Biomechanical analysis of an induced joint dysfunction (subluxation-mimic) in the thoracic spine of rabbits

OBJECTIVE: The purpose of the present experiment was to evaluate functional biomechanics of the lesioned area in rabbits subjected to surgically placed vertebral lesions which may mimic a subluxation. It was hypothesized that wedging a bar between three adjacent vertebrae would lead to visual and palpatory alterations and also to a decrease in range of motion (ROM) at the affected segments. DESIGN: A controlled laboratory experiment was performed to measure directly ROM and to evaluate the functional and anatomic relationships of vertebrally lesioned rabbits. SUBJECTS: Twelve healthy adult New Zealand rabbits of either sex, weighing 3-5 kg, were maintained in the PCC animal facilities under normal husbandry conditions. Six operated controls and six experimentally lesioned rabbits were available for analysis. INTERVENTIONS: Rabbits were anesthetized and a vertebral lesion surgically placed at various locations along the thoracic spine. A stainless steel bar was implanted to produce a putative partial fixation and misalignment of three adjacent segments. The middle spinous process was forced contralaterally and slightly rotated relative to the adjacent two. At intervals ranging from a few weeks to several months postsurgery, the animals were evaluated for spinal ROM and also by visual and palpatory means for spinal misalignment. MAIN OUTCOME MEASURE: X rays, using rubber foam molds to standardize positioning, were taken pre- and postsurgery to measure ROM. Statistical analysis was made to compare ROM between the lesioned and adjacent areas of experimental and control animals. RESULTS: All but one of the experimental animals, but none of the controls, showed some reduced ROM on palpation at autopsy. Radiographic measures, however, showed that the ROM in the experimental animals as a group was not significantly reduced compared to control values, nor was there a significant ROM decrease compared to nonlesioned motor units within the experimental group. In some individual animals, however, there was a significant decrease in spinal ROM. CONCLUSIONS: This study failed to demonstrate any effect of the vertebral lesion on spinal ROM as measured radiographically, although by palpation the lesioned area did appear to be partially fixated in most animals. This surprising result may perhaps be explained by the large variability in measurements, the small number of subjects used or by inadequacies of X-ray positioning. Further work on biomechanical effects of vertebral lesions is clearly required.     

Biomechanical comparison of the dewar and interspinous cervical spine fixation techniques

STUDY DESIGN: This study evaluates and compares the stiffness of two cervical spine fixation techniques. OBJECTIVES: This biomechanical study was carried out to compare the interspinous and Dewar cervical spine fixation techniques. SUMMARY OF BACKGROUND DATA: Interspinous wiring is a commonly used method of fixation in the cervical spine. The Dewar technique is less commonly known and practiced, and clinical experience has suggested that it may be a more stable technique. METHODS: Cervical spine specimens stabilized with the interspinous and "Dewar" techniques were biomechanically tested in flexion and in torsion. Stiffness and energy absorption under moderate loads were compared. The Dewar technique uses contoured double corticocancellous iliac grafts as internal grafts/splints fixed to the spine with threaded pins and wire. The interspinous technique is a single interspinous wire loop. Eleven fresh human cervical spines were harvested from cadavers. The spines were destabilized at C4-C5 by sectioning all tissue except the anterior longitudinal ligament. Each fixation technique was applied alternatively and tested on each spine. RESULTS: In torsion testing (n = 5), the Dewar fusion was 61% stiffer than the interspinous technique (P < 0.02). Dewar: 11.3 N/mm (s.d. 4.9 N/mm) and interspinous: 8.4 N/mm (SD 3.3 N/mm). In flexion testing (n = 6), the Dewar technique was 35% stiffer than the interspinous technique (P < 0.10). Dewar: 655.4 Nmm/degree (SD 293 Nmm/degree) and interspinous: 406.8 Nmm/degree (SD 113.0 Nmm/degree). Energy absorption with the interspinous technique was greater in flexion (P < 0.10) and in torsion (P < 0.005), indicating more deformation with the interspinous technique. There was no statistically significant difference between the means of specimens tested first and those tested second independently of the fixation technique. CONCLUSIONS: These tests indicate that the Dewar cervical spine fixation is stiffer than the single interspinous wire in both flexion and particularly torsion. This project is the only biomechanical study of the Dewar technique that we are aware of, and the results support the clinical findings regarding the effectiveness of this technique.     

