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.

Production of biohythane from food waste via an integrated system of continuously stirred tank and anaerobic fixed bed reactors

The continuous production of biohythane (mixture of biohydrogen and methane) from food waste using an integrated system of a continuously stirred tank reactor (CSTR) and anaerobic fixed bed reactor (AFBR) was carried out in this study. The system performance was evaluated for an operation period of 200days, by stepwise shortening the hydraulic retention time (HRT). An increasing trend of biohydrogen in the CSTR and methane production rate in the AFBR was observed regardless of the HRT shortening. The highest biohydrogen yield in the CSTR and methane yield in the AFBR were 115.2 (±5.3)L H2/kgVSadded and 334.7 (±18.6)L CH4/kgCODadded, respectively. The AFBR presented a stable operation and excellent performance, indicated by the increased methane production rate at each shortened HRT. Besides, recirculation of the AFBR effluent to the CSTR was effective in providing alkalinity, maintaining the pH in optimal ranges (5.0-5.3) for the hydrogen producing bacteria.

Does cemented or cementless single-stage exchange arthroplasty of chronic periprosthetic hip infections provide similar infection rates to a two-stage? A systematic review

Background

The best surgical modality for treating chronic periprosthetic hip infections remains controversial, with a lack of randomised controlled studies. The aim of this systematic review is to compare the infection recurrence rate after a single-stage versus a two-stage exchange arthroplasty, and the rate of cemented versus cementless single-stage exchange arthroplasty for chronic periprosthetic hip infections.

Methods

We searched for eligible studies published up to December 2015. Full text or abstract in English were reviewed. We included studies reporting the infection recurrence rate as the outcome of interest following single- or two-stage exchange arthroplasty, or both, with a minimum follow-up of 12 months. Two reviewers independently abstracted data and appraised quality assessment.

Results

After study selection, 90 observational studies were included. The majority of studies were focused on a two-stage hip exchange arthroplasty (65 %), 18 % on a single-stage exchange, and only a 17 % were comparative studies. There was no statistically significant difference between a single-stage versus a two-stage exchange in terms of recurrence of infection in controlled studies (pooled odds ratio of 1.37 [95 % CI = 0.68-2.74, I² = 45.5 %]).

Similarly, the recurrence infection rate in cementless versus cemented single-stage hip exchanges failed to demonstrate a significant difference, due to the substantial heterogeneity among the studies.

Conclusion

Despite the methodological limitations and the heterogeneity between single cohorts studies, if we considered only the available controlled studies no superiority was demonstrated between a single- and two-stage exchange at a minimum of 12 months follow-up. The overalapping of confidence intervals related to single-stage cementless and cemented hip exchanges, showed no superiority of either technique.

One-stage versus two-stage exchange arthroplasty for infected total knee arthroplasty: a systematic review

PURPOSE

Infection complicating total knee arthroplasty (TKA) has serious implications. Traditionally the debate on whether one- or two-stage exchange arthroplasty is the optimum management of infected TKA has favoured two-stage procedures; however, a paradigm shift in opinion is emerging. This study aimed to establish whether current evidence supports one-stage revision for managing infected TKA based on reinfection rates and functional outcomes post-surgery.

METHODS

MEDLINE/PubMed and CENTRAL databases were reviewed for studies that compared one- and two-stage exchange arthroplasty TKA in more than ten patients with a minimum 2-year follow-up.

RESULTS

From an initial sample of 796, five cohort studies with a total of 231 patients (46 single-stage/185 two-stage; median patient age 66 years, range 61-71 years) met inclusion criteria. Overall, there were no significant differences in risk of reinfection following one- or two-stage exchange arthroplasty (OR -0.06, 95 % confidence interval -0.13, 0.01). Subgroup analysis revealed that in studies published since 2000, one-stage procedures have a significantly lower reinfection rate. One study investigated functional outcomes and reported that one-stage surgery was associated with superior functional outcomes. Scarcity of data, inconsistent study designs, surgical technique and antibiotic regime disparities limit recommendations that can be made.

CONCLUSION

Recent studies suggest one-stage exchange arthroplasty may provide superior outcomes, including lower reinfection rates and superior function, in select patients. Clinically, for some patients, one-stage exchange arthroplasty may represent optimum treatment; however, patient selection criteria and key components of surgical and post-operative anti-microbial management remain to be defined.

LEVEL OF EVIDENCE

III.

Use of a New Knee Prosthesis as an Articulating Spacer in Two-Stage Revision of Infected Total Knee Arthroplasty

Purpose

To report our experience with two-stage revision using a new femoral component (NFC) spacer (Depuy Synthes) as an articulating spacer.

