Is spinal stenosis assessment dependent on slice orientation? A magnetic resonance imaging study

Introduction: Lumbar spinal stenosis (LSS) treatment is based primarily on the clinical criteria providing that imaging confirms radiological stenosis. The radiological measurement more commonly used is the dural sac cross-sectional area (DSCA). It has been recently shown that grading stenosis based on the morphology of the dural sac as seen on axial T2 MRI images, better reflects severity of stenosis than DSCA and is of prognostic value. This radiological prospective study investigates the variability of surface measurements and morphological grading of stenosis for varying degrees of angulation of the T2 axial images relative to the disc space as observed in clinical practice. Materials and methods: Lumbar spine TSE T2 three-dimensional (3D) MRI sequences were obtained from 32 consecutive patients presenting with either suspected spinal stenosis or low back pain. Axial reconstructions using the OsiriX software at 0°, 10°, 20° and 30° relative to the disc space orientation were obtained for a total of 97 levels. For each level, DSCA was digitally measured and stenosis was graded according to the 4-point (A-D) morphological grading by two observers. Results: A good interobserver agreement was found in grade evaluation of stenosis (k=0.71). DSCA varied significantly as the slice orientation increased from 0° to +10°, +20° and +30° at each level examined (P<0.0001) (−15 to +32% at 10°, −24 to +143% at 20° and −29 to +231% at 30° of slice orientation). Stenosis definition based on the surface measurements changed in 39 out of the 97 levels studied, whereas the morphology grade was modified only in two levels (P<0.01). Discussion: The need to obtain continuous slices using the classical 2D MRI acquisition technique entails often at least a 10° slice inclination relative to one of the studied discs. Even at this low angulation, we found a significantly statistical difference between surface changes and morphological grading change. In clinical practice, given the above findings, it might therefore not be necessary to align the axial cuts to each individual disc level which could be more time-consuming than obtaining a single series of axial cuts perpendicular to the middle of the lumbar spine or to the most stenotic level. In conclusion, morphological grading seems to offer an alternative means of assessing severity of spinal stenosis that is little affected by image acquisition techniqu

A CT-based study investigating the relationship between pedicle screw placement and stimulation threshold of compound muscle action potentials measured by intraoperative neurophysiological monitoring

Purpose: Neurophysiological monitoring aims to improve the safety of pedicle screw placement, but few quantitative studies assess specificity and sensitivity. In this study, screw placement within the pedicle is measured (post-op CT scan, horizontal and vertical distance from the screw edge to the surface of the pedicle) and correlated with intraoperative neurophysiological stimulation thresholds. Methods: A single surgeon placed 68 thoracic and 136 lumbar screws in 30 consecutive patients during instrumented fusion under EMG control. The female to male ratio was 1.6 and the average age was 61.3years (SD 17.7). Radiological measurements, blinded to stimulation threshold, were done on reformatted CT reconstructions using OsiriX software. A standard deviation of the screw position of 2.8mm was determined from pilot measurements, and a 1mm of screw—pedicle edge distance was considered as a difference of interest (standardised difference of 0.35) leading to a power of the study of 75% (significance level 0.05). Results: Correct placement and stimulation thresholds above 10mA were found in 71% of screws. Twenty-two percent of screws caused cortical breach, 80% of these had stimulation thresholds above 10mA (sensitivity 20%, specificity 90%). True prediction of correct position of the screw was more frequent for lumbar than for thoracic screws. Conclusion: A screw stimulation threshold of >10mA does not indicate correct pedicle screw placement. A hypothesised gradual decrease of screw stimulation thresholds was not observed as screw placement approaches the nerve root. Aside from a robust threshold of 2mA indicating direct contact with nervous tissue, a secondary threshold appears to depend on patients' pathology and surgical condition

International comparative study of low back pain care pathways and analysis of key interventions

Purpose Low back pain (LBP) is a major public health problem worldwide. Significant practice variation exists despite guidelines, including strong interventionist focus by some practitioners. Translation of guidelines into pathways as integrated treatment plans is a next step to improve implementation. The goal of the present study was to analyze international examples of LBP pathways in order to identify key interventions as building elements for care pathway for LBP and radicular pain. Methods International examples of LBP pathways were searched in literature and grey literature. Authors of pathways were invited to fill a questionnaire and to participate in an in-depth telephone interview. Pathways were quantitatively and qualitatively analyzed, to enable the identification of key interventions to serve as pathway building elements. Results Eleven international LBP care pathways were identified. Regional pathways were strongly organized and included significant training efforts for primary care providers and an intermediate level of caregivers in between general practitioners and hospital specialists. Hospital pathways had a focus on multidisciplinary collaboration and stepwise approach trajectories. Key elements common to all pathways included the consecutive screening for red flags, radicular pain and psychosocial risk factors, the emphasis on patient empowerment and self-management, the development of evidence-based consultable protocols, the focus on a multidisciplinary work mode and the monitoring of patient-reported outcome measures. Conclusion Essential building elements for the construction of LBP care pathways were identified from a transversal analysis of key interventions in a study of 11 international examples of LBP pathways

