Deep Learning-Assisted Multiphoton Microscopy to Reduce Light Exposure and Expedite Imaging in Tissues With High and Low Light Sensitivity

Purpose

Two-photon excitation fluorescence (2PEF) reveals information about tissue function. Concerns for phototoxicity demand lower light exposure during imaging. Reducing excitation light reduces the quality of the image by limiting fluorescence emission. We applied deep learning (DL) super-resolution techniques to images acquired from low light exposure to yield high-resolution images of retinal and skin tissues.

Methods

We analyzed two methods: a method based on U-Net and a patch-based regression method using paired images of skin (550) and retina (1200), each with low- and high-resolution paired images. The retina dataset was acquired at low and high laser powers from retinal organoids, and the skin dataset was obtained from averaging 7 to 15 frames or 70 frames. Mean squared error (MSE) and the structural similarity index measure (SSIM) were outcome measures for DL algorithm performance.

Results

For the skin dataset, the patches method achieved a lower MSE (3.768) compared with U-Net (4.032) and a high SSIM (0.824) compared with U-Net (0.783). For the retinal dataset, the patches method achieved an average MSE of 27,611 compared with 146,855 for the U-Net method and an average SSIM of 0.636 compared with 0.607 for the U-Net method. The patches method was slower (303 seconds) than the U-Net method (<1 second).

Conclusions

DL can reduce excitation light exposure in 2PEF imaging while preserving image quality metrics.

Translational Relevance

DL methods will aid in translating 2PEF imaging from benchtop systems to in vivo imaging of light-sensitive tissues such as the retina.

A Clinical Perspective on the Automated Analysis of Reflectance Confocal Microscopy in Dermatology

BACKGROUND AND OBJECTIVES

Non-invasive optical imaging has the potential to provide a diagnosis without the need for biopsy. One such technology is reflectance confocal microscopy (RCM), which uses low power, near-infrared laser light to enable real-time in vivo visualization of superficial human skin from the epidermis down to the papillary dermis. Although RCM has great potential as a diagnostic tool, there is a need for the development of reliable image analysis programs, as acquired grayscale images can be difficult and time-consuming to visually assess. The purpose of this review is to provide a clinical perspective on the current state of artificial intelligence (AI) for the analysis and diagnostic utility of RCM imaging.

STUDY DESIGN/MATERIALS AND METHODS

A systematic PubMed search was conducted with additional relevant literature obtained from reference lists.

RESULTS

Algorithms used for skin stratification, classification of pigmented lesions, and the quantification of photoaging were reviewed. Image segmentation, statistical methods, and machine learning techniques are among the most common methods used to analyze RCM image stacks. The poor visual contrast within RCM images and difficulty navigating image stacks were mediated by machine learning algorithms, which allowed the identification of specific skin layers.

CONCLUSIONS

AI analysis of RCM images has the potential to increase the clinical utility of this emerging technology. A number of different techniques have been utilized but further refinements are necessary to allow consistent accurate assessments for diagnosis. The automated detection of skin cancers requires more development, but future applications are truly boundless, and it is compelling to envision the role that AI will have in the practice of dermatology. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Fast, large area multiphoton exoscope (FLAME) for macroscopic imaging with microscopic resolution of human skin

We introduce a compact, fast large area multiphoton exoscope (FLAME) system with enhanced molecular contrast for macroscopic imaging of human skin with microscopic resolution. A versatile imaging platform, FLAME combines optical and mechanical scanning mechanisms with deep learning image restoration to produce depth-resolved images that encompass sub-mm² to cm² scale areas of tissue within minutes and provide means for a comprehensive analysis of live or resected thick human skin tissue. The FLAME imaging platform, which expands on a design recently introduced by our group, also features time-resolved single photon counting detection to uniquely allow fast discrimination and 3D virtual staining of melanin. We demonstrate its performance and utility by fast ex vivo and in vivo imaging of human skin. With the ability to provide rapid access to depth resolved images of skin over cm² area and to generate 3D distribution maps of key sub-cellular skin components such as melanocytic dendrites and melanin, FLAME is ready to be translated into a clinical imaging tool for enhancing diagnosis accuracy, guiding therapy and understanding skin biology.

Portable all-fiber dual-output widely tunable light source for coherent Raman imaging

We present a rapidly tunable dual-output all-fiber light source for coherent Raman imaging, based on a dispersively matched mode-locked laser pumping a parametric oscillator. Output pump and Stokes pulses with a maximal power of 170 and 400 mW, respectively, and equal durations of 7 ps could be generated. The tuning mechanism required no mechanical delay line, enabling all-electronic arbitrary wavelength switching across more than 2700  cm - 1 in less than 5 ms. The compact setup showed a reliable operation despite mechanical shocks of more than 25  m / s 2 and is, thus, well suited for operation in a mobile cart. Imaging mouse and human skin tissue with both the portable light source and a commercial laboratory-bound reference system yielded qualitatively equal results and verified the portable light source being well suited for coherent Raman microscopy.

