Ballistic gelatin calibration standardisation.

INTRODUCTION: A review of ballistic gelatin calibration standards has highlighted that data used from studies with different calibrations methods may not be able to be compared. Calibration of ballistic gelatin did not occur until the mid-1980s when Fackler recognised the deficiencies of uncalibrated gelatin. He determined that the calibration standard should be 85±5 mm of ball bearing penetration for a 180 m/s impact velocity. This study looks to improve on and optimise current ballistic gelatin calibration standards METHODS: Nine 0.177 cal (4.5 mm) spheres were fired using a Daisy Powerline air rifle at velocities between 134 m/s and 224 m/s at 25 gelatin blocks (n=225). Velocities were measured using an Oehler Model 36 Chronograph with three Model 57 screens. Depth of penetration (DoP) was measured from the entry surface to the back end of the sphere via a Mitutoyo Absolute vernier calliper. RESULTS: The R-squared regression model showed that all batches had a close fit to the regression line. Using the R-squared regression model, the equation y=0.584x - 20.02 (where x is the velocity) returned a DoP of 84.918 mm for a 180 m/s impact and therefore needed minimal adjustment to align with Fackler's 85 mm DoP. The equation can be adjusted to y=0.584x - 20.12 to return a DoP of 85 mm for 180 m/s. CONCLUSIONS: We propose that the calibration standard of ballistic gelatin with 4.5 mm spheres is DoP=0.584x - 20.12 where DoP is the depth of penetration (mm) and x is the impact velocity (m/s), The measured DoP should be within 5% of the calculated DoP.

Viability of Bos taurus scapulae as a flat bone proxy for ballistic testing.

BACKGROUND: Handguns and rifles are often involved in violent deaths such as homicide and suicide. Consequently, forensic investigations are important to clarify the nature of ballistic trauma. METHODS: This study investigated the differences in entrance and exit wound morphology with Bos taurus (bovine) scapulae that have two cortical layers surrounding a central cancellous bone section which are comparable with human flat bones, with a series of experiments using six different calibres (0.22 Long Rifle, 9×19 mm North Atlantic Treaty Organization, 0.40 Smith & Wesson, 0.45 Automatic Colt Pistol, 5.56×45 mm and 7.62×51 mm). B. taurus (bovine) scapulae were used for closed range 30 cm simulated executions. RESULTS: The ballistic experiments presented similarities in entrance wound morphology and exit wound bevelling with that of recognised forensic cases. As muzzle velocity increased, bevelling increased. Circumferential delamination is clearly visible with full metal jacket rounds, yielding similar bone damage morphology as human crania. CONCLUSION: Bovine scapulae seem appropriate for ballistic simulations of flat bone injuries on the macroscopic level, if the correct portion of the scapulae is deployed. More research is needed to further substantiate these interpretations.

Microscopic and macroscopic comparisons of 0.223 soft point and full metal jacket ammunition with bos taurus scapulae as a proxy to human flat bones.

BACKGROUND: The prevalence of civilian 0.223 ammunition is widespread. Due to low costs and the same dimensions as a 5.56×45 mm North Atlantic Treaty Organization, this round is exceptionally popular. However, recent mass shootings have employed soft point (SP) expanding ammunition to cause grievous wounds compared with military full metal jacket (FMJ) rounds that do not rapidly expand on impact. METHODS: The aim of this given study is to compare FMJ and SP rounds to determine if there are diagnostic differences between the bullet types in the wounds inflicted to flat bones. Bos taurus scapulae were used for 25 m simulated cranial gunshot injuries. Scanning electron microscopy was employed to assess the difference in wound morphology and elemental analysis between SP and FMJ rounds. RESULTS: Entrance and exit wound morphology change significantly between the two different types of ammunition as seen with circumferential delamination which is indicative of FMJ rounds and is not seen with the softer SP hunting rounds. Lead staining of the entrance wound is visible on only the SP rounds. CONCLUSION: Gunshot flat bone wound morphology is distinctively different between SP and FMJ rounds. Circumferential delamination is only seen with FMJ due to the hardness of the round. Lead staining is only seen with SP rounds due to bullet composition.

Hydrodynamic control of titania nanotube formation on Ti-6Al-4V alloys enhances osteogenic differentiation of human mesenchymal stromal cells.

