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PubMed2006

Does rotational strain at screw tightening affect the attainment or maintenance of osseointegration?

OBJECTIVES: This study investigated whether rotational strain affects osseointegration. MATERIAL AND METHODS: A total of 135 male rats were divided into five groups: 2-w rotation, 4-w rotation, 8-w rotation, 12-w rotation and control. Two hundred and seventy implants were inserted in rat tibia. The control group received no strain, while the 2-w, 4-w, 8-w and 12-w rotation groups received rotational strain at 2, 4, 8 and 12 weeks after implant placement, respectively. Removal torque (N cm) was measured in vivo. Bone contact rate (%) was calculated histomorphologically. Immunostaining for osteonectin (ON), osteopontin (OPN) and osteocalcin (OCN) was performed. The removal torque and bone contact rate were analyzed using one-way analyses of variance and the Scheffé method. RESULTS: At 4 weeks, the torque was significantly higher in the 2-w rotation group (1.30+/-0.44 N cm) than in the control group (0.79+/-0.67 N cm). From 8 to 16 weeks, the strained groups showed no significant differences from the control group. From the bone contact rates, bone formation was larger in the 4-week rotation group (62.9+/-10.7%) than in the control group (42.1+/-17.9%) at 8 weeks. The 4-week rotation group showed higher bone contact rate (61.1+/-11.3%) compared with the other strained groups and maintained this higher value until 16 weeks, showing no significant difference from the control group (72+/-5.2%). At the implant-bone interface, OPN was widely distributed and OCN was detected at a low level; however, ON could not be observed in any group. CONCLUSIONS: The bone contact rate changed when rotational strain was exerted at different periods after implant placement. However, the removal torque and distribution of extracellular matrix proteins were not adversely affected by the rotational strain.

Animals↗

PubMed1996

Errors in the control of joint rotations associated with inaccuracies in overarm throws.

1. Accurate overarm throwing requires precise control of joint rotations so that the ball is released at the appropriate time on the appropriate hand trajectory. Inaccuracy in throws, in turn, must result from errors in the control of joint rotations. But do high and low throws result from disorders in the joint rotations that produce the hand trajectory or in those that cause ball release? Are they due to error at a particular joint or to accumulation of errors across a number of joints? The objective was to answer these questions and thereby to gain insight into the CNS control of joint rotations in a skilled arm movement task. 2. Ten subjects--male, right-handed recreational ball players, all accurate throwers--sat with a fixed trunk and threw tennis balls at a 9 x 9 grid of 6-cm target squares 1.5 or 3 m away. Rotations of five arm segments in three dimensions were measured at 1,000 Hz with the magnetic-field search-coil technique. Hand trajectory (translation) was computed from these rotations. 3. The cause of ball high-low inaccuracy was investigated by determining its relation with hand kinematic parameters that could potentially affect it. No statistically significant relation was found between height of ball impact on the target and height of the hand trajectory. In contrast, statistically significant relations appeared between height of ball impact on the target and both hand trajectory length at ball release (for 8 of 10 subjects) and finger and hand orientation in space at ball release (for all 10 subjects). 4. Three hypotheses were proposed to explain the variable finger and hand orientations in space at ball release, i.e., that they resulted from errors in velocity of rotation at one or more proximal joints (wrist, elbow, shoulder), timing of onset of rotation at one or more proximal joints, or timing of ball release (due to incorrect velocity or timing of onset of finger opening). All three mechanisms could result in inappropriate finger and hand orientations in space at ball release, but the pattern of joint space trajectories would be different in each case. 5. High and low throws did not follow the joint space paths predicted by the first two hypotheses. Instead, as predicted by the third hypothesis, a separation of traces occurred when finger extension was plotted against wrist flexion or against elbow extension, e.g., for a given amplitude of wrist flexion, finger extension was large for the high throws and small for the low throws. 6. In agreement, when all throws were considered, a statistically significant (P < 0.005) relation was found between ball impact height on the target and the amplitude of finger extension, for a fixed amplitude of wrist flexion (10 subjects), and for a fixed amplitude of elbow extension (8 subjects). Only two subjects showed a statistically significant relation between ball impact height and the amplitude of wrist flexion, for a fixed amplitude of elbow extension. 7. The separation of finger extension-wrist flexion traces in joint space for high and low throws was due to a difference in the timing of onset of finger rotation with respect to the wrist rather than to an inappropriate velocity of the finger (or the wrist). 8. As expected, all 10 subjects showed statistically significant relations between the time of onset of finger extension and both finger orientation in space at ball release and height of ball impact on the target. 9. It is concluded that in fast arm-only throws made by male recreational ball players, high and low throws do not primarily result from variability in the height of the hand trajectory or from variability in the amplitude of one or more proximal joints due to errors in the velocity or timing of onset of these joint rotations. Instead, in most cases, they result from inappropriate timing of onset of rotation of the fingers with respect to the rotations of the other joints and thus to inappropriate timing of ball release. These findings emphasize the im

