Anissa Chaibi
email: anissa.chaibi@ipag.fr

Adel Ben Youssef
email: adel.ben-youssef@unice.fr

Leila Peltier-Ben Aoun

E-Skills, Brains And Performance Of The Firms: ICT And Ability Of Firms To Conduct Successful Projects In Luxembourg

Keywords: Innovation, Usage of ICT, Depth of ICT adoption, Ordered models, Innovative projects. JEL Classification: L21, O31, O33

This paper provides original empirical evidence on the causal links between e-skills, usage of Information and Communication Technologies (ICT) and firm's performance using a sample of Luxembourgian manufacturing and services firms. Firm performance is measured in terms of innovation (success of new projects settled). Our main findings are: (i) there's no relationship between the absorptive technology capacity of the firm (measured by ICT staff and Training) and the probability of the implementation of successful ICT projects, (ii) there is a positive effect of e-applications usage (ICT usage) on the probability of the implementation of successful new projects, and (iii) there is an asymmetric effect of usage of e-commerce and eadministration confirming findings of the recent literature.

INTRODUCTION

There is an increasing evidence on the fact that information and communication technologies (ICT) are fostering the international innovation at the macroeconomic level [START_REF] Cardona | The contribution of ICT to productivitykey conclusions from surveying the empirical literature[END_REF][START_REF] Baquero | Mobile communication networks and Internet technologies as drivers of technical efficiency improvement[END_REF] and the implementation of innovative projects by firms at the micro-economic level (Bertschek et al. 2013[START_REF] Colombo | ICT services and small businesses' productivity gains: An analysis of the adoption of broadband Internet technology[END_REF], Ben Youssef et al. 2012a[START_REF] Ben Youssef | Intra-firm diffusion of innovation: Evidence from Tunisian SME's regarding Information and Communication Technologies[END_REF], Peltier-Ben AounandVincente Cuervo 2011). ICT have the potential to induce several structural changes inside the firm such as increasing its labour productivity, increasing its total factor productivity, modifying its internal organisation, changing of employees' behaviour and contextual performances, linking the firms to networks of knowledge and innovation and increase their ability to innovate.

First generations of ICT have played a major role in these changes. However, their innovative outcomes were contingent to the capacity of the firm to have the needed complementary assets like "brains" (human capital). Several papers have shown that ICT are complementary to human capital, technological absorptive capacity of the firm (Hollenstein and Worter, 2008[START_REF] Bellon | The missing link between adoption and usage of ICT in the south Mediterranean countries[END_REF][START_REF] Basant | ICT Adoption and Productivity in Developing Countries: New Firm Level Evidence from Brazil and India[END_REF]) and organizational change [START_REF] Bresnahan | Information Technology, Workplace Organization and the Demand for Skilled Labor: Firm-Level Evidence[END_REF][START_REF] Bertschek | Productivity effects of organizational change: microeconometric evidence[END_REF], Arvinatis and Loukis, 2009).

The picture seems changing nowadays and the latest generations of ICT are cheaper, have better output elasticity [START_REF] Cardona | The contribution of ICT to productivitykey conclusions from surveying the empirical literature[END_REF], more impact on the productivity of the firm (Engelstätter andSirbu, 2013, Colombo et al. 2013), better customized to the needs of the firms and have deeper impact on the firms' innovation capacity (Bertschek et al. 2013). Cloud computing is a perfect example of this radical change in the scope and purpose of the new ICT with powerful impact on productivity and innovation. This paper contributes to the existing literature by providing original empirical evidence on the causal link between the innovative performance of the firm and human capital (ICT skills, e-skills) and usage of e-applications (ICT) using a sample of Luxembourgian manufacturing and services firms. The new waves of technologies make it easier to use intensively ICTs and to catch more easily the innovation spillovers than in the past. Firms are engaging more efficiently in innovation and are implementing more successfully their projects.

The dataset stems from the 2008 survey on Information and Communication Technologies (ICT) Usage and e-Commerce in Enterprises in the case of Luxembourg (STATEC) in order to explore our hypothesis. We have only considered the firms that have implemented a new ICT project in the last two years (2006)(2007)(2008). This leads to a sample size of 916 firms (1,305 firms if weighted). We use an Ordered Logit Model [START_REF] Greene | Econometric Analysis, Sixth Edition[END_REF] estimated by maximum likelihood in order to examine the intensity of success of a new ICT project.

The paper provides two main results. First, our econometric analysis shows absence of correlation between the success of implementation of a project by the firm and the ICT absorptive capacity. Last waves of ICT seem less e-skills consuming. Second, the impact of e-applications use on the success of implementation of a new project by the firm is well established for several applications like e-selling, e-banking and e-administration. However, the relation is not established for all the applications. Moreover, firms seem using differently the different sides of the applications.

The paper is organized as follows. Section 2 summarizes the related literature and examines some of the firms' features that, in the rest of the paper, will be used as explanatory variables of ICT use. Section 3 presents the sample's characteristics and introduces our econometric approach. Section 4reports and discusses the results. Finally, section 5concludes.

Background discussion and hypothesis

In this section we provide a brief discussion of the main channels through which new waves of ICT can modify the innovation ability of the firm. We discuss then the three hypotheses that will be tested.

An increasing intensity of ICT usage by firms

The intensity of usage of ICT has significant impact on firm's performance. Asterbo (2004) has claimed the needs for scholars to focus more on intensity of usage (depth of adoption) and less on adoption of ICT itself. In fact the intensity of usage reveals how people are engaging in better coordination, more efficient production systems, more flexible practices within the firms, and management of more innovative projects. As the intensity of usage increases, the associated benefits increase.

The new waves of ICT have changed radically the intensity of use of these technologies. New waves of ICT are associated with an increase in the capacity of the bandwidth allowing the use of more advanced Internet usages to the firms. Several papers have showed that Broadband is associated with better economic performance to the firms [START_REF] Colombo | ICT services and small businesses' productivity gains: An analysis of the adoption of broadband Internet technology[END_REF]. For example, Bertschek et al. (2013) found that broadband Internet enabled firms to reorganize and reshape their business processes and to improve their products or services. This innovation activity induced by broadband usage may have been translated into productivity gains in later periods. [START_REF] Polder | Product, Process and Organizational Innovation: Drivers, Complementarity and Productivity Effects[END_REF] take a firm-level perspective to analyze the role of ICT and R&D for innovation success and productivity of Dutch firms. They find that the use of broadband Internet is particularly important for services firms where broadband is positively related to product and process innovation as well as to organizational innovation. By contrast, in the manufacturing sector, broadband is significant only for product and organizational innovation. For process innovation it is rather e-commerce that plays a significant role.

Complementary assets are less needed

Implementation and use of first generations of ICT were not associated necessarily with observed performance' improvement at the firm level. This fact was explained mainly by lack of adoption of new organizational practices [START_REF] Bresnahan | Information Technology, Workplace Organization and the Demand for Skilled Labor: Firm-Level Evidence[END_REF], lack of technological absorptive capacity of these technologies [START_REF] Hollenstein | The determinants of the adoption of information and communication technologies (ICT). An empirical analysis based on firm-level data for the Swiss business sector[END_REF][START_REF] Bellon | The missing link between adoption and usage of ICT in the south Mediterranean countries[END_REF]) and lack of e-skills [START_REF] Ben Youssef | The complementarities between ICT Use, New Organizational Practices and Workers Contextual Performance: Evidence from Europe in 2005 and 2010[END_REF]). This effect is the main effect stressed by disequilibrium theory of innovation 1 adoption. The adoption of a given innovation or technology depends on the technological absorptive capacity built by the firm over time. The more the firm is able to absorb 1The first tradition is the epidemic models [START_REF] Mansfield | Intra-firm Rates of Diffusion of an Innovation[END_REF][START_REF] Mansfield | Industrial Research and Technological Innovation: An Economic Analysis[END_REF]. In this approach, it is assumed that the use of a innovation increases over time as the risk attached to further adoption is reduced through learning. Thus, it's assumed that the usage pattern is S shaped curve following a logistic curve.

the technology the more the depth of adoption is important. The accumulation of e-skills by the firm (The dedicated staff for ICT) and in general the average qualifications of the staff are considered as the main indicators for this absorptive capacity.

