Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Rotation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMedDate not supplied

Latent inhibition of rotation chair-induced nausea in healthy male and female volunteers.

OBJECTIVES: Pre-exposure to an environment in which a nausea-inducing body rotation will subsequently be given constitutes a latent inhibition procedure that might act to reduce anticipatory and postrotation nausea. METHODS: This was tested in 24 healthy subjects randomly assigned to receive no pre-exposure (group 0), a single pre-exposure (group 1), or three pre-exposures (group 3). Rotation was standardized as 5 x 1 minute rotation, but the subjects could terminate it on request. Nausea was determined on a 7-item symptom rating scale before, during, and after rotation on days 3 and 4, whereas anticipatory nausea was measured before presumed rotation on day 5. Saliva cortisol and tumor necrosis factor alpha (TNF-alpha) levels were determined at baseline before, directly, and 15 and 30 minutes after rotation every day, and before presumed rotation on day 5. RESULTS: Pre-exposure significantly reduced the degree of anticipatory nausea on day 5. Cortisol levels increased with rotation and were higher at baseline on days 4 and 5, but subjects habituated from day 3 to day 4; levels were lower in women than in men. In contrast, TNF-alpha decreased with rotation but showed no habituation. For both cortisol and TNF-alpha, no effects on postrotational nausea were found. CONCLUSION: It is concluded that repetitive pre-exposure (latent inhibition) reduces anticipatory but not postrotation nausea; behavioral measures (rotation time) and measures of acute stress (cortisol, TNF-alpha) do not respond to latent inhibition. Thus, Pavlovian conditioning rules are effective in healthy humans with anticipatory nausea but not with postrotation nausea. Hormonal responses--TNF-alpha decrease with stress, compensatory cortisol increase--and gender-related effects on learning and habituation are discussed with regard to psychophysiological and psychoimmunological processes.

Adult↗
PubMed2006

Rotation recovery from spherical images without correspondences.

This paper addresses the problem of rotation estimation directly from images defined on the sphere and without correspondence. The method is particularly useful for the alignment of large rotations and has potential impact on 3D shape alignment. The foundation of the method lies in the fact that the spherical harmonic coefficients undergo a unitary mapping when the original image is rotated. The correlation between two images is a function of rotations and we show that it has an SO(3)-Fourier transform equal to the pointwise product of spherical harmonic coefficients of the original images. The resolution of the rotation space depends on the bandwidth we choose for the harmonic expansion and the rotation estimate is found through a direct search in this 3D discretized space. A refinement of the rotation estimate can be obtained from the conservation of harmonic coefficients in the rotational shift theorem. A novel decoupling of the shift theorem with respect to the Euler angles is presented and exploited in an iterative scheme to refine the initial rotation estimates. Experiments show the suitability of the method for large rotations and the dependence of the method on bandwidth and the choice of the spherical harmonic coefficients.

Algorithms↗
PubMed1999

Canal and otolith afferent activity underlying eye velocity responses to pitching while rotating.

Pitching the head while rotating (PWR) combines periodic activation of the semicircular canals and the otoliths to generate pitch and roll eye deviations and continuous horizontal nystagmus. Monkeys were tested after individual pairs of semicircular canals were plugged and single units were recorded in the vestibular nerve while the animals were sinusoidally pitched 20-40 deg about a spatial horizontal axis with 5- and 16-s periods and simultaneously rotated about a spatial vertical axis at 30-120 deg/s. As previously shown, the steady-state horizontal response disappeared after plugging the vertical semicircular canals, but was maintained when the lateral canals were plugged. When the left anterior and right posterior canal (LARP) pair was left intact, the steady-state response depended on the axis about which the pitching took place. When the axis was normal to the LARP plane, there was no steady-state response. When the pitching axis was perpendicular to the LARP normal, the response was maximal. Firing rates of otolith units were approximately in phase with pitch position, and the addition of rotation about a vertical axis did not change the response. Lateral canal units did not have a steady-state modulation during pitch or constant velocity rotation. During PWR, they oscillated at twice the pitch frequency. This corresponded to the frequency at which the canal was maximally activated as it aligned with the plane of rotation. The amplitude of modulation increased proportionally to rotational velocity, but the phase remained the same. These characteristics were unchanged during roll while rotating (RWR), which induces little continuous nystagmus. Anterior and posterior canal units were maximally excited near pitch-velocity maxima and minima, respectively, during pure pitching. During PWR, however, the phases of both components simultaneously shifted toward each other and toward being in phase with otolith units. The peak excitation tended toward a forward-pitch position when the rotation was to the ipsilateral side, and toward a backward pitch position when the rotation was to the contralateral side. With 120-deg/s rotation during a 16-s pitch period, the phase difference between anterior and posterior canal units was as small as 17 deg. These data support the postulate that the correlation between vertical canal and otolith units is the critical factor in generating continuous unidirectional horizontal nystagmus during PWR.

