In vitro biomechanical comparison of transpedicular versus translaminar C-2 screw fixation in C2–3 instrumentation

2007 ◽  
Vol 7 (4) ◽  
pp. 414-418 ◽  
Author(s):  
Chandan Reddy ◽  
Aditya V. Ingalhalikar ◽  
Scott Channon ◽  
Tae-Hong Lim ◽  
James Torner ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Upper Cervical Spine ◽  
Lateral Mass ◽  
C2 Pedicle Screw ◽  
Laminar Screw ◽  
Significant Difference ◽  
Flexion Extension ◽  
C2 Laminar Screw

Object In instrumentation of the upper cervical spine, placement of pedicle screws into C-2 is generally safe, although there is the potential for injury to the vertebral arteries. Owing to this risk, translaminar screws into C-2 have been used. The aim of this study was to compare the stability of the in vitro cadaveric spine using C-2 laminar compared with C-2 pedicle screws in C2–3 instrumentation. Methods Eight fresh frozen human cadaveric cervical spines (C1–6) were potted at C1–2 and C5–6. Pure moments in increments of 0.3 Nm to a maximum of 1.5 Nm were applied in flexion, extension, right and left lateral bending, and right and left axial rotation. Each specimen was tested sequentially in three modes: 1) intact; 2) C2 pedicle screw–C3 lateral mass fixation; and 3) C2 laminar screw–C3 lateral mass fixation. The sequence of fixation testing was randomized. Motion was tracked with reflective markers attached to C-2 and C-3. Results Spinal levels with instrumentation showed significantly less motion than the intact spine in all directions and with all loads greater than 0.3 Nm (p < 0.05). Although there was no significant difference between C2 pedicle screw–C3 lateral mass fixation and C2 laminar screw–C3 lateral mass fixation, generally the former type of fixation was associated with less motion than the latter. Conclusions When pedicle screws in C-2 are contraindicated or inappropriate, laminar screws in C-2 offer a safe and acceptable option for posterior instrumentation.

scholarly journals Posterior spinal fusion using a unilateral C1 posterior arch screw and a C2 laminar screw for atlantoaxial fracture dislocation

2019 ◽  
Vol 7 ◽  
pp. 2050313X1984927 ◽  
Author(s):  
Yuichi Ono ◽  
Naohisa Miyakoshi ◽  
Michio Hongo ◽  
Yuji Kasukawa ◽  
Yoshinori Ishikawa ◽  
...  
Keyword(s):  
Pedicle Screws ◽  
Fracture Site ◽  
Fracture Dislocation ◽  
Posterior Arch ◽  
Lateral Mass ◽  
Laminar Screw ◽  
Upper Cervical ◽  
Lateral Mass Screws ◽  
The Right ◽  
C2 Laminar Screw

Introduction: C1 lateral mass screws and C2 pedicle screws are usually chosen to fix atlantoaxial (C1–C2) instability. However, there are a few situations in which these screws are difficult to use, such as in a case with a fracture line at the screw insertion point and bleeding from the fracture site. A new technique using a unilateral C1 posterior arch screw and a C2 laminar screw combined with a contralateral C1 lateral mass screws–C2 pedicle screws procedure for upper cervical fixation is reported. Case Report: A 24-year-old woman had an irreducible C1–C2 anterior dislocation with a type III odontoid fracture on the right side due to a traffic accident. The patient underwent open reduction and posterior C1–C2 fixation. On the left side, a C1 lateral mass screws and a C2 pedicle screws were placed. Because there was bleeding from the fracture site and a high-riding vertebral artery was seen on the right side, a C1 posterior arch screw and a C2 laminar screw were chosen. Eight months after the surgery, computed tomography scans showed healing of the odontoid fracture with anatomically correct alignment. Conclusions: Although there have been few comparable studies, fixation with unilateral C1 posterior arch screw–C2 laminar screw could be a beneficial choice for surgeries involving the upper cervical region in patients with fracture dislocation or arterial abnormalities.

