Sam Azimi
email: azimi@univ-paris12.fr

Alexandre Ludwig

Daniel R Thevenot

Jean-Louis Colin

Trace metal determination in total atmospheric deposition in rural and urban areas

Keywords: Trace elements, Atmospheric fallout, Sampling procedures, Anthropogenic impacts

The wet, dry and total atmospheric depositions of some metals (Al, Cd, Cr, Cu, Fe, Na, Pb and Zn) were sampled at two sites and atmospheric fallout fluxes were determined for these locations. This work, led by two different research groups, allowed to reach two main goals: to define a simple analytical procedure to secure accurate shipboard sampling and analysis of atmospheric deposition, and to assess anthropogenic impacts of heavy metals to the environment. The first step about the validation step showed that the prevalent deposition type was dry deposition which represents 40, 60 and 80% for Cd, Cu and Pb, respectively. This prevalence of dry deposition in total atmospheric fallout supported the necessity of funnel wall rinsing which contains 30, 50 and 40% of collected Cd, Cu and Pb, respectively. Moreover, the reproducibility of atmospheric deposition collection was determined. The second step was performed by comparing two sampling sites. A rural sampling site, situated in Morvan's regional park (250 km south-east of Paris), was chosen for its isolation from any local and regional contamination sources. Fluxes obtained in this area were compared with those obtained at an urban site (Creteil, suburb of Paris) allowing ćomparison between urban and rural areas and demonstrating the impact of anthropogenic activities on atmospheric deposition of Cr, Cu and Pb.

Introduction

Metal transfer through the atmosphere is a significant part of the biogeochemical cycle of these elements [START_REF] Galloway | Trace metals in atmospheric deposition: a review and assessment[END_REF]. There are two processes which increase heavy metal concentra-tions in the atmosphere: natural and anthropogenic (D 'Almeida et al., 1991). Natural sources are mainly composed of soil, sea water and volcanic dusts and gases. Anthropogenic emissions come from industrial gases and aerosols or fossil-fuel combustion [START_REF] Pacyna | Estimation of the atmospheric emissions of trace elements from anthropogenic sources in Europe[END_REF]. Incineration of urban waste water treatment sludge and of urban waste were identified as major atmospheric sources of trace metals [START_REF] Sweet | Sources of toxic element in urban air in Illinois[END_REF][START_REF] Sullivan | Using emission factors to characterise heavy metal emissions from sewage sludge incinerators in Australia[END_REF]. Metallic pollutants may be transported over long distances by very small particles [START_REF] Koutrakis | Physico-chimie de l'aerosol urbain: identification ét quantification des principales sources par analyse multivariable[END_REF]. These particles when aggregated or washed out by rain are called atmospheric deposition, respectively, dry and wet. Dry deposition of particles occurs by direct impact and gravitational settling on land or water surfaces. In wet deposition, aerosols and gases are dissolved or suspended in water droplets or ice crystals. Besides such long-range transport processes, significant dry and wet depositions also occur locally, and atmospheric sources in urban area may play an important role in the metal contamination of dry and wet depositions [START_REF] Person | Contribution des principales sources en metaux et metalloıdes a la ´´p ollution particulaire dans l'agglomeration Parisienne[END_REF]. Since heavy metals present high toxicity and high lability in atmospheric fallout [START_REF] Golomb | Atmospheric deposition of toxic onto Massachusetts Bay-I[END_REF], their monitoring is important both in urban and rural areas.

The main objective of this work was to validate a weekly collection procedure, both in urban and rural sites, focussing mostly on the determination of total atmospheric deposition. Therefore, during 8 weeks, atmospheric fallout was collected weekly in a rural area in order to set up a sampling and analysis procedure for low concentration of heavy metals. Indeed, a literature survey (Church et al., 1984;[START_REF] Landing | Methods for measuring mercury in rainfall and aerosols in Florida[END_REF][START_REF] Garnaud | Transfert and geochemical evolution of metal pollution in an urban catchment[END_REF][START_REF] Thoni | Testing the Bergerhoff method to determine the bulk deposition loads of 49 elements[END_REF] showed that the collection procedures used by different laboratories or institutions present significant differences. Besides the material, size and location of the collector itself, its management, i.e. the collection period, its replacement at the end of each period or the rinsing of aerosol particles adsorbed on the funnel wall are quite different.

The study was completed by an urban collection period of 16 weeks allowing a comparison between urban and rural atmospheric depositions as well as a determination of temporal trends at the urban site.

This work was performed within two research groups, the 'Centre d'Enseignement et de Recherche sur l'Eau, la Ville et l'Environnement' (CER-EVE) and the 'Laboratoire Inter Universitaire des Systemes Atmospheriques' (LISA), both situated `ẃithin the Creteil University Campus.

´2. Material and methods

Sampling sites

Two sampling sites were selected to assess the spatial heterogeneity of atmospheric depositions. During a first campaign, from November 1999 to April 2000, four collectors were placed on the roof of University Paris XII-Val de Marne (5 km southeast of Paris, Creteil, France, 20 m above ground ĺevel), within an urban area, at 200 m from a highway (A86) and 6 km from an urban waste incineration plant. During a second campaign, from May to July 2000, four other collectors were placed at Saint-Brisson (Morvan's natural park, 250 km south-east of Paris, France) within a rural area surrounded by forest and lakes, at 2 km from the closest village and 30 km from the closest town. A weekly sampling period was chosen for an accurate determination of sampling volume and of heavy metal concentration [START_REF] Colin | Physico-chimie de la phase aqueuse atmospherique[END_REF].

Total deposition collection

A simple system made with a high-density polyethylene (HDPE) bottle (1l ) connected to a HDPE funnel was used for total deposition (TD) collection. The funnel cross-sectional areas were 1135 cm for CEREVE's and 1810 cm for 2 2 LISA's. All this equipment was placed inside a PVC pipe with PVC needles on top to prevent bird nesting (Fig. 1a). Collector heights varied with site. At Creteil, the collecting funnel was ṕlaced at 1.5 m above the gravel covered university roof (20 m above the ground) and LISA's at 2 m above the same roof. At Saint Brisson, collection heights were 1.3 and 2 m, respectively, above the grass-covered ground. Comparison between the CEREVE and LISA collectors enabled the assessment of the influence of collection heights on atmospheric deposition measurement. Moreover, the CEREVE TD collector was placed at the same height as the separate dry and wet deposition (DD and WD) collectors (ARS 1000) in order to allow an accurate comparison of TD and the sum DDq WD. Collection bottles were filled in advance with 20 ml of 10% nitric acid (Nitric acid 65% Suprapur, Merck) in order to dissolve particulate matter and to avoid trace metal adsorption on bottle walls. When the rain volume was high, nitric acid was added, within the laboratory clean room, to obtain a final pH of 1. At the end of each collection period (7 days), the funnel was rinsed with 100 ml of a 10% nitric acid solution (Nitric acid 65% Suprapur, Merck) and the resulting solution was collected into a separate clean HDPE bottle.

