Anchor Positions Research Articles

Tightly-coupled ultra-wideband-aided monocular visual SLAM with degenerate anchor configurations

This paper proposes an enhanced tightly-coupled sensor fusion scheme using a monocular camera and ultra-wideband (UWB) ranging sensors for the task of simultaneous localization and mapping. By leveraging UWB data, the method can achieve metric-scale, drift-reduced odometry and a map consisting of visual landmarks and UWB anchors without knowing the anchor positions. Firstly, the UWB configuration accommodates any degenerate cases with an insufficient number of anchors for 3D triangulation ( $$N\le 3$$ and no height data). Secondly, a practical model for UWB measurement is used, ensuring more accurate estimates for all the states. Thirdly, selected prior range measurements including the anchor-world origin and anchor–anchor ranges are utilized to alleviate the requirement of good initial guesses for anchor position. Lastly, a monitoring scheme is introduced to appropriately fix the scale factor to maintain a smooth trajectory as well as the UWB anchor position to fuse camera and UWB measurement in the bundle adjustment. Extensive experiments are carried out to showcase the effectiveness of the proposed system.

Structural dissimilarity from self drives neoepitope escape from immune tolerance.

T-cell recognition of peptides incorporating nonsynonymous mutations, or neoepitopes, is a cornerstone of tumor immunity and forms the basis of new immunotherapy approaches including personalized cancer vaccines. Yet as they are derived from self-peptides, the means through which immunogenic neoepitopes overcome immune self-tolerance are often unclear. Here we show that a point mutation in a non-major histocompatibility complex anchor position induces structural and dynamic changes in an immunologically active ovarian cancer neoepitope. The changes pre-organize the peptide into a conformation optimal for recognition by a neoepitope-specific T-cell receptor, allowing the receptor to bind the neoepitope with high affinity and deliver potent T-cell signals. Our results emphasize the importance of structural and physical changes relative to self in neoepitope immunogenicity. Considered broadly, these findings can help explain some of the difficulties in identifying immunogenic neoepitopes from sequence alone and provide guidance for developing novel, neoepitope-based personalized therapies.

Abstract 4413: Accurate neoantigen prediction depends on mutation position relative to patient-specific MHC anchor location

Abstract Neoantigens (neoAgs) are short peptide sequences resulting from somatic mutations specifically found in tumor populations. They can be loaded onto major histocompatibility complex (MHC) class I or II molecules to allow recognition by cytotoxic T cells. Accurate neoAg prediction is critical for the design of personalized vaccines and may improve prediction of response to immune checkpoint blockade therapy. The effectiveness of a neoAg-based vaccine relies in part on whether the sequence presented to T cells has previously been exposed to the immune system. Incorrectly selecting for wildtype (WT) peptides will result in susceptibility to central tolerance and potentially induce auto-immunity. As the vast majority of somatic mutations found are single nucleotide variants, changes between the WT and mutant (MT) peptide are subtle and must be interpreted cautiously. An important yet currently overlooked factor in neoAg predicting pipelines is the position of the mutation within the peptide relative to its anchor positions for the patient's human leukocyte antigen (HLA) alleles. Current pipelines consider simple filtering strategies (e.g. MT peptide IC50 < 500 nM and WT/MT binding affinity fold change (agretopicity) > 1); however, only a subset of positions on the loaded peptide sequence are presented to the T cell receptor for recognition, while other positions are responsible for anchoring to the MHC, making these positional considerations critical for predicting T cell responses. We have collected peptide data, through clinical collaborations and The Cancer Genome Atlas (TCGA), for over 200 commonly observed HLA alleles and computationally predicted high probability anchor positions with respect to different peptide lengths (8-11mers). We observed unique anchoring patterns among different HLA alleles, varying in sequence positions and number of anchoring locations within the binding groove. To demonstrate the importance of positional information on prioritization of neoAgs, we are additionally analyzing 1000 TCGA patient samples where potential neoAgs are filtered according to different criteria including: A) MT IC50 < 500 nM, B) MT IC50 < 500 nM and agretopicity > 1, C) MT IC50 < 500 nM with data-driven filtering based on peptide mutation position, MHC anchor position and WT IC50 value. The number of potentially misclassified neoAg candidates will be accessed using experimentally validated neoAg datasets. Currently, prediction pipelines have relatively low accuracy when prioritizing neoAgs for T cell response in patients. By accounting for additional positional information, we hope to significantly reduce the number of false positive neoAgs and increase prediction accuracy. Our anchor results will be implemented as a visualization guide for tumor immunogenomics boards for clinical trials and incorporated into our existing neoAg prioritization pipeline, pVACtools. Citation Format: Huiming Xia, Megan M. Richters, Cody A. Ramirez, Cristina Puig-Saus, Kelsy C. Cotto, Gavin P. Dunn, Todd Fehniger, Antoni Ribas, William E. Gillanders, Obi L. Griffith, Malachi Griffith. Accurate neoantigen prediction depends on mutation position relative to patient-specific MHC anchor location [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4413.

