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PubMed2004

Axial and rotational alignment of the leg.

The axial and rotational alignments of the lower extremity are commonly referenced independently, with minimal research on whether coexistent axial and rotational malalignment cause pathologies. The present study analyzed whether a correlation exists between the axial and rotational alignments of the leg. The methodology to measure both alignments was adapted for computer tomography. Fifty patients were analyzed at five reference images to determine axial and rotational alignment. The reference images included the femoral head, the femoral shaft (at the level of the lesser trochanter), the distal femur, the proximal tibia, and the ankle joint. Axial alignment was calculated by using horizontal and vertical measurements of the location of the femoral head, the distal femur, and the ankle joint. Rotational alignments of femur, knee, and tibia were calculated using four angles: proximal femoral, distal femoral, proximal tibial, and ankle joint angles defined relative to a fixed reference. Pearson correlation analysis between axial alignment and the three mentioned rotational alignments were calculated. The correlation coefficient values ranged between -0.15-0.07 when comparing axial to rotational alignment, indicating that a week correlation exists between the two alignments. Though these results were derived using highly reproducible methods, the hypothesis of an existing correlation between the axial and rotational alignments of the leg was rejected. These findings allow for an improved understanding of lower extremity mechanics, which merit importance when considering pathologies of the leg and the surgical techniques that could ultimately benefit patients suffering from these pathologies.

Adult↗
PubMed2005

Instantaneous rotation axes during active head movements.

Rotation axes were calculated during active head movements using a motion analysis system. The mean rotation axis for 1 Hz head pitch when seated was posterior (6 mm) and inferior (21 mm) to the interaural axis, shifting 16 mm downwards when standing. During seated 2 Hz head pitch the rotation axis was close to the interaural axis, shifting downwards 15 mm when standing. This downward shift suggests that cervical vertebrae were recruited during head pitch with the trunk unsupported. The proximity of the pitch axis to the otoliths implies minimal otolith activation during small-amplitude, high-frequency pitch rotations, such as those encountered during locomotion. The mean rotation axis for 1 Hz yaw rotation was located slightly posterior (10 mm) to the interaural axis at the midpoint between the vestibular labyrinths when both seated and standing. In addition, the orientation of the plane of yaw rotation relative to the stereotaxic horizontal plane (pitched 5 degrees nose-down) was essentially fixed in head coordinates, regardless of the pitch orientation of the head, suggesting that yaw movements occur about an axis restricted by the mechanical structure of the atlanto-axial joint. The results demonstrate that the instantaneous rotation axes technique overcomes the inherent instability of the helical-axis representation for small head movements.

Adult↗
PubMed2006

Rotation rate and duration effects on the somatogyral illusion.

INTRODUCTION: Aviation spatial disorientation mishaps remain a concern, especially due to their fatality rate. Some of the most insidious disorientations are due to vestibular stimuli in the absence of visual cues. A category of such disorientations are known as somatogyral illusions. METHODS: To determine the effects of spin rate and duration on the perception of the somatogyral illusion, we examined the subjective response of pilots and non-pilots to rotation around the yaw axis in a flight simulator in a manner that would mimic two vestibular illusions found in flight: the washout of the semi-circular canals following sustained turns, and the illusory counter-rotation following return to straight and level flight. There were 29 subjects (14 pilots) who were seated blindfolded in a flight simulator which accelerated to constant plateau rotation rates of 20, 70, and 120 degrees x s(-1) and then decelerated to stationary; plateaus were 10, 20, or 40 s. Subjects reported 1) the time when the perception of rotation ceased (i.e., the subjective time until washout was reached); 2) the relative magnitude of the counter-rotation experienced; and 3) the time until the perception of counter-rotation ceased. Subjects also manipulated a slider to provide a continuous subjective measure of their experience of rotation. RESULTS: The two time measures increased with increases in both the duration and magnitude of the spin. The increase in perceived washout time with spin rate was non-linear (geometric). There was an interaction between spin duration and spin rate on the experience of illusory counter-rotation magnitude such that at low rates, spin duration had no effect, but its effect increased at faster rates. The time constant of adaptation of the semicircular canals was estimated to be 8.3 s. DISCUSSION: The effects were validated against a model of semicircular canal and cupola adaptation, which predicted the data with high accuracy. Pilots and non-pilots did not differ in their illusory experience.

