Two-stage total joint replacement for hip or knee septic arthritis: post-traumatic etiology and difficult-to-treat infections predict poor outcomes

PURPOSE

Septic arthritis (SA) is a rare but significant clinical challenge in orthopedics that can impact patients' quality of life. This study aims to examine the clinical outcomes of patients undergoing two-stage total joint replacement (TJR) in hip and knee SA and analyze potential predictors of treatment failure.

METHODS

A retrospective analysis was conducted using data from a prospectively collected institutional arthroplasty registry from January 1st, 2012, to January 1st, 2019. Patients with hip or knee SA who underwent a two-stage TJR and had at least two years of follow-up were included. Demographic characteristics, surgical variables, and outcomes were collected and analyzed from clinical and surgical data. Statistical analysis was performed using IBM SPSS Statistics, with statistical significance at p < 0.05.

RESULTS

One hundred and fourteen patients (61 with hip SA, 53 with knee SA) were included in the study. The mean follow-up was 72.8 months. Postoperatively, both clinical and functional outcomes significantly improved, as indicated by the Hip Society Score (HHS) and Knee Society Score (KSS). The overall success rate of the two-stage protocol was 89.5%. Complications that did not require revision occurred in 21% of cases. The most identified pathogen was methicillin-sensitive Staphylococcus aureus (MSSA). Difficult-to-treat (DTT) infections and post-traumatic etiology were identified as predictors of treatment failure in patients undergoing two-stage TJR for hip and knee SA.

CONCLUSIONS

Two-stage TJR in hip and knee SA demonstrated favorable clinical outcomes at mid-term follow-up. The procedure significantly improved functional scores and achieved a high success rate, while DTT infections and post-traumatic etiology were associated with a higher risk of treatment failure.

Systematic review and meta-analysis of single-stage vs two-stage revision for periprosthetic joint infection: a call for a prospective randomized trial

BACKGROUND

Periprosthetic joint infection (PJI) is a severe complication of joint arthroplasty that causes significant pain and economic loss. This study aimed to determine whether the current evidence supports single-stage revision for PJI based on reinfection and reoperation rates.

METHODS

We searched the PubMed, EBSCO, Medline, and Cochrane Library databases from inception to 30 May 2023 to identify studies that compared single-stage revision and two-stage revision for PJI. Data on reinfection and reoperation rates were pooled.

RESULTS

This meta-analysis included a total of 40 studies with 8711 patients. Overall, there was no significant difference between single- and two-stage revision regarding the postoperative reinfection rate and reoperation rate. Subgroup analysis by surgery period and different surgical sites revealed no difference between the two groups in the reinfection and reoperation rates.

CONCLUSIONS

Based on the available evidence, our study did not identify a significant difference in reinfection and reoperation rates between single- and two-stage revision for PJI. Given the limitations in inclusion/exclusion criteria and the observed heterogeneity, we acknowledge the complexity of drawing strong conclusions. Therefore, we suggest that the choice between single- and two-stage revision should be carefully considered on an individual basis, taking into account patient-specific factors and further research developments.

Comparison of temporary external and percutaneous k-wire fixations for treatment of ankle fracture-dislocations

PURPOSE

Ankle fracture-dislocations are among the most severe injuries, and the use of an external fixator as a recommended fixation method has some disadvantages. The aim of this study was to compare the clinical outcomes and complication rates of external and K-wire fixations in the treatment of ankle fracture dislocations.

METHODS

A total of 67 patients with ankle fracture-dislocations requiring temporary external or percutaneous K-wire fixation were included. The exclusion criteria were pilon fractures, open fractures, and those who required acute open reduction internal fixation (ORIF). The American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, a 10-point visual analog scale (VAS) score (range 0-10), and complications before and after the definitive surgery were recorded.

RESULTS

A significant difference between the two groups was not observed for age, sex, affected side, fracture type, smoking status, or diabetes. The average AOFAS scores were 83.2 and 83.3, the median VAS scores were 3 and 3, and the complication rates were 32.4% and 6.7% in the external and K-wire fixation groups, respectively (p = 0.010). However, skin necrosis, re-dislocation of the ankle, surgical wound infection, and posttraumatic ankle osteoarthritis frequency were not significantly different between the groups, except for pin-sites infection (p = 0.036).

CONCLUSION

Ankle fracture-dislocations using percutaneous k-wire fixation showed a low rate of complications and favorable clinical outcomes. This method could be a good alternative treatment option for ankle fracture-dislocations.

Analysing the mechanism of food waste anaerobic digestion enhanced by iron oxide in a continuous two-stage process

The food waste (FW) digestion performance can be enhanced by introducing iron oxide (IO) into digesters. However, the role of IO in continuous two-stage digesters in enhancing the FW anaerobic digestion remains unclear. In this study, the effect of IO on the bioenergy recovery from a two-stage digestion process was investigated. The bioenergy recovery was significantly increased by up to 208.43 % with IO addition. The activities of dehydrogenase, α-amylase, and protease increase by 0.82-1.44, 7.24-14.56 and 7.97-20.45 times, respectively, as compared with that of the blank. With IO addition, the metabolic pathway in hydrolytic-acidogenic (HA) reactor shifted from lactic acid fermentation to butyric fermentation, which promoted stable methane production in methanogenic (MG) reactor. The activity of coenzyme F420 increased by 19.19-39.01 times, indicating that IO facilitated FW digestion by promoting hydrogenotrophic methanogenesis. The enhancement in the enzyme activity was attributable to the Fe2+ generated by dissimilatory iron reduction. According to the microbial analysis, IO enhanced interspecies hydrogen transfer between Methanobacterium and Syntrophomonas. Furthermore, IO improved direct interspecies electron transfer between Geobacter sulfurreducens and Methanosarcina. The effluent recirculation strategy greatly facilitated the hydrolysis and acidification of FW, which was critical for improving the two-stage process performance.

Two-stage revision in periprosthetic joint infection of the hip using a new intraoperatively molded articulating spacer design

Purpose

The treatment of periprosthetic joint infection (PJI) after total hip arthroplasty (THA) is still under debate. Two-stage exchange arthroplasty is the most common surgical procedure performed. This study analyzed a new functional articulating hip spacer called "Spaceflex" regarding the mechanical-related complications, the recurrent/persistent infection during the interval period, the overall infection-free survivorship after reimplantation, the overall complication/reoperation after reimplantation and the evaluation of patient-reported outcome measures (PROMs) at three intervals of time: before the first stage, during the interval period, and at the final follow-up after reimplantation.

Methods

A consecutive series of 56 patients with chronic hip PJI undergoing two-stage prosthetic revision using a new intraoperatively molded articulating hip spacer design implanted by the same experienced surgeons was examined from January 2017 to December 2021. The demographic and clinical characteristics of the included patients were analyzed. Specifically, PROMs before the first stage, during the interval period, and at the final follow-up after reimplantation and complications reported during the interval period and after reimplantation were examined.

Results

The new functional articulating hip spacer was characterized by a low mechanical complication rate (5.8%) and an overall two-stage procedure success rate of 90.6% at the last follow-up. PROMs improved with the spacer during the interval period and at the final follow-up. Furthermore, the reinfection rate was in line with other case series with different spacer designs. Finally, low postoperative complication rates after reimplantation have been demonstrated.

Conclusions

Two-stage revision performed with a modular articulating spacer allows patients to preserve satisfactory functional and quality-of-life outcomes in the postoperative period, with a low risk of mechanical complications and without increasing the reinfection rate.

Disentangling the sources of bank inefficiency: a two-stage network multi-directional efficiency analysis approach

To disentangle the sources of bank inefficiency, this paper presents an extended two-stage network multi-directional efficiency analysis (NMEA) approach by taking the internal structure of the banking system into account. The proposed two-stage NMEA approach extends the conventional "black-box" MEA approach, providing a unique efficiency decomposition and identifying which variables drive the inefficiency for banking systems with a two-stage network structure. An empirical application of Chinese listed banks from 2016 to 2020 during the 13th Five-year Plan reveals that the overall inefficiency of sample banks is primarily sourced from the deposit-generating subsystem. Additionally, different types of banks display differentiated evolution modes over different dimensions, confirming the importance of applying the proposed two-stage NMEA approach.

Functional Outcome after Reimplantation in Patients Treated with and without an Antibiotic-Loaded Cement Spacers for Hip Prosthetic Joint Infections

Purpose

A staged revision with placement of a temporary antibiotic-loaded cement spacer after removal of the implant is the "gold standard" for treatment of chronic prosthetic joint infection (PJI). It enables local delivery of antibiotics, maintenance of limb-length and mobility, easier reimplantation. However, bacterial colonization of spacers and mechanical complications can also occur. The aim of this study is to evaluate functional results and infection control in two-stage treatment of total hip arthroplasty (THA) PJI with and without a spacer.

Materials and Methods

A retrospective review of 64 consecutive patients was conducted: 34 underwent two-stage revision using a cement spacer (group A), 30 underwent two-stage revision without a spacer (group B). At the final follow-up, functional evaluation of patients with a THA in site, without PJI recurrence, was performed using the Harris hip score (HHS). Measurement of limb-length and off-set discrepancies was performed using anteroposterior pelvic X-rays.

