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At least 1,063 records · Page 59Linked to original sources
PubMed2006

[The application of laser holograph-speckle interferometry for measuring rotation of abutment teeth].

OBJECTIVE: To explore the rotation of abutment teeth of fixed partial denture in chewing and to analyze the effect of rotation on the stability of abutment teeth. METHODS: Left mandible (without the second premolar and the first molar) was used for specimen. Holograph-speckle interferometry was employed for measuring the rotation angle. RESULTS: The maximal rotation angle was no more than 0.6 degrees and change of the angle was obviously in nonlinearity, when load increased from 9.8 N to 225.4 N. CONCLUSIONS: The laser holograph-speckle interferometry could be used to measure rotation of abutment teeth. The intricate surface contacting was the main reason for rotation and this rotation had no bad effect on abutment teeth of fixed partial denture in daily use.

Adult↗
PubMed1991

The effect of the three columns of the spine on the instantaneous axis of rotation in flexion and extension.

Instrumentation designed for stabilization and correction of spinal deformities must limit the amount of motion in flexion and extension. In flexion or extension, the vertebral bodies move about a specific point called the instantaneous axis of rotation. The ability of the implant to limit this motion is a function of its relation to the axis of rotation of the spine. The goal of this study was threefold: 1) to define the instantaneous axis of rotation of the spine in flexion and extension; 2) to study the effect of the loss of the three columns of the spine on the location of the instantaneous axis of rotation; and 3) to determine how the above parameters relate to the choice of anterior or posterior instrumentation. Ten human cadaver spines were subjected to compressive loads in flexion and extension. The columns of the spine were then destroyed in sequence at L3. The instantaneous axis of rotation for each vertebral body was found by the method of Reuleaux, and the effect of the compromise of the columns on the location of the instantaneous axis of rotation was noted. Understanding the exact location of the instantaneous axis of rotation after a specific injury would allow the clinician to objectively choose the best surgical approach and the appropriate instrumentation.

Humans↗
PubMed1991

Voluntary rotation in the human knee joint.

The structures responsible for the restriction of knee joint rotation were established by means of sequential destruction of the menisci, cruciate ligaments, capsular and collateral ligaments; the capsular and collateral ligaments restrict both medial and lateral rotation. The anterior cruciate ligament was also found to restrict medial rotation, thus acting as a synergist to the capsular and collateral ligaments. The posterior cruciate ligament was found to have no effect on rotation. Under no circumstances do the cruciates as a pair restrict medial rotation as this is drastically increased as a consequence of the removal of the capsular and collateral ligaments, and the lateral meniscus. The axis of medial rotation ran through the medial tubercle of the intercondylar eminence while that of lateral rotation was located slightly lateral to it.

Biophysical Phenomena↗
PubMed1991

Facial growth rotation--reflections on definition and cause.

The phenomenon of growth rotation of the jaws during facial development is examined by means of profile roentgencephalometric analysis of a male subject followed from age 4 years to adulthood, with reference to metallic implants and stable natural bony structures. The rotation of the corpora of the jaws, termed total rotation, and its components, matrix and intramatrix rotation, are defined. A description is given of the compensatory remodelling process. The concept of facial growth rotation as essentially a primary phenomenon is supported by a report of an identical facial rotation pattern in growing Macaca mulatta, suggesting that facial growth rotation is common in primates.

Adolescent↗
PubMed1990

[An analysis of the rotational motion in three dimensional motion of the shoulder complex].

An apparatus was developed using a personal computer to measure three dimensional motion including rotation of the shoulder complex quantitatively. Euler angles were introduced to describe three dimensional motions. The rotation angle was calculated by integrating the components of angular velocity vectors of the Euler angles around the long axis of the humerus. Two kinds of measurements were performed on both the normal and contracted shoulders; One is measurement of the rotational motion accompanying abduction, flexion, extension, horizontal flexion and horizontal extension. The other is measurement of three dimensional range of motion and the rotational motion when the shoulder moves as far as possible in three dimensional space (maximum circumduction). External rotation occurred during abduction, and internal rotation occurred during flexion. In maximum circumduction, a linear relationship was found between three dimensional range of motion and the amount of rotational motion.