scholarly journals Biomechanical Evaluation of Cortical Bone Trajectory Fixation with Traditional Pedicle Screw in the Lumbar Spine: A Finite Element Study

2021 ◽  
Vol 11 (22) ◽  
pp. 10583
Author(s):  
Kuo-Chih Su ◽  
Kun-Hui Chen ◽  
Chien-Chou Pan ◽  
Cheng-Hung Lee
Keyword(s):  
Finite Element ◽  
Lumbar Spine ◽  
Cortical Bone ◽  
Pedicle Screw ◽  
Spinal Surgery ◽  
Pedicle Screws ◽  
Element Model ◽  
Cortical Bone Trajectory ◽  
Significant Difference ◽  
Flexion Extension

Cortical bone trajectory (CBT) is increasingly used in spinal surgery. Although there are many biomechanical studies, the biomechanical effect of CBT in combination with traditional pedicle screws is not detailed. Therefore, the purpose of this study was to investigate the effects of the traditional pedicle screw and CBT screw implantation on the lumbar spine using finite element methods. Based on the combination of the traditional pedicle screw and the CBT system implanted into the lumbar spine, four finite element spinal lumbar models were established. The models were given four different load conditions (flexion, extension, lateral bending, and axial rotation), and the deformation and stress distribution on the finite element model were observed. The results show that there was no significant difference in the structural stability of the lumbar spine model between the traditional pedicle screw system and the CBT system. In addition, CBT may reduce stress on the endplate. Different movements performed by the model may have significant biomechanical effects on the spine and screw system. Clinical spinal surgeons may also consider using the CBT system in revision spinal surgery, which may contribute to smaller wounds.

Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization

2010 ◽  
Vol 12 (2) ◽  
pp. 183-189 ◽  
Author(s):  
Hakan Bozkuş ◽  
Mehmet Şenoğlu ◽  
Seungwon Baek ◽  
Anna G. U. Sawa ◽  
Ali Fahir Özer ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Stress Shielding ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Bending Moments ◽  
Axial Loads ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Lumbar Stabilization

Object It is unclear how the biomechanics of dynamic posterior lumbar stabilization systems and traditional rigid pedicle screw-rod systems differ. This study examined the biomechanical response of a hinged-dynamic pedicle screw compared with a standard rigid screw used in a 1-level pedicle screw-rod construct. Methods Unembalmed human cadaveric L3–S1 segments were tested intact, after L4–5 discectomy, after rigid pedicle screw-rod fixation, and after dynamic pedicle screw-rod fixation. Specimens were loaded using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording motion optoelectronically. Specimens were then loaded in physiological flexion-extension while applying 400 N of compression. Moment and force across instrumentation were recorded from pairs of strain gauges mounted on the interconnecting rods. Results The hinged-dynamic screws allowed an average of 160% greater range of motion during flexion, extension, lateral bending, and axial rotation than standard rigid screws (p < 0.03) but 30% less motion than normal. When using standard screws, bending moments and axial loads on the rods were greater than the bending moments and axial loads on the rods when using dynamic screws during most loading modes (p < 0.05). The axis of rotation shifted significantly posteriorly more than 10 mm from its normal position with both devices. Conclusions In a 1-level pedicle screw-rod construct, hinged-dynamic screws allowed a quantity of motion that was substantially closer to normal motion than that allowed by rigid pedicle screws. Both systems altered kinematics similarly. Less load was borne by the hinged screw construct, indicating that the hinged-dynamic screws allow less stress shielding than standard rigid screws.

