Pedicle Screw Constructs Research Articles

Comparative study of low-density versus high-density pedicular screw implantations in management of adolescent idiopathic scoliosis: a randomized clinical trial

BackgroundA number of studies have yielded disparate findings regarding the relationship between implant density and curve correction in adolescent idiopathic scoliosis (AIS) surgery. This study compared the efficacy and safety of low-density (LD) versus high-density (HD) pedicular screw implants in the correction of deformity in AIS regarding clinical, radiological, and quality of life outcomes. MethodsThis study was a single-blind, parallel, randomized trial that enrolled 20 adolescent patients with idiopathic scoliosis scheduled for posterior spinal fusion surgery with all pedicle screw constructs. Patients were randomized into two groups of 10 patients each. The LD group included patients in whom the number of screws per fused spinal level had a density of 1.5 or less, while the HD group had a density greater than 1.5. The primary outcomes were the radiological findings of curve correction. The secondary outcomes included the correlation between implant density and curve correction, the amount of blood loss, operation time, number of screws, fusion level, hospital stay duration, and quality of life assessed by the Scoliosis Research Society 22r questionnaire. ResultsRadiologically, the postoperative main curves Cobb angles and their changes were comparable between both approaches without statistical correlation with the implant density (p˃0.05). The LD approach significantly shortened the operative time (p=0.015), number of screws (p=0.011), implant density (p<0.001), and hospital stay (p<0.001). However, quality of life scores before surgery and at final follow-up did not differ between the two techniques (p˃0.05). ConclusionsThe use of a low-density approach is an effective and safe methodology for attaining satisfactory deformity correction in AIS patients. Furthermore, this approach confers the additional advantage of reduced operative time, number of screws, implant density, and hospital stay in comparison to the high-density approach.Trial registration Pan African Clinical Trial Registry, PACTR202404611444119. Registered 28 March 2024-Retrospectively registered, https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=29382

Outcome of the surgical treatment of adolescent idiopathic scoliosis using the Scoliosis Research Society outcome questionnaire

Background Adolescent idiopathic scoliosis (AIS) is a structural deformity of the spine. Posterior deformity correction represents the gold standard of the surgical treatment of AIS. The fixation technique was shifted from hybrid fixation to the all pedicle screw construct, which could produce superior deformity correction. Patient-oriented outcome questionnaires have become an important measure of the success of surgical correction. This study was conducted to assess the outcome of all pedicle screw constructs in treating AIS using the Scoliosis Research Society (SRS)-24 outcome questionnaire. Patients and methods Seventy-nine AIS patients were included with a minimum 2-year follow-up. Clinical and radiographic measurements were evaluated at preoperative, postoperative, and final follow-up periods. Complications and results of the SRS-24 questionnaire were analyzed. Sex, Lenke classification, levels of the lowest instrumented vertebra, curve magnitude, and percentage of curve correction were correlated with the SRS-24 questionnaire results. Results There were 59 females and 20 males. The mean age of the patients was 14.2 ± 2.5 years. According to Lenke classification, the majority of the curves were type 1 (57 patients), followed by type 5 (11 patients), type 2 (six patients), type 3 (three patients), type 6 (two patients), and no type 4. The mean preoperative major curve Cobb angle was 59.3 ± 9.045° and the mean postoperative Cobb angle was 5.82 ± 5.932°. The average score for SRS-24 was 4.17. The mean preoperative pain score was 3.29, which improved to 4.30 after at least 2 years of follow-up (P˂0.005). Statistically significant improvement was seen in the general self-image, function from back condition, and level of activity. After surgery, the mean score for self-image was 4.19, and for function was 3.55. The postoperative function was the lowest, while the postoperative satisfaction score was the best of all domains, with a mean score of 4.55. About 90% of patients were satisfied with the results of their surgical correction. Magnitude of curve and amount of correction did not significantly alter the SRS scores. Conclusion All pedicle screw construct is an efficient and safe method in AIS correction. The surgical treatment in our AIS patients has resulted in a perceived benefit in all domains of SRS-24 questionnaire.

