Robust Visual Question Answering: Datasets, Methods, and Future Challenges.

Visual question answering requires a system to provide an accurate natural language answer given an image and a natural language question. However, it is widely recognized that previous generic VQA methods often tend to memorize biases present in the training data rather than learning proper behaviors, such as grounding images before predicting answers. Therefore, these methods usually achieve high in-distribution but poor out-of-distribution performance. In recent years, various datasets and debiasing methods have been proposed to evaluate and enhance the VQA robustness, respectively. This paper provides the first comprehensive survey focused on this emerging fashion. Specifically, we first provide an overview of the development process of datasets from in-distribution and out-of-distribution perspectives. Then, we examine the evaluation metrics employed by these datasets. Third, we propose a typology that presents the development process, similarities and differences, robustness comparison, and technical features of existing debiasing methods. Furthermore, we analyze and discuss the robustness of representative vision-and-language pre-training models on VQA. Finally, through a thorough review of the available literature and experimental analysis, we discuss the key areas for future research from various viewpoints.

XTQA: Span-Level Explanations for Textbook Question Answering.

Textbook question answering (TQA) is the task of correctly answering diagram or nondiagram (ND) questions given large multimodal contexts consisting of abundant essays and diagrams. In real-world scenarios, an explainable TQA system plays a key role in deepening humans' understanding of learned knowledge. However, there is no work to investigate how to provide explanations currently. To address this issue, we devise a novel architecture toward span-level eXplanations for TQA (XTQA). In this article, spans are the combinations of sentences within a paragraph. The key idea is to consider the entire textual context of a lesson as candidate evidence and then use our proposed coarse-to-fine grained explanation extracting (EE) algorithm to narrow down the evidence scope and extract the span-level explanations with varying lengths for answering different questions. The EE algorithm can also be integrated into other TQA methods to make them explainable and improve the TQA performance. Experimental results show that XTQA obtains the best overall explanation result mean intersection over union (mIoU) of 52.38% on the first 300 questions of CK12-QA test splits, demonstrating the explainability of our method (ND: 150 and diagram: 150). The results also show that XTQA achieves the best TQA performance of 36.46% and 36.95% on the aforementioned splits. We have released our code in https://github.com/dr-majie/opentqa.

Comparison of intra-articular injection of ArtiAid®-Mini with Ostenil®-Mini for trapeziometacarpal osteoarthritis: A double-blind, prospective, randomized, non-inferiority trial.

OBJECTIVES: This study aims to compare the effectiveness and safety of intra-articular hyaluronic acid (HA) injections of ArtiAid®-Mini (AAM) and Ostenil®-Mini (OM) for the treatment of trapeziometacarpal joint osteoarthritis. PATIENTS AND METHODS: Between February 2018 and April 2020, this 24-week, double-blind, prospective, randomized, non-inferiority trial included a total of 17 patients (8 males, 9 females; mean age: 60.3±9.5 years; range, 42 to 76 years) who were treated with either intra-articular AAM (n=8) or OM (n=9). The primary outcome was pain according to a change in Visual Analog Scale (VAS) at 12 weeks after the last injection. The secondary outcomes included the change of VAS at Weeks 2, 4, and 24 after the injection, satisfaction, range of motion (ROM) of trapeziometacarpal joint, pinch strength, grip strength, and adverse events at Weeks 2, 4, 12, and 24 after the injection. RESULTS: Eight patients with AAM and eight patients with OM completed the follow-up. No significant differences in primary and secondary outcomes were observed between the two groups at baseline and each time point (p>0.05). The intra-group differences were significant in each time point. CONCLUSION: The intra-articular injection of either AAM or OM is effective and safe for patients with trapeziometacarpal osteoarthritis up to 24 weeks.

SocialSift: Target Query Discovery on Online Social Media With Deep Reinforcement Learning.

