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 433 records · Page 24Linked to original sources
PubMed2002

Enhancement of IMRT delivery through MLC rotation.

Multileaf collimator (MLC) based intensity modulated radiation therapy (IMRT) techniques are well established but suffer several physical limitations. Dosimetric spatial resolution is limited by the MLC leaf width; interleaf leakage and tongue-and-groove effects degrade dosimetric accuracy and the range of leaf motion limits the maximum deliverable field size. Collimator rotation is used in standard radiation therapy to improve the conformity of the MLC shape to the target volume. Except for opposed orthogonal fields, collimator rotation has not been exploited in IMRT due to the complexity of deriving the MLC leaf configurations for rotated sub-fields. Here we report on a new way that MLC-based IMRT is delivered which incorporates collimator rotation, providing an extra degree of freedom in deriving leaf sequences for a desired fluence map. Specifically, we have developed a series of unique algorithms that are capable of determining rotated MLC segments. These IMRT fields may be delivered statically (with the collimator rotating to a new position in between sub-fields) or dynamically (with the collimator rotating and leaves moving simultaneously during irradiation). This introductory study provides an analysis of the rotating leaf motion calculation algorithms with focus on radiation efficiency, the range of collimator rotation and number of segments. We then evaluate the technique by characterizing the ability of the algorithms to generate rotating leaf sequences for desired fluence maps. Comparisons are also made between our method and conventional sliding window and step-and-shoot techniques. Results show improvements in spatial resolution, reduced interleaf effects and maximum deliverable field size over conventional techniques. Clinical application of these enhancements can be realized immediately with static rotational delivery although improved dosimetric modelling of the MLC will be required for dynamic delivery.

Algorithms↗
PubMed1996

Force analysis of rotator cuff muscles.

A 3-dimensional static biomechanical model of the glenohumeral joint was used to investigate rotator cuff muscle forces during maximal isometric exertions (abduction, adduction, internal rotation, and external rotation) and static arm elevation. Muscle moment arms and cross sectional areas were determined from studies of cadaveric specimens, and maximal isometric strength data were collected using a Cybex II dynamometer. Predicted posterior deltoid forces were very low during abduction in the scapular plane. The model predicted the highest rotator cuff muscle forces during maximal internal rotation (subscapularis) and external rotation (infraspinatus, teres minor, and supraspinatus) exertions. The results indicate that abduction exertions may not produce the greatest loads on the supraspinatus tendon, and that analyses of arm elevation may underestimate the potential loads on the rotator cuff. The strong effect of external rotation exertions on supraspinatus and infraspinatus forces suggest that ergonomic efforts to prevent rotator cuff disease should include reduction of internal rotation loading on the arm. Moreover, it may be important to include warnings about external rotation exertions, in addition to arm elevation, in patient education.

Adult↗
PubMed2001

Optimizing femoral component rotation in total knee arthroplasty.

Femoral component rotation is important in total knee arthroplasty to optimize patellofemoral and tibiofemoral kinematics. More recently, the epicondylar axis has been cited as the definitive landmark for femoral component rotation. However, there are few studies to support the validity of this rotational landmark and its effect on the patellofemoral and tibiofemoral articulations. In the current study, a total knee arthroplasty was done in 11 knees from cadavers. The knees were tested with various femoral component rotations from 5 degrees internal rotation to 5 degrees external rotation referenced to the epicondylar axis and to the posterior femoral condyles. Each knee acted as its own internal control. The knees were actively ranged from 0 degrees to 100 degrees by a force on the quadriceps tendon in an Oxford knee simulator. Three-dimensional kinematics of all three components were measured whereas a multiaxial transducer imbedded in the patella measured patellofemoral forces. Femoral component rotation parallel to the epicondylar axis resulted in the most normal patellar tracking and minimized patellofemoral shear forces early in flexion. This optimal rotation also minimized tibiofemoral wear motions. These beneficial effects of femoral rotation were less reproducibly related to the posterior condyles. Rotating the femoral component either internal or external to the epicondylar axis worsened knee function by increasing tibiofemoral wear motion and significantly worsening patellar tracking with increased shear forces early in flexion. Based on the current study, the femoral component should be rotationally aligned parallel to the epicondylar axis to avoid patellofemoral and tibiofemoral complications.