Abstract 2396: Tumor treating fields (TTFields) for spinal metastasis: Clinical trial concept for use of conductive implants as waveguides to enhance TTFields strength

Abstract Tumor treating fields (TTFields) is a FDA-approved electric fields-based therapy for glioblastoma (GBM) and malignant pleural mesothelioma. We describe a novel approach to increase the strength and therapeutic effect of TTFields at vertebral tumor targets, using spinal implants as electrically-conductive waveguides. In vivo anti-cancer efficacy is achieved with TTFields strength &amp;gt;1 V/cm. If the tumor is surrounded by tissues of lower conductivity (e.g., the skull in the case of GBM), then the TTFields strength reaching the tumor is decreased. Surgical treatment of radiation-refractory spinal metastases is difficult and provides a short-term benefit at the expense of a lengthy recovery. Such resections require bone removal that disrupts the spinal stability, necessitating reconstruction with titanium (Ti) pedicle screw constructs that are electrically conductive. We theorize that astute placement of Ti hardware in the proximate spinal levels post-resection would have a waveguiding effect of electrical current from the surrounding muscle towards the tumor. This would in turn boost TTFields strength achieved around the resection cavity, decreasing the chances of tumor recurrence. Bomzon et al. described a computational model of the distribution of TTFields in a realistic human torso. The simulation demonstrated that a TTFields strength of 3 V/cm can be achieved, which is approximately 3-fold greater than what is achieved in the brain parenchyma in the context of TTFields for GBM. In a more generic simulation using a 0.5 × 100 mm waveguide targeting a tumor deeper in the torso (480 mA), we found 21.8 vs. 61.2 cm3 volumes achieving ≥ the 1.0 V/cm efficacy floor, without and with the waveguide, respectively, a 2.8-fold increase. At a higher amplitude (550 mA) and stronger TTFields strength threshold of ≥1.5 V/cm, a negligible volume was attained with no waveguide (0.1 cm3), whereas a volume of 17.6 cm3 was attained around the tip of the waveguide when present. Based on compelling pre-clinical data, a prospective clinical trial is being designed in which patients with radiation-refractory spinal metastasis from any number of primary sites will undergo resection. Next, primary cultures of their tumor cells will be made and evaluated for the TTFields frequency that maximizes cell death on a per-patient basis. Patients will then undergo postoperative local TTFields therapy ± systemic therapy. The primary endpoint will be safety and efficacy of such an approach, with future aims focusing on local control rates. The application of TTFields as an adjunct to surgery may offer a new therapeutic option for patients with spinal metastasis who would otherwise not be considered surgical candidates. Similarly, waveguides may be used throughout the head and body to increase TTFields efficacy. Citation Format: Claudio E. Tatsui, Kristen W. Carlson, Chirag B. Patel. Tumor treating fields (TTFields) for spinal metastasis: Clinical trial concept for use of conductive implants as waveguides to enhance TTFields strength [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2396.

Establishing finite element model credibility of a pedicle screw system under compression-bending: An end-to-end example of the ASME V&V 40 standard

Computational modeling and simulation (CM&S) is a key tool in medical device design, development, and regulatory approval. For example, finite element analysis (FEA) is widely used to understand the mechanical integrity and durability of orthopaedic implants. The ASME V&V 40 standard and supporting FDA guidance provide a framework for establishing model credibility, enabling deeper reliance on CM&S throughout the total product lifecycle. Examples of how to apply the principles outlined in the ASME V&V 40 standard are important to facilitating greater adoption by the medical device community, but few published examples are available that demonstrate best practices. Therefore, this paper outlines an end-to-end (E2E) example of the ASME V&V 40 standard applied to an orthopaedic implant. The objective of this study was to illustrate how to establish the credibility of a computational model intended for use as part of regulatory evaluation. In particular, this study focused on whether a design change to a spinal pedicle screw construct (specifically, the addition of a cannulation to an existing non-cannulated pedicle screw) would compromise the rod-screw construct mechanical performance. This question of interest (?OI) was addressed by establishing model credibility requirements according to the ASME V&V 40 standard. Experimental testing to support model validation was performed using spinal rods and non-cannulated pedicle screw constructs made with medical grade titanium (Ti-6Al-4V ELI). FEA replicating the experimental tests was performed by three independent modelers and validated through comparisons of common mechanical properties such as stiffness and yield force. The validated model was then used to simulate F1717 compression-bending testing on the new cannulated pedicle screw design to answer the ?OI, without performing any additional experimental testing. This E2E example provides a realistic scenario for the application of the ASME V&V 40 standard to orthopedic medical device applications.

