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Augmentation of an anterior solid rod construct with threaded cortical bone dowels. A biomechanical study
D A Spiegel1, D S Drummond, B W Cunningham
1Children's Hospital of Philadelphia, Pennsylvania, USA.
Spine
|December 10, 1999
Summary
Solid disc space implants significantly increased spinal construct stiffness in a bovine model, enhancing lordosis and potentially improving fusion rates. This anterior instrumentation proved superior to posterior constructs in most biomechanical tests.
Area of Science:
- Biomechanical study of spinal instrumentation.
- In vitro analysis of anterior and posterior spinal constructs.
Background:
- Anterior instrumentation for scoliosis offers improved correction but risks kyphosis and nonunion.
- Posterior segmental spinal instrumentation is a common alternative.
Purpose of the Study:
- To evaluate if multilevel solid disc space implants enhance construct rigidity.
- To assess maintenance or improvement of anterior column length with implants.
Main Methods:
- Static, nondestructive biomechanical testing of 15 calf spines.
- Comparison of anterior constructs (rod/rib graft vs. rod/dowels) and posterior constructs (rod vs. rod/anterior release/graft).
- Mechanical tests included axial compression, rotation, flexion/extension, and lateral bending.
Main Results:
- The anterior rod/dowel construct demonstrated superior stiffness in axial compression, flexion/extension, and lateral bending compared to other anterior and posterior constructs.
- All reconstructions restored stiffness to intact levels, except for dowels alone in axial rotation.
- Anterior dowels promoted greater lordosis than rib grafts.
Conclusions:
- Disc space augmentation with solid implants increases spinal construct stiffness, except in axial rotation.
- This anterior approach offers biomechanical advantages over posterior instrumentation, particularly after anterior release.
- Enhanced rigidity and lordosis may improve arthrodesis rates and maintain sagittal alignment.