Analysis of Variance↗
PubMed2004

Kinematics of the subaxial cervical spine in rotation in vivo three-dimensional analysis.

STUDY DESIGN: Three-dimensional intervertebral motions of the subaxial cervical spine during head rotation were investigated in healthy volunteers using three-dimensional magnetic resonance imaging (MRI). OBJECTIVES: To document intervertebral coupled motions of the subaxial cervical spine during rotation. SUMMARY OF BACKGROUND DATA: In vivo three-dimensional kinematics of the subaxial cervical spine in rotation have not previously been well described, since they are too complicated to follow using conventional radiography or computed tomography techniques. METHODS: Ten healthy volunteers underwent three-dimensional MRI of the cervical spine in 11 positions with 15 degrees increments during head rotation using a 1.0-T imager. Relative motions of the subaxial cervical spine were calculated by automatically superimposing a segmented three-dimensional MRI of the vertebra in the neutral position over images of each position using volume registration. Three-dimensional motions of adjacent vertebrae were represented with 6 df (6 degrees of freedoms) by Euler angles and translations on the coordinate system defined by Panjabi, then visualized in animations using surface bone models. RESULTS: Mean axial rotation of the subaxial cervical spine in maximum head rotation (69.5 degrees ) was 2.2 degrees at C2-C3, 4.5 degrees at C3-C4, 4.6 degrees at C4-C5, 4.0 degrees at C5-C6, 1.6 degrees at C6-C7, and 1.5 degrees at C7-T1. Coupled lateral bending with axial rotation was observed in the same direction as axial rotation at all levels (C2-C3, 3.6 degrees ; C3-C4, 5.4 degrees; C4-C5, 5.0 degrees ; C5-C6, 5.3 degrees ; C6-C7, 4.9 degrees ; C7-T1, 1.2 degrees ). Coupled extension with axial rotation occurred in the middle cervical region (C2-C3, 1.4 degrees ; C3-C4, 2.3 degrees ; C4-C5, 1.5 degrees ), while in the lower cervical region, flexion was coupled with axial rotation (C5-C6, 0.9 degrees ; C6-C7, 2.4 degrees ; C7-T1, 3.0 degrees ). CONCLUSIONS: We investigated intervertebral motions of the subaxial cervical spine during head rotation using a three-dimensional imaging system, and obtained the first accurate depictions of in vivo coupled motion. These findings will be helpful as the basis for understanding abnormal conditions.

Adult↗
PubMed1992

Intercostal muscles are used during rotation of the thorax in humans.

To test the idea that the lateral intercostal muscles may be more suited to aid in rotational than respiratory movements of the thorax, we inserted bipolar fine-wire electrodes in external and internal intercostal muscles in the right midaxillary line in nine sitting subjects and examined the pattern of contraction of these muscles during voluntary axial rotations of the thorax (30-35 degrees), resting breathing, and CO2-induced hyperpnea. The right external intercostal muscles were strongly recruited in rotations to the left but were not active in rotations to the right. In contrast, the right internal intercostal muscles were active in rotations to the right but not in rotations to the left. Rotations completed in 1 or 2 s were associated with an early burst of electromyographic activity, followed by a low plateau that persisted while the rotation was held. Rotations made very gradually over 5-10 s were associated with gradually rising electromyographic activity. The amplitude of activity recorded during 30-35 degrees rotations was equivalent to that measured when minute ventilation was increased by CO2 to 50 l/min. We conclude that the lateral intercostal muscles have a major role in producing axial rotations of the thorax.

