Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel.

Human adipose-derived stromal cells (hASCs) are widely known for their immunomodulatory and anti-inflammatory properties. This study proposes a method to protect cells during and after their injection by encapsulation in a hydrogel using a droplet millifluidics technique. A biocompatible, self-hardening biomaterial composed of silanized-hydroxypropylmethylcellulose (Si-HPMC) hydrogel was used and dispersed in an oil continuous phase. Spherical particles with a mean diameter of 200 µm could be obtained in a reproducible manner. The viability of the encapsulated hASCs in the Si-HPMC particles was 70% after 14 days in vitro, confirming that the Si-HPMC particles supported the diffusion of nutrients, vitamins, and glucose essential for survival of the encapsulated hASCs. The combination of droplet millifluidics and biomaterials is therefore a very promising method for the development of new cellular microenvironments, with the potential for applications in biomedical engineering.

Clinical and economic evaluation of ambulatory endovascular treatment of peripheral arterial occlusive lesions.

BACKGROUND: Ambulatory management of patients is an alternative to conventional hospitalization. In this study we evaluate the results of a prospective cohort study of patients receiving ambulatory endovascular treatment for peripheral arterial lesions. METHODS: From June 2008 to October 2010, ambulatory management was proposed for endovascular treatment of peripheral arterial lesions. An arterial closure device (Angio-Seal(®); St. Jude Medical) was used. For ambulatory treatment, patients were prohibited from driving a vehicle at discharge, had to be accompanied the first night after the procedure, had to live <1 hour from a medical facility, had to be reachable by telephone the day after the intervention, and had to remain hospitalized in the event of a complication. The principal criterion was morbimortality at 1 month. Secondary criteria were clinical improvement, patency, complications related to the arterial closure, and costs evaluation at 1 month. RESULTS: Forty-five patients were included and 50 ambulatory procedures were carried out. The patients presented with claudication (92%) or a critical ischemia (8%) of the lower extremities. All procedures were carried out by femoral puncture (retrograde in 94% and anterograde in 6% of the cases). The patients presented with iliac (68%) and femoropopliteal (64%) lesions. Lesions included stenoses (70%), thromboses (16%), and intrastent restenoses (14%). The rate of failure of ambulatory hospitalization was 16% (n = 8) without a serious undesirable event: 2 patients were hospitalized after a surgical conversion for iliac rupture and disinsertion of stent; 3 patients developed a hematoma during the intervention at the point of puncture; and in 3 cases the system of percutaneous closure failed. The mean duration of hospitalization was 1.36 ± 1.33 days. At 1 month, clinical improvement was observed in 97.5% of cases, with a primary patency of 100%. No perioperative rehospitalization or puncture site complications were observed. Ambulatory management made it possible to save 42 days of hospitalization, with associated costs of 10,971€, compared with conventional hospitalization. The additional costs related to use of the Angio-Seal amounted to 7427€. CONCLUSION: Ambulatory endovascular treatment of patients presenting with peripheral arterial lesions is reliable and effective and may contribute to savings in healthcare spending.

Use of clinical biological tests of haemostasis to evaluate topical haemostatics.

INTRODUCTION: In addition to traditional means, topical haemostatics are currently used to avoid haemorrhage during surgery. Although they have been reported to be effective, there is a low level of proof of their clinical efficacy, which is at odds with their levels of use. This study used two methods to better understand their in vitro mechanism of action. METHODS: Two clinical biology assays were used to measure the action of topical haemostatics on primary and secondary haemostasis. Calibrated samples of collagen sponges and polypropylene non-woven gauze were tested. Platelet aggregation was assessed using a multichannel aggregometer. A thrombin generation assay (TGA) was used with a fluorogenic readout. Tissue factor solutions were used to activate coagulation. RESULTS: In terms of primary haemostasis, collagen sponges stimulated platelet aggregation, in particular between 2 and 5 min after incubation with platelet-rich plasma and with no dose effect. In regard to coagulation, the kinetics of thrombin generation was enhanced. Polypropylene non-woven gauze did not exhibit any effect on platelet aggregation, although it did have a weak effect on the kinetics of thrombin generation. CONCLUSION: Collagen is well known to exert a haemostatic effect due to its action on platelet aggregation. By contrast, polypropylene non-woven gauze has not been shown to have any effect on platelet aggregation other than a minor impact on thrombin generation. The results obtained with the devices tested are in agreement with the literature. Platelet aggregation biological assays and TGA measurements appear to be suitable for evaluation of these medical products.

