Hip Surveillance and Management of Hip Displacement in Children with Cerebral Palsy: Clinical and Ethical Dilemmas.

Hip displacement is the second most common musculoskeletal deformity in children with cerebral palsy. Hip surveillance programs have been implemented in many countries to detect hip displacement early when it is usually asymptomatic. The aim of hip surveillance is to monitor hip development to offer management options to slow or reverse hip displacement, and to provide the best opportunity for good hip health at skeletal maturity. The long-term goal is to avoid the sequelae of late hip dislocation which may include pain, fixed deformity, loss of function and impaired quality of life. The focus of this review is on areas of disagreement, areas where evidence is lacking, ethical dilemmas and areas for future research. There is already broad agreement on how to conduct hip surveillance, using a combination of standardised physical examination measures and radiographic examination of the hips. The frequency is dictated by the risk of hip displacement according to the child's ambulatory status. Management of both early and late hip displacement is more controversial and the evidence base in key areas is relatively weak. In this review, we summarise the recent literature on hip surveillance and highlight the management dilemmas and controversies. Better understanding of the causes of hip displacement may lead to interventions which target the pathophysiology of hip displacement and the pathological anatomy of the hip in children with cerebral palsy. We have identified the need for more effective and integrated management from early childhood to skeletal maturity. Areas for future research are highlighted and a range of ethical and management dilemmas are discussed.

Australian hip surveillance guidelines at 10 years: New evidence and implementation.

Optimum management of hip displacement in children with cerebral palsy (CP) is facilitated by an approach that focuses on anticipatory and preventive measures. Hip surveillance programs for children with CP were developed at the beginning of the new millennium, with the purpose of identifying hip displacement sufficiently early to permit a choice of effective management options. In the early years, hip surveillance was guided by epidemiological analysis of population-based studies of prevalence. In Australia, a National Hip Surveillance in CP Working Group was first convened in 2005. This resulted in a 2008 Consensus Statement of recommendations published and endorsed by Australasian Academy of Cerebral Palsy and Developmental Medicine (AusACPDM). The group undertook that the recommendations should be reviewed every 5 years to ensure currency and congruency with the emerging evidence base. As new evidence became available, hip surveillance guidelines developed, with the most recent 2020 Australian Hip Surveillance Guidelines endorsed by the AusACPDM. Implementing comprehensive hip surveillance programs has now been shown to improve the natural history of hip dislocations and improve quality of life. Standardised hip surveillance programs can also facilitate planning for multicentre research through harmonisation of data collection. This, in turn, can help with the identification of robust new evidence that is based on large cohort or population studies. Here a review of evidence informing the updated 2020 Hip Surveillance Guidelines is presented.

Epidemiology of scoliosis in cerebral palsy: A population-based study at skeletal maturity.

AIM: This study investigated the prevalence of scoliosis in a large, population-based cohort of individuals with cerebral palsy (CP) at skeletal maturity to identify associated risk factors that may inform scoliosis surveillance. METHODS: Young people with CP born between 1990 and 1992 were reviewed through routine orthopaedic review or a transition clinic. Classification of CP was recorded by movement disorder, distribution, gross and fine motor function. Clinical examination was undertaken and those with clinical evidence of scoliosis or risk factors had radiographs of the spine. Scoliosis severity was measured and categorised by Cobb angle. RESULTS: Two hundred and ninety-two individuals were evaluated (78% of the birth cohort) at a mean age of 21 years, 4 months (range 16-29 years). Scoliosis (Cobb angle >10°) was found in 41%, with strong associations to the Gross Motor Function Classification System (GMFCS), Manual Abilities Classification System (MACS) and dystonic/mixed movement disorders. Those at GMFCS V were 23.4 times (95%CI 9.9-55.6) more likely to develop scoliosis than those at GMFCS I. Severe curves (Cobb >40°, 13% of the cohort) were found almost exclusively in those functioning at GMFCS IV and V, and were 18.2 times (95%CI 6.9-48.5) more likely to occur in those with dystonia than those with spasticity. CONCLUSIONS: Scoliosis was very common in young people with CP, with prevalence and severity strongly associated with GMFCS and MACS level and dystonic movement disorder. Severe curves were almost exclusively found in non-ambulant children. Clinical screening for scoliosis should occur for all children with CP, with radiographic surveillance focusing on those functioning at GMFCS IV and V.