Differences in Failure Mode Between Simple and Mattress Suture Configuration in Arthroscopic Bankart Repairs: A Cadaveric Study.

Background:Traumatic anterior shoulder dislocations disrupt the anteroinferior labrum (Bankart lesion), leading to high rates of instability and functional disability, necessitating stabilization.Purpose:To investigate modes and locations of repair failure between simple and horizontal mattress suture configurations after arthroscopic Bankart repair using suture anchors in a cadaveric model.Study Design:Controlled laboratory study.Methods:A total of 48 fresh-frozen human cadaveric shoulders from 48 specimens underwent creation of Bankart lesions from either the 3:00 to 6:00 o’clock position on the right glenoid or the 6:00 to 9:00 o’clock position on the left glenoid. Shoulder laterality between specimens was alternated and randomized to either simple or mattress suture repair configurations. In each shoulder, anchors were placed on the glenoid at the 3:00, 4:30, and 6:00 o’clock positions on the right or 6:00, 7:30, and 9:00 o’clock positions on the left and were secured via standard arthroscopic knot-tying techniques. Specimens were tested in the supine anterior apprehension position using a servohydraulic testing machine that was loaded to failure, simulating a traumatic anterior dislocation. After dislocation, open inspection of specimens was performed, and failure mode and location were documented. Differences in failure mode and location were compared using nominal multivariate generalized estimating equations.Results:Simple suture repairs most frequently failed at the labrum, while mattress suture repair failed at the capsule. Regardless of configuration, repairs failed most commonly at the 3:00 o’clock position on the right shoulder and 9:00 o’clock position on the left shoulder. Compared with mattress suture repairs, simple suture repairs failed at a significantly higher rate at the 6:00 o’clock position.Conclusion:Traumatic anterior shoulder dislocation after arthroscopic Bankart repair in a cadaveric model resulted in simple suture configuration repairs failing most commonly via labral tearing compared with capsular tearing in mattress repairs. Both repair configurations failed predominately at the anterior anchor position, with simple suture repairs failing more commonly at the inferior anchor position.Clinical Relevance:Horizontal mattress suture configurations create a larger area of repair, decreasing the risk of repair failure at the labrum. The extra time required for mattress suture placement at the inferior anchor position is used effectively, resulting in lower biomechanical failure rates.

Experimental pull-out tests and design indications for strength anchors installed in masonry walls

This study deals with the identification of the mechanical behavior of chemical anchors embedded in masonry walls. 108 pull-out tests are carried out in five types of masonry walls built with clay brick or vertically perforated units with cement mortar. Different parameters are taken into account: embedment depths, masonry type, anchor position (injection either in brick units or in mortar joints). The axial load capacity and the failure mode are observed for each test. The results are examined by means of elastic and plastic models assessing the efficiency of anchors installed in headers, stretchers or mortar joints. The anchors injected in mortar joints are shown to have much greater pull-out capacity than that found for anchors in bricks. Passing from 90 to 160 mm of embedment depth, a minimum increase by 40% of pull-out strength is observed. The most common failure modes are the sliding failure, which occurs for short anchors or weak masonry, and mixed sliding/cone failure, for long anchors or strong masonry. An analytical model is proposed to design anchors in order to avoid or at least to limit brittle masonry failures and to identify the field of application of uniform stress models.

Impact of Cysteine Residues on MHC Binding Predictions and Recognition by Tumor-Reactive T Cells.