Wet and dry depositions collection

Sampling of TD was supplemented with separate collection of dry and wet atmospheric depositions at each site, using an ARS 1000 equipment (MTX Italia SPA, Modane, Italy). Both types of samples were collected in polyethylene cylindrical vessels (29 cm inner diameter) covered with a single lid which automatically moves from one container to the other, according to a rain probe (Fig. 1b). Wet deposition was collected in a 17-l vessel and transferred into smaller bottles (1l) for easier transport to the laboratory. The vessel used for dry deposition was partially filled with purity water (18.2 MV Milli-Q water, Millipore S.A.) to a depth of 1 cm in order to avoid resuspension of collected particles. The evaporation of this water was compensated by an automatic pump triggered by an optical fibre sensor for water level. As it was done for TD collection funnel, DD and WD vessels were rinsed with 100 ml of a 10% nitric acid solution and the resulting solution was collected in separate clean HDPE bottle.

At the end of each collection period, all collection materials, i.e. for TD, DD and WD, were replaced by clean ones.

Collector and vessel cleaning

For each laboratory this procedure was applied to all materials in contact with wet, dry or total atmospheric fallout samples, i.e. bottles, funnels, ARS vessels, caps and filtration units. The CER-EVE procedure was: (1) washing with a sponge and dishwasher detergent, outside of the clean room, and rinsing with deionised water (Milli-Ro, Millipore S.A.); (2) introducing into the clean room and complete immersion into a 2% Extran bath during 24 h; (3) rinsing with ultra pure water and complete immersion in a 10% nitric acid bath (Nitric Acid 68% Normapur, Prolabo) during 24 h.

The LISA procedure was: (1) washing with dishwasher detergent outside the clean room; (2) complete immersion during 24 h in a 2% HCl bath (HCl 36% Normapur, Merck), then rinsing the material with deionised water before introducing into the clean room (class 1000); (3) rinsing with ultra pure water in the clean room and complete immersion into a 2% HCl bath for at least 4 days.

The final step was similar in both laboratories: rinsing with ultra pure water and drying before sealing into double plastic bags. All procedures in the clean rooms were performed under class 10 or 100 laminar hoods.

Membranes used for sample filtration (Sartorius, cellulose nitrate, 0.45 mm porosity) were treated in the clean room before any use: (1) immersion into a 5% nitric acid solution during 24 h; (2) rinsing with ultra pure water and storing in a ultra pure water bath.

Trace metal analysis

After samples were brought back to the laboratory and nitric acid was added (when necessary), samples were kept in a dark room at 5 8C during 7 days in order to dissolve most of particles. Then, samples were filtered under a class 100 laminar hood with 0.45 mm porosity filters. The 60-ml sub-samples obtained were kept at 5 8C until their analysis. The analytical technique used by CER-EVE was a Graphic Furnace Atomic Absorption Spectrometer (GF-AAS Perkin-Elmer 1100 B) with Argon flow (Linde, N56) and deuterium lamp for non-specific absorption correction (matrix effect). For cadmium determination, ammonium di-hydrogeno-phosphate (NH H PO Merck, 4 2 4 Suprapur) was added for matrix modification and prevention of cadmium loss by volatilisation. The analytical technique used by LISA was an ICP-AES (Perkin-Elmer Optima 3000) equipped with an ultrasonic nebulisor.

Results and discussion

Validation procedures

Prevalent deposition mechanism

Atmospheric deposition of aerosols and gases occurs in two modes: wet and dry. To obtain total atmospheric loading, it is necessary to measure both wet and dry deposition [START_REF] Golomb | Atmospheric deposition of toxic onto Massachusetts Bay-I[END_REF]. The measurement of wet deposition is relatively straightforward; it involves the analysis of trace quantities of pollutants, often in concentrations of mgØl , in aqueous solution. The measurement of y1 dry deposition is more problematic. In direct measurement of dry deposition, an artificial surface is usually used that simulates the natural surface onto which dry deposition is occurring. In this work, for direct measurements of such depositions, a layer of ultra pure water in a bucket served as a surrogate water surface. A similar method of dry deposition onto a surrogate water surface was used by [START_REF] Golomb | Atmospheric deposition of toxic onto Massachusetts Bay-I[END_REF] and [START_REF] Morselli | Heavy metals in atmospheric surrogate dry deposition[END_REF]. Such a device clearly avoids possible resuspension of aerosols, which have reached this water surface. Nevertheless, in industrial or urban areas, DD was often sampled by immobilising aerosols deposited on an horizontal surface covered with an adhesive polymer named 'DIEM small plate' (NF X 43-007-1973). Such adhesion is not complete and aerosols or their metal components may be washed out by rain and wind. Evaluation of this loss was done by the comparison of the DD collector and the rinsing step of the funnel walls which simulated a dry nature surface.

In countries with temperate climate and limited precipitation, it is important to evaluate the relative importance of DD through aerosol settling and of WD through rain. Indeed, during wet weekly periods, with average daily rainfall amounts above 10 mmØday , Cd, Cu and especially Pb are y1 mainly deposited as DD (Fig. 2): the mean relative importance of DD at the rural site reaches 40, 60 and 80% for Cd, Cu and Pb, respectively. This prevalence of DD has also been observed at Creteil: the relative importance of DD reached 67, 73 and 76% for Cd, Cu and Pb, respectively. In central Paris [START_REF] Garnaud | Transfert and geochemical evolution of metal pollution in an urban catchment[END_REF], DD represented 77, 83 and 87% of TD for Cd, Cu and Pb, respectively. These results show the importance of DD relative to WD in both areas.

