The artificial bowel sphincter for faecal incontinence: a single centre study

Background and aims Faecal incontinence (FI) is a socially devastating problem. The treatment algorithm depends on the aetiology of the problem. Large anal sphincter defects can be treated by sphincter replacement procedures: the dynamic graciloplasty and the artificial bowel sphincter (ABS).
Introduction
Faecal incontinence (FI) is a complex problem. The resulting social isolation is a major concern, which results in a reduced quality of life [1]. The real prevalence is unknown, but studies show a higher prevalence than expected [2–5]. Most patients are females with one or more vaginal deliveries in the past. Direct trauma to the anal sphincter complex can give immediate problems or problems later in life [6, 7].
The initial therapy should be conservative, e.g. diet modifications, medication, biofeedback physiotherapy or retrograde irrigation. Surgical intervention is indicated when conservative treatment fails. An anal repair is usually the first choice of treatment for a minor sphincter defect. Satisfactory results are achieved in a tension-free repair in 47–100% of the cases [8]. Long-term results are less satisfying [9]. Sacral nerve modulation (SNM) has proven to be effective for treating faecal incontinence in patients with an intact sphincter complex [10]. Sphincter replacing therapy is indicated in patients with large sphincter defects or completely disrupted sphincters and in case of SNM failure. The sphincter replacement procedures are grossly divided in the dynamic graciloplasty (DGP) [11, 12] or the artificial bowel sphincter (ABS). The first artificial bowel sphincter for faecal incontinence was a urinary prosthesis (AMS 800, AMS) placed by Christiansen in 1987 [13]. Modifications had to be made to suit the anal sphincter for use in patients with faecal incontinence.
Until 1997, patients with faecal incontinence due to large anal sphincter defects were treated with DGP in our institution [16]. Since then, the ABS was introduced in our institution for the same indication. Because the operating technique is similar, there was no learning curve to be dealt with. Is this study, the results of the ABS implantations for the treatment of feacal incontinence in a large volume centre are presented.
Materials and methods
This study is a non-randomised, non-controlled, prospective single-centre study. Thirty-four patients with persisting or recurrent end-stage FI were included between 1997 and 2006.The majority of patients had large (>33% of circumference) anal sphincter defects. A sufficient length of the perineum was a prerequisite for ABS implantation. Previous sphincter replacement surgery was no exclusion criterion for implantation of an ABS. All patients underwent a full preoperative examination consisting of a defaecography, endo-anal ultrasound (SDD 2000, Multiview, Aloka, Japan, 7,5 Mhz endo-anal transducer), pudendal nerve terminal motor latency measurement (St Mark’s pudendal electrode) and anal manometry using a Konigsberg catheter (Konigsberg Instrument, Pasadena CA, USA) connected to a polygraph (Synectics Medical, Stockholm, Sweden). An Acticon artificial bowel sphincter (ABS, American Medical Systems, Minneapolis, MN, USA) was used in all patients. The Williams incontinence score was used to classify the symptoms. Anal manometry was routinely performed during the follow-up and used to objectivity ABS function. The follow-up appointments were scheduled at 1, 3, 6, 12 months and annually. Infection necessitating explantation was a primary endpoint. A re-intervention was a secondary endpoint.
The system implantation has been described extensively elsewhere [14, 15], but will be summarised here. The ABS implant consists of three parts: an inflatable balloon, a cuff and a pump. Under strict systemic and local antibiotic prophylaxes, the cuff is placed around the anus using two lateral incisions. The pump is placed in the labia majora or scrotum, and the pressure-regulating balloon is placed in cavum Retzii. Care is taken not to perforate the rectum. If a perforation occurs, the procedure is stopped. After proper wound healing, the patient is eligible for another implantation procedure.
Data are expressed as the mean with the range between parenthesis. Data were analysed using the commercially available GraphPad Prism 4.00 software (GraphPad Software, San Diego, USA). The Wilcoxon signed rank test was used for non-parametric paired values. Statistical significance was set at p < 0.05.
Results
The patient population existed of 25 women and nine men. The aetiology of the faecal incontinence is shown in Table 1. Three patients were previously treated with a DGP. The average age was 55.3 (23.8–75.6) years. The mean period of faecal incontinence before the placement of the ABS was 11.0 (1.0–48.0) years. One patient had a rectum perforation during the initial surgery, and placement of the ABS was abandoned. She awaits a second implant attempt. Thirty-three patients were implanted. The mean follow-up was 17.4 (0.8–106.3) months. The mean procedure time was 68.1 min (38.0–105.0). In 24 patients, the length of the cuff was 11 cm, in three patients 10 cm, in two patients 13 cm, in two patients 12 cm, in one patient 14 and in one patient 9. The width of the cuff was in all, but one patient, 2.9 cm. There was one patient with a cuff off 2.0 cm. All patients received a pressure-regulating balloon of 91–100 cm H2O. The mean postoperative hospital stay was 3.5 (2.0–12.0) days.
Table 1Aetiology and previous surgical treatmentNumberSexEtiologyPrevious treatment1FHysterectomy, cervix carcinoma, radiotherapy2MAnal atresiaDGP3FTwo breech deliveries: ruptureAnal repair, SNM4FEpisiotomy, hysterectomyPNE5MPelvic trauma: urethra/rectum ruptureRepair and colostomy6MTrauma, partial spinal cord lesionPNE7FDelivery trauma: total rupture, hysterectomyAnal repair, SNM8FDelivery trauma: rupture9MAnal atresia10MClassical hemorroidectomy11FEpisiotomy, hysterectomyPNE12FDelivery trauma: ruptureTwo anal repairs, PNE13FDelivery trauma: total ruptureTwo anal repairs, 14FDelivery trauma: ruptureAnal repair15FDelivery trauma: rupture, cauda syndromeAnal repair16FDelivery trauma: rupture, hysterectomyAnal repair17FDelivery trauma: rupture, hysterectomyAnal repair18MAnal atresiaDGP19FDelivery trauma: ruptureAnal repair20FDelivery trauma: rupturePre-/post-anal repair, PNE21FDelivery trauma: rupture, hysterectomyAnal repair, PNE22FDelivery trauma: rupturePost-anal repair, SNM22MLow anterior resection T2NOM023FDelivery trauma: rupture24MPelvic crush trauma: urethra/rectum ruptureRepair and colostomy25FDelivery trauma: rupture26FDelivery trauma: total rupture12 anal repairs27FDelivery trauma: ruptureAnal repair, colostomy28FDelivery trauma: ruptureAnal repair29MPelvic trauma30FDelivery trauma, uterus extirpatie DGP31FDelivery traumaPNE32FClassical hemorroidectomySECCA33FDelivery trauma, total ruptureAnal repair, Thiersch wire34FDelivery trauma, hysterectomyPNEF Female, M male, DGP dynamic graciloplasty, SNM sacral neuromodulation, PNE percutaneous nerve evaluation
The mean preoperative Williams score of 4.8 (4–5) decreased significantly after ABS placement to 2.1 (1–5; Fig. 1). The mean preoperative anal resting pressure was 58.1 (17.0–128.0) mmHg. This was not significantly altered after implantation (60.3 (21.0–93.0 mmHg; p = 0.89). The mean preoperative squeeze pressure was 80.1 (25.0–149.0) mmHg, which increased to 120.5 (65.0–154.0) mmHg after implantation (p = 0.003; Fig. 2).
