STUDY DESIGN: An in vitro biomechanical study. PURPOSE: To evaluate the mechanical properties of the spinal segment in the intact, injured, and stabilized state after fixation by an Arcofix implant. OVERVIEW OF LITERATURE: Several types of thoracolumbar spine injury necessitates anterior instrumentation. The Arcofix plate represents the latest generation of angular stablity systems. The biomechanical properties of these implants have not been sufficiently studied yet. METHODS: A total of ten porcine specimens (levels Th12-L3) were prepared. The tests were performed for intact, injured, and implanted specimens. In each state, the specimen was subjected to a tension load of a prescribed force, and subsequently, twisted by a given angle. The force load was 200 N. 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. The amplitude of the load alternating cycle was 3°. Another parameter that was evaluated was the area of the hysteresis loop. The area corresponds to the deformation energy which is dissipated during the cycle. RESULTS: A statistically significant difference was found between the intact and injured states as well as between the injured and implanted specimens. The statistical evaluation also showed a statistically different value of the hysteresis loop area. In the case of instability, the area decreased to 33% of the physiological value. For the implanted sample, the area increased to 170% of the physiological value. CONCLUSIONS: The Arcofix implant with its parameters appears to be suitable and sufficiently stable for the treatment of the anterior column of the spine.

Department of Traumatology Faculty of Medicine Masaryk University Brno Czech Republic

Institute of Solid Mechanics Mechatronics and Biomechanics Faculty of Mechanical Engineering Brno University of Technology Brno Czech Republic

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Faro FD, White KK, Ahn JS, et al. Biomechanical analysis of anterior instrumentation for lumbar corpectomy. Spine (Phila Pa 1976) 2003;28:E468–E471. PubMed

Flamme CH, Hurschler C, Heymann C, von der Heide N. Comparative biomechanical testing of anterior and posterior stabilization procedures. Spine (Phila Pa 1976) 2005;30:E352–E362. PubMed

Hitchon PW, Goel VK, Rogge TN, et al. In vitro biomechanical analysis of three anterior thoracolumbar implants. J Neurosurg. 2000;93:252–258. PubMed

Kocis J, Navrat T, Florian Z, Wendsche P. Biomechanical testing of spinal segment fixed by thoracolumbar spine locking plate on the swine lumbar spine. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2010;154:345–354. PubMed

Vesely R, Florian Z, Wendsche P, Tosovsky J. Biomechanical evaluation of the MACS-TL internal fixator for thoracic spinal stabilisation. Acta Vet Brno. 2008;77:97–102.

Vesely R, Wensche P, Kocis J. Instable fractures of upper thoracic spine (T1-T10) Urazova chirurgie [Trauma Surg] 2003;11:34–37.

Wilke HJ, Wenger K, Claes L. Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants. Eur Spine J. 1998;7:148–154. PubMed PMC

Panjabi MM. The stabilizing system of the spine. Part II: neutral zone and instability hypothesis. J Spinal Disord. 1992;5:390–396. PubMed

Panjabi MM. Clinical spinal instability and low back pain. J Electromyogr Kinesiol. 2003;13:371–379. PubMed

Allen MJ, Turner AS, Sairyo K, Ferrara L. Basic science symposium III: animal models for orthopaedic implant evaluation. SAS J. 2008;2:195–200. PubMed PMC

Kettler A, Liakos L, Haegele B, Wilke HJ. Are the spines of calf, pig and sheep suitable models for preclinical implant tests? Eur Spine J. 2007;16:2186–2192. PubMed PMC

Busscher I, van der Veen AJ, van Dieen JH, Kingma I, Verkerke GJ, Veldhuizen AG. In vitro biomechanical characteristics of the spine: a comparison between human and porcine spinal segments. Spine (Phila Pa 1976) 2010;35:E35–E42. PubMed

Kouwenhoven JW, Smit TH, van der Veen AJ, Kingma I, van Dieen JH, Castelein RM. Effects of dorsal versus ventral shear loads on the rotational stability of the thoracic spine: a biomechanical porcine and human cadaveric study. Spine (Phila Pa 1976) 2007;32:2545–2550. PubMed

Disch AC, Knop C, Schaser KD, Blauth M, Schmoelz W. Angular stable anterior plating following thoracolumbar corpectomy reveals superior segmental stability compared to conventional polyaxial plate fixation. Spine (Phila Pa 1976) 2008;33:1429–1437. PubMed