Materials and Methods

In this retrospective study, we reviewed 22 two-stage revisions that were performed using an NFC spacer in 22 patients suspected of having an infected total knee arthroplasty (TKA) from December 2010 to March 2013. The result was considered successful when eradication of infection was achieved using only one NFC spacer.

Results

The average time from primary TKA to the first stage procedure was 29.1 months and the average time from the first stage procedure until the final second stage procedure was 12.7 weeks. The average range of motion increased from 82° preoperatively to 104° postoperatively. The American Knee Society Knee score increased from 29.3 points to 66 points. The Function score increased from 29.5 points to 64 points. Four cases were reinfected after two-stage revision. The mean follow-up was 37.6 months.

Conclusions

The new articulating spacer showed promising short-term results both with regard to eradication of infection and functional improvement.

Two-stage total hip arthroplasty for patients with advanced active tuberculosis of the hip

Background

Treatment of advanced active tuberculosis (TB) of the hip is confronted with great challenges. Although one-stage total hip arthroplasty (THA) is considered as a safe procedure for most patients by some authors, there are still exceptions. The purpose of this paper was to investigate the feasibility and effectiveness of two-stage THA for selected patients with advanced active TB of the hip.

Methods

Nine consecutive patients with advanced active tuberculous arthritis of the hip were reviewed in this study. Out of these nine patients, the hips of five were destroyed extensively with difficulties of thorough debridement at one operation, and the hips of the other four were detected of sinus tracts. Nine patients received the two-stage total hip arthroplasty (THA) protocol and the perioperative antituberculous medication between January 2008 and December 2013. During the first stage, a debridement was carried out after at least 2 weeks of antituberculous chemotherapy to remove abscesses and infected and necrotic tissues as thoroughly as possible, followed by antituberculous chemotherapy for a minimum of 3 months (average 4.2 months). During the second stage, hip prosthesis was implanted if the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) were normal and the wound was well healed. Antituberculous chemotherapy was continued for 6–9 months postoperatively to constitute a total duration of a minimum of 12 months after the first operation. The patients were then evaluated based on the reactivation of infection, the Harris hip score system, X-ray, ESR, and CRP.

Results

The average follow-up was 40 months (range, 18–72 months). No reactivation of TB or superimposed infection was observed in all patients. The ESR and CRP returned to the normal level with no liver injury. The average Harris hip score was increased from 35 (range, 15–55) preoperatively to 91.5 (range, 83–97) at the final follow-up. The X-ray film showed no prosthesis shift or loosening.

Conclusions

Two-stage THA is an alternative treatment option for patients with advanced active tuberculosis of the hip under some difficult conditions. The hip with sinus tracts or destroyed extensively with difficulties of thorough debridement at one operation may be regarded as indications.

Is the continuous two-stage anaerobic digestion process well suited for all substrates?

Two-stage anaerobic digestion systems are often considered to be advantageous compared to one-stage processes. Although process conditions and fermenter setups are well examined, overall substrate degradation in these systems is controversially discussed. Therefore, the aim of this study was to investigate how substrates with different fibre and sugar contents (hay/straw, maize silage, sugar beet) influence the degradation rate and methane production. Intermediates and gas compositions, as well as methane yields and VS-degradation degrees were recorded. The sugar beet substrate lead to a higher pH-value drop 5.67 in the acidification reactor, which resulted in a six time higher hydrogen production in comparison to the hay/straw substrate (pH-value drop 5.34). As the achieved yields in the two-stage system showed a difference of 70.6% for the hay/straw substrate, and only 7.8% for the sugar beet substrate. Therefore two-stage systems seem to be only recommendable for digesting sugar rich substrates.

A comparison between one-stage and two-stage procedures for the creation of brachiobasilic arteriovenous fistulas

INTRODUCTION

Vascular access is essential to end-stage renal failure patients requiring haemodialysis. Many patients require multiple fistula formation attempts in order to gain good access, making secondary and tertiary fistula options vital. Brachiobasilic fistulas are well established, but there is little evidence to compare the different surgical techniques in creating them. This study aimed to determine the patency and complication rates associated with these procedures.

METHODS

Retrospective data was collected by reviewing case notes to determine fistula survival time and surgical setting. Patency, complications and required interventions were recorded for each group at three time intervals. The Kaplan-Meier method was used to calculate survival for each cohort.

