Can the acetabular position be derived from a pelvic frame of reference?
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ABSTRACT:
SUBMITTER: Dandachli W
PROVIDER: S-EPMC2650052 | biostudies-other | 2009 Apr
REPOSITORIES: biostudies-other
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Project description:BackgroundTransverse acetabular ligament (TAL) is a 3-dimensional structure which cannot be defined by a single plane. Therefore, we aimed at describing the orientation of different parts of TAL with respect to anterior pelvic plane (APP) and correlate it with gender, body mass index (BMI), and Lewinnek's safe zone.MethodsA total of 109 consecutive patients undergoing imageless navigated THA were prospectively studied. Computer navigation was used as the measurement tool. APP was registered for navigation. After excision of osteophytes, a trial component matching the size of unreamed acetabular cavity was aligned with acetabular rim, outer and inner margins, and middle of TAL to record cup orientation with computer tracker.ResultsNinety-nine patients (41 males and 58 females, mean BMI of 28.8kg/m2) were studied after applying exclusion criteria. Mean acetabular inclination was 55.15°, 53.00°, 47.70°, and 42.60° respectively, for acetabular rim, outer, middle, and inner margins of the TAL. Corresponding mean acetabular anteversion was 6.63°, 7.41°, 11.23° and 14.90°respectively. Overall, 17.17%, 28.28%, 47.47% and 71.71% of cup orientation corresponding to acetabular rim, outer, middle, and inner margin of TAL respectively, were within Lewinnek's safe zone. No association was established between BMI and acetabular orientation. Males had overall lesser anteversion than females.ConclusionWe describe orientation of outer, middle, and inner margins of TAL, as reference planes for TAL, in relation to APP. The anteversion differs significantly with gender. A knowledge about these will assist surgeon in component placement during THA, with inner margin of TAL providing the best chance of orientation out of the studied landmarks.
| S-EPMC7818603 | biostudies-literature
Project description:BackgroundDeviations from a conventional physiologic posture are often a cause of complaint. According to current literature, the upright physiological spine posture exhibits inclinations in the sagittal plane but not in the coronal and transverse planes, but individual vertebral body positions of asymptomatic adults have rarely been described using surface topography. Therefore, this work aims to form a normative reference dataset for the thoracic and lumbar vertebral bodies and for the pelvis in all three planes in asymptomatic women.MethodsIn a prospective, cross-sectional, monocentric study, 100 pain-free asymptomatic women, aged 20-64 years were enrolled. Habitual standing positions of the trunk were measured using surface topography. Data were analyzed in all three planes. Age sub-analysis was: 1) ages ≤ 40 years and 2) ages ≥ 41 years. Two-sample t-tests were used for age comparisons of the vertebral bodies, vertebra prominence (VP)-L4, and global parameters. One-sample t-tests were used to test deviations from symmetrical zero positions of VP-L4.ResultsCoronal plane: on average, the vertebral bodies were tilted to the right between the VP and T4 (maximum: T2 - 1.8° ± 3.2), while between T6 and T11 they were tilted to the left (maximum: T7 1.1° ± 1.9). T5 and L2 were in a neutral position, overall depicting a mean right-sided lateral flexion from T2 to T7 (apex at T5). Sagittal plane: the kyphotic apex resided at T8 with - 0.5° ± 3.6 and the lumbar lordotic apex at L3 with - 2.1° ± 7.4. Transverse plane: participants had a mean vertebral body rotation to the right ranging from T6 to L4 (maximum: T11 - 2.2° ± 3.5). Age-specific differences were seen in the sagittal plane and had little effect on overall posture.ConclusionsAsymptomatic female volunteers standing in a habitual posture displayed an average vertebral rotation and lateral flexion to the right in vertebral segments T2-T7. The physiological asymmetrical posture of women could be considered in spinal therapies. With regard to spinal surgery, it should be clarified whether an approximation to an absolutely symmetrical posture is desirable from a biomechanical point of view? This data set can also be used as a reference in clinical practice.Trial registrationThis study was registered with WHO (INT: DRKS00010834) and approved by the responsible ethics committee at the Rhineland-Palatinate Medical Association (837.194.16).