Musculoskeletal Pathology in Cerebral Palsy: A Classification System and Reliability Study.

This article presents a classification of lower limb musculoskeletal pathology (MSP) for ambulant children with cerebral palsy (CP) to identify key features from infancy to adulthood. The classification aims to improve communication, and to guide referral for interventions, which if timed appropriately, may optimise long-term musculoskeletal health and function. Consensus was achieved by discussion between staff in a Motion Analysis Laboratory (MAL). A four-stage classification system was developed: Stage 1: Hypertonia: Abnormal postures are dynamic. Stage 2: Contracture: Fixed shortening of one or more muscle-tendon units. Stage 3: Bone and joint deformity: Torsional deformities and/or joint instability (e.g., hip displacement or pes valgus), usually accompanied by contractures. Stage 4: Decompensation: Severe pathology where restoration of optimal joint and muscle-tendon function is not possible. Reliability of the classification was tested using the presentation of 16 clinical cases to a group of experienced observers, on two occasions, two weeks apart. Reliability was found to be very good to excellent, with mean Fleiss' kappa ranging from 0.72 to 0.84. Four-stages are proposed to classify lower limb MSP in children with CP. The classification was reliable in a group of clinicians who work together. We emphasise the features of decompensated MSP in the lower limb, which may not always benefit from reconstructive surgery and which can be avoided by timely intervention.

More than an X-ray: Experiences and perspectives of parents of children with cerebral palsy when engaging in hip surveillance.

AIM: We explored the experiences of parents of children with cerebral palsy (CP) when engaging in hip surveillance for their child and aimed to identify the barriers and facilitators they encounter. METHODS: We conducted a pragmatic qualitative study through five focus groups conducted with 23 parents and primary care givers of young people with cerebral palsy. A semi-structured topic guide was used to facilitate discussion. Recordings were transcribed verbatim and transcripts analysed using content analysis. RESULTS: Six major categories emerged: (i) hip surveillance is a shared responsibility; (ii) knowledge is empowering; (iii) hip surveillance should be proactive rather than reactive; (iv) consistency and support from health professionals is valuable; (v) good communication is crucial; and (vi) challenges associated with having an X-ray may not be appreciated. Participants made recommendations related to: service model enhancements, information provision and improving both communication and the experience of having an X-ray. CONCLUSION: Despite having a good understanding of the need and importance of hip surveillance for their child, several barriers to parent engagement exist. Findings will inform the implementation of a family-centred model for hip surveillance and may be relevant to those undertaking or planning the implementation of hip surveillance in other areas.

Reliability of Radiographic Assessments of the Hip in Cerebral Palsy.

