{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T17:22:05Z","timestamp":1770744125982,"version":"3.49.0"},"reference-count":25,"publisher":"Journal of Neurosurgery Publishing Group (JNSPG)","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["SPI"],"published-print":{"date-parts":[[2016,6]]},"abstract":"<jats:sec>\n<jats:title>OBJECTIVE<\/jats:title>\n<jats:p>In the management of isthmic spondylolisthesis, the pedicle screw system is widely accepted surgical strategy; however, there are few reports on the biomechanical behavior of pedicle screws in spondylolytic vertebrae. The purpose of the present study was to compare fixation strength between pedicle screws inserted through the traditional trajectory (TT) and those inserted through a cortical bone trajectory (CBT) in spondylolytic vertebrae by computational simulation.<\/jats:p><\/jats:sec>\n<jats:sec>\n<jats:title>METHODS<\/jats:title>\n<jats:p>Finite element models of spondylolytic and normal vertebrae were created from CT scans of 17 patients with adult isthmic spondylolisthesis (mean age 54.6 years, 10 men and 7 women). Each vertebral model was implanted with pedicle screws using TT and CBT techniques and compared between two groups. First, fixation strength of a single screw was evaluated by measuring axial pullout strength. Next, vertebral fixation strength of a paired-screw construct was examined by applying forces simulating flexion, extension, lateral bending, and axial rotation to vertebrae.<\/jats:p><\/jats:sec>\n<jats:sec>\n<jats:title>RESULTS<\/jats:title>\n<jats:p>Fixation strengths of TT screws showed a nonsignificant difference between the spondylolytic and the normal vertebrae (p = 0.31\u20130.81). Fixation strength of CBT screws in the spondylolytic vertebrae demonstrated a statistically significant decrease in pullout strength (21.4%, p &lt; 0.01), flexion (44.1%, p &lt; 0.01), extension (40.9%, p &lt; 0.01), lateral bending (38.3%, p &lt; 0.01), and axial rotation (28.1%, p &lt; 0.05) compared with those in the normal vertebrae. In the spondylolytic vertebrae, no statistically significant difference was observed for pullout strength between TT and CBT (p = 0.90); however, the CBT construct showed lower vertebral fixation strength in flexion (39.0%, p &lt; 0.01), extension (35.6%, p &lt; 0.01), lateral bending (50.7%, p &lt; 0.01), and axial rotation (59.3%, p &lt; 0.01) compared with the TT construct.<\/jats:p><\/jats:sec>\n<jats:sec>\n<jats:title>CONCLUSIONS<\/jats:title>\n<jats:p>CBT screws are less optimal for stabilizing the spondylolytic vertebra due to their lower fixation strength compared with TT screws.<\/jats:p><\/jats:sec>","DOI":"10.3171\/2015.11.spine15926","type":"journal-article","created":{"date-parts":[[2016,2,19]],"date-time":"2016-02-19T15:01:49Z","timestamp":1455894109000},"page":"910-915","source":"Crossref","is-referenced-by-count":52,"title":["Biomechanical evaluation of lumbar pedicle screws in spondylolytic vertebrae: comparison of fixation strength between the traditional trajectory and a cortical bone trajectory"],"prefix":"10.3171","volume":"24","author":[{"given":"Keitaro","family":"Matsukawa","sequence":"first","affiliation":[{"name":"Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yoshiyuki","family":"Yato","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, National Hospital Organization, Murayama Medical Center, Musashimurayama, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hideaki","family":"Imabayashi","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Naobumi","family":"Hosogane","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takashi","family":"Asazuma","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, National Hospital Organization, Murayama Medical Center, Musashimurayama, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kazuhiro","family":"Chiba","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama; and"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1754","reference":[{"key":"b1-spine15926","series-title":"Spine (Phila Pa 1976)","doi-asserted-by":"publisher","first-page":"E1297","DOI":"10.1097\/BRS.0000000000000553","article-title":"Effect of physiological loads on cortical and traditional pedicle screw fixation","volume":"39","author":"Baluch","year":"2014"},{"key":"b2-spine15926","series-title":"J Spinal Disord Tech","article-title":"Minimizing pedicle screw pullout risks: a detailed biomechanical analysis of screw design and placement","author":"Bianco","year":"2014"},{"key":"b3-spine15926","series-title":"Med Eng Phys","doi-asserted-by":"publisher","first-page":"275","DOI":"10.1016\/S1350-4533(02)00219-9","article-title":"Biomechanical investigation of pedicle screw-vertebrae complex: a finite element approach using bonded and contact interface conditions","volume":"25","author":"Chen","year":"2003"},{"key":"b4-spine15926","series-title":"J Spinal Disord Tech","doi-asserted-by":"publisher","first-page":"260","DOI":"10.1097\/BSD.0b013e3182417103","article-title":"What is the optimum fusion technique for adult isthmic spondylolisthesis\u2014PLIF or PLF? 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