Fig. 1Mean pre- and postoperative Williams score (1 = continent, 2 = incontinent to flatus, 3 = incontinent to liquid stool, 4 = occasional incontinence to normal stool <1, 5 = fully incontinent)Fig. 2Baseline resting pressure versus deflated ABS pressure and baseline squeeze pressure vs inflated ABS pressure pre- and postoperatively (at last follow-up)
Thirteen patients (39%) complained about a rectal evacuation problem. In 12 patients, this could be managed conservatively. One patient had a revision of the system with placement of a wider anal cuff. Seven patients (21.2%) had an infection of the system, which led to seven explantations. One of these patients has been implanted successfully with a new ABS (Fig. 3).
Fig. 3Flow chart of implanted patients
In one patient, the ABS was successfully converted to a dynamic graciloplasty. In two patients, a colostomy was performed. The other three patients had no other interventions.
One patient was explanted due to persisting peri-anal pain without an infection. She received a colostomy. Twenty-six reinterventions (including explantations) had to be performed. This means 0.79 re-intervention per implanted patient.
Discussion
There is a large experience in our institution with the DGP [16]. However, since 1997, the ABS is also performed in our institution for the same area of indications as the DGP. When a patient qualifies for a sphincter replacement procedure, he or she can decide whether an ABS or DGP will be performed. Nonetheless, sufficient perineal length is a prerequisite for ABS implantation in a female patient. We believe that the risk for late erosion of the ABS is higher in the case of severe, cloaca-like malformations of the perineum. In these cases, a DGP is the preferred procedure. All patients in this study had an adequate perineal length.
In the beginning, the initial infection rate of the DGP was a problem, but improved as a result of technical modifications and the introduction of systemic and local antibiotic prophylaxis. The same prophylaxis protocol was used for the implantation of ABS. However, despite meticulous application of the antimicrobial protocol, the infection rate of the ABS implantations in our patient population remains high and is comparable with other series [14, 15]. We believe that this infection rate is likely to remain a serious problem in every attempt to place a corpus alienum around the anus through peri-anal incisions.
To overcome this problem of infection, Finlay et al. [17] have developed a new prosthetic sphincter, which is placed above the pelvic floor musculature by means of a laparotomy. It was hypothesised that this sphincter will function as a new puborectal sling in this position. Till now, 12 patients are implanted. Infectious complications, however, occurred in three patients (25%), with subsequent removal of the system. Technical problems occurred in five of the nine remaining patients during follow-up. Technical failure is also one of the main problems of the ABS. Twelve of our patients had some sort of technical failure. This is also known from other studies concerning the ABS [18].
Only limited data on long-term follow-up of a sufficient number of ABS sphincters are available. There is one multicentre study with disappointing long-term data where the initial data were promising [19]. The anal manometry data of this patient population suggest poor action of the ABS. The authors conclude that the ABS acts as a passive barrier causing a rectal outlet obstruction. Our manometry data contradict with this conclusion. We strongly believe that the ABS acts as an active sphincter. In our experience, the patients need to deflate the anal cuff to defecate. Nevertheless, constipation can be a problem. Thirteen of our patients complained about constipation. This could be solved in the majority of patients by conservative means. One patient needed a wider anal cuff to treat an outlet obstruction.
The indications for sphincter replacement surgery are decreasing in our institution since the introduction of SNM. The relative numbers of DGPs and ABSs decreased, while the number of SNM has increased. This implicates that ABS and DGP are reserved for the more severe complicated cases of faecal incontinence. A higher complication rate is therefore expected. However, the placement of an ABS remains an alternative to a colostomy in the well-informed and motivated patient even if a DGP has failed.
Conclusion
The artificial bowel sphincter is an effective treatment option for severe faecal incontinence. Even in experienced hands, the risk of infection, explantation and system malfunctioning remain high. In well-informed and motivated patients, it is worthwhile to proceed to implantation, as the alternative is a colostomy. Our data suggest that the ABS acts as an active sphincter and not as a passive barrier.

artificial bowel sphincter
faecal incontinence
single centre


The “Health Benefit Basket” in France

The French “Health Benefit Basket” is defined principally by positive lists of reimbursed goods and services; however, global budget-financed hospital-delivered services are more implicitly defined. The range of reimbursable curative care services is defined by two coexisting positive lists/fee schedules: the Classification Commune des Actes Médicaux (CCAM) and the Nomenclature Générale des Actes Professionnels (NGAP). The National Union of Health Insurance Funds has been updating these positive lists since August 2004, with the main criterion for inclusion being the proposed procedure’s effectiveness. This is assessed by the newly created High Health authority (replacing the former ANAES). In addition, complementary health insurers are consulted in the inclusion process due to their important role in French healthcare financing.
The French health insurance system, a mix of explicit and implicit regulations, offers wide-ranging reimbursement in the fields of preventive, curative, rehabilitative, and palliative care. The present analysis of the health benefit basket in France is being carried out during a period of reforms. This contribution describes the structure of the statutory health insurance system, followed by a description of the entitlements and benefits and of the actors involved in the decision-making process with its criteria for services of curative care, HC1. Finally, we analyze the main changes which may affect the health basket in France.
The structure of the French statutory health insurance system
The financial management of health care in France is undertaken mainly by the statutory health insurance system as a branch of the wider social security system. The health insurance system’s current structure is based on its founding text, the Ordinance of 4 October 1945 and subsequent legislative measures. This system has covered the entire population of France since 1 January 2000 when the Couverture Maladie Universelle (CMU, Universal Health Coverage Act) extended basic health insurance cover to all legal residents of France. The French statutory health insurance system is a compulsory scheme and covers all households regardless of health status, income, number of persons, etc. It provides a somewhat uniform field of reimbursement, with the “basket of goods and services” covered by the insurance funds being identical for all the statutory schemes with the reimbursement rate being the same for the three main insurance schemes since 2000. The exceptions are the Alsace-Moselle region’s local scheme and certain public sector schemes [1]. Membership in one of the health insurance funds of the statutory health insurance depends on the profession of each person. In the context of the CMU, however, participation depends on legal residence in France and on the level of income. Any dependants of the insured person are also covered by his/her health insurance.
The three main health insurance schemes are as follows: (a) The General Scheme (Régime général) covers employees in commerce and industry and their families (about 84% of the population) as well as persons receiving CMU, estimated in late 2003 at about 1,500,000 person (2.4% of the population) [2]. (b) The Agricultural Scheme (Mutualité sociale agricole) covers farmers and agricultural employees and their families (about 7.2% of the population). (c) The Scheme for the Non-agricultural Self-Employed (CANAM) covers craftsmen and self-employed persons, including self-employed professionals such as lawyers (about 5% of the population). Another ten work-related schemes cover specific sections of the population.
