Quadriceps muscle function following anterior cruciate ligament reconstruction: systemic differences in neural and morphological characteristics.

Quadriceps muscle dysfunction is common following anterior cruciate ligament reconstruction (ACLR). Data considering the diversity of neural changes, in-concert with morphological adaptations of the quadriceps muscle, are lacking. We investigated bilateral differences in neural and morphological characteristics of the quadriceps muscle in ACLR participants (n = 11, month post-surgery: 69.4 ± 22.4) compared to controls matched by sex, age, height, weight, limb dominance, and activity level. Spinal reflex excitability was assessed using Hoffmann reflexes (H:M); corticospinal excitability was quantified via active motor thresholds (AMT) and motor-evoked potentials (MEP) using transcranial magnetic stimulation. Cortical activation was assessed using a knee flexion/extension task with functional magnetic resonance imaging (fMRI). Muscle volume was quantified using structural MRI. Muscle strength and patient-reported outcomes were also collected. 2 × 2 RM ANOVAs were used to evaluate group differences. Smaller quadriceps muscle volume (total volume, rectus femoris, vastus medialis, and intermedius) and lower strength were detected compared to contralateral and control limbs. Individuals with ACLR reported higher levels of pain and fear and lower levels of knee function compared to controls. No differences were observed for H:M. ACLR individuals demonstrated higher AMT bilaterally and smaller MEPs in the injured limb, compared to the controls. ACLR participants demonstrated greater activation in frontal lobe areas responsible for motor and pain processing compared to controls, which were associated with self-reported pain. Our results suggest that individuals with ACLR demonstrate systemic neural differences compared to controls, which are observed concurrently with smaller quadriceps muscle volume, quadriceps muscle weakness, and self-reported dysfunction.

Implications of Thoracic Epidural Analgesia on Hospital Charges in Rib Fracture Patients.

Objective: Rib fractures are present in more than 150,000 patients admitted to US trauma centers each year. Those who fracture two or more ribs are typically treated with oral analgesic drugs and are discharged with few complications. The cost of this care generally reflects its brevity. When a patient fractures three or more ribs, there is an elevated risk of complication. In response, treatments are often broadened and their durations prolonged; this affects cost. While health, function, and survival have been widely explored, patient billing has not. Thus, we evaluated the financial implications of one mode of treatment for patients with rib fractures: thoracic epidural analgesia (TEA). Methods: We retrospectively analyzed the registry of a level II trauma center. All patients who fractured one or more ribs (n = 1,344) were considered; 382 of those patients were not candidates for epidural placement and were eliminated from analyses. Epidural placement was determined by individual clinicians. We used multiple linear regressions to determine predictors of cost. Results: After eliminating patients who were not eligible to receive TEA, the average patient bill was $59,123 ($10,631 per day of treatment). The administration of TEA predicted a 25% reduction in total billing (99% CI = -$21,429.55- -$7,794.66) and a 24% reduction in per-day billing (99% CI = -$3,745.99- -$1,276.14). Conclusions: Patients who received TEA were more severely injured and required longer treatments; controlling for these variables, the use of TEA associated with reductions in the cost of receiving care. From an administrative and insurance perspective, more frequent reliance on TEA may be indicated.

Improved Outcomes Associated with the Liberal Use of Thoracic Epidural Analgesia in Patients with Rib Fractures.

