MR guidance and thermometry of percutaneous laser disc decompression in open MRI: an initial clinical investigation

Objectives

To assess the feasibility, safety and efficacy of real-time MR guidance and thermometry of percutaneous laser disc decompression (PLDD).

Methods

Twenty-four discs in 22 patients with chronic low-back and radicular pain were treated by PLDD using open 1.0-T magnetic-resonance imaging (MRI). A fluoroscopic proton-density-weighted turbo spin-echo (PDw TSE) sequence was used to position the laser fibre. Non-spoiled gradient-echo (GRE) sequences were employed for real-time thermal monitoring based on proton resonance frequency (PRF). Radicular pain was assessed over 6 months with a numerical rating scale (NRS).

Results

PLDD was technically successful in all cases, with adequate image quality for laser positioning. The PRF-based real-time temperature monitoring was found to be feasible in practice. After 6 months, 21 % reported complete remission of radicular pain, 63 % at least great pain relief and 74 % at least mild relief. We found a significant decrease in the NRS score between the pre-intervention and the 6-month follow-up assessment (P?<?0.001). No major complications occurred; the single adverse event recorded, moderate motor impairment, resolved.

Conclusions

Real-time MR guidance and PRF-based thermometry of PLDD in the lumbar spine under open 1.0-T MRI appears feasible, safe and effective and may pave the way to more precise operating procedures.

Key Points

? Percutaneous laser disc decompression (PLDD) is increasingly used instead of conventional surgery. ? Open 1.0-T MRI with temperature mapping seems technically successful in monitoring PLDD. ? Pain relief was at least ‘great’ in 64?% of patients. ? No major complications occurred. ? Open 1.0-T MRI appears a safe and effective option for patient-tailored PLDD.     

Functional characterization of ether‐à‐go‐go‐related gene potassium channels in midbrain dopamine neurons – implications for a role in depolarization block

Bursting activity by midbrain dopamine neurons reflects the complex interplay between their intrinsic pacemaker activity and synaptic inputs. Although the precise mechanism responsible for the generation and modulation of bursting in vivo has yet to be established, several ion channels have been implicated in the process. Previous studies with nonselective blockers suggested that ether‐à‐go‐go‐related gene (ERG) K⁺ channels are functionally significant. Here, electrophysiology with selective chemical and peptide ERG channel blockers (E‐4031 and rBeKm‐1) and computational methods were used to define the contribution made by ERG channels to the firing properties of midbrain dopamine neurons in vivo and in vitro. Selective ERG channel blockade increased the frequency of spontaneous activity as well as the response to depolarizing current pulses without altering spike frequency adaptation. ERG channel block also accelerated entry into depolarization inactivation during bursts elicited by virtual NMDA receptors generated with the dynamic clamp, and significantly prolonged the duration of the sustained depolarization inactivation that followed pharmacologically evoked bursts. In vivo, somatic ERG blockade was associated with an increase in bursting activity attributed to a reduction in doublet firing. Taken together, these results show that dopamine neuron ERG K⁺ channels play a prominent role in limiting excitability and in minimizing depolarization inactivation. As the therapeutic actions of antipsychotic drugs are associated with depolarization inactivation of dopamine neurons and blockade of cardiac ERG channels is a prominent side effect of these drugs, ERG channels in the central nervous system may represent a novel target for antipsychotic drug development.     

Posterior stabilization of subaxial cervical spine trauma: indications and techniques

The use of instrumentation for stabilization following cervical trauma has evolved rapidly in the past few decades. Nonoperative maneuvers, including traction, extended bed rest, and cast immobilization, have given way to wiring or screw rod constructs that allow immediate fixation and early mobilization of the patient. These procedures can be performed soon after trauma and with a minimum of surgical risk. They offer immediate stability of the injured spine, and can prevent the sequelae of acute cervical spinal cord injury that may accompany prolonged bed rest, thus allowing early rehabilitation and the potential for improved recovery. Current techniques for posterior cervical spine stabilization following trauma include spinous process or facet wiring [1-9], lateral mass plating [10-18], and cervical pedicle screws [19-27]. Several radiological tools, including MRI [28] and reformatted CT, yield precise details of the injured spine and allow the treating physician to determine which, if any, fixation technique offers the best chance of recovery with the least amount of risk. The goals of surgery following acute cervical spine injury include decompressing the injured spinal cord or nerve root, maintaining alignment, providing stability to the spine, promoting healing and fusion, and allowing early mobilization. This article will review indications for posterior cervical spine surgery, as well as the techniques that are currently available to help achieve the above-noted goals. We also report a recent retrospective review of 5-year data in treating posterior cervical trauma with lateral mass and pedicle screw fixation.     

MR-guided discography using an open 1 Tesla MRI system

Objective  

To evaluate the feasibility of MR-guided discography using an open 1 Tesla MRI system.     