Results

Most patients in group B were older with more comorbidities preoperatively. Thirty-three patients (97.1%) in group A underwent THA reimplantation versus 22 patients (73.3%) in group B (P<0.001). No significant differences in limb-length and off-set were observed. The results of functional evaluation performed during the final follow-up (mean, 41 months) showed better function in patients in group A (mean HHS, 76.3 vs. 55.9; P<0.001).

Conclusion

The use of antibiotic-loaded cement spacer seems superior in terms of functional outcomes and reimplantation rate. Resection arthroplasty might be reserved as a first-stage procedure in patients who are unfit, who might benefit from a definitive procedure.

Revision surgery for periprosthetic elbow infection: eradication rate, complications, and functional outcomes-a systematic review

INTRODUCTION

The aim of this systematic review was to investigate the outcomes of revision surgery after periprosthetic elbow infection (PEI).

MATERIAL AND METHODS

Eighteen studies with 332 PEI that underwent revision surgery were included. Demographics, laboratory and microbiological data, types of implants, surgical techniques with complications and reoperations, eradication rates, and clinical and functional outcomes were reported.

RESULTS

Staphylococcus aureus was the most common microorganism (40%). Pre-operatively, the mean white blood cell count was 8400 ± 4000 per microliter; the mean C-reactive protein level was 41.6 ± 66.9 mg/dl, and the mean erythrocyte sedimentation rate was 45 ± 66.9 mm/h. The Coonrad-Morrey total elbow prosthesis represented 41.2% of the infected implant, and it also represented the most common system used for the PEI revision surgery. Two-stage revision and debridement and implant retention (DAIR) were the most common procedures performed for PEI, and, on the whole, they represented 35.7 and 32.7%, respectively. The eradication rate was 76% with 2-stage, 71% with resection arthroplasty (RA), 66.7% with 1-stage, 57.7% with DAIR, and 40% with arthrodesis (EA). DAIR showed a significantly lower eradication rate than 2-stage (P = 0.003). The mean postoperative Mayo Elbow Performance Score was significantly higher in patients who underwent DAIR, and 2-stage compared with RA (P < 0.001 for all). Postoperative flexion-extension ROM was significantly higher in patients who underwent DAIR compared with 1-stage, 2-stage, and RA (P < 0.001 for all). Moreover, 1-stage and 2-stage showed a significantly greater postoperative flexion-extension ROM compared with RA (P < 0.001 for all). Reoperations occurred in 40% of patients after EA, 33.3% after 1-stage, 26.9% after DAIR and RA, and 24.1% after 2-stage. Conversion to amputation occurred in 2.2% of patients after RA and 1% after DAIR.

CONCLUSIONS

Two-stage revision and DAIR are the most common procedures used to manage PEI; however, the former procedure showed a significantly higher eradication rate. Resection arthroplasty showed a high eradication rate, but postoperative lower clinical and functional outcomes limit the indications for this technique. One-stage procedure showed a limited role in the current practice of PEI treatment.

LEVEL OF EVIDENCE

Level IV.

Total hip arthroplasty for destructive septic arthritis of the hip using a two-stage protocol without spacer placement

INTRODUCTION

The optimal treatment of patients with a degenerative joint disease secondary to an active or chronic septic arthritis of the hip is unclear. The aim of the present study was to report on our experience with two-stage total hip arthroplasty (THA) using a contemporary treatment protocol without spacer insertion.

MATERIALS AND METHODS

Our prospective institutional database was used to identify all patients with degenerative septic arthritis treated with a non-spacer two-stage protocol between 2011 and 2017. Clinical outcomes included interim revision, periprosthetic infection (PJI) and aseptic revision rates. Restoration of leg-length and offset were assessed radiographically. Modified Harris hip score (mHHS) were obtained. Treatment success was defined using the modified Delphi consensus criteria. Mean follow-up was 62 months (13-110).

RESULTS

A total of 33 patients with a mean age of 60 years (13-85) were included. 55% of the cohort was male and average Charlson Comorbidity Index (CCI) was 3.7 (0-12). 21 patients (64%) had an active/acute infection and 12 patients (36%) were treated for chronic/quiescent septic arthritis. Overall, 11 patients (33%) had treatment failure, including 5 patients who failed to undergo THA, 2 interim re-debridement for persistent infection, and 4 patients who developed PJI after an average of 7 months (0.3-13) following THA. The most common identified pathogen was Staphylococcus aureus (42.4%). No aseptic revision was recorded following THA. Leg-length and offset were successfully restored. Mean mHHS improved from 35.2 points to 73.4 points.

CONCLUSION

Two-stage THA without spacer placement is a viable treatment option for destructive septic arthritis of the hip, demonstrating comparable rates of infection control and functional outcome. However, definitive resection arthroplasty is not uncommon in these often critically ill patients.

Reinfection rates after one- and two-stage revision surgery for hip and knee arthroplasty: a systematic review and meta-analysis

PURPOSE

Revisions for periprosthetic joint infection of knee and hip arthroplasty can be performed following one- or two-stage treatment protocols. Current literature is inconclusive whether one protocol is superior to the other, as prior literature reported similar reinfection rates for both treatment options. We aimed to provide a systematic review and meta-analysis of current literature on septic arthroplasty revisions.

METHODS

Between April 2015 and December 2020, Medline, Embase, and The Cochrane Library were searched for studies reporting reinfection outcomes in patients treated with one-stage and two-stage knee or hip revision arthroplasty. Two reviewers independently extracted data and disagreements were resolved by a third investigator. We utilized a double arcsine transformation, prior to pooling using a random-effects model.

RESULTS

For hip revision arthroplasty, we identified 14 one-stage studies (n = 1237) with a pooled reinfection rate of 5.7% (95% CI 3.7-8.1%), and 46 two-stage studies (n = 5009) with a reinfection rate of 8.4% (95% CI 6.9-9.9%). For knee revision arthroplasty, 6 one-stage studies (n = 527) and 48 two-stage studies (n = 4344) were identified with reinfection rates of 12.7% (7.0-19.7%) and 16.2% (13.7-19.0%), respectively. Overall, reinfection rates did not vary substantially after subgroup analysis. Limitations of our study are the limited amount of one-stage studies that introduce a potential bias.

CONCLUSION

The reinfection rates following one- and two-stage hip and knee arthroplasty revisions were similar. Knee reinfection rates have increased compared to the previous analysis. Individual patient characteristics and adequate treatment algorithms are needed for a more individual selection approach, until a randomized trial is performed.

Hypoalbuminemia Increases Mortality after Two-Stage Revision Total Joint Arthroplasty

Objectives

This study aimed to evaluate the effect of hypoalbuminemia on failure rates and mortality after a two-stage revision for PJI.

Methods

199 Patients (130 knees and 69 hips) with a mean age of 64.7 ± 10.7 years who underwent a two-stage exchange were retrospectively reviewed at a mean of 51.2 ± 39.7 months. Failure of treatment was defined as any revision within the follow-up period, failure to undergo reimplantation, or death within one year of initiating treatment.

Results

There were 71 failures (35.7%), including 38 septic failures (19.1%). We found no differences between successful revisions and failures regarding hypoalbuminemia (43% vs. 42% prior to stage 1, P=1 and 32% vs. 29% prior to stage 2, P=0.856). There were also no differences in hypoalbuminemia rates between septic failures and the rest of the cohort (42% vs. 43% prior to stage 1, P=1.0 and 34% vs. 30% prior to stage 2, P=0.674). Hypoalbuminemia prior to stage 2 was a significant predictor of mortality based on multivariate analysis (odds ratio 5.40, CI 1.19-24.54, P=0.029). Hypoalbuminemia was independently associated with a greater length of stay by 2.2 days after stage 1 (P=0.002) and by 1.0 days after the second stage reimplantation (P=0.004).

Conclusion

Preoperative hypoalbuminemia is a significant predictor of mortality and increased length of stay following two-stage revision but is not a predictor of failure of PJI treatment. Further study is required to understand if hypoalbuminemia is a modifiable risk factor or a marker for poor outcomes.

Analysis of the clinical efficacy of two-stage revision surgery in the treatment of periprosthetic joint infection in the knee: A retrospective study

BACKGROUND

Periprosthetic joint infection (PJI) is a catastrophic complication that can occur following total knee arthroplasty (TKA). Currently, the treatment for PJI mainly includes the use of antibiotics alone, prosthetic debridement lavage, primary revision, secondary revision, joint fusion, amputation, etc.

AIM

To explore the clinical effect of two-stage revision surgery for the treatment of PJI after TKA.

METHODS

The clinical data of 27 patients (3 males and 24 females; age range, 47–80 years; mean age, 66.7 ± 8.0 years; 27 knees) with PJI treated with two-stage revision surgery in our hospital between January 1, 2010 and December 31, 2020 were analyzed retrospectively. The following outcomes were compared for changes between preoperative and last follow-up results: Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), visual analogue scale (VAS) scores, Hospital for Special Surgery (HSS) scores, knee range of motion (ROM), and infection cure rates.