Among the prohibitively large volume of posts (e.g., tweets in Twitter) on online social networks (OSNs), how to design effective queries to explore the ones of interest is a pressing problem. There are two main challenges to address the problem. First, given public application programming interfaces (APIs) for querying posts related to keywords from an extremely large vocabulary, how to infer the keywords relevant to our target interest using as few queries as possible? Second, how to deal with the agnostics of OSN's API? i.e., as different social networks typically have different running mechanisms, even with some randomness in returning results, how to build the knowledge of the API returns w.r.t. target interests from scratches? To address the above two challenges, we propose a target query discovery framework based on a deep reinforcement learning approach, named SocialSift. SocialSift intelligently interacts with OSNs' keyword-based API and develops its own knowledge in searching the optimal queries w.r.t. the target interests as well as OSN APIs. Specifically, to address the first challenge, we are inspired by the human searching experience, and recognize learning to query with context awareness to reduce the searching space, by qualifying keywords from returned results and keeping the tracks of the query trial history, or say contexts. As for addressing the second challenge, we treat OSNs' APIs as black boxes and probabilistically quantify query-interest pairs guided by rewards, which is a well-curated indicator w.r.t. target interests. Empirical results on three popular OSNs: Twitter, Reddit, and Amazon demonstrate our SocialSift significantly outperforms the state-of-the-art baselines by 12% in retrieving target posts.

The effect of hole size on failure loads of the distal humerus fenestration in Outerbridge-Kashiwagi arthroplasty: A biomechanical study.

OBJECTIVE: The aim of this study was to biomechanically assess the effect of humeral-fenestration size in the Outerbridge-Kashiwagi arthroplasty on the ultimate failure load of the distal humerus in a synthetic bone model. METHODS: We biomechanically tested the influence of different humeral-fenestration sizes on the failure load of the distal humerus in Outerbridge-Kashiwagi arthroplasty. A total of 50 synthetic humerus models were divided into 5 groups based on the fenestration size: 10 mm, 12 mm, 15 mm, 18 mm, and 20 mm. All the samples were randomly assigned to receive either axial or anteroposterior (AP) loading and then loaded to failure at a rate of 2 mm/min on a material testing machine. The data regarding ultimate failure loads under the axial and AP loading were analyzed. RESULTS: Under the AP loading, the mean ultimate failure loads of the 18 mm and 20 mm groups were lower than those of the other groups. Under the axial loading, the mean ultimate failure load of the 10 mm group was significantly greater than that of the 15 mm, 18 mm, and 20 mm groups. Additionally, the ultimate failure load of the 20 mm group was significantly lower than that of the 12 mm, 15 mm, and 18 mm groups. CONCLUSION: The distal humeral fenestrations with a size greater than 18 mm may offer poor biomechanical properties in the Outerbridge-Kashiwagi ulnohumeral arthroplasty.

Patients older than 55 years prefer biceps tenodesis over tenotomy to the same degree as young patients.

BACKGROUND: 55 years of age used to be the cutoff point when deciding between biceps tenotomy and tenodesis for treating biceps tendon pathologies. METHODS: Patients aged ≥18 years who had tendonitis in the long head of the biceps and were admitted for arthroscopic surgery were included. A questionnaire with a series of questions assessing patients' current symptoms, their concerns about their outcomes, and personal demographic information was introduced to the participants on the day before the surgery. The patients' preference toward tenotomy and tenodesis was assessed, and χ2 tests and logistic regressions were used to test the association with the categorical and ordinal variables, respectively. RESULTS: A total of 135 patients enrolled in the study, with 83 males and 52 females, the mean age of which was 56 years (range, 18-75 years). Of all patients, 86 (63.7%) preferred biceps tenodesis as opposed to tenotomy; meanwhile, there was no difference in preference toward tenodesis in each age- and gender-subgroup (range, 55.1% to 71.4%). The different subgroups had specific factors that were predictive of choosing either a tenotomy or tenodesis. In most subgroups, concerns about postoperative arm appearance and the so-called "Popeye" deformity due to tenotomy were factors predictive of choosing biceps tenodesis, whereas concern about longer rehabilitation due to tenodesis was the factor predictive of choosing biceps tenotomy. CONCLUSIONS: Biceps tenodesis is a more preferable choice for patients with biceps tendinopathies in all age and gender subgroups. Patients' concerns on postoperative arm appearance, "Popeye" deformity due to tenotomy, and longer rehabilitation due to tenodesis are the most important predictive factors.