Rinsing step

The device used most frequently for collecting TD consists of a funnel connected to a receiving bottle (Fig. 1a). When aerosols settle on the funnel wall, they easily adhere, adsorb and accumulate on its walls and are mostly transferred to the bottle during a rain event. An unknown and poorly controlled part of such aerosols accumulated on Pb as well as rainfall amounts (mm) during each sampling period. funnel walls may be resuspended during windy periods: this is not the case of aerosol trapped by the water layer of the DD collector. Thus, the sum of DD and WD metal fluxes, as determined by ARS 1000 equipment, is larger than the TD metal flux, during the same period: at the rural site, cumulated fluxes of DDqWD are 4 and 1.5 times higher than TD, for Pb and Cd, respectively. In the urban area, the same comparison for Cd, Cu and Pb collected by ARS 1000 and TD collector shows no difference, i.e. (DDqWD)yTD ratio calculated for cumulated fluxes are 1.07, 1.11 and 0.94 for Cd, Cu and Pb, respectively. This differ-ence between urban and rural areas is probably caused by the highest amount of metals adsorbed on the TD funnel walls in urban area. Indeed, a thin black soot layer was deposited on the funnel walls at Creteil site. This latter, playing a role śimilar to the water layer in the DD collector, may prevent particles deposited on funnel walls to be resuspended by wind. We have attempted to demonstrate this adsorption mechanism by rinsing the funnel at the end of each collection period and by determining heavy metals in the sample obtained during such an acid rinsing step. Fig. 3 demonstrates that during the whole campaign performed at Creteil, the atmospheric metal fluxes calculated from samples obtained by acid rinsing of the funnel are significant, reaching a relative importance of 30, 50 and 40% for Cd, Cu and Pb, respectively. In the rural area, the relative importance of the rinsing step is lower and reaches 14, 13 and 30% for Cd, Cu and Pb, respectively. The lower importance of the rinsing step in a rural area, i.e. without an adhesive system (water or soot), demonstrates the possible resuspension of aerosols by wind. However, the acid rinsing procedure of funnels is probably far from being complete: this is especially clear in urban areas where black soot deposits have been often observed [START_REF] Garnaud | Transfert and geochemical evolution of metal pollution in an urban catchment[END_REF]. Such black deposits are not totally released by acid rinsing and even after long immersion in detergent bath, it is often necessary to wipe them out with tissues. Although some procedures used by regional or international networks, monitoring total atmospheric deposits, neglect the amount of metals deposited on the funnels, we are convinced that at the end of each sampling period, such funnels should be acid rinsed and replaced by clean ones.

Collection procedure reproducibility

A comparison was performed between our two research groups at both the Creteil and Morvan ´sites. Each laboratory used its own clean room, reagents, material and analytical technique. The statistical one-tailed t-test was used to compare the mean flux values obtained by each laboratory at each site. Results obtained both in rural and urban areas showed no significant difference between the two research groups for the 99% CI. Furthermore, if we exclude Zn flux in the rural site, we could observe a good agreement between values measured at each site with published data collected in similar land occupation sites [START_REF] Tripathi | Atmospheric deposition of Pb, Cd, Cu and Zn in Bombay, India[END_REF][START_REF] Vukmirovic | Resuspension of trace metals in Belgrade under conditions of drastically reduced emission levels[END_REF][START_REF] Hovmand | Heavy metal bulk deposition and aerosol concentrations in rural Denmark 1992-1996[END_REF][START_REF] Garnaud | Transfert and geochemical evolution of metal pollution in an urban catchment[END_REF][START_REF] Ridame | Trend in total atmos-pheric deposition fluxes of aluminium, iron, and trace metals in the northwestern Mediterranean over the past decade (1985-1997)[END_REF]. Indeed, our results are in the same order of magnitude than previous studies.

Validation of trace metal analysis

The validation procedure presents three steps using laboratory blanks (LB), field blanks (FB) and samples certified for trace metals.

LBs were chosen as the rinsing solutions (10% nitric acid) which were used for the rinsing step: the metal analysis was performed after the filtration of the solution through a 0.45 mm pore filter in our clean room. This procedure allows the assessment of possible contamination by sample handling within the clean room. The detection limit (DL) of both GF-AAS and ICP-AES (Desboeufs et al., 1999) have been calculated as three times the standard deviation of 10 laboratory blanks analysis.

FBs were prepared to assess the material contamination during transport and installation on sites. Total deposition FB was prepared using 20 ml of 10% nitric acid which had been transported to the sampling site, placed on the standing PVC pipe and brought back to the laboratory. Dry deposition FB was prepared as the water layer contained in the collecting vessel, transported back to the laboratory just after filling it on the site. Wet deposition FB was prepared using the rinsing solution, which was poured into a clean sampling bucket at the sampling site, and brought back to the laboratory. Table 1 compares The accuracy of the analytical results was verified using three samples certified in trace metals:

(1) NIST 1643d 'Trace elements in water', US Department of Commerce, National Institute of Standards and Technology, Gaithersburg, MD 20 899, USA; (2) SPS-SW1 'Surface Water (batch 105)', Spectra-Pure Standards, Promochem, Molshelm, France; and (3) SLRS 'Saint-Laurent River Surface', Geological Survey Quality Assurance Branch, Canada. These certified samples were chosen because they had heavy metal concentrations similar to those found in atmospheric depo-sition (Table 2). These certified samples were introduced into each set of analysed samples. For some elements (Cd, Cu, Fe and Na), deviation between measured and certified values are less than 10%. In the Pb case, there is a relatively high deviation between certified and measured values (54%) for low concentrated samples, but this level is 10 times lower than 90% of measured values in the rural area. For other elements (Al, Cr and Zn), the deviation is between 15 and 25%, but measured concentrations are included in the uncertainty interval given for the certified values. Therefore, analytical conditions are considered as validated for atmospheric trace metal analysis.

Flux assessment

The uncertainty of concentration measurement varies from method to method (i.e. ICP-AES and GF-AAS), and also from species to species. Generally, the concentration measurements of standard samples were within 10-20% of the nominal values. However, in atmospheric deposition measurement the major source of uncertainty is not the concentration measurement, but in the method of collecting deposition samples [START_REF] Golomb | Atmospheric deposition of toxic onto Massachusetts Bay-I[END_REF]. For wet deposition, there may be some loss of the fine rain drops (or light snow flakes), especially under wind conditions. For dry deposition measurement, both the water layer method and the funnel method have major uncertainties that are difficult to quantify. Bucket and funnel walls present a significant aerodynamic interfer- ence to particle (and gaseous molecule) deposition. Particles, especially in the sub-micron to micron size range, are subject to Brownian, wind and turbulent eddy motion, and may be blown over and around the bucket or funnel walls rather than deposited into it. Once inside the funnel or bucket, the particles may adhere to the walls or deposit in the bottom of the collector. While we did rinse the collector walls with acid and analysed the rinse solution for metals, the deposition area was taken only as the top area of the collector.

