Effects of neural oscillation power and phase on discrimination performance in a visual tilt illusion.

Neural oscillations reflect fluctuations in the relative excitation/inhibition of neural systems1,2,3,4,5 and are theorized to play a critical role in canonical neural computations6,7,8,9 and cognitive processes.10,11,12,13,14 These theories have been supported by findings that detection of visual stimuli fluctuates with the phase of oscillations prior to stimulus onset.15,16,17,18,19,20,21,22,23 However, null results have emerged in studies seeking to demonstrate these effects in visual discrimination tasks,24,25,26,27 raising questions about the generalizability of these phenomena to wider neural processes. Recently, we suggested that methodological limitations may mask effects of phase in higher-level sensory processing.28 To test the generality of phasic influences on perception requires a task that involves stimulus discrimination while also depending on early sensory processing. Here, we examined the influence of oscillation phase on the visual tilt illusion, in which a center grating has its perceived orientation biased away from the orientation of a surround grating29 due to lateral inhibitory interactions in early visual processing.30,31,32 We presented center gratings at participants' subjective vertical angle and had participants report whether the grating appeared tilted clockwise or counterclockwise from vertical on each trial while measuring their brain activity with electroencephalography (EEG). In addition to effects of alpha power and aperiodic slope, we observed robust associations between orientation perception and alpha and theta phase, consistent with fluctuating illusion magnitude across the oscillatory cycle. These results confirm that oscillation phase affects the complex processing involved in stimulus discrimination, consistent with its purported role in canonical computations that underpin cognition.

Establishing gaze markers of perceptual load during multi-target visual search.

Highly-automated technologies are increasingly incorporated into existing systems, for instance in advanced car models. Although highly automated modes permit non-driving activities (e.g. internet browsing), drivers are expected to reassume control upon a 'take over' signal from the automation. To assess a person's readiness for takeover, non-invasive eye tracking can indicate their attentive state based on properties of their gaze. Perceptual load is a well-established determinant of attention and perception, however, the effects of perceptual load on a person's ability to respond to a takeover signal and the related gaze indicators are not yet known. Here we examined how load-induced attentional state affects detection of a takeover-signal proxy, as well as the gaze properties that change with attentional state, in an ongoing task with no overt behaviour beyond eye movements (responding by lingering the gaze). Participants performed a multi-target visual search of either low perceptual load (shape targets) or high perceptual load (targets were two separate conjunctions of colour and shape), while also detecting occasional auditory tones (the proxy takeover signal). Across two experiments, we found that high perceptual load was associated with poorer search performance, slower detection of cross-modal stimuli, and longer fixation durations, while saccade amplitude did not consistently change with load. Using machine learning, we were able to predict the load condition from fixation duration alone. These results suggest monitoring fixation duration may be useful in the design of systems to track users' attentional states and predict impaired user responses to stimuli outside of the focus of attention.

Phase resets undermine measures of phase-dependent perception.

As interest increases in the possible effects of the phase of neural oscillations on perception and cognition, new conceptual and methodological challenges arise. One prominent challenge is the stimulus-induced phase reset, which has the capacity to obscure the effects of phase in the postreset period.

Neurophysiological evidence against attentional suppression as the source of the same-location cost in spatial cueing.

Spatial cues that mismatch the colour of a subsequent target have been shown to slow responses to targets that share their location. The source of this 'same location cost' (SLC) is currently unknown. Two potential sources are attentional signal suppression and object-file updating. Here, we tested a direct prediction of the suppression account using data from a spatial-cueing study in which we recorded brain activity using electroencephalography (EEG), and focusing on the event-related PD component, which is thought to index attentional signal suppression. Correlating PD amplitude with SLC magnitude, we tested the prediction that if attentional signal suppression is the source of the SLC, then the SLC should be positively correlated with PD amplitude. Across 48 participants, SLC and PD magnitudes were negatively correlated, in direct contradiction to a suppression account of the SLC. These results are compatible with an object-file updating account of the SLC in which updating is facilitated by reactive suppression of the to-be-updated stimulus information.

Late guidance resolves the search slope paradox in contextual cueing.