OBJECTIVE: Each year, more than 150,000 patients with rib fractures are admitted to US trauma centers; as many as 10% die. Effective pain control is critical to survival. One way to manage pain is thoracic epidural analgesia. If this treatment reduces mortality, more frequent use may be indicated. METHODS: We analyzed the patient registry of a level II trauma center. All patients admitted with one or more rib fractures (N = 1,347) were considered. Patients who were not candidates for epidural analgesia (N = 382) were eliminated. Mortality was assessed with binary logistic regressions. RESULTS: Across the total population, mortality was 6.7%; incidence of pneumonia was 11.1%; mechanical ventilation was required in 23.8% of patients, for an average duration of 10.0 days; average stay in the hospital was 7.7 nights; and 49.7% of patients were admitted to the ICU for an average of 7.2 nights. Epidural analgesia was administered to 18.4% of patients. After matching samples for candidacy, patients who received epidurals were 3.7 years older, fractured 2.6 more ribs, had higher injury severity scores, and were more likely to present with bilateral fractures, flail segments, pulmonary contusions, hemothoraces, and pneumothoraces. Despite greater injury severity, mortality among these patients was lower (0.5%) than those who received alternative care (1.9%). Controlling for age, injury severity, and use of mechanical ventilation, epidural analgesia predicted a 97% reduction in mortality. CONCLUSION: Thoracic epidural analgesia associates with reduced mortality in rib fracture patients. Better care of this population is likely to be facilitated by more frequent reliance on this treatment.

Optical performance test and validation of microcameras in multiscale, gigapixel imagers.

Wide field-of-view gigapixel imaging systems capable of diffraction-limited resolution and video-rate acquisition have a broad range of applications, including sports event broadcasting, security surveillance, astronomical observation, and bioimaging. The complexity of the system integration of such devices demands precision optical components that are fully characterized and qualified before being integrated into the final system. In this work, we present component and assembly level characterizations of microcameras in our first gigapixel camera, the AWARE-2. Based on the results of these measurements, we revised the optical design and assembly procedures to construct the second generation system, the AWARE-2 Retrofit, which shows significant improvement in image quality.

Laterality of quiet standing in old and young.

"Quiet standing" is standing without intended movement. To the naked eye, a person "quiet standing" on a rigid surface of support is stationary. In the laboratory quiet standing is indexed by behavior (at the millimeter scale) of the center of pressure (COP), the point location of the vertical ground reaction force vector (GRF). We asked whether quiet standing is lateralized and whether the COP dynamics of the right and left legs differ. In answer, we reexamined a previous quiet standing experiment (Kinsella-Shaw et al. in J Mot Behav 38:251-264, 2006) that used dual, side-by-side, force plates to investigate effects of age and embedding environment. All participants, old (M age = 72.2 ± 4.90 years) and young (M age = 22.8 ± 0.83 years), were right handed and right footed. Cross-recurrence quantification of the anterior-posterior and mediolateral coordinates of each COP revealed that, independent of age, and with no right GRF bias, right-leg coordination was (1) more dynamically stable and less noisy than left-leg coordination and (2) more responsive to changes in degree of visible structure. The results are considered in the context of theories of laterality inclusive of lateralized differences in postural dynamics.

Optomechanical design of multiscale gigapixel digital camera.

Recent developments in multiscale imaging systems have opened up the possibility for commercially viable wide-field gigapixel cameras. While multiscale design principles allow tremendous simplification of the optical design, they place increased emphasis on optomechanics and system level integration of the camera as a whole. In this paper we present the optomechanical design of a prototype two-gigapixel system (AWARE-2) that has been constructed and tested.

Effects of footedness and stance asymmetry confirm an inter-leg metastable coordination dynamics of standing posture.

We investigated the patterns of coordination between the left and right legs that support the task of maintaining an upright standing posture. We used cross-wavelet analyses to assess coordination between the centers of pressure under the left and right feet. We recruited participants with a lateralized functional preference for their right leg, and we manipulated whether these participants stood with symmetric/asymmetric stances and whether their eyes were open or closed. Our hypotheses were derived from the Haken-Kelso-Bunz (HKB) model of interlimb coordination dynamics. Consistent with HKB model predictions, we observed (1) coordination taking the form of metastable, transient epochs of stable phase relations, (2) preferences for in-phase and anti-phase coordination patterns, and (3) changes in pattern stability and phase leads associated with both stance asymmetry and right-side lateral preference. The form and stability of observed coordination patterns were mediated by the availability of visual information. Our findings confirm the existence of a metastable coordination dynamic associated with the task of maintaining upright stance. We discuss the implications of these findings in the context of evaluating the utility of the HKB model for understanding the functional organization of the posture system.