Arm↗

PubMed1996

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. I. Linear acceleration responses during off-vertical axis rotation.

1. The dynamic properties of otolith-ocular reflexes elicited by sinusoidal linear acceleration along the three cardinal head axes were studied during off-vertical axis rotations in rhesus monkeys. As the head rotates in space at constant velocity about an off-vertical axis, otolith-ocular reflexes are elicited in response to the sinusoidally varying linear acceleration (gravity) components along the interaural, nasooccipital, or vertical head axis. Because the frequency of these sinusoidal stimuli is proportional to the velocity of rotation, rotation at low and moderately fast speeds allows the study of the mid-and low-frequency dynamics of these otolith-ocular reflexes. 2. Animals were rotated in complete darkness in the yaw, pitch, and roll planes at velocities ranging between 7.4 and 184 degrees/s. Accordingly, otolith-ocular reflexes (manifested as sinusoidal modulations in eye position and/or slow-phase eye velocity) were quantitatively studied for stimulus frequencies ranging between 0.02 and 0.51 Hz. During yaw and roll rotation, torsional, vertical, and horizontal slow-phase eye velocity was sinusoidally modulated as a function of head position. The amplitudes of these responses were symmetric for rotations in opposite directions. In contrast, mainly vertical slow-phase eye velocity was modulated during pitch rotation. This modulation was asymmetric for rotations in opposite direction. 3. Each of these response components in a given rotation plane could be associated with an otolith-ocular response vector whose sensitivity, temporal phase, and spatial orientation were estimated on the basis of the amplitude and phase of sinusoidal modulations during both directions of rotation. Based on this analysis, which was performed either for slow-phase eye velocity alone or for total eye excursion (including both slow and fast eye movements), two distinct response patterns were observed: 1) response vectors with pronounced dynamics and spatial/temporal properties that could be characterized as the low-frequency range of "translational" otolith-ocular reflexes; and 2) response vectors associated with an eye position modulation in phase with head position ("tilt" otolith-ocular reflexes). 4. The responses associated with two otolith-ocular vectors with pronounced dynamics consisted of horizontal eye movements evoked as a function of gravity along the interaural axis and vertical eye movements elicited as a function of gravity along the vertical head axis. Both responses were characterized by a slow-phase eye velocity sensitivity that increased three- to five-fold and large phase changes of approximately 100-180 degrees between 0.02 and 0.51 Hz. These dynamic properties could suggest nontraditional temporal processing in utriculoocular and sacculoocular pathways, possibly involving spatiotemporal otolith-ocular interactions. 5. The two otolith-ocular vectors associated with eye position responses in phase with head position (tilt otolith-ocular reflexes) consisted of torsional eye movements in response to gravity along the interaural axis, and vertical eye movements in response to gravity along the nasooccipital head axis. These otolith-ocular responses did not result from an otolithic effect on slow eye movements alone. Particularly at high frequencies (i.e., high speed rotations), saccades were responsible for most of the modulation of torsional and vertical eye position, which was relatively large (on average +/- 8-10 degrees/g) and remained independent of frequency. Such reflex dynamics can be simulated by a direct coupling of primary otolith afferent inputs to the oculomotor plant. (ABSTRACT TRUNCATED)

Acceleration↗

PubMed2004

Excessive humeral external rotation results in increased shoulder laxity.