Visual search is facilitated by statistical learning of repeated search contexts, termed 'contextual cueing'. Repeated displays are thought to enhance attentional guidance, but this has been challenged by the absence of search-slope differences between repeated and novel displays. Here we use eye-tracking to resolve this paradox by calculating a measure of when during search the contextual cueing benefit emerges. In 24 human participants we observe typical reaction time and fixation count benefits for repeated contexts, but no slope differences between repeated and novel search contexts. Eye-tracking showed that the attentional guidance benefit emerged over time, occurring later for larger set sizes, and producing similar response time benefits for small and large set sizes. We argue that repeated and novel contexts have similar slopes because learning benefits are confined to target-adjacent regions of roughly equivalent area across set sizes. This finding rules out one of the strongest pieces of evidence against an attentional account of contextual cueing.

Behavioral and electrophysiological evidence for a dissociation between working memory capacity and feature-based attention.

When attending to visual objects with particular features, neural processing is typically biased toward those features. Previous work has suggested that maintaining such feature-based attentional sets may involve the same neural resources as visual working memory. If so, the extent to which feature-based attention influences stimulus processing should be related to individuals' working memory capacity. Here we used electroencephalography (EEG) to record brain activity in 60 human observers while they monitored stimulus streams for targets of a specific color. Distractors presented at irrelevant locations evoked strong electrophysiological markers of attentional signal enhancement (the N2pc and PD components) despite producing little or no behavioral interference. Critically, there was no relationship between individual differences in the magnitude of these feature-based biases on distractor processing and individual differences in working memory capacity as measured using three separate working memory tasks. Bayes factor analyses indicated substantial evidence in support of the null hypothesis of no relationship between working memory capacity and the effects of feature-based attention on distractor processing. We consider three potential explanations for these findings. One is that working memory and feature-based attention draw upon distinct neural resources, contrary to previous claims. A second is that working memory is only related to feature-based attention when the attentional template has recently changed. A third is that feature-based attention tasks of the kind employed in the current study recruit just one of several subcomponents of working memory, and so are not invariably correlated with an individual's overall working memory capacity.

Awareness is related to reduced post-stimulus alpha power: a no-report inattentional blindness study.

Delineating the neural correlates of sensory awareness is a key requirement for developing a neuroscientific understanding of consciousness. A neural signal that has been proposed as a key neural correlate of awareness is amplitude reduction of 8-14 Hz alpha oscillations. Alpha oscillations are also closely linked to processes of spatial attention, providing potential alternative explanations for past results associating alpha oscillations with awareness. We employed a no-report inattentional blindness (IB) paradigm with electroencephalography to examine the association between awareness and the power of 8-14 Hz alpha oscillations. We asked whether the alpha-power decrease commonly reported when stimuli are perceived is related to awareness, or other factors that commonly confound awareness investigations, specifically task-relevance and visual salience. Two groups of participants performed a target discrimination task at fixation while irrelevant non-salient shape probes were presented briefly in the left or right visual field. One group was explicitly informed of the peripheral probes at the commencement of the experiment (the control group), whereas the other was not told about the probes until halfway through the experiment (IB group). Consequently, the IB group remained unaware of the probes for the first half of the experiment. In all conditions in which participants were aware of the probes, there was an enhanced negativity in the event-related potential (the visual awareness negativity). Furthermore, there was an extended contralateral alpha-power decrease when the probes were perceived, which was not present when they failed to reach awareness. These results suggest alpha oscillations are intrinsically associated with awareness itself.

Predictive coding of visual motion in both monocular and binocular human visual processing.

Neural processing of sensory input in the brain takes time, and for that reason our awareness of visual events lags behind their actual occurrence. One way the brain might compensate to minimize the impact of the resulting delays is through extrapolation. Extrapolation mechanisms have been argued to underlie perceptual illusions in which moving and static stimuli are mislocalised relative to one another (such as the flash-lag and related effects). However, where in the visual hierarchy such extrapolation processes take place remains unknown. Here, we address this question by identifying monocular and binocular contributions to the flash-grab illusion. In this illusion, a brief target is flashed on a moving background that reverses direction. As a result, the perceived position of the target is shifted in the direction of the reversal. We show that the illusion is attenuated, but not eliminated, when the motion reversal and the target are presented dichoptically to separate eyes. This reveals extrapolation mechanisms at both monocular and binocular processing stages contribute to the illusion. We interpret the results in a hierarchical predictive coding framework, and argue that prediction errors in this framework manifest directly as perceptual illusions.

Taking a closer look at visual search: Just how feature-agnostic is singleton detection mode?