Adaptation, Physiological↗
PubMed2007

Rotational bed therapy to prevent and treat respiratory complications: a review and meta-analysis.

BACKGROUND: Immobility is associated with complications involving many body systems. OBJECTIVE: To review the effect of rotational therapy (use of therapeutic surfaces that turn on their longitudinal axes) on prevention and/or treatment of respiratory complications in critically ill patients. METHODS: Published articles evaluating prophylaxis and/or treatment were reviewed. Prospective randomized controlled trials were assessed for quality and included in meta-analyses. RESULTS: A literature search yielded 15 nonrandomized, uncontrolled, or retrospective studies. Twenty prospective randomized controlled trials on rotational therapy were published between 1987 and 2004. Various types of beds were studied, but few details on the rotational parameters were reported. The usual control was manual turning of patients by nurses every 2 hours. One animal investigation and 12 clinical trials addressed the effectiveness of rotational therapy in preventing respiratory complications. Significant benefits were reported in the animal study and 4 of the trials. Significant benefits to patients were reported in 2 of another 4 studies focused on treatment of established complications. Researchers have examined the effects of rotational therapy on mucus transport, intrapulmonary shunt, hemodynamic effects, urine output, and intracranial pressure. Little convincing evidence is available, however, on the most effective rotation parameters (eg, degree, pause time, and amount of time per day). Meta-analysis suggests that rotational therapy decreases the incidence of pneumonia but has no effect on duration of mechanical ventilation, number of days in intensive care, or hospital mortality. CONCLUSIONS: Rotational therapy may be useful for preventing and treating respiratory complications in selected critically ill patients receiving mechanical ventilation.

Beds↗
PubMed1991

Effects of pre-exposures to a rotating optokinetic drum on adaptation to motion sickness.

The purpose of this study was to investigate the effects of two different pre-exposure procedures on adaptation to motion sickness in a rotating circular vection drum. The 45 subjects were randomly divided into three groups. The control group only had a standard 16-min exposure to the drum rotating at 60 degrees/s with no pre-exposure. The incremental exposure group had two separated 4-min pre-exposure periods at 15 degrees/s and 30 degrees/s in the rotating drum immediately prior to the standard 16-min exposure period in the drum rotating at 60 degrees/s. The abrupt-exposure group had the same pre-exposure procedure except the pre-exposure drum rotation speed was 60 degrees/s and was followed by the same standard exposure periods. Subjective motion sickness reports and a measure of gastric myoelectric activity (electrogastrogram, EGG) were obtained during the standard 16-min drum rotation period in all three groups. The results showed that subjects in the incremental exposure group reported significantly fewer motion sickness symptoms during the standard 16-min rotation period than did the subjects in the abrupt exposure group and the control group. Subjects in the incremental exposure group also had less tachyarrhythmia, abnormal gastric myoelectric activity associated with nausea, during the 16-min rotation period than did the subjects in the control and abrupt exposure group. Incremental exposure to motion stimuli may be a useful method for training resistance to visually-induced motion sickness.

Adaptation, Physiological↗
PubMed1985

The effect of egg rotation on the differentiation of primordial germ cells in Xenopus laevis.