Adult↗
PubMed1980

Responses of Purkinje cells of cerebellar vermis to sinusoidal rotation of neck.

1. The response of Purkinje (P) cells located in the vermal cortex of the cerebellar anterior lobe to sinusoidal rotation of the neck was investigated in precollicular decerebrate cats. The head of the animal was fixed in a sterotaxic frame while the spinous process of the second cervical vertebra was held by a clamp rigidly fixed to the tilting table. It was then possible to elicit a selective neck input by rotating the neck and the body simultaneously along the longitudinal axis of the animal while maintaining the head in horizontal position. 2. Among the 95 P-cells tested for neck stimulation, 35 units showed a mossy fiber (MF) or a climbing fiber (CF) response to sinusoidal rotation of the axis vertebra at the frequency of 0.026 Hz and at the peak amplitude of displacement of 5--10 degrees. The response consisted in a periodic modulation of the discharge frequency during sinusoidal rotation of the neck. Most of these units were excited during side-down rotation of the neck, but were inhibited during side-up rotation. 3. The threshold amplitude of neck rotation responsible for the MF-induced responses varied in different units from 1 to 3 degrees at the frequency of 0.026 Hz. The sensitivity of the units, expressed in percentage change of the average firing rate per degree of displacement, either did not change or very slightly decreased as a result of increasing amplitude of stimulation from 1--3 degrees to 10--15 degrees at the frequency of 0.026 Hz or by increasing frequency of neck rotation from 0.015 to 0.15 Hz at the amplitude of neck displacement of 5--10 degrees. 4. Changes in amplitude or frequency of stimulation at the parameters reported above did not greatly modify the phase of the unit responses relative to the side-down position of the neck. These findings indicate that the MF and CF responses of P-cells to sinusoidal rotation of the neck depended on changes in neck position and not on changes in velocity of neck rotation. 5. The observation that the majority of responding P-cells located in the vermal cortex of the cerebellar anterior lobe increased their firing rate during side-down rotation of the neck is discussed in relation to the results of stimulation and lesion experiments, indicating that postural changes can be elicited either during asymmetric stimulation of neck receptors or by unilateral interruption of the neck afferents.

Afferent Pathways↗
PubMed1998

Off-centric rotation axes in natural head movements: implications for vestibular reafference and kinematic redundancy.

Until now, most studies concerning active head movements in three dimensions have used the classical rotation vector description. Although this description yields both the orientation of the head rotation axis and the amount of rotation, it is incomplete because it cannot specify the location of this rotation axis in space. The latter is of importance for a proper picture of the vestibular consequences of active head movements and has relevance for the problem of how the brain deals with the inherent kinematic redundancy of the multijoint head-neck system. With this in mind, we have extended the rotation vector description by applying the helical axes approach, which yields both the classical rotation vector as well as the location of the rotation axis in space. Subjects (n = 7), whose head movements were recorded optically, were instructed to shift gaze naturally to targets in 12 different directions at an eccentricity of 40 degrees. The results demonstrate that the axes for these head movements occupy consistently different spatial locations. For purely horizontal movements, the rotation axis is located near a point midway between the two ear canals. For gaze shifts in other directions, the rotation axes are located below the ear canals along two circles, one for movements with an upward component (up circle), the other (typically larger in size) for movements with a downward component (down circle). Purely vertical movement (up and down) axes were located on the lower pole of the up and down circles, respectively. It was found that both circles, the upper poles of which coincided, became larger in size as movement amplitude increased, which means that the axis location shifts to lower and more eccentric locations with respect to the skull for larger flexion and extension movements. Although this pattern could be recognized in most subjects, there were consistent intersubject differences in the absolute size of the circles, their increase with movement amplitude, and in the relative sizes of the up and down circles. Because multiple vertebrae are involved in head movements, there are theoretically many possibilities to execute a certain head movement. The differences in circle patterns among subjects indicate different strategies in resolving this kinematic redundancy problem, a fact that was not apparent from the classical rotation vector part of our description, which yielded a rather uniform picture. A simple model suggests that the downward shift of the location of the rotation axis requires a modulation in vestibulo-ocular reflex gain of </=10% to maintain fixation of a near target during vertical head movement. The involvement of the otolith system in this process remains to be determined.

