Tuning the Biodegradation Rate of Silk Materials via Embedded Enzymes

Conventional thinking when designing biodegradable materials and devices is to tune the intrinsic properties and morphological features of the material to regulate their degradation rate, modulating traditional factors such as molecular weight and crystallinity. Since regenerated silk protein can be directly thermoplastically molded to generate robust dense silk plastic-like materials, this approach afforded a new tool to control silk degradation by enabling the mixing of a silk-degrading protease into bulk silk material prior to thermoplastic processing. Here we demonstrate the preparation of these silk-based devices with embedded silk-degrading protease to modulate the degradation based on the internal presence of the enzyme to support silk degradation, as opposed to the traditional surface degradation for silk materials. The degradability of these silk devices with and without embedded protease XIV was assessed both in vitro and in vivo. Ultimately, this new process approach provides direct control of the degradation lifetime of the devices, empowered through internal digestion via water-activated proteases entrained and stabilized during the thermoplastic process.

Plastic and elastic biomechanical properties of anterior cruciate ligament autografts

BACKGROUND

Anterior cruciate ligament (ACL) rupture is a common orthopedic injury, occurring in roughly 68.6 per 100,000 persons annually, with the primary treatment option being ACL reconstruction. However, debate remains about the appropriate graft type for restoring the native biomechanical properties of the knee. Furthermore, plastic graft elongation may promote increased knee laxity and instability without rupture. This study aims to investigate the plastic properties of common ACL-R graft options.

METHODS

Patellar tendon (PT), hamstring tendon (HT), and quadriceps tendon (QT) grafts were harvested from 11 cadaveric knees (6 male and 5 female) with a mean age of 71(range 55-81). All grafts were mechanically tested under uniaxial tension until failure to determine each graft's elastic and plastic biomechanical properties.

RESULTS

Mechanically, the QT graft was the weakest, exhibiting the lowest failure force and the lowest failure stress (QT < HT, p = 0.032). The PT was the stiffest of the grafts, having a significantly higher stiffness (PT > QT, p = 0.0002) and Young's modulus (PT > QT, p = 0.001; PT > HT, p = 0.041). The HT graft had the highest plastic elongation at 4.01 ± 1.32 mm (HT > PT, p = 0.002). The post-yield behavior of the HT tendon shows increased energy storage capabilities with the highest plastic energy storage (HT > QT, p = 0.012) and the highest toughness (HT > QT, p = 0.032).

CONCLUSION

Our study agrees with prior studies indicating that the failure load of all grafts is above the requirements for everyday activities. However, grafts may be susceptible to yielding before failure during daily activities. This may result in the eventual loss of functionality for the neo-ACL, resulting in increased knee laxity and instability.

Electrical impedance myography for the early detection of muscle ischemia secondary to compartment syndrome: a study in a rat model

Acute Compartment Syndrome (ACS) is one of the most devastating orthopedic conditions, affecting any of the body's many compartments, which, if sufficiently severe, may result in disability and amputation. Currently, intra-compartmental pressure measurements serve as the gold standard for diagnosing ACS. Diagnosing limbs at risk for ACS before irreversible damage to muscle and nerve is critical. Standard approaches for diagnosing impending compartment syndrome include clinical evaluation of the limb, such as assessment for "tightness" of the overlying skin, reduced pulses distally, and degree of pain, none of which are specific or sensitive. We have proposed a novel method to detect ACS via electrical impedance myography (EIM), where a weak, high-frequency alternating current is passed between one pair of electrodes through a region of tissue, and the resulting surface voltages are measured via a second pair. We evaluated the ability of EIM to detect early muscle ischemia in an established murine model of compression-induced muscle injury, where we collected resistance, reactance, and their dimensionless product, defined as Relative Injury Index (RII) during the study. Our model generated reproducible hypoxia, confirmed by Hypoxyprobe™ staining of endothelial regions within the muscle. Under conditions of ischemia, we demonstrated a reproducible, stable, and significant escalation in resistance, reactance, and RII values, compared to uninjured control limbs. These data make a reasonable argument for additional investigations into using EIM for the early recognition of muscle hypoperfusion and ischemia. However, these findings must be considered preliminary steps, requiring further pre-clinical and clinical validation.

Pediatric Maisonneuve and Tillaux Fractures with Lateral Ankle Dislocation: A Pediatric "Logsplitter" Injury: A Case Report

CASE

A 12-year-old adolescent boy presented with a proximal fibula fracture and lateral ankle dislocation consistent with a Maisonneuve fracture (MF) associated with a transsyndesmotic ankle dislocation. The dislocation was reduced under conscious sedation in the emergency department. Postreduction imaging studies demonstrated a Tillaux fracture. The patient underwent surgical stabilization of the Tillaux fragment and of the distal tibiofibular syndesmosis. At the 26-month follow-up, the patient remained active without restrictions.

CONCLUSION

Operative treatment of a concurrent MF, Tillaux fracture with lateral ankle dislocation, or a pediatric "logsplitter" injury resulted in satisfactory alignment and function of the ankle joint.

Outcomes of fixation of Vancouver B periprosthetic fractures around cemented versus uncemented stems

BACKGROUND

The incidence of periprosthetic femur fracture (PPFF) in the setting of total hip arthroplasty (THA) is steadily increasing. We seek to address whether there is a difference in outcomes between Vancouver B fracture types managed with ORIF when the original stem was a press-fit stem versus a cemented stem.

METHODS

In this retrospective cohort study at a level 1 trauma center, we identified 136 patients over 65 years-of-age with Vancouver B-type fractures sustained between 2005 and 2019. Patients were treated by ORIF and had either cemented or press-fit stems prior to their injury. Outcomes were subsidence of the femoral implant, time to full weight bearing, rate of the hip implant revision, estimated blood loss (EBL), postoperative complications, and the one-year mortality rate.

RESULTS

A total of 103 (75.7%) press-fit and 33 (24.3%) cemented patients were reviewed. Patient baseline characteristics, Vancouver fracture sub-types, and implant characteristics were not found to be significantly different between groups. The difference in subsidence rates, postoperative complications, and time to weight bearing were not significantly different between groups. EBL and one-year mortality rate were significantly higher in the cemented group.

CONCLUSIONS

In geriatric patients with Vancouver B type periprosthetic fractures managed with ORIF, patients with an originally press fit stem may have lower mortality, lower estimated blood loss, and similar subsidence and hospital length of stays when compared to those with a cemented stem.