Animals↗
PubMed2003

Does head rotation contribute to gaze stability during passive translations?

Active translations of human subjects are nearly perfectly compensated by a combined rotation of both the eyes and the head. Because vestibuloocular reflex (VOR) gain is less than perfect during passive translations with near targets in head-fixed subjects, there is a possibility that the compensatory head rotation observed during natural behavior represents a vestibularly driven head reflex [translational vestibulocollic reflex (TVCR)]. The TVCR could elicit a horizontal rotation of the head during lateral linear acceleration that contributes to gaze stabilization. To investigate this hypothesis, we examined whether a horizontal rotation of the head contributes to gaze stability during passive lateral translation in rhesus monkeys whose head was free to rotate in the horizontal plane. Motion frequency was varied between 0.5 and 5 Hz while animals fixated targets at distances of 12-102 cm. We did not find evidence supporting the existence of a TVCR. Specifically, during motion at frequencies between 0.5 and 2 Hz, horizontal head rotation was negligible. During 4- and 5-Hz oscillations, there was a clear and consistent horizontal rotation of the head, but responses were always anticompensatory to gaze stabilization; that is, the head rotated in the same direction as head translation and oppositely to the direction of gaze rotation. Furthermore, there was no difference in gaze stability between the head-free and head-fixed conditions. Thus we conclude that the compensatory head rotation observed in human studies of active gaze movements could represent a strategy and/or a motor command contribution to gaze stabilization, rather than a simple vestibularly driven reflex.

Acceleration↗
PubMed1994

Rotational kinematics of the human vestibuloocular reflex. II. Velocity steps.

1. Gain matrices were used to quantify the three-dimensional vestibuloocular reflex (VOR) in five human subjects who were accelerated over 1 s and then spun at a constant 150 degrees/s for 29 s in darkness. Rotations were torsional, vertical and horizontal, about earth-vertical and earth-horizontal axes. 2. Elements on the main diagonal of the gain matrices were much smaller than the optimal value of -1, and torsional gain was weaker than vertical or horizontal. Off-diagonal elements, indicating cross talk, were minimal except for a small but consistent horizontal response to torsional head rotation. 3. Downward slow phases were more than twice as fast as upward at the start of rotation about both earth-vertical and earth-horizontal axes, but the asymmetry vanished later in the rotation. 4. During earth-vertical-axis rotation, all matrix elements decayed to zero. The main-diagonal torsional and vertical gains waned with time constants close to that of the cupula (6.7 and 7.3 s). Velocity storage prolonged the horizontal response to horizontal head rotation (time constant 14.2 s) but not the horizontal response to torsion (7.7 s). A simple explanation is that velocity storage acts on a central estimate of head motion that accurately distinguishes horizontal from torsional and that the inappropriate horizontal eye velocity response to torsion occurs because of cross talk downstream from velocity storage. 5. During earth-horizontal-axis rotation, the torsional, vertical, and horizontal main-diagonal elements declined, with time constants of 7.6, 8.2, and 7.9 s, to maintained nonzero values, all equal to about -0.1. Off-diagonal elements, including the horizontal response to torsion, decayed to zero, so that the otolith-driven reflex, late in the rotation, was equally strong in all dimensions and almost free of detectable cross talk. 6. The difference between gain curves over the course of earth-vertical- and earth-horizontal-axis rotations was not constant but increased with time, suggesting that the VOR response to earth-horizontal-axis rotation is not a simple sum of canal and otolith reflexes.

