An Evaluation of the Safety and Effectiveness of Total Hip Arthroplasty as an Outpatient Procedure: A Matched-Cohort Analysis.

BACKGROUND: Outpatient hip arthroplasty is being performed more routinely; however, safety remains a concern. The purpose of this study was to compare the rate of adverse events of outpatient total hip arthroplasty (THA) and assess barriers to discharge. METHODS: We examined 136 patients who underwent unilateral THA by one surgeon and were discharged on the same day of surgery. Using propensity matching, 136 inpatients who received the same procedure, and were discharged on postoperative day one or later, were identified. For each cohort, 90-day occurrence of adverse events, readmissions, and emergency visits were recorded and compared. Adverse events were graded using the OrthoSAVES tool. A secondary objective was to assess potential barriers to same-day discharge. RESULTS: Within 90 days postoperatively, 12 outpatients (8.82%) and 14 inpatients (10.29%) developed an adverse event. There were no significant differences between the rate or severity of adverse events between the 2 groups and no serious adverse events in either group. In the outpatient group, there was a correlation between the dosage of spinal anesthetic (bupivacaine) given and time required to stay in postanesthetic care unit postoperatively. CONCLUSION: When comparing the 2 groups, there were no differences in adverse events at 90 days. At our center, in the appropriate patient population, outpatient THA is a safe and cost-effective option. A potential barrier to mobility postoperatively and successful same-day discharge is the time required to stay in postanesthetic care unit postoperatively, which was significantly correlated with an increased dose of spinal anesthetic given in our outpatient cohort.

Tactile-auditory shape learning engages the lateral occipital complex.

Shape is an object property that inherently exists in vision and touch, and is processed in part by the lateral occipital complex (LOC). Recent studies have shown that shape can be artificially coded by sound using sensory substitution algorithms and learned with behavioral training. This finding offers a unique opportunity to test intermodal generalizability of the LOC beyond the sensory modalities in which shape is naturally perceived. Therefore, we investigated the role of the LOC in processing of shape by examining neural activity associated with learning tactile-shape-coded auditory information. Nine blindfolded sighted people learned the tactile-auditory relationship between raised abstract shapes and their corresponding shape-coded sounds over 5 d of training. Using functional magnetic resonance imaging, subjects were scanned before and after training during a task in which they first listened to a shape-coded sound transformation, then touched an embossed shape, and responded whether or not the tactile stimulus matched the auditory stimulus in terms of shape. We found that behavioral scores improved after training and that the LOC was commonly activated during the auditory and tactile conditions both before and after training. However, no significant training-related change was observed in magnitude or size of LOC activity; rather, the auditory cortex and LOC showed strengthened functional connectivity after training. These findings suggest that the LOC is available to different sensory systems for shape processing and that auditory-tactile sensory substitution training leads to neural changes allowing more direct or efficient access to this site by the auditory system.

Can you hear shapes you touch?

Shape is an inherent property of objects existing in both vision and touch but not audition. Can shape then be represented by sound artificially? It has previously been shown that sound can convey visual information by means of image-to-sound coding, but whether sound can code tactile information is not clear. Blindfolded sighted individuals were trained to recognize tactile spatial information using sounds mapped from abstract shapes. After training, subjects were able to match auditory input to tactually discerned shapes and showed generalization to novel auditory-tactile pairings. Furthermore, they showed complete transfer to novel visual shapes, despite the fact that training did not involve any visual exposure. In addition, we found enhanced tactile acuity specific to the training stimuli. The present study demonstrates that as long as tactile space is coded in a systematic way, shape can be conveyed via a medium that is not spatial, suggesting a metamodal representation.

Generalized learning of visual-to-auditory substitution in sighted individuals.

Visual-to-auditory substitution involves delivering information about the visual world using auditory input. Although the potential suitability of sound as visual substitution has previously been demonstrated, the basic mechanism behind crossmodal learning is largely unknown; particularly, the degree to which learning generalizes to new stimuli has not been formally tested. We examined learning processes involving the use of the image-to-sound conversion system developed by Meijer [Meijer, P., 1992. An experimental system for auditory image representations. IEEE Trans Biom Eng. 39 (2), 112-121.] that codes visual vertical and horizontal axes into frequency and time representations, respectively. Two behavioral experiments provided training to sighted individuals in a controlled environment. The first experiment explored the early learning stage, comparing performance of individuals who received short-term training and those who were only explicitly given the conversion rules. Both groups performed above chance, suggesting an intuitive understanding of the image-sound relationship; the lack of group difference indicates that this intuition could be acquired simply on the basis of explicit knowledge. The second experiment involved training over a three-week period using a larger variety of stimuli. Performance on both previously trained and novel items was examined over time. Performance on the familiar items was higher than on the novel items, but performance on the latter improved over time. While the lack of improvement with the familiar items suggests memory-based performance, the improvement with novel items demonstrated generalized learning, indicating abstraction of the conversion rules such that they could be applied to interpret auditory patterns coding new visual information. Such generalization could provide a basis for the substitution in a constantly changing visual environment.