Ultrasonographic Features of Trigger Finger in Patients With Hyperuricemia.

PURPOSE: The purpose of the current study was to compare demographic differences and ultrasonographic features in primary trigger finger and trigger finger in association with hyperuricemia. METHODS: Between October 2008 and February 2010, a prospective review of consecutive cases of 54 patients with trigger finger and hyperuricemia, 76 patients with a trigger finger without hyperuricemia, and 80 control cases were enrolled. The clinical results were analyzed by descriptive epidemiology, an ultrasonographic measurement of the thickness of A1 pulley, cross-sectional area of the flexor tendon and synovium. RESULTS: The middle finger was primarily affected, followed by the index and ring fingers in both trigger finger groups. The thickness of A1 pulley, cross-sectional area of the flexor tendon, and flexor tendon with synovium in trigger finger without hyperuricemia group were significantly larger than that in trigger finger with hyperuricemia and control groups. There was no significant difference between trigger finger with hyperuricemia and control groups. Double-contour sign and tophus were only observed in trigger finger with hyperuricemia group. CONCLUSIONS: Thickness of A1 pulley, cross-sectional area of the flexor tendon, and flexor tendon with synovium were significantly larger in trigger finger without hyperuricemia group. These findings were not evident in trigger finger with hyperuricemia group.

The incidence of occult and missed surgical neck fractures in patients with isolated greater tuberosity fracture of the proximal humerus.

BACKGROUND: Occult and missed surgical neck fractures can be found in patients diagnosed with isolated greater tuberosity (GT) fracture during the follow up period. The purpose of this study was to retrospectively assess the incidence rate of occult and missed surgical neck fractures in those initially diagnosed with isolated GT fracture. METHODS: Records of patients diagnosed as having an isolated GT fracture were retrieved from a database in a medical center. Two senior orthopedic surgeons blindly reviewed all images of these patients three times to classify GT fracture types (split, avulsion and depression types), and recorded any surgical neck fractures found. Then a meeting was help to confirm the fracture types and presence of surgical neck fracture. RESULTS: Occult surgical neck fractures were found in 5 out of 68 (7.4%) patients, whereas missed surgical neck fractures were found in 3 out of 68 (4.4%) patients. In total, 32 patients had split type GT fracture, 32 had avulsion type and 4 had depression type. For those with occult surgical neck fractures, 7 had the split type GT fracture, while the remaining one had the avulsion type. Although the proportion of occult surgical neck fracture was higher in the split-type GT fracture (21.9%) than in the avulsion-type GT fracture (3.1%), the difference was not statistically significant (p = 0.056). CONCLUSION: Occult humeral surgical neck fractures occurred in 7.4% of isolated greater tuberosity fractures after re-evaluation, while missed humeral surgical neck fractures occurred in 4.4%.

Ultrasound-guided percutaneous carpal tunnel release in patients on hemodialysis: early experiences and clinical outcomes.

Purpose: The purpose of the current study was to evaluate the effectiveness of ultrasound-guided percutaneous carpal tunnel release in hemodialysis patients with carpal tunnel syndrome. Methods: From February 2009 to April 2013, a prospective review of 113 consecutive cases of ultrasound-guided percutaneous carpal tunnel release was carried out in 84 hemodialysis patients. Results were analyzed by clinical subjective scale, two self-administered questionnaires, and functional evaluations at seven time points (1 week and 1, 3, 6, 12, 18, and 24 months). Results: Satisfactory symptom improvement in patients was 82%, 80%, 86%, 89%, 90%, 91%, and 90% at 1 week and 1, 3, 6, 12, 18, and 24 months postoperatively, respectively. Moderate pain was suffered in 11.5% of patients within 1 week, 8.8% within 1 month, 2.7% within 3 months, and none after 12 months postoperatively. Static two-point discrimination and Semmes-Weinstein monofilament examinations presented significant improvements after 1 week and 1 month postoperatively and with time. Postoperative grip power demonstrated recovery and a significant increase after 3 and 6 months postoperatively. Three-jaw chuck-pinch strength showed significant increase after 1 month postoperatively. There were no operative complications. Conclusion: Ultrasound-guided percutaneous carpal tunnel release is an effective and safe procedure in hemodialysis patients with carpal tunnel syndrome. The advantages include a less invasive procedure, no tourniquet needed, only limited infiltration anesthesia, minimal soft-tissue exploration, and relatively short operation time. Our data suggest this technique can reliably relieve clinical symptoms, with early restoration of grip and pinch strength.