Acceleration↗
PubMed2001

Effects of rotational stress of different duration on NK cell activity, proinflammatory cytokines, and POMC-derived peptides in mice.

Previous studies have shown that the same stressor, depending on intensity, controllability, or duration, can have different effects on the immune system. The purpose of this study was to determine the effect of 10- and 20-min rotation on natural killer (NK) cell activity and also to establish if changes in body temperature, proinflammatory cytokine (IL-1beta, IL-6, and TNF-alpha) levels, and proopiomelanocortin (POMC)-derived peptide (ACTH and beta-endorphin) levels parallel the changes in NK cell activity in mice. We found that 10-min rotation significantly increased NK cell activity as compared to both the control (home cage) group and the 20-min-rotation group, while NK cell activity in the 20-min group was not significantly changed compared to the control group. Both 10 and 20 min of rotational stress decreased body temperature and induced significant changes in the proinflammatory cytokine and POMC-derived peptide levels as compared to the control group. The pattern of proinflammatory cytokine expression was quite different between the 10- and 20-min rotation groups. All three proinflammatory cytokines were expressed sequentially (at 0 h after rotation TNF-alpha, at 6 h IL-1beta and IL-6, and at 24 h IL-6) in the 10-min rotation group, while the 20-min rotation group had a small increase in IL-1beta (6.7 +/- 1.8 pg/ml) at 0 h and increased levels of IL-6 at 6 and 24 h. There was a dissociation of ACTH and beta-endorphin expression in both groups resulting in significantly more beta-endorphin (p < 0.05) in the 10-min group at 6 h and significantly more ACTH (p < 0.04) in the 20-min group at 6 h. IL-1beta and beta-endorphin have both been shown to have a direct stimulatory effect on NK cell activity. Therefore, we suspect that the significant increase in both IL-1beta and beta-endorphin at 6 h in the 10-min-rotation group may be involved in the increased NK cell activity observed at 24 h in the 10-min-rotation group.

Adrenocorticotropic Hormone↗
PubMed1997

Dynamics of left ventricular apex rotation during angioplasty: a sensitive index of ischemic dysfunction.

BACKGROUND: Apex rotation has been shown to provide a reliable index of the dynamics of left ventricular (LV) twist. In this study, we aimed to characterize twist at baseline and during acute ischemia in 20 patients undergoing percutaneous transluminal coronary angioplasty to the left anterior descending (LAD) artery and to test whether an old myocardial infarction or collateral flow affected twist dynamics. METHODS AND RESULTS: Among patients with no previous infarction, five had no collaterals (group A) and six had angiographically visible collaterals (group B). Previous anterior infarction was present in nine patients (group C). Data were acquired with the LAD angioplasty wire passed beyond the apex using a view aligned with the LV long axis. Frame-by-frame dynamics of apex rotation were measured from the angular movement of the portion of the wire that traversed the apex. Aortic pressure recordings allowed precise temporal definition of the cardiac cycle. Dynamics of apex rotation were measured at fixed intervals until 60 seconds of occlusion and up to 60 seconds of reperfusion. In group A, counterclockwise apex rotation (twist) during ejection of -22.0+/-1.7 degrees (mean+/-SEE) was followed by rapid clockwise rotation (untwist) during isovolumic relaxation. During 60 seconds of ischemia, maximum apex rotation decreased to -8.2+/-2.0 degrees (P<.001 versus baseline). In group B, baseline apex rotation was similar (-26.2+/-6.9 degrees) to that in group A, but ischemia had less effect, with apex rotation values of -17.7+/-3.4 degrees (P<.05 versus group A values). Group C was characterized by reduced baseline apex rotation values (-9.7+/-3.1 degrees, P<.05 versus group A values), with little change observed during ischemia (-8.1+/-2.6 degrees). CONCLUSIONS: Apex rotation, an index of ventricular twist, is sensitive to acute ischemia in patients without previous myocardial infarction. Visible collaterals to the ischemic region attenuate the acute ischemic response at 60 seconds. Previous myocardial infarction causes abnormalities in the baseline twist pattern with no further deterioration at 60 seconds of ischemia.