The availability of MHC-binding prediction tools has been useful in guiding studies aimed at identifying candidate target Ags to generate reactive T cells and to characterize viral and tumor-reactive T cells. Nevertheless, prediction algorithms appear to function poorly for epitopes containing cysteine (Cys) residues, which can oxidize and form disulfide bonds with other Cys residues under oxidizing conditions, thus potentially interfering with their ability to bind to MHC molecules. Analysis of the results of HLA-A*02:01 class I binding assays carried out in the presence and absence of the reducing agent 2-ME indicated that the predicted affinity for 25% of Cys-containing epitopes was underestimated by a factor of 3 or more. Additional analyses were undertaken to evaluate the responses of human CD8+ tumor-reactive T cells against 10 Cys-containing HLA class I-restricted minimal determinants containing substitutions of α-aminobutyric acid (AABA), a cysteine analogue containing a methyl group in place of the sulfhydryl group present in Cys, for the native Cys residues. Substitutions of AABA for Cys at putative MHC anchor positions often significantly enhanced T cell recognition, whereas substitutions at non-MHC anchor positions were neutral, except for one epitope where this modification abolished T cell recognition. These findings demonstrate the need to evaluate MHC binding and T cell recognition of Cys-containing peptides under conditions that prevent Cys oxidation, and to adjust current prediction binding algorithms for HLA-A*02:01 and potentially additional class I alleles to more accurately rank peptides containing Cys anchor residues.

Glenoid Reaction to Biocomposite and PEEK Suture Anchors Following Arthroscopic Labral Repairs

Objectives:Biocomposite and all-suture suture anchors have been shown to cause reactive changes in the humerus and glenoid when used for arthroscopic rotator cuff and glenoid labrum repairs. The purpose of this study was to quantify glenoid anchor widening using biocomposite or PEEK suture anchors for arthroscopic shoulder stabilization. Our hypothesis was that biocomposite and PEEK anchors would lead to significant reactive changes in the glenoid as evidenced by a difference in postoperative tunnel size compared to suture anchor diameter.Methods:We searched the Military Data Repository for all patients with a history of a glenoid labrum repair who underwent a postoperative CT scan of the affected shoulder in our hospital market region. CT scans were measured using organic IMPAX tools to calculate the width and length of bone tunnels as described by Tompane et al. Bone mineral density was calculated by measuring the average Hounsfield Units through four axial segments of the glenoid neck in a best fit circle of cancellous bone. Tunnel widening was defined as an increase in width greater than 0.1mm compared to the drill size for each implant. Measurements were made by two independent observers blinded to other patient factors. Patient charts were also reviewed to obtain anchor data, injury, and surgical variables. Univariate analysis was performed to compare differences between tunnel widths and anchor sizesResults:We analyzed 146 bone tunnels in 37 shoulders that met inclusion criteria. The mean age was 23 (18-45), with 126 male and 20 females. The average time to CT scan from labrum repair was 782 days (159-2210). The majority of CT scans (33) were obtained after recurrent instability events, 2 were obtained for preoperative planning prior to shoulder arthroplasty, and 2 were obtained to evaluate the glenoid prior to military commissioning. The average number of anchors used per shoulder was 5. There were 17 PEEK and 129 biocomposite anchors included. There were 113 Arthrex, 28 Mitek, and 3 Zimmer Biomet anchors included in the data. There were 81 anchors in the anterior inferior quadrant, 21 anterior superior, 37 posterior inferior, and 6 in the posterior superior quadrant of the glenoid. The mean difference between tunnel and anchor width was 0.002mm across the data set. Fifty-five biocomposite anchors (43.6%) showed an increased tunnel diameter of greater than 0.1mm compared to anchor size. 7 PEEK anchors (41%) demonstrated an increased tunnel diameter greater than 0.1mm. Additionally, 14 tunnels demonstrated an increased width greater than 1mm compared to anchor size and all were biocomposite anchors. There was no difference in tunnel widening between biocomposite and PEEK anchors (p=0.34). The average change in width across widened tunnels was 0.07mm. The average change in tunnel size across all anchors was 0.02mm. On univariate analysis, bone mineral density, anchor size, anchor position, time to CT scan, composition, and age were not shown to have a statistically significant correlation.Conclusion:At short term 2 year follow-up there was no difference in tunnel widening between PEEK and biocomposite suture anchors. Although the majority of bone tunnels did not demonstrate significant widening compared to the implant size, 43.6% of biocomposite and 41% PEEK anchors generated reactive changes greater than 0.1mm. There were no clear trends in anchor type or location that clearly contributed to tunnel widening.