Humans↗
PubMed1990

[Rotational instability of the lumbar spine--a three-dimensional motion study using bi-plane X-ray analysis system].

The purpose of this study is to investigate the rotational instability of the lumbar spine using bi-plane X-ray analysis system and to clarify mechanical etiology of the lumbar instability. The following results were obtained. (1) The range of rotational motion was about 2 to 3 degrees at each motion segment in the normal lumbar spine. The rotational motion was significantly large in spondylolysis, spondylolisthesis, and degenerative spondylolisthesis. (2) The rotational instability and the flexion-extension instability correlated to each other in spondylolysis and spondylolisthesis. However, in degenerative spondylolisthesis, the rotational instability and the antero-posterior instability were correlated to each other. (3) Instantaneous axis of rotation (IAR) was located at the posterior part of the intervertebral disc in the normal L4 vertebra, and more posteriorly in the L5 vertebra, while the IAR was located anteriorly in spondylolysis, and posteriorly in degenerative spondylolisthesis. (4) When the trunk was twisted, the lumbar lordotic angle was generally decreased, and the lumbar spine showed scoliotic curvature convex to the twisted direction. The apex was located at the L4/5 intervertebral level. Highly significant increases in flexion motion associated with rotation were observed at the pathological levels of spondylolysis and degenerative spondylolisthesis.

Adult↗
PubMed1990

Hip rotation and in-toeing gait. A study of normal subjects from four years until adult age.

In a selected population, from four years old up to adult age, the function of 1522 hips of 761 apparently normal subjects of both genders were studied to define: (1) the lower and upper limits of normal hip rotation; and (2) the frequency of in-toeing gait related to age and gender. Internal and external rotation were measured with the subject lying prone with flexed knees. Presence of in-toeing gait was noted. A significant reduction of internal rotation with age was found in both females and males. In all age groups, females had significantly higher range of internal rotation than males. External rotation did not show the same age and gender dependency. Sixteen percent of all subjects had an in-toeing gait. The frequency decreased from 30% in the four-year-old group to 4% in adults. The subjects with in-toeing had a significantly increased internal rotation and decreased external rotation.

Adolescent↗
PubMed1989

Torsional strength of the ankle in vitro. The supination-external-rotation injury.

Nineteen fresh-frozen anatomic specimens of the ankle were mounted in an experimental test device with the foot in supination. Torque versus rotation curves were recorded as each foot was rotated externally to failure. The mean failure torque was 45.3 Nm, the mean rotation to failure was 41.4 degrees, and the mean energy absorbed to failure was 10.6 Nm. Twelve specimens failed by fracture of the fibula, five by failure of lateral ligaments with no fibular fracture, one by a subtalar dislocation, and one by fracture of the calcaneous through a fixation screw hole. There were no statistically significant differences in torque or energy to failure between those specimens that failed by fibular fracture and those with ligamentous failure alone. Rotation to failure was 6 degrees greater in the ligamentous failure group. Ankles with less initial rotatory laxity tended to fail at higher torque levels. The mean ankle fracture torque measured in this study is similar to previously reported mean ligamentous failure torque for the knee flexed to 20 degrees and rotated externally to failure. In a prior in vivo study, approximately 10 Nm of external foot torque and 20 degrees of foot rotation could be tolerated prior to the initiation of pain. The present study indicates that these in vivo pain threshold levels represent approximately 50% of the rotation to failure and 25% of the torque to failure.

Ankle Injuries↗
PubMed1989

Rotational stability of a posterior stabilized total knee arthroplasty.

The effect of the posterior stabilizing mechanism on rotational stability in total knee arthroplasty (TKA) was investigated in six cadaver knees using a special knee-testing device. The device evaluated varus-valgus, rotational, and anteroposterior (AP) stability in the normal knee compared to a posterior stabilized TKA with either a rotationally constrained or an unconstrained articular surface. None of the stability parameters was significantly different from normal in either configuration of the tibial surface, but the constrained surface did decrease rotational deflection compared to the rotationally unconstrained surfaces. These findings show that rotational constraint in a posterior stabilized TKA is not necessary to achieve rotational stability as long as varus-valgus stability is achieved by appropriately tensioning the collateral ligaments.

