Accuracy of free hand pedicle screw installation in the thoracic and lumbar spine by a young surgeon: an analysis of the first consecutive 306 screws using computed tomography

Abstract

Study design: A retrospective cross-sectional study.

Purpose: The purpose of this study is to evaluate the accuracy and safety of free-hand pedicle screw insertion performed by a young surgeon.

Overview of literature: Few articles exist regarding the safety of the free-hand technique without inspection by an experienced spine surgeon.

Methods: The index surgeon has performed spinal surgery for 2 years by himself. He performed fluoroscopy-assisted pedicle screw installation for his first year. Since then, he has used the free-hand technique. We retrospectively reviewed the records of all consecutive patients undergoing pedicle screw installation using the free-hand technique without fluoroscopy in the thoracic or lumbar spine by the index surgeon. Incidence and extent of cortical breach by misplaced pedicle screw was determined by a review of postoperative computed tomography (CT) images.

Results: A total of 36 patients received 306 free-hand placed pedicle screws in the thoracic or lumbar spine. A total of 12 screws (3.9%) were identified as breaching the pedicle in 9 patients. Upper thoracic spine was the most frequent location of screw breach (10.8%). Lateral breach (2.3%) was more frequent than any other direction. Screw breach on the right side (9 patients) was more common than that on the left side (3 patients) (p<0.01).

Conclusions: An analysis by CT scan shows that young spine surgeons who have trained under the supervision of an experienced surgeon can safely place free-hand pedicle screws with an acceptable breach rate through repetitive confirmatory steps.

Keywords: Accuracy; Lumbar: Free hand; Pedicle screw; Safety; Thoracic.

Fig. 1

Postoperative computed tomography images show the relationship between the pedicle and the screw. (A) Screws were placed inside the pedicle. (B) The right screw was placed 2 mm beyond the medial side of the pedicle. We defined this as a medial breach. (C) The right screw was inserted more than 2 mm lateral of the pedicle wall.

Fig. 2

A curved pedicle probe was initially navigated into the lateral side to a depth of 20 mm (the approximate depth of the pedicle) to diminish the likelihood of medial pedicle perforationⒶ. Then the probe was removed, and all four walls were examined by palpation with a ball tipped sound. A curved pedicle probe redirected the probe into the medial side to a depth of 40 mmⒷ.

Fig. 3

Confirmation of intraosseous screw placement using intraoperative anteroposterior (A) and lateral (B) radiographs. Screw heads were located with the harmonious position in the lumbar spine.

Fig. 4

Pie graph showing the incidence of pedicle screw installation by disease category.

Fig. 5

The number of pedicle screws at each level. Among 306 screws, 141 screws were placed in the thoracic spine and 165 screws in the lumbar spine. The lumbar spine was the most frequent site, followed by the upper thoracic (T3-5), and then the mid-lower thoracic spine.

Fig. 6

Screw breach on the right side occurred with nine screws. Three screws breached the pedicle on the left side. The breach rate of the upper thoracic (T3-5) and lumbar spine was 10.8% and 5.2%, respectively.