Trajectory analysis and pullout strength of self-centering lumbar pedicle screws

2009 ◽  
Vol 10 (5) ◽  
pp. 486-491 ◽  
Author(s):  
Neil R. Crawford ◽  
K. Zafer Yüksel ◽  
Şeref Doğan ◽  
Octavio Villasana-Ramos ◽  
Julio C. Soto-Barraza ◽  
...  
Keyword(s):  
Optimal Trajectory ◽  
Trajectory Analysis ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Pullout Strength ◽  
Insertion Point ◽  
Screw Insertion ◽  
Constant Displacement ◽  
Straight Ahead ◽  
Lumbar Pedicle

Object An experiment was performed to study the limits of the ability of screws designed to center themselves in the pedicle during insertion, and to study whether straight-ahead versus inward screw insertion trajectories differ in their resistance to pullout. Methods Forty-nine human cadaveric lumbar vertebrae were studied. Pedicle screws were inserted in trajectories starting 0°, 10°, 20°, or 30° from the optimal trajectory, either medially or laterally misdirected. The surgeon then inserted the screw with forward thrust but without resisting the screw's tendency to reorient its own trajectory during insertion. On the opposite pedicle, a control screw was inserted with the more standard inward-angled anatomical trajectory and insertion point. Cortical wall violation during insertion was recorded. Screws were then pulled out at a constant displacement rate while ultimate strength was recorded. Results Lateral misdirection as small as 10° was likely to lead to cortical wall violation (3 of 7 violations). Conversely, medial misdirection usually resulted in safe screw insertion (1 of 21 violations for 10°, 20°, or 30° medial misdirection). The resistance to pullout of screws inserted in a straight-ahead trajectory did not differ significantly from that of screws inserted along an inward trajectory (p = 0.68). Conclusions Self-tapping, self-drilling pedicle screws can redirect themselves to a much greater extent during medial than during lateral misdirection. The cortical wall is more likely to be violated laterally than medially. The strength of straight-ahead and inward trajectories was equivalent.

Fixation Strength of Pedicle and Cortical Lumbar Vertebral Screws after Laminectomy: A Cadaver Study

2018 ◽  
Vol 79 (04) ◽  
pp. 273-278
Author(s):  
Dai-Soon Kwak ◽  
Ho-Jung Cho ◽  
Ho Chang ◽  
Moon Park ◽  
In-Sung Kim ◽  
...  
Keyword(s):  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Cadaver Study ◽  
Fixation Strength ◽  
Pullout Strength ◽  
Screw Insertion ◽  
Cortical Screw ◽  
Significant Difference ◽  
Midline Approach ◽  
Biomechanical Strength

Background and Study Aim Cortical screws were proposed as an alternative to the traditional pedicle screws. Diverse experimental results support the biomechanical superiority of cortical screws compared to pedicle screws. Laminectomy is often part of multilevel lumbar surgeries. Laminectomy might weaken the medial bony edge at the entry of the divergently oriented screw and, thereby, the screw purchase. This study investigated the biomechanical strength of lumbar cortical screw after laminectomy. Objective To compare the fixation strength of cortical screws and traditional pedicle screws after lumbar laminectomy. Material and Methods A total of 120 pedicles from 60 lumbar vertebrae of 12 cadavers (8 men, 4 women) were assessed. The mean age of the cadavers was 73.4 ± 6.2 years (range: 62–82 years). Using a posterior midline approach, we inserted the traditional pedicle screws into one and the cortical screws into the other side of each vertebra. Laminectomy was performed after screw insertion. Vertical pullout strength and toggle strength testing were performed to compare the fixation strength between the two sides. Results After laminectomy, the pullout strength of the cortical screws was 718.92 ± 340.76 N, and that of the pedicle screws was 625.78 ± 287.10 N (p = 0.183). The toggle strength of the cortical screws was 544.83 ± 329.97 N; that of the pedicle screws was 613.17 ± 311.70 N (p = 0.145). No significant difference was found in biomechanical strength between the two types of screws. Conclusion Despite laminectomy, lumbar cortical screws offers comparable pullout and toggle biomechanical strength as traditional pedicle screws.

