Childhood long-term survivors now experience significant late effects from the primary cancer itself or from therapy. Cisplatin, an alkylating agent used in treatment for osteosarcoma, has been associated with irreversible high-frequency sensorineural hearing loss. There were 27 osteosarcoma patients treated at Department of Pediatrics, National University Hospital from 1997 to 2005. Twelve of these were long-term survivors, i.e. survived more than 2 years from initial diagnosis. Pre-chemotherapy audiogram was performed in 50% (n=6) of patients and the audiogram results were not available in the remainder (n=6, 50%) as it was either not done or records were not available. Prior to year 2003, Cisplatin was administered at a dose of 100mg/ m2/course (EOI regimen) in 50% of cases, and after year 2003, 120mg/m2/course (T12 regimen) in 45%. Median cumulative dose of cisplatin was 550mg/m2 (cumulative dose range, 240 – 800 mg/m2). Out of 12 patients, 7 patients (58%) experienced cisplatin induced ototoxicity. According to NCI Toxicity Criteria, Grade I ototoxicty was observed in two cases (30%), grade 2 toxicity in five cases (70%), and bilateral sensorineural hearing loss was noted in six of the survivors. One long term survivor required a hearing aid. Six of them had and renal tubulopathy (NCI Toxicity Grade 2) was noted simultaneously in 35% of cases (n=4). The incidence of cisplatin induced ototoxicity is high in our small series of long-term survivors of osteosarcoma. Baseline pre-chemotherapy testing, close monitoring during treatment and further follow-up are essential for this subset of patients receiving high doses of cisplatin. The study was funded by Singapore Cancer Syndicate (POU-097)

Abstract

Ceramic-on-ceramic (CoC) articulations in total hip arthroplasty (THA) have low wear, but the unique risk of fracture. After revision for CoC fracture, ceramic third bodies can lead to runaway wear of cobalt chrome (CoCr) causing extremely elevated blood cobalt. We present five cases of ceramic liner fractures revised to a CoCr head associated with the rapid development of severe cobalt toxicity.

We identified 5 cases of fractured CoC THA treated with revision to CoCr on highly cross-linked polyethylene (HXLPE) – three to conventional bearings and two to modular dual mobility bearings (CoCr acetabular liner, CoCr femoral head, and HXLPE). Mean follow up was 2.5 years after CoCr/HXLPE re-revision.

Symptoms of cobalt toxicity occurred at average 9.5 months after revision for ceramic fracture (range 6–12). All patients developed vision and hearing loss, balance difficulties, and peripheral neuropathy. Several had cardiomyopathy, endocrinopathy, and local skin discoloration. Two reported hip pain. Re-revision for cobalt toxicity occurred at an average of 22 months (range 10–36) after revision for ceramic fracture. Average serum cobalt level at re-revision was 991 μg/L (range 734–1302, normal <1 μg/L). All CoCr heads exhibited massive wear with asphericity; deep tissues exhibited prominent metallosis. Treatment consisted of debridement and revision to a ceramic head with HXLPE. Serum cobalt improved to an average of 25 μg/L at final follow up. All patients reported partial improvement in vision and hearing; peripheral neuropathy and balance did not recover.

Systemic cobalt toxicity is a rare but devastating complication of ceramic fracture in THA treated with cobalt-alloy bearings. Cobalt alloy bearings should be avoided in this setting. The diagnosis of systemic cobalt toxicity requires a high index of suspicion and was typically delayed following systemic symptoms. Debridement and revision to a ceramic-on-HXLPE leads to improvement but not resolution of cobalt toxicity complications.

Circulating cobalt and chromium from metal-on-metal implants cause rare but fatal autopsy-diagnosed cardiotoxicity. Concern exists that milder cardiotoxicity may be common and under-recognized. Unacceptably high failure rates of metal-on-metal hip implants have prompted regulatory authorities to issue worldwide safety alerts. Despite this, approximately 1 million patients continue to live with metal-on-metal implants, putting them at risk of systemic toxicity. Although blood cobalt and chromium levels are easily measured and track local toxicity, no non-invasive tests for organ deposition exist.