These problems seem to be partially solved by the newest generations of ICT, which are lowering the skills requirements and offering new possibilities for the firms. The newest waves of ICT have the potential to induce firms to more successful innovative process with less efforts and means. Firms are capitalizing on their experience in the management of last waves of technologies. Several contributions have shown and demonstrated that firms have built over the last two decades capabilities in matter of use of these technologies and as a consequence the impacts on the productivity and on the performances are more rapid and more visible.

One needs also to note that the ICT production providers are better taking into account the storage capacity constraints and security issues of the firms. Firms have non-limited storage capacities with the new Internet paradigm: Cloud computing. Taken together, the new waves of ICT are leading to more rapid impact on the performance of the firm than the last generations of ICTs and are fostering the ability of the firm to innovate and to set new projects successfully.

More selection of e-applications

Thousands of e-applications are available for citizens and firms nowadays through several rivalry platforms. Identification of the value-adding innovation (application) and its effective usage is a learning process. Economic literature has identified recently that innovation like e-commerce has several facets and firms may use them differently. Hollenstein and Heinz (2008) have demonstrated that the degree of diffusion of the two types of e-commerce strongly differs. Firms may value differently the real costs and benefits of them at each point of the time. In some cases, there is rationality to not use these technologies and in some case to use them less! Since then their effects also may differ in term of performance of the firms. This is also the case of e-administration, e-banking, e-training... Firms may adopt differently the services associated to these innovations. The technologies that are more adopted are expected to have deeper impact on productivity and performance.

Hypotheses

From the previous discussion we can formulate the following three hypotheses: Hypothesis 1:ICT need e-skills in order to improve the success to implement new projects.

This hypothesis discusses the absorptive capacity effect of new ICTs.

Hypothesis 2:Implementing successful projects depend on the intensity of usage of standard e-applications like e-banking, e-Commerce, e-administration…

Hypothesis 2 gives a clear argument in favour of equilibrium theory of intra-firm diffusion 2 of innovation and shows that the adoption of innovation is associated to expected returns.

Hypothesis 3: Implementing successful projects depend differently from one side or another of the e-applications.

This hypothesis tests the asymmetric adoption process observed recently in many countries. This observation confirms also the equilibrium theory since the adoption is only linked to the expected returns.

Database, sample characteristics and econometric model

Database

The data used in this study is the 2008 Survey on Information and Communication Technologies (ICT) Usage and e-Commerce in Enterprises in the case of Luxembourg (STATEC, 2006(STATEC, , 2007)). It contains information about ICT adoption and use and it includes valuable data on the type of competition faced by firms, which is a key factor to explain technological diffusion as indicated by Porter (1990). This dataset covers firms with at least 10 employees in manufacturing and services, except for financial activities 3 . We will only consider the firm whom has implemented a new ICT project in the last two years (2006)(2007)(2008). This leads to a sample size of 916 firms (1,305 firms if weighted).

Dependent variables

As mentioned above, in order to measure successful ICT projects we only consider firms who have implemented new ICT projects during the period 2006-2008 (period covered by the survey). The evaluation of the impact of this implementation is measured through a score. This score is groups 3 variables as follows:

RESS =1 if the implementation has moderate or significant impact on the release of resources in the firm, 0 otherwise. REV = 1 if the implementation has moderate or significant impact on the increase of the revenue of the firm, 0 otherwise. COST =1 if the implementation has moderate or significant impact on the reduction of the costs of communication in the firm, 0 otherwise. We will not make the assumption that one effect is better for the firm than another. Moreover, we will not distinguish between moderate impact and significant impact.

2Equilibrium theory of intra-firm diffusion suggests a non-linear and discontinuous diffusion pattern [START_REF] Karshenas | Technological diffusion[END_REF]. At each moment, technology use in time t will only extend to the point where the marginal expected profit gain from further adoption equals the cost of adoption (appropriately defined) of the new technology. Over time either the marginal gain and/or the cost of adoption may change and as they do so the level of use will change [START_REF] Battisti | The intra-firm diffusion of new process technology[END_REF] ».

3 Firms from financial sector are not concerned by the e-commerce part of the survey.

Indeed, due to the subjective value of the answer it is easy to understand that, what is considered as a moderate impact for one firm can be considered as a significant impact for another. Whereas, "feeling no impact" is considered as a common knowledge for every firm. We finally, only consider the binomial answer: "yes, I perceived" an effect or "No, I did not".

The dependent variable goes from the value 0 where the ICT project(s) implemented has(have) no impact on the previous possibilities to 3 where the ICT project(s) implemented has(have) an impact on all the previous possibilities. Thanks to the construction of the variable, it can be considered as an intensity of successful ICT projects. Due to the nature of our dependent variable we will use an ordered Logit model. In order to test the first hypothesis, we will consider that usage of Internet for training and educations as well as having IT personnel are the variables reflecting the e-skills component. They must have significant and positive impact on implementing successfully projects.

Independent

In order to test for the second hypothesis we consider the following practices as the e-applications reflecting the usage of new ICTs: use of Internet for banking services (E-banking), adoption of E-Commerce (e-selling or e-puchasing), Internet for treating an administrative procedure (E-administration). Our assumption suggests a positive and significant sign.

Finally, to test the last hypothesis two practices will be split. First, e-commerce distinguishing between e-selling and e-purchasing. Second, the e-administration will be derived in downloading procedures or uploading documents. We expect that the sign may be positive or negative and the significance is not found for the two side of the innovation.

Model Specification

The Ordered Logit Model (see [START_REF] Greene | Econometric Analysis, Sixth Edition[END_REF]) is a regression model for ordinal dependent variables. It can be thought of as an extension of the logistic regression model for dichotomous dependent variables, allowing for more than two (ordered) response categories 5 . The model cannot be consistently estimated using ordinary least squares; it is usually estimated using maximum likelihood.

The model is built around a latent regression in the same manner as the binomial Logit model. We begin with 𝑦 * = 𝑥 ′ 𝛽 + 𝜀 Where 𝑦 * is the exact but unobserved dependent variable (in our study the intensity of success of a new ICT project).

What we do observe is

𝑌 = 0 𝑖𝑓 𝑦 * ≤ 𝜇 1 1 𝑖𝑓 𝜇 1 ≤ 𝑦 * ≤ 𝜇 2 2 𝑖𝑓 𝜇 2 ≤ 𝑦 * ≤ 𝜇 3 3 𝑖𝑓 𝜇 3 ≤ 𝑦 * ≤ 𝜇 4
And we must have 0 ≤ 𝜇 1 ≤ 𝜇 2 ≤ 𝜇 3 for all the probabilities to be positive.

The 𝜇are unknown parameters to be estimated with 𝛽. The feelings on the intensity of the success of the ICT project depends on certain measurable factors𝑥 ′ and certain unobservable factors 𝜀. In principle, the firm could answer with their own 𝑦 * if asked to do so. Given only, four possible answers, they choose the cell that most closely represents their own feelings on the feeling. We then have

𝑃 𝑌 = 0 = 1 1 + exp (𝑌 𝑖-𝜇 1 ) 𝑃 𝑌 = 1 = 1 1 + exp (𝑌 𝑖-𝜇 2 ) - 1 1 + exp (𝑌 𝑖-𝜇 1 ) 𝑃 𝑌 = 2 = 1 1 + exp (𝑌 𝑖-𝜇 3 ) - 1 1 + exp (𝑌 𝑖-𝜇 2 ) 𝑃 𝑌 = 3 = 1 - 1 1 + exp (𝑌 𝑖-𝜇 3 )
5 The model only applies to data that meet the proportional odds assumption, that the relationship between any two pairs of outcome groups is statistically the same. This means that the coefficients that describe the relationship between, say, the lowest versus all higher categories of the response variable are the same as those that describe the relationship between the next lowest category and all higher categories, etc.Because the relationship between all pairs of groups is the same, there is only one set of coefficients.

Results

Descriptive Statistics

Table 1 gives a first outlook of our samples. We will not consider the size and economic activities representation, it will be discuss more deeply in table 3. Moreover, there is no significant difference from sample 1 and 2, so we will only comment sample1 (hereafter referenced as "sample" for ease to read).