Junction Plasmon Driven Population Inversion of Molecular Vibrations: A Picosecond Surface-Enhanced Raman Spectroscopy Study

Molecular surface-enhanced Raman spectra recorded at single plasmonic nanojunctions using a 7 ps pulse train exhibit vibrational up-pumping and population inversion. The process is assigned to plasmon-driven, dark, impulsive electron-vibration (e-v) excitation. Both optical (Raman) pumping and hot-electron mediated excitation can be rejected by the characteristic spectra, which allow the simultaneous measurement of vibrational temperature of the molecules and electronic temperature of the metal. Vibrational populations are determined from anti-Stokes to Stokes intensity ratios, while the electron temperature is obtained from the anti-Stokes branch of the electronic Raman scattering continuum. Population inversion survives in high-frequency vibrations that effectively decouple from the metal.

Particle sensing with confined optical field enhanced fluorescence emission (Cofefe)

We describe the development and performance of a new type of optical sensor suitable for registering the binding/dissociation of nanoscopic particles near a gold sensing surface. The method shares similarities with surface plasmon resonance microscopy but uses a completely different optical signature for reading out binding events. This new optical read-out mechanism, which we call confined optical field enhanced fluorescence emission (Cofefe), uses pulsed surface plasmon polariton fields at the gold/liquid interface that give rise to confined optical fields upon binding of the target particle to the gold surface. The confined near-fields are sufficient to induce two-photon absorption in the gold sensor surface near the binding site. Subsequent radiative recombination of the electron-hole pairs in the gold produces fluorescence emission, which can be captured by a camera in the far-field. Bound nanoparticles show up as bright confined spots against a dark background on the camera. We show that the Cofefe sensor is capable of detecting gold and silicon nanoparticles, as well as polymer nanospheres and sub-μm lipid droplets in a label-free manner with average illumination powers of less than 10 μW/μm2.

Pyrroloquinoline quinone prevents developmental programming of microbial dysbiosis and macrophage polarization to attenuate liver fibrosis in offspring of obese mice

Increasingly, evidence suggests that exposure to maternal obesity creates an inflammatory environment in utero, exerting long‐lasting postnatal signatures on the juvenile innate immune system and microbiome that may predispose offspring to development of fatty liver disease. We found that exposure to a maternal Western‐style diet (WD) accelerated fibrogenesis in the liver of offspring and was associated with early recruitment of proinflammatory macrophages at 8‐12 weeks and microbial dysbiosis as early as 3 weeks of age. We further demonstrated that bone marrow‐derived macrophages (BMDMs) were polarized toward an inflammatory state at 8 weeks of age and that a potent antioxidant, pyrroloquinoline quinone (PQQ), reversed BMDM metabolic reprogramming from glycolytic toward oxidative metabolism by restoring trichloroacetic acid cycle function at isocitrate dehydrogenase. This resulted in reduced inflammation and inhibited collagen fibril formation in the liver at 20 weeks of age, even when PQQ was withdrawn at 3 weeks of age. Beginning at 3 weeks of age, WD‐fed mice developed a decreased abundance of Parabacteroides and Lactobacillus, together with increased Ruminococcus and decreased tight junction gene expression by 20 weeks, whereas microbiota of mice exposed to PQQ retained compositional stability with age, which was associated with improved liver health. Conclusion: Exposure to a maternal WD induces early gut dysbiosis and disrupts intestinal tight junctions, resulting in BMDM polarization and induction of proinflammatory and profibrotic programs in the offspring that persist into adulthood. Disrupted macrophage and microbiota function can be attenuated by short‐term maternal treatment with PQQ prior to weaning, suggesting that reshaping the early gut microbiota in combination with reprogramming macrophages during early weaning may alleviate the sustained proinflammatory environment, preventing the rapid progression of nonalcoholic fatty liver disease to nonalcoholic steatohepatitis in offspring of obese mothers. (Hepatology Communications 2018;2:313‐328)

CdS/ZnS core-shell nanocrystal photosensitizers for visible to UV upconversion

Herein we report the first example of nanocrystal (NC) sensitized triplet-triplet annihilation based photon upconversion from the visible to ultraviolet (vis-to-UV). Many photocatalyzed reactions, such as water splitting, require UV photons in order to function efficiently. Upconversion is one possible means of extending the usable range of photons into the visible. Vis-to-UV upconversion is achieved with CdS/ZnS core-shell NCs as the sensitizer and 2,5-diphenyloxazole (PPO) as annihilator and emitter. The ZnS shell was crucial in order to achieve any appreciable upconversion. From time resolved photoluminescence and transient absorption measurements we conclude that the ZnS shell affects the NC and triplet energy transfer (TET) from NC to PPO in two distinct ways. Upon ZnS growth the surface traps are passivated thus increasing the TET. The shell, however, also acts as a tunneling barrier for TET, reducing the efficiency. This leads to an optimal shell thickness where the upconversion quantum yield (Φ'UC) is maximized. Here the maximum Φ'UC was determined to be 5.2 ± 0.5% for 4 monolayers of ZnS shell on CdS NCs.

