Gridding Microsurgical Anatomy of Far Lateral Approach in the Three-Dimensional Model.

Objective: The far lateral craniotomy involves osteotomy of various portions of occipital condyle. Intracranial operation exposing clivus encounters complicated neurovascular anatomy. The aim of the present study was to make refinement for the anatomy of far lateral approach by gridding route in the 3-dimensional model.

Methods: Computed tomography and magnetic resonance imaging data were used to construct 3-dimensional model containing osseous and neurovascular structures of skull base. Then, far lateral approach was simulated by triangular prism and divided into gridding surgical route. The relationship of surgical route and osseous and neurovascular structures was observed. Measurement of volume was performed to evaluate surgical exposure.

Results: Observation of 3-dimensional model showed bony drilling of far lateral approach started with the occipital condyle and passed through the lateral edge of foramen magnum. The cerebellum and medulla oblongata were exempted from the surgical route exposing clivus. The anatomy variances of operative space, osseous, and neurovascular structures in the gridding route were displayed clearly and compared objectively.

Conclusion: The gridding operative spaces for the far lateral approach are useful to disclose the detailed discrepancy in the different surgical region. The volumetric measurement provides quantified information to facilitate a better understanding of the anatomy variance.