Development of a DNA damage-induced senescence model in osteoarthritic chondrocytes.

Senescent cells (SnCs) have been described to accumulate in osteoarthritis (OA) joint tissues in response to injury, thereby participating in OA development and progression. However, clinical therapeutic approaches targeting SnCs using senolysis, although promising in preclinical OA models, have not yet proven their efficacy in patients with knee OA. This pitfall may be due to the lack of understanding of the mechanisms underlying chondrocyte senescence. Therefore, our study aimed to generate models of chondrocyte senescence. This study used etoposide, to induce DNA damage-related senescence or chronic exposure to IL-1ß to entail inflammation-related senescence in human OA chondrocytes. Several hallmarks of cellular senescence, such as cell cycle arrest, expression of cyclin-dependent kinase inhibitors, DNA damages, and senescence-associated secretory profile were evaluated. Chronic exposure to IL-1ß induces only partial expression of senescence markers and does not allow us to conclude on its ability to induce senescence in chondrocytes. On the other hand, etoposide treatment reliably induces DNA damage-related senescence in human articular chondrocytes evidenced by loss of proliferative capacity, DNA damage accumulation, and expression of some SASP components. Etoposide-induced senescence model may help investigate the initiation of cellular senescence in chondrocytes, and provide a useful model to develop therapeutic approaches to target senescence in OA.

Assay of in vitro osteoclast activity on dentine, and synthetic calcium phosphate bone substitutes.

Resorption of synthetic bone substitute materials is essential for the integration of these materials into the natural bone remodeling process. Osteoclast behavior in the presence of calcium phosphate bioceramics (CaPB) is partially understood, and a better understanding of the underlying mechanisms is expected to facilitate the development of new synthetic bone substitutes to improve bone regeneration. In the present study, our aim was to investigate osteoclastic resorption of various synthetic CaPB. We used neonatal total rabbit bone cells to generate osteoclasts. Osteoclast-generated resorption on dentine and multiple CaPB was investigated by quantifying the surface resorbed and measuring tartrate resistant acid phosphatase (TRAP) enzyme activity. In this study, we observed that osteoclastic cells responded in a different way to each substrate. Both dentine and CaPB were resorbed but the quantitative results for the surface resorbed and TRAP activity showed a specific response to each substrate and that increased mineral density seemed to inhibit osteoclast activity.

Characterization of the age-dependent intervertebral disc changes in rabbit by correlation between MRI, histology and gene expression.

BACKGROUND: The present study was conducted to address whether the intervertebral disc of rabbit could be considered (i) as a valuable model to provide new insights into the tissue and cellular changes of Nucleus pulposus aging and (ii) as an appropriate tool to investigate the efficacy of Nucleus pulposus cell-based biotherapies. METHODS: Lumbar intervertebral disc from rabbits with increasing ages (1, 6 and 30 month-old) were compared by MRI and histological observation using Pfirrmann's grading and Boos' scoring respectively. The expression of transcripts (COL2A1, AGC1, COL1A1, MMP13, BMP2, MGP and p21) in Nucleus pulposus cells were analysed by quantitative real-time PCR. RESULTS: MRI analysis indicated an early age-dependent increase in the Pfirrmann's grading. Histological Boos' scoring was also increased. The analysis of transcript expression levels showed that COL2A1 and AGC1 were down-regulated as a function of age. Conversely, COL1A1, MMP-13, BMP-2, MGP and p21 were significantly up-regulated in the Nucleus pulposus cells of aged rabbit intervertebral disc. CONCLUSIONS: Our study describes the consistency of the rabbit as a model of intervertebral disc changes as a function of age by correlating tissue alteration with cellular modification measured.

