Total Knee Arthroplasty with Non-Stemmed Tibial Components among Obese Patients: Clinical and Radiologic Evaluation and Review of Literature.

Objective: This study aimed to evaluate the radiologic and clinical outcomes of TKA with non-stemmed tibial components in relation to their body mass index (BMI). Methods: In this retrospective cohort study, the outcome of TKA with non-stemmed tibial components based on their BMI was evaluated (BMI<30 vs. BMI≥30). The patients' function was assessed using the International Knee Documentation Committee (IKDC) and Lysholm knee questionnaires. Radiologic evaluation for probable signs of loosening was performed using two quantitative scoring systems by Ewald and Bach et al. Moreover, we reviewed the current literature on the application of non-stemmed tibial components in obese patients. Results: Twenty-one patients (two men and 19 women) with BMI≥30 and a mean age of 65.1±9.5 years, and 22 patients (three men and 19 women) with BMI<30 and a mean age of 63.6±8.5 years were studied. The mean follow-up periods with BMI≥30 (47.0±19.8 months) and BMI<30 (49.2±18.7 months) were comparable (p=0.618). No patients in either group experienced clinical loosening. Besides, none of the patients had any kind of revision surgery. The patients in both BMI groups had comparable IKDC scores (both the total score and its sub-scores; p>0.05). Furthermore, the total Lysholm knee scores were similar in both groups (p=0.122). Using both scoring systems, the peri-prosthetic bone radiolucency near the tibial components was similar in both groups (p>0.999). Conclusion: The present study found no significant difference in the radiologic or clinical outcome of non-stemmed TKA in patients with BMIs under and over 30.

Effect of continuous intra-incisional bupivacaine on postoperative pain in non-traumatic spinal fixation surgeries: a randomized controlled trial

Abstract Background Continuous injection of local anesthetics by using surgical wound catheters for postoperative pain relief has gained acceptance in recent years. However, whether this method can be alternatively used instead of systemic opioids in different surgical procedures has not yet been elucidated. Objectives The aim was to investigate the effect of continuous injection of bupivacaine through a catheter inside the surgical wound on reducing the postoperative pain of lumbar spine fusion surgeries. Methods In this clinical trial, 31 patients undergoing non-traumatic lumbar spine stabilization surgery were randomly assigned to receive (n = 15) or do not receive (n = 16) bupivacaine through a catheter inside the surgical wound, postoperatively. Pain intensity (NRS), dose of required morphine, and drug-related complications within 24 hours of intervention were assessed and compared by the Mann-Whitney and independent t-test. Results Mean pain intensity was significantly lower in the case group over the first postoperative hour in the recovery room (p < 0.001), which continued for the first 2 hours after entering the ward. The mean morphine intake was lower in the bupivacaine group during the first postoperative 24 hours (16 ± 0.88 vs. 7.33 ± 0.93 mg, p < 0.001). The two groups were not significantly different regarding drug-related complications. Conclusion Continuous intra-incisional infusion of bupivacaine helped better pain reduction during the early postoperative hours while sparing morphine consumption in the first postoperative day.

Effect of continuous intra-incisional bupivacaine on postoperative pain in non-traumatic spinal fixation surgeries: a randomized controlled trial.

BACKGROUND: Continuous injection of local anesthetics by using surgical wound catheters for postoperative pain relief has gained acceptance in recent years. However, whether this method can be alternatively used instead of systemic opioids in different surgical procedures has not yet been elucidated. OBJECTIVES: The aim was to investigate the effect of continuous injection of bupivacaine through a catheter inside the surgical wound on reducing the postoperative pain of lumbar spine fusion surgeries. METHODS: In this clinical trial, 31 patients undergoing non-traumatic lumbar spine stabilization surgery were randomly assigned to receive (n = 15) or do not receive (n = 16) bupivacaine through a catheter inside the surgical wound, postoperatively. Pain intensity (NRS), dose of required morphine, and drug-related complications within 24 hours of intervention were assessed and compared by the Mann-Whitney and independent t-test. RESULTS: Mean pain intensity was significantly lower in the case group over the first postoperative hour in the recovery room (p < 0.001), which continued for the first 2 hours after entering the ward. The mean morphine intake was lower in the bupivacaine group during the first postoperative 24 hours (16 ± 0.88 vs. 7.33 ± 0.93 mg, p < 0.001). The two groups were not significantly different regarding drug-related complications. CONCLUSION: Continuous intra-incisional infusion of bupivacaine helped better pain reduction during the early postoperative hours while sparing morphine consumption in the first postoperative day.