Influence of anatomical variations on lumbar foraminal stenosis pathogenesis

Introduction: Symptomatic foraminal stenosis has been observed in patients with degenerative disc disease, scoliosis, asymmetrical disc degeneration and spondylolisthesis. Nevertheless not all patients with the above pathologies will develop symptomatic foraminal stenosis. We hypothesised that symptomatic patients have anatomical predisposition to foraminal stenosis, namely a larger pedicle height (PH) to vertebral body height (VH) ratio, leaving less room below the pedicle for the exiting nerve root compared to asymptomatic patients. Patient sample: 66 Patients were divided in two groups. The surgical group consisted of 37 patients (average age of 61years) who presented with severe radicular symptoms resisting to conservative measures and requiring decompression and transforaminal lumbar interbody fusion (TLIF). The control group consisted of 29 patients (average age of 51years) presenting with low back pain (LBP) but with no radicular symptoms and who were treated conservatively. Methods: We measured VH at the level of the posterior wall as well as PH on parasagittal images (CT or MRI) on all lumbar levels (L1 to L5). Statistical analysis was performed using Student's t test. Results: No difference in PH was found between the two groups for L1 to L4 levels. By contrast, there was a highly statistically significant difference in VH between the two groups from L1 to L4 level. In the surgical group, the VH was smaller (p<0.001). Conclusions: Symptomatic patients with foraminal stenosis have smaller VH leading to lesser space beneath the pedicle and putting the exiting nerve root at risk in cases of spondylolisthesis or disc degeneration

Consensus interdisciplinaire CHUV-HUG sur la prise en charge des douleurs du dos.Son application lausannoise dans la filière du dos

Back pain is a considerable economical burden in industrialised countries. Its management varies widely across countries, including Switzerland. Thus, the University Hospital and University of Lausanne (CHUV) recently improved intern processes of back pain care. In an already existing collaborative context, the two university hospitals in French-speaking Switzerland (CHUV, University Hospital of Geneva), felt the need of a medical consensus, based on a common concept. This inter-hospital consensus produced three decisional algorithms that bear on recent concepts of back pain found in literature. Eventually, a fast track was created at CHUV, to which extern physicians will have an organised and rapid access. This fast track aims to reduce chronic back pain conditions and provides specialised education for general practitioners-in-training

A CT-based study investigating the relationship between pedicle screw placement and stimulation threshold of compound muscle action potentials measured by intraoperative neurophysiological monitoring.

PURPOSE: Neurophysiological monitoring aims to improve the safety of pedicle screw placement, but few quantitative studies assess specificity and sensitivity. In this study, screw placement within the pedicle is measured (post-op CT scan, horizontal and vertical distance from the screw edge to the surface of the pedicle) and correlated with intraoperative neurophysiological stimulation thresholds. METHODS: A single surgeon placed 68 thoracic and 136 lumbar screws in 30 consecutive patients during instrumented fusion under EMG control. The female to male ratio was 1.6 and the average age was 61.3 years (SD 17.7). Radiological measurements, blinded to stimulation threshold, were done on reformatted CT reconstructions using OsiriX software. A standard deviation of the screw position of 2.8 mm was determined from pilot measurements, and a 1 mm of screw-pedicle edge distance was considered as a difference of interest (standardised difference of 0.35) leading to a power of the study of 75 % (significance level 0.05). RESULTS: Correct placement and stimulation thresholds above 10 mA were found in 71 % of screws. Twenty-two percent of screws caused cortical breach, 80 % of these had stimulation thresholds above 10 mA (sensitivity 20 %, specificity 90 %). True prediction of correct position of the screw was more frequent for lumbar than for thoracic screws. CONCLUSION: A screw stimulation threshold of &gt;10 mA does not indicate correct pedicle screw placement. A hypothesised gradual decrease of screw stimulation thresholds was not observed as screw placement approaches the nerve root. Aside from a robust threshold of 2 mA indicating direct contact with nervous tissue, a secondary threshold appears to depend on patients' pathology and surgical conditions