The effect of intervertebral disc damage on the mechanical strength of the annulus fibrosus in the adjacent segment.

BACKGROUND CONTEXT: A herniated intervertebral disc (IVD) is a common injury in the human population. Despite the injury being isolated to a singular IVD in the spine, it is important to look at the biomechanical effects that a damaged IVD has on the entire spine, specifically the IVD adjacent to the injury. PURPOSE: This study examined the effects of a damaged IVD on the mechanical properties of the annulus fibrosus (AF) in the adjacent cranial IVD. STUDY DESIGN: Basic science study using an in-vitro porcine model. METHODS: Sixteen porcine cervical spines were used; specifically spinal levels C3/4/5 were assigned to one of two experimental groups: 1) a control group that was not subjected any injuries (n=8); 2) an experimental group that experienced an injury to the anterolateral part of the disc, reaching the nucleus pulposus but without affecting the posterior portion of the AF in the C4/5 functional spine unit (FSU) (n=8). Each specimen underwent a previously published precondition compression protocol of 300 N of compression for 15 minutes followed by a cyclical compression protocol of compression protocol of 0.5 Hz sinusoidal waveform at 300 to 1200 N for 2 hours (3600 cycles). Post compression, the C3/4 AF was dissected to obtain two multilayer samples (one anterior and one posterior) as well as a peel sample (from the posterolateral region). A tensile strength test was conducted to examine the strength of the interlamellar matrix (peel sample) and the overall strength of the AF (multilayer samples). RESULTS: Significant results were found in the peel test samples. Specifically, experimental specimens were less stiff compared than control specimens (p<.01). In addition, experimental specimens also had a lower average strength then control specimens (p<.01). This reduction in both interlamellar strength and stiffness increases the risk of delamination in the experimental samples. In contrast, there were no differences found between the two groups when examining the AF as a whole through the multilayer tests (p>.05). CONCLUSIONS: It appears that a damaged IVD impacts the biomechanics of the spine and specifically the mechanical properties of the adjacent IVD. Specifically, the observed weakening of the interlamellar matrix in these adjacent IVDs may predispose it to delamination and subsequently degeneration or herniation. CLINICAL SIGNIFICANCE: These findings may help clinicians when treating patients who have experienced a disc herniation or severe degeneration, as they may potentially experience accelerated adjacent disc degeneration.

Examining the protective role of the posterior elements of the spine against endplate fractures in a porcine model.

Previous studies have shown that the posterior elements/facet joints provide strength to the overall functional spine unit (FSU) by taking 3-25% of vertical compressive load off the intervertebral disc (IVD). However, little is known regarding whether this offloading has a protective effect against endplate fracture. Therefore, the purpose of this study was to investigate if the posterior elements provide a protective role to the endplate in porcine cervical spines under fracture-inducing conditions. Twenty-two cervical porcine FSUs (C5/6 level) were randomized into two groups: 1) a control group which had their posterior elements left intact (n = 11); 2) an experimental group which had the posterior elements removed (n = 11). Each FSU underwent a previously reported rapid IVD pressurization protocol in order to create endplate fractures. Briefly, hydraulic fluid was rapidly injected into the IVD via a standard inflation needle inserted through the anterior annulus which was connected to a hydraulic pump and pressure transducer. Post pressurization, each FSU was dissected to determine the presence and size of endplate fracture. Peak pressurization and rate of pressurization were not found to differ between intact and cut specimens (p = 0.313 and 0.101, respectively). In contrast, significantly, more cut FSUs sustained an endplate fracture (11/11) compared to intact FSUs (5/11); p = 0.012. Further, cut FSUs resulted in a fracture area 1.91 times greater in size compared to the fractures seen in the intact FSUs (p = 0.011). Therefore, posterior elements appear to decrease the risk and severity of endplate fracture.

The 2015 U.S. Soccer Federation header ban and its effect on emergency room concussion rates in soccer players aged 10-13.

BACKGROUND: In 2015, the U.S. Soccer Federation banned heading for players aged 10-13. PURPOSE/QUESTION: To assess the change in proportion of children aged 10-13 playing soccer in the US presenting to an Emergency Department (ED) with a concussion in relation to any other injury before and after the ban. METHODS: Analysis was restricted to soccer athletes between 10-13 years that reported to a National Electronic Injury Surveillance System (NEISS) participating hospital ED following injury in 2013-2014 and 2016-2017. Multivariable logistic regression was performed to assess the association between year of injury and concussion diagnosis in relation to other injury diagnosis after adjusting for age, sex, and ethnicity. RESULTS: Concussion in relation to other injuries showed a significant increase in 2016-2017 when compared to 2013-2014 after adjustment (OR= 1.286, 95%CI = 1.090-1.517). CONCLUSIONS: These results suggest that banning heading may not reduce concussion within this population. However, significant confounders, including increased reporting, were not controlled for.

CONTEXTE: En 2015, la U.S. Soccer Federation a interdit le coup de tête au ballon aux joueurs de 10 à 13 ans. OBJECTIF/QUESTION: Déterminer le changement de proportion de jeunes joueurs de soccer américains de 10 à 13 ans arrivant en salle des urgences avec une commotion cérébrale liée à d'autres types de blessures subies avant et après l'interdiction. MÉTHODOLOGIE: L'analyse s'est limitée aux jeunes joueurs de soccer âgés de 10 à 13 ans, s'étant présentés à une salle des urgences d'un hôpital participant au registre National Electronic Injury Surveillance System (NEISS), après avoir subi une blessure entre 2013 et 2014 et entre 2016 et 2017. Une régression logistique multivariée a servi à évaluer le rapport entre l'année de la blessure et le diagnostic de la commotion cérébrale et un autre diagnostic de blessure après correction pour tenir compte de l'âge, du sexe et de l'origine ethnique. RÉSULTATS: Le rapport entre commotion cérébrale et autres blessures a considérablement augmenté en 2016­2017par rapport à ce qu'il était en 2013­2014 après correction (RR = 1,286, IC à 95 % = 1,090­1,517). CONCLUSIONS: Ces résultats laissent supposer que l'interdiction de coups de tête au ballon peut ne pas réduire le nombre de commotions cérébrales dans cette population. Cependant, il y a eu d'importantes variables confondantes, comme l'augmentation du nombre de cas signalés, pour lesquelles aucun contrôle n'a été inclus.