In-store customer traffic and path monitoring in small-scale supermarket using UWB-based localization and SSD-based detection

Nowadays, retailers are embracing the Internet of Things as the latest technology to drive superior customer experience. Leverage data sources from sensors, beacons and mobile devices to identify and analyze in-store customer shopping behavior. With this motivation, this study implemented an in-store customer traffic and path monitoring system for supermarket using image processing and object detection. the system utilized the ultra-wideband indoor positioning technique to monitor the customer shopping path and the single shot multibox detection technique to monitor the real-time customer traffic. The customer monitoring system was implemented and evaluated in an actual small-scale supermarket. Results showed that the detection model prediction score and the traffic counting both obtained an accuracy score of 99%. In addition, the localization system achieved the minimum error difference of 9.73% for x coordinate and 3.86% for y coordinate between pre-determined positions and the actual anchor position readings. Furthermore, the system successfully generated the most frequent path and the total customer traffic of the day. In the future, this work can aid retail owners make better choices, run businesses more efficiently, and deliver improved customer service.

Anchor Calibration for Real-Time-Measurement Localization Systems

This article investigates the effect of additional calibration modules (CMs) in a 3-D real-time localization system during the calibration of the anchor position. A quick calibration is desirable for new anchors that are positionally undetermined in the working coordinate system. Three localization methods were tested for the anchor calibration: multidimensional scaling, semidefinite programming, and iterative trilateration. First, the accuracy of the anchor localization was studied by simulating a change in the number of additional CMs and their positions. Second, tests on a real system with ultrawideband modules were performed to validate the improvements in the anchor calibration when using the additional CMs. The experimental results revealed an improvement in the anchor localization for all three methods, where the average positional error was improved by 0.01 m in the first scenario and 0.30 m in the second scenario. The MDS method had the best absolute performance, with an average positional error that was as much as two times less in comparison with the other two methods. This investigation demonstrates that the positional error can be successfully reduced by using additional CMs. The calibration of anchor positions in the working coordinate system using additional CMs resulted in a 3-D error of less than 0.32 m.

Gordian

Accurate localization from Cyber-Physical Systems (CPS) is a critical enabling technology for context-aware applications and control. As localization plays an increasingly safety-critical role, location systems must be able to identify and eliminate faulty measurements to prevent dangerously inaccurate localization. In this article, we consider the range-based localization problem and propose a method to detect coordinated adversarial corruption on anchor positions and distance measurements. Our algorithm, G ordian , rapidly finds attacks by identifying geometric inconsistencies at the graph level without requiring assumptions about hardware, ranging mechanisms, or cryptographic protocols. We give necessary conditions for which attack detection is guaranteed to be successful in the noiseless case, and we use that intuition to extend G ordian to the noisy case where fewer guarantees are possible. In simulations generated from real-world sensor noise, we empirically show that G ordian ’s trilateration counterexample generation procedure enables rapid attack detection even for combinatorially difficult problems.

Anchor loss optimization for magnetic flux modulation structure of magnetoresistive sensor

Piezoelectric driven magnetic flux modulation is an effective method to suppress 1/f noise of magnetoresistive sensor, and obtaining a modulation structure with high quality factor (Q factor) is of great significance in improving the modulation performance. In this paper, influence of anchor positions on the Q factor was investigated with simulation and experiment methods. First, Q factor dependent on damping of each material was analyzed, and the upper limit for studying the anchor loss was given. The displacement and stress distributions of the ceramic substrate were also simulated, so as to indirectly guide the selection of anchor locations. Then a fixture was applied to investigate the Q factor under different clamped positions, and the results shows that the clamping condition does have a great effect on the Q factor, and the smaller the stress and displacement at the support are, the larger the Q factor is. Accordingly, the modulation structure was fixed to the package base in a diagonally fixed manner or short side centers fixed manner, and the maximal Q factor reached 920, which is much higher than that under other fixed manners.

