Int. J. Morphol., 35(3):1129-1132, 2017.

 

Morphological Analysis on the Occipital Condyles and Review of the Literature

 

Análisis Morfológico de los Cóndilos Occipitales y Revisión de la Literatura

 

José Aderval Aragão¹; Guilherme Machado de Santana²; Rebeca Zelice da Cruz de Moraes²; Iapunira Catarina Sant'Anna Aragão³; Felipe Matheus Sant'Anna Aragão³ & Francisco Prado Reis⁴

1 Associate Professor, Department of Morphology and the Postgraduate Applied Health Science Programs, Federal University of Sergipe (UFS), and Titular Professor of the Medical School, Tiradentes University (UNIT), Aracaju, Sergipe, Brazil.

2 Medical student at the Federal University of Sergipe (UFS), Aracaju, Sergipe, Brazil.

3 Medical Student, University Center of Volta Redonda (UNIFOA), Volta Redonda, Rio de Janeiro, Brazil.

4 Titular Professor, Medical School of Tiradentes University (UNIT), Aracaju, Sergipe, Brazil.

Correspondence to:

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SUMMARY: Most anatomical and biomechanical studies on the craniovertebral junction have involved morphological or morphometric analysis on the occipital condyles. Some of these studies have provided important findings based on different surgical procedures. The shape, size and angle of the occipital condyles and the locations of the intracranial and extracranial orifices of the hypoglossal canal are highly important because they may affect the lateral approaches to the craniovertebral junction. To determine the frequency of occurrence of different morphological types of occipital condyle. 214 occipital condyles in 107 dry human skulls were analyzed and the classification of their morphological types was determined through assessing digitized photographic images. Among the 107 skulls analyzed, 59.8 % were male and 40.2 % were female. Their ages ranged from 11 to 91 years, with a mean of 57.56 years. Of the total of 10 morphological types of occipital condyle that were found, more than 50 % were of the "8", "S" and ring types. Condyles of "8" and "S" shape were the main types found in male skulls: the "8" shape prevailed on the left side and the "S" shape on the right side. However, in female skulls, these two types had equal bilateral distribution.

KEY WORDS: Skull; Occipital condyle; Atlanto-occipital joint; Surgical anatomy; Craniofacial abnormalities; Morphology; Occipital bone.

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RESUMEN: La mayor parte de los estudios anatómicos y biomecánicos de la unión cráneo-vertebral han sido realizados sobre el análisis morfológico o de la morfometría de los cóndilos occipitales. Algunos de estos trabajos tienen previsto importantes hallazgos basados en diferentes procedimientos quirúrgicos. De tal forma, el tamaño y ángulo del cóndilo occipital bien como su localización de los orificios intracraneales y extracraneales del canal hipogloso son de gran importancia, ya que pueden afectar a los enfoques laterales de la unión cráneo-vertebral. El objetivo del estudio fue determinar la prevalencia de los tipos morfológicos de cóndilos occipitales. Fueron analizados 214 cóndilos de 107 cráneos secos de humanos y la clasificación de los tipos morfológicos fue determinada a partir de los análisis de estudio de imágenes fotográficas digitalizadas. De los 107 cráneos que fueron analizados, 59,8 % eran de sexo masculino y 40,2 % de sexo femenino, cuyas edades comprendidas entre 11 y 91 años con una media de 57.56 años. De un total de 10 tipos morfológicos de los cóndilos occipitales encontrados, más del 50 % eran de tipo ocho, S y anillo. Los cóndilos en forma de "8" y "S" fueron los principales tipos encontrados, en el sexo masculino, la forma en "8" prevaleció en el lado izquierdo, y el tipo morfológico en "S", en el lado derecho del cráneo. Mientras que en el sexo femenino esos dos tipos tuvieron una equitativa distribución bilateral.

PALABRAS CLAVE: Cráneo; Cóndilo occipital; Articulación atlanto-occipital; Anatomía quirúrgica; Anomalías craneofaciales; Morfología; Hueso occipital.

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INTRODUCTION

Assessment and morphological analysis on the bones that make up the neurocranium and viscerocranium of the human skeleton are very important in forensic anthropology and play a significant role in investigations to estimate and determine the sex, age, ethnicity and height of unknown individuals (Kumar & Nagar, 2014).

The occipital condyles are anatomical structures that are located laterally to the foramen magnum of the occipital bone, at the external base of the skull (Kavitha et al., 2013; Natsis et al., 2013). These structures make a connection with the vertebral column through the atlanto-occipital joint (Kavitha et al., Bayat et al., 2014; Das at al., 2006; Naderi et al., 2005; Ozer et al., 2011; Kizilkanat et al., 2006). The integrity of the occipital condyles is very important for the stability of the craniovertebral junction, such that variations in their shape, size and angle correspond equally to variations in the atlanto-occipital joint (Naderi et al., Ozer et al.).

The occipital condyles have been described as bone structures with an oval outline that are arranged obliquely in such a way that the anterior extremity is more medial than the posterior extremity, thus presenting a convex anteroposterior surface (Kavitha et al.; Ozer et al.). The condylar canal is located posteriorly to the occipital condyles. In some cases, the occipital condyles may project significantly towards the foramen magnum (Muthukumar et al., 2005). The canal of the hypoglossal nerve is located at the anterolateral margin of this foramen (Kizilkanat et al.).

