An Analytical Solution for Stress Transfer between a Broken Prestressing Wire and Mortar Coating in PCCP

A prestressed concrete cylinder pipe (PCCP) consists of a concrete core, a steel cylinder, prestressing wires, and a mortar coating. Most PCCP failures are related to the breakage of prestressing wires. It is thus expected that the load-bearing capacity of PCCP is significantly affected by the length of the prestress loss zone and the stress distribution in the broken wire. Based on a tri-linear bond-slip model, the length of prestress loss zone and the stress transfer mechanism between a broken wire and a mortar coating are analysed in this paper. During the breaking (unloading) process of a prestressing wire, the interfacial bondline exhibits the following three stages: elastic stage, elastic-softening stage, and elastic-softening-debonding stage. The closed-form solutions for the interfacial slip, the interfacial shear stress, and the axial stress in the broken wire are derived for each stage. The solutions are verified by the finite element predictions. A parametric study is presented to investigate the effects of the size of the prestressing wires, the prestressing level, the interfacial shear strength, and the residual interfacial shear strength on the interfacial stress transfer. For an example PCCP with an inner diameter of 4 m, the length of prestress loss zone increases from 500 mm to 3300 mm as the radius of prestressing wire increases from 1 mm to 7 mm. It increases from 2700 mm to 7700 mm when the interfacial shear strength reduces from 3.94 MPa to 0.62 MPa and reduces from 13,200 mm to 7300 mm as the residual interfacial shear stress factor increases from 0.1 to 0.9.

Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

Here we present an enantioselective aminalization of aldehydes catalyzed by Brønsted acids based on pentacarboxycyclopentadienes (PCCPs). The cyclization reaction using readily available anthranilamides as building blocks provides access to valuable 2,3-dihydroquinazolinones containing one stereogenic carbon center with good enantioselectivity (ee up to 80%) and excellent yields (up to 97%).

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

An enantioselective aza-Piancatelli rearrangement has been developed using a chiral Brønsted acid based on pentacarboxycyclopentadiene (PCCP). This reaction provides rapid access to valuable chiral 4-amino-2-cyclopentenone building blocks from readily available starting material and is operationally simple.

A Scalable, One-Pot Synthesis of 1,2,3,4,5-Pentacarbomethoxycyclopentadiene

1,2,3,4,5-Pentacarbomethoxycyclopentadiene (PCCP) is a strong organic acid and a precursor to useful organocatalysts, including chiral Brønsted acids and silicon-based Lewis acids. The synthetic route to PCCP, first reported in 1942, is inconvenient for a number of reasons. The two-step synthesis requires the purification of intermediates from intractable side-products, high reaction temperatures, and extensive labor (3 days). We have developed an improved procedure that delivers PCCP efficiently in 24 hours in one pot at ambient temperature and without isolation.

Comparative outcome of PFNA, Gamma nails, PCCP, Medoff plate, LISS and dynamic hip screws for fixation in elderly trochanteric fractures: a systematic review and network meta-analysis of randomized controlled trials

The ideal implant for the treatment of an unstable intertrochanteric femoral fracture is still a matter of discussion. The aim of this systematic review is to conduct a network meta-analysis of randomized controlled trials (RCTs) comparing clinical outcomes between dynamic hip screws (DHS), Medoff sliding plating, percutaneous compression plating (PCCP), proximal femoral nails (PFN), Gamma nails and less invasive stabilization system fixation in femoral trochanteric fractures in the elderly. These clinical outcomes consist of total intra-operative time, intra-operative fluoroscopy time, intra-operative blood loss, blood component transfusion, length of hospital stay, postoperative general complications, wound complications, late complications and reoperation rates. This systematic review was conducted using PubMed and Scopus search engines for RCTs comparing clinical outcomes between treatments from inception to February 22, 2015. Thirty-six of 785 studies identified were eligible. Compared to the other implants, PCCP showed the lowest total operative time and units of blood transfusion with an unstandardized mean difference (UMD) of 29.27 min (95% CI 5.24, 53.50) and 0.89 units (95% CI 0.52, 1.25). The lowest incidence of general complications, wound complications and late complications of PCCP was 0.09 (95% CI 0.04, 0.18), 0.01 (95% CI 0.01, 0.04) and 0.05 (95% CI 0.02, 0.11), respectively, when compared to others. The lowest fluoroscopic time was with DHS with an UMD of 0.24 min (95% CI 0.16, 0.32), whereas the lowest blood loss and shortest hospital stay were with PFN with an UMD of 233.61 ml of blood loss (95% CI 153.17, 314.04) and 7.23 days of hospital stay (95% CI 7.15, 7.31) when compared to all other fixation methods. Reoperation rates of all implants had no statistically significant difference. The network meta-analysis suggested that fixation with PCCP significantly shortens operative time and decreases the units of blood transfusion required, while also lowering risks of general complications, wound complications and late complications when compared to fixation. Use of PFN showed the least intra-operative blood loss and shortest hospital stay. Multiple active treatment comparisons indicate that PCCP fixation in trochanteric fractures in the elderly is the treatment of choice in terms of intra-operative outcomes and postoperative complications.

A meta-analysis of percutenous compression plate versus intramedullary nail for treatment of intertrochanteric HIP fractures

INTRODUCTION

Intertrochanteric hip fracture is associated with increased morbidity. Currently, a dramatic change in practice was demonstrated, with the intramedullary fixation rate increasing, despite a lack of evidence in the literature supporting the change. As a minimally invasive technique, percutaneous compression plating (PCCP) has been advocated to reduce blood loss, relieve pain, and lead to faster rehabilitation for treatment of intertrochanteric hip fractures. The purpose of this meta-analysis was to estimate the outcomes and complications of the PCCP versus intramedullary nail (IMN) fixation for intertrochanteric fractures.

METHODS

A comprehensive search of related literature was conducted to identify all articles in Medline, Embase, Scopus, Research Gate, and the Cochrane Central Register of Controlled Trials published on or between January 1998 and January 2016. All studies that compared PCCP with IMN in treating adult patients with intertrochanteric fractures were included. Main outcomes about the two fixation method were collected and analysised using the Review Manager 5.1 provided by The Cochrane Collaboration.

RESULTS

Six trials involving 908 fractures met the inclusion criteria. Compared with IMN, PCCP had similar operation time, intraoperative blood loss, mortality, system complications, function score, function recovery, and reoperation rate (P > 0.05). But hospital stay, transfusion need, and incidence of implant-related complications significantly favored the PCCP (P < 0.05).

CONCLUSIONS

The PCCP was associated with less transfusion need, reduced hospital stay, and fewer incidence of implant-related complications compared with IMN. Although a change in practice was occurred, the patients treated with IMN seemed to face the potential for more complications. Owing to the limitations of this systematic review, more high-quality randomized controlled trials (RCTs) are still needed to confirm this conclusion.