Recurrent Dislocation After Total Hip Arthroplasty: Controversies and Solutions.

Instability remains one of the most common complications after total hip arthroplasty and a notable cause of patient morbidity as well as patient and surgeon dissatisfaction. Isolated dislocations can often be managed successfully with closed reduction; however, recurrent instability poses a substantial diagnostic and therapeutic challenge. The causes are varied and may be related to patient, surgical, and implant factors. A thorough evaluation is important in determining the cause of instability and effectively managing this difficult problem. Management options include component revision for malposition, modular exchange, or revision to specialized components, such as larger femoral heads, constrained liners, or dual-mobility articulations.

Constrained Acetabular Liners.

BACKGROUND: Dislocation remains one of the most common complications after total hip arthroplasty. Constrained acetabular liners were developed to address the problem of recurrent instability. They have been in clinical use since the mid 1980s and function by capturing the femoral head. METHOD: The aim of this review is to highlight the mechanism of action, development, and advances in constrained liner design, together with an emphasis on the modes of failure and the authors' opinion on the current indications for the use of these implants. RESULTS: A systematic review of the literature summarizes the current body of published evidence on the results of constrained liners. Overall, at best level III evidence is available. In the 38 studies included, this study considered a total of 2852 constrained liners with a mean follow-up 4.3 years (range 0.8-20 years), which had a mean dislocation and/or constrained failure rate of 11.4% (95% confidence interval 10.3-12.6). CONCLUSION: Constrained acetabular liners remain an important option in the armamentarium of the revision hip surgeon. At this point in time with current designs and published results, they should remain a salvage device. The implantation of a constrained liner should be considered when all other factors related to the total hip arthroplasty have been optimized, especially component malposition.

Impaction Grafting Made Easy.

BACKGROUND: Impaction bone grafting is an established reconstruction technique to address bone loss in revision total hip arthroplasty. Intuitively, it would seem to be a very attractive method as "missing bone is replaced with bone." The potential restoration of bone stock is of particular value in the younger patient who may be facing future revision procedures. METHODS AND RESULTS: Although undoubtedly some units have published good results with this method, more recent long-term data have revealed some of the limitations of this reconstruction technique. The aim of this review is to highlight these most recent data on impaction bone grafting and provide the author's opinion on the current role for this technique, as well as reviewing some technical considerations. CONCLUSION: Impaction bone grafting remains an important technique in the armamentarium of the revision hip surgeon. More recent long-term data have allowed refinement of the indications and on the acetabular side, and it should be used with caution in association with severe bone defects.

Can a reconstruction algorithm in major acetabular bone loss be successful in revision hip arthroplasty?

Aims: The aims of this study were to determine the success of a reconstruction algorithm used in major acetabular bone loss, and to further define the indications for custom-made implants in major acetabular bone loss. Methods: We reviewed a consecutive series of Paprosky type III acetabular defects treated according to a reconstruction algorithm. IIIA defects were planned to use a superior augment and hemispherical acetabular component. IIIB defects were planned to receive either a hemispherical acetabular component plus augments, a cup-cage reconstruction, or a custom-made implant. We used national digital health records and registry reports to identify any reoperation or re-revision procedure and Oxford Hip Score (OHS) for patient-reported outcomes. Implant survival was determined via Kaplan-Meier analysis. Results: A total of 105 procedures were carried out in 100 patients (five bilateral) with a mean age of 73 years (42 to 94). In the IIIA defects treated, 72.0% (36 of 50) required a porous metal augment; the remaining 14 patients were treated with a hemispherical acetabular component alone. In the IIIB defects, 63.6% (35 of 55) underwent reconstruction as planned with 20 patients who actually required a hemispherical acetabular component alone. At mean follow-up of 7.6 years, survival was 94.3% (95% confidence interval 97.4 to 88.1) for all-cause revision and the overall dislocation rate was 3.8% (4 of 105). There was no difference observed in survival between type IIIA and type IIIB defects and whether a hemispherical implant alone was used for the reconstruction or not. The mean gain in OHS was 16 points. Custom-made implants were only used in six cases, in patients with either a mega-defect in which the anteroposterior diameter > 80 mm, complex pelvic discontinuity, and massive bone loss in a small pelvis. Conclusion: Our findings suggest that a reconstruction algorithm can provide a successful approach to reconstruction in major acetabular bone loss. The use of custom implants has been defined in this series and accounts for < 5% of cases.

