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PubMed1998

Viewer-centered temporal biasing of 3-D rotation percepts.

The perceived direction of rotation of a 3-D cloud of dots can be biased by a prior rotation (Jiang, Pantle, and Mark, 1998 Perception & Psychophysics 60 275-286). In a series of experiments, it is shown that the temporal rotation bias is reversed by a 180 degrees change of head orientation between two rotation sequences; i.e. the perceived direction of rotation reverses for the second of two sequences when head orientation is changed. The bias is, therefore, viewer-centered. Perceptual reversals are not obtained when the orientation of the head is changed and returned to its original position between rotation sequences. It was also found that the viewer-centered bias combined additively with viewer-independent near-far luminance information. Finally, the bias was manifest when 3-D depth was re-established, but not maintained, between rotation sequences. A model, in descriptive and flowchart forms, is used to explain the integration of world-centered information and a viewer-centered temporal bias on the presence/absence of perceptual reversals of the rotating virtual sphere. In the model, the temporal bias is the result of the coupling of depth values to persisting 2-D retinal motion signals.

Computer Graphics↗
PubMed2001

Purine but not pyrimidine nucleotides support rotation of F(1)-ATPase.

The binding change model for the F(1)-ATPase predicts that its rotation is intimately correlated with the changes in the affinities of the three catalytic sites for nucleotides. If so, subtle differences in the nucleotide structure may have pronounced effects on rotation. Here we show by single-molecule imaging that purine nucleotides ATP, GTP, and ITP support rotation but pyrimidine nucleotides UTP and CTP do not, suggesting that the extra ring in purine is indispensable for proper operation of this molecular motor. Although the three purine nucleotides were bound to the enzyme at different rates, all showed similar rotational characteristics: counterclockwise rotation, 120 degrees steps each driven by hydrolysis of one nucleotide molecule, occasional back steps, rotary torque of approximately 40 piconewtons (pN).nm, and mechanical work done in a step of approximately 80 pN.nm. These latter characteristics are likely to be determined by the rotational mechanism built in the protein structure, which purine nucleotides can energize. With ATP and GTP, rotation was observed even when the free energy of hydrolysis was -80 pN.nm/molecule, indicating approximately 100% efficiency. Reconstituted F(o)F(1)-ATPase actively translocated protons by hydrolyzing ATP, GTP, and ITP, but CTP and UTP were not even hydrolyzed. Isolated F(1) very slowly hydrolyzed UTP (but not CTP), suggesting possible uncoupling from rotation.

Adenosine Triphosphate↗
PubMed2006

Contributions of joint rotations to racquet speed in the tennis serve.

The purpose of this study was to measure the contributions of the motions of body segments and joints to racquet head speed during the tennis serve. Nine experienced male players were studied using three-dimensional film analysis. Upper arm twist orientations were calculated with two alternative methods using joint centres and skin-attached markers. The results showed that skin-attached markers could not be used to calculate accurate upper arm twist orientations due to skin movement, and that the use of joint centres produced errors of more than 20 degrees in the upper arm twist orientation when the computed elbow flexion/extension angle exceeded 135 degrees in the final 0.03 s before impact. When there were large errors in the upper arm twist orientation, it was impossible to obtain accurate data for shoulder or elbow joint rotations about any axis. Considering only the contributors that could be measured within our standards of acceptable error, the approximate sequential order of main contributors to racquet speed between maximum knee flexion and impact was: shoulder external rotation, wrist extension, twist rotation of the lower trunk, twist rotation of the upper trunk relative to the lower trunk, shoulder abduction, elbow extension, ulnar deviation rotation, a second twist rotation of the upper trunk relative to the lower trunk, and wrist flexion. The elbow extension and wrist flexion contributions were especially large. Forearm pronation made a brief negative contribution. Computed contributions of shoulder internal rotation, elbow extension and forearm pronation within the final 0.03 s before impact were questionable due to the large degree of elbow extension. Near impact, the combined contribution of shoulder flexion/extension and abduction/adduction rotations to racquet speed was negligible.

Acceleration↗
PubMed2002

Impact of night-float rotation on sleep, mood, and alertness: the resident's perception.