Heavy metal impact

Comparison between urban and rural deposition fluxes

Total atmospheric deposition fluxes were compared using fluxes integrated over the whole campaigns conducted at our urban and rural sites (Fig. 4). The impact of human activities in Creteil area ćould be seen on several metals like Pb, Cu, Cd, Na, Al, Cr and Fe. This influence was more obvious for Cu, Cd and Pb which have only anthropogenic sources, as opposed to four other metals, which also have many natural sources [START_REF] Pacyna | Estimation of the atmospheric emissions of trace elements from anthropogenic sources in Europe[END_REF][START_REF] Person | Contribution des principales sources en metaux et metalloıdes a la ´´p ollution particulaire dans l'agglomeration Parisienne[END_REF][START_REF] Sullivan | Using emission factors to characterise heavy metal emissions from sewage sludge incinerators in Australia[END_REF]. Total atmospheric Zn fluxes were surprisingly high at our rural site of the Morvan regional park. The high concentration of this element was probably induced by work done during our sampling period on building roof, which is made with Zn-covered metal sheets located 100 m from our collectors. Indeed, we have noticed that our TD determination for Zn in Morvan park is higher than previous works done in rural areas [START_REF] Migon | Measurement of trace metal wet, dry and total atmospheric fluxes over the Ligurian Sea[END_REF][START_REF] Ridame | Trend in total atmos-pheric deposition fluxes of aluminium, iron, and trace metals in the northwestern Mediterranean over the past decade (1985-1997)[END_REF] and lower than other results in urban areas [START_REF] Tripathi | Atmospheric deposition of Pb, Cd, Cu and Zn in Bombay, India[END_REF][START_REF] Vukmirovic | Resuspension of trace metals in Belgrade under conditions of drastically reduced emission levels[END_REF]. Such differences may be related to the presence of point sources, which are clearly site-specific.

Evolution of trace metal deposition fluxes

Determination of DD and WD fluxes was performed at the same Creteil site in 1994 using the śame collecting equipment ARS 1000 [START_REF] Garnaud | Transfert and geochemical evolution of metal pollution in an urban catchment[END_REF]. Fig. 5 shows the 5-year trend of Pb, Cu and Cd TD fluxes assessed by the sum of DD and WD: a decrease appears for all three heavy metals. Indeed, Pb, Cu and Cd fluxes drop by a factor of 5, 2 and 2, respectively. During both sampling periods registered rainfall amount was not very different, i.e. 800 and 600 mmØyear in 1994 and y1 1999, respectively: such a weak difference could not explain such a high TD decrease. Better treatment of smoke emissions by various waste or sludge incinerators or power plants is more likely to be responsible for such large improvements in air quality.

Conclusions

During 8 weeks, atmospheric fallouts were collected weekly in a rural area in order to set up a sampling and analysis procedure for low concentrated heavy metal samples. The study was completed by a 16-week urban collection period, thus allowing a comparison between urban and rural atmospheric depositions as well as a determination of temporal trends at Creteil. Á simple method of total atmospheric deposition collection using a HDPE funnel and bottle standing at 1.5 m above the ground within a PVC pipe was assessed. Twenty millilitres of nitric acid was placed into the bottle before the sampling period in order to dissolve all the collected particles. Nevertheless, the funnel acid rinsing appeared to be an important step of the collection procedure. This step is clearly related to the importance of DD within TD, as evidenced both in rural and urban sites. The analytical techniques used (GF-AAS and ICP-OES) in this work allowed the determination of low concentration levels of some heavy metals like Al, Fe, Na, Pb, Cu and Zn. But for some other metals (Cd and Cr), an improvement has to be achieved in material cleaning and collection procedures to ensure the quality of their determination. Comparison of trace metal deposition fluxes determined separately at CEREVE and LISA, showed good agreement: this resulted in well-defined collection and analytical procedures, including thorough vessel cleaning and the use of clean rooms.

An illustration of the impact of human activities on urban atmospheric fallout was evidenced by comparing Morvan and Creteil heavy metal TD: the most important differences in Pb and Cd were related to their emission by anthropogenic sources. Such urban impact was found to decrease very significantly between 1994 and 1999 for Pb, Cu and Cd TD fluxes, demonstrating the recent improvement in the treatment of smoke produced by anthropogenic activities.

Fig. 1 .

 1 Fig. 1. Atmospheric fallout collectors: (a) total atmospheric deposition collector and (b) separate wet and dry atmospheric deposition collector (ARS 1000, MTX Italia, Modane, Italy).

Fig. 2 .

 2 Fig. 2. Week average of Morvan's daily flow of dry (DD) and wet (WD) atmospheric depositions (mgØm Ød ) for Cd, Cu and y2 y1

Fig. 3 .

 3 Fig. 3. Comparison of Cd, Cu and Pb total deposition rate (kg m year ) integrated over both campaigns performed at Cre-y2 y1 teil and Morvan sites (1999-2000): each deposition rate is the sum of the contribution of samples present in collecting bottles (bottom part) and obtained during acid rinsing of collecting funnels (top part).

  DL, LB and FB for each analytical technique (GF-AAS and ICP-AES), as well as 10th and 90th percentiles (d 10 and d ) of metal concentrations determined at the 90 Morvan site. Tenth percentile was taken for com-

Fig. 4 .

 4 Fig. 4. Comparison of urban (Creteil) and rural (Morvan) total átmospheric deposition rate (kgØkm Øyear ) integrated over y2 y1

Fig. 5 .

 5 Fig. 5. Comparison between total atmospheric annual deposition rate (kgØkm Øyear ) integrated during 5 month cam-y2 y1 paigns performed at Creteil in 1994-1995 and 1999-2000 ẃinter periods, using the sum of monitored DD and WD fluxes, and mean rainfall amount (mmØyear ) during both sampling y1

Table 1

 1 Comparison of detection limits (DL), laboratory and field blank mean and standard deviation results obtained using GF-AAS and ICP-AES, and 10th (d ) and 90th (d ) percentiles of metal concentrations in TD samples collected at Morvan site (mgØl )

	y1

Table 2

 2 Samples certified concentration used in this work as well as 10th (d ) and 90th (d ) percentiles concentration values of metal in . are the certified values; M.V. are the measured values which were obtained by the median of 10 analysed samples; D is the deviation between certified and measured values. Values in bold were obtained by GF-AAS.

	10	90

Acknowledgments

This work was supported by the atmospheric department of ADEME and by the PIREN-Seine research program (CNRS GDR 1067). The authors are grateful to Vincent Rocher (CEREVE) and Myriam Harry (Laboratoire de Biologie des Sols et des Eaux) for their scientific support.


