Results in treatment of distal femur fractures using polyaxial locking plate

Indications and techniques of locked plate fixation for the treatment of challenging fractures continue to evolve. As design variant of classic locked plates, the polyaxial locked plate has the ability to alter the screw angle and thereby, enhance fracture fixation. The aim of this observational study was to evaluate clinical and radiographic results in 89 patients with 90 fractures of the distal femur treated, between June 2006 and November 2011, with such a polyaxial locked plating system (Polyax™ Locked Plating System, DePuy, Warsaw, IN, USA). Seventy-seven fractures formed the report of this study. These cases were followed up until complete fracture healing or for a mean time of 77 weeks. At the time of last follow-up, 58 of 77 fractures (75.3 %) progressed to union without complication and radiographic healing occurred at a mean time of 16.3 weeks. Complications occurred in ten fractures that did not affect the healing and in nine fractures that showed delayed or non-union. The mean American Knee Society Score at the time of final follow-up was 83 for the Knee Score and 71.1 for the Functional Score. In conclusion, there is a high union rate for complex distal femoral fractures associated with a good clinical outcome in this series.

The role of surgical treatment in the rehabilitation protocols of thoraco-lumbar spine injuries

BACKGROUND

Rehabilitation is a crucial issue in the management of spinal cord injuries (SCI) but, in these patients, the primary treatment can bias the outcome of recovery protocols.

AIM

Purpose of this paper is to review our case load in the treatment of surgical failures and to define the role of surgery in thoraco-lumbar injuries rehabilitation.

PATIENTS AND METHODS

Between 2000 and 2009 seventy patients with post-traumatic paraplegia were referred to Surgical Department as rehabilitation was unfeasible due to inadequate spine injury treatment. Forty-six had had surgery, 24 were treated conservatively Twenty-five patients had a thoracic lesion, 9 a lumbar lesion and 36 a lesion of the thoraco-lumbar junction. A total of 44 surgical procedures were performed (by anterior, posterior or anterior-posterior).

RESULTS

On postoperative imaging sagittal alignment was found good in 93% of cases and acceptable in 7%. All patients regained the sitting position within 5 days after surgery. Wound healing problems requiring revision were observed in 4 cases. Major complications were a cerebro spinal fluid (CSF) leakage and a massive pulmonary embolism case in the early post-op.

CONCLUSIONS

Wrong primary treatment frequently leads to demanding revision procedures with increased risks for the patient and more than double costs for the health care system. Whatever the technique a stable spine is the target in surgery of SCI allowing a quick and effective rehabilitation without external orthosis.

Posterior lumbar fusion by peek rods in degenerative spine: preliminary report on 30 cases

PURPOSE

Pre-curved peek rods to support posterior lumbar fusion have been available in the market since 4 years. Potential advantages using this new technology are increased load sharing on the anterior column promoting interbody fusion, reduced stress on bone-screw interface decreasing the rate of screw mobilization and, in the long term, reduced incidence of adjacent level disc degeneration.

METHODS

The authors retrospectively reviewed 30 cases in which posterior fusion was supported by peek rods, analyzing early complications, rate of fusion and clinical outcome.

RESULTS

At an average follow-up of 18 months, both clinical and radiographic results were satisfactory with only one case requiring surgical revision for a mechanical complication.

CONCLUSIONS

The semi-rigid systems can now be considered a viable option in the lumbar degenerative disease, although clinical evaluations are necessary in the longer term.

Analytical results on channel capacity in uncompensated optical links with coherent detection

Based on a recently introduced model of non-linear propagation, we propose analytical formulas for the capacity limit of polarization-multiplexed ultra-dense WDM uncompensated coherent optical systems at the Nyquist limit, assuming both lumped and ideally distributed amplification. According to these formulas, capacity fundamentally depends on the transmitted power spectral density and on the total optical WDM bandwidth, whereas it does not depend on symbol-rate. Also, capacity approximately decreases by 2 [bit/s/Hz] for every doubling of link length. We show examples of capacity calculations for specific ultra-long-haul links with different polarization-multiplexed (PM) constellations, i.e. ideal PM-Gaussian, PM-QPSK (quadrature-phase shift keying) and PM-QAM (quadrature amplitude modulation). We show that the launch power maximizing capacity is independent of link length and modulation format. We also discuss the usable range of PM-QAM systems and validate analysis with simulations.