On Binomial and Poisson Sums Arising from the Displacement of Randomly Placed Sensors

We re-visit the asymptotics of a binomial and a Poisson sum which arose as (average) displacement costs when moving randomly placed sensors to anchor positions. The first-order asymptotics of these sums were derived in several stages in a series of recent papers. In this paper, we give a unified approach based on the classical Laplace method with which one can also derive more terms in the asymptotic expansions. Moreover, in a special case, full asymptotic expansions can be given which even hold as identities. This will be proved by a combinatorial approach and systematic ways of computing all coefficients of these identities will be discussed as well.

TDOA-Based Joint Synchronization and Localization Algorithm for Asynchronous Wireless Sensor Networks

This paper presents a joint synchronization and localization algorithm based on the time-difference-of-arrival (TDOA) for asynchronous Wireless Sensor Networks (WSNs), where the positions of anchors are relatively fixed but unknown. To obtain time synchronization and anchor positions, each anchor broadcasts signals periodically, while other anchors receive the broadcasting signals and stamp times-of-arrival (TOAs). Based on these TOAs, we estimate the internal clock parameters and anchor positions in three steps: least square estimation (LSE) of the relative clock skew based on TDOAs, maximum likelihood localization (MLE) of anchors using biased time of flight (TOF), and LSE estimation of relative clock offsets. Anchor pairs stamp the TDOAs when a tag (a wireless sensor node that requires localization) transmits a signal. The biased TDOAs, due to asynchronous local clocks, are compensated by relative clock offset estimation. The maximum likelihood estimation is used for the tag localization based on the Gaussian noise model. We evaluate the performance of the proposed synchronization and localization algorithm using the Cramer-Rao lower bound (CRLB). Simulations are carried out to verify the validity of the algorithm in this paper.

Complications and Return to Activity After Arthroscopic Repair of Isolated Type II SLAP Lesions: A Systematic Review Comparing Knotted Versus Knotless Suture Anchors.

Background:Superior labral anterior to posterior (SLAP) tears are one of the most common injuries to the shoulder, with the type II variant representing the most frequently encountered subtype.Purpose:To systematically review the literature to better understand outcomes after arthroscopic repair of isolated type II SLAP lesions using knotted versus knotless anchors based on implant number, implant location, patient position, and portal position.Study Design:Systematic review; Level of evidence, 4.Methods:A systematic review investigating all studies in the literature between January 2000 and June 2019 reporting on patients undergoing arthroscopic repair for isolated type II SLAP lesions using knotted versus knotless suture anchors was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using the PubMed, BIOSIS Previews, SPORTDiscus, PEDro, and Embase databases.Results:A total of 234 patients undergoing isolated arthroscopic repair of type II SLAP lesions using suture anchors were identified, with 76% (179/234) treated using knotted anchors versus 24% (55/234) treated using knotless anchors. Complications were reported in 12% of patients treated using knotted anchors versus no patients treated using knotless anchors (P = .008). The incidence of complications for knotted anchor repair was not significantly affected by patient position (P = .22) or portal position (P = .19). Using multiple regression analysis, we found no significant association with the incidence of complications when analyzing for anchor design (R 2 = 0.02; P = .06) or anchor position (R 2 = 0.02; P = .92). No significant difference in return-to-activity timing was appreciated based on anchor type (P = .28), patient position (P = .98), or portal position (P = .97) in patients treated using knotted anchors.Conclusion:Patients treated using knotted anchors were significantly more likely to experience a postoperative complication compared with patients treated using knotless anchors after arthroscopic repair of isolated type II SLAP lesions. Despite the increased incidence of a postoperative complication after knotted anchor fixation compared with knotless anchor fixation, multiple regression analysis showed that anchor design and anchor position were not significantly predictive of the incidence of complications. Given the increasing popularity of knotless anchor fixation, further study on the long-term outcomes after knotless repair for isolated type II SLAP lesions is warranted.

