#96 Comparison of Cranial Facet Joint Violation Rates between Open and Percutaneous Pedicle Screw Placement Using Intraoperative 3-D CT Computer Navigation

General Session: Cutting Edge Technology - Imaging Guidance

Presented by: E.R.G. Santos

Author(s):

S.C. Yson (1)
J.N. Sembrano (1)
P.C. Sanders (1)
E.R.G. Santos (1)
C.T. Ledonio (1)
D.W. Polly, Jr. (1), (2)

(1) University of Minnesota, Orthopaedic Surgery, Minneapolis, MN, USA
(2) University of Minnesota, Neurosurgery, Minneapolis, MN, USA

Abstract

Study Design: Retrospective study comparing cranial facet joint violation rates of open and percutaneous pedicle screw insertion techniques using 3-Dimensional Image-guidance.

Objective: To determine the rate of cranial facet joint violation in intraoperative CT (O-arm) image-guided lumbar pedicle screw instrumentation and compare facet joint violation rates between open and percutaneous techniques.

Summary of Background Data: Facet joint violation by pedicle screws can potentially result in a higher rate of adjacent segment degeneration. Reported cranial facet joint violation rates range from 7% to 100%. Intraoperative image-guidance, which has enhanced pedicle screw placement accuracy, may aid in avoiding impingement of the cranial facet joints.

Methods: We reviewed 188 cases of 3D image-guided lumbar pedicle screw instrumentation from November 2006 to December 2011. Surgeries were conducted at one institution by three fellowship-trained spine surgeons. The cranial screws (ranging from L1 to L5) of each construct were graded according to the Seo classification (0 = no impingement; 1 = screw head in contact/suspected to be in contact with facet joint; 2 = screw clearly invaded the facet joint) on intraoperative axial CT (O-arm) images. Grading was performed by three independent reviewers. If there was a difference in evaluation, a consensus was reached to arrive at a single grade for each screw. Chi-square was used to determine significance between the open and percutaneous group (α=0.05).

Results and Discussion: A total of 370 screws (245 open, 125 percutaneous) were graded. Overall facet joint violation rate was 18.9% (Grade 1 = 16.2%, Grade 2 = 2.7%). Open technique (Grade 1 = 22.4%, Grade 2 = 4.1%) had a significantly higher violation rate than percutaneous technique (Grade 1 = 4%, Grade 2 = 0%) (p< 0.0001). Screws inserted percutaneously have more lateral entry points which tend to avoid the facet joint. There is a trend of an increasing likelihood of facet joint violation from L1 to L5 reflecting the difficulty of avoiding the facet joints at the more caudal levels due to facet orientation and presence of the iliac crests.

Conclusion: The use of intra-operative CT (O-arm) image-guidance in lumbar pedicle screw placement resulted in a facet joint violation rate at the lower end of the reported range in literature. The percutaneous technique has a significantly lower cranial facet violation rate than the open technique. Moreover, none of the facet joint violations in the percutaneous screw group showed complete impingement of the joint (Grade 2).