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Experimental studies have provided evidence that the visual processing areas of the primate brain represent facial identity and facial expression within different subpopulations of neurons. For example, in non-human primates there is evidence that cells within the inferior temporal gyrus (TE) respond primarily to facial identity, while cells within the superior temporal sulcus (STS) respond to facial expression. More recently, it has been found that the orbitofrontal cortex (OFC) of non-human primates contains some cells that respond exclusively to changes in facial identity, while other cells respond exclusively to facial expression. How might the primate visual system develop physically separate representations of facial identity and expression given that the visual system is always exposed to simultaneous combinations of facial identity and expression during learning? In this paper, a biologically plausible neural network model, VisNet, of the ventral visual pathway is trained on a set of carefully-designed cartoon faces with different identities and expressions. The VisNet model architecture is composed of a hierarchical series of four Self-Organising Maps (SOMs), with associative learning in the feedforward synaptic connections between successive layers. During learning, the network develops separate clusters of cells that respond exclusively to either facial identity or facial expression. We interpret the performance of the network in terms of the learning properties of SOMs, which are able to exploit the statistical indendependence between facial identity and expression.

Brodie’s abscess is a subacute form of osteomyelitis which generally occurs in the metaphysis of the femur and tibia in the pediatric population. Pathogens are most commonly Gram-positive bacteria, notably Staphylococcus and Streptococcus. In this article, we describe a young pediatric patient presenting with subacute ankle pain with a subsequent diagnosis of Brodie’s abscess of the talus secondary to Morganella morganii. We review the presentation, diagnosis, and treatment of this unique patient. To our knowledge, this is the first report of Morganella morganii as a cause of Brodie’s abscess.

Abstract Background: There are no existing multisite national data on obese youth presenting for pediatric weight management. The primary aim was to describe BMI status and comorbidities among youth with obesity presenting for pediatric weight management (PWM) at programs within the Pediatric Obesity Weight Evaluation Registry (POWER). Methods: Data were collected from 2009–2010 among 6737 obese patients ages 2–17. Patients were classified in three groups by BMI (kg/m2) cutoffs and percent of the 95th percentile for BMI: (1) obesity; (2) severe obesity class 2; and (3) severe obesity class 3. Weighted percentages are presented for baseline laboratory tests, blood pressure, and demographics. Generalized logistic regression with clustering was used to examine the relationships between BMI status and comorbidities. Results: Study youth were 11.6 ± 3.4 years of age, 56% female, 31% black, 17% Hispanic, and 53% publicly insured. Twenty-five percent of patients had obesity (n = 1674), 34% (2337) had severe obesity class 2, and 41% (2726) had severe obesity class 3. Logistic regression revealed that males (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.5–2.0), blacks (OR, 1.7; 95% CI, 1.5–2.0), age <6 years (OR, 2.0; 95% CI, 1.5–2.6), and public insurance (OR, 1.8; 95% CI, 1.5–2.0) had a higher odds of severe obesity class 3. Severe obesity class 3 was associated with higher odds of laboratory abnormalities for hemoglobin A1c (OR, 1.7; 95% CI, 1.3–2.2), alanine aminotransferase ≥40 U/L (OR, 1.9; 95% CI, 1.3–2.6), and elevated systolic blood pressure (OR, 2.5; 95% CI, 2.0–3.0). Conclusions: Youth with obesity need earlier access to PWM given that they are presenting when they have severe obesity with significant comorbidities.

