• Yuichi Kasai, Permsak Paholpak, Kriengkrai Nabudda, Taweechok Wisanuyotin, Winai Sirichativapee, Weerachai Kosuwon, Tetsutaro Mizuno, and Takaya Kato.
• Department of Orthopaedics, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
• Spine. 2020 Nov 1; 45 (21): E1386-E1390.

Study DesignAn in vitro biomechanical study.ObjectiveThe purpose of this study is to discuss whether pedicle screw systems can control spinal rotational instability in a functional spinal unit of lumbar spine on human cadaver.Summary Of Background DataRotational experiments using deer lumbar cadaveric models showed that rotational range of motion (ROM) of the model fixed by a pedicle screw system with crosslinking after total facetectomy for both the sides was larger than that in the intact model, and stated that spinal rotational instability could not be controlled using a pedicle screw system.MethodsA rotation experiment using 10 functional spinal units (L3-4) of lumbar spine on human cadavers was performed by preparing the four models (intact model, damaged model, pedicle screw model, and crosslink (CL) model) in stages, then calculating and comparing rotational ROM among the four models.ResultsRotational ROM in the CL model was still larger than that of the intact model in all the samples. And, rotational ROM decreased in the order of damaged model > pedicle screw model > CL model > intact model. Statistical analysis revealed significant differences between all models (P < 0.001).ConclusionsPedicle screw systems may not control severe spinal rotational instability in human lumbar cadaveric models with total facetectomy on both the sides. This may represent a major biomechanical drawback to the pedicle screw system.Level Of EvidenceN/A.

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