When deadman theory meets footprint decortication: a suture anchor biomechanical study.

BACKGROUND: The optimal insertion angle for suture anchor insertion has long been of great interest. Although greater tuberosity decortication is commonly performed during rotator cuff repair, the effect of decortication on the suture anchor insertion angle remains unclear. The purpose of this study was to compare the pullout strength of threaded suture anchors inserted at 45° and 90° in decorticated and non-decorticated synthetic bone models. METHODS: Two kinds of synthetic bones were used to simulate the decorticated and non-decorticated conditions, for which 40 metallic suture anchors were used. Anchors were inserted at 45° and 90° in both decorticated and non-decorticated models and tested under cyclic loading followed by load-to-failure testing. The number of completed cycles, ultimate failure load, and failure modes was recorded. RESULTS: In the decorticated model, the ultimate failure load of anchors inserted at 45° (67.5 ± 5.3 N) was significantly lower than that of anchors inserted at 90° (114.1 ± 9.8 N) (p <  0.001). In the non-decorticated model, the ultimate failure load of anchors inserted at 45° (591.8 ± 58 N) was also significantly lower than that of anchors inserted at 90° (724.9 ± 94 N) (p = 0.003). Due to the diverse failure modes in the non-decorticated model, specimens with a failure mode of suture anchor pullout were analyzed in greater detail, with results showing a significantly larger pullout strength for anchors inserted at 90° (781.6 ± 53 N) than anchors inserted at 45° (648.0 ± 43 N) (p = 0.025). CONCLUSION: Regardless of decortication, the pullout strength of anchors inserted at 90° was greater than those inserted at 45°. The clinical relevance is that inserting suture anchors at 90° is recommended due to the significantly larger ultimate failure load in both decorticated and non-decorticated bones.

Correlation Between IL-20 and De Quervain's Disease Severity.

De Quervain's disease is a stenosing tenosynovitis of the first dorsal compartment of the wrist. Histopathological studies have reported that the thickening of the first dorsal retinaculum is characterized by degeneration rather than inflammation. However, significant infiltration of mast cells and macrophages was noted in a torn tendon study, which suggested that innate immune pathways are part of the mechanism that mediates early tendinopathy. Recently, Interleukin-20 (IL-20) has been reported to provoke potent inflammation and regulate angiogenesis and chemotaxis, which are important for the pathogenesis of inflammatory diseases. The main purpose of our study was to investigate the correlation between IL-20 and tumor necrosis factor (TNF-α) and clarify the potential predictor of tendinopathy progression. Hematoxylin and eosin (H & E) and immunohistochemistry (IHC) staining were used to score and analyze the clinical outcome. TNF-α, IL-20 and related inflammation cytokines were examined. Moreover, the tenocytes were cultured with a stimulator and were used to examine inflammatory cytokine secretions. A real-time polymerase chain reaction (Real-time PCR) was used to detect the gene expression profile. The IHC data showed that TNF-α is up-regulated in grade III de Quervain's. The analysis data showed that IL-20 is positively correlated with TNF-α and disease severity. The real-time PCR showed that the inflammation stimulator enhanced the expression of IL-20 mRNA expression. Inflammation cytokines such as TNF-alpha, transforming growth factor-ß (TGF-ß) and IL-1 have been used as predictors of de Quervain's; IL-20 is a new predictor based on this study. In the future, IL-20 expression's involvement in the molecular mechanism of the severity of de Quervain's should be further investigated.