Eggs of X. laevis were rotated (sperm entrance point downwards) either through 90 degrees (1 X 90 embryos) or 180 degrees in two 90 degrees steps (2 X 90 embryos) at approximately 25-30 min postfertilization after cooling to 13 degrees C. The embryos were kept in their off-axis orientation and cooled until the early gastrula stage. Rotation resulted in relocation of egg constituents with slight changes in the distribution of outer cortical and subcortical components and major changes in inner constituents where the heavy yolk and cytoplasm appeared to reorient as a single coherent unit to maintain their relative positions with respect to gravity. Development of rotated embryos was such that regions of the egg which normally give rise to posterior structures instead developed into anterior structures and vice versa. Germ plasm was displaced in the vegetal-dorsal-animal direction (the direction of rotation) and was segregated into dorsal micromeres and intermediate zone cells in 2 X 90 embryos and dorsal macromeres and intermediate zone cells in 1 X 90 embryos. In consequence, at the gastrula stage, cells containing germ plasm were situated closer to the dorsal lip of the blastopore after rotation--in 2 X 90 gastrulas around and generally above the dorsal lip. Hence, in rotated embryos, the cells containing germ plasm were invaginated earlier during gastrulation and therefore were carried further anteriorly in the endoderm to a mean position anterior to the midpoint of the endoderm. The number of cells containing germ plasm in rotated embryos was not significantly different from that in controls at all stages up to and including tail bud (stage 25). However at stages 46, 48 and 49 the number of primordial germ cells was reduced in 1 X 90 embryos in one experiment of three and in 2 X 90 embryos in all experiments. We tested the hypothesis that the decreased number of primordial germ cells in the genital ridges was due to the inability of cells to migrate to the genital ridges from their ectopic location in the endoderm. When anterior endoderm was grafted into posterior endodermal regions the number of primordial germ cells increased slightly or not at all suggesting that the anterior displacement of the cells containing germ plasm was not the only factor responsible for the decreased number of primordial germ cells in rotated embryos. Other possible explanations are discussed.

Animals↗
PubMed1983

[An experimental study on the parallel operation of image: a case of mental rotation].

The parallel operation of images using mental rotation task was examined from the following two points of view: (1) Whether or not a pair of letter images could be mentally rotated in parallel (Exp. 1), and (2) Whether or not an image pattern composed of two letters could become an object of a single mental rotation (Exp.2). Exp. 1 showed that two images were serially rotated in group S which was slower in rotation of two letter images, while they were rotated in parallel in group F which was faster (Fig. 4). This result was interpreted as a trade-off between the correctness and the speed of response. Exp. 2 showed that the velocity of mental rotation was the same for two-letters image as for one-letter image in both groups, S and F (Fig. 5). This result indicated that the image pattern of two-letters could be an object of a single rotation, and suggested that image processing would include an image register in which multiple images are stored in parallel.

Adult↗
PubMed1995

Effects of posterior instrumentation on axial rotation of the lumbar spine: an in vitro biomechanical study.

We tested the hypothesis that instrumentation applied across two levels of the lumbar spine inhibits rotation at these levels and that this inhibition is accompanied by more rotation at the levels above and below. The rotation in the transverse plane of each of the five lumbar vertebrae of 10 cadaveric lumbar spines was produced by dead weights applied to a torsion bar attached at T12. The lumbar spines were first measured without instrumentation being applied. Three different types of instrumentation were then applied in turn across two levels of each lumbar spine: AO internal fixation from L2 to L4, lumbosacral Louis plates from L4 to S1, and Cotrel-Dubousset (CD) pedicular screws and rods from L2 to L4 and then from L4 to S1. For each of these four, a set of measurements of rotation in the transverse plane was taken. The Louis plates allowed less rotation across L4-S1 than CD, although the result was not significant. The AO fixator applied across L2-L4 allowed significantly less rotation across L2-L4 than CD. The AO fixator was compared with the spine with no instrumentation to determine if less rotation across L2-L4 was associated with more rotation across L1-L2 and L4-L5; the differences were significant (p < 0.05).

Biomechanical Phenomena↗
PubMed1994

Rotation: a valid premanipulative dizziness test? Does it predict safe manipulation?

OBJECTIVE: The purpose of this study was to investigate the validity of cervical spine rotation as a test of patency of the vertebral arteries (VAs) and the internal carotid arteries (ICAs). DESIGN: A descriptive study was undertaken. SETTING: Testing was carried out in a private clinical vascular unit attached to a large Sydney public hospital. PARTICIPANTS: Twenty healthy volunteers, both male and female, who were free of risk factors commonly associated with vascular disease, participated in the study. INTERVENTIONS AND MAIN OUTCOME MEASURES: An AutoSector 5 Duplex Doppler ultrasound instrument was used to record mean and peak frequency of blood flow (a measure of blood velocity) in the right and left VAs and ICAs in the cervical spine positions of neutral, 45 degrees contralateral rotation and full range contralateral rotation. To determine general hemodynamic stability, blood pressure and heart rate were recorded pre- and posttest, as well as in all tested positions. RESULTS: There was a significant trend for blood velocity to increase in 45 degrees contralateral rotation and to decrease in full rotation (p < .01). This trend was not consistent across vessels. Blood velocity decreased with rotation from neutral head position in the right VA, and continued to increase throughout rotation in the right ICA. CONCLUSION: It appears that sustained rotation influences blood velocity in the extracranial vessels. This may have relevance in patients with abnormal blood flow who are candidates for cervical manipulation.

