• Oliver Tannous, Ehsan Jazini, Tristan B Weir, Kelley E Banagan, Eugene Y Koh, Greg Anderson D D, Daniel E Gelb, and Steven C Ludwig.
• *Department of Orthopaedics, University of Maryland, Baltimore, MD †Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA.
• Spine. 2017 Aug 1; 42 (15): 1189-1194.

Study DesignA comparative study of facet joint violation (FJV) using two percutaneous surgical techniques.ObjectiveTo compare the rate of iatrogenic FJV and medial pedicle wall breach between two methods of percutaneous pedicle screw instrumentation in the thoracic and lumbar spine.Summary Of Background DataVariable iatrogenic damage to the facet joints has been reported to occur with percutaneous pedicle screw techniques, compared with the open approach, which has been associated with adjacent segment disease. Technical variations of percutaneous pedicle screw placement may pose different risks to the facet joint.MethodsAttending spine surgeons percutaneously placed pedicle screws in seven human cadaveric spines from T2 to L5. At each level, screws were instrumented on one side using the 9 or 3 o'clock reference point of the pedicle on the posteroanterior view with a lateral-to-medial trajectory (LMT) and on the contralateral side using the center of the pedicle with an owl's eye trajectory (OET). Postoperative screw placement was assessed with computed tomography and then open cadaveric dissection. Outcome measures included FJV and medial pedicle wall breach.ResultsOverall, 17 of 105 screws placed with an LMT versus 49 of 105 screws placed with an OET violated or abutted the facet joint (P <0.0001). This significant difference was observed at the thoracic (T2-T10), thoracolumbar (T11-L1), and lumbar (L2-L5) levels (P = 0.003, 0.035, and 0.018, respectively). Medial pedicle wall breach occurred with 11 LMT screws and seven OET screws (P = 0.077), and no breach was considered critical.ConclusionA significantly higher FJV rate was observed using the OET versus the LMT in the thoracic, thoracolumbar, and lumbar spine. No statistically significant differences in medial pedicle wall breach occurred between the techniques. Thus, the LMT of minimally invasive pedicle screw fixation may reduce iatrogenic damage to the facet joints.Level Of Evidence3.

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