Effectiveness of Facetectomy in Correction of Adolescent Idiopathic Scoliosis.

Surgical correction of adolescent idiopathic scoliosis (AIS) using the facetectomy technique with the utilization of segmental pedicle screws aims to achieve correction of coronal and sagittal imbalances and preserve normal neurological function. In this study, we aimed to certify the effectiveness of the facetectomy technique in the correction of AIS by analyzing technique outcomes. This is a retrospective, single-center study. From January 2018 to March 2022, a total of 51 patients with AIS who underwent inferior facetectomy with segmental pedicle screw constructs at the Royal Rehabilitation Center were reviewed. Radiological parameters including the major curve Cobb angle, and global coronal balance were evaluated preoperatively, postoperatively, and at the final follow-up. Surgical parameters and complications were also reported. The mean major curve Cobb angle was 59.5 ± 4.9° preoperatively, 13.6 ± 2.7° postoperatively, and 14.5 ± 2.6° at the final follow-up, with correction rates of 77.2% and 75.7%, respectively. The mean global coronal balance was 2.7 ± 1.1 cm preoperatively, 1.7 ± 0.73 cm postoperatively, and 1.4 ± 0.55 cm at the final follow-up. Two cases of pleural injuries were reported intraoperatively. Postoperatively, two cases experienced superficial wound infections, one experienced pulmonary embolism, and one patient had revision surgery due to the loosening of a single screw. None of these complications lasted long. When combined with posterior segmental pedicle screw constructs, inferior facetectomy can provide an effective rate of correction in a reasonably safe manner.

The potential of proximal junctional kyphosis prevention using a novel tether pedicle screw construct: an in silico study comparing the influence of standard and dynamic techniques on adjacent-level range of motion and load pattern.

A tether pedicle screw (TPS) enables individual stepless pretensioning and is placed at one or two levels above the upper instrumented vertebra (UIV+1 and UIV+2, respectively). This study aimed to evaluate a novel customized TPS for the prevention of proximal junctional kyphosis (PJK) and to investigate the potential to generate a smoother force transition from cranial to long fusion during trunk flexion, instead of an abrupt change at the UIV, following adult spinal deformity surgery. A finite element model was designed based on an adult patient with spinal deformity instrumented from T10 to S1. Five different sagittal balance types and implant configurations were tested. The proximal range of motion (ROM) and intervertebral stress were examined, with a special focus on their respective discontinuities. Tension shielding at UIV/UIV+1 by the TPS was consistent irrespective of sagittal profiles. The use of TPSs at UIV+1 and UIV+2 increased the efficacy in reducing spinal ROM discontinuity at UIV/UIV+1, as compared with the use of TPSs at UIV+1 only. Through the use of two pairs of TPSs cranial to the UIV, the optimal tension configuration could be defined to avoid a reduction effect at UIV+1. Neither the addition of transition rods to the TPSs nor the use of transition rods in combination with standard pedicle screws improved the junctional mechanics when compared with TPSs at UIV+1/UIV+2. A smoother motion discontinuity at the UIV can be achieved via implementation of a TPS strategy. This new technology shows favorable in silico mechanics for reducing the risk of PJK.

FUSIONLESS ALL PEDICLE SCREWS POSTERIOR DEFORMITY CORRECTION IN AIS IMMATURE PATIENTS PERMITS RESTORATION OF THE NORMAL VERTEBRAL MORPHOLOGY AND REMOVAL OF THE INSTRUMENTATION ONCE BONE MATURITY IS REACHED