Public Health Impact of Using Biosimilars, Is Automated Follow up Relevant?

Biologic reference drugs and their copies, biosimilars, have a complex structure. Biosimilars need to demonstrate their biosimilarity during development but unpredictable variations can remain, such as micro-heterogeneity. The healthcare community may raise questions regarding the clinical outcomes induced by this micro-heterogeneity. Indeed, unwanted immune reactions may be induced for numerous reasons, including product variations. However, it is challenging to assess these unwanted immune reactions because of the multiplicity of causes and potential delays before any reaction. Moreover, safety assessments as part of preclinical studies and clinical trials may be of limited value with respect to immunogenicity assessments because they are performed on a standardised population during a limited period. Real-life data could therefore supplement the assessments of clinical trials by including data on the real-life use of biosimilars, such as switches. Furthermore, real-life data also include any economic incentives to prescribe or use biosimilars. This article raises the question of relevance of automating real life data processing regarding Biosimilars. The objective is to initiate a discussion about different approaches involving Machine Learning. So, the discussion is established regarding implementation of Neural Network model to ensure safety of biosimilars subject to economic incentives. Nevertheless, the application of Machine Learning in the healthcare field raises ethical, legal and technical issues that require further discussion.

Identification of phenotypic discriminating markers for intervertebral disc cells and articular chondrocytes.

OBJECTIVE: The present study was conducted to improve our knowledge of intervertebral disc (IVD) cell biology by comparing the phenotype of nucleus pulposus (NP) and annulus fibrosus (AF) cells with that of articular chondrocytes (ACs). METHODS: Rabbit cells from NP and AF were isolated and their phenotype was compared with that of AC by real-time PCR analysis of type I (COL1A1), II (COL2A1) and V (COL5A1) collagens, aggrecan transcript (AGC1), matrix Gla protein (MGP) and Htra serine peptidase 1 (Htra1). RESULTS: Transcript analysis indicated that despite certain similarities, IVD cells exhibit distinct COL2A1/COL1A1 and COL2A1/AGC1 ratios as compared with AC. The expression pattern of COL5A1, MGP and Htra1 makes it possible to define a phenotypic signature for NP and AF cells. CONCLUSIONS: Our study shows that NP and AF cells exhibit a clearly distinguishable phenotype from that of AC. Type V collagen, MGP and HtrA1 could greatly help to discriminate among NP, AF and AC cells.

In vitro cytotoxic effects of secondary metabolites of DEHP and its alternative plasticizers DINCH and DINP on a L929 cell line.

BACKGROUND: Phthalic acid esters are widely used to improve the plasticity of PVC in medical devices (MD). The most famous plasticizer is DEHP, whose use in medical devices has been contested by the European authorities since 2008. Several alternative plasticizers are being considered to replace DEHP, such as DEHT, TOTM, DINP or DINCH, but they are also released from the PVC throughout their life cycle and are metabolized in the same way as DEHP. OBJECTIVES: Our study focuses on the in vitro cytotoxicity of two alternative plasticizers (DINCH and DINP) contained in certain medical devices. They are likely to migrate and be transformed in vivo into the primary and secondary metabolites by a metabolism similar to that of DEHP. This preliminary study is the first to assess the in vitro cytotoxicity of oxidized metabolites of DINCH and DINP based on the EN ISO 10-993-5 standards documents. METHODS: We have studied the complete multi-step organic synthesis of secondary metabolites of DINP and DINCH and have performed cytotoxicity tests on L929 murine cells according to the EN ISO 10993-5 standard design for the biocompatibility of a MD. The tested concentrations of obtained metabolites (0.01, 0.05 and 0.1 mg/mL) covered the range likely to be found for DEHP (total metabolism) in biological fluids coming into direct contact with the MD. The concentrations tested in our study were chosen based on a complete transformation of the plasticizers released after direct contact between a MD and the patient's blood. RESULTS: Only 7-oxo-MMeOCH is cytotoxic at the highest concentration (0.1 mg/mL) after 7 days of exposure, just like 5-oxo-MEHP for the same concentration. By contrast, 7-OH-MMeOP, 7-cx-MMeOP, 7-oxo-MMeOP, 7-OH-MMeOCH and 7-cx-MMeOCH were not found to be cytotoxic. CONCLUSION: The known concentrations of these secondary metabolites in urinary samples are in the µg/L range, i.e. about 100-1000 times lower than the concentrations tested in this study. Cytotoxicity is known to be dose-dependent but it is not always the case for endocrine perturbations and the secondary metabolites could induce endocrine perturbations at very low doses.