BACKGROUND: The quantitative relationship between increased anterior shoulder laxity and increased humeral external rotation observed in throwers remains unclear. HYPOTHESIS: An elongated anterior capsule, especially the anterior band of the inferior glenohumeral ligament, produced by excessive humeral external rotation will result in increased anterior shoulder laxity and increased humeral external rotation. STUDY DESIGN: Controlled laboratory study. METHODS: Seven cadaveric shoulders were tested to measure the humeral rotational range of motion, glenohumeral translations, and length of the anterior band of the inferior glenohumeral ligament. Data were collected for the intact shoulders and after nondestructive stretching of 10%, 20%, and 30% beyond maximum humeral external rotation. RESULTS: Nondestructive excessive external rotational stretching resulted in a significant increase in superior (30%, 3.3 mm) and inferior (30%, 2.3 mm) length of the anterior band of the inferior glenohumeral ligament, external rotation (30%, 35 degrees), and anterior (30%, 2.4 mm), inferior (30%, 2.2 mm), and anterior-posterior (30%, 5.1 mm) translations. There were significant positive linear correlations between the length of the anterior band of the inferior glenohumeral ligament, external rotation, and anterior translation. CONCLUSIONS: Excessive humeral external rotation results in an elongation of the anterior band of the inferior glenohumeral ligament and an increase in anterior and inferior glenohumeral translations and humeral external rotation. CLINICAL RELEVANCE: Repetitive excessive humeral external rotation observed in throwers may be one of the biomechanical causes for increased shoulder laxity and increased humeral external rotation.

Adult↗

PubMed2005

Rotational motion changes in the glenohumeral joint of the adolescent/Little League baseball player.

BACKGROUND: Differences in range of motion and rotational motion between the dominant and nondominant shoulders in throwing athletes are well documented, although the age at which these changes begin to occur is not known. HYPOTHESIS: Changes in glenohumeral rotational motion in the shoulder of the Little League/adolescent baseball player occur during the most formative years of physical development. STUDY DESIGN: Cross-sectional study. METHODS: Elevation, internal rotation at 90 degrees of abduction, and external rotation at 90 degrees of abduction were measured in the dominant and nondominant shoulders of 294 baseball players, aged 8 to 16 years. RESULTS: Analysis of variance revealed 2-way interactions between arm dominance by age for elevation (P = .005) and internal rotation (P = .001). Significant differences were noted between dominant and nondominant arms for internal rotation at 90 degrees (P = .001) and external rotation at 90 degrees (P = .001). Elevation, internal rotation at 90 degrees , external rotation at 90 degrees , and total range of motion varied significantly (P = .001) among age groups. Elevation in the dominant arms of 16-year-olds was on average 5.3 degrees less than in 8-year-olds (179.6 degrees vs 174.3 degrees ). In the nondominant arms, mean elevation for 16-year-olds was 5.6 degrees less than in 8-year-olds (179.7 degrees vs 174.1 degrees ). Internal rotation at 90 degrees for the dominant arms averaged 39.0 degrees at age 8 and only 21.3 degrees at age 16. In the non-dominant arms, internal rotation for 8-year-olds averaged 42.2 degrees and only 33.1 degrees for 16-year-olds. CONCLUSIONS: Elevation and total range of motion decreased as age increased. These changes may be consequences of both bone and soft tissue adaptation. The most dramatic decline in total range of motion was seen between the 13-year-olds and 14-year-olds, in the year before peak incidence of Little Leaguer's shoulder. This decrease in rotational motion may cause increased stress at the physis during throwing.

Adolescent↗

PubMed2002

Scaling of rotational inertia in murine rodents and two species of lizard.

Because the force required to rotate a body about an axis is directly proportional to its rotational inertia about the axis, it is likely that animals with high rotational inertia would be constrained in their turning abilities. Given that rotational inertia scales with mass(1.67) in geometrically similar animals, whereas the ability to apply torque scales with mass(1.00), larger animals would be expected to have more difficulty turning than smaller animals of similar shape. To determine how rotational inertia scales with body mass, we used the fact that the period of a physical pendulum is proportional to its rotational inertia(0.50), and measured rotational inertia in two groups of vertebrates with greatly different body shapes: murine rodents (Mus domesticus and Rattus norvegicus) and lizards (Iguana iguana and Varanus exanthematicus). Rotational inertia did not deviate significantly from isometric scaling in the murine rodents as a group or in the varanid lizards, scaling with mass(1.63) and mass(1.59), respectively. Although rotational inertia did scale with negative allometry in iguanas and rats alone, with mass(1.56) and mass(1.42), respectively, it still increased much more quickly with increasing mass than the predicted ability to apply torque. This suggests either that these animals are not constrained by rotational inertia because of their relatively small size or that larger rodents and lizards are poorer turners than smaller ones. The murine rodents had a 3.0- to 4.9-fold lower rotational inertia than similarly sized lizards of either species. Given that the basal synapsids had body proportions and limb configurations similar to those of modern lizards, we suggest that the loss of the large muscular tail and elongated body form during the evolution of cynodonts and mammals reduced rotational inertia and probably improved turning ability.