Surgeon-Directed Arthroscopic Infiltration Between the Popliteal Artery and Capsule of the Knee (IPACK) Block: Technical Description

Advances in regional anesthesia techniques for knee surgery have led to drastic improvements in postoperative pain control and have reduced reliance on perioperative opioid analgesics. The infiltration between the popliteal artery and capsule of the knee (IPACK) block has been a useful tool for providing posterior knee analgesia as an adjuvant to traditional femoral or adductor canal blocks in knee surgery. We present a simple and reproducible technique for the arthroscopic administration of this block.

Modified Grammont Soft-Tissue Distal Patellar Realignment and Medial Patellofemoral Ligament Reconstruction for Patellofemoral Instability in Pediatric Patients

Patellar dislocation is a relatively common pediatric injury, which often results in recurrent patellofemoral instability. An increased tibial tubercle-trochlear groove distance predisposes to patellofemoral instability and can be corrected with a distal realignment procedure. Soft-tissue distal realignment procedures must be used in the pediatric population to avoid the risks of premature physeal closure associated with tibial tubercle osteotomies. Several soft-tissue distal realignment procedures have been described, with no consensus as to the optimal technique. When combined with medial patellofemoral ligament reconstruction, distal realignment procedures can restore patellofemoral stability through the entire flexion arc. This article describes a modification of the Grammont distal patellar realignment procedure in conjunction with medial patellofemoral ligament reconstruction for the management of pediatric patellofemoral instability.

Complications and predictors of morbidity for hip fracture surgery in patients with chronic liver disease

BACKGROUND

Despite the fact that patients with chronic liver disease (CLD) are at increased risk of complications after a fracture of the hip, there remains little information about the risk factors for acute postoperative complications and their overall outcome.The aim of this study was to describe inpatient postoperative complications and identify predictors of postoperative morbidity.

METHODS

Patients with CLD who had been treated for a fracture of the hip between April 2005 and August 2019 were identified from a retrospective search of an intramural trauma registry based in the Northeastern United States. Medical records were reviewed for baseline demographics, preoperative laboratory investigations, and outcomes.

RESULTS

The trauma registry contained 110 patients with CLD who had undergone surgery for a fracture of the hip. Of these, patients with a platelet-count of ⩽100,000/µL were 3.81 (95% CI, 1.59-9.12) times more likely to receive a transfusion than those with a platelet-count of >100,000/µL. Those with a Model for End-stage Liver Disease (MELD) score of >9 were 5.54 (2.33-13.16) times more likely to receive a transfusion and 3.97 (1.06-14.81) times more likely to develop postoperative delirium than those with a MELD score of ⩽9.Of patients without chronic kidney disease, those with a creatinine of ⩾1.2 mg/dL were 6.80 (1.79-25.87) times more likely to develop acute renal failure (ARF) than those with a creatinine of <1.2 mg/dL. In a multivariable model, as MELD score was increased, the odds of developing a composite postoperative complication, which included transfusion, ARF, delirium, or deep wound infection, were 1.29 (1.01-1.66). Other tools used to assess surgical risks, Charlson Comorbidity Index, Elixhauser, and American Society of Anesthesiologist scores, were not predictive.

CONCLUSIONS

Patients with CLD who undergo surgery for a hip fracture have a high rate of postoperative complications which can be predicted by the preoperative laboratory investigations identified in this study and MELD scores, but not by other common comorbidity indices.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Revision Arthroplasty Versus Open Reduction and Internal Fixation of Vancouver Type-B2 and B3 Periprosthetic Femoral Fractures

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Revision arthroplasty (RA) continues to be considered the gold standard in the surgical treatment of Vancouver type-B2 and B3 periprosthetic femoral fractures. However, open reduction and internal fixation (ORIF) has been associated with satisfactory outcomes. Thus, there is an ongoing discussion regarding the optimal surgical strategy for the treatment of these fractures.

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In this systematic review and meta-analysis, no significant differences in clinical and radiographic outcome were observed between ORIF and RA in the treatment of Vancouver type-B2 periprosthetic femoral fractures.

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ORIF of Vancouver type-B3 periprosthetic femoral fractures was associated with higher revision and reoperation rates than those after RA.

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Compared with RA, a significantly higher rate of subsidence was found in the ORIF group in Vancouver type-B2 periprosthetic femoral fractures whereas no significant difference in terms of loosening was observed.

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In the comparison of RA and ORIF for the treatment of Vancouver type-B2 and B3 fractures, the percentage of patients achieving full weight-bearing did not differ significantly.

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Mortality rates did not differ between RA and ORIF in the treatment of Vancouver type-B2 and B3 fractures.

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Overall complication rates did not differ between RA and ORIF in the treatment of Vancouver type-B2 and B3 fractures.

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We found a high heterogeneity in applied surgical and fixation techniques in the ORIF group.

Lack of Surgeon Standardization on Implant Selection in Ankle Fracture Fixation May Increase Costs and Decrease Contribution Margin

BACKGROUND

Surgical standardization has been shown to decrease costs without impacting quality; however, there is limited literature on this subject regarding ankle fracture fixation. Methods. Between October 5, 2015 and September 27, 2017, a total of 168 patients with isolated ankle fractures who underwent open reduction, internal fixation (ORIF) were analyzed. Financial data were analyzed across ankle fracture classification type, implant characteristics, and surgeons. Bivariate analyses were conducted. One-way analysis of variance was used to compare hardware costs across all 5 surgeons. Linear regression analysis was used to determine if hardware cost differed by surgeon when accounting for fracture type.

RESULTS

The mean contribution margin was $4853 (SD $6446). There was a significant difference in implant costs by surgeon (range, lowest-cost surgeon: $471 [SD $283] to $1609 [SD $819]; P < .001). There was no difference in the use of a suture button or locking plate by fracture type (P = .13); however, the cost of the implant was significantly higher if a suture button or locking plate was used ($1014 [SD $666] vs $338 [SD $176]; P < .001). There was an association between surgeon 3 (β = 200.32 [95% CI 6.18-394.47]; P = .043) and surgeon 4 (β = 1131.07 [95% CI 906.84-1355.30]; P < .001) and higher hardware costs.

CONCLUSIONS

Even for the same ankle fracture type, a wide variation in implant costs exists. The lack of standardization among surgeons accounted for a nearly 3.5-fold difference, on average, between the lowest- and highest-cost surgeons, negatively affecting contribution margin.

LEVELS OF EVIDENCE

Level IV.

