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Background. Anterolateral oblique corpectomy is an alternative approach to treatment of multilevel cervical spinal disease. It is stated that the approach does not cause instability in the patients with hard discs, so fusion or instrumentation is not required. The authors undertook a study on stability of the cervical spine by an animal model to establish if this approach causes instability.Material and methods. Thirty-seven C3 to C6 spinal segments obtained from 3 to 4-year-old male sheep were used.In vitromaximal loading values were obtained from seven sheep cervical specimens for flexion, extension, lateral flexion in both directions, axial rotation in both directions and axial loading, and load deformation curves were drawn by an electrohydrolic testing machine. Other specimens were divided into three groups: Control (n?=?10), C4 (n?=?10) and C4-5 (n?=?10) groups. In two study groups, one or two level oblique corpectomies were performed. In the control and study groups, biomechanical tests were obtained according to the maximal loading values. Load-deformation curves were drawn and displacement amounts were determined for all seven movements.Results. No statistically significant differences were observed in load deformation curves and displacement amounts between all three groups for seven movements.Conclusion. These results support the opinion that anterolateral oblique corpectomy does not cause cervical instability. [ABSTRACT FROM AUTHOR]

This study tries to explain the reason why the Jefferson fracture is a burst fracture, using two different biomechanical models: a finite element model (FEM) and a cadaver model used to determine strain distribution in C1 during axial static compressive loading. For the FEM model, a three-dimensional model of C1 was obtained from a 29-year-old healthy human, using axial CT scans with intervals of 1.0 mm. The mesh model was composed of 8200 four-noded isoparametric tetrahedrons and 37,400 solid elements. The material properties of the cortical bone of the vertebra were assessed according to the previous literature and were assumed to be linear isotropic and homogeneous for all elements. Axial static compressive loads were applied at between 200 and 1200 N. The strain and stress (maximum shear and von Mises) analyses were determined on the clinically relevant fracture lines of anterior and posterior arches. The results of the FEM were compared with a cadaver model. The latter comprised the C1 bone of a cadaver placed in a methylmethacrylate foam. Axial static compressive loads between 200 and 1200 N were applied by an electrohydraulic testing machine. Strain values were measured using strain gauges, which were cemented to the bone where the clinically relevant fracture lines of the anterior and posterior arches were located. As a result, compressive strain was observed on the outer surface of the anterior arch and inferior surface of the posterior arch. In addition, there was tensile strain on the inner surface of the anterior arch and superior surface of the posterior arch. The strain values obtained from the two experimental models showed similar trends. The FEM analysis revealed that maximum strain changes occurred where the maximum shear and von Mises stresses were concentrated. The changes in the C1 strain and stress values during static axial loading biomechanically prove that the Jefferson fracture is a burst fracture. [ABSTRACT FROM AUTHOR]