Safety of Pedicle Screws in Adolescent Idiopathic Scoliosis Surgery

Pedicle Morphology Analysis in Adolescents with Lenke Type 5 Idiopathic Scoliosis in Thai Population

Background  The surgical management of adolescent idiopathic scoliosis (AIS) often incorporates the utilization of pedicle screws, which are three-column construct devices. A comprehensive understanding of the pedicle morphology is essential for determining the appropriate pedicle screw diameter. While previous studies have examined pedicle morphology in Lenke type 1 AIS, there is a scarcity of information about the pedicle morphology in Lenke type 5 AIS, especially in the Thai population. Objective  The aim of this study is to analyze the morphology of the thoracolumbar pedicle, specifically the pedicle width and trajectory length on both the concave and convex sides within a sample of the Thai population diagnosed with Lenke type 5 AIS. Materials and Methods  In this study, we used computed tomography (CT) measurements to examine the thoracolumbar pedicle morphology in Lenke type 5 AIS patients in the Thai population. We also analyzed the pedicle width and trajectory length on both concave and convex sides in 112 AIS patients with Lenke type 5 curvature. Results  A total of 3,808 pedicles from 112 consecutive AIS patients of Lenke type 5 were enrolled in the study. It was observed that the transverse pedicle width was notably smaller on the concave side compared with the convex side in the apical region of the thoracolumbar spine (T12 to L2). Additionally, the pedicle width of T3 was also found to be significantly smaller on the concave side. Moreover, it was noted that the pedicle trajectory length is significantly longer on the concave side, indicating that the concave side in the apical region may have the capacity to accommodate a slightly longer pedicle screw at T3, T6, L2, L3, and L4. Conclusion  Our analysis of measurements indicates that the thoracolumbar pedicle morphology in Lenke type 5 AIS among the Thai population typically shows smaller widths and longer trajectory lengths on the concave side. This information enhances our understanding of the appropriate selection of pedicle screw diameter and length for treating Lenke type 5 AIS in the Thai population.

Pedicle screw fixation combined with posterior decompression and bone grafting for thoracolumbar spinal fractures can enhance curative effect and spinal cord function

OBJECTIVE

To explore the efficacy of pedicle screw fixation (PSF) combined with posterior decompression and bone grafting for thoracolumbar spinal fractures (TLSFs) and its influence on spinal cord function.

METHODS

In this retrospective study, 94 patients with TLSFs treated in the China-Japan Friendship Hospital rom June 2015 and September 2020 were selected, including 53 cases in the joint group treated with PSF combined with posterior decompression and bone grafting, and 41 cases in the control group with PSF alone. The two groups were compared in terms of operation time, intra-operational blood loss, length of hospital stay and wound healing as well as the pre- and post-treatment spinal cord function, and patients' clinical outcomes. Pre- and post-operatively, the pain severity was evaluated by the Visual Analogue Scale (VAS), the spinal dysfunction was assessed by Oswestry Disability Index (ODI), and the injured vertebral height and Cobb angles of the thoracolumbar spine (TLS) were compared. The clinical efficacy and postoperative complication rates of the two groups were observed and compared.

RESULTS

Less operative time, intraoperative bleeding, hospitalization time and wound healing time were determined in the joint group compared with the control group (all P<0.05). The postoperative sensory function and motor function were also better in the joint group (all P<0.05). Postoperatively, the joint group showed lower VAS and ODI scores than in the control group, with lower upper and lower TLS Cobb angles, and higher height of the anterior and posterior margins of the fractured vertebra (all P<0.05). The total effective rate was higher, and the incidence of postoperative complications was significantly lower in the joint group compared with the control group.

CONCLUSION

PSF combined with posterior decompression and bone grafting is effective in the treatment of TLSFs, which can not only significantly improve the spinal cord function and alleviate spinal dysfunction, but also help to relieve pain and reduce postoperative complications.