Is the MitraClip® procedure profitable in a high-volume French hospital?

BACKGROUND: Mitral regurgitation is the second most frequent valvulopathy managed by surgery in Europe. For patients who have a contraindication to surgery or a high surgical risk, the percutaneous MitraClip® implantation procedure has emerged as a favourable alternative approach, but elevated procedural costs are a medicoeconomic concern. AIM: The objective of this study was to evaluate whether the MitraClip® procedure is profitable in a high-volume French hospital. METHODS: Patients eligible for mitral valve repair with a MitraClip® device, and covered by the French National Health Service, were included retrospectively in this single-centre study between September 2016 and June 2018. Subgroups were considered based on medicoeconomic severity level. The study primary endpoint was the difference between hospital costs and revenues, calculated for each patient. Secondary endpoints included profit based on severity level, breakdown of costs and adverse events during hospitalization. RESULTS: Twenty-two patients were included in the study. The mean hospital cost and revenue were €30,039±2476 and €30,331±2720 per patient, respectively, resulting in a profit of €292±2039 per patient. The total estimated profit was €6429 for the whole study period. The largest benefits were observed for patients assigned to the higher medicoeconomic severity levels (levels 2 and 3). Profit increased following a reduction in the device cost (€1136±2415 per patient). The price of the device represented 78% of the total costs. CONCLUSIONS: Percutaneous MitraClip implantation is a financially neutral procedure for a French university hospital, but this depends on patient severity level.

A comparative profitability analysis of transcatheter versus surgical aortic valve replacement in a high-volume French hospital.

BACKGROUND: Current scientific guidelines have extended the indication for transcatheter aortic valve replacement (TAVR) to patients who present an intermediate risk for surgery and have been so far considered for conventional surgery. We previously demonstrated that the TAVR procedure generated profits despite elevated costs, but comparison with surgery has not been performed. The objective of this study was to assess the profitability of the TAVR procedure compared with conventional surgery in a high-volume French hospital. Consecutive patients eligible for transfemoral TAVR or surgical aortic valve replacement (SAVR) were included retrospectively in this single-centre study between September 2014 and December 2015. The primary endpoint was the profitability of each procedure (defined as the ratio between the profit and total revenues), calculated for each patient. Secondary composite endpoints included major adverse events in the 30 days following procedure and breakdown of costs. RESULTS: Two hundred and thirty-eight patients were included in the TAVR group and 341 in the SAVR group. TAVR patients presented higher operative risk scores and more comorbidities. Compared with SAVR, TAVR was associated with higher profits (€2732 ± 1768 per patient vs. €2177 ± 2437 per patient, P < 0.001) but also higher costs (€27,778 ± 4961 vs. €17,813 ± 6071, P < 0.001) resulting in lower profitability (9.3 ± 5.7% vs. 11.7 ± 10.1%, P < 0.001). The price of the bioprosthesis represented 70% of the TAVR total cost. CONCLUSIONS: TAVR performed in carefully selected patients was associated with higher profits than SAVR, but also higher costs resulting in lower profitability.