Biomechanical versus inertial information: Stable individual differences in perception of self-rotation.

When turning without vision or audition, people tend to perceive their locomotion as a change in heading relative to objects in the remembered surroundings. Such perception of self-rotation depends on sensitivity to information for movement from biomechanical activity of the locomotor system or from inertial activation of the vestibular and postural systems. The authors report 3 experiments that investigated the relative contributions of biomechanical and inertial information to perceiving the speed of self-rotation. Using a circular treadmill, the proportions of the 2 sources of proprioceptive information were varied, creating walking conditions with a constant rate of biomechanical activity but with variable speeds of rotation relative to inertial space. The results reveal stable individual differences in sensitivity to information for the perception of locomotion. Just more than half of the participants based their perceived speed of self-rotation on biomechanical information, whereas the others based theirs on inertial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biomechanical analysis of single- versus double-screw fixation in slipped capital femoral epiphysis at physiological load levels

Slipped capital femoral epiphyses in 12 pairs of bovine femora were pinned with a single screw on one side and two screws on the other. The specimens were subjected to physiological shear loads across the epiphysis (100 cycles at 1.1 Hz; 400 N for slow walking, and 900 N for fast walking). The rates of creep were decreased 23% with double screws compared to single screws at slow walking, and 30% at fast walking; this was not statistically significant. Single-screw fixation in slipped epiphyses is thus recommended, because the small gains in resistance to cyclic creep at physiological loading were not statistically different, and did not offset the increased risks of complications with multiple screws.     

Learned helplessness in task-orienting versus performance-orienting testing conditions.

Fifth- and 6th-grade subjects (Ss; 51 boys and 59 girls) were classified as low or high in effort orientation based on the number of items in the Intellectual Achievement Responsibility Questionnaire for which lack of effort was selected as an explanation for failure. On a computerized, 2-choice discrimination learning task, half of the Ss were given directions designed to reduce concerns about performance and to direct attention toward the task ("task-orientation" instruction condition); half were given "performance-orienting" instructions. The computer was programmed to ensure that all Ss failed to solve all four problems. Analyses of problem-solving strategies revealed that fewer low-effort-orientation Ss used effective strategies in the performance- than in the task-orienting condition. The instructions did not affect the proportion of high-effort orientation Ss who used effective strategies. The results suggest that task-orienting strategies may facilitate the performance of children who tend to de-emphasize the role of effort. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stamp collecting versus science: Validation as hypothesis testing.

Discusses the continuing arguments with respect to the unitarian vs trinitarian view of the validation process. It is argued that an emerging position is that the threefold distinction among validation models presented by L. J. Cronbach and P. E. Meehl (see record 1956-03730-001) is not as useful as it once was. The present author suggests that the validation process be considered nothing more and nothing less than traditional hypothesis testing. It is further suggested that as a result of a tendency to label validity approaches as correct or incorrect in a given situation, Title VII cases often resemble a primitive form of stamp collecting, with the test in question as the metaphorical stamp. There are only 3 spaces to be filled—the content, construct, and criterion-related space. Depending on the type of test, the litigants set out if all the requirements have been met in a checklist fashion. The issue of the role of constructs in psychological measurement is considered, as is the general status of construct-validation strategies in employment testing. The unique knowledges, skills, and abilities that psychologists bring to the discussion of validity and inference are discussed. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chordoma of the mobile spine. A clinicopathologic analysis of 40 patients