Comparison of changes in shoulder functions between biceps tenotomy and tenodesis in an animal model.

OBJECTIVES: Tenotomy and tenodesis of the long head of biceps tendon are effective pain-relieving treatments. However, there is no consensus on the functional outcome after these surgical procedures. We hypothesized that there would be no difference in ambulation parameters after recovery from the surgery between rats that underwent tenotomy versus tenodesis procedures. METHODS: Twenty-four New Zealand rats were used and randomly divided into three groups. Each group received one of the following surgeries: tenotomy, tenodesis, and sham operation. A video-based walking track system was applied for gait analysis at day -1, 1, 3, 5, 7, 14 and 21 for each rat. Temporal and spatial parameters were obtained, and asymmetric index was calculated for each parameter. RESULTS: Compared to the tenotomy and sham-operated groups, the rats in the tenodesis group had shorter stance phase, longer swing time, longer step length, smaller paw length, smaller intermediary toe-spread length, smaller toe-spread length, and larger foot angle right after the tenodesis procedure. After day 14, all parameters were equivalent to those of the sham-operated group. At the end of the study, there were no functional changes found in tenotomy and tenodesis groups compared with the sham-operated group and preoperative status. CONCLUSION: Transient functional alterations in temporal and spatial parameters are found after tenotomy and tenodesis in a rat model. The functional changes in the tenodesis group existed for a longer period than in tenotomy group; however, and all parameters showed no significant differences when compared with the sham group at the conclusion of the study.

Longer stitch interval in the Krackow stitch for tendon graft fixation leads to poorer biomechanical property.

PURPOSE: The purpose of this study was to analyze the effects of different intervals between stitch throws on tendon graft fixation with the Krackow stitch. METHODS: Forty-four porcine flexor profundus tendons were randomly divided into four groups of 11 specimens each. The Krackow stitch with various stitch intervals (2.5, 5.0, 7.5, and 10.0 mm) were evaluated, and named the K-2.5, K-5.0, K-7.5, and K-10.0 groups, respectively. A braided nonabsorbable suture was used to complete each suture-tendon construct. All specimens were pretensioned to 100 N for three cycles, cyclically loaded from 50 to 200 N for 200 cycles, and then finally loaded to failure. Elongation after cyclic loading, ultimate load to failure, and the mode of failure were recorded. RESULTS: There were significant differences in elongation after cyclic loading among the K-2.5 (31% ± 5%), K-5.0 (32% ± 4%), K-7.5 (34% ± 5%), and K-10.0 (41% ± 8%) groups ( p = 0.004); the post hoc analysis showed significantly smaller values in the K-2.5 and K-5.0 groups than in the K-10.0 group ( p = 0.002 and 0.003, respectively). The stitch interval was correlated with elongation after cyclic loading ( r = 0.52, p < 0.001). Ultimate loads to failure and cross-sectional area were not significantly different across the four groups. CONCLUSION: The Krackow stitch with stitch intervals of 2.5 and 5.0 mm had significantly smaller elongation after cyclic loading than with an interval of 10.0 mm in this porcine biomechanical study. The stitch interval was moderately correlated with elongation after cyclic loading.

Biomechanical properties of suprapectoral biceps tenodesis: double knotless screw fixation is superior to single knotless screw fixation.