INTRODUCTION: Children with cerebral palsy are at risk for progressive hip displacement. Since surveillance for hip displacement uses specific radiographic measurements to guide decision making, it is important to establish the reliability of these measurements, which include Reimer's migration percentage (MP), acetabular index or acetabular angle (AI or AA), and pelvic obliquity (PO). The purpose of this study was to determine the intraobserver and interobserver reliability of these radiographic measures among an international group of pediatric orthopaedic surgeons participating in the prospective international multicenter Cerebral Palsy Hip Outcomes Project (CHOP) currently underway to evaluate the outcomes of hip interventions in cerebral palsy. METHODS: Two compact discs (CDs) containing the same 25 anteroposterior pelvis radiographs in Digital Imaging and Communications in Medicine (DICOM) format were provided to participating surgeons at least 2 weeks apart. To reduce the likelihood of recall or any effects of learning or fatigue, the order of the radiographs varied on the 2 CD versions, and participating surgeons received the 2 CDs in random order. The intraclass correlation coefficients (ICCs) were calculated to assess interobserver and intraobserver reliability. Mean absolute differences of hip measurements obtained at 2 time points were also calculated. RESULTS: The MP had the highest reliability followed by PO, AI, and AA with a mean intrarater ICC (SD; range) of 0.95 (0.04; 0.84 to 0.98); 0.92 (0.03; 0.85 to 0.97); 0.84 (0.05; 0.75 to 0.92); and 0.82 (0.14; 0.51 to 0.98); respectively. The mean interrater ICC (SD; range) for MP, PO, AI, and AA were 0.94 (0.05; 0.78 to 0.99); 0.90 (0.04; 0.76 to 0.99); 0.79 (0.08; 0.52 to 0.93); and 0.69 (0.23; 0.42 to 0.98) for MP, PO, AI, and AA, respectively. The mean (SD; 95% confidence interval) for the absolute difference between the 2 measurements for the raters was 4.9% (2.9%; 3.4%-6.4%); 3. 8 degrees (1.2 degrees; 3.1-4.5 degrees); 2.6 degrees (1.5 degrees; 1.7-3.5 degrees); and 1.3 degrees (0.3 degrees; 1.29-1.31 degrees) for MP, AI, AA, and PO, respectively. CONCLUSIONS: MP is a reproducible measure with excellent intrarater and interrater reliability. However, differences in MP of <7% should be treated with caution as these might be a consequence of measurement error. Although we found a high level of intrarater and interrater reliability of the AI, AA, and PO, these measurements are more variable and not ideal for use as discrete outcome measures. Instead, these parameters might be useful for prognostication and decision making when consistent trends are observed longitudinally over time which might be better indications of true change.

Health professionals' experiences and barriers encountered when implementing hip surveillance for children with cerebral palsy.

AIM: This study aimed to explore health professionals' experiences of implementing hip surveillance for young people with cerebral palsy (CP) and to identify any barriers they encounter. METHODS: A cross-sectional web-based survey of health professionals supporting children with CP was conducted. Responses were analysed through mixed methods. Responses to items presented as ordinal scales were analysed using descriptive statistics, and open-ended responses through a qualitative approach to identify themes. RESULTS: A total of 32 paediatricians, 2 rehabilitation specialists and 50 physiotherapists completed the survey, with respondents working within both hospital- and community-based settings. Barriers most frequently reported were inconsistency in radiology practice and reporting (35%), parent engagement (32%), limited communication between clinicians (31%), lack of clarity in lines of responsibility (27%) and forgetting to undertake surveillance (26%). Four major themes were identified through qualitative analysis: (i) recognition of the importance of clinical guidelines to hip surveillance; (ii) the value of each role in the team around a child; (iii) the challenge of sharing responsibility; and (iv) the importance of communication in facilitating collaboration. CONCLUSIONS: Barriers can be encountered at each phase of the hip surveillance process, but there are also factors that act as facilitators. Locally, the results will inform the development of an enhanced state-wide approach to hip surveillance for all children with CP. The identified barriers do not appear unique to the local context, and the findings may be transferable to other settings. Awareness of the potential barriers and facilitators would be valuable to those implementing hip surveillance in other areas.

Classifying Adverse Events Following Lower Limb Orthopaedic Surgery in Children With Cerebral Palsy: Reliability of the Modified Clavien-Dindo System.

BACKGROUND: The modified Clavien-Dindo (MCD) system is a reliable tool for classifying adverse events (AEs) in hip preservation surgery and has since been utilized in studies involving lower limb surgery for ambulant and nonambulant children with cerebral palsy (CP). However, the profile of AEs recorded in children with CP compared with typically developing children is different, and the reliability of the MCD in CP is unknown. This study aimed to evaluate the interrater and intrarater reliability of the MCD system for classifying AEs following lower limb surgery in children with CP. METHODS: Eighteen raters were invited to participate, including clinicians from surgical, nursing, and physical therapy professions, and individuals with CP. Following a MCD familiarization session, participants rated 40 clinical scenarios on 2 occasions, 2 weeks apart. Fleiss' κ statistics were used to calculate interrater and intrarater reliability. RESULTS: The overall Fleiss' κ value for interrater reliability in the first rating was 0.70 (95% confidence interval, 0.61-0.80), and increased to 0.75 (95% confidence interval, 0.66-0.84) in the second rating. The average Fleiss' κ value for intrarater reliability was 0.78 (range, 0.48 to 1.00). Grading of more severe AEs (MCD III to V) achieved near perfect agreement (κ, 0.87 to 1.00). There was a lower level of agreement for minor AEs (MCD I-II) (κ, 0.53 to 0.55). A κ score of 0 to 0.2 was deemed as poor, 0.21 to 0.4 as fair, 0.41 to 0.6 as good, 0.61 to 0.8 as very good, and 0.81 to 1.0 as almost perfect agreement. CONCLUSIONS: The MCD System demonstrates a very good interrater and intrarater reliability following lower limb surgery in children with CP. The MCD can be used by clinicians from different health care professions with a high level of reliability. The MCD may improve standardization of AE recording with a view to accurate audits and improved clarity in outcome studies for CP. LEVEL OF EVIDENCE: Level II-diagnostic.