In order to obtain bioactive bone-implant interfaces with enhanced osteogenic capacity, various approaches have been developed to modify surface physicochemical properties of bio-inert titanium and titanium alloys. One promising strategy involves fabricating highly ordered nanotubes (NT) on implant surfaces via electrochemical anodization. However, few studies have applied this technique to Ti-6Al-4V alloys most commonly adopted for the fabrication of osteo-integrated surfaces on orthopedic implants. In this study, we investigated the influence of electrolyte hydrodynamics to NT fabrication on Ti-6Al-4V in ethylene glycol based electrolyte and evaluated the osteogenic differentiation capacity of human mesenchymal stromal cells (hMSCs) on different diameter NT surfaces. Computational Fluid Dynamics (CFD) analysis was used to simulate electrolyte flow profiles under various stirring conditions (e.g. stirrer bar location and flow direction) and their correlation to NT formation. Polished Ti-6Al-4V disks (240 grit) were anodized at 20 and 40 V under optimal electrolyte flow conditions for comparison of NT diameter-controlled osteogenic differentiation and mineralization potential of hMSCs over 21 days culture in osteogenic media. Ti-6Al-4V surfaces anodized with 20 and 40 V resulted with NTs diameter approx. 39 and 83 nm, respectively. Electrolyte hydrodynamics (flow profile) significantly influenced the uniformity of NT formation. Here, a uniform velocity and shear stress profile at the surface promoted homogeneous NT growth, whereas large variation in either flow velocity or shear stress to the surface impaired mature NT formation. After 21 days of culture, fluorescence staining demonstrated significantly greater osteocalcin and osteopontin expression, and increased mineralized deposits (xylenol orange staining) on fluctuating NT surfaces anodized under 20 V (Ø 39 nm) relative to flat NT layer anodized with 40 V (Ø 83 nm) and polished controls. This study provides a systematic investigation of NT formation with respect to the electrolyte hydrodynamic effects to NT growth on Ti-6Al-4V alloys, demonstrating the feasibility of a one-step anodization process for generating uniform NT under optimal hydrodynamics. Optimized wavy micro-/nano-topography with Ø 39 nm NT stimulated osteogenic differentiation capacity of hMSCs on Ti-6Al-4V alloys and confirmed the potential application of anodization to improve osteo-integrative surfaces in orthopedic implants.

The Value of Routine Intravenous Tranexamic Acid in Total Hip Arthroplasty: A Preliminary Study.

OBJECTIVE: To determine the effect on the need for transfusion when intravenous tranexamic acid (TXA) is administered intraoperatively in patients undergoing total hip arthroplasty (THA). METHOD: A prospective, double blinded, randomised control trial of 88 patients undergoing THA was randomly allocated to receive 1 g of intravenous TXA or normal saline on induction of anaesthesia. All patients received spinal anaesthesia. The primary outcome measure was transfusion rate, and the secondary outcomes were intraoperative blood loss, haemoglobin levels, length of hospital stay, functional scores, and thromboembolic complications. RESULTS: 19.0% of patients given TXA required a blood transfusion, compared with 20.5% given placebo (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (. CONCLUSIONS: 1 g IV TXA administered on induction did not significantly reduce the need for blood transfusion, postoperative blood loss, functional scores, or the length of stay in patients undergoing THA. This trial is registered with ACTRN12610001065088.

Prognostic impact of baseline tumour immune infiltrate on disease-free survival in patients with completely resected, BRAFv600 mutation-positive melanoma receiving adjuvant vemurafenib.