How modular porous metal augments have changed the management of acetabular bone loss at primary or revision total hip arthroplasty.

The advent of modular porous metal augments has ushered in a new form of treatment for acetabular bone loss. The function of an augment can be seen as reducing the size of a defect or reconstituting the anterosuperior/posteroinferior columns and/or allowing supplementary fixation. Depending on the function of the augment, the surgeon can decide on the sequence of introduction of the hemispherical shell, before or after the augment. Augments should always, however, be used with cement to form a unit with the acetabular component. Given their versatility, augments also allow the use of a hemispherical shell in a position that restores the centre of rotation and biomechanics of the hip. Progressive shedding or the appearance of metal debris is a particular finding with augments and, with other radiological signs of failure, should be recognized on serial radiographs. Mid- to long-term outcomes in studies reporting the use of augments with hemispherical shells in revision total hip arthroplasty have shown rates of survival of > 90%. However, a higher risk of failure has been reported when augments have been used for patients with chronic pelvic discontinuity.

Outcomes of novel 3D-printed fully porous titanium cup and a cemented highly cross-linked polyethylene liner in complex and revision total hip arthroplasty.

INTRODUCTION: A novel fully porous acetabular titanium shell has been designed to reduce stiffness mismatch between bone and implant and promote osseointegration in complex (cTHA) and revision total hip arthroplasty (rTHA). A highly cross-linked polyethylene (XLPE) liner is cemented within the cup to reduce wear rates and increase survivorship. This study reported the outcomes of an XLPE liner cemented into a novel 3D-printed fully porous cup in cTHA and rTHA. METHODS: Presented was a multicenter retrospective review of 40 patients (6 cTHA and 34 rTHA) who underwent THA with a fully porous titanium acetabular cup and cemented XLPE liner. Data were collected on demographics, surgical information, outcomes, including osseointegration and migration and implant survivorship. RESULTS: On average, patients were 71.42 ± 9.97 years old and obese (BMI: 30.36 ± 6.88 kg/m2) and were followed up for a mean time of 2.21 ± 0.77 years. Six patients underwent cTHA and 34 patients underwent rTHA. The mean hospital length of stay was 5.34 ± 3.34 days. Three (7.5%) 90-day readmissions were noted. Harris Hip Scores improved, on average, from 53.87 ± 12.58 preoperatively to 83.53 ± 12.15 postoperatively (P<0.001). One case of acetabular shell aspetic loosening with migration was noted. Thirty-nine of the 40 acetabular components were fully osseointegrated without migration. Two patients underwent re-revision surgery for PJI and one patient received acetabular shell+liner re-revision due to aseptic loosening. Kaplan-Meier analysis showed an all-cause revision-free survival rate of 95.0% at 6 months and 1 year, and 92.0% at 4-years. Aseptic acetabular cup, liner dislocation/loosening, and fracture-free survival was 100% at 6 months and 1-year, and 97.1% at 2 years. CONCLUSION: The combined use of a novel 3D-printed fully porous titanium acetabular shell and cemented XLPE acetabular liner yielded excellent rates of osseointegration, and all-cause and acetabular aseptic loosening survivorship at a minimum 1-year follow-up. Further long-term studies are needed to assess the longevity of this construct.

Foam-in-Vein: Characterisation of Blood Displacement Efficacy of Liquid Sclerosing Foams.