Adult↗
PubMed1999

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. II. Responses after canal plugging.

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral plugging of the three semicircular canals. During the period (1-4 days) that animals were kept in darkness after plugging, the gain during steps of acceleration (3, 000 degrees /s(2), peak velocity = 150 degrees /s) was 0.61 +/- 0.14 (mean +/- SD) for contralesional rotations and 0.33 +/- 0.03 for ipsilesional rotations. Within 18-24 h after animals were returned to light, the VOR gain for contralesional rotations increased to 0. 88 +/- 0.05, whereas there was only a slight increase in the gain for ipsilesional rotations to 0.37 +/- 0.07. A symmetrical increase in the gain measured at the plateau of head velocity was noted after animals were returned to light. The latency of the VOR was 8.2 +/- 0. 4 ms for ipsilesional and 7.1 +/- 0.3 ms for contralesional rotations. The VOR evoked by sinusoidal rotations of 0.5-15 Hz, +/-20 degrees /s had no significant half-cycle asymmetries. The recovery of gain for these responses after plugging was greater at lower than at higher frequencies. Responses to rotations at higher velocities for frequencies >/=4 Hz showed an increase in contralesional half-cycle gain, whereas ipsilesional half-cycle gain was unchanged. A residual response that appeared to be canal and not otolith mediated was noted after plugging of all six semicircular canals. This response increased with frequency to reach a gain of 0.23 +/- 0.03 at 15 Hz, resembling that predicted based on a reduction of the dominant time constant of the canal to 32 ms after plugging. A model incorporating linear and nonlinear pathways was used to simulate the data. The coefficients of this model were determined from data in animals with intact vestibular function. Selective increases in the gain for the linear and nonlinear pathways predicted the changes in recovery observed after canal plugging. An increase in gain of the linear pathway accounted for the recovery in VOR gain for both responses at the velocity plateau of the steps of acceleration and for the sinusoidal rotations at lower peak velocities. The increase in gain for contralesional responses to steps of acceleration and sinusoidal rotations at higher frequencies and velocities was due to an increase in the gain of the nonlinear pathway. This pathway was driven into inhibitory cutoff at low velocities and therefore made no contribution for rotations toward the ipsilesional side.

Acceleration↗
PubMed2000

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. III. Responses after labyrinthectomy.

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral labyrinthectomy. Spontaneous nystagmus was measured at the beginning and end of each testing session. During the period that animals were kept in darkness (4 days), the nystagmus at each of these times measured approximately 20 degrees /s. Within 18-24 h after return to the light, the nystagmus (measured in darkness) decreased to 2.8 +/- 1.5 degrees /s (mean +/- SD) when recorded at the beginning but was 20.3 +/- 3.9 degrees /s at the end of the testing session. The latency of the VOR measured from responses to steps of acceleration (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) was 8.4 +/- 0.3 ms for responses to ipsilesional rotations and 7.7 +/- 0.4 ms for contralesional rotations. During the period that animals were kept in darkness after the labyrinthectomy, the gain of the VOR measured during the steps of acceleration was 0.67 +/- 0.12 for contralesional rotations and 0.39 +/- 0.04 for ipsilesional rotations. Within 18-24 h after return to light, the VOR gain for contralesional rotations increased to 0.87 +/- 0.08, whereas there was only a slight increase for ipsilesional rotations to 0.41 +/- 0. 06. A symmetrical increase in the gain measured at the plateau of head velocity was noted after the animals were returned to light. The VOR evoked by sinusoidal rotations of 2-15 Hz, +/-20 degrees /s, showed a better recovery of gain at lower (2-4 Hz) than at higher (6-15 Hz) frequencies. At 0.5 Hz, gain decreased symmetrically when the peak amplitude was increased from 20 to 100 degrees /s. At 10 Hz, gain was decreased for ipsilesional half-cycles and increased for contralesional half-cycles when velocity was raised from 20 to 50 degrees /s. A model incorporating linear and nonlinear pathways was used to simulate the data. Selective increases in the gain for the linear pathway accounted for the recovery in VOR gain for responses at the velocity plateau of the steps of acceleration and for the sinusoidal rotations at lower peak velocities. The increase in gain for contralesional responses to steps of acceleration and sinusoidal rotations at higher frequencies and velocities was due to an increase in the contribution of the nonlinear pathway. This pathway was driven into cutoff and therefore did not affect responses for rotations toward the lesioned side.

