636 - Evaluating the Feasibility of Minimally Invasive Lateral Mass Screw In...

Oral Posters: MIS

Presented by: A. Kumar - View Audio/Video Presentation (Members Only)

Author(s):

A. Kumar(1), R. Merrill(2), S. Qureshi(3)

(1) Louisiana State University, New Orleans, LA, United States
(2) Icahn School of Medicine at Mount Sinai, New York, NY, United States
(3) Mount Sinai Medical Center, Department of Orthopedic Surgery, New York, NY, United States

Abstract

Introduction: Minimally invasive techniques for instrumenting the lumbar spine are common in the modern hospital setting, however the same is not true for the cervical spine. Stripping the posterior ligamentous tension band and paraspinal musculature for the placement of lateral mass screws may contribute to development of postoperative kyphosis and chronic pain. The purpose of this study was to investigate and evaluate the feasibility of minimally invasive lateral mass fixation of the cervical spine in a controlled setting.

Materials and Methods: Lateral mass screws were placed bilaterally into each level from C3 to C7 of 4 cadaveric specimens. Fluoroscopic guidance in the AP plane was utilized to plan an incision one vertebral body below the level of interest, just medial to the lamina-facet junction. Incision through skin and fascia allowed sequential dilation to accommodate a 14mm tubular retractor. Exposure of the lateral mas allowed visualization of a central starting point that was confirmed with a lateral fluoroscopic image. A starting hole was then created using a bur and followed by a cannulated drill, guidewire and placement of a cannulated 2.5mm screw. Screw trajectory and accuracy were assessed using fluoroscopy and 3D fluoroscopic reconstructions (Figures 1 and 2)

Results: Lateral mass screws were completely within the substance of the lateral mass 87.5% of the time, with a 12.5% incidence of lateral or anterior breach of the cortical margins. The typical angle of divergence achieved was 12.8 degrees with 45.5 degrees of cranial angulation. There was no incidence of penetration into the transverse foramen or spinal canal.

Conclusion: Minimally invasive placement of lateral mass screws through a tubular retractor is a viable technique for instrumenting the posterior cervical spine. Despite restrictions from the soft tissues and spinous process, we were able to achieve a trajectory through the tubular retractor that is within the range of techniques described for the open placement of lateral mass screws. Further refinement of the technique is warranted including clinical trials comparing patient outcomes with traditional open techniques.

Figure 1

Figure 2