The aim of this study was to report the restauration of the normal vertebral morphology and the absence of curve progression after removal the instrumentation in AIS patients that underwent posterior correction of the deformity by common all screws construct whitout fusion. A series of 36 AIS immature patients (Risser 3 or less) were include in the study. Instrumentation was removed once the maturity stage was complete (Risser 5). Curve correction was assessed at pre and postoperative, before instrumentation removal, just post removal, and more than two years after instrumentation removal. Epiphyseal vertebral growth modulation was assessed by a coronal wedging ratio (WR) at the apical level of the main curve (MC). The mean preoperative coronal Cobb was corrected from 53.7°±7.5 to 5.5º±7.5º (89.7%) at the immediate postop. After implants removal (31.0±5.8 months) the MC was 13.1º. T5–T12 kyphosis showed a significant improvement from 19.0º before curve correction to 27.1º after implants removal (p&lt;0.05). Before surgery, WR was 0.71±0.06, and after removal WR was 0.98±0.08 (p&lt;0.001). At the end of follow-up, the mean sagittal range of motion (ROM) of the T12-S1 segment was 51.2±21.0º. SRS-22 scores improved from 3.31±0.25 preoperatively to 3.68±0.25 at final assessment (p&lt;0.001). In conclusion, fusionless posterior approach using a common all pedicle screws construct correct satisfactory scoliotic main curves and permits removal of the instrumentation once the bone maturity is reached. The final correction was highly satisfactory and an acceptable ROM of the previously lower instrumented segments was observed.

Does hybrid instrumentation using sublaminar bands give comparable results to all pedicle screw constructs in surgical correction of adolescent idiopathic scoliosis? a systematic review and meta-analysis of current evidence.

Does hybrid instrumentation using sublaminar bands give comparable results to all pedicle screw constructs in surgical correction of adolescent idiopathic scoliosis? a systematic review and meta-analysis of current evidence.

Quantification of MRI Artifacts in Carbon Fiber Reinforced Polyetheretherketone Thoracolumbar Pedicle Screw Constructs prior to Spinal Stereotactic Radiosurgery

Carbon fiber reinforced polyetheretherketone (CFRP) is a nonmetallic material that is a subject of growing interest in the field of spinal instrumentation manufacturing. The radiolucency and low magnetic susceptibility of CFRP has potential to create less interference with diagnostic imaging compared with titanium implants. However, an objective comparison of the image artifact produced by titanium and CFRP implants has not been described. Spinal oncology, particularly after resection of spinal tumors and at the time of spinal stereotactic radiosurgery planning, relies heavily on imaging interpretation for evaluating resection, adjuvant treatment planning, and surveillance. We present a study comparing measurements of postoperative magnetic resonance imaging artifacts between titanium and CFRP pedicle screw constructs in the setting of separation surgery for metastatic disease. The diameter of the signal drop around the screws (pedicle screw artifact) and the diameter of the spinal canal free from artifacts (canal visualization) were measured in consecutive patients who had spinal instrumentation followed by spinal stereotactic radiosurgery in the June 2019 to May 2022 timeframe. The spinal cord presented a shift at the screw level in sagittal images which was also measured (Sagittal Distortion, SagD). Fifty patients, corresponding to 356 screws and 183 vertebral levels, were evaluated overall. CFRP produced less artifacts in all the 3 parameters compared with titanium: mean pedicle screw artifact (CFRP = 5.8 mm, Ti = 13.2 mm), canal visualization (CFRP = 19.2 mm, Ti = 15.5 mm), and SagD (CFRP = .5 mm, Ti = 1.9 mm), all P < .001. In practice, these findings translate into better-quality magnetic resonance imaging. The initial perceived advantages are easier evaluation of postoperative imaging, facilitating radiation treatment planning, recurrence detection, and avoidance in repeating a suboptimal computed tomography myelogram. Further clinical studies analyzing long-term outcomes of patients treated with CFRP implants are necessary.

The surgical management of scheurmann’s kyphosis: Efficacy and safety of a low density posterior pedicle screw construct

Background: To see if employing a low pedicle screw density in the posterior therapy of Scheuermann kyphosis is safe, radiologically effective, and clinically effective. Methods: Patients with Scheuermann kyphosis underwent posterior surgical correction between 2016 and 2019. Low Screw Density, peri apical Ponte osteotomies and cantilever correction maneuver were our surgical technique for deformity correction. Two observers performed a radiological evaluation of the before and postoperative Spinopelvic parameters. Validated Arabic version of Scoliosis Research Society 22 questionnaire were used to assess the preoperative and postoperative clinical results. Cost saving analysis was performed. Results: This study enlisted the participation of thirty patients. The patients mean age 21.8 ±3.4 years and mean follow up 34.8±7.9 months. The mean surgical time was 165.33 ±17.9 minutes , the mean number of osteotomies was 4.2± 0.8 , and the mean blood loss was 770± 139.3cc.The mean preoperative dorsal kyphosis 87.5°±4.6 °and the mean postoperative dorsal kyphosis 43.1°± 3.7° at final follow up (P&lt;0.001).The mean preoperative scoliosis research society 22 questionnaire 2.8±0.4 and the mean postoperative scoliosis research society 22 questionnaire 4.3±0.8 at final follow up (P&lt;0.001). Conclusions: Posterior Surgical Intervention with low Screw Density construct and periapical Ponte osteotomies is safe , radiologically , clinically and cost effective way in surgical management of Scheuermann kyphosis. Study Design: Prospective Cohort Study. Level of Evidence: Level IV.