Source: ICT survey 2008, STATEC, authors' calculation

About the general context on the market, we note that almost 40% of our sample is part of a group, and 90% have at least a national reputation. When considering the ICT equipment it appears that some technologies are fully adopted (Mail) or almost (Intranet), while some more specific and more recent are less diffused (e.g. Extranet, Visio or Video conference). Moreover, even if around 7 firms over 10 have introduced an Intranet, the number of services offered is on average around 2. So even if Luxembourgish firms are well equipped compared to the other EU countries there is still a gap to fill.

If we point our interest not anymore on ICT adoption but on ICT use the first descriptive results show some discrepancy. Firms use Internet first of all to benefit from banking and/or financial services. But it is still encouraging that a third of our sample uses Internet for training. Furthermore, almost all firms of our sample use Internet to obtain something (information, forms…) from public authorities. More than a half of our sample practices the automated exchange of data. The main reason to use this technology is to exchange information and then to receive or send orders, billing remaining the last motivation. Finally, we note that e purchasing is three times more widespread than e selling. We observe that as mentioned in the literature we cannot anymore consider ICT by their nature but we have to consider their uses. And it appears that the variety of use has deeply enlarged in these recent years.

Regarding the workforce in the firms, we observe that only 40% of these firms (who have implemented new ICT projects) employ ICT or IT specialists, but almost 70% of them declare resorting to external services to perform those ICT functions required for the firm. But when it comes to firm security, in 40% of the case they use internal resources to meet their needs and they are 66% of the firms that increase their employees' awareness of security issues.

All these first statistics show that, what we consider as determinant to explain the success of a new ICT project, i.e. the behavior of adoption and use are heterogeneous among our sample.

Table 2 shows the distribution of intensity score experienced by firms that have implemented new ICT projects over the past two years. The first but not least result is that not every firm which has implemented a new ICT project has seen an impact on its performance in the sense defined in the previous section.

Table2. Intensity of performance perceived.

0 1 2 3 (%)
13.0 23.8 25.8 37.2 Source: ICT survey 2008, STATEC, authors' calculation Indeed, 13% of our sample did not perceived any impact contrary to the 37.2% of firms, which have declared a perceived impact in all categories censed before (representing the performance). This result confirm the fact it is more useful to consider the model in term of intensity instead of just considering the fact that the firm perceived something or not (with a simple binomial model such as a Logit or a Probit model).

Econometric Results

Table 4 summarizes results from the estimation of ordered logit models. The first hypothesis about the absorptive capacity of the firm and successful project is not verified. In fact our results show that there's no relation between the proxies of absorptive capacity (Training, ICT staff) and the performance of the firms in terms of setting successful projects. Our main explanation is that the new technologies (ICTs) need marginal efforts in matter of training and staff and not substantial efforts contrarily to the lasts innovations. Setting a website nowadays may take few minutes with interactive solution ready to be hosted in a server. This was not the case some years ago, where the firm needs to employ Webmaster, to spend a lot of money for building its architecture and to make it livable. Social Medias and other applications are lowering the requirements in matter of "brains" for the firms allowing them to use these innovations more frequently. What is true for a website is also true for several other applications for the firms.

The second hypothesis, about the relationship between the intensity of use of eapplications (innovations) and successful ICT Project, is verified for most of eapplications. Our results show that the use of e-banking, e-administration (uploading documents) and e-selling improve the probability of setting successful project. This result confirms previous finding by [START_REF] Polder | Product, Process and Organizational Innovation: Drivers, Complementarity and Productivity Effects[END_REF]. In fact, as the constraints are lowered and the human capital requirements are lesser, firms are more engaged in using the e-applications. These applications allow them to acquire new competencies in matter of management of projects and these skills are transferable to other projects management. Another complementary explanation relies to the fact, that e-applications as e-banking, e-selling, e-administration permits to save costs and to use the resources for other projects, improving by this their probability of success. Thirdly, most of new projects are entirely or partly eprojects and are using e-skills. The intensive use of e-applications permits to accumulate those e-skills and to use them in others projects. Lastly, one needs to mention that the e-security matters. Firms engage more projects as their awareness about security increases. Most of the firms are increasing the security awareness of their employees and building e-skills in this particular area. The firm staff awareness of security issues has a positive and important impact on the probability of success on the implementation of a new project.

The third hypothesis is about the asymmetric and selective impact of eapplications. Our results show clearly that the impacts of the two side of one innovation have differentiated impacts on the performance of the firm. Our results find that while e-banking, e-commerce (e-selling) and e-government (upload document) have an impact on the performance of the firm, there is no impact for epurchasing, e-training and downloading documents for e-administration issues. Several explanations can be given in order to explain such findings.

Firstly, as mentioned in [START_REF] Hollenstein | Inter-and intra-firm diffusion of technology: The example of E-commerce. An Analysis based on Swiss firm-level data[END_REF] and Peltier-Ben Aoun and Vicente (2011) e-commerce cannot be studied as a whole. E-commerce has to be split in e-selling and e-purchasing. This is natural because by definition epurchasing is a Business to Business (B2B) activity where e-selling is B2B and a Business to Consumer (B2C) process. Implementing e-purchasing seems easier than e-selling. E-selling requires a platform where the consumer or the other firm can purchase the goods or services offered by the firm. When a firm is involved in this type of e-commerce we can assume that it has deployed the skills and organization needed to favor this kind of process and that firm are more able to gain from the implementation of other ICT project.

Secondly, for e-administration, when a firm interacts with public authorities, it faces to different requirements for downloading information or documents than for filling in documents or submitting a proposal in a public electronic tender. The first one needs basic ICT (computer, Internet connection) while the second requires more extensive facilities. As we have observed for the e-commerce, there is an asymmetric behavior in interacting with the public authorities. A "downloading" behavior has no impact in the perceived effect of the implementation of a new ICT project whereas an "uploading" interaction with the public authorities has a positive impact with the possible success of a new ICT project.

Conclusion

Luxembourg is a country often depicted as well equipped in Information and Communication Technologies. Indeed, almost all firms, with at least 10 employees, own computers, are connected to the Internet and exchange mail. Moreover, more than 40% of those firms adopt the e-commerce (e-selling or e-purchasing).

Nevertheless, we observe a decline in the adoption of since 2007. So, the diffusion of this new technology and its impact is not yet clear. In this paper, we focused our attention on the impact of different types of new technologies related to the Internet such as e-banking, e-commerce, e-administration and e-training on the performance of the firm measured by the implementation of successful projects.

The first aim of this paper was to show that technological evolution is permitting better use of the technologies with lesser e-skills needs. Since then, the performance of the firm is less dependent on e-skills (ICT skills) and Brains (Human Capital). Our results confirm this intuition. Secondly, we show that most of e-applications used by the firms have an impact on the performance of the firm. However, while the firms are using a diversity of application, they are selective in using only one side of the innovation and not the others (e-commerce and eadministration). Our analysis emphasizes the asymmetric effect of some specific ICT such as E-commerce and E-administration. We explain this phenomenon by the fact that both activities require different logistics in the firm. We have shown the significant impact of e-selling and interacting with public authorities in order to fill in an application. While, e-purchasing and interact with the public authorities in order to download information or documents are not significant.

Firm

  has used internal resources for security needs Dummy Firm has used internal resources and consultants for security needs Dummy Firm staff is aware of security issues Dummy Automated data exchange Firm receives or sends e-invoices Dummy Firm sends orders to suppliers or receives orders from customers Dummy Firm sends or receives product information Dummy ICT personnel ICT or IT are present in the firm Dummy ICT/IT functions requiring ICT specialist were completely or partially guaranteed by external service providers Dummy The economic activity is defined through the NACE LUX rev1.1 classification and we have distinguished the following segmentation:  Manufacturing  Construction  Trade Hotel and Restaurant  Transport and Communications  Financial activities and other services  Real Estate activities Size  Between 10 and 49 employees  Between 50 and 249 employees  At least 250 employees

Table 4 .

