The minipig as a potential model for pedicle screw fixation: morphometry and mechanics
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(2019) 14:246
RESEARCH ARTICLE
Open Access
The minipig as a potential model for pedicle screw fixation: morphometry and mechanics Robert A. Harper1, Ferris M. Pfeiffer2 and Theodore J. Choma3*
Abstract Background: While there are several different animal models for use in the characterization of spinal fixation, none have emerged as a definitive model for comparative studies in spinal fixation methods. The purpose of this study is to establish morphometric data of porcine vertebrae and to characterize the feasibility of pedicle screw fixation in porcine spines for potential comparative human study. Methods: Four spines from 45 to 50 kg Hanford minipigs were cleaned of soft tissue and analyzed by computed tomography and dual-energy x-ray absorptiometry. Two 5 × 30-mm pedicle screws were placed in each vertebra and tested to failure using a combined moment-load protocol. Results: Pedicle widths were measured from L6-T5. Widths ranged from 7.15 mm (T6) to 9.24 mm (T14). Posterior cortex to anterior cortex depth ranged from 25.9 to 32.6 mm. Mean bone mineral density was 1.0665 g/cm2 (range 1.139–1.016). Force-to-failure demonstrated mean 1171.40 N (+ 115.34). Conclusion: Our baseline morphometric and compositional data demonstrate that porcine vertebrae can serve as a useful model for comparative studies due to their similar pedicle widths and bone mineral density to the human vertebra. This biomechanical data could provide a baseline comparison for future studies. This study also suggests that the minipig could be a suitable model for comparative studies due to similarities in pedicle width and bone mineral density to the human vertebrae. Keywords: Bone mineral density, Pedicle screw, Morphometric characterization, Spinal fixation, Biomechanical analysis, Porcine vertebra model
Introduction There is no generally accepted single animal model for spinal fixation methods. Several different study animals have been used in the characterization of spinal fixation, including sheep [1, 2], cow [3–7], and pig [8], but none has emerged as a gold standard for comparative study. The minipig is an established research animal for comparative human studies in areas as diverse as dermatology [9], endocrinology/diabetes [10], cardiology [11], immunology [12], pharmacology [13], and toxicology [14] due to similarities to human systems. The porcine * Correspondence: [email protected] This study was presented as a poster at the One AO Meeting in Las Vegas, NV, in February 2015. 3 Department of Orthopaedic Surgery, University of Missouri, 1100 Virginia Avenue DC953.00, Columbia, MO 65212, USA Full list of author information is available at the end of the article
spine may also be an important model for human spinal fixation and instrumentation techniques. McClain et al. found key similarities of porcine to the human vertebra in their analysis of the morphometry of the L4 vertebra in several large animal species [15]. Dath et al. compiled a database of porcine vertebral measurements—including pedicle width, end plate size, a
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