Radiographical Results of Adolescent Idiopathic Scoliosis with Major Curve at Proximal Thoracic Spine.

Adolescent idiopathic scoliosis (AIS) with a major curve at the main thoracic (MT) area is classified as Lenke type 1, 2, or 3 depending on the flexibility of the proximal thoracic (PT) curve and lumbar curve. No definite classification has been established for a major curve at the PT spine. The purpose of this study is to investigate the radiographic characteristics before and after correction surgery for AIS with a major curve at the PT area. This is a retrospective cohort study at a single academic institution. Twelve patients with a major curve at the PT spine participated in our study and followed for at least two years after surgery. We evaluated the pre- and postoperative Cobb angles of the curve, curve range, location of the apex, sagittal parameters, and shoulder balance-related parameters. All patients were treated by posterior correction and fusion surgery using pedicle screw constructs. The patients were classified as having a double-curve (DC) type, in which the MT curve was structural, or a single-curve (SC) type, in which the MT curve was corrected to less than 25° on supine side-bending films. The mean correction rates for the PT curve were favorable in both groups (DC, 65.7%±9.6%; SC, 39.2%±4.9%). The mean Cobb angle of the lumbar curve improved in the DC group (preoperative, 17.1°±4.0°; postoperative, 5.0°±4.2°) but deteriorated in the SC group (preoperative, 7.1°±1.2°; postoperative, 12.4°±4.4°) after surgery. We illustrated the postoperative radiographical changes of 12 consecutive patients with the major curve at the PT curve. Although posterior correction and fusion surgery corrected the PT curve satisfactorily in both DC and SC patients, the Cobb angle of the lumbar curve deteriorated after surgery in all SC patients. Surgeons need to pay attention to the fusion area, especially LIV, when operating the SC curve type.

Interspinous-Interbody Fusion via a Strictly Lateral Surgical Approach: A Biomechanical Stabilization Comparison to Constructs Requiring Both Lateral and Posterior Approaches.

Objective Lumbar fusion performed through lateral approaches is becoming more common. The interbody devices are generally supported by supplemental posterior fixation implanted through a posterior approach, potentially requiring a second incision and intraoperative repositioning of the patient. A minimally invasive lateral interspinous fixation device may eliminate the need for intraoperative repositioning and avoid disruption of the supraspinous ligament. The objective of this in vitrobiomechanical study was to investigate segmental multidirectional stability and maintenance of foraminal distraction of a lateral interspinous fixation device compared to commonly used pedicle screw and facet screw posterior fixation constructs when combined with lumbar interbody cages. Methods Six human cadaver lumbar spine specimens were subjected to nondestructive quasistatic loading in the following states: (1) intact; (2) interspinous fixation device alone and (3) with lateral interbody cage; (4) lateral lumbar interbody cage with bilateral pedicle screws; (5) lateral lumbar interbody cage with unilateral pedicle screws; and (6) lateral lumbar interbody cage with facet screws. Multidirectional pure bending in 1.5 Nm increments to 7.5 Nm, and 7.5 Nm flexion-extension bending with a 700 N compressive follower load were performed separately with optoelectronic segmental motion measurement. Relative angular motions of L2-L3, L3-L4, and L4-L5 functional spinal units were evaluated, and the mean instantaneous axis of rotation in the sagittal plane was calculated for the index level.Foraminal height was assessed during combined flexion-extension and compression loading for each test construct. Results All implant configurations significantly restricted flexion-extension motion compared with intact (p < 0.05). No significant differences were found in flexion-extension when comparing the different posterior implants combined with lateral lumbar interbody cages. All posterior fixation devices provided comparable neuroforaminal distraction and maintained distraction during flexion and extension. Conclusions When combinedwith lateral lumbar interbody cages, the minimally invasive lateral interspinous fixation device effectively stabilized the spine and maintained neuroforaminal distraction comparable to pedicle screw constructs or facet screws. These results suggest the lateral interspinous fixation device may provide a favorable alternative to other posterior systems that require patient repositioning during surgery and involve a greater disruption of native tissues.