3D Bioprinted Bacteriostatic Hyperelastic Bone Scaffold for Damage-Specific Bone Regeneration

Current strategies for regeneration of large bone fractures yield limited clinical success mainly due to poor integration and healing. Multidisciplinary approaches in design and development of functional tissue engineered scaffolds are required to overcome these translational challenges. Here, a new generation of hyperelastic bone (HB) implants, loaded with superparamagnetic iron oxide nanoparticles (SPIONs), are 3D bioprinted and their regenerative effect on large non-healing bone fractures is studied. Scaffolds are bioprinted with the geometry that closely correspond to that of the bone defect, using an osteoconductive, highly elastic, surgically friendly bioink mainly composed of hydroxyapatite. Incorporation of SPIONs into HB bioink results in enhanced bacteriostatic properties of bone grafts while exhibiting no cytotoxicity. In vitro culture of mouse embryonic cells and human osteoblast-like cells remain viable and functional up to 14 days on printed HB scaffolds. Implantation of damage-specific bioprinted constructs into a rat model of femoral bone defect demonstrates significant regenerative effect over the 2-week time course. While no infection, immune rejection, or fibrotic encapsulation is observed, HB grafts show rapid integration with host tissue, ossification, and growth of new bone. These results suggest a great translational potential for 3D bioprinted HB scaffolds, laden with functional nanoparticles, for hard tissue engineering applications.

Comparison of Patellofemoral Kinematics and Stability After Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament Reconstruction

BACKGROUND

There is a lack of evidence regarding the optimum extensor-sided fixation method for medial patellofemoral ligament (MPFL) reconstruction. There is increased interest in avoiding patellar drilling via soft tissue-only fixation to the distal quadriceps, thus reconstructing the medial quadriceps tendon-femoral ligament (MQTFL). The biomechanical implications of differing extensor-sided fixation constructs remain unknown.

HYPOTHESIS

The null hypothesis was there would be no differences between traditional MPFL reconstruction and MQTFL reconstruction with respect to resistance to lateral translation, patellar position, or patellofemoral contact pressures.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine adult knee specimens were mounted on a jig that applied static, physiologic loads to the quadriceps tendons. Patellar position and orientation, knee flexion angle, and patellofemoral pressure were recorded at 8 different flexion angles between 0° and 110°. Additionally, a lateral patellar excursion test was conducted wherein a load was applied directly to the patella in the lateral direction with the knee at 30° of flexion and subjected to 2-N quadriceps loads. Testing was conducted under 4 conditions: intact, transected MPFL, MQTFL reconstruction, and MPFL reconstruction. For MQTFL reconstruction, the surgical technique established by Fulkerson was employed. For MPFL reconstruction, a traditional technique was utilized.

RESULTS

The patellar excursion test showed no significant difference between the MQTFL and intact states with respect to lateral translation. MPFL reconstruction led to significantly less lateral translation (P < .05) than all other states. There were no significant differences between MPFL and MQTFL reconstructions with respect to peak patellofemoral contact pressure. MPFL and MQTFL reconstructions both resulted in increased internal rotation of the patella with the knee in full extension.

CONCLUSION

Soft tissue-only extensor-sided fixation to the distal quadriceps (MQTFL) during patella stabilization appears to re-create native stability in this time 0 cadaver model. Fixation to the patella (MPFL) was associated with increased resistance to lateral translation.

CLINICAL RELEVANCE

Evolving anatomic knowledge and concern for patellar fracture has led to increased interest in MQTFL reconstruction. Both MQTFL and MPFL reconstructions restored patellofemoral stability to lateral translation without increasing contact pressures under appropriate graft tensioning, with MQTFL more closely restoring native resistance to lateral translation at the time of surgery.

Effect of rotator cuff muscle activation on glenohumeral kinematics: A cadaveric study

Healthy shoulder function requires the coordination of the rotator cuff muscles to maintain the humeral head's position in the glenoid. While glenohumeral stability has been studied in various settings, few studies have characterized the effect of dynamic rotator cuff muscle loading on glenohumeral translation during shoulder motion. We hypothesize that dynamic rotator cuff muscle activation decreases joint translation during continuous passive abduction of the humerus in a cadaveric model of scapular plane glenohumeral abduction. The effect of different rotator cuff muscle activity on glenohumeral translation was assessed using a validated shoulder testing system. The Dynamic Load profile is a novel approach, based on musculoskeletal modeling of human subject motion. Passive humeral elevation in the scapular plane was applied via the testing system arm, while the rotator cuff muscles were activated according to the specified force profiles using stepper motors and a proportional control feedback loop. Glenohumeral translation was defined according to the International Society of Biomechanics. The Dynamic load profile minimized superior translation of the humeral head relative to the conventional loading profiles. The total magnitude of translation was not significantly different (0.805) among the loading profiles suggesting that the compressive forces from the rotator cuff primarily alter the direction of humeral head translation, not the magnitude. Rotator cuff muscle loading is an important element of cadaveric shoulder studies that must be considered to accurately simulate glenohumeral motion. A rotator cuff muscle activity profile based on human subject muscle activity reduces superior glenohumeral translation when compared to previous RC loading profiles.

Comparison of surgical and non-surgical treatments for 3- and 4-part proximal humerus fractures: A network meta-analysis

INTRODUCTION

Common treatment strategies for proximal humerus fractures include non-surgical treatment, open reduction internal fixation, hemiarthroplasty, and reverse total shoulder arthroplasty. There is currently no consensus regarding the superiority of any one surgical strategy. We used network meta-analysis of randomized controlled trials to determine the most successful treatment for proximal humerus fractures.

METHODS

MEDLINE, EMBASE, Web of Science, and Cochrane Central electronic databases were searched for randomized controlled trials comparing 3- and 4-part proximal humerus fracture treatments. Data extraction included the mean and standard deviation of clinical outcomes (Constant, DASH), adverse events, and additional surgery rates. Standard Mean Difference was used to compare clinical outcome scores, and pooled risk ratios were used to compare adverse events and additional surgeries.

RESULTS

Eight randomized controlled trials were included for network meta-analysis. Non-surgical treatment was associated with a lower rate of additional surgery and adverse events compared to open reduction internal fixation. Reverse total shoulder arthroplasty resulted in fewer adverse events and a better clinical outcome score than hemiarthroplasty. Non-surgical treatment produced similar clinical scores, adverse event rates, and additional surgery rates to hemiarthroplasty and reverse total shoulder arthroplasty.

