Instrumenting the small thoracic pedicle: the role of intraoperative computed tomography image–guided surgery

Abstract

Object Traditionally, instrumentation of thoracic pedicles has been more difficult because of their relatively smaller size. Thoracic pedicles are at risk for violation during surgical instrumentation, as is commonly seen in patients with scoliosis and in women. The laterally based “in-out-in” approach, which technically results in a lateral breach, is sometimes used in small pedicles to decrease the comparative risk of a medial breach with neurological involvement. In this study the authors evaluated the role of CT image–guided surgery in navigating screws in small thoracic pedicles. Methods Thoracic (T1–12) pedicle screw placements using the O-arm imaging system (Medtronic Inc.) were evaluated for accuracy with preoperative and postoperative CT. “Small” pedicles were defined as those ≤ 3 mm in the narrowest diameter orthogonal to the long axis of the pedicle on a trajectory entering the vertebral body on preinstrumentation CT. A subset of “very small” pedicles (≤ 2 mm in the narrowest diameter, 13 pedicles) was also analyzed. Screw accuracy was categorized as good (< 1 mm of pedicle breach in any direction or in-out-in screws), fair (1–3 mm of breach), or poor (> 3 mm of breach). Results Twenty-one consecutive patients (age range 32–71 years) had large (45 screws) and small (52 screws) thoracic pedicles. The median pedicle diameter was 2.5 mm (range 0.9–3 mm) for small and 3.9 mm (3.1–6.7 mm) for large pedicles. Computed tomography–guided surgical navigation led to accurate screw placement in both small (good 100%, fair 0%, poor 0%) and large (good 96.6%, fair 0%, poor 3.4%) pedicles. Good screw placement in very small or small pedicles occurred with an in-out-in trajectory more often than in large pedicles (large 6.8% vs small 36.5%, p < 0.0005; vs very small 69.2%, p < 0.0001). There were no medial breaches even though 75 of the 97 screws were placed in postmenopausal women, traditionally at higher risk for osteoporosis. Conclusions Computed tomography–guided surgical navigation allows for safe, effective, and accurate instrumentation of small (≤ 3 mm) to very small (≤ 2 mm) thoracic pedicles.

Reliability of the Planned Pedicle Screw Trajectory versus the Actual Pedicle Screw Trajectory using Intra-operative 3D CT and Image Guidance

“…5,6 Examples of these techniques include the use of anatomic landmarks, 7 laminotomy for palpation of the pedicle, plain radiography, fluoroscopic imaging (standard or image guidance), 8,9 and CT image guidance. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Extensive literature has been published describing the technique, benefits, and drawbacks of each method, as well as comparisons between different approaches. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] With its increasing use has come a multitude of studies regarding the safety of this technique.…”

Clinical outcomes following spinal fusion using an intraoperative computed tomographic 3D imaging system

“…3 In contrast, freehand pedicle screw insertion (69%-94%) and fluoroscopic guidance insertion (28%-85%) were reported to be significantly less accurate, with several studies corroborating this observation. 2,[4][5][6][7]8,[12][13][14][15][16][17] Despite evidence suggesting greater accuracy associated with intraoperative CT navigation, no studies have investigated the clinical ramifications of greater accuracy. Identifying the long-term benefits of O-arm-assisted navigation is critical to determine the role of navigation in improving patient care.…”

Das intraoperative CT

“…Alle 52 Schrauben perforierten den Pedikel um nicht mehr als 1 mm im postoperativen CT. In keinem Fall war eine Perforation nach medial beobachtet worden [7].…”