Night-float rotations were designed to alleviate the workload of residents on night call and thereby improve patient safety. However, the impact of the night float on residents is yet to be surveyed. We assessed the impact of the night-float rotation on pediatric residents using an anonymous questionnaire that covered topics, based on recall, about sleep, mood, alertness, adjustment, and others. The study was conducted in a major tertiary pediatric teaching hospital in the United States. Participants were pediatric residents who had completed one or two night-float rotations and were in active training at our teaching hospital at the time of the study. Fifty-two of 60 eligible residents (87%) responded. Sleep duration during the night-float rotation was shorter than during day-shift work in 24 residents (46%), longer in 20 (38%), and unchanged in eight (15%). A higher proportion of residents took longer to fall asleep, had more difficulty falling asleep, had more sleep interruptions, and felt less rested upon awakening. Twenty-four residents (46%) felt that their bodies never adjusted to the night shift. Also, 22 residents (43%) felt moody or depressed in contrast to seven (14%) who felt depressed during the daytime rotation (p = 0.0001). Twenty-one residents (41%) felt they were slower in their thinking during the night float than daytime rotations. The results suggest that disturbances of sleep and mood and decreased alertness, typical of night shift, are present in the night-float rotation. Residency programs should monitor closely the impact of the night-float rotation on resident well being and patient safety. The impact of night-shift work should be considered in the design of night-float schedules, and teaching should be provided for residents to learn coping strategies for night-shift work.

Affect↗
PubMed2004

Opioid rotation in children with cancer.

The purpose of this retrospective study was to determine the therapeutic value of opioid rotation in a large pediatric oncology center. The details for opioid prescriptions, over the course of a year, were obtained from the medical records of children with cancer who had a rotation of opioid during their admission. Twenty-two children or 14% of children on opioid therapy underwent 30 opioid rotations. Mucositis was the cause of pain in 19 (70%) children, bone pain in 3 (11%) children, and postoperative, visceral, or neuropathic pain in the remainder. The opioid was rotated either for excessive side effects with adequate analgesia (70%), excessive side effects with inadequate analgesia (16.7%), or tolerance (6.7%). Five (23%) children required two rotations, 3 during the same admission. The favored rotations were morphine to fentanyl in 20 (67%) children and fentanyl to hydromorphone in 6 (20%). Adverse opioid effects were resolved in 90% of cases, all failures occurred when morphine was rotated to fentanyl. There was no significant loss of pain control or increase in mean morphine equivalent dose requirements. Opioid rotation had a positive impact on managing dose-limiting side effects of, or tolerance to, opioid therapy during cancer pain treatment in children. This was accomplished without loss of pain control or having to significantly increase the dose of opioid therapy.

Adolescent↗
PubMed1995

Rotational dynamics of luteinizing hormone receptors on bovine and ovine luteal cell plasma membranes.

To determine whether LH receptor rotational diffusion is similar in closely related species, we compared the rotational correlation times of LH receptors on bovine CL membranes with those of LH receptors on sheep small luteal cells and luteal cell plasma membranes using time-resolved phosphorescence anisotropy techniques. After binding of erythrosin isothiocyanate (ErITC)-derived bovine LH (bLH), ErITC-ovine LH (oLH), or ErITC-hCG, there was no difference in the initial and final anisotropy at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, indicating that the bLH receptor was rotationally immobile on the time scale of our experiments. On these same membrane preparations, the epidermal growth factor (EGF) receptor occupied by ErITC-murine EGF exhibited temperature-dependent rotational correlation times of 80 +/- 5 microseconds, 111 +/- 7 microseconds, 254 +/- 4 microseconds, and > 1000 microseconds at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, respectively. Slower rotational times for EGF receptor observed at higher temperatures suggested the occurrence of temperature-dependent receptor aggregation. Like the bLH receptor, the oLH receptor on intact cells and on CL plasma membranes was rotationally immobile on the time scale of our experiments when occupied by ErITC-hCG. However, the oLH-occupied receptors on small luteal cells and on luteal cell membranes had comparable rotational correlation times at 37 degrees C. These results suggest that bLH receptors are present in large, rotationally immobile structures, whereas the receptor-containing structure formed on ovine luteal cells depends on whether that receptor is occupied by hCG or oLH. Also, despite the similarities between reproductive function in these species, the LH-occupied receptor appears to be organized differently in the plasma membranes of these hormone-responsive luteal cells.

Animals↗
PubMedDate not supplied

Ultrasonography of the rotator cuff. Normal and pathologic anatomy.

