Installing Quinol Proton/Electron Mediators onto Non-Heme Iron Complexes Enables Them to Electrocatalytically Reduce O2 to H2O at High Rates and Low Overpotentials.

We prepare iron(II) and iron(III) complexes with polydentate ligands that contain quinols, which can act as electron proton transfer mediators. Although the iron(II) complex with N-(2,5-dihydroxybenzyl)-N,N',N'-tris(2-pyridinylmethyl)-1,2-ethanediamine (H2qp1) is inactive as an electrocatalyst, iron complexes with N,N'-bis(2,5-dihydroxybenzyl)-N,N'-bis(2-pyridinylmethyl)-1,2-ethanediamine (H4qp2) and N-(2,5-dihydroxybenzyl)-N,N'-bis(2-pyridinylmethyl)-1,2-ethanediamine (H2qp3) were found to be much more active and more selective for water production than a previously reported cobalt-H2qp1 electrocatalyst while operating at low overpotentials. The catalysts with H2qp3 can enter the catalytic cycle as either Fe(II) or Fe(III) species; entering the cycle through Fe(III) lowers the effective overpotential. On the basis of their TOF0 values, the successful iron-quinol complexes are better electrocatalysts for oxygen reduction than previously reported iron-porphyrin compounds, with the Fe(III)-H2qp3 arguably being the best homogeneous electrocatalyst for this reaction. With iron, the quinol-for-phenol substitution shifts the product selectivity from H2O2 to water with little impact on the overpotential, but unlike cobalt, this substitution also greatly improves the activity, as assessed by TOFmax, by hastening the protonation and oxygen binding steps. The addition of a second quinol further enhances the activity and selectivity for water but modestly increases the effective overpotential.

Reliability of Spatiotemporal Characteristics During Single-Legged Hop and Bilateral Drop Jump Tasks Using an Instrumented Pressure Walkway.

Background: Single-legged hop tests have been widely used to assess performance-based outcomes after anterior cruciate ligament (ACL) reconstruction. Traditional single, triple, or 6-meter (6m) timed hop tests only measure distance or time as the principal variables, neglecting other variables, such as individual hop distances within a series of hops, flight time, and stance time. The development of portable instrumented pressure walkways has made it possible to collect parameters such as hop velocity, flight time, stance time, distance, and pressure outside of a laboratory setting. However, the reliability of instrumented pressure walkways in measuring spatial and temporal variables during single-legged hop tests is unknown. This study aimed to determine if the Zeno walkway can reliably measure spatiotemporal (ST) characteristics of hop tests. Study Design: Cross-Sectional Study. Methods: Individuals (n=38) in this cross-sectional study performed single, triple, and 6m hop tests on a pressure-sensitive Zeno walkway. Twenty-one participants completed follow-up testing between one and 14 days later. Intraclass correlation coefficients (ICC(3,k)) were used to assess test-retest reliability of ST variables. The accuracy of vertical jump height and 6m hop timing were also measured. Results: All ST variables demonstrated excellent test-retest reliability (ICC > 0.86) with small minimal detectable change (MDC) values during single-legged hop tests. Six-meter hop time and jump height during a bilateral drop jump were also accurately measured by the walkway. Conclusion: An instrumented pressure walkway is a novel tool to reliably assess non-traditional parameters of clinically relevant hop and jump tests such as flight time, stance time, and jump height after lower extremity injury, surgery, and rehabilitation. Level of Evidence: 3b.

Measuring gravitational attraction with a lattice atom interferometer.

Despite being the dominant force of nature on large scales, gravity remains relatively elusive to precision laboratory experiments. Atom interferometers are powerful tools for investigating, for example, Earth's gravity1, the gravitational constant2, deviations from Newtonian gravity3-6 and general relativity7. However, using atoms in free fall limits measurement time to a few seconds8, and much less when measuring interactions with a small source mass2,5,6,9. Recently, interferometers with atoms suspended for 70 s in an optical-lattice mode filtered by an optical cavity have been demonstrated10-14. However, the optical lattice must balance Earth's gravity by applying forces that are a billionfold stronger than the putative signals, so even tiny imperfections may generate complex systematic effects. Thus, lattice interferometers have yet to be used for precision tests of gravity. Here we optimize the gravitational sensitivity of a lattice interferometer and use a system of signal inversions to suppress and quantify systematic effects. We measure the attraction of a miniature source mass to be amass = 33.3 ± 5.6stat ± 2.7syst nm s-2, consistent with Newtonian gravity, ruling out 'screened fifth force' theories3,15,16 over their natural parameter space. The overall accuracy of 6.2 nm s-2 surpasses by more than a factor of four the best similar measurements with atoms in free fall5,6. Improved atom cooling and tilt-noise suppression may further increase sensitivity for investigating forces at sub-millimetre ranges17,18, compact gravimetry19-22, measuring the gravitational Aharonov-Bohm effect9,23 and the gravitational constant2, and testing whether the gravitational field has quantum properties24.