We recently demonstrated the utilisation of a T2* protocol (cardiovascular MRI) to detect cobalt and chromium deposition within the liver of a patient with elevated blood cobalt levels (confirmed by liver biopsy tissue analysis and X-ray fluorescence spectroscopy).

We sought to detect and constrain the correlation between blood metal ions and a comprehensive panel of established markers of early cardiotoxicity. In addition we applied T2* protocols with the aim of detecting cardiac metal deposition.

90 patients were recruited through RNOH clinics into this prospective single centre blinded study. Patients were divided into 3 age and gender-matched groups according to type of implant and blood metal ion levels as follows: [Group A] Non-metal bearing hip implants; [Group B] Metal-on-metal implants, low blood metal ion levels (<7ppb); and [Group C] Metal-on-metal implants, high blood levels (>7ppb).

All underwent detailed cardiovascular phenotyping using cardiac MRI (with T2*, T1 and ECV mapping, in addition to LV size and ejection fraction), advanced echocardiography (LV size and ejection fraction), and cardiac blood biomarker (Troponin and BNP) sampling in the same sitting at the Heart Hospital London. Primary outcomes were pre-specified. See study flow diagram – figure 1. (The study was registered with clinicaltrials.gov: NCT02331264).

Blood cobalt levels were significantly different between groups (0.17ppb (range 0·10–0·47, SD 0·08) vs. 2·47 (0·72–6·9, SD 1·81) vs. 30·0 (7·54–118.0, SD 29·1) respectively for groups A, B and C).

No significant between-group differences were found for LV size, ejection fraction (CMR or echocardiography), LA size, T1, T2*, ECV, BNP or troponin, with all results within normal ranges. There was no relationship between blood cobalt levels and either left ventricular ejection fraction or T2* (r=-0·022 and r=-0·108 respectively). Although small, the study was sufficiently powered to detect, as a minimum, a difference in ejection fraction of 4.8% (Cohen's d effect size 0·8).

Using best available technologies, exposure of patients with metal-on-metal hip implants to high (but not extreme) blood cobalt and chromium levels has no detectable effect on the heart. We believe these findings will offer reassurance to one million patients worldwide living with a metal-on-metal hip implant and will support clinicians caring for such patients.

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Tranexamic acid (TXA) is an anti-fibrinolytic medication commonly used to reduce peri-operative bleeding. Increasingly, topical administration as an intra-articular injection or peri-operative wash is being administered at concentrations between 10–100mg/ml. This study investigated effects of TXA on human periarticular tissues and primary cell cultures using clinically relevant concentrations.

Tendon, synovium and cartilage obtained from routine orthopaedic surgeries were used ex vivo or cultured for in vitro studies using various concentrations of TXA. They were stained with 5-chloromethylfluorescein diacetate and propidium iodide and imaged using confocal microscopy to identify the proportion of live and dead cells. The in vitro effect of TXA on primary cultured tenocytes, synovial like fibroblast (FLS) cells and chondrocytes was investigated using cell viability assays (MTT), fluorescent microscopy and multi-protein apoptotic arrays for cell death.

There was significant (p<0.01) increase in cell death in all tissue treated with 100mg/ml TXA, ex vivo. MTT assays revealed significant (p<0.05) decrease in cell viability following treatment with 50 or 100mg/ml of TXA within 4 hours of all cell types cultured in vitro. Additionally, there was significant (p<0.05) increase in cell apoptosis detected by fluorescent microscopy within 1 hour of exposure to TXA. Furthermore, multi-protein apoptotic arrays detected increased apoptotic proteins within 1 hour of TXA treatment in tenocytes and FLS cells.