Background: Optimal timing of anterior cruciate ligament (ACL) reconstruction has been a topic of controversy. Reconstruction has historically been delayed for at least 3 weeks, given previous studies reporting a high risk of postoperative arthrofibrosis and suboptimal clinical results. Purpose: To prospectively evaluate postoperative range of motion following acutely reconstructed ACLs with patellar tendon autograft. Study Design: Case series; Level of evidence, 4. Methods: Patients (age >18 years) who had ACL reconstruction as soon as possible after injury, regardless of the condition or preoperative range of motion of the injured knee, underwent reconstruction with patellar tendon autograft. An identical standard surgical technique and postoperative rehabilitation were employed for all patients. Postoperative assessment included active range of motion measurements with a goniometer. Subjective outcomes were assessed with the Knee injury and Osteoarthritis Outcome Score (KOOS). Results: A total of 25 consecutive patients who met the inclusion criteria were enrolled. The mean age was 27.9 years (range, 20-48 years), and 19 were men. The time from injury to surgery was a mean 4.5 days (range, 1-9 days). The mean objective follow-up was 10.9 months (range, 3 days–19.4 months), and range of motion was regained at a mean 4.4 months (range, 1-9 months). Three meniscal repairs and 3 microfractures were performed concomitantly. There was 1 graft failure at 3 years postoperatively, noted at 50 months of subjective follow-up. There was no loss of extension >3° as compared with the contralateral knee in any patient. There was no loss of flexion >5° as compared with the contralateral knee in any patient who completed objective follow-up. The mean KOOS at final subjective follow-up was 82.8 (range, 57.7-98.8) at a mean 56.6 months postoperative (n = 14/24; range, 48-58 months). Conclusion: Excellent clinical results can be achieved following ACL reconstruction performed ≤9 days after injury with patellar tendon autograft. The authors found that early ACL reconstructions do not result in loss of motion or suboptimal clinical results as long as a rehabilitation protocol emphasizing extension and early range of motion is employed.

Category: Ankle; Trauma Introduction/Purpose: Syndesmotic screw fixation is frequently required in rotational ankle injuries. Fibular malreduction after syndesmotic screw fixation occurs in as many as 52% of cases, which has been shown to detrimentally affect subjective outcomes and increase the probability of developing arthritis. The glidepath technique has been proposed as a useful technique to prevent malreduction. We hypothesize that the glidepath technique reduces the occurrence of fibular malreduction and results in improved outcomes compared to clamping. Methods: A retrospective cohort study comparing 25 patients reduced with a clamp compared to 18 patient using the glidepath technique. The glidepath technique, described by Needleman, the fibula is manually reduced and a Kirschner wire is placed through the fibula and tibia along the transmalleolar axis, parallel to the superior border of the ankle mortise. CT scans of the injured and contralateral ankles were obtained postoperatively to assess reduction. Malreduction is defined as >2mm difference between the anterior or posterior incisura-fibular distance of the injured ankle compared to the contralateral side. Prospective outcomes were assessed using the AOFAS and VR-12 scores at preoperative, 3 month, 6 month and 1 year followup of the glidepath cohort only. Results: We found a statistically significant reduction in malreduced syndesmoses using the glidepath technique when compared with the clamping technique. In our study, 17% (3/18) were malreduced using the glidepath technique, compared with 48% (12/25 patients) with clamping (p=0.005). The three malreductions seen in our study were anterior, we had no posterior malreductions. Compared with the clamping cohort that had 10/25 posterior malreductions and 2/25 anterior malreductions. Mean outcomes at 3,6 and 1 year scores were AOFAS 76, 86,86; VR-12 46,53,50/ 42,44,47 (physical/mental) respectively. Conclusion: Historically, malreduction for syndesmotic fixation is as high as 52%. The glidepath technique is a viable reduction maneuver that has lower rates of malreduction compared to clamping in our study. This is the first ever CT confirmed study measuring syndesmosis reduction utilizing manual reduction. The value of this technique is that is does not require an open reduction, arthroscopic visualization/reduction or CT guidance to achieve syndesmotic reduction.

Category: Hindfoot; Other Introduction/Purpose: While lengthening of the lateral column through a calcaneal neck osteotomy is an integral component of flatfoot reconstruction in younger patients with flexible planovalgus deformities, concern exists as to the effect of this intra- articular osteotomy on subtalar motion. The purpose of this study is to quantify the alterations in subtalar motion following lateral column lengthening (LCL). Methods: The subtalar motion of 14 fresh frozen cadaveric feet was assessed using a three-dimensional motion capture system and materials testing system (MTS). Following potting of the tibia and calcaneus, optic markers were placed into the tibia, calcaneus and talus. The MTS was used to apply a rotational force across the subtalar joint to a torque of 5Nm. Abduction/adduction, supination/pronation, and plantarflexion/dorsiflexion about the talus was recorded. Specimens then underwent LCL via a calcaneal neck osteotomy which was maintained with a 12mm porous titanium wedge. Repeat subtalar motion analysis was performed and compared to pre-LCL motion using a paired t-test. Results:: No statistically significant differences in subtalar abduction/adduction (10.9O vs. 11.8O degrees, p=.48), supination/pronation (3.5O vs. 2.7O, p=.31), or plantarflexion/dorsiflexion (1.6O vs 1.0O, p=.10) were identified following LCL. Conclusion:: No significant changes in subtalar motion were observed following lateral column lengthening in this biomechanical cadaveric study. While these findings do not obviate concerns of clinical subtalar stiffness following planovalgus deformity correction, they suggest that diminished postoperative subtalar motion may be due to soft tissue scarring rather than alterations of joint anatomy.