Surface-enhanced coherent anti-Stokes Raman imaging of lipids

This work describes in detail a wide-field surface-enhanced coherent anti-Stokes Raman scattering (CARS) microscope, which enables enhanced detection of sample structures in close proximity (∼100  nm) of the substrate interface. Unlike conventional CARS microscopy, where the sample is illuminated with freely propagating light, the current implementation uses evanescent fields to drive Raman coherences across the entire object plane. By coupling the pump and Stokes excitation beams to the surface plasmon-polariton mode at the interface of a 30 nm thick gold film, we obtained strong CARS signals from cholesteryl oleate droplets adhered to the surface. The surface-enhanced CARS imaging system visualizes lipid structures with vibrational selectivity using illumination doses per unit area that are more than four orders of magnitude lower than in point-scanning CARS microscopy.

A Kinetic Study of In Vitro Lysis of Mycobacterium smegmatis

The traditional diagnostic tests for tuberculosis consist of an acid fast stain and a culture test from a sputum sample. With the emergence of drug resistant strains of tuberculosis, nucleic acid amplification has become the diagnostic test of choice. The nucleic acid amplification test consists of four steps: sputum sample collection, lysis of bacilli to release DNA, DNA amplification by PCR and detection of PCR products. The DNA extraction step has been largely overlooked and this study describes a systematic approach to measure the kinetics of cell lysis in a Tris-EDTA buffer. Mycobacterium smegmatis is a saphorytic, fast-growing mycobacterium that is often used as a surrogate of Mycobacterium tuberculosis in laboratory studies. M. smegmatis cells have been transformed with green fluorescent protein (GFP) genes. Transformed cells are lysed in a temperature-controlled cuvette that is equipped with optical input/output. The fluorescence signal increases when the GFP is released from lysed cells, and the extent of lysis of the loaded cells can be followed in real time. The experimental results are complemented by two theoretical models. The first model is based on a Monte Carlo simulation of the lysis process and the accompanying probability density function as described by the Fokker-Planck equation. The second model follows a chemical reaction engineering approach: the cell wall is modeled as layers, where each layer is made up of 'blocks'. Blocks can only be removed if they are exposed to the lysis solution and the model describes the rate of block exposure and removal. Both models are consistent with the experimental results. The main findings are: (1) the activation energy for M. smegmatis lysis by Tris-EDTA buffer is 22.1kcal/mole, (2) cells lyse on the average after 14-17% loss in cell wall thickness locally, (3) with the help of the models, the initial distribution in cell wall thickness of the population can be resolved, (4) near complete lysis of the cells is accomplished in 200 seconds at 80°C (90 seconds at 90°C). The results can be used to design an optimal lysis protocol that compromises between shorter processing times at higher temperature and reduced thermal damage to DNA at lower temperature.

Selectivity and stability of organic films at the air–aqueous interface

It has recently been determined that organic compounds represent a significant percentage of the composition of certain atmospheric aerosols. Amphiphilic organics, such as fatty acids and alcohols, partition to the interface of aqueous aerosols. In this way, the air-aqueous interface of an aerosol has the ability to act as both a concentrator and a selector of organic surfactants. Isotherms of nonanoic acid, stearic acid, 1-octadecanol, and a binary of mixture of nonanoic and stearic acids were used to infer the packing ability and molecular orientation of the surfactants at the interface. The selectivity of the air-aqueous interface was studied by monitoring the composition of binary organic films as a function of film exposure time. The films were formed, aged, and collected with the use of a Langmuir trough. The composition of the aged film was determined via GC-MS. Surfactants with differing carbon number and chemical functionalities were studied. These included stearic acid, lauric acid, 1-octadecanol, and octadecane. The stability and packing ability of stearic and lauric acid films were examined as a function of subphase pH. The relevance of these findings as they relate to the composition and structure of organic aerosols as well as recent surface-sensitive aerosol field measurements is discussed.

One step forward and two steps back: the dangers of walking backwards in therapy

Walking backwards has been used in therapy to improve balance and gait. There has not been any systematic investigation into the effectiveness or safety of walking backwards. We present two cases in which walking backwards during physical therapy resulted in a fall and considerable morbidity. The only clear indication for treatment by walking backwards should be a task-specific need to do so, and only then if adequate safety can be assured.