Forty-eight patients with shoulder pain and 15 normal volunteers underwent rotator cuff imaging using high resolution real time ultrasound. The potential diagnostic value of sonography in detecting rotator cuff tears was evaluated by correlating ultrasound findings with surgical findings in 19 patients, 12 of whom also underwent preoperative arthrography. The preoperative ultrasound diagnosis was correct in 18 of the 19 patients undergoing surgery for possible rotator cuff tears. In the group of 12 surgical patients undergoing both preoperative arthrography and sonography, ultrasound correctly predicted the presence of a rotator cuff tear in 12 of 12 patients, while arthrography predicted cuff tears in only nine of 12. Good anatomic definition of the rotator cuff was obtained in both symptomatic and asymptomatic groups. The characteristic appearance of the normal and pathologic rotator cuff is described. Rotator cuff sonography promises to be a valuable new diagnostic tool for evaluating patients with suspected rotator cuff tears.

Adult↗
PubMed2004

Rotational malalignment of the tibia following reamed intramedullary nail fixation.

OBJECTIVE: To determine the incidence and severity of tibial malrotation following reamed intramedullary nail fixation as measured by computerized tomography and to determine the repeatability of computed tomography measurement in the assessment of rotational malreduction. DESIGN: Prospective cohort. SETTINGS: Level 1 trauma center. PARTICIPANTS: Twenty-five consecutive patients with 25 tibial shaft fractures. INTERVENTION: All patients were treated with reamed intramedullary nailing. Appropriate radiographs and a postoperative lower extremity computed tomography scan were obtained for each patient who consented to the study. MAIN OUTCOME MEASURE: Rotational alignment of affected tibia as compared to a version of the normal contralateral limb. Malrotation was defined as an internal/external rotation deformity greater than 10degrees. RESULTS: Malrotation, comparing the fractured limb to normal limb, was determined using a similar measurement method previously described in the literature. Two patients declined inclusion, and in one case, the computed tomography was not acceptable for analysis. Malrotation, comparing the fractured limb to the normal limb, was determined using the measurements from axial computed tomography images. Results revealed a mean absolute rotational difference of 6.7degrees (SD +/-6.3degrees). Rotational malreduction ranged from 15degrees of internal rotation to 22degrees of external rotation. Five of the 22 tibia (22%) were malrotated greater than 10degrees. A larger degree of deformity was seen with certain injury patterns. The intraobserver and interobserver repeatability testing revealed a mean absolute difference between paired malrotation calculations of 3.4degrees and 3.9degrees, respectively, and a repeatability coefficient of 8degrees for both. CONCLUSION: Computed tomography measurement is a repeatable method of assessing tibial torsion and in this study revealed a significantly higher incidence of rotational malreduction than that previously reported in the literature.

Adolescent↗
PubMed1997

Intraoperative optoelectronic analysis of three-dimensional vertebral displacement after Cotrel-Dubousset rod rotation. A preliminary report.

STUDY DESIGN: This study analyzed intraoperatively the three-dimensional displacement of vertebrae during rotation of the Cotrel-Dubousset rod for scoliosis correction, using an optoelectronic method. OBJECTIVE: To evaluate three-dimensional transitions and rotations of instrumented and uninstrumented vertebrae, produced by the Cotrel-Dubousset instrumentation "derotation" maneuver. SUMMARY OF BACKGROUND DATA: Published reports indicate that Cotrel-Dubousset instrumentation has been more effective in producing spinal derotation than vertebral axial derotation, but no study analyzed intraoperatively the effects on the vertebrae produced solely by rotation of the rod. METHODS: Eight patients with idiopathic scoliosis treated with Cotrel-Dubousset instrumentation underwent intraoperative optoelectronic monitoring using infrared cameras (Vicon). Markers were implanted in the spinous processes of the lower and upper instrumented vertebrae (LIV, UIV), the adjacent uninstrumented vertebrae below and above (-LIV, +UIV), and the apical vertebra. During rod rotation, acquisition and processing of cameras data were performed to obtain three-dimensional displacements of vertebrae. RESULTS: Translations and rotations of LIV and UIV were in identical directions to those of -LIV and +UIV, respectively. Orientation of the LIV hook influenced the displacement of LIV and -LIV. Posterior translation of the apical vertebra was commonly observed in thoracic King II, III, or V curvatures (apical vertebra = T9), and anterior translation in King I and IV and thoracolumbar curvatures (apical vertebra = T11-T12). Axial rotation of the apical vertebra was increased in thoracic curvatures and decreased in thoracolumbar and lumbar curvatures. Lateral translation was the major displacement observed. CONCLUSIONS: Rotation of the rod produces rotational and translational changes along each axis. These results are preliminary, but substantial. Technical improvement would allow more accurate results in the near future.