Iatrogenic L5 Nerve Injury Following Decortication of the Sacral Ala in Posterolateral Lumbosacral Fusion Surgery.

STUDY DESIGN: Cadaver study. OBJECTIVES: To investigate the risk of the L5 nerve injury following sacral ala decortication performed during lumbosacral posterolateral fusion surgery. METHODS: Fourteen fresh cadaver pelvises were dissected through an anterior approach and the L5 nerves on both sides were explored and macroscopically examined by direct observation. Then, the corticotomy of the sacral ala was performed at 0°, 20°, and 30° angles to the sagittal plane through the posterior approach. The site of sacral ala decortication was checked on each side and its distance to the L5 nerve root was measured. RESULTS: The tip of the osteotome was in the danger zone (5 mm medial to 5 mm lateral to the L5 nerve) in all cases (100%) where the osteotome had 0° angle to the sagittal plane. For those with a 20° angle, the osteotome tip laid in the danger zone in 83% and intermediate zone (between 6 to 15 mm lateral to the nerve) in 17% of cases. For those with a 30° angle, the tip was in the safe zone (>15 mm lateral to the nerve) in all cases (100%). CONCLUSION: Osteotomy of the sacral ala with <30° angle to the sagittal plane risks injury to the L5 nerve; whereas osteotomy angle >30° would not cause any injury to the nerve. It should be considered as a possible cause of iatrogenic L5 nerve injury in patients undergoing posterolateral lumbosacral fusion.

Analysis of the Effect and Prognostic Factors Associated with Postural and Instrumental Reduction in Thoracolumbar Burst Fractures.

BACKGROUND: Axial load on thoracolumbar junction, both mechanical and anatomical transitional zone, causes the compression and flexion of the spine, and consequently thoracolumbar burst fractures. OBJECTIVE: This study aimed to investigate the effect and prognostic factors associated with the postural and instrumented reduction on the restoration of vertebral height and kyphosis angle in thoracolumbar burst fractures. MATERIAL AND METHODS: This retrospective cohort study was conducted on 41 patients with A3, A4, and B type thoracolumbar burst fractures, subjected to postural and instrumented reduction for the restoration of vertebral height and kyphosis angle. The magnitude and correction of kyphotic deformity and percentage of vertebral body collapse were measured before and after postural reduction, and after instrumental insertion to find if they were affected by fracture type and level, time-to-surgery, and use of pedicular screws at the fractured level. RESULTS: Postural and instrumental reduction significantly improved both the kyphosis angle and the percentage of vertebral body height, regardless of AO types (p.value <0.001 and p.value <0.001, respectively). AO type A3, and A4 comparing to type B, has better restoration of kyphosis angle by postural (p-value=0.013, p-value=0.007, respectively) and instrumental reduction. (p-value=0.006, p-value=0.014, respectively). Evaluation of time to surgery showed that performing operation during the first four days would result in better correction of kyphosis angle (p-value 0.015). CONCLUSION: AO type A3, and A4, time to surgery before 4 days, and fracture level at L2 were favorable prognostic factors to better restoration of kyphosis angle using both postural and instrumented reduction.

Distinct Functional Groups Emerge from the Intrinsic Properties of Molecularly Identified Entorhinal Interneurons and Principal Cells.