Singleton detection mode is a state in which spatial attention is set to prioritize any objects that differ from all other objects present on any feature dimension. Relatively little research has been devoted to confirming the consequences such a search mode has for stimulus processing. It is often implied that when observers employ singleton detection mode, all singletons capture attention equally, and when observers search for a single feature, only that feature captures attention. The experiment presented here contradicts these implications. We had observers search for colored singleton targets preceded by spatially uninformative colored singleton cues, and we recorded stimulus-evoked neural responses using electroencephalography (EEG). When observers had to respond to targets defined by two possible colors (a task intended to encourage singleton detection mode), cue validity effects were apparent for both target-color cues and irrelevant-color cues, and these effects were accompanied by an N2pc in the EEG data. Importantly, however, the target-color cues evoked significantly larger cue validity effects and N2pc components than did the irrelevant-color cues. In contrast, when observers had to respond to targets defined by one color (a task intended to encourage feature search mode), only cues of that color evoked a cue validity effect. Interestingly, the N2pcs produced by irrelevant cues did not differ between feature and singleton search, suggesting that the behavioral difference was not due to different attentional orienting. Rather, we suggest that behavioral singleton capture is due to a diminished same-location cost being produced by irrelevant-color cues.

Detecting Unattended Stimuli Depends on the Phase of Prestimulus Neural Oscillations.

Neural oscillations appear important for perception and attention processes because stimulus detection is dependent upon the phase of 7-11 Hz oscillations before stimulus onset. Previous work has examined stimulus detection at attended locations, but it is unknown whether unattended locations are also subject to phasic modulation by ongoing oscillatory activity, as would be predicted by theories proposing a role for neural oscillations in organizing general neural processing. Here, we recorded brain activity with EEG while human participants of both sexes detected brief visual targets preceded by a spatial cue and determined whether performance for cued (attended) and uncued (unattended) targets was influenced by oscillatory phase across a range of frequencies. Detection of both attended and unattended targets depended upon an ∼5 Hz theta rhythm and an ∼11-15 Hz alpha rhythm. Critically, detection of unattended stimuli was more strongly modulated by the phase of theta oscillations than was detection of attended stimuli, suggesting that attentional allocation involves a disengagement from ongoing theta sampling. There was no attention-related difference in the strength of alpha phase dependence, consistent with a perceptual rather than attentional role of oscillatory phase in this frequency range. These results demonstrate the importance of neural oscillations in modulating visual processing at both attended and unattended locations and clarify one way in which attention may produce its effects: through disengagement from low-frequency sampling at attended locations.SIGNIFICANCE STATEMENT Past work on the interaction between oscillatory phase and neural processing has shown the involvement of posterior ∼7-11 Hz oscillations in visual processing. Most studies, however, have presented stimuli at attended locations, making it difficult to disentangle frequencies related to attention from those related to perception. Here, we compared the oscillatory frequencies involved in the detection of attended and unattended stimuli and found that ∼11-15 Hz oscillations were related to perception independently of attention, whereas ∼5 Hz oscillations were more prominent for the detection of unattended stimuli. This work demonstrates the importance of neural oscillations for mediating stimulus processing at both attended and unattended locations and clarifies the different oscillatory frequencies involved in attention and perception.

Conjunction search is relational: Behavioral and electrophysiological evidence.

Attention selects behaviorally relevant stimuli for further capacity-limited processing and gates their access to awareness. Given the importance of attention for conscious perception, it is important to determine the factors and mechanisms that drive attention. A widespread view is that attention is biased to the specific feature values of a conjunction target (e.g., vertical, red, medium). By contrast, the results of the present study show that attention is tuned to the 2 relative features that distinguish a conjunction target from the irrelevant nontargets (e.g., larger and bluer). Moreover, an irrelevant conjunction cue that is briefly presented prior to the target can automatically attract attention, even in the absence of any feature contrasts. Importantly, automatic orienting to the conjunction cue was completely independent of the physical similarity between cue and target, and depended only on whether the conjunction cue matched the relative features of the target. These results demonstrate that attentional orienting is determined by a mechanism that can rapidly extract information about feature relationships and guide attention to the stimulus that best matches the relative attributes of the target. These results are difficult to reconcile with extant feature-specific accounts or object-based accounts of attention and argue for a relational account of conjunction search. (PsycINFO Database Record

Distinct roles of theta and alpha oscillations in the involuntary capture of goal-directed attention.

