAXIMUM 742.00 750.00 1475.00MEAN 608.70 602.54 1211.24

Table 1 - Reference values for the study in male skulls.

RIGHT AREA LEFT AREA TOTAL AREA(D) (mm2) (E) (mm2) (T) (mm2)

MINIMUM 539.00 612.50 1248.00MAXIMUM 945.00 910.00 1855.00MEAN 752.10 753.22 1505.32

Figure 3 - Means of the total area by sex, with 95% confidence intervals.

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RESUMO

PAIVA LAS e col. – Determinação dosexo em crânios humanos atravésdo processo mastóide. Rev. Hosp.Clín. Fac. Med. S. Paulo 58(1):15-20, 2003.

OBJETIVO: Avaliar a signifi-cância da medida da área formada pelaprojeção xerográfica de três pontoscraniométricos relacionados ao proces-so mastóide, que são, o porion, oasterion e o mastoidale, na determina-ção do sexo em crânios humanos.

MÉTODO: Foram utilizados 60crânios, sendo 30 masculinos e 30 fe-mininos. De cada crânio foi realizadauma xerocópia de cada lado sendo as-sinalados os pontos craniométricospara demarcação de um triângulo. Fo-ram utilizados os valores em mm3 daárea do triângulo de cada lado (D) e

(E), e o valor correspondente aosomatório dessas duas medidas (T).

RESULTADOS: A sobreposiçãodos valores da área direita (D) entre oscrânios masculinos e femininos foi de60%, dos valores da área esquerda (E)foi de 51,67% e dos valores da área to-tal (T) foi de 36,67%. A análise da di-ferença dos valores, entre os sexos,mostrou ser significativa nas três áre-as estudadas. No estudo da área total(T), preferida devido à assimetria en-tre os lados da crânio, o valor médiopara os crânios masculinos foi 1505,32mm2, acima do valor máximo encon-trado em crânios femininos. O valormédio para crânios femininos foi1211,24 mm2, abaixo do valor mínimoencontrado em crânios masculinos.

CONCLUSÕES: O trabalho mos-tra uma significativa diferença entre os

valores nas três áreas de estudo, (D),(E) e (T). Os valores da área total (T)apresentam menor sobreposição entreos sexos devendo ser preferencialmen-te usados na determinação do sexo emcrânios. Para a população em estudo,os valores da área total iguais ou su-periores a 1447,40 mm2 significam,com nível de confiança igual ou supe-rior a 95%, pertencerem os crânios aosexo masculino. Para os valores da áreatotal iguais ou inferiores a 1260,36mm2, com nível de confiança igual ousuperior a 95%, pertencem os crâniosao sexo feminino.

DESCRITORES: Medicina legal.Antropologia forense. Antropo-metria. Mastóide. Características se-xuais.

REFERENCES

1. ALVES ES – Medicina legal e deontologia. Curitiba, Ed. doAutor, 1965.

2. ARBENZ GO – Medicina legal e antropologia forense. Rio deJaneiro, Atheneu, 1988.

3. REICHS KJ – Forensic osteology. Springfield, Thomas, 1986.

4. BASS WM – Human osteology: a laboratory and field manualof the human skeleton. Columbia, David R. Evans Editor,1971.

5. UBELAKER DH – Human skeletals remains. Chicago, Aldine,1978.

6. STEWAR TD – Essentials of forensic anthropology. Springfield,Thomas, 1979.

7. RATHBUM TA, BUIKSTRA JE – Human identification.Springfield, Thomas, 1984.

8. KROGMAN WM, ÍSCAN MY – The human skeleton in forensicmedicine. 2nd ed. Springfield, Thomas, 1986.

9. HOSHI H – Sex difference in the shape of the mastoid process innorma occipitalis and its importance to sex determination of thehuman skull. Okajima’s Folia Anat Jpn 1962; 38: 309-17.

10. WHALL J, HENKE W – Die pars petrosa als diagnostikum für diemultivariat-biometrisch geschlechtsbestimmung vonleichenbrandmaterial. Z Morphol Anthropol 1980; 70: 258-68.

11. HELMUTH H – Einige mabe des processus mastoideus beimmenschen und seine bedeutung für die geschlechtsbetimmung.Z Morphol Anthropol 1968; 60: 75-84.

12. SCHMITT HP, SATERNUS K – Beiträge zur forensischenosteologie. Der processus mastoideus alsidentifikationsmerkmal? Z Rechtsmedizin 1970; 17:1-103.

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13. DEMOULIN F – Importance de certaines mesures crâniennes (enparticulier de la longueur sagittale de la mastoide) dans ladetermination sexuelle des crânes. Bull et Mém de la SocD’Anthropol 1972; 9: 259 – 64.

14. BROCA P – Instruction craniologique. In: DECHAMBRE D. -Dictionaire encyclopédique des sciences médicales. Paris,Asselin/Masson, 1879; t.22, p.642.

15. MARTIN R – Lerbuch der anthropologie. 2 Aufl Bd 1928; 2:737-41 apud HOSHI H, 1962. p.309.

16. SCHULTZ AH – Anthropologische untersuchungen na derschädelbasis. Arch Anthrop 1917; 17: 1-103 apud HELMUTHH, 1968. p. 75.

17. SCHAEFER U – Greuzen und möglichkeiten deranthropologischen untersuchung von leichenbränden. In:Bericht über den Internat Kongr f Vor und Frühgeschichte,5., Hamburg 1958 apud HELMUTH H, 1968. p. 76.

18. KEEN JA – A study of the differences between male and femaleskull. Am Phys Anthropol 1950; 8: 65-79.

sexing the human skull through the mastoid … · sexing the human skull through the mastoid...

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