Locational uncertainty in georeferencing public health datasets

The assignment of locational attributes to a study subject in epidemiologic analyses is commonly referred to as georeferencing. When georeferencing study subjects to a point location using their residential street address, most researchers rely on the street centerline data model. This study assessed the potential locational bias introduced using street centerline data. It also evaluated georeferencing effects on a location-dependent, exposure assessment process. For comparison purposes, subjects were georeferenced to the center of their residential parcel of land using digitized parcel maps. A total of 10,026 study subjects residing in Jefferson County, Alabama were georeferenced using both street centerline and residential parcel methods. The mean nondirectional, linear distance between points georeferenced using both methods was 246 ft with a range of 11 to 13,260 ft. Correlation coefficients comparing differences in exposure estimates were generated for all 10,026 subjects. Coefficients increased as the geographic areas of analysis around study subjects increased, indicating the influence of nondifferential exposure misclassification.

Does the chronic prostatitis/pelvic pain syndrome differ from nonbacterial prostatitis and prostatodynia?

PURPOSE

The new consensus classification considers the chronic prostatitis/pelvic pain syndrome (CPPS) based on presence or absence of leukocytes in the expressed prostatic secretions, post-massage urine or seminal fluid analysis. We compared classification based on evaluation of these 3 specimens to the traditional classification based on expressed prostatic secretion examination alone.

MATERIALS AND METHODS

A prospective clinical and laboratory protocol was used to evaluate symptomatic patients who had no evidence of urethritis, acute bacterial prostatitis or chronic bacterial prostatitis.

RESULTS

Thorough clinical and microbiological evaluation of 310 patients attending our prostatitis clinic was used to select a population of 140 subjects who provided optimal expressed prostatic secretion, post-massage urine and semen specimens. Inflammation was documented in 111 (26%) of 420 samples, including 39 expressed prostatic secretion samples with 500 or greater leukocytes/mm.3, 32 post-massage urine samples with 1 or greater leukocytes/mm.3 and 40 seminal fluid specimens with 1 or greater million leukocytes/mm.3. Of the 140 subjects 73 (52%) had inflammatory chronic prostatitis/pelvic pain according to the consensus criteria but only 39 (28%) had nonbacterial prostatitis according to traditional expressed prostatic secretion criteria (p <0.001).

CONCLUSIONS

The new consensus concept of inflammatory chronic prostatitis/pelvic pain includes almost twice as many patients as the traditional category of nonbacterial prostatitis.

Observation of a partially opened triple-helix conformation in 1-->3-beta-glucan by fluorescence resonance energy transfer spectroscopy

This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a triple-helix (1-->3)-beta-D-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the triple-helix glucans with NaOH produces single-helix conformers. FRET spectra of the triple-helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened triple-helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened triple-helix rather than a single helix, is formed by treating the triple-helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the triple-helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using the Limulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the triple-helix. Partially open conformers were more biologically active than the intact triple-helix.

Characterization of an aerosol chamber for human exposures to endotoxin

The objective of this study was to develop and characterize an exposure chamber in which human subjects could be exposed to low dust concentrations carrying an endotoxin coating. An exposure chamber, dust dispersion method, and endotoxin characterization technique were developed for inhalation exposures. A 6.27 m3 exposure chamber was designed and constructed from cinder block, glass windows, and Plexiglas. Using an acetone adhesion process, Enterobacter agglomerans were adsorbed onto respirable cellulose particles to create the endotoxin aerosol. The size distribution of the endotoxin-treated particles was verified using light microscopy and cascade impactors. A dry powder dust generator was refined to consistently disperse small quantities of the aerosol into the chamber to maintain dust concentrations at approximately 250 micrograms/m3. Dust levels during the chamber exposures were monitored using a portable continuous aerosol monitor (PCAM). During initial exposure runs, PCAM monitoring stations were positioned at different locations within a 0.5-meter matrix to document mixing patterns. Total dust and cascade impactor samples were collected throughout each exposure period to characterize the chamber operating system and insure the mean airborne dust concentration fulfilled target levels. A one-factor analysis of variance at the 95 percent confidence interval illustrated that there was not a statistically significant difference in the mean dust concentration throughout the exposure runs compared to the individual runs. Together the consistency of the total dust filters, endotoxin concentrations, and aerosol-monitoring instrument were adequate to allow use of the chamber for experimental studies involving human volunteers.

Preliminary report on the results of the second phase of a round- robin endotoxin assay study using cotton dust

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Review of methods applicable to the assessment of mold exposure to children

This article presents discussion of the assessment of the exposure of children to fungi, substances derived from fungi, and the environmental conditions that may lead to exposure. The principles driving investigations of fungal contamination and subsequent exposure are presented as well as guidelines for conducting these investigations. A comprehensive description of available research sampling and analysis techniques is also presented.