 4 Results from ordered logit estimation. Dependent variable: Intensity of success perceived from the implementation of an ICT project.

		sample1	sample2
	Employment
	10-49	ref.	ref.
	50-249	-0.18	-0.19
	250 and more	-0.61	-0.30
	Economic Activity
	Manufacturing	ref.	ref.
	Construction	-0.49 *	-0.49 *
	Trade	-0.27	-0.2
	Hotels and restaurants	-0.05	0.13
	Transports and communications	-0.24	-0.17
	Housing and other services		-0.54
	Finance	-0.36	-0.33
	Market position
	Group	0.33 *	0.29 *
	Leader	-0.07	-0.12
	Local notoriety	ref.	ref.
	National notoriety	0.44 **	0.46 *
	International notoriety	0.51 *	0.54 *
	ICT equipments
	Intranet	0.46 **	0.42 *
	Extranet	-0.02	-0.01
	Mail	-0.02	-0.02
	Visio-conference	-0.08	-0.08


Adel Ben Youssef

Ludivine Martin
email: ludivine.martin@ceps.lu

Nessrine Omrani

The Complementarities between Information Technologies Use, New Organizational Practices and Employees' Contextual Performance: Evidence from Europein 2005 and 2010*

Keywords: Performancecontextuelle -Technologies de l'information -Nouvelles pratiques organisationnelles -Employés Classification JEL: J81, M12, M54, L23

This article investigates the relationships between Information Technologies (IT), new organizational practices and workers" contextual performance in the European context. Our empirical results are based on data about more than 11000 employees from 16 European countries in 2005 and more than 16000 in 2010. First, our results underline asymmetric effects of IT use. Internet use is, indeed, positively related to all aspects of contextual performance in 2010, while computer use has been only positively associated with interpersonal contextual performance in 2005. Second, we find that most of the considered new organizational practices have a positive relationship with employees" contextual performance.

Contextual Performance -Information Technologies -New Organizational Practices -Employees

Lescomplémentarités entre l'usage destechnologies de l'information, les nouvellespratiques organisationnelleset la performancecontextuelledes employés : Analyses européennes en 2005 et 2010

Cet article analyseles relations entre lesTechnologies de l"Information(TI), les nouvelles pratiquesorganisationnellesetla performancecontextuelledes employésdans le contexte européen. Nos résultats empiriquessont basés surdes bases de données concernantplus de11000employésde 16 pays européensen 2005et plus de16000en 2010. Premièrement,nos résultatssoulignent des effetsasymétriques del"usage des TI.L"usage d"Internetest, en effet, positivement lié àtous les aspects dela performancecontextuelleen 2010, tandis que l"usagede l"informatiqueestassocié positivement seulement à laperformance contextuelleinterpersonnelle en 2005. Deuxièmement,nous constatons quela plupart desnouvelles pratiques organisationnellesconsidéréesontune relation positive avecla performancecontextuelledes employés.

Introduction

The objective of this article is to propose an economic analysis of Information Technologies (IT) usage (Internet and computer), New Organizational Practices (NOP) and employees" performance in Europe measured by contextual performance as defined by Coleman and Borman (2000). IT and NOP are generally viewed as complementary assets impacting firm performance [START_REF] Ichniowski | The Effects of Human Resource Management Practices on Productivity: a study of steel finishing lines[END_REF]Black and Lynch, 2001;[START_REF] Bresnahan | Information technology, workplace organization, and the demand for skilled labor: Firm-level evidence[END_REF]Askenazy and Caroli, 2010). As such, looking at the links between IT andemployees" performance, one needs to consider the adoption of NOP by firms.

Although several empirical researchers analysed the links between ITuse, NOPand the performance of the firm, research at the employee level are scarce4 . One of the main explanations of this scarcity is related to the lack of individual measures for workers" efforts and performance. Our article contributes to this line of research by focusing on the organizational changes (NOP) adopted simultaneously with IT and their relationships withemployees" performance. This work has three main novelties.First, while most of the related literature focuses on labour productivity as the main indicator of employees" performance, we propose in this paper an alternative research strategy by focusing on contextual performance of workers as a performance indicator. We argue that IT investments and NOP motivate workers and develop their behavioural performance5 . IT, for example, mediates relations inside the firm and may induce self-improving behaviours. NOP, such as team work, are the support to interpersonal relations.Therefore, IT and NOP mainly influence the behavioural dimension of workers" performance.Second, our analyses are based on rich European data including the responses of 11098 European workers from 16 countries in 2005 and 16354 in 2010. This allows us to control for a very detailed set of workers, job, firms and country characteristics that enable us to properly isolate the links between IT investments, NOP and employees"contextual performance.Third, we provide new explanations on how firms have adjusted their organizational structure in order to harnessthe dividends from changes in IT uses. Behind IT there are several technologies with asymmetric links with performance. Our main findings show asymmetric links between IT use and NOP on workers" contextual performance. While Internet use is, indeed, positively related to all aspects of contextual performance in 2010, computer use was positively associated with contextual performance in 2005 but the link disappears in 2010.

The article is structured as follows. Section 2 reviews the literature related to IT use, NOP and employees" contextual performance. Section 3 presents the data. Section 4 presents and discusses the results. Finally, section 5 concludes.

Research background

This section discusses the analytical relationships between IT use, NOP and contextual performance.

Contextual Performance

During the lastdecades, advances have been made in clarifying and extending the concept of employees"job performance [START_REF] Viswesvaran | Modeling job performance: Is there a general factor?[END_REF].One of the most accepted work in this area is theone of Borman and Motowidlo (1997). According to these authorsemployee"s performance is made up oftask performance (in-role behaviour) and contextual performance (extra-role behaviour). Task performance is defined as "the effectiveness with which the job incumbent performs activities that contribute to the organization" (Borman and Motowidlo, 1997, p.99). Contextual performance includes "volunteering to carry out tasks and activities that are not formally part of the job and helping and cooperating with others in the organization to get tasks accomplished" (Borman and Motowidlo, 1997, p.99).

Contextual performance measuresare widely used nowadays in Human Resource Management (HRM) and help firms to appreciate theeffectivenessof their HRM policies. The most popular measure proposed by Coleman and Borman (2000) has three dimensions: Interpersonal Citizenship Performance (ICP), Organizational Citizenship Performance (OCP) and Job/Task Conscientiousness (JTC). ICP consists of helping others by cooperating, offering suggestions, teaching them useful knowledge or skills, directly performing some of their tasks and providing emotional support for their personal problems. OCP is related to organizational support, to represent the organization favourably by defending and promoting it, as well as expressing satisfaction and showing loyalty by staying with the organization despite temporary hardships, supporting the organization"s mission and objectives, and suggesting improvements. JTC is related to conscientious initiative, it consists of makingextra effort, taking initiatives to do all that is necessary to accomplish objectives and developing own knowledge and skills by taking advantage of opportunities outside the organization using own time and resources.

IT use, NOP and contextualperformance

Many firms recently experienced a reorganization of their workplace with the adoption of new organizational practicessuch as job rotation, teamwork, just-in-time and total quality management (Osterman, 2000;Cappelli and Neumark, 2001). Van Reenen (2011) provides empirical evidence that suggests that changing management practices improve firms" productivity. Moreover, other papers show that performance associated with IT use depends strongly on the adoption of NOP (e.g. Greenan and Mairesse, 2000).

An important literature studied the consequences of these organizational changes on firms" performance and skill requirements (e.g. [START_REF] Ichniowski | The Effects of Human Resource Management Practices on Productivity: a study of steel finishing lines[END_REF]Black and Lynch, 2001). Using either industry or firm-level data, they showa positive impact of new work practices upon firms" productivity and performance especially when they are combined with IT. Most of this literature assumes productivity as the main measurement of performance and assess the question at the industry or firm level. But, to our knowledge, no applied empirical research has tried to examine whether the complementarity is also valid with contextual performance at the individual level.

Employees" behaviours within the firm differ from oneindividual to another. Thesebehaviours depend on the employee and theorganization"s needs and dynamics. Organization"s needs are affected by the speed of technological change. So, similar to productivity growth, contextual performance follows technological and organizational change. Management practices as complementary technologies modify the organizational practices inside the firms [START_REF] Van Reenen | Does competition raise productivity through improving management quality?[END_REF]. IT and associated NOP are recognized as a major source of improvements inside firms about, among others, communication, collaboration, exchange of information and ideas (Rubery and Grimshaw, 2001). More precisely, at least, Internet and Computer usecan be related to three main behavioural changes. First, IT use may induce more cooperative behaviour. Second, IT use may impact organizational citizenship behaviours within the firms. Third, IT use may induce selfimproving behaviours. HRM practices are recognized to be positively linked with workers" organizational commitment (White and Bryson, 2013).HRM practices enhance worker involvement, make the work design less rigid and permit to decentralize managerial tasks.