Statutory health insurance funds three-quarters of the health expenditure and therefore leaves considerable scope for complementary sources of funding. An estimated 85% of the population have complementary health insurance. Taking into account recipients of Couverture Maladie Universelle Complémentaire (Complementary Universal Health Coverage 6% of the population), about 91% of the French population are covered by the complementary health insurance scheme, which covers the same health basket as the statutory schemes and not other goods and services [3]. The most important benefit catalogues for France and their underlying criteria are displayed in Tables 1 and 2 while the following sections are confined to curative health care services.Table 1 Catalogues and implicit regulationGBRCCAMNGAPLSAC ATUMed. dev.NABM Sp. reg.HC.1 Curative care services  1. Inpatient curative care++–––––  2. Day-patient curative care++–––––  3. Outpatient curative care+–––––    3.1. Basic medical and diagnostic services++–––––    3.2. Outpatient dental care++–––––    3.3. All other specialized health care++–––––    3.4. All other outpatient curative care (paramedical)––+––––    3.5. Services of curative home care+–+––––HC.2 Services of rehabilitative care  1. Inpatient rehabilitative care+–––––+  2. Day cases of rehabilitative care+–––––+  3. Outpatient rehabilitative care+–+––––  4. Services of rehabilitative home care+–+–––+HC.3 Services of long-term nursing care  1. Inpatient long-term nursing care+–––––+  2. Day cases of long-term nursing care+–––––+  3. Long-term nursing care: home care+–+––––HC.4 Ancillary health care services  1. Medical analysis laboratory+––––+–  2. Diagnostic imaging++–––––  3. Patient transport and emergency rescue +–––––+HC.5 Medical goods dispensed to outpatients  1. Prescribed medicines+––+–––  2. Other medical nondurables+–––+––  3. Therapeutic devices and other medical durables+–––+––HC.6 Prevention and public health services––––––+GBR General Benefit Regulation, CCAM list of physicians’ and dentists’ technical procedures, NGAP list of physicians’ consultations and other health professionals’ activity, LSAC ATU positive lists of drugs, Med. dev. positive lists of medical devices, NABM positive lists NABM biology procedure, Sp. reg. specific regulationTable 2 Benefit-defining laws/decrees, catalogues and implicit regulationGBRCCAM, NGAPLSAC ATUMed. dev.NABM Sp. reg.Legal status: law, decreeLawUNCAM decisionMinisterial orderMinisterial orderUNCAM decisionAdministrative documentDecision makerParliament UNCAM, on the advice of HAS and UNOCMinisters of health and social security, on the advice of the Transparency CommissionMinisters of health and social security on the advice of the ad hoc CommissionUNCAM, on the advice of HAS and UNOCOriginal purpose: entitlements, reimbursement, target settingReimbursementPositive listPositive listPositive listPositive listPositive listTariffsFee schedulePrices or reference pricesReference pricesFee schedulePositive-negative definition of benefitsPositivePositivePositivePositivePositivePositiveDegree of explicitnessa3 (except inpatient care: 1)33332 or 3If itemized: goods/procedures only; linked to indicationsMainly goods and procedures; linked to indicationsProcedures, sometimes linked to indicationsPharmaceutical products, linked to indicationsGoods linked to indicationsProcedures linked to indicationsMainly indicationsUpdating–RegularlyRegularlyRegularlyRegularly–GBR General Benefit Regulation, CCAM list of physicians’ and dentists’ technical procedures, NGAP list of physicians’ consultations and other health professionals’ activity, LSAC ATU positive lists of drugs, Med. dev. positive lists of medical devices, NABM positive lists NABM biology procedure, Sp. reg. specific regulationa 1, “all necessary”; 2, “areas of care”; 3 “items”
Organizational structure and actors involved in the definition of the benefit basket for curative services
In France the general conditions of the reimbursement system are established by law. Health benefit catalogues are drawn up at national level with the whole range of goods and services reimbursed by the statutory scheme being specified in Article L.321-1 of the Social Security Code (SSC) [4]. The reimbursement of goods and services depends on their inclusion in positive lists, according to Articles L.162-1-7, L.162-17, and L. 165-1 of the SSC. Until 2004 positive lists were officially enforced by ministerial orders detailing the inclusion of new goods and services. Ministers made their decisions upon the advice of ad hoc scientific commissions and agencies, for example, the National Agency for Accreditation and Evaluation in Health Care (ANAES). The inclusion of all the listed procedures depends on ANAES advice which considers the effectiveness and/or safety of these procedures and the conditions under which they need to be performed.
Reimbursement is legal only when goods or services are provided in an appropriate medical context. Reimbursement for all goods and all paramedical procedures depends on the provision of a prescription, which serves as confirmation of the necessity of such goods and services. For some types of treatment, such as physiotherapy and spa treatment, the prescription from a physician does not provide the needed status for reimbursement. Coverage by statutory health insurance is subject to the prior authorization (entente préalable) of the physicians advising the health insurance funds, after examination of the patient’s case history and a possible interviewing of the patient.
According to Article L.322-2 of the SSC, the insured person’s copayment is fixed by a decision of Union Nationale des Caisses d’Assurance Maladie (UNCAM, National Union of Health Insurance Funds) within rate limits defined by a Council of State decree. The copayment can be either a percentage of the charges or a lump sum. The patient’s contribution to the total cost of treatment varies according to the type of treatment, being higher for outpatient care and drugs compared to hospital treatment. The copayment must be paid by the insured person or, where applicable, by their complementary health insurance fund.
Council of State decrees also define copayment exemption conditions (Article L.322-3 of the SSC). The most important exemptions are linked to the health status, especially in the case of one person suffering from one of 30 specified long-term illnesses, for example, diabetes, AIDS, cancer, and psychiatric illness, and if the patient is suffering from one or several incapacitating diseases. Other health status-based exemptions concern, for example, disabled persons under the age of 20 years and pregnant women during the final 4 months of pregnancy.
The health benefit basket is explicitly defined by positive lists of goods for both the public and the private sectors. Positive lists only apply to services delivered by private sector professionals in their own practices or in private for-profit hospitals. Conversely, services dispensed in public hospitals or private not-for-profit hospitals were mainly the subject of implicit definition since they were paid for by a global budget, which means in practice that basically every dispensed service was reimbursed. The situation is currently undergoing an important reform.
HC1 services qualifying for reimbursement by the health insurance system include: (a) inpatient care and treatment in public or private healthcare institutions; (b) outpatient care provided by general practitioners, specialists, dentists, and midwives; and (c) diagnostic services and care prescribed by physicians and performed by laboratories and paramedical professionals, such as nurses, physiotherapists and speech therapists.
In July 2005, two health benefit catalogues for curative services exist: (a) The Classification Commune des Actes Médicaux (CCAM), which revises the previous medical services catalogue, has been adopted in 2005 with its application still only partial [5]. (b) The general fee schedule (Nomenclature Générale des Actes Professionnels, NGAP), which is the medical procedures positive list for health professionals in private practice, in their own surgeries and consulting rooms and in private-for-profit hospitals, remains in force until the CCAM is fully implemented.