Three-dimensional morphological analysis of the thoracic pedicle and related radiographic factors in adolescent idiopathic scoliosis

Background

This study aimed to investigate the laterality of the pedicle morphology at the apical vertebra (AV) level and identify the radiographic factors associated with the laterality ratio of the pedicle morphology at the AV level in patients with adolescent idiopathic scoliosis (AIS).

Methods

Overall, 684 pedicles in 57 AIS patients aged 10–20 years, who underwent preoperative computed tomography (CT) and had Lenke type 1 or 2 with right convex main thoracic curves (MTC), were evaluated. Pedicle diameters of the MTC were assessed. We defined and compared the region containing two vertebrae adjacent to the AV (APEX±1) and the region containing two vertebrae adjacent to the neutral vertebra. We analyzed the pedicle diameter and laterality ratio of APEX±1 and performed multiple linear regression analysis to identify the radiographic factors associated with the laterality of the pedicle diameter.

Results

On the concave side of APEX±1, the pedicles of 15 patients (26.3%) did not accept a 4-mm-diameter pedicle screw (PS), even with 25% cortical bone width expansion. Laterality ratio differences in the pedicle diameters of the cortical bone width in APEX±1 were large in patients with more proximal AV level (p < 0.001) and smaller apical vertebral rotation (AVR) (p = 0.029).

Conclusions

Preoperative planning to accurately select and insert the PS in AIS should be based on the anatomical limitations in APEX±1, AV level, and AVR degree. In APEX±1, the correlation between AVR and the laterality ratio of the pedicle diameter may be useful for pathoetiological interpretation of the AIS deformity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05799-4.

Morphometric analysis of the proximal thoracic pedicles in Lenke II and IV adolescent idiopathic scoliosis: an evaluation of the feasibility for pedicle screw insertion

PURPOSE

Pedicles on the concave side of the proximal thoracic (PT) curve in adolescent idiopathic scoliosis (AIS) patients with Lenke II and IV deformities tend to be narrow and dysplastic, making pedicle screw (PS) insertion challenging. The aim of this study was to evaluate the feasibility for PS placement in these patients using pedicle chord length, diameter, and channel morphology.

METHODS

In this retrospective study, 56 consecutive AIS patients with Lenke II or IV curves who underwent instrumented posterior spinal fusion (PSF) were studied. The mean age at surgery was 14.8 years and the mean PT curve measured 45°. Two independent investigators evaluated all visible pedicles from T₁ to T₆ vertebral levels using axial images from intraoperative computed tomography-guided navigation recording the pedicle: (1) maximum transverse diameter 'd' at the isthmus, (2) maximum chord length 'l', and (3) qualitative assessment of the channel morphology (types A-D).

RESULTS

Two hundred and sixty-eight concave and 264 convex pedicles were measured. The mean 'd' of the concave pedicles at T₃ and T₄ was < 3.0 mm, compared to > 5.0 mm for the convex counterparts (p < 0.001). Of all concave pedicle channels, 48% had morphology characteristics that were riskier for PS cannulation (type C or D) compared to 2% of all convex pedicle channels (type A or B) (p < 0.001).

CONCLUSION

Almost half of all concave pedicles have morphologic characteristics that make them too small to accommodate a PS. Though PSs could be inserted using an in-out-in technique in these patients, alternative fixation anchors may improve strength and safety.

Understanding the Aorta-Spine Relation in Idiopathic Scoliosis: Value of Noncontrast CT-Derived Curved Coronal Reformats and 3D Volume Images

BACKGROUND

Investigating axial position and longitudinal bending of the aorta in relation to spine curvature in adolescent idiopathic scoliosis patients could help surgeons in planning of spine surgeries.

