Treatment of lumbar disc herniation: Evidence-based practice

Andrew J Schoenfeld1, Bradley K Weiner21Department of Orthopedic Surgery, William Beaumont Army Medical Center, Texas Tech University Health Sciences Center, El Paso, TX, USA; 2Weill Cornell Medical College and The Methodist Hospital, Houston, TX, USAClinical question: What is the best treatment for lumbar disc herniations? Results: For patients failing six weeks of conservative care, the current literature supports surgical intervention or prolonged conservative management as appropriate treatment options for lumbar radiculopathy in the setting of disc herniation. Surgical intervention may result in more rapid relief of symptoms and restoration of function.Implementation: While surgery appears to provide more rapid relief, many patients will gradually get better with continued nonoperative management; thus, patient education and active participation in decision-making is vital.Keywords: lumbar disc, herniation, back pain, spin

Instabilities in a Two-Component, Species Conserving Condensate

We consider a system of two species of bosons of equal mass, with interactions $U^{a}(|x|)$ and $U^{x}(|x|)$ for bosons of the same and different species respectively. We present a rigorous proof -- valid when the Hamiltonian does not include a species switching term -- showing that, when $U^{x}(|x|)>U^{a}(|x|)$, the ground state is fully "polarized" (consists of atoms of one kind only). In the unpolarized phase the low energy excitation spectrum corresponds to two linearly dispersing modes that are even a nd odd under species exchange. The polarization instability is signaled by the vani shing of the velocity of the odd modes.Comment: To appear in Phys. Rev.

Outcomes of decompression for lumbar spinal canal stenosis based upon preoperative radiographic severity

BACKGROUND: The relationship between severity of preoperative radiographic findings and surgical outcomes following decompression for lumbar degenerative spinal canal stenosis is unclear. Our aim in this paper was to gain insight into this relationship. We determined pre-operative radiographic severity on MRI scans using strict methodological controls and correlated such severity with post-operative outcomes using prospectively collected data. METHODS: Twenty-seven consecutive patients undergoing decompression for isolated degenerative spinal canal stenosis at L4-L5 were included. We measured cross-sectional area on MRI using the technique of Hamanishi. We categorized the severity of stenosis using Laurencin and Lipson's 'Stenosis Ratio'. We determined pre-operative status (prospectively) and post-operative outcomes using Weiner and Fraser's 'Neurogenic Claudication Outcome Score'. We determined patient satisfaction using standardized questionnaires. Each of these is a validated measure. Formal statistical evaluation was undertaken. RESULTS: No patients (0 of 14) with a greater than 50% reduction in cross-sectional area on pre-operative MRI had unsatisfactory outcomes. In contrast, outcomes for patients with less than or equal to 50% reduction in cross-sectional area had unsatifactory outcomes in 6 of 13 cases, with all but one negative outcome having a cross-sectional area reduction between 32% and 47%. CONCLUSION: The findings suggest that there appears to be a relationship between severity of stenosis and outcomes of decompressive surgery such that patients with a greater than 50% reduction in cross sectional area are more likely to have a successful outcome

Quantitative high-resolution 7T MRI to assess longitudinal changes in articular cartilage after anterior cruciate ligament injury in a rabbit model of post-traumatic osteoarthritis

Objective To demonstrate an ultra-high field (UHF) 7 T delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) protocol for quantitative post-traumatic osteoarthritis (PTOA) detection and monitoring in a rabbit anterior cruciate ligament transection (ACLT) model. Design ACL transections were performed unilaterally in 5 rabbits (33-weeks-old, 3.5 ± 0.5 kg) to induce PTOA. MRI exams were performed at 7 T prior to and 2, 4, 7 and 10-weeks after ACLT using a modified dGEMRIC protocol. Voxel-based T1 and T2 maps were created over manually drawn femoral cartilage ROIs from the center of the tibial plateau to the posterior meniscus. Femoral, tibial, and patellar epiphyses were harvested 10-weeks post-surgery and processed for μCT imaging and histology. Results Quantitative analysis revealed a 35% and 39% decrease in dGEMRIC index in the medial ACLT knee compartment 7- and 10-weeks post-surgery, respectively (p = 0.009 and p = 0.006) when compared to baseline. There was no significant change in the lateral ACLT compartment or in either compartment of the control knees. Visual inspection of histology confirmed PTOA in the ACLT knees. Osteophytes were found only in ACLT knees (osteophyte volume in femur: 94.53 ± 44.08 mm3, tibia: 29.35 ± 13.79 mm3, and patella: 3.84 ± 0.92 mm3) and were significantly larger in the medial compartments of the femur than lateral (p = 0.0312). Conclusion The dGEMRIC technique quantitatively applied at 7 T UHF-MRI demonstrates site-specific cartilage degeneration in a large animal PTOA model. This should encourage further investigation, with potential applications in drug and therapeutic animal trials as well as human studies

Excitation-assisted inelastic processes in trapped Bose-Einstein condensates

We find that inelastic collisional processes in Bose-Einstein condensates induce local variations of the mean-field interparticle interaction and are accompanied by the creation/annihilation of elementary excitation. The physical picture is demonstrated for the case of three body recombination in a trapped condensate. For a high trap barrier the production of high energy trapped single particle excitations results in a strong increase of the loss rate of atoms from the condensate.Comment: 4 pages, no figure

Bose-Einstein condensation in trapped dipolar gases

We discuss Bose-Einstein condensation in a trapped gas of bosonic particles interacting dominantly via dipole-dipole forces. We find that in this case the mean-field interparticle interaction and, hence, the stability diagram are governed by the trapping geometry. Possible physical realisations include ultracold heteronuclear molecules, or atoms with laser induced electric dipole moments.Comment: 4 pages, 4 figure

Rosen-Zener model in cold molecule formation

The Rosen-Zener model for association of atoms in a Bose-Einstein condensate is studied. Using a nonlinear Volterra integral equation, we obtain an analytic formula for final probability of the transition to the molecular state for weak interaction limit. Considering the strong coupling limit of high field intensities, we show that the system reveals two different time-evolution pictures depending on the detuning of the frequency of the associating field. For both limit cases we derive highly accurate formulas for the molecular state probability valid for the whole range of variation of time. Using these formulas, we show that at large detuning regime the molecule formation process occurs almost non-oscillatory in time and a Rosen-Zener pulse is not able to associate more than one third of atoms at any time point. The system returns to its initial all-atomic state at the end of the process and the maximal transition probability is achieved when the field intensity reaches its peak. In contrast, at small detuning the evolution of the system displays large-amplitude oscillations between atomic and molecular populations. We find that the shape of the oscillations in the first approximation is defined by the field detuning only. Finally, a hidden singularity of the Rosen-Zener model due to the specific time-variation of the field amplitude at the beginning of the interaction is indicated. It is this singularity that stands for many of the qualitative and quantitative properties of the model. The singularity may be viewed as an effective resonance-touching

Manipulation of Cold Atomic Collisions by Cavity QED Effects

We show how the dynamics of collisions between cold atoms can be manipulated by a modification of spontaneous emission times. This is achieved by placing the atomic sample in a resonant optical cavity. Spontaneous emission is enhanced by a combination of multiparticle entanglement together with a higher density of modes of the modified vacuum field, in a situation akin to superradiance. A specific situation is considered and we show that this effect can be experimentally observed as a large suppression in trap-loss rates.Comment: RevTex, 2 EPS figures; scheduled for Phys. Rev. Lett. 19 Feb 01, with minor change