Experimental validation of an analytical model for nonlinear propagation in uncompensated optical links

Link design for optical communication systems requires accurate modeling of nonlinear propagation in fibers. This topic has been widely analyzed in last decades with partial successes in special conditions, but without a comprehensive solution. Since the introduction of coherent detection with electronic signal processing the scenario completely changed because this category of systems shows better performances in links without in-line dispersion management. This change to uncompensated transmission allowed to modify the approach in the study of nonlinear fiber propagation and in recent years a series of promising analytical models have been proposed. In this paper, we present an experimental validation over different fiber types of an analytical model for nonlinear propagation over uncompensated optical transmission links. Considering an ultra-dense WDM system, we transmitted ten 120-Gb/s PM-QPSK signals over a multi-span system probing different fiber types: SSMF, PSCF and NZDSF. A good matching was found in all cases showing the potential of the analytical model for accurate performance estimation that could lead to powerful tools for link design.

Effect of pre-breathing oxygen at different depth on oxidative status and calcium concentration in lymphocytes of scuba divers

AIM

In-water pre-breathing oxygen at various depths reduces decompression-induced bubble formation and platelet activation, but it could induce side effects such as oxidative stress. The aim of this study was to investigate the effect of in-water pre-breathing oxygen, at different depths, on the oxidative status and intracellular calcium ([Ca(2+) ]i) of peripheral blood lymphocytes isolated from six divers. They participated in a 4-diving protocol. Two week recovery time was allowed between successive dives. Before diving, all divers, for 20 min, breathed normally at sea level (dive 1), 100% oxygen at sea level (dive 2), 100% oxygen at 6 msw (dive 3), 100% oxygen at 12 msw (dive 4). Then they dived to 30 msw for 20 min with air tank.

METHODS

Blood samples were collected before and after each dive. Hydrogen peroxide (H(2) O(2) ) levels, catalase (CAT) activity, mRNA expression of CAT, glutathione peroxidase (GPx) and superoxide dismutase (SOD), and the [Ca(2+) ]i in lymphocytes were measured.

RESULTS

The dives slightly decreased lymphocyte number and significantly reduced lymphocyte H(2) O(2) levels. CAT activity was higher after scuba diving and, dive 3 enhanced mRNA gene expression of CAT, GPx and SOD. The [Ca(2+) ]i was higher after dive 1 and 2 than pre-diving, while was maintained at pre-diving value after dive 3 and 4.

CONCLUSION

Our results suggest that pre-breathing oxygen, in particular at 12 msw, may enhance lymphocyte antioxidant activity and reduce reactive oxygen species levels. Pre-breathing oxygen in water may also preserve calcium homeostasis, suggesting a protective role in the physiological lymphocyte cell functions.

Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects

Coherent-detection (CoD) permits to fully exploit the four-dimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarization-switched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links.

Fundamental performance limits of optical duobinary

We present a rigorous analysis defining the fundamental performance limits of duobinary line-coding for optical communications. First, we compare the back-to-back performance of duobinary and intensity modulation systems in an AWGN channel satisfying the Nyquist criterion, with both linear and quadratic receiver. We show that, also for duobinary and quadratic receiver, matched filtering is the best achievable condition. Then, we derive a detailed performance analysis of duobinary in an ASE-noise-limited direct-detection optical system considering noise on the entire space of polarizations. We show that for duobinary line-coding the expression of the bit error rate depends both on the shape of the transmitted pulse and on the receiver optical filter. Comparing duobinary coded and uncoded intensity modulation systems, we show the intrinsic advantages of using the duobinary line-coding in a system based on quadratic detection. Finally, some results for realistic setups are obtained through simulation and compared to the fundamental limits in order to show how close to those limits state-of-the-art systems can operate.

Performance evaluation and assessment of receiver impairments of a novel PolSK transceiver based on differential demodulation

We present a novel transceiver setup for Polarization Shift Keying (PolSK) modulation using a simple transmitter and a receiver based on differential demodulation. The transmitter is made up of a LiNbO(3) phase modulator with the input fiber pigtailed at 45 degrees with respect to the principal axes of the modulator. The receiver is composed of an asymmetric Mach-Zehnder Interferometer (AMZI) and a couple of balanced photodetectors (BPD), as usually employed for receiving DPSK. To our knowledge, it is the first time such receiver structure is applied to PolSK. In order to fully assess the system performance of the proposed setup, we have carried out numerical simulations using a semi-analytical technique for bit-error-rate evaluation and performed experimental measurements at 10 Gbit/s. After having optimized transceiver performances, we evaluated the resilience to receiver impairments to verify the viability of a realistic implementation. Surprisingly, PolSK shows a better sensitivity using a single-end receiver (with the AMZI tuned at the minimum transmittance point) than using a balanced one. Another improvement has been obtained optimizing the driving voltage at the transmitter: this leads to a "non-ideal" PolSK modulation with non-orthogonal symbols, which shows an enhanced performance thanks to a synchronous phase modulation.