Forces, moments, and acceleration acting on a restrained dummy during simulation of three possible accidents involving a wheelchair negotiating a curb: comparison between lap belt and four-point belt

The objective of this study was to determine the effect of two types of restraining belts (lap belt and a four-point belt) on an instrumented dummy during three situations: wheelchair hitting straight into curb (SIC); wheelchair falling straight off a curb (SOC); wheelchair falling diagonally off a curb (DOC). A fully instrumented (50th percentile Hybrid III) dummy was seated in a standard wheelchair and restrained with one of the belts. The wheelchair rolled down a ramp reaching a platform at 2.4 miles per hour (comfortable walking speed). Three types of experiments were performed: SIC, SOC, DOC. Each experiment was repeated at least three times. Forces, moments, and acceleration were monitored and recorded via 48 sensors placed at the head, spine, and limbs. All experiments were videotaped and photographed. The data were averaged and compared with standards that have been previously established in car crash testing and with data recently obtained in a similar study using a nonrestrained dummy. Our results showed that in the SIC experiments, low magnitude forces, moments, and acceleration of no clinical significance were recorded with both types of belts. The wheelchair remained upright and the dummy safely seated. In the SOC experiments, the two belts prevented the dummy's ejection from the chair and, thus, have been effective in lowering the forces, moments, and acceleration and preventing significant injuries to the head and neck regions. In the DOC experiments, the lap belt proved to be somewhat more effective than the four-point belt in lowering the extension forces at the upper neck and the moments at the lower neck below injury levels. It also kept the head injury criteria well below injury level. We postulate that the four-point belt was less effective because of its more extensive body fixation, which leads to concentration of moments and forces at the head and lower neck regions. The results of this study show that restraining systems can enhance the safety of wheelchair occupants in certain incidents. It has been demonstrated that the lap belt is as effective as the four-point belt system in SIC and SOC incidents. In DOC falls, neither belt could prevent falls and trauma to the head and neck region. The lap belt, however, was somewhat superior. We recommend that wheelchairs be equipped with a lap belt and patients be encouraged to buckle-up while using the wheelchair outdoors.

Forces, moments, and accelerations acting on an unrestrained dummy during simulations of three wheelchair accidents

To determine the magnitude and distribution of the forces, moments, and accelerations acting on an individual sitting in a wheelchair during three possible accidents occurring while negotiating a sidewalk curb, experimental trials were performed in a bioengineering laboratory using a 50th percentile Hybrid III dummy seated in a standard wheelchair. A ramp was designed with an adjustable incline to allow the wheelchair to reach the edge of a sidewalk height platform at the desired forward speed of 2.5 miles per hour (comfortable walking speed). The wheelchair velocity was monitored via an optical pickup. Three types of accidents were simulated: (1) a wheelchair hitting straight into a curb; (2) a wheelchair falling forward straight off a curb; (3) a wheelchair falling diagonally off a curb. Each experiment was repeated three times. Each run was photographed using high-speed cameras and videotaped from three perspectives: frontal, lateral, and overhead. The results were averaged and compared with published injury Assessment Values (IAV) and Head Injury Criteria (HIC). Of significance were the following results. In the straight into a curb experiments, the wheelchair remained upright and the dummy seated. Low magnitude forces (23-73 N), moments (1-12 Nm), and accelerations (0.2-1 G) were recorded at the neck and head. The HIC was low at 0.3. These results were of no clinical significance. In the straight off a curb experiments, properly attached footrests prevented the wheelchair from toppling over but did not prevent the dummy from falling off the wheelchair. Forces (187-4,176 N), moments (3-178 Nm), and accelerations (131-206 G) of great magnitude were recorded at the head and neck when the dummy fell off the wheelchair. These values were above IAV. The HIC was 960. In the diagonally off a curb experiments, both the wheelchair and the dummy fell sideways. High-magnitude forces (274-2,313 N), moments (4-110 Nm), and acceleration (140-236 G) were recorded in the head and neck regions. The HIC was 975. These values were close to IAV and may signify potential serious injuries.

Outcome for patients with leukemia, multiple myeloma and lymphoma who relapse after high dose therapy and autologous stem cell support

Relapses after autologous transplantation are a serious clinical problem in patients with haematological diseases. The decision making for handling of such patients is difficult and the aim of this retrospective analysis of posttransplant relapses was 1) to obtain information of practical importance for the management of future relapses and 2) to evaluate the basis for clinical phase I-II trials of salvage therapy combined with biological modifiers. Included in the study were 283 patients with acute leukemia, multiple myeloma and malignant lymphoma who relapsed after autologous transplantations during a five year period from 1989 to 1994. Chemo- and radiotherapy was given to 229 patients after relapse or due to progressive disease and the response evaluated after 90 days. Fifty four patients (24%) obtained a complete remission and 44 patients (19%) partial responses. The overall median survival from relapse was 5 months. In the group given salvage treatment the median survival was 7 months and in the 54 patients who obtained remission the median survival was 15 months. So far 6 of 14 patients in continuous complete remission have a remission time after relapse longer than the time in remission after transplantation. Survival after relapse depended upon the time from transplantation to relapse, primary disease and if salvage therapy was given. In conclusion posttransplant relapses can be treated but the strategy has to be evaluated in future clinical trials.