Humans↗
PubMed1988

Rotational dynamics and protein-protein interactions in the Ca-ATPase mechanism.

We have varied the degree of protein-protein interactions among Ca-ATPase polypeptide chains in sarcoplasmic reticulum using the cleavable homobifunctional cross-linker dithiobissuccinimidyl propionate and have measured both the rotational mobility and calcium-dependent ATPase activity of the Ca-ATPase in order to assess 1) the nature of the microsecond rotational motion measured by saturation transfer EPR (ST-EPR) of the spin-labeled Ca-ATPase and 2) the functional significance of this rotational motion. The Ca-ATPase was labeled specifically and covalently with a maleimide spin label, with full preservation of enzymatic activity. ST-EPR experiments show that cross-linking increases the enzyme's effective rotational correlation time (tau r), thus decreasing its rotational mobility (tau r-1). As the degree of cross-linking is varied, tau r is proportional to the mean molecular weight of the cross-linked aggregate, as predicted by theory, adding to the evidence that ST-EPR measures the overall rotational mobility of the Ca-ATPase with respect to the membrane normal. Furthermore, enzymatic activity correlates with overall protein rotational mobility, suggesting that this motion is functionally important. The second-order inactivation profile resulting from the use of either cross-linking or chemical modification with fluorescein isothiocyanate as modes of inactivation indicates that protein-protein interactions are critical to the reaction mechanism. However, the pattern of cross-linking observed on polyacrylamide gels demonstrates that cross-linking occurs in a random manner, indicating that no specific and stable oligomeric complexes exist. In order to rationalize both the functional need for protein mobility and the evidence that protein-protein interactions are critical and random, we propose that the enzymatic cycle of the Ca-ATPase involves the making and breaking of functionally important protein-protein interactions.

Animals↗
PubMed1988

Lipid fluidity directly modulates the overall protein rotational mobility of the Ca-ATPase in sarcoplasmic reticulum.

We have developed a quantitative and relatively model-independent measure of lipid fluidity using EPR and have applied this method to compare the temperature dependence of lipid hydrocarbon chain fluidity, overall protein rotational mobility, and the calcium-dependent enzymatic activity of the Ca-ATPase in sarcoplasmic reticulum. We define membrane lipid fluidity to be T/eta, where eta is the viscosity of a long chain hydrocarbon reference solvent in which a fatty acid spin label gives the same EPR spectrum (quantitated by the order parameter S) as observed for the same probe in the membrane. This measure is independent of the reference solvent used as long as the spectral line shapes in the membrane and the solvent match precisely, indicating that the same type of anisotropic probe motion occurs in the two systems. We argue that this empirical measurement of fluidity, defined in analogy to the macroscopic fluidity (T/eta) of a bulk solvent, should be more directly related to protein rotational mobility (and thus to protein function) than are more conventional measures of fluidity, such as the rate or amplitude of rotational motion of the lipid hydrocarbon chains themselves. This new definition thus offers a fluidity measure that is more directly relevant to the protein's behavior. The direct relationship between this measure of membrane fluidity and protein rotational mobility is supported by measurements in sarcoplasmic reticulum. The overall rotational motion of the spin-labeled Ca-ATPase protein was measured by saturation-transfer EPR. The Arrhenius activation energy for protein rotational mobility (11-12 kcal/mol/degree) agrees well with the activation energy for lipid fluidity, if defined as in this study, but not if more conventional definitions of lipid fluidity are used. This agreement, which extends over the entire temperature range from 0 to 40 degrees C, suggests that protein mobility depends directly on lipid fluidity in this system, as predicted from hydrodynamic theory. The same activation energy is observed for the calcium-dependent ATPase activity under physiological conditions, suggesting that protein rotational mobility (dependent on lipid fluidity) is involved in the rate-limiting step of active calcium transport.

Animals↗
PubMed1981

Rotational diffusion of erythrocyte membrane proteins.

