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Biomedical subjects

L Penning

Publications and source records attributed to L Penning.

At least 19 recordsLinked to original sources
PubMed2004

Measurement of angular and linear segmental lumbar spine flexion-extension motion by means of image registration.

BACKGROUND: The presently available method of measuring segmental lumbar spine mobility by means of superimposition of lumbar spine radiographs in flexion and extension lacks precision due to differences in the cortical outline of the vertebral bodies in flexed and extended position. The introduction of digital image processing has opened the possibility of computerised superimposition ('matching') of digital vertebral body images by means of image registration. Theoretically this technique allows more accurate image matching and, consequently, greater precision of measurement because the whole vertebral body image (not only its cortical outline) can be chosen as region of interest, with registration of all available digital information within this region. METHODS: To check accuracy and convenience of the new method, two computer program experts performed five image registration measurements of the five lumbar motion segments in five consecutive flexion-extension studies of old lumbar fracture, spondylolytic spondylolisthesis and degenerative anterolisthesis. For comparison an experienced radiologist performed the same repeated measurements with the manual superimposition method. RESULTS: Measurement error of the image registration method proved to be significantly smaller than that of the manual superimposition method. There was no overlap between the 95% confidence intervals of the mean standard deviations of experts A and B using the image registration method and the 95% confidence interval of the mean standard deviations of the experienced radiologist using the manual superimposition method. Besides, the image registration method proved to be more convenient because the whole procedure from import of the image data to display of the measurement outcomes lasted 2-3 min compared to 3-6 min for the superimposition method.

Algorithms↗
PubMed2004

CCR5 receptor expression is down-regulated in HIV type 2 infection: implication for viral control and protection.

HIV-2 is known to display an attenuated phenotype in vivo with prolonged time to disease and decreased rate of transmission. Observational studies in Senegal have demonstrated protection from HIV-1 infection, although the putative mechanism for immunoprotection remains undefined. We evaluated HIV-2-seropositive women from a cohort of commercial sex workers in Dakar, Senegal and identified individuals with very low surface CCR5 receptor expression on CD4+ T cells. In vitro up-regulation of the CCR5 receptor was readily achieved. Down-regulation of the CCR5 was not correlated with activation markers (HLA-DR), beta-chemokine levels, or plasma viral loads. A correlation was observed with HIV-2-specific CD8+ T cell activity as measured by intracellular cytokine production. We postulate that down-regulation of the CCR5 receptor in HIV-2 infection contributes to slower disease course and to the protective mechanism against HIV-1 superinfection, mediated in part by HIV-2-specific cellular immune responses.

CD4-Positive T-Lymphocytes↗
PubMed2000

Psoas muscle and lumbar spine stability: a concept uniting existing controversies. Critical review and hypothesis.

Psoas muscle (PM) function with regard to the lumbar spine (LS) is disputed. Electromyographic studies attribute to the PM a possible role as stabilizer. Anatomical textbooks describe the PM as an LS flexor, but not a stabilizer. According to more recent anatomical studies, the PM does not act on the LS, because it tends to pull the LS into more lordosis by simultaneously flexing the lower and extending the upper region, but due to the short moment arms of its fascicles, this would require maximal muscular effort and would expose the LS motion segments to dangerous compression and shear. The findings of the present study indicate that the described opposite action of the PM on upper and lower LS regions, performed passively and requiring minimal muscular effort, may serve to stabilize the LS in an upright stance. It was demonstrated that a vertically placed elastic metal strip, modelled into a lordotic configuration to imitate the LS, will be brought into more lordosis, with maintenance of vertical position, if a string fastened at its upper end is pulled downward in a very specific direction. Conversely, any increase of lordosis of the strip brought about by vertical downward pushing of its top, will be stabilized by tightening the pulling string in the same specific direction. As this direction corresponded with the psoas orientation, the experiments show that the PM probably functions as a stabilizer of the lordotic LS in an upright stance by adapting the state of contraction of each of its fascicles to the momentary degree of lordosis imposed by factors outside the LS, such as general posture, general muscle activity and weight bearing. The presence of multiple PM fascicles, all of about equal length, and attaching to all LS levels, facilitates this function.

Biomechanical Phenomena↗
PubMed1995

Kinematics of cervical spine injury. A functional radiological hypothesis.

This paper, based on functional radiological knowledge of normal cervical spine kinematics, develops the hypothesis that compressive vertebral injury can be produced by abrupt reversal of curve between hyperflexed and hyperextended parts of the cervical spine. Reversal of curve occurs when the main vector of a compressive force passes between two centers of flexion-extension motion. The hypothesis more clearly explains reverse dislocation of fractured vertebrae than the current concept of Whitley and Forsyth of motion of the head through an arc. The mechanism of injuries with characteristics of hyperflexion of one segment and hyperextension of an adjacent segment, e.g., in certain types of hangman's fractures, is better understood. The hypothesis is expected to be helpful in guiding experimental cervical spine injury, as it relates direction of force to level and type of the resulting vertebral injury.

Biomechanical Phenomena↗
PubMed1994

[Backward hypertranslation of the head: participation in the whiplash injury mechanism of the cervical spine?].

Based upon a review of the literature, a theory is developed that in whiplash injury the primary mechanism of the trauma is not hyperantiflexion but hypertranslation of the head backwards. Thus a hyperanteflexion (not hyperretroflexion) of the upper cervical spine, probably especially of the atlanto-axial segment, is induced, causing an overstretching of the ligaments concerned (also the alar ligaments) and the joint capsule. The disorder of the propriosensitive information concerning the position of the head relative to the body with chronic disturbances of posture and equilibrium is explained by the thus generated chronic ligamentous instability of the upper cervical spine. In humans our theory is not yet sufficiently supported by experimental results.