Accuracy of percutaneous lumbar pedicle screw placement using the oblique or “owl's-eye” view and novel guidance technology

2010 ◽  
Vol 13 (4) ◽  
pp. 509-515 ◽  
Author(s):  
Cary Idler ◽  
Kevin W. Rolfe ◽  
Josef E. Gorek
Keyword(s):  
Pedicle Screw ◽  
Facet Joint ◽  
Pedicle Screws ◽  
Guidance System ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
Screw Insertion ◽  
Percutaneous Pedicle Screw ◽  
Clinical Series ◽  
Lumbar Pedicle

Object This study was conducted to assess the in vivo safety and accuracy of percutaneous lumbar pedicle screw placement using the owl's-eye view of the pedicle axis and a new guidance technology system that facilitates orientation of the C-arm into the appropriate fluoroscopic view and the pedicle cannulation tool in the corresponding trajectory. Methods A total of 326 percutaneous pedicle screws were placed from L-3 to S-1 in 85 consecutive adult patients. Placement was performed using simple coaxial imaging of the pedicle with the owl's-eye fluoroscopic view. NeuroVision, a new guidance system using accelerometer technology, helped align the C-arm trajectory into the owl's-eye view and the cannulation tool in the same trajectory. Postoperative fine-cut CT scans were acquired to assess screw position. Medical records were reviewed for complications. Results Five of 326 screws breached a pedicle cortex—all breaches were less than 2 mm—for an accuracy rate of 98.47%. Five screws violated an adjacent facet joint. All were at the S-1 superior facet and included in a fusion. No screw violated an adjacent mobile facet or disc space. There were no cases of new or worsening neurological symptoms or deficits for an overall clinical accuracy of 100%. Conclusions The owl's-eye technique of coaxial pedicle imaging with the C-arm fluoroscopy, facilitated by NeuroVision, is a safe and accurate means by which to place percutaneous pedicle screws for degenerative conditions of the lumbar spine. This is the largest series reported to use the oblique or owl's-eye projection for percutaneous pedicle screw insertion. The accuracy of percutaneous screw insertion with this technique meets or exceeds that of other reported clinical series or techniques.

Biomechanical Effects of Lumbar Pedicle Screw Insertion Depth on Screw Loosening and Fulcrum Location

2013 ◽  
Author(s):  
Laura E. Buckenmeyer ◽  
Kristophe J. Karami ◽  
Ata M. Kiapour ◽  
Vijay K. Goel ◽  
Constantine K. Demetropoulos ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Screw Loosening ◽  
Pullout Strength ◽  
Insertion Depth ◽  
Bone Implant ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Increased Risk ◽  
Screw Length

Osteoporosis is a critical challenge in orthopedic surgery. Osteoporotic patients have an increased risk of loosening and failure of implant constructs due to a weaker bone-implant interface than with healthy bone. Pullout strength of pedicle screws is enhanced by increased screw insertion depth. However, more knowledge is needed to define optimal pedicle screw insertion depth in relation to screw-bone interface biomechanics and the resulting loosening risk. This study evaluates the effects of screw length on loosening risk in the osteoporotic lumbar spine.

scholarly journals CT-to-fluoroscopy registration versus scan-and-plan registration for robot-assisted insertion of lumbar pedicle screws

2022 ◽  
Vol 52 (1) ◽  
pp. E8
Keyword(s):  
Pedicle Screw ◽  
Lumbar Fusion ◽  
Pedicle Screws ◽  
Retrospective Chart Review ◽  
Robot Assisted ◽  
Registration Method ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Radiology Reports ◽  
Lumbar Pedicle

OBJECTIVE Pedicle screw insertion for stabilization after lumbar fusion surgery is commonly performed by spine surgeons. With the advent of navigation technology, the accuracy of pedicle screw insertion has increased. Robotic guidance has revolutionized the placement of pedicle screws with 2 distinct radiographic registration methods, the scan-and-plan method and CT-to-fluoroscopy method. In this study, the authors aimed to compare the accuracy and safety of these methods. METHODS A retrospective chart review was conducted at 2 centers to obtain operative data for consecutive patients who underwent robot-assisted lumbar pedicle screw placement. The newest robotic platform (Mazor X Robotic System) was used in all cases. One center used the scan-and-plan registration method, and the other used CT-to-fluoroscopy for registration. Screw accuracy was determined by applying the Gertzbein-Robbins scale. Fluoroscopic exposure times were collected from radiology reports. RESULTS Overall, 268 patients underwent pedicle screw insertion, 126 patients with scan-and-plan registration and 142 with CT-to-fluoroscopy registration. In the scan-and-plan cohort, 450 screws were inserted across 266 spinal levels (mean 1.7 ± 1.1 screws/level), with 446 (99.1%) screws classified as Gertzbein-Robbins grade A (within the pedicle) and 4 (0.9%) as grade B (< 2-mm deviation). In the CT-to-fluoroscopy cohort, 574 screws were inserted across 280 lumbar spinal levels (mean 2.05 ± 1.7 screws/ level), with 563 (98.1%) grade A screws and 11 (1.9%) grade B (p = 0.17). The scan-and-plan cohort had nonsignificantly less fluoroscopic exposure per screw than the CT-to-fluoroscopy cohort (12 ± 13 seconds vs 11.1 ± 7 seconds, p = 0.3). CONCLUSIONS Both scan-and-plan registration and CT-to-fluoroscopy registration methods were safe, accurate, and had similar fluoroscopy time exposure overall.