MS Bertrand Moal

MD Frank Schwab

MD b , Christopher P Ames

MD, PhD Justin S Smith

MS a , Praveen Devon Ryan

MD b , V Mummaneni

MD d Gregory M Mundis

BS a , Jamie S Terran

MD Eric Klineberg

MD f , Robert A Hart

MD Oheneba Boachie-Adjei

MD c , Christopher I Shaffrey

PhD Wafa Skalli

PhD Virginie Lafage
email: virginie.lafage@gmail.com

Radiographic Outcomes of Adult Spinal Deformity Correction: A Critical Analysis of Variability and Failures Across Deformity Patterns

Keywords: Adult spinal deformity, spinopelvic alignment, Surgical treatment, SRSeSchwab classification, Radiographic effectiveness

Study Design: Multicenter, prospective, consecutive, surgical case series from the International Spine Study Group. Objectives: To evaluate the effectiveness of surgical treatment in restoring spinopelvic (SP) alignment. Summary of Background Data: Pain and disability in the setting of adult spinal deformity have been correlated with global coronal alignment (GCA), sagittal vertical axis (SVA), pelvic incidence/lumbar lordosis mismatch (PI-LL), and pelvic tilt (PT). One of the main goals of surgery for adult spinal deformity is to correct these parameters to restore harmonious SP alignment. Methods: Inclusion criteria were operative patients (age greater than 18 years) with baseline (BL) and 1-year full-length X-rays. Thoracic and thoracolumbar Cobb angle and previous mentioned parameters were calculated. Each parameter at BL and 1 year was categorized as either pathological or normal. Pathologic limits were: Cobb greater than 30 , GCA greater than 40 mm, SVA greater than 40 mm, PI-LL greater than 10 , and PT greater than 20 . According to thresholds, corrected or worsened alignment groups of patients were identified and overall radiographic effectiveness of procedure was evaluated by combining the results from the coronal and sagittal planes.

Introduction

Although great diversity of deformity patterns exists among patients with adult spinal deformity (ASD), one common objective of any realignment procedure is to restore harmonious spinopelvic alignment in the coronal and sagittal planes.

Several sagittal radiographic parameters define and quantify regional and global spinopelvic alignment: the sagittal vertical axis (SVA), which assesses the global alignment of the spine versus the pelvis; the pelvic incidence minus the lumbar lordosis (PI-LL), which reflects the harmony between lumbar lordosis and the morphologic pelvic incidence; and the pelvic tilt (PT), which characterizes the extent of pelvic compensation for truncal inclination. Recent studies have identified these 3 radiographic parameters as most highly correlated with patient-reported outcomes; accordingly, they were incorporated as the key parameters in the Scoliosis Research Society (SRS) eSchwab classification for ASD [START_REF] Schwab | Radiographic spino-pelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis[END_REF]. This validated classification [START_REF] Schwab | Sagittal realignment failures following pedicle subtraction osteotomy surgery: are we doing enough?[END_REF] defines the threshold of pathological values for the 3 parameters based on correlation with clinical scores: SVA greater than 40 mm, PI-LL greater than 10 , and PT greater than 20 .

The SRSeSchwab classification defines different coronal curve patterns based on Cobb angle measurement and location of the apex of the coronal deformity (thoracic, thoracolumbar/lumbar, or double). Historically, the coronal Cobb angle has been considered the most important parameter for the diagnosis and management strategy of patients with ASD. Glassman et al. [START_REF] Glassman | Correlation of radiographic parameters and clinical symptoms in adult scoliosis[END_REF] and Schwab et al. [START_REF] Schwab | Radiographic spino-pelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis[END_REF], however, suggested in 2 prospective multicenter studies that the magnitude of coronal deformity is less crucial than the restoration of sagittal alignment in assessing pain and disability, although Glassman et al. [START_REF] Glassman | Correlation of radiographic parameters and clinical symptoms in adult scoliosis[END_REF] demonstrated an association between global coronal alignment (GCA) (an offset of the C7 plumbline and the sacral line) of greater than 40 mm in the frontal plane and deterioration in patient outcomes.

From a clinical point of view, interpreting information from several different radiographic parameters in multiple planes can be difficult; an analysis of individual measurements taken independently may help identify the most important parameters to correct.

The objective of this study was to evaluate the effectiveness of surgical treatment in restoring or correcting SVA, PIeLL, PT, coronal Cobb angle, and GCA.

Materials and Methods

Patient population and data collection

This study was a retrospective analysis of a consecutive series of ASD patients enrolled in a prospective multicenter study (10 sites) evaluating operative patients with X-rays at baseline and 1 year after surgery. Subjects were enrolled according to an institutional review boardeapproved protocol at each site. Inclusion criteria for the database were age greater than 18 years and a radiographic diagnosis of ASD, defined as at least 1 of the following: Cobb angle greater than 20 , SVA greater than 50 mm, PT greater than 25 , and thoracic kyphosis greater than 60 . Exclusion criteria were the presence of inflammatory arthritis, tumors, or neuromuscular disease. Demographic and medical history data were collected. Standing anteroposterior and lateral spine radiographs were analyzed at baseline and 1 year after surgery using validated software [START_REF] Champain | Validation of new clinical quantitative analysis software applicable in spine orthopaedic studies[END_REF][START_REF] Rillardon | Validation of a tool to measure pelvic and spinal parameters of sagittal balance[END_REF] (Spineview; Laboratory of Biomechanics Arts et Metiers Par-isTech, Paris, France) to measure thoracic (T) and thoracolumbar (L) coronal Cobb angles, GCA, SVA, PI-LL, and PT (Fig. 1). For the present study, patients without complete sets of X-rays at baseline and 1 year after the surgery were excluded.

Baseline classification

Each patient was individually classified according to the SRSeSchwab classification of ASD [A,B] (Fig. 2), which distinguishes 8 groups based on deformity pattern (Table 1).

Surgical correction of individual parameters

Each radiographic parameter was analyzed at baseline and 1 year postoperatively to identify whether it met the following deformity thresholds: Cobb angle greater than 30 , GCA greater than 40 mm, SVA greater than 40 mm, PI-LL greater than 10 , and PT greater than 20 . The researchers used the comparison between baseline and 1 year to individually categorize patients into one of the following treatment efficiency groups for each parameter (Table 2): ''consistently normal,'' ''radiographic deterioration,'' ''persistent deformity,'' and ''radiographic correction.''

Overall effectiveness

At 1 year, the overall radiographic effectiveness of the realignment procedure was evaluated individually by combining the results from the coronal and sagittal planes to make the following 4 groups: 1) no deformity: patients who did not meet the deformity threshold for any of the 5 parameters; 2) coronal deformity: patients who met only coronal deformity threshold(s) (Cobb angle and/or GCA); 3) sagittal deformity: patients who met only sagittal deformity threshold(s) (SVA, PT, and/or PI-LL); and 4) combined deformity: patients who met at least 1 coronal and 1 sagittal deformity threshold.