Screening and referral for children with physical disabilities.

The clinical care of children with physical disabilities is a major priority for paediatricians and paediatric orthopaedic surgeons. Cerebral palsy (CP) is the prototypical condition and remains the most common cause of physical disability in developed countries. The incidence is approximately 2 per 1000 live births, translating to between 600 and 700 new children per annum in Australia, with approximately 34 000 children and adults currently living with CP. This figure is predicted to rise inexorably over the next 20 years. The care of children with physical disabilities, including those with CP, is usually coordinated by paediatricians, general practitioners and allied health teams including physiotherapists, with input from paediatric orthopaedic surgeons when appropriate. The emphasis in care for children with CP has moved from 'reactive' to 'proactive'. In the past, children are often referred when symptomatic, for example when a hip dislocation had occurred and became painful. The emphasis now is on coordinated, multidisciplinary care in which musculoskeletal manifestations of disability are identified by screening programmes. Systematic screening, especially when population-based and linked to a register, avoids children getting 'lost in the system'. Early and more effective interventions may be offered for the prevention of contractures, dislocation of the hip and spinal deformities. In this review, we will focus on the assessment of gait in children with physical disabilities, and monitoring for hip and spine deformity.

Hip health at skeletal maturity: a population-based study of young adults with cerebral palsy.

AIM: We studied 'hip health' in a population-based cohort of adolescents and young adults with cerebral palsy to investigate associations between hip morphology, pain, and gross motor function. METHOD: Ninety-eight young adults (65 males, 33 females) from the birth cohort were identified as having developed hip displacement (migration percentage >30) and were reviewed at a mean age of 18 years 10 months (range 15-24y). Hip morphology was classified using the Melbourne Cerebral Palsy Hip Classification Scale (MCPHCS). Severity and frequency of pain were recorded using Likert scales. Gross motor function was classified by the Gross Motor Function Classification System (GMFCS). RESULTS: Hip pain was reported in 72% of participants. Associations were found between pain scores and both hip morphology and GMFCS. Median pain severity score for MCPHCS grades 1 to 4 was 2 (interquartile range [IQR] 1.0-3.0) compared to 7 (IQR 6.0-8.0) for grades 5 and 6 (severe subluxation or dislocation). Hip surveillance and access to surgery were associated with improved hip morphology and less pain. INTERPRETATION: Poor hip morphology at skeletal maturity was associated with high levels of pain. Limited hip surveillance and access to surgery, rather than GMFCS, was associated with poor hip morphology. The majority of young adults who had access to hip surveillance, and preventive and reconstructive surgery, had satisfactory hip morphology at skeletal maturity and less pain.

Australian hip surveillance guidelines for children with cerebral palsy: 5-year review.

