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 cord may result in more severe myelopathy and irreversible histological damage. Patients with myelopathy, however, may be relatively stable for long periods of time, whereas others may deteriorate rapidly. This presentation highlights the results from a study that evaluates the impact of duration of symptoms on surgical outcomes in patients with DCM.
The first objective of this study was to evaluate the association between duration of symptoms and preoperative disease severity, disability and quality of life. Based on our results, there were no correlations between duration of symptoms and the mJOA, Nurick, NDI or SF-36 PCS and MCS. These findings suggest differences in the natural history of DCM and patterns of disease onset. Some patients may be relatively stable for long periods of time, whereas others may rapidly progress following the onset of symptoms. The onset of DCM may also differ substantially across patients; some experience a more sudden onset of symptoms, whereas in others, the disease may develop slowly and insidiously.
The second objective of this study was to identify important duration of symptoms cut-offs, above which there is a negative impact on surgical outcomes. Based on our results, there was a significant difference in the change in mJOA at one-year between patients treated within four months of symptom onset and those decompressed after four months. Twenty-nine and 30 months were also identified as important cut-offs.
The final objective of this study was to evaluate whether the duration of symptoms cut-offs vary based on preoperative myelopathy severity. In patients with severe disease (mJOA<12), 29 and 30 months were identified as two important cut-offs; however, the differences in outcome between the “short” and “long” duration group only approach statistical significance. In patients with moderate disease severity, every one-month delay in surgical decompression negatively impacted outcomes. This subgroup of patients likely reflects patients with progressive myelopathy; it is critical to intervene as early as possible to halt further neurologic decline, prevent irreversible damage to the spinal cord and optimize outcomes. Finally, in patients with mild myelopathy, there were no differences in outcomes between a “short” and “long” duration of symptoms group at any cut-off. As a result, delay in surgery in this subset of patients may not have a significant impact on outcomes.
Patients with spinal metastes live longer than predicted
Presentation by C Carrwik, C Olerud and Y Robinson
Spine metastases are common among cancer patients and selecting the best treatment for each patient is a challenge for the spine surgeon. Surgery for the right patient might improve quality of life, but will usually not benefit patients with very short life expectancy.
Several scoring systems are available to predict survival and helping the clinician to select surgical or non-surgical treatment.
Researchers at Uppsala University, Sweden, have evaluated the scores for 315 adult patients (213 men, 102 women, mean age 67 years) undergoing spinal surgery due to spinal metastatic disease between 2006 and 2012 at Uppsala University Hospital.
Data was collected prospectively for the Swedish Spine Register and retrospectively from the medial records. From the data, predicted survival according to four scoring systems (Tokuhashi, Revised Tokuhashi, Tomita, Modified Bauer) were calculated and then compared with actual survival from the Swedish Population Register.
The mean survival time after surgery for all patients included was 12.4 months (CI 10.6-14.2) and the median 5.9 months (CI 4.5-7.3). 28 per cent of the patients were dead within three months after surgery, while 39 per cent were alive more than 12 months after surgery. All of the scores predicted a lower rate of long-surviving patients and were better in estimating short survival.
Precision in estimating survival per score
Modified Bauer Score was the best of the scores to predict short survival. Patients who had long expected survival according to Revised Tokuhashi score had the longest true median survival. However, the Revised Tokuhashi Score had the highest proportion of underestimated survival and could be regarded as the most defensive score in this material.
As a retrospective study lacking control group, the study certainly has its weaknesses, but it is a large single-centre cohort with high quality on patient characteristics and survival.
The study suggests that the scoring systems are valuable for simplifying communication but should be used with caution for treatment decisions. All scoring systems used clinically should undergo regular revisions to reflect oncological advancements, according to the authors.
Session Details:
Date: Friday, 13 October 2017
Time: 10.30am–12pm
Room: Plenary Hall of the CCD – Convention Centre Dublin
Chairs: Michael Ogon and Björn Rydevik
