Central cone design demonstrates greater micromotion compared to keel design in cementless tibial baseplates: A biomechanical analysis.

PURPOSE: The purpose of this study was to compare micromotion of two new cementless tibial baseplates to a cementless design with well-published clinical success. METHODS: Three cementless tibial baseplate designs (fixed-bearing [FB] with keel and cruciform pegs, rotating-platform with porous central cone and pegs, FB with cruciform keel and scalloped pegs) were evaluated on sawbone models. Loading was applied to the baseplate at a rate of 1 Hz for 10,000 cycles, which represents 6-8 weeks of stair descent. This time frame also represents the approximate time length for the induction of biologic fixation of cementless implants. Compressive and shear micromotion at the sawbone-implant interface were measured. RESULTS: At the end of the loading protocol, the central cone rotating-platform design exhibited greater micromotion at the anterior (p < 0.001), posterior (p < 0.001) and medial locations (p = 0.049) compared to the other two implants. The central cone design also exhibited greater translational micromotion in the sagittal plane at the medial (p = 0.001) and lateral locations (p = 0.034) and in the coronal plane anteriorly (p = 0.007). CONCLUSION: The cementless central cone rotating-platform baseplate demonstrated greater vertical and translational micromotion compared to the two FB baseplates with a keel underloading. This may indicate lower initial mechanical stability in implants without a keel, which possibly affects osseointegration. The implication of this is yet unknown and requires further long-term clinical follow-up to correlate these laboratory findings. LEVEL OF EVIDENCE: V (biomechanical study).

Electrodermal and central measures of the tonic orienting reflex (OR).

Sokolov described both phasic and tonic aspects of the Orienting Reflex (OR), but subsequent research and theory development has focussed primarily on the phasic OR at the expense of the tonic OR. The present study used prestimulus skin conductance level (SCL) during a dishabituation paradigm to model the tonic OR, examining its amplitude patterning over repeated standard stimulus presentations and a change stimulus. We expected sensitisation (increased amplitude) following the initial and change trials, and habituation (decrement) over the intervening trials. Prestimulus EEG alpha level was explored as a potential central measure of the tonic OR (as an inverse correlate), examining its pattern over stimulus repetition and change in relation to the SCL model. We presented a habituation series of innocuous auditory stimuli to two groups (each N = 20) at different ISIs (Long 13-15 s and Short 5-7 s) and recorded electrodermal and EEG data during two counterbalanced conditions; Indifferent: no task requirements; Significant: silent counting. Across groups and conditions, prestimulus SCLs and alpha amplitudes generally showed the expected trials patterns, confirming our main hypotheses. Findings have important implications for including the assessment of Sokolov's tonic OR in modelling central and autonomic nervous system interactions of fundamental attention and learning processes.

Effects of interstimulus interval and significance on electrodermal and central measures of the phasic orienting reflex (OR) in a dishabituation task.

Although the P300 event-related potential (ERP) is the most likely central measure of Sokolov's Orienting Reflex (OR), there are few systematic comparisons with the skin conductance response (SCR), the "gold standard" electrodermal OR measure. We examine habituation, stimulus significance, and inter-stimulus interval (ISI) effects in SCRs and components of the P300 from single-trial ERPs in an auditory dishabituation paradigm. Single trial ERP components were separated by temporal principal components analysis, and five components of the P300 were examined as potential phasic OR measures: P3a, P3b, Novelty P3, and two Slow Waves (SW1, SW2). Across the factors of ISI and significance, SCRs showed decrement over trials, recovery at a deviant, and dishabituation at the subsequent standard. This general pattern was not present in any of the components of the P300. SCRs were also larger to significant stimuli and at the long ISI; effects differed between P300 components. The electrodermal SCR showed the complete profile over trials expected of the phasic OR, and was enhanced by stimulus significance, confirming it as the model measure of Sokolov's phasic OR. Components of the P300 failed to match this profile, but instead appear to reflect different aspects of the stimulus processing involved in OR elicitation.

Stimulus intensity effects and sequential processing in the passive auditory ERP.

