Methods: Twenty-four patients with AIS (Cobb >65°) underwent surgery at a single center between January 2014 and December 2021. The first 10 patients underwent surgery using only IOT (T group), whereas the subsequent 14 patients underwent surgery with a combination of IOT and PO (TP group). Results: The mean preoperative Cobb angles in the T and TP groups were 89.35°±6.05° and 92.32°±9.28°, respectively (p=0.59). The mean flexibility index (FI) of the T and TP groups were 0.31±0.016 and 0.36±0.03, respectively (p=0.41). The mean postoperative Cobb angle in the T and TP groups were 40.25°±5.95° and 19.1°±3.20°, respectively (p=0.041). Apical vertebral rotation improved from mean grade 3.2 (2–4) to grade 2.6 (1–3) in the T group and from mean grade 3.6 (2–4) to mean grade 1.8 (1–3) in the TP group. Postoperatively, the mean thoracic kyphosis was 13.84°±2.10° and 21.02°±1.68° in T and TP groups (p=0.044). Transient signal-loss intraoperatively was noted in two patients, one in each group. No episodes of postoperative neurological deficits were reported. No incidences of pseudarthrosis/implant-related complications were reported at the end of 2 years in either group. Conclusions IOT and PO complement one another and can be safely combined without an attributable risk of neurological injury.

Methods: Twenty-four patients with AIS (Cobb >65°) underwent surgery at a single center between January 2014 and December 2021. The first 10 patients underwent surgery using only IOT (T group), whereas the subsequent 14 patients underwent surgery with a combination of IOT and PO (TP group). Results: The mean preoperative Cobb angles in the T and TP groups were 89.35°±6.05° and 92.32°±9.28°, respectively (p=0.59). The mean flexibility index (FI) of the T and TP groups were 0.31±0.016 and 0.36±0.03, respectively (p=0.41). The mean postoperative Cobb angle in the T and TP groups were 40.25°±5.95° and 19.1°±3.20°, respectively (p=0.041). Apical vertebral rotation improved from mean grade 3.2 (2–4) to grade 2.6 (1–3) in the T group and from mean grade 3.6 (2–4) to mean grade 1.8 (1–3) in the TP group. Postoperatively, the mean thoracic kyphosis was 13.84°±2.10° and 21.02°±1.68° in T and TP groups (p=0.044). Transient signal-loss intraoperatively was noted in two patients, one in each group. No episodes of postoperative neurological deficits were reported. No incidences of pseudarthrosis/implant-related complications were reported at the end of 2 years in either group. Conclusions IOT and PO complement one another and can be safely combined without an attributable risk of neurological injury.

Methods: Twenty-four patients with AIS (Cobb >65°) underwent surgery at a single center between January 2014 and December 2021. The first 10 patients underwent surgery using only IOT (T group), whereas the subsequent 14 patients underwent surgery with a combination of IOT and PO (TP group). Results: The mean preoperative Cobb angles in the T and TP groups were 89.35°±6.05° and 92.32°±9.28°, respectively (p=0.59). The mean flexibility index (FI) of the T and TP groups were 0.31±0.016 and 0.36±0.03, respectively (p=0.41). The mean postoperative Cobb angle in the T and TP groups were 40.25°±5.95° and 19.1°±3.20°, respectively (p=0.041). Apical vertebral rotation improved from mean grade 3.2 (2–4) to grade 2.6 (1–3) in the T group and from mean grade 3.6 (2–4) to mean grade 1.8 (1–3) in the TP group. Postoperatively, the mean thoracic kyphosis was 13.84°±2.10° and 21.02°±1.68° in T and TP groups (p=0.044). Transient signal-loss intraoperatively was noted in two patients, one in each group. No episodes of postoperative neurological deficits were reported. No incidences of pseudarthrosis/implant-related complications were reported at the end of 2 years in either group. Conclusions IOT and PO complement one another and can be safely combined without an attributable risk of neurological injury.

Methods: Four FE models of multilevel posterior cervical fixation were created and tested by FEA in various permutations and combinations. Generic differences in fixation were determined, and the following parameters were assessed: (1) maximum moment at failure, (2) maximum angulation at failure, (3) maximum stress at failure, (4) point of failure, (5) intervertebral disc stress, and (6) influence of adding a C2 pars screw to the multilevel construct. Results: The maximum moment at failure was higher in the LMS fixation group than in the TPS group. The maximum angulation in flexion allowed by LMS was higher than that by TPS. The maximum strain at failure was higher in the LMS group than in the TPS group. The maximum stress endured before failure was higher in the TPS group than in the LMS group. Intervertebral stress levels at C6–C7 and C7–T1 intervertebral discs were higher in the LMS group than in the TPS group. For both models where C2 fixation was performed, lower von Mises stress was recorded at the C2–C3 intervertebral disc level. Conclusions Ending a multilevel posterior cervical fixation construct with TPS fixation rather than LMS fixation at the C7 vertebra provides a stiff and more constrained construct system, with higher stress endurance to compressive force. The constraint and durability of the construct can be further enhanced by adding a C2 pars screw in the fixation system.