BACKGROUND: We conducted a retrospective exploratory analysis to evaluate the effects of baseline tumour immune infiltrate on disease-free survival (DFS) outcomes in patients with fully resected stage IIC-IIIC melanoma receiving adjuvant vemurafenib monotherapy or placebo in the BRIM8 study. PATIENTS AND METHODS: BRIM8 was a phase III, international, double-blind, randomised, placebo-controlled study. Eligible patients with BRAFV600 mutation-positive, completely resected melanoma were randomly assigned to oral vemurafenib (960 mg twice daily) or matching placebo for 52 weeks. The primary end point was DFS. The association of CD8+ T-cell infiltration and programmed death ligand 1 (PD-L1) expression with DFS, as measured by immunohistochemistry, was explored retrospectively. RESULTS: Four hundred ninety-eight patients were randomly assigned to receive adjuvant vemurafenib (n = 250) or placebo (n = 248); tumour samples were available for biomarker analysis for approximately 60% of patients. In the pooled biomarker population, placebo-treated patients with <1% CD8+ T cells in the tumour centre had shorter median DFS than those with ≥1% CD8+ T cells (7.7 versus 47.8 months). DFS benefit from vemurafenib versus placebo was greater in patients with <1% CD8+ T cells [hazard ratio (HR) 0.56; 95% confidence interval (CI) 0.34-0.92) than in patients with ≥1% CD8+ T cells (HR 0.77; 95% CI 0.48-1.22). Likewise, median DFS was shorter among placebo-treated patients with <5% versus ≥5% PD-L1+ immune cells (IC) in the tumour (7.2 versus 47.8 months). A greater DFS benefit with vemurafenib versus placebo was observed in patients with <5% PD-L1+IC (HR 0.36; 95% CI 0.24-0.56) than in patients with ≥5% PD-L1+IC (HR 0.99; 95% CI 0.58-1.69). CONCLUSIONS: The presence of CD8+ T cells and PD-L1+IC are favourable prognostic factors for DFS. Treatment with adjuvant vemurafenib may overcome the poor DFS prognosis associated with low CD8+ T-cell count or PD-L1 expression. CLINICALTRIALS. GOV IDENTIFIER: NCT01667419.

Intact vitreous humor as a potential extracellular matrix hydrogel for cartilage tissue engineering applications.

Decellularisation of tissues, utilising their biochemical cues, poses exciting tissue engineering (TE) opportunities. However, removing DNA from cartilage (dCart) requires harsh treatments due to its dense structure, causing loss of bioactivity and limiting its application as a cartilaginous extra cellular matrix (ECM). In this study, we demonstrate for the first time the successful application of vitreous humor (VH), a highly hydrated tissue closely resembling the glycosaminoglycan (GAG) and collagen composition of cartilage, as an ECM hydrogel to support chondrogenic differentiation. Equine VH was extracted followed by biochemical quantifications, histological examinations, cytotoxicity (human mesenchymal stromal cells, hMSCs and human articular chondrocytes, hACs) and U937 cell proliferation studies. VH was further seeded with hACs or hMSCs and cultured for 3-weeks to study chondrogenesis compared to scaffold-free micro-tissue pellet cultures and collagen-I hydrogels. Viability, metabolic activity, GAG and DNA content, chondrogenic gene expression (aggrecan, collagen I/II mRNA) and mechanical properties were quantified and matrix deposition was visualised using immunohistochemistry (Safranin-O, collagen I/II). VH was successfully extracted, exhibiting negligible amounts of DNA (0.4 ±â€¯0.4 µg/mg dry-weight) and notable preservation of ECM components. VH displayed neither cytotoxic responses nor proliferation of macrophage-like U937 cells, instead enhancing both hMSC and hAC proliferation. Interestingly, encapsulated cells self-assembled the VH-hydrogel into spheroids, resulting in uniform distribution of both GAGs and collagen type II with increased compressive mechanical properties, rendering VH a permissive native ECM source to fabricate cartilaginous hydrogels for potential TE applications. STATEMENT OF SIGNIFICANCE: Fabricating bioactive and cell-instructive cartilage extracellular matrix (ECM) derived biomaterials and hydrogels has over recent years proven to be a challenging task, often limited by poor retention of inherent environmental cues post decellularisation due to the dense and avascular nature of native cartilage. In this study, we present an alternative route to fabricate highly permissive and bioactive ECM hydrogels from vitreous humor (VH) tissue. This paper specifically reports the discovery of optimal VH extraction protocols and cell seeding strategy enabling fabrication of cartilaginous matrix components into a hydrogel support material for promoting chondrogenic differentiation. The work showcases a naturally intact and unmodified hydrogel design that improves cellular responses and may help guide the development of cell instructive and stimuli responsive hybrid biomaterials in a number of TERM applications.

A 96-well microplate bioreactor platform supporting individual dual perfusion and high-throughput assessment of simple or biofabricated 3D tissue models.