Adult↗
PubMedDate not supplied

Humeral retroversion and its relationship to glenohumeral rotation in the shoulder of college baseball players.

BACKGROUND: Previous studies have documented changes in musculature, bony anatomy, and glenohumeral rotation in the dominant shoulder of baseball players. HYPOTHESIS: In a group of asymptomatic college baseball players the total range of motion in the dominant and nondominant shoulders will be similar. Any measured increase in external rotation and decrease in internal rotation occurring between the two sides will be consistent and directly correlate with an increased angle of humeral retroversion in the dominant extremity. STUDY DESIGN: Descriptive anatomic study. METHODS: Fifty-four asymptomatic college baseball players were examined. Standard measurements of glenohumeral range of motion were made and humeral retroversion was determined radiologically. RESULTS: Total rotational motion, measured at 90 degrees of glenohumeral abduction, was 159.5 degrees for the dominant shoulders and 157.8 degrees for the nondominant shoulders. Mean differences in external and internal rotation in the dominant versus nondominant extremities were 9.7 degrees and 8.2 degrees, respectively. Humeral retroversion measured 36.6 degrees +/- 9.8 degrees in the dominant and 26 degrees +/- 9.4 degrees in the nondominant extremity. The mean difference in retroversion correlated significantly by Pearson's product moment with the difference in external (P = 0.001) and internal (P = 0.003) rotation measurements. CONCLUSIONS: There is a pattern of increased external rotation and decreased internal rotation in the dominant extremity that significantly correlates with an increase in humeral retroversion. The loss of internal rotation and gains in external rotation may be more strongly related to adaptive changes in proximal humeral anatomy than to changes in the soft tissues.

Adolescent↗
PubMedDate not supplied

The anterior cruciate ligament in controlling axial rotation. An evaluation of its effect.

Changes in axial tibial rotation after anterior cruciate ligament sectioning were evaluated in 14 fresh human knee joints. Simulation of vertical stance in a quadriceps-stabilized knee was performed. Internal and external rotational torques were applied before and after anterior cruciate ligament sectioning. Pivot shift tests were done in the intact and anterior cruciate ligament sectioned knee. Results of pivot shift tests were all negative before sectioning and positive after isolated sectioning. No significant change in axial rotation occurred between the intact and sectioned knee for external rotation (P = 0.24) or internal rotation (P = 0.12). Presence of a load at the femoral housing in both the intact and ligament-sectioned knees caused a significant change in external rotation (P < 0.0001). No significant change was noted in internal rotation between loaded and unloaded states (P = 0.70). Total tibial rotation in the intact knee was noted to vary between 31 degrees at 0 degree of flexion and 42 degrees at 60 degrees of flexion. These results suggest that the anterior cruciate ligament does not play a significant role in limiting axial rotation and that rotational instability is not a major factor after isolated anterior cruciate ligament rupture.

Aged↗
PubMed2001

Influence of increased rotational inertia on the turning performance of humans.