RESULTS

All 27 patients were followed up (range, 13–112 mo). The ESR (14.5 ± 6.3 mm/h) and CRP (0.6 ± 0.4 mg/dL) of the patients at the last follow-up were significantly lower than those at admission; the difference was statistically significant (P < 0.001). The postoperative VAS score (1.1 ± 0.7), HSS score (82.3 ± 7.1), and knee ROM (108.0° ± 19.7°) were significantly improved compared with those before the surgery; the difference was statistically significant (P < 0.001). Of the 27 patients, 26 were cured of the infection, whereas 1 case had an infection recurrence; the infection control rate was 96.3%.

CONCLUSION

Two-stage revision surgery can effectively relieve pain, control infection, and retain good joint function in the treatment of PJI after TKA.

"Recommendations for periprosthetic joint infections (PJI) prevention: the European Knee Associates (EKA)-International Committee American Association of Hip and Knee Surgeons (AAHKS)-Arthroplasty Society in Asia (ASIA) survey of members"

PURPOSE

Periprosthetic joint infections (PJIs) represent a devastating consequence of total joint arthroplasty. The European Knee Associates (EKA), the American Association of Hip and Knee Surgeons (AAHKS) International Committee, and the Arthroplasty Society in Asia (ASIA) board members were interested in quantifying differences in arthroplasty surgeons' use of various PJI prevention measures to provide clinical recommendations to reduce PJI incidence.

METHODS

A prospective Microsoft Forms online survey was distributed among EKA, AAHKS International Committee, and ASIA members and their affiliated arthroplasty surgeons. The survey consisted of 20 single and multiple response questions focused on PJI prevention strategies at three perioperative periods: preoperatively, intraoperatively, and postoperatively.

RESULTS

Three hundred and ninety-four arthroplasty surgeons from 6 different continents completed the survey. Preoperative: (A) PJI Risk Stratification: 40.6% routinely set thresholds (e.g., BMI, HgbA1C) to be met to qualify for surgery, 36.5% only review past medical history; 9.1% use machine learning to personalize PJI risk; (B) BMI limit: 36% no limit; 15.4% BMI < 35; 30.9% BMI < 40; 17.2% BMI < 45; (C) Nutritional status: 55.3% do not screen; among those who screen their patients (44.7%), albumin is the single most used marker (86.3%); (D) Hyperglycemia/Diabetes: 83.3% check this comorbidity; 88.1% use HgbA1C as single best screening test; (E) MRSA nasal colonization: 63.7% do not test; 28.9% test all patients; 7.4% test selectively. Intraoperative: (A) Antibiotic prophylaxis in high-risk patients: 43.4% use single antibiotic for 24 h; 21.3% use double antibiotic for 24 h; 14.2% use single/double antibiotic for 7 days postoperatively; (B) Skin-cleansing: 68.7% at home (45.6% chlorhexidine sponge; 11.9% clippers); (C) Intraoperative skin disinfection: 46.9% single chlorhexidine; 25% double chlorhexidine-povidone-iodine;15.4% single povidone-iodine; (D) Tranexamic acid (TXA) to reduce bleeding/SSI: 96% yes (51% double IV dose, 35.2% single IV dose, 23.6% intra-articular injection); (E) Surgical suction drain: 52% do not use drains; 19.7% use a drain < 24 h; (F) Intra-articular lavage: 64.9% use only saline; 28.1% use dilute povidone-iodine; (G) Antibiotic local delivery to prevent PJI: 82.4% use antibiotic-added cement. Postoperative: (A) Routine monitoring of PJI serologic markers: 42% only in symptomatic patients; 34.2% do not; 20.8% in all patients; (B) Serologic markers to rule in/out PJI: 95.9% CRP; 71% SEDRATE; 60.6% WBC; (C) Synovial fluid test to rule in/out PJI: 79.6% culture/sensitivity; 69.5% WBC count; 31.4% CRP.

CONCLUSIONS

This survey demonstrated that notable differences still exist in the application of PJI preventive measures across different geographic areas: Optimizing the patient preoperatively and applying multimodal intraoperative strategies represent newer, clinically relevant steps in the effort to reduce the burden of PJI. More uniform guidelines still need to be produced from international scientific societies in order facilitate a more comprehensive approach to this devastating complication.

LEVEL OF EVIDENCE

IV.

Estimating interactions in individual participant data meta-analysis: a comparison of methods in practice

Medical interventions may be more effective in some types of individuals than others and identifying characteristics that modify the effectiveness of an intervention is a cornerstone of precision or stratified medicine. The opportunity for detailed examination of treatment-covariate interactions can be an important driver for undertaking an individual participant data (IPD) meta-analysis, rather than a meta-analysis using aggregate data. A number of recent modelling approaches are available. We apply these methods to the Perinatal Antiplatelet Review of International Studies (PARIS) Collaboration IPD dataset and compare estimates between them. We discuss the practical implications of applying these methods, which may be of interest to aid meta-analysists in the use of these, often complex models.Models compared included the two-stage meta-analysis of interaction terms and one-stage models which fit multiple random effects and separate within and between trial information. Models were fitted for nine covariates and five binary outcomes and results compared.Interaction terms produced by the methods were generally consistent. We show that where data are sparse and there is low heterogeneity in the covariate distributions across trials, the meta-analysis of interactions may produce unstable estimates and have issues with convergence. In this IPD dataset, varying assumptions by using multiple random effects in one-stage models or using only within trial information made little difference to the estimates of treatment-covariate interaction. Method choice will depend on datasets characteristics and individual preference.

Optimal timing of postmastectomy radiotherapy in two-stage prosthetic breast reconstruction: An updated meta-analysis

BACKGROUND

There is no consensus on the timing of postmastectomy radiotherapy (PMRT) in relation to the exchange procedure in breast cancer patients undergoing the immediate two-stage prosthetic breast reconstruction. This meta-analysis investigated the reconstruction failure, complications, and cosmesis between PMRT to the tissue expander (TE) and PMRT to the permanent implant (PI).

METHODS

A literature search was conducted in PubMed and Embase databases until February 2022. Studies presenting at least one aspect relating to reconstruction failure, complications, and cosmesis between two cohorts were included. Newcastle-Ottawa Scale (NOS) was used to assess the risk of bias in included studies.

RESULTS

Eleven studies presenting 1447 patients were enrolled. Three studies were prospective controlled research. The risk for implant loss was higher in PMRT to TE cohort (RR 1.75; 95% CI, 1.03 to 2.98; p = 0.04); meanwhile, the PMRT to TE cohort had a significantly lower risk of capsular contracture (RR 0.47; 95% CI, 0.29 to 0.78; p = 0.003). However, the synthesized result should be interpreted sensibly due to heterogeneity in statistical methods and definitions.

CONCLUSION

Delivering PMRT to PI may reduce the risk of implant loss, while delivering PMRT to TE can reduce the risk of severe capsular contracture. More high-quality studies are warranted for the refinement of clinical practice.

Successful year-round mainstream partial nitritation anammox: Assessment of effluent quality, performance and N2O emissions

For two decades now, partial nitritation anammox (PNA) systems were suggested to more efficiently remove nitrogen (N) from mainstream municipal wastewater. Yet to date, only a few pilot-scale systems and even fewer full-scale implementations of this technology have been described. Process instability continues to restrict the broad application of PNA. Especially problematic are insufficient anammox biomass retention, the growth of undesired aerobic nitrite-oxidizers, and nitrous oxide (N₂O) emissions. In this study, a two-stage mainstream pilot-scale PNA system, consisting of three reactors (carbon pre-treatment, nitritation, anammox - 8 m³ each), was operated over a year, treating municipal wastewater. The aim was to test whether both, robust autotrophic N removal and high effluent quality, can be achieved throughout the year. A second aim was to better understand rate limiting processes, potentially affecting the overall performance of PNA systems. In this pilot study, excellent effluent quality, in terms of inorganic nitrogen, was accomplished (average effluent concentrations: 0.4 mgNH₄-N/L, 0.1 mgNO₂-N/L, 0.9 mgNO₃-N/L) even at wastewater temperatures previously considered problematic (as low as 8 °C). N removal was limited by nitritation rates (84 ± 43 mgNH₄-N/L/d), while surplus anammox activity was observed at all times (178 ± 43 mgN/L/d). Throughout the study, nitrite-oxidation was maintained at a low level (<2.5% of ammonium consumption rate). Unfortunately, high N₂O emissions from the nitritation stage (1.2% of total nitrogen in the influent) were observed, and, based on natural isotope abundance measurements, could be attributed to heterotrophic denitrification. In situ batch experiments were conducted to identify the role of dissolved oxygen (DO) and organic substrate availability in N₂O emission-mitigation. The addition of organic substrate, to promote complete denitrification, was not successful in decreasing N₂O emission, but increasing the DO from 0.3 to 2.9 mgO₂/L decreased N₂O emissions by a factor of 3.4.

One-Stage Versus Two-Stage Gastric Bypass as Redo Surgery After Failed Adjustable Gastric Banding-Observation Comparative Multicenter Study

BACKGROUND

This study investigates the outcome of one-stage and two-stage Roux-Y gastric bypass (RYGB) as a revision procedure after failed adjustable gastric banding (AGB).

MATERIAL AND METHODS

Data of patients who underwent a one-stage RYGB (OS-RYGB) or a two-stage RYGB (TS-RYGB) revision procedure after failing AGB between 2005 and 2019 were analyzed. Outcome criteria were perioperative complications, operating time, change in weight and BMI, and remission of comorbidities at 1-year follow-up.