Mechanisms of attention assign priority to sensory inputs on the basis of current task goals. Previous studies have shown that lateralized neural oscillations within the alpha (8-14Hz) range are associated with the voluntary allocation of attention to the contralateral visual field. It is currently unknown, however, whether similar oscillatory signatures instantiate the involuntary capture of spatial attention by goal-relevant stimulus properties. Here we investigated the roles of theta (4-8Hz), alpha, and beta (14-30Hz) oscillations in human goal-directed visual attention. Across two experiments, we had participants respond to a brief target of a particular color among heterogeneously colored distractors. Prior to target onset, we cued one location with a lateralized, non-predictive cue that was either target- or non-target-colored. During the behavioral task, we recorded brain activity using electroencephalography (EEG), with the aim of analyzing cue-elicited oscillatory activity. We found that theta oscillations lateralized in response to all cues, and this lateralization was stronger if the cue matched the target color. Alpha oscillations lateralized relatively later, and only in response to target-colored cues, consistent with the capture of spatial attention. Our findings suggest that stimulus induced changes in theta and alpha amplitude reflect task-based modulation of signals by feature-based and spatial attention, respectively.

Contextual cueing improves attentional guidance, even when guidance is supposedly optimal.

Visual search through previously encountered contexts typically produces reduced reaction times compared with search through novel contexts. This contextual cueing benefit is well established, but there is debate regarding its underlying mechanisms. Eye-tracking studies have consistently shown reduced number of fixations with repetition, supporting improvements in attentional guidance as the source of contextual cueing. However, contextual cueing benefits have been shown in conditions in which attentional guidance should already be optimal-namely, when attention is captured to the target location by an abrupt onset, or under pop-out conditions. These results have been used to argue for a response-related account of contextual cueing. Here, we combine eye tracking with response time to examine the mechanisms behind contextual cueing in spatially cued and pop-out conditions. Three experiments find consistent response time benefits with repetition, which appear to be driven almost entirely by a reduction in number of fixations, supporting improved attentional guidance as the mechanism behind contextual cueing. No differences were observed in the time between fixating the target and responding-our proxy for response related processes. Furthermore, the correlation between contextual cueing magnitude and the reduction in number of fixations on repeated contexts approaches 1. These results argue strongly that attentional guidance is facilitated by familiar search contexts, even when guidance is near-optimal. (PsycINFO Database Record

Opening a New Level II Trauma Center Near an Established Level I Trauma Center: Is This Good for Trauma Care?

OBJECTIVES: To describe how the initiation and later removal of a provisional level II trauma center (PL2TC) status at a community hospital affected the volume and severity of injured patients seen at an established academic level 1 trauma center (AL1TC). METHODS: Census data including counts of injury ICD-9 codes and patients seen in the emergency department (ED) and trauma center at an AL1TC were collected monthly from January 2010 to October 2014. An interrupted time series analysis was used to model the monthly census data with 2 time interruptions to describe the change in patient volume at the interruptions. The interruptions were (1) the initiation of the PL2TC status at a nearby community hospital and (2) the subsequent removal of the PL2TC status. RESULTS: The number of diagnoses, encounters, and patients seen at the AL1TC ED decreased while the PL2TC was operating. After the removal of the PL2TC status, there was a 19.4% increase in the ED patient volume per month at the AL1TC. The number of orthopaedic trauma patients seen through the ED at the AL1TC dropped 11.1% per month when the PL2TC began functioning as a trauma center. However, the volume of orthopaedic patients at the AL1TC did not recuperate after the PL2TC lost level 2 status. CONCLUSIONS: A significant decrease in patient volume was seen at the AL1TC with the initiation of the PL2TC in close proximity. Orthopaedic patient volume did not recuperate after the removal of the PL2TC status.

Open Calcaneus Fractures and Associated Injuries.

