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Biomedical subjects

G W Knight

Publications and source records attributed to G W Knight.

At least 19 recordsLinked to original sources
PubMed2000

The biomechanical effect of postoperative hypolordosis in instrumented lumbar fusion on instrumented and adjacent spinal segments.

STUDY DESIGN: Change in lumbar lordosis was measured in patients that had undergone posterolateral lumbar fusions using transpedicular instrumentation. The biomechanical effects of postoperative lumbar malalignment were measured in cadaveric specimens. OBJECTIVES: To determine the extent of postoperative lumbar sagittal malalignment caused by an intraoperative kneeling position with 90 degrees of hip and knee flexion, and to assess its effect on the mechanical loading of the instrumented and adjacent segments. SUMMARY OF BACKGROUND DATA: The importance of maintaining the baseline lumbar lordosis after surgery has been stressed in the literature. However, there are few objective data to evaluate whether postoperative hypolordosis in the instrumented segments can increase the likelihood of junctional breakdown. METHODS: Segmental lordosis was measured on preoperative standing, intraoperative prone, and postoperative standing radiographs. In human cadaveric spines, a lordosis loss of up to 8 degrees was created across L4-S1 using calibrated transpedicular devices. Specimens were tested in extension and under axial loading in the upright posture. RESULTS: In patients who underwent L4-S1 fusions, the lordosis within the fusion decreased by 10 degrees intraoperatively and after surgery. Postoperative lordosis in the proximal (L2-L3 and L3-L4) segments increased by 2 degrees each, as compared with the preoperative measures. Hypolordosis in the instrumented segments increased the load across the posterior transpedicular devices, the posterior shear force, and the lamina strain at the adjacent level. CONCLUSIONS: Hypolordosis in the instrumented segments caused increased loading of the posterior column of the adjacent segments. These biomechanical effects may explain the degenerative changes at the junctional level that have been observed as long-term consequences of lumbar fusion.

Adult↗
PubMed1998

The effect of magnification on student performance in pediatric operative dentistry.

Previous research has shown that accurate student self-evaluation is related to higher quality dental products. Variance in student performance still remains. Enhancement of visual perception could contribute to product improvement. Only one study has evaluated the effects of magnification on simulated dental patient care. The present study sought to determine if magnification had a positive effect on student-generated products in pediatric amalgam preparations. Fifty-two third-year students were randomly assigned to experimental (magnification) or control (no magnification) groups. Members of the experimental group used magnification in their daily work in the pediatric dentistry clinic. No significant differences between the groups' preparations or evaluations of standard preparations were found. Further study should address these issues: 1) possible effects of specific training in the use of magnification devices; 2) whether the tolerance for error in dental preparations is so great that finer vision contributes little to product improvement; 3) the role of tactile sensation in evaluation and preparation; and 4) the possible benefits of magnification for effect of age. Based on this study, it seems that requiring students to purchase magnification devices may not be justified.

Age Factors↗
PubMed1997

Using questions to facilitate motor skill acquisition.

For the process of question-guided problem-solving to work successfully, several conditions must exist: 1) presence of valid and reliable criteria for evaluating product (DO) and performance (DP), 2) development of learning resources such as life-sized examples, 3) training sessions in the application of criteria and use of the process for both faculty and students, and 4) faculty commitment to the process. The process helps to establish conditions in which learning occurs. Underlying its structure is the requirement for incorporation of discrimination tasks. Question-guided problem-solving structures the learner's approach to the task in a way that facilitates the refinement of independent learning strategies over time. Further, it promotes effective use of time in laboratory or clinic. Through repeated interactions, the faculty may better monitor student progress, diagnose student learning problems, suggest remedial strategies, and evaluate their outcomes. By providing instruction that includes opportunities to practice the subskills of problem-solving in an interactive cooperative environment, students systematically monitor learning by asking good questions and, through questioning, are empowered to solve problems.

Education, Dental↗
PubMed1996

Patient-centered competency-based education in fixed prosthodontics.

Revision of a traditional fixed prosthodontic curriculum was undertaken in response to observed private practice patterns, recent literature in fixed prosthodontics, and an increasingly crowded dental school curriculum. The revision was further motivated by the commitment of the faculty to become patient-centered in all components of instruction. The resultant preclinical and clinical curriculum emphasizes patient care activities and minimizes student-generated laboratory products. This program is characterized as patient-driven, competency-based, and criterion-referenced, and it places heavy reliance on validated pedagogical strategies, which include evaluation of self and peers. The curriculum requires the development of good communication skills with peers, faculty, and commercial laboratories and creates time for the student to develop critical patient care skills without requiring more curriculum time. The new fixed prosthodontic curriculum appears to be consistent with current private general practice, national licensing examinations, and the recommendations of the Institute of Medicine's report to dental education.