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Project description:Seeing the image of a newscaster on a television set causes us to think that the sound coming from the loudspeaker is actually coming from the screen. How images capture sounds is mysterious because the brain uses different methods for determining the locations of visual versus auditory stimuli. The retina senses the locations of visual objects with respect to the eyes, whereas differences in sound characteristics across the ears indicate the locations of sound sources referenced to the head. Here, we tested which reference frame (RF) is used when vision recalibrates perceived sound locations. Visually guided biases in sound localization were induced in seven humans and two monkeys who made eye movements to auditory or audiovisual stimuli. On audiovisual (training) trials, the visual component of the targets was displaced laterally by 5-6 degrees. Interleaved auditory-only (probe) trials served to evaluate the effect of experience with mismatched visual stimuli on auditory localization. We found that the displaced visual stimuli induced ventriloquism aftereffect in both humans (approximately 50% of the displacement size) and monkeys (approximately 25%), but only for locations around the trained spatial region, showing that audiovisual recalibration can be spatially specific. We tested the reference frame in which the recalibration occurs. On probe trials, we varied eye position relative to the head to dissociate head- from eye-centered RFs. Results indicate that both humans and monkeys use a mixture of the two RFs, suggesting that the neural mechanisms involved in ventriloquism occur in brain region(s) using a hybrid RF for encoding spatial information.
| S-EPMC2804958 | biostudies-literature
Project description:Repetitive experience with the same visual stimulus and task can remarkably improve behavioral performance on the task. This well-known perceptual-learning phenomenon is usually specific to the trained retinal- or visual-field location, which is taken as an indication of plastic changes in retinotopic visual areas. In previous studies of perceptual learning, however, a change in stimulus location on the retina is accompanied by positional changes of the stimulus in nonretinotopic frames of reference, such as relative to the head and other objects. It is unclear, therefore, whether the putative location specificity is exclusively retinotopic or if it could also depend on nonretinotopic representation of the stimulus, which is particularly important for multisensory and sensorimotor integration as well as for maintenance of stable visual percepts. Here, by manipulating subjects' gaze direction to control spatial and retinal locations of stimuli independently, we found that, when the stimulated retinal regions were held constant, the improvement with training in motion-direction discrimination of two successively displayed stimuli was restricted to the relative spatial position of the stimuli but independent of their absolute locations in head- and world-centered frame. These findings indicate location specificity of perceptual learning beyond retinotopic frame of reference, suggesting a pliable spatiotopic mechanism that can be specifically shaped by experience for better spatiotemporal integration of the learned stimuli.
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Project description:A 74-year-old female patient presented to our clinic with pelvic discontinuity after multiple revision total hip surgeries requiring custom triflange acetabular reconstruction, which we accomplished through a direct anterior approach to the hip. The direct anterior approach to the hip has grown in popularity but still has the reputation of being a minimally invasive approach without the capacity for extensile exposure in the revision setting. We describe the extensile technique and demonstrate through our case the ability to perform the most challenging cases through this approach and discuss the potential benefits of its utilization.
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Project description:BackgroundNerve injury during acetabular and pelvic fracture fixation can have devastating consequences for trauma patients already in a compromised situation.Questions/purposesThis study aims to evaluate the efficacy of multimodality intraoperative neurophysiologic monitoring during acetabular and pelvic fracture fixation in identifying emerging iatrogenic nerve injury.MethodsSixty patients were retrospectively identified after surgical fixation following acetabular or pelvic fracture. Neuromonitoring during surgery was performed using three different modalities, transcranial electric motor evoked potential (tceMEP), somatosensory evoked potential (SSEP), and electromyographic (EMG) monitoring. Each modality was evaluated for sensitivity and specificity of detecting an intraoperative nerve injury.ResultstceMEP monitoring was found to be 100% sensitive and 86% specific at detecting an impending nerve injury. The sensitivity and specificity of SSEP were 75% and 94%, while EMG sensitivity was unacceptably low at 20% although specificity was 93%.ConclusionsMultimodality neuromonitoring of transcranial electric motor and peroneal nerve somatosensory evoked potentials with or without spontaneous EMG monitoring is a safe and effective method for detecting impending nerve injury during acetabular and pelvic surgery.
