Biomechanical Testing of Posterior Atlantoaxial Fixation Techniques

✓ The biomechanical characteristics of four different methods of C1–2 cable fixation were studied to assess the effectiveness of each technique in restoring atlantoaxial stability. Biomechanical testing was performed on the upper cervical spines of four human cadaveric specimens. Physiological range loading was applied to the atlantoaxial specimens and three-dimensional motion was analyzed with stereophotogrammetry. The load–deformation relationships and kinematics were measured, including the stiffness, the angular ranges of motion, the linear ranges of motion, and the axes of rotation. Specimens were nondestructively tested in the intact state, after surgical destabilization, and after each of four different methods of cable fixation. Cable fixation techniques included the interspinous technique, the Brooks technique, and two variants of the Gallie technique. All specimens were tested immediately after fixation and again after the specimen was fatigued with 6000 cycles of physiological range torsional loading. All four cable fixation methods were moderately flexible immediately; the different cable fixations allowed between 5° and 40° of rotational motion and between 0.6 and 7 mm of translational motion to occur at C1–2. The Brooks and interspinous methods controlled C1–2 motion significantly better than both of the Gallie techniques. The motion allowed by one of the Gallie techniques did not differ significantly from the motion of the unfixed destabilized specimens. All cable fixation techniques loosened after cyclic loading and demonstrated significant increases in C1–2 rotational and translational motions. The bone grafts shifted during cyclic loading, which reduced the effectiveness of the fixation. The locations of the axes of rotation, which were unconstrained and mobile in the destabilized specimens, became altered with cable fixation. The C1–2 cables constrained motion by shifting the axes of rotation so that C-1 rotated around the fixed cable and graft site. After the specimen was fatigued, the axes of rotation became more widely dispersed but were usually still localized near the cable and graft site. Adequate healing requires satisfactory control of C1–2 motion. Therefore, some adjunctive fixation is advocated to supplement the control of motion after C1–2 cable fixation (that is, a cervical collar, a halo brace, or rigid internal fixation with transarticular screws).

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Salvage posterior atlantoaxial fixation techniques: A retrospective study

Neurocirugía ◽

10.1016/j.neucir.2021.08.002 ◽

2021 ◽

Author(s):

Mehmet Seçer ◽

Oğuz Durmuş Karakoyun ◽

Murat Ulutaş ◽

Aykut Gökbel ◽

Kadir Çınar ◽

...

Keyword(s):

Retrospective Study ◽

Fixation Techniques ◽

Atlantoaxial Fixation

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Atlantoaxial stabilization using multiaxial C-1 posterior arch screws

Journal of Neurosurgery Spine ◽

10.3171/spi.2008.10.08294 ◽

2008 ◽

Vol 9 (6) ◽

pp. 522-527 ◽

Cited By ~ 10

Author(s):

Michael B. Donnellan ◽

Ioannis G. Sergides ◽

William R. Sears

Keyword(s):

Clinical Results ◽

Posterior Arch ◽

Lateral Mass ◽

Normal Anatomy ◽

Novel Technique ◽

Vertebral Arteries ◽

Fixation Techniques ◽

Atlantoaxial Fixation ◽

Atlantoaxial Stabilization ◽

Lateral Mass Screws

The authors present a novel technique of atlantoaxial fixation using multiaxial C-1 posterior arch screws. The technique involves the insertion of bilateral multiaxial C-1 posterior arch screws, which are connected by crosslinked rods to bilateral multiaxial C-2 pars screws. The clinical results are presented in 3 patients in whom anomalies of the vertebral arteries, C-1 lateral masses, and/or posterior arch of C-1 presented difficulty using existing fixation techniques with transarticular screws, C-1 lateral mass screws, or posterior wiring. The C-1 posterior arch screws achieved solid fixation and their insertion appeared to be technically less demanding than that of transarticular or C-1 lateral mass screws. This technique may reduce the risk of complications compared with existing techniques, especially in patients with anatomical variants of the vertebral artery, C-1 lateral masses, or C-1 posterior arch. This technique may prove to be an attractive fixation option in patients with normal anatomy.

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Subaxial Sagittal Alignment After Atlantoaxial Fixation Techniques

Journal of Spinal Disorders & Techniques ◽

10.1097/bsd.0000000000000144 ◽

2015 ◽

Vol 28 (1) ◽

pp. E49-E55 ◽

Cited By ~ 16

Author(s):

Shigeki Oshima ◽

Hideki Sudo ◽

Manabu Ito ◽

Kuniyoshi Abumi

Keyword(s):

Sagittal Alignment ◽

Fixation Techniques ◽

Atlantoaxial Fixation

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Comparison of 2 plating techniques for lateral clavicle fractures, using a new standardized biomechanical testing setup

Journal of Applied Biomaterials & Functional Materials ◽

10.5301/jabfm.5000377 ◽

2017 ◽

Vol 16 (2) ◽

pp. 107-112

Author(s):

Cyrill Suter ◽

Martin Majewski ◽

Andrej M. Nowakowski

Keyword(s):

Standardized Testing ◽

Computer Aided Design ◽

Fatigue Testing ◽

Clavicle Fracture ◽

Biomechanical Testing ◽

Bending Test ◽

Plate Technique ◽

Lateral Clavicle ◽

Fixation Techniques ◽

Clavicle Fractures

Background: Conservative treatment of lateral clavicle fractures (Neer type II) often ends with unsatisfactory results for patients. Operative treatment is thus gaining acceptance. A retrospective study found success using a double plate technique for these injuries. For the current study, a standardized testing setup was developed to compare the mechanical properties of single versus double plate technique for lateral clavicle fractures. Methods: Six synthetic bones were tested for each technique. Neer type IIB fractures were created using computer-aided design (CAD). Fatigue testing was carried out with a cantilever bending test. Parameters measured were cycles undergone, failure load and stiffness at the point of failure. Results: The standardized testing setup was able to provide reproducible failures. The double plate technique lasted about 16,000 more cycles and withstood an additional 22.4 N on average. Conclusions: The new modified standardized testing setup produced reproducible fixation failures for both clavicle fracture fixation techniques. The double plate technique seems to be mechanically superior to the single plate technique.