Adult↗
PubMed1994

[Angiographic examination of the vertebral artery at the atlantoxial joint during head rotation].

Stenosis or occlusion of the vertebral artery at the atlantoaxial joint associated with head rotation is generally considered an uncommon cause of vertebrobasilar insufficiency. This rotational contralateral (to the face) vertebral artery occlusion is considered to be a "physiological phenomenon". The purpose of the present article is to investigate whether stenosis or occlusion of the vertebral artery at the atlantoaxial joint really occurs with head rotation. The authors performed vertebral angiography both in the neutral position and with contralateral rotation of the head (about 80 - 90 degrees) on 39 patients (44 vertebral arteries), who didn't have any disease of the cervical region or of the posterior cranial fossa. The authors discussed the angiographic findings concerning the vertebral artery at the atlantoxial joint during contralateral rotation of the head. In some cases a vertebral artery was stretched with head rotation. However occlusion or stenosis of the vertebral artery was never found to occur at the atlantoaxial joint level in any of the cases. This result indicates that rotational vertebral artery occlusion is not a "physiological phenomenon". There may be many other developmental and degenerative factors contributing to this rotational occlusion, such as atherosclerosis, kinking, and tortuosity of the vertebral artery, hyperosteosis, tightness of the paravertebral muscle, stenosis of transverse foramen and the depth of the vascular groove of the atlas.

Adult↗
PubMed1993

Relationships between trunk rotation and arm swing in human walking.

In order to correlate the trunk rotation and arm swing with walking, the angular change of the horizontal rotation of the shoulder and pelvic girdle, and of the arm swing during one stride were recorded simultaneously in connection with the ground reaction force (GRF). The pelvic girdle rotated clockwise early in the left stance phase and then described a counter-clockwise rotation, while the shoulder girdle rotated in an opposite direction to the pelvic girdle. The shoulder girdle rotation, however, stopped transiently in accordance with the acceleration phase in the GRF. The maximum extension of the arm swing was coincident with the immobility period of the shoulder girdle. From above findings, it may be concluded that the arm swing is affected by the acceleration force of the contralateral through counter-rotation of the trunk, and that the stability of the upper body is maintained by stopping of the shoulder girdle rotation.

Adult↗
PubMed1993

The effects of axial rotational alignment of the femoral component on knee stability and patellar tracking in total knee arthroplasty demonstrated on autopsy specimens.

Four fresh-frozen anatomic knee specimens were tested for knee stability, patellar tracking, and patellofemoral contact points with the femoral component positioned in 5 degrees internal, 5 degrees external, or neutral axial rotational alignment of the femoral component referenced on the posterior femoral condyles. The externally rotated specimens had varus-valgus stability of the knee that was closest to the normal control. The internally rotated specimens shifted into valgus alignment with flexion. Patellar tracking also was closest to normal in the externally rotated specimens. Patellofemoral contact was more evenly distributed between the medial and lateral contact areas in the externally rotated specimens than in the internally rotated or in the neutral specimens. Internal rotation of the femoral component in the knee with perpendicular resection of the tibia causes undesirable changes in knee stability, patellar tracking, and patellofemoral contact points. Neutral positioning produces similar but less negative effects on knee stability and patellar kinematics. External rotation improves both patellar tracking and knee stability characteristics.

Biomechanical Phenomena↗
PubMed1996

Ossification of the coracoacromial ligament: association with rotator cuff pathology of the shoulder.

The objective of this study was to assess the association of ossification of the coracoacromial ligament (CAL) observed on conventional radiographs with the presence of rotator cuff pathology as demonstrated by magnetic resonance imaging (MRI), arthrography, and/or surgery. Conventional radiographs (internal and external rotation and outlet and axillary views) on eight patients showed ossification of the coracoacromial ligament. Rotator cuff integrity was assessed by physical examination in all 8 patients, by arthrography in 3 patients, and by MRI in 2 patients. Surgery was performed on four of the patients. Physical examination showed impingement findings and decreased rotator cuff strength suggestive of rotator cuff disease in all eight patients. The arthrograms and MRI examinations showed the presence of full-thickness rotator cuff tears. Four of these patients underwent surgery and the rotator cuff defects were confirmed and repaired. Identification of ossification of the CAL on conventional radiographs should be recognized as strongly suggestive of associated significant rotator cuff pathology.