Spinolaminar locking plates improve fixation strength compared to pedicle screws: a biomechanical analysis.

Pedicle screw loosening is a significant complication of posterior spinal fixation, particularly among osteoporotic patients and in deformity constructs. In orthopedic trauma surgery, locking plates and screws have revolutionized the fixation of osteoporotic fractures. We have combined the traumatology principle of fixed-angle locking plate fixation with the spine principles of segmental instrumentation. A novel spinolaminar locking plate was designed based on morphometric studies of human thoracolumbar vertebrae. The plates were fixed to cadaveric human lumbar spines and connected to form 1-level L1-L2 or L4-L5 constructs and compared to similar pedicle screw constructs. Pure moment testing was performed to assess range of motion before and after 30,000 cycles of cyclic fatigue. Post-fatigue fixture pullout strength was assessed by applying a continuous axial tensile force oriented to the principal axis of the pedicle until pullout was observed. Spinolaminar plate fixation resulted in superior pullout strength compared to pedicle screws (1,065 ± 400N vs. 714 ± 284N, p = 0.028). Spinolaminar plates performed equivalently to pedicle screws in range of motion reduction during flexion/extension and axial rotation. Pedicle screws outperformed the spinolaminar plates in lateral bending. Finally, no spinolaminar constructs failed during cyclic fatigue testing, whereas one pedicle screw construct did. The spinolaminar locking plate maintained adequate fixation post-fatigue, particularly in flexion/extension and axial rotation compared to pedicle screws. Moreover, spinolaminar plates were superior to pedicle screw fixation with respect to cyclic fatiguing and pullout strength. The spinolaminar plates offer a viable option for posterior lumbar instrumentation in the adult spine.

Let's think beyond the pedicle: A biomechanical study of a new conceptual extra pedicular screw and hook construct

BackgroundTranspedicular screws have proven the test of time, yet they are not devoid of complications. Many newer techniques such as 2 D and 3D fluoroscopy,O arm Navigation assisted surgery, robotic assisted surgery have come into existence to the increase precision in pedicle screw insertion. But, complications do occur in their presence. We propose an Extra pedicular screw and hook system (EPSH) system with similar biomechanical property, better safety profile and short learning curve compared to traditional pedicle screw. PurposeTo Compare the pull out strength of Traditional Pedicle screw Vs Extra pedicular screw and hook system(EPSH). MethodsBiomechanical testing was conducted according ASTM F543 guidelines to compare the pull-out strength of EPSH based construct and traditional pedicle screw construct. Six saw bone samples in each group considered. Screw of 5.5 mm diameter and length of 35 mm was used in both the groups. Pull out strength assessed by giving 5 mm/min axial load. The axial load Vs displacement of the screw were recorded and plotted. The maximum load required for screw failure is noted in both the group. Statistical analysis was done. ResultsThe mean peak load of pedicle screw group was found to be 1670.9 ± 393.2 N with mean displacement at peak load was found to be 13.44 ± 1.7 mm and in EPSH group it was 1416.4 ± 341.4 N and 15.78 ± 3.9 mm respectively. A paired t-test showed no statistical difference(p < 0.05) between 2 groups. ConclusionEPSH has shown to have almost similar biomechanical property as that pedicle screw construct. With Addition of the hook, it provides an extra rotational stability as well. Being an extra-pedicular screw it has high safety profile and needs less expertise for insertion.

Intermittent pedicle screw application provides better kyphosis restoration in adolescent idiopathic scoliosis for Lenke type 1 and type 2 curves.