Rotational diffusion of band 3 proteins in human erythrocyte membranes is measured by observing flash-induced transient dichroism of the triplet probe, eosin-maleimide. At physiological temperature, both fast and slowly rotating populations of band 3 are present in the membrane. Rotational motion of band 3 is the same in membranes from young and old erythrocytes and is unchanged when the cholesterol:phospholipid mole ratio is varied from 1.34 to 1.66. Antibodies against glycophorin A immobilize band 3, indicating an association between these two integral membrane proteins. However, glycophorin A has little effect on the rotational motion of the complex, since band 3 rotation in En(a-) membranes (which lack glycophorin A) is similar to that observed in normal membranes. Cleavage of the cytoplasmic segment of band 3 by trypsin produces a considerable enhancement of band 3 rotational mobility. A similar effect is seen following extraction of bands 2.1 and 4.1 by sequential low salt-high salt treatment. It is concluded that up to 40% of band 3 has restricted rotational mobility due to interaction with the erythrocyte cytoskeleton.

Blood Proteins↗
PubMed1981

Somitogenesis in the amphibian Xenopus laevis: scanning electron microscopic analysis of intrasomitic cellular arrangements during somite rotation.

The intrasomitic changes in cell arrangement which accompany somite rotation during somitogenesis in Xenopus laevis were analysed with the scanning electron microscope (SEM). Longitudinal, horizontal fractures of whole embryos were examined at various dorsoventral levels of stage-22 to -24 embryos. Observations of the gross morphological features of somitogenesis, and the cellular changes which accompany somite segmentation and somite rotation were made. Several of these observations lead to modifications of previous models for the cellular basis of somitogenesis in Xenopus. Individual cellular rearrangements, rather than simultaneous block rotation of a whole somite, appear to be responsible for the 90 degrees rotation of myotomal cells within a single somite. Cellular arrangements in fused somites were also examined. Some ultraviolet-irradiated embryos displayed a complete lack of a notochord. The somites in those embryos were fused across the midline beneath the neural tube. The dorsal and ventral arms of the somites are not fused. Normal rotation occurs only in the dorsal and ventral arms while, in the majority of cases, cells in the fused region fail to rotate normally. In some cases, individual cells in the fused region undergo partial rearrangement. Those observations support the notion that individual cellular rearrangements account for the rotation of the whole somite.

Animals↗
PubMed1995

Postoperative shoulder rotators strength in stages II and III impingement syndrome.

In healthy subjects, the shoulder internal rotator muscle strength overrides the external rotators. This has been confirmed in different isokinetic studies showing the ratio of the relative strengths of the internal to external rotators to range from 1.3 to 1.5 points, depending on the study. The authors previously reported a decrease in the relative strength ratio of the internal to external rotators to close to 1 in patients suffering from Neer's impingement syndrome. The aim of the present study was to assess, long after surgery (mean, 44.5 months), the isokinetic strength performance of shoulder rotator muscles in 72 patients who had had operative treatment for chronic subacromial impingement using anterior acromioplasty, sometimes combined with cuff repair surgery. Tests were conducted with a Biodex Multi-Joint System in the plane of the scapula and in 45 degrees abduction at 60 degrees and 180 degrees per second. Peak torque and average power were calculated. The mean ratios of relative strengths of the internal to external rotators ranged from 1.3 to 1.6 points depending on the parameter studied and the test speed. These results indicate that surgery restores normal muscular balance between shoulder rotator muscles affected by the impingement syndrome.

Acromion↗
PubMed1994

Rotational deformity of the distal humerus in cubitus varus.

The medial rotation deformity of the distal humerus usually exists in the cubitus varus deformity but has received little attention. Study of this deformity in 29 cases of cubitus varus was carried out using the osteotomized bony specimens that were removed during closed wedge osteotomy in order to determine the actual bone deformity. The average duration of the varus deformity was 5.6 yrs (range 1 to 11). The medial rotation deformity of the distal humerus averaged 27 degrees (range 15 to 45). There was no correlation between the degree of rotation and that of the varus deformity (correlation coefficient r = 0.15). The affected-side shoulder compensated well in both internal and external rotation, and had a greater arc of rotation than that of the normal side. The affected-side shoulder exhibited an internal rotation deformity with an average of 16 degrees (range 5 to 25), with restriction of external rotation of only 13 degrees (range 0 to 20) in comparison to normal side shoulder.