Auditory stimulus intensity of innocuous tones is generally thought to have a direct effect on the amplitude of ERP components, but these effects have rarely been explored across a wide component range, or in multiple paradigms. Here we investigate component sensitivity to stimulus intensity differences in two studies. Study 1 (N = 36) employed a between-participants paradigm in which repeated trains of standard stimuli were presented as 50 or 80 dB SPL 1000 Hz tones. Study 2 (N = 18) used a within-participant presentation of alternating 60 and 80 dB SPL 1000 Hz tones. Electrode caps with 19 channels (referred to linked ears) generated ERPs covering the first 600 ms of each participant's EEG responses; these were submitted to separate temporal PCAs in each study. A similar series of components was obtained in each study: P1, N1a, N1b, N1c, P2, P3a, P3b, nP3, SW1, and SW2; an N2 was found in Study 2 only. Loud tones in Study 1 produced greater amplitudes in all components except SW1. In Study 2, Loud cf. Soft tones produced smaller P1 and nP3, larger N1 components, P2, and P3a, with no effect on N2, P3b, SW1 or SW2. These results indicate similar sequential processes underlying sensory processing in one- and two-stimulus paradigms, with the later stimulus intensity effects varying with paradigm.

The Effect of Sensory Deficit After Total Knee Arthroplasty on Patient Satisfaction and Kneeling Ability.

BACKGROUND: Skin numbness after total knee arthroplasty is a common complication. The incidence in the literature is variable from 27% to 100%. However, there is conflicting evidence about the consequences of this complication. The purpose of this study was to evaluate if postoperative numbness influenced patient satisfaction or kneeling ability. METHODS: We recruited patients who underwent a total knee arthroplasty for osteoarthritis one to 5 years before the study. Sensation was measured using a Semmes-Weinstein, 10-gram monofilament. Measurements were taken in several zones around the incision, and overall sensory status was classified as full numbness, partial numbness, and no numbness. Patients completed a questionnaire evaluating their subjective numbness, overall satisfaction, and kneeling ability. We evaluated the effect of numbness on satisfaction and function. RESULTS: A total of 96 patients were enrolled. Thirty-four patients were classified as no sensory deficit, 29 as partial deficit, and 33 as full deficit. There were no differences in demographics. Out of all the patients that were found to have a sensory deficit, 54.8% of them did not report any subjective numbness. Average patient-reported satisfaction scores were 8.76/10, 8.97/10, and 8.48/10 for no numbness, partial numbness, and full numbness, respectively. Eleven out of 96 patients noted an inability to kneel. There was no statistical difference for satisfaction scores or kneeling ability between the groups. CONCLUSION: Sensory deficit after total knee arthroplasty is a frequently reported complication. However, the majority of the patients do not report subjective sensory deficits. Postoperative numbness does not appear to affect patient satisfaction or kneeling ability.

Components in the P300: Don't forget the Novelty P3!

This study investigated stimulus-response patterns of temporal principal components analysis (PCA)-derived event-related potential (ERP) components in a classical auditory habituation paradigm with long interstimulus intervals. The skin conductance response (SCR) was included as the "gold standard" model of the Orienting Reflex. Thirty participants were presented with a single series of 10 identical 60 dB tones, followed by a change trial at a different frequency. Single-trial, electrooculography-corrected ERPs were submitted to temporal PCA. The main focus was on the components expected in the P300/Late Positive Complex (LPC), and their electromagnetic tomography-derived cortical sources. Nine components were identified between 90 and 470 ms poststimulus (in temporal order): three N1 subcomponents, P2, four LPC components, and a negative Slow Wave (SW). The expected order of P3a, P3b, Novelty P3 (nP3), and positive Slow Wave (+SW) in the LPC was confirmed. SCR demonstrated strong exponential decay and recovery. P3b and nP3 each showed exponential decrement over trials, but only nP3 showed recovery at the change trial. Novelty effects failed to reach significance for the other LPC components, and were not apparent in non-LPC components. Frontal lobe activity in Brodmann areas 6, 8, and 9 was common to P3a, P3b, nP3, and +SW, consistent with the functional integration of these components in the LPC. Individual components had specific sources, although some sources overlapped between components or were reactivated later in the LPC. These data provide a fresh perspective on the components of the LPC and their cortical sources, and offer a processing model for the P300 in a habituation task, potentially generalizable to other paradigms.