CONCLUSION

Non-surgical treatment results in fewer complications and additional surgeries compared to open reduction internal fixation. Preliminary data supports reverse total shoulder arthroplasty over hemiarthroplasty, but more evidence is needed to strengthen this conclusion.

Diagnostic Modalities for Acute Compartment Syndrome of the Extremities: A Systematic Review

Importance

Acute compartment syndrome (ACS) can cause catastrophic tissue damage leading to permanent muscle and nerve loss. Acute compartment syndrome is a clinical diagnosis, with intracompartmental pressure (ICP) used in equivocal cases. There are no reliable diagnostic methods. The clinical evaluation is impossible to standardize, and the threshold for ICP has been known to be unreliable; thus, guidelines for diagnosis can result in overtreatment or delayed diagnosis.

Objective

To present and review the advantages and disadvantages of each diagnostic modality and identify gaps that need to be addressed in the future and to review the most used and appropriate animal and human ACS models.

Evidence Review

We included clinical studies and animal models investigating diagnostic modalities for ACS of the extremities. A MEDLINE and Web of Science search was performed. The protocol for the study was registered on PROSPERO (CRD42017079266). We assessed the quality of the clinical studies with Newcastle-Ottawa scale and reported level of evidence for each article.

Findings

Fifty-one articles were included in this study, reporting on 38 noninvasive and 35 invasive modalities. Near-infrared spectroscopy and direct ICP measurement using a Stryker device were the most common, respectively. Cadaveric studies used saline infusions to create an ACS model. Most studies with human participants included injured patients with acquired ACS or at risk of developing ACS. In healthy human participants, tourniquets formed the most commonly used ACS model. Application of tourniquets and infusion of saline or albumin were the most used ACS models among animal studies.

Conclusions and Relevance

This article reports on the most common as well as many new and modified diagnostic modalities, which can serve as inspiration for future investigations to develop more effective and efficient diagnostic techniques for ACS. Future studies on diagnostic modalities should include the development of tools for continuous assessment of ICP to better identify the earliest alterations suggestive of impending ACS. With the advent of such technologies, it may be possible to develop far less aggressive and more effective approaches for early detection of ACS.

Tendon lengthening after achilles tendon rupture-passive effects on the ankle joint in a cadaveric pilot study simulating weight bearing

BACKGROUND

In recent years, primary Achilles tendon ruptures have increased due to the aging population's participation in physically demanding activities. These injuries commonly occur during recreational sports and frequently lead to a long-term reduction in activity despite treatment. Non-operative methods of treatment for Achilles tendon ruptures may result in the Achilles healing in a lengthened position compared to the pre-injury state. This study uses a cadaveric model that simulates static weight bearing to explore the effect of a lengthened Achilles tendon on ankle joint load distribution.

METHODS

Five lower limb cadaveric specimens were placed on a custom jig, where a 334 N (75 lb) load was applied at the femoral head, and the foot was supported against a plate to simulate static double-leg stance. A pressure mapping sensor was inserted into the ankle joint. A percutaneous triple hemiresection tendo-Achilles lengthening procedure (Hoke procedure) was performed on each specimen to simulate tendon lengthening after conservative treatment. Contact pressure, peak pressure, and center-of-pressure were measured for native and tendon-lengthened conditions.

RESULTS

Tendon rupture did not significantly alter average contact pressure, peak contact pressures, or center-of-pressure in the ankle joint compared with native tendon.

CONCLUSION

Achilles lengthening does not significantly change contact pressures of the ankle joint in this model . This result suggests that the passive restraint on ankle joint translation imposed by the Achilles tendon is minimal without muscle activation.

Thermoplastic moulding of regenerated silk

Early insights into the unique structure and properties of native silk suggested that β-sheet nanocrystallites in silk would degrade prior to melting when subjected to thermal processing. Since then, canonical approaches for fabricating silk-based materials typically involve solution-derived processing methods, which have inherent limitations with respect to silk protein solubility and stability in solution, and time and cost efficiency. Here we report a thermal processing method for the direct solid-state moulding of regenerated silk into bulk 'parts' or devices with tunable mechanical properties. At elevated temperature and pressure, regenerated amorphous silk nanomaterials with ultralow β-sheet content undergo thermal fusion via molecular rearrangement and self-assembly assisted by bound water to form a robust bulk material that retains biocompatibility, degradability and machinability. This technique reverses presumptions about the limitations of direct thermal processing of silk into a wide range of new material formats and composite materials with tailored properties and functionalities.

The Effect of Gentamycin in the Irrigating Solution to Prevent Joint Infection after Anterior Cruciate Ligament (ACL) Reconstruction

BACKGROUND

Arthroscopic reconstruction of ACL is an effective method to restore knee stability after ACL rupture. Postoperative septic arthritis (SA) is very uncommon while the incidence of serious complications range between 0.14% and 1.8%. Some of the devastating consequences of septic arthritis can encompass hyaline cartilage damage, arthrofibrosis, and in rare cases amputation. The purpose of this study was to evaluate the effect of gentamicin irrigation solutions as a process to restrain septic arthritis following arthroscopic ACL reconstruction.

METHODS

In this retrospective cohort study, 1464 patients who underwent ACL reconstruction with hamstring tendon autograft in our institution over 7 years (February 2008 to January 2015) were included. The patients were divided into two groups based on the type of intra-articular irrigation solution used during the surgery. Patients in Group 1 (Saline) received intra-articular irrigation with normal saline (0.9 % sodium chloride) solution, while those in Group 2 (Gentamycin) received intra-articular irrigation with gentamicin (80 mg/L) added to the normal saline solution. Data about postoperative infection, its course, management, and outcome were obtained from patients' records.

RESULTS

Seven patients developed SA, four of whom were from SALINE group (2.2%) and three from Gentamycin group (0.23%). The incidence rate of SA after arthroscopic ACL reconstruction was significantly lower (P <0.05) when irrigated with gentamicin solution than merely with saline solution.

CONCLUSION

Gentamicin irrigation solution has a preservative and protective effect against SA development following arthroscopic ACL reconstruction. We recommend evaluating this technique as a way in order to depreciate the prevalence of SA after ACL reconstruction.