Traditional 2D monolayer cell cultures and submillimeter 3D tissue construct cultures used widely in tissue engineering are limited in their ability to extrapolate experimental data to predict in vivo responses due to their simplistic organization and lack of stimuli. The rise of biofabrication and bioreactor technologies has sought to address this through the development of techniques to spatially organize components of a tissue construct, and devices to supply these tissue constructs with an increasingly in vivo-like environment. Current bioreactors supporting both parenchymal and barrier tissue constructs in interconnected systems for body-on-a-chip platforms have chosen to emphasize study throughput or system/tissue complexity. Here, we report a platform to address this disparity in throughput and both system complexity (by supporting multiple in situ assessment methods) and tissue complexity (by adopting a construct-agnostic format). We introduce an ANSI/SLAS-compliant microplate and docking station fabricated via stereolithography (SLA), or precision machining, to provide up to 96 samples (Ø6 × 10 mm) with two individually-addressable fluid circuits (192 total), loading access, and inspection window for imaging during perfusion. Biofabricated ovarian cancer models were developed to demonstrate the in situ assessment capabilities via microscopy and a perfused resazurin-based metabolic activity assay. In situ microscopy highlighted flexibility of the sample housing to accommodate a range of sample geometries. Utility for drug screening was demonstrated by exposing the ovarian cancer models to an anticancer drug (doxorubicin) and generating the dose-response curve in situ, while achieving an assay quality similar to static wellplate culture. The potential for quantitative analysis of temporal tissue development and screening studies was confirmed by imaging soft- (gelatin) and hard-tissue (calcium chloride) analogs inside the bioreactor via spectral computed tomography (CT) scanning. As a proof-of-concept for particle tracing studies, flowing microparticles were visualized to inform the design of hydrogel constructs. Finally, the ability for mechanistic yet high-throughput screening was demonstrated in a vascular coculture model adopting endothelial and mesenchymal stem cells (HUVEC-MSC), encapsulated in gelatin-norbornene (gel-NOR) hydrogel cast into SLA-printed well inserts. This study illustrates the potential of a scalable dual perfusion bioreactor platform for parenchymal and barrier tissue constructs to support a broad range of multi-organ-on-a-chip applications.

Ten-year survival and seven-year functional results of cementless Oxford unicompartmental knee replacement: A prospective consecutive series of our first 1000 cases.

BACKGROUND: Cementless fixation is an alternative to cemented unicompartmental knee replacement (UKR), with several advantages over cementation. This study reports the ten-year survival and seven-year clinical outcome of cementless Oxford unicompartmental knee replacement (OUKR). METHODS: This prospective study describes the clinical outcome and survival of the first 1000 consecutive cementless medial OUKRs implanted at two centres for recommended indications. RESULTS: The 10-year survival was 97% (CI 95%: 92-100%), with 25 knees being revised. The commonest reason for revision was progression of arthritis laterally, which occurred in nine knees, followed by primary dislocation of the bearing, which occurred in six knees. There were two dislocations secondary to trauma and a ruptured ACL, and two tibial plateau fractures. Although there were no definite cases of aseptic loosening, two early revisions were related to tibial fixation: one for pain and a radiolucent line and one for incomplete seating of the component with a radiolucent line. There were four revisions for pain, but the cause of the pain was uncertain: in one there was tibial overhang and in two there was patellofemoral degeneration, which possibly contributed to the pain. There were no deep infections. The mean OKS improved from 23 (SD 8) to 42 (SD 7) at a mean follow-up of 7.0 years (p < 0.001). There was no significant difference in survival or clinical outcome between the designer and independent centre. CONCLUSIONS: The cementless OUKR is a safe and reproducible procedure with excellent 10-year survival and clinical results in the hands of both designer and independent surgeons.

Is tranexamic acid toxic to articular cartilage when administered topically? What is the safe dose?

Aims: The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage. Materials and Methods: The cellular morphology, adhesion, metabolic activity, and viability of human chondrocytes when increasing the concentration (0 mg/ml to 40 mg/ml) and length of exposure to TXA (0 to 12 hours) were analyzed in a 2D model. This was then repeated, excluding cellular adhesion, in a 3D model and confirmed in viable samples of articular cartilage. Results: Increasing concentrations above 20 mg/ml resulted in atypical morphology, reduced cellular adhesion and metabolic activity associated with increased chondrocyte death. However, the cell matrix was not affected by the concentration of TXA or the length of exposure, and offered cellular protection for concentrations below 20 mg/ml. Conclusion: These results show that when in vitro chondrocytes are exposed to higher concentrations of TXA, such as that expected following recommended intra-articular administration, cytotoxicity is observed. This effect is dose-dependent, such that a tissue concentration of 10 mg/ml to 20 mg/ml could be expected to be safe. Cite this article: Bone Joint J 2018;100-B:404-12.