Competency-Based Education↗
PubMed1994

Design and validation of mirror skills instruction.

Students contorted to achieve direct vision indicate that training of mirror skills is absent or ineffective. Training referenced in the literature is not described or amounts to practice using a mirror to perform a psychomotor task often marginally related to dental procedures. No complete task analysis of mirror use is reported. In this study, the authors applied instructional engineering principles to 1) analyze the task and design instruction, 2) validate instruction, and 3) foster mirror use. First-year students (experimentals) completed the new mirror instruction as well as the regular course instruction. A randomly selected group of second-year students who had not completed the mirror instruction but had completed a similar course comprised the control group for the validation. Sets of randomly grouped experimental subjects evaluated a maxillary preparation using mirror vision at three times during the semester and one time a year later. The controls evaluated the same preparation the first time only. Accuracy in describing the critical features of the preparation was used as an indicator of mirror skill. All subjects were observed for mirror use during a practical examination involving maxillary preparations. All groups were equivalent on entering GPA, DAT-A, and DAT-P. Experimental groups made significant improvement in measures of mirror vision skill over time. Experimental groups 2, 3, and 4 significantly outperformed controls on the same measures and demonstrated significantly higher rate of mirror use during the practical exam. The mirror skills instruction appears valid.

Chi-Square Distribution↗
PubMed1992

Long-term outcomes for remedial students.

A recent survey of dental schools concluded that current efforts toward remediation are inadequate. A remedial waxing course providing recognition training before production attempts, emphasis on formative self- and peer-evaluation of projects, and application of a highly structured format for ensuring relevant practice had been developed and favorably evaluated previously. The current report follows the progress of two differently trained remedial groups and the remainder of the class in two courses following remediation. On the five subsequent practical examinations analyzed, the experimental group continued to perform at the class mean. On one practical examination, the experimental group significantly outperformed the traditional group (p less than 0.02). For three of the five examinations, the traditional group was significantly outperformed by the class. One of the six students in the experimental group required additional remediation. Of the seven in the traditionally remediated group, one left school and four required additional remediation. An apparent changing remediation pattern in the preclinical training period is described and possible reasons for the change are explored.

Dental Amalgam↗
PubMed1990

Teaching recognition skills to improve products.

All 86 first year dental students in a Conservative Restorations course completed five sets of instructional tasks. Tasks followed a discrimination learning paradigm, a sequence based on the principal that recognition skills are a prerequisite for production skills. Recognition skill measures and production quality measures were collected for pre- and post-test Class 1 amalgam preparations. Significant improvement was found in three of the five recognition skill measures and in quality of production. Stepwise multiple regression analysis showed that a measure of student agreement with faculty evaluations accounted for 46.3 percent of the variance in post-test production scores whereas traditional admissions measures accounted for less than 4 percent of the variance. Additionally, students who improved recognition skill showed a corresponding improvement in products. The paradigmatic teaching model appears to be valid for Class 1 cavity preparations.

Dental Amalgam↗
PubMed1990

Discrimination training and formative evaluation for remediation in basic waxing skills.

In a quasi-experimental design the "experimental" group (n = 6) received discrimination training and self-evaluation exercises on four waxing projects and four handpiece projects over 13 hours. An equivalent "conventional" group (n = 7) received verbal feedback with models on seven waxing projects over 13 hours. Both groups took a posttest using plastic molars with two-surface preparations to be restored in wax. In blind evaluations of final products, the experimental group outperformed the conventional group. Results demonstrate the efficiency and effectiveness of structured discrimination and self-evaluation training in improving motor skills.

Dental Casting Technique↗
PubMed1989

Factors influencing the penetration of wires into the neural canal during segmental wiring.

We evaluated the influence of the penetration of wires into the neural canal during segmental wiring in a three-part study. First we examined the anatomy of the thoracic spine, specifically the laminar and interlaminar dimensions, as well as the epidural space. In the second part, we evaluated the depth of penetration of wires into the spinal canal at the time of their passage during spinal segmental instrumentation, using direct laboratory measurements for three configurations of the wire: first with a straight wire, and then with two wires of varying curvature. The measurements were repeated after removal of a portion of the lamina. In the third and final part of the study, we assessed the relationship between the observed penetration of the wires and the depth of penetration as calculated using mathematical models for the three wire configurations. When a wire with the largest possible diameter of curvature was passed under the lamina, there was significantly less penetration using the curved-wire configuration. This was seen in calculated models, as well as in normal specimens of the thoracic spine that were obtained from cadavera. Little epidural space was found to be available for passage of the wire. In most instances, passage of the wire must result in contact with and displacement of the dural sac and its contents. To minimize the depth of penetration at any given spinal level, it is recommended that the wire be curved to the maximum degree that will allow it to pass under the lamina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens.