Rat Model of Adhesive Capsulitis of the Shoulder

This proposal aims to create an in vivo rat model of adhesive capsulitis for researching potential treatment options for this condition and other etiologies of comparable arthrofibrosis. The model includes extra-articular fixation of the shoulder in rats via scapular to humeral suturing, resulting in a secondary contracture without invading the intra-articular space and resulting in decreased rotational ROM and increased joint stiffness. We used 10 Sprague-Dawley rats for the purpose of this study. Baseline ROM measurements were taken before glenohumeral immobilization. The rats were subjected to 8 weeks of immobilization before the fixation sutures were removed and changes in ROM and joint stiffness were evaluated. To evaluate whether immobilization resulted in a significant reduction in ROM, changes in kinematics were calculated. ROM was measured at each time point in the follow-up period and was compared to the baseline internal and external ROM measurements. In order to evaluate the stiffness, joint kinetics were calculated by determining the differences in torque (text and tint ) needed to reach the initial external rotation of 60° and initial internal rotation of 80°. After the removal of the extra-articular suture fixation on follow-up day 0, we found a 63% decrease in total ROM compared to baseline. We observed continuous improvement until week 5 of follow-up, with the progress slowing down around a 19% restriction. On week 8 of follow-up, there was still an 18% restriction of ROM. Additionally, on follow-up day 0, we found the torque increased by 13.3 Nmm when compared to baseline. On week 8, the total torque was measured to be 1.4 ± 0.2 Nmm higher than initial measurements. This work introduces a rat model of shoulder adhesive capsulitis with lasting reduced ROM and increased stiffness.

Pressure Distribution in the Ankle and Subtalar Joint With Routine and Oversized Foot Orthoses

BACKGROUND

Foot orthoses are used to treat many disorders that affect the lower limb. These assistive devices have the potential to alter the forces, load distribution, and orientation within various joints in the foot and ankle. This study attempts to quantify the effects of orthoses on the intra-articular force distribution of the ankle and subtalar joint using a cadaveric testing jig to simulate weight bearing.

METHODS

Five lower-limb cadaveric specimens were placed on a custom jig, where a 334-N (75-lb) load was applied at the femoral head, and the foot was supported against a plate to simulate double-leg stance. Pressure-mapping sensors were inserted into the ankle and subtalar joint. Mean pressure, peak pressure, contact area, and center of force were measured in both the ankle and subtalar joints for barefoot and 2 medial foot orthosis conditions. The 2 orthosis conditions were performed using (1) a 1.5-cm-height wedge to simulate normal orthoses and (2) a 3-cm-height wedge to simulate oversized orthoses.

RESULTS

The contact area experienced in the subtalar joint significantly decreased during 3-cm orthotic posting of the medial arch, but neither orthosis had a significant effect on the spatial mean pressure or peak pressure experienced in either joint.

CONCLUSION

The use of an oversized orthosis could lead to a decrease in the contact area and alterations in the distribution of pressure within the subtalar joint.

CLINICAL RELEVANCE

The use of inappropriate orthoses could negatively impact the force distribution in the lower limb.

Comparison of adverse events and postoperative mobilization following knee extensor mechanism rupture repair: A systematic review and network meta-analysis

BACKGROUND

Extensor mechanism rupture (EMR) of the knee is a rare but potentially debilitating injury that often occurs due to trauma. While a wide variety of surgical treatments have been reported, there is currently no consensus on the most successful treatment method. The timing of post-operative joint mobilization is also critical for successful recovery after EMR repair. Despite the traditional method of complete immobilization for 6 weeks, there is an increasing trend towards early post-operative knee mobilization. The purpose of this network meta-analysis was to compare adverse event rates and function outcomes between repair methods and between post-operative mobilization protocols.

METHODS

MEDLINE, EMBASE, Web of Science, and Cochrane Central electronic databases were searched in August 2016 for observational studies involving repair of acute, traumatic EMRs. Data extraction included functional outcomes, adverse events, and additional surgeries. Cohort studies that were used in functional outcome analysis were assessed for risk of bias by the Newcastle-Ottawa Quality Assessment Scale (NOS).

RESULTS

Twenty-three studies (709 patients) were included for adverse event analysis. There were no significant differences in adverse event or additional surgery rates between EMR repair methods However, early mobilization produced significantly higher adverse event rates (p=0.02) and total event rates (p<0.001) than late mobilization, but the difference in additional surgery rates was not significant (p=0.06). Six studies (85 patients) were included for functional outcome analysis. There were no significant differences in thigh girth atrophy or muscle strength compared to the contralateral leg between patients treated with transosseous drill holes and simple end-to-end sutures.

CONCLUSIONS

We performed the first network meta-analysis to date comparing treatment of EMRs. Our results support the current body of knowledge that there is no single superior repair method. Although there is an increasing trend towards early or immediate post-operative knee mobilization, we found that early mobilization is associated with significantly higher adverse event and total event rates compared to fixed immobilization for a minimum of 6 weeks, implicating an increased financial burden and decreased quality of life associated with early post-operative mobilization.

The Effect of Orthotics on Ankle and Subtalar Joint Orientation and Load Distribution Utilizing a Novel System to Simulate Weight Bearing in a Cadaveric Model

Category:

Ankle, Basic Sciences/Biologics, Hindfoot, Biomechanics

Introduction/Purpose:

Orthotics are commonly prescribed by orthopaedic surgeons to address the hindfoot and midfoot deformity resulting from posterior tibial tendon dysfunction. The public however will often purchase over the counter orthotics for generalized complaints of foot pain that is not associated with any significant deformity or foot pathology. The mechanical axis of the lower limb may be altered in patients who use orthotics despite a normal foot alignment. We hypothesize that patients with normal alignment who use orthotics may adversely change ankle and subtalar joint orientation and load distribution.

Methods:

Five fresh frozen lower limb cadaveric specimens without known skeletal condition were used. The femoral head was potted with PMMA and TekScan pressure sensors were inserted into the ankle and subtalar joint. The specimens were placed on a custom jig, which allowed for load cell modulated loading of the leg; 75 lb load (half body weight) was applied at the femoral head while the foot was supported against a fixed plate keeping the ankle in neutral position. Testing was achieved by placing an orthotic under the medial half of the plantar talonavicular joint level. Mean pressure (MP), peak pressure (PP), contact area (CA), and center of force (COF) were measured in both the ankle and subtalar joints under three conditions; barefoot (BASE), with a 1.5 cm (ORT1) and 3 cm (ORT2) height orthotic. Each condition was tested three times per specimen. Displacement of COF was calculated relative to its location at baseline.

