gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018)

23.10. - 26.10.2018, Berlin

Does transition zone structure influence the herniation process?

Meeting Abstract

  • presenting/speaker Kelly Wade - Institut für Unfallchirurgische Forschung und Biomechanik , Ulm, Germany
  • Nikolaus Berger-Roscher - Institut für Unfallchirurgische Forschung und Biomechanik , Ulm, Germany
  • Fabio Galbusera - Institut für Unfallchirurgische Forschung und Biomechanik , Ulm, Germany
  • Volker Rasche - Klinik für Innere Medizin II, Universitätsklinikum Ulm, Ulm, Germany
  • Hans-Joachim Wilke - Institut für Unfallchirurgische Forschung und Biomechanik , Ulm, Germany

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018). Berlin, 23.-26.10.2018. Düsseldorf: German Medical Science GMS Publishing House; 2018. DocST27-967

doi: 10.3205/18dkou145, urn:nbn:de:0183-18dkou1455

Veröffentlicht: 6. November 2018

© 2018 Wade et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe http://creativecommons.org/licenses/by/4.0/.


Gliederung

Text

Objectives: Our recent investigation found that defects in the inner and mid posterior annulus visualised with 11.7 T micro-MRI were associated with herniations when discs were subjected to complex loading, implying that this region plays an important role in the herniation process. Exposure to complex loading also created similar defects in previously intact discs. The present study aimed to investigate whether these defects influenced the resulting herniation at the microstructural level. A parallel aim was to explore the transition zone (inner annulus and nucleus) of healthy discs with a multi-scalar approach to better characterise its architecture and identify potential reasons for failure.

Methods: Microstructural examination was performed on thirty mature (3-5 year old) ovine lumbar motion segments exposed to complex loading conditions, causing 11 to suffer nucleus migration or herniation apparent under 11.7 T micro-MRI. Fixation and decalcification enabled discs to be cryosectioned and imaged with standard light microscopy. A further 15 healthy lumbar discs were imaged with micro-MRI, after which the transition zone of the disc was isolated from the endplates and fixed under load to capture detail in a single imaging plane. They were then cryosectioned and examined using light microscopy. From these samples, 18 sections were examined with scanning electron microscopy.

Results and conclusion: All but one of the tested discs suffered outer annulus failure visible at the microstructural level. Those discs that suffered herniation or migration of the nucleus exhibited failure of alternate lamellae in the mid and outer annulus. Those discs which had not suffered migration exhibited delamination and disruption of these lamellae.

Micro-MRI imaging of the healthy, untested discs revealed bundles of radially oriented fibres between the inner annulus and nucleus. Ultrastructural investigation revealed that these bundles consist of nucleus fibrils branching out at multiple radial depths and interweaving with the lamellae of the inner annulus.

Microstructural analysis showing the mid and inner annulus lamellae remaining continuous following testing indicates that this region was able to contain the pressure generated within the nucleus. That discs failed when it was compromised shows that it plays an important role in preventing failure under acute loading. However, the observation of disruption and delamination of the lamellae following testing indicates that it is vulnerable to fatigue type damage.

Ultrastructural investigation of the transition zone of intact discs shows for the first time how the three-dimensional network of the nucleus is interwoven with the lamellae of the annulus. Correlation with micro-MRI images shows that this integration occurs at multiple radial depths across the annular wall. This illustrates both how this network enables load transfer within the disc and how it could be vulnerable to repetitive loading regimes causing relative motion between lamellae.