Animals↗

PubMed2006

Association of a large lateral extension of the acromion with rotator cuff tears.

BACKGROUND: Factors predisposing to tearing of the rotator cuff are poorly understood. We have observed that the acromion of patients with a rotator cuff tear very often appears large on anteroposterior radiographs or during surgery. The purpose of this study was to quantify the lateral extension of the acromion in patients with a full-thickness rotator cuff tear and in patients with an intact rotator cuff. METHODS: The lateral extension of the acromion was assessed on true anteroposterior radiographs made with the arm in neutral rotation. The distance from the glenoid plane to the lateral border of the acromion was divided by the distance from the glenoid plane to the lateral aspect of the humeral head to calculate the acromion index. This index was determined in a group of 102 patients (average age, 65.0 years) with a proven full-thickness rotator cuff tear, in an age and gender-matched group of forty-seven patients (average age, 63.7 years) with osteoarthritis of the shoulder and an intact rotator cuff, and in an age and gender-matched control group of seventy volunteers (average age, 64.4 years) with an intact rotator cuff as demonstrated by ultrasonography. RESULTS: The average acromion index (and standard deviation) was 0.73 +/- 0.06 in the shoulders with a full-thickness tear, 0.60 +/- 0.08 in those with osteoarthritis and an intact rotator cuff, and 0.64 +/- 0.06 in the asymptomatic, normal shoulders with an intact rotator cuff. The difference between the index in the shoulders with a full-thickness supraspinatus tear and the index in those with an intact rotator cuff was highly significant (p < 0.0001). CONCLUSIONS: A large lateral extension of the acromion appears to be associated with full-thickness tearing of the rotator cuff.

Acromion↗

PubMed2006

The demographic and morphological features of rotator cuff disease. A comparison of asymptomatic and symptomatic shoulders.

BACKGROUND: Very little comparative information is available regarding the demographic and morphological characteristics of asymptomatic and symptomatic rotator cuff tears. This information is important to provide insight into the natural history of rotator cuff disease and to identify which factors may be important in the development of pain. The purpose of the present study was to compare the morphological characteristics and prevalences of asymptomatic and symptomatic rotator cuff disease in patients who presented with unilateral shoulder pain. METHODS: Five hundred and eighty-eight consecutive patients in whom a standardized ultrasonographic study had been performed by an experienced radiologist for the assessment of unilateral shoulder pain were evaluated with regard to the presence and size of rotator cuff tears in each shoulder. The demographic factors that were analyzed included age, gender, side, and cuff thickness. All of these factors were evaluated with regard to their correlation with the presence of pain. RESULTS: Of the 588 consecutive patients who met the inclusion criteria, 212 had an intact rotator cuff bilaterally, 199 had a unilateral rotator cuff tear (either partial or full thickness), and 177 had a bilateral tear (either partial or full thickness). The presence of rotator cuff disease was highly correlated with age. The average age was 48.7 years for patients with no rotator cuff tear, 58.7 years for those with a unilateral tear, and 67.8 years for those with a bilateral tear. Logistic regression analysis indicated a 50% likelihood of a bilateral tear after the age of sixty-six years (p < 0.01). In patients with a bilateral rotator cuff tear in whom one tear was symptomatic and the other tear was asymptomatic, the symptomatic tear was significantly larger (p < 0.01). The average size of a symptomatic tear was 30% greater than that of an asymptomatic tear. Overall, patients who presented with a full-thickness symptomatic tear had a 35.5% prevalence of a full-thickness tear on the contralateral side. CONCLUSIONS: There is a high correlation between the onset of rotator cuff tears (either partial or full thickness) and increasing age. Bilateral rotator cuff disease, either symptomatic or asymptomatic, is common in patients who present with unilateral symptomatic disease. As the size of a tear appears to be an important factor in the development of symptoms, we recommend surveillance at yearly intervals for patients with known rotator cuff tears that are treated nonoperatively.

