The anatomic study of clival screw fixation for the craniovertebral region

Abstract

Purpose To study the anatomic parameters related to clival screw and establish reference data concerning the craniovertebral fixation technique. Methods Morphometric measurement of the clivus and the surrounding anatomic structures were obtained on 41 dry bone specimens. Then, 2-D CT reconstruction of the craniovertebral region of 30 patients (19 men and 11 women, ranging in age from 20-64 years with an average age of 38.8 years) were performed to measure the safety range for a 3.5-mm screw placement. Nine entry points were evaluated. Finally, one male fresh cadaver specimen (age 46 years) was dissected to observe the craniovertebral region. Results The clivus faces the basilar artery, the V * XII cranial nerves, the pons, and ventral medulla oblongata at its intracranial surface. The longitudinal diameter of extracranial clivus was 25.87 ± 2.64 mm. The narrowest diameter of the clivus was 12.84 ± 1.08 mm, the distance between the left and right hypoglossal canal was 32.70 ± 2.09 mm at its widest part. The distance between the left and right structures, the maximum value was 49.31 ± 4.16 mm at carotid canal, the minimum value was 16.54 ± 2.04 mm at the occipital condyle. The measurement of clival screws placement simulation via 2-D CT reconstruction images shows the maximum upper insertion angle of three components the optimal entry points, the candidate points, the limit entry points was 130.19°, 125.23°and 85.72°, and the total mean screw length was 7.57, 10.13 and 15.6 mm at the vertical entry angle, respectively. Conclusions Clival screw placement is a viable option for craniovertebral fixation. There is a safe scope for the screw length and angle of the screw placement. And, these parameters obtained in the present study will be helpful for anyone contemplating the use of clival screw fixation.

Anatomy and Clinical Importance of the Extracranial Clivus and Surrounding Structures

“…Extracranically the pharyngeal tubercle could be a safe landmark for the disscetion of soft tissues to exposure the clivus (Ji et al, 2012). It is for this reason that the pharyngeal tubercle is considered as a potential landmark in this study.…”

“…The topography of the region has been well established by anatomists and surgeons (Jackson; Patel et al); however a lack of knowledge regarding the bony landmarks can endanger surgical approach techniques (Jackson). The clivus, an important bony component of the skull base, is a combination of the corpus ossis sphenoidalis and basal part of the occipital bone: it is pitched at 45° to the vertical (Ji et al, 2012(Ji et al, , 2015.…”

“…Skull base pathologies adversely affect the quality of life and can be potentially life-threatening abnormalities (Ji et al, 2012). Inflammatory lesions, tumors, traumatic lesions, developmental disorders and deformity can result in partial or complete disruption of this important area (Ji et al, 2012).…”

“…Inflammatory lesions, tumors, traumatic lesions, developmental disorders and deformity can result in partial or complete disruption of this important area (Ji et al, 2012). For example, clival chordomas account for 0.15-1 % of all intracranial tumors (Erdem et al, 2003;Jian et al, 2011), there location varying depending on whether they are at the upper clival (basisphenoid) or lower clival (basiocciput) region (Stippler et al, 2009).…”

“…Yet, in spite of its well-preserved morphology its stability is vulnerable due to multiple pathologies, such as tumors, injury, inflammation and deformity (Shin et al, 2006;Ji et al, 2012Ji et al, , 2015Ji et al, , 2016a, which can lead to pressure on the spinal cord and neurovascular structures (Shin et al;Ji et al, 2016). CJC fixation methods can be divided into anterior, posterior and combined approaches.…”