Animals↗
PubMed1988

Dimensions of the spinal canal in individuals symptomatic and non-symptomatic for sciatica: a CT study.

Measurements obtained in 50 spinal CT studies of patients referred for suspected lumbo-sacral nerve root compression, were compared to those of a group of 30 individuals asymptomatic in this respect, who had been referred for abdominal pathology. Transverse ligamentous interfacet and transverse dural dimensions were significantly reduced in the sciatica group, with usually normal interpedicular and sagittal dimensions ruling out idiopathic developmental stenosis. The borderline value for ligamentous interfacet distance (ILD) at L4-5 appeared to be 11 mm.

Humans↗
PubMed1988

Radioanatomy of upper airways in flexion and retroflexion of the neck.

Ten flexion-retroflexion radiographs of the cervical spine (in lateral projection) were utilized to study anatomical configuration and topography of the upper air passages in these two positions. Measurement of AP diameters revealed narrowing in flexion and widening in retroflexion, being maximal at the region of the epiglottis, and minimal at the regions of larynx and trachea. The distance from the pharyngeal attachment of the skull-base, to the upper chest aperture proved to be markedly greater in retroflexion than in flexion. As the pharynx virtually does not change its length during these movements, it is drawn up (with respect to the upper chest aperture) in retroflexion, and pushed down in flexion, over a mean distance of 42 mm. The up and down movement of the upper part of the trachea is slightly less: 38 mm. No correction for radiological magnification of 15-20%.

Adult↗
PubMed1988

Functional diagnostics of the cervical spine using computer tomography.

35 healthy adults and 137 patients after cervical spine injury were examined by functional CT. The range of axial rotation at the level occiput/atlas, atlas/axis and the segment below were measured in all subjects. A rotation occiput/atlas of more than 7 degrees, and C1/C2 more than 54 degrees could indicate segmental hypermobility, a rotation at the segment C1/C2 less than 29 degrees to hypomobility. According to the postulated normal values based upon a 98% confidence level, out of 137 patients examined after cervical spine injury and with therapy-resistant neck pain, 45 showed signs of segmental hypermobility of the upper cervical spine, 17 showed hyper- or hypomobility at different levels, 10 patients presented segmental hypomobility at C1/C2 level alone. In all patients, according to the clinical assessment, functional pathology was suspected in the upper cervical spine. Surgical correction of rotary instability should be considered as a possible therapeutic procedure after successful diagnostic stabilisation of the cervical spine by minerva cast.

Adolescent↗
PubMed1988

Functional radiographic diagnosis of the cervical spine: flexion/extension.

The cervical spines of 59 adults were examined by means of functional roentgenograms. They were divided into two groups consisting of 28 healthy adults and 31 patients who had sustained soft tissue injury to the cervical spine and who were complaining of neck pain. Roentgenographic lateral views were taken in active flexion and extension as well as in passive maximal flexion and extension. Measurements using the techniques of Penning and Buetti-Bauml were made by three observers independently. There was a highly significant difference between the active and passive segmental ranges of motion in healthy adults. Based on the normal values obtained in this study, 19 hypermobile segments could be diagnosed during the active examination, while 31 hypermobile segments were found during the passive examination. In addition, the active examination found 60 hypomobile segments, while the passive examination showed only 43 hypomobile segments. The Penning Method of measurement was found to be more reliable than that of Buetti-Bauml. If possible, the functional roentgenogram examination of the cervical spine in the sagittal plane should be performed by including passive movement and the range of motion should be compared with the normal values obtained by passive examination.

Adult↗
PubMed1987

Posture-dependent bilateral compression of L4 or L5 nerve roots in facet hypertrophy. A dynamic CT-myelographic study.

In 12 patients with myelographic evidence of bilateral root involvement at the L3-L4 or L4-L5 levels postmyelographic computerized tomography (CT) studies were performed in flexion and extension. They showed concentric narrowing of the spinal canal in extension and widening with relief of nerve root involvement in flexion. This could be attributed to the presence of marked degenerative hypertrophy of the facet joints, narrowing the available space for dural sac and emerging root sleeves. In extension of the lumbar spine, bulging of the disc toward the hypertrophic facets causes a pincers mechanism at the anterolateral angles of the spinal canal with the risk of bilateral root compression. This mechanism is enhanced in these cases by marked dorsal indentation of the dural sac because of anterior movement of the dorsal fat pad in extension. The authors believe that the radiologically described mechanism forms the anatomic basis of neurogenic claudication and posture-dependent sciatica.

Humans↗
PubMed1987

Rotation of the cervical spine. A CT study in normal subjects.

A computed tomography (CT) study of rotation of the cervical spine was undertaken in normal subjects aged 20 to 26 years. Section scans through the neck were made with the head in maximal rotation to the right or the left. Occiput, cervical spine, and first thoracic vertebra, thus, were depicted in different degrees of rotation with respect to the sagittal plane. These differences indicated the maximal degree of rotation in each of the eight segments between occiput and thoracic spine. Mean values for these segments were 1.0 degree, 40.5 degrees, 3.0 degrees, 6.5 degrees, 6.8 degrees, 6.9 degrees, 5.4 degrees and 2.1 degrees, respectively. Measurement error proved to be relatively small. By means of CT sections in the plane of the intervertebral joints (in three subjects in midposition, in one subject in maximal rotation of the head to one side) an axis of rotation could be constructed from the anatomic shape of the uncovertebral joints. The theory of Hall that the unciform processes are essential for rotation is confirmed and further elaborated.

Adult↗