Reliability of a stool consistency classification system.

PURPOSE: Reliability and validity are important measures of the quality of a research or clinical instrument. This research determined the inter-rater and test-retest reliability of a stool consistency classification system and the agreement between the subjects' and expert investigators' classifications. METHODS: Two studies were conducted with adult volunteers. Stool consistency was described by words only and words + diagrams. To determine inter-rater reliability, subjects in each of 3 groups (20 nurses, 20 nursing students, and 20 lay persons) classified the consistency of 12 stool specimens. To determine test-retest reliability, 43 additional subjects classified the consistency of 9 stool specimens in 2 sessions. OUTCOME MEASURES: Outcome measures were reported per individual stool specimen and for all stool specimens. The outcome measures were the consistency classifications by the 3 groups of raters when the 2 types of descriptors (word only and word + diagram) were used. Other outcomes were the consistency classifications of the subjects on the 2 days of stool evaluation and the classifications of the subjects compared with those of the investigators. RESULTS: No significant difference was found among the stool consistency classifications among nurses, nursing students, or lay persons. Classifications were similar for 11 of 12 stool specimens when either word-only or word + diagram descriptions were used. No significant difference was found among the classifications between days 1 and 2. At least 75% of the subjects' classifications of stool consistency in both studies agreed highly with those of the investigators. CONCLUSIONS: The reliability and validity of the stool consistency classification system are good. The word-only descriptions of the consistency classifications appeared to be equally as effective as the word + diagram descriptions.

Effect of scale on the behavior of atrazine in surface waters.

Field runoff is an important transport mechanism by which agricultural pesticides, including atrazine, move into the hydrologic environment. Atrazine is chosen because it is widely used, is transported in runoff relatively easily, is widely observed in surface waters, and has relatively little loss in the stream network. Data on runoff of atrazine from experimental plot and field studies is combined with annual estimates of load in numerous streams and rivers, resulting in a data set with 408 observations that span 14 orders of magnitude in area. The load as a percent of use (LAPU) on an annual basis is the parameter that is compared among the studies. There is no difference in the mean or range of LAPU values for areas from the size of experimental field plots (> or = 0.000023 ha) and small watersheds (< 100,000 ha). The relatively invariant LAPU value observed across a large range of watershed areas implies that the characteristics of atrazine itself (application method and chemical properties) are important in determining the extent of runoff. The variable influences on the extent of runoff from individual watershed characteristics and weather events are superimposed on the relatively invariant LAPU value observed across the range of watershed areas. The results from this study establish the direct relevance for agricultural field plot studies to watershed studies across the full range of scale.

Peer reviewed: testing water quality for pesticide pollution.

U.S. GeologicalSurvey investigations reveal widespread contamination of the nation's water resources.

Learning and tolerance to the ataxic effect of ethanol.

It has been well documented that drug-associated cues are important for the development and expression of drug tolerance. The Pavlovian conditioning analysis of tolerance emphasizes the importance of a drug-associated cues to tolerance by equating a drug administration with a learning trial. According to this analysis, tolerance should be subject to external inhibition, the disruption of a conditional response by a novel stimulus. We previously reported that tolerance to the ataxic effect of ethanol was attenuated by a novel strobe/noise presentation (31). In this article we report evidence of a compensatory CR in rats tolerant to the ataxic effect of ethanol as tested on the tilting plane. Both the compensatory CR and tolerance were disrupted by the presentation of a novel strobe/noise stimulus providing converging evidence that the attenuation of tolerance by a novel stimulus results from external inhibition of Pavlovian conditioning. The disruption of ethanol tolerance and the conditional response mediating tolerance was also apparent when the novel omission of the strobe/noise stimulus was used as the external inhibitor in rats made tolerant to ethanol with the stimulus on. Finally, we have shown that the disruptive effect of a novel stimulus on ethanol tolerance is decreased when there is a 10-day delay between the final tolerance development session and testing, demonstrating that the interval between training and testing is important when assessing associative tolerance.

