Related Experiment Video
Updated: Aug 16, 2026

Method to Measure Tone of Axial and Proximal Muscle
Published on: December 14, 2011
Torsional stability of cross-link configurations: a biomechanical analysis
Antonio Valdevit1, Helen E Kambic, Robert F McLain
1Department of Biomedical Engineering, The Cleveland Clinic Foundation, OH 44195, USA.
Background Context:
Cross-link systems have been used to augment segmental spinal instrumentation since the earliest introduction of these fixation systems. Although transverse cross-links have little impact on sagittal motion of spinal constructs, cross-linkage does affect torsional rigidity. Despite the wide variety of cross-link designs, almost all have been configured as transverse devices. The relative mechanical benefit of different cross-link configurations is not known.
Purpose:
The purpose of this study was to compare the torsional stability of three different cross-link configurations.
Study Design:
Biomechanical analysis of segmental instrumentation constructs using porcine spines.
Methods:
Thoracic porcine spines (T4 to T10) were instrumented with 6.5-mm conical pedicle screws and 7.0-mm connecting rods from T5 to T9. Terminal vertebrae were embedded in polymethylmethacrylate (PMMA) after a T7 corpectomy. Four cross-link configurations were tested in a randomized manner: Un-cross-linked Control (CONT); Transverse Rod-Rod (RR); Transverse Screw-Screw (SS); and Diagonal Screw-Screw (DX) Cross-links. The specimens were rotated to 3 Nm at a rate of 0.2 degrees/s and cycled six times with data acquisition over the final two cycles. Stiffness, rotation, and energy data were normalized to each control. A Newman-Keuls repeated measures analysis of variance was used to infer significant differences.
Results:
Diagonal cross-link configurations provided the most rigid construct. Transverse cross-links did not significantly change torsional behavior compared with the unlinked control. Rotation and energy expended were not significantly greater torsional stiffness compared with other constructs tested (p<.01).
Conclusions:
The diagonal cross-link configuration provided increased torsional stiffness as compared with unlinked or transverse configurations. This observation should be considered in future cross-link designs.
Related Concept Videos
Stability of structures
Torsion of Noncircular Members
Eccentric Axial Loading in a Plane of Symmetry
Thin-Walled Hollow Shafts
Symmetric Member in Bending
Design of Transmission Shafts - Stress Analysis