Reliability of an Instrumented Pressure Walkway for Measuring Walking and Running Characteristics in Young, Athletic Individuals.

Background: Spatiotemporal parameters of gait are useful for identifying pathological gait patterns and presence of impairments. Reliability of the pressure-sensitive ZenoTM Walkway has not been established in young, active individuals without impairments, and no studies to this point have included running. Purpose: The purposes of this study were to 1) determine if up to two additional trials of walking and running on the ZenoTM Walkway are needed to produce consistent measurements of spatiotemporal variables, and 2) establish test-retest reliability and minimal detectable change (MDC) values for common spatiotemporal variables measured during walking and running. Study Design: Cross-Sectional Laboratory Study. Methods: Individuals (n=38) in this cross-sectional study walked and ran at self-selected comfortable speed on a pressure-sensitive ZenoTM Walkway. Twenty-one participants returned for follow-up testing between one and 14 days later. Intraclass correlation coefficients (ICCs) were used to assess reliability of spatiotemporal variable means using three, four, or five passes over the ZenoTM Walkway and to assess test-retest reliability of spatiotemporal variables across sessions. Results: All variables showed excellent reliability (ICC > 0.995) for walking and running when measured using three, four, or five passes. Additionally, all variables demonstrated moderate to excellent test-retest reliability during walking (ICC: 0.732-0.982) and running (ICC: 0.679-0.985). Conclusion: This study establishes a reliable measurement protocol of three one-way passes when using the ZenoTM Walkway for walking or running analysis. This is the first study to establish reliability of the ZenoTM Walkway during running and in young, active individuals without neuromusculoskeletal pathology. Level of Evidence: 3b.

Short-term fear of movement improves less after anterior cruciate ligament reconstruction with concomitant meniscus repair.

BACKGROUND: Psychological response is important in return-to-sport decisions for athletes recovering from anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare psychological response after ACLR with a concomitant meniscus repair compared to isolated ACLR. METHODS: Thirty-five individuals completed the Tampa Scale of Kinesiophobia (TSK) and Anterior Cruciate Ligament Return-to-Sport after Injury (ACL-RSI) scale before ACLR and 2, 4, and 6 months after ACLR. Participants were dichotomized based on presence of concomitant meniscus repair (Yes/No). Separate group X time repeated measures analyses of variance were conducted for both scales. RESULTS: Participants were 65.7% female, 19.1 ± 4.7 years old with BMI of 24.9 ± 4.4 kg/m2. Sixteen individuals had an isolated ACLR with 19 individuals having an ACLR with concomitant meniscus repair. For the TSK, there was a group × time interaction effect(p = 0.028), with improvement in TSK scores for the isolated ACLR group (ACLR:2 months = 24.8 ± 3.7; 4 months = 22.0 ± 5.7; 6 months: 19.9 ± 5.9; Meniscus Repair:2 months = 25.5 ± 4.7; 4 months = 24.1 ± 5.0; 6 months: 23.8 ± 4.7). Six months after ACLR, TSK scores were worse in the meniscus repair group(p = 0.036). For the ACL-RSI, there was no interaction(p = 0.07). CONCLUSION: Concomitant meniscus repair with ACLR results in less post-operative improvement in kinesiophobia through 6 months after ACLR compared to isolated ACLR.

Transferable nano-patterned ALD membrane.

We demonstrate fabrication of nano-patterned thin ALD (Atomic layer deposition) membrane (suspended/transferable) by using a bi-layer resist process where the bottom layer resist acts as a sacrificial layer. This method enables an all dry deterministic transfer of nano-patterned ALD membrane on desired substrate, allowing assembly of multitude of hetero-structures and functionalities that are not yet accessible. Unlike conventional ways of achieving patterned alumina membrane reported in literature our technique requires significantly less fabrication steps and paves the way for novel ALD membrane-based technology.