INTRODUCTION: The purpose of this study is to biomechanically evaluate a new technique of double knotless screw fixation for suprapectoral biceps tenodesis and compare the results with that of the single knotless screw fixation as well as the interference screw fixation. METHODS: 24 fresh-frozen human cadaveric shoulders with a mean age of 68.3 ± 9 years were studied. The specimens were randomly divided into three experimental biceps tenodesis groups (n = 8): single knotless screw, double knotless screw and interference screw. Each tenodesis specimen was mounted on a mechanical testing machine, preloaded for 2 min at 5 N, tested with cyclic loading from 5 to 70 N for 500 load cycles and subjected to an axial load to failure test (1 mm/s). The ultimate failure load, stiffness, cyclic displacement and mode of failure were evaluated. RESULTS: The interference screw fixation had the highest ultimate failure load (215.8 ± 43.1 N) and stiffness (25.7 ± 5.2 N/mm) which were significantly higher than the corresponding results for the single and double knotless screw groups (P = 0.0029). The double knotless screw group had the second highest ultimate failure load (162.8 ± 13.8 N) and stiffness (15.1 ± 4.1 N/mm) which were significantly higher than the corresponding results for the single knotless screw technique (P = 0.0002). The most common mode of failure was suture slippage for both the double (7/8) and single knotless screw (6/8) groups while biceps tendon tearing occurred most often for the interference screw group (6/8). CONCLUSION: In this biomechanical study, the double knotless screw fixation was found to have a significantly greater ultimate failure load and stiffness than the single knotless screw fixation but lower values than the interference screw fixation.

A Biomechanical Evaluation of Various Double Krackow Suture Techniques for Soft-Tissue Graft Fixation.

PURPOSE: The purpose of this study was to compare the biomechanical properties among the different double Krackow suture techniques for tendon graft fixation. METHODS: Thirty porcine flexor profundus tendons were randomly divided into 3 groups of 10 specimens each. Three different double Krackow suture techniques were evaluated, namely, the McKeon's double Krackow (MDK) suture, Wilson's double Krackow (WDK) suture, and Ostrander's modified Krackow (OMK) suture. All suture configurations were completed with a braided nonabsorbable suture. Each suture-tendon construct was pretensioned to 100 N for 3 cycles, cyclically loaded from 50 to 200 N for 200 cycles, and then finally loaded to failure. Elongation after cyclic loading, ultimate load to failure, and the mode of failure were recorded for each specimen. RESULTS: There were significant differences in elongation after cyclic loading among the MDK suture (7.9 ± 3.6 mm, 14% ± 6%), WDK suture (11.6 ± 2.2 mm, 22% ± 3%), and OMK suture (9.6 ± 3.3 mm, 17% ± 6%; P = .018). In addition, although the post hoc analysis showed that elongation after cyclic loading in the MDK suture was significantly less than the WDK suture (P = .004), ultimate failure load and cross-sectional area were not significantly different across the 3 groups. CONCLUSIONS: In this porcine in vitro biomechanical study, the MDK suture had significantly smaller elongation after cyclic loading than the WDK suture; however, high elongation values may have a potential for risk of clinical laxity. The ultimate failure load was not different across the MDK, WDK, and OMK sutures. CLINICAL RELEVANCE: Smaller elongation during cyclic loading in a suture-tendon construct represents a lower possibility of tendon graft loosening after ligament reconstruction surgery. The double Krackow suture techniques are attractive options for tendon graft fixation in ligament reconstruction, and the MDK suture could possibly be the optimal choice among the double Krackow suture techniques.

Arthroscopic Transtendinous Biceps Tenodesis With All-Suture Anchor.

There are several methods for long head of the biceps (LHB) tenodesis, yet the optimal option is still debatable. Here we introduce a technique for arthroscopic suprapectoral biceps tenodesis with an all-suture anchor, the transtendinous biceps tenodesis technique. The LHB tenodesis is performed by using the Y-Knot anchor (1.3-mm). A standard suprapectoral approach is used for the tenodesis. A 1.3-mm drill bit is used to drill through the midportion of the biceps tendon and underlying bone to make a pilot hole. Next, the Y-Knot anchor is passed through the tendon and anchored on the underlying bone. A wrapping suture technique is then used to wrap around, tension, and secure the LHB tendon with the aid of a shuttling polydioxanone suture. The construct is fixed by tying down both suture limbs in a nonsliding fashion. This Technical Note describes an alternative method for all-arthroscopic suprapectoral biceps tenodesis using an all-suture anchor with a small diameter to minimize trauma to the tendon.

Effects of decompression on behavioral, electrophysiologic, and histomorphologic recovery in a chronic sciatic nerve compression model of streptozotocin-induced diabetic rats.