Inpatient curative service
The Social Security Act of 18 December 2003 (Loi de financement de la sécurité sociale, LFSS) changed the inpatient acute care funding rules, but implementation is still in progress. The situation will continue to change during the next few years for at least two reasons. Firstly, the positive list for physicians’ procedures, the CCAM, applies to both private and public hospitals (Article 162-1-7 of the SSC), which had not been the case before. Secondly, the implementation of the per-case payment reform that will lead to the result of both sectors being brought into line. These situations before and after the reforms of 2004-2005 are shown in Table 3.Table 3 Definition of benefit catalogues for inpatient care Before 2004–2005After 2004–2005Funding rules depend upon hospital status: PH and PNFPH, vs. PFPHNew funding rules making the basket more explicitRange of reimbursed medical procedures defined at least for PFPH but not for other services, e.g., nursing careSame list of medical procedures for both private and public hospitals (Article 162-1-7 of the SSC),No positive list for PH, an implicit coverage for all services in PH and PNFPH mainly financed by the global budgetSame prospective per-case payment system for PH and PFPH for all medical, surgery and obstetrics services, based on DRG-type classification of GHS, but tariffs still differ from PH to PFPH.Basket of reimbursable drugs defined for PH and PFPHBasket of reimbursable drugs defined for PH and PFPHPH public hospital,
PNFPH private non-for-profit hospital, PFPH private-for-profit hospital, DRG diagnosis-related group, GHS homogeneous stay group
As seen in Table 3, there has been no positive list to define reimbursable services in public and in private not-for-profit hospitals, in which inpatient services were regulated by implicit coverage. However, the implementation of the per-case payment system will simplify the situation as all medical, surgery and obstetrics services in all hospitals will be included in it. The reform will also change the remuneration schemes of inpatient and outpatient care. Services provided in inpatient or outpatient acute care will be financed through a payment-per-case system. This is based on a diagnosis-related group type of classification of 700 Groupes Homogènes de Malades (GHM), considering comorbidities. A nationally fixed tariff (Groupe Homogène de Séjours, GHS, Homogeneous Group of Stays) is applied to each GHM [6]. Outpatient procedures will be paid on a fee-for-service basis, and organ retrieval and emergency services by annual lump sum payments. This payment system also includes earmarked funding (Missions d’intérêt général et Aide à la contractualisation, MIGAC) to finance other activities, such as research and education, but also certain healthcare activities promoted by contracts between hospitals and regional health agencies. The new GHS payment system has been in operation since 1 March 2005 for private-for-profit hospitals. Procedures carried out by physicians are always paid separately and directly to the physicians concerned on a fee-for-service basis, while in public hospitals, tariffs include specialists’ salaries. Since July 2005, the CCAM is used as the general fee schedule and can be considered as the positive list for private for hospitals. Health insurance funds will not finance any stay if one of these procedures does not apply. CCAM is currently available only for technical procedures such as surgery, medical imaging, and radiotherapy performed by physicians. Paramedical services, including, physiotherapy, which are linked to inpatient medical procedures, are reimbursed only if they are an essential part of the medical treatment. Regarding the definition of the health basket, the rules for day-case patient care are the same as those applicable to inpatient care. GHS tariffs refer to day hospital treatment.
Outpatient curative care
Patients who need health care have until now been free to choose which physician to consult and have also been allowed to refer themselves to specialists. Only few general practitioners have begun playing the role of gatekeepers, although a few of them have been making some attempts in this regard since 1996. Recent health insurance reforms are about to change this situation. Since 1 July 2005 all those benefiting from health insurance coverage in France are obliged to choose their main physician (médecin traitant). As a result there will be higher user charges if a person chooses to consult a specialist directly without being referred by her/his “gate-keeping” médecin traitant general practitioner [7]. The basket of reimbursable outpatient curative services is defined by a positive list which is also used as a fee-schedule for health professionals in private practice. Until March 2005 the NGAP was the only list and applied to all services. This will be replaced by the new CCAM classification. In a rather lengthy process CCAM is currently being developed. At this stage CCAM specifies only technical procedures such as diagnosis, surgery, and radiology performed by specialists and dentists. CCAM is also being used in public hospitals to charge for outpatient care and to specify the reimbursement rate. This classification is not yet used for specialist consultations or procedures carried out by other healthcare professionals who are still in use of the NGAP. The CCAM is fully comprehensive in content as it contains details of all medical procedures, even those that are not reimbursable. Each procedure corresponds to only one label and one code, eliminating any ambiguity and making it easy to use. The classification is structured according to the anatomical classification and specialities. There are 17 chapters which are based on the organ system to which the procedures refer. The CCAM is based on the rule of procedural totality, meaning that each label implicitly contains all the operations necessary for the performance of the medical procedure. It was drawn up as a resource-based relative value scale (RBRVS) by the main health insurance fund (CNAMTS) with the collaboration of health professionals, and the ANAES being involved in the selection of effective procedures.
Since the reform of 13 August 2004 the UNCAM, which includes representatives of the three main sickness funds, is in charge of preparing and updating the positive lists. UNCAM will be assisted in its decision making by the advice of the two newly created bodies, the High Health Authority (Haute Autorité de Santé), which replaced the ANAES and the National Union of Complementary Health Insurance Organizations (Union Nationale des Organismes d’Assurance Maladie Complémentaire, UNOC). The same criteria used for the NGAP will be used for the taxonomy of medical procedures leaving room for improvements in medical services and achieving cost-containment at the same time [8]. Nevertheless, the ministries of health and social security retain the right to reject UNCAM’s decisions and to include or exclude goods and services in or from the list, especially if public health issues are concerned. A commission comprising healthcare professionals’ unions and representatives of UNCAM has been created to determine the general rules for drawing up the RBRVS and then for validating the scale proposed by the health insurance fund services. In addition, UNCAM is responsible for negotiating the tariffs of medical procedures with healthcare professionals’ unions and for determining the levels of copayment and coinsurance.
Other outpatient services such as auxiliary services provided by nurses, physiotherapists, orthoptists, speech therapists and chiropodists must be provided on medical prescription in order to be reimbursed. In the area of complementary and alternative medicine (CAM) special recognition is given to acupuncture and homeopathy. These two therapies are thus recognized and may be legally practiced, but only by physicians or licensed physiotherapists on medical prescriptions for acupuncture. A few osteopathy and chiropractic procedures have recently been included in the CCAM in addition to certain vertebral manipulations which were already listed in the NGAP. The range of services covered by statutory health insurance does not include cosmetic surgery and some other treatments and services of uncertain effectiveness such as spa treatments. The issue of the allocation of scarce resources means that choices must be made which may result in the nonreimbursement of certain procedures, for example, bone density measurement when performed in the private sector as a preventive measure, and the imposition of limits on the frequency for which they can be reimbursed, such as mammography for cancer screening purposes.
Home care services
The entitlements laid down in the SSC include services provided by independent physicians (home visits) and by other health professionals such as nurses and hospital-at-home services. Regarding palliative care at home, according to Article R 162-1-10 of the SSC, a multidisciplinary team of health professionals can be organized at the special request of a person whose state of health demands it, to provide palliative home care. The remuneration can be paid on a fee-for-service basis or as a lump sum.
Discussion
This study faces a number of limitations which may affect the analysis of the French health benefit basket. Firstly, the study was carried out in a period of changes related to the redefinition of the medical procedures for both inpatient and outpatient care. This will make some statements in the previous catalogue become obsolete. Furthermore, the introduction of the new CCAM catalogue has been postponed several times due to conflicts of interest between health professionals, especially those between the physicians’ unions and the health insurance funds. The catalogue deals with the two issues of the remuneration of healthcare professionals and the state regulation. Secondly, the recent health insurance reform (Health Insurance Act, 13 August 2004) affects all actors involved in the definition of the benefit catalogue and thus the decision criteria. The High Health Authority, for instance, is expected to have considerable powers. At the same time, UNCAM is also playing an important role in the drawing up of the positive lists of procedures. However, the ministers of health and social security still retain their right to reject the UNCAM’s decisions. It could be asked whether the change regarding the delegation of the task of drawing up benefit catalogues to a so-called “self-governing body” is fully effective, as this is the case in Germany. It is too early to assess the consequences that these new regulations will bring about, but it can be anticipated that it might well be a case of plus ça change, plus c’est la même chose, as both the French government and the physicians have always played a major role in the healthcare decision-making process. Thirdly, the French system offers a mix of explicit regulation for ambulatory care, pharmaceuticals and medical devices, dental care, etc., with benefit catalogues and positive lists and of implicit regulation for a large part of inpatient care [9]. Altogether the package of health care services covered is comprehensive and wide-ranging although that the additional billing is rather high for certain types of goods and services. As a consequence of the implicitness of the coverage with particular respect to inpatient care, we have noted some differences between principles and practice, indicating that not all services are actually covered to the same extent. The interviews carried out at the Ministry of Health confirmed this finding.