Repair of pars interarticularis defect utilizing a pedicle and laminar screw construct: a new technique based on anatomical and biomechanical analysis

2012 ◽  
Vol 17 (1) ◽  
pp. 61-68 ◽  
Author(s):  
Rakesh D. Patel ◽  
Humberto G. Rosas ◽  
Michael P. Steinmetz ◽  
Paul A. Anderson
Keyword(s):  
Pedicle Screw ◽  
Spinal Canal ◽  
Biomechanical Analysis ◽  
Laminar Screw ◽  
Functional Spinal Unit ◽  
Significant Difference ◽  
Flexion Extension ◽  
Pars Interarticularis ◽  
Before And After ◽  
Biomechanical Tests

Object The theoretical advantage of pars interarticularis repair over spinal fusion to correct pars defects is that the treatment is a direct osteosynthesis that preserves motion at the involved functional spinal unit. Several techniques and constructs have been used to achieve greater rigidity, but these techniques may risk entry into the spinal canal, and adverse events are common. A pedicle and laminar screw construct placed entirely outside the spinal canal may offer greater stiffness and achieve higher pars defect healing rates. The purpose of this study was to biomechanically assess an intralaminar screw construct in cadaveric lumbar spines in comparison with other types of constructs typically used in pars repair and to quantify the sizes of screws that can be placed safely in both normal and spondylolytic vertebrae. Methods The L-4 and L-5 laminae in patients with spondylolysis and in controls who underwent CT (n = 41, each group) were measured by analysis of conventional axial CT images and multiplanar reformations constructed on a Vitrea workstation to determine the feasibility of translaminar fixation with a 4.5-mm-diameter screw. Biomechanical tests for torsion and flexion-extension were performed on 8 fresh human cadaveric lumbar spines before and after modeling for bilateral spondylolytic defects. Three pars repair techniques were tested at each level and in the following sequence: pedicle screw–cable, pedicle screw–rod–hook, and pedicle screw–intralaminar screw. Results The majority of laminae can accept 4.5 × 25-mm screws. The cable construct allowed the greatest motion and least stability across the defect in all biomechanical tests. The hook and laminar screw constructs performed similarly in all tests and exhibited no significant difference in stiffness. Conclusions A surgically placed intralaminar screw construct may be a safe and effective alternative to current pars repair methods.

Biomechanical Effect of the C2 Laminar Decortication on the Stability of C2 Intralaminar Screw Construct and Biomechanical Comparison of C2 Intralaminar Screw and C2 Pars Screw

2011 ◽  
Vol 69 (suppl_1) ◽  
pp. ons1-ons7 ◽  
Author(s):  
Jae Taek Hong ◽  
Tomoyuki Takigawa ◽  
Ranjith Udayakunmar ◽  
Hun Kyu Shin ◽  
Peter Simon ◽  
...  
Keyword(s):  
Axial Rotation ◽  
Insertion Torque ◽  
Lateral Mass ◽  
Pullout Strength ◽  
Lateral Bending ◽  
Biomechanical Stability ◽  
Laminar Screw ◽  
Flexion Extension ◽  
The Stability ◽  
C2 Laminar Screw

Abstract BACKGROUND: There have been no reports of biomechanical stability of C1-2 constructs after decortication of the C2 lamina. In addition, few studies have compared the stability of C2 laminar screw and pars screw constructs. OBJECTIVE: To compare the biomechanical stability of 3 different C1-2 construct conditions (C2 pars screw, C2 intralaminar screw, C2 intralaminar construct with C2 laminar decortication). METHODS: Fourteen fresh-frozen cadaveric cervical specimens (C1-3) were used. In 7 specimens, pure moments of 1.5 Nm were applied in flexion/extension, lateral bending, and axial rotation. Each specimen was tested in the normal state, in the destabilized state (after odontoidectomy and resection of transverse atlantal ligament), and after application of constructs. After kinematic study, these 7 specimens underwent axial pullout strength testing of pars screw and 50% decorticated C2 intralaminar screws. In another 7 specimens, insertion torque and pullout strength were measured to compare the pars screw and intact C2 intralaminar screw. RESULTS: There were no statistically significant differences between the intact C2 intralaminar and 50% decorticated C2 intralaminar screw constructs in terms of range-of-motion limitations. The C2 pars screw construct was significantly superior to the C2 laminar screw construct in lateral bending (P &lt; .01) and axial rotation (P &lt; .01) and equivalent to the C2 laminar screw construct in flexion/extension (P = .42). There was no significant pullout strength difference between the 3 kinds of C2 screw. CONCLUSION: The C1 lateral mass-C2 pars screws construct was stronger than the C1 lateral mass-C2 intralaminar screw construct. Decortication of C2 laminar (up to 50%) did not affect the immediate stability of the C1-2 construct.