Our study provides evidence of TXA cytotoxicity to human peri-articular tissues ex vivo and in vitro at concentrations and durations of treatment routinely used in clinical environments. Clinicians should therefore show caution when considering use of topical TXA administration.

Cryoprotectant toxicity has become more relevant because of increased use of high concentrations of cryoprotectants for vitrification of biologic tissues. A single toxicity model that integrates cryoprotectant concentration, time and temperature is essential to optimize the cryopreservation of tissues. The Weibull probabilistic distribution has been used in environmental toxicology research. This objective of this study was to fit the Weibull model to experimental data for chondrocyte recovery from articular cartilage exposed to various concentrations of dimethyl sulfoxide at different temperatures as a function of time. This study indicated that the Weibull model is an appropriate model to describe cryoprotectant toxicity to chondrocytes in articular cartilage.

This study was designed to examine the toxicity of dimethyl sulfoxide (DMSO) on chondrocytes in porcine articular cartilage (AC) as a function of time, temperature and concentration.

The Weibull model is suitable for modeling cryoprotectant toxicity in cartilage and can be further extended to other cellular and tissue systems.

The model provides a simple method to predict toxicity and to assess the feasibility of cryopreservation protocols.

The model proved to be a good fit for the entire data set of concentration, temperature and time, yielding an R2 value of 0.87 and a maximum discrepancy of 20% between the experimental data and the model. Estimates of the model’s parameters within a confidence interval of 95% were found to be: _=30±2, _=0.67±0.05, _C=0.38±0.03, _T=−2300±300 and _CT=700±100.

Sliced porcine AC was exposed to DMSO (1, 3, 5, 6M) at different temperatures (0, 22, 37°C) for various durations. Cellular viability was determined by membrane integrity stains. Experimental data for chondrocyte recovery was fit to the global Weibull probabilistic distribution model using SPSS SigmaPlot 2000 to estimate the five parameters.

A model integrating concentration, time, and temperature of exposure is required to optimize addition and removal protocols of high concentrations of cryoprotectant for cryopreservation. The Weibull distribution is a simple and flexible model used to describe similar processes. In the current study, chondrocyte viability decreased with increased concentration, temperature and time of exposure. The model indicated a significant interaction between the toxic effects of concentration and temperature.

A 35-year-old female (age 35Yrs) had primary MOM total hip arthroplasty (THA) in 2008. At 8 months this patient postoperatively developed headaches, memory loss, vertigo, and aura-like symptoms that progressed to seizures. At 18 months review, she complained of progressive hip pain, a popping sensation and crepitus with joint motion. This patient weighed 284lbs with BMI of 38.5. Radiographs revealed the cup had 55° inclination, 39° anteversion (Fig. 1). Metal ion concentrations were high (blood: Co=126 mcg/L, Cr= 64mcg/L). Revision was performed in November 2010 A dark, serous fluid was observed, along with synovitis. The implants were well fixed and the femoral head could not be removed; thus the stem was removed by femoral osteotomy. With the head fused on this femoral stem, for the 1^st time it was possible to precisely determine the habitual patterns of MOM wear relative to her in-vivo function. We investigated (1) size and location of wear patterns and (2) signs of cup-stem impingement to help explain her symptoms developed over 32 months follow-up.

The retrieved MOM was a Magnum™ with head diameter 50mm and 50×56mm cup (Biomet). This was mounted on a Taperloc™ lateralized porous-coated stem. Components were examined visually and wear damage mapped by stereo-microscopy, interferometry, CMM, SEM, and EDS. Main-wear zone (MWZ) areas were calculated using standard spherical equations¹ and centroidal vectors determined.