Central administration of leptin inhibits food intake and activates the sympathetic nervous system in rhesus macaques

The present study was performed to determine the effects of central administration of leptin on food intake and sympathetic nervous system activity in a nonrodent species, the rhesus monkey. Peripheral administration of leptin at doses (1 and 3 microg/kg, s.c.) that produced increments of circulating leptin concentrations within a physiological range did not inhibit food intake over the subsequent 3 days. In contrast, leptin (1 microg/kg, intracerebroventricularly) had no acute effect on food intake, but caused a significant and sustained suppression (40-50%) of food intake during the entire following day (P < 0.01). In addition, circulating norepinephrine levels increased by 55 +/- 16% (P < 0.02) 1 h after intracerebroventricular leptin administration, but did not increase after artificial cerebrospinal fluid administration. These results indicate that leptin can provide a signal to the central nervous system that decreases food intake in primates and in addition acutely activates the sympathetic nervous system. However, the results showing an acute increase in circulating leptin concentrations after peripheral administration of human leptin suggest that in primates, increases in circulating leptin within the physiological range do not acutely regulate food intake. Leptin may be more important in regulating food intake when there are sustained changes in circulating concentrations of leptin (e.g. with obesity, prolonged energy restriction, or diabetes).

An evaluation of the prevalence of latex sensitivity among atopic and non-atopic intensive care workers

BACKGROUND

Exposure to latex is known to cause an array of symptoms, including pruritus, dermatitis, erythema, and urticaria. Workers at elevated risk for latex exposure include health care personnel whose repeated patient contact or surgical work require extensive use of latex gloves. This study evaluated the prevalence of latex allergies in atopic and non-atopic intensive care workers and sought to determine the impact of risk factors such as frequency of glove use and hand washing on latex sensitization.

METHODS

We evaluated the prevalence of latex sensitivity in 122 intensive care unit (ICU) workers using a questionnaire and skin prick test. Atopy and latex sensitivity were determined by skin prick test using a battery of common inhalant allergens and an extract prepared from the gloves used in the ICU. Frequency of glove use and hand washing were determined by questionnaire.

RESULTS AND CONCLUSIONS

Forty ICU workers (32.8%) were considered atopic by having at least one positive response to the inhalant allergens. Atopic ICU workers were more likely to have positive latex skin test than non-atopic ICU workers (atopic vs. non-atopic workers: p < 0.001, odds ratio = 14.2). Frequency of current glove use or hand washing frequency were not significant predictors of a positive response to latex; however, a positive history of atopic eczema and family history of allergies, as determined by questionnaire were significant predictors of a positive response to latex antigens.

Monocyte responsiveness and a T-cell subtype predict the effects induced by cotton dust exposure

The aim of the study was to evaluate whether peripheral cellular parameters could predict susceptibility to decreased lung function and associated symptoms, in response to a single exposure to cotton dust. Previously nonexposed subjects (n = 42) inhaled an aerosol of cotton dust in a model cardroom during a period of 5 h. The subjects were examined before the exposure for FEV1, procoagulant activity (PCA) in blood mononuclear cells (BMNC), and serum IgE antibodies against a pool of inhalant antigens. Blood lymphocytes were typed into the helper/inducer (CD4+) and cytotoxic/suppressor (CD8+) T cells in combination with surface markers subdividing these populations. A questionnaire was used to identify atopic and nonatopic subjects. Immediately after exposure, the subjects were tested for FEV1 and PCA, and symptoms were recorded with a questionnaire. The dust exposure induced a decrease in FEV1 that was larger for the atopic group, but did not change the PCA in BMNC. The decrease in FEV1 was positively related to the preexposure PCA in both atopics and nonatopics. Symptoms from the airways after the exposure were reported to the same extent in the atopic and nonatopic group, and the subject group reporting chest tightness had a larger preexposure PCA. The atopic group had a larger proportion of blood CD8+ T lymphocytes negative for the monoclonal antibody anti-S6F1 (CD8+S6F1-), and in this group the decrease in FEV1 was significantly related to the proportion of this cell type. Also, in the atopic group, the proportion of CD8+S6F1- cells correlated positively with the preexposure PCA, and a negative correlation was found for this cell and serum levels of IgE.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the association of acute overshift change in pulmonary function and atopy using OSHA cotton dust surveillance data

OSHA surveillance data were collected for 769 individuals employed in four different cotton textile mills. Current workers were asked to complete a questionnaire about personal and family history of atopy or asthma. Both surveillance and survey data were available for 502 individuals. The prevalence of atopy in the population as reported by questionnaire was 18%, while asthma was reported by 4%. Dust levels at the four mills were in compliance with the cotton dust standard during the period of surveillance. No relationship was found between a self-reported history of atopy or asthma and the magnitude or frequency of acute overshift declines in forced expiratory volume during 1 second (FEV1). Nonsmokers had annual changes in FEV1 and forced vital capacity (FVC) comparable to nonexposed populations. In one of the four mills surveyed, annual declines in FEV1 and FVC for current smokers were significantly greater than declines for smokers in the other mills or the general smoking population (p < 0.02). This mill effect was also observed for subjects who were categorized as atopic (p < 0.02). For nonsmokers there appears to be no significant adverse health effect from exposure to the levels of cotton dust observed in these mills.