RESULTS

37 brachiobasilic arteriovenous fistulas were created in 35 patients. 17 fistulas were one-stage procedures; 20 fistulas were made in two stages. Survival proportions were measured as 70.6%, 58.8% and 51.5% for the one-stage procedure and 95%, 90% and 78% for the two-stage procedure at 1 month, 1 year and 2 years respectively with p = 0.0385.

DISCUSSION

Native brachiobasilic fistulas have advantages over prosthetic grafts. There are technical aspects which make the two-staged procedure preferable, including being more amenable to a day case surgery setting. Despite this, there is a lack of relative outcome differences in the literature, thus necessitating further work.

CONCLUSION

Our data suggests creation of brachiobasilic fistulas using a two-staged procedure may result in improved patency rates. Complication rates were found to be statistically equivocal, with fistuloplasties and embolectomy shown to be effective in fistula salvage.

Utilising biohydrogen to increase methane production, energy yields and process efficiency via two stage anaerobic digestion of grass

Real time measurement of gas production and composition were used to examine the benefits of two stage anaerobic digestion (AD) over a single stage AD, using pelletized grass as a feedstock. Controlled, parallel digestion experiments were performed in order to directly compare a two stage digestion system producing hydrogen and methane, with a single stage system producing just methane. The results indicated that as well as producing additional energy in the form of hydrogen, two stage digestion also resulted in significant increases to methane production, overall energy yields, and digester stability (as indicated by bicarbonate alkalinity and volatile fatty acid removal). Two stage AD resulted in an increase in energy yields from 10.36 MJ kg(-1) VS to 11.74 MJ kg(-1) VS, an increase of 13.4%. Using a two stage system also permitted a much shorter hydraulic retention time of 12 days whilst maintaining process stability.

Influence of different substrates on the performance of a two-stage high pressure anaerobic digestion system

The two-stage autogenerative high-pressure digestion technique is a novel and promising approach for the production of gaseous fuels or upgraded biogas. This new technique is described in the patent DE 10 2011 015415 A1 and integrates biogas production, its upgrading and pressure boosting in one process. Anaerobic digestion under elevated pressure conditions leads to decreasing pH-values in the digestate due to the augmented formation of carboxylic acid. Model calculations carried out to evaluate the two-stage design showed that the pH-value in the pressurized anaerobic filter has a major influence on the methane content of the biogas produced. Within this study, the influence of the nitrogen content as one of the most important buffering substances on the performance of the system has been tested. The results show that higher NH4 contents lead to higher pH-values in the digester and as a consequence to higher methane contents.

Two-stage arthroplasty using functional temporary prosthesis to treat infected arthroplasty and septic arthritis of the hip

AIMS

This study introduced a modified technique in two-stage revision arthroplasty to insert functional spacer using modular components coated with antibiotic-impregnated polymethylmethacrylate.

METHODS

Since June 2006, we used the construct in twenty-three consecutive patients (17 with infected arthroplasty, and 6 with septic arthritis of the hip).

RESULTS

Mean follow-up was 48 months (range 30-84 months). Two patients were excluded (no second stage), two patients had persistent infection, 19 patients received successful re-implantation at the second-stage.

CONCLUSION

The technique provides a construct that can be used safely and successfully as a functional, spacer in two-stage revision arthroplasty.

Two-stage revision using a modified articulating spacer in infected total knee arthroplasty

PURPOSE

To evaluate clinical results of two-stage revision using a modified articulating spacer for treatment of infected total knee arthroplasty (TKA).

MATERIALS AND METHODS

We retrospectively reviewed 20 cases treated by two-stage revision arthroplasty using a modified articulating spacer under the diagnosis of infected TKA from January 2006 to December 2011. The mean follow-up period was 22.3 months. The first operation consisted of debridement after removal of the prosthesis, reinsertion of the femoral component after autoclaving, and implantation of antibiotic-loaded cement with a new polyethylene in the proximal tibia.

RESULTS

The mean period between the primary TKA and the first stage operation was 39 months and between the first stage operation and the revision arthroplasty was 3.3 months. The average range of motion (ROM) increased from 69.8° preoperatively to 102.8° postoperatively (p<0.001). The mean Knee Society knee score increased from 33.8 points to 85.3 points (p<0.001). The mean Knee Society function score increased from 35 points to 87.5 points (p<0.001). The mean Hospital for Special Surgery score increased from 57.6 points preoperatively to 82.6 points postoperatively (p<0.001). Two cases (10%) were re-infected after the revision arthroplasty.

CONCLUSIONS

Two-stage revision arthroplasty using an articulating cement spacer can be an effective therapy not only for the treatment of an infected TKA but also for recovery of knee ROM and function.