Open calcaneus fractures are usually the result of high-energy mechanisms and are associated with other orthopedic and whole body system injures. Understanding the difference between open versus closed fractures is essential for the provider, and they must be vigilant for the associated injuries that present with this condition. We performed a retrospective medical record review of 62 patients (64 calcaneus fractures) with open calcaneus fractures from January 2003 to January 2013 presenting at a level 1 trauma center. Sex, age, laterality, mechanism of injury, wound appearance, initial management, and associated injures were recorded. The most common mechanisms were motor vehicle accidents (35 [56.4%]) and falls from >6 ft (15 [24.1%]). Four (6.4%) patients had a posterior tibial artery transection. Eight (12.9%) patients had a femoral shaft fracture, 14 (22.5%) an ipsilateral ankle fracture, 16 (25.8%) a metatarsal fracture, and 11 (17.7%) had associated midfoot fractures. Of the midfoot fractures, 12 (19.3%) patients had a talus fracture and 5 (8.0%) a cuboid fracture. Spinal fractures were present in 9 (14.5%) of the patients, with lumbar fractures occurring in 6 (9.6%) patients. Fifteen (24.1%) patients had associated upper extremity fractures. Thirteen (20.9%) patients had an associated pulmonary injury, including 8 pneumothoraces. Ten (16.1%) patients had a closed head injury and 6 (9.6%) had an abdominal injury. Fifteen (23.4%) patients were treated with percutaneous wire fixation and 7 (10.9%) with open reduction internal fixation. A total of 44 (68.7%) fractures were treated without internal fixation. Overall, 5 (8.0%) patients with an open calcaneus fracture eventually underwent a below-the-knee amputation. Open calcaneus fractures are severe, high-energy injuries with the potential for considerable morbidity to the patient, given the high rate of concomitant orthopedic and whole body system injuries. Type III open injuries have an increased risk of requiring subsequent amputation. The management of these injuries should include intravenous antibiotics, tetanus prophylaxis, and urgent debridement and irrigation.

Capture by colour: evidence for dimension-specific singleton capture.

Previous work on attentional capture has shown the attentional system to be quite flexible in the stimulus properties it can be set to respond to. Several different attentional "modes" have been identified. Feature search mode allows attention to be set for specific features of a target (e.g., red). Singleton detection mode sets attention to respond to any discrepant item ("singleton") in the display. Relational search sets attention for the relative properties of the target in relation to the distractors (e.g., redder, larger). Recently, a new attentional mode was proposed that sets attention to respond to any singleton within a particular feature dimension (e.g., colour; Folk & Anderson, 2010). We tested this proposal against the predictions of previously established attentional modes. In a spatial cueing paradigm, participants searched for a colour target that was randomly either red or green. The nature of the attentional control setting was probed by presenting an irrelevant singleton cue prior to the target display and assessing whether it attracted attention. In all experiments, the cues were red, green, blue, or a white stimulus rapidly rotated (motion cue). The results of three experiments support the existence of a "colour singleton set," finding that all colour cues captured attention strongly, while motion cues captured attention only weakly or not at all. Notably, we also found that capture by motion cues in search for colour targets was moderated by their frequency; rare motion cues captured attention (weakly), while frequent motion cues did not.

A comparison of glycosaminoglycan distributions, keratan sulphate sulphation patterns and collagen fibril architecture from central to peripheral regions of the bovine cornea.

This study investigated changes in collagen fibril architecture and the sulphation status of keratan sulphate (KS) glycosaminoglycan (GAG) epitopes from central to peripheral corneal regions. Freshly excised adult bovine corneal tissue was examined as a function of radial position from the centre of the cornea outwards. Corneal thickness, tissue hydration, hydroxyproline content, and the total amount of sulphated GAG were all measured. High and low-sulphated epitopes of keratan sulphate were studied by immunohistochemistry and quantified by ELISA. Chondroitin sulphate (CS) and dermatan sulphate (DS) distributions were observed by immunohistochemistry following specific enzyme digestions. Electron microscopy and X-ray fibre diffraction were used to ascertain collagen fibril architecture. The bovine cornea was 1021±5.42 µm thick at its outer periphery, defined as 9-12 mm from the corneal centre, compared to 844±8.10 µm at the centre. The outer periphery of the cornea was marginally, but not significantly, more hydrated than the centre (H=4.3 vs. H=3.7), and was more abundant in hydroxyproline (0.12 vs. 0.06 mg/mg dry weight of cornea). DMMB assays indicated no change in the total amount of sulphated GAG across the cornea. Immunohistochemistry revealed the presence of both high- and low-sulphated epitopes of KS, as well as DS, throughout the cornea, and CS only in the peripheral cornea before the limbus. Quantification by ELISA, disclosed that although both high- and low-sulphated KS remained constant throughout stromal depth at different radial positions, high-sulphated epitopes remained constant from the corneal centre to outer-periphery, whereas low-sulphated epitopes increased significantly. Both small angle X-ray diffraction and TEM analysis revealed that collagen fibril diameter remained relatively constant until the outer periphery was reached, after which fibrils became more widely spaced (from small angle x-ray diffraction analysis) and of larger diameter as they approached the sclera. Depth-profiled synchrotron microbeam analyses showed that, at different radial positions from the corneal centre outwards, fibril diameter was greater superficially than in deeper stromal regions. The interfibrillar spacing was also higher at mid-depth in the stroma than it was in anterior and posterior stromal regions. Collagen fibrils in the bovine cornea exhibited a fairly consistent spacing and diameter from the corneal centre to the 12 mm radial position, after which a significant increase was seen. While the constancy of the overall sulphation levels of proteoglycans in the cornea may correlate with the fibrillar architecture, there was no correlation between the latter and the distribution of low-sulphated KS.