PURPOSE: To determine susceptibility to decompression surgery in diabetic and nondiabetic peripheral neuropathy using a chronic compression neuropathy model. MATERIALS AND METHODS: Twenty-four streptozotocin-induced diabetic rats were randomly divided into three groups: group I, chronic compression of the left sciatic nerve for 4 weeks with decompression; group II, similar without decompression; and group III, sham exposing the sciatic nerve only. The other 24 nondiabetic rats were assigned to groups IV-VI, which received compression-decompression, compression, and the sham operation, respectively. Mixed-nerve-elicited somatosensory evoked potentials (M-SSEPs) and compound muscle action potentials (CMAPs) were measured to verify the compression neuropathy in the posttreatment follow-up. Behavioral observations in thermal hyperalgesia tests were quantified before electrophysiologic examinations. Treated and contralateral nerves were harvested for histomorphologic analysis. RESULTS: Chronic compression of sciatic nerve induced significant reduction of amplitude and increment of latency of M-SSEP and CMAP in both diabetic and nondiabetic rats. Diabetic group changes were more susceptible. Decompression surgery significantly improved both sensory and motor conduction, thermal hyperalgesia, and the mean myelin diameter of the rat sciatic nerve in both diabetic and nondiabetic groups. Near full recovery of motor and sensory function occurred in the nondiabetic rats, but not in the diabetic rats 8 weeks postdecompression. CONCLUSION: Behavioral, electrophysiologic, and histomorphologic findings indicate that decompression surgery is effective in both diabetic and nondiabetic peripheral neuropathy.

Augmentation by cerclage wire improves fixation of vertical shear femoral neck fractures-A biomechanical analysis.

BACKGROUND: Femoral neck fractures in young individuals are typically vertical shear fractures. These injuries are difficult to stabilize due to a significant varus displacement force across the hip with weight bearing. The purpose of this study was to evaluate the biomechanical stability offered by the addition of an augmented wire to conventional inverted triangle triple screw fixation for stabilizing vertical shear femoral neck fracture. METHODS: Sixteen medium 4th-generation synthetic composite femurs (Sawbones Pacific Research Laboratories, Vashon, WA) were divided into two groups. Vertical osteotomy was performed to mimic Pauwels III femoral neck fracture. Group A (n=8) was fixed with three parallel 6.5-mm cannulated screws (Stryker) with washer in inverted triangle configuration. In group B (n=8), all the screws were set using methods identical to group A, with the addition of the cerclage wire. Both groups were tested with nondestructive axial compression test at 7 and 25° of valgus stress, respectively. Then axial cyclic loading test with 1000N was applied for 1000 cycles, and interfragmentary displacement was measured with Fastrak magnetic tracking system (Polhemus, Colchester, VT, USA). Finally, destructive axial compression test was conducted at 7°of valgus stress. RESULTS: Axial stiffness showed that group B had a 66% increase (879N/mm vs. 1461N/mm, P<0.01) at 7° valgus and a 46% increase (1611N/mm vs. 2349N/mm, P<0.01) at 25° valgus in comparison with group A. Interfragmentary fracture displacement after cyclic loading was significantly less for group B compared with group A (0.34 vs 0.13mm, P=0.0016). For axial failure load, there was 42% increase in group B compared with group A (2602N/mm vs. 3686N/mm, P=0.0023). CONCLUSIONS: Our study demonstrates that the addition of a cerclage wire to inverted triangle triple screws provides substantial improvement in mechanical performance regarding fixation of vertically oriented femoral neck fractures when compared with the conventional construct. Our study provides support from a mechanical analysis perspective for the reported clinical usefulness of the cerclage wire.

Lateral Hindfoot Impingement After Nonunion of Fracture of the Lateral Process of the Talus.

Fracture of the lateral process of the talus is a relatively uncommon ankle injury, and the diagnosis is easily delayed. Lateral hindfoot impingement is characteristically related to chronic hindfoot valgus malalignment, with lateral ankle pain localized to the subtalar region. In a review of the published data, lateral hindfoot impingement after nonunion of fracture of the lateral process of the talus was not found. We present the case of a patient with such an injury. The patient was treated operatively and was followed for 18 months.