Acceleration↗
PubMed2006

The effect of cyclic loading on rotated bone-tendon-bone anterior cruciate ligament graft constructs.

BACKGROUND: Single-incision anterior cruciate ligament reconstruction with a bone-patellar tendon-bone construct is commonly performed with 180 degrees rotation of the graft. It has been hypothesized that further rotation of the graft to 540 degrees can effectively shorten the graft to address graft length-tunnel mismatch. Initial biomechanical failure characteristics of rotated constructs have been reported, but cyclic loading of tendons has not been performed. HYPOTHESIS: Graft rotation affects the biomechanical properties of the construct. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-five bone-patellar tendon-bone composite porcine right knee specimens were randomized into 3 groups and were externally rotated to 0 degrees , 180 degrees , or 540 degrees . Each group was then cyclically loaded in an artificial synovial fluid medium between 50 and 250 N for 5,000 cycles, loaded between 50 and 500 N for an additional 5,000 cycles, and finally subjected to load-to-failure testing. RESULTS: Graft rotation shortened constructs by 1.7 +/- 0.8 mm at 180 degrees of rotation and 7.6 +/- 2.0 mm at 540 degrees of rotation (P < .01). There was a statistically significant increase in strain during cyclic loading at 540 degrees . No significant differences in maximum load, yield stress, yield strain, or modulus of elasticity were detected in single-cycle load-to-failure testing after cyclic loading. CONCLUSION: Rotation of bone-patellar tendon-bone constructs to 540 degrees predictably shortens the effective graft length at the expense of increased strain with cyclic loading at stresses equivalent to walking and running. CLINICAL RELEVANCE: Although rotation to 540 degrees potentially addresses graft length-tunnel mismatch, further clinical evaluation is required to evaluate the impact of increased strain on knee laxity and to determine the effects of physiologic loading of rotated bone-patellar tendon-bone constructs in vivo.

Animals↗
PubMed2002

The aerodynamic effects of wing rotation and a revised quasi-steady model of flapping flight.

We used a dynamically scaled model insect to measure the rotational forces produced by a flapping insect wing. A steadily translating wing was rotated at a range of constant angular velocities, and the resulting aerodynamic forces were measured using a sensor attached to the base of the wing. These instantaneous forces were compared with quasi-steady estimates based on translational force coefficients. Because translational and rotational velocities were constant, the wing inertia was negligible, and any difference between measured forces and estimates based on translational force coefficients could be attributed to the aerodynamic effects of wing rotation. By factoring out the geometry and kinematics of the wings from the rotational forces, we determined rotational force coefficients for a range of angular velocities and different axes of rotation. The measured coefficients were compared with a mathematical model developed for two-dimensional motions in inviscid fluids, which we adapted to the three-dimensional case using blade element theory. As predicted by theory, the rotational coefficient varied linearly with the position of the rotational axis for all angular velocities measured. The coefficient also, however, varied with angular velocity, in contrast to theoretical predictions. Using the measured rotational coefficients, we modified a standard quasi-steady model of insect flight to include rotational forces, translational forces and the added mass inertia. The revised model predicts the time course of force generation for several different patterns of flapping kinematics more accurately than a model based solely on translational force coefficients. By subtracting the improved quasi-steady estimates from the measured forces, we isolated the aerodynamic forces due to wake capture.