Sclerotherapy is among the least invasive and most commonly utilised treatment options for varicose veins. Nonetheless, it does not cure varicosities permanently and recurrence rates are of up to 64%. Although sclerosing foams have been extensively characterised with respect to their bench-top properties, such as bubble size distribution and half-life, little is known about their flow behaviour within the venous environment during treatment. Additionally, current methods of foam characterisation do not recapitulate the end-point administration conditions, hindering optimisation of therapeutic efficacy. Here, a therapeutically relevant apparatus has been used to obtain a clinically relevant rheological model of sclerosing foams. This model was then correlated with a therapeutically applicable parameter-i.e., the capability of foams to displace blood within a vein. A pipe viscometry apparatus was employed to obtain a rheological model of 1% polidocanol foams across shear rates of 6 s-1 to 400 s-1. Two different foam formulation techniques (double syringe system and Tessari) and three liquid-to-gas ratios (1:3, 1:4 and 1:5) were investigated. A power-law model was employed on the rheological data to obtain the apparent viscosity of foams. In a separate experiment, a finite volume of foam was injected into a PTFE tube to displace a blood surrogate solution (0.2% w/v carboxymethyl cellulose). The displaced blood surrogate was collected, weighed, and correlated with foam's apparent viscosity. Results showed a decreasing displacement efficacy with foam dryness and injection flowrate. Furthermore, an asymptotic model was formulated that may be used to predict the extent of blood displacement for a given foam formulation and volume. The developed model could guide clinicians in their selection of a foam formulation that exhibits the greatest blood displacement efficacy.

Minimum 2-Year Outcomes of a Novel 3D-printed Fully Porous Titanium Acetabular Shell in Revision Total Hip Arthroplasty.

Background: Fully porous acetabular shells are an appealing choice for patients with extensive acetabular defects undergoing revision total hip arthroplasty (rTHA). This study reports on the early outcomes of a novel 3-D printed fully porous titanium acetabular shell in revision acetabular reconstruction. Methods: A multicenter retrospective study of patients who received a fully porous titanium acetabular shell for rTHA with a minimum of 2 years of follow-up was conducted. The primary outcome was rate of acetabular revision. Results: The final study cohort comprised 68 patients with a mean age of 67.6 years (standard deviation 10.4) and body mass index of 29.5 kg/m2 (standard deviation 5.9). Ninety-four percent had a preoperative Paprosky defect grade of 2A or higher. The average follow-up duration was 3.0 years (range 2.0-5.1). Revision-free survivorship at 2 years was 81% for all causes, 88% for acetabular revisions, and 90% for acetabular revision for aseptic acetabular shell failure. Eight shells were explanted within 2 years (12%): 3 for failure of osseointegration/aseptic loosening (4%) after 15, 17, and 20 months; 3 for infection (4%) after 1, 3, and 6 months; and 2 for instability (3%). At the latest postoperative follow-up, all unrevised shells showed radiographic signs of osseointegration, and none had migrated. Conclusions: This novel 3-D printed fully porous titanium shell in rTHA demonstrated good survivorship and osseointegration when used in complex acetabular reconstruction at a minimum of 2 years. Level of evidence: IV, case series.

Foam-in-vein: A review of rheological properties and characterization methods for optimization of sclerosing foams.

Varicose veins are chronic venous defects that affect >20% of the population in developed countries. Among potential treatments, sclerotherapy is one of the most commonly used. It involves endovenous injection of a surfactant solution (or foam) in varicose veins, inducing damage to the endothelial layer and subsequent vessel sclerosis. Treatments have proven to be effective in the short-term, however recurrence is reported at rates of up to 64% 5-year post-treatment. Thus, once diagnosed with varicosities there is a high probability of a permanently reduced quality of life. Recently, foam sclerotherapy has become increasingly popular over its liquid counterpart, since foams can treat larger and longer varicosities more effectively, they can be imaged using ultrasound, and require lower amounts of sclerosing agent. In order to minimize recurrence rates however, an investigation of current treatment methods should lead to more effective and long-lasting effects. The literature is populated with studies aimed at characterizing the fundamental physics of aqueous foams; nevertheless, there is a significant need for appropriate product development platforms. Despite successfully capturing the microstructural evolution of aqueous foams, the complexity of current models renders them inadequate for pharmaceutical development. This review article will focus on the physics of foams and the attempts at optimizing them for sclerotherapy. This takes the form of a discussion of the most recent numerical and experimental models, as well as an overview of clinically relevant parameters. This holistic approach could contribute to better foam characterization methods that patients may eventually derive long term benefit from.

