Comparison of Lateralizing Calcaneal Osteotomies for Varus Hindfoot Correction

Background: There is limited consensus on the optimal operative technique for correcting heel varus in patients with Charcot-Marie-Tooth (CMT) disease. This comparative study evaluated the ability of 4 lateralizing calcaneal osteotomies, with and without Dwyer wedge resection and coronal rotation of the posterior tuberosity, to correct severe heel varus. Methods: The computed tomography (CT) scan of a teenage CMT patient with severe hindfoot varus was used to create 3-dimensional (3D)–printed models of the talus, calcaneus, and cuboid. A custom jig facilitated precise replication of the osteotomy cuts. Four different configurations were created: oblique osteotomy with lateralization, oblique osteotomy with lateralization and internal rotation of the posterior tuberosity, Dwyer wedge resection with lateralization, and Dwyer wedge resection with lateralization and internal rotation. CT scans were performed on each model before and after osteotomy. Statistical analysis was used to evaluate differences in several predefined radiographic parameters. Results: The sequential transformations generated increasing lateral translation of the weight-bearing calcaneus. Dwyer wedge osteotomy significantly improved lateralization (effect = 8.0 mm), valgus hindfoot angle (effect = 6.1 degrees), and coronal calcaneal tilt (effect = −17.6 degrees) compared with the oblique osteotomy. Internal rotation of the posterior tuberosity further improved lateralization (effect = 3.3 mm), valgus hindfoot angle (effect = 2.5 degrees), and coronal calcaneal tilt (effect = −11.7 degrees). Dwyer osteotomy models had on average 5-mm shorter posterior tuberosity lengths than the oblique osteotomies. The addition of rotation did not significantly affect length. Conclusions: Significant lateralization of the posterior tuberosity was achieved in all transformations. The Dwyer wedge osteotomy improved hindfoot valgus angle, coronal calcaneal tilt, and lateralization of the weight-bearing surface compared with oblique osteotomy. Posterior tuberosity internal rotation further lateralized the plantar surface and normalized weight bearing. Lateralization, combined with Dwyer osteotomy and coronal plane internal rotation, achieved the greatest correction of varus heel. Clinical Relevance: This study compares multiple lateralizing calcaneal osteotomies and proposes a combined technique of lateralization, Dwyer wedge resection, and coronal plane rotation to address advanced cavovarus hindfoot deformities.

It's the Other Way Around! Early Modulation of Sensory Distractor Processing Induced by Late Response Conflict

Understanding the neural processes that maintain goal-directed behavior is a major challenge for the study of attentional control. Although much of the previous work on the issue has focused on prefrontal brain areas, little is known about the contribution of sensory brain processes to the regulation of attentional control. The present EEG study examined brain oscillatory activities invoked in the processing of response conflict in a lateralized Eriksen single-flanker task, in which target letters were presented at fixation and single distractor letters were presented either left or right to the targets. Distractors were response compatible, response incompatible, or neutral in relation to the responses associated with the targets. The behavioral results showed that responses to targets in incompatible trials were slower and more error prone than responses in compatible trials. The electrophysiological results revealed an early sensory lateralization effect in (both evoked and induced) theta power (3–6 Hz) that was more pronounced in incompatible than compatible trials. The sensory lateralization effect preceded in time a midfrontal conflict effect that was indexed by an increase of (induced) theta power (6–9 Hz) in incompatible compared with compatible trials. The findings indicate an early modulation of sensory distractor processing induced by response conflict. Theoretical implications of the findings, in particular with respect to the theory of event coding and theories relating to stimulus–response binding [Henson, R. N., Eckstein, D., Waszak, F., Frings, C., & Horner, A. Stimulus-response bindings in priming. Trends in Cognitive Sciences, 18, 376–384, 2014; Hommel, B., Müsseler, J., Aschersleben, G., & Prinz, W. The theory of event coding (TEC): A framework for perception and action planning. Behavioral and Brain Sciences, 24, 849–878, 2001], are discussed.

Brain-Electrical Correlates of Negative Location Priming Under Sustained and Transient Attentional Context Conditions

In the present study event-related potentials (ERPs) and event-related lateralizations (ERLs) were analyzed to investigate mechanisms of attentional inhibition engaged when a target stimulus has to be located within a simultaneous target-distractor display. The putative after-effects of inhibition were examined with a prime-probe technique by comparing a “DT” condition (the prime Distractor location becomes the probe Target location) with a control condition (the probe target appears at a previously empty position). The specific aim was to dissociate more “automatic” aspects from more “controlled” aspects associated with the inhibition of distractor locations. To do so, we compared physically identical prime-probe pairs in a sustained-attention context (same target throughout a block) and a transient-attention context (trial-by-trial target specification). Three early ERP/ERL components showed differential effects for DT compared to control: (1) the posterior N1 with a diminished amplitude contralateral to the visual half-field side of target presentation, (2) the N2pc with an enhanced amplitude contralateral to the visual half-field side of target presentation, and (3) the posteriorly distributed N2 with a nonlateralized enhancement for DT compared to control. These effects were differently affected by the context manipulation. While the N2pc effect was observed exclusively under sustained attention, the N1 lateralization effect and the N2 effect were not differentially modulated. The N1 lateralization effect seems consistent with an inhibition-of-return explanation. The N2pc and N2 effects are supposed to be reflecting different aspects of a biased-competition model of distractor inhibition.

Tactile-Evoked Potentials in Schizophrenia

SummaryEEG potentials evoked by tactile stimulation of the forearm (tactile-evoked potentials or TEPs) were recorded simultaneously from both cerebral hemispheres in a group of schizophrenics and a group of healthy control subjects. Differences between the groups were found for the early waves of the TEPs: in the control subjects the first two positive waves (P25 and P50) and the first negative wave (N35) recorded from the hemisphere on the same side as the stimulation were slower (i.e. had longer latency) than those recorded from the hemisphere contralateral to the stimulation. This lateralization effect’ was not seen in the schizophrenic subjects. It was concluded that the TEPs recorded from the hemisphere ipsilateral to the stimulus were not being transmitted from the other hemisphere via the corpus callosum and must therefore have been transmitted via direct ipsilateral pathways from the periphery.In a second experiment the drug pindolol was administered to schizophrenic subjects but differences in P50 latency between ipsilateral and contralateral hemispheres were found equally in both drug and placebo groups. We also found slight evidence to suggest that the more severely ill the patient the more similar the TEP latencies recorded from the contralateral and the ipsilateral hemispheres.