Inhibitory interneurons are an important source of synaptic inputs that may contribute to network mechanisms for coding of spatial location by entorhinal cortex (EC). The intrinsic properties of inhibitory interneurons in the EC of the mouse are mostly undescribed. Intrinsic properties were recorded from known cell types, such as, stellate and pyramidal cells and 6 classes of molecularly identified interneurons (regulator of calcineurin 2, somatostatin, serotonin receptor 3a, neuropeptide Y neurogliaform (NGF), neuropeptide Y non-NGF, and vasoactive intestinal protein) in acute brain slices. We report a broad physiological diversity between and within cell classes. We also found differences in the ability to produce postinhibitory rebound spikes and in the frequency and amplitude of incoming EPSPs. To understand the source of this intrinsic variability we applied hierarchical cluster analysis to functionally classify neurons. These analyses revealed physiologically derived cell types in EC that mostly corresponded to the lines identified by biomarkers with a few unexpected and important differences. Finally, we reduced the complex multidimensional space of intrinsic properties to the most salient five that predicted the cellular biomolecular identity with 81.4% accuracy. These results provide a framework for the classification of functional subtypes of cortical neurons by their intrinsic membrane properties.

A comparison of H-reflex in the triceps surae muscle group in patients with S1 radiculopathy.

Despite differences in the anatomical and physiological characteristics of the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (Sol) muscles, it is common practice to investigate them as single triceps surae H-reflex recordings. The aim of this study was to compare the latencies of H-reflex recordings from the Sol, MG, and LG in patients with explicit magnetic resonance imaging (MRI) evidence of unilateral S1 radiculopathy and also compare their diagnostic yield in varied clinical characteristics (i.e., symptom duration and severity of involvement). We found a significant difference between H-reflex latencies of Sol and the two others (p < 0.05 for both comparisons). Although Sol had more sensitivity in patients with positive straight leg raising (SLR) of 30°-50° and also the sub-acute phase of the disease, and MG and LG had more sensitivity in the acute phase of the disease and patients with positive SLR of 50°-70°, there were no statistically significant differences between diagnostic ability of the three heads of the triceps surae in various clinical settings and they can be used interchangeably in patients with suspected S1 radiculopathies.

Selective degeneration of a physiological subtype of spinal motor neuron in mice with SOD1-linked ALS.

Amyotrophic lateral sclerosis (ALS; Lou Gehrig's disease) affects motor neurons (MNs) in the brain and spinal cord. Understanding the pathophysiology of this condition seems crucial for therapeutic design, yet few electrophysiological studies in actively degenerating animal models have been reported. Here, we report a novel preparation of acute slices from adult mouse spinal cord, allowing visualized whole cell patch-clamp recordings of fluorescent lumbar MN cell bodies from ChAT-eGFP or superoxide dismutase 1-yellow fluorescent protein (SOD1YFP) transgenic animals up to 6 mo of age. We examined 11 intrinsic electrophysiologic properties of adult ChAT-eGFP mouse MNs and classified them into four subtypes based on these parameters. The subtypes could be principally correlated with instantaneous (initial) and steady-state firing rates. We used retrograde tracing using fluorescent dye injected into fast or slow twitch lower extremity muscle with slice recordings from the fluorescent-labeled lumbar MN cell bodies to establish that fast and slow firing MNs are connected with fast and slow twitch muscle, respectively. In a G85R SOD1YFP transgenic mouse model of ALS, which becomes paralyzed by 5-6 mo, where MN cell bodies are fluorescent, enabling the same type of recording from spinal cord tissue slices, we observed that all four MN subtypes were present at 2 mo of age. At 4 mo, by which time substantial neuronal SOD1YFP aggregation and cell loss has occurred and symptoms have developed, one of the fast firing subtypes that innvervates fast twitch muscle was lost. These results begin to describe an order of the pathophysiologic events in ALS.

Evaluation of bone mineral status in adolescent idiopathic scoliosis.

BACKGROUND: Several reports have suggested low bone mineral density (BMD) in patients with adolescent idiopathic scoliosis (AIS). We determined bone mineral status in patients with AIS to evaluate the effect of brace treatment on BMD. METHODS: BMD was measured in 46 patients (mean age, 17.8 ± 4.9 years) with AIS (17 with brace and 29 without brace) by dual-energy X-ray absorptiometry scan and compared the results to an age-matched (mean age, 16.6 ± 3.9 years) control group (n = 54). RESULTS: The AIS group had significantly lower bone mass at the lumbar spine (Z-score, -1.500 vs. -0.832) and hip (Z-score, -1.221 vs. -0.754) except at the femoral neck. No difference in BMD was found between patients with AIS who used a brace and those who did not. CONCLUSIONS: The results confirmed that BMD was low in AIS patients and it was not affected by brace treatment.

