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Biomedical subjects

M J Pearcy

Publications and source records attributed to M J Pearcy.

53 records · Page 3Linked to original sources
PubMed1987

Dynamic back movement measured using a three-dimensional television system.

A technique for the measurement of rotational human back movements in three dimensions has been developed. The spatial coordinates of reflective markers on rigs attached to the back surface were calculated using a calibrated television/computer system. A mathematical analysis of the change in these coordinates, as subjects performed set manoeuvres, was developed to provide unique descriptions of the rotational movements in terms of clinical angles related to anatomical frames of reference. The technique produced angles of rotation with maximum errors about any axis of +/- 2 degrees, with a root mean square error of less than 1 degree. The analysis of back movements using surface markers was shown to be feasible from studies of six volunteers who demonstrated consistent patterns of movement which were similar to previously reported patterns of spinal movement measured radiographically.

Back↗
PubMed1986

Temperature dependence of the tensile properties of interspinous ligaments of sheep.

The dependence on temperature of the tensile properties of interspinous ligaments was examined to establish whether in vitro studies at room temperature reflect behaviour in vivo at higher temperatures. Specimens consisting of sheep interspinous ligaments attached to their adjacent spinous processes were mounted in specially designed holding devices in an Instron material testing machine; the specimens were immersed in saline and tests were conducted at four temperatures between 19 degrees C and 46 degrees C. Control tests demonstrated the repeated testing to a load up to half the fail load did not affect the response of the ligaments. No difference was found in the mechanical characteristics of the ligaments at the different temperatures but the ligaments expanded at the higher temperatures, resulting in an increase in extension over which they demonstrated an initial low stiffness characteristic. Thus although temperature did not directly affect the response of the ligaments to load, the thermal expansion of the soft tissue elements may have implications for the function and mobility of spinal joints if measured at room rather than body temperature.

Animals↗
PubMed1986

Vertebral motion measured using biplanar radiography before and after Harrington rod removal for unstable thoracolumbar fractures of the spine.

The use of Harrington distraction rods for stabilization of fracture dislocation of the thoracolumbar spine is well established. For better initial stabilization and later return of flexibility we routinely use a long rod but fuse over a short segment and then remove the rods at 1 year. A biplanar radiographic technique was used to assess vertebral motion both before and after removal of Harrington rods in five patients. The investigation showed the rod acted to restrict movement and relieved loads on the spine that they spanned. Although all the patients regained considerable spinal flexibility once the rods were removed, none of the intervertebral joints measured could be considered solidly fused. However, the pattern of movement remained abnormal 6 months after rod removal with many intervertebral joints exhibiting lateral flexion and axial rotation during voluntary flexion extension. Despite this, a long rod/short fuse stabilization with routine rod removal after 1 year combines the initial advantage of operative stabilization and is shown to allow a return of spinal flexibility subsequently.

Evaluation Studies as Topic↗
PubMed1986

The effect of water content on the stiffness of seating foams.

The chairbound, disabled person requires a supportive cushion to distribute pressure in order to reduce the risk of pressure sores and any alteration to the load carrying capacity of the cushion may have a deleterious effect on its ability to provide adequate support. The National Health Service supplies two basic grades of polyurethane foam for wheelchair cushions and this study investigated the effect of water content on their compressive load carrying capacity. Both foams became less stiff and exhibited greater than 20% increase in deformation when containing 20% water by volume at loads encountered in seating. This decrease in stiffness may result in a dramatic change in the pressure distribution under a patient particularly if only a small section of the cushion becomes wet. This result emphasizes the need to fit waterproof coverings to these foam cushions and to maintain the integrity of the covering.

Humans↗
PubMed1985

Posterior intertransverse fusion assessed clinically and with biplanar radiography.

Biplanar radiography was used to assess bony union after intertransverse fusion. The patients were assessed clinically and the fusion status was compared with the clinical result. Posterolateral intertransverse fusion was shown to be capable of fusing the motion segment almost completely. However, the strictly measured fusion rate was only 27%, but this increased to 91% when partial fusions were included. The fusion rate from conventional plain films assessed by the radiologist was 82%, which is similar to other reports. On clinical examination, a satisfactory result was obtained in 82%, but there was no clear correlation with fusion status.

Adolescent↗
PubMed1985

Lumbar intervertebral disc heights in normal subjects and patients with disc herniation.

