SYMPOSIA PAPER Published: 01 January 2003
STP11144S

Transverse Connectors: Clinical Objectives, Biomechanical Parameters Involved in Their Achievement, and Summary of Current and Needed In Vitro Tests

Source

The clinical objectives for using transverse connectors (TCs) on different implant constructs are compiled. Results from a survey of 2499 clinical cases, hand held-loaded models, linkage analysis, and finite element analysis were used to identify the important biomechanical characteristics and parameters of constructs affecting the need for a TC and of the TC itself that are involved in achieving the clinical objectives. These were compared to those tested in ASTM standards to evaluate existing and needed TC tests. Axial and torsional gripping characteristics of TC interconnections are adequately tested with ASTM F 1798-97. ASTM F 1717-01 axial test protocol can reveal the effect of TCs on the flexion fatigue life of longitudinal members, however the torsional test protocol results have questionable clinical relevance due to fixtures constraining 3 of 6 construct relative degrees-of-freedom. A substitute gimbal-gimbal or gimbal- pushrod fixture is proposed. The following are proposed to test TC characteristics that are not tested with current ASTM standards: an H construct for testing TC lateral bending characteristics, an unconstrained 3D test for transfixed thoracolumbar constructs having different combinations of hook-claw-wire and screw foundations, and a fixture to test torsional characteristics of constructs having sacroiliac foundations.

Author Information

Carson, WL
University of Missouri-Columbia, Columbia, Missouri, USA
Asher, MA
The University of Kansas Medical Center, Kansas City, Kansas, USA
Boachie-Adjai, O
The Hospital for Special Surgery, New York, New York, USA
Akbarnia, B
San Diego Center for Spinal Disorders, La Jolla, California, USA
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Details
Developed by Committee: F04
Pages: 191–208
DOI: 10.1520/STP11144S
ISBN-EB: 978-0-8031-5480-3
ISBN-13: 978-0-8031-3463-8