Animals↗
PubMed1977

Effect of rotation on radiographic dimensions of the humerus and femur.

Ten humeri and ten femora were radiographed in nine positions of longitudinal rotation. In each position total, medullary and cortical widths of the diaphyses (TW, MW, CW) were measured to assess the effect of rotation on these dimensions. The results were expressed as differences from the values in the neutral position (delta TW, delta MW, delta CW). In the humerus, medial rotation produced greater changes than lateral rotation. Though rotation in either direction increased CW, the systematic error due to medial rotation to only 5 degrees (approximately +0.0058 cm per degree) was more than double that due to lateral rotation. In the femur, lateral rotation had the greater effect, producing a marked decrease in CW (approximately -0.0072 cm per degree). Medial rotation produced only a slight increase in CW. The ratios CW/TW ("cortical index") and CA/TA ("area ratio") were calculated and expressed as differences from the values in the neutral position (delta CW/TW, delta CA/TA). Rotation affected these variables much less than the linear dimensions. Furthermore, through the variance of delta TW, delta MW and delta CA/TA increased only slightly or not at all. These results suggest that if radiographic morphometry is to be applied to the humerus and femur, these ratios rather than transverse dimensions should be used. Sequential changes in CW may be totally obscured by small rotational errors.

Anthropometry↗
PubMed1994

Rotational injury of cervical facets: CT analysis of fracture patterns with implications for management and neurologic outcome.

OBJECTIVE: Imaging studies of patients with rotational facet injuries of the cervical spine were retrospectively reviewed to determine the prevalence and pattern of associated fractures, to correlate injury pattern with recommended surgical stabilization, and to assess neurologic outcome. MATERIALS AND METHODS: Radiographs and CT scans obtained for 40 consecutive patients with rotational facet injuries of the cervical spine during a 70-month period were retrospectively reviewed to determine injury level, presence, and orientation of facet fractures, and concurrent nonfacet injuries. Imaging findings were reviewed to assess the likelihood of instability and to determine the most appropriate stabilization requirement. Medical records were reviewed to ascertain mechanism of injury, initial neurologic deficit, and surgical findings. RESULTS: Among the 40 patients with cervical rotational facet injuries, 11 (27%) had pure unilateral facet dislocation or subluxation without associated fractures, and 29 (73%) had concurrent facet fractures involving the inferior facet of the rotated vertebra (n = 13), the superior facet of the subjacent vertebra (n = 9), or both (n = 7). Injury of the rotated vertebra was unilateral in 22 patients but bilateral in 18 patients. Facet fractures frequently extended into the ipsilateral lamina or articular pillar or both. An avulsion fracture from the posteroinferior aspect of the rotated vertebral body, indicating disk disruption, occurred in 10 patients (25%), and seven patients (17%) had complete isolation of an articular pillar. Facet fractures were confirmed for 27 patients who underwent surgical stabilization. Neurologic deficits developed in 29 (73%) of the 40 patients and included radiculopathy in 11 patients and cord syndromes in 18 patients. Pure dislocation without a facet fracture was more likely to lead to a cord syndrome (p = .006). CONCLUSION: Cervical rotational facet injuries are often accompanied by facet fractures and bilateral damage of the rotated vertebra. These injuries contribute to rotational instability and require specific internal fixation based on a precise delineation of all injuries. Facet dislocations without fractures have a significantly higher association with cord syndromes than do rotational facet injuries with fractures. CT, particularly with parasagittal reformations, is valuable in identifying all injuries of the rotated and subjacent vertebrae.

Adolescent↗
PubMed2002

Actions of the scalene muscles for rotation of the cervical spine in macaque and human.

