Coupling of dynamics and contact mechanics of artificial hip joints in a pendulum model

To date, fully coupled dynamics and contact mechanics analysis is still limited by expensive computational cost and long computing time and has not been addressed comprehensively, particularly in the hip joint. To understand the influence of different parameters on the biomechanics of the total hip replacement (THR) and improve its design, two numerical approaches were developed and implemented in finite element models to investigate the coupling between the dynamics response and the contact mechanics for three different THR configurations, metal-on-polyethylene (MOP), metal-on-metal (MOM), and ceramic-on-ceramic (COC). The dynamic force and the contact pressure distribution at the bearing surfaces from the two methods were predicted and compared. The influences of various parameters (motion angle, load applied in the pendulum, friction coefficient, geometry, and material properties) were subsequently investigated. From the comparisons, the decoupled method, based on the rigid-body dynamics and the quasi-static elastic contact mechanics, was adequate to predict the performance of the THRs efficiently. The load had the greatest influence on the dynamics/contact mechanics among other factors.

Study To Evaluate the Efficacy and Safety of Zoladex Combined with CEF Chemotherapy as Neo-Adjuvant Therapy in Hormone Responsive, Premenopausal, Operable Breast Cancer Patients

Purpose: To evaluate the efficacy and safety of Zoladex combined with CEF chemotherapy as neo-adjuvant therapy in hormone responsive, premenopausal, operable breast cancer patients.Patients and Methods: 119 patients with hormone responsive, premenopausal, operable breast cancer have been enrolled. Zoladex 3.6 mg was administered by subcutaneous injection per 4 weeks for 3 cycles, concurrently, CEF (CTX 600mg/m2, EPI 60-90 mg/m2, 5-Fu 500 mg/m2) were given per 3 weeks for 4 cycles as neo-adjuvant therapy. The primary objective was pathological complete response (PCR) rate in the breast. The secondary objectives included clinical complete response (CR) rate, clinical partial response (PR) rate, clinical overall response rate (ORR), safety and toxicity, change of biological marker status (ER, PR, HER-2) pre- and post-therapy.Results: 31 patients (26.1%) achieved clinical complete response and 76 patients (63.9%) achieved clinical partial response; the overall clinical response rate was 90.0%. 14 patients (11.8%) achieved pathologic complete response to T0/Tis, N0 and 20 patients (16.8%) achieved pathologic complete response to T0/Tis, Nx. When stratified by the clinical lymph-node status, the clinical partial response rate in clinical lymph-node negative group was significantly better than clinical lymph-node positive group (p=0.02). When stratified by the hormonal status, the clinical partial response rate in ER+PR+ group was significantly better than ER+PR- and ER-PR+ group (p=0.0471). There was no significant difference between HER-2+ group and HER-2- group when stratified by the HER-2 status. There was no treatment-related death and no grade 3 or grade 4 toxicity. The common adverse events were nausea (grade1 65.5%, grade2 18.5%), vomiting (grade1 58.8%, grade2 13.4%), alopecia (grade1 45.4%, grade2 54.6%). Other adverse events with more than 5% incidence included neutropenia (grade1 5.0%) and hepatic dysfunction (grade1 9.2%). There was no drug discontinuation and no drug delay or dose reduction occurred. Hormonal receptor became negative post-therapy in 11 patients' (9.2%), which clinical response rate significantly lower compared with post-therapy hormonal receptor positive group (p<0.001). The change of HER-2 status had no relationship with clinical efficacy. 109(91.6%) patients achieved amenorrhea after the first cycle of Zoladex, 10(8.4%) patients achieved amenorrhea after the second cycle of Zoladex. Mean period of amenorrhea was 6 months (4–17 months). 43 patients have been followed up for more than 1 year after operation and among them 6(14.0%) patients still remain amenorrhea.Conclusion: Zoladex combined with CEF chemotherapy as neo-adjuvant therapy in hormone responsive, premenopausal breast cancer patients was more effective and had no more toxicity than CEF chemotherapy alone. This regimen was most effective especially in the clinical lymph-node negative group and ER/PR double positive group. The clinical response rate will be lower if the hormonal receptor became negative after therapy. The efficacy of this regimen has no relationship with HER-2 status.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4087.