Surgical management of nontuberculous thoracic and lumbar vertebral osteomyelitis: report of 33 cases.

BACKGROUND: Thirty-three patients with nontuberculous pyogenic thoracic and lumbar vertebral osteomyelitis were treated surgically. Indications for surgery were either progression of disease despite adequate antibiotic therapy, neurologic deficit, or both. The most common initial symptom was back pain. Seven patients had diabetes, seven patients were intravenous drug users, two patients were receiving immunosuppressive therapy, and seven patients had a debilitating disease. Eleven had infections elsewhere in their bodies. Prior to surgery organisms were grown from blood in 10 patients and at surgery in 15 patients. METHODS: Infection was evident on plain films in all patients, and either a CT scan or MRI was obtained in each. The lateral extracavitary approach was used for resection of granulation tissue and infected bone ventral to the dura. Interbody bone grafts were placed in 19 patients, usually when bone resection was extensive. Posterior instrumentation was placed in 17 patients at a second procedure 10 days-2 weeks following initial operation. Intravenous antibiotics were administered for 4-6 weeks following surgery, and solid fusion was obtained in all patients. RESULTS: Neurologic deficit was present in 28 patients prior to surgery and was functionally significant in 18 patients. Of the 11 patients with severe paraparesis, 10 achieved good functional recovery. These patients were able to walk, three with assistance and seven without, and all those who were unable to void regained this ability. CONCLUSIONS: Surgical debridement, interbody fusion, and posterior instrumentation is a safe and effective treatment for vertebral osteomyelitis and is indicated when neurologic deficit or bone destruction progress despite adequate antibiotic therapy.

Finite element modeling of cervical laminectomy with graded facetectomy.

In this study, an anatomically accurate three-dimensional finite element model of the human lower cervical spine (C4-C6) was used to study the biomechanical effects of cervical laminectomy with and without graded facetectomy. The intact finite element model was validated under flexion, extension, lateral bending, and axial torsion load vectors of 1.8 Nm magnitude. The moment rotation response of the finite element model matched well with experimental data. The gross external (angular motion) and the internal (superior and inferior intervertebral disc stress) responses were delineated under the four physiological loading modes for these iatrogenic changes. Results indicated that laminectomy markedly altered the cervical angular motion and the disc stress under flexion compared with all other loading modes. Facetectomy increased the angular motion and the inferior disc stress notably under flexion but did not affect the adjacent superior disc stress. Facet resection of > 50% caused pronounced increases in angular rotation and intervertebral disc stresses. These findings suggest that the resection of more than one-half of this structure may require additional procedures to restore the strength of the cervical column. Although gross external motion response can be obtained by experimental studies, the internal stress response can only be determined using mathematical models such as the finite element model used in the present study. The accentuated changes in the disc stress compared with the changes in the external rotation may be clinically relevant because increased internal load/stress can result in disc degeneration. The present three-dimensional finite element model offers additional information to better understand the extrinsic and intrinsic responses of the iatrogenically altered cervical spine.

Finite element modeling of the C4-C6 cervical spine unit.

This study was conducted to develop a detailed, three-dimensional, anatomically accurate finite element model of the human cervical spine structure using close-up computed tomography scans and to validate against experimental data. The finite element model of the three vertebra segment C4-C6 unit consisted of 9178 solid elements and 1193 thin shell elements. The force-displacement response under axial compression correlated well with experimental data. Because of the inclusion of three levels in the spinal structure, it was possible to determine the internal mechanics of the various components at each level. The applicability of the model was illustrated by adopting appropriate material properties from literature. Results indicated that, the stresses in the anterior column were higher compared to the posterior column at the inferior level, while the opposite was found to be true at the superior level. The superior and inferior endplate stresses were higher in the middle vertebral body compared to the adjacent vertebrae. In addition, the stresses in the cancellous core of the middle, unconstrained vertebral body were higher. The present three-dimensional finite element model offers an additional facet to a better understanding of the biomechanics of the human cervical spine.