A method for the measurement of intervertebral disc heights from lateral radiographs obtained in controlled conditions was examined for intra- and interobserver errors. The use of a strict criterion for the positioning of marks on the images of the vertebrae was shown to enable reproducible measurements to be made with a maximum error of 0.7 mm. Measurements of anterior and posterior disc heights and disc depths were made for 11 normal subjects and ten male patients with prolapsed intervertebral discs, while standing upright. The level of the prolapsed discs were shown to have reduced height compared with normal before surgery, and further narrowing 3 months after surgery. The unaffected discs of the patients were the same height as those of the controls. The technique is proposed as suitable for the investigation of the effect on intervertebral discs of procedures such as the injection of chymopapain.

Adult↗
PubMed1985

A prospective study of lumbar spinal movements before and after discectomy using biplanar radiography. Correlation of clinical and radiographic findings.

The significance of alteration of lumbar spinal motion in cases of herniated disc was examined using a three-dimensional x-ray technique (biplanar radiography) before and 3 months after discectomy. Fifteen consecutive cases of disc herniation were studied prospectively. Predictions of clinical examination, myelography, and motion study for the level and site of the lesion were correlated with the operative findings for their accuracy in localization of the lesion. Changes in lumbar spinal motion after surgery were also correlated with the clinical results. The clinical and myelographic predictions were similar to previously published studies. The present study showed that patients with a sequestrated or prolapsed disc lesion (as opposed to bulging disc) had an abnormally large lateral bend or axial rotation during flexion and extension at the level above, which reduced after surgery. Primary lumbar spinal motions (flexion and extension) were generally reduced to half of the normal value and were not significantly altered by surgery. The restriction of lumbar spinal motion was not significantly reflected in the clinical results, which were satisfactory in most cases. Discectomy by fenestration and minimal resection of the lamina did not produce instability.

Adolescent↗
PubMed1985

Spinal movements in ankylosing spondylitis and the effect of treatment.

Fourteen male patients with ankylosing spondylitis, admitted for a 2-week period of inpatient treatment, had their spinal mobility assessed on admission and at the end of treatment by clinical measures and a three-dimensional radiographic technique. The patients were given injections of low-dose corticotrophin (ACTH) or placebo under a double-blind protocol. Initially all the patients had restricted movements compared with normal. After treatment all showed some improvement of mobility but no additional benefit accrued from ACTH. Clinical measures of mobility must be interpreted with care as the changes in these measurements were not closely reflected in the lumbar movements measured radiographically. Changes seen in plain radiographs were of little predictive value for improvements in mobility.

Adrenocorticotropic Hormone↗
PubMed1985

Stereo radiography of lumbar spine motion.

The technique of Biplanar Radiography for the computer analysis of orthogonal radiographs of the human spine enables the calculation of three-dimensional coordinates for anatomical landmarks on the vertebrae. Three-dimensional intervertebral movements are deduced from the changes in the relative orientations of the vertebrae as a subject moves from one position to another. The three-dimensional coordinates of the anatomical landmarks on the vertebrae were found to have an RMS error of less than 1 mm. The RMS errors for translational movements were less than 2 mm and for rotations were less than 1.5 degrees. This study of normal subjects has defined the ranges of voluntary flexion and extension, axial rotation, and lateral bending in the lumbar spines of young males. The range of flexion plus extension at each lumbar intervertebral joint is approximately 14 degrees with the L4/5 level being slightly more mobile than the others. There are approximately 2 degrees of axial rotation at each joint with L3/4 and L4/5 being slightly more mobile. Lateral bending of approximately 10 degrees occurs at the upper three levels while there is significantly less movement of 6 degrees and 3 degrees at L4/5 and L5/S1 respectively. In flexion and extension accompanying axial rotation of 2 degrees or more and lateral bending of 3 degrees or more occurred rarely and any larger accompanying rotation at an intervertebral joint should be considered abnormal. During twisting and side bending axial rotation to the right is accompanied by lateral bending to the left and vice versa at the three upper levels. At L5/S1 axial rotation and lateral bending generally accompany each other in the same direction while L4/5 is a transitional level. During lateral bending there is also generally extension at the upper levels and flexion at L5/S1. The measurement in vivo of the accompanying rotations in the other planes has demonstrated that there is no simple mechanical coupling of the rotations. Finally, this study has provided a base line of normal movements to which the movements seen in pathological conditions can be compared.

Adult↗
PubMed1984

In-patient regime for the treatment of ankylosing spondylitis: an appraisal of improvement in spinal mobility and the effects of corticotrophin.

Twenty-one patients with ankylosing spondylitis were admitted for two weeks bedrest, postural and mobilizing exercises. Eleven received low-dose corticotrophin and 10 received placebo injections during their admission and all were reviewed after two months. In-patient therapy resulted in significant improvements in function, early morning stiffness, spinal pain, lumbar extension and lateral flexion, finger-floor distance and wall-tragus distance. These improvements were maintained at two months. Biplanar radiography confirmed significant improvements of lumbar spine mobility in 14 male subjects studied. Less improvement occurred in neck movements and these were not maintained. There were no differences between the two treatment groups.