Automated 3D bioassembly of micro-tissues for biofabrication of hybrid tissue engineered constructs.

Bottom-up biofabrication approaches combining micro-tissue fabrication techniques with extrusion-based 3D printing of thermoplastic polymer scaffolds are emerging strategies in tissue engineering. These biofabrication strategies support native self-assembly mechanisms observed in developmental stages of tissue or organoid growth as well as promoting cell-cell interactions and cell differentiation capacity. Few technologies have been developed to automate the precise assembly of micro-tissues or tissue modules into structural scaffolds. We describe an automated 3D bioassembly platform capable of fabricating simple hybrid constructs via a two-step bottom-up bioassembly strategy, as well as complex hybrid hierarchical constructs via a multistep bottom-up bioassembly strategy. The bioassembly system consisted of a fluidic-based singularisation and injection module incorporated into a commercial 3D bioprinter. The singularisation module delivers individual micro-tissues to an injection module, for insertion into precise locations within a 3D plotted scaffold. To demonstrate applicability for cartilage tissue engineering, human chondrocytes were isolated and micro-tissues of 1 mm diameter were generated utilising a high throughput 96-well plate format. Micro-tissues were singularised with an efficiency of 96.0 ± 5.1%. There was no significant difference in size, shape or viability of micro-tissues before and after automated singularisation and injection. A layer-by-layer approach or aforementioned bottom-up bioassembly strategy was employed to fabricate a bilayered construct by alternatively 3D plotting a thermoplastic (PEGT/PBT) polymer scaffold and inserting pre-differentiated chondrogenic micro-tissues or cell-laden gelatin-based (GelMA) hydrogel micro-spheres, both formed via high-throughput fabrication techniques. No significant difference in viability between the construct assembled utilising the automated bioassembly system and manually assembled construct was observed. Bioassembly of pre-differentiated micro-tissues as well as chondrocyte-laden hydrogel micro-spheres demonstrated the flexibility of the platform while supporting tissue fusion, long-term cell viability, and deposition of cartilage-specific extracellular matrix proteins. This technology provides an automated and scalable pathway for bioassembly of both simple and complex 3D tissue constructs of clinically relevant shape and size, with demonstrated capability to facilitate direct spatial organisation and hierarchical 3D assembly of micro-tissue modules, ranging from biomaterial free cell pellets to cell-laden hydrogel formulations.

Five-year follow-up of a prospective randomised trial comparing ceramic-on-metal and metal-on-metal bearing surfaces in total hip arthroplasty.

AIMS: The primary aim of this independent prospective randomised trial was to compare serum metal ion levels for ceramic-on-metal (CoM) and metal-on-metal (MoM) bearing surfaces in total hip arthroplasty (THA). Our one-year results demonstrated elevation in metal ion levels above baseline with no significant difference between the CoM and MoM groups. This paper reviews the five-year data. PATIENTS AND METHODS: The implants used in each patient differed only in respect to the type of femoral head (ceramic or metal). At five-year follow-up of the 83 enrolled patients, data from 67 (36 CoM, 31 MoM) was available for comparison. RESULTS: The mean serum cobalt (Co) and chromium (Cr) ion levels remained above baseline in both groups (CoM: Co 1.16 µg/l (0.41 to 14.67), Cr 1.05 µg/l (0.16 to 12.58); MoM: Co 2.93 µg/l (0.35 to 30.29), Cr 1.85 µg/l (0.36 to 17.00)) but the increase was significantly less in the CoM cohort (Co difference p = 0.001, Cr difference p = 0.002). These medium-term results, coupled with lower revision rates from national joint registries, suggest that the performance of CoM THA may be superior to that of MoM. CONCLUSION: While both bearing combinations have since been withdrawn these results provide useful information for planning clinical surveillance of CoM THAs and warrants continued monitoring. Cite this article: Bone Joint J 2017;99-B:1298-1303.