Sampling environments containing organic dust

Assessment of airborne organic dust in different environments is necessary to better understand the relationship between exposure and disease. Exposure assessment requires a well-defined sampling strategy which addresses the following questions: Where, how long, who, how many, and when? For assessing exposure to organic dust, the question of "what?" must be included because, in most cases, the specific toxins or appropriate surrogates for exposure have not been identified. For most environments with organic dust, these questions have not been adequately addressed. However, a large database exists for cotton dust. Cotton is used as a model of organic dust to illustrate the application of exposure assessment: 1) to develop a dose-response relationship between aerosolized dust and specific health effects; 2) to evaluate the effects of process change on gravimetric dust levels and for compliance with the cotton dust standard; and 3) to identify specific biologically active components in the dust.

An in vitro comparison of the permeation of chemicals in vapor and liquid phase through pig skin

This study used pig skin to compare vapor and liquid permeation of benzene, n-butanol, and toluene in vitro. Vapors of radio-labeled chemicals were generated by passing purified air through two saturators in series containing the labeled chemical. The generated vapor was directed into the donor compartment of a modified liquid permeation cell. For liquid permeation experiments, neat chemicals were dosed directly on the surface of the skin. The variability of the generated concentrations for the vapor phase of each chemical ranged from 3-7%. The mean flux of the liquid chemicals was significantly higher than those of the vapor phase. There was no significant difference in the flux of the individual chemicals in the liquid phase. In the vapor phase test, the flux of toluene and benzene were not significantly different; however, for n-butanol the flux was significantly lower than the for either benzene or toluene.

Bronchial reactivity, atopy, and airway response to cotton dust

Studies of cotton textile workers have found an association between atopy and drop in FEV1 over a workshift. We studied the response of previously nonexposed volunteers with and without a history of mild atopy to a 5-h exposure to 1 mg/m3 of respirable cotton dust in a model cardroom. All participants were nonsmokers, had no history of asthma, and had normal spirometry. Twenty atopic subjects gave a personal history of mild respiratory allergy to pollen, dusts, or animals that had been confirmed by a physician. Thirty-two nonatopic subjects had no history of allergy. Spirometry and a methacholine challenge test were performed 1 to 2 days prior to exposure. Spirometry was repeated immediately before exposure to cotton dust; spirometry and a methacholine challenge were performed immediately after exposure. Atopic subjects showed a significantly higher mean serum IgE level to Phadiatop, a screening test to common inhalant allergens, than did nonatopic subjects (mean percent binding, 32.1 versus 1.5; p < 0.001). Atopic subjects had a significantly greater mean fall in FEV1 during exposure (8.3% versus 4.9%, p < 0.05). The difference in FEV1 decline between atopic and nonatopic subjects was similar in magnitude to that reported for workshift FEV1 declines between textile workers with and without mild atopy. Atopic subjects had significantly higher baseline methacholine responsiveness than did nonatopic subjects (26% versus 0% reaching a PD20, p < 0.0005). After cotton dust exposure, there was a significant increase in airway reactivity in both groups (68% versus 20% reaching a PD20, p < 0.0005). For all subjects combined baseline responsiveness was significantly related to the change in FEV1 after exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

The histomorphologic sequence of dural repair. Observations in the canine model

This study was undertaken to investigate the histopathologic events of the dural reparative process. Uniform 2-mm dural defects were created in adult beagles, repaired, and then examined in a 6-week period. Primary fibroblastic bridging of the durotomy was not seen until Postoperative Day 6, and it was not until Postoperative Day 10 that ablation of this defect was uniformly seen. Cerebrospinal fluid egress through the dural defects was prevented in the vast majority of cases by the formation of an internal patch composed of proliferative elements of pia and arachnoid mater.

Quantification of leakage pressures after durotomy repairs in the canine

This study was undertaken to investigate the relative strengths of dural repair using standard suture techniques, suture supplemented with tissue adhesive, and tissue adhesive alone. Uniform 2 mm dural defects were created in adult beagles, repaired, and then subjected to pressurization testing. Defects repaired with suture alone initially leaked within the range of physiologic pressurization, while those supplemented with tissue adhesive or repaired with tissue adhesive alone failed at higher pressurization levels. Histologic sections obtained from the dura treated with fibrin adhesive sealant demonstrated minimal inflammatory response not significantly different than those sections examined at sites repaired by suture alone. A new substance, fibrin adhesive sealant, appears to be useful in effecting dural repair due to its ability to withstand pressures greater than those obtained with suture alone.