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Restabilization of the Occipitocervical Junction After a Complete Unilateral Condylectomy: A Biomechanical Comparison of Unilateral and Bilateral Fixation Techniques

Operative Neurosurgery ◽

10.1093/ons/opz341 ◽

2019 ◽

Vol 19 (2) ◽

pp. 157-164 ◽

Cited By ~ 1

Author(s):

Ilyas M Eli ◽

Michael Karsy ◽

Darrel S Brodke ◽

Kent N Bachus ◽

William T Couldwell ◽

...

Keyword(s):

Biomechanical Testing ◽

Axial Rotation ◽

Neurological Injury ◽

Occipital Condyle ◽

Posterior Fixation ◽

Lateral Bending ◽

Flexion Extension ◽

Fixation Techniques ◽

The Difference ◽

Biomechanical Comparison

Abstract BACKGROUND Occipitocervical instability may result from transcondylar resection of the occipital condyle. Initially, patients may be able to maintain a neutral alignment but severe occipitoatlantal subluxation may subsequently occur, with cranial settling, spinal cord kinking, and neurological injury. OBJECTIVE To evaluate the ability of posterior fixation constructs to prevent progression to severe deformity after radical unilateral condylectomy. METHODS Eight human cadaveric specimens (Oc-C2) underwent biomechanical testing to compare stiffness under physiological loads (1.5 N m). A complete unilateral condylectomy was performed to destabilize one Oc-C1 joint, and the contralateral joint was left intact. Unilateral Oc-C1 or Oc-C2 constructs on the resected side and bilateral Oc-C1 or Oc-C2 constructs were tested. RESULTS The bilateral Oc-C2 construct provided the greatest stiffness, but the difference was only statistically significant in certain planes of motion. The unilateral constructs had similar stiffness in lateral bending, but the unilateral Oc-C1 construct was less stiff in axial rotation and flexion-extension than the unilateral Oc-C2 construct. The bilateral Oc-C2 construct was stiffer than the unilateral Oc-C2 construct in axial rotation and lateral bending, but there was no difference between these constructs in flexion-extension. CONCLUSION Patients who undergo a complete unilateral condylectomy require close surveillance for occipitocervical instability. A bilateral Oc-C2 construct provides suitable biomechanical strength, which is superior to other constructs. A unilateral construct decreases abnormal motion but lacks the stiffness of a bilateral construct. However, given that most patients undergo a partial condylectomy and only a small proportion of patients develop instability, there may be scenarios in which a unilateral construct may be appropriate, such as for temporary internal stabilization.

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Unilateral C-1 posterior arch screws and C-2 laminar screws combined with a 1-side C1–2 pedicle screw system as salvage fixation for atlantoaxial instability

Journal of Neurosurgery Spine ◽

10.3171/2015.4.spine14517 ◽

2016 ◽

Vol 24 (2) ◽

pp. 315-320 ◽

Cited By ~ 5

Author(s):

Jin Guo-Xin ◽

Wang Huan

Keyword(s):

Biomechanical Testing ◽

Pedicle Screws ◽

Atlantoaxial Instability ◽

Posterior Arch ◽

Lateral Bending ◽

Significant Difference ◽

Flexion Extension ◽

Intact Condition ◽

Atlantoaxial Fixation ◽

Group B

OBJECT Atlantoaxial instability often requires surgery, and the current methods for fixation pose some risk to vascular and neurological tissues. Thus, new effective and safer methods are needed for salvage operations. This study sought to assess unilateral C-1 posterior arch screws (PASs) and C-2 laminar screws (LSs) combined with 1-side C1–2 pedicle screws (PSs) for posterior C1–2 fixation using biomechanical testing with bilateral C1–2 PSs in a cadaveric model. METHODS Six fresh ligamentous human cervical spines were evaluated for their biomechanics. The cadaveric specimens were tested in their intact condition, stabilization after injury, and after injury at 1.5 Nm of pure moment in 6 directions. The 3 groups tested were bilateral C1–2 PSs (Group A); left side C1–2 PSs with an ipsilateral C-1 PAS + C-2 laminar screw (Group B); and left side C1–2 PSs with a contralateral C-1 PAS + C-2 LS (Group C). During the testing, angular motion was measured using a motion capture platform. Data were recorded, and statistical analyses were performed. RESULTS Biomechanical testing showed that there was no significant difference among the stabilities of these fixation systems in flexion-extension and rotation control. In left lateral bending, the bilateral C1–2 PS group decreased flexibility by 71.9% compared with the intact condition, the unilateral C1–2 PS and ipsilateral PAS+LS group decreased flexibility by 77.6%, and the unilateral C1–2 PS and contralateral PAS+LS group by 70.0%. Each method significantly decreased C1–2 movements in right lateral bending compared with the intact condition, and the bilateral C1–2 PS system was more stable than the C1–2 PS and contralateral PAS+LS system (p = 0.036). CONCLUSIONS A unilateral C-1 PAS + C-2 LS combined with 1-side C-1 PSs provided the same acute stability as the PS, and no statistically significant difference in acute stability was found between the 2 screw techniques. These methods may constitute an alternative method for posterior atlantoaxial fixation.

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