• Andrea Luca, Claudia Ottardi, Alessio Lovi, Marco Brayda-Bruno, Tomaso Villa, and Fabio Galbusera.
• Department of Spine Surgery III, IRCCS Istituto Ortopedico Galeazzi, Milan, Italy. aluca.md@gmail.com.
• Eur Spine J. 2017 Oct 1; 26 (Suppl 4): 450-456.

Study DesignThe investigation was based on finite-element simulations.ObjectivePedicle subtraction osteotomy (PSO) is an effective but technical demanding surgical technique, associated with a high risk of rod failure. The present study aims at investigating the role of the anterior support in combination with PSO, with a numerical comparative analysis.MethodsAn osteotomy was simulated at the L3 level of a lumbosacral spine. An implantation of various combinations of devices for the anterior (1 or 2 cages of different material) and posterior stabilization (1 or 2 rods) was then performed. ROM, loads, and stresses acting on the rods were calculated.ResultsA 4-8% reduction of the ROM was obtained introducing one or two cages in the instrumented model. However, the anterior support had only a minor influence on the ROM. The load on the posterior instrumentation decreased up to 8% using one cage and about 15% with two anterior devices. A 20-30% reduction of the stresses on the rods was calculated inserting one cage and up to 50% using two cages. Following the introduction of the anterior support, the greatest stress reduction was observed in the model having two cages and spinal fixators with two rods.ConclusionsThe use of cages is crucial to ensure anterior support and decrease loads and stresses on the posterior instrumentation.

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