Author(s)

Michio Hongo^1*, Yuji Kasukawa¹, Akiko Misawa², Daisuke Kudo¹, Ryota Kimura¹, Naohisa Miyakoshi¹

¹Department of Orthopedic Surgery, Akita University Graduate School of Medicine, Akita, Japan.
²Department of Orthopedic Surgery, Akita Prefectural Center on Development and Disability, Akita, Japan.

Background: Insertion of the pedicle screws (PS) into the proximal thoracic spine is occasionally challenging owing to the small size of the pedicles and the proximity to the spinal cord. An appropriate anchor placement method for the concave side of the proximal thoracic curve has not been established yet. This study aimed to evaluate the pedicle size and position of PS on the concave side of the proximal thoracic curve in patients with adolescent idiopathic scoliosis (AIS). Methods: Forty consecutive patients with AIS who underwent correction and fusion with all PS constructs, including the proximal thoracic curve in the fusion area, were included. After identifying the screws inserted on the concave side of the proximal thoracic curve, the pre-operative morphology and postoperative position of the inserted PS, including the end vertebrae, were analyzed using computed tomography (CT). Screw perforations were categorized into four grades depending on the degree of perforation from the pedicle wall on postoperative CT and were classified using an outcome-based classification. Results: A total of 109 screws were inserted on the concave side of the proximal thoracic curve. The average width of all pedicles was 3.5 ± 1.1 mm. The width of 90 pedicles (83%) was <4.5 mm. Based on categorization by the degree of perforation, there were only 17 screws with Grade 0 (no perforation). Perforation was found in 92 pedicles (84%), including Grade 1 in 76 screws, Grade 2 in nine screws, and Grade 3 in seven screws. In the outcome-based classification, 101 screws (93%) were classified as Type I (acceptable) and eight screws as Type II (unacceptable). None of the screws were classified as Type III (grievous). Conclusion: Perforations were found in 84% of the PS on the concave side of the proximal thoracic curve; however, 93% of the PS were considered acceptable in the outcome-based classification. Thus, we conclude that the in-out-in technique may be both feasible and effective.

Pedicle Screw, Proximal Thoracic Curve, Adolescent Idiopathic Scoliosis

Hongo, M. , Kasukawa, Y. , Misawa, A. , Kudo, D. , Kimura, R. and Miyakoshi, N. (2022) Pedicle Screw Insertion for Concave Side of Proximal Thoracic Curve in Adolescent Idiopathic Scoliosis. Open Journal of Orthopedics, 12, 327-334. doi: 10.4236/ojo.2022.127031.