The head-cup mismatch was 427um with the cup revealing a form factor of 228um. The cup showed wear area of 1275mm² that extended up to the cup rim over 150°arc. The cup rim was worn thin over a 90° arc with loss of cup bevel. The head showed an elliptical wear area of 2200mm² located centrally on the superior-medial surface (ellipsoidal ratio ×1.2). Compared to the hemispherical surface (50mm: hemi-area = 3927mm²), the worn area represented hemi-area ratio of 56%. The centroidal vectors measured 8° anterior and 24° superior to the head's polar axis (Fig. 2). Stripe wear damage revealed multiple impingement sites. SEM and EDS revealed stripes were contaminated by metal transfer from the stainless-steel instruments used at revision. The main impingement position was identified (Fig. 3) indicating the site of repetitive subluxations whereby the subluxing head thinned the cup, i.e. “edge wear”.

Cup and head wear patterns corresponded well, reinforcing our definition of the MWZ locations in vivo. The femoral MWZ was centrally located superiorly and medially with respect to the polar axis of the femoral neck and head. The noted impingement position indicated this patient had experienced repetitive subclinical subluxations (RSS).² The taper inside the fused head may also have been a contributory factor that we cannot ignore. Nevertheless her excessive cup thinning was likely a result of a steep cup and considerable anteversion allowing the femoral head to sublux over the cup rim, thus thinning the cup and wearing the rim bevel, and producing MOM wear debris.

Background:

Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions.

Orthopedic metallic medical devices are essential in the treatment of a wide range of skeletal diseases and disabilities. However, they are often related with surgery complications due to acute prosthetic joint infections (PJI) causing devastating complications. Gallium (Ga) antibacterial activity has been recently demonstrated: in aqueous solutions, Ga ionize in a trivalent form Ga³⁺ that can replace Fe³⁺ in bacterial metabolism thus leading to bacteria death. However, it is not yet clear whether such effect is typical to Ga³⁺ release, and how this would affect longer term performance. Here we investigated Ga addition into titanium alloys using metallurgical methods. The study has confirmed that metallurgical addition of gallium even in small amounts (1–2% wt.) to titanium alloys have highly efficient antibacterial function without any visible cytostatic or cytotoxic effects. The presence of gallium within the metal matrix might ensure that antibacterial effect will persist for a long time towards multi-drug resistant S. aureus, which might not be possible if gallium or other metal are only in thin degradable coatings or similar formulations. A 5-logs decrease in CFU number was detected for alloys with 2% Ga and more after 72 h (alamar blue and CFU count assays). The alloys also show to be in vitro cytocompatible with both mature U2OS osteoblasts and progenitor pre-osteoblasts hFOB. Since gallium is metallurgically analogous to aluminium in titanium alloys, it might be used without affecting other alloy properties.

Introduction

Local anaesthetic has been reported to have a detrimental effect on human chondrocytes both in vitro and in vivo. Magnesium, an NMDA-receptor antagonist, may be an alternative intra-articular analgesic agent following arthroscopy. We aimed to report the dose response effect of commonly used local anaesthteitc on chondrocyte viability and also report on the effect of adding magnesium to local anaesthetic.

Background: Animal studies have shown that 0.9% NaCl causes inhibition of proteoglycan metabolism in articular cartilage yet it continues to be the most commonly used irrigation fluid for arthroscopic surgery. Ringer’s solution and non ionic fluids have been shown to cause less damage. There is currently no such comparison in human articular cartilage. The aim of this study was to assess the effect of different irrigation fluids on arthritic and non arthritic human articular cartilage.

Materials and Methods: Non arthritic cartilage specimens were obtained from femoral heads of hip fracture patients undergoing hemiarthroplasty where there were no radiological or macroscopic signs of osteoarthritis. Arthritic articular cartilage was obtained from tibial plateau of total knee arthroplasty patients or femoral heads with macroscopic signs of osteoarthritis. Cartilage explants were exposed to either 0.9% normal saline or Ringer’s solution, 1.5% Glycine, 10% Mannitol or a control solution of M199 culture medium. 0.5% bupivacaine, which has been shown to be toxic to chondrocytes, was used as a second control solution. The specimens were then incubated in culture medium containing radiolabelled 35-SO4 for 16 hours and uptake was measured as counts per gram per minute.