Odontoid fracture and C1-C2 subluxation in psoriatic cervical spondyloarthropathy. A case report

STUDY DESIGN

Case presentation and review of pertinent literature.

OBJECTIVES

To present an unusual case and alert other physicians to possible missed diagnoses.

SUMMARY OF BACKGROUND DATA

An unusual case is presented of a young man with server psoriatic spondyloarthropathy and fusion of C2-C7 (Type II cervical psoriatic ankylosing disease) who fell at home, sustaining an unrecognized fracture of the odontoid process leading to subluxation of C1-C2 and the transitory tetraplegia. The patient presented with torticollis, and the fracture was unrecognized for a long period of time.

METHODS

Case presentation.

RESULTS

This patient became independent in all activities of daily living after surgery and rehabilitation despite persistence of torticollis.

CONCLUSIONS

A patient who presents clinically with traumatic torticollis after minor trauma and who also has psoriasis and ankylosis of the cervical spine should be suspected of having a fracture-subluxation until definitely proven otherwise. In the present case, the late diagnosis delayed surgical stabilization.

The instrumented walker: usage patterns and forces

Studies documenting the forces that are transmitted through a walker's frame are still scant. The purpose of this study was to evaluate the pattern and magnitude of forces that are transmitted through the frame of a walker during ambulation. A standard aluminum walker was instrumented. Gauges, which were mounted on all four legs, recorded axial, frontal, and sagittally oriented forces. A custom made computerized system registered the forces during 30 seconds of data acquisition. Twelve patients with ambulation dysfunction were tested with this system. Two different usage patterns emerged from the study. One usage pattern was observed in patients who were using the walker as a mean to reduce the amount of weight transmitted through the lower extremity. The second pattern was observed in patients with severe balance problems. These patients used the walker to enhance their balance and stability. The system described allows walker usage pattern analysis. Better understanding of force distribution and usage patterns may lead to improved or new walker design.

Clinical, serological and PCR evidence of cytomegalovirus infection in the central nervous system in infancy and childhood

Over a 3-year-period (Dec. 1990-Nov. 1993) 12 children were found PCR-positive for CMV-DNA in CSF and brain biopsies. Three of the patients were immunologically compromised. During the same period CSF samples from 10 shunt-operated children and 143 virological routine CSF samples were PCR CMV negative. Clinical association with positive PCR-CMV reaction was considered likely in 6 patients: two boys developed prolonged fever and meningoencephalitis following neurosurgery, one infant girl had a course compatible with congenital inclusion disease, and three had prolonged fever following transplantation. Clinical association was deemed probable in 3 infant girls: one had neonatal infection, meningitis and intraventricular haemorrhage, one had neonatal encephalitis and failure to thrive, and one with neonatal seizures and encephalitis developed brain atrophy. Clinical association was judged possible in 3 patients: one infant girl with no signs of encephalitis developed brain atrophy, one had an Aicardi Type 1 syndrome and one 2 1/2-year-old boy had an acute encephalitis with insufficient serological support for CMV but was 12 months later PCR positive for CMV. We conclude that CMV may be an overlooked infectious agent of the CNS also in immunocompetent children. PCR aids in rapid diagnosis of CMV infection in the immunocompromised. CMV may occasionally be disclosed with PCR in other conditions as a probably non-relevant observation.

Total knee arthroplasty in Parkinson's disease

Total knee arthroplasty in Parkinson's disease (PD) has been reported only twice in the literature. Parkinson's disease is considered a contra-indication for total knee replacement by some authors. We report on a 77-year-old man with PD who underwent total knee arthroplasty for severe degenerative joint disease. The patient had a somewhat prolonged but successful rehabilitation as an inpatient and continued to make gains following discharge. Currently he is an independent functional ambulator. Based on our experience with this patient, we recommend that patients with PD who maintain ambulatory function prior to surgery and are cognitively able to integrate new knowledge and follow commands should be considered candidates for total knee replacement if it is indicated. Our patient demonstrates, however, that even in patients suffering from mild PD the rehabilitation process may be significantly prolonged and more difficult than in patients without PD. Objective studies evaluating the role of pre-surgical rehabilitation are needed.