Long-stem revision prosthesis for salvage of failed fixation of extracapsular proximal femoral fractures.

A retrospective review was made of radiographs and case notes of patients with failed fixation of extracapsular proximal femoral fractures subsequently managed with long-stem revision arthroplasty. Follow-up radiographs, objective scoring, mobility, and complications were assessed. Twenty five hips were managed with long-stem hip arthroplasty in 24 patients with a mean age of 73 years. The mean follow-up was 24 months. Patients received uncemented acetabular components and long-stem uncemented femoral implants. Complications included two intraoperative femoral fractures which were strut-grafted, three wound infections (one required washout), and one recurrent dislocation managed conservatively. Average postoperative Oxford Hip score was 29. We report a low complication rate and no specific implant related problems, with good functional outcome as evidenced by the outcome scores and mobility status following salvage arthroplasty.

In vitro and ex vivo evaluation of the biological performance of sclerosing foams.

Since the first reports on foam sclerotherapy, multiple studies have been conducted to determine the physical properties and behavior of foams, but relatively little is known about their biological effects on the endothelial cells lining the vessel wall. Moreover, a systematic comparison of the biological performance of foams produced with different methods has not been carried out yet. Herein, a 2D in vitro method was developed to compare efficacy of commercially available polidocanol injectable foam (PEM, Varithena) and physician-compounded foams (PCFs). Endothelial cell attachment upon treatment with foam was quantified as an indicator of therapeutic efficacy, and was correlated with foam physical characteristics and administration conditions. An ex vivo method was also developed to establish the disruption and permeabilisation of the endothelium caused by sclerosing agents. It relied on the quantitation of extravasated bovine serum albumin conjugated to Evans Blue, as an indicator of endothelial permeability. In our series of comparisons, PEM presented a greater overall efficacy compared to PCFs, across the different biological models, which was attributed to its drainage dynamics and gas formulation. This is consistent with earlier studies that indicated superior physical cohesiveness of PEM compared to PCFs.

Physical Vein Models to Quantify the Flow Performance of Sclerosing Foams.

Foam sclerotherapy is clinically employed to treat varicose veins. It involves intravenous injection of foamed surfactant agents causing endothelial wall damage and vessel shrinkage, leading to subsequent neovascularization. Foam production methods used clinically include manual techniques, such as the Double Syringe System (DSS) and Tessari (TSS) methods. Pre-clinical in-vitro studies are conducted to characterize the performance of sclerosing agents; however, the experimental models used often do not replicate physiologically relevant physical and biological conditions. In this study, physical vein models (PVMs) were developed and employed for the first time to characterize the flow behavior of sclerosing foams. PVMs were fabricated in polydimethylsiloxane (PDMS) by replica molding, and were designed to mimic qualitative geometrical characteristics of veins. Foam behavior was investigated as a function of different physical variables, namely (i) geometry of the vein model (i.e., physiological vs. varicose vein), (ii) foam production technique, and (iii) flow rate of a blood surrogate. The experimental set-up consisted of a PVM positioned on an inclined platform, a syringe pump to control the flow rate of a blood substitute, and a pressure transducer. The static pressure of the blood surrogate at the PVM inlet was measured upon foam administration. The recorded pressure-time curves were analyzed to quantify metrics of foam behavior, with a particular focus on foam expansion and degradation dynamics. Results showed that DSS and TSS foams had similar expansion rate in the physiological PVM, whilst DSS foam had lower expansion rate in the varicose PVM compared to TSS foam. The degradation rate of DSS foam was lower than TSS foam, in both model architectures. Moreover, the background flow rate had a significant effect on foam behavior, enhancing foam displacement rate in both types of PVM.

The prevention and treatment of dislocation following total hip arthroplasty: efforts to date and future strategies.