Statistical analysis

The authors evaluated differences in demographic data between deformity classification groups at baseline using analysis of variance. A significance threshold was established at p ! .05. At baseline, the distribution of patients with sagittal deformity was expressed for the different combinations of sagittal parameter. At baseline and 1 year, the proportion of patients in the entire sample with a deformity was calculated for each parameter independently. Then, for patients with deformity at baseline, the fraction of patients in the radiographic correction and persistent deformity groups was calculated by comparison with 1-year data for each parameter. Similarly, for patients without deformity at baseline, the fraction of patients in the radiographic deterioration and consistently normal groups was established for each parameter. Finally, the proportion of patients in each postoperative classification group was

Results

Enrollment

A total of 316 surgical patients were enrolled in this study between 2008 and 2011; 252 had adequate baseline radiographs and 215 patients had adequate baseline radiographs and 1-year follow-up (Table 3). Of those 215 patients, 161 had adequate baseline and 1-year radiographs and were the only ones included in this study.

Demographics and curve type

This study included 161 ASD patients (24 males and 137 females) with a mean age of 55 AE 15 years (Table 4). Eighty percent of the patients had a coronal Cobb angle greater than 30 ; patients with thoracic curve (13%) were less common than patients with thoracolumbar/lumbar curve (34%) or double curve (33%). Analysis of sagittal spinopelvic parameters revealed that 71% of patients had a sagittal deformity (SVA, PI-LL, or PT meeting deformity thresholds), 54% of whom had both coronal and sagittal deformity (thoracic/sagittal [TS], thoracolumbar/sagittal [LS], and double sagittal [DS]) and 17% of whom had a pure sagittal deformity (S). A total of 5 patients (3%) were unclassifiable because of the difference between the inclusion criteria for the database (coronal Cobb angle greater than 20 ) and the SRSeSchwab classification threshold for deformity in the coronal plane (Cobb angle greater than 30 ). These patients were removed from the analysis of treatment efficiency.

Patients with pure thoracic coronal curves (T) were significantly younger ( T, L, andD) (p ! .05). A total of 37% of patients had a history of spine surgery. The rate of history of spine surgery varied between 0% and 60%, depending of the type of curve. Patients with sagittal deformity (with or without coronal deformity) were more likely to have had prior surgery than patients without sagittal deformity.

Sagittal deformity: distribution of sagittal parameters combinations

At baseline, the most frequent sagittal deformity (44%) was a combination of the 3 parameters (SVA, PI-LL, and PT) (Table 5). The second most frequent sagittal deformity was defined by only a pelvic retroversion (20%). Three percent of patients with sagittal deformity had only a mismatch between the PI and LL.

Review of individual radiographic parameters

Figure 3 shows radiographic treatment effectiveness for the different parameters. Table 6 expresses the distribution of patients meeting radiographic deformity thresholds at baseline and 1 year after surgery. Table 7 expresses the percentage of patients who were persistently deformed, out of the population with deformity at baseline; and Table 7 expresses the percentage of patient who had deteriorated radiographically, out of the population without deformity at baseline.

Coronal Cobb angle

At baseline, coronal Cobb angle greater than 30 was the most common deformity (80% of the total population). The Cobb angle was persistently present in 30% of those patients, and so was corrected in 70%, which made it also the most consistently corrected parameter. Cobb angle was the parameter that deteriorated least frequently: Only 3 patients (9%) had deterioration; all had a preoperative Cobb angle close to 30 , and deterioration was between 3 and 7 . Postoperatively, 26% of patients had a Cobb angle greater than 30 .

Global coronal alignment

At baseline, GCA was the least frequent deformity (25%; 41 patients); 93% of these patients (38) had a thoracolumbar curve (L, LS, double curve, or DS). The GCA was corrected in 54% of those patients. However, GCA was also one of the most likely deteriorated parameters, because 18% of patients with a normal alignment at baseline met the threshold for deformity 1 year after surgery. This led to an overall rate of postoperative coronal malalignment of 25%, the same as the preoperative deformity rate.

Sagittal vertical axis

At baseline, 46% of the patients had an SVA that met the deformity threshold. A total of 54% of these patients were radiographically corrected, whereas 11% of patients with a normal preoperative SVA deteriorated. Postoperatively, a total of 27% of the patients had an SVA meeting the deformity threshold.

Pelvic incidence/lumbar lordosis mismatch

At baseline, 42% of the patients had a PI-LL value that met deformity thresholds. 51% of these subjects were radiographically corrected, whereas 14% of patients with a normal preoperative PI-LL deteriorated. Postoperatively, 29% of patients had PI-LL that met the deformity threshold.

Pelvic tilt

At baseline, 58% of patients had a PT meeting the deformity threshold (ie, substantial pelvic retroversion); this represented the most frequent deformity among the sagittal parameters. Only 24% of these patients were radiographically corrected, and 24% with a normal baseline PT deteriorated postoperatively. Overall, 54% of patients had a PT that met the deformity threshold at 1 year.

Overall results at 1 year

Table 8 lists the overall deformity distribution at 1 year. A total of 23% of patients had no deformity in either the coronal or sagittal plane, 35% had a deformity only in the sagittal plane, 14% only in the coronal plane, and 27% in both the coronal and sagittal planes. Patients with baseline deformity in the coronal plane only (T, L, or D) were more SVA, sagittal vertical axis; PI-LL, mismatch between pelvic incidence and lumbar lordosis; PT, pelvic tilt. likely to have complete resolution of the deformity, especially patients with lumbar curves (75%). For patients presenting with coronal and sagittal deformity at baseline, this sagittal deformity was not corrected for 68% (DS) to 86% (S), depending on the type of curve.

Discussion

Adult spinal deformity encompasses a broad range of radiographic patterns, which makes it challenging to dissociate the intrinsic parameters of the deformity from those related to compensatory mechanisms. Recent reports have brought to light the difficulty in restoring spinopelvic alignment after 3-column osteotomies [START_REF] Schwab | Sagittal realignment failures following pedicle subtraction osteotomy surgery: are we doing enough?[END_REF][START_REF] Smith | Change in classification grade by the SRS-Schwab adult spinal deformity classification predicts impact on health-related quality of life measures: prospective analysis of operative and non-operative treatment[END_REF]. One common limitation to these studies is that they tend to focus on a single parameter and are often limited to a single plane (coronal or sagittal).