RESULTS

Data from 230 patients after OS-RYGB and 197 after TS-RYGB were analyzed. The total perioperative complication rates were not significantly different between the two groups (overall p > 5%). In the category of other complications, there was a significant difference between the two groups, with a lower rate in TS-RYGB than in OS-RYGB (p = 0.020). Wound infections occurred more frequently after TS-RYGB than after OS-RYGB (p = 0.015). Mean operating time differed significantly between the two groups (OS-RYGB (149.9 min) and TS-RYGB 191 min; p < 0.001). The change in hypertension was significantly higher in OS-RYGB (37.9 vs. 21.1%; p = 0.007). Other comorbidities showed no significant change within 1 year after surgery. Regarding the change in BMI, %TWL, and %EWL, there were no significant benefits for either group (p = 0.574, 0.762, and 0.378, respectively).

CONCLUSION

Removing a failed AGB using the OS- or TS-RYGB is safe and feasible. The decision between OS- and TS-RYGB is still individual and depends on the patient's general condition, the desired goal of the procedure, and the personal competence of the surgeon. Further studies are needed to clarify long-term outcome and effect of both procedures.

Two-stage streaming keyword detection and localization with multi-scale depthwise temporal convolution

A keyword spotting (KWS) system running on smart devices should accurately detect the appearances and predict the locations of predefined keywords from audio streams, with small footprint and high efficiency. To this end, this paper proposes a new two-stage KWS method which combines a novel multi-scale depthwise temporal convolution (MDTC) feature extractor and a two-stage keyword detection and localization module. The MDTC feature extractor learns multi-scale feature representation efficiently with dilated depthwise temporal convolution, modeling both the temporal context and the speech rate variation. We use a region proposal network (RPN) as the first-stage KWS. At each frame, we design multiple time regions, which all take the current frame as the end position but have different start positions. These time regions (or formally anchors) are used to indicate rough location candidates of keyword. With frame level features from the MDTC feature extractor as inputs, RPN learns to propose keyword region proposals based on the designed anchors. To alleviate the keyword/non-keyword class imbalance problem, we specifically introduce a hard example mining algorithm to select effective negative anchors in RPN training. The keyword region proposals from the first-stage RPN contain keyword location information which is subsequently used to explicitly extract keyword related sequential features to train the second-stage KWS. The second-stage system learns to classify and transform region proposal to keyword IDs and ground-truth keyword region respectively. Experiments on the Google Speech Command dataset show that the proposed MDTC feature extractor surpasses several competitive feature extractors with a new state-of-the-art command classification error rate of 1.74%. With the MDTC feature extractor, we further conduct wake-up word (WuW) detection and localization experiments on a commercial WuW dataset. Compared to a strong baseline, our proposed two-stage method achieves relatively 27-32% better false rejection rate at one false alarm per hour, while for keyword localization, the two-stage approach achieves more than 0.95 mean intersection-over-union ratio, which is clearly better than the one-stage RPN method.

Transforming waste activated sludge into medium chain fatty acids in continuous two-stage anaerobic fermentation: Demonstration at different pH levels

Bioenergy recovery in the form of medium-chain fatty acids (MCFAs) from waste activated sludge (WAS) is increasingly attractive, which are valuable building blocks for fuel production. This study experimentally demonstrated the long-term MCFAs (C6-C8) production from WAS in two-stage anaerobic sludge fermentation at different pH conditions, using continuously operated bench-scale anaerobic reactors. The WAS was continuously converted to short chain fatty acids (SCFAs, 3500-3800 mg chemical oxygen demand (COD)/L) at the first stage via alkaline anaerobic fermentation, which was directly fed into the second stage as both substrates and inoculum for MCFAs production through chain elongation (CE). The productions of MCFAs at the second stage were continuously studied under three different pH conditions (i.e., 10, 7 and 5.5). The results demonstrated that there was no significant MCFAs production at pH 10 during the steady state, whereas the MCFAs productions were clearly observed at both pH 7 and pH 5.5, with much higher MCFAs production from WAS at pH 7 (i.e., 10.32 g COD/L MCFAs) than that at pH 5.5 (i.e., 8.73 g COD/L MCFAs) during the steady state. A higher MCFAs selectivity of 62.3% was also achieved at pH 7. The relatively lower MCFAs production and selectivity at pH 5.5 was likely due to the higher undissociated MCFAs generated at pH 5.5, which would pose toxicity impact on CE microbes and thus inhibit the CE process. Microbial community analysis confirmed that the relative abundances of CE related microbes (e.g., Clostridium sensu stricto 12 sp. and Clostridium sensu stricto 1) increased at pH 7 compared to those at pH 5.5, which enabled more efficient MCFAs production from WAS.

Simple Scalable Protein Expression and Extraction Using Two-stage Autoinducible Cell Autolysis and DNA/RNA Autohydrolysis in Escherichia coli

Recombinant protein expression is extensively used in biological research. Despite this, current protein expression and extraction methods are not readily scalable or amenable for high-throughput applications. Optimization of protein expression conditions using traditional methods, reliant on growth-associated induction, is non-trivial. Similarly, protein extraction methods are predominantly restricted to chemical methods, and mechanical methods reliant on expensive specialized equipment more tuned for large-scale applications. In this article, we outline detailed protocols for the use of an engineered autolysis/autohydrolysis E. coli strain, in two-stage fermentations in shake-flasks. This two-stage fermentation protocol does not require optimization of expression conditions and results in high protein titers. Cell lysis in an engineered strain is tightly controlled and only triggered post-culture by addition of a 0.1% detergent solution. Upon cell lysis, a nuclease digests contaminating host oligonucleotides, which facilitates sample handling. This method has been validated for use at different scales, from microtiter plates to instrumented bioreactors. Graphic abstract: Two-stage protein expression, cell autolysis and DNA/RNA autohydrolysis. Reprinted with permission from Menacho-Melgar et al. (2020a). Copyright 2020 John Wiley and Sons.

Latissimus dorsi muscle flap transfer through endoscopic approach combined with the implant after tissue expansion for breast reconstruction of mastectomy patients

BACKGROUND

Implant-based breast reconstruction is easy to be performed but has flaws that an unnatural appearance might be presented when no sufficient coverage existing. While autologous tissue reconstruction also has disadvantages like donor site scar and skin patch effect. There is a demand for a new method to obtain natural and aesthetic appearance while surmounting drawbacks of conventional breast reconstruction surgery.

METHODS

A retrospective review of thirty-one patients undergoing tissue expander (TE)/implant two-stage breast reconstruction with latissimus dorsi muscle flap (LDMF) transfer through endoscopic approach in Peking University Third Hospital from April 2016 to August 2020 was performed. The LDMF harvest time, drain time, and complications were reviewed. The 3D volume was obtained to assess the volume symmetry of bilateral breasts. The BREAST-Q reconstruction module was used to evaluate the satisfaction.

RESULTS

The mean endoscopic LDMF harvest time was 90.4 min. In the mean follow-up of 11.2 months, there were no severe capsular contracture happened. The reconstructed side achieved good volume symmetry to the contralateral side (P = 0.256). Based on the evaluation of the BREAST-Q scores, the outcome of Satisfaction with Breasts was excellent or good in 87.1% of the cases.

CONCLUSIONS

The novel type of two-stage breast reconstruction protocol, which includes tissue expansion followed by implant insertion with endoscopy-assisted LDMF transfer, could effectively reduce visible scars, avoid the patch effect, while require short time for LDMF harvest and present low incidence of complications. It is a promising method for breast reconstruction because it achieves good outcomes in the mastectomy patients.

Two-stage arthroplasty for septic arthritis of the hip and knee: A systematic review on infection control and clinical functional outcomes

INTRODUCTION

Septic arthritis of the native hip and knee joint poses particular challenges to orthopedic surgeons. Patients often suffer from several comorbidities, and it could be challenging to find a balance between infection control and adequate function. Two-stage arthroplasty has been addressed as a reliable solution, however the literature on the topic is composed of case series with small sample size. This systematic review aimed to analyze data on infection control and clinical functional outcomes of patients who underwent two-stage arthroplasty for septic arthritis of the hip and knee.

METHODS

An electronic search of studies published from January 1st, 2000, to June 1st, 2021, was conducted using eight different databases. Following the Cochrane Handbook of Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Revies and Meta-analysis two authors reviewed the available literature and reference lists to identify papers eligible for inclusion.

RESULTS

A total of 21 studies were included, involving 435 procedures. The mean age was 57.3 ± 6.2 (45.8-71.8) years. The mean follow-up was 53.7 ± 18.6 (12-86.7) months. The mean infection eradication was 93.3 ± 6.4%. Mean Harris Hip Score improved from 32.1 ± 10.6 (11.5-42.9) to 87.5 ± 5.7 (80.6-97.8). Mean Knee Society Score improved from 42.9 ± 7.6 (35.9-58.0) to 86.1 ± 5.4 (80.1-96.0).

