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Biomedical subjects

G N Kawchuk

Publications and source records attributed to G N Kawchuk.

11 recordsLinked to original sources
PubMed2001

The diagnostic performance of vertebral displacement measurements derived from ultrasonic indentation in an in vivo model of degenerative disc disease.

STUDY DESIGN: The diagnostic performance of a newly described variable was assessed in an in vivo model of disc degeneration using a split-pair experimental design. OBJECTIVE: To determine if vertebral displacement measures generated from ultrasonic indentation could distinguish between experimental and control groups of animals. SUMMARY OF BACKGROUND DATA: Few procedures are available that noninvasively assess subcutaneous vertebral mechanics. Information from such a procedure would be of value in determining potential clinical relevance of spinal mechanics with respect to low back pain. METHODS: Eight adolescent pigs underwent endplate perforation surgery to initiate lumbar disc degeneration. After 4 months of recovery, these and eight age-matched controls were assessed by ultrasonic indentation, a noninvasive procedure that quantifies vertebral displacements in the plane of loading-indentation. Each animal then received a facetectomy and was reindented at the same location as confirmed by ultrasonic imaging. Discal materials were removed postmortem for analysis. RESULTS: Degenerative discs exhibited morphologic changes consistent with early degenerative disc disease. Prefacetectomy comparison of vertebral displacement measures between control and experimental animals resulted in sensitivity, specificity, and diagnostic accuracy values of 75.0%, 83.3%, and 77%, respectively. After facetectomy these values increased to 87.5%, 83.3%, and 85%, respectively. These measures of diagnostic performance were comparable or superior to those of existing clinical techniques (invasive or otherwise) used to assess degenerative conditions of the spine. CONCLUSIONS: The results of this study suggest that noninvasive measures of vertebral displacement are clinically significant and possess the additional advantages of being objective and noninvasive.

Animals↗
PubMed2001

Sources of variation in spinal indentation testing: indentation site relocation, intraabdominal pressure, subject movement, muscular response, and stiffness estimation.

BACKGROUND: Force-displacement properties of spinal tissues assessed by blunt indentation are thought to have clinical relevance; however, numerous variables with respect to spinal indentation have yet to be identified or characterized completely. OBJECTIVE: To identify and quantify, where possible, previously unidentified or incompletely characterized variables with respect to spinal indentation. DESIGN: Multiprotocol design. METHODS: Four experiments were performed: (1) Twelve asymptomatic subjects were indented with concurrent electromyography during conditions of rest, held inspiration, increased intraabdominal pressure and lumbar extension. (2) Changes in the recumbent position of 12 subjects were measured while a series of movements was performed in restrained and unrestrained conditions. (3) Ten clinicians attempted to locate, and to relocate, a subcutaneous anatomical landmark through visualization/palpation and ultrasonic imaging. (4) Performances of 3 methods of force-displacement curve modeling were compared with respect to stiffness estimation. RESULTS: (1) Spinal stiffness increased significantly in a minority of subjects awaiting indentation and in a majority of subjects during increases in intraabdominal pressure. (2) Changes in subject position were significantly reduced by a restraint system. (3) With respect to interclinician error in locating and relocating an indentation site, there was significant improvement with the use of ultrasonic visualization. (4) The error associated with linear techniques used to model curvilinear force-displacement data plots increased with increasing linear intervals. CONCLUSION: Several sources of variation in spinal indentation were identified: indentation site relocation, intraabdominal pressure, subject movement, muscular response, and stiffness estimation. These variables, which have been unaccounted for in previous indentation studies, might be responsible for the change or lack of change in force-displacement properties between preintervention and postintervention indentation trials.

Adult↗
PubMed2000

Ultrasonic quantification of osseous displacements resulting from skin surface indentation loading of bovine para-spinal tissue.

OBJECTIVE: To validate an ultrasound-based technique which quantifies uni-planar subcutaneous displacement of an osseous object resulting from an externally applied load. BACKGROUND: Many spinal conditions are thought to be characterized by aberrant vertebral displacements yet the invasive nature of many investigative techniques has left the clinical significance of this relation incompletely understood. METHOD: Six bovine bone/paravertebral tissue preparations were indented by one of two ultrasonic transducers (5 and 7 MHz) fitted to an electromechanical actuator. The resulting osseous displacement along the principal indentation axis was calculated by subtracting the change in transducer/bone distance between ultrasonic images collected at tissue contact and maximal load from the change in actuator displacement. A dial gauge contacting the bone was used as a displacement criterion measure. RESULTS: Using the 7 MHz transducer, the mean error of the technique was 6.74% (SD=3.98) while the mean error associated with the 5 MHz transducer was 12.73% (SD=7.49). CONCLUSIONS: This non-invasive technique is capable of quantifying subcutaneous uni-planar bone displacement with an accuracy comparable to similar invasive techniques over a comparable displacement range. RelevanceThis non-invasive technique may be beneficial in assessing the significance of vertebral displacements in conditions such as hypermobility and osteoarthritis, as well as in studies of manipulative therapy.