scholarly journals Cortical threaded pedicle screw improves fatigue strength in decreased bone quality

2020 ◽  
Author(s):  
Lukas Weiser ◽  
Kay Sellenschloh ◽  
Klaus Püschel ◽  
Michael M. Morlock ◽  
Lennart Viezens ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Pedicle Screw ◽  
Bone Quality ◽  
Quantitative Computed Tomography ◽  
Pedicle Screws ◽  
Fatigue Load ◽  
Head Displacement ◽  
Significant Difference ◽  
Vertebral Bodies

Abstract Purpose Inadequate anchoring of pedicle screws in vertebrae with poor bone quality is a major problem in spine surgery. The aim was to evaluate whether a modified thread in the area of the pedicle could significantly improve the pedicle screw fatigue strength. Methods Fourteen human cadaveric vertebral bodies (L2 and L3) were used for in vitro testing. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by standard pedicle screws with a constant double thread on the right pedicle and a partial doubling of the threads–quad thread–(cortical thread) in the area of the pedicle on the left pedicle. Pulsating sinusoidal, cyclic load (0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied orthogonal to the screw axis. The baseline force remained constant (50 N). Fatigue test was terminated after exceeding 5.4-mm head displacement (~ 20° screw tilting). Results The mean fatigue load at failure was 264.9 N (1682 cycles) for the standard screws and was increased significantly to 324.7 N (2285 cycles) by the use of cortical threaded screws (p = 0.014). This effect is particularly evident in reduced BMD (standard thread 241.2 N vs. cortical thread 328.4 N; p = 0.016), whereas in the group of vertebrae with normal BMD no significant difference could be detected (standard thread 296.5 N vs. cortical thread 319.8 N; p = 0.463). Conclusions Compared to a conventional pedicle screw, the use of a cortical threaded pedicle screw promises superior fatigue load in vertebrae with reduced bone quality.

Motion Preserving Surgery Using O-Arm for Unstable Hangman Fracture

2019 ◽  
Vol 16 (01) ◽  
pp. 02-09
Author(s):  
Satish Kumar Verma ◽  
Pankaj Kumar Singh ◽  
Dattaraj Parmanand Sawarkar ◽  
Amandeep Kumar ◽  
Deepak Agarwal ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Upper Cervical Spine ◽  
Lateral Mass ◽  
Radiological Findings ◽  
Screw Insertion ◽  
Bony Fusion ◽  
Axis Vertebra ◽  
Pars Interarticularis ◽  
The Mean

