Jon Park, M.D., FRCSC

Modified Polyaxial S1 Screw Placement in Patients with Difficult Sacral Anatomy - Technical Report

M Kalani, G Li, S Mindea, J Park. Cureus 5(1): e83. doi:10.7759/cureus.83. 2013

Modified Polyaxial S1 Screw Placement in Patients with Difficult Sacral Anatomy - Technical Report Published: January 18, 2013 Abstract We present a case of a patient with unfavorable sacral angles and narrow iliac window created by large bilateral iliac crests who underwent L5/S1 anterior lumbar interbody fusion (ALIF) followed by posterior fixation using L5-pedicle screws and L5/S1-facet screws for lumbar degenerative disease. Due to the difficult sacral anatomy, S1 pedicle screw placement was deemed technically difficult. The use of a L5/S1 facet screw reduced the need for retraction and muscle dissection or inserting a pedicle screw via new incision. Although no longer the most commonly performed form of posterior instrumented fusion, facet screw fixation has similar pseudoarthrosis rates when compared to transpedicular screw fixation. Transfacet fixation, however, is less invasive compared to transpedicular fixation and can be incorporated with the traditional ALIF procedure. Moreover, facet screw fixation affords 4-cortical purchase of the facet joints and can be used in obese patients, patients with hypertrophic iliac crests and those with unfavorable sacral angles.