Morphometric Analysis of the Occipital Condyle and Its Surgical Importance

Abstract

IntrOductIOnThe human Occipital Condyle (OC) is the distinctive bony structure linking the skull and the vertebral column [1]. The OC partly cover the fringe of the foramen magnum anteriorly and form an articulation with the superior articular facets on the lateral masses of the atlas inferiorly. Each OC which is oval in outline and oriented obliquely is traversed by hypoglossal canal. A condylar fossa is situated just posterior to the OC and can contain a posterior condylar canal for an emissary vein from the sigmoid sinus. Laterally, the occipital bone connects with the petrous part of the temporal bone anteriorly and the mastoid process posteriorly [2].During interventional operations; the direction, angle and position of the nail may change according to the OC morphometry and the difference in measurements may alter the surgical procedure [3]. Occipital plates are frequently utilized during occipitocervical fixation but the complex anatomy of the craniocervical junction poses challenge during these procedures [4]. The surgical mistakes in this region may damage the neuro-vascular structure and result in craniocervical instability. Further, the management of ventrally placed space-occupying lesion at the level of foramen magnum necessitates the use of dorsal approach as high rate of morbidity and complications are frequently linked with ventral approaches. This requires transcondylar approach demanding partial resection of the OC which is a vital step for entrance to the ventral and ventrolateral foramen magnum [1]. Hence, the surgical instrumentation of the craniovertebral region necessitates a thorough anatomical knowledge of the OC.Differences exist in OC morphometric values across different study populations. So far, out of the studies available, few determine the morphometry of OC, especially in the Indian population [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The present study quantified morphometric characteristics of the OC which are mandatory for safe screw placement during surgical instrumentation of this region. MAterIAls And MethOdsThe present study included 228 OC of 114 adult human skulls of unknown sex which were part of the osteological collection of the Department of Anatomy. The study commenced in July, 2015 and accomplished in May, 2016. Skulls that were damaged or those with deformities, which may influence measurements, were excluded from the study and only intact skulls in good condition were studied. All linear measurements were ascertained using digital Vernier's calliper with 0.01mm precision while angular measurements were recorded with software Image J. [Table/ Fig-1

Morphometric Study of Human Adult Occipital Condyle, Hypoglossal Canal and Foramen Magnum in Dry Skull of Modern Egyptians

“…Nevertheless, the results were nearly agreed with that of Indian skulls demonstrated by Saluja [20] (28.16 mm and 26.93 mm respectively), but slightly higher than the measurements of Pereira [19] (26.07 mm and 25.75 mm respectively). Also Pereira showed that the mean distances between the basion to the midpoint of the right OC was 14.87 mm and for the left one was 14.63 mm that were higher than the Egyptian measurements shown by the present study (16 mm and 15.78 mm respectively).…”

“…According to Indian skulls, Saluja [20] found that the mean right condylar sagittal angle was 41.10° and the left one was 44.04° which indicates higher condylar angles in Indians than in Egyptians. On the other hand, they also demonstrated in their study that the mean AICD was 17.81 mm which was nearly similar to our results.…”

Morphometry of the Occipital Condyle and Basilar Process of Nigerian Skulls

“…[29] The mean anterior (AICD) and posterior intercondylar (PICD) distances for the Nigerian skulls were found to 18.09±2.15mm and 30.85±2.98mm. The mean AICD observed in this study was larger than the values;15.39±7.0mm, 17.63mm and 17.81±2.93mm reported by Agnihotriet al (2014), [20] Kumarand Nagar (2014), [30] and Salujaet al (2016), [16] respectively, but lower than the values of Naderiet al (2005), [31] and Mahajan et al (2011), [26] as they reported 21mm, 21.28±3.03mm, 21.28±3.03mm. However the mean PICD obtained in this study was much smaller than the values of Naderiet al (2005), [31] [41.6mm], Mahajan et al (2011), [26] [40.61±3.34mm], Agnihotriet al (2014), [20] [35.60±8.4mm], Kumarand Nagar (2014), [30] [42.02mm] and Salujaet al (2016), [16] [38.91±4.16mm].…”

“…[17] Kavithaet al (2013), [28] reported 21.97mm and 22.34mm for the right and left respectively while Salujaet al (2016), [16] reported mean values of 22.75±2.90mm for Indians. Due to the irregularity in the dimension of the width of OC, this study evaluated two dimensions; minimum (MnOC) and maximum (MxOC) width.…”

“…[5][6][7][8] The occipital condyle (OC) and basilar process (BP) are structures located at the skull base which forms part of the floor of the cranial cavity which by location, differentiates the brain from facial structures and suprahyoid neck (Rautet al, 2012). [9] Name & Address of Corresponding Author Aigbogun (Jr) [8,13,14] with higher values reported for the Asians (Bozbugaet al, 1999; Yu et al, 2015; Salujaet al, 2016), [14][15][16] and lower values for the Caucasians and Australians (Wen et al 1997;Bazyatet al, 2014), [17,18] while for Africans the values fall between values of Asians and Caucasians (Salihet al, 2014; Agnihotriet al, 2014). [19,20] Only a few studies have reported morphometric values for the basilar process (clivus), with dimensions ranging from 24mm to 27mm (Oliviera, 1975; Wescott and Moore-Jansen, 2001), [21,22] and higher values for whites when compared to blacks (Wescott and Moore-Jansen, 2001).…”