Results:

The MP, PP and CA showed a constant decrease from BASE to ORT1 and ORT2. Despite this relation, the only comparison that was significantly different was that between peak pressure values of the baseline and ORT2 conditions of the subtalar joint. The average displacement of COF from BASE was 0.14 mm and 0.42 mm medially, and 0.26 mm and 0.46 mm posteriorly at the ankle joint with ORT1 and ORT2 respectively. The average displacement of COF from BASE was 0.03 mm laterally and 0.08 mm posteriorly with ORT1, and 0.2 mm medially and 0.46 mm posteriorly with ORT2 at the subtalar joint.

Conclusion:

Foot deformities have an impact on the articular forces in the lower limb. Our results agree with previous studies about the role of foot deformity on the distribution of body weight forces and its consequences across the ankle and subtalar joint. Our novel study also demonstrates that orthotics and orthotics of varying sizes can change the mean pressure, peak pressure, contact area center of force in the ankle and subtalar joint. This study proves the feasibility of its design for studying intra-articular pressure changes in a lower limb cadaveric model with simulated weight bearing.

A randomized, double-blind, placebo-controlled trial of coenzyme Q10 in Huntington disease

OBJECTIVE

To test the hypothesis that chronic treatment of early-stage Huntington disease (HD) with high-dose coenzyme Q10 (CoQ) will slow the progressive functional decline of HD.

METHODS

We performed a multicenter randomized, double-blind, placebo-controlled trial. Patients with early-stage HD (n = 609) were enrolled at 48 sites in the United States, Canada, and Australia from 2008 to 2012. Patients were randomized to receive either CoQ 2,400 mg/d or matching placebo, then followed for 60 months. The primary outcome variable was the change from baseline to month 60 in Total Functional Capacity score (for patients who survived) combined with time to death (for patients who died) analyzed using a joint-rank analysis approach.

RESULTS

An interim analysis for futility revealed a conditional power of <5% for the primary analysis, prompting premature conclusion in July 2014. No statistically significant differences were seen between treatment groups for the primary or secondary outcome measures. CoQ was generally safe and well-tolerated throughout the study.

CONCLUSIONS

These data do not justify use of CoQ as a treatment to slow functional decline in HD.

CLINICALTRIALSGOV IDENTIFIER

NCT00608881.

CLASSIFICATION OF EVIDENCE

This article provides Class I evidence that CoQ does not slow the progressive functional decline of patients with HD.

Histological characterization of dilated cardiomyopathy in the juvenile toy Manchester terrier

Dilated cardiomyopathy (DCM), the most common form of cardiomyopathy in the dog, most often occurs in certain breeds. The objective of this study was to describe a rapidly progressive form of DCM that has been recently recognized in juvenile Toy Manchester Terrier dogs (TMTs). The clinical history and gross findings were reviewed in a group of 14 TMTs, and histologic sections of heart were examined in 12 of those 14 TMTs with DCM. Histochemical and histomorphometric analyses were employed to compare the heart in TMTs affected by DCM with that of control dogs. TMTs ranged in age from 10 to 58.3 weeks, with males and females being equally affected. Affected TMT hearts contained foci of degeneration and loss of myofibers with fibrosis and mild lymphoplasmacytic infiltrates. Less prominent features included foci of acute myofiber degeneration and necrosis with or without intralesional mineralization and mild to moderate suppurative and lymphoplasmacytic infiltrates. Morphometric quantification demonstrated that the right ventricle was more severely affected (P ≤ .05) than the left ventricle with variable involvement of the interventricular septum. Immunohistochemistry for canine parvovirus was negative in all heart samples. However, the absence of parvoviral antigen does not rule out a possible viral or autoimmune cause. The presence of these myocardial lesions among closely related dogs suggests a genetic contribution to this disease process in the TMT.

Transport of Bacillus anthracis from the lungs to the draining lymph nodes is a rapid process facilitated by CD11c+ cells

Inhalational anthrax is established after inhaled Bacillus anthracis spores are transported to the lung associated lymph nodes. Dendritic cells (CD11c+ cells) located in the lungs are phagocytes that maintain many capabilities consistent with transport. This study investigates the role of dendritic cells as conduits of spores from the lung to the draining lymph nodes. The intratracheally spore-challenged mouse model of inhalational anthrax was utilized to investigate in vivo activities of CD11c+ cells. FITC labeled spores were delivered to the lungs of mice. Subsequently lung associated lymph nodes were isolated after infection and CD11c+ cells were found in association with the labeled spores. Further investigation of CD11c+ cells in early anthrax events was facilitated by use of the CD11c-diphtheria toxin (DT) receptor-green fluorescent protein transgenic mice in which CD11c+ cells can be transiently depleted by treatment with DT. We found that the presence of CD11c+ cells was necessary for efficient traffic of the spore to lung associated lymph nodes at early times after infection. Cultured dendritic cells were used to determine that these cells are capable of B. anthracis spore phagocytosis, and support germination and outgrowth. This data demonstrates that CD11c+ cells are likely carriers of B. anthracis spores from the point of inhalation in the lung to the lung associated lymph nodes. The cultured dendritic cell allows for spore germination and outgrowth supporting the concept that the CD11c+ cell responsible for this function can be a dendritic cell.

Research in action: mammography utilization following breast cancer awareness campaigns in Lebanon 2002-05

Four consecutive annual surveys of 1200 women each were conducted in Lebanon in connection with the National Breast Cancer Awareness campaigns (2002-05) to measure the prevalence of mammography utilization and the impact of these campaigns, and to highlight regional and demographic differences. The utilization of mammography in the previous 12 months was low and increased only slightly over 4 years (from 11% to 18%). In the 2005 campaign, it was twice as high (25%) in greater Beirut than in mostly rural areas, and among women aged 40-59 years (about 21%) compared with younger (12%) or older (11%) women. In each wave, repeat mammograms were less common than first time screening.

Bacillus anthracis anthrolysin O and three phospholipases C are functionally redundant in a murine model of inhalation anthrax

Although traditionally considered to be an extracellular pathogen, Bacillus anthracis has a brief intracellular step to initiate anthrax. At the onset of infection, B. anthracis must withstand the bactericidal activities of the macrophage. Recently, three phospholipases C (PLCs) were shown to contribute to macrophage-associated growth of B. anthracis by presumably aiding in the escape of the bacterium from phagocytic vacuoles following phagocytosis. However, in the absence of all three PLCs, vegetative bacilli were still observed growing in association with the macrophage, albeit to a lesser extent, implicating that additional factors are involved in this process. In this study, the contributions of the previously identified cholesterol-dependent cytolysin anthrolysin O (ALO) to B. anthracis pathogenesis were investigated following challenges of bone marrow-derived macrophages and intratracheal inoculations of mice. Disruption of ALO alone yielded no differences in virulence in mice. However, combinatorial deletions of ALO with the three PLCs resulted in attenuation in both tissue culture and murine challenges, suggesting that these toxins may have overlapping roles in anthrax pathogenesis.

