Morphological analysis and morphometry of the foramen magnum: an anatomical investigation

Abstract

AIM:The objectives were to study the morphology of the foramen magnum in dry skulls and to evaluate its antero-posterior diameter, transverse diameter and the foramen magnum index. MATeRIAL and MeTHods:The foramen magna of 53 dry human cadaver skulls that were obtained from the neuroanatomy laboratory were examined. Different shapes of the foramen magnum were macroscopically noted and classified. The antero-posterior and transverse diameters were measured and the average foraminal index was calculated. ResULTs:The foramen magnum shapes were determined as a round shape in 22.6% of cases, egg shape in 18.9%, tetragonal in 18.9%, oval in 15.1%, irregular in 15.1%, hexagonal in 5.6% and pentagonal in 3.8% of the cases. In 20.7% of skulls, the occipital condyle was observed to protrude into the foramen. The mean antero-posterior and transverse diameter of the foramen magnum was determined as 31 ± 2.4 mm and 25.2 ± 2.4 mm respectively. The average foramen magnum index was 1.2 ± 0.1. CoNCLUsIoN:The present study has determined the various shapes of foramen magnum and its morphometry. The data obtained may be of useful to the neurosurgeon in analyzing the morphological anatomy of craniovertebral junction. The findings are also enlightening for the anthropologists, morphologists and clinical anatomists. BULGULAR:Foramen magnum şekilleri vakaların %22,6'sında yuvarlak, %18,9'unda yumurta şekilli, %18,9'unda tetragonal, %15,1'inde oval, %15,1'inde düzensiz, %5,6'sında ekstragonal ve %3,8'inde pentagonaldi. Kafataslarının %20,7'sinde oksipital kondilin foramene doğru çıkıntı yaptığı gözlendi. Foramen magnumun ortalama anteroposterior ve transvers çapı sırasıyla 31±2,4 mm ve 25,2±2,4 mm olarak belirlendi. Ortalama foramen magnum indeksi 1,2±0,1 bulundu. soNUÇ: Mevcut çalışma foramen magnumun çeşitli şekilleri ve morfometrisini belirlemiştir. Elde edilen veriler nörocerraha kraniyovertebral bileşke morfolojik anatomisini analiz etmek açısından faydalı olabilir. Bulgular ayrıca antropologlar, morfologlar ve klinik anatomistler için faydalıdır.ANAHTAR sÖZCÜKLeR: Foramen magnum, Morfoloji, Morfometri, Şekil, Kafatası

Morphological Analysis of Occipital Condyles and Foramen Magnum as a Guide for Lateral Surgical Approaches

“…When FM index is ≥ 1.2, the foramen is accepted to be ovoid [30]. Our FM index is similar to those of Kizilkanat et al [34] and Chethanet al [13] (Table 2).…”

“…In early fetal growth, during the development of skull base, FM is one of the centers of ossification [37,38] and because of evolutionary changes in FM, shapes are variable [8]. The irregular shape of FM may cause developmental anomalies of the bone and soft tissues at the CVJ [13]. In our study, the most common FM shape was tetragonal (24%).…”

“…In transcondylar approach, the diameters of FM should be well known for a safe OC resection [13]. In our study, the anteroposterior diameter of FM was 35, 18±2,94mm.…”

“…Before surgery, clinical and radiological diagnostic procedures should be done and anatomical structures must be well identified [13].…”

“…The parameters were anterior and posterior intercondylar distances FM shape was classified into seven types according to Chethan et al [13]: round, egg-shaped, tetragonal, oval, irregular, hexagonal and pentagonal ( Figure 6). FM index was calculated by dividing the anteroposterior diameter of FM by transverse diameter.…”