scholarly journals Correlation between the Computed Tomography Values of the Screw Path and Pedicle Screw Pullout Strength: An Experimental Study in Porcine Vertebrae

2020 ◽  
Vol 14 (3) ◽  
pp. 265-272
Author(s):  
Atsushi Ikeura ◽  
Taketoshi Kushida ◽  
Kenichi Oe ◽  
Yoshihisa Kotani ◽  
Muneharu Ando ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Bone Mineral Density ◽  
Pedicle Screw ◽  
Bone Mineral ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Mineral Density ◽  
Screw Insertion ◽  
Pull Out ◽  
Pull Out Strength

Study Design: Biomechanical study.Purpose: To assess the correlation between the computed tomography (CT) values of the pedicle screw path and screw pull-out strength.Overview of Literature: The correlation between pedicle screw pull-out strength and bone mineral density has been well established. In addition, several reports have demonstrated a correlation between bone mineral density and CT values. However, no previous biomechanical studies investigated the correlation between CT values and pedicle screw pull-out strength.Methods: Sixty fresh-frozen lumbar vertebrae from 6-month-old pigs were used. Before screw insertion, the CT values of the screw path were obtained for each sample. Specimens were then randomly divided into three equal groups. Each group had one of three pedicle screws inserted: 4.0-mm LEGACY (4.0-LEG), 4.5-mm LEGACY (4.5-LEG), or 4.5-mm SOLERA (4.5-SOL) (all from Medtronic Sofamor Danek Inc., Memphis, TN, USA). Each screw had a consistent 30-mm thread length. Axial pull-out testing was performed at a rate of 1.0 mm/min. Correlations between the CT values and pedicle screw pull-out strength were evaluated using Pearson’s correlation coefficient analysis.Results: The correlation coefficients between the CT values of the screw path and pedicle screw pull-out strength for the 4.0-LEG, 4.5-LEG, and 4.5-SOL groups were 0.836 (<i>p</i> <0.001), 0.780 (<i>p</i> <0.001), and 0.873 (<i>p</i> <0.001), respectively. Greater CT values were associated with greater screw pull-out strength.Conclusions: The CT values of the screw path were strongly positively correlated with pedicle screw pull-out strength, regardless of the screw type and diameter, suggesting that the CT values could be clinically useful for predicting pedicle screw pull-out strength.

scholarly journals Application of a Novel Attachable Magnetic Nerve Stimulating Probe in Intraoperative Lumbar Pedicle Screw Placement: A Porcine Model Study

2021 ◽  
Vol 11 (17) ◽  
pp. 7801
Author(s):  
Tae Sik Goh ◽  
Sung-Chan Shin ◽  
Hyun-Keun Kwon ◽  
Eui-Suk Sung ◽  
Se Bin Jun ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Porcine Model ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Screw Placement ◽  
Lumbar Spine Surgery ◽  
Pedicle Screw Placement ◽  
Significant Difference ◽  
Screw Malpositioning ◽  
Lumbar Pedicle

Pedicle screw instrumentation is a fundamental technique in lumbar spine surgery. However, several complications could occur when placing a pedicle screw, the most serious being damage to the neural structures. We developed an attachable magnetic nerve stimulating probe used for triggered electromyography (t-EMG) to avoid these. This study aimed to investigate the efficacy of this probe for intraoperative neuromonitoring (ION) during lumbar pedicle screw placement in a porcine model. Forty pedicle screws were inserted bilaterally into the pedicles of the fourth and fifth lumbar vertebrae of five pigs; 20 were inserted typically into the pedicle without nerve damage (Group A), and the other 20 were inserted through the broken medial wall of the pedicle to permit contact with the neural structures (Group B). We measured the triggered threshold for pedicle screw placement through the conventional nerve probe and our newly developed magnetic probe. There was no significant difference in the triggered threshold between the two instruments (p = 0.828). Our newly developed magnetic stimulating probe can be attached to a screwdriver, thus preventing real-time screw malpositioning and making it practical and equally safe. This probe could become indispensable in revision spine surgeries with severe adhesions or endoscopic spine surgeries.