Dissociation of temperature changes and anorexia after experimental colitis and LPS administration in rats.

The acute phase of inflammation induces both anorexia and fever. Because several analyses suggest a linkage between the meal size and body temperature, we assessed whether temperature changes were causal to anorexia in situations involving acute inflammation. Specifically, we evaluated whether elevations of body temperature could account for the reduced food intake after induction of experimental colitis [via intrarectal infusions of trinitrobenzene sulfonic acid (TNB)] or injection of 100 micrograms/kg lipopolysaccharide (LPS). Temperature was monitored telemetrically in rats via implanted temperature transmitters. TNB-treated rats demonstrated a 5-day anorexia that resulted specifically from a decrease in meal size. Although TNB-treated rats were hypothermic on the day of treatment, no other body temperature changes were noted. LPS reduced food intake and elevated temperature, but these two effects were uncorrelated temporally. Although these results do not identify the mechanisms of anorexia, the findings indicate clearly that the anorexia associated with the acute inflammatory response is not secondary to fever.

Disruption of tolerance to the ataxic effect of ethanol by an extraneous stimulus.

According to a conditioning analysis, pharmacological conditional responses (CRs) contribute to tolerance. We previously reported that, as expected on the basis of this model, tolerance to the hypothermic effect of ethanol is attenuated by "external inhibition," for instance, by presentation of a novel stimulus (a strobe). However, results of more recent research indicate that novel stimuli augment the hypothermic effect of ethanol in rats receiving the drug for the first time. It is possible, therefore, that a novel stimulus apparently attenuates ethanol tolerance because it augments ethanol-hypothermia, rather than because it functions as an external inhibitor. Two experiments were designed to evaluate external inhibition of tolerance to another effect of ethanol-ataxia. Although the initial ataxic effect of the drug (unlike the hypothermic effect) is not enhanced by a novel stimulus, the stimulus reinstated ethanol-induced ataxia in tolerant rats. The results demonstrate external inhibition of ethanol tolerance in a preparation not confounded by the effects of the novel stimulus on initial responding to ethanol.

Intravertebral pressure changes caused by spinal microtrauma.

Clinical studies indicate variations in intravertebral pressures in patients with and without low back pain. It is known that not all patients with back pain have abnormal lumbar radiographs and, furthermore, microfractures of the endplate may be one of the causes in the origin of low back pain. Consequently, this study was conducted to determine the interrelationship between microtrauma and intraosseous pressures in the lumbar spine. Miniature pressure transducers were inserted into the vertebral bodies and spinous processes of human cadaver spinal units. Radio-opaque medium was injected into the nucleus to fluoroscopically monitor the movement of the fluid from the disc as the preparation was loaded up to the initiation of microtrauma (before reaching the ultimate load-carrying capacity). The onset of injury was evidenced by the microfracture of one of the two endplates and impregnation of the contrast medium into the spongiosa. After relaxation, another cycle of loading was applied by limiting the deflections to the maximum compression sustained under the intact configuration. The load, stiffness, and energy-absorbing capacities were lower (P < 0.05) for the injured specimen compared with the intact configuration. The intraosseous pressures were higher (P < 0.05) in the vertebral body and the spinous process of the vertebra where the endplate exhibited microtrauma in the injured cycle compared with the intact cycle. In contrast, the intraosseous pressures in the vertebral body and the spinous process at the level where the endplate remained intact were not significantly different between the two cycles of loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of microtrauma in the lumbar spine with intraosseous pressures.