Adolescent↗
PubMed2002

Effect of derotation osteotomy of the femur on hip and pelvis rotations in hemiplegic and diplegic children.

The purpose of this study was to evaluate hip and pelvis rotations in groups of hemiplegic and diplegic children before and after surgical correction of fixed internal rotation deformity of the hip. Twenty-two children with cerebral palsy (eight diplegia, 14 hemiplegia) having fixed internal rotation deformity at the hip were treated by multilevel surgery which included derotation osteotomy of the femur. Evaluation was done before and at a mean of 3.1 years after surgery using three-dimensional computerized gait analysis. Preoperatively, the patients in the hemiplegia group had a significantly greater compensatory external rotation of the pelvis than those in the diplegic group. Post-operatively there were no significant differences between the two groups. In the hemiplegia group the external rotation of the pelvis was corrected after correction of hip rotation by derotation osteotomy. Patients in the diplegia group showed significant improvements in the hip rotation with no significant change in the pelvis rotation after multilevel surgery.

Adolescent↗
PubMed2003

An analysis of rotating-platform total knee replacements.

Rotating-platform, mobile-bearing total knee replacements have been developed to improve knee kinematics, lower contact stresses on the polyethylene tibial component, minimize constraint, and allow implant self-alignment. The purpose of the current study was to examine some of these parameters. Gait studies during normal gait showed that the stance phase was associated with knee flexion between 8 degrees and 15 degrees. Contact area studies have shown two types of rotating-platform total knee replacements, namely gait congruous (congruous only during the stance phase of gait) and totally congruous (congruous up to 90 degrees knee flexion) implants. Knee simulator studies have shown increased gravimetric wear with rotating-platform total knee replacements compared with their fixed-bearing counterparts. Rotate-only implants had less gravimetric wear than rotate and translate rotating-platform total knee replacements. Clinical studies show similar outcomes (knee scores, range of motion, and complications) when rotating-platform and fixed-bearing total knee replacements are compared. Although attractive, the benefits of rotating-platform total knee replacements still need to be proven.

Gait↗
PubMedDate not supplied

Factors associated with internal hip rotation gait in patients with cerebral palsy.

Internal rotation gait is common in children with cerebral palsy. Factors thought to contribute include femoral anteversion, hip flexor tightness, imbalance of hip rotators, and hamstring and adductor tightness. The exact cause of internal rotation must be defined before contemplating surgery. We investigated the prevalence of internal hip rotation and associated factors, which are considered to influence this walking pattern, in patients with cerebral palsy. Gait laboratory data of 222 patients with cerebral palsy were studied retrospectively. Two groups were selected; those with maximum dynamic hip internal rotation of more than 27 degrees and those with less than 20 degrees. Of 222 patients, 27.0% (diplegia, 61.7%; hemiplegia, 38.3%) had at least one hip with dynamic internal rotation of more than 27 degrees. This study suggests that dynamic hip internal rotation is multifactorial in origin. The most significant differences in clinical measures were found in values of passive hip external rotation range, femoral anteversion and hip flexor contracture. We discuss the role of early treatment of hip flexion contracture.

Adolescent↗
PubMed2005

Estimation of transverse plane pelvic rotation using a posterior-anterior radiograph.