Environmental Risk Factors for Osteoarthritis: The Impact on Individuals with Knee Joint Injury.

Osteoarthritis is a debilitating chronic condition involving joint degeneration, impacting over 300 million people worldwide. This places a high social and economic burden on society. The knee is the most common joint impacted by osteoarthritis. A common cause of osteoarthritis is traumatic joint injury, specifically injury to the anterior cruciate ligament. The purpose of this review is to detail the non-modifiable and modifiable risk factors for osteoarthritis with particular focus on individuals after anterior cruciate ligament injury. After reading this, health care providers will better comprehend the wide variety of factors linked to osteoarthritis.

Clinical Management of Patellar Tendinopathy.

Patellar tendinopathy is a common yet misunderstood condition that afflicts a variety of patient populations. This lack of understanding affects the ability of clinicians to provide effective treatment interventions. Patients with tendinopathy often report long-term and low to moderate levels of pain, diminished flexibility, and reduced strength, as well as decreased physical function. Load-management strategies combined with exercise regimens focused on progressive tendon loading are the most effective treatment options for patients with patellar tendinopathy. This review will provide an evidence-based approach to patellar tendinopathy, including its pathoetiology, evaluation, and treatment strategies.

Knee joint unloading and daily physical activity associate with cartilage T2 relaxation times 1 month after ACL injury.

Osteoarthritis (OA) is prevalent after anterior cruciate ligament (ACL) injury, but mechanismsunderlying its development are poorly understood. The purpose of this study was to determine if gait biomechanics and daily physical activity (PA) associate with cartilage T2 relaxation times, a marker of collagen organization and water content, 1 month after ACL injury. Twenty-seven participants (15-35 years old) without chondral lesions completed magnetic resonance imaging, three-dimensional gait analysis, and 1 week of PA accelerometry. Interlimb differences and ratios were calculated for gait biomechanics and T2 relaxation times, respectively. Multiple linear regression models adjusted for age, sex, and concomitant meniscus injury were used to determine the association between gait biomechanics and PA with T2 relaxation times, respectively. Altered knee adduction moment (KAM) impulse, less knee flexion excursion (kEXC) and higher daily step counts accounted for 35.8%-65.8% of T2 relaxation time variation in the weightbearing and posterior cartilage of the medial and lateral compartment (all p ≤ .011). KAM impulse was the strongest factor for T2 relaxation times in all models (all p ≤ .001). Lower KAM impulse associated with longer T2 relaxation times in the injured medial compartment (ß = -.720 to -.901) and shorter T2 relaxation in the lateral compartment (ß = .713 to .956). At 1 month after ACL injury, altered KAM impulse, less kEXC, and higher PA associated with longer T2 relaxation times, which may indicate poorer cartilage health. Statement of Clinical Significance: Gait biomechanics and daily PA are modifiable targets that may improve cartilage health acutely after ACL injury and slow progression to OA.

Platelet-Rich Plasma versus Corticosteroid Injection for the Treatment of Lateral Epicondylitis: A Systematic Review of Systematic Reviews.

BACKGROUND: Lateral epicondylitis (LE) is one of the most commonly reported musculoskeletal disorders in the upper extremity. The mechanism of LE is repetitive motion that causes a strain of the extensor tendons. This consequently causes pain and tendinosis at the tendinous attachment site on the lateral epicondyle. Most cases of LE are treated nonoperatively with a variety of interventions, such as injections. PURPOSE: The aim of this systematic review (SR) is to synthesize the current evidence on the efficacy of platelet rich plasma (PRP) injections versus corticosteroid (CS) injections as treatment interventions for LE. STUDY DESIGN: Systematic Review. METHODS: Online databases were searched from database inception to February 24th, 2020 for relevant SR's evaluating PRP vs. CS injections as treatment methods for LE. Two independent researchers searched and screened for articles that were systematic reviews that directly compared PRP to CS injections for LE. RESULTS: A total of five SR's were included in this review that were published between 2016 and 2020. CS injections were more efficacious for short-term pain relief, and PRP injections were more efficacious for long-term pain relief and improved function. CONCLUSION: PRP injections appear to be a more effective long-term treatment option than CS injections for those with LE who did not respond to conservative management. LEVEL OF EVIDENCE: 1.

Early Ambulation After Hip Fracture Surgery Is Associated With Decreased 30-Day Mortality.