Data

We use theEuropean Working Condition Survey (EWCS) data collected by Eurofound in 2005 and 2010. As we aim to analyse the contextual performance of employees within firms, we exclude self-employees, employees in one-person firms and those with less than one year of seniority in the firm. We also restrict the sample to 16 countries with comparable living and working conditions, that is to say, countries that belong to the Euro Zone in 2005, Nordic countries and the United Kingdom. The number of employees in 2005 is 11098 and 16354 in 2010.Weights are constructed in order to ensure that the distribution by region, locality size, gender, age, economic activity and occupation is representative of the active population (based on the Labour Force Survey -Eurostat).

A data mining technique is used to form groups of workers relatively to their behavioural proximity on the three dimensions of workers" contextual performance described above. 8binary or ordered variables are used to construct the Interpersonal Citizenship Performance -ICP index, 16for the Organizational Citizenship Performance -OCP index and 3for the Job/Task Conscientiousness-JTC index. 6 We perform a Multiple Correspondence Analysis (MCA) followed by a cluster-analysis. The cluster-analysis permits to regroup individuals in classes that are the most homogeneous according to their similarities with respect to all variables. 7 The indexes are ordered from the lowest "performing" group of worker to the best one (Table 1). For our analysis ofIT use at work, we retain the frequency of computer and Internet use. 8 The number of non-IT users decreased between 2005 and 2010 (Table 2).

To characterize the new organizational practices of firms we introduce two types of measures of workplace practices.First, to characterize new models of production such as Just-In-Time andTotal Quality Management, the following variables are introduced: "work schedule fixed by employer","meeting precise quality standards" and "information about health and safety risks". The new models of production can modify the behaviour of workers as they have an impact on the time available to produce anddeliver products or services, on the quality of outputs, and on worker environment and safety. Wealso controlfor the degree of non-painful workingconditions facedby workers ("Quality of the job environment").Second, to characterize the Human Resources Management (HRM)practices of firms, we introduce variables capturing practices that enhance worker involvement, make the work design less rigid and permit to decentralize managerial tasks. We also introduce a variable that captures the resort to "formal assessment" used by managers to give feedback and rewards. "Job rotation" and "telework" are introduced to capture a less rigid work design that can strengthen employees" performance [START_REF] Bloom | Are family-friendly workplace practices a valuable firm resource?[END_REF].Finally, the variable "team work" is included to capture a well-developed workplace practice that permits jointdecision makingandincreases the involvement of workers (Jones and Kato, 2011). Firms implement more of all forms of NOP in 2010 compared to 2005 (Table 2).

been determined according to 4 rules: pseudo T-squared, pseudo-F, Cubic Clustering Criterion and the dendrogram"sshape. 8 The use of Internet concerns the professional use of Internet and e-mails whatever the IT support. Different control variables are introduced in our analyses and are related to several characteristics of employees, their job, the firm and the country.These controls allow us to properly isolate the links between IT investments, NOP and workers contextual performance.9 Regarding employee"s characteristics, the EWCS survey provides information about gender, age, level of education and marital status.The survey also provides informationon the job characteristics. We have information on the income, on the nature of the contract (permanent, full time), onseniority in the firm, on occupation (8 groups) and on commuting time between the house and the workplace. It is important to note that during their commuting time employees have, especially in 2010, the possibility to use their Smartphone or Tablets to work.Regarding the firm"s characteristics, 8 economic sectorsand 4 firms" size are used. With respect to the specificities of the 16 countries,we consider the country growth rate, the country unemployment rate and the percentage of post-secondary educated people.

Results

Table 3 gives the results of our analyses obtained with ordered probit models. We find that IT uses have significantly positive linkswith workers" contextual performance, but these links depend on the nature of the IT considered.

First, our results show strong evidence that Internet useispositively associated with all the facets of the contextual performance (except for ICP in 2005). The more workers use Internet the higher is their Organizational CitizenshipPerformance (OCP) and Job/Task Conscientiousness (JTC)in 2005 and 2010. While in 2005 Internet has no significant link withInterpersonal Citizenship Performance (ICP), the picture changed and we find a positive relationship in 2010. Internet is modifying the way people are working and interacting inside the firm and is allowing more flexibility in the way the tasks are done by workers. It is enhancing cooperative behaviours, citizenship behaviours and self-improvement behaviours. Second, our results show an interesting result for computer usage. In fact, computer usage has a positive link with ICP in 2005 but a negative one withJTC. However, these linksdisappear in 2010. One possible explanation is the fact that computersare an old and stabilized IT and the links with contextual performance depend on the age of the IT. An alternative explanation is that computer use can be considered more as a complement to Internet use in 2005than as a distinct effect, a complementarity that disappears with new devices allowing access to Internet such as Smartphones, Tablets.

The results about new organizational practices are in line with recent research focusing on HRM and organizational commitment (e.g. White and Bryson, 2013). We find that NOP are positively related to workers" contextual performance. All the studied new organizational practices have at least one positive relation with contextual performanceexcept for the case of the work schedule determined by the employer that has a negative link with contextual performance. At the same time, NOP have a differentiated association with the three facets of contextual performance.Formal assessment has a significant link with all the facets of contextual performance in 2005 and we find the same conclusion in 2010. Job rotation has only a significant and positive link with ICP (and no relations with OCP and JTC). This is the case in 2005 and 2010.Our results also reveal that the more employees are involved in telework the greater aretheir contextual performances in 2010. While in 2005 telework had a positive association only with JTC and a negative one with ICP. Teamwork has a positive link with the three dimensions of contextual performance in 2010, but no significant link in 2005, except a positive one with ICP. A firm that provides "information about health and safety risks" and non-painful working conditions seem to favour the performance of workers in terms of ICP and OCP in 2005 and in 2010. In 2010, these NOP are negatively related with JTC.While "Meeting precise quality standard"was initially positively associated with two contextual performances (ICP and OCP) in 2005 we find only one positive association with OCP in 2010.Moreover, our results show that organizational practices which are based on certain rigidity, like a work schedule fixed by the employer, have a negative link with contextual performance. This negative association changes over the years. While, this practice is negatively related to OCP and JTC in 2005, we find that the negative links appear with ICP and OCP in 2010. Our study confirms that information technologies are contributing to the setting of a new productive model associated with higher results in the areaof contextual performance. The new organizational model using team work, telework, job rotation and intensive use of Internet induce higher contextual performance of workers. Management of European firms is changing in order to adjust to technology and to improve workers" contextual performance [START_REF] Van Reenen | Does competition raise productivity through improving management quality?[END_REF].

Sensitivity analyses

We conduct additional sensitivity analyses in order to gauge the robustness of the resultsconcerning IT use. 10 We estimate a trivariate ordered probit model using a technique developed by [START_REF] Roodman | Fitting fully observed recursive mixed-process models with CMP[END_REF] to take into account the potential correlations between contextual performances. The correlations show independence except a positive dependence between ICP and OCP. Despite this correlation, the results are very similar with the ones obtained with our three independent ordered probit modelsshownin Table 3.Moreover, in order to take into account as much as possible the potential endogeneity or a reverse causality of IT use, we estimate simultaneously the frequency of Internet use (or the frequency of computer use) and one of the indexes of contextual performance (via bivariate ordered probit models, [START_REF] Roodman | Fitting fully observed recursive mixed-process models with CMP[END_REF]. In the estimates of the frequency of IT use, we introduce the same variables as earlier and two variablesobtained from Eurostat that explain the frequency of IT use but not the indexes of employees" contextual performance: the average rate of high bandwidth Internet connection in firms in the countryand the average percent of people in the country able to perform five of six IT activities. The results are in line with those presented in Table 3.