Is transcatheter aortic valve replacement a profitable procedure in a high-volume French hospital?

BACKGROUND: Transcatheter aortic valve replacement (TAVR) has revolutionized the prognosis of inoperable patients with severe aortic valve stenosis. Yet, the implantation of expensive prostheses in patients with comorbidities may be questionable in an era when healthcare costs are becoming a major concern. AIM: The objective of this study was to assess whether the TAVR procedure is profitable in a high-volume French hospital. METHODS: Consecutive patients eligible for transfemoral TAVR using the SAPIEN bioprostheses (Edwards Lifesciences, Irvine, CA, USA) were included retrospectively in this single-centre study between September 2014 and December 2015. Three medicoeconomic severity-level subgroups were considered. The primary clinical endpoint was the difference between hospital costs and revenues, calculated for each patient. Secondary composite endpoints included major adverse events within 30 days and breakdown of costs. RESULTS: Overall, 189 patients were included in the analysis. Three patients died (two from non-cardiac causes) within 30 days of the procedure. The mean hospital cost was €27,530±3814 per patient, and the mean hospital income was €30,313±2681 per patient (P<0.001), resulting in a significant profit of €2783±1743 per patient. The total estimated profit was €525,000 for the whole study period. The largest benefits were observed for patients assigned to the lowest severity level. The price of the bioprosthesis represented 71% of the total costs. CONCLUSIONS: The TAVR procedure performed in carefully selected patients was profitable for the academic centre, regardless of the level of severity assigned to the patients.

Patients' exposure to PVC plasticizers from ECMO circuits.

BACKGROUND: ECMO is a therapeutic act with a high risk of exposure to diethylhexylphthalate (DEHP), plasticizer from PVC tubings. The replacement of this plasticizer with alternative compounds is recommended but the risks associated with the use of new plasticizers have not been evaluated in ECMO situations. METHODS: Ex vivo ECMO models were performed with different flow rates over 6 days to evaluate the migration of plasticizers and their potential toxic risk for patient. The release of plasticizers during ECMO was measured and compared to reference value (derived no effect level, DNEL) and to cytotoxic concentration carried out with MTT test. RESULTS: Trioctyltrimellitate (TOTM), main plasticizer present in circuit (44% w/w), is weakly released during ECMO. Concentrations are not cytotoxic and exposure doses are lower than DNEL. In contrast, DEHP doses are higher than the DNEL despite a lower presence of DEHP in the circuit (0.2%). We have shown that DEHP is not coming from the circuit but from the priming bag. Replacing this bag with a multilayer one avoids the exposure to DEHP. CONCLUSION: Our study shows that circuits made of PVC plasticized with TOTM against DEHP improves the safety of ECMO.

The affordability of minimally invasive procedures in major lung resection: a prospective study.

OBJECTIVES: Minimally invasive procedures are used for the surgical treatment of lung cancer. Two techniques are proposed: video-assisted thoracic surgery or robotic-assisted thoracic surgery. Our goal was to study the economic impact of our long-standing program for minimally invasive procedures for major lung resection. METHODS: We conducted a single-centre, 1-year prospective cost study. Patients who underwent lobectomy or segmentectomy were included. Patient characteristics and perioperative outcomes were collected. Medical supply expenses based on the microcosting method and capital depreciation were estimated. Total cost was evaluated using a national French database. RESULTS: One hundred twelve patients were included, 57 with and 55 without robotic assistance. More segmentectomies were performed with robotic assistance. The median length of stay was 5 days for robotic-assisted and 6 days for video-assisted procedures (P = 0.13). The duration of median chest drains (4 days, P = 0.36) and of operating room time (255 min, P = 0.55) was not significantly different between the groups. The overall conversion rate to thoracotomy was 9%, significantly higher in the video-assisted group than in the robotic group (16% vs 2%, P = 0.008). No difference was observed in postoperative complications. The cost of most robotic-assisted procedures ranged from €10 000 to €12 000 (median €10 972) and that of most video-assisted procedures ranged from €8 000 to €10 000 (median €9 637) (P = 0.007); median medical supply expenses were €3 236 and €2 818, respectively (P = 0.004). The overall mean cost of minimally invasive techniques (€11 759) was significantly lower than the mean French cost of lung resection surgical procedures (€13 424) (P = 0.001). CONCLUSIONS: The cost at our centre of performing minimally invasive surgical procedures appeared lower than the cost nationwide. Robotic-assisted thoracic surgery demonstrated acceptable additional costs for a long-standing program.