Influence of the meniscus on friction and degradation of cartilage in the natural knee joint

BACKGROUND

Total meniscectomy has been shown to cause early-onset arthritis in the underlying cartilage and bone in the knee joint, demonstrating that the meniscus plays an important protective role in the load carrying capacity. Relationships between friction and wear in synovial joints are complex due to the biphasic nature of articular cartilage and the time dependency of tribological responses. Determination of friction and wear in the whole natural joint in vitro or in vivo is technically difficult and the tribological effect of meniscectomy has not been previously studied in an articulating knee joint.

OBJECTIVE

The aim of this study was to use a tribological simulation of the medial compartmental bovine knee, to investigate friction and wear, with and without the meniscus. We hypothesised that meniscectomy would lead to elevated contact stress and frictional coefficient across the joint.

METHODS

Skeletally mature bovine medial compartmental knee joints were dissected and mounted in a pendulum friction simulator, which was used to apply physiologically relevant loading and motion. Wear was quantified using micro-MRI scans and surface profilometry.

RESULTS

Knees tested with the intact meniscus showed no change in surface roughness and no detectable cartilage loss or deformation. However, increased contact stress and frictional coefficient upon removal of the meniscus, led to immediate surface fibrillation, biomechanical wear and permanent deformation of cartilage.

CONCLUSIONS

This study presents, for the first time, an in vitro model simulation system to investigate the tribological effects of meniscectomy and meniscus repair and regeneration.

Chondroitin sulphate: an effective joint lubricant?

OBJECTIVE

The effect of chondroitin sulphate (CS) treatment on the friction and deformation characteristics of native and glycosaminoglycan (GAG) deficient articular cartilage was investigated.

METHODS

Friction tests were conducted at 0.4 MPa load, in Static and Dynamic models, to determine the startup coefficient of friction (COF) and dynamic COF, respectively. Native cartilage: For each cartilage pin and plate couple, the COF was determined under three consecutive tests - (1) baseline COF in PBS (2) COF in CS lubricant and (3) COF again in PBS, after 24h CS treatment. GAG deficient cartilage: For each cartilage pin and plate couple, the baseline COF was determined in PBS initially and again following enzymatic treatment to deplete GAGs. The specimens were then soaked in CS solution for 24h and the COF determined again in PBS. In a similar manner, friction tests were replaced with indentation tests to study the deformation of the tissue.

RESULTS

CS at 50mg/ml significantly lowered the startup COF of native cartilage both as a lubricant and a treatment solution. In the dynamic model, where the fluid load support is sustained at a high level, CS failed to have any effect on the COF of native cartilage. GAG depletion raised the friction and deformation levels of cartilage, and subsequent CS treatment failed to lower them to their native levels.

CONCLUSION

CS proved to be an effective lubricant for cartilage under mixed-mode lubrication conditions. However, supplemental CS that diffused into the specimens had no influence on the fluid load support of cartilage.

Stepwise regression analysis of the determinants of blood tacrolimus concentrations in Chinese patients with liver transplant

Tacrolimus (FK506) is one of the immunosuppressive drugs used effectively to prevent allograft rejection after liver transplantation. Narrow therapeutic range and individual variance in pharmacokinetics make it difficult to establish a fixed dosage for all patients. Genetic polymorphism in drug metabolizing enzymes and in transporters may influence tacrolimus exposure. A stepwise regression analysis was used to analyze the relationship between blood concentrations of tacrolimus (54 blood samples at the day of 1 week, 2 week and one month after liver transplantation) and genetic & non-genetic factors in 18 Chinese liver transplant patients. The equation of multiple stepwise regression was: Y (tacrolimus' blood concentration) = 34.534 - 0.247 (age) - 0.510 (weight) + 1.688 (dose) + 6.876 (recipient's CYP3A5 genotype) - 3.097 (donor's CYP3A5 genotype), P < 0.01. The factors impacting patient's tacrolimus blood concentrations in a descending order are weight, recipient's CYP3A5 genotype, dose, age, donor's CYP3A5 genotype. Among those, patient's weight and recipient's CYP3A5 genotype could significantly impact the blood concentration of tacrolimus. The influence of recipient's CYP3A5 gene polymorphism is much more obvious than that of donor's. Neither donor's nor recipient's MDR1 genetic polymorphisms were correlated with the blood concentration of tacrolimus.