Adrenocorticotropic Hormone↗
PubMed1984

Axial rotation and lateral bending in the normal lumbar spine measured by three-dimensional radiography.

A three-dimensional radiographic technique was used to investigate the ranges of active axial rotation and lateral bending plus the accompanying rotations in the planes other than that of the primary voluntary movements in two groups of normal male volunteers. There was approximately 2 degrees of axial rotation at each intervertebral joint with L3-4 and L4-5 being slightly more mobile. Lateral bending of approximately 10 degrees occurred at the upper three levels, while there was significantly less movement of 6 degrees and 3 degrees at L4-5 and L5-S1, respectively. In the upper lumbar spine, axial rotation to the right was accompanied by lateral bending to the left and vice versa. At L5-S1, axial rotation and lateral bending generally accompanied each other in the same direction, while L4-5 was a transitional level. These measurements in vivo demonstrated that there was no simple mechanical coupling of the rotations, and that the lordotic shape of the lumbar spine together with muscular control are probably the two principal factors determining the relation between the primary and accompanying rotations.

Adult↗
PubMed1984

Lumbar intervertebral disc and ligament deformations measured in vivo.

The physiologic deformations of the anterior and posterior margins of the annulus fibrosus and the interspinous ligaments were defined in flexion and extension by accurate measurements taken from lateral roentgenograms of the lumbar spines of 11 normal males. The anterior and posterior disc heights were shown to compress and extend up to 35% and 60%, respectively, while the interspinous distance extended up to 369%. In relation to the known mechanical characteristics in vitro, these deformations implied that the soft-tissue elements were lax or in compression during part of the range of motion. Significantly, the interspinous ligament could be active only in the extremes of flexion. These data provide basic information for further studies of the function of the soft parts of the intervertebral joints.

Adult↗
PubMed1983

Correlation between radiographic and clinical measurement of lumbar spine movement.

Clinical and radiological techniques were used to examine the lumbar movements of 11 male subjects with no history of low back pain. The clinical techniques were shown liable to large errors, particularly where distances between skin marks were measured. The use of an inclinator was the only clinical technique found to be reproducible by different observers. Comparison with the radiological techniques showed that the clinical measures only gave indices of back movement which did not reflect true intervertebral movement.

Adolescent↗
PubMed1982

Movements of the lumbar spine measured by three-dimensional X-ray analysis.

Techniques for the calculation from biplanar radiographs of the three-dimensional coordinates of anatomical landmarks on human lumbar vertebrae, and of the movements in three dimensions of the vertebrae between different positions of the spine are presented. The calculation of three-dimensional coordinates uses a calibration procedure based on direct linear transformation. Coordinate systems are used to define the orientations of each vertebra, and movements are derived from coordinate transformations between neighbouring vertebrae. The root mean square error in determining the absolute locations of anatomical landmarks was found to be less than 1 mm. For the movements of one vertebra relative to its neighbour the root mean square errors for translations were less than 2 mm and for rotations were less than 1.5 degrees. The system has been used to assess patients after spinal fusions and is currently being used in the diagnosis and assessment of patients with specific pathologies.

Humans↗
PubMed1982

Material properties of Velcro fastenings.

An assessment of the material properties of three types of touch and close fasteners (Velcro) in general orthopaedic usage is presented. The materials were tested under various loading regimes using an Instron testing machine. The force-extension curves were analyzed and values determined for both the stiffness and strength of the various attachments. Particular reference was made to the alteration in attachment strength after cyclic loading. The strength of the standard Velcro was found to be least affected after cyclic loading to simulate continuous usage. A recommendation is made on the specific application of each type of Velcro based on their material properties.

Humans↗
PubMed1981

Skin surface PO2 measurement and the effect of externally applied pressure.

The effect of externally applied load on the partial pressure of oxygen in tissue, measured at the skin surface (PSO2) was examined by applying a load to a transcutaneous O2 monitor mounted on the skin of healthy subjects. The load was increased every 4 minutes, and the PSO2 was recorded at the end of the 4-minute period. Three sites were investigated: the sacrum, the greater trochanteric area, and the lateral aspect of the thigh. Mean initial values for the 3 sites were found to be 10.1, 11.1, and 10.1 kPa, respectively. On increasing the applied load, values were found to reduce gradually at first and then at an increasing rate to zero at the "cut-off" load. The mean cut-off pressure for the 3 areas was 15.2, 18.8, and 18.1 kPa.

Humans↗