Aged↗
PubMedDate not supplied

[Subacromial impingement syndrome and rotator cuff tear. Ultrasonography of 140 cases].

We investigated the role of rotator cuff impingement in causing tears of supraspinatus and biceps tendons and the comparative reliability of plain radiography and sonography (US). One hundred forty patients with symptoms referrable to the rotator cuff were examined with plain radiography and US of the shoulder. US findings were correlated with MR or double contrast arthrography results in 10 patients and 39 patients were submitted to surgery (acromionplasty). Radiographic studies were performed first and diagnosed rotator cuff impingement (63 patients) caused by abnormal acromial margins or size (23 patients), by acromioclavicular joint protrusion (17 patients), by anterior acromial osteophytosis (10 patients), or by massive periarthritic calcifications (13 patients). In the same 140 patients. US showed normal cuffs in 46 cases, tendonitis in 34, calcific tendonitis in 13, partial-thickness cuff tears in 13, full-thickness cuff tears in 20 and biceps tendon tears in 14 cases. Six of 13 partial tears were studied with MRI, with 4 true positives and 2 false positives. US diagnosis was confirmed by arthrography in 4 complete tears. Twenty-nine of 39 patients undergoing acromionplasty were examined only with plain radiography and US. US accurately diagnosed all 20 massive full-thickness tears, with no false positives nor false negatives (US versus surgery and arthrography). Eleven true positives, 2 false positives and no false negative were observed in 13 partial-thickness cuff tears (US versus surgery and MRI). These findings suggest that rotator cuff US and plain radiography are easily performed, reproducible routine examinations to study the whole rotator cuff and the acromioclavicular joint in the many patients who need an accurate, safe, painless, rapid and cost-effective differential diagnosis, leaving it up to the surgeon to consider MRI or arthrography. Rotator cuff impingement tendonitis, overuse or calcific tendonitis, partial-thickness cuff tears and full-thickness tears ranging from light to severe cause similar shoulder pain and weakness on arm raising. The differential diagnosis must distinguish all these common causes of shoulder dysfunction and cuff problems from other conditions. We conclude that US and plain radiography are accurate routine tests of rotator cuff integrity and rotator cuff impingement.

Adult↗
PubMed1997

The rotation of maxillary first molars, mandibular first molars, and maxillary first premolars in acceptable occlusions.

The rotation of the maxillary molars is considered important in the orthodontic treatment of malocclusions. In this study, a computer analysis program was developed to examine the rotations of maxillary molars, mandibular molars, and maxillary first premolars in casts of permanent dentitions with acceptable occlusions. Ninety-three sets of untreated 'acceptable occlusion' models from the collection of the Foundation for Orthodontic Research (FOR) were scanned on a flat bed scanner. The images were analysed using custom software. Measurements were made by relating maxillary first permanent molars to the midline, archform, opposite canine, and mandibular first permanent molars. The mandibular first molars and maxillary first premolars were also analysed and their rotations measured. The mean rotations of the maxillary first molars, measured as the angle between a line joining the tips of the buccal cusps and a line tangent to the appropriate archwire form (from Ricketts' Pentamorphic Arches) at the first molars, were 0.59 and -0.72 degree (positive values represent mesio-lingual rotations) for the right and left, respectively. For the mandibular molars, these means were 6.34 and 8.40 degrees, respectively. The mean differences in rotation between buccal cusp tips of maxillary and mandibular first molars in occlusion were 5.75 and 9.12 degrees for the right and left, respectively, with the mandibular being more mesio-lingually rotated. The differences between left and right were significant for all measurements. The present study brings into question the suitability of our present "straight wire" prescriptions in producing similar occlusions. It also suggests that scanning models for computer analysis may be a practical and precise way to measure similar rotations in untreated normal and treated occlusions.