Early energy and protein reduction: effects on growth, blood profiles and expression of genes related to protein and fat metabolism in broilers

1. A total of 320-d-old Ross broilers were used in a 6-week study to investigate the effects of feeding lower energy and protein diets from d 8 to 14 on growth performance, blood profiles, and gene expression of leptin and myostatin. 2. Broilers were randomly allotted to 4 treatments, each treatment applied to 4 pens with 20 birds in each. During first week, all the birds were fed on a common starter diet (13.4 MJ ME/kg, 230 g/kg CP and 11.0 g/kg lysine). The birds were then subjected to their respective treatment diets from d 8 to 14. Treatment diets comprised two ME levels, 13.4 and 12.0 MJ/kg, each with two levels of CP, 230 and 184 g/kg. This was followed by feeding common starter and finisher diets for the last 4 weeks. 3. Dietary protein reduction resulted in poor performance and feed efficiency while energy reduction resulted in poor feed efficiency between d 8 and 14. From d 14 to 42 birds previously fed diets lower in energy and protein showed similar body weight gain and feed intake to well-fed birds. Moreover from d 8 to 14, birds fed on energy and protein-reduced diets had lower nutrient metabolisability coefficients. 4. The blood urea nitrogen (BUN) and relative weights of heart and breast muscle were lower in birds fed protein-reduced diets while energy reduction resulted in lower plasma glucose, abdominal fat and intestinal weight at d 14. At d 42, birds fed on the protein-reduced diets had lower BUN, breast muscle weight and small intestine length, while feeding on the energy-reduced diets resulted in lower abdominal fat. 5. Upregulated myostatin mRNA expression in breast muscle and downregulation of leptin mRNA expression in abdominal fat were observed in birds fed on protein and energy-reduced diets, respectively. 6. In conclusion, early nutrient reduction affected growth performance and produced lesser abdominal fat in broilers. Moreover, early energy and/or protein reduction could change muscle and fat metabolism by regulating the expressions of myostatin and leptin.

Impact of hypertension on coronary artery spasm as assessed with intracoronary acetylcholine provocation test

Both hypertension and coronary artery spasm (CAS) are associated with endothelial dysfunction. Thus, a higher incidence of CAS is expected in hypertensive patients. We evaluated the impact of hypertension on CAS with intracoronary acetylcholine (ACh) provocation test. A total of 986 patients (685 hypertensive patients vs 301 normotensive patients) who underwent coronary angiography with ACh provocation test were enrolled. ACh was injected into the left coronary artery in incremental doses of 20, 50 and 100 microg min(-1). Significant CAS was defined as a transient >70% luminal narrowing with concurrent chest pain and/or ST-segment changes. Although the incidences of significant ACh-induced CAS were similar between hypertensive and normotensive patients (35.8 vs 39.2%, P=0.303), multivariate logistic analysis showed that hypertension was negatively associated with ACh-induced CAS (odds ratio: 0.70, 95% confidence interval: 0.51-0.94, P=0.020). The angiographic characteristics of ACh-induced CAS were similar between these two groups. Subgroup analysis regarding the impact of the status of blood pressure control on CAS showed that hypertensive patients with controlled blood pressure had a significantly higher incidence of CAS than those with uncontrolled blood pressure (45.2 vs 27.9%, P<0.001), and that uncontrolled blood pressure was negatively associated with ACh-induced CAS (odds ratio: 0.56, 95% confidence interval: 0.40-0.79, P=0.001). In conclusion, despite the expected endothelial dysfunction, hypertension and uncontrolled blood pressure are negatively associated with CAS, suggesting that the mechanisms and risk factors of CAS may be significantly different from those of coronary artery disease.