There is still no consensus on the optimum pedicle screw density required for the desired thoracic kyphosis restoration in adolescent idiopathic surgery (AIS). The aim of this study to evaluate the effect of pedicle screw density on thoracic kyphosis restoration in AIS surgery. The data of 106 patients from two centers that operated for Lenke type 1 and 2 AIS were retrospectively reviewed. Two groups were constituted according to the pedicle screw density: intermittent pedicle screw constructs (IPSC) (n = 52 patients) and consecutive pedicle screw construct (CPSC) (n = 54 patients) groups. The preoperative and at least 24-month follow-up radiographs and SRS-22 scores were evaluated. The Cobb angle of the main and concomitant curves in the coronal plane and the sagittal plane were measured and compared. The mean follow-up period for the IPSC and CPSC groups was 72.3 ± 37.2 and 62.9 ± 28.8months, respectively. In the SRS-22 questionnaire, there was no significant difference between the two groups in terms of self-image/appearance domain scores (p = 0.466), but better results were obtained in the IPSC group in terms of treatment satisfaction domain scores (p = 0.010) and better thoracic kyphosis restoration was achieved in IPSC group radiologically for Lenke type 1 curves with - 81.4 ± 81.4% in the IPSC group and 6.8 ± 83.8% in the CPSC group (p < 0.001). It was considered that better thoracic kyphosis restoration could be achieved with the less lordotic effect of IPSC in Lenke type 1 curves. Although the current situation had a significant impact on radiological outcomes, its effect on SRS-22 scores was limited.

Residual motion of cortical versus pedicle screw constructs after decompression, interbody fusion and cross-link augmentation

PurposeTo compare the residual range of motion (ROM) of cortical screw (CS) versus pedicle screw (PS) instrumented lumbar segments and the additional effect of transforaminal interbody fusion (TLIF) and cross-link (CL) augmentation.MethodsROM of thirty-five human cadaver lumbar segments in flexion/extension (FE), lateral bending (LB), lateral shear (LS), anterior shear (AS), axial rotation (AR), and axial compression (AC) was recorded. After instrumenting the segments with PS (n = 17) and CS (n = 18), ROM in relation to the uninstrumented segments was evaluated without and with CL augmentation before and after decompression and TLIF.ResultsCS and PS instrumentations both significantly reduced ROM in all loading directions, except AC. In undecompressed segments, a significantly lower relative (and absolute) reduction of motion in LB was found with CS 61% (absolute 3.3°) as compared to PS 71% (4.0°; p = 0.048). FE, AR, AS, LS, and AC values were similar between CS and PS instrumented segments without interbody fusion. After decompression and TLIF insertion, no difference between CS and PS was found in LB and neither in any other loading direction. CL augmentation did not diminish differences in LB between CS and PS in the undecompressed state but led to an additional small AR reduction of 11% (0.15°) in CS and 7% (0.05°) in PS instrumentation.ConclusionSimilar residual motion is found with CS and PS instrumentation, except of slightly, but significantly inferior reduction of ROM in LB with CS. Differences between CS and PS in diminish with TLIF but not with CL augmentation.

Residual motion of different posterior instrumentation and interbody fusion constructs

PurposeTo elucidate residual motion of cortical screw (CS) and pedicle screw (PS) constructs with unilateral posterior lumbar interbody fusion (ul-PLIF), bilateral PLIF (bl-PLIF), facet-sparing transforaminal lumbar interbody fusion (fs-TLIF), and facet-resecting TLIF (fr-TLIF).MethodsA total of 35 human cadaver lumbar segments were instrumented with PS (n = 18) and CS (n = 17). Range of motion (ROM) and relative ROM changes were recorded in flexion/extension (FE), lateral bending (LB), axial rotation (AR), lateral shear (LS), anterior shear (AS), and axial compression (AC) in five instrumentational states: without interbody fusion (wo-IF), ul-PLIF, bl-PLIF, fs-TLIF, and fr-TLIF.ResultsWhereas FE, LB, AR, and AC noticeably differed between the instrumentational states, AS and LS were less prominently affected. Compared to wo-IF, ul-PLIF caused a significant increase in ROM with PS (FE + 42%, LB + 24%, AR + 34%, and AC + 77%), however, such changes were non-significant with CS. ROM was similar between wo-IF and all other interbody fusion techniques. Insertion of a second PLIF (bl-PLIF) significantly decreased ROM with CS (FE -17%, LB -26%, AR -20%, AC -51%) and PS (FE − 23%, LB − 14%, AR − 20%, AC − 45%,). Facet removal in TLIF significantly increased ROM with CS (FE + 6%, LB + 9%, AR + 17%, AC of + 23%) and PS (FE + 7%, AR + 12%, AC + 13%).Conclusionbl-PLIF and TLIF show similarly low residual motion in both PS and CS constructs, but ul-PLIF results in increased motion. The fs-TLIF technique is able to further decrease motion compared to fr-TLIF in both the CS and PS constructs.

