Biomechanical and Morphometric Evaluation of Occipital Condyle for Occipitocervical Segmental Fixation

Abstract

Two recent novel techniques of occipital fixation are the occipitoatlantal (C0-C1) transarticular screw technique and the direct occipital condyle screw technique. The present study evaluated and compared the biomechanical stability of the direct occipital condyle screw and C0-C1 transarticular screw with the established method for craniocervical spine fixation using the midline occipital keel screw and C1 lateral mass screw. Morphometric evaluation of the occipital condyle and the hypoglossal canal was performed to avoid hypoglossal nerve injury during the screw placement. Thirteen recently frozen cadaveric specimens were used. The occipital condyle anatomy and the hypoglossal canal dimension were measured using reconstructed computed tomography images. Insertion torque and pullout strength were evaluated to compare the midline occipital keel screw, C0-C1 transarticular screw, C1 lateral mass screw, and direct occipital condyle screw. The dimensions of the occipital condyle allow use of a 3.5 or 4.0-mm diameter screw. Mean pullout strength was 1619.6 N for the midline occipital keel screw, 870.7 N for the C0-C1 transarticular screw, 707.0 N for the C1 lateral mass screw, and 431.7 N for the direct occipital condyle screw. Mean insertion torque was 0.55 Nm for the midline occipital keel screw, 0.32 Nm for the C0-C1 transarticular screw, 0.14 Nm for the C1 lateral mass screw, and 0.11 Nm for the direct occipital condyle screw. The condylar anatomy allows direct insertion of the occipital condyle screw and C0-C1 transarticular screw. These techniques are suitable options for the treatment of craniovertebral junction instabilities in selected patients.

Morphometry of Occipital Condyles in Craniovertebral Surgeries

“…In our study the mean angle of occipital condyle to sagittal plane on the right was 30.52 degree and on the left side 29.6 degree but it was not significant. Kizilkanat et al [14] and Hong et al [3] found the angle of occipital condyle to sagittal plane as 31.5 and 33.5 degree respectively. Our finding goes hand in hand with Kizilkanat et al [14], Naderi et al [4].In the present study the angle of occipital condyle to the horizontal plane was measured on both sides.…”

“…During this procedure the occipital condyle is resected fully or partially. In a study conducted by Hong et al [3], the occipital condye measurements were used in techniques such as transarticular and direct occipital screwing. Therefore a thorough knowledge of the measurements of occipital condyle is necessary for a The craniovertebral junction is an important landmark for the surgeons and radiologists to expose the posterior cranial fossa.…”

A modified transcondylar screw to accommodate anatomical skull base variations

“…Classical techniques, such as occipital condyle screw[27] or occipital cervical plate,[1] are often sufficient for occipitocervical stabilization. However, these traditional fusion techniques fail due to screw “pull-out” from occiput,[4] screw fracture, and subaxial delayed instability with degenerative changes.…”

Occipital condyle-c1 complex screw for fixation of basilar invagination patients with atlas assimilation

“…nerves, which can be caused by tips of other types of screws (3, 11,12). Further biomechanical studies on the stability of these types of occipital condyle-C1 lateral mass complex screws are needed.…”