CONCLUSIONS

Two-stage arthroplasty for hip and knee septic arthritis provided high infection control rate and excellent function. Further high-quality studies should be oriented on providing a validated algorithm for diagnosis and treatment of this condition.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and IV studies.

coli

We report that two-stage dynamic control improves bioprocess robustness as a result of the dynamic deregulation of central metabolism. Dynamic control is implemented during stationary phase using combinations of CRISPR interference and controlled proteolysis to reduce levels of central metabolic enzymes. Reducing the levels of key enzymes alters metabolite pools resulting in deregulation of the metabolic network. Deregulated networks are less sensitive to environmental conditions improving process robustness. Process robustness in turn leads to predictable scalability, minimizing the need for traditional process optimization. We validate process robustness and scalability of strains and bioprocesses synthesizing the important industrial chemicals alanine, citramalate and xylitol. Predictive high throughput approaches that translate to larger scales are critical for metabolic engineering programs to truly take advantage of the rapidly increasing throughput and decreasing costs of synthetic biology.

Individual Patient Data Meta-Analysis and Network Meta-Analysis

Meta-analyses are often conducted using trial-level summary data. However, when individual patient data (IPD ) is available, there is greater flexibility in the analysis and a wider range of statistical models that can be fitted. There are two approaches to fitting IPD models. The traditional two-stage approach involves analyzing each trial individually in the first stage and then combining trial estimates of treatment effectiveness in the second stage using methods developed for aggregate data meta-analysis. Growing in popularity is the one-stage approach in which trials are analyzed and synthesized within one statistical model whilst the clustering of patients within trials is accounted for. This chapter outlines both fixed effect and random effects one- and two-stage meta-analysis models for continuous, binary, and time-to-event outcomes. The meta-analysis framework is then extended to the scenario where there are more than two treatments and network meta-analysis models are described.The availability of IPD provides greater statistical power for investigating interactions between treatments and covariates. Treatment-covariate interactions contain both within- and across-trial information where the across-trial information may be subject to ecological bias. This chapter presents network meta-analysis models separating out the within- and across-trial information and finishes by considering practical solutions for dealing with missing covariate data, assessing the consistency assumption, combining IPD and aggregate data and specific considerations for time-to-event outcomes.

Biological methanation of injected hydrogen in a two-stage anaerobic digestion process

In the field of biological hydrogen methanation, ideal process parameters are underexplored for continuous two-stage systems with anaerobic filters. The present study aims at filling this gap for continuous in-situ reactors while applying different hydrogen injection rates. The results of the study demonstrate an almost complete acid degradation on the output side of the anaerobic filter fed by hydrolysate from maize silage and silage effluent. Most of the oxidizable substances were transferred to methane, but hydrogen could not be completely converted. With fully stoichiometric hydrogen addition, a methane production rate of 0.88 ± 0.06 m³d^-1 per m³ reactor volume was reached. With half stoichiometric hydrogen addition, a hydrogen conversion rate of 75.53 ± 3.77% was obtained. The present approach proved to be a promising contribution to power-to-gas technology, as a considerable amount of hydrogen had to be converted into methane while carbon dioxide was fixed.

Accounting for variation in the required sample size in the design of group-sequential trials

INTRODUCTION

Most literature on optimal group-sequential designs focuses on minimising the expected sample size. We highlight other factors for consideration.

METHODS

We discuss several quantities less-often considered in adaptive design: the median and standard deviation of the random required sample size, and the probability of committing an interim error. We consider how the optimal timing of interim analyses changes when these quantities are accounted for.

RESULTS

Incorporating the standard deviation of the required sample size into an optimality framework, we demonstrate how and when this quantity means using a group-sequential approach is not optimal. The optimal timing of an interim analysis is shown to be highly dependent on the pre-specified preference for minimising the expected sample size relative to its standard deviation.

CONCLUSIONS

Examining multiple factors, which measure the advantages and disadvantages of group-sequential designs, helps determine the best design for a specific trial.

Convergence analysis of sample average approximation for a class of stochastic nonlinear complementarity problems: from two-stage to multistage

In this paper, we consider the sample average approximation (SAA) approach for a class of stochastic nonlinear complementarity problems (SNCPs) and study the corresponding convergence properties. We first investigate the convergence of the SAA counterparts of two-stage SNCPs when the first-stage problem is continuously differentiable and the second-stage problem is locally Lipschitz continuous. After that, we extend the convergence results to a class of multistage SNCPs whose decision variable of each stage is influenced only by the decision variables of adjacent stages. Finally, some preliminary numerical tests are presented to illustrate the convergence results.

Two-stage transcrestal sinus floor elevation-insight into replantation: Six case reports

BACKGROUND

Transcrestal sinus floor elevation (TSFE) has been widely used in the oral clinic when the residual bone height (RBH) exceeds 5 mm. However, when there is insufficient RBH in the posterior maxilla, two-stage TSFE may be an option.

CASE SUMMARY

This article introduces the concept of two-stage TSFE. Six patients had osseointegration failure after TSFE. For the first-stage surgery, we restricted the vertical bone augmentation as much as possible. At the second-stage surgery, the increased RBH was 3.28 ± 1.55 mm, which was beneficial for surgery. Five implants functioned successfully on schedule, but one implant failed again during the healing period. A third surgery was performed, and the implant functioned successfully.

CONCLUSION

When RBH was less than 5 mm, two or more procedures of TSFE might result in a higher RBH.

MANet: A two-stage deep learning method for classification of COVID-19 from Chest X-ray images

The early detection of infection is significant for the fight against the ongoing COVID-19 pandemic. Chest X-ray (CXR) imaging is an efficient screening technique via which lung infections can be detected. This paper aims to distinguish COVID-19 positive cases from the other four classes, including normal, tuberculosis (TB), bacterial pneumonia (BP), and viral pneumonia (VP), using CXR images. The existing COVID-19 classification researches have achieved some successes with deep learning techniques while sometimes lacking interpretability and generalization ability. Hence, we propose a two-stage classification method MANet to address these issues in computer-aided COVID-19 diagnosis. Particularly, a segmentation model predicts the masks for all CXR images to extract their lung regions at the first stage. A followed classification CNN at the second stage then classifies the segmented CXR images into five classes based only on the preserved lung regions. In this segment-based classification task, we propose the mask attention mechanism (MA) which uses the predicted masks at the first stage as spatial attention maps to adjust the features of the CNN at the second stage. The MA spatial attention maps for features calculate the percentage of masked pixels in their receptive fields, suppressing the feature values based on the overlapping rates between their receptive fields and the segmented lung regions. In evaluation, we segment out the lung regions of all CXR images through a UNet with ResNet backbone, and then perform classification on the segmented CXR images using four classic CNNs with or without MA, including ResNet34, ResNet50, VGG16, and Inceptionv3. The experimental results illustrate that the classification models with MA have higher classification accuracy, more stable training process, and better interpretability and generalization ability than those without MA. Among the evaluated classification models, ResNet50 with MA achieves the highest average test accuracy of 96.32% in three runs, and the highest one is 97.06%. Meanwhile, the attention heat maps visualized by Grad-CAM indicate that models with MA make more reliable predictions based on the pathological patterns in lung regions. This further presents the potential of MANet to provide clinicians with diagnosis assistance.

Laparoscopic Sleeve Gastrectomy Following Failed Laparoscopic Adjustable Gastric Banding-a Comparison Between One- and two-Stage Procedures, an Israeli National Database Study

PURPOSE

The optimal revisional bariatric surgery procedure following a previous failed gastric band surgery is yet to be determined. The aim of our study was to compare single- and two-stage laparoscopic sleeve gastrectomy (LSG) following laparoscopic adjustable gastric banding (LAGB) in terms of short- and mid-term outcomes.

MATERIALS AND METHODS

Patients who underwent LSG after a failed LAGB in Israel during 2014-2017 were included. Data were obtained from the Israeli National Bariatric Surgery Registry. Data analyzed included comorbidities, postoperative complications, and anthropometric outcomes.

RESULTS

Of 595 patients included in the data analysis, 381 (64%) underwent one-stage and 214 (36%) had two-stage LSG. No differences were observed between the groups in complication rates (5.0 vs. 5.1%, p=0.93). Percent of total weight loss was lower following one-stage than two-stage procedure at both 6 months (19.3±9.3 vs. 21.5±8.1%; p=0.02) and 1 year postoperative (24.9±10.4 vs. 27.8±9.9%; p=0.02). No difference was observed in the percent excess weight loss (51 vs. 56%; p=0.34 and 66 vs. 72%; p=0.38, at 6 months and 12 months postoperative, respectively). In a regression analysis, percent excess weight loss was greater in the two-stage procedure (p=0.02), with no difference in the complication rates (p=0.98).

CONCLUSION

Single-step LSG had a similar safety profile as two-stage LSG following a failed LAGB. Better weight loss was seen following two-stage LSG. Further prospective studies should investigate long-term follow-up after one- and two-stage procedure.