Dislocation continues as one of the common complications following primary Total Hip Arthroplasty (THA). Considering revision THA, dislocation is also one of the leading causes of failure and the subsequent need for re-revision surgery. This article aims to highlight the efforts to date that surgeons have utilised together with the implants employed to both prevent and treat THA dislocation. A fundamental principal in the management of THA instability is identification of the risk factors for dislocation and these are considered in 5 subgroups; patient factors, surgeon factors, implant design, implant orientation and soft tissue factors. Risk stratification is proposed as a future method of deciding upon best treatment for those patients most at danger of THA dislocation and subsequent continued instability.

Osteoclastogenesis-related cytokines and peri-prosthetic osteolysis in revision metal-on-metal total hip replacements.

PURPOSE: Peri-prosthetic osteolysis is a major cause for revision hip arthroplasty; various cytokines including those in the osteoclastogenesis pathway have been identified as potentially key in the osteolysis process. Adverse reactions to metal debris in metal-on-metal total hip replacements have led to an increase in revision procedures. This study examines the levels of osteoclastogenesis-related cytokines in serum and synovial fluid samples obtained from patients at the time of revision metal-on-metal total hip replacement and compares between patients with and without radiographic evidence of peri-prosthetic osteolysis. METHODS: Sandwich ELISA techniques were used to detect IL-6, IL-18, M-CSF, sRANKL and OPG in the samples. Results were analysed with linear regression, Fisher's tests and t-tests; p<0.05 considered significant. Samples from 36 patients (18 with osteolysis, 18 without osteolysis) were analysed. RESULTS: There was wide variation in the detectable levels of cytokines. No significant differences were found between patients with and without osteolysis in mean synovial fluid levels of IL-6 (p = 0.863), IL-18 (p = 0.324), M-CSF (p = 0.508), sRANKL (p = 0.884), OPG (p = 0.776) or mean serum levels of OPG (p = 0.993) or sRANKL (p = 0.565) (insufficient detection of IL-6, IL-18 or M-CSF in serum samples). A correlation was found between synovial fluid levels of IL-6 and OPG in patients without osteolysis (r2 = 0.618, p<0.001) but not with osteolysis (r2 = 0.0004). CONCLUSIONS: These results indicate that the process of peri-prosthetic osteolysis is complex and multifactorial; there may also be an influence of metallosis. Further research is needed to increase understanding of peri-prosthetic osteolysis and influence clinical practice.

Synthesis and characterisation of cationically modified phospholipid polymers.

Phospholipid-like copolymers based on 2-(methacryloyloxyethyl) phosphorylcholine were synthesised using monomer-starved free radical polymerisation methods and incorporating cationic charge in the form of the choline methacrylate monomer in amounts varying from 0 to 30 wt%, together with a 5 wt% silyl cross-linking agent in order to render them water-insoluble once thermally cured. Characterisation using a variety of techniques including nuclear magnetic resonance spectroscopy, high-pressure liquid chromatography and gel permeation chromatography showed the cationic monomer did not interfere with the polymerisation and that the desired amount of charge had been incorporated. Gravimetric and differential scanning calorimetry methods were used to evaluate the water contents of polymer membranes cured at 70 degrees C, which was seen to increase with increasing cation content, producing materials with water contents ranging from 50% to 98%. Surface plasmon resonance indicated that the coatings swelled rapidly in water, the rate and extent of swelling increasing with increasing cation level. Dynamic contact angle showed that coatings of all the polymers possessed a hydrophobic surface when dry in air, characteristic of the alkyl chains expressed at the surface (>100 degrees advancing angle). Rearrangement of the hydrophilic groups to the surface occurred once wet, to produce highly wettable surfaces with a decrease in advancing angle with increasing cation content. Atomic force microscopy showed all polymer films to be smooth with no features in topographical or phase imaging. Mechanical properties of the dry films were also unaffected by the increase in cation content.

High failure rate of the R3 metal-on-metal total hip arthroplasty.