STUDY DESIGN: Experimental and analytical study of transverse plane pelvic rotation. OBJECTIVES: To determine how pelvic rotation projected onto the transverse plane relates to coronal plane anatomic landmark location. SUMMARY OF BACKGROUND DATA: Current spine deformity instrumentation may be used to apply transverse plane loads to the spine that may be transmitted to regions not included in the instrumentation, including the pelvis. METHODS: An anatomically correct, sawbones model of an adult female pelvis was marked with lead shot at prominent radiographic landmarks, rotated at different angles in the sagittal, transverse, and coronal planes, and left/right (L/R) ratios of the medial-lateral distances between similar landmarks determined. An analytical equation was also derived to determine the degree of rotation in the transverse plane, using medial-lateral and anterior-posterior distances between same landmarks. RESULTS: The L/R ratio for the coronal plane distance between the inferior ilium at the sacro iliac joint (SI) and anterior superior iliac spine (ASIS), the SI-ASIS measurement, proved the most reliable of the four ratios studied to determine the extent of pelvic rotation in the transverse plane. Assuming the pelvis is symmetric, the most important factor is location of the compared landmarks. A long distance between the landmarks in both the coronal and transverse plane and a large angle between the line joining the two landmarks and the coronal plane of the pelvis, as viewed in the transverse plane, are best. Transverse plane pelvic rotation up to 20 degrees is accurately reflected nearly linearly by L/R SI-ASIS ratios. CONCLUSIONS: Bony pelvis landmarks visible on coronal plane radiographs can be used to estimate transverse plane pelvic rotation, but precise conversion to degrees rotation requires additional information on specific patient pelvic morphology.

Adult↗
PubMed2004

Effect of an intensive care unit rotating empiric antibiotic schedule on the development of hospital-acquired infections on the non-intensive care unit ward.

OBJECTIVE: We have previously shown that a rotating empirical antibiotic schedule could reduce infectious mortality in an intensive care unit (ICU). We hypothesized that this intervention would decrease infectious complications in the non-ICU ward to which these patients were transferred. DESIGN: Prospective cohort study. SETTING: An ICU and the ward to which the ICU patients were transferred at a university medical center. PATIENTS: All patients treated on the general, transplant, or trauma surgery services who developed hospital-acquired infection while on the non-ICU wards. INTERVENTIONS: A 2-yr study consisting of 1-yr non-protocol-driven antibiotic use and 1-yr quarterly rotating empirical antibiotic assignment for patients treated in the ICU from which a portion of the patients were transferred. MEASUREMENTS AND MAIN RESULTS: There were 2,088 admissions to the non-ICU wards during the nonrotation year and 2,183 during the ICU rotation year. Of these patients, 407 hospital-acquired infections were treated during the nonrotation year and 213 were treated during the ICU rotation (19.7 vs. 9.8 infections/100 admissions, p <.0001). During the ICU rotation year a decrease in the rate of resistant Gram-positive and resistant Gram-negative infections on the non-ICU wards occurred (2.5 vs. 1.6 infections/100 admissions, p =.04; 1.0 vs. 0.4 infections/100 admissions, p =.03). Subgroup analysis revealed that the decrease in resistant infections on the wards was due to a reduction in resistant Gram-positive and resistant Gram-negative infections among non-ICU ward patients admitted initially from areas other than the ICU implementing the antibiotic rotation (e.g., home, other ward, or a different ICU) (1.8 vs. 0.5 infections/100 admissions, p =.0001; 0.7 vs. 0.2 infections/100 admissions, p =.02), not due to differences for those transferred to the ward from the rotation ICU (10.4 vs. 9.7 infections/100 admissions, p = 1.0; 4.3 vs. 1.9 infections/100 admissions, p =.3). No differences in infection-related mortality were detected. CONCLUSIONS: An effective rotating empirical antibiotic schedule in an ICU is associated with a reduction in infectious morbidity (hospital-acquired and resistant hospital-acquired infection rates) on the non-ICU wards to which patients are transferred.

Anti-Bacterial Agents↗
PubMed2007

Lateral acetabular rotation improves anterior hip subluxation.

Surgical reorientation of the acetabulum is used to improve stability of subluxated or dysplastic hips, but the specific mechanical consequences of reorientation have not been quantified. I used a rigid body spring model of the human hip to study the effects of different acetabular positions on hip stability during single-limb stance. The model predicted subluxation direction and magnitude, and the effective joint contact area, as functions of acetabular position. Frontal plane acetabular orientation varied from 20 degrees medial rotation to 50 degrees lateral rotation, corresponding to center-edge angles from 0 degrees to 70 degrees. Sagittal acetabular orientation varied from 45 degrees anterior rotation to 15 degrees posterior rotation. Center-edge angles less than 20 degrees produced progressive anterolateral subluxation, with dislocation occurring when center-edge angles were less than 0 degrees. Lateral subluxation disappeared when cen-ter-edge angles were 30 degrees or greater. Anteroposterior subluxation was controlled by anterior or posterior rotation of the acetabulum in the presence of low center-edge angles, but there was no specific position of stability that effectively stabilized the femoral head. Anterior subluxation also was controlled by lateral rotation of the acetabulum. Joint contact area increased 1% for every 3 degrees lateral acetabular rotation. The anterolateral subluxation associated with hip dysplasia can be controlled by acetabular reorientation. Joint contact area will increase, thereby reducing peak joint pressure. Anterior and lateral subluxation can be improved by lateral rotation alone, which may reduce the severity of anterior femoroacetabular impingement after periacetabular osteotomy.

