Get acquainted with three of the six abstract submissions for EUROSPINE 2017, which have been elected as Best of Show and will be presented in the respective session; The Best of Show and Award papers on 13 October 2017. Don’t miss the opportunity to cast your vote by using the EUROSPINE app and help elect this year’s Best Podium Award.
Disc wall structural abnormalities may act as initiation sites for herniation
Presentation by Kelly Wade, Nikolaus Berger-Roscher, Marija Josipovic, Volker Rasche, Fabio Galbusera, Hans-Joachim Wilke, Institute of Orthopaedic Research and Biomechanics, Ulm University, Ulm, Germany
Both epidemiologic studies and clinical observations suggest that complex postures, such as combinations of bending, twisting and lifting, are more likely to provoke disc herniation. Previously, it has not been possible to non-destructively assess disc structure prior to testing or apply components of complex loading in sequence to determine their effects. In this study, we scanned 30 motion segments with experimental micro MRI (11.7T) before and after they were tested in a recently developed 6-DOF disc-loading simulator. They were subjected to different combination of four loading conditions (0-12° flexion, 0-9° lateral bending, 0-4° axial rotation, 0-1500 N axial compression) for 1,000 loading cycles at 2 Hz. Load and posture increased in 10 steps. After testing, they were formalin fixed and decalcified to enable cryosectioning, then analysed microstructurally using light microscopy.
Unsurprisingly, motion segments subjected to the most extreme combinations were most likely to suffer damage. Overall, ten discs suffered annular failure as judged by examination of the high resolution MRI images, with four of these involving subligamentous herniation of inner disc material and the remaining protrusion of inner disc material into the outer annulus. Most interesting was the finding that all discs that herniated contained distinctive irregularities in the posterior mid-inner annulus that were visible in the pretest MRI images as can be seen in Figure 1.
Figure 1: Transverse 11.7T MRI section through an ovine disc prior to testing (A) with the distinctive pattern of irregularities in the posterior annulus highlighted in red. Following testing (B) inner disc material is seen extruding through this region, as highlighted in blue.
Further microstructural investigation revealed that the outer annular-endplate junction had failed in 29 out of the 30 tested discs. This likely occurred at 60-70 per cent (step 6 to 7) of the final posture, prior to full load application.
The failure of the posterior mid-outer annulus at the endplate junction is likely a consequence of the relatively rapid applied loading and the extreme posture that the discs were subjected to. Since this occurred at 60-70 per cent of the peak load and created a large defect in the posterior annulus, the remaining mid-inner annulus would therefore have had to contain the pressure generated in the nucleus for the remainder of the test. We can thus conclude that the mid-inner annulus is capable of containing the inner contents of the disc under substantial compressive load.
Further, that the characteristic irregularities we observed in the pre-test micro-MRI scans of the discs that herniated disrupt this mid-inner region and act as initiation sites for herniation since inner disc material migrated through them when the disc is overloaded regardless of the posture applied.
Is preoperative duration of symptoms a significant predictor of functional outcomes in patients undergoing surgery for the treatment of degenerative cervical myelopathy?
Presentation by Lindsay Tetreault et al. Toronto Western Hospital, Department of Neurosurgery, Canada
Surgery is generally effective for the treatment of degenerative cervical myelopathy (DCM); however, outcomes are often dependent on a number of preoperative factors, such as baseline severity score, symptomatology, co-morbidities and age. Furthermore, a longer duration of symptoms is often predictive of worse functional outcomes, as longstanding compression of the spinal c