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Updated: Nov 2, 2025
Subject-specific Musculoskeletal Model for Studying Bone Strain During Dynamic Motion
Published on: April 11, 2018
A Biomechanical Model for Testing Cage Subsidence in Spine Specimens with Osteopenia or Osteoporosis Under Permanent
Stefan Schleifenbaum1, Robin Heilmann1, Elena Riemer1
1Zentrum zur Erforschung der Stuetz- und Bewegungsorgane, University of Leipzig, Leipzig, Germany; Department of Orthopedic, Trauma and Plastic Surgery, University Hospital Leipzig, Leipzig, Germany.
Background:
Intervertebral fusions in cases of reduced bone density are a tough challenge. From a biomechanical point of view, most current studies have focused on the range of motion or have shown test setups for single-component tests. Definitive setups for biomechanical testing of the primary stability of a 360° fusion using a screw-rod system and cage on osteoporotic spine are missing. The aim of this study was to develop a test stand to provide information about the bone-implant interface under reproducible conditions.
Methods:
After pretesting with artificial bone, functional spine units were tested with 360° fusion in the transforaminal lumbar interbody fusion technique. The movement sequences were conducted in flexion/extension, right and left lateral bending, and right and left axial rotation on a human model with osteopenia or osteoporosis under permanent maximum load with 7.5 N-m.
Results:
During the testing of human cadavers, 4 vertebrae were fully tested and were inconspicuous even after radiological and macroscopic examination. One vertebra showed a subsidence of 2 mm, and 1 vertebra had a cage collapsed into the vertebra.
Conclusions:
This setup is suitable for biomechanical testing of cyclical continuous loads on the spine with reduced bone quality or osteoporosis. The embedding method is stable and ensures a purely single-level setup with different trajectories, especially when using the cortical bone trajectory. Optical monitoring provides a very accurate indication of cage movement, which correlates with the macroscopic and radiological results.