Results of a locking-hook spinal rod for fractures of the thoracic and lumbar spine

The results of a consecutive series of 110 patients treated with the locking-hook spinal rod are presented. A prospective protocol was completed in 95 patients. Pain was absent or mild in 93%. In those patients with a partial neurologic deficit, there was recovery of at least one Frankel grade in 84%. The overall kyphotic deformity was reduced from 21 to 17 degrees. In those patients in whom no anterior surgery was performed, the deformity improved from 21 to 13 degrees. No rod fractures occurred, and the overall instrument complication rate was 13.7%, of which one was due to infection and four secondary to uncrimped nuts, for a true complication rate of 8.4%. The locking-hook spinal rod has proven to be a satisfactory internal fixation device in the treatment of unstable thoracolumbar fractures.

The neuroradiographic diagnosis of lumbar herniated nucleus pulposus: I. A comparison of computed tomography (CT), myelography, CT-myelography, discography, and CT-discography

The accuracy of five imaging modalities for the diagnosis of lumbar herniated nucleus pulposus (HNP) is compared prospectively in 124 patients, all of whom underwent surgical exploration. All tests were read independently of each other and the level of confidence in each diagnosis was recorded. The results are based on negative (106) as well as positive (125) findings at the 231 disc sites (level and side) explored. Computed tomography-discography (disco-CT) was the most accurate test (87%) compared to 77% for CT-myelography (myelo-CT), 74% for CT, 70% for myelography, 64% for disc injection pain, and 58% for discography. The false positive rate was lower for disco-CT (19%) than for myelo-CT (24%), CT (24%), and myelography (30%). The false negative rate was also lower for disco-CT (8%) than for myelo-CT (22%), CT (29%), and myelography (30%). Disco-CT was the most accurate test (94%) in patients who had prior disc surgery compared with 81% for myelo-CT, 80% for CT, and 74% for myelography. Disco-CT was also the most accurate test for patients with foraminal HNP (91% compared with 71% for CT, 65% for myelo-CT, and 58% for myelography). Disc injection reproduced the patient's clinical pain pattern in only 36% of herniated discs. This test has high specificity (89%), but low sensitivity (43%). The risks from myelography followed by discography within a 72-hour period are similar to those reported for myelography alone. Disco-CT is the most accurate of these tests (P less than 0.05) for the diagnosis of lumbar HNP.(ABSTRACT TRUNCATED AT 250 WORDS)

The neuroradiographic diagnosis of lumbar herniated nucleus pulposus: II. A comparison of computed tomography (CT), myelography, CT-myelography, and magnetic resonance imaging

The accuracy of computed tomography (CT), myelography, CT-myelography (myelo-CT) and magnetic resonance imaging (MRI) for the diagnosis of lumbar herniated nucleus pulposus (HNP) is compared prospectively in 59 patients, all of whom underwent surgical exploration. All tests were read independently of each other and the level of confidence in each diagnosis was recorded. The results are based on the negative (61) as well as positive (59) findings at the 120 disc sites (level and side) explored. Magnetic resonance imaging was the most accurate test (76.5%) compared with myelo-CT (76.0%), CT (73.6%), and myelography (71.4%). The false positive rate was lowest for MRI (13.5%) followed by myelography (13.7%), CT (13.8%), and myelo-CT (21.1%). The false negative rate was lowest for myelo-CT (27.2%) followed by MRI (35.7%), CT (40.2%), and myelography (44.1%). In that subset of 19 patients who had prior surgery, myelography was the most accurate means of diagnosing lumbar HNP (88.8%), followed by MRI (83.3%), myelo-CT (78.4%), and CT (72.6%). The false positive rates in these patients were 11.6% for myelography, 13.2% for MRI, 14.5% for CT, and 16.4% for myelo-CT; the false negative rates were 22.7% for MRI, 24.4% for myelography, 29.5% for myelo-CT, and 47.7% for CT. Magnetic resonance imaging compares very favorably with other currently available imaging modalities for diagnosing lumbar HNP. Magnetic resonance imaging is painless, has no known side effects or morbidity, no radiation exposure, and is noninvasive. The authors recommend it as the procedure of choice for the diagnosis of most lumbar disc herniations.

Update-1988. Current status of internal fixation of thoracolumbar fractures

Rigid internal fixation has become the preferred method of treatment for unstable thoracolumbar fractures in most American spine centers. In most cases, posterior instrumentation alone is adequate, but occasionally an anterior procedure is necessary. A number of internal fixation devices are now available to the orthopaedic surgeon. Controversy exists regarding the number of levels that need to instrumented and the optimal form of internal fixation.