Acetabulum↗
PubMed2002

Instability of a thin film flowing on a rotating horizontal or inclined plane.

In this paper the instability of a thin fluid film flowing under the effects of gravity, Coriolis, and centrifugal forces is investigated. It is supposed that the film flows far from the axis of rotation on a plane which may be horizontal or inclined with respect to the horizontal. In the former case, the flow is only driven by the centrifugal force while in the latter case, the flow is driven by the components of centrifugal force and gravity along the plane. This case may also be considered as the flow down a rotating cone but far from the apex. The stabilizing influence of rotation on the film flow increases with the rotation rate. Up to a certain critical rate of rotation, the film flowing down the rotating inclined plane (or cone) is more stable than the flow on the horizontal rotating plane while above this rate of rotation the situation is reversed. The instability above the critical rate is associated with a finite wave number in contrast to the vanishing wave number of the instability below the critical rate. The possibility of Ekman layer instabilities is also investigated. An equation describing the nonlinear evolution of surface waves is also obtained. Moreover, this equation is simplified for the case in which the amplitudes are very small. An equation including dissipation as well as dispersion is derived whose solutions may possess solitary waves, as in the case of similar equations considered in the literature. These solutions are likely to correspond to the solitary spiral waves observed in experiments.

Journal Article↗
PubMed2003

Effect of rotation on a developed turbulent stratified convection: the hydrodynamic helicity, the alpha effect, and the effective drift velocity.

An effect of rotation on a developed turbulent stratified convection is studied. Dependences of the hydrodynamic helicity, the alpha tensor, and the effective drift velocity of the mean magnetic field on the rate of rotation and an anisotropy of turbulent convection are found. It is shown that in an anisotropic turbulent convection the alpha effect can change its sign depending on the rate of rotation. The evolution of the alpha effect is much more complicated than that of the hydrodynamic helicity in an anisotropic turbulent convection of a rotating fluid. Different properties of the effective drift velocity of the mean magnetic field in a rotating turbulent convection are found: (i) a poloidal effective drift velocity can be diamagnetic or paramagnetic depending on the rate of rotation; (ii) there is a difference in the effective drift velocities for the toroidal and poloidal magnetic fields; (iii) a toroidal effective drift velocity can play a role of an additional differential rotation. The above effects and an effect of a nonzero divergence of the effective drift velocity of the toroidal magnetic field on a magnetic dynamo in a developed turbulent stratified convection of a rotating fluid are studied. Astrophysical applications of the obtained results are discussed.

Journal Article↗
PubMed2005

Rotation flaps.

BACKGROUND: Rotation flaps are arcuate repairs that redistribute tension vectors and recruit adjacent and/or distant tissue laxity. Rotation allows for the closure of wounds that cannot be repaired along a single tension vector. A rich and evolving literature details the evolution of rotation as an elegant method of repair for surgical wounds. OBJECTIVE: The goal of this article is to understand the basic principles and proper execution of tissue rotation for the repair of facial operative wounds, with special attention given to the concept of pivotal restraint and with a step-by-step regional approach. METHODS AND MATERIALS: A review of the literature of dermatologic surgery, plastic surgery, and otolaryngology leads to a detailed understanding of rotation flap design and execution. RESULTS: Proper rotation flap design allows for the closure of large and complex wounds that will not close along one motion while minimizing tension vectors that affect adjacent free margins. CONCLUSIONS: The concept and execution of rotation are integral to the practice of dermatologic surgery. Proper design and undermining are essential to create an adequately sized flap and to free pivotal restraint to facilitate wound closure. In many cases, the arc of a rotation flap may be hidden within a natural cosmetic boundary, allowing for an elegant and minimally visible reconstruction.

Humans↗