METHODS

Noncontrast computed tomography (CT) scans of 27 consecutive patients with adolescent idiopathic scoliosis (19 right and 8 left curves) and 16 control subjects were retrospectively reviewed. Using semiautomated software, centerline was drawn along the descending aorta, and curved reformat was generated. Aorta tortuosity index (TI) was calculated as (centerline length/straight line distance) - 1 × 100. The spine centerline was drawn from T1 to L5, and curve index (CI) was similarly calculated. The aorta centerline angle was measured. Apical vertebral-rotation angle and multilevel aorto-vertebral angles were measured on axial CT. Three-dimensional volume-rendered images of the aorta were generated using a manual region grow function.

RESULTS

Mean (± standard deviation) Cobb's angle was 63.8 ± 34.6°. The spine CI of patients (9.7 ± 7.11) was significantly higher than controls (0.28 ± 0.22), P = .00001. Aorta TI in scoliosis was significantly higher than controls (6.4 ± 7.2 versus 0.6 ± 0.5, P = .0001). The aorta centerline angle was steeper in scoliosis than controls (140 ± 26.8° versus 170 ± 3.6°). Correlations were excellent between the aorta TI and each of Cobb's angle, spine CI, and vertebral rotation angle (r = 0.851 to 0.867, all P < .001). Aorto-vertebral angles were significantly different between right scoliosis and left scoliosis patients and control groups at T6, T7, T8, L2, and L3 levels.

CONCLUSIONS

Aortic curvature increases in proportion to the degree of scoliosis. The aorta follows the concavity of scoliosis in right and left curves. In the axial CT plane, the aorta in both right and left scoliosis is maximally rotated away from its normal position at T7 and is closest to its normal position at T11 to T12.

CLINICAL RELEVANCE

Quantitative evaluation of aortic curvature combined with preoperative reconstructed CT images could be beneficial for surgeons in planning of spine surgeries.

COMPARATIVE STUDY OF THE TYPES OF FIXATION IN ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Objective: To conduct a comparative study of the results obtained in the treatment of adolescent idiopathic scoliosis (AIS) with different types of fixations (traditional, selective and multiple), and to evaluate the correction of angular deformity in the frontal plane by the Cobb and sacral clavicular angle (SCA) methods. Methods: A study of a group of 278 patients with AIS who underwent selective, traditional, and multiple fixation surgeries. Results: Significant corrections of both the Cobb angle and the SCA were observed. Conclusions: In the multiple fixation surgeries there was a 100% correction between the preoperative and postoperative SCA values and a 50% correction in the traditional and selective fixations, a difference considered significant. Regarding the Cobb angle, the three fixations presented corrections between preop and postop with significant differences. Level of evidence III; Retrospective Study.

The Nottingham radiation protocol for O-arm navigation in paediatric deformity patients: a feasibility study

BACKGROUND

O-arm assisted pedicle screw placement has been proven to be more accurate than free-hand technique. Radiation exposure remains the primary drawback. We determined the feasibility and safety of a reduced radiation protocol in paediatric patients undergoing scoliosis correction.

METHODS

A reduced radiation protocol for a medtronic O-arm navigational system was devised. 3D CT reconstructions of an anthropomorphic pelvic phantom indicated adequate image quality after reduction to 14% of current manufacturer default factors. A feasibility study to test the image quality was undertaken on four patients, one with syndromic and three with idiopathic scoliosis each receiving progressively reducing radiation exposure of 60%, 50%, 40% and 14% of what would have been delivered using the manufacturer default protocol. This represented 32% of the mayo clinic protocol. It was achieved by reducing the x-ray tube current to 10 mA while keeping the tube potential at 90 kVp.

RESULTS

A low dose O-arm protocol was able to generate adequate image quality while delivering as little as 14% (for lumbar region reconstructions) of the recommended protocol radiation dose. The total radiation dose delivered with this protocol was approximately 0.8 milliSieverts for a single spin. This effective dose represents < 1/3 of average UK and < 1/6 average US annual radiation exposure. There were no neurological or implant-related complications.