Results: In non arthritic cartilage, the inhibition of proteoglycan synthesis was 0% with Ringer’s solution (p> 0.05), 3% with Glycine and Mannitol (p> 0.05), 12% with 0.9% NaCl (p> 0.05) and 75% with 0.5% bupivacaine (p< 0.001).

In arthritic cartilage, the inhibition was 15% with Ringer’s solution (p> 0.05), 20% with Mannitol (p> 0.05), 30% with 0.9% NaCl and Glycine (p=0.04) and 85% with 0.5% bupivacaine (p< 0.001).

Conclusion: Normal saline was most harmful to human articular cartilage. Ringer’s solution was the best solution for joint irrigation. We have provided yet more evidence to suggest that 0.5% bupivacaine is severely toxic to articular cartilage.

Introduction: Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

Methods: We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

Results: We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Discussion: We concluded that large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential side-effects of long-term exposure to elevated these metal ions is considered. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

Background

There are several case reports of chondrolysis following joint arthroscopy. Continuous post-operative infusion of local anaesthetic solutions, especially 0.5% Bupivacaine, has been implicated as the causative factor in many of these cases. Recent in vitro studies have shown that even a single exposure of articular cartilage to different local anaesthetic solutions can cause apoptosis and mitochondrial dysfunction in chondrocytes leading to cell death. There is currently no study looking at methods to prevent this toxicity of local anaesthetic solutions to articular cartilage. Glucosamine has a protective and reparative effect on articular cartilage and a Cochrane review in 2007 found that it provides mild benefit in pain and function in patients with arthritis.

Introduction: Purified plaster of Paris can be used as a resorbable carrier material for local antibiotic therapy. Clinical use already has been published with vancomycin and the aminoglycosides gentamycin and tobramycin. Calcium sulphate pellets with vancomycin can be manufactured during operation from Osteoset^® and vancomycin powder, whereas calcium sulphate with tobramycin is available as ready-to-use pellets under the brand name Osteoset T^®. Results are promising. However, no data on systemic serum levels in humans have been published so far, despite well known toxicity issues of these antibiotics in systemic therapy.

Methods: Following implantation of calcium sulphate with vancomycin or tobramycin, systemic serum levels of these antibiotics have been measured for up to 10 days, and prospectively gathered. Considering serum levels and renal function, pharmacokinetics have been estimated.

Results: Between August 2006 and February 2008, calcium sulphate with vancomycin has been implanted in 15 patients, and with tobramycin in 12 patients. Whereas vancomycin levels remained very low, tobramycin levels close to the usually accepted trough levels could be observed at 24h post-operation.

Conclusion: Vancomycin added to calcium sulphate has a safe systemic profile. On the contrary, significant serum levels of tobramycin can be measured more than 24h after implantation. Caution is mandatory when using this antibiotic, and explantation should be considered if levels too high are observed.

Introduction: Late effects of treatment in pediatric oncology patients are major issues of follow up care. Success in overall survival of patients with Ewing’s sarcoma/PNET (ES/PNET) correlates with cumulative doses of alkylating agents especially. Renal toxicity is subject of interest due to irreversible tubulopathy and need of many concomitant nephrotoxic drugs given during treatment.

Objectivee: Patients suffered from ES/PNET on Euro Ewing 99 protocol were eligible for evaluation of renal functions during therapy and follow up.

Methods: Design ofthis study was single institution observational. Total of 20 patients were included 9 females and 11 males. Renal toxicity was assessed as glomerular filtration rate according to Schwartz’s formula (GFR), serum creatinine (S-crea), fractionated phosphate reabsorption (Tp/Ccrea), daily phosphate waste in urine (U-P), daily protein waste in urine (U-Pr) and minimal signs of Fanconi syndrome (FS; positive urine glucose and/or protein).

