Contribution of Dynamic Surgical Guidance to the Accurate Placement of Pedicle Screws in Deformity Surgery: A Retrospective Case Series

Abstract

We assessed the contribution of a dynamic surgical guidance (DSG) probe in the accurate placement of thoracic and lumbar pedicle screws (PSs) in patients with spinal deformity. A retrospective review was performed of 98 patients (104 procedures) with various spinal deformities, who had received posterior instrumentation with PSs inserted using either DSG or the conventional free-hand (FH) technique. A total of 882 PSs were inserted using DSG (DSG group) and 603 using the FH technique (FH group). The DSG probe was preferably chosen for large osteosyntheses and severe deformities. Two neurosurgeons, unaware of the surgical groups, reviewed all the intraoperative computed tomography scans and assessed all the PS placements. Of the PSs used, 95.4% in the DSG group and 92.2% in the FH group were correctly placed (P= 0.0136). The difference in screw placement accuracy was greater at the thoracic level (DSG group, 92.5%; vs. FH group, 87.0%; P= 0.0310) than at the lumbar level (DSG group, 98.0%; vs. FH group, 95.4%; P= 0.0385). Severe (>4 mm) lateral breaches occurred in 24 cases (4.0%) in the FH group but in only 5 (0.6%) in the DSG group (P < 0.0001). No severe medial breach was observed in either group. Despite having more patients with severe deformities in the DSG group, PS insertion was significantly more accurate with DSG. This technique also reduced the severe unacceptable lateral misplacement rate (>4 mm) and, consequently, the incidence of intraoperative screw revisions even in patients with severe deformities.