Bilateral brachial plexus palsy after immediate breast reconstruction with TRAM flaps

Although most postoperative upper extremity neuropathies are caused by extremes of position or intraoperative manipulation of the arm, nerve injury is possible without either of these. Pedicled TRAM flap surgery, during which no axillary retraction or hyperabduction of the arm is used, is not free of risk for neural injury. More studies are needed to specifically define risk-related maneuvers for these and other anesthetized patients.

Diabetic lumbar radiculopathy: sciatica without disc herniation

Three patients with diabetic radiculopathy (DR) are presented. The clinical aspects of DR, its management, and differential diagnosis are reviewed. Diabetic radiculopathy commonly presents with severe unilateral pain of sudden onset that is usually located in the lower extremity, frequently in the proximal segments. Occasionally, bilateral asymmetric pain may be observed. The pain is severe and may require narcotic medications. Sphincteric involvement is rare. Weakness of hip or thigh muscles, decreased sensation and hypo- or areflexia are commonly observed. The clinical picture can resemble that of high lumbar disc herniation. Electrodiagnostic and radiological studies may help differentiate between the two conditions.

Nocturnal low back pain in pregnancy: polysomnographic correlates

Thirteen women in late stages of pregnancy underwent a polysomnographic study. Eight women (61%) complained of mild nocturnal back pain or back discomfort. Five women (39%) did not complain of nocturnal back pain. The two groups did not differ in total bed time, total sleep time, sleep latency, and wake after sleep onset (WASO). A significant decrease in rapid eye movement (REM) sleep and an increase in stage 2 were observed in the pain group. The same group had a statistically significant decrease in the basal O2 saturation level. The pain group also spent a longer time sleeping in the supine position. We hypothesize that a prolonged stay in the supine position leads to obstruction of the vena cava. In the presence of inadequate collateral circulation, increased pressure and venostasis in combination with a decrease in basal oxygen saturation may lead to hypoxemia, compromise the metabolic supply of the neural structures, and result in pain. It appears, therefore, that the vascular system plays an important role in the pathogenesis of pain. The role played by the disturbed sleep architecture in the production of pain remains to be established. It is possible that the changes observed in sleep architecture result from pain rather than contribute to pain production.

Sleep in normal late pregnancy

Twelve women in their third trimester of pregnancy and 10 age-matched nonpregnant controls underwent complete polysomnography for one night in the laboratory. Seven of the original women returned for a second study 3-5 months postpartum. During late pregnancy, women showed increased wake after sleep onset (WASO) and a lower sleep efficiency in comparison with the control group. The percentage of rapid eye movement (REM) sleep was significantly decreased and the percentage of stage 1 significantly increased compared to the nonpregnant group. At 3-5 months postpartum, a significant reduction in WASO and increased sleep efficiency were noted. However, only a slight increase was noted in REM sleep during the postpartum period compared to the prepartum period. The most frequent sleep complaints in the pregnant group were restless sleep, low back pain, leg cramps and frightening dreams. In summary, in accordance with their complaints, women in their third trimester demonstrated polysomnographic patterns of sleep maintenance insomnia.

The effect of ice on intra-articular temperature in the knee of the dog

The effect of surface cooling on intra-articular temperature was examined in dogs' knees. Four treatment protocols were examined: local ice compress application for 5, 15 and 30 min and local ice bath immersion for 15 min. Intra-articular temperatures were recorded using a needle microprobe inserted into the knee and continuous temperature recordings were made before, during and after the treatment. Rectal temperatures were also simultaneously recorded. Intra-articular temperatures rapidly dropped during icing. Five minutes of ice compress application resulted in a 2.2 +/- 1.2 degrees C intra-articular temperature drop with no change in rectal temperature. After 15 min of ice compress application, the joint temperature fell 4.1 +/- 1.3 degrees C with no change in rectal temperature. Thirty minutes of local ice compress application dropped the knee temperature 6.5 +/- 4.0 degrees C with a slight 0.5 +/- 0.3 degrees C drop in rectal temperature. Fifteen minutes of ice water immersion caused a much greater drop in intra-articular temperatures (20.2 +/- 8.4 degrees C) than could be achieved with ice compress. Rectal temperatures fell slightly during immersion (1.6 +/- 0.3 degrees C). After the removal of any type of cryotherapy, intra-articular temperatures continued to drop for several minutes and then a prolonged rewarming period commenced. The mean time required to return to baseline intra-articular temperature varied from 22-60 min, depending on the type and duration of cryotherapy. We conclude that brief periods of topical cold application to a dog's knee can induce significant and long lasting depression of intra-articular temperatures and that this is a local effect not dependent on core temperature cooling.

Obesity. A risk factor for knee dislocation

Complete dislocation of the knee joint is a severe injury that is commonly the result of high-velocity injuries and often associated with disruption of the popliteal artery. We report two cases in which obesity appeared to be the principal cause of knee dislocation with vascular compromise. Preventive measures in extremely obese patients are recommended.