Profundus tendon lacerations were repaired in the central toes of 216 chickens, and the digits were either immobilized in a cast or allowed immediate constrained motion in a tethering splint. The effect of digital motion on the early phases of tendon healing was investigated by comparing the rupture strengths of the two groups during the first 40 days after repair. The repairs in immobilized digits showed marked decreases in strength during the first 20 days, while the tendons in mobilized digits showed immediate and progressive gains in strength through the time intervals studied. By 5 days, the difference in strength between the two groups was significant (p less than 0.05), and the magnitude of this difference increased with time. The model developed in this study demonstrates that an initial loss of flexor tendon repair strength is not inevitable. Immediate constrained digital mobilization allows progressive tendon healing without an intervening phase of tendon softening.

Animals↗
PubMed1987

Analysis of the morphometric characteristics of the thoracic and lumbar pedicles.

A total of 2,905 pedicle measurements were made from T1-L5. Measurements were made from spinal computerized tomography (CT) scan examinations and individual vertebral specimen roentgenograms. Parameters considered were the pedicle isthmus width in the transverse and sagittal planes, pedicle angles in the transverse and sagittal planes, and the depth to the anterior cortex in a line parallel to the midline of the vertebral body and along the pedicle axis. There was no significant difference between data obtained from CT scans and specimen roentgenograms. Pedicles were widest at L5 and narrowest at T5 in the transverse plane. The widest pedicles in the sagittal plane were seen at T11, the narrowest at T1. Due to the oval shape of the pedicle, the sagittal plane width was generally larger than the transverse plane width. The largest pedicle angle in the transverse plane was at L5. The posterolateral to anterolateral pedicle axis orientation in the transverse plane, seen at other levels throughout the thoracolumbar spine, reversed at T12. In the sagittal plane, the pedicles angled caudally at L5 and cephaladly from L3-T1. The depth to the anterior cortex was significantly longer along the pedicle axis than along a line parallel to the midline of the vertebral body at all levels with the exception of T12 and T11.

Adult↗
PubMed1986

A biomechanical analog of curve progression and orthotic stabilization in idiopathic scoliosis.

A biomechanical analog of curve progression and orthotic stabilization in idiopathic scoliosis has been developed using the classical theory of curved beam-columns. The interaction of the spinal musculature and other supporting structures is incorporated in the model using an equivalent flexural rigidity. The stability of a given scoliotic curve relative to a normal spine is described in terms of the so-called critical load ratio (Pc/Pe). This dimensionless quantity appears in the exact solution of the governing differential equation and boundary conditions. It is defined as the ratio of the load bearing capacity of a scoliotic spine (Pc) to that of a normal spine where the load bearing capacity of a normal spine is defined as Euler's buckling load (Pe). The computation of Pc/Pe is based upon a maximum allowable moment criterion. This model is used to study the effect of the degree of initial curvature and curve pattern in the frontal plane on the stability of untreated idiopathic scoliosis. Although restricted to two-dimensions, the model appears to demonstrate the synergistic effects of end support, transverse loading, and curve correction on improvement in relative stability of an orthotically supported scoliotic curve. The results of this study are in qualitative agreement with clinical findings that are based on long-term studies of natural history of idiopathic scoliosis and of patients undergoing orthotic management for scoliosis.

Biomechanical Phenomena↗
PubMed1986

Waxing tests as predictors of students' performance in preclinical dentistry.

Poor prediction of psychomotor performance in dentistry using traditional admissions tests and prior academic performance, as well as the serious consequences of poor performance for both students and faculty, suggest that better predictors are needed. Two tests of waxing skill were incorporated into the first semester freshman dental anatomy course and administered to one class of 131 students. Data were collected for eight preclinical performance measures. Results showed that neither the academic portion of the DAT nor the entering grade point average predicted performance on any of the psychomotor measures at a statistically significant level. In all cases, the first, second, or both waxing tests were better predictors than the perceptual portion of the DAT. These waxing tests may be useful in the early identification of students with psychomotor deficiencies for admissions decisions and/or for designing and evaluating the effectiveness of early instructional intervention strategies on performance.

Anatomy↗