The rotational inertia of an animal can be expected to influence directly its ability to execute rapid turning maneuvers. We hypothesized that a ninefold increase in rotational inertia would reduce maximum turning performance to one-ninth of control values. To test this prediction, we increased rotational inertia about the vertical axis of six human subjects and measured their ability to turn during maximum-effort jump turns. We measured the free moment about a vertical (i.e. yaw) axis as the subjects performed maximum-effort jump turns under three conditions: (i) unencumbered, (ii) wearing a backpack with a control weight and (iii) wearing a backpack of the same mass that increased the rotational inertia of the subject to 9.2 times that with the control weight. Rotational inertia measurements allowed us to estimate the angle turned during the take-off period (i.e. from jump initiation until the feet leave the ground) and the angular power and work of the maximum-effort turns. Surprisingly, the angle turned during take-off in the increased inertia trials was 44.7 % of that of the control trials, rather than the 10.9 % (9.2-fold reduction) expected on the basis of the increase in rotational inertia. When the subjects turned with increased rotational inertia, the maximum and mean torques exerted were, on average, 142 % and 190 %, respectively, of the values recorded during the control trials. Maximum torques during increased rotational inertia trials actually approached isometric maxima. In the increased rotational inertia trials, the angular impulse was 252 % of that of the control trials and the take-off period was 130 % of that of the control trials. By exerting larger torques over longer take-off periods, the subjects were able partially to compensate for the excess rotational inertia. In contrast to the observed changes in torque, maximum and mean angular power were highest in the unencumbered trials and lowest in the increased inertia trials. On the basis of a decreased ability to generate vertical force when turning and of our estimates of angular power, we speculate that the greater than expected turning performance was due (i) to adjustments in the pattern of muscle recruitment and (ii) to a reduction in the velocity of muscle shortening that resulted in increased muscle forces.

Biomechanical Phenomena↗
PubMed2005

The variability of femoral rotational alignment in total knee arthroplasty.

BACKGROUND: Several reference axes are used to establish femoral rotational alignment during total knee arthroplasty, but debate continues with regard to which axis is most accurately and easily identified during surgery. Computer-assisted navigation systems have been developed in an attempt to more accurately and consistently align implants during total knee arthroplasty, but it is unknown if navigation systems can improve the accuracy of femoral rotational alignment as compared with that achieved with more traditional techniques involving mechanical guides. The purposes of the present study were to characterize the variability associated with femoral rotational alignment techniques and to determine whether the use of a computer-assisted surgical navigation system reduced this variability. METHODS: Eleven orthopaedic surgeons used five alignment techniques (including one computer-assisted technique and four traditional techniques) to establish femoral rotational alignment axes on ten cadaveric specimens, and the orientation of these axes was recorded with use of a navigation system. These derived axes were compared against a reference transepicondylar axis on each femur that was established after complete dissection of all soft tissues. RESULTS: There was no difference between the mean errors of all five techniques (p > 0.11). Only 17% of the knees were rotated <5 degrees from the reference transepicondylar axis, with alignment errors ranging from 13 degrees of internal rotation to 16 degrees of external rotation. There were significant differences among the surgeons with regard to their ability to accurately establish femoral rotational alignment axes (p < 0.001). CONCLUSIONS: All techniques resulted in highly variable rotational alignment, with no technique being superior. This variability was primarily due to the particular surgeon who was performing the alignment procedure. A navigation system that relies on directly digitizing the femoral epicondyles to establish an alignment axis did not provide a more reliable means of establishing femoral rotational alignment than traditional techniques did.

Arthroplasty, Replacement, Knee↗
PubMed2005

The effect of rotator cuff tear size on shoulder strength and range of motion.

STUDY DESIGN: Prospective cohort study. OBJECTIVES: To determine the effect of rotator cuff tear size on shoulder strength and range of motion. BACKGROUND: Patients with rotator cuff pathology typically present with weakness and motion loss in various motions. The extent to which the presence of a rotator cuff tear and the size of the tear affect strength and range of motion is not well understood. METHODS AND MEASURES: Sixty-one patients scheduled for surgery, with a diagnosis of a rotator cuff tear and/or subacromial impingement, underwent examination for shoulder pain, function, range of motion, and strength. The extent of rotator cuff pathology was documented during subsequent surgery (presence of tear, tear size, tear thickness). RESULTS: There were 10 massive tears, 15 large tears, 13 medium tears, 12 small tears, and 11 rotator cuffs without a tear. Patients had marked weakness in abduction strength at 90 degrees and 10 degrees of abduction, in external rotation strength at 90 degrees, and in the "full can test" (all, P<.0001). Marked range of motion losses in shoulder flexion and external rotation at 0 degrees and 90 degrees abduction (all, P<.001) were also observed. Abduction strength deficit at 10 degrees was affected by rotator cuff tear size (P<.0001). Twenty of 25 patients with large or massive tears had deficits greater than 50%, compared with only 1 of 11 patients with no tear, 2 of 12 patients with a small tear, and 5 of 13 patients with a medium tear (P<.0001). Other strength and range of motion deficits or indices of pain and function were unaffected by tear size. CONCLUSIONS: Weakness of greater than 50% relative to the contralateral side in shoulder abduction at 10 degrees of abduction was indicative of a large or massive rotator cuff tear.