The objective of this study was to evaluate the ability of surgical treatment to radiographically restore spinopelvic alignment while taking into account the type of deformity. With the exception of the coronal Cobb angle, all radiographic parameters were chosen based on their reported clinical relevance (ie, correlation with patient-reported outcomes), as demonstrated in large cohorts of patients representing the full spectrum of ASD [START_REF] Schwab | Radiographic spino-pelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis[END_REF][START_REF] Glassman | Correlation of radiographic parameters and clinical symptoms in adult scoliosis[END_REF]. Several studies have shown correlation between clinical scores and coronal or sagittal global alignment (GCA/SVA) [START_REF] Schwab | Radiographic spino-pelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis[END_REF][START_REF] Glassman | Correlation of radiographic parameters and clinical symptoms in adult scoliosis[END_REF][START_REF] Smith | Change in classification grade by the SRS-Schwab adult spinal deformity classification predicts impact on health-related quality of life measures: prospective analysis of operative and non-operative treatment[END_REF][START_REF] Lafage | Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity[END_REF][START_REF] Blondel | Impact of the magnitude and percentage global sagittal plane correction on health related quality of life at 2 years follow up[END_REF]. In an exception to these results, Sanchez-Mariscal et al. [START_REF] Sanchez-Mariscal | Correlation of radiographic and functional measurements in patients who underwent primary scoliosis surgery in adult age[END_REF] demonstrated only a low correlation between clinical scores after primary surgery and sagittal malalignment (PT and SVA) in 59 ASD patients. Based on multivariate analysis, the only significant predictor of disability was PT. However, the extent of deformity (ie, whether the patient had sagittal imbalance) and the effect of the surgery were not taken into account. To avoid the former problem, the current study compared radiographic parameters to thresholds of clinical relevance [START_REF] Schwab | Radiographic spino-pelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis[END_REF][START_REF] Glassman | Correlation of radiographic parameters and clinical symptoms in adult scoliosis[END_REF][START_REF] Smith | Change in classification grade by the SRS-Schwab adult spinal deformity classification predicts impact on health-related quality of life measures: prospective analysis of operative and non-operative treatment[END_REF].

However, the current method was limited in that it did not account for the absolute magnitude of surgical correction with regard to the severity of deformity at baseline. As such, a patient with a severe baseline deformity who had significant surgical correction would still be considered undercorrected if he or she did not reach the deformity threshold. The decision to overlook this issue was motivated by 2 reasons. First, the thresholds were defined by databases that included operative and nonoperative patients with and without previous surgery. Therefore, patients with severe baseline deformity and significant restoration were incorporated into the calculation of thresholds. Second, the objective of this study was to analyze the radiographic effectiveness of the surgery, not the clinical effect.

Analysis by parameter

The results illustrate that a large number of patients are insufficiently corrected and that deterioration in alignment is not a negligible phenomenon; notably, for coronal malalignment (GCA), the number of patients who were corrected was similar to that of patients who deteriorated (Fig. 3). Whereas the clinical impact of the Cobb angle remains controversial, scoliosis is nevertheless the most common deformity in ASD surgical patients (80% in this database). In this study, it was also the parameter with the highest rate of correction. This may reflect a historical bias to predominantly treating the most obvious aspect of ASD, even though sagittal parameters have been shown to be more influential on clinical scores [START_REF] Blondel | Impact of the magnitude and percentage global sagittal plane correction on health related quality of life at 2 years follow up[END_REF][START_REF] Blondel | Reciprocal sagittal alignment changes after posterior fusion in the setting of adolescent idiopathic scoliosis[END_REF][START_REF] Ploumis | A correlation of radiographic and functional measurements in adult degenerative scoliosis[END_REF].

Each sagittal parameter represents a different component of an individual's deformity. Whereas in 44% of the cases the sagittal deformity was a combination of the 3 sagittal parameters, it also appears that great variability of combinations exist between patients. The PI-LL represents a regional disharmony between PI, a morphologic parameter, and LL. The surgeon can directly affect this parameter. The considerable rate of inadequate PI-LL correction (48% in the total sample) may illustrate insufficient consideration of this important relationship. Pelvic tilt was the parameter that most often deteriorated, as well as the one least often corrected. Pelvic tilt represents a pelvic compensatory mechanism. Although the surgeon cannot directly modify this parameter, several models of PT prediction have been developed [START_REF] Lafage | Spino-pelvic parameters after surgery can be predicted: a preliminary formula and validation of standing alignment[END_REF], and complete correction of structural sagittal deformity should obviate the need for pelvic compensation. Results from this study illustrate the gap between the scientific community and clinical practice. The combination of the 3 sagittal parameters revealed that sagittal deformity was present in 71% of patients preoperatively and 62% postoperatively, again perhaps indicating a lack of focus on sagittal imbalance during surgery.

Analysis by curve type

The diversity of curve types in ASD patients has often been noted, rendering the analysis of ASD patients as a single group inadequate. In contrast to adolescent idiopathic scoliosis [START_REF] Lenke | Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis[END_REF][START_REF] Lenke | The Lenke classification system of operative adolescent idiopathic scoliosis[END_REF], there has been limited consensus regarding the classification of ASD [START_REF] Smith | Classification of sagittal thoracolumbo-pelvic alignment of the adolescent spine in standing and its relationship to low back pain[END_REF]. The researchers' choice was to use the recently described SRSeSchwab classification of ASD because of its simplicity (only 4 radiographic parameters must be evaluated) and clinical relevance. Only 23% of patients experienced complete radiographic correction of the deformity. Highly varying rates of correction were observed between the different SRSeSchwab curve types. These differences may relate to differences in overall complexity between curve types and variability in baseline severity of deformity. Although patients with baseline deformity in the coronal plane only (T, L, or D) had a greater chance of achieving complete correction than patients with sagittal deformity, there was still substantial variability in the likelihood of correction between coronal groups. In particular, double curves appear to be much more difficult to completely correct than single curves. These results may help identify the risks of radiographic malalignment or deterioration that vary between SRSeSchwab curve types.

This study represents a detailed analysis of surgical realignment outcomes across ASD patterns. The large numbers of patients who were insufficiently corrected and who deteriorated highlight the need to continue research to determine which parameters are most important, and to develop surgical procedures that consistently improve radiographic outcomes. Although this study did not identify factors leading to suboptimal radiographic outcome, several aspects of surgical treatment warrant scrutiny. In addition to appropriate surgical planning, it appears essential to develop better intraoperative tools to allow feedback to the surgeon so that operative intervention aligns with planning goals. Longer follow-up analysis is important to assess variations in compensatory parameters (notably PT), as well as alignment of nonfused portions of the spine. Furthermore, correlation between radiographic correction and clinical benefit requires further analysis. Data are shown as patients (% [n]) falling into the following groups: no deformity (no parameters meeting deformity thresholds), coronal deformity (coronal Cobb angle and/or global coronal alignment meeting thresholds), sagittal deformity (sagittal vertical axis, pelvic tilt, and/or pelvic incidence and lumbar lordosis mismatch meeting thresholds), and combined deformity (at least 1 coronal and 1 sagittal parameter meeting thresholds) groups by Scoliosis Research SocietyeSchwab curve type.