Biomechanical analyses of surgical correction techniques in idiopathic scoliosis: significance of bi-planar characteristics of scoliotic spines

Biomechanical analyses of Harrington distraction, Harrington distraction-compression, Cotrel and Luque correction techniques simulated mechanically on a three-dimensional mathematical model of scoliotic spines are developed and relationships between mechanical forces and achievable corrections are derived in terms of Cobb angle, vertebral inclination from the frontal plane, and bi-plane bending stiffness of motion segments. For all four systems, nomograms between Cobb angles and corrective forces with correction factors as parameters are prepared in terms of given bi-plane characteristics of scoliotic spines. Parametric studies to show the influence of the torsion plane bending stiffness of motion segments and vertebral inclinations from the frontal plane on the mechanical effectiveness of the surgical correction techniques are presented. The mechanical effectiveness of each of the four surgical correction techniques determined with the use of this model compares reasonably well with the clinical findings.

Enhancement of lumbar spine fusion by use of translaminar facet joint screws

From January 1983 to March 1986 the authors have performed 88 consecutive lumbosacral spine fusion, enhanced with translaminar facet screws, as described by F. Magerl of St. Gallen, Switzerland. Forty-three patients have a follow-up of 12 months or greater, for a mean follow-up time of 16 months. The median time to fusion in this group was 6 months, with a range of 6 weeks to 10 months. Ninety-three percent of the patients were found to be clinically improved, and 91% of patients were judged solidly fused on evaluation of motion radiographs. Compared with our previously reported results for lumbar fusion without internal fixation, supplementation of lumbar fusion by translaminar facet screw fixation significantly improved the clinical results, as well as the time required for fusion, with no significant increased risk.

Irreducible sacroiliac dislocation of the pelvic ring with caudal displacement. A case report

An irreducible sacroiliac dislocation of the pelvic ring with resultant caudal displacement of the injured hemipelvis occurred in a 15-year-old female. Because of interposed soft tissue and bone, closed reduction was not possible. Early open reduction through a posterior approach and internal fixation resulted in a painless pelvis. Sacral root avulsion resulted in permanent neurologic deficit that has been successfully managed with an orthosis.

Decompression and circumferential stabilization of unstable spinal fractures

A technique of anterior decompression of the spinal canal with anterior strut grafts, followed by posterior instrumentation and local fusion, is described in a group of 18 patients with unstable thoracolumbar fractures. All patients were found to have greater than 50% encroachment of the spinal canal and a preoperative kyphosis of 21.8 degrees. At follow-up 81% of patients with incomplete neurological lesions improved at least one Frankel Grade. Residual encroachment on the spinal canal was 4.6% and at follow-up the kyphotic angle was 17.1 degrees. Complications included one anterior graft loosening (not requiring revision), three loosened rods, only one of which required revision, and one fractured Harrington rod which did not require revision. The authors conclude that this technique is an effective and safe method for treating unstable thoracolumbar injuries and is recommended if anterior instrumentation is unavailable.

The neurological outcome following surgery for spinal fractures

Sixty consecutive patients with spinal injuries and encroachment upon the spinal canal of greater than 20% were assessed for neurological outcome. The patients were divided into two groups, those undergoing posterior surgery alone, and those undergoing anterior surgery for formal decompression with or without anterior or posterior instrumentation. In those patients undergoing posterior surgery, an improvement rate in the neurological function of 83% was noted in patients with incomplete lesions, whereas an 88% improvement rate was found in those undergoing the anterior procedure. There was no statistical difference in outcome between these two groups. Positive correlations were found between the level of injury and Frankel grades. The cord lesions tended to demonstrate more severe neurological deficit, whereas the cauda equina lesions were associated with a lesser severity of neurologic deficit. A component of dislocation to the injury also resulted in a more severe neurological deficit. There was no apparent difference between the degree of bony encroachment of the spinal canal and the initial Frankel grade, nor was there a clear difference between those patients undergoing anterior versus posterior surgery.

The effect of Harrington rod contouring on lumbar lordosis

The effect of Harrington rod sagittal plane contouring, or lack of it, on total lumbar, segmental lumbar, and lumbosacral lordosis was studied retrospectively in a series of 36 patients operated on for idiopathic scoliosis. Regardless of contouring, there was a decrease in total lumbar lordosis and lordosis above L4, with an increase in lordosis below L5. Although not statistically significant, patients with contoured rods had less loss of segmental (L1-4) lordosis and less increase in segmental lumbosacral lordosis (L4-S1) than the noncontoured group. Although helpful, additional steps beyond concave rod contouring appear to be necessary to consistently preserve lumbar lordosis.

Risk of iatrogenic septic arthritis in the presence of bacteremia: a rabbit study

This study of rabbits determined the risk of producing iatrogenic septic arthritis by arthrocentesis in the presence of bacteremia. In bacteremic animals, three of 20 knees became infected following joint aspiration, and six of 20 knees became infected on injection of 0.2 ml of bacteremic blood. Spontaneous joint sepsis did not develop, even in bacteremic animals. Prophylactic cefazolin before joint aspiration prevented the development of iatrogenic septic arthritis but did not prevent the recovery of bacteria from an infected joint. Therefore, there is an increased risk of development of joint sepsis in this animal model following a traumatic aspiration in the presence of bacteremia. This risk can be minimized by intravenous antibiotics without decreasing the likelihood of recovery of an organism if the joint is septic.