Results: Median age at time of diagnosis was 11.7 years. Median follow up from time of diagnosis was 1.2 months. Median dose of ifosfamide was 87 g/ m2. Median GFR decreased from 2.7ml/s to 2.2 ml/s (p=0.001). Median of S-crea was initially 48 μl/l and 58.1 μl/l at time of last follow up (p< 0.001). Median of Tp/Ccrea was 1.2 mmol/l and decreased to 1.1 mmol/ l at the end of treatment (p= 0.026). U-P was initially and finally 11.9 mmol and 25.1mmol, respectively (p = 0.008). Median of tubular reabsorption of phosphate decreased from 95% initially to 90% (p=0.001). Daily waste of protein increased from 0.11 g to 0.43 g (p= 0.051). Minimal signs of FS developed in 9 of 17 patients (53%).

Conclsions: Patients with high cumulative doses of ifosfamide are at risk of renal impairement. Despite statistically significant differences of severeral measures observed in this study, clinical impact of post treatment values does not exceed grade 1 toxicity. Observation of minimal signs of FS developed in 53% of patients is of concern and further treatment of ES/PNET should be carefully focused on late effect too.

Anterior cruciate ligament injury is the most common and economically costly sport injuries, frequently requiring expensive surgery and rehabilitation. Post-operative knee septic arthritis represents a serious complication with an incidence rate between 0.14% and 1.7%. A common practice to avoid septic arthritis is the “vancomycin wrap”, consisting in the soaking of the graft for 10–15 minutes within a sterile gauze swab previously saturated with 5 mg/mL vancomycin. Even though several studies have been conducted to investigate vancomycin toxicity on different musculoskeletal tissues or cells, little is known about the effect of such antimicrobial on tendon-derived cells.

The aim of this study was to determine the in vitro toxicity of different concentrations of vancomycin at different time points on human primary tenocytes (hTCs).

hTCs were isolated from hamstring grafts of patients undergoing anterior cruciate ligament reconstruction. After expansion, cells were treated with different concentrations of vancomycin (2.5, 5, 10, 25, 50 and 100 mg/mL) for 10, 15, 30 and 60 minutes. In vitro toxicity was evaluated measuring: metabolic activity through the reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT Assay); cytotoxicity (Live/Dead assay); and cell apoptosis (Annexin V apoptosis kit).

The metabolic activity of hTCs was affected by vancomycin treatment starting from 10 mg/mL at all time points (p < 0.05) and dropped down at 100 mg/mL at all time points (0.05 < p < 0.001). Cells viability resulted to be unaffected only by 2.5 mg/mL vancomycin at all time points. Vancomycin resulted to be cytotoxic starting from 10 mg/mL after 15 minutes of treatment and at all higher concentrations under study at all time points. Cells died when treated with vancomycin concentrations higher than 5 mg/mL but not through apoptosis, as confirmed by negative staining for Annexin V.

In our experimental conditions, vancomycin resulted to be toxic on hTCs at concentrations higher than 5 mg/mL. The use of this antibiotic on tendons to prevent infections could be useful and safe for resident cells if used at a concentration of 2.5 mg/mL up to 1 hour of treatment.

Osteosarcoma is the most common malignant bone tumour in children and young people. Approximately 40% patients respond poorly to highly toxic preoperative MAP (methotrexate adriamycin, cisplatin) chemotherapy with consequent inferior survival. The role of genetic polymorphisms in drug response and toxicity is reported in acute leukaemia and some solid tumours. Recent evidence in osteosarcoma suggests increased chemotherapy toxicity is associated with improved survival. The aim of this pilot study is to investigate the influence of drug target and metabolising gene polymorphisms on tumour response and chemotherapy toxicity in osteosarcoma.