BACKGROUND: Chordomas are lobulated neoplasms composed of physaliphorous cells and their precursors; some have atypical, epithelioid, or spindle cell features. Fewer than one-sixth of chordomas arise in the mobile (cervical, thoracic, or lumbar) spine. Forty-eight percent originate in the sacrococcygeal region and 39% in the sphenoocciput. METHODS: The study included 40 patients, 27 men and 13 women (2:1), with chordoma of the mobile spine. Their clinical and histopathologic features are described. RESULTS: Nineteen tumors (48%) were located in the cervical spine, 7 (17%) in the thoracic spine, and 14 (35%) in the lumbar area. Most patients underwent subtotal removal of the tumor and postoperative irradiation. Variations in histologic appearance, including an occasional chondroid background, did not affect biologic behavior. Twenty-three patients (58%) were alive 5 years after surgery. Eventually, 25 patients (63%) died of tumor. Metastasis developed in two patients (5%). In contrast to some other studies metastasis was a rare occurrence. CONCLUSION: Chordoma of the mobile spine is a slow-growing, recurring neoplasm of low metastatic potential that incapacitates by locally aggressive growth.     

Performance of blacks and whites in computerized versus manual testing environments.

Discusses the problems of research on race and IQ, and describes a study which compared the results of manual and computer testing in judging the performance of blacks and whites. Ss were 10 white and 10 black male high school students. Performance by whites was the same under both procedures. Blacks performed significantly lower in manual tests, but in computerized tests their performance improved and was indistinguishable from that of whites. Theoretical reasons for these findings are discussed. It is felt that the computerized testing procedure circumvents many problems of earlier research. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multivariate analysis versus multiple univariate analyses.

The argument for preceding multiple analysis of variance ({anovas}) with a multivariate analysis of variance ({manova}) to control for Type I error is challenged. Several situations are discussed in which multiple {anovas} might be conducted without the necessity of a preliminary {manova}. Three reasons for considering multivariate analysis are discussed: to identify outcome variable system constructs, to select variable subsets, and to determine variable relative worth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanics of the external fixation test in the lumbar spine. A roentgen stereophotogrammetric analysis

The subjects of this study were 48 asymptomatic patients who had surgery for small hepatocellar carcinoma (HCC). There were 42 men and six women with mean (s.d.) tumour size of 3.31 (1.46) cm and age 55.0 (7.4) years. Follow-up was for a minimum of 10 years. The main concern of this study was a univariate analysis of factors that might affect long-term survival after surgery, which was 50 per cent at 5 years and 31 per cent at 10 years. A high incidence of recurrent HCC (37 of 48 patients) was observed but reoperation further prolonged life in some cases. The significant prognostic factors detected by multivariate analysis were: histological classification, functional liver reserve and histology of the resection margin. Tumour size, gross appearance of tumour, presence of liver cirrhosis, serum alpha-fetoprotein level, age or sex did not affect the prognosis.     

Kinematic analysis of posterolateral fusion in the lumbosacral spine

Three cases operated upon with posterolateral fusion in the lumbosacral spine have been subjected to a kinematic postoperative analysis with the aid of a roentgen stereophotogrammetric method. The primarily diseased intervals became comparatively rigid in spite of significant residual mobility, in two of the patients, not until 174 days postoperatively. Three levels of operation displayed unrestricted residual mobility.     

A reply to Bagnato and Neisworth: Intelligent versus intelligence testing of preschoolers.

Replies to the article by S. J. Bagnato and J. T. Neisworth (see record 1995-04117-001) discussing the use of intelligence tests (ITs) with infants and preschool children. Bagnato and Neisworth are seen as assuming that all ITs are the same and as ignoring the differences between testing infants and young children. They also overemphasize the importance of IT scores and overlook the observations of a competent tester. An ideal assessment would use both a curriculum-based approach and ITs, since they provide answers to different questions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biomechanical analysis and clinical treatment of blunt renal trauma

