{
  "abstract": "Objective: While pedicle screw placement at the fracture level improves stability in short-segment posterior instrumentation for thoracolumbar fractures, the optimal screw length remains controversial. The biomechanical effect of screw length at the fracture level has not been clearly defined under controlled conditions. This study compared short (≤50% vertebral body length) and long (≥70%) screws in a sheep burst fracture model.\n\nMethods: Twenty-one fresh sheep thoracolumbar spines with experimentally induced L1 burst fractures (AO Type A4) were randomly divided into 3 groups: Group 1 (no fracture-level screw), Group 2 (short screws: ≤ 50% of the vertebral body length [20 mm]), and Group 3 (long screws: ≥ 70% of the body length [35 mm]). All specimens were instrumented with pedicle screw constructs. Stability was assessed under axial compression, flexion–extension, lateral bending, and axial rotation using a Shimadzu AG-X testing machine (Kyoto, Japan). Axial displacement was recorded to derive range of motion (ROM) as a primary indicator of construct stability. Post-hoc power analysis revealed 58% power to detect a 0.5 mm displacement difference; therefore, results are interpreted as “no statistically significant difference” rather than equivalence.\n\nResults: Incorporating a fracture-level screw significantly improved stability vs. Group 1 (P < .01). No significant differences were observed between short and long screws in axial compression ROM (0.91 ± 0.19 mm vs. 0.89 ± 0.26 mm, P = .87), flexion/extension ROM (1.41 ± 0.20 mm [3.2° ± 0.5°] vs. 1.17 ± 0.24 mm [2.7° ± 0.6°], P = .12), lateral bending ROM (1.27 ± 0.31 mm [2.9° ± 0.7°] vs. 0.88 ± 0.11 mm [2.0° ± 0.3°], P = .09), or axial rotation failure displacement (80.44 ± 41.31 mm vs. 71.44 ± 29.51 mm, P = .23). Fragment displacement was significantly greater in the long-screw group (3.51 ± 1.25 mm) than in the short-screw group (0.00 ± 0.00 mm, P < .001).\n\nConclusion: Within the limitations of this sheep model and with only 58% power to detect a 0.5 mm difference, short screws (≤50% vertebral body length) demonstrated no statistically significant difference in biomechanical stability compared to long screws (≥70%) in short segment posterior fixation under the tested conditions. However, long screws were associated with significant anterior fragment displacement, a potentially clinically relevant finding requiring further computed tomography (CT)-based validation. These findings suggest a potential advantage of short screws in avoiding anterior fragment displacement without compromising biomechanical stability. However, given the study’s power limitations and the absence of CT-based fragment displacement validation, these results are preliminary. Clinical recommendations require confirmation in adequately powered human studies with formal equivalence testing and post-instrumentation CT imaging.\n\nCite this article as: Aydemir S, Ozturk AM, Karakasli A, et al. Length of the fractured level screw has no significant effect on biomechanical stability in shortsegment thoracolumbar fixation—in vitro biomechanical study in a sheep model. Acta Orthop Traumatol Turc., 2026; 60(5), 01021, doi: 10.5152/j.aott.2026.261021.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Orthopedics and Traumatology, İzmir American Hospital, İzmir, Türkiye",
    "Department of Orthopaedics and Traumatology, Ege University School of Medicine, İzmir, Türkiye",
    "Department of Orthopaedics and Traumatology, Dokuz Eylül University School of Medicine, İzmir, Türkiye",
    "Department of Biomechanics, Dokuz Eylül University, İzmir, Türkiye",
    "Department of Orthopaedics and Traumatology, Ankara Oncology Research and Training Hospital, Ankara, Türkiye",
    "Department of Orthopaedics and Traumatology, İzmir City Hospital, İzmir, Türkiye"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 7,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Selahaddin Aydemir",
      "orcid": "0000-0002-4201-8239"
    },
    {
      "affs": [
        1
      ],
      "name": "Anıl Murat Öztürk",
      "orcid": "0000-0001-8674-8877"
    },
    {
      "affs": [
        2
      ],
      "name": "Ahmet Karakaşlı",
      "orcid": "0000-0003-4049-954X"
    },
    {
      "affs": [
        3
      ],
      "name": "Reşit Buğra Hüsemoğlu",
      "orcid": "0000-0003-1979-160X"
    },
    {
      "affs": [
        4
      ],
      "name": "Mustafa Çeltik",
      "orcid": "0000-0002-0517-6684"
    },
    {
      "affs": [
        5
      ],
      "name": "Onur Süer",
      "orcid": "0000-0002-6751-0705"
    },
    {
      "affs": [
        2
      ],
      "name": "Ömer Akçalı",
      "orcid": "0000-0002-2823-2001"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/45s87g2wkkp2y.bib",
  "cited_by": 0,
  "doi": "10.5152/j.aott.2026.261021",
  "fulltext_url": "https://www.aott.org.tr/index.php/pub/article/view/4231",
  "id": "45s87g2wkkp2y",
  "issns": [
    "1017-995X",
    "2589-1294"
  ],
  "landing_url": "https://doi.org/10.5152/j.aott.2026.261021",
  "language": "en",
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
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      "2746|Spinal Fractures and Fixation Techniques"
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  "openalex": "W7223565938",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-23",
  "publisher": "Turkish Association of Orthopaedics and Traumatology",
  "ris": "https://research.draconitic.com/paper/45s87g2wkkp2y.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T13:44:25Z",
      "native_id": "cab2265d0c9844e0bf528203142a7998",
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  ],
  "title": "Length of the fractured level screw has no significant effect on biomechanical stability in short-segment thoracolumbar fixation—in vitro biomechanical study in a sheep model",
  "title_text": "Length of the fractured level screw has no significant effect on biomechanical stability in short-segment thoracolumbar fixation—in vitro biomechanical study in a sheep model",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T13:44:25Z",
  "url": "https://research.draconitic.com/paper/45s87g2wkkp2y",
  "venue": "Acta Orthopaedica et Traumatologica Turcica",
  "versions": []
}