Finally, the drawing-up of the positive lists still remains hotly contested among those at the health and social security ministries who were interviewed for this study. Current French health policy combines the harmonization of regulation with the reduction in health inequalities on the basis of improved knowledge of public health needs. However, this policy is being implemented in a context of increasing health expenditure and especially of increasing user charges. It is a contradictory situation in which things that have been received by the one hand have again been taken away by the other one.

france
health benefit plans
health services
health priorities
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Eye–hand coordination during manual object transport with the affected and less affected hand in adolescents with hemiparetic cerebral palsy

In the present study we investigated eye–hand coordination in adolescents with hemiparetic cerebral palsy (CP) and neurologically healthy controls. Using an object prehension and transport task, we addressed two hypotheses, motivated by the question whether early brain damage and the ensuing limitations of motor activity lead to general and/or effector-specific effects in visuomotor control of manual actions. We hypothesized that individuals with hemiparetic CP would more closely visually monitor actions with their affected hand, compared to both their less affected hand and to control participants without a sensorimotor impairment. A second, more speculative hypothesis was that, in relation to previously established deficits in prospective action control in individuals with hemiparetic CP, gaze patterns might be less anticipatory in general, also during actions performed with the less affected hand. Analysis of the gaze and hand movement data revealed the increased visual monitoring of participants with CP when using their affected hand at the beginning as well as during object transport. In contrast, no general deficit in anticipatory gaze control in the participants with hemiparetic CP could be observed. Collectively, these findings are the first to directly show that individuals with hemiparetic CP adapt eye–hand coordination to the specific constraints of the moving limb, presumably to compensate for sensorimotor deficits.
Introduction
Cerebral palsy (CP) is an umbrella-term describing a group of disorders of movement and posture leading to activity limitations, and that are caused by damage to the fetal or infant brain (Bax et al. 2005). In this study, we focused on the most common subtype of cerebral palsy, spastic hemiparesis, which typically occurs after unilateral lesions to the cerebral cortex or corticospinal pathways (Kwong et al. 2004). This condition is characterized by impaired control of muscle tone and spasticity in the upper and lower limbs of the contralesional, “affected”, side of the body (Albright 1996), generally progressing from proximal to distal (Freund 1987; Steenbergen et al. 2000b), and often accompanied by sensory deficits of proprioception and tactile perception (Cooper et al. 1995). These symptoms induce limitations on manual actions performed with the affected hand (AH), in particular related to fine motor skills such as fingertip force control (Eliasson et al. 1991). These limitations are further amplified by more central deficits in the integration of different modalities, such as matching proprioceptive and visual spatial information (Wann 1991), and integrating sensory information with motor output (Gordon et al. 2006). While the less affected hand (LAH) is usually spared from severe sensorimotor impairments (but see, Steenbergen and Meulenbroek 2006 for subtle deficits at the less affected body side), there is converging evidence for more high-level deficits in prospective control, or motor planning, in particular, in individuals with right hemiparesis (Mutsaarts et al. 2005, 2006; Steenbergen et al. 2000a, 2004; te Velde et al. 2005).
These studies on manual control have advanced our knowledge about the different levels at which the motor system affects CP as well as the behavioural reorganisation during the performance of actions (e.g., van Roon et al. 2005b). Yet, up to date, eye–hand coordination has not been investigated, despite preliminary evidence suggesting that it may contribute to deficits in action performance in individuals with CP (van der Meer et al. 1995; van der Weel et al. 1996). Even indirect evidence regarding the role of visual feedback for manual action performance in CP is scarce. Wann (1991) investigated visuo-proprioceptive integration in adolescents with CP. Comparing arm postures in a bimanual position-matching task under different conditions of sensory feedback, he found that, in contrast to adult controls, participants with CP employed very similar end postures (joint angle configurations) with the left and right arm in conditions in which vision of one or both arms was prevented. This was interpreted as evidence that they relied more strongly on purely proprioceptive information rather than on a shared visuospatial-proprioceptive representation and that the encoding of visual and proprioceptive information into a common egocentric frame may be problematic in these individuals. This would suggest that individuals with CP more strongly depend on continuous visual feedback for guiding manual actions to visual targets, compared to neurologically healthy adults.
Moreover, as the severity of the motor impairment, and concomitant proprioceptive impairment, increases from proximal to distal (e.g., Steenbergen et al. 2000b), it may be expected that actions with the affected-hand involving more fine motor control, such as grasping, need closer visual monitoring to provide additional feedback. In line with this, Steenbergen and colleagues (1996), studying bimanual actions in participants with hemiparetic CP, made the anecdotal observation that (overt) visual attention seemed to be drawn to the affected side of the body. However, in contrast to the reasoning above, a recent study that scrutinized the effect of removing visual information of the moving limb on end-point accuracy in a straight-line drawing task (van Roon et al. 2005a) found no specific adverse effect of this manipulation in participants with tetraparetic cerebral palsy when using their relatively less-impaired hand compared to control participants. Thus, up to date, there is no consensus on the role of visual guidance for the control of manual actions in CP.
Besides the sensorimotor impairments of the AH, more high-level aspects of action control, such as motor planning and prospective control, have been shown to be compromised as well in hemiparetic CP. In research on motor planning in individuals with CP, the LAH is used, as this hand has no (or small) movement restrictions, as is often the case with the AH. Hence, the higher-order process of motor planning can be studied without the confounding effects of possible movement restrictions. Atypical performance with the LAH was found for instance in tasks involving planning of the hand’s posture at the end of the action (Steenbergen and Gordon 2006; Steenbergen et al. 2000a), in particular, in individuals with right hemiparesis (Steenbergen et al. 2004). In these tasks, individuals have to pick up objects and place them in another orientation on a designated target. Ample evidence in controls suggest that individuals pick-up objects with a grip that allows them to end the task with a comfortable posture, even when this means that they have to sacrifice comfort of the start grip (see Steenbergen and Gordon 2006). This “end state comfort” effect was not present in individuals with CP, indicating a higher-level impairment of movement planning. Prospective control in individuals with hemiparetic CP was recently investigated in a collision avoidance task (te Velde et al. 2005). This study found later, hand-movement initiation in individuals with right as compared to left hemiparesis, again indicating reduced anticipation of action requirements. The extent to which deficits in motor planning or prospective control may be related to deviations in visual monitoring, with its typically anticipatory role for action control (Johansson et al. 2001) has not been investigated yet in individuals with CP.
In the present study, we examined eye–hand coordination in an unconstrained object prehension task in individuals with hemiparetic CP and neurologically healthy controls. To manipulate task difficulty, an obstacle was present in half of the trials, inducing a more complex transport trajectory. Participants performed the task with each hand separately. Based on the registration of eye and hand movements, we calculated several measures of temporal and spatial aspects of eye–hand coordination. Besides giving a first descriptive account of gaze patterns during object manipulation in a population with congenital hemiparesis, we addressed two hypotheses. Our first and main research question concerned the way in which individuals with hemiparetic CP adapt eye–hand coordination to the sensorimotor impairments of their affected hand. We hypothesized that individuals with CP would use increased visual monitoring when they perform the task with their AH as compared to performance with the LAH and to performance of control participants. Second, we examined eye–hand coordination when the task was performed with the LAH in participants with CP. Based on the previously established deficits in action planning, we hypothesized that gaze patterns are less anticipatory in general, in individuals with CP. Given the limited knowledge on visumotor control in CP and on the role of eye-movements for action planning, this second research question was much more exploratory than the first.