Selective functional interactions between excitatory and inhibitory cortical neurons and differential contribution to persistent activity of the slow oscillation.

The neocortex depends upon a relative balance of recurrent excitation and inhibition for its operation. During spontaneous Up states, cortical pyramidal cells receive proportional barrages of excitatory and inhibitory synaptic potentials. Many of these synaptic potentials arise from the activity of nearby neurons, although the identity of these cells is relatively unknown, especially for those underlying the generation of inhibitory synaptic events. To address these fundamental questions, we developed an in vitro submerged slice preparation of the mouse entorhinal cortex that generates robust and regular spontaneous recurrent network activity in the form of the slow oscillation. By performing whole-cell recordings from multiple cell types identified with green fluorescent protein expression and electrophysiological and/or morphological properties, we show that distinct functional subpopulations of neurons exist in the entorhinal cortex, with large variations in contribution to the generation of balanced excitation and inhibition during the slow oscillation. The most active neurons during the slow oscillation are excitatory pyramidal and inhibitory fast spiking interneurons, receiving robust barrages of both excitatory and inhibitory synaptic potentials. Weak action potential activity was observed in stellate excitatory neurons and somatostatin-containing interneurons. In contrast, interneurons containing neuropeptide Y, vasoactive intestinal peptide, or the 5-hydroxytryptamine (serotonin) 3a receptor, were silent. Our data demonstrate remarkable functional specificity in the interactions between different excitatory and inhibitory cortical neuronal subtypes, and suggest that it is the large recurrent interaction between pyramidal neurons and fast spiking interneurons that is responsible for the generation of persistent activity that characterizes the depolarized states of the cortex.

Evaluation of the oscillatory interference model of grid cell firing through analysis and measured period variance of some biological oscillators.

Models of the hexagonally arrayed spatial activity pattern of grid cell firing in the literature generally fall into two main categories: continuous attractor models or oscillatory interference models. Burak and Fiete (2009, PLoS Comput Biol) recently examined noise in two continuous attractor models, but did not consider oscillatory interference models in detail. Here we analyze an oscillatory interference model to examine the effects of noise on its stability and spatial firing properties. We show analytically that the square of the drift in encoded position due to noise is proportional to time and inversely proportional to the number of oscillators. We also show there is a relatively fixed breakdown point, independent of many parameters of the model, past which noise overwhelms the spatial signal. Based on this result, we show that a pair of oscillators are expected to maintain a stable grid for approximately t = 5mu(3)/(4pisigma)(2) seconds where mu is the mean period of an oscillator in seconds and sigma(2) its variance in seconds(2). We apply this criterion to recordings of individual persistent spiking neurons in postsubiculum (dorsal presubiculum) and layers III and V of entorhinal cortex, to subthreshold membrane potential oscillation recordings in layer II stellate cells of medial entorhinal cortex and to values from the literature regarding medial septum theta bursting cells. All oscillators examined have expected stability times far below those seen in experimental recordings of grid cells, suggesting the examined biological oscillators are unfit as a substrate for current implementations of oscillatory interference models. However, oscillatory interference models can tolerate small amounts of noise, suggesting the utility of circuit level effects which might reduce oscillator variability. Further implications for grid cell models are discussed.

Ionic basis of ON and OFF persistent activity in layer III lateral entorhinal cortical principal neurons.