Conclusion

Existing literature focuses mainly on the impact of IT use and NOP on firms" performance (e.g. [START_REF] Ichniowski | The Effects of Human Resource Management Practices on Productivity: a study of steel finishing lines[END_REF]Black and Lynch, 2001) and research on employees"performance is scarce. Studying the relationships between IT use, NOP and employees" behaviours inside the firm is important as employees are at the heart of the success of an organization [START_REF] Pfeffer | Competitive advantage through people[END_REF].Moreover, while most of the related literature focuses on productivity as the main indicator of workers" performance, we propose an alternative research strategy by focusing on workers" contextual performance. Although contextual performance is central concern for organizational researchers, research effort concentrates on individuals characteristics, ignoring recent organizational changes and IT use. We argue that employees using IT and working in firms providing NOP may develop behaviours that benefit the organization.

Our resultsconfirmedthat IT usesarepositively associated with contextual performance and are in line with previous research showing that IT ispositively related with workers" motivation and involvement (e.g. Barthélémy and Cette, 2007;[START_REF] Martin | The effects of ICT use on employee's motivations: an empirical evaluation[END_REF]. Furthermore, our findings contribute to the literature about IT impact by proposing an alternative measurement of performance and rely on the asymmetric effects of IT. The links between IT useand workers" contextual performance depend strongly on the considered technology. In 2010, while Internet use is positively related to all the facets of contextual performance, we find that computer use has no significant link with contextual performance dimensions.Our analysesalso confirmed that New Organizational Practices are positively associated with workers" contextual performance and are consistent with the literature on high-involvement work practices underlyingincreases in labour productivity and worker"s commitment (e.g. Osterman, 2000;WhiteandBryson, 2013).More precisely, most of the considered NOP have at least one positive link with at least one aspect of contextual performance.

Our article provides several contributions to the existing literature. First, our article contributes to the debate about the complementarities between IT and NOP and provides an analysis at the employee level that is needed in a literature that is almost limited tothe firm level. We show how IT useismodifying the behaviour of workers, and how managersuse NOP as "complementary technologies". A new industrial and organizational model seems present in Europe resulting in higher workers performance. Second, we resort to richand large databases that permit to provide robust analyses. Third, our analyses arebased on organizational research, HRM research and industrial organization literature in order to enrich these research areas.

Our paper is, of course, not without limitations. First, the European data were collected at two points in time on two samples of employees. It allows us to find significant associations between variables, but no final conclusions about causality can be drawn. Second, because the survey was not defined specifically for our analyses, deepened richer picture may be obtained by examining other types of IT uses in order to have better understanding of the impact of specifics IT useson workers" contextual performance. For example, further research could analyze other data that contain information on other well diffused technologies within firms such as Enterprise Resource Planning or social networks.

Table 1 .

 1 Descriptive statistics of the contextual performance indicators

				2005		2010
			Mean (%)	Std. Dev.	Mean (%)	Std. Dev.
		1	18.15	0.39	17.38	0.38
		2	14.97	0.36	19.81	0.4
	ICP	3	30.55	0.46	30.07	0.46
		4	7.71	0.27	8.58	0.28
		5	28.63	0.45	24.16	0.43
		1	11.05	0.31	9.52	0.29
		2	23.51	0.42	32.12	0.47
	OCP	3	52.52	0.5	46.67	0.5
		4	5.08	0.22	4.94	0.22
		5	7.84	0.27	6.75	0.25
		1	73.49	0.44	65.82	0.47
	JTC	2	13.34	0.34	19.90	0.4
		3	4.55	0.21	6.16	0.24
		4	8.61	0.28	8.12	0.27
	# obs.			11098		16354
	Weighted statistics.

Table 2 .

 2 Descriptive statistics of IT use and NOP

		2005		2010
		Mean	SD	Mean	SD	Min Max
	Frequency of IT use
	Internet use	2.45	1.61	2.70	1.65	1	5
	1. Never	46.77	0.5	39.55	0.5
	2. Almost never	11.33	0.32	11.82	0.32
	3. Around 1/4 of the time	12.63	0.33	13.12	0.34	0	100
	4. Around half of the time	8.86	0.28	10.04	0.3
	5. Almost all of the time or all of the time	20.41	0.4	25.47	0.44
	Computer use	2.55	1.57	2.73	1.57	1	5
	1. Never	38.14	0.49	32.01	0.47
	2. Less than 1/4 of the time	19.77	0.4	20.60	0.41
	3. Less than 3/4 of the time	12.05	0.33	13.31	0.34	0	100
	4. Almost all of the time	8.92	0.29	10.70	0.31
	5. All of the time	21.12	0.41	23.38	0.42
	NOP
	Work schedule fixed by employer	16.79	0.37	22.02	0.41	0	100
	Meeting precise quality standards	76.01	0.43	76.67	0.42	0	100
	Information about health and safety risks	2.24	0.69	2.35	0.66	1	3
	Quality of the job environment	4.33	1.61	4.40	1.55	1	6
	Formal assessment	40.20	0.49	43.42	0.5	0	100
	Job rotation	48.82	0.5	50.36	0.5	0	100
	Telework	7.57	0.27	11.02	0.31	0	100
	Team work	61.24	0.49	64.51	0.48	0	100
	# obs.	11098		16354
	Weighted statistics.

Table 3 .

 3 Ordered probit models

			2005			2010
		ICP	OCP	JTC	ICP	OCP	JTC
	Frequency of IT use
	Internet use	-0.001	0.065***	0.144***	0.024*	0.046***	0.08***
		(0.024)	(0.01)	(0.03)	(0.014)	(0.016)	(0.031)
	Computer use	0.062***	0.024	-0.068***	0.005	0.014	-0.001
		(0.017)	(0.024)	(0.020)	(0.019)	(0.016)	(0.022)
	NOP
	Work schedule fixed by	-0.049	-0.096***	-0.352***	-0.102*	-0.112*	-0.011
	employer	(0.057)	(0.034)	(0.067)	(0.062)	(0.064)	(0.045)
	Meeting precise quality	0.084***	0.108**	0.018	-0.032	0.117***	0.022
	standards	(0.027)	(0.05)	(0.051)	(0.037)	(0.027)	(0.052)
	Information about health	0.191***	0.342***	-0.055	0.240***	0.302***	-0.052***
	and safety risks	(0.012)	(0.019)	(0.037)	(0.032)	(0.032)	(0.018)
	Quality of the job	0.054***	0.056***	-0.022	0.032***	0.05***	-0.049***
	environment	(0.015)	(0.011)	(0.022)	(0.007)	(0.01)	(0.006)
	Formal assessment	0.19***	0.12**	0.086**	0.099**	0.081*	0.105***
		(0.041)	(0.052)	(0.041)	(0.039)	(0.041)	(0.032)
	Job rotation	0.246***	0.058	0.026	0.128***	0.03	0.045
		(0.044)	(0.042)	(0.073)	(0.013)	(0.041)	(0.033)
	Telework	-0.08*	-0.007	0.677***	0.085**	0.214***	0.664***
		(0.048)	(0.062)	(0.088)	(0.038)	(0.065)	(0.054)
	Team work	0.222***	0.005	-0.039	0.189***	0.075***	0.083***
		(0.028)	(0.04)	(0.064)	(0.033)	(0.018)	(0.032)
	Employee charac.		Included			Included
	Job charac.		Included			Included
	Firmscharac.		Included			Included
	Country charac.		Included			Included
	Cut 1	0.448	0.016	0.981	0.078	-0.149	1.045***
		(0.303)	(0.259)	(0.651)	(0.439)	(0.465)	(0.327)
	Cut 2	0.967***	0.935***	1.611**	0.733	1.045**	1.847***
		(0.308)	(0.301)	(0.650)	(0.455)	(0.473)	(0.365)
	Cut 3	1.829***	2.641***	1.922***	1.552***	2.577***	2.266***
		(0.34)	(0.28)	(0.647)	(0.461)	(0.477)	(0.336)
	Cut 4	2.065***	2.958***		1.82***	2.905***
		(0.35)	(0.284)		(0.452)	(0.476)
	Observations		11098			16354
	Pseudo R-squared	0.053	0.0721	0.164	0.0352	0.0581	0.127
	Log Lik.	-20924	-17263	-10349	-32812	-26518	-18738
	Robust standard errors adjusted for 16 clusters (countries) in parentheses. Weighted estimations. Coefficients
	*significant at 10%; ** significant at 5%; *** significant at 1%.

e.g.Barthélémy and Cette (2007) have considered the effects of IT and NOP on the paceand intensity of work in France. Their results suggest that workers are more involved outside their legal working-hours but have more autonomy and flexibility to do their assigned tasks.