Female↗

PubMed1990

Catecholaminergic responses to rotational stress in rat brain stem: implications for amphetamine therapy of motion sickness.

The fact that amphetamine, a noradrenaline releaser, prevents motion sickness leads the hypothesis of Wood and Graybiel that the noradrenergic neuron system in the brain stem acts against the development of motion sickness. To evaluate the hypothesis, the effects of rotational stress on the turnovers of noradrenaline and dopamine in the rat brain stem were examined. Rats were rotated about two axes simultaneously (double rotational) or about one axis (single rotation) for 60 min. Measurement of kaolin intake (pica) induced by rotation, as an index of motion sickness, showed that double rotation produced motion sickness, whereas single rotation did not. Both single and double rotation significantly increased the turnovers of noradrenaline and dopamine in the brain stem. However, there were no significant differences between the increases in catecholamine turnover induced by double and single rotations. Moreover, pretreatment of rats with methamphetamine (5 mg/kg) just before double rotation, which prevented the induction of motion sickness by double rotation, did not affect increases of the catecholamine turnover in the brain stem by double rotation. These findings do not support the hypothesis of Wood and Graybiel, suggesting that the catecholaminergic neuron systems in the brain stem are not involved in motion sickness and that the therapeutic effect of methamphetamine is not due to its direct effect on the brain stem.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1982

Rotation of cells in an alternating electric field: theory and experimental proof.

Protoplasts of Avena sativa rotate in an alternating electric field provided that at least two cells are located close to each other. An optimum frequency range (20 to 30 kHz) exists where rotation of all cells exposed to the field is observed. Below and above this frequency range, rotation of some cells is only occasionally observed. The angular velocity of rotation depends on the square of the electric field strength. At field strengths above the value leading to electrical breakdown of the cell membrane, rotation is no longer observed due to deterioration of the cells. The absolute value of the angular velocity of rotation at a given field strength depends on the arrangement of the cells in the electric field. A maximum value is obtained if the angle between the field direction and the line connecting the two cells is 45 degrees. With increasing distance between the two cells the rotation speed decreases. Furthermore, if two cells of different radii are positioned close to each other the cell with the smaller radius will rotate with a higher speed than the larger one. Rotation of cells in an alternating electric field is described theoretically by interaction between induced dipoles in adjacent cells. The optimum frequency range for rotation is related to the relaxation of the polarization process in the cell. The quadratic dependence of the angular velocity of rotation on the field strength results from the fact that the torque is the product of the external field and the induced dipole moment which is itself proportional to the external field. The theoretical and experimental results may be relevant for cyclosis (rotational streaming of cytoplasm) in living cells.

Cell Membrane↗

PubMed1995

The impact of an ambulatory rotation on medical student interest in internal medicine. The Society of General Internal Medicine Task Force on Career Choice in Internal Medicine.

OBJECTIVE: To determine whether students who take ambulatory rotations in internal medicine are more likely to choose internal medicine careers. DESIGN: National survey. SETTING AND PARTICIPANTS: The intended sample was 1,650 senior U.S. medical students from 16 medical schools, of whom 1,244 (76%) responded. Representative schools nationwide were selected using a stratified, random-sampling method. MEASUREMENTS: The questionnaire asked about characteristics of the ambulatory rotation, perceptions of internal medicine, and factors influencing students toward or away from an internal medicine career. RESULTS: Ambulatory rotations were taken by 543 students (43%). Of these rotations, 73% were required, 74% were during the fourth year, 77% were in general internal medicine, 73% provided continuity of care, and 19% were during the medicine clerkship. Overall, 24% of the students chose careers in general (9%) or subspecialty internal medicine (15%). Thirty percent of the students who did ambulatory rotations planned internal medicine careers, compared with 19% of the students who had no rotation [odds ratio (OR) = 1.8, 95% confidence interval (CI) 1.3 to 2.4, p = 0.0001]. This association was of similar magnitudes for students completing required rotations (OR = 1.6, 95% CI 1.2 to 2.2, p = 0.002) and for students completing rotations before or in proximity to when they chose careers (OR = 1.7, 95% CI 1.1 to 2.4, p = 0.01). Ninety percent of the 543 students who had ambulatory rotations were satisfied with the experience. Thirty-eight percent of the highly satisfied students chose internal medicine careers, compared with 21% of the students who had low or moderate satisfaction (p = 0.0001). CONCLUSIONS: An ambulatory rotation is strongly associated with positive perceptions of, attraction to, and choice of a career in internal medicine. Research is needed to determine specific components of an effective rotation. Further development of ambulatory rotations could help attract more students to internal medicine.