Natural and human environment interactively drive spread pattern of COVID-19: A city-level modeling study in China

A novel Coronavirus COVID-19 has caused high morbidity and mortality in China and worldwide. A few studies have explored the impact of climate change or human activity on the disease incidence in China or a city. The integrated study concerning environment impact on the emerging disease is rarely reported. Therefore, based on the two-stage modeling study, we investigate the effect of both natural and human environment on COVID-19 incidence at a city level. Besides, the interactive effect of different factors on COVID-19 incidence is analyzed using Geodetector; the impact of effective factors and interaction terms on COVID-19 is simulated with Geographically Weighted Regression (GWR) models. The results find that mean temperature (MeanT), destination proportion in population flow from Wuhan (WH), migration scale (MS), and WH*MeanT, are generally promoting for COVID-19 incidence before Wuhan's shutdown (T1); the WH and MeanT play a determinant role in the disease spread in T1. The effect of environment on COVID-19 incidence after Wuhan's shutdown (T2) includes more factors (including mean DEM, relative humidity, precipitation (Pre), travel intensity within a city (TC), and their interactive terms) than T1, and their effect shows distinct spatial heterogeneity. Interestingly, the dividing line of positive-negative effect of MeanT and Pre on COVID-19 incidence is 8.5°C and 1 mm, respectively. In T2, WH has weak impact, but the MS has the strongest effect. The COVID-19 incidence in T2 without quarantine is also modeled using the developed GWR model, and the modeled incidence shows an obvious increase for 75.6% cities compared with reported incidence in T2 especially for some mega cities. This evidences national quarantine and traffic control take determinant role in controlling the disease spread. The study indicates that both natural environment and human factors integratedly affect the spread pattern of COVID-19 in China.

One-stage versus two-stage revision of the infected knee arthroplasty - a randomized multicenter clinical trial study protocol

Background

A two-stage prosthesis exchange procedure has been the gold standard in surgical treatment of the chronically infected knee arthroplasty so far. This includes 2 surgeries/hospitalizations and an interim period of 2–3 months between surgeries with impaired health, functional status and quality of life of the patients. A one-stage exchange procedure holds many obvious advantages compared to the two-stage approach, but outcomes of a one-stage versus two-stage procedures have never been investigated in a randomized clinical trial. The purpose of this study is primarily to investigate time-adjusted differences in functional status of patients after one-stage versus two-stage revision. Secondary, to report time-adjusted differences in quality of life, complications (including re-revisions due to infection) and mortality.

Methods

This study is a pragmatic, multi-center, randomized, non-inferiority trial comparing one-stage versus two-stage revision of the infected knee arthroplasty. Seven Danish hospitals are currently participating in the study, but additional hospitals can enter the study if adhering to protocol. Ninety-six patients will be included prospectively. Follow-up will be with PROM-questionnaires and clinical controls up to 10 years. The patients who are not able to participate in the randomized trial are followed in a parallel cohort study.

PROM’s

Oxford Knee Score and EQ5D + EQ5D VAS questionnaires are completed preoperatively and sent out to the study participants at 6 weeks, 3, 6, 9, 12, 18 and 24 months as well as 5 and 10 years postoperatively. In addition a tailor made cost questionnaire on the non-treating hospital resource use, community health and social service use, travel costs, time off work and informal care are sent out.

Discussion

If one of the two treatment alternatives is found superior in both domains of quality of life (both knee-specific and generic) and health economics, that treatment should be promoted. Other outcomes will open informed discussions about treatment strategies for periprosthetic knee infections.

Trial registration

The randomized trial is registered on ClinicalTrials.gov with ID NCT03435679, initial release date January 31, 2018 and the cohort study is registered with ID NCT04427943, submitted January 8, 2020 and posted June 11, 2020.

Two-stage

This study investigated the anaerobic bioconversion efficiency of rice straw in continuously stirred tank reactor (CSTR) applying longer hydraulic retention time (HRT) and higher load. Two HRT distributions and two loads were studied and compared for one-stage and two-stage CSTR systems. The results indicated that the two system with longer HRT (60d) and higher load (160g TS·L^-1) obtained 11.06% and 14.28%, 15.24% and 19.38%, more biogas and methane productions than those of one-stage system with HRT (50d) and load (140g TS·L^-1), respectively, while maintained stable operation at higher loads. It was also found that the microbial richness, diversity, and bacterial and archaeal community compositions showed some differences between two systems with different HRTs and loads, which was thought to be one of reasons leading to the differences in bioconversion efficiencies. The study indicated that two-stage system applying longer HRT and higher load could be one of the effective methods for more bioenergy recovery from rice straw.

Inclusion of non-inferiority analysis in superiority-based clinical trials with single-arm, two-stage Simon's design

INTRODUCTION

Non-inferiority (NI) analysis is not usually considered in the early phases of clinical development. In some negative phase II trials, a post-hoc NI analysis justified additional phase III trials that were successful. However, the risk of false positive achievements was not controlled in these early phase analyses. We propose to preplan NI analyses in superiority-based Simon's two-stage designs to control type I and II error rates.

METHODS

Simulations have been proposed to assess the control of type I and II errors rates with this method. A total of 12,768 two-stage Simon's design trials were constructed based on different assumptions of rejection response probability, desired response probability, type I and II errors, and NI margins. P-value and type II error were calculated with stochastic ordering using Uniformly Minimum Variance Unbiased Estimator. Type I and II errors were simulated using the Monte Carlo method. The agreement between calculated and simulated values was analyzed with Bland-Altman plots.

RESULTS

We observed the same level of agreement between calculated and simulated type I and II errors from both two-stage Simon's superiority designs and designs in which NI analysis was allowed. Different examples has been proposed to explain the utility of this method.

CONCLUSION

Inclusion of NI analysis in superiority-based single-arm clinical trials may be useful for weighing additional factors such as safety, pharmacokinetics, pharmacodynamic, and biomarker data while assessing early efficacy. Implementation of this strategy can be achieved through simple adaptations to existing designs for one-arm phase II clinical trials.

Prospective evaluation of the effect of early nasal layer closure on definitive repair in cleft palate patients

Introduction

The cleft palate is one of the most common congenital anomalies treated by plastic surgeons. The cleft width increases the tension of repair and necessitates excessive dissection that might affect maxillary growth. Decreasing the width of cleft minimize tension, dissection and may limit the impact on maxillary growth.

Objectives

The purpose of the study was to evaluate the effect of nasal layer closure of the hard palate at the time of cleft lip repair in patients with complete cleft lip and palate, to demonstrate the efficacy of narrowing the gap and to reduce the incidence of fistulae or other complications.

Methods

Thirty patients less than 1 year of age were included in this prospective observational study. A superiorly based vomer flap was used to repair the nasal layer of the cleft hard palate at the time of primary cleft lip repair. 12–14 weeks after the vomer flap, the cleft soft and hard palate was definitively repaired. Alveolar and palatal gaps were recorded during the 1st and 2nd operations to demonstrate the reduction of the gap defect.

Results

The mean reduction of the alveolar cleft width in patients who had a vomer flap in the first stage was 4.067 mm and the mean reduction of the palatal gap was 4.517 mm. Only 3 patients developed small fistula on the repaired nasal layer that was discovered and corrected during definitive palatoplasty.

Conclusion

Nasal layer closure is a simple surgical technique that can be used to close the hard palate at the time of cleft lip repair. It is a valuable addition to cleft lip and palate repair that may prevent some cleft palate surgical complications.

Exploring the roles of zero-valent iron in two-stage food waste anaerobic digestion

This research investigated the roles of zero-valent iron (ZVI) in a two-stage food waste digestion process. ZVI was added separately to hydrolytic-acidogenic (HA) and methanogenic (MG) stages to understand its impacts on FW hydrolysis-acidification, methanogenesis and bioenergy recovery efficiency. Results showed that ZVI effectively enhanced the overall performance of digestion as compared with the controls without ZVI. Supplementing with ZVI could facilitate the HA process along with faster hydrogen generation. In addition, ZVI shortened the lag phase of MG stage by 42.43-57.23% and raised the maximum methane production rate and yield by 33.99-38.20% and 11-13%, respectively, compared with the controls. Supplementing ZVI to the HA stage could simultaneously raise the bioenergy recovery efficiency of the HA and MG stages by 71.92% and 96.96%, respectively. Further studies demonstrated that iron corrosion contributed little to hydrogen and methane production. The enrichment of syntrophic bacteria, Pseudomonas, and methanogens, and the enhancement of electron transfer among those microbes was supposed to be the main possible mechanism for the enhancement of methanogenesis with ZVI assisted.

Revisional Gastric Bypass After Failed Adjustable Gastric Banding-One-Stage or Two-Stage Procedure?

BACKGROUND

Revisional laparoscopic Roux-en-Y gastric bypass (R-LRYGB) is the preferred procedure after failed adjustable gastric banding. Little is known about whether a one-stage procedure (one surgery for band removal and R-LRYGB) or a two-stage procedure (first band removal and later R-LRYGB) is superior. Aim of this study is to compare early- and long-term results of both methods at our institution.

METHODS

Retrospective analysis of 165 (m 26/f 139) consecutive patients (98 one-stage, 67 two-stage) with R-LRYGB. Mean follow-up time was 50.1 ± 38.8 months. Indications for one-stage vs. two-stage procedures, operating time, peri- and postoperative complications, morbidity, mortality, and length of stay (LOS) were analyzed. Data are reported as total numbers (%) and mean ± standard deviation.