Long-haul 10 Gbit/s linear and non-linear IMDD transmission over uncompensated standard fiber using a SQRT-metric MLSE receiver

We experimentally demonstrated Intensity-Modulated Direct-Detection (IMDD) single-channel 1,040 km linear transmission and 800 km non-linear transmission at 10 Gb/s over standard single-mode (G.652) fiber, without any optical dispersion compensation or mitigation, using a Maximum-Likelihood Sequence-Estimation (MLSE) receiver employing the square-root (SQRT) branch metric with off-line processing. These experiments were designed as to probe the limits of the MLSE approach. They successfully showed that long-haul uncompensated transmission is in principle possible with MLSE, even in the presence of large uncompensated dispersion and strong intra-channel fiber non-linearities, provided that enough complexity can be built into the receiver. In the linear 1,040 km experiment, a Bit Error Rate (BER) of 10(-3) was achieved with an Optical Signal-to-Noise Ratio (OSNR) penalty with respect to back-to-back of 2.9 dB, using two samples per bit and 16,384 trellis states. Several other set-ups were tested as well, including the use of only one sample per bit and fewer trellis states. In the non-linear 800 km experiment, power was ramped up to 12 dBm, exciting substantial Kerr non-linearity, whose induced spectral-broadening exacerbated the effects of the large uncompensated dispersion of the link. Using an MLSE receiver with 1,024 states, we demonstrated a non-linear threshold of 9 dBm. We benchmarked this experiment towards simulations addressing various electrical and optical dispersion compensation strategies. We also carried out an analysis of error run-lengths, on both experiments, which showed that error burstiness may change considerably depending on the number of processor states, OSNR and the amount of non-linearity in the link.

Cryptogenic cerebral infarction in a young patient with very high lipoprotein(a) serum level as the only risk factor

Lipoprotein(a) [Lp(a)] is a plasma lipoprotein that consists of a low-density lipoprotein (LDL)-like particle containing APO B-100 and apolipoprotein(a), linked by a disulphide bridge. There is evidence that higher serum level of Lp(a) is a predictor of various vascular diseases, such as myocardial infarction, coronary stenosis, re-occlusion of aortocoronary bypass vein grafts, peripheral atherosclerosis and cerebral infarction [1-4]. We describe a young man with a cryptogenic stroke with very high serum level of Lp(a) as the only vascular risk factor.

Atherosclerotic adult Moya-Moya disease in a patient with hyperhomocysteinaemia

Moya-Moya is a rare cerebrovascular occlusive disease characterized by bilateral stenosis or occlusion at the terminal portion of the internal carotid artery and abnormal vascular network at the base of the brain, named "moya-moya". In children, Moya-Moya disease usually presents with ischemic cerebrovascular events, mainly TIA or lacunar stroke, leading to mental deterioration. In adults, especially in females, it presents with intracranial haemorrhages. We describe the case of an adult patient with an atherosclerotic Moya-Moya disease which presented with a cerebral borderzone infarction.

Spatial anisotropy in the encoding of three-dimensional passive limb position by the spinocerebellum

In an earlier study, we found that the encoding of limb position in the sagittal plane across the population of spinocerebellar Purkinje cells was anisotropic with a preferential gradient along horizontal direction. The aim of this study was to extend to a three-dimensional (3D) workspace the analysis of the relationships between Purkinje cells activity and rat's forelimb spatial position. In anesthetized animals, the extracellular activity of 121 neurons was recorded while a robot passively placed the limb in 18 positions within a cubic workspace (3x3x3 cm). In order to characterize the relationship between spatial locations and Purkinje cell activity we performed a backward stepwise regression starting from a model with three independent variables representing the antero-posterior, the medial-lateral and the vertical axes of workspace. Regression analysis showed that the firing of most cells was modulated exclusively along the antero-posterior (25%) or the medial-lateral (38%) axis, while a small portion was related only to the vertical axis (8%), indicating a generalized nonuniform sensitivity of Purkinje cells to limb displacement in 3D space.