Animals↗
PubMed1998

Validation of displacement measurements obtained from ultrasonic images during indentation testing.

Biomechanical features of soft tissue are commonly investigated by indentation, a procedure where a blunt probe is advanced and the ensuing deformation of the tissue surface recorded. If it were possible to visualize subsurface anatomy during the indentation process, biomechanical investigation of internal tissue features might be feasible. The purpose of this experiment was to determine the accuracy of ultrasonically-derived measures of displacement obtained during indentation testing of an ultrasonic phantom. Using a 5-MHz sector transducer mounted to an automated indentation device, ultrasonic estimates of distance between a stationary target surface and the moving ultrasonic transducer were obtained and validated to a criterion. Depending on the method used to locate the target surface on the resulting B-mode image, the mean displacement error ranged from 14.37% to 22.05%. Use of this protocol for human tissue assessment, in vivo or otherwise, may be appropriate if the displacements of interest are greater than the error of the procedure.

Algorithms↗
PubMed1995

Forces and relative vertebral movements during SMT to unembalmed post-rigor human cadavers: peculiarities associated with joint cavitation.

OBJECTIVE: The purpose of this study was to compare the relative movements between adjacent vertebrae that were accompanied by a cavitation sound to those relative movements wherein no cavitation sound was recorded, during spinal manipulative treatments (SMTs) to T12 of an unembalmed human cadaver. SETTING: The experiment was conducted in the gross anatomy laboratory at the University of Calgary. SUBJECTS: One 77-yr-old male cadaver was used. INTERVENTIONS: High speed cinematography and embedded bone pin markers were used to record the movements of T10, T11, and T12, during the manipulations. A pressure pad was used to measure the posterior-to-anterior (p-to-a) forces exerted by the clinician onto the cadaver. Two uniaxial accelerometers were used to record the p-to-a accelerations of T11 and T12. The clinician delivered five p-to-a thrusts to the right transverse process of T12. P-to-a forces, p-to-a accelerations, and relative (between T10 and T11, and, T11 and T12) p-to-a translations, lateral translations, and axial rotations, were calculated for each thrust. MAIN RESULTS: A cavitation sound was recorded by the T12 accelerometer during the fourth manipulation. The p-to-a force parameters of the fourth trial were not different from those of the other trials. However, the relative lateral translations between the adjacent vertebrae were substantially greater during the fourth manipulation, compared to the other trials. CONCLUSIONS: The characteristics of the relative lateral translations between adjacent vertebrae suggest that the cavitation sound recorded during the fourth manipulation may have been associated with greater laterally applied forces than those during the other manipulations to T12, wherein no cavitation was recorded.

Acceleration↗
PubMed1993

Forces exerted during spinal manipulative therapy.

Spinal manipulative therapy has been widely recognized in the medical fields as a conservative treatment modality for spinal dysfunction and pain. Spinal manipulative therapy consists of an application of a thrusting force on a specific part of the spine in a well-defined direction. The magnitude of this force has been associated with positive treatment effects, such as realigning vertebral bodies, mobilizing spinal joints, relaxing back musculature through reflex pathways, and producing a respiratory burst. However, direct force measurements during spinal manipulative therapy in a clinically relevant situation have not been performed to date. The purpose of this study was to measure the forces exerted onto patients during spinal manipulative therapy on various locations of the spinal column. Force measurements were obtained using a thin, flexible pressure mat. The results indicate that peak and preload forces are considerably smaller for spinal manipulative therapy performed on the cervical spine compared to corresponding values obtained on the thoracic spine and sacroiliac joint. Furthermore, for treatments on the thoracic spine and sacroiliac joint, a significant relation was found to exist between preload and peak forces.

Biomechanical Phenomena↗
PubMed1993

Cavitation sounds during spinal manipulative treatments.