This study was conducted to determine the relationship between intraosseous pressure and vertebral microtrauma in the lumbar spine. Functional spinal units were excised from human cadavers. Radio-opaque dye was injected into the nucleus. Miniature transducers were inserted into the vertebrae to record intraosseous pressures. Compressive loading was applied quasistatically (2 mm/sec) until injury occurred. Movement of the contrast medium was monitored under fluoroscopy. The subchondral endplate was the most vulnerable component for initiation of injury to the lumbar spine segment. In the initial stages of loading, the vertebral endplates gradually bulged outward, with the contrast medium staying within the nucleus. However, at higher physiologic load levels, before reaching the limiting load, the deformations increased, resulting in buckling of one of the endplates. This was followed by the contrast medium impregnating the spongiosa. Microlevel trauma was not observed radiographically after load removal, indicating that one cannot always equate a normal radiograph with normal spinal anatomy. Mean forces, deformations, stiffnesses, energies, and strains were 7.8 kN (+/- 1.4), 5.23 mm (+/- 0.78), 1940 N/mm (+/- 226), 18.7 J (+/- 4.4), and 35.5% (+/- 3.7), respectively. Pressure in the vertebral body containing the injured endplate before the onset of microtrauma was different (P < 0.05) from the pressure after injury; the pressures in the body containing the intact endplate, however, were not statistically different. Significant differences (P < 0.05) in the intraosseous pressures occurred between the two spinal levels at low-level physiologic loads before the onset of microtrauma.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical effects of laminectomy on thoracic spine stability.

Thoracic columns (T1-L1 levels) from 15 fresh human cadavers were used to quantify alterations in the biomechanical response after laminectomy. Eight specimens were tested intact (Group I); the remaining seven preparations were tested after two-level laminectomy (Group II) at the midheight of the column. All specimens were fixed at the proximal and distal ends and loaded until failure. Force and deformation were collected by use of a data acquisition system. Failure of the Group I specimens included compressive fractures with or without posterior element distractions, generally at the midheight of the column. Group II preparations failed at the superior aspect of laminectomy or at a level above laminectomy, suggesting an increased load sharing. Biomechanical responses of the Group II preparations were significantly different (P < 0.05) from those of the Group I specimens at deformations from the physiological to the failure range. In addition, failure forces for Group II preparations were significantly lower (P < 0.001) than for Group I specimens. The stiffness and energy-absorbing capacities of the laminectomized specimens were also significantly different (P < 0.05) from those of the intact columns. In contrast, the deflections at failure for the two groups were not statistically different, suggesting that the human thoracic spine is deformation sensitive. Our data demonstrate that a two-level laminectomy decreases the strength and stability of the thoracic spine throughout the loading range. Although this is not a practical concern with an otherwise intact vertebral column, laminectomy, when other abnormalities such as vertebral fracture, tumor, or infection exist, may require stabilization by fusion and instrumentation.

Kinematics of the lumbar spine following pedicle screw plate fixation.

This investigation was conducted to determine the kinematic response of the lumbar spine instrumented with transpedicular screws and plates. Seven unembalmed human cadaveric lumbar spines were used. Retroreflective targets were inserted into the bony landmarks of each vertebral body, facet column, and spinous process. The specimen was quasistatically loaded until failure (initial cycle) using an electrohydraulic testing device at a rate of 2.5 mm/sec. After radiography, the specimen was again loaded (injury cycle) to the failure compression determined in the previous cycle. Transpedicular screws then were inserted bilaterally at one level proximal and distal to injury. The stabilized cycle of loading was conducted using the procedure adopted in the injury cycle. Comparative analysis of the localized kinematic data between the stabilized and injured columns indicated a reduction in motion between fixated levels, increasing the rigidity of the column. At levels proximal and distal to fixation, however, motion increased, indicating added flexibility. These alterations in the motion, observed during single-cycle loading, may be further accentuated in vivo, leading to hypermobility and degeneration of the spine.

The thermoplastic Minerva body jacket: a clinical comparison with other cervical spine splinting techniques.