Integration of three investigations of Novelty, Intensity, and Significance in dishabituation paradigms: A study of the phasic Orienting Reflex.

Data from three published studies examining autonomic and ERP measures in variants of a dishabituation paradigm were re-analysed to clarify ambiguous novelty results. The three studies manipulated 1. Novelty, 2. Novelty and Intensity, and 3. Novelty and Significance, in auditory dishabituation paradigms at very long interstimulus intervals (ISIs). The question of whether any single ERP matches SCR as the benchmark for the phasic Orienting Reflex (OR) was also addressed. Finally, we aimed to align the re-analysed measures of this and the previous analyses with processes of Preliminary Process Theory (PPT). The SCR demonstrated decrement, recovery, and dishabituation. A summary temporal PCA extracted PN (Processing Negativity), P3a, P3b, Novelty P3, and classic SW for detailed analysis. P3b and SW showed decrement but no recovery at the change trial, while Respiratory pause (RP) and Novelty P3 demonstrated decrement and recovery, but no dishabituation. Post hoc exploration of observed power versus sample size for each of these findings confirmed their robustness. No decrement for PN was also confirmed. Five autonomic and ERP groupings emerged and aligned with modules of processing in PPT: ECR1 (cardiac deceleration), P1, N1-3, and PN - stimulus registration; RP and Novelty P3 - Novelty registration; Peripheral Vasoconstriction (PVC) and P3b - Intensity registration; and ECR2 (cardiac acceleration) and classic SW - Response system. The SCR was confirmed as the sole index of the phasic OR. The pattern of results for the Late Positive Complex (LPC) components (P3a, P3b, Novelty P3, and SW) suggests each is differentially sensitivity to selective determinants of the phasic OR, and consequently the summary LPC is presented as the most appropriate central index of the phasic OR.

Significance and Novelty effects in single-trial ERP components and autonomic responses.

The phasic orienting reflex (OR) was investigated in two counterbalanced blocks of an auditory dishabituation paradigm differing in stimulus Significance (operationalised as tone counting). Twelve tones were presented at very long, randomly-varying interstimulus intervals (ISIs). Novelty and Significance were varied within subjects. Stimulus-response patterns were assessed to find ERP matches for autonomic measures. The phasic OR index was represented by the skin conductance response (SCR). SCR decremented over 10 standard trials, showed recovery on trial 11 (change trial), enhancement to re-presentation of the standard tone (trial 12: dishabituation), and a main effect of Significance over the first 10 trials - demonstrating the formal criteria for an OR index. The evoked cardiac response (HR) subcomponents ECR1 (deceleration) and ECR2 (acceleration) showed no trial effects, but ECR2 showed a Significance effect. Respiratory pause (RP) decreased linearly over trials, and showed recovery, but no dishabituation or Significance effect. Temporal PCA was applied to single-trial EOG-corrected data. Ten ERP components were extracted: P1, N1-3, N1-1, PN, P2, P3a, P3b, HabP3, a Frontal Slow Wave (FSW), and the Classic SW. The dependent measures showed 4 distinct patterns. Pattern 1: No trial or Significance effects (ECR1, P1, N1-3, P3a, FSW); Pattern 2: No trial effect but a Significance effect (ECR2, N1-1, P2); Pattern 3: Trial but not Significance effects (RP, PN, P3b, HabP3); Pattern 4: Both trial and Significance effects (SCR and Classic SW). The evidenced fractionation of autonomic and central measures is compatible with Preliminary Process Theory (PPT), contrary to the notion of a unitary OR.

Trials and intensity effects in single-trial ERP components and autonomic responses in a dishabituation paradigm with very long ISIs.