Strategies for prevention of byssinosis

Cotton dust is a heterogeneous mixture of plant parts and contaminants from the soil, weeds, and microorganisms. Research to control byssinosis has focused on methods to reduce the trash associated with harvested fiber and control the dust in the textile mill environment. Dust control has been effective in reducing the prevalence of byssinosis, but because cotton dust is a heterogeneous mixture of components, simple reduction in dust levels does not always assure the prevention of byssinosis. Research to identify the agents that cause byssinosis and development of methods to eliminate those agents from cotton is needed to prevent new cases of byssinosis.

Biomechanical studies of an anterior pelvic external fixation frame intended for control of vertical shear fractures

Biomechanical testing of an experimental pelvic external fixation frame incorporating a large tubular horizontal member was carried out on formalin-fixed cadaver pelves with simulated vertical shear injuries. The device was tested with 5 mm standard and 6 mm experimental pins, and was compared to a Pittsburgh triangular (PT) frame constructed of standard Hoffmann components. Tested by vertical loading, the experimental frame with 5 mm standard pins was 1.9 times as stiff as the PT frame, and with the 6 mm experimental pins it was 2.4 times as stiff as the PT frame. Clinical trials are needed to determine efficacy in vivo.

Assessment of fracture healing by spectral analysis

The 'in vivo' impulse response of long bones was investigated with the object of assessing the reliability of data taken under various conditions. The ultimate goal of the research is to develop a non-invasive method of monitoring the healing of long bones. A spectrum analyser was developed specifically for this investigation and is presented here.

Biomechanical evaluation of the Ender's pins, the Harris nail, and the dynamic hip screw for the unstable intertrochanteric fracture

While intramedullary fixation may have less operative morbidity than sliding plate systems, there also may be a loss of stability and strength of the fixation. In a biomechanical study with simulated unstable intertrochanteric fractures in cadaver femurs, multiple Ender's pins were 18% stronger than the single Harris nail. Compression hip screws were three times stronger than the Harris nail and two and one-half times stronger than Ender's pins. The compression hip screw was five times more rigid than either condylocephalic system.

Internal fixation in lumbosacral spine fusion. A biomechanical and clinical study

While the posterolateral technique is the accepted fusion method for chronic mechanical back pain, the results are variable and the indications are narrow. In an attempt to resolve this problem the role of internal fixation has been explored. Relative stiffness and strength under flexion loading of four lumbosacral fixation systems--(1) translaminar facet joint screws, (2) Luque rectangular box, (3) Luque fixation to the pelvis via the Galveston technique, and (4) two-part pelvic spinal rod system--were evaluated and compared to the normal spine with and without posterior ligaments. The stiffness of the normal intact spine was found to be nonlinear: the bending moment is a function of the square of the flexion rotation. Internal fixation resulted in a twofold increase in stiffness. Facet screws were 20% stiffer and the pelvic-spinal system 2.3 times stiffer (p = 0.001) than the Luque systems but all had similar strength. A retrospective study of 135 consecutive posterolateral lumbosacral spine fusions was conducted to determine what factors improved the fusion rate, clinical results, and time to fusion. Diagnosis and previous surgical treatment, discectomy or fusion, were of no significance. The radiographic and clinical results were highly correlated (p = 0.0001). Electrical stimulation failed to improve the results. Internal fixation with facet joint screws or rods to the pelvis was found to statistically decrease the pseudarthrosis rate and reduce the time required for spine fusion (p = 0.02). The surgical technique consists of translaminar facet screws and segmental fixation to the pelvis using a new implant system.

Long bone defects treated with demineralized bone

This study was undertaken to determine the potential of demineralized bone alloimplant (DBA) for healing long bone defects. We removed 25 mm of bone from the junction of the proximal and middle thirds of both ulnas in seven adult male mongrel dogs. On one side of each animal the devascularized bone was replaced as a cortical autograft (CA) and on the other side, the defect was filled with DBA. Because of implant error, there were only five CAs to evaluate, of which two had achieved clinical union. Of the seven DBAs only one achieved union. The bone in and around the defect was quantified on each specimen roentgenogram and was compared to the size of the original defect. The CA defects were filled 139% +/- 11% with bone that was partly new and partly remnants of the replaced autograft. The demineralized alloimplant defects were filled 143% +/- 45% with bone which, of course, was all newly formed. The difference between the two groups was not significant. We concluded that the DBA was an excellent osteogenic stimulant, but that it did not prevent nonunion in this model.