scholarly journals Transpedicular fixation of the spine with two-level navigation templates for narrow pedicles

2021 ◽  
Vol 18 (2) ◽  
pp. 26-33
Author(s):  
A. V. Kosulin ◽  
D. V. Elyakin ◽  
D. O. Korchagina ◽  
N. A. Lukina ◽  
Yu. I. Shibutova ◽  
...  
Keyword(s):  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Ct Scanning ◽  
Cortical Layer ◽  
Screw Placement ◽  
Screw Insertion ◽  
Scoliotic Deformity ◽  
Small Width ◽  
Transpedicular Screw ◽  
Free Hand Technique

Objective. To assess the correctness of transpedicular screw insertion in thoracic and lumbar vertebrae using two-level navigation templates for narrow pedicles.Material and Methods. Two-level navigation templates were used in surgical treatment of four patients aged 14–17 years with scoliotic deformity and multiple pedicles of small width (less than 4.35 mm). In each patient, the least favorable zones were selected for implantation using navigation templates. The rest of planned pedicle screws were inserted using free-hand technique. All patients underwent CT scanning postoperatively. Screws inserted to pedicles less than 4.35 mm in width  were classified as correctly placed if they did not extend beyond the medial cortical layer by more than 2 mm.Results. Out of 68 pedicles planned for screw placement, 42 were narrower than 4.35 mm. In the pedicles difficult for implantation, 29 screws were inserted using navigation templates and 13 by free-hand technique. Screws classified as correctly placed were 28 from those inserted with navigation templates and 9 from those implanted by free-hand technique. Difference in results of screw placement in narrow pedicles with navigation templates and by free-hand technique was statistically significant (exact Fisher test, p < 0.05).Conclusion. Transpedicular screw placement with two-level navigation templates in narrow pedicles is more correct than insertion by free hand technique.

Adjustment of Suboptimally Placed Lumbar Pedicle Screws Decreases Pullout Strength and Alters Biomechanics of the Construct: A Pilot Cadaveric Study

2015 ◽  
Vol 83 (3) ◽  
pp. 368-375 ◽  
Author(s):  
Rishi Kumar Wadhwa ◽  
Jai Deep Thakur ◽  
Imad Saeed Khan ◽  
Jeremy James ◽  
Osama Ahmed ◽  
...  
Keyword(s):  
Pedicle Screws ◽  
Cadaveric Study ◽  
Pullout Strength ◽  
Lumbar Pedicle

scholarly journals Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

2013 ◽  
Vol 47 (3) ◽  
pp. 238 ◽  
Author(s):  
ShyamK Saraf ◽  
RavindraP Singh ◽  
Vakil Singh ◽  
Ashish Varma
Keyword(s):  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Cadaveric Study ◽  
Pullout Strength

scholarly journals Should we use cortical bone screws for cortical bone trajectory?

2015 ◽  
Vol 22 (4) ◽  
pp. 416-421 ◽  
Author(s):  
Masaki Ueno ◽  
Rina Sakai ◽  
Kensei Tanaka ◽  
Gen Inoue ◽  
Kentaro Uchida ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Animal Experiments ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Screw Thread ◽  
Pullout Strength ◽  
Cortical Bone Trajectory ◽  
Cancellous Screws ◽  
The Difference ◽  
Increased Strength

OBJECT In 2009, Santoni et al. reported cortical bone trajectory (CBT) as a method of inserting pedicle screws to obtain more solid fixation, and proposed the use of cortical trajectory screws with a more closely placed thread (cortical screws) for CBT. Since the entry trajectory in CBT differs from that in the traditional trajectory, it is unclear whether the increased strength derives from the specific trajectory or the shape of the screw thread in contact with the cortical bone. Whether the use of cortical screws is always required with CBT thus remains unclear. The authors therefore investigated the relationship between screw entry trajectory and screw thread characteristics and pullout strength in animal experiments. METHODS Lumbar vertebrae (L1–L4) from 4-month-old female pigs were randomly assigned to one of 4 groups, with cancellous screws or cortical screws inserted via the traditional trajectory or CBT. For pullout strength testing, the screw was pulled out vertically against the direction of insertion. Rod pullout testing (toggle testing) was also performed, and the peak breaking strength was measured. RESULTS The maximum pullout strength was significantly greater for CBT using cortical screws than for the traditional trajectory using cancellous screws. Pullout strength tended to be higher when cortical screws were used in both CBT and the traditional trajectory, although the difference was not significant. Toggle testing showed no significant differences among the 4 groups. CONCLUSIONS The specific unconventional trajectory seemed to have a major impact on the increased strength obtained with CBT.

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