We report our failures with the use of the R3 metal-on-metal bearing. Forty six patients had an R3 acetabular system metal-on-metal THR in our centre between March 2007 and March 2009. All operations were performed using femoral components and appropriately matched femoral heads manufactured by Smith and Nephew. Twelve patients underwent revision surgery for adverse reaction to metal debris (ARMD). The median acetabular inclination was 40 degrees (range 21.1-49.1) and the median acetabular anteversion was 7.5 degrees (range 3.3-10.4). The median serum Cobalt was 9.9 µg/L (range 3.1-45) and the median serum Chromium was 5.8 µg/L (range 1.8-19.3). The time to revision was 39.2 months (range 13-53). Our current failure rate is 24%.

Identification of cardiac dysfunction in sepsis with B-type natriuretic peptide.

BACKGROUND: B-type natriuretic peptide (BNP) is secreted in response to myocardial stretch and has been used clinically to assess volume overload and predict death in congestive heart failure. More recently, BNP elevation has been demonstrated with septic shock and is predictive of death. How BNP levels relate to cardiac function in sepsis remains to be established. STUDY DESIGN: Retrospective review of prospectively gathered sepsis database from a surgical ICU in a tertiary academic hospital. Initial BNP levels, patient demographics, baseline central venous pressure levels, and in-hospital mortality were obtained. Transthoracic echocardiography was performed during initial resuscitation per protocol. RESULTS: During 24 months ending in September 2009, two hundred and thirty-one patients (59 ± 3 years of age, 43% male) were treated for sepsis. Baseline BNP increased with initial sepsis severity (ie, sepsis vs severe sepsis vs septic shock, by ANOVA; p < 0.05) and was higher in those who died vs those who lived (by Fisher's exact test; p < 0.05). Of these patients, 153 (66%) had early echocardiography. Low ejection fraction (<50%) was associated with higher BNP (by Fisher's exact test; p < 0.05) and patients with low ejection fraction had a higher mortality (39% vs 20%; odds ratio = 3.03). We found no correlation between baseline central venous pressure (12.7 ± 6.10 mmHg) and BNP (526.5 ± 82.10 pg/mL) (by Spearman's ρ, R(s) = .001) for the entire sepsis population. CONCLUSIONS: In surgical sepsis patients, BNP increases with sepsis severity and is associated with early systolic dysfunction, which in turn is associated with death. Monitoring BNP in early sepsis to identify occult systolic dysfunction might prompt earlier use of inotropic agents.

Application of cryoprobe 1H nuclear magnetic resonance spectroscopy and multivariate analysis for the verification of corsican honey.

Proton nuclear magnetic resonance spectroscopy ((1)H NMR) and multivariate analysis techniques have been used to classify honey into two groups by geographical origin. Honey from Corsica (Miel de Corse) was used as an example of a protected designation of origin product. Mathematical models were constructed to determine the feasibility of distinguishing between honey from Corsica and that from other geographical locations in Europe, using (1)H NMR spectroscopy. Honey from 10 different regions within five countries was analyzed. (1)H NMR spectra were used as input variables for projection to latent structures (PLS) followed by linear discriminant analysis (LDA) and genetic programming (GP). Models were generated using three methods, PLS-LDA, two-stage GP, and a combination of PLS and GP (PLS-GP). The PLS-GP model used variables selected by PLS for subsequent GP calculations. All models were generated using Venetian blind cross-validation. Overall classification rates for the discrimination of Corsican and non-Corsican honey of 75.8, 94.5, and 96.2% were determined using PLS-LDA, two-stage GP, and PLS-GP, respectively. The variables utilized by PLS-GP were related to their (1)H NMR chemical shifts, and this led to the identification of trigonelline in honey for the first time.

The development of cryoprobe nuclear magnetic resonance spectroscopy for the rapid detection of organic contaminants in potable water.

The detection of trace levels of a range of organic contaminants (including pesticides, toxins and an explosive) in potable water, using cryoprobe NMR spectroscopy with limited sample preparation and rapid acquisition times, is described. Emphasis is placed on the applicability of NMR spectroscopy for use in emergency scenarios as the unbiased nature of the technique facilitates the detection and characterization of unknown compounds at levels as low as 50 microg L(-1).