The effect of internal fixation without arthrodesis on human facet joint cartilage

Internal fixation of the spine combined with limited or no fusion has been advocated in the treatment of thoracolumbar fractures, spondylolisthesis, and severe juvenile spinal deformities. Internal fixation without arthrodesis of canine facet joints has been shown to result in the irreversible gross and histologic findings typical of osteoarthritis. Surgery was performed in eight patients for the treatment of thoracolumbar fractures. In each patient, Harrington distraction instrumentation was placed across at least two vertebral segments above and below the fused area. Instrumentation was removed six to 26 months following the initial surgery. A unilateral partial facetectomy was performed at the facet joint above the lower Harrington hook. Gross examination of the facet joints revealed areas of fibrillation, fissures, and thinning of the normal cartilaginous surface characteristic of osteoarthritis. Histologic examination revealed consistent areas of erosion of the vascular tidemark, osteophyte formation, subchondral remodeling, fibrillation, and loss of the normal cartilage cellularity. These findings were consistent with the histologic appearance of osteoarthritis. Internal fixation of the spine without arthrodesis is not an innocuous procedure and may be a predisposing factor in the development of symptomatic spinal arthritis.

A study of external skeletal fixation systems for unstable pelvic fractures

This study was undertaken to determine the feasibility of constructing an anterior pelvic external fixator capable of resisting displacement of vertical shear fractures. Newly designed tapered thread pins for cancellous bone had better bone pin fixation and their greater 6-mm diameter provided more than twice the stiffness of Hoffmann 4-mm pins when tested in clusters. Using these pins and a more rigid anterior frame as one model, various pelvic fixators were tested to determine their resistance to vertical shear forces. These tests determined that this new fixator was 16 times stiffer than a Bonnel single anterior frame and five times stiffer than a double anterior frame (both constructed of Hoffmann components). Extrapolation from the data shows that 13 mm of posterior fracture displacement would occur with loads of one half body weight using the new fixator. Additionally it was noted that Hoffmann frames constructed with two 5-mm pins performed as well as those using three 4-mm pins.

Surgical management of thoracolumbar spinal injuries. General principles and controversial considerations

Based on a review of the literature and experience with over 100 surgically treated thoracolumbar spinal injuries, the following information summarizes present knowledge of the subject. Reduction and internal fixation of the injured spine allows early mobilization of all patients, regardless of neurologic deficit, while protecting the neurologic structures from further injury and enhancing their recovery. The ability of the posterior ligamentous complex and the anterior bony column to withstand physiologic loads must be assessed by the history, physical examination, and radiography; then the injured structures should be protected from load or their function replaced by an appropriate surgical implant. Maximum neurologic recovery can be expected with prompt and complete decompression by reduction of the deformity, restoration of the spinal canal, and rigid internal fixation. The internal fixation system selected must provide compression for posterior injuries and distraction for anterior injuries, resist bending in combined injuries, and always restore normal spine shape. The rod-long, fuse-short technique provides the advantages of a more accurate reduction and a more secure fixation, and the minimum length of the fused region results in a more normal spine. The advantages of prompt and rigid but temporary internal fixation justify the risks both short- and long-term.

A locking hook spinal rod system for stabilization of fracture-dislocations and correction of deformities of the dorsolumbar spine. A biomechanic evaluation

Existing internal fixation systems for the injured or deformed spine present problems with overdistraction and control of the contoured rod necessary for transverse forces. A locking hook spinal rod avoids these problems by using a locking cover to secure the lamina in the hook and meshing radial grooves to lock the contoured rod to both the upper and lower hooks in 6 degrees intervals of rotation. The 7-mm stainless-steel rod is 50% stronger than the 1/4-in Harrington rod and also avoids the weakening effect of the notches. Cadaver spine testing gives nearly a threefold increase in failure strength (125 +/- 17 Nm versus 44.1 +/- 2.1).

Prophylaxis and management of hamstring muscle injuries in intercollegiate football players

Hamstring muscle strains were responsible for the loss of playing time of a significant number of football players at the University of Nebraska in the early 1970s. After the acquisition of a Cybex II isokinetic dynamometer, the number of injuries was noted to decrease. A retrospective study was performed over the period 1973 to 1982. Players in Group I, from 1973 to 1977, underwent a training program consisting of a supervised winter running program and self-designed year-long stretching, running, and weight lifting. Hamstring injuries were managed with rest, ice, and elevation initially and, by the third day, mild running was instituted. On the average, by the 14th day the athlete had demonstrated adequate speed and agility and was allowed to return to action. Group II consisted of players from the 1978 to 1982 period. These players received supervised winter running programs and staff-designed year-long stretching, running, and weight lifting programs. In addition, all athletes had baseline testing of hamstrings and quadriceps. Deficits were corrected to a desired ratio of 0.60. Injured players in Group II were treated with rest, ice, and elevation initially. High speed isokinetic workouts were begun on the third day with testing on the fifth day. They were allowed to begin jogging when the peak torque of hamstrings equaled 70% of baseline. Players returned to action when peak-torque reached a level of 95% of the baseline score or a hamstrings:quadriceps ratio of 0.55 or greater. Average time out of action was 2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute bronchoconstriction induced by cotton dust: dose-related responses to endotoxin and other dust factors