Category: Midfoot/Forefoot; Other Introduction/Purpose: While lengthening of the lateral column through a calcaneal neck osteotomy is an integral component of flatfoot reconstruction in younger patients with flexible planovalgus deformities, the procedure has been implicated in iatrogenic calcaneocuboid (CC) subluxation and subsequent degenerative changes at the CC articulation. The purpose of this study is to characterize alterations at the CC joint following lateral column lengthening (LCL) as well as to determine if Steinman pin stabilization of the CC joint prior to distraction maintains a normal CC relationship. Methods: Seven matched pairs of fresh frozen cadaveric feet underwent pre-procedure plain radiography and cross-sectional computed tomography (CT) imaging. LCL via a calcaneal neck osteotomy was then performed. One foot of each matched pair had a single smooth Steinman pin placed centrally across the CC joint prior to osteotomy distraction. Distraction across each osteotomy was then performed and maintained with a 12mm porous titanium wedge. Repeat imaging was obtained and compared to pre-procedure studies to quantify sagittal and rotational differences at the CC articulation Results: Following LCL, plain radiography demonstrated statistically significant increases in the percentage of the calcaneal articular surface dorsal to the superior aspect of the cuboid in both the pinned (8.2% vs 17.6%, p=0.02) and unpinned (12.5% vs 16.3%, p=0.04) specimens. No difference in the percentage of subluxation was found between the two groups following LCL. CT imaging demonstrated statistically significant increases in rotation between the calcaneus and cuboid following LCL in both the pinned (7.6O +- 5.6O, p=0.01) and unpinned (17O +- 12.3O, p=0.01) specimens. Though a greater degree of rotation was present in the unpinned specimens following LCL, this difference was not statistically significant (p=0.28). Conclusion: Both sagittal and rotatory subluxation seem to occur at the CC joint following LCL regardless of pin stabilization. As a single pin would be expected to limit pure translation while having little effect on rotation, it is possible that the rotational changes identified on three-dimensional imaging are interpreted as dorsal translation when viewed two dimensionally using plain radiography. Consideration should therefore be given to CC stabilization with two pins during LCL to prevent this rotatory subluxation.

Understanding when a polynomial is nonnegative on a region is a fundamental problem in applied mathematics. Although exact conditions for nonnegativity are computationally intractable, there has been a surge of recent work giving sufficient conditions for nonnegativity to address its many practical applications. A major trend in this direction has been the use of convex optimization to characterize polynomials that are sums of squares (SOS); nevertheless, this well-studied condition can be computationally intensive for polynomials of moderate degree and dimension.This thesis addresses the challenge of balancing computational cost against the strength of sufficient conditions for nonnegativity. We make progress towards bridging the gap between simple but crude sufficient conditions, and the more powerful but expensive SOS approach. In the first part, we introduce new certificates of nonnegativity that may be used when SOS is too expensive yet cheaper sufficient conditions are too conservative. For this, we leverage different features of the polynomials, including its Bernstein coefficients, a lower-degree interpolant, or its harmonic decomposition.In the second part, we construct coordinate-invariant sufficient conditions for nonnegativity and study the symmetry properties of the space of Gram matrices. By considering it as a representation of GL(n,R) and combining this module structure with classical invariant theory, we construct an explicit equivariant map for nonnegativity certification. We further introduce an alternative approach using equivariant neural networks, analyzing their benefits and limitations.