Bacillus anthracis phospholipases C facilitate macrophage-associated growth and contribute to virulence in a murine model of inhalation anthrax

Several models of anthrax pathogenesis suggest that early in the infectious process Bacillus anthracis endospores germinate and outgrow into vegetative bacilli within phagocytes before being released into the blood. Here, we define the respective contributions of three phospholipases C (PLCs) to the pathogenesis of B. anthracis. Genetic deletions of the PLCs were made in the Sterne 7702 background, resulting in the respective loss of their activities. The PLCs were redundant both in tissue culture and in murine models of anthrax. Deletion of all three PLC genes was required for attenuation of virulence in mice after intratracheal inoculation. This attenuation may be attributed to the inability of the PLC-null strain to grow in association with the macrophage. Complementation of these defects in both models of anthrax was achieved by expression of the PLC genes in trans. The functional redundancy between PLCs in the virulence of B. anthracis implies that their activities are important for anthrax pathogenesis.

The superoxide dismutases of Bacillus anthracis do not cooperatively protect against endogenous superoxide stress

The Bacillus anthracis chromosome encodes four unique, putative superoxide dismutase (sod) genes. During exponential growth and sporulation, sodA1, sodA2, and sodC are transcribed constitutively throughout the growth cycle as individual genes. In contrast, the transcription of sod15 occurs mainly during late exponential and sporulation phases as part of a four-gene operon that may be involved in spore formation. Vegetative cell and spore lysates of wild-type Sterne and superoxide dismutase deletion (Deltasod) mutants show detectable SOD activity for SODA1 and SODA2, and protein analysis suggests that these two proteins form active homodimers and heterodimers. A comparison of the growth of parental versus Deltasod mutants under various chemical oxidative stresses indicates that DeltasodA1 mutants are particularly sensitive to endogenously produced superoxide, whereas DeltasodA2, Deltasod15, and DeltasodC mutants remain as resistant to this stress as the parental strain. In addition, in mouse survival assays, Deltasod15 and DeltasodA1 were responsible for less end-point death, but the level of decreased virulence does not fall within a statistically significant range. Collectively, these data show that sodA1 acts as a major protectant from intracellular superoxide stress, that sod15 is transcribed as part of an operon that may play a role in cell morphology, and that sodA2 and sodC may have minor roles that are not apparent in the conditions tested here.

The dltABCD operon of Bacillus anthracis sterne is required for virulence and resistance to peptide, enzymatic, and cellular mediators of innate immunity

In the environment, the gram-positive bacterium Bacillus anthracis persists as a metabolically dormant endospore. Upon inoculation into the host the endospores germinate and outgrow into vegetative bacilli able to cause disease. The dramatic morphogenic changes to the bacterium during germination and outgrowth are numerous and include major rearrangement of and modifications to the bacterial surface. Such modifications occur during a time in the B. anthracis infectious cycle when the bacterium must guard against a multitude of innate immune mediators. The dltABCD locus of B. anthracis encodes a cell wall d-alanine esterification system that is initiated by transcriptional activation during endospore outgrowth. The level of transcription from the dltABCD operon determined B. anthracis resistance to cationic antibacterial peptides during vegetative growth and cationic peptide, enzymatic, and cellular mediators of innate immunity during outgrowth. Mutation of dltABCD was also attenuating in a mouse model of infection. We propose that the dltABCD locus is important for protection of endosporeforming bacteria from environmental assault during outgrowth and that such protection may be critical during the establishment phase of anthrax.

Characterization of Bacillus anthracis germinant receptors in vitro

Bacillus anthracis begins its infectious cycle as a metabolically dormant cell type, the endospore. Upon entry into a host, endospores rapidly differentiate into vegetative bacilli through the process of germination, thus initiating anthrax. Elucidation of the signals that trigger germination and the receptors that recognize them is critical to understanding the pathogenesis of B. anthracis. Individual mutants deficient in each of the seven putative germinant receptor-encoding loci were constructed via temperature-dependent, plasmid insertion mutagenesis and used to correlate these receptors with known germinant molecules. These analyses showed that the GerK and GerL receptors are jointly required for the alanine germination pathway and also are individually required for recognition of either proline and methionine (GerK) or serine and valine (GerL) as cogerminants in combination with inosine. The germinant specificity of GerS was refined from a previous study in a nonisogenic background since it was required only for germination in response to aromatic amino acid cogerminants. The gerA and gerY loci were found to be dispensable for recognition of all known germinant molecules. In addition, we show that the promoter of each putative germinant receptor operon, except that of the gerA locus, is active during sporulation. A current model of B. anthracis endospore germination is presented.

Egg-laying-hormone immunoreactivity in the neural ganglia and ovary of Haliotis asinina Linnaeus

Immunoreactivity against the abalone egg-laying hormone (aELH) was detected in the fine granules of type 1 and 2 neurosecretory (NS) cells, neurites in the neuropil, and blood sinuses in the connective tissue sheath of the cerebral, pleuropedal, and visceral ganglia of the tropical abalone, Haliotis asinina Linnaeus. The number of positive NS cells, and the intensity of staining in the ganglia, varied and might be related to the stage of ovarian cycle. At any stage, positive cells were most numerous in the pleuropedal, and least numerous in the visceral ganglion. In addition, several cells of the statocyst and associated nerves also exhibited the immunoreactivity. In the ovary, the most intense reactivity was detected in the follicular and granular cells adjacent to mature oocytes, in the trabeculae and the ovarian capsule. The cytoplasm of mature oocytes was also moderately stained. The results indicate that the cerebral, pleuropedal, and visceral ganglia are the main sites of aELH-producing cells. The ovary may also produce aELH locally.