Adolescent↗
PubMedDate not supplied

Sagittal plane rotation of the pelvis during lumbar posteroanterior loading.

OBJECTIVE: To determine the extent of sagittal plane rotation of the pelvis during lumbar spine posteroanterior loading. DESIGN: Quantitative study. SETTING: Biomechanics Laboratory, Faculty of Health Sciences, University of Sydney. PARTICIPANTS: Ten male and female subjects with no recent history of significant low back pain. INTERVENTION: A mechanical device was used to apply forces to the L3 spinous process. Data were collected during slow cyclical loading. MAIN OUTCOME MEASURE: The stiffness of the posteroanterior movement at the point of loading was measured, together with the sagittal plane rotation of the pelvis and the resistance to rotation provided by the bed on which the subject lay. RESULTS: Mean pelvic rotation was 2.1 degrees per 100 N applied force (SD 1.01 degrees/100 N). Mean posteroanterior stiffness was 13.4 N/mm (SD 3.13 N/mm) and resistance to pelvic rotation was 2.71 Nm/degree of pelvic rotation (SD 0.84 Nm/degree). CONCLUSION: During posteroanterior force application there is pelvic rotation of a magnitude that may be sufficient to have clinical significance. Abnormalities found during lumbar posteroanterior force application may originate in tissues caudad to the lumbar spine itself.

Adult↗
PubMed1994

Geometric and mechanical properties of the coracoacromial ligament and their relationship to rotator cuff disease.

One of the most common causes of pain and disability in the upper limb is inflammation of the rotator cuff tendons. When no significant bony abnormality exists in the surrounding structures, the coracoacromial ligament has been implicated as a possible cause of impingement on the cuff tendons. Geometric and mechanical properties of 20 coracoacromial ligaments, 10 from shoulders with rotator cuff tears and 10 from normal shoulders, were accurately determined. In comparing rotator cuff tear and normal specimens, statistically significant changes in geometric properties were measured in the lateral band, but not in the medial band, of the ligament. The lateral band, which is the region most likely to impinge on the rotator cuff, was shorter and had a larger cross-sectional area in specimens with rotator cuff tears. Although there were no statistical differences in structural properties of the ligament between normal and rotator cuff tear groups, significant changes were evident in material properties. Previously reported histologic differences in the ligament in shoulders with rotator cuff tears are supported by the decreased material properties measured in the current study. Whether the differences in the coracoacromial ligament cause impingement or are due to impingement is still unknown at this time.

Acromioclavicular Joint↗
PubMed1994

[Criteria for legal assessment of rotator cuff rupture].

The judgement of the correlation between an accident and a rotator cuff tear has an important role in legal and private accident insurance. Owing to the high morbidity of degenerative alterations and ruptures of the rotator cuff tendons, the causality of an acute traumatic rupture can be difficult to demonstrate, which means assessments are often controversial. In a retrospective study we evaluated 25 orthopaedic assessments and tried to find rules for an objective estimation. The judgement of correlation between trauma and rotator cuff tear should be based on four pillars: history, trauma mechanism, initial findings and course of the functional deficit. Possible mechanisms of traumatic rupture are discussed from various angles. Important clinical findings, e.g. a functional supraspinatus deficit, should be fully documented. X-Rays of both shoulders can lead to indirect demonstration of preexistent changes in the rotator cuff. Sonographic evaluation can show up the rotator cuff tear and demonstrate signs of acute injury. After persistent pain and functional deficit, in a few cases operative and microscopic findings will lead to a correct estimate of causality. Because of the diagnostic uncertainty a 20-point score is introduced for retrospective assessment of the history (2 points), trauma mechanism (3 points), initial clinical, radiological and sonographic findings (10 points) and course of functional deficit (5 points) to evaluate the role of trauma in rotator cuff tears. Using this score trauma can be classified as the main or partial cause or as irrelevant to the pathogenesis of rotator cuff tears.

Adult↗