Methods
Participants
In total, 16 individuals took part in the study. Six participants with hemiparetic CP constituted the experimental group and ten participants with no known history of neurological disorders served as controls. Control participants were all right handed (Dutch version of the Edinburgh handedness inventory, Oldfield 1971) University students (9 females, 20–25 years). The six participants of the experimental group (5 females, 14–19 years) were students at the Werkenrode Institute (Groesbeek, The Netherlands), where they followed an adapted educational programme. They had been asked to take part in the study based on their condition (viz. congenital spastic hemiparesis). Additional requirements were no known oculomotor disturbance (such as nystagmus), and having the motor, cognitive and attentional capacities to perform the experimental task as assessed by initial screening. All were able to walk and sit independently, and able to read and write with their LAH.
Consent was obtained prior to the experiment, both in verbal form from the participants during the initial screening session, as well as in written form from their parents or caregivers. In a separate session taking place after the experiment, the participants with CP performed two standardised dexterity tests, the Box and Block test for gross dexterity (Mathiowetz et al. 1985) and the Purdue pegboard test for fine dexterity (Tiffin 1968). One of the participants was not available for the manual dexterity testing afterwards. Table 1 shows the results of these tests as well as other participant information. For the Purdue–Pegboard test, the norm score for individuals at the age of 16–17 years is 49.5 for the preferred hand. Standardised norm scores for the Box and Block test are not available for individuals younger than 20 years. For the youngest age group available, individuals between 20 and 24, the norm score is 88.2 for the preferred hand. The performance of the participants with CP was consistently below these norms, even when using the LAH.
Table 1Participant information for the participants with cerebral palsyParticipantAgeParetic sideB and Ba, cPPb, cCP115Right15/380/33CP217Left24/520/42CP317Left16/326/27CP415Right15/430/33CP514Left18/423/33CP619RightNAdNAdaBox and Blocks testbPurdue–Pegboard testcAffected hand/less affected handdNot available for testing
All participants received the same reimbursement (€6 per hour) for taking part. The study was approved by the local ethics committee and performed in accordance with the standards laid down in the 1964 Declaration of Helsinki.
Setup and procedure
The experimental setup is depicted in Fig. 1. Participants were comfortably seated on a chair approximately centered at the midline of the table, which constituted the working region for the experiment. Two objects (blue and green), two target regions, and an optional obstacle were placed on the table, as well as a fixation target (see Fig. 1 and caption for details). Two loudspeakers, placed below the table, were used to verbally instruct the participant through a pre-recorded voice. The experimenter sat facing the participant at a separate table. From this position he was able to supervise the experiment by instructing the participant, starting and terminating the trials, and monitoring participants’ performance (directly and via a computer monitor that showed the eye movement recording system’s output in real time).
Fig. 1Experimental setup (top view). The participant is seated at the table, with the right hand resting at the starting position. Positions of objects (blue and green cylinder, 6 cm in height, 3 cm in diameter, with an enlarged stabilizing basis of 6 cm in diameter), target regions (blue and green disc, 10 cm in diameter, contralateral to the corresponding object), optional obstacle (cylinder, 15 cm in height, 6 cm in diameter), and the pre-trial fixation target (red ball 2 cm in diameter mounted on a frame at about eye height) are shown. The experimenter was seated at a separate desk facing the participant. The dashed line represents the object transport movement from object to target region in a “blue” trial. The x- and z-axis of the Optotrak system were approximately aligned to the axes indicated here, the y-axis was orthogonal to both (vertical axis)
For each participant, the experiment consisted of eight conditions in a 2 × 2 × 2 factorial design, with the factors hand (AH/LAH for the participants with CP, NPH/PH for controls), obstacle (present, absent) and side (blue, green). In each of these conditions, five trials were performed, yielding a total of 40 trials per subject. The factors hand and obstacle were blocked while side was randomized within blocks. The order of the blocks was partially counterbalanced between participants. Prior to each trial, the participant was instructed to rest the “inactive” hand in his/her lap, such that it did not interfere with the task.
Each trial started with the task-hand resting at the starting position, and with gaze directed to the fixation target. After a variable delay (500–1,500 ms), the pre-recorded instruction “green” or “blue” (in Dutch) was played, upon which, the participant was to grasp the corresponding object and transport it to and place it on the contralateral target region of the same color. When an obstacle was present, the object had to pass in front of it, that is, between obstacle and participant (see Fig. 1, dashed arrow-line). After placing the object on the target region, the participant moved his/her hand back to the starting position and the experimenter put the cylinder back to its original location. When a trial failed, for instance because the cylinder slipped out of the participant’s hand, it was immediately repeated. This never occurred more than twice in a single participant.
Data acquisition
During the experiment, hand and head movements were recorded using an Optotrak 3020 system (sampling rate set at 125 Hz). Four Optotrak markers were located on the Eyelink helmet (see below) to monitor position and orientation of the head. Hand movements were recorded by means of a marker placed on the back, each of the participant’s hands near the head of the second metacarpal. For two participants with CP, this position did not guarantee sufficient visibility of the marker on the AH due to individual grasping patterns (excessive arm pronation leading to a thumb-down grasping posture). In these instances, the marker was placed more laterally on the hand. As we were mainly interested in the temporal aspects of the movements kinematics, this adjustment did not affect the measurement in a relevant way. The coordinate frame of the Optotrak system was oriented such that x, y and z axes roughly corresponded to the horizontal, vertical and posterior–anterior dimension with respect to the participant’s position (see Fig. 1).
Gaze direction was assessed using a head mounted Eyelink II system (sampling frequency 500 Hz), which was calibrated twice during the experiment, before each of the main blocks that corresponded to the obstacle present/absent conditions. To calibrate the system, the subject was asked to look at 10–15 points covering the frontal working plane. These points were manually indicated by the experimenter by using a stick on the end of which both a fixation target (small red ball with a diameter of 13 mm) and an Optotrak marker were attached. This “interactive” calibration method was chosen because pilot recordings revealed that two participants with CP failed to follow the instructions of the standard calibration procedure (employing a calibration board with LEDs). In addition, the “interactive” method allowed for constant monitoring of the Eyelink system’s output by the experimenter (see “Setup and procedure”).
The position of the fixation target and the position of the eye relative to the Eyelink helmet were used to compute gaze direction. Gaze direction was subsequently transformed to a 2D signal by projecting it to the xy-plane. Linear regression between this direction and the raw Eyelink data was used to calibrate the system. Although calibration error (deviation between actual and reconstructed gaze direction for the calibration targets) was relatively large—on average, 5° of visual angle, increasing towards the periphery—it was well within the precision requirements needed to answer our research questions. Particular care was taken in the analysis of eye movements (see “Eye movements”) to minimize the effect of this inaccuracy.
Preprocessing
The raw Optotrak data were partially interpolated with cubic spline interpolation (up to ten successive samples, corresponding to 80 ms) and low-pass filtered (third order Butterworth filter with cut-off frequency of 10 Hz). Hand velocity was computed by 3-point numerical differentiation.
The raw Eyelink signal was transformed to relative gaze direction and integrated with the helmet position and orientation to yield absolute gaze direction. Approximate fixations were computed as the intersection of gaze direction with the plane parallel to the xy-plane (see Fig. 1) and containing the centers of objects and target regions. Only data from one eye (selected by visual inspection for each individual participant) were used for further analysis. Gaze data were partially interpolated (up to four successive samples, corresponding to 8 ms, using cubic spline interpolation) and low-pass filtered (third order Butterworth with cut-off frequency of 20 Hz). Subsequently, gaze velocity, acceleration, and jerk (second time differential of velocity) were computed by repeated 3-point numeric differentiation.