Modular Tissue Assembly Strategies for Biofabrication of Engineered Cartilage.

This review describes the prospects of applying modular assembly techniques and strategies for fabrication of advanced tissue engineered cartilage constructs. Articular cartilage is a tissue that has important functions in preserving and enabling locomotion. However, its limited intrinsic repair capacity and lack of current long-term clinical solutions makes it a candidate for repair or regeneration via tissue engineering strategies. Key advances in biofabrication and 3D bioprinting techniques allowing the specific placement of cells and tissues enable novel strategies to be adopted with increased chances of success. In particular, modular assembly, where separate biological components such as microtissue units, cellular building blocks or spheroids are combined with structural scaffold components to create a functional whole, offers potential as a new strategy for engineering of articular cartilage. Various modular assembly or bottom-up fabrication strategies have been investigated or applied for engineering of a range of tissues and cell types, however, modular approaches to cartilage engineering have been limited thus far. The integrative nature of many current approaches to engineering of articular cartilage means optimization of separate components (such as the scaffold and cells) is challenging, resulting in strategies which are less amenable to clinical scale-up or modification. In addition, current tissue engineering strategies may not replicate the function and complex structure of native tissue. This review outlines recent developments in fabrication of cellular or tissue modules as well as scaffold design where it impacts modular biofabrication, and discusses existing modular approaches applicable to articular cartilage regeneration and repair. Modular tissue assembly approaches allow complex hybrid constructs to be fabricated with direct control over both structural and cellular organization of pre-formed tissue units. The combination of modular assembly with automated biofabrication technologies may offer solutions to the development of optimal tissue-engineered cartilage constructs.

The impact of patient and surgical factors on the rate of infection after primary total knee arthroplasty: an analysis of 64,566 joints from the New Zealand Joint Registry.

AIMS: The aim of this study was to identify risk factors for prosthetic joint infection (PJI) following total knee arthroplasty (TKA). PATIENTS AND METHODS: The New Zealand Joint Registry database was analysed, using revision surgery for PJI at six and 12 months after surgery as primary outcome measures. Statistical associations between revision for infection, with common and definable surgical and patient factors were tested. RESULTS: A total of 64 566 primary TKAs have been recorded on the registry between 1999 and 2012 with minimum follow-up of 12 months. Multivariate analysis showed statistically significant associations with revision for PJI between male gender (odds ratio (OR) 1.85, 95% confidence interval (CI) 1.24 to 2.74), previous surgery (osteotomy (OR 2.45 95% CI 1.2 to 5.03), ligament reconstruction (OR 1.85, 95% CI 0.68 to 5.00)), the use of laminar flow (OR 1.6, 95% CI 1.04 to 2.47) and the use of antibiotic-laden cement (OR 1.93, 95% CI 1.19 to 3.13). There was a trend towards significance (p = 0.052) with the use of surgical helmet systems at six months (OR 1.53, 95% CI 1.00 to 2.34). CONCLUSION: These findings show that patient factors remain the most important in terms of predicting early PJI following TKA. Furthermore, we found no evidence that modern surgical helmet systems reduce the risk of PJI and laminar flow systems may actually increase risk in TKA. The use of this registry data assists the estimation of the risk of PJI for individual patients, which is important for both informed consent and the interpretation of infection rates at different institutions. TAKE HOME MESSAGE: Infection rates in TKA are related to both individual patient and surgical factors, and some modern methods of reducing infection may actually increase infection risk.

The rates of wear of X3 highly cross-linked polyethylene at five years when coupled with a 36 mm diameter ceramic femoral head in young patients.

Polyethylene wear debris can cause osteolysis and the failure of total hip arthroplasty. We present the five-year wear rates of a highly cross-linked polyethylene (X3) bearing surface when used in conjunction with a 36 mm ceramic femoral head. This was a prospective study of a cohort of 100 THAs in 93 patients. Pain and activity scores were measured pre- and post-operatively. Femoral head penetration was measured at two months, one year, two years and at five years using validated edge-detecting software (PolyWare Auto). At a mean of 5.08 years (3.93 to 6.01), 85 hips in 78 patients were available for study. The mean age of these patients was 59.08 years (42 to 73, the mean age of males (n = 34) was 59.15 years, and females (n = 44) was 59.02 years). All patients had significant improvement in their functional scores (p < 0.001). The steady state two-dimensional linear wear rate was 0.109 mm/year. The steady state volumetric wear rate was 29.61 mm(3)/year. No significant correlation was found between rate of wear and age (p = 0.34), acetabular component size (p = 0.12) or clinical score (p = 0.74). Our study shows low steady state wear rates at five years in X3 highly cross-linked polyethylene in conjunction with a 36 mm ceramic femoral head. The linear wear rate was almost identical to the osteolysis threshold of 0.1 mm/year recommended in the literature.