Moesin, one of the ERM (ezrin; radixin; moesin) family members, is directly associated with the cytoplasmic domain of CD44, which is now thought to be related to the metastatic potential of tumor cells. Using immunohistochemistry we investigated the expression of moesin in normal epidermis and various kinds of epithelial skin tumors: squamous cell carcinoma, verrucous carcinoma, Bowen's disease, solar keratosis, keratoacanthoma, basal cell carcinoma, and extramammary Paget's disease. Normal skin showed positive epidermal staining for moesin with the exception of the stratum corneum. The expression of moesin varied with the type of skin tumor. In basal cell carcinoma, Bowen's disease, and extramammary Paget's disease, moesin expression was either faint or negative. In contrast to Bowen's disease, invasive squamous cell carcinoma showed more intense and heterogeneous staining of the cytoplasm and the cell membrane. Verrucous carcinoma was weakly positive, with a tendency for the moesin to be distributed in the cell membrane. The staining pattern of moesin varied among the different kinds of epithelial skin tumors, and its expression was generally similar to that of the standard form of CD44. These results suggest that moesin is closely inter-related with CD44 in epithelial skin cells as seen in other cellular systems, and that the variable pattern of moesin staining among the skin tumor cells could reflect expression disorders associated with the transformation.     

Multidimensional scaling versus components analysis of test intercorrelations.

Considers the relation between coordinate estimates in components analysis and multidimensional scaling (MDS) and reviews algebraic relations between metric MDS and components analysis. Previous studies suggest that the same relations usually characterize components and nonmetric MDS analyses of correlation matrices. Merits of the MDS and factor approaches are compared, and results are related to other methodological issues surrounding research on the general ability factor, response tendencies in self-ratings, and halo in employee evaluations. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heredity versus environment: An integrative analysis.

C. S. Jencks's (1972) method of analysis of the heredity–environment data is presented, but with the important modification that cognizance is taken of the principle of genetic variation with age, that is, that the genotypic value (G) varies with age. As a result of this modification and a more critical examination of the IQ data, a solution is obtained that agrees with Jencks's figure for covariance, but supports C. Burt and M. Howard's (1956) and A. R. Jensen's (see record 1969-09740-001) emphasis on heredity in that it assigns 75% of the remaining variance to heredity and only 25% to environment. The present study can be regarded as integrative in that (a) it eliminates most of the discrepancies in the field and (b) it uses Jencks's approach, albeit modified, to produce what is essentially Burt's result. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of same-day tests versus traditional overnight testing

Within the last decade, major technologic advances have been made in clinical microbiology that have resulted in the availability of a wide variety of different methods for the rapid reporting of test results. Included among these technologies are rapid methods for producing antimicrobial susceptibility reports that many regard as the most important information generated by the microbiology laboratory. Ideally, the early availability of this important information should favorably affect patient care by enabling the more judicious use of alternative drug therapies that are equally efficacious yet less toxic and less costly to the patient. Clinicians appear to have been reluctant to modify initial empiric therapies, however, despite the availability of the rapid antimicrobial susceptibility report. This article addresses some of the issues responsible for this long-standing problem and discusses and explores various strategies that can be implemented for improving the use and for controlling the cost of antimicrobial agents within the hospital.     

The practitioner's view of IQ testing and profile analysis.

This study surveyed nationwide 354 nationally certified school psychologists on the perceived usefulness of the Wechsler Intelligence Scale for Children-III (WISC-III) in general and profile analysis in particular. Practitioners were asked questions assessing the frequency of use and perceived usefulness of various features of the WISC-III. A total of 89% of the respondents regularly used profile analysis and almost 70% listed it as among the most beneficial feature of the WISC-III. Practitioners rated the WISC-III as very useful for determining diagnosis and educational placement, but less useful for developing instructional strategies and curriculum plans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Component analysis versus common factor analysis: A Monte Carlo study.

Compares component and common factor analysis using 3 levels of population factor pattern loadings (.40, .60, .80) for each of the 3 levels of variables (9, 18, 36). Common factor analysis was significantly more accurate than components in reproducing the population pattern in each of the conditions examined. The differences decreased as the number of variables and the size of the population pattern loadings increased. The common factor analysis loadings were unbiased, had a smaller standard error than component loadings, and presented no boundary problems. Component loadings were significantly and systematically inflated even with 36 variables and loadings of .80. (PsycINFO Database Record (c) 2010 APA, all rights reserved)