Parameters influencing the outcome after total disc replacement at the lumbosacral junction. Part 1: misalignment of the vertebrae adjacent to a total disc replacement affects the facet joint and facet capsule forces in a probabilistic finite element analysis

Purpose

After total disc replacement with a ball-and-socket joint, reduced range of motion and progression of facet joint degeneration at the index level have been described. The aim of the study was to test the hypothesis that misalignment of the vertebrae adjacent to the implant reduces range of motion and increases facet joint or capsule tensile forces.

Methods

A probabilistic finite element analysis was performed using a lumbosacral spine model with an artificial disc at level L5/S1. Misalignment of the L5 vertebra, the gap size of the facet joints, the transection of the posterior longitudinal ligament, and the spinal shape were varied. The model was loaded with pure moments.

Results

Misalignment of the L5 vertebra reduced the range of motion up to 2°. A 2-mm displacement of the L5 vertebra in the anterior direction already led to facet joint forces of approximately 240 N. Extension, lateral bending, and axial rotation caused maximum facet joint forces between 280 and 380 N, while flexion caused maximum forces of approximately 200 N. A 2-mm displacement in the posterior direction led to capsule forces of approximately 80 N. Additional moments increased the maximum facet capsule forces to values between 120 and 230 N.

Conclusions

Misalignment of the vertebrae adjacent to an artificial disc strongly increases facet joint or capsule forces. It might, therefore, be an important reason for unsatisfactory clinical results. In an associated clinical study (Part 2), these findings are validated.     

E-Learning in der Orthopädie und Unfallchirurgie

Background

Additional internet-based learning tools (e-learning) are successfully used in the curricula of many disciplines and are highly accepted among students. However, in orthopedics and traumatology e-learning is underrepresented and scientific papers are rare. The aim of the present pilot study was to evaluate the acceptance of the e-learning module network for students in traumatology and orthopedics (NESTOR) among users and non-users and to analyze the effect of this additional learning tool on knowledge acquisition.

Material and methods

A total of 544 students were asked to complete evaluation questionnaires at the end of two semesters using different ones for NESTOR users and non-users. The gain of knowledge was analyzed by two written knowledge tests (pre-post test, 20 multiple choice questions) at the beginning and end of the semester comparing these two groups.

Results

A total of 191 students took part in the evaluation and 152 completed both written tests. The NESTOR users showed a high acceptance of the e-learning system and non-users considered e-learning beneficial as well. Reasons given for not using NESTOR were lack of time, lack of information about the existence of NESTOR and a lack of interest in this discipline and e-learning in general. Both groups significantly increased their level of knowledge during the course of the semester (p?Conclusion The presented data support the high acceptance among users and the benefit of the e-learning project NESTOR in teaching students in orthopedics and traumatology. Based on experience and these results the permanent implementation of an additional e-learning module in the curriculum can be recommended for other faculties. In this process the critical comments of the non-users determined in the present study should be addressed.     

Percutaneous discography: comparison of low-dose CT, fluoroscopy and MRI in the diagnosis of lumbar disc disruption

Aim: To compare the diagnostic accuracy of low-dose computed tomography (CT), magnetic resonance imaging (MRI) and fluoroscopy in percutaneous discography in patients scheduled for lumbar spondylodesis. Material and methods: Within a prospective pilot study, 18 disc segments of 11 patients with radicular or pseudoradicular pain prior to anteroposterior spondylodesis were evaluated. After injection of a mixture of non-ionic iodine-containing contrast agent and gadolinium-based contrast medium into the disc spaces, all patients underwent conventional fluoroscopy, as well as low-dose CT and MRI. The occurrence of memory pain during contrast injection was recorded. CT, MRI and fluoroscopic images were analyzed independently by two readers blinded to the clinical findings. Results: There was 100% agreement between CT and MRI discography in the detection, localization and grading of degenerative changes. In contrast, conventional fluoroscopy identified only 9 of the 12 abnormal segments. Memory pain following puncture was identified in 3 of the 12 affected segments. Summary: Low-dose CT and MRI discography have a similar accuracy in the assessment of disc disruption and they are superior to fluoroscopic discography.     

Diagnostische Standards bei extraduralen Tumoren und Metastasen der Wirbelsäule

Because of the heterogeneous clinical and paraclinical symptoms accompanied by the urgent necessity to rapidly find a diagnosis, the differential diagnostic delineation of spinal tumors from back pain related to other reasons is a special challenge in the orthopedic practice. Employing an algorithm based on anamnesis, clinical, radiological and paraclinical examinations, a guideline-related biopsy as well as histological processing of the biopsy material, tumor lesions can usually be classified regarding entity, dignity and extent. Following this a treatment strategy can be defined. Because of the necessity of an interdisciplinary approach the diagnostic algorithm should be planned during a tumor conference and performed in specialized centers.