Are we achieving what the algorithm tells us? Analysis of lumbar pedicle subtraction osteotomies with pre-bent rods.

Comparative study of pedicle screw trajectory in scoliosis surgery: freehand technique versus navigated angular guidance using the PYTHEAS Your Guided Trajectory.

Agreement Between Automated Pedicle Screw Planning and Surgeon-Selected Implant Dimensions in Thoracic and Lumbar Spine Surgery: A Three-Year Single-Center Study

Background: Automated pedicle screw planning (ASP) can initialize trajectories and implant dimensions, but correlation with implanted screws does not establish agreement. We quantified the association and agreement between ASP recommendations and actual intraoperative implant selection (AIS) and examined pathology, asymmetric planning, and available safety outcomes. Methods: This retrospective single-center study included 103 consecutive patients treated with thoracic or lumbar instrumentation from January 2021 to January 2024. The dataset contained 351 bilateral screw-pair records. Pearson and Spearman correlations, linear regression, and Bland–Altman analyses were supplemented by patient-clustered bootstrap 95% confidence intervals (CIs), pathology-stratified estimates, and a sensitivity analysis excluding a verified 94 mm iliac-fixation observation. Results: Diameter showed moderate correlation (Pearson’s r = 0.635, 95% CI 0.542–0.721; Spearman’s rho = 0.679, 95% CI 0.554–0.767; both p < 0.001). Length also showed moderate correlation (Pearson’s r = 0.675, 95% CI 0.565–0.754; Spearman’s rho = 0.600, 95% CI 0.450–0.714; both p < 0.001). For ASP minus AIS, the diameter bias was −0.75 mm (95% CI −0.86 to −0.64), with limits of agreement from −2.00 to 0.50 mm. The length bias was −0.15 mm (95% CI −1.05 to 0.79), with limits from −12.30 to 12.00 mm. The 94 mm value was verified as a genuine iliac-fixation observation; excluding it changed Pearson’s r only from 0.675 to 0.679. Asymmetric ASP length recommendations occurred in 115/351 pairs (32.8%), usually by 5 mm. Conclusions: ASP tracked overall implant-size trends but did not provide interchangeable estimates of surgeon-selected dimensions. Its systematic diameter underestimation and broad pair-level differences support its use as an initialization and review aid, with final sizing retained as a surgeon decision.

Accuracy and safety of individualized 3D-printed guides for L4 pedicle screw placement: An in vitro comparison with the free-hand technique.

Pedicle screw fixation is widely utilized for lumbar stabilization, but deviation from the planned pedicle corridor may result in cortical breach and neurovascular injury. Individualized 3D-printed guides may help transfer preoperative planning to screw insertion. However, their guiding performance and measurement reliability still require quantitative validation in controlled L4 models. This in vitro comparative study evaluated the accuracy, safety, and measurement reliability of guide-assisted L4 pedicle screw placement. Five L4 vertebrae were selected from a public spine CT dataset to design and print individualized guides and corresponding bone models. Bilateral screw placement was performed in both the guide-assisted and free-hand groups. Postoperative CT scans were registered to preoperative planning models to assess entry point deviation, 3D angular error, axial and sagittal plane angular errors, and Gertzbein-Robbins (GR) grading. Registration quality and the reliability of repeated measurements were also evaluated. The guide-assisted group showed lower positional and angular errors than the free-hand group across all quantitative metrics, and this pattern was consistent across the five paired specimens. A higher strict Grade A rate was observed in the guide-assisted group, although both groups achieved a 100% clinically acceptable rate (Grade A + B). These findings suggest that individualized 3D-printed guides may improve the reproduction of planned L4 pedicle screw trajectories in printed bone models. Because only five independent L4 specimens were included and PLA models cannot reproduce bone density or tactile feedback needed for free-hand placement, the between-group comparison should be interpreted as exploratory in vitro geometric evidence. The workflow provides a quantitative framework for the in vitro evaluation of guide-assisted screw placement.

Utilization of posterior column osteotomies with posterior spinal fusion for correction of Lenke type 5 adolescent idiopathic scoliosis: a systematic review.

How changes in segmental lordosis impact L1-pelvic-angle after adult spinal deformity surgery: Which lumbar levels matter most?

PURPOSE Achieving target L1-pelvic-angle (L1PA) is heavily influenced by segmental lordosis changes during adult spinal deformity (ASD) surgery. Understanding the effect of changing each lordotic segmental level on L1PA will aid in preoperative planning and intraoperative alignment assessment in ASD. In patients undergoing ASD surgery, we aimed to evaluate the impact of segmental lordosis changes on postoperative L1PA. METHODS A retrospective cohort study (2009-24) was performed for ASD surgery patients. Inclusion criteria were: ≥5-level fusion and sagittal/coronal deformity. Primary exposure variable was change in segmental lordosis at each lumbar level. Primary outcome was the change in L1PA. Multivariable regression controlling for preoperative and change in segmental lordosis at each level was performed. RESULTS Of 180 patients (mean age:59 ± 19 years, 32% males), mean preoperative/postoperative L1PA were 14 ± 11° and 12 ± 9°, respectively. L1/2: Mean change in lordosis was 7 ± 6°. For a 10° increase in L1/2 lordosis, the L1PA increased by 0.33° (β = -0.03, p = 0.684). L2/3: Mean change in lordosis was 8 ± 8°. For a 10° increase in L2/3 lordosis, the L1PA decreased by 0.01° (β = 0.00, p = 0.991). L3/4: Mean change in lordosis was 9 ± 8°. For a 10° increase in L3/4 lordosis, the L1PA decreased by 1.05° (β = 0.10, p = 0.086). L4/5: Mean change in lordosis was 9 ± 8°. For a 10° increase in L4/5 lordosis, the L1PA decreased by 1.78° (β = 0.18, p = 0.001). L5/S1: Mean change in lordosis was 11 ± 12°. For a 10° increase in L5/S1 lordosis, the L1PA decreased by 1.41° (β = 0.14, p = 0.002). CONCLUSION Changes in segmental lordosis at the L4/5 level were associated with greatest decrease in L1PA following ASD surgery, followed by L5/S1 and L3/4. Changes at L5/S1 influenced the L1PA slightly less than L4/5. These findings suggest that focusing on adding lordosis at the L4/5 and L5/S1 level will result in the greatest improvement in L1PA.

Minimally invasive surgery in adult spinal deformity: sagittal alignment correction potential and clinical outcomes. A systematic review of the literature.