Patients who have completed MAP chemotherapy are eligible. Chemotherapy toxicity (CTCAE grade) is collected from patient records. Tumour response is graded as good (> 90% necrosis) or poor (< 90% necrosis) in resection specimen. Peripheral blood DNA is typed for genome-wide single nucleotide polymorphisms (SNP) using the Illumina 610 Quad array and analysed using Bead Studio software. Standard PCR techniques are used to genotype the Thymidylate synthase (TS) gene (folate pathway) for the presence of 2 or 3 copies of a 28 base pair repeat (2R/3R) and a G/C SNP in the 3R allele.

52 patients have entered to date: 33 good responders, 12 poor and 7 unevaluable for response. Median age 18 years (range 10–51), males:females 1.3:1. Median follow up is 39 months (range 2–76) with 11 patients relapsing. 23 patients have TS genotype 2R/2R, nineteen 2R/3R, six 3R/3R, three 2R/4R and one 2R/7R. Neither TS repeat or G/C SNP genotype correlated with histological response or degree of methotrexate stomatitis. Interestingly, presence of the 2R allele was significantly related to relapse (p=0.01) but may reflect small patient numbers. Recurrent methotrexate stomatitis (> 2 episodes of CTCAE grade 2) was weakly correlated with no relapse (p=0.07). Analysis of SNP array data with emphasis on MAP pathway polymorphisms will be presented when complete.

Introduction. Cobalt chrome femoral head has been used widely in total hip arthroplasty and has shown favorable outcome. However, there is still of concern of potential metal toxicity from the wear debris. In the other hand, titanium is well known for its biocompatibility but it is not used in bearing surface of arthroplasty due to its brittleness. Recently, coating of the prosthesis using plasma electrolytic oxidation (PEO) has shown favorable surface protection. Thus, in this study, we tried to find out whether the PEO coating on the titanium surface would provide surface protection. Materials and methods. Five Titanium alloy (Ti-6Al-4V) ball mimicking femoral head was manufactured and was coted using plasma electrolytic oxidation. Wear rate was tested using validated wear tester with 10N compression force at 80rpm. The amount of wear was detected by measuring change of weight after wear test was completed. This was compared with femoral head manufactured with titanium alloy without PEO coating. Toxicity of the debris was also tested using MTT assay with human osteoblast cell line. Results. Compare to the base titanium metal, PEO coated metal head has shown to provide surface protection. The wear rate has significantly decreased with PEO coating (median value : 0.00015g/mm. 2. vs 0.00006 g/mm. 2. ). MTT assay revealed no cytotoxicity with the amount of debris generated from the wear test. Conclusion. The result of the current study indicate that the PEO coating on the titanium femoral head can significantly decrease the wear rate and is non cytotoxic. This indicates that the femoral head manufactured with titanium alloy and PEO coating maybe a potential alternative to be used in total hip arthroplasty