Loosely-Coupled Ultra-wideband-Aided Scale Correction for Monocular Visual Odometry

In this paper, we propose a method to address the problem of scale uncertainty in monocular visual odometry (VO), which includes scale ambiguity and scale drift, using distance measurements from a single ultra-wideband (UWB) anchor. A variant of Levenberg–Marquardt (LM) nonlinear least squares regression method is proposed to rectify unscaled position data from monocular odometry with 1D point-to-point distance measurements. As a loosely-coupled approach, our method is flexible in that each input block can be replaced with one’s preferred choices for monocular odometry/SLAM algorithm and UWB sensor. Furthermore, we do not require the location of the UWB anchor as prior knowledge and will estimate both scale and anchor location simultaneously. However, it is noted that a good initial guess for anchor position can result in more accurate scale estimation. The performance of our method is compared with state-of-the-art on both public datasets and real-life experiments.

Arthroscopic-assisted 6U approach for foveal reattachment of triangular fibrocartilage complex with an anchor: Clinical and radiographic outcomes at 4 years’ mean follow-up

The main objective of this study was to evaluate the long-term clinical and radiological outcomes of arthroscopic-assisted foveal repair of proximal triangular fibrocartilage complex (TFCC) tears with an anchor. The secondary objective was to look for ligament damage associated with TFCC tears. Twenty-four patients who underwent foveal repair of the TFCC were evaluated retrospectively: 16 stage 2 and 8 stage 3 in the Atzei-EWAS classification. The TFCC was repaired with an anchor using an expanded 6U approach. Systematic testing of intrinsic and extrinsic ligaments was performed. The assessment criteria were pain on a visual analog scale (VAS), wrist joint range of motion, grip strength and pronation-supination strength, and the QuickDASH and PRWE outcome scores. X-rays were also taken to assess anchor position and to look for distal radioulnar (DRU) joint damage. The average follow-up was 44 months. After the surgical repair, pain was reduced (7.36±1.3 preoperatively vs. 0.69±1.3 postoperatively; P<0.001), the QuickDASH score improved (52.1±16 vs. 21.7±7; P<0.001), the PRWE score improved (83.7±35 vs. 9.3±12; P<0.001) as did strength (35 vs. 43kg; P<0.001). The DRU joint stability was also significantly improved. The time away from work was 2.6 months. During the arthroscopy exploration, 25% of patients had an ulnotriquetral ligament lesion and 8% had an ulnolunar ligament lesion in combination with their TFCC tear. Fifteen anchors were positioned in the anatomical fovea (62%). No DRU joint damage was noted. Six patients had neurapraxia of the dorsal branch of the ulnar nerve, although it recovered spontaneously. One patient still had hypoesthesia of the ulnar side of the fifth finger at 48 months. Arthroscopic-assisted foveal repair of the TFCC yields good results in terms of pain, strength and DRU joint stability. In one-quarter of cases, TFCC foveal tears are associated with lesions of the ulnotriquetral ligament. There is no long-term degeneration of the DRU joint.

Finite Element Analysis of Multi-Position Fatigue Fracture Damage of Nuclear Pipeline Based on X-ray Scattering

The traditional finite element analysis method has poor performance in identification, and there are errors in the selected identification position, resulting in the fact that the accuracy of the results of the finite element analysis is not high. Therefore, based on the characteristics of X-ray scattering, a new finite element analysis method for multi-position fatigue fracture of damage nuclear pipeline is proposed. In this method, a nuclear pipe model is constructed and the three-dimensional scattering identification density of X-ray is established. Based on the creep curve, the material parameters of the nuclear pipeline are analyzed, and the damage index grade is divided according to the yield strength and other parameters; the equivalent stress is calculated, and the constitutive relationship between the material and the damage index is described according to the damage value. The classical scattering formula and Stokes formula are introduced to locate the position of the X-ray cut in node by setting the spatial and temporal distribution function. The parameters of random dynamic change are calculated, and the anchor nodes and position nodes are set to locate the scanning range of damage nuclear pipeline. Experimental results show that compared with the traditional three methods, the proposed method has higher recognition rate and more accurate finite element analysis results. It can be seen that the performance of this method is superior.