Adult↗
PubMed1993

Nystagmus responses in normal subjects during eccentric sinusoidal rotation.

Earth vertical axis rotation provides a method of stimulating the horizontal semicircular canals. By placing subjects off from the axis of rotation, the otolith organs may also be stimulated by additional linear acceleration forces. In the present study, we compared the rotation with subjects placed on axis to those placed in an eccentric position, either facing outward or turned 90 degrees facing the direction of the rotation. When the subject was facing outward, sinusoidal eccentric rotation at 0.64 Hz produced a significantly higher vestibulo-ocular reflex (VOR) gain than did on-axis rotation. No increase in VOR gain was observed during eccentric rotation with the subject facing the direction of the rotation. These findings suggest that the gain enhancement due to eccentric rotation is a result of tangential linear acceleration, probably sensed by the utriculus. This study raises the possibility of using eccentric rotation for the diagnosis of the patients with otolith dysfunction.

Acceleration↗
PubMed2003

Clockwise and counterclockwise rotating shifts: effects on vigilance and performance.

INTRODUCTION: Arguments against counterclockwise shift schedules, such as those used in air traffic control, are prevalent in the literature; however, few studies have examined direction of rotation in rapidly rotating schedules. The present study directly compared clockwise (CW) and counterclockwise (CCW) rapidly rotating shiftwork schedules on measures of complex and vigilance task performance. METHODS: Participants (n = 28) worked day shifts for the first week of the study (0800-1600 h), followed by 2 wk of either a CW (n = 14) or CCW (n = 14) shiftwork schedule. Participants completed three 1.5-h sessions on the Multiple Task Performance Battery (MTPB) on each shift. Each session contained active- and passive-task components. In addition, participants completed a 0.5-h Bakan Vigilance Test at the beginning and end of each shift. RESULTS: A three-way, rotation condition by shift by session interaction (F (8,19) = 3.0, p < 0.05) for the active task composite scores and a rotation condition by shift interaction (F (4,23) = 6.2, p < 0.05) for the Bakan Vigilance Task indicated that effects of rotation condition were modulated by shift type, such that on particular shifts, performance in the CCW rotation was actually better than in the CW rotation. DISCUSSION: These data do not support the hypothesis that a CW rotation will result in better outcomes on complex or vigilance task performance. The results of this study indicate that two problem areas in both CW and CCW rapidly rotating shift schedules are early morning and midnight shifts.

Aviation↗
PubMed2003

[Habituation of horizontal eye nystagmus in pigeon during alternation of central and eccentric rotations].

Intact pigeons were rotated in the horizontal plane in the dark in different positions relatively to the rotation axis. At central rotations, the pigeon's head was in the rotation axis whereas at eccentric rotations it was displaced from the axis. Series of central and eccentric rotations were alternated. Each series consisted of 2-5 rotations using angular velocity trapezoids. All stimuli producing habituation were used at most 14 times each. Eccentric rotations did not prevent a gradual decrease of peak velocities of the slow component of primary nystagmus on transition from one series of central rotations to another in 17 pigeons (group 1). The increase of peak velocities was observed in 2 pigeons (group 2). In group 1, a direct dependence among alterations of this parameter of primary nystagmus, modifications of its duration, and variations of peak velocities of secondary nystagmus, were observed. If two identical stimuli did not follow in sequence directly, the effect of the second one produced same nystagmus changes as were observed in present pigeon by comparison of the first and last responses in the series of the central rotations. If they follow one by one, in many cases the second stimulus in the pair produced an increase of peak velocity of primary and secondary nystagmus and rise of delay of the point of primary nustagmus peak velocity. These variations were not random (probability, > 95%).

