Marinko Rade

2014 young investigator award winner: In vivo magnetic resonance imaging measurement of spinal cord displacement in the thoracolumbar region of asymptomatic subjects: part 1: straight leg raise test.

Study Design. Controlled radiological study. Objective. To investigate noninvasively in vivo spinal cord displacement in the vertebral canal during the passive straight leg raise (SLR) in asymptomatic subjects. The basic assumption is that the cord follows L5 and S1 nerve roots displacement by similar magnitude and direction (principle of linear dependence). Summary of Background Data. It is generally accepted that the SLR produces some caudal movement mainly of L5 and S1 nerve roots, but the magnitude of this displacement is still a matter of debate. Methods. Sixteen asymptomatic volunteers were scanned with 1.5-T magnetic resonance scanner (Siemens Avanto, Erlangen, Germany) using T2-weighted turbo spin-echo fat-saturation sequence. The displacement of the medullar cone relative to the vertebral endplate of the adjacent vertebra during the passive SLR was quantified and compared with the position of the conus in the neutral (anatomic) position. Each movement was performed twice for evaluation of reproducibility. The measurements were repeated by 2 observers. Four practitioners performed the maneuvers in a random sequence to avoid series effects. Results. Compared with the neutral (anatomic) position, the medullar cone displaced caudally in the spinal canal by 2.31 ± 1.2 mm with right (P ⩽ 0.001) and 2.35 ± 1.2 mm with left SLR (P ⩽ 0.001). Spearman correlations proved higher than 0.99 for intra and interobserver reliability, as well as results reproducibility testing for each maneuver. Conclusion. The data show that the spinal cord in the thoracolumbar region slides distally in response to the clinically applied SLR test. The high correlation values in this study show that these movements are consistent and reproducible. Because of the neural continuum, the authors speculate that this movement might be directly proportional to the sliding of the L5 and S1 neural roots. This study offers baseline measurements on which further studies in diagnosis of lumbar disc protrusion and radiculopathy may be developed. Level of Evidence: 5

Slump Test: Effect of Contralateral Knee Extension on Response Sensations in Asymptomatic Subjects and Cadaver Study

Study Design. Part 1: A randomized, single-blind study on the effect of contralateral knee extension on sensations produced by the slump test (ST) in asymptomatic subjects. Part 2: A cadaver study simulating the nerve root behavior of part 1. Objective. Part 1: Test if contralateral knee extension consistently reduces normal stretch sensations with the ST. Part 2: Ascertain in cadavers an explanation for the results. Summary of Background Data. In asymptomatic subjects, contralateral knee extension reduces stretch sensations with the ST. In sciatica patients, contralateral SLR also can temporarily reduce sciatica. We studied this methodically in asymptomatic subjects before considering a clinical population. Methods. Part 1: Sixty-one asymptomatic subjects were tested in control (ST), sham, or intervention (contralateral ST) groups and their sensation response intensity compared. Part 2: Caudal tension was applied to the L5 nerve root of 3 cadavers and tension behavior of the contralateral neural tissue recorded visually. Results. Part 1: Reduction of stretch sensations occurred in the intervention group but not in control and sham groups (P ⩽ 0.001). Part 2: Tension in the contralateral lumbar nerve roots and dura reduced in a manner consistent with the responses in the intervention (contralateral ST) group. Conclusion. Part 1: In asymptomatic subjects, normal thigh stretch sensations with the ST reduced consistently with the contralateral ST, showing that this is normal and may now be compared with patients with sciatica. Part 2: Contralateral reduction in lumbar neural tension with unilateral application of tension-producing movements also occurred in cadavers, supporting the proposed explanatory hypothesis.

Effect of glenohumeral forward flexion on upper limb myoelectric activity during simulated mills manipulation; relations to peripheral nerve biomechanics

BackgroundIt is generally accepted that muscles may activate via the common nociceptive flexion reflex (NFR) in response to painful stimuli associated with tensile or compressive forces on peripheral nerves. Following the basic assumption that the radial nerve may be stressed around the elbow during the execution of the Mills manipulation, t wo positions considered to have different mechanical effects on the radial nerve and the brachial plexus were tested in order to i) explore whether muscles are activated in certain patterns with concomitant changes in nerve tension, ii) establish whether muscle responses can be modified with mechanical unloading of the brachial plexus.MethodsMuscle responses were quantified bilaterally in eight subjects (N = 16) during Mills Manipulation (MM) pre-manipulative positioning and a Varied position that putatively produces less mechanical tension in the brachial plexus. End range pre-manipulative stretch was used in order to simulate the effects of Mills manipulation. Electromyographic signals were recorded with a 16 channel portable EMG unit and correlated with kinematic data from three charge-coupled device adjustable cameras which allowed for precise movement tracking.ResultsCompared with the Standard Mills manipulation position, the Varied position produced significantly reduced myoelectric activity (P ≤ .001) in all test muscles. Additional subjective data support the notion that certain muscle activity patterns were protective.ConclusionIt seems that protective muscles are selectively activated in a specific pattern in order to protect the radial nerve from mechanical tension by shortening its pathway, suggesting integration of muscle and neural mechanisms. Furthermore, the significantly decreased myoelectric activity with reduced mechanical tension in the brachial plexus may help controlling collateral effects of the Mills manipulation itself, making it potentially safer and more specific.

Intervertebral Disc Biology: Genetic Basis of Disc Degeneration

Purpose of ReviewThis review aims to highlight recent advances in understanding the genetic basis of intervertebral disc degeneration (IDD).Recent FindingsIt has been known for some time that IDD is highly heritable. Recent studies, and in particular the availability of agnostic techniques such as genome-wide association studies, have identified new variants in a variety of genes which contribute to the risk of IDD and to back pain.SummaryA variety of genetic variants are involved in IDD. Some are shared with variants predisposing to back pain, but few have been identified reliably in either phenotype. Further research is required to explain fully the high heritability and how the genetic variants influence cell biology to lead to IDD.

Normal multiplanar movement of the spinal cord during unilateral and bilateral straight leg raise: Quantification, mechanisms and overview.

The purpose of this investigation was to provide a full set of normal data describing neural biomechanics within the vertebral canal in all three planes with unilateral and bilateral SLR tests to allow for clinical comparison with clinical cases. This is done following the notion that, due to neural continuum, tensile forces are transmitted through the lumbosacral nerve roots and dura to the conus medullaris (linear dependency principle). In this controlled radiologic study 10 asymptomatic volunteers were scanned with 1.5T magnetic resonance scanner (Siemens Magnetom Aera, Erlangen, Germany) using different scanning sequences for planning and for measurement purposes. Conus displacement in both antero‐posterior direction (sagittal slices) and lateral direction (axial slices) was quantified during unilateral passive left, right SLR, and bilateral SLR and compared with the position of the conus in the neutral (anatomic) position. It is shown that the conus medullaris displaced laterally and anteroposteriorly in response to unilateral and bilateral SLRs. Pearsons correlations were higher than 0.95 for both intra‐ and inter‐observer reliability. The observed power was higher than 0.99 for all the variables tested. Following this, the authors conclude that lateral and antero‐posterior displacement of conus medullaris into the vertebral canal occurs consistently with unilateral and bilateral SLRs following directions predicted by tension vectors. Summative information collected in this line of research in neuroradiology is here presented. We believe we have presented the first conclusive and complete full set of normal data on non‐invasive, in vivo, normative measurement of spinal cord displacement with the SLR ever presented.