Related Experiment Video
Updated: Aug 10, 2026

Creating Rigidly Stabilized Fractures for Assessing Intramembranous Ossification, Distraction Osteogenesis, or Healing of Critical Sized Defects
Published on: April 11, 2012
Biomechanics of long segment fixation: hook patterns and rod strain
T J Choma1, D Chwirut, D W Polly
1Orthopaedic Surgery Service, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA.
Abstract:
This is an in vitro study of the mechanical effects of varying hook attachment patterns in long segment kyphotic deformity. In such cases, the optimal implant bulk, fatigue life, and construct rigidity to reliably achieve fusion are still unquantified. Rod strains were measured for multiple laminar hook patterns in a synthetic thoracic spine test bed. Stresses were calculated from strain data. The model displayed similar flexion bending stiffness to the thoracic spine. None of the hook patterns significantly changed overall construct stiffness. Greatest rod strains were seen when utilizing away-facing apical hooks. This model was too stiff to detect differences in construct stiffness. Nonetheless, rod stress analysis showed that for multisegment thoracic constructs, particularly with fixed kyphosis, minimizing apical hooks will minimize rod strain. If periapical hooks are necessary, orienting the hooks toward the apex will minimize rod strain.
Related Concept Videos
Applications of Stress
The...
Normal Strain under Axial Loading
Deformation of Member under Multiple Loadings
In the case of a member with a variable cross-section, the strain is not constant but depends on the position. The deformation of an...
Stability of structures
Strain Energy
Consider a rod that is fixed at one end and subjected to an axial force at the free end. This axial force induces stress within the rod, leading to its elongation. As the axial force increases, so does the elongation of the rod, illustrating a direct relationship between the force applied and the resulting...
Impact Loading
In cases of elastic deformation,...