The phasic orienting reflex (OR) was investigated using single-trial data collected concurrently from 4 autonomic measures and event-related potentials (ERPs). In an auditory dishabituation paradigm, twelve indifferent tones of two intensities (60 or 80 dB, intensity change on trial 11, counterbalanced between subjects) were presented at very long interstimulus intervals (ISIs). Novelty and intensity based stimulus-response patterns were examined seeking ERP analogues of autonomic measures representing pre-OR and OR processing. Skin conductance response (SCR) represented the phasic OR index. EOG-corrected ERP data for 16 subjects were decomposed by a temporal Principal Components Analysis (PCA). SCR diminished over 10 standard trials, recovered on change trial 11, dishabituated to the re-presentation of the standard tone on trial 12, and showed intensity effects at the change - formal requirements for an OR index. The evoked cardiac response (HR) showed no trial or intensity effects. Respiratory pause (RP) decreased linearly over trials and showed recovery but no dishabituation or intensity effect. Peripheral vasoconstriction (PVC) failed to decrement but exhibited an intensity effect. Ten identifiable ERP components were extracted: Na, P1, N1-1, PN, P2, P3a, P3b, a novelty-sensitive HabP3, an intensity-sensitive IntP3, and the Slow Wave (SW). Pattern 1 showed no trial or intensity effects (HR, P1, PN, P2); Pattern 2 showed no trial effect but an intensity effect (PVC, Na, N1-1, P3a); and Pattern 3 demonstrated habituation and an intensity effect (SCR, RP, P3b, HabP3, IntP3, SW). The observed fractionation of autonomic and central measures is consistent with Preliminary Process Theory (PPT) rather than the notion of a unitary OR.

Trial effects in single-trial ERP components and autonomic responses at very long ISIs.

Single-trial data from autonomic and ERP measures were used to capture the rapidly decreasing initial responses characteristic of the orienting reflex (OR) to repeated stimuli. Stimulus-response patterns were compared to determine central analogues of autonomic indices of processes leading to the OR, and the OR itself. Participants were presented with 12 indifferent tones in an auditory dishabituation paradigm. Temporal principal component analysis (PCA) decomposed EOG-corrected ERP data for 16 subjects. Response patterns of ERPs, cardiac, and respiratory responses were compared to the phasic skin conductance response (SCR). SCR decremented over trials, recovered on the change trial, and dishabituated to the representation of the standard, meeting the formal definition of habituation required of the OR. The evoked cardiac response showed no trial effects. Respiratory pause (RP) decreased linearly over trials, recovering marginally on the change trial. Nine identifiable ERP components were extracted: P1, N1-3, N1-1, processing negativity (PN), P2, P3a, P3b, a novelty-sensitive P3 component (labelled HabP3), and the slow wave (SW). P3b and SW showed decrement over trials, but with no recovery, HabP3 showed decrement and increased response on the change trial, while the P1, N1 subcomponents, P2 and P3a were insensitive to novelty. Stimulus-response patterns of the RP and HabP3 suggest sensitivity to novelty processing, while the P1, N1-3, N-1, PN, P2, P3a and cardiac deceleration appear to mark processing prior to novelty, such as stimulus transient detection (cardiac deceleration) and/or intensity processing. This study supports predictions of preliminary process theory, demonstrating fractionation of 3 autonomic and 9 ERP components to novelty, and disconfirming the unitary nature of the OR.

Linking components of event-related potentials and autonomic measures of the orienting reflex.

This study examined autonomic measures and event-related potentials (ERPs) associated with elicitation and habituation of the basic Orienting Reflex (OR). Subjects received 16 innocuous tones with intensity alternating between 60 and 80 dB, at long inter-stimulus intervals. There was no stimulus-related task, so we could examine the effects of stimulus novelty and intensity in the absence of task demands. Cardiac, respiratory, peripheral vasoconstriction, and electrodermal measures were recorded, as well as continuous EEG. Single-trial ERPs were obtained, and components extracted by Principal Components Analysis were examined for potential response fractionation in the central indices of stimulus processing. The predicted fractionation of autonomic measures was obtained: cardiac deceleration showed no systematic change with intensity or trials, respiratory pause showed a substantial main effect of trials but no intensity effects, peripheral vasoconstriction showed intensity but no trials effects, and electrodermal responses showed substantial main effects of trials and intensity. A range of intensity and novelty effects were obtained in components identified as the N1, P3a, P3b, Novelty P3, and the classic Slow Wave. The different stimulus-response profiles of the ERP components are discussed in relation to the autonomic response profiles within the context of a sequential processing theory of OR elicitation.