Adult↗

PubMed2005

The degrees to which transtrochanteric rotational osteotomy moves the region of osteonecrotic femoral head out of the weight-bearing area as evaluated by computer simulation.

BACKGROUND: Transtrochanteric rotational osteotomy is a technical demanding procedure. Currently, the pre-operative planning of the transtrochanteric rotational osteotomy is mostly based on X-ray images. The surgeons would need to reconstruct the three-dimensional structure of the femoral head and the necrosis in their mind. This study develops a simulation platform using computer models based on the computed tomography images of the femoral head to evaluate the degree to which transtrochanteric rotational osteotomy moves the region of osteonecrotic femoral head out of the weight-bearing area in stance and gait cycle conditions. Based on this simulation procedure, the surgeons would be better informed before the surgery and the indication can be carefully assessed. METHOD: A case with osteonecrosis involving 15% of the femoral head was recruited. Virtual models with the same size lesion but at different locations were devised. Computer models were created using SolidWorks 2000 CAD software. The area ratio of weight-bearing zone occupied by the necrotic lesion on two conditions, stance and gait cycle, were measured after surgery simulations. FINDINGS: For the specific case and virtual models devised in this study, computer simulation showed the following two findings: (1) The degrees needed to move the necrosis out of the weight-bearing zone in stance were less by anterior rotational osteotomy as compared to that of posterior rotational osteotomy. However, the necrotic region would still overlap with the weight-bearing area during gait cycle. (2) Because the degrees allowed for posterior rotation were less restricted than anterior rotation, posterior rotational osteotomies were often more effective to move the necrotic region out of the weight-bearing area during gait cycle. INTERPRETATION: The computer simulation platform by registering actual CT images is a useful tool to assess the direction and degrees needed for transtrochanteric rotational osteotomy. Although the results indicated that anterior rotational osteotomy was more effective to move the necrosis out of the weight-bearing zone in stance for models devised in this study, in circumstances where the necrotic region located at various locale, considering the limitation of anterior rotation inherited with the risk of vascular compromise, it might be more beneficial to perform posterior rotation osteotomy in taking account of gait cycle.

Computer Simulation↗

PubMed2005

How should medical student surgical rotations be structured to optimize education?

BACKGROUND: Surgical rotations for medical students have traditionally been service-based, with students observing surgical cases in an area of concentration specific to their assigned service. This may result in a lack of exposure to other surgical fields. To overcome this problem, students may rotate through focused "mini-rotations" in surgical subspecialties. We evaluated improvements in knowledge for students exposed to the two following types of surgical education: (1) traditional service-based rotations and (2) focused mini-rotations in a surgical subspecialty. METHODS: Third-year medical students (n = 281) were assigned to a 4-week rotation on one of three services, with students on one service having a focused exposure to endocrine surgery. General surgical services included (1) surgical oncology/endocrine, (2) trauma, and (3) general surgery. In addition, all students were required to do a "mini-rotation" on vascular surgery for 2 days. To determine if there was a difference in learning between service-based (endocrine) versus mini-rotation-based (vascular) approaches to surgical education, a pre- and postrotation endocrine/vascular exam was administered. RESULTS: Students with exposure to endocrine surgery had a 2-fold improvement in endocrine exam test scores (P = 0.001) compared to students on other general surgery services. There was no difference in vascular exam scores between students on different surgical rotations, reflecting the fact that all students had exposure to vascular surgery. CONCLUSION: Service-based rotations can lead to disproportionate learning experiences due to variations in exposure. "Mini-rotations" appear to equalize learning opportunities by providing all students with exposure to surgical subspecialties. These results suggest that educational experiences may be maximized by incorporating focused mini-rotations in surgical subspecialties.