INTRODUCTION: Hip fractures frequently present in complicated patients and are fraught with high morbidity and mortality rates. Postoperatively, delayed ambulation has been identified as a factor associated with increased mortality, although its magnitude has yet to be quantified. Therefore, this article aims to evaluate mortality after hip fracture surgery because it relates to early postoperative ambulation, taking into account preexisting comorbidity burden. METHODS: This is a retrospective review of patients older than age 65 years who underwent surgical fixation for hip fractures because of a low-energy mechanism. Ambulation during the first 3 postoperative days was recorded along with age and preexisting comorbidity burden (Modified 5-Factor Frailty Index), and 30-day and 1-year mortality statuses were examined. Multivariable logistic regression was used to analyze the association between postoperative ambulation and mortality. RESULTS: Of 485 patients initially identified, 218 met the inclusion criteria. Overall mortality rates were 6.4% at 30 days and 18.8% at 1 year. Two-thirds of patients ambulated in the first 3 postoperative days versus one-third who did not. Patients who did not ambulate had both significantly increased 30-day mortality (odds ratio [OR] 4.42, P = 0.010, 95% confidence intervals [CIs] 1.42 to 13.75) and 1-year mortality (OR 2.26, P = 0.022, 95% CI 1.12 to 4.53). After multivariable logistic regression accounting for age and comorbidity status, ambulation remained strongly associated with 30-day (OR 3.87, P = 0.024, 95% CI 1.20 to 12.50) but not 1-year mortality (OR 1.66, P = 0.176, 95% CI 0.80 to 3.48). Although neither were significant at 30 days, both increasing age (OR 1.05, P = 0.020, 95% CI 1.01 to 1.10) and Modified 5-Factor Frailty Index (OR 1.62, P = 0.005, 95% CI 1.16 to 2.26) correlated with increased mortality at 1 year. CONCLUSION: Early ambulation after hip fracture surgery bears a notable, almost four-fold, association with early postoperative mortality independent of age and medical comorbidities. Our results support a growing body of evidence that ambulation is a powerful tool that should continue to be emphasized to optimize mortality in hip fracture patients.

Open Treatment for Unstable Osteochondritis Dissecans of the Knee: Autologous Bone Grafting and Bioabsorbable Fixation.

Osteochondritis dissecans is a common osteochondral abnormality affecting the knee. In unstable lesions, the underlying bone can be significantly abnormal and necessitate treatment. Although many techniques exist, we favor an open surgical approach to ensure that the bone is properly managed. Autologous bone graft can easily be obtained locally and used to restore the bony architecture. The subsequent use of bioabsorbable implants provides a robust means of fixation that allows for single-stage surgery. This Technical Note describes a straightforward but reliable approach to a challenging pathology.

Acromioclavicular joint injuries in overhead athletes: a concise review of injury mechanisms, treatment options, and outcomes.

PURPOSE OF THE REVIEW: To review the relevant literature surrounding acromioclavicular (AC) joint injuries particularly pertaining to overhead athletes. RECENT FINDINGS: The AC joint is a unique anatomic and biomechanical portion of the shoulder that can be problematic for athletes, particularly throwers, when injured. Treatment of these injuries remains a topic in evolution. Low-grade injuries (Rockwood types I & II) are typically treated non-operatively while high-grade injuries (types IV, V, and VI) are considered unstable and often require operative intervention. Type III AC separations remain the most controversial and challenging as no clear treatment algorithm has been established. A wide variety of surgical techniques exist. Unfortunately, relatively little literature exists with regard to overhead athletes specifically. Treatment of AC joint injuries remains challenging, at times, particularly for overhead athletes. Operative indications and techniques are still evolving, and more research is needed specifically surrounding overhead athletes.

Chondral Delamination of Fresh Osteochondral Allografts after Implantation in the Knee: A Matched Cohort Analysis.

INTRODUCTION: Delamination of the chondral surface of an osteochondral allograft (OCA) from the underlying cancellous bone has been described as a mode of failure after implantation in the knee. Our hypothesis was that increased storage time of the OCA is associated with increased risk of graft delamination after implantation. METHODS: Prospective data on 13 patients with evidence of OCA delamination identified on magnetic resonance imaging or during subsequent surgery from 2000 to 2015 were reviewed. A cohort of 33 patients without evidence of graft delamination were then matched to the delamination group based on recipient age, sex, body mass index (BMI), and chondral defect location. The matched cohort size was established based on a power calculation for determining differences in OCA storage times. All patients had a minimum 2-year follow-up. RESULTS: There was no difference in donor age, donor sex, and graft storage time between groups (30 vs. 31 days, P = 0.78). There were no differences between number of previous ipsilateral knee surgeries (1.8 vs. 0.84, P = 0.26), BMI (26.8 vs. 25.0 kg/m2, P = 0.31), total chondral defect size (6.5 vs. 5.8 cm2, P = 0.41) or preoperative Marx activity scores between groups. CONCLUSION: There is no association between OCA storage time, activity level scores, or number of previous ipsilateral knee surgeries and graft delamination in our patient population. Further work is needed to identify the etiology for this mode of failure of OCAs.