Fifty-four healthy humans, selected for their acute airway responsiveness to cotton dust, had spirometric tests immediately before and after 6 hours of exposure to card-generated cotton dust from seven different cottons (of several grades and growing regions). During exposures, we measured airborne concentrations of viable fungi and bacteria (total and gram negative), vertically elutriated gravimetric dust, and vertically elutriated endotoxin. Correlation between each of these five exposure indices and exposure-related acute changes in forced expiratory volume in 1 s showed a statistically significant relationship between all of the indices except concentration of viable fungi. Of the other four indices, endotoxin was the most highly correlated (r = -0.94; p less than 0.00001), and gravimetric dust was the least correlated (r = -0.34; p less than 0.05). These findings suggest that gram-negative endotoxin may play a major role in the acute pulmonary response to inhaled cotton dust.

A comparison of grafting materials in experimental bone grafts

The abilities of seven different materials to stimulate healing of experimental defects in the ulna and scapula of the adolescent rabbit were compared. The results were evaluated radiographically and with vital fluorescent stain histology. By average radiographic score (ARS), defects implanted with autogenous iliac crest (ARS = 2.79) did significantly better (P<.01) than controls with nothing implanted (ARS = 2.00). Models implanted with hydroxyapatite (ARS = 1.75), collagen (ARS = 1.62), or frozen lyophilized cortical allograft (ARS = 2.21) were not significantly different (P>.05) from the control. Killing of graft cells with 5000 rads of cobalt-60 radiation did not significantly (P>.05) change the score for autogenous iliac crest (ARS = 2.56). The performance of demineralized allograft matrix (ARG = 2.84) was virtually the same as autogenous crest. Indexing terms: Demineralized bone, hydroxyapatite, alloimplant, osteogenesis.

Diagnosis of post-traumatic syringohydromyelia presenting as neuropathic joints. Report of two cases and review of the literature

Two paraplegic men with post-traumatic syringohydromyelia presented initially with neuropathic arthropathy of the elbow and shoulder, respectively. Both patients had sustained spinal trauma years earlier and had been lost to orthopedic and neurosurgical follow-up study. Characteristic history and physical findings were present in both patients. Conventional myelography failed to demonstrate the lesion in the first patient. The diagnosis in the second patient was confirmed by lumbar injection of low-dose metrizamide followed by immediate and delayed computerized axial tomography in the supine and lateral positions. Both patients were treated by surgical decompression and subarachnoid shunts with arrest of the neurologic deterioration. To the authors' knowledge, this is the first report of patients with post-traumatic syringohydromyelia presenting with neuropathic joints. The present case reports illustrate the need for long-term follow-up studies of patients with spine injury in specialty clinics. The use of computerized axial tomography and low-dose intrathecal metrizamide is advocated for diagnosing post-traumatic syringohydromyelia.

Complicated extremity fractures. The relation between external fixation and nonunion

In a series of 20 tibial fractures and ten radial fractures treated by external fixation, no association was found between the development of non-union and degree of soft tissue injury, delay in fixator application, or diaphyseal versus metaphyseal fracture site. Although the absence of fracture callus on roentgenograms of long bones immobilized by external skeletal fixation portends nonunion, no obvious cause-and-effect relation could be determined.

A locking hook-spinal rod: current status of development

A locking hook spinal rod previously demonstrated to be sufficiently stable and strong in cadaver experiments has been employed in 30 unstable thoraco-lumbar spinal injuries with results superior to Harrington instrumentation.

Reduction, stability, and strength provided by internal fixation systems for thoracolumbar spinal injuries

Anterior, posterior, and combined thoracolumbar spinal injuries were simulated in human cadaver specimens and then stressed in flexion, before and after stabilization, with Weiss Springs, Roy-Camille plates, vertebral body plates, and Harrington compression and distraction rods. The reduction, stability, and strength were determined for each implant-injury combination. For posterior ligamentous injuries, the Harrington compression system on the laminae gave reduction in extension, stability to that of the intact spine, and failure at 87.6 Nm bending load with 14.1 J energy absorption. For anterior vertebral body fracture, Harrington distraction rods from three vertebrae above to three below the injury gave a reduction in extension with stability similar to that of the intact spine. Failure occurred at 81.6 Nm load, one-third greater than with rods two levels above to two below, and 14.0 J energy absorption, twice that for the short rod. The more unstable combined anterior and posterior injury was satisfactorily reduced only by the long distraction system, which failed at 44.1 Nm load, twice that for the short rod, and 5.7 J energy absorption. By accurately determining what structures have been injured, and appropriate fixation device can be selected and the strength of the stabilized spine estimated. A thorough understanding of the biomechanics of the spine is essential for successful clinical utilization of these experimental data.