Data reduction
Hand movements
Hand movements were identified using an absolute velocity threshold (0.20 m/s) and a direction criterion (start of a new movement indicated by a reversal of horizontal direction). These criteria provided the algorithms for the semi-automatic custom-written selection routines for the segmentation of the trials. Based on this segmentation, the grasp time (interval between the hand reaching and leaving the object region) and hand movement duration (interval between the hand leaving the object and reaching the target region) were determined. Analysis of eye–hand coordination was confined to the object transport phase that is from onset of the hand movement away from the object region till the end, reaching the target region. The duration of this movement was determined.
Eye movements
Saccades were detected using a jerk (second time differential of velocity) criterion, which has been shown to be more reliable than methods based purely on gaze velocity or acceleration, especially for head-free eye movement recordings. A saccade was scored whenever jerk exceeded 200.000°/s3, with an additional velocity requirement (50°/s) (see Wyatt 1998, for similar analaysis). Saccade termination was determined as the first moment after saccade onset at which velocity dropped below 50°/s. The total number of saccades registered in the experiment was 4,613. Saccade initiation/termination time was determined when none of the first or last eight samples (16 ms) were missing. Saccade peak velocity was determined, when in addition no more than four samples were missing in a row throughout the entire saccade. According to these criteria, saccade initiation and termination time could not be determined in 5.5% of all saccades, and peak velocity could not be determined in 10.5% of all saccades.
To test for potential group differences in basic eye movement kinematics, saccade main sequences were plotted, based on the saccades for which the peak velocity could be determined. Main sequences showed, for both groups, the typical linear relationship between amplitude and duration (e.g., Carpenter 1988), and the log-linear relationship between amplitude and peak velocity for all participants of both groups. No significant group differences were found in gradient or intercept of linear regressions of these relationships (all p > 0.05, Welch’s unpaired t-test).
Subsequently, for each trial the “object-leaving” and the “target-reaching” saccade were determined (in many trials these saccades coincided since there was a single gaze shift from object to target). Automatic detection of these saccades was complicated by the fact that precision of gaze data was not sufficient for a procedure based on landmark regions around object and target. Therefore, the following semi-automatic two-step procedure was adopted. First, fixations to object and target were determined automatically, assuming that these occurred before (up to −600 ms) the beginning and at the end of object transport. Fixation periods were defined as intervals of at least 200 ms, during which, the standard deviation of absolute gaze fixation was smaller than 5 mm. Note that this automatic procedure did not use absolute landmark regions but relative position information—this was possible because the object and target were placed at the lateral extremes of the working region of the experiment. For the obstacle, an analogous procedure was not possible.
Choices of this first step were inspected trial by trial and manually corrected if necessary. Obstacle fixations were not taken into account since it was not always possible to reliably distinguish them from other, frequently occurring intermediate fixations between object and target. Second, an automatic routine was used to detect the object-leaving saccade, defined as the first saccade, at the end of which, gaze had moved more than 10° horizontally relative to the object fixation. Based on an analogous 10° criterion, the target-reaching saccade was determined at the end of object transport. Thus, small (<10°) corrective saccades at the end of object transport were ignored in the definition of the target-reaching saccade.
Eye–hand coordination
Visual monitoring during object transport was quantified by the number of intermediate fixations, that is, the number of gaze shifts minus one occurring between the object-leaving and the target-reaching saccade. Note that this number does not include potential small corrective saccades at the end of object transport, since the target-reaching saccade was defined as the last saccade of horizontal amplitude >10° reaching the target region.
To examine temporal coordination between eye and hand at the beginning and end of object transport, two variables were computed: the movement onset asynchrony (MOA) and the movement termination asynchrony (MTA). The MOA was defined as the interval between the start of the object transport movement and the onset of the object-leaving saccade, with larger (positive) values corresponding to later gaze departure. Similarly, the MTA was determined by the delay between the termination of the object transport movement and the end of the target-reaching saccade, with smaller (negative) values corresponding to earlier target fixation. To eliminate a potential confounds with hand kinematics (in particular in the comparison of AH and LAH in participants with CP), both MOA and MTA were normalized with respect to hand movement duration (expressed as percentage of the latter).
With respect to our experimental hypotheses, we predicted that closer visual monitoring would be reflected in greater gaze-hand proximity (smaller average angular distance), larger number of intermediate gaze fixations, and delayed gaze departure from the object region (that is, a longer MOA). Regarding prospective control, we assumed that less anticipatory gaze patterns would be reflected in delayed departure from the object region (longer MOA) and delayed arrival on target (shorter/less negative MTA).
Statistical analysis
Data from one control participant were excluded due to insufficient quality of the Eyelink data, leaving data from six experimental and nine control subjects for statistical analysis. For each of the five variables of hand kinematics and eye–hand coordination introduced in “Data reduction”, the means averaged across all replications in each condition were submitted to a three-way repeated measures ANOVA with one between-subject factor (group: CP/control) and two within-subject factors (hand: AH/LAH, NPH/PH; obstacle: present/absent). Subsequent analyses of simple effects were performed using paired t-tests for within-subject factors, and Welch’s unpaired t-test (no equal variance assumed) for the between-subject factor. To correct for multiple (five) ANOVAs, the critical significance level was set to 0.01.
Results
Of the total 15 × 40 = 600 trials, seven trials were entirely rejected due to insufficient data quality (no more than two trials in any individual participant).
Sample trials
Figures 2 and 3 show representative trials from participants with CP and control participants. Horizontal components of head and hand position and gaze fixation (see “Data reduction”) are plotted on the vertical axis, as a function of time. The intervals and durations of the (non-normalized) MOA and MTA are indicated by vertical arrows and numerically in the plots. To allow comparisons between the plots, all data shown are from obstacle present trials. Visual inspection indicates qualitatively similar patterns (saccadic gaze shifts to future hand targets) in all conditions, and for both participant groups. Complete visual tracking of the trajectory of the hand was found only in a few trials (detected by visual inspection) in two participants with CP when using their AH. For these trials, MOA and/or MTA could not be determined.
Fig. 2Sample trials of two control participants, using their PH (a, c) and NPH (b, c) in trials with the obstacle present. Interpolated data points are represented by dashed lines. Vertical arrows at the top and bottom of the plots specify the intervals defining the MOA and MTA (beginning/end of hand and eye movement), with numerical values of these measures addedFig. 3Sample trials of two participants with CP, using their LAH (a, c) and AH (b, d) in trials with the obstacle present. Note the delayed gaze departure (longer MOA) and increased number of intermediate fixations for the AH compared to the LAH and to both hands of control participants (Fig. 2). Interpolated data points are represented by dashed lines. Vertical arrows at the top and bottom of the plots specify the intervals defining the MOA and MTA (beginning/end of hand and eye movement), with numerical values of these measures added
The representative trials shown in Fig. 2 (control participants using their PH and NPH) and Fig. 3 (participants with CP using their LAH and AH) illustrate some general trends when participants with CP use their AH. These are a prolonged MOA, a larger number of intermediate fixations and a greater gaze-hand proximity compared to the other combinations of group and task hand. These observations are in agreement with the hypothesis of increased visual monitoring (see Eye–hand coordination”), and this is corroborated by the statistical analysis presented below. In contrast, no clear pattern with respect to the MTA is obvious from these data plots, nor from the statistical analysis.
Dependent variables
Values for the different dependent variables are summarized in Table 2. Due to missing samples, some of the measures reported below could not be determined in a number of trials. This number did not exceed 40 out of 600 trials (never more than five out of ten in a single condition and participant) for any of the variables.