Occult Infection in Aseptic Joint Loosening and the Diagnostic Role of Implant Sonication.

Our aim was to determine the incidence of occult infection and to examine the role of ultrasound sonication of the implants in cases of presumed aseptic loosening in a prospective trial. Joint swabs, aspirates, and deep tissue samples were obtained from around the prosthesis for routine microbiology. Each prosthesis was sonicated and the sonicate examined with Gram staining and extended cultures. There were 106 joints in the study of which 54 were revised for aseptic loosening and 52 were assigned to the control revision group. There were 9 positive cultures with 8/54 positive cultures in the aseptic loosening group and 1/52 in the control revision group (p = 0.017, associated OR 47.7). We found concordant results between sonication fluid culture and conventional samples in 5/9 cultures. Preoperative inflammatory markers were not prognostic for infection. Coagulase-negative Staphylococcus was the most commonly cultured organism (7/9). Previously unrecognised infection was present in 15% of patients undergoing revision for aseptic loosening. Ultrasound sonication of the removed prosthesis was less sensitive than conventional sampling techniques. We recommend routine intraoperative sampling for patients having revision for aseptic loosening, but we do not support the routine use of ultrasound sonication for its detection.

The five-year radiological results of the uncemented Oxford medial compartment knee arthroplasty.

This study reports on the first 150 consecutive Oxford cementless unicompartmental knee arthroplasties (UKA) performed in an independent centre (126 patients). All eligible patients had functional scores (Oxford knee score and high activity arthroplasty score) recorded pre-operatively and at two- and five-years of follow-up. Fluoroscopically aligned radiographs were taken at five years and analysed for any evidence of radiolucent lines (RLLs), subsidence or loosening. The mean age of the cohort was 63.6 years (39 to 86) with 81 (53.1%) males. Excellent functional scores were maintained at five years and there were no progressive RLLs demonstrated on radiographs. Two patients underwent revision to a total knee arthroplasty giving a revision rate of 0.23/100 (95% confidence interval 0.03 to 0.84) component years with overall component survivorship of 98.7% at five years. There were a further four patients who underwent further surgery on the same knee, two underwent bearing exchanges for dislocation and two underwent lateral UKAs for disease progression. This was a marked improvement from other UKAs reported in New Zealand Joint Registry data and supports the designing centre's early results.

Should a Patients BMI Status be Used to Restrict Access to Total Hip and Knee Arthroplasty? Functional Outcomes of Arthroplasty Relative to BMI - Single Centre Retrospective Review.

We reviewed the experience of a dedicated orthopaedic elective service to determine whether we could establish a BMI group where arthroplasty was no longer effective as assessed by the patient's functional outcome. This was a prospective observational study with retrospective analysis of data collected on 1439 total hip arthroplasty, 934 total knee arthroplasty and 326 unicompartment knee arthroplasty patients. Functional scores (WOMAC, Oxford hip and knee scores and HAAS) were obtained preoperatively and at 12 months post op. Patients had their BMI recorded at the preoperative assessment and were divided into BMI groups (BMI<25, BMI 25-30, BMI 30-35 and BMI > 35). Patients with a BMI of ≤ 30 had significantly better functional scores at 12 months post op compared to those with a BMI of > 35. The absolute gain in functional scores from pre op to 12 months post op did not differ significantly between BMI groups, the only significant difference we found for absolute gain showed patients with a BMI of > 35 have a greater increase in HAAS scores following total hip arthroplasty compared to patients with a BMI of 30 or less (p = 0.0435). Our patients with higher BMI's had worse preoperative and post operative functional scores but their benefit from surgery measured by the change in functional scores showed no difference compared to patients with lower BMI. We could find no reason on the basis of the 12-month results to limit surgery to obese patients because of an expected poorer functional outcome.