Caffeine effects on resting-state electrodermal levels in AD/HD suggest an anomalous arousal mechanism.

The effect of a single oral dose of caffeine was examined in a randomised double-blind placebo-controlled repeated-measures cross-over study. Eighteen children with AD/HD, aged between 8 and 13 years, were individually age- and gender-matched with a control group. All children participated in two sessions, one week apart. Skin conductance level (SCL) from a 3 min eyes-closed epoch, commencing 30 min after ingestion of caffeine or placebo, was examined. Across conditions, mean SCL was lower in the AD/HD group than controls, confirming hypoarousal in AD/HD. Caffeine produced an increase in SCL, and this increase did not differ between the groups. However, arousal increases were dose-dependent in controls, but not in AD/HD. Rather, caffeine-induced arousal increases in the AD/HD group were positively related to their hyperactivity/impulsivity levels. This suggests an anomalous arousal mechanism in AD/HD functionally related to impairment in one symptom dimension.

Single-trial event-related potentials and autonomic measures of the orienting reflex.

We aimed to clarify the event-related potentials (ERPs) associated with elicitation and habituation of the basic Orienting Reflex (OR). Participants were presented with 16 innocuous tones, alternating in intensity, at long variable inter-stimulus intervals, with no task. This allowed us to examine stimulus novelty and intensity effects in the absence of stimulus-related task demands. Single-trial ERPs were extracted to obtain estimates of the early N1 and the late positive complex (LPC) to each stimulus. Electrodermal responses showed substantial main effects of trials and intensity, supporting their functionality as an OR index. Cardiac deceleration showed no systematic change with intensity or trials, suggesting that it marks the transient onset of each stimulus, early in the stimulus-processing sequence. Respiratory pause showed a substantial main effect of trials but no intensity effect, suggesting that it reflects an intermediate processing stage. A main effect of intensity, but no simple trial effect, was apparent in the N1, suggesting that it reflects a different intermediate processing stage. The subsequent LPC showed only a topographic interaction with trials and intensity, failing to support any substantive role in OR processing. These different stimulus-response profiles are discussed in the context of a sequential processing model of the OR.

Single-trial event-related potentials and the orienting reflex to monaural tones.

We aimed to clarify the event-related potentials (ERPs) involved in elicitation and habituation of the orienting reflex (OR), seeking parallels with two autonomic measures reflecting different stages in OR-related processing. Participants were presented with 8 unexpected innocuous novel tones to one ear at long variable inter-stimulus intervals, and horizontal eye movement in the direction of the ear of stimulation was taken as a behavioural measure of the OR. Skin conductance, heart rate, and 19 EEG channels were also recorded. Single-trial ERPs were decomposed using principal components analysis for intervals covering the early N1 complex and the late positive complex (LPC). Eye movements at trial 1 showed significant directional differences with ear of stimulation, and this difference reduced over trials, providing behavioural evidence of OR elicitation and habituation. Electrodermal responses, Processing Negativity, and the Novelty P3 showed substantial main effects of trials, suggesting their close links to the OR. Cardiac deceleration and Component 1 of the N1 complex showed no change over trials, suggesting their association in marking the transient onset of each stimulus. Component 3 of the N1 complex, P3a, P3b, and early and late Slow Waves showed only topographic changes over trials, and their dominant continuation over the stimulus sequence rules them out as OR markers. Theory development is required to clarify the non-OR role of the LPC. These results point to the usefulness of a sequential-processing approach to the OR in accommodating the range of subcomponents in the ERP. These data also illustrate the value of single-trial ERP analysis in simple paradigms with very long inter-stimulus intervals.