There are several anatomical studies in the literature reporting the importance of morphometric variations of the occipital condyles (Kumar & Nagar, 2014, Kavitha et al., Natsis et al., Bayat et al., Das et al., Naderi et al., Ozer et al., Kizilkanat et al., Muthukumar et al., Avci et al., 2011, Bozbuga et al., 1999, Kalthur et al., 2014, El-Gaidi et al., 2014, Gapert et al., 2009) and radiological studies have also been conducted (Avci et al., Le et al., 2011, Hong et al., 2011, Noble & Smoker, 1996). Knowledge of the topography of different neurovascular structures located around the region of the occipital condyles is highly important with regard to conducting neurosurgical procedures (transcondylar approach) and obtaining good results. Notions of this knowledge should be one of the main issues to be analyzed during the preoperative decision-making process (Kumar & Nagar, Naderi et al., Ozer et al., Kizilkanat et al., Avci et al.).

Most of the descriptions found in textbooks do not deal with anatomical variations of the occipital condyles (Gardner et al., 1988; Hollinshead, 1991; Drake et al., 2010; Moore et al., 2011). This indicates that there is still a need for studies on the morphometric variations of the occipital condyles. The present study had the aim of determining the frequency of occurrence of different morphological types of occipital condyles.

MATERIAL AND METHOD

We analyzed 214 occipital condyles in dry human skulls belonging to the Forensic Anatomy and Anthropology Study and Research Center of Tiradentes University (UNIT), Aracaju, Sergipe, Brazil. Skulls that appeared to be complete in the region of the occipital condyles and which were identified regarding sex and age were analyzed. The classification of the morphological types of occipital condyles was determined through examining digitized photographic images that had been obtained using a digital camera (Sony DSLR-A100K) and had been save in JPEG format (Joint Photographic Experts Group). The present study was approved by the Research Ethics Committee of the Federal University of Sergipe, under protocol number 0357.0.107.000-11.

RESULTS

Among the 107 skulls that were analyzed in the present study, 64 (59.8 %) were male and 43 (40.2 %) were female. Their ages ranged from 11 to 91 years, with a mean of 57.56 years. The morphological types that were found are represented in Fig. 1 and their frequency of distribution according to sex is presented in Table I. It can be seen that the type in an "8" shape was most prevalent, followed by the "S" and ring types, and that condyles of irregular shape were least prevalent. Symmetrical and asymmetrical forms were found respectively in 26.2 % and 73.8 % of the skulls.

Fig. 1. Morphology of occipital condyles. 1) "8" shape, 2) "S" shape, 3) ring, 4) triangular,
5) quadrilateral, 6) biconvex, 7) reniform, 8) oval, 9) condyle in two parts, 10) irregular.

Table I. Distribution of different morphological types of occipital condyle, according to sex.

DISCUSSION

Several classifications have been created to define different morphological types of occipital condyle, but without determining the prevalence of each of these types (Bozbuga et al.; Olivier, 1975; Guidotti, 1984). Guidotti analyzed 741 skulls belonging to the Institute of Anatomy of the University of Siena and propose a classification of occipital condyles based on (1) division of their surface into planes; (2) partition without interruption of the joint surface; (3) partition with an evident angle but without separation of the two surfaces; and (4) duplication of condyles. Bozbuga et al. classified occipital condyles as follows: (1) two forms of semicircle; (2) oval; (3) lozenge; (4) bean; (5) prismatic; (6) flattened; (7) convex; (8) flattened convex; (9) plane; (10) short and wide; (11) planar and long; and (12) small and convex.

Table II shows the variance and discordance regarding the morphological types of occipital condyles, along with their prevalence. From an analysis on skulls from the Turkish population, Ozer et al. and Naderi et al. concluded that occipital condyles of oval shape were the commonest. According to Sinha et al. (2014) and Natsis et al. the "S" shape was the main type. However, Bayat et al. and Fetouh & Awadalla (2009) reported that occipital condyles of reniform shape were most prevalent. In the present study, the main morphological type of occipital condyle was found to be the "8" shape. A similar finding was reported by Kalthur et al. from a study on individuals in the Indian population. A comparison of incidence rates among morphological types of occipital condyle reported by some authors is shown in Table III.

Table II. Most frequent morphological types of occipital condyle in different studies.

Table III. Morphological comparison of occipital condyles in various studies.

CONCLUSION

In the present study, occipital condyles of "8" and "S" shape were the main types found. Among the male skulls, the "8" shape was most prevalent on the right side, while the "S" shape was most prevalent on the right side. Among the female skulls, these two types had the same distribution bilaterally.

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Corresponding author:

José Aderval Aragão

Rua Aloisio Campos 500
Bairro Atalaia
Aracaju, Sergipe
CEP: 49035-020
BRAZIL

E-mail: jaafelipe@infonet.com.br

Received: 12-04-2017
Accepted: 25-07-2017