Fig. 1 .

 1 Fig. 1. Coronal and sagittal radiographic parameters and threshold associated used for the radiographic analysis. GCA, global coronal alignment; SVA, sagittal vertical axis; PT, pelvic tilt; PI, pelvic incidence; LL, lumbar lordosis.

Fig. 2 .

 2 Fig. 2. Scoliosis Research SocietyeSchwab classification defined by coronal curve type and 3 sagittal spinopelvic modifiers. SVA, sagittal vertical axis; PT, pelvic tilt; PI, pelvic incidence; LL, lumbar lordosis.

Fig. 3 .

 3 Fig. 3. Radiographic treatment efficiency by parameters (in %). GCA: global coronal alignement, SVA, sagittal vertical axis; PI-LL, pelvic incidenceelumbar lordosis; PT, pelvic tilt.

Table 2

 2 Treatment efficiency groups for Cobb angle, global coronal alignment, sagittal vertical axis, pelvic incidence/lumbar lordosis mismatch, and pelvic tilt.

	Treatment efficiency	Meet deformity	Meet deformity
	group	threshold at	threshold at 1 year
		baseline?	postoperatively?
	Consistently normal	No	No
	Radiographic deterioration	No	Yes
	Persistent deformity	Yes	Yes
	Radiographic correction	Yes	No

Table 1

 1 Different curve types based on Scoliosis Research SocietyeSchwab classification for adult spinal deformity.

	Curve group	Acronym	Coronal criteria	Sagittal criteria
	Thoracic	T	Type T	All modifiers at grade 0
	Thoracic/sagittal	TS	Type T	At least 1 modifier at grade þ or þþ
	Thoracolumbar	L	Type L	All modifiers at grade 0
	Thoracolumbar/sagittal	LS	Type L	At least 1 modifier at grade þ or þþ
	Double	D	Type D	All modifiers at grade 0
	Double sagittal	DS	Type D	At least 1 modifier at grade þ or þþ
	Sagittal only	S	Type N	At least 1 modifier at grade þ or þþ
	Unclassified	U	Type N	All modifier at grade 0

  31 AE 12 years) than those with other curve types (p ! .05). Within the group of patients with thoracolumbar/lumbar coronal curves (L and LS), patients with sagittal deformities (LS: age, 63 AE 8 years; body mass index [BMI], 28 AE 8) were older and had a greater BMI than patients without sagittal deformity (L: age, 47 AE 13 years; BMI, 23 AE 3) (p ! .05). Patients with only sagittal deformity (S: age, 67 AE 13 years) were older than any of the groups with only coronal deformities (

Table 3

 3 Number of patients enrolled, with adequate baseline radiographs, with adequate baseline radiographs and 1-year follow-up, and with adequate baseline and 1-year radiographs, by site.

	Number of patients	Total	Site
			A	B	C	D	E	F	G	H	I	J
	Enrolled	315	59	14	51	6	33	25	15	15	58	39
	Enrolled and adequate baseline radiographs	252	55	10	42	6	26	19	15	9	36	34
	Enrolled, adequate baseline radiographs, and 1-year follow-up	215	55	10	42	4	20	10	15	8	21	30
	Enroll, adequate baseline, and 1-year radiographs	161	51	6	31	4	16	9	10	7	3	24

U, unclassified; T, thoracic; TL, thoracic sagittal; L, thoracolumbar; LS, thoracolumbar sagittal; D, double; DS, double sagittal; S, sagittal.

Table 5

 5 At baseline, distribution of patients with sagittal deformity for different combinations of sagittal parameters.

	Distribution of patients with sagittal deformity (% [n])
	SVA	PI-LL	PT	SVAþPI-LL	SVAþPT	PI-LLþPT	SVAþPI-LLþPT	Total
	12 [14]	3 [3]	20 [23]	2 [2]	8 [7]	12 [13]	44 [50]	100 [113]

Table 6

 6 Distribution of patients who met radiographic deformity thresholds at baseline and 1 year after surgery, for different parameters.

	Distribution of patients (% [n])
	Baseline	1 year

Table 7

 7 Patients persistently deformed, of population with deformity at baseline.

	Patients at 1 year (% [n])
	Cobb angle	Global coronal	Sagittal	Pelvic incidence	Pelvic tilt
		alignment	vertical axis	and lumbar
				lordosis mismatch
	30 [39]	44 [18]	46 [34]	49 [33]	76 [71]
	9 [3]	18 [22]	11 [10]	14 [13]	24 [16]

Table 8

 8 Postoperative categorization.

	Type of curve	Thoracic	Thoracolumbar	Double	Thoracic sagittal	Thoracolumbar	Double	Sagittal	Total
						sagittal	sagittal
	No deformity	55 [6]	75 (9)	38 (6)	20 (2)	5 (2)	16 (6)	14 (4)	23 (37)
	Coronal deformity	18 (2)	13 (5)	25 (4)	10 (1)	13 (5)	16 (6)	0	14 (23)
	Sagittal deformity	18 (2)	13 (2)	25 (4)	50 (5)	45 (14)	32 (11)	75 (17)	35 (57)
	Combined deformity	9 (1)	0	13 (2)	20 (2)	37 (17)	35 (14)	11 (7)	27 (44)

, Medtronic; royalties from Aesculap, Lanx; grant from Baxano Surgical; stock/stock options from Baxano Surgical, Doctors Research Group, Visualase; patent for Fish and Richardson, PC); JSS (grant from DePuy Spine to ISSG; consultancy/honorarium from Biomet, DePuy, Medtronic, Globus; fellowship funding and research support from AOSpine; research support from AANS/CNS Joint Spine Section; fellowship support from NREF); DR (none); PVM (royalties from DePuy Spine, Qualified Medical Publishers, Thieme Publishers; honoraria from DePuy Spine and Globus); GMM (personal fees from Nuvasive; grant from Nuvasive; royalties from K2M); JST (none); EK (grants from OREF, Synthes DePuy, AOSpine; personal fees from Synthes DePuy, Stryker, AOSpine, Alphasic); RAH (consultancy for DePuy, Eli Lilly, Medtronic; research support from K2M; royalties from K2M, DePuy); CIS (grant from ; royalties from Biomet, Medtronic; patents for Medtronic, Biomet); WS (none); VL (grant from DePuy Synthes Spine; board membership with Nemaris Inc.; consultancy for MSD; grants from DePuy, ISSG, SRS; payment for lectures including service on speakers bureaus for MSD, DePuy, K2M; stock/stock options for Nemaris Inc). This work was partially funded via a research grant from DePuy Spine and from the Scoliosis Research Society.