Hyperbaric oxygenation ameliorates indomethacin-induced enteropathy in rats by modulating TNF-alpha and IL-1beta production

The effect of hyperbaric oxygenation (HBO2) was investigated in a rat model of indomethacin-induced enteropathy. Enteropathy was induced by two subcutaneous injections of indomethacin (7.5 mg/kg) 24 hr apart. Six groups of rats (n=8) were treated with and without HBO2 (100% oxygen at 2.3 atm absolute) for 1 hr once or twice a day for 2 or 5 days. Disease activity index (DAI) and total ulcer length were measured. Other rats were randomized into two groups (n=16) with and without HBO2 (1 hr once a day) and four rats were killed in each group at 12, 24, 48, and 72 hr after the final injection of indomethacin. Serum and intestinal mucosal TNF-alpha, IL-1beta, myeloperoxidase (MPO), and iNOS expression was measured. HBO2 treatment significantly attenuated indomethacin -induced intestinal ulceration and improved DAI. Indomethacin increased MPO activity and iNOS expression, and these were reduced by HBO2 treatment, with a concomitant reduction in TNF-alpha and IL-1beta. Our data suggest that HBO2 treatment has a beneficial effect on indomethacin-induced enteropathy and this effect is possibly mediated by decreased production of TNF-alpha and IL-1beta.

Phase-specific sensory representations in spinocerebellar activity during stepping: evidence for a hybrid kinematic/kinetic framework

The dorsal spinocerebellar tract (DSCT) provides a major mossy fiber input to the spinocerebellum, which plays a significant role in the control of posture and locomotion. Recent work from our laboratory has provided evidence that DSCT neurons encode a global representation of hindlimb mechanics during passive limb movements. The framework that most successfully accounts for passive DSCT behavior is kinematics-based having the coordinates of the limb axis, limb-axis length and orientation. Here we examined the responses of DSCT neurons in decerebrate cats as they walked on a moving treadmill and compared them with the responses passive step-like movements of the hindlimb produced manually. We found that DSCT responses to active locomotion were quantitatively different from the responses to kinematically similar passive limb movements on the treadmill. The differences could not be simply accounted for by the difference in limb-axis kinematics in the two conditions, nor could they be accounted for by new or different response components. Instead, differences could be attributed to an increased relative prominence of specific response components occurring during the stance phase of active stepping, which may reflect a difference in the behavior of the sensory receptors and/or of the DSCT circuitry during active stepping. We propose from these results that DSCT neurons encode two global aspects of limb mechanics that are also important in controlling locomotion at the spinal level, namely the orientation angle of the limb axis and limb loading. Although limb-axis length seemed to be an independent predictor of DSCT activity during passive limb movements, we argue that it is not independent of limb loading, which is likely to be proportional to limb length under passive conditions.

Recurrent cerebrovascular ischaemic events in patients with interatrial septal abnormalities: a follow-up study

The aim of this study was to evaluate the risk of recurrent ischaemic cerebrovascular events (stroke or transient ischaemic attack (TIA)) in patients with patent foramen ovale (PFO) or atrial septal aneurysm (ASA) treated with different therapeutic regimens. We enrolled 86 patients aged 18-60 years with an unexplained ischaemic stroke or TIA referred to our inpatient department in the period May 1994-December 1999. Follow-up lasted until April 2003. Patients were excluded if the stroke or TIA was related to large-artery atherosclerosis, small artery occlusion, major cardiac sources of embolism or other uncommon causes. During a follow-up (mean+/-SD) of 64.1+/-28.8 months (range 8.1-105.6) a recurrent ischaemic cerebrovascular event occurred in 11/86 patients (12.8%) (5 TIA and 6 strokes). Eight events (4 TIA, 4 strokes) occurred in the 59 patients with PFO alone, three (1 TIA, 2 strokes) in the 21 with PFO plus ASA and none in the 6 patients with ASA alone. In the overall population the cumulative risk of recurrent stroke/TIA was 1.2% at 2 years, 5.5% at 4 years, 7.6% at 6 years and 23.6% at 8 years, and was similar in patients with PFO alone vs. patients with PFO plus ASA (9.0% vs. 6.1% at 6 years, 26.0% vs. 23.1% at 8 years; p>0.05). Nine cerebral ischaemic events (4 TIA, 5 strokes) occurred in the 48 patients treated with antiplatelet drugs (7 in patients with PFO, 2 in patients with PFO plus ASA), and two (1 TIA, 1 stroke) in the 17 patients treated with oral anticoagulants (1 with PFO, 1 with PFO plus ASA). No events occurred in patients submitted to transcatheteral closure.