Although contextual performance is central concern for organizational researchers, they investigatedmainly individuals ignoring IT use and NOP.

All of the variables used are available upon request from the corresponding author.

The classification is based on individuals" coordinates obtainedwiththe MCA. The hierarchical clustering method uses the Ward index to measure the distance between classes. The choice of the number of classes has

Descriptive statistics of our control variables are availableupon request from the corresponding author.

The results are not reported here but are available upon request from the corresponding author.

*The authors gratefully acknowledge the participants of the 62th annual meeting of the French Economic Association (Aix-en-Provence,


Rosalie Plantefève

Nazim Haouchine

Jean-Pierre Radoux

Stephane Cotin

Automatic Alignment of pre and intraoperative Data using Anatomical Landmarks for Augmented Laparoscopic Liver Surgery

Each year in Europe 50,000 new liver cancer cases are diagnosed for which hepatic surgery combined to chemotherapy is the most common treatment. In particular the number of laparoscopic liver surgeries has increased significantly over the past years. This type of minimally invasive procedure which presents many benefits for the patient is challenging for the surgeons due to the limited field of view. Recently new augmented reality techniques which merge preoperative data and intraoperative images and permit to visualize internal structures have been proposed to help surgeons during this type of surgery. One of the difficulties is to align preoperative data with the intraoperative images. We propose in this paper a semi-automatic approach for solving the ill-posed problem of initial alignment for Augmented Reality systems during liver surgery. Our registration method relies on anatomical landmarks extracted from both the laparoscopic images and three-dimensional model, using an image-based soft-tissue reconstruction technique and an atlas-based approach, respectively. The registration evolves automatically from a quasi-rigid to a non-rigid registration. Furthermore, the surface-driven deformation is induced in the volume via a patient specific biomechanical model. The experiments conducted on both synthetic and in vivo data show promising results with a registration error of 2 mm when dealing with a visible surface of 30% of the whole liver.

Introduction

Context: Minimally invasive surgery is regarded as one of the major advances in surgery of last decades considering the benefits for patient in term of time recovery and reduced pain. Yet, one problem remains: the surgeon still needs to register mentally the preoperative data onto the laparoscopic view to determine the tumours and vessels location. The introduction of optics in the clinical routines have motivated several research groups to investigate the benefits of Augmented Reality to help surgeons during the procedure [START_REF] Nicolau | Augmented reality in laparoscopic surgical oncology[END_REF]. Indeed, Augmented Reality has the potential to provide an enriched visual feedback to the surgeon by the fusion of intraoperative images and three-dimensional preoperative data such as tumours and vascular network.

Previous work: In this context several methods have been proposed to solve the numerous challenges that present the abdominal cavity, ranging from occluded regions due to instrument [START_REF] Puerto-Souza | Toward long-term and accurate augmented-reality display for minimally-invasive surgery[END_REF], organ tracking disturbance due to blur or smoke [START_REF] Yip | Tissue tracking and registration for image-guided surgery[END_REF], and unpredictable deformations produced by heart beating, breathing or manipulation with instruments [START_REF] Haouchine | Image-guided simulation of heterogeneous tissue deformation for augmented reality during hepatic surgery[END_REF]. However, despite these numerous techniques, very few works have investigated the initial alignment between the laparoscopic images and the three-dimensional model. Indeed, the initialisation is often assumed to be done manually [START_REF] Puerto-Souza | Toward long-term and accurate augmented-reality display for minimally-invasive surgery[END_REF][START_REF] Haouchine | Image-guided simulation of heterogeneous tissue deformation for augmented reality during hepatic surgery[END_REF][START_REF] Su | Augmented reality during robot-assisted laparoscopic partial nephrectomy: Toward real-time 3d-ct to stereoscopic video registration[END_REF], which can be a major source of error given the significant deformations that the organs may undergo during the surgery. In addition, since gas is insufflated (pneumoperitoneum) to increase the working space [START_REF] Bano | Simulation of pneumoperitoneum for laparoscopic surgery planning[END_REF], the preoperative data may no longer correspond to the intraoperative image. In order to optimize the trocars placement on the skin, in [START_REF] Bano | Simulation of pneumoperitoneum for laparoscopic surgery planning[END_REF] it is proposed to simulate the pneumoperitoneum using only a preoperative model and patient-specific biomechanical parameters. The evaluation of their method on real data highlights its potential usability for Augmented Reality. Based on this work, Oktay et al. [START_REF] Oktay | Biomechanically driven registration of pre-to intra-operative 3d images for laparoscopic surgery[END_REF] propose to exploit the intraoperative data acquired from CT-scans after insufflation as an additional constraint to drive the simulation. Although this method provides accurate registration, it relies on intraoperative scans. Another intraoperative registration method is presented in [START_REF] Dagon | A framework for intraoperative update of 3d deformable models in liver surgery[END_REF]. The authors use an intraoperative ultrasound probe to register the vessel tree on a three dimentional liver model. However, since our aim is to register the laparoscopic data recorded by a camera, such information is not available. Clements et al. [START_REF] Clements | Robust surface registration using salient anatomical features for image-guided liver surgery: Algorithm and validation[END_REF] introduced an ICP-based approach to aid in the initial pose estimation. Using salient anatomical features, identifiable in both the preoperative images and intraoperative liver surface data, this method is able to reach a reasonable solution, but is restrained to rigid transformations. To handle deformations, biomechanical models are often used to regularize the registration methods. For instance, in [START_REF] Ferrant | Registration of 3-d intraoperative mr images of the brain using a finiteelement biomechanical model[END_REF] a registration of intraoperative MR brain images is proposed where the model is based on linear elasticity and the finite element method. Moreover the method proposed by Clements relies on manual estimation of anatomical structures position which is too cumbersome to be done in a clinical context. A solution could be to use anatomical atlases to gather information about features positions. In [START_REF] Bardinet | A three-dimensional histological atlas of the human basal ganglia. atlas deformation strategy and evaluation in deep brain stimulation for parkinson disease[END_REF] the authors use a histological atlas containing detailed anatomical information to target small brain structure in a pre operative MRI for neurosurgery planning.

Methods

The overall computational flow of our method involves two main steps: detection of anatomical landmarks on both laparoscopic images and preoperative data, and a nonrigid feature-based registration similar to the Iterative Closest Point (ICP).

Pre and Intraoperative Data Computation

We define a set of landmarks that are chosen to be visible on stereoscopic images and in at least one preoperative imaging technique (see Fig. 1). These landmarks will be labelled on one frame of the endoscopic data and on the three-dimensional model. Stereo Endoscopic Scene Estimation: On one of the stereo endoscopic images, the falciform ligament, the ridge line and the liver surface are defined manually as anatomical landmarks of the liver. The operator selects (e.g. by clicking) some points on the border of the regions of interest to form closed areas. This selection takes only a few seconds.

Once the targeted regions are selected, we build for each of them a three-dimensional point cloud using the method described in [START_REF] Haouchine | Image-guided simulation of heterogeneous tissue deformation for augmented reality during hepatic surgery[END_REF] that relies on a sparse stereo matching technique to recover the liver surface shape. These point clouds are labelled according to their corresponding regions as illustrated in Fig. 2.

Preoperative Anatomical Landmarks Detection: The three-dimensional model is obtained form the CT images via a standard semi-automatic segmentation process described in [START_REF] Yushkevich | User-guided 3D active contour segmentation of anatomical structures: Significantly improved efficiency and reliability[END_REF]. The resulting mesh is then augmented with the same anatomical landmarks as the ones detected in the stereoscopic images. For the liver one landmark is automatically detected on the three-dimensional model: the ridge line. This landmark can be easily identified in most human livers. The automatic detection of the ridge line on the three-dimensional model of the liver is performed as follows: the edges separating two triangles with sufficiently different normals are selected as seeds. The definition of the threshold is based on statistics on the normals differences for the whole mesh.