Table 2Mean and standard deviation (between participants) of dependent variablesDependent variableParticipants with CPControl participantsLAHaAHbPHcNPHdNo obstacleObstacleNo obstacleObstacleNo obstacleObstacleNo obstacleObstacleHand movement duration (s)  Mean0.811.051.051.600.610.83 0.650.87 SEM0.030.050.030.150.010.020.020.03Object grasp time Mean0.220.251.071.160.0630.0710.0860.094 SEM0.030.040.140.160.0090.010.0170.015Number of intermediate fixations Mean0.240.820.76 1.300.06 0.73 0.07 0.61 SEM0.090.340.241.210.040.220.060.26Movement onset asynchrony (% hand movement duration) Mean−6.881.5313.4 14.62−4.45 0.02−3.143.84  SEM5.814.964.372.124.844.214.844.37Movement termination asynchrony (% hand movement duration) Mean−76.8 −61.2 −49.5 −51.4 −75.7 −65.6 −71.5 −62.2  SEM5.396.872.843.644.393.784.643.56aLess affected handbAffected handcPreferred handdNon-preferred hand
Grasp time showed main effects of group, hand as well as a group–hand interaction (ANOVA, all p-values < 0.0001). Both, with the AH and the LAH participants with CP showed a longer grasp time than controls using either hand. The simple effect of hand was only present in participants with CP (longer grasp time with the AH compared to the LAH).
Hand movement durations for object transport showed main effects of group, hand, and obstacle, as well as a group–hand interaction (ANOVA, all p-values < 0.0001). Simple effect analysis revealed that the effect of hand was present in both groups, but more pronounced in participants with CP. Moreover, the movement duration was longer in participants with CP and in the presence of an obstacle (Fig. 4).
Fig. 4Mean ± SEM of the movement onset asynchrony (MOA) as a function of participant group, task hand and obstacle presence. MOA was normalized with respect to hand movement duration
Regarding the number of intermediate fixations during object transport, a main effect of obstacle [F(1,13) = 15.06, p < 0.002] was found, as well as a group–hand interaction [F(1,13) = 12.36, p < 0.005]. Analysis of simple effects showed that the number of intermediate fixations was larger in the obstacle present condition than in the obstacle absent condition. With respect to the group–hand interaction, significant differences were found between participants with CP using their AH and control participants using either hand (higher number of intermediate fixations for CP using AH), but not between the AH versus LAH of participants with CP.
Temporal eye–hand coordination at the beginning of object transport, as quantified by MOA (see Fig. 4), showed main effects of hand [F(1,13) = 17.25, p < 0.002] and a group–hand interaction [F(1,13) = 12.55, p < 0.005]. The simple effect of hand was present in participants with CP, with longer MOA in the AH condition, but not in control participants. Moreover, there was a significant difference (prolonged MOA) between participants with CP using their AH and control participants using either hand.
With respect to MTA, a main effect of hand [F(1,13) = 25.68, p < 0.0005], a group–hand interaction [F(1,13) = 14.189, p < 0.005] were found, as well as a marginally significant group–hand–obstacle interaction [F(1,13) = 8.19, p = 0.013]. The simple effect of hand was present only in participants with CP, with a shorter (less negative) MTA when using the AH. Also the difference between participants with CP using the AH and control participants using either hand was significant (shorter MTA in participants with CP using the AH).
Discussion
The main question we pursued in the present study was whether and in which way individuals with hemiparetic CP adapt eye–hand coordination to their sensorimotor impairments, in particular, when actions are performed with the affected hand (AH). We hypothesized that participants with CP would more closely monitor actions performed with their AH, compared to actions performed with their less affected hand (LAH) and compared to neurologically healthy control participants using either hand. Qualitatively, eye–hand coordination patterns were similar among control participants and participants with CP, regardless of the hand used to perform the task. That is, anticipatory saccadic gaze shifts were used to fixate future “action sites”—such as object, target, or intermediate fixations—in advance. Notwithstanding these qualitative resemblances, a more fine-grained analysis of temporal and spatial aspects of eye–hand coordination did confirm our hypothesis of increased visual monitoring when moving with the AH. Depending on the measure employed, this effect was present when comparing performance with the AH to control participants using either hand (increased number of intermediate fixations), or in addition for comparing performance with the AH to performance with the LAH in participants with CP (delayed gaze departure from object and hand, i.e., a longer MOA).
It is important to note that our main result regarding visual monitoring is an interaction effect of group and task hand (effect of task hand was present only in the experimental group). Therefore, it cannot be explained by potential group differences in oculomotor control or gaze data quality. Moreover, despite previous findings that did not find a strong relationship between gaze-exit time relative to hand action and task speed (Flanagan and Johansson 2003), we decided to normalize our measures of temporal eye–hand coordination in order to exclude any potential confounding effects of hand kinematics. This normalization may be considered rather conservative. Without normalizing, the effects of task and participant group on MOA may have even been stronger.
A second, and more speculative hypothesis of the present study was that in general, gaze patterns might be less anticipatory in participants with CP, contributing to deficits in prospective control and action planning that have been reported in this population (Steenbergen et al. 2000a, 2004; te Velde et al. 2005), in particular, individual with right hemiparesis. The present study found no evidence in support of this hypothesis. Although participants with CP did show a prolonged MOA, that is, a delayed gaze departure that may indicate less anticipation, this effect was restricted to the AH. No significant differences in the MOA were found between actions of participants with CP using their LAH and control participants using their PH. Similarly, for our measure of temporal eye–hand coordination at the end of object transport (the movement termination asynchrony, MTA), a delayed gaze arrival on target was only present in participants with CP using their AH, not as a general group effect. In addition, preliminary analyses had shown no difference between individuals with left and right hemiparesis with respect to any of our dependent variables. Thus our results suggest that deficits in prospective action control found in CP are not directly related to atypical eye–hand coordination. However, this statement is made with caution as we only tested a small number of participants (n = 6 in total, n = 3 for each left and right hemiparesis).
An unexpected finding of the present study was that gaze frequently departed from the object region only after the hand movement had started, in particular, in the presence of the obstacle. This was also the case in control participants and is in contrast to the results of Johansson et al. (2001), who reported that in the majority of the trials gaze departure from the grasp site occurred even before the fingertips had reached the object. These contrasting findings may in part be explained by differences in the experimental set-up. In the present study the distance between initial object position and the target was much larger compared to the one used by Johansson et al. (2001), leading to longer hand movement durations. This potential confounding effect of hand movement duration needs to be addressed in future research, for instance, by systematically manipulating hand movement distance in order to disentangle components of online and prospective control in the MOA. Also, task complexity might play a role. In a block-stacking task, Flanagan and Johansson (2003) found gaze to depart on average just before hand movement onset, which is more consistent with our present findings.
In sum, we found evidence in support the hypothesis of increased visual monitoring of manual actions of individuals with hemiparetic CP performing actions with their AH, both at the beginning and during object transport. This may reflect a strategy of visual compensation for sensorimotor deficits (see also, Mulder et al. 2001). However, since the functional significance of the observed gaze patterns was not addressed in the present study, the question whether and by which neurophysiological mechanisms vision enhances manual performance requires further research. Generalizability of our results is certainly limited by the fact that our experimental group was relatively small (n = 6) and highly selective, considering the high variability in the CP population regarding intellectual and motor abilities. In particular, the null-findings on anticipatory control and the comparison of individuals with left and right hemiparesis should be considered preliminary and require further investigation. On the other hand, the fact that we did find significant effects with respect to online visual control (number of intermediate fixations and MOA) despite the small number of participants suggests that the observed effects are robust.

prehension
visuomotor control
sensorimotor impairment
adaptation
affected side
congenital brain damage