OBJECTIVE: The purpose of this study was to confirm a practitioner's perception of cavitation during spinal manipulative therapy in a clinically relevant situation using accelerometer recordings. DESIGN: Experimental study. SETTING: Human Performance Laboratory and Sports Medicine Center, University of Calgary. PARTICIPANTS: Twenty-eight patients from a single practitioner's patient pool who had pain in the area of the thoracic spine. INTERVENTION: Spinal manipulative treatment (SMT) on the transverse process of T4 using a reinforced unilateral contact and delivering a thrust in the posterior to anterior direction. MAIN OUTCOME MEASURES: Instantaneous acceleration signals obtained from the spinous process of T3 during SMT and the practitioner's perception if cavitation had occurred or not at the end of each treatment. CONCLUSIONS: It appears that cavitation may be measured during SMT using accelerometry and that a practitioner's perception of the occurrence of cavitation during SMT is very accurate.

Back Pain↗
PubMed1992

Forces generated during spinal manipulative therapy of the cervical spine: a pilot study.

OBJECTIVE: To determine the forces imparted to the cervical spine using direct sampling methods during a clinical episode of spinal manipulative therapy. DESIGN: Quantitative study. SETTING: Human Performance Laboratory, University of Calgary. PARTICIPANTS: Two doctor/patient pairs. Patients were selected by the treating chiropractors from their existing patients pools. INTERVENTIONS: SMT to the cervical spine (toggle method) on three separate occasions over a 2-wk period. The clinical relevancy of the treatment was assessed via before and after measures of tissue compliance. MAIN OUTCOME MEASURE: a) Forces during manipulation: preload and peak forces. b) Duration of applied forces. RESULTS: a) Mean peak force = 117.7 N (+/- 15.6 N). b) Mean duration of force = 101.7 msec (+/- 14.7 msec). CONCLUSION: The forces obtained with direct sampling methods compare favorably to previous measurements obtained from indirect sampling techniques, yet the force duration times are smaller (faster) using the direct method.

Biomechanical Phenomena↗
PubMedDate not supplied

Ultrasonic indentation: a procedure for the noninvasive quantification of force-displacement properties of the lumbar spine.

BACKGROUND: Alterations in the normal force-displacement (FD) properties of spinal tissues have been associated with specific forms of pathology, such as degenerative disk disease. Unfortunately, few current procedures exist that assess spinal FD properties in an accurate, reliable, and noninvasive manner. Consequently, the clinical relevance of the relation between spinal disorders and spinal FD properties is not fully understood. OBJECTIVE: To investigate the accuracy and reliability of spinal FD measures obtained through use of a procedure in which real-time ultrasonic imaging (ultrasonic indentation) is used during load-controlled external indentation. SETTING: McCaig Centre for Joint Injuries and Arthritis Research, University of Calgary. METHODS: The bench-top accuracy and reliability of ultrasonic indentation were assessed by cyclic indentation of a spring-mounted platform. These data were compared with criterion data derived from a materials testing machine. A porcine preparation was then used to assess the accuracy of ultrasonic indentation-generated estimates of vertebral displacement in comparison with a criterion of optically tracked displacement. In addition, previously unreported parameters relating to indentation accuracy (frame deflection and off-axis loading) were characterized. RESULTS: Reliability of ultrasonic indentation ranged between 0.99 and 1.00 (intraclass correlation coefficient). Error values in force, displacement, and stiffness ranged from 0.81% to 13.62% over varying experimental conditions. CONCLUSIONS: Ultrasonic indentation is a unique procedure that is capable of assessing, noninvasively, FD properties of spinal tissues, including vertebral displacement in the indentation plane. The results of this study suggest that ultrasonic indentation is a potentially useful technique for quantifying spinal FD properties in vivo.

Animals↗
PubMedDate not supplied

Biomechanical characterization (fingerprinting) of five novel methods of cervical spine manipulation.

OBJECTIVE: To determine the biomechanical characteristics of five clinically common methods of cervical spine manipulation. DESIGN: Descriptive study. SETTING: Human Performance Lab, University of Calgary. PARTICIPANTS: Five volunteer practitioners treating symptomatic patients from their own clinical populations. INTERVENTION: Five commonly used methods of cervical spine manipulation: lateral break (LAT), Gonstead (GON), Activator (ACT), toggle (TOG), rotation (ROT). MAIN OUTCOME MEASURE: Mean thrust duration (msec), normalized mean peak force (N), slope (N/msec), force profile (graphic representation of the above values. RESULTS: Outcome measures for each manipulative technique were as follows: LAT = normalized mean peak force of 102.2 N at 86.7 msec, GON = 109.8 N at 91.9 msec, ACT = 40.9 N at 31.8 msec, TOG = 117.6 N at 47.5 msec, ROT = 40.5 N at 79.1 msec. CONCLUSION: The observed differences and similarities in force profiles between the five techniques studied here may partly be the manifestation of how a particular technique delivers force to the cervical spine. The clinical significance of force profile characterization is not yet known.

Biomechanical Phenomena↗