Trifurcate Origin of Long Head of Biceps Brachii: A Case Report and Literature Review.

INTRODUCTION: Variant anatomy of the intra-articular portion of the long head of the biceps tendon (LHBT) is rare, and its clinical significance is poorly understood. However, these variants are encountered with increasing frequency due to increasing use of shoulder arthroscopy. CASE REPORT: We report a case of a trifurcate intra-articular LHBT, a variation which, to our knowledge, has not been previously described. The patient was an adult male presenting with chronic atraumatic shoulder pain that worsened with overhead activity. On arthroscopy, the LHBT was found to have three origins from the (1) supraspinatus tendon, (2) superior labrum, and (3) rotator interval that joined together distally within the biceps tunnel. We believe the split tendon may have caused impingement the biceps tunnel; therefore, the patient was treated with subpectoral tenodesis. He also underwent subacromial decompression and rotator cuff debridement. CONCLUSION: This case highlights the importance of surgeon and radiologist awareness of split LHBT variant anatomy, such that misdiagnosis and unnecessary treatment may be avoided.

Management of the Stiff Shoulder With Arthroscopic Circumferential Capsulotomy and Axillary Nerve Release.

Management of the stiff shoulder is a common and frequently daunting clinical scenario. Arthroscopic capsular release is usually an option for management of severe, chronic glenohumeral joint contractures when conservative treatment fails. Technical hurdles including a thickened capsule, reduction in joint volume, and difficulty with positioning the shoulder intraoperatively can make this procedure challenging. In addition, incomplete release and recalcitrant stiffness are frequent issues. We believe a complete release of the capsule entails special attention to the axillary pouch and requires identification and protection of the axillary nerve. We present a technique for a complete arthroscopic circumferential capsulotomy and detail our approach to safely dissect and protect the axillary nerve under arthroscopic visualization.

Biceps Tenodesis: Anatomic Tensioning.

Biceps tenodesis is a commonly employed surgical intervention for refractory symptoms related to the biceps-labral complex, those intra-articular and those within the extra-articular bicipital tunnel. While a litany of surgical techniques exists, the optimal method for ensuring an anatomic length-tension relationship during tenodesis remains elusive. Appropriate tensioning may limit undesirable outcomes such as cramping or cosmetic deformity. We describe herein our technique as a simple and efficient means to establish patient-specific, anatomic tensioning of the long head of the biceps during tenodesis.

Orthopaedic Perspective on Barefoot and Minimalist Running.

In recent years, there has been a movement toward barefoot and minimalist running. Advocates assert that a lack of cushion and support promotes a forefoot or midfoot strike rather than a rearfoot strike, decreasing the impact transient and stress on the hip and knee. Although the change in gait is theorized to decrease injury risk, this concept has not yet been fully elucidated. However, research has shown diminished symptoms of chronic exertional compartment syndrome and anterior knee pain after a transition to minimalist running. Skeptics are concerned that, because of the effects of the natural environment and the lack of a standardized transition program, barefoot running could lead to additional, unforeseen injuries. Studies have shown that, with the transition to minimalist running, there is increased stress on the foot and ankle and risk of repetitive stress injuries. Nonetheless, despite the large gap of evidence-based knowledge on minimalist running, the potential benefits warrant further research and consideration.

Arthroscopic-Assisted Fixation of Ideberg Type III Glenoid Fractures.

Operative treatment of scapular fractures with extension into the glenoid can be a challenging clinical scenario. Though traditionally addressed in an open fashion, the morbidity of this approach, complemented by advancements in arthroscopic technique and instrumentation, has led to increasing use of arthroscopic-assisted fixation. We describe our technique, including pearls and pitfalls, for minimally invasive fixation of Ideberg type III glenoid fractures. This approach minimizes morbidity, allows optimal visualization and reduction, and provides good functional results.