Biomechanical Characteristics of Hybrid Hook-Screw Constructs in Short-Segment Thoracic Fixation

Ex vivo biomechanical testing of human cadaveric thoracic spine segments. To determine whether a hybrid construct, using a combination of pedicle screws (PSs) and lamina hooks, was equivalent to a PS construct, in a short-segment thoracic spine fixation model. Comparisons have been made among PS, la...

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Bibliographic Details
Published in:Spine (Philadelphia, Pa. 1976) Pa. 1976), 2008-01, Vol.33 (2), p.173-177
Main Authors: ALEXANDER JONES, G, KAYANJA, Mark, MILKS, Ryan, LIEBERMAN, Isador
Format: Article
Language:English
Subjects:
Biological and medical sciences
Bone Density
Bone Screws
Cadaver
Cerebrospinal fluid. Meninges. Spinal cord
Elasticity
Equipment Failure Analysis
Humans
Internal Fixators
Medical sciences
Nervous system (semeiology, syndromes)
Neurology
Orthopedic surgery
Prosthesis Design
Prosthesis Failure
Radiography
Spinal Fusion - instrumentation
Stress, Mechanical
Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases
Thoracic Vertebrae - diagnostic imaging
Thoracic Vertebrae - surgery
Weight-Bearing
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Summary:Ex vivo biomechanical testing of human cadaveric thoracic spine segments. To determine whether a hybrid construct, using a combination of pedicle screws (PSs) and lamina hooks, was equivalent to a PS construct, in a short-segment thoracic spine fixation model. Comparisons have been made among PS, lamina hook, and hybrid screw-hook constructs, but these have generally been in long-segment scoliosis correction. In this study, we compared the hybrid and screw-only constructs in a short-segment thoracic fixation. For pullout testing, matched specimens were used for PS (n = 8) and hybrid (n = 8) constructs. Construct stiffness, and the force required for construct failure, were measured. Dynamic testing was carried out on specimens in the PS (n = 7) and hybrid (n = 7) groups in compression, flexion, extension, and left and right lateral bending. Each group was tested intact, after instrumentation, and after corpectomy. When compared with the hybrid group, a significantly greater force was required for construct failure in the PS group, and these PS constructs were significantly stiffer. No differences were found between groups in dynamic testing. A construct employing PSs is significantly stiffer and more resistant to pullout failure than a hook-screw hybrid construct.
ISSN:0362-2436
1528-1159
DOI:10.1097/BRS.0b013e31816044b6