CONCLUSIONS

Our low dose O-arm radiation protocol significantly reduces the radiation exposure compared to the manufacturer recommended Mayo clinic protocol providing operational image quality to allow accurate screw placement in spinal deformity.

Increasing loads and diminishing returns: a biomechanical study of direct vertebral rotation

STUDY DESIGN

Biomechanical simulation of DVR and pure-moment testing on thoracic spines.

OBJECTIVES

Characterize load-deformation response of thoracic spines under DVR maneuvers until failure, and compare to pure-moment testing of same spines. Despite reports of surgical complications, few studies exist on increase in ROM under DVR torque. Biomechanical models predicting increases from surgical releases have consistently used "pure-moments", a standard established for non-destructive measurement of ROM. Yet, DVR torque is not accurately modeled using pure moments and, moreover, magnitudes of torque applied during DVR maneuvers may be substantially higher than pure-moment testing.

METHODS

Cadaveric thoracic spines (N = 11) were imaged, then prepared. Polyaxial pedicle screws were implanted at T7-T10 after surgical releases. Bilateral facetectomies and Ponte osteotomies were completed at T10-T11. A custom apparatus, mounted into an 8-dof MTS load frame, was used to attach to pedicle screws, allowing simulation of surgical DVR maneuvers. Motions of vertebrae were measured using optical motion tracking. Torque was increased until rupture of the T10-T11 disc or fracture at the pedicle screw sites at any level. The torque-rotation behavior was compared to its behavior under pure-moment testing performed prior to the DVR maneuver.

RESULTS

Under DVR maneuvers, failure of the T10-T11 discs accompanied in most cases by pedicle screw loosening, occurred at 13.7-54.7 Nm torque, increasing axial rotation by 1.4°-8.9°. In contrast, pure-moment testing (4 Nm) increased axial rotation by only 0.0°-0.9°.

CONCLUSIONS

DVR resulted in substantially greater correction potential increases compared to pure-moment testing even at the same torque. These results suggest increased flexibility obtained by osteotomies and facetectomies is underestimated using pure-moment testing, misrepresenting clinical expectations. The present study is an important and necessary step toward the establishment of a more accurate and ultimately surgically applied model.

LEVEL OF EVIDENCE

III.

Conventional versus stereotactic image guided pedicle screw placement during spinal deformity correction: a retrospective propensity score-matched study of a national longitudinal database

PURPOSE/AIM

To compare complications, readmissions, revisions, and payments between navigated and conventional pedicle screw fixation for treatment of spine deformity.

METHODS

The Thomson Reuters MarketScan national longitudinal database was used to identify patients undergoing osteotomy, posterior instrumentation, and fusion for treatment of spinal deformity with or without image-guided navigation between 2007-2016. Conventional and navigated groups were propensity-matched (1:1) to normalize differences between demographics, comorbidities, and surgical characteristics. Clinical outcomes and charges were compared between matched groups using bivariate analyses.

RESULTS

A total of 4,604 patients were identified as having undergone deformity correction, of which 286 (6.2%) were navigated. Propensity-matching resulted in a total of 572 well-matched patients for subsequent analyses, of which half were navigated. Rate of mechanical instrumentation-related complications was found to be significantly lower for navigated procedures (p = 0.0371). Navigation was also associated with lower rates of 90-day unplanned readmissions (p = 0.0295), as well as 30- and 90-day postoperative revisions (30-day: p = 0.0304, 90-day: p = 0.0059). Hospital, physician, and total payments favored the conventional group for initial admission (p = 0.0481, 0.0001, 0.0019, respectively); however, when taking into account costs of readmissions, hospital payments became insignificantly different between the two groups.

CONCLUSIONS

Procedures involving image-guided navigation resulted in decreased instrumentation-related complications, unplanned readmissions, and postoperative revisions, highlighting its potential utility for the treatment of spine deformity. Future advances in navigation technologies and methodologies can continue to improve clinical outcomes, decrease costs, and facilitate widespread adoption of navigation for deformity correction.