Fully threaded sacroiliac lag screws have higher load to failure when compared to partially threaded screws: A biomechanical study |
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| Institution: | 1. R Adams Cowley Shock Trauma Center, Department of Orthopaedics, University of Maryland Medical Center, Baltimore, MD, USA;2. Department of Orthopaedic Surgery and Rehabilitation Medicine, SUNY Downstate Medical Center, Brooklyn, NY, USA;1. Department of Orthopaedics, All India Institute of Medical Sciences, Bathinda, Punjab, 151001, India;2. Department of Orthopaedics, All India Institute of Medical Sciences, Bhubaneswar, Odisha, 751019, India;3. Muskuloskelettales Zentrum Klinikum Neumarkt, Akademisches Lehrkrankenhaus der Friedrich-Alexander-Universität Erlangen-Nürnberg, Nürnberger Str. 12, D-92318, Neumarkt i. d. OPf., Germany;4. Orthopaedic Surgery, Manipal Hospitals, Bangalore, India;5. Institute of Orthopedic Surgery, Max Super Speciality Hospital, Mohali, India;1. The North West Pelvic and Acetabular Surgery Service, Wrightington Hospital, Salford Royal Hospital, Manchester Royal Infirmary, United Kingdom;2. Salford Royal Hospital, United Kingdom;1. Krishna Institute of Medical Sciences, Hyderabad, India;2. Orthopaedics, ESIC Medical College, Hyderabad, India;1. Hi-Tech Medical College, Pandara, Bhubaneswar, Odisha, 751025, India;2. Pelvic and Acetabular Reconstruction Unit, Southmead Hospital, Bristol, BS10 5NB, UK;3. Sardar Vallabhbhai Patel Institute of Medical Sciences and Research Hospital, Smt. NHL Municipal Medical College, Ellis Bridge, Ahmedabad, Gujarat, 380006, India;1. Department of Orthopaedics PGIMER, Chandigarh, India;2. Department of Pulmonary Medicine PGIMER, Chandigarh, India;3. Department of Anaesthesia and Intensive Care, PGIMER, Chandigarh, India;4. Department of Radiodiagnosis and Imaging, PGIMER, Chandigarh, India;5. Department of General Surgery PGIMER, Chandigarh, India |
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| Abstract: | The purpose of this study is to compare biomechanical properties of fully and partially threaded iliosacral screws. We hypothesise that fully threaded screws will have a higher yield force, and less deformation than partially threaded screws following axial loading. Twenty sawbone blocks were uniformly divided to simulate vertical sacral fractures. Ten blocks were affixed with fully threaded iliosacral screws in an over-drilled, lag-by-technique fashion whilst the remaining ten were fixed with partially threaded lag-by-design screws. All screws measured 7.3-mm x 145 mm, and were inserted to a 70% of calculated maximal insertional torque, ensuring uniform screw placement throughout across models. Continuous axial loads were applied to 3 constructs of each type to failure to determine baseline characteristics. Five hundred loading cycles of 500 N at 1 Hz were applied to 4 constructs of each type, and then axially loaded to failure. Force displacement curves, elastic, and plastic deformation of each construct was recorded. Fully threaded constructs had a 428% higher yield force, 61% higher stiffness, 125% higher ultimate force, and 66% lower yield deformation (p < 0.05). The average plastic deformation for partially threaded constructs was 336% higher than fully threaded constructs (p = 0.071), the final elastic deflection was 10% higher (p = 0.248), and the average total movement was 21% higher (p = 0.107). We conclude from this biomechanical study that fully threaded, lag-by-technique iliosacral screws can withstand significantly higher axial loads to failure than partially threaded screws. In addition, fully threaded screws trended towards exhibiting a significantly lower plastic deformation following cyclical loading. |
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| Keywords: | Trans-iliac Trans-sacral Fully threaded Partially threaded Lag screw Pelvic ring Sacral |
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