Phase II study of postoperative chemoradiotherapy for esophageal carcinoma

e15606

Background: Esophageal squamous cell carcinoma is still a virulent disease diagnosed at late stage and remains a major cause of carcinoma mortality in China. The preoperative chemoradiotherapy had been applied to patients with esophageal carcinoma in an effort to reduce the relapse and improve survival. However, randomized controlled trails have shown conflicting results. Intergroup study 0116 demonstrated that postoperative chemoradiotherapy significantly improved overall survival in gastric carcinoma patients. The question remains whether postoperative chemoradiotherapy can improve overall survival in patients with esophageal carcinoma. Our planning study was to investigate the role of postoperative chemoradiotherapy in the multimodality treatment for locally advanced esophageal carcinoma. Methods: From October 2000 to October 2007, Fifty-two patients who underwent esophagectomy with stage II-III esophageal carcinoma were enrolled. All patients received 50Gy of postoperative radiotherapy over 25 fractions in 5 weeks. Two cycles of chemotherapy (Paclitaxel 135mg/m2 d1,cisplatin 20mg/m2d1–3) were administered concurrently on days 1–3 and days 29–31 of radiotherapy. Results: Of the total 52 patients, 28 (54%) developed grade 3 or 4 toxicity.At the time of analysis, 23 patients died. The median follow-up for surviving patients was 23.5 months. The median survival time was 37.2 months. Incidences of tumor recurrence were 53.8 % (28/52) of patients. As expected, distant metastasis was predominant. The 2-year local-regional control survival, distant metastasis-free survival and relapse-free survival were 60.01%, 71.38% and 42.01%, respectively. 1-year and 3-year overall survival were 82.19% and 47.13%, respectively. Conclusions: This novel postoperative chemoradiation regimen for treatment of patients with stage II-III esophageal cancer has a tolerable toxicity and promising 3-year overall survival.

No significant financial relationships to disclose.

Effect of nominal stress on the long term friction, deformation and wear of native and glycosaminoglycan deficient articular cartilage

OBJECTIVES

Earlier in vitro studies have shown that the coefficient of friction (COF) of cartilage decreases with increasing load at the lower end of the physiological loading spectrum. At these lower load levels, depletion of glycosaminoglycans (GAGs) from native cartilage has been shown to elevate the COF levels. The current study evaluated the long-term friction, deformation and wear of native and GAG deficient cartilage at a wide range of physiological stress levels in vitro.

METHODS

A pin-on-plate machine (sliding velocity: 4 mm/s and stroke length: 4 mm) was used to measure the COF of native and GAG deficient cartilage at applied contact stress levels of 0.5 MPa, 2 MPa, and 3.15 MPa in 7h long friction tests with phosphate buffered saline (PBS) lubrication. The resultant deformation and wear of the cartilage samples due to the friction tests were measured using a height vernier apparatus and lubricant analysis respectively.

RESULTS AND CONCLUSIONS

An increase in contact stress from 0.5 MPa to 3.15 MPa resulted in an increase in the COF and wear of native cartilage samples, due to cartilage tissue's inability to rehydrate itself completely and maintain a high fluid load support at the 4 mm stroke length under high contact stress levels. There was no effect of increasing contact stress levels on the COF and wear of GAG deficient cartilage samples due to the very high deformations observed in these samples and the smoothening of their surfaces under the higher loads, leading to the development of conforming surfaces during articulation.

Evaluation of endoscopic-ultrasound-guided celiac ganglion irradiation with iodine-125 seeds: a pilot study in a porcine model

BACKGROUND AND STUDY AIMS

Implantation of iodine-125 ( (125)I) seeds under the guidance of endoscopic ultrasonography (EUS) has been proved to be a safe alternative treatment option for advanced pancreatic cancer. The main purpose of this study was to evaluate the feasibility and safety of EUS-guided radiation of the celiac ganglia with (125)I seeds in a porcine model.

METHODS

Twelve domestic pigs were randomly divided into three groups. The pigs in group A had blank seeds implanted, and groups B and C had 0.4 mCi and 0.8 mCi (125)I seeds implanted, respectively. Enhanced CT scan and 3-D vascular remodeling were used to check the location of the seeds. All animals were killed and celiac ganglia were checked at 14 and at 60 days after procedure. Necrosis and apoptosis in celiac ganglia and adjacent vessels and organs were also observed.