Introduction. The use of irrigation solution during surgical procedures is a common and effective practice in reduction of bioburden and the risk of subsequent infection. The optimal irrigation solution to accomplish this feat remains unknown. Many surgeons commonly add topical antibiotics to irrigation solutions assuming this has topical effect and eliminates bacteria. The latter reasoning has never been proven. In fact a few prior studies suggest addition of antibiotics to irrigation solution confers no added benefit. Furthermore, this practice adds to cost, has the potential for anaphylactic reactions, and may also contribute to the emergence of antimicrobial resistance. We therefore sought to compare the antimicrobial efficacy and cytotoxicity of irrigation solution containing polymyxin-bacitracin versus other commonly used irrigation solutions. Methods. Using two in vitro breakpoint assays of Staphylococcus aureus (ATCC#25923) and Escherichia coli (ATCC#25922), we examined the efficacy of a panel of irrigation solutions containing topical antibiotics (500,000U/L Polymyxin-Bacitracin 50,000U/L; Vancomycin 1g/L; Gentamicin 80mg/L), as well as commonly used irrigation solutions (Normal saline 0.9%; Povidone-iodine 0.3%; Chlorhexidine 0.05%; Castile soap 0.45%; and Sodium hypochlorite 0.125%) following 1 minute and 3 minutes of exposure. Surviving bacteria were counted in triplicate experiments. Failure to eradicate all bacteria was considered to be “not effective” for that respective solution and exposure time. Cytotoxicity analysis in human fibroblast, osteoblast, and chrondrocyte cells exposed to each of the respective irrigation solutions was performed by visualization of cell structure, lactate dehydrogenase (LDH) activity and evaluation of vital cells. Toxicity was quantified by determination of LDH release (ELISA % absorbance; with higher percentage considered a surrogate for cytotoxicity). Descriptive statistics were used to present means and standard deviation of triplicate experimental runs. Results. Polymyxin-Bacitracin, Saline and Castile soap irrigation at both exposure times were not effective at eradicating S aureus or E coli (Figure 1). In contrast, Povidone-iodine, Chlorhexidine, and Sodium hypochlorite irrigation were effective at eradicating both S aureus and E coli. Vancomycin irrigation was effective at S aureus eradication but not against E coli, whereas Gentamicin irrigation showed partial efficacy against E coli eradication but none against S aureus. The greatest cytotoxicity was seen with Chlorhexidine (49.4% ± 1.9). This was followed by Castile soap (33.2% ±3.9), Vancomycin (9.01% ±5.1), Polymyxin-Bacitracin (8.45% ±1.5), and Gentamicin irrigation (4.72% ±2.3) (Figure 2 and Figure 3 microscopy images). Povidone-iodine and Sodium hypochlorite showed least cytotoxicity (0.05% ±0.08 and 0.11%±0.19, respectively). Similar trends were seen at both exposure times and across fibroblasts, osteoblasts and chondrocytes. Discussion. This in vitro study suggests that addition of polymyxin-bacitracin to saline irrigation solution is a futile exercise. Taken within the context of its associated expense, risk of hypersensitivity and impact upon antimicrobial resistance, our findings bring its widespread clinical usage into question. Povidone-iodine may be a more effective option, with a more favorable cytotoxicity profile than the other commonly used irrigation solutions. Clinical outcomes should be studied to determine the most effective agent, concentration, and exposure time for intraoperative irrigation

Childhood cancer survival has increased dramatically over the last 30 years. Childhood Cancer Survivor Study- SG was established to evaluate the outcome and toxicities experienced by long term childhood cancer survivors in Singapore. There were 429 cases of hematological malignancies (HM) and 342 cases of solid tumors (ST) diagnosed and treated at National University Hospital (NUH) Singapore from May 1981 to December 2007. There were seven long term survivors for Osteosarcoma (OS) out of 26 patients seen during the study period. Median age at diagnosis was 13.8 (range, 6.4–15.8 years) and median follow-up was 7.9 (range, 2.6 – 13.2 years). Cumulative doses of chemotherapy received included: cisplatin (240 – 800 mg/m2); doxorubicin 150 – 450 mg/m2); methotrexate (16 – 144 Grams/m2); ifosfamide (27–80 mg/m2); and etoposide (1000 – 3300 mg/ m2). According to the NCI Criteria for Toxicity (CTC version 2.0), three patients experiences grade 2 sensorineural hearing loss; three cases of grade 1 cardiomyopathy; three cases of grade 1 renal tubulopathy; and six cases of post surgical complications (infection-3, length discrepancy-3, poor fitting prosthesis-2). Many of the patients did not have baseline pre-treatment evaluations such as audiograms, renal function, echocardiograms and similar proportion were not adequately followed-up post treatment. This is the first analysis and report in the country on treatment related outcome and toxicity in long-term survivors of childhood cancers such as osteosarcoma and other solid tumors. Authors recommend that future treatment protocols for childhood cancer in Singapore should incorporate pre- and post-treatment evaluations and close follow-up of young survivors with establishment of a multi-disciplinary late effects clinic