Biomechanical Evaluation of the MACSTL Internal Fixator for Thoracic Spinal Stabilisation

Abstract

Unstable fractures of the thoracic spine in humans represent a serious social and economic issue. They may lead to persistent consequences and chronic disease. The anatomical and biomechanical characteristics of the thoracic spine are different from all the other spinal parts due to its higher mobility. The vertebrae of the chest area are less mobile, conferring a higher degree of rigidity to the spine. To destabilize this relatively rigid system, a considerable force is necessary.The treatment of unstable spinal fractures is solely surgical. The decompression of the spinal canal with reposition and stabilisation of the fracture is indicated urgently. This intervention is performed mostly from the posterior approach in the first phase. However, the anterior spinal column is the structure responsible for the stability of the spine. Therefore, the recent advances in spine surgery focus on this area of expertise. For this reason, we carried out a bio-mechanical study aimed at assessing the effectiveness of two surgical tactics used. The study consisted of comparative experiments performed by computer-aided device on segments of pig cadavers (n = 5). The experiment involved a comparison of segments of the thoracic spine under the following conditions: an anatomically intact segment, a spine segment with an artificially created anterior instability, and a segment with an applied internal fixator. The experiment compared the mechanical characteristics of these segments.The experiment has demonstrated that after application of the internal fixator used for stabilisation of the injured anterior spinal column at defined pre-loading of 200 N, the stability of damaged spinal segment in torsion increased twofold. It was also verified that sufficient stability can be ensured using the Modular Anterior Construct System (MACS TL ) implant for ventral stabilisation of thoracic spine unstable injuries. Endoscopic application of this implant represents an additional advantage of this surgical procedure. Thoracic spine, unstable fractures, anterior approach, biomechanical study, swine, model Unstable fractures of the thoracic spine represent a serious social and economic issue in human medicine. On one hand, these injuries involving damage to the spinal cord can result in irreversible persistent consequences; on the other hand, such traumas with minimal force without radiographic signs develop into a chronic condition that can result in permanent disability.The thoracic spine is the longest section of the spine with a prevalence of trauma exposure, especially in its lower area. Anatomical and biomechanical characteristics of the thoracic spine differ from other, more flexible, sections of the spine. The chest limits motion and contributes greatly to spinal rigidity. This is obvious especially in extension movements. Flexion and lateral rotation in the thoracic area are, however, limited in comparison to other parts of the spine. Apart from the skeleton, the ligament apparatus is also important for spinal stability. In bio-mecha...

Biomechanical Testing of Spinal Segment Fixed by Arcofix System on the Swine Spine

“…For certain types of fractures or other disorders of the anterior column of the spine (including tumours, spondylodiscitis), isolated anterior stabilizing intervention is recommended when we perform a partial or complete corpectomy with the substitution of a vertebral body by a bone graft or other type of implant [ 1 2 3 4 5 6 ]. We use combined anterior and posterior stabilization, especially in cases when it is necessary to first influence a kyphotic deformity from behind and then to create conditions in the front for healing (desis).…”

“…Load values were defined based on experience with measurements of a similar nature. According to previous experiments [ 4 5 ], we determined the maximum safety force load to be 200 N. A higher load could lead to the specimen loosening from the duracryl block. The torsion load had a deformation character, i.e., the control variable was the twisting angle and the measured variable was the moment of a couple.…”

“…Forces along the long stiff kyphotic thoracic spine switch abruptly into the mobile losrdotic lumbar spine at the thoracolumbar junction. The anterior approach is recommended for reconstruction of the anterior spinal column, particularly in burst fractures of the thoracolumbar junction [ 1 2 3 4 5 6 ]. Arcofix (Synthes Inc., West Chester, PA, USA) represents the latest generation of angular stable plates for anterior spinal column stabilization.…”

Biomechanical Testing of Spinal Segment Fixed by Thoracolumbar Spine Locking Plate on the Swine Lumbar Spine

“…Posterior stabilization in unstable injuries of the thoracolumbar spine is regarded as a standard procedure 1,7 . On the basis of clinical and biomechanical investigations, a number of authors now advocate reconstructing the axial load -bearing ability of the anterior spine using different materials for vertebral body replacement [2][3][4][5] . The primary stability of ventral fixation system has been improved over the past years and special implants supporting minimally invasive procedures have been developed.…”

“…The reconstruction of the anterior column of the thoracolumbar spine has become more common in the last few years owing to disappointing results of exclusively posterior treatment that produce lack of about ten degrees of kyphosis correction after removal of the instrumentation 1 .There have been many biomechanical studies evaluating spinal reconstruction methods in corporectomy models 2,3 . Much of the biomechanical testing of spinal implants has used in vitro models [4][5][6] . Animal spines have been used as they are easier to obtain than human spines and can be selected by age and comparable size.…”