Analysis of Variance↗
PubMedDate not supplied

Strength after surgical repair of the rotator cuff.

Forty-two consecutive patients (20 men and 22 women, age range 39 to 78 years) with full-thickness rotator cuff tears underwent a comprehensive isokinetic strength assessment before and at 3-month intervals for 1 year after surgery. All patients underwent acromioplasty and rotator cuff repair and were treated with a standardized postoperative rehabilitation program. Isokinetic strength testing was performed in flexion/extension, abduction/adduction, and external/internal rotation at 60 degrees/sec. The unaffected contralateral shoulder was tested for comparison. Clinical outcomes were assessed with the University of California Los Angeles Shoulder Rating Scale (maximum = 35 points). The average University of California Los Angeles score was 31.2 by 1 year after operation. Patients with small and medium tears had an average rating of 33.5, whereas those with large and massive tears had an average score of 28.3. Strength increased gradually during the first postoperative year. The preoperative mean peak torque was 54%, 45%, and 64% of the uninvolved shoulder in flexion, abduction, and external rotation, respectively; after operation it increased to 78%, 80%, and 79% by 6 months and 84%, 90%, and 91% by 12 months. The greatest improvement in strength consistently occurred during the first 6 months after surgery. Patients also showed marked increases in both work and power. By 12 months after operation mean work had increased to 70% in flexion and abduction and 90% in external rotation of the uninvolved shoulder. Similarly, mean power had increased to 68%, 79%, and 90% of the uninvolved shoulder in flexion, abduction, and external rotation, respectively, by 12 months after operation. Recovery of strength correlated primarily with the size of the tear: for small and medium tears recovery of strength was almost complete during the first year, and for large and massive tears it was much slower and less consistent. By using isokinetic strength evaluation we found that recovery of strength after rotator cuff repair requires at least 1 year of rehabilitation.

Adult↗
PubMed2006

Optimal size and location for corneal rotational autografts: a simplified mathematical model.

OBJECTIVE: To calculate clinical guidelines for the optimal location and size of a rotational autokeratoplasty. METHODS: The ideal graft size and trephine decentration for a rotational autograft were calculated based on scar location using geometric models. Mathematical variables were set to maximize postoperative visual acuity and for generalization of the geometric model. This model was used in a rotational autokeratoplasty of a patient with a history of a corneal scar and diplopia. An 8-mm autograft was decentered 0.5 mm superiorly and rotated 180 degrees to relocate the scar to the superior aspect of the cornea, out of the patient's vision. RESULTS: For cases that satisfy the given variables, a graft diameter of 8 mm with a decentration of 0.5 mm balances maximization of scar removal and scar movement superiorly, with minimization of discrepancy in corneal thickness after rotation. For scars that are alpha degrees from horizontal, the graft should be rotated 180 - alpha degrees . By using these calculations, the autograft in this case successfully resolved the diplopia and improved visual acuity. CONCLUSIONS: A rotational autograft can be an effective alternative to standard penetrating keratoplasty for some patients with corneal scars. We establish a mathematical model for most clinical instances of a rotational autograft, in which an 8-mm graft with a decentration of 0.5 mm best satisfies the goals of surgery.

Adult↗
PubMed2003

Statistical thermodynamics of internal rotation in a hindering potential of mean force obtained from computer simulations.

A method of statistical estimation is applied to the problem of one-dimensional internal rotation in a hindering potential of mean force. The hindering potential, which may have a completely general shape, is expanded in a Fourier series, the coefficients of which are estimated by fitting an appropriate statistical-mechanical distribution to the random variable of internal rotation angle. The function of reduced moment of inertia of an internal rotation is averaged over the thermodynamic ensemble of atomic configurations of the molecule obtained in stochastic simulations. When quantum effects are not important, an accurate estimate of the absolute internal rotation entropy of a molecule with a single rotatable bond is obtained. When there is more than one rotatable bond, the "marginal" statistical-mechanical properties corresponding to a given internal rotational degree of freedom are reduced. The method is illustrated using Monte Carlo simulations of two public health relevant halocarbon molecules, each having a single internal-rotation degree of freedom, and a molecular dynamics simulation of an immunologically relevant polypeptide, in which several dihedral angles are analyzed.

Algorithms↗