Updated Criteria for Fusion Level Selection in Adolescent Idiopathic Scoliosis Including Use of Three-Dimensional Analysis.

The development of new technologies and an enhanced understanding of the three-dimensional deformity in adolescent idiopathic scoliosis has led to advances in surgical management of adolescent idiopathic scoliosis. Posterior spinal approaches with pedicle screw constructs are now standard of care because they allow for powerful rotation maneuvers with three-column deformity correction. Selective fusion of the main curve while allowing for spontaneous correction of compensatory curves should be attempted whenever possible in the interest of limiting fusion size and preserving spinal mobility. Recent research provides updated criteria to determine optimal candidates for selective fusion. These criteria must be weighed against patient goals and patient-specific factors to limit complications and maximize chances of successful deformity correction.

Using Proximal Hooks as a Soft-Landing Strategy to Prevent Proximal Junctional Kyphosis in the Surgical Treatment of Scheuermann's Kyphosis.

To evaluate the occurrence of proximal junctional kyphosis (PJK) as well as both the clinical and radiologic outcomes of patients who underwent surgery for Scheuermann?s Kyphosis (SK) using either exclusively pedicle screws or a combination of proximal hooks and pedicle screws constructs. Surgically treated 37 patients with the diagnosis of SK were evaluated retrospectively. The patients were divided into two groups based on the type of instrumentation employed. The first group contained 22 patients with only pedicle screws (PP) while the second group consisted of 15 patients with mixed constructs that were proximal hooks and pedicle screws (HP) at the rest of the levels. The clinical and radiological data were compared in patients who were followed up for a minimum of 2 years. The average duration of follow-up for the PP group was approximately 94.7 ± 53.1 months, whereas the HP group had an average follow-up period of around 103 ± 64.4 months. After conducting the analyses, no statistically significant findings were identified in the measurements taken for the SRS-22 scores in preoperative, postoperative, and the most recent follow-up radiographs (p > 0.05). It is worth noting that among patients who exclusively utilized pedicle screws, both the proximal (p=0.045) and distal (p=0.030) junctional kyphosis angles experienced more pronounced increases compared to hybrid structures. While no notable distinction was observed between the two groups, patients with pedicle screws fixation had a higher PJK angle. Conversely, the use of hooks at the upper end seems to be a preventive measure against the development of PJK.

Axial Neck-Shoulder Pain After Posterior Correction and Fusion for Adolescent Idiopathic Scoliosis With Structural Thoracic Curve: Does Cranial Fusion Level Affect Neck Symptoms?

A retrospective cohort study using prospectively collected data. To investigate the incidence and impact of fusion to the upper thoracic spine on neck-shoulder symptoms after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Axial neck-shoulder pain is established as a sequela of posterior cervical spine surgery and is mainly caused by the dissection of extensor muscles in the cervical and upper thoracic spine. Sixty-three female patients with AIS who underwent PSF using segmental pedicle screw constructs for structural main thoracic curve with a minimum 2-year follow-up were included. Axial neck-shoulder pain was assessed using the visual analog scale and cervical spine function domain score of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire. The patients were divided into 2 groups, a higher group (underwent fusion up to T3 or above, n=27) and a lower group (underwent fusion up to T4 or below, n=36), and radiologic and clinical outcomes were compared. The incidence of axial neck-shoulder pain (visual analog scale ≥30) preoperatively and at the 2-year follow-up was 29 and 40%, respectively. The pain and mental health domains of the Scoliosis Research Society-22 and cervical spine function domain of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire were correlated with the severity of axial neck pain. In the comparison of clinical outcomes between the 2 groups, the pain domain score of the Scoliosis Research Society-22 in the lower group was significantly better than that in the higher group at the 2-year follow-up ( P <0.05). Other parameters showed no significant differences preoperatively or at the 2-year follow-up. Female patients with AIS had a relatively high incidence of axial neck-shoulder pain after PSF, which affected their health-related quality of life. Both groups showed similar clinical outcomes, and the cranial fusion level did not affect axial neck-shoulder pain and cervical spine function. Level 3.