Calcinosis circumscripta in the dog: a retrospective pathological study

Calcinosis circumscripta is an uncommon syndrome of ectopic idiopathic, dystrophic, metastatic or iatrogenic mineralization characterized by deposition of calcium salts in soft tissues. This paper is a retrospective study of 77 canine cases. The age of dogs in the study varied from 4 months to 15 years and 55% were <1 year old, 74% <2 years old and 88% <4 years old. Several pure and mixed, typically large breed dogs were affected so that 28.6, 13 and 9% were German Shepherd, Rottweiler and Labrador Retriever respectively. The size of lesions varied from 2 mm to 13 cm in diameter but most lesions were between 0.5 cm and 3 cm in diameter. Lesions were solitary in 82% of the affected dogs, and occurred most commonly on the hind feet (50%) and tongue (23%). With multiple lesions there was no apparent body symmetry. Microscopically, most lesions were well-defined single or multiple variably sized aggregates of amorphous to granular, lightly to darkly basophilic material with or without peripheral granulomatous reaction and surrounded by varying amounts of fibrous connective tissue. Additionally, three small nodular masses in the wall of the jejunum of a dog were diagnosed as calcinosis circumscripta. This is the first reported case of idiopathic intestinal calcinosis circumscripta in the dog.

A phase I study of oral ZD 1839 given daily in patients with solid tumors: IND.122, a study of the Investigational New Drug Program of the National Cancer Institute of Canada Clinical Trials Group

PURPOSE

To define the maximum tolerated dose (MTD), the dose limiting toxicity (DLT), the biological active (BA) dose and the pharmacokinetics (PK) of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor ZD1839 (Iressa) when administered continuously as a once daily dose in patients with advanced, incurable solid tumours.

PATIENTS AND METHODS

Twenty-eight patients were enrolled in cohorts of three from three National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) centers. ZD1839 was given at doses from 150 to 800 mg daily orally and patients underwent a pretreatment and a 28 day post treatment tumor biopsy, while PK sampling was performed on days 8, 15, 22, 29, and a toxicity assessment every 28 days.

RESULTS

All twenty-eight patients were evaluable for non-hematological and hematological toxicity. Twenty-seven were evaluable for response. The MTD was not reached but DLT included reversible rash and diarrhea. One patient with urachal cancer had a transient 55% decrease in tumor size and two other patients (breast and non-small cell lung cancer) had minor responses; three additional patients had pharmacodynamic evidence of target effect. PK demonstrated steady state within the first 2 weeks of dosing and dose dependent exposure.

CONCLUSION

It appears that ZD 1839 at a dose of 800 m/day was tolerable, although some patients required dose modification for diarrhea. Doses above 250 m/day demonstrate biologic activity and could be consider for future study in a variety of EGFR positive tumor types.

Bacillus anthracis requires siderophore biosynthesis for growth in macrophages and mouse virulence

Systemic anthrax infections can be characterized as proceeding in stages, beginning with an early intracellular establishment stage within phagocytes that is followed by extracelluar stages involving massive bacteraemia, sepsis and death. Because most bacteria require iron, and the host limits iron availability through homeostatic mechanisms, we hypothesized that B. anthracis requires a high-affinity mechanism of iron acquisition during its growth stages. Two putative types of siderophore synthesis operons, named Bacillus anthracis catechol, bac (anthrabactin), and anthrax siderophore biosynthesis, asb (anthrachelin), were identified. Directed gene deletions in both anthrabactin and anthrachelin pathways were generated in a B. anthracis (Sterne) 34F2 background resulting in mutations in asbA and bacCEBF. A decrease in siderophore production was observed during iron-depleted growth in both the DeltaasbA and DeltabacCEBF strains, but only the DeltaasbA strain was attenuated for growth under these conditions. In addition, the DeltaasbA strain was severely attenuated both for growth in macrophages (MPhi) and for virulence in mice. In contrast, the DeltabacCEBF strain did not differ phenotypically from the parental strain. These findings support a requirement for anthrachelin but not anthrabactin in iron assimilation during the intracellular stage of anthrax.

Crystal structure of the anthrax lethal factor

Lethal factor (LF) is a protein (relative molecular mass 90,000) that is critical in the pathogenesis of anthrax. It is a highly specific protease that cleaves members of the mitogen-activated protein kinase kinase (MAPKK) family near to their amino termini, leading to the inhibition of one or more signalling pathways. Here we describe the crystal structure of LF and its complex with the N terminus of MAPKK-2. LF comprises four domains: domain I binds the membrane-translocating component of anthrax toxin, the protective antigen (PA); domains II, III and IV together create a long deep groove that holds the 16-residue N-terminal tail of MAPKK-2 before cleavage. Domain II resembles the ADP-ribosylating toxin from Bacillus cereus, but the active site has been mutated and recruited to augment substrate recognition. Domain III is inserted into domain II, and seems to have arisen from a repeated duplication of a structural element of domain II. Domain IV is distantly related to the zinc metalloprotease family, and contains the catalytic centre; it also resembles domain I. The structure thus reveals a protein that has evolved through a process of gene duplication, mutation and fusion, into an enzyme with high and unusual specificity.

Laparoscopic fundoplication for symptomatic but physiologic gastroesophageal reflux

Esophageal pH monitoring identifies some patients who have physiologic amounts of esophageal acid exposure but have a strong correlation between symptoms of esophageal reflux events. These patients with symptomatic physiologic reflux probably have enhanced sensory perception of reflux events and may be difficult to control with acid-suppressive therapy. Little is known about the role of fundoplication in such patients. Patients with no endoscopic evidence of gastroesophageal reflux disease and a normal 24-hour pH composite score (<22.4 in our laboratory), but a symptom index (SI = number of symptoms with pH <4/total number of symptoms) greater than 50% were offered laparoscopic fundoplication if acid-suppressive therapy was unsatisfactory. This group comprised 18 (4%) of 459 patients undergoing fundoplication at our institution. Heartburn, dysphagia, and reflux symptoms were scored on a scale of 0 to 10 with patients on and off medicine preoperatively, and at a mean of 7.2 months (range 1 to 32 months) postoperatively. The 18 patients with symptomatic physiologic reflux (6 males and 12 females) had heartburn as a major complaint. Preoperative response to proton pump inhibitors for heartburn was 72% and for all symptoms was 60%. The group had a mean pH composite score of 14 (range 4 to 22). The symptom used to calculate the symptom index was heartburn in 12 patients, regurgitation in three, chest pain in two, and cough in one. An average of 18 symptoms (range 2 to 56) were recorded. The mean symptom index was 82% (range 50% to 100%). A Nissen fundoplication was performed in nine patients and a Toupet fundoplication in nine. Surgery was successful (>90%) in alleviating reflux symptoms in 14 patients and partially successful (>75%) in three of the remaining four patients. Gas bloat and dysphagia were seen in one patient each. Fundoplication is effective at relieving reflux symptoms in carefully selected patients with symptomatic physiologic reflux, with minimal side effects.

Congenital hepatic fibrosis in calves

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