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.

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.

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.

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.

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.

Effect of intraarticular pressure on glenohumeral kinematics during a simulated abduction motion: a cadaveric study.

BACKGROUND: The current understanding of glenohumeral joint stability is defined by active restrictions and passive stabilizers including naturally-occurring negative intraarticular pressure. Cadaveric specimens have been used to evaluate the role of intraarticular pressure on joint stability, although, while the shoulder's negative intraarticular pressure is universally acknowledged, it has been inconsistently accounted for. HYPOTHESIS: During continuous, passive humeral abduction, releasing the native intraarticular pressure increases joint translation, and restoring this pressure decreases joint translations. STUDY DESIGN: Descriptive Laboratory Study. METHODS: A validated shoulder testing system was used to passively abduct the humerus in the scapular plane and measure joint translations for seven (n = 7) cadaveric specimens. The pressure within the glenohumeral joint was measured via a 25-gauge needle during passive abduction of the arm, which was released and subsequently restored. During motion, the rotator cuff muscles were loaded using stepper motors in a force feedback loop and electromagnetic sensors were used to continuously measure the position of the humerus and scapula. Joint translation was defined according to the instant center of rotation of the glenohumeral head according to the recommendations by the International Society of Biomechanics. RESULTS: Area under the translation versus abduction angle curve suggests that releasing the pressure within the capsule results in significantly less posterior translation of the glenohumeral head as compared to intact (85-90˚, p < 0.05). Posterior and superior translations were reduced after 70˚ of abduction when the pressure within the joint was restored. CONCLUSION: With our testing system employing a smooth continuous passive motion, we were able to show that releasing intraarticular pressure does not have a major effect on the path of humeral head motion during glenohumeral abduction. However, both violating the capsule and restoring intraarticular pressure after releasing alter glenohumeral translations. Future studies should study the effect of simultaneous external rotation and abduction on the relationship between joint motion and IAP, especially in higher degrees of abduction. CLINICAL RELEVANCE: Thoroughly simulating the glenohumeral joint environment in the cadaveric setting may strengthen the conclusions that can be translated from this setting to the clinic.

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.

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 (ß = 200.32 [95% CI 6.18-394.47]; P = .043) and surgeon 4 (ß = 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.

Strain Variation in Clostridioides difficile Cytotoxicity Associated with Genomic Variation at Both Pathogenic and Nonpathogenic Loci.

Clinical disease from Clostridioides difficile infection can be mediated by two toxins and their neighboring regulatory genes located within the five-gene pathogenicity locus (PaLoc). We provide several lines of evidence that the cytotoxicity of C. difficile may be modulated by genomic variants outside the PaLoc. We used a phylogenetic tree-based approach to demonstrate discordance between cytotoxicity and PaLoc evolutionary history, an elastic net method to show the insufficiency of PaLoc variants alone to model cytotoxicity, and a convergence-based bacterial genome-wide association study (GWAS) to identify correlations between non-PaLoc loci and changes in cytotoxicity. Combined, these data support a model of C. difficile disease wherein cytotoxicity may be strongly affected by many non-PaLoc loci. Additionally, we characterize multiple other in vitro phenotypes relevant to human infections, including germination and sporulation. These phenotypes vary greatly in their clonality, variability, convergence, and concordance with genomic variation. Finally, we highlight the intersection of loci identified by the GWAS for different phenotypes and clinical severity. This strategy to identify overlapping loci can facilitate the identification of genetic variation linking phenotypic variation to clinical outcomes. IMPORTANCE Clostridioides difficile has two major disease-mediating toxins, A and B, encoded within the pathogenicity locus (PaLoc). In this study, we demonstrate via multiple approaches that genomic variants outside the PaLoc are associated with changes in cytotoxicity. These genomic variants may provide new avenues of exploration in the hunt for novel disease-modifying interventions. Additionally, we provide insight into the evolution of several additional phenotypes also critical for clinical infection, such as sporulation, germination, and growth rate. These in vitro phenotypes display a range of responses to evolutionary pressures and, as such, vary in their appropriateness for certain bacterial genome-wide association study approaches. We used a convergence-based association method to identify the genomic variants most correlated with both changes in these phenotypes and disease severity. These overlapping loci may be important for both bacterial function and human clinical disease.

Outcomes After Operative Fixation of Vancouver B2 and B3 Type Periprosthetic Fractures.

OBJECTIVES: The incidence of periprosthetic femur fracture in the setting of total hip arthroplasty is steadily increasing. Although the traditional dogma is that loose femoral components must be revised, we propose that in a frail geriatric population, anatomic reduction and fixation of Vancouver B2 and B3 periprosthetic fracture variants can restore stem stability and provide similar outcomes as revision arthroplasty. DESIGN: Retrospective cohort study. SETTING: Level 1 trauma center, tertiary academic medical center. PATIENTS/PARTICIPANTS: We identified 94 patients over 65 years of age with Vancouver B2 and B3 fractures sustained between 2005 and 2019. INTERVENTION: Patients were treated by either open reduction and internal fixation (ORIF) or revision arthroplasty (RA) with or without fixation. MAIN OUTCOME MEASUREMENTS: Outcomes were mortality, time to full weight-bearing after surgery, intraoperative estimated blood loss, perioperative complications, reoperation, subsidence rate, and Patient-Reported Outcomes Measurement Information System pain and physical function scores. RESULTS: A total of 75 (79.8%) ORIF and 19 (20.2%) RA patients were reviewed. One-year mortality for our cohort was 26.3%, and there was no significant difference between groups. Mean time to weight bear and surgical complication rates were similar between groups. The ORIF group had a significantly shorter time to surgery than the RA group. The RA group had greater incidence and amount of subsidence as well as estimated blood loss than the ORIF group. CONCLUSIONS: In geriatric patients with Vancouver B2 and B3 type periprosthetic fractures with known loose stems, ORIF may offer a similarly safe method of treatment than revision arthroplasty. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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.

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

¼: 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. ¼: 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. ¼: ORIF of Vancouver type-B3 periprosthetic femoral fractures was associated with higher revision and reoperation rates than those after RA. ¼: 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. ¼: 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. ¼: Mortality rates did not differ between RA and ORIF in the treatment of Vancouver type-B2 and B3 fractures. ¼: Overall complication rates did not differ between RA and ORIF in the treatment of Vancouver type-B2 and B3 fractures. ¼: We found a high heterogeneity in applied surgical and fixation techniques in the ORIF group.

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.

Draft Genome Sequences of Five Historical Bacillus anthracis Strains.

Bacillus anthracis is the causative agent of anthrax, a disease of livestock, wildlife, and humans. Here, we present the draft genome sequences of five historical B. anthracis strains that were preserved as lyophilates in glass vials for decades.

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 ß-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 ß-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.