Abstract
Objective:
Endoscopic endonasal approaches to the craniovertebral junction (CVJ) and clivus are becoming more commonly performed for ventral skull base pathology. These approaches may involve disruption of the occipitocondylar joint to gain access to the lesion. Our goal was to study the biomechanical implications of progressive anterior unilateral condylectomy.
Methods:
Seven human cadaveric specimens with intact skull and upper cervical spines underwent nondestructive biomechanical testing during flexion-extension, lateral bending, and axial rotation at C0-C1 and C1-C2 joints using a standardized frameless stereotaxis technique. Each specimen served as its own control and underwent testing in the intact state prior to condylar resection. The specimens were tested after inferior third clivectomy, and after progressive unilateral condylectomy performed in 25% increments.
Results:
At C0-C1, statistically significant increases in range of motion in flexion-extension and axial rotation were seen after clivectomy alone and worsened with greater extent of condylectomy. In lateral bending, hypermobility was noted only after 100% condylectomy. Dramatic instability was demonstrated after 100% condylectomy in flexion-extension (
P
< 0.000) and lateral bending (
P
< 0.000). At C1-C2, statistically significant increases in range of motion were seen after 50% condylectomy in flexion-extension and 100% condylectomy in lateral bending. No change was noted in axial rotation. Changes in range of motion were largely caused by changes in the lax zone.
Conclusions:
This evaluation revealed a nuanced picture of the biomechanical consequences of endonasal condylectomy at the CVJ. Based on biomechanical criteria, surgical fusion procedures are advised when 75% or more of the condyle has been disrupted, but may also be needed in cases where less aggressive condylectomy has been performed if symptoms develop.