Haptic selective attention by foot and by hand.

Nonvisual perceptions of a wielded object's spatial properties are based on the quantities expressing the object's mass distribution, quantities that are invariant during the wielding. The mechanoreceptors underlying the kind of haptic perception involved in wielding - referred to as effortful, kinesthetic, or dynamic touch - are those embedded in the muscles, tendons, and ligaments. The present experiment's focus was the selectivity of this muscle-based form of haptic perception. For an occluded rod grasped by the hand at some intermediate position along its length, participants can attend to and report selectively the rod's full length, its partial lengths (fore or aft of the hand), and the position of the grip. The present experiment evaluated whether participants could similarly attend selectively when wielding by foot. For a given rod attached to and wielded by foot or attached to (i.e. grasped) and wielded by hand, participants reported (by magnitude production) the rod's whole length or fractional length leftward of the point of attachment. On measures of mean perceived length, accuracy, and reliability, the degree of differentiation of partial from full extent achieved by means of the foot matched that achieved by means of the hand. Despite their neural, anatomical, and experiential differences, the lower and upper limbs seem to abide by the same principles of selective muscle-based perception and seem to express this perceptual function with equal facility.

Effects of visual environment on quiet standing by young and old adults.

The authors manipulated the circumstances in which individuals are typically embedded when standing upright by manipulating the intensity of light and the stationary structure of the environment. They expected that the manipulations would affect 12 older participants (aged 65-82 years) more than it would 12 younger participants (aged 22-24 years). Linear (e.g., total path length) and nonlinear (e.g., maximum line length of recurrent points in phase space) measures of the center of pressure time series confirmed that expectation. Moreover, for some measures, there was a suggestion that participants' visual contrast sensitivity (an index of neurophysiological age) was a more important contributing factor overall than was their chronological age. In the Discussion, the authors highlight the significance of interactive effects of environmental, organismic, and task constraints on quiet standing.

Interleg coordination in quiet standing: influence of age and visual environment on noise and stability.

The authors reexamined reported effects of age, illumination, and stationary visible structure on the net center of pressure (COP) derived from dual, side-by-side force plates (J. Kinsella-Shaw, S. Harrison, C. Colon-Semenza, & M. Turvey, 2006 ) from the perspective of axial postural control. They questioned how left and right COP(x)(t), COP(y)(t), and vertically oriented ground reactive force, GRF(z)(t), coordinated during quiet standing. The Cross-recurrence Quantification (CRQ) revealed that coordination was primarily between fluctuations of similar direction, with coordination of left and right COP(y) (t) (anteroposterior fluctuations) dominant. CRQ also revealed that (a) illumination and structure affected the interlimb dynamics of older (M age = 72.2 ± 4.90 years) participants more than their younger (M age = 22.8 ± 0.83 years) counterparts, and (b) older participants exhibited greater interlimb entrainment (dynamical stability) in the presence of greater interlimb noise.

Deterministic and stochastic postural processes: effects of task, environment, and age.

Upright standing is always environmentally embedded and typically co-occurs with another (suprapostural) activity. In the present study, the authors investigate how these facts affect postural dynamics in an experiment in which younger (M age = 20.23 years, SD = 2.02 years) and older (M age = 75.26 years, SD = 4.87 years) participants performed a task of detecting letters in text or maintaining gaze within a target while standing upright in a structured or nonstructured stationary environment. They extracted the coefficients of drift (indexing attractor strength) and diffusion (indexing noise strength) from the center of pressure (COP) time series in anteroposterior (AP) and mediolateral (ML) axes. COP standard deviation decreased with drift and increased with diffusion. The authors found that structure reduced AP diffusion for both groups and that letter detection reduced younger SDAP (primarily by diffusion decrease) and increased older SDML (primarily by drift decrease). For older and younger participants, ML drift was lower during letter detection. Further, in older letter detection, larger visual contrast sensitivity was associated with larger ML drift and smaller SDML, raising the hypotheses that ML sway helps information detection and reflects neurophysiological age.