Abstract Aim To evaluate clinical outcomes, radiological findings (displacement and angulation), and bony fusion in cases of unstable hangman’s fracture. Introduction Hangman fracture, also known as traumatic spondylolisthesis of axis vertebra, is classically defined as bilateral pars interarticularis fracture of axis vertebra. Opinions vary regarding optimal treatment of unstable hangman’s fractures. Some authors have recommended use of rigid orthosis, whereas others have recommended internal fixation. The peculiar anatomy of the upper cervical spine is highly variable, and presence of surrounding neurovascular structures makes axis pedicle screw fixation even more technically challenging. The advent of intraoperative three-dimensional navigation systems facilitates safe and accurate instrumentation. Materials and Methods This article analyzes patients operated for type II and IIa hangman’s fractures during the period from September 2011 to August 2018 by two neurosurgeons. The patients’ age, sex, mechanism of injury, associated injuries, and neurologic status were noted. The authors retrospectively assessed the clinical outcome, radiological findings (displacement and angulation), and bony fusion. Result Eighteen patients with age ranging from 17 to 81 years, were operated using computed tomography-based (O-arm) navigation. Accuracy of screw insertion, preoperative and postoperative displacement, and angulation of C2 over C3 were evaluated. Bony fusion was assessed in all patients. A total of 92 screws were inserted: 36 screws in C2 pedicle, 34 in C3 lateral mass, 20 in C4 lateral mass, and 2 in C5 lateral mass. Of these 92 screws, 36 C2 pedicle screws were inserted under O-arm guidance. The mean preoperative C2–C3 displacement was 4.5 ± 2.1 mm, and the mean postoperative displacement was 1.8 ± 1.1 mm with a mean reduction of 2.7 ± 1.4 mm. The mean preoperative C2–C3 angulation was 10.2 ± 7.6 degrees and the postoperative angulation was 2.52 ± 4.62 degrees with a mean reduction of 8.2 ± 11.6 degrees. Screw malplacement was seen in two C2 pedicle screws (2/36, 5.5%). All C2 pedicle screw breaches were of grade 2. Excellent anatomical reduction in all cases could be achieved as established by the improvement in morphological parameters of fracture. Conclusion This series using O-arm in unstable hangman fracture demonstrates that intraoperative O-arm-based navigation is a safe, accurate, and effective tool for screw placement in patients with unstable hangman fracture.

Biomechanics of C-7 transfacet screw fixation

2009 ◽  
Vol 11 (3) ◽  
pp. 338-343 ◽  
Author(s):  
Eric M. Horn ◽  
Phillip M. Reyes ◽  
Seungwon Baek ◽  
Mehmet Senoglu ◽  
Nicholas Theodore ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Normal Condition ◽  
Small Diameter ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Lateral Bending ◽  
Screw Insertion ◽  
Loading Mode ◽  
Significant Difference ◽  
Flexion Extension

Object The small diameter of the pedicle can make C-7 pedicle screw insertion dangerous. Although transfacet screws have been studied biomechanically when used in pinning joints, they have not been well studied when used as part of a C7–T1 screw/rod construct. The authors therefore compared C7–T1 fixation using a C-7 transfacet screw/T-1 pedicle screw construct with a construct composed of pedicle screws at both levels. Methods Each rigid posterior screw/rod construct was placed in 7 human cadaveric C6–T2 specimens (14 total). Specimens were tested in normal condition, after 2-column instability, and once fixated. Nondestructive, nonconstraining pure moments (maximum 1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while recording 3D motion optoelectronically. The entire construct was then loaded to failure by dorsal linear force. Results There was no significant difference in angular range of motion between the 2 instrumented groups during any loading mode (p > 0.11, nonpaired t-tests). Both constructs reduced motion to < 2° in any direction and allowed significantly less motion than in the normal condition. The C-7 facet screw/T-1 pedicle screw construct allowed a small but significantly greater lax zone than the pedicle screw/rod construct during lateral bending, and it failed under significantly less load than the pedicle screw/rod construct (p < 0.001). Conclusions When C-7 transfacet screws are connected to T-1 pedicle screws, they provide equivalent stability of constructs formed by pedicle screws at both levels. Although less resistant to failure, the transfacet screw construct should be a viable alternative in patients with healthy bone.

IN VITRO STUDY OF BIOMECHANICAL BEHAVIOROF ANTERIORAND TRANSFORAMINAL LUMBARINTERBODY INSTRUMENTATION TECHNIQUES

Neurosurgery ◽  
2006 ◽  
Vol 59 (6) ◽  
pp. 1271-1277 ◽  
Author(s):  
Thomas K. Niemeyer ◽  
Marco Koriller ◽  
Lutz Claes ◽  
Annette Kettler ◽  
Kathrin Werner ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Interbody Fusion ◽  
Screw Fixation ◽  
Axial Rotation ◽  
Pedicle Screw Fixation ◽  
Lumbar Interbody Fusion ◽  
Biomechanical Behavior ◽  
Significant Difference ◽  
Flexion Extension

