ORIGINAL ARTICLE ON THE MORPHOLOGICAL STUDY OF FORAMEN MAGNUM

Introduction: Centrally in the deepest part of posterior cranial fossa is the largest foramen, Foramen magnum surrounded by basilar part of occipital bone on either side. Because of relation between the FM and the vital structures passing through it, study on its morphometric features is of great signicance. Aim and objectives: The objectives were to study the various morphological features of the foramen magnum in dry skulls using an analogue Vernier calliper. Materials and methods: 50 dry skulls (8 base skulls, 42 full skulls) of human cadaver of unknown age and sex were obtained to study the morphometric features like shapes, anteroposterior and transverse diameters and FM index in the department of Anatomy, Kanyakumari Government medical college, Asaripallam. Results: The classication of determined shapes were round in 29.7%, hexagonal in 18.2%, egg shaped in 16.9%, oval in 12.7%, tetragonal in 11.4%, pentagonal in 3.7% and irregular in 7.4%. In 12% of the skulls the occipital condyles were found to protrude into the foramen. The mean value of anteroposterior and transverse diameter was found to be 35 ±1.2mm, and 28 ± 1.4 mm respectively and average foramen magnum index was 1.25 ± 0.8. Conclusion: Foramen magnum dimensions are used for sex determination. The structural integrity of foramen magnum is usually preserved in re accidents and explosions due to its resistant nature and secluded anatomical position. The data obtained from protrusion of occipital condyles would help in neurosurgical approach of foramen magnum meningiomas.

An investigation of craniocervical stability post-condylectomy

Background: Occipital condylectomy is often necessary to gain surgical access to various neurological pathologies. As the lateral limit of the craniovertebral junction (CVJ), partial condylectomy can lead to iatrogenic craniocervical instability. What was once considered an inoperable location is now the target of various complex neurosurgical procedures such as tumor resection and aneurysm clipping. Methods: In this study, we will review the anatomical structure of the CVJ and provide the first comprehensive assessment of studies investigating craniovertebral stability following condylectomy with the transcondylar surgical approaches. Furthermore, we discuss future considerations that must be evaluated to optimize the chances of preserving craniocervical stability postcondylectomy. Results: The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. The current findings have only examined overall dimensions and have not established a significant correlation into how the shape of the occipital condyles can affect mobility. Occipitocervical fusion should only be considered after 50% condyle resection. In terms of indicators of anatomical stability, components of range of motion (ROM) such as the neutral zone (NZ) and the elastic zone (EZ) have been discussed as potential measures of craniocervical mobility. These components differ by the sense that the NZ has little ligament tension, whereas the EZ does represent ROM where ligaments experience tension. NZ is a more sensitive indicator of instability when measuring for instability postcondylectomy. Conclusion: Various transcondylar approaches have been developed to access this region including extreme-lateral and far-lateral condylectomy, with hopes of preserving as much of the condyle as possible and maintaining postoperative craniocervical stability.

Morphology and morphometric study of occipital condyles

Introduction: The occipital condyles are undersurface protruberances of the occipital bone in vertebrates, which articulate with the superior facets of the atlas vertebra. The condyles are oval or reniform in shape, and their anterior extremities directed forward and medially and are closer together than the posterior end. Aim: The aim of the study is to provide important anatomical parameters for lateral transcondylar approach. Materials and Methods: 200 occipital condyles in 100 dry human skulls ( 73 males and 27 females) were studied. The measured parameters included length, width, height, shape, anterior and posterior intercondylar distance, distance between basion and opesthion, distance from anterior tip of the condyle to the basion and opestion and distance from posterior tip to the basion and opesthion. Measurements were made using Vernier Callipers. Results: The mean length, width and height of the occipital condyles in males is greater than females. The anterior intercondylar distance is more in females whereas posterior intercondylar distance is more in males. The mean distance from basion to opesthion / anteroposteriordiamerer of foramen magnum is more in males than in females. The mean distance between the anterior tip of occipital condyles to basion is more in females than in males on both the sides. Conclusion: The knowledge of condylar anatomy helps the surgeon in making important decisions regarding extent and direction of condylar drilling and minimizing injury and retraction of neural structures. KEY WORDS: Occipital Condyles, Foramen Magnum, Intercondylar distance, Basion, Opesthion.

Anatomical Parameters for Occipital Condyle Screws: An Analysis of 500 Condyles Using CT Scans

Study Design: Retrospective observational study. Objective: To establish occipital condyle dimensions (length, width, height), as well as the medialization angle necessary for safe occipital condyle screw placement in occipitocervical fixation. Methods: Between 1/2014-6/2014, patients who presented to a single level 1 academic trauma center emergency room and received computed tomography (CT) imaging of the cervical spine as part of routine clinical care were identified. After excluding patients with cervical fractures, neoplastic disease, or infection, 500 condyles representing 250 patients were analyzed. Condyle length, height, and width (all reported in millimeters [mm]) were evaluated on the sagittal, coronal, and axial series, respectively. Medialization angle (reported in degrees) was evaluated on the axial series of CT imaging. Measurements were compared by sex and age. Results: The average condyle length, width, and height were 18.6 millimeters (mm) (range, 14.5-23.0 mm), 10.5 mm (range, 7.4-13.8 mm), and 11.3 mm (7.1-15.3 mm), respectively. Additionally, the average occipital condyle medialization angle was 23° (range, 14-32°). Occipital condyles of men were significantly longer, wider, and taller (all comparisons, p < 0.05). The medialization angle was significantly steeper for women than men (p < 0.05). No measurement differences were appreciated by age. Conclusion: Our findings are similar to previous studies in the field; however, length appears slightly shorter. Further, measurement differences were appreciated by sex but not age. Thus, our measurement findings emphasize the importance of preoperative planning utilizing individual patient anatomy to ensure safe placement of occipital condyle screws for optimal outcomes.

Anatomical and Radiological study of the posterior cranial base in relationship to occipital condyles and Foramen magnum

Detailed morphometric analysis is required for various surgical approaches in the craniovertebraljunction. High mortality and morbidity are anticipated for the surgical procedures when undertaken without in-depth anatomical knowledge. With so much clinical importance in this area, our study will present a thorough understanding in terms of skull and CT values. The main aim of this study is to give the morphometric details of occipital condyles and foramen magnum in cadaveric skulls and CT scans. Seventy dried human skulls and 70 CT images on the three-dimensional volume-rendered reconstruction of the skull base was used for this study. The length and width of the occipital condyle of right and the left side was 22.21 ±5.20 mm; 22.05±4.83 mm; 12.57 ± 2.50 and 12.68 ± 2.92mm respectively in cadaver skull. The length and width of occipital condyles in CT scans for right and left side was 21.61 ± 3.09 mm; 21.58 ± 3.50 mm; 13.04 ± 1.58 mm and 13.13 ± 2.54 mm respectively. The Anteroposterior and transverse diameters of the foramen magnum in cadaveric skulls and CT images was 33.17 ± 7.23; 29.22 ± 6.17; 34.15 ± 2.88 and 28.14 ± 2.43 mm respectively. Each surgical approach and the radiological diagnostic procedures have their limitations. Moreover, analysis of cranial base dimensions of occipital condyles and foramen magnum can be considered as a reliable method for sex determination. Hence this study will a useful guide for surgeons, radiologists, anthropologists and forensic experts.