RESULTS

EUS-guided implantations of (125)I seeds in celiac plexus were successful at first procedure in 10 animals. The remaining two animals were implanted successfully the next day. No severe complications occurred in any animal and no damage was found in the surrounding organs. At day 60 after operation, the apoptotic index in the ganglia was 0.53 in the 0.4 mCi group and 0.94 in the 0.8 mCi group. No apoptotic cells were found in the control group implanted with blank seeds. Damage to vessels and surrounding organs by radioactive seeds was observed in only one pig at each time point.

CONCLUSION

EUS-guided implantation of (125)I seeds beside the celiac ganglia is a safe procedure and can induce apoptosis of local neurons. This new method may lead to an alternative treatment for pain accompanying pancreatic diseases in human.

Effects of metabolizable energy and lysine restrictions on growth performance, blood profiles, and expression of myostatin and leptin genes in broilers

To investigate the effects of metabolizable energy and lysine restriction on performance, and gene expression of leptin and myostatin, three hundred twenty day-old Ross broiler chicks were randomly allotted to four treatments. Birds were subjected to their respective diets comprising two levels of ME (3200; 2880 kcal kg-1) and two levels of lysine (1.10; 0.88%) during days 8 to 21. The dietary crude protein levels were reduced with the proportion to the lysine levels, while ratios of essential amino acids relative to lysine were similar for all diets. During restriction, weight gain, breast muscle and abdominal fat yield were lower in birds fed lysine-restricted diets. Relative myostatin mRNA abundance was increased in breast muscle of lysine-restricted birds, while expression of leptin mRNA in abdominal fat was downregulated by energy and lysine restriction. During realimentation, birds previously fed with energy and/or lysine-restricted diets had comparable performance as birds fed unrestricted diets. At day 42, energy and lysine restriction increased relative myostatin mRNA expression in breast muscle and birds previously fed diet restricted in both energy and lysine had the highest relative myostatin mRNA expression (energy × lysine interaction, P < 0.001). The relative leptin mRNA abundance was significantly lower in birds previously fed energy-restricted diets. These results indicated that early energy and lysine restriction from day 8 to 21 exhibited growth compensation during realimentation. In addition, myostatin and leptin mRNA expression in breast muscle and abdominal fat were modulated by nutritional treatments and were closely associated with changes in breast muscle yield and abdominal fat deposition. Key words: Metabolizable energy, lysine, myostatin, leptin, broiler

Abundant expression of CXCL9 (MIG) by stromal cells that include dendritic cells and accumulation of CXCR3+ T cells in lymphocyte-rich gastric carcinoma

The neoplastic environment is generally regarded as an immunosuppressive milieu. However, a group of cancers are characterized by the abundance of tumour-infiltrating lymphocytes (TILs). Here we examined the possible roles of chemokines in the formation of lymphoid stroma in lymphocyte-rich gastric carcinomas (GCs), including EBV(+) cases and conventional GCs. Regardless of EBV positivity, TILs in lymphocyte-rich GCs predominantly expressed CXCR3, while its ligand CXCL9 was abundantly expressed by stromal cells and a portion of cancer cells. CXCL9(+) stromal cells were judged to include dendritic cells, because they partly co-expressed fascin, DC-sign, CD83, DC-lamp or HLA-DR. T cells in close contact with CXCL9(+) cells showed frequent labelling of Ki-67 (approximately 10%), suggesting the immunostimulatory activity of CXCL9(+) stromal cells. The T-cell zone of the regional lymph nodes of lymphocyte-rich GCs also abounded with CXCR3(+) T cells and CXCL9(+) stromal cells. This indicated a close similarity between cancer stroma and regional lymph nodes of lymphocyte-rich GCs. Quantitative RT-PCR also confirmed the strong expression of CXCR3, CXCL9 and IFNgamma in lymphocyte-rich GCs. In contrast, conventional GCs contained less abundant CXCR3(+) T cells and few CXCL9(+) stromal cells. Collectively, the CXCL9-CXCR3 axis plays a pivotal role in the formation of lymphoid stroma in lymphocyte-rich GCs. Given similar findings in the regional lymph nodes, the lymphoid stroma of lymphocyte-rich GCs may represent a tertiary lymphoid tissue with predominantly Th1-shifted immune responses.