Abstract OBJECTIVE To study the biomechanical behavior of lumbar interbody instrumentation techniques using titanium cages as either transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF), with and without posterior pedicle fixation. METHODS Six fresh-frozen lumbar spines (L1–L5) were loaded with pure moments of ±7.5 Nm in unconstrained flexion-extension, lateral bending, and axial rotation. Specimen were tested intact, after implantation of an ALIF or TLIF cage “stand-alone” in L2–L3 or L3–L4, and after additional posterior pedicle screw fixation. RESULTS In all loading directions, the range of motion (ROM) of the segments instrumented with cage and pedicle screw fixation was below the ROM of the intact lumbar specimen for both instrumentation techniques. A significant difference was found between the TLIF cage and the ALIF cage with posterior pedicle screw fixation for the ROM in flexion-extension and axial rotation (P&lt; 0.05). Without pedicle screw fixation, the TLIF cage showed a significantly increased ROM and neutral zone compared with an ALIF cage “stand-alone” in two of the three loading directions (P&lt; 0.05). CONCLUSION With pedicle screw fixation, the ALIF cage provides a higher segmental stability than the TLIF cage in flexion-extension and axial rotation, but the absolute biomechanical differences are minor. The different cage design and approach show only minor differences of segmental stability when combined with posterior pedicle screw fixation.

Cable-Strengthened C2 Pedicle Screw Fixation in the Treatment of Congenital C2-3 Fusion, Atlas Occipitalization, and Atlantoaxial Dislocation

Neurosurgery ◽  
2012 ◽  
Vol 71 (5) ◽  
pp. 976-984 ◽  
Author(s):  
Shenglin Wang ◽  
Chao Wang ◽  
Huijie Leng ◽  
Weidong Zhao ◽  
Ming Yan ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Pedicle Screw ◽  
Screw Fixation ◽  
Pedicle Screws ◽  
Pedicle Screw Fixation ◽  
Atlantoaxial Dislocation ◽  
C2 Pedicle Screw ◽  
Significant Difference ◽  
Solid Fusion ◽  
C2 Fixation

Abstract BACKGROUND: Atlas occipitalization and congenital C2-3 fusion often result in atlantoaxial dislocation (AAD) and superior odontoid migration that requires occipitocervical fixation. The widely used technique is posterior occiput-C2 fixation with pedicle screws. However, congenital C2-3 fusion cases tend to have thinner C2 pedicles that are inadequate for normal-sized pedicle screw fixation. With the presence of AAD, the strength of the fixation is further compromised as the C2 pedicle screws (C2PS) sustain considerable cephalic shearing force during the reduction procedure. Therefore, a novel technique has been developed to augment the C2 pedicle screw fixation with a strengthening cable. OBJECTIVE: To introduce and assess this new technique. METHODS: Seventy-six patients who underwent this procedure were reviewed. The position of the instrument and resultant fusion were examined retrospectively. In the biomechanical test, 6 fresh specimens were subjected to 2 types of fixation in the order of Oc-C2 screw-plate fixation followed by additional use of strengthening cable. Under 3 loading modes (extension-flexion, lateral bending, and axial rotation), the relative movement between the occiput and C2 was measured and compared in the form of range of motion. RESULTS: The average follow-up time was 26 months. Solid fusion was achieved in 75 patients (98.7%) as assessed radiologically. The only patient who experienced hardware failure eventually obtained solid fusion between the occiput and C2 after revision. Biomechanically, there was significant difference between the occiput and C2 fixation and cable-strengthened fixation in range of motion for all modes. CONCLUSION: This technique is a promising option for the treatment of AAD with congenital C2-3 fusion and occipitalization. Biomechanically, this technique can reduce the occipital-axial motion significantly compared with occiput-C2 fixation.

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