RESULTS

Mean age at R-LRYGB was 43.9 ± 10.7 vs. 44.3 ± 10.7 years with a BMI of 37.1 ± 6.8 vs. 39.8 ± 7.1 (one-stage vs. two-stage). In the one-stage group, the main indication for revisional surgery was weight regain (57.1%), followed by dilatation of the esophagus or pouch (37.7%) and gastroesophageal reflux disease (GERD) (36.7%), whereas in the two-stage group, it was band erosion (52.2%) and dilatation of the esophagus or pouch (17.9%) and GERD (11.9%). There was no significant difference in operative time (208.5 ± 61.2 vs. 206.3 ± 73.5 min), LOS (8.6 ± 3.4 vs. 9.3 ± 5.7 days) or mortality (0% overall). Major complications (Clavien-Dindo ≥ IIIa) occurred similarly often in both groups: 15.3% vs. 16.9% (one-stage vs. two-stage).

CONCLUSION

Both approaches achieve good results. However, the one-stage R-LRYGB is the preferable procedure because it reduces costs and LOS by doing without an additional surgical procedure.

Unilateral Tissue Expander/Implant Two-Stage Breast Reconstruction with the Assistance of Three-Dimensional Surface Imaging

BACKGROUND

In China, traditional preoperative planning of unilateral breast reconstruction mainly depends on anthropometric measurement and visual assessment. Thus, the lack of objective assessment of breast volume and shape would likely result in suboptimal reconstruction outcomes. Three-dimensional surface imaging (3D-SI), which could provide objective measurement data of the breast, may be a promising solution to this problem.

METHODS

A retrospective review of patients undergoing tissue expander (TE)/implant breast reconstruction without any mammoplasty surgery on the contralateral sides in our hospital from August 2013 to May 2018 was performed. All the patients underwent unilateral mastectomy with immediate or delayed insertion of TE, followed by an exchange of a silicone gel implant without contralateral procedures. 3D images were obtained at the time of preoperation, the routine expansion visit, and post-exchange of implant. The breast volume measured by 3D-SI served as a guide to conduct the surgery management, such as in deciding the total volume of expansion and guiding the final implant size selection. 3D-SI also provided objective data to evaluate the final outcomes of the reconstruction.

RESULTS

Fifty-one patients were included in this study, in which eighteen patients underwent immediate TE insertion and thirty-three patients underwent delayed TE insertion. The ptosis degree of contralateral breasts was assessed as follows: forty-four were normal, and seven showed mild ptosis. The average expansion degree was controlled at 161.6% ± 14.1% compared to the contralateral breasts. The volume of implants exchanged had a strong linear correlation with the 3D volume of the contralateral breasts at the end of expansion (P < 0.01). The mean time of follow-up was 9.1 ± 6.6 months. There was only one patient who experienced TE leakage with secondary infection and received TE exchange. For the immediate reconstruction group, the overall breast symmetry improved at the completion of implant exchange (P < 0.01), with an average asymmetry of 5.3% ± 4.0% compared with 10.6% ± 6.1% initially. For the delayed reconstruction group, the reconstructed side achieved good volume symmetry to the contralateral side (P > 0.05). There was no significant difference in breast basal width between bilateral breasts post-reconstruction (P > 0.05).

CONCLUSION

3D-SI serves as a valuable adjunct by providing accurate 3D volume of breasts within TE/implant breast reconstruction in Chinese patients without obvious breast ptosis, which could facilitate surgeons to achieve good reconstructive outcomes.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

One- and two-stage surgical revision of infected elbow prostheses following total joint replacement: a systematic review

Background

Prosthetic joint infection (PJI) is a challenging complication of total elbow replacement (TER). Potential surgical treatments include one- or two-stage revision; however, the best treatment for elbow PJI is not clearly defined. We conducted a systematic review in accordance with PRISMA guidelines to compare the clinical effectiveness of one- and two-stage revision surgery for elbow PJI using re-infection (recurrent and new infections) rates; mortality; clinical measures of function, pain, and satisfaction; and non-infection related adverse events.

Methods

MEDLINE, Embase, Web of Science, and The Cochrane Library were searched up to June 2019 to identify observational cohort studies and randomised controlled trials (RCTs) that had recruited patients with elbow PJI following TER and treated with one- or two-stage revision. Of 96 retrieved articles, 2 one-stage and 6 two-stage revision studies were eligible. No RCT was identified. Arcsine transformation was used in estimating rates with 95% confidence intervals (CIs).

Results

Staphylococcus aureus was the most common causative organism for PJI of the elbow (24 of 71 elbow PJIs). The re-infection rate (95% CI) for one-stage (7 elbows) ranged from 0.0% (0.0–79.3) to 16.7% (3.0–56.4) and that for two-stage revision (87 elbows) from 0.0% (0.0–49.0) to 20.0% (3.6–62.4). Non-infection related adverse event rate for one-stage (based on a single study) was 16.7% (3.0–56.4) and that for two-stage ranged from 11.8% (4.7–26.6) to 20.0% (3.6–62.4). There were no mortality events recorded following one- or two-stage revision surgery and postoperative clinical measures of function, pain, and satisfaction could not be effectively compared because of limited data.

Conclusions

No strong conclusions can be drawn because of limited data. The one-stage revision may be potentially at least as clinically effective as two-stage revision, but further data is needed. There are clear gaps in the existing literature and studies are urgently warranted to assess the clinical effectiveness of one- and two-stage revision strategies for PJI following TER.

Systematic review registration

PROSPERO 2018: CRD42018118002.

Strategies for validating biomarkers using data from a reference set

Candidate biomarkers discovered in the laboratory need to be rigorously validated before advancing to clinical application. However, it is often expensive and time-consuming to collect the high quality specimens needed for validation; moreover, such specimens are often limited in volume. The Early Detection Research Network has developed valuable specimen reference sets that can be used by multiple labs for biomarker validation. To optimize the chance of successful validation, it is critical to efficiently utilize the limited specimens in these reference sets on promising candidate biomarkers. Towards this end, we propose a novel two-stage validation strategy that partitions the samples in the reference set into two groups for sequential validation. The proposed strategy adopts the group sequential testing method to control for the type I error rate and rotates group membership to maximize the usage of available samples. We develop analytical formulas for performance parameters of this strategy in terms of the expected numbers of biomarkers that can be evaluated and the truly useful biomarkers that can be successfully validated, which can provide valuable guidance for future study design. The performance of our proposed strategy for validating biomarkers with respect to the points on the receiver operating characteristic curve are evaluated via extensive simulation studies and compared with the default strategy of validating each biomarker using all samples in the reference set. Different types of early stopping rules and boundary shapes in the group sequential testing method are considered. Compared with the default strategy, our proposed strategy makes more efficient use of the limited resources in the reference set by allowing more candidate biomarkers to be evaluated, giving a better chance of having truly useful biomarkers successfully validated.

Obesity and smoking predict the results of two-stage exchange in septic revision hip arthroplasty: A cohort study

BACKGROUND

Prosthetic joint infection (PJI) is deemed to be the most serious complication following total hip arthroplasty. Obesity and smoking are known risk factors for PJI. However, the influence of these variables on infection free survival, of septic revision hip arthroplasty, is yet to be explored. The aim of this study was to determine the effect of obesity and smoking on the outcome of two-stage prosthetic exchange surgery.

PATIENTS AND METHODS

A consecutive series of 97 hips in 94 patients (69 male, 25 female, mean age 66±12 years), undergoing two-stage revision surgery for hip PJI, were investigated retrospectively, after a mean follow-up of 60 (24-170) months. Survival was estimated using Kaplan-Meyer curves. A multivariate cox-regression model was applied to test for the influence of smoking or obesity (BMI≥30) after adjusting 16 potential patient-dependant variables.

HYPOTHESIS

The study hypothesis was that smoking and high BMI are predictors for the failure of septic revision hip arthroplasty. Failure of septic revision hip arthroplasty was defined as failure to eradicate the infection or eradication of the infection but failure to preserve the arthroplasty.

RESULTS

Kaplan-Meier showed a cumulative survival proportion of 80.4%(standard error S.E 4%), of the definitive implant, at 5 years. Obese patients (BMI≥30) and smokers had a significantly lower 5-year survival of 60.9% (S.E 1%) and 50.6% (S.E 1.4%), respectively (p=0.001).

DISCUSSION

Obesity and smoking are both factors determining infection free survival in two-stage revision hip arthroplasty. Clinicians should be aware of potential complications and anticipate a higher likelihood of conversion to a Girdlestone resection or even amputation in this group of patients.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Comparable perioperative outcomes, long-term outcomes, and quality of life in a retrospective analysis of ulcerative colitis patients following 2-stage versus 3-stage proctocolectomy with ileal pouch-anal anastomosis

PURPOSE

Many surgeons assume 3-stage ileal pouch-anal anastomosis (IPAA) is safer than 2-stage IPAA in patients with active ulcerative colitis (UC), although recent data suggest outcomes are comparable. This study aimed to compare perioperative complications, late complications, and functional outcomes after 2- versus 3-stage IPAA in patients with active UC.

METHODS

A retrospective review was conducted of patients who underwent 2- or 3-stage IPAA for active UC from 2000 to 2015 in a high-volume institution. Patients completed quality-of-life surveys 6 months following ileostomy reversal. Perioperative and late complications were recorded. Outcomes were compared with the Fisher exact test, and multivariable logistic regression was used to adjust for potential confounders.