Animals↗
PubMed1997

Rotation osteotomies for osteonecrosis of the femoral head.

Twenty consecutive rotation osteotomies for idiopathic necrosis of the femoral head with an average followup of 6.5 years were reviewed. The original technique used a nail plate for rotation and fixation of the fragments and proved to be reliable for precision of rotation, osteotomy fusion, and absence of mechanical or vascular complications. There were 16 anterior extension Sugioka osteotomies with 52 degrees average rotation, and four posterior flexion Kempf osteotomies with 77 degrees average rotation. The status of 18 surgically treated hips after 5 years was seven failures, two fair results, and nine satisfactory results. Rotation osteotomies are recommended only when the necrotic zone of the femoral head can be removed from the major weightbearing zone of the acetabulum, when the hip is in extension. In Sugioka's anterior rotation, the necrotic zone, although unloaded in extension, usually remains in contact with the acetabular major bearing zone (40 degrees around apex) in hip flexion. Thus, it is recommended only for Ficat Stage 2 nonflattened heads. In Kempf's posterior rotation, the necrotic zone is unloaded in hip extension and flexion, so Stage 3 is not a contraindication for this osteotomy. In addition, osteotomies are not recommended when the necrosis extends deeper than the proximal third of the femoral head. In these large necroses, there may be an overloading of the healthy part of the rotated head, resulting in its secondary mechanical deterioration. If these conditions are fulfilled, rotation osteotomy of the proximal femur may, in patients younger than 45 years of age, delay for a decade the degradation of hips with idiopathic osteonecrosis.

Acetabulum↗
PubMed2003

Intrinsic rotation and molecular structure.

The intrinsic rotation, limiting value of specific rotation at zero concentration, of (R)-(-)-epichlorohydrin was measured in four different solvents, CH(3)OH, CH(2)Cl(2), CHCl(3) and CCl(4). It was found that the sign of rotation in CH(3)OH, and CH(2)Cl(2) solvents is opposite to that in CCl(4). The intrinsic rotation in CHCl(3) is close to zero. This observed pattern was explained using density functional calculations of specific rotation using very large basis sets. It was found that the g-I and g-II conformations of epichlorohydrin have nearly the same magnitude of specific rotation but with opposite sign. When these two conformations have equal populations, as in CHCl(3) solvent, the net rotation is close to zero. When g-II conformation dominates, as in CCl(4) solvent, the observed sign of rotation will be opposite to that when g-I conformation dominates, as in CH(2)Cl(2) and CH(3)OH solvents. A combination of intrinsic rotation measurement with density functional prediction of specific rotation is demonstrated to be a practical method for determining the structures of molecules.

Journal Article↗
PubMed2001

Correlation between vertebral body rotation and two-dimensional vertebral bone density measurement.

The aim of this study was to determine the effect of vertebral rotation, as seen in idiopathic scoliosis, on bone mineral density determination for the lumbar spine. Bone mineral content, biplanar vertebral segment area and calculated bone mineral density of each vertebra from L1 to L4 were obtained for a human cadaveric specimen. The average density for the entire L1-L4 segment was also recorded. This was done with the spine in the midline position as well as in rotation up to a maximum of 60 degrees either side of the midline. The spine was rotated in each direction using 10 degrees increments and two bone density readings were done at each rotation interval. The measured biplanar vertebral segment area increased with increasing rotation from 0 degrees to 50 degrees but decreased after 50 degrees of rotation (r = 0.73, p<0.001). The bone mineral density was significantly negatively correlated with the degree of rotation (r = -0.92, p<0.001). The decrease in measured bone mineral density was nearly 20% when the lumbar spine was rotated from neutral to 60 . This study demonstrates that degree of spinal rotation influences apparent bone mineral density by increasing the apparent vertebral segment area. The measurement change may be as high as 20%. This fact should be considered when investigating scoliotic patients with vertebral segment rotation.

Absorptiometry, Photon↗