Related Experiment Video
Updated: Feb 12, 2026
Imaging of the Microstructural Failure Mechanism in the Human Hip
Published on: September 29, 2023
The Influence of Concordant Complex Posture and Loading Rate on Motion Segment Failure: A Mechanical and
Meredith L Schollum1, Kelly R Wade1, Zhi Shan2
1Department of Chemical and Materials Engineering, Experimental Tissue Mechanics Laboratory, University of Auckland, Auckland, New Zealand.
Study Design:
Microstructural investigation of compression-induced herniation of a lumbar disc held in a concordant complex posture.
Objective:
To explore the significance of loading rate in a highly asymmetric concordant posture, comparing the mechanisms of failure to an earlier study using a nonconcordant complex posture.
Summary Of Background Data:
A recent study with a nonconcordant complex posture (turning in the opposite direction to that which the load is applied) demonstrated the vulnerability of the disc to loading that is borne by one set of oblique-counter oblique fiber sets in the alternating lamellae of the annulus, and aggravated by an elevated loading rate. Given the strain rate-dependent properties of the disc it might be expected that the outcome differs if the posture is reversed.
Methods:
Forty-one motion segments from ovine 16 spines were split into two cohorts; adopting the previously employed low rate (40 mm/min) and surprise rate (400 mm/min) of loading. Both groups of damaged discs were then analyzed microstructurally.
Results:
With the lower rate loading the concordant posture significantly reduced the load required to cause disc failure than earlier described for nonconcordant posture (6.9 vs. 8.4 kN), with more direct tears and alternate lamella damage extending to the anterior disc. Contrary to this result, with a surprise rate, the load at failure was significantly increased with the concordant posture (8.08 vs. 6.96 kN), although remaining significantly less than that from a simple flexed posture (9.6 kN). Analysis of the damage modes and postures suggest facet engagement plays a significant role.
Conclusion:
This study confirms that adding shear to the posture lowers the load at failure, and causes alternate lamella rupture. Load at failure in a complex posture is not determined by loading rate alone. Rather, the strain rate-dependent properties of the disc influence which elements of the system are brought into play.
Level Of Evidence:
N/A.
Related Concept Videos
01:30Factors Influencing Heart Rate
Let us explore the significant factors affecting heart rate, including age, body temperature, posture, acute pain, chemical influences,...
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
01:05Mechanism of Ciliary Motion
The cilia are made up of microtubules in a 9+2 arrangement, with nine microtubule doublet ring bundles, surrounding a pair of central singlet microtubule bundles. The doublet microtubule bundles are...
01:22Factors Influencing the Rate of Chemical Reactions
Concentration and Pressure:
The more particles present within a given space, the more likely those particles are to bump into one another....
01:20Kendall's Coefficient of Concordance
03:08Rate-Determining Steps
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...