Principal neurons in layer III of the rat lateral entorhinal cortex (LEC) generate a self-sustained plateau potential and persistent spiking following the application of a brief suprathreshold excitatory stimulus delivered in the presence of the muscarinic receptor agonist carbachol. This persistent activity can be terminated by application of a second excitatory stimulus, and these cells can be repeatedly toggled between on and off states by consecutive excitatory stimuli. However, the ionic mechanisms that underlie the production of on and off states in layer III LEC neurons are unknown but seem to involve activity-dependent conductances, since they can be initiated by trains of action potentials evoked by either depolarizing current pulses applied to the cell or by repetitive spiking induced by activation of excitatory synaptic inputs. In this study, we obtained intracellular recordings from rat layer III LEC neurons in vitro, and a series of pharmacological and ionic substitution experiments were performed to identify mechanisms involved in the induction and termination of persistent spiking. Our data indicate that initiation of the on state depends on spike-evoked calcium influx and subsequent activation of calcium-activated nonselective cationic current. Moreover, we show that termination of persistent firing in response to an excitatory stimulus can be blocked by tetraethylammonium or iberiotoxin, suggesting that the activation of calcium-activated potassium current mediated by large conductance calcium-activated K(+) (i.e., BK) channels is required to induce the off state.

Switching between "On" and "Off" states of persistent activity in lateral entorhinal layer III neurons.

Persistent neural spiking maintains information during a working memory task when a stimulus is no longer present. During retention, this activity needs to be stable to distractors. More importantly, when retention is no longer relevant, cessation of the activity is necessary to enable processing and retention of subsequent information. Here, by means of intracellular recording with sharp microelectrode in in vitro rat brain slices, we demonstrate that single principal layer III neurons of the lateral entorhinal cortex (EC) generate persistent spiking activity with a novel ability to reliably toggle between spiking activity and a silent state. Our data indicates that in the presence of muscarinic receptor activation, persistent activity following an excitatory input may be induced and that a subsequent excitatory input can terminate this activity and cause the neuron to return to a silent state. Moreover, application of inhibitory hyperpolarizing stimuli is neither able to decrease the frequency of the persistent activity nor terminate it. The persistent activity can also be initiated and terminated by synchronized synaptic stimuli of layer II/III of the perirhinal cortex. The neuronal ability to switch "On" and "Off" persistent activity may facilitate the concurrent representation of temporally segregated information arriving in the EC and being directed toward the hippocampus.

Mechanism of graded persistent cellular activity of entorhinal cortex layer v neurons.

Working memory is an emergent property of neuronal networks, but its cellular basis remains elusive. Recent data show that principal neurons of the entorhinal cortex display persistent firing at graded firing rates that can be shifted up or down in response to brief excitatory or inhibitory stimuli. Here, we present a model of a potential mechanism for graded firing. Our multicompartmental model provides stable plateau firing generated by a nonspecific calcium-sensitive cationic (CAN) current. Sustained firing is insensitive to small variations in Ca2+ concentration in a neutral zone. However, both high and low Ca2+ levels alter firing rates. Specifically, increases in persistent firing rate are triggered only during high levels of calcium, while decreases in rate occur in the presence of low levels of calcium. The model is consistent with detailed experimental observations and provides a mechanism for maintenance of memory-related activity in individual neurons.

Morphological and electrophysiological properties of lateral entorhinal cortex layers II and III principal neurons.

The intrinsic electrophysiology and morphology of neurons from layers II and III of the lateral entorhinal cortex (EC) was investigated in a rat brain slice preparation by intracellular recording and biocytin labeling. Morphologically, we distinguished three groups of layer II principal neurons. The most numerous group included cells with multiple radiating dendrites that spread over layers II and I in a fan-like fashion. While morphologically "fan" neurons were similar to the "stellate" cells of the medial EC, electrophysiologically the fan cells lacked the persistent rhythmic subthreshold oscillations and the very pronounced time-dependent inward rectification typical of the stellate cells. The second group consisted of pyramidal cells that manifested regular spike firing and had a more negative resting potential and a longer spike duration than the fan cells. In the third group we included all those neurons that had diverse multipolar appearances distinct from the fan cells. Neurons in this group had electrophysiological profiles intermediate between those of the fan and pyramidal cells. All neurons recorded in layer III were pyramidal in shape with a basal dendritic tree that could extend into layer V and an axon that could also give off collaterals into layer V. Electrophysiologically, layer III pyramidal cells were very similar to those of layer II. On the basis of these and other data we suggest that in different EC regions layer II neurons may be conducting more input-dependent specialized processing, while cells from layer III may perform a more global or generalized function.