Then, the ridge line is extended from the seed edges; if no extension is found the seeds are removed. Iteratively the ridge line is reconstructed. The other landmarks (only the falciform ligament for the liver) are transferred via a statistical atlas of the liver surface containing the landmarks location [START_REF] Plantefeve | Atlasbased transfer of boundary conditions for biomechanical simulation[END_REF]. This atlas is constructed with a set of pre operative medical images of the organ of interest. The imaging modality should be chosen such that the selected anatomical landmarks are visible. For each image an expert perform a manual segmentation of the organ and anatomical landmarks. Then all the segmentations are aligned in a common reference frame and the mean shape and standard deviations are computed. This atlas is finally registered on the three-dimensional model.

Feature-based Registration

Our approach relies on a non-rigid registration which computes the elastic transformation that maximizes the shape similarity between the source and target configurations.

One ICP is computed per labelled area and they are all solved simultaneously. The normal thresholds prune the pairs for which their normal dot product n p t • n p s < n t , n t ∈ [0; 1]. These thresholds must be set according to the deformation characteristics and they should be smaller for larger deformations. The ICP algorithm aims at reducing the global distance between the {p t , p s } pairs.

Model of deformation:

A biomechanical model is associated to the augmented threedimensional model. As the three-dimensional model and the points extracted from the stereoscopic images are two representations of the same liver, they share the same biomechanical behaviour. Different constitutive laws can be used to model the liver such as hyperelastic formulation [START_REF] Marchesseau | Multiplicative jacobian energy decomposition method for fast porous visco-hyperelastic soft tissue model[END_REF]. For computational efficiency we rely on a corotational formulation as proposed by [START_REF] Felippa | A unified formulation of small-strain corotational finite elements: I. theory[END_REF]. A fast finite element approach is used to compute the deformation of the organ. This computation can be performed very efficiently thus making it very suitable for the ICP algorithm. Regarding the parameters of the model, the Young's modulus can be patient specific (e.g. obtained by elastography) or is set to the average value found in the literature [START_REF] Yeh | Elastic modulus measurements of human liver and correlation with pathology[END_REF]. The Poisson ratio is set to 0.4 as the liver is nearly incompressible (fluid exchanges allow for some volume variation).

Definition of constraints:

The constraints are imposed on the system with a penalty force:

f = m ∑ i f i , (1) with
f i = p i ∑ j f i arctan(kx i j ) (2)
where m is the number of labelled area, p i the number of corresponding pairs in the area i, f i a penalty factor, k a scale factor and x i j the vector between the j-th target point and its projection. The k value is related to the point cloud noise and is used to avoid overfitting as a lower value decrease the force intensity for small distances. When registering non-rigidly the complete surface model w.r.t. the reconstructed part, the process may suffer from inaccuracy due to the limited knowledge of correspondence between the two. Therefore, the labelled areas are penalized differently to use the anatomical landmarks as anchor points for the registration. Moreover, all the f i are not constant over time to ensure that the registration evolves from a quasi-rigid (i.e. the applied forces are too small to produce a significant deformation) to non-rigid state. During the registration we detect when the mechanical system has reached a plateau and then update the f i values. In case of liver, the falciform ligament is the most reliable anatomical feature. It also corresponds to a very small area and therefore does not contribute much to the deformation. For that reason, f i corresponding to this landmark is constant during the registration process. The other f i are of the form

2 f imax ( n v i ) 2 ( n v i
) 2 +1 for n < v i (i.e. they are set to 0 at the beginning of the registration) and f i max for n > v i where n is the plateau index and v i a speed coefficient. v i and f i max must be set so that the objective function is more convex in the early stage of registration and that the minimum become more precise over time. Therefore, the v i and f i max of small area must be smaller than those corresponding to the large area. According to our tests, the algorithm shows low sensitivity w.r.t. the parameters. The registration is stopped when n = max(v i ) + 1.

Registration method: At each simulation step the following equation is solved

K(u)u = f ( 3
)
where u is the displacement vector, K the non-linear stiffness provided by the FE formulation and f = dE(u) du is the vector of constraint forces. The pairing is then recomputed generating a new force. Finally, during the simulation the anatomical landmarks provide a coarse registration that improves the robustness of the ICP method, whereas the biomechanical model plays a role of regularization and allows for an accurate solution of local deformations.

Results

This section presents the results obtained using our method. We conduct experiments on two different type of data: computer-generated data and liver data during in vivo surgical procedure. For convergence an average of 3700 iterations is needed. Each iteration takes 700 ms on average and the solver represent around 20% of a time step. In order to insure the success of the method, the anatomical features must be at least partially visible.

Evaluation with in silico data

We evaluated our method by registering a three-dimensional model of the liver segmented from CT-scans (source) on the same model that had undergone both a rigid and non-rigid transformations (target). In order to obtain the target liver, we apply a pressure on the surface of the model to simulate two different deformations possibly induced by the pneumoperitoneum, and a random rigid transformation (cf Fig. 4). In real situations only partial surface information is acquired by the laparoscopic camera. To evaluate the amount of information needed to achieve an accurate registration faces of the deformed model are deleted to keep only a portion of its surface from 50% to 10%.

The results presented in Fig. 5 show that even with only 10% of visible surface and a poor initial alignment our method is able to perform the registration with a mean error lower than 4 mm. The deformation 1 was more important on the liver face opposed to the camera view. This fact could explain the lower quality of the results. The plot also suggests that for a small deformation the non-rigid part of the method does not introduce any improvement when compared to the quasi-rigid part as soon as 20% or less of the surface is visible. In these two cases the visible area underwent a small deformation comparatively to the other cases. However, the mean Hausdorff distance calculated between the registered three-dimensional model and the visible part does not exceed 0.3 mm.

Experiments with in vivo data

To assess our approach in a real surgical environment (specular lights, instrument occlusions . . . ) and to evaluate the ability of our non-rigid registration to estimate the initial pose, we tested our method on in vivo laparoscopic images of a human liver. The results illustrated in Fig. 6 report a visually correct initial non-rigid registration of the liver model on the laparoscopic image with only a partial and noisy three-dimensional surface reconstruction. For this simulation we used the same parameter values as for the in silico data (see the caption of Fig. 5) except for k = 2π.10 1 (90% of the force intensity at 10

Conclusion

In this paper, we proposed a semi-automatic method for initial alignment of an organ preoperative three-dimensional model onto an endoscopic view of the same organ. This method relies on a feature-based registration framework which evolves from a quasirigid state to a non rigid state. The anatomical features used to guide the registration are selected manually on the endoscopic view and are transferred via an atlas to the three-dimensional model. We evaluated the method using ten synthetic data and two real endoscopic views. The results show that the method deforms accurately the threedimensional model when the visible surface corresponds to 30% or more of the entire organ surface. It was also demonstrated that the registration works with real endoscopic data. In the future, we will add information about the organ silhouette. We also plan to limit the constraint forces applied during the registration according to real forces imposed on the organ boundary during the intervention.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Our registration method must acurately register the three-dimensional model onto the laparoscopic view. The ridge line and a section of the falciform ligament are used as anatomical features to guide the registration process.

Fig. 3 .

 3 Fig. 3. Main steps of the ICP-like registration method.

Fig. 4 .

 4 Fig. 4. Registration results on synthetic data. The source model is in transparent red, the target surface used for the registration is in blue and the whole target surface in green wireframe. The first row shows the initial pose, the second row the result after the quasi-rigid registration and the last row the final result. Each column shows the results for different target surface areas. The target surface of the columns from left to right correspond to 50%, 40%, 30%, 20% and 10% of the whole surface. The black arrows indicate the virtual camera angle.

Fig. 5 .

 5 Fig. 5. Registration results on synthetic data showing the error w.r.t. the variation in visible surface area for deformation 1 and 2. Liver Young modulus: Y M = 50kPa, f liga max = Y M/10, f ridge max = Y M/3, v ridge = 2, f sur f max = 2Y M, v sur f = 25, d t = 0.95, n t = 0 and k = 2π.10 3 (90% of the force intensity at 10 -3 mm). The blue lines represent the mean Hausdorff distance between the non deformed source model and the same model after deformation.

Fig. 6 .

 6 Fig. 6. Registration results on in vivo data on two different views of a human liver. The registered mesh is shown in red while the partial reconstructed patch is depicted in blue.

Acknowledgement

The authors would like to thank the anonymous reviewers for their valuable comments and suggestions and Igor Peterlik for his thorough re-reading of this article.