Biomaterial-assisted cell therapy in osteoarthritis: From mesenchymal stem cells to cell encapsulation.

Osteoarthritis (OA) is a degenerative and inflammatory joint disease that affects the cartilage, subchondral bone, and joint tissues. Although current drug therapies can provide a degree of symptomatic relief from pain, they fail to prevent joint damage. Mesenchymal stem/stromal cells (MSCs) have generated significant interest in terms of medical applications because they exert their therapeutic properties by secretion of bioactive factors that have potent immunomodulatory, antiapoptotic, antifibrotic, and anti-inflammatory effects. However, intra-articular injection of MSCs has major limitations including cell death upon injection and massive leakage from the injection site. Encapsulation of MSCs has therefore been developed as a way to overcome these limitations and to deliver therapeutic bioactive factors in several pathologies. In this review, we first briefly highlight the main therapeutic properties of MSCs and their applications in OA treatment. We then focus on MSC encapsulation and the current advances this strategy offers for the treatment of OA.

Polysaccharide Hydrogels Support the Long-Term Viability of Encapsulated Human Mesenchymal Stem Cells and Their Ability to Secrete Immunomodulatory Factors.

While therapeutically interesting, the injection of MSCs suffers major limitations including cell death upon injection and a massive leakage outside the injection site. We proposed to entrap MSCs within spherical particles derived from alginate, as a control, or from silanized hydroxypropyl methylcellulose (Si-HPMC). We developed water in an oil dispersion method to produce small Si-HPMC particles with an average size of about 68 µm. We evidenced a faster diffusion of fluorescein isothiocyanate-dextran in Si-HPMC particles than in alginate ones. Human adipose-derived MSCs (hASC) were encapsulated either in alginate or in Si-HPMC, and the cellularized particles were cultured for up to 1 month. Both alginate and Si-HPMC particles supported cell survival, and the average number of encapsulated hASC per alginate and Si-HPMC particle (7102 and 5100, resp.) did not significantly change. The stimulation of encapsulated hASC with proinflammatory cytokines resulted in the production of IDO, PGE2, and HGF whose concentration was always higher when cells were encapsulated in Si-HPMC particles than in alginate ones. We have demonstrated that Si-HPMC and alginate particles support hASC viability and the maintenance of their ability to secrete therapeutic factors.

In vitro cytotoxic effects of DEHP-alternative plasticizers and their primary metabolites on a L929 cell line.

Phthalic acid esters have been widely used to improve the plasticity of PVC medical devices. They carry a high exposure risk for both humans and the environment in clinical situations. Our study focuses on the cytotoxicity of alternative plasticizers. Postulated primary metabolites were synthesized, not being commercially available. Cytotoxicity assays were performed on L929 murine cells according to the ISO-EN 10993-5 standard design for the biocompatibility of medical devices. The tested concentrations of plasticizers (0.01, 0.05 and 0.1 mg/ml) covered the range likely to be found in biological fluids coming into direct contact with the medical devices. DEHP, DINP and DINCH were cytotoxic at the highest concentration (0.1 mg/ml) for 7 days of exposure. Their corresponding metabolites were found to be more cytotoxic, for the same concentration. By contrast, TOTM and its corresponding metabolite MOTM were not found to be cytotoxic. DEHA showed no cytotoxicity, but its corresponding monoester (MEHA) produced a cytotoxic effect at 0.05 mg/ml. In clinical situations, medical devices can release plasticizers, which can come into contact with patients. In vivo, the plasticizers are quickly transformed into primary metabolites. It is therefore important to measure the effects of both the plasticizers and their corresponding metabolites. Standard first-line cytotoxicity assays should be performed to ensure biocompatibility.