| S-EPMC3772159 | biostudies-literature
Project description:The anterolateral approach in the supine position provides excellent visualization of the acetabulum. The main advantage of the approach, a low dislocation rate, has been demonstrated in the literature, while the purported disadvantage of abductor dysfunction has not been clearly delineated in the literature. The technique requires meticulous attention to preservation of the gluteus medius and minimus tendons. Impingement and dislocation are avoided by careful attention to the preparation of acetabulum, critical assessment of the implanted components, and intraoperative trialing. Leg lengths are assessed through direct palpation of the malleoli. Routine use of postoperative hip precautions is not necessary when this approach is utilized. The anterolateral approach in the supine position allows for a reproducible result with a low dislocation rate.Level V, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
| S-EPMC2600976 | biostudies-other
Project description:Vision requires a reference frame. To what extent does this reference frame depend on the structure of the visual input, rather than just on retinal landmarks? This question is particularly relevant to the perception of dynamic scenes, when keeping track of external motion relative to the retina is difficult. We tested human subjects' ability to discriminate the motion and temporal coherence of changing elements that were embedded in global patterns and whose perceptual organization was manipulated in a way that caused only minor changes to the retinal image. Coherence discriminations were always better when local elements were perceived to be organized as a global moving form than when they were perceived to be unorganized, individually moving entities. Our results indicate that perceived form influences the neural representation of its component features, and from this, we propose a new method for studying perceptual organization.
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Project description:Spatial navigation is an essential human skill that is influenced by several factors. The present study investigates how gender, age, and cultural background account for differences in reference frame proclivity and performance in a virtual navigation task. Using an online navigation study, we recorded reaction times, error rates (confusion of turning axis), and reference frame proclivity (egocentric vs. allocentric reference frame) of 1823 participants. Reaction times significantly varied with gender and age, but were only marginally influenced by the cultural background of participants. Error rates were in line with these results and exhibited a significant influence of gender and culture, but not age. Participants' cultural background significantly influenced reference frame selection; the majority of North-Americans preferred an allocentric strategy, while Latin-Americans preferred an egocentric navigation strategy. European and Asian groups were in between these two extremes. Neither the factor of age nor the factor of gender had a direct impact on participants' navigation strategies. The strong effects of cultural background on navigation strategies without the influence of gender or age underlines the importance of socialized spatial cognitive processes and argues for socio-economic analysis in studies investigating human navigation.
| S-EPMC4466779 | biostudies-other
Project description:Background and purpose - Hip dislocation is one of the most common complications following total hip arthroplasty (THA). Several factors that affect dislocation have been identified, including acetabular cup positioning. Optimal values for cup inclination and anteversion are debatable. We performed a systematic review to describe the different methods for measuring cup placement, target zones for cup positioning, and the association between cup positioning and dislocation following primary THA. Methods - A systematic search of literature in the PubMed database was performed (January and February 2016) to identify articles that compared acetabular cup positioning and the risk of dislocation. Surgical approach and methods for measurement of cup angles were also considered. Results - 28 articles were determined to be relevant to our research question. Some articles demonstrated that cup positioning influenced postoperative dislocation whereas others did not. The majority of articles could not identify a statistically significant difference between dislocating and non-dislocating THA with regard to mean angles of cup anteversion and inclination. Most of the articles that assessed cup placement within the Lewinnek safe zone did not show a statistically significant reduction in dislocation rate. Alternative target ranges have been proposed by several authors. Interpretation - The Lewinnek safe zone could not be justified. It is difficult to draw broad conclusions regarding a definitive target zone for cup positioning in THA, due to variability between studies and the likely multifactorial nature of THA dislocation. Future studies comparing cup positioning and dislocation rate should investigate surgical approach separately. Standardized tools for measurement of cup positioning should be implemented to allow comparison between studies.
| S-EPMC5251254 | biostudies-literature