STUDY DESIGN: Multiple single-subject design in 2 parts: 1 in anesthetized monkeys and a follow-up in human cadavers. OBJECTIVES: To determine whether anterior, middle, and posterior scalene muscles rotate the cervical spine to the same (ipsilateral to the muscle) or opposite (contralateral to the muscle) side. BACKGROUND: Some physical therapy and anatomy textbooks indicate that all 3 scalenes rotate the cervical spine to the same side, some indicate that all rotate to the opposite side, and the rest ascribe different functions to the different scalenes. METHODS AND MEASURES: While under anesthesia, macaques (n = 3) already scheduled for euthanasia were implanted with stimulating electrodes in each scalene muscle on one side, and then a neuromuscular junction blocker was administered to prevent confounding movement from brachial plexus stimulation. Three observers independently rated the direction of rotation produced by electrical stimulation. Postmortem dissection of the macaques was used to determine which direction of passive rotation stretched each scalene. Postmortem analyses in 2 human cadavers were also conducted to determine which direction of rotation stretched the human scalenes. RESULTS: Electrical stimulation in the macaque produced rotation to the same side for each of the 3 scalenes. Passive rotation to the opposite side put each scalene muscle of the macaque on stretch. In the human, rotation to the opposite side also stretched each scalene. CONCLUSIONS: All 3 scalene muscles produce rotation of the cervical spine to the same side. Maximum stretching of the scalenes should include rotation to the opposite side.

Animals↗
PubMed1999

The effects of roll vs. pitch rotation in humans under orthostatic stress.

BACKGROUND: It has been known since 1953 that pre-exposure to less than +1 Gz will reduce subsequent +Gz-tolerance. With few exceptions, during operational flying, the transition from hypogravity to hypergravity involves roll as well as pitch rotation. We examined the effect of roll vs. pitch rotation while undergoing transition from hypogravity to +1 Gz on a tilt table. METHODS: Twelve subjects (28-47 yr old) were rotated at 45 degrees x s(-1) from head-up (HU) at 15 degrees relative to gravitational vertical to 135 degrees head-down (HD) and back to the HU position after different HD dwell times. HD dwell times were set at 7, 15, and 30 s. The subject was rotated about the interaural axis (pitch) and about the naso-occipital axis (roll). Both the HD dwell times and axes of rotation were randomized within and across subjects. BP and heart rate were recorded during the HU-HD-HU maneuver. RESULTS: Analysis of variance, repeated measure design revealed that the rate and magnitude of BP decrease induced by the HD to HU maneuver is significantly higher (p < 0.01) in roll than in pitch during all HD dwell times. The decrease of BP at 7s is significantly (p < 0.01) higher than at 15s and 30s. Heart rate increases significantly higher (p < 0.01) in pitch than in roll at 7s-dwell time. CONCLUSION: Our results suggest that the compensatory mechanism to orthostatic stress is more efficient in response to pitch than roll rotation. This is reflected from the findings that the mean magnitude of OH (orthostatic hypotension) and the rate of BP decrease induced by the HD-HU maneuver is significantly greater in roll rotation than pitch rotation. The mean HR increase post HD-HU rotation is significantly higher in the pitch than the roll rotation. The significant rate of BP decrease during HD-HU roll rotation could have important implications for maintaining G-tolerance and spatial orientation during subsequent exposure to hypergravity.

Adaptation, Physiological↗
PubMed1992

Shoulder computed arthrotomography: role of internal and external rotation.

Computed arthrotomography of the shoulder is the best investigation for instability of the glenohumeral joint. The purpose of this paper is to evaluate the role of internal rotation and external rotation in detecting glenoid and capsular lesions. From October 1989 to December 1991, 74 double-contrast CT arthrograms of the shoulder were performed with both internal and external rotation. Most of these patients were referred for instability problems or shoulder pain of vague origin. Of the 49 abnormalities of the anterior portion of glenoid labrum, 44 (89.8%) were identified on the scans with internal rotation; however, 5 (10.2%) was seen only in external rotation view. Most of the anterior capsular abnormalities occurred on the internal rotation. Only one of 74 examination was evidenced solely on external rotation. There were relatively few posterior labral or capsule abnormalities. Of the five, two were seen solely on external rotation. The results suggest that internal rotation scans detect most of the lesions; however, with the help of external rotation view, 10% increase in diagnostic yield can be expected for anterior labral abnormalities. Although few posterior labral or capsule lesions occur, external rotation examination does play an important role in this respect.

