Perbandingan pullout strength sekrup pedikel antara lintasan konvensional, lintasan kortikal infero-superior, dan lintasan kortikal supero-inferior pada lumbal babi Yorkshire: suatu studi biomekanik = Pedicle screw pullout strength comparison between conventional pedicle screw trajectory, cortical infero-superior trajectory, and cortical supero-inferior trajectory in yorkshire lumbar porcine: a biomechanical study