Ventral Subaxial Cervical Access Using Tailored Access Osteotomies, A Cadaveric Study

Abstract

BACKGROUND: Ventral lesions of the subaxial cervical spine are challenging because approaches must circumvent endodermal and neurovascular structures. OBJECTIVE: To use cadaveric study to describe 4 posterolateral approaches to the ventral subaxial cervical spine with various facilitating techniques and osteotomies. METHODS: Three cadaveric specimens of the cervical spine were sequentially subjected to multilevel laminectomy (Type 1), transfacet (Type 2), transpedicular (Type 3), and extreme lateral transforaminal (Type 4) approaches. Approach working angles and proportion of visualized zones were compared, the former calculated using trigonometric methods. RESULTS: There was a significant stepwise increase in working angle in the ventral space, associated with increasing osteotomy type, from an average of 3.7°in single-level type 1 to 19.47°in the type 4 osteotomy. Regarding anatomic zones, proportional partial and total visualization achieved with Type 2 to 4 approaches were significantly greater than with Type 1. Complex osteotomies allowed superior access to be obtained to contributing and adjacent vessels of the ventral spinal axis. CONCLUSION: Ventral subaxial cervical lesions are difficult to access. We report increased working angles using quantified cadaveric data in increasingly complex posterior and posterolateral approaches graded as type 1 through 4. We advocate continued translational research in such approaches to lesions often considered to lie in surgically inaccessible locations.

In Reply: Ventral Subaxial Cervical Access Using Tailored Access Osteotomies, A Cadaveric Study

“…Simultaneously, we argue that extended bilateral transection be considered in applicable cases because we found the technique to be associated with statistically significant increases in cord rotation as compared with limited and unilateral dentatolysis. 1 We echo the statement that dentate sectioning may affect poorly understood cerebrospinal fluid flow dynamics, as the authors illustrate in a referenced computational model describing variances in flow patterns in simulated spinal canals with absent bilateral dentate ligaments and dorsal and ventral nerve rootlets. 2,9 We encourage further inquiry into this topic.…”

“…Concerning dentatolysis, our report queried available cord rotation offered by limited and extended unilateral vs bilateral sectioning. 1 Although we do not suspect the described durotomy would necessarily affect parenchymal rotation within the central canal, we will be happy to verify it using our model. 1,2 We also agree that unilateral dentatolysis may be sufficient in lesions where marked spinal cord rotation is not necessary to achieve adequate working space.…”

“…1 Although we do not suspect the described durotomy would necessarily affect parenchymal rotation within the central canal, we will be happy to verify it using our model. 1,2 We also agree that unilateral dentatolysis may be sufficient in lesions where marked spinal cord rotation is not necessary to achieve adequate working space. Simultaneously, we argue that extended bilateral transection be considered in applicable cases because we found the technique to be associated with statistically significant increases in cord rotation as compared with limited and unilateral dentatolysis.…”

“…We appreciate the academic inquiry provided by Dickerman et al regarding our submission quantifying posterolateral approaches to the ventral cervical spine in a cadaveric model. 1,2 In their letter, the authors advocate for the application of our method of assessing approach working angles to their described “trapdoor” variant of durotomy. 2 The described approach uses lateral cuts at the cranial and caudal extents of a midline durotomy to increase visualization of the ventral space, as illustrated in their referenced case involving the safe resection of a proximal thoracic meningioma using a three-level laminectomy and unilateral transpedicular approach with costotomy.…”

“…Concerning the comment regarding difficult access in patients with high body mass indices 2 (a concept with which we are very familiar as Louisiana continues to suffer one of the highest state prevalences of obesity, trailing only Alabama, Mississippi, and West Virginia), 10 our methodology uses the distance and angle from the skin edge to the working space of operative field, accounting for variations in neck circumference. 1…”