A retrospective analysis of the efficacy of a variety of external stabilization techniques used in 155 cases of unstable cervical spine injuries is presented. The movement at each intervertebral level was evaluated during thermoplastic Minerva body jacket stabilization in 18 additional patients. Many currently available approaches to external stabilization of the cervical spine were, thus, assessed. Thermoplastic Minerva body jacket stabilization offered superior segmental immobilization compared with published data for the halo. It is concluded that some unstable injuries to the high cervical spine might best be treated with a halo device, whereas mid to low cervical injuries and the remaining upper cervical spine injuries appear to be optimally treated with a Minerva jacket. Lesser injuries may be treated with a variety of available orthoses. The thermoplastic Minerva body jacket offers a superior limitation of intervertebral movement compared with other commonly used braces, including the halo jacket, for most cervical spine injuries. The technique of application of the thermoplastic Minerva body jacket is reviewed.

Increased sacroiliac joint uptake after lumbar fusion and/or laminectomy.

Of 753 adult patients undergoing SPECT and planar bone scintigraphy for the evaluation of low back pain, 43 (6%) showed either unilateral or bilateral increased sacroiliac joint (SIJ) uptake. Five of the 58 abnormal joints were only identified with SPECT (9%), whereas 20 of the 58 abnormal joints were much more convincingly demonstrated by SPECT (34%). Fifteen of the 43 patients with increased SIJ uptake had undergone prior lumbar laminectomy and/or spinal fusion. Such spinal surgery can increase impact loading on the SIJ, leading to mechanical overload and sacroiliitis. Degenerative joint disease, trauma, or other benign pathology accounted for the remaining patients with increased SIJ uptake. The authors conclude that for patients with a history of lumbar spinal fusion and/or laminectomy, increased SIJ uptake usually is caused by altered spinal mechanics rather than malignancy or infection.

Strength and kinematic response of dynamic cervical spine injuries.

This study was conducted to evaluate the biodynamic strength and localized kinematic response of the human cervical spine under axial loading applied to the head. Intact ligamentous fresh human cadaveric head-neck complexes were subjected to dynamic compressive forces with a custom-designed electrohydraulic testing device at varying rates. The structure included the effects of anterior and posterior cervical spine muscles with a system of pulleys, dead weights, and spring tension. Localized kinematic data were obtained from retroreflective targets placed on the bony landmarks of the specimen at every level of the spinal column. Input forces, accelerations, displacement, and output generalized force histories were recorded as a function of time with a digital data acquisition system at dynamic sampling rates in excess of 8,000 Hz. High-speed photography at 1,000-1,200 frames/sec also was used. Pathologic alterations to the head-neck complex were evaluated with conventional radiography, computed tomography, and cryomicrotomy. In all specimens, cervical spine injuries occurred as a result of impact. Compressive forces recorded at the distal end of the preparation indicated large-duration, short-magnitude pulses in contrast to short-duration, high-amplitude input waveforms at the head, suggesting decoupling characteristics of the head-neck system. Cervical vertebral body accelerations were consistently smaller than the accelerations recorded on the head. Kinematic data demonstrated temporal deformation characteristics as well as a plausible sequence of spinal deformations leading to injury, which were correlated with the pathoanatomic alterations documented with the post-test computed tomographic and sequential cryomicrotome sections.

Traumatic facial injuries with steering wheel loading.

This study was conducted to evaluate the biomechanics of facial fractures caused by steering wheel loading. Twelve intact fresh human cadaver heads were impacted onto standard or energy-absorbing steering wheels with a custom-designed and validated vertical-drop apparatus. Either zygoma was impacted once at a velocity of 2.0-6.9 m/s. The specimens were oriented to permit a direct comparison between pretest and posttest radiography, and two-dimensional and three-dimensional CT images. Bone mineral content was determined, and biomechanical forces, accelerations, and deformations were recorded. More severe fractures were associated with higher forces on the zygoma. With increasing velocities, fractures initiated at the zygomatic region propagated to other unilateral regions such as the mandible and orbit or to the contralateral side. Less facial trauma was observed with energy-absorbing steering wheels compared with standard wheels at similar impact velocities. Bone mineral content did not correlate well with specimen age or with fracture severity. Clinically significant fractures were identifiable on 3-D CT images. The flexibility of 3-D CT in evaluating the spatial extent of facial abnormalities in different orientations may have significant impact in planning surgical procedures.