Low-back pain in pregnancy. Abdominal muscles, sit-up performance, and back pain

An attempt was made to determine the effect of pregnancy on the abdominal muscles and to correlate changes in abdominal muscles strength with low-back pain during pregnancy. The study included 328 women. Group A consisted of 164 pregnant women; group B consisted of 164 non-pregnant women. The race, age, height, weight, parity, profession, time devoted to physical fitness per week, abdominal length, and relation between the abdominal length to height were recorded. A detailed history relating to backache prior to and during pregnancy was obtained. Each woman was asked to perform a single sit-up. The results of the study indicate that about 10% of pregnant women develop severe low-back pain that interferes with daily life activities. About 49% of the non-pregnant women complained of LBP. The pain did not interfere with activities of daily living. During pregnancy, due to overstretching of the abdominal muscles, the ability to perform a sit-up is significantly decreased. Whereas all non-pregnant women could perform a sit-up, 16.6% of pregnant women could not perform a single sit-up. There was no statistically significant correlation between the sit-up performance and backache. It may be concluded that during pregnancy the abdominal muscles become insufficient.

Isthmic spondylolisthesis in pycnodysostosis

Pycnodysostosis is an inborn skeletal syndrome manifested by short stature with a concomitant spinal deformity and by dense sclerotic fragile bones. We report a 35-year-old woman with pycnodysostosis and isthmic spondylolisthesis. Pycnodysostosis should be added to the differential diagnosis of spondylolisthesis.

Night backache in pregnancy. Hypothetical pathophysiological mechanisms

One hundred women responded to a questionnaire dealing with night backache during pregnancy. All the women were in the second half of their pregnancy. Sixty seven per cent of the women reported discomfort and/or backache during the night. We hypothesize that hypervolemia combined with obstruction of the inferior vena cava, caused by the enlarging uterus, is the underlying pathomechanism leading to night backache. Patients with inadequate venous collateral circulation may develop excessive pressure within the venous system, the vertebral bodies and overdistension of venous channels distal to the occluded zone. These changes may lead to hypoxemia, metabolic disturbances, irritation of unmyelinated nerves and result in night backache.

Dermatitis-sympathetic dysfunction in carpal tunnel syndrome. A case report

A 52-year-old woman complained of numbness affecting the thumb, index, and middle fingers of both hands. The patient was managed with night splints with partial relief of symptoms. As a house cleaner, the patient was routinely exposed to water and detergents. About a year later, the patient developed contact dermatitis in the fingertips innervated by the median nerves. Electromyographic studies confirmed the presence of bilateral carpal tunnel syndrome. The temperature of all the fingertips was measured. The median innervated fingertips were warmer than those innervated by the ulnar nerves. The median sympathetic fibers may be compromized by compression in the carpal tunnel. This caused vasodilation, increased finger temperature, and lack of sweating in the median innervated fingers. Due to regular exposure to water and detergents, the susceptible dry fingertips developed contact dermatitis. The patient was managed conservatively, and the rash and numbness disappeared.

The shoulder abduction relief sign in cervical radiculopathy

A patient with C6 cervical radiculopathy reported that sustained shoulder abduction significantly diminished this upper extremity pain. The patient was instructed to adopt this position for prolonged periods during rest and at work. Pain relief was temporary and lasted as long as the arm was in abduction. Relief of pain, induced by arm abduction, may be observed in cervical radiculopathy in which the lower cervical roots are involved. Reduced tension at the nerve root is the probable underlying mechanism that leads to pain relief. Shoulder abduction can be used not only as a diagnostic sign but also may be incorporated in the conservative management of patients suffering from cervical radiculopathy affecting the lower cervical roots.

Gluteal abscess causing sciatica in a patient with systemic lupus erythematosus

Low back pain and sciatica may be caused by pathology remote from disc and lumbosacral vertebral segments. We report on a 59-year-old patient with systemic lupus erythematosis whose history illustrates this point. The patient was evaluated and diagnosed to have a septic arthritis of the wrist and lumbar spinal stenosis, for which she was treated. The patient's failure to respond to therapy led to further evaluation. A massive gluteal abscess was identified and drained, and with appropriate antibiotic therapy, the patient recovered. Patients with lupus have increased likelihood of infection, and their evaluation should include a search to discover unusual locations in cases that are unresponsive to standard and seemingly appropriate therapy.

Low back disorders: conservative management

Painful disorders of the low back may arise from a large variety of mechanisms and there is no simple, single solution to them. They have a great social and economic cost in industrialized countries. The major syndromes of low back pain and sciatica are reviewed, including myofascial pain syndromes, disc herniations, radiculopathies, spinal stenosis and facet syndromes. Non-operative management is reviewed, including bed rest, medications, traction, manipulation, external supports, physical modalities, therapeutic exercise, trigger point injection and chemonucleolysis. Prevention should become the main goal of physicians dealing with this multifaceted problem.