Visual search for color and shape: when is the gaze guided by feature relationships, when by feature values?

One of the most widespread views in vision research is that top-down control over visual selection is achieved by tuning attention to a particular feature value (e.g., red/yellow). Contrary to this view, previous spatial cueing studies showed that attention can be tuned to relative features of a search target (e.g., redder): An irrelevant distractor (cue) captured attention when it had the same relative color as the target (e.g., redder), and failed to capture when it had a different relative color, regardless of whether the distractor was similar or dissimilar to the target. The present study tested whether the same effects would be observed for eye movements when observers have to search for a color or shape target and when selection errors were very noticeable (resulting in an erroneous eye movement to the distractor). The results corroborated the previous findings, showing that capture by an irrelevant distractor does not depend on the distractor's similarity to the target but on whether it matches or mismatches the relative attributes of the search target. Extending on previous work, we also found that participants can be pretrained to select a color target in virtue of its exact feature value. Contrary to the prevalent feature-based view, the results suggest that visual selection is preferentially biased toward the relative attributes of a search target. Simultaneously, however, visual selection can be biased to specific color values when the task requires it, which rules out a purely relational account of attention and eye movements.

Feature specificity in attentional capture by size and color.

Top-down guidance of visual attention has classically been thought to operate in a feature-specific manner. However, recent studies have shown that top-down visual attention can also be guided by information about target-nontarget feature relations (e.g., larger, redder, brighter). Here we recommend a minimal set of cues for differentiating between relational and feature-specific attentional guidance and examine contrasting predictions for the guidance of attention by size and color stimuli in a spatial cueing paradigm. In Experiment 1 we demonstrate that in search for size, when both feature-specific and relational strategies are available, participants adopt a relational search strategy. Experiment 2 shows that when feature-specific information is the only reliable information to guide attention to the target, participants are able to adopt a feature-specific set for size information. Finally, in Experiment 3 we extend our paradigm to differentiate between feature-specific and relational strategies in search for color. Together, these experiments help to clarify the conditions under which different attentional guidance strategies will be employed, and demonstrate a useful minimum cue requirement for differentiating between these two forms of top-down guidance. Implications for current theories of attention are discussed.

Complications following limb-threatening lower extremity trauma.

OBJECTIVE: Our objective is to report the nature and incidence of major complications after severe lower extremity trauma. DESIGN: Multicenter, prospective, observational study. SETTING: Eight level-1 trauma centers. PATIENTS/PARTICIPANTS: Five hundred forty-five patients were followed for 2 years. INTERVENTION: Amputation or reconstruction. MAIN OUTCOME MEASUREMENTS: The type and number of complications associated with these injuries were recorded at baseline, 3-, 6-, 12-, and 24-month intervals. RESULTS: One hundred forty-nine underwent amputation during the initial hospitalization. The revision amputation rate was 5.4%. Among the amputation group, a complication was noted most frequently at 3 months (24.8%), and the most commonly seen complication was wound infection (34.2%). Wound complications including dehiscence (13.4%) were seen more commonly in the amputation group. Three hundred seventy-one limb reconstructions were performed with 25 patients (3.9%) requiring late amputation. The most frequently reported complication was at 6 months for the salvage group (37.7%), and the most commonly seen complication was wound infection (23.2%). Not surprisingly, osteomyelitis (8.6%) and nonunions (31%) were seen more commonly in the salvage group. Complications of wound infection, osteomyelitis, nonunion, malunion, and prominent hardware resulted in rehospitalization in at least one-third of patients. However, patients who underwent reconstruction were more likely to be hospitalized for these complications. CONCLUSIONS: Patients with severe lower extremity injuries can expect a significant number of complications, most notably wound infection, nonunion, wound necrosis, and osteomyelitis. A large portion of these will require additional inpatient or operative treatment. Patients electing for reconstruction can expect a higher risk of complications.