RESULTS

We identified 212 patients who underwent 2- or 3-stage IPAA for active UC, of whom 157 patients (74.1%) underwent 2-stage procedures and 55 (25.9%) underwent 3-stage procedures. More patients undergoing 2-stage procedures were taking immunomodulators preoperatively (46.3% vs. 23.1%, p = 0.01), but there was no difference in use of steroids (p = 0.09) or biologic agents (p = 0.85). Three-stage procedures were more likely to be urgent (78.6% vs. 30.2%, p < 0.001). There were no differences in perioperative complications (p = 0.50), anastomotic leak (p = 0.94), pouchitis (p = 0.45), pouch failure (p = 0.46), perceived quality of life (p = 0.68), number of bowel movements per day (p = 0.27), or sexual satisfaction (p = 0.21) between the 2- and 3-stage groups.

CONCLUSIONS

Patients undergoing 2-stage compared to 3-stage IPAA for active ulcerative colitis have comparable outcomes and quality of life following ileostomy reversal. Two-stage IPAA appears to be safe and appropriate, even in high-risk patients.

One- and two-stage surgical revision of peri-prosthetic joint infection of the hip: a pooled individual participant data analysis of 44 cohort studies

One-stage and two-stage revision strategies are the two main options for treating established chronic peri-prosthetic joint infection (PJI) of the hip; however, there is uncertainty regarding which is the best treatment option. We aimed to compare the risk of re-infection between the two revision strategies using pooled individual participant data (IPD). Observational cohort studies with PJI of the hip treated exclusively by one- or two-stage revision and reporting re-infection outcomes were retrieved by searching MEDLINE, EMBASE, Web of Science, The Cochrane Library, and the WHO International Clinical Trials Registry Platform; as well as email contact with investigators. We analysed IPD of 1856 participants with PJI of the hip from 44 cohorts across four continents. The primary outcome was re-infection (recurrence of infection by the same organism(s) and/or re-infection with a new organism(s)). Hazard ratios (HRs) for re-infection were calculated using Cox proportional frailty hazards models. After a median follow-up of 3.7 years, 222 re-infections were recorded. Re-infection rates per 1000 person-years of follow-up were 16.8 (95% CI 13.6-20.7) and 32.3 (95% CI 27.3-38.3) for one-stage and two-stage strategies respectively. The age- and sex-adjusted HR of re-infection for two-stage revision was 1.70 (0.58-5.00) when compared with one-stage revision. The association remained consistently absent after further adjustment for potential confounders. The HRs did not vary importantly in clinically relevant subgroups. Analysis of pooled individual patient data suggest that a one-stage revision strategy may be as effective as a two-stage revision strategy in treating PJI of the hip.

Bio-hythane production from cassava residue by two-stage fermentative process with recirculation

The two-stage hythane fermentation of cassava residue low in protein, rich in iron, and deficient in nickel and cobalt, resulted in failure after long-term operation, showing a radical decrease in methane production along with an increase in volatile fatty acids (VFAs) accumulation in the second stage. Based on the gap between theoretical demand and existing content of nutrients, the effect of their additions on hythane fermentation was validated in the repeated batch experiment and continuous experiment. The proliferation of hydrolysis bacteria, acidogens, and hydrogen producing bacteria and methanogens was guaranteed by sufficient N (0.7g/L), S (30mg/L), Ni (1.0mg/L), and Co (1.0mg/L), and the metabolism of a sustainable hythane fermentation was recovered. In this optimal nutrient combination of above trace elements, the highest hythane yield (426m³ hythane with 27.7% of hydrogen from 1ton of cassava residue) was obtained.

Two-stage anaerobic digestion of sugar beet silage: The effect of the pH-value on process parameters and process efficiency

The study investigated the influence of the target pH-values 4.5, 5, 5.5 and 6 in the acidification reactor on process parameters, such as substrate-specific methane yield and the intermediates, in the two-stage anaerobic digestion of sugar beet silage. The total specific methane yield (Nlkg^-1CODd^-1) increased with an increase in the pH (pH 4.5: 140.58±70.08, pH 5: 181.21±55.71, pH 5.5: 218.32±51.01, pH 6: 256.47±28.78). The pH-value also had an effect on the dominant intermediate in hydrolysate. At the pH-value of 4.5, almost no acidification and microbial activity was observed. At pH 5 and 5.5, butyric acid production dominated, guided by H₂ production. At pH 6 acetic acid was the main product. The absence of H₂ and the highest SMY makes it favorable under practical aspects.

Did the International ALPPS Meeting 2015 Have an Impact on Daily Practice? The Hamburg Barmbek Experience of 58 Cases

Background

ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) was introduced only 10 years ago and has gained wide acceptance as a variation of staged procedures in liver surgery. It has been criticized for its high morbidity and mortality, which all centers reported in their initial series.

Methods

After a world expert meeting in Hamburg in 2015 where all experts in the field met to discuss this method, caveats were extracted and formulated. We researched our complete prospective ALPPS database to see if the recommendations had any impact on outcome.

Results

In total, we performed 58 ALPPS procedures in our center. 33 patients were operated on before, 25 after the meeting. Results in terms of morbidity and mortality were significantly better after the meeting, as were patient selection and strategy.

Conclusion

In our own center's experience, the implementation of the meetings' recommendations and the information gathered through this valuable exchange had a dramatic impact on results. Having performed 58 ALPPS procedures in total, we can now conclude that ALPPS has become much safer in our hands since the 2015 meeting and that morbidity and mortality are no longer the issue to be discussed. Future research must focus on oncologic outcomes in these patients.

Experimental data on load test and performance parameters of a LENZ type vertical axis wind turbine in open environment condition

Performance and load testing data of a three bladed two stage LENZ type vertical axis wind turbine from the experiments conducted in an open environment condition at Hindustan Institute of Technology and Science, Chennai (location 23.2167°N, 72.6833°E) are presented here. Low-wind velocity ranging from 2 to 11 m/s is available everywhere irrespective of climatic seasons and this data provides the support to the researchers using numerical tool to validate and develop an enhanced Lenz type design. Raw data obtained during the measurements are processed and presented in the form so as to compare with other typical outputs. The data is measured at different wind speeds prevalent in the open field condition ranging from 3 m/s to 9 m/s.

Methane production and characteristics of the microbial community in a two-stage fixed-bed anaerobic reactor using molasses

Molasses is a typical feedstock for fermentation, but the effluent is hard to treat. In this study, molasses containing a high concentration of organic matter was treated by a two-stage Fix-bed reactor system with an increased organic loading rate (OLR). The results indicated at high molasses loading rate, the two-stage system was more efficient (i.e. organic matter removal, the COD of effluent and biogas production) than the single-stage system. The relative abundance of Anaerolineaceae and W5_norank was higher in the first stage (R1), where these organisms digest carbohydrates, while the second stage (R2) had higher relative abundance of Synergistaceae and SB-1_norank, which digest VFAs and decomposition-resistant compounds to produce compounds used by hydrogen methanogens. The qPCR analysis demonstrated that the Methanosaetaceae dominated the archaeal community in the first stage (R1), while Methanomicrobiales and Methanobacteriales were predominant in the second stage (R2), where they were involved in hydrogen production.

Influence of pressures up to 50bar on two-stage anaerobic digestion

The concept of pressurized two-stage anaerobic digestion integrates biogas production, purification and pressure boosting within one process. The produced methane-rich biogas can be fed into gas grids with considerably less purification effort. To investigate biogas production under high pressures up to 50bar, a lab scale two-stage anaerobic digestion system was constructed including one continuously operated pressurized methane reactor. This investigation examined the effects of different operating pressures in methane reactor (10, 25, 50bar) on biogas quantity and quality, pH value and process stability. By increasing operating pressures in methane reactor, the pH value decreased from 6.65 at 10bar to 6.55 at 50bar. Simultaneously, methane content increased from 79.08% at 10bar to 90.45% at 50bar. The results show that methane reactors can be operated up to 50bar pressure continuously representing a viable alternative to commonly used gas upgrading methods because of reduced purification effort.

Two-stage CO2-laser-assisted bilateral cordectomy for cT1b glottic carcinoma

PURPOSE

The aim of the present paper was to investigate the oncological safety of two-stage bilateral cordectomy for the treatment of cT1b glottic SCC, and to compare its oncological outcome and synechia development rate with those of single-stage procedures.

MATERIALS AND METHODS

A retrospective cohort study was performed at the Otolaryngology Unit of Vittorio Veneto Laryngeal Cancer Center (Italy). The prognostic significance of clinical, pathological and surgical factors was also investigated, in terms of recurrence rate and disease-free survival, in a univariate statistical setting.

RESULTS

Our results indicate that patients treated with primary two-stage bilateral cordectomy achieved local control in 96% of cases, with 95% disease-specific and 88% overall survival rates, and a 95% organ preservation rate, with anterior synechiae developing in 1 case. Involvement of the deep surgical margins correlated with a worse prognosis. Patients developed anterior synechiae less frequently after two-stage bilateral cordectomy, and experienced no higher recurrence rate or shorter disease-free survival than patients treated with a single-stage procedure.

CONCLUSIONS

Two-stage bilateral cordectomy is a safe and effective procedure. In selected patients it could be considered the primary approach for the treatment of early glottic cT1b carcinomas.