Kinematic and non-kinematic signals transmitted to the cat cerebellum during passive treadmill stepping

Previous work from this laboratory has shown that activity in the dorsal spinocerebellar tract (DSCT) relates strongly to global hindlimb kinematics variables during passive displacements of the hindlimb. A linear relationship to limb axis orientation and length variables accounts for most of the response variance for passive limb positioning and movement. Here we extend those observations to more natural movements by examining the information carried by the DSCT during passive stepping movements on a treadmill, and we compare it to information transmitted during passive robot-driven hindlimb movements. Using a principal component analysis approach, we found that a linear relationship between the responses and hindlimb kinematics was comparable across experimental conditions. We also observed systematic non-linearities in this relationship for both types of movement that could be attributed to events corresponding to the touch-down and lift-off phases of the movement. We concluded that proprioceptive information transmitted to the cerebellum by the DSCT during locomotion has at least two major components. One component is associated with limb kinematics (limb orientation) and may be more or less related to the metrics of the step (stride length, for example) or its velocity. The other component is associated with limb length and/or limb loading, and it may signal some aspect of limb stiffness.

Apolipoprotein E Polymorphism and Stroke Subtypes in an Italian Cohort

BACKGROUND

Studies have indicated that apolipoprotein E (ApoE)-epsilon4 is a risk factor for ischemic cerebrovascular diseases (ICVD), but the existence of this association is still controversial. The aims of this study were: (1) to compare ApoE genotype and allele frequencies in Italian cases with ICVD and in healthy control subjects and (2) to compare ApoE allele frequencies among ischemic stroke subtypes.

METHODS

A hospital-based cohort of 302 Italian subjects with ICVD and 228 healthy subjects have been recruited to investigate the role of ApoE polymorphisms as risk factors for ICVD. TOAST criteria were employed to stratify ICVD cases by subtypes.

RESULTS

No significant differences in ApoE genotype and allele frequencies were found between cases and control subjects. The frequency of ApoE-epsilon4 was lower in cases than in control subjects (6% vs. 10.1%), although not significantly. No differences in ApoE genotype and allele frequencies were evident among ICVD subtypes. However, out of 36 ApoE-epsilon4 alleles 23 (3.7%) were found in subjects with ICVD related to primary degenerative arterial disease related to large vessel disease and small vessel disease, and 13 (2.1%) in remaining subjects. Using logistic regression analysis we assessed whether ApoE-epsilon4 allele was independently associated with risk of ICVD related to a primary degenerative arterial disease compared to other ICVD subtypes. While classical risk factors were significantly associated with higher risk for ICVD due to large vessel disease and small vessel disease than other ICVD subtypes, the role of ApoE-epsilon4 allele was not significant (OR 1.25, 95% CI 0.57-2.74).

CONCLUSION

Our study shows similar ApoE-epsilon4 genotype and allele frequencies in patients with ICVD and in control subjects. No differences were found among different ICVD subtypes either.

Modulation of dorsal spinocerebellar responses to limb movement. I. Effect of serotonin

Spinocerebellar neurons (DSCT) receive converging sensory information from various sensory receptors in the hindlimbs and lower trunk. Previous studies have shown that sensory processing by DSCT neurons results in a representation of global hindlimb kinematic parameters such as the length and the orientation of the limb axis. In addition to the sensory input, the DSCT circuitry also receives a descending input from the raphe nuclei in the brain stem. Recent studies have demonstrated that the raphe serotonergic terminals synapse directly on DSCT neurons and exert a differential modulatory influence on their sensory inputs. We examined the role of serotonergic modulation on the DSCT representation of hindlimb kinematic parameters by recording DSCT activity during passive hindlimb movements before and after perturbing serotonergic transmission. We used two types of perturbation: electrical stimulation of the raphe areas in the brain stem to release serotonin in the spinal cord (42 neurons) and intravenous administration of serotonergic agonists or antagonists, mostly the 5HTP2 antagonist ketanserin (30 neurons). We found that movement responses were altered in approximately 70% of the DSCT units studied with each protocol. Changes could include shifts in mean firing rate, increases or decreases in response amplitude, and changes in response waveform. We used a principal component analysis (PCA) to examine waveform components and to determine how they contributed to the response waveform changes caused by serotonin perturbation. Such changes could be explained by new or different response components that might indicate a modification in the data processing or by a different weighting of existing components that might indicate a modification of synaptic weighting. The results were consistent with the second alternative. We found that the same underlying response components could account for both control responses and those altered by serotonin perturbations. The observed changes in waveform could be entirely accounted for by a re-weighting of response components. In particular, the changes observed after raphe stimulation could be accounted for by selective changes in the weighting of the first principal component (PC) with only minor changes of the weighting of the second PC. Because these response components were shown previously to correlate with the limb axis orientation and length trajectories respectively, the finding is consistent with the idea that limb axis length and orientation information are processed separately within the spinal circuitry.