Quantitative and reliable in vitro method combining scanning electron microscopy and image analysis for the screening of osteotropic modulators.

The increased generation and up-regulated activity of bone resorbing cells (osteoclasts) play a part in the impairment of bone remodeling in many bone diseases. Numerous drugs (bisphosphonates, calcitonin, selective estrogen receptor modulators) have been proposed to inhibit this increased osteoclastic activity. In this report, we describe a pit resorption assay quantified by scanning electron microscopy coupled with image analysis. Total rabbit bone cells with large numbers of osteoclasts were cultured on dentin slices. The whole surface of the dentin slice was scanned and both the number of resorption pits and the total resorbed surface area were measured. Resorption pits appeared at 48 h and increased gradually up to 96 h. Despite the observation of a strong correlation between the total resorption area and the number of pits, we suggest that area measurement is the most relevant marker for osteoclastic activity. Osteotropic factors stimulating or inhibiting osteoclastic activity were used to test the variations in resorption activity as measured with our method. This reproducible and sensitive quantitative method is a valuable tool for screening for osteoclastic inhibitors and, more generally, for investigating bone modulators.

Novel biomaterials for bisphosphonate delivery.

One type of gem-bisphosphonate (Zoledronate) has been chemically associated onto calcium phosphate (CaP) compounds of various compositions. For that purpose, CaP powders of controlled granulometry have been suspended in aqueous Zoledronate solutions of variable concentrations. Using mainly (31)P NMR spectroscopy, two different association modes have been observed, according to the nature of the CaP support and/or the initial concentration of the Zoledronate solution. beta-tricalcium phosphate (beta-TCP) and mixtures of hydroxyapatite and beta-TCP (BCPs) appear to promote Zoledronate-containing crystals formation. On the other hand, at concentrations <0.05 mol l(-1) CDAs (calcium deficients apatites) seem to undergo chemisorption of the drug through a surface adsorption process, due to PO(3) for PO(4) exchange, that is well described by Freundlich equations. At concentrations >0.05 mol l(-1), crystalline needles of a Zoledronate complex form onto the CDAs surface. The ability of such materials to release Zoledronate, resulting in the inhibition of osteoclastic activity, was shown using a specific in vitro bone resorption model.

A cost-minimization analysis in minimally invasive spine surgery using a national cost scale method.

INTRODUCTION: The last decade has seen the emergence of minimally invasive spine surgery. However, there is still no consensus on whether percutaneous osteosynthesis (PO) or open surgery (OS) is more cost-effective in treatment of traumatic fractures and degenerative lesions. The objective of this study is to compare the clinical results and hospitalization costs of OS and PO for degenerative lesions and thoraco-lumbar fractures. METHODS: This cost-minimization study was performed in patients undergoing OS or PO on a 36-month period. Patient data, surgical and clinical results, as well as cost data were collected and analyzed. The financial costs were calculated based on diagnosis related group reimbursement and the French national cost scale, enabling the evaluation of charges for each hospital stay. RESULTS: 46 patients were included in this cost analysis, 24 patients underwent OS and 22 underwent PO. No significant difference was found between surgical groups in terms of patient's clinical features and outcomes during the patient hospitalization. The use of PO was significantly associated with a decrease in Length Of Stay (LOS). The cost-minimization revealed that PO is associated with decreased hospital charges and shorten LOS for patients, with similar clinical outcomes and medical device cost to OS. CONCLUSIONS: This medico-economic study has leaded to choose preferentially the use of minimally invasive surgery techniques. This study also illustrates the discrepancy between the national health system reimbursement and real hospital charges. The medico-economic is becoming critical in the current context of sustainable health resource allocation.