Education, Medical, Undergraduate↗

PubMed2005

Measurement of prostate rotation during insertion of needles for brachytherapy.

BACKGROUND AND PURPOSE: The purpose of this study is to investigate whether prostate rotation due to needle insertion for prostate brachytherapy is predictable and if so, to quantify this rotation, and to see whether locking needles reduce the magnitude of prostate rotation. PATIENTS AND METHODS: The measurements are done at the beginning of the procedure for brachytherapy with a Foley catheter in situ. After a needle is inserted into the prostate, a 3D ultrasound scan is made. Then the seeds are delivered using RAPID Strands (Oncura), and the needle is withdrawn. A second 3D scan is made. The needle and seed positions are determined in these scans. To determine the rotation of the prostate, the angle between the needle and the seed trajectory is calculated. RESULTS: The prostate rotations have been measured in 16 patients, eight without the use of locking needles and eight with locking needles. In total 62 needles were inserted. The maximum rotation was 13.8 degrees and occurred in the coronal plane when no locking needles were used with a significant correlation (P<0.01, R=0.637) between the place of insertion and rotation. It was shown that the method (with or without locking needles) had a significant (P<0.001) influence on the rotation in the coronal plane. Rotations in the sagittal plane ranged from -8.5 degrees to +10.2 degrees without correlation with the insertion point of the needle or the use of locking needles. CONCLUSIONS: This study showed that prostate rotation during needle insertion for prostate brachytherapy is relatively large and unpredictable. Locking needles reduce prostate rotation in the coronal plane, but not in the sagittal plane. Minimising this rotation is necessary for accurate seed delivery, especially when a robotic implantation technique is used.

Brachytherapy↗

PubMed2004

PCR amplification of RoTat 1.2 VSG gene in Trypanosoma evansi isolates in Kenya.

A direct card agglutination test for Trypanosoma evansi, CATT/T. evansi based on the predominant variable antigen-type (pVAT) RoTat 1.2 was evaluated previously in the field in Isiolo District, Kenya. Sixteen out of 51 (31.4%) parasitologically positive camels were negative by the antibody detection test. In the present study, trypanosomes isolated from the camels were analysed in an attempt to determine the cause of the false negative results of CATT/T. evansi. A total of 20 field isolates comprised 16 stocks from camels that were negative by CATT/T. evansi, and 4 from CATT/T. evansi-positive camels. In addition, 15 known T. evansi and four T. brucei were used as reference. Purified DNA samples were tested using an established RoTat 1.2-based polymerase chain reaction (PCR) that yields a 488 bp product for the specific detection of T. evansi. Antibodies to RoTat 1.2 variant surface glycoprotein (VSG) were used in Western blotting to detect RoTat 1.2 VSG linear epitopes. Results of PCR and Western blot showed that the 16 stocks isolated from CATT/T. evansi-negative camels fell into three groups. In Group 1, both the RoTat 1.2 VSG gene and the VSG were absent in three stocks. In five trypanosome stocks in Group 2, the RoTat 1.2 VSG gene was detected, but Western blot was negative indicating absence of the expressed VSG. Five other stocks containing the RoTat 1.2 VSG gene were also in this group. The RoTat 1.2 VSG gene was detected and Western blot was positive in all four trypanosome stocks in Group 3. All four stocks from CATT/T. evansi-positive camels contained the RoTat 1.2 VSG gene and the expressed VSG. The reference T. evansi KETRI 2479 lacked the RoTat 1.2 VSG gene and there was no immune reactivity detected by Western blot. The rest of the reference T. evansi stocks examined contained the RoTat 1.2 VSG gene. All the four T. brucei samples examined were negative by PCR and Western blot. In conclusion, this study showed that the RoTat 1.2 VSG gene was absent from some T. evansi trypanosomes in Kenya.

Animals↗

PubMed2000

Do the hamstrings and adductors contribute to excessive internal rotation of the hip in persons with cerebral palsy?