Vertebral artery damage complicating cervical manipulation

Cervical manipulation may result in serious neurologic injury arising specifically from trauma to the vertebrobasilar system. The vertebral arteries are susceptible to trauma at three locations: in the transverse foraminae, at the atlantoaxial joint, and at the occipitoatlantal joint. Because of frequent inequality in the size of the two vertebral arteries, damage to the larger artery may lead to ischemia of the brain stem. Vertebral artery obstruction may be produced by extension with rotation, even within normal ranges of motion. Neurologic injury following manipulation requires accurate diagnosis and prompt manipulation requires accurate diagnosis and prompt anticoagulant therapy.

Disseminated intravascular coagulopathy in patients with cancer undergoing operation for pathological fractures of the hip

Disseminated intravascular coagulopathy is a serious complication of numerous pathological conditions, particularly metastatic cancer. It is rarely encountered in orthopaedic surgery. Prompt recognition and treatment is required to prevent death. We describe two patients with pathological fractures of the proximal femur due to metastatic disease who died from disseminated intravascular coagulation after operation. A high index of suspicion, careful monitoring of the clotting mechanism and prompt treatment are required.

Low-back pain in pregnancy

Two hundred women were interviewed within 24-36 hours after giving birth. The patients were not examined. It was found that 56% of the patients suffered from low-back pain during pregnancy. The percentage of Caucasians was statistically higher in the back pain group. The percentage of Hispanics was statistically higher in the no pain group. Among the variables that were compared in both groups were the age, the weight gained by the mothers during pregnancy, the baby's weight, the number of previous pregnancies, number of prior children. None of the variables reached a statistically significant level. The pain group complained of pain the low-back area, which radiated in 45.5% of cases to the lower extremities. In about one-third of the patients the pain increased as the day wore on, whereas in another one-third the pain increased during the night and disturbed sleep. Standing, sitting, forward bending, lifting, and walking tended to increase the pain. Most of the patients started suffering from back pain between the fifth and seventh months of pregnancy. Several theories to explain the occurrence of backache during pregnancy are discussed.

Spine fractures in ankylosing spondylitis

Patients with ankylosing spondylitis are susceptible to spine fracture, usually in the cervical spine. Less frequently, the thoracic and lumbar spine is affected. The fracture line may involve anterior and posterior elements. Frequently, it extends through the entire width of the spine. As a result the fracture tends to be unstable and may cause neurologic damage. Prompt immobilization and reduction of the dislocated spine followed by stabilization may prevent neurologic damage. We report a 45-year-old man who fell and sustained a fracture dislocation of L2 vertebra. The patient was operated and stabilized with Harrington rods. A deep wound infection developed, which did not respond to antibiotic therapy and led to removal of the rods. In spite of bed immobilization with a body jacket the fracture remained unstable and dislocated. As a result the patient sustained severe neurologic damage. Many fractures in patients with ankylosing spondylitis occur following minor trauma. We feel that a very important aspect of ankylosing spondylitis management is prevention of these fractures. Alerting patients of their spine fragility and teaching then how to evade situations leading to spinal trauma may help in avoiding this situation.

The simultaneous application of an interspinous compressive wire and Harrington distraction rods in the treatment of fracture-dislocation of the thoracic and lumbar spine

During open reduction of thoracolumbar fracture-dislocation, the normal constraints to distraction and lengthening may be ruptured and allow instrumentation to exert deleterious traction of the spinal cord. An interspinous wire across the unstable segment together with a Harrington rod may be used to prevent potential overdistribution of the spinal cord. Thirty-six patients with fracture-dislocation of the thoracolumbar spine were treated by open reduction with Harrington rods and interspinous wiring. Of 15 patients with a partial cord lesion, four made complete recovery, and nine of the remaining 11 became ambulators. Six patients with a complete paraplegia did not improve; 15 patients remained neurologically intact following the procedure. The compressive wire and Harrington rods act in concert and enable correction of kyphosis and restoration of vertebral and discal height while protecting the cord against traction. The technique is safe and does not add to operative time.

Surgical treatment of lumbar spinal stenosis in the elderly

Unrelenting sciatica or intermittent neurogenic claudication in the elderly may be caused by degenerative lumbar spinal stenosis. This rather common condition is produced by advanced multilevel disc degeneration leading to facet hypertrophy, infolding of ligamentum flavum, descent of the pedicles, and occasional disc herniation. The symptoms of lumbar spinal stenosis usually do not improve with time. Despite the advanced age of some patients, surgical decompression may offer significant relief. Of 19 patients who underwent lumbar decompressive laminectomy, 18 showed sufficient improvement to return to normal daily activities.