Prediction of peptide binding to MHC using machine learning with sequence and structure-based feature sets

Selecting peptides that bind strongly to the major histocompatibility complex (MHC) for inclusion in a vaccine has therapeutic potential for infections and tumors. Machine learning models trained on sequence data exist for peptide:MHC (p:MHC) binding predictions. Here, we train support vector machine classifier (SVMC) models on physicochemical sequence-based and structure-based descriptor sets to predict peptide binding to a well-studied model mouse MHC I allele, H-2Db. Recursive feature elimination and two-way forward feature selection were also performed. Although low on sensitivity compared to the current state-of-the-art algorithms, models based on physicochemical descriptor sets achieve specificity and precision comparable to the most popular sequence-based algorithms. The best-performing model is a hybrid descriptor set containing both sequence-based and structure-based descriptors. Interestingly, close to half of the physicochemical sequence-based descriptors remaining in the hybrid model were properties of the anchor positions, residues 5 and 9 in the peptide sequence. In contrast, residues flanking position 5 make little to no residue-specific contribution to the binding affinity prediction. The results suggest that machine-learned models incorporating both sequence-based descriptors and structural data may provide information on specific physicochemical properties determining binding affinities.

Anatomic Acetabular Labral Repair

The important role of the acetabular labrum in maintaining stability and optimising fluid pressurisation of the hip joint is well recognised. Preservation and repair of the labrum is now considered an essential component of the arthroscopic management of labral tears and bony deformity correction in patients with symptomatic femoroacetabular impingement and hip dysplasia. Biomechanical studies have demonstrated improved stability and restoration of the sealing properties, vital for hydrostatic fluid pressurisation and reduction in cartilage contact forces, with labral repair. Clinical studies have shown labral repair, not only to have better results compared with debridement, but in conjunction with bony deformity correction, is durable, with successful medium to long-term outcome. Although a number of repair techniques have evolved to restore anatomy and function of the labrum, there are many deficiencies with traditional looped and pierced repair techniques including elevation and bunching, loss of fluid seal, rigidity of the labral body, low anchor positioning increasing risk of joint penetration, disruption of the important chondrolabral junction, and iatrogenic damage to labral tissue. Anatomic labral repair protects the intact chondrolabral junction and important fibrovascular attachments to the labrum; utilising a suspension repair technique the labral body is free from suture and iatrogenic injury, and remains stable but mobile to optimise the flap seal mechanism, vital for fluid pressurisation; the high anchor position reduces risk of joint penetration. Minimum 2-year clinical outcome demonstrates the excellent results from anatomic labral repair which protects and restores the anatomy, blood supply, and function of the labrum. This article describes the applied anatomy and the vital functions of the acetabular labrum, discusses the principles and controversies surrounding standard repair methods and details the operative technique, rationale and outcome for anatomic labral repair.

Low Risk of Recurrence After Posterior Labral Repair of the Shoulder in a High-Risk United States Military Population

PurposeTo examine the results of isolated arthroscopic posterior labral repair of the shoulder in an active military population, looking specifically at the reoperation rate and rate of return to previous military activity with a minimum follow-up period of 2 years.MethodsA retrospective case series was performed in active-duty military service members who underwent isolated, primary arthroscopic posterior labral repair at a single academic military treatment facility between 2009 and 2015 and had at least 2 years of follow-up. Patients were excluded if they were of non–active-duty status, had insufficient follow-up (<2 years), or had undergone a concurrent procedure. Injury presentation, demographic data, and surgical data (i.e., surgical positioning, number of anchors, and anchor placement location) were compiled manually. Outcomes including the rate of return to active duty, recurrence of symptoms, and need for revision surgery were evaluated.ResultsSixty-five patients were included. After arthroscopic repair, a high rate of return to previous military duties (83%) was noted at short- to mid-term follow-up (mean ± standard deviation, 3.04 ± 1.30 years), with 1 patient (1.5%) requiring revision arthroscopic repair and 10 patients (15.5%) showing activity-limiting shoulder pain preventing a return to active duty. Intraoperative positioning (P = .17), a low anchor position (P = .27), and the number of anchors used (P = .62) were not found to be significant contributors to continued postoperative pain or recurrent instability.ConclusionsArthroscopic intervention resulted in a reliable rate of glenohumeral stability with a low rate of surgical revision and a high rate of return to military duty at short- to mid-term follow-up. However, 1 in 6 military service members showed significant, activity-limiting shoulder pain postoperatively that did not permit a return to previous military activities after surgical intervention.Level of EvidenceLevel IV, therapeutic case series.