Children with cerebral palsy frequently walk with excessive internal rotation of the hip. Spastic medial hamstrings or adductors are presumed to contribute to the excessive internal rotation in some patients; however, the capacity of these muscles to produce internal rotation during walking in individuals with cerebral palsy has not been adequately investigated. The purpose of this study was to determine the hip rotation moment arms of the medial hamstrings and adductors in persons who walk with a crouched, internally-rotated gait. Highly accurate computer models of three subjects with cerebral palsy were created from magnetic resonance images. These subject-specific models were used in conjunction with joint kinematics obtained from gait analysis to calculate the rotational moment arms of the muscles at body positions corresponding to each subject's internally-rotated gait. Analysis of the models revealed that the medial hamstrings, adductor brevis, and gracilis had negligible or external rotation moment arms throughout the gait cycle in all three subjects. The adductor longus had an internal rotation moment arm in two of the subjects, but the moment arm was small (<4 mm) in each case. These findings indicate that neither the medial hamstrings nor the adductor brevis, adductor longus, or gracilis are likely to be important contributors to excessive internal rotation of the hip. This suggests that these muscles should not be lengthened to treat excessive internal rotation of the hip and that other factors are more likely to cause internally-rotated gait in these patients.

Adolescent↗

PubMed1979

Differential polarized phase fluorometric investigations of diphenylhexatriene in lipid bilayers. Quantitation of hindered depolarizing rotations.

Differential polarized phase fluorometry has been used to investigate the depolarizing rotations of 1,6-diphenyl-1,3,5-hexatriene (DPH) in isotropic solvents and in lipid bilayers. For DPH dissolved in isotropic solvents, there is a precise agreement between the observed and predicted values for maximum differential tangents, indicating that in these media DPH is a free isotropic rotator. In lipid bilayers the tangent defects (i.e., the differences between the calculated and the observed maximum differential tangents) are too large to be explained by anisotropy in the depolarizing rotations but are accounted for by hindered isotropic torsional motions for the fluorophore [Weber, G (1978) Acta Phys. Pol A 54, 173]. This theory describes the depolarizing rotations of the fluorophore by its rotational rate R (in radians/second) and the limiting fluorescence anisotropy (r) at times long compared with the fluorescence lifetime. Through the combined use of both steady-state anisotropy measurements and differential phase measurements, we have demonstrated that one may obtain unique solutions for both R and r. For DPH embedded in vesicles prepared from dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholines, the depolarizing motions are highly hindered at temperatures below the transition temperature (Tc) but are unhindered above Tc. The apparent rotational rates of the probe do not change significantly at Tc. These data suggest that the changes observed in the steady-state anisotropy near Tc derive primarily from changes in the degree to which the probe's rotations are hindered, and only to a small extent from changes in rotational rate. For DPH embedded in bilayers that contained 25 mol % cholesterol, no clear transition occurred and the rotations appeared to be hindered at all temperatures. The rotational motions of DPH embedded in dioleolyphosphatidylcholine were found to be far less hindered, but the rotational rates were similar to those obtained in the saturated phosphatidylcholines. Finally, the data show that in an anisotropic environment, such as that of a lipid bilayer, steady-state fluorescence anisotropy measurements alone cannot yield quantitatively meaningful rotational rates. Extrapolation of steady-state aniosotropy data to the quantitation of membrane viscosity is therefore difficult, if not invalid; however, qualitative comparisons can be useful.

Fluorescence Polarization↗

PubMed2005

Characteristics of job rotation in the Midwest US manufacturing sector.

Job rotation has been advocated as a suitable intervention to control work-related musculoskeletal disorders. However, little is known regarding the prevalence of job rotation, methods used to identify jobs for rotation or the benefits or limitations of job rotation. A web-based questionnaire was developed to survey job rotation practices from Midwest US manufacturing companies. Results indicated that 42.7% of the companies contacted used job rotation, where the median time for which they had used job rotation was 5 years. Job rotation was used mainly to reduce exposure to risk factors for work-related injuries and to reduce work related injuries, whereas supervisor decisions and ergonomic analyses were used to select jobs for the rotation scheme. Major limitations to successful implementation of job rotation included rotation of individuals with medical restrictions, decreased product quality and lack of jobs to rotate to. These findings suggest that further study is needed to determine if exposure to risk factors is reduced through current efforts.

Data Collection↗