Adolescent↗
PubMed2003

Forearm and elbow injury: the influence of rotational position.

BACKGROUND: The purpose of this study was to develop an axial loading forearm fracture model and to determine the influence of forearm rotation on the fracture pattern. METHODS: Twenty-six cadaveric arms were thawed in saline solution. Pressure-sensitive film was sealed and was placed through a lateral arthrotomy into the radiocapitellar joint. The arm was potted at the proximal part of the humerus with the elbow in extension. Rotational range of motion was measured with use of a goniometer starting from a supinated position (0 degrees ). Specimens were placed in a vertical position at various angles of forearm rotation, and a 27-kg mass was raised to 90 cm and was dropped onto the distal part of the radius. The pressure film was removed and was analyzed to determine the radiocapitellar joint contact area following impact. Each arm was dissected, and the injury pattern was assessed. RESULTS: Both-bone forearm fractures (proximal radial fractures with concomitant distal ulnar fractures) occurred at 5 degrees +/- 2.6 degrees of rotation, isolated radial head fractures occurred at 44.4 degrees +/- 5.2 degrees of rotation, and Essex-Lopresti fractures (radial head fractures with tearing of the interosseous membrane) occurred at 70 degrees +/- 25.2 degrees of rotation. The distribution of Essex-Lopresti and radial head fractures was significantly different at a cutpoint of 54 degrees of forearm rotation (p = 0.009), and the distribution of radial head fractures and both-bone forearm fractures was significantly different at a cutpoint of 10 degrees of forearm rotation (p = 0.001). The percent contact area of the radial head varied with the injury pattern (p = 0.029). Marginal radial head fractures occurred at 46.7 degrees +/- 6.6 degrees of rotation with a contact area of 30.9% +/- 8.6%, while comminuted radial head fractures occurred at 74.4 degrees +/- 27.2 degrees of rotation with a contact area of 53.9% +/- 8.3%. CONCLUSION: The amount of forearm rotation at the time of axial load impact directly influenced the injury pattern. Furthermore, the radial head contact area and the fracture severity increased in pronation compared with supination.

Aged↗
PubMed2005

Patellofemoral pain and asymmetrical hip rotation.

BACKGROUND AND PURPOSE: Patellofemoral joint problems are the most common overuse injury of the lower extremity, and altered femoral or hip rotation may play a role in patellofemoral pain. The purpose of this case report is to describe the evaluation of and intervention for a patient with asymmetrical hip rotation and patellofemoral pain. CASE DESCRIPTION: The patient was a 15-year-old girl with an 8-month history of anterior right knee pain, without known trauma or injury. Prior to intervention, her score on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was 24%. Right hip medial (internal) rotation was less than left hip medial rotation, and manual muscle testing showed weakness of the right hip internal rotator and abductor muscles. The intervention was aimed at increasing right hip medial rotation, improving right hip muscle strength (eg, the muscle force exerted by a muscle or a group of muscles to overcome a resistance), and eliminating anterior right knee pain. OUTCOMES: After 6 visits (14 days), passive left and right hip medial rotations were symmetrical, and her right hip internal rotator and abductor muscle grades were Good plus. Her WOMAC score was 0%. DISCUSSION: The patient had right patellofemoral pain and an uncommon pattern of asymmetrical hip rotation, with diminished hip medial rotation and excessive hip lateral (external) rotation on the right side. The patient's outcomes suggest that femoral or hip joint asymmetry may be related to patellofemoral joint pain.

Adolescent↗