AIM: To ensure hip surveillance guidelines reflect current evidence of factors influencing hip displacement in children with cerebral palsy (CP). METHOD: A three-step review process was undertaken: (1) systematic literature review, (2) analysis of hip surveillance databases, and (3) national survey of orthopaedic surgeons managing hip displacement in children with CP. RESULTS: Fifteen articles were included in the systematic review. Quantitative analysis was not possible. Qualitative review indicated hip surveillance programmes have decreased the incidence of hip dislocation in populations with CP. The Gross Motor Function Classification System was confirmed as the best indicator of risk for displacement, and evidence was found of hip displacement occurring at younger ages and in young adulthood. Femoral geometry, pelvic obliquity, and scoliosis were linked to progression of hip displacement. A combined data pool of 3366 children from Australian hip surveillance databases supported the effectiveness of the 2008 Consensus Statement to identify hip displacement early. The survey of orthopaedic surgeons supported findings of the systematic review and database analyses. INTERPRETATION: This review rationalized changes to the revised and renamed Australian Hip Surveillance Guidelines for Children with Cerebral Palsy 2014, informing frequency of radiographic examination in lower risk groups and continuation of surveillance into adulthood for adolescents with identified risk factors.

Progressive resistance training and mobility-related function in young people with cerebral palsy: a randomized controlled trial.

AIM: The aim of this study was to investigate whether individualized resistance training improves the physical mobility of young people with cerebral palsy (CP). METHOD: Forty-eight participants with spastic diplegic CP (26 males, 22 females; mean age 18y 1mo, SD 1y 11mo) classified as level II or III on the Gross Motor Function Classification System were allocated randomly to progressive resistance training or usual-care control. Resistance training was completed twice weekly for 12 weeks at a community gymnasium under the supervision of a physiotherapist. Exercises were based on instrumented gait analysis and targeted muscles contributing to walking difficulties. Outcomes at 12 weeks and 24 weeks included objective measures of mobility (6-min walk test, instrumented gait analysis, and Gross Motor Function Measure dimensions D and E), participant-rated measures of mobility (Functional Mobility Scale and Functional Assessment Questionnaire), and muscle performance. RESULTS: The strength of targeted muscles increased by 27% (95% CI 8-46%) compared with control group. There were no between-group differences in any objective measure of mobility at 12 weeks (6-min walk test: mean difference 0.1m; 95% CI -21 to 21m) or at 24 weeks. Participant-rated mobility improved (Functional Mobility Scale at 5m: mean 0.6 units; 95% CI 0.1-1.1 units; Functional Assessment Questionnaire: 0.8 units; 95% CI 0.1-1.6 units) compared with control group at 12 weeks. INTERPRETATION: Individualized progressive resistance training increased strength in adolescents and young adults with spastic diplegic CP. Despite participant-rated benefits, the increased strength did not result in objective improvements in mobility.

The impact of complementary and alternative medicine on hip development in children with cerebral palsy.

AIM: This study aimed to evaluate the effect of complementary and alternative medicine (CAM) approaches on long-term surgical requirements, and clinical and radiographic outcomes for children with cerebral palsy and hip displacement. METHOD: Twenty-three children with cerebral palsy and early hip displacement who were offered preventive hip surgery and whose parents declined in favour of CAM approaches were followed (13 males, 10 females; mean age 13 y 9 mo [SD 3 y 1 mo]; mean length of follow-up 10 y 2 mo [SD 2 y 11 mo]; 17 with spastic quadriplegia, two with spastic triplegia, and four with spastic diplegia; three with gross motor function classified at Gross Motor Function Classification System [GMFCS] level II, four at level III, six at level IV, and 10 at level V). Principal outcome measures were progression of hip displacement (measured by migration percentage: the percentage of the femoral head sitting outside of the acetabulum), eventual need for reconstructive or salvage surgery, and long-term hip morphology (classified by the Melbourne Cerebral Palsy Hip Classification Scale). The results were compared with a previously reported cohort of 46 children who had surgery when recommended (31 males, 15 females; mean age 13 y 11 mo [SD 1 y 6 mo]; mean length of follow-up 10 y 10 mo; 10 with diplegia and 36 with quadriplegia; three at GMFCS level II, 11 at level III, 20 at level IV, and 12 at level V). RESULTS: Outcomes for 23 children who had pursued CAM were analysed (mean length of follow-up 10 y 2 mo). Hip displacement progressed in one or both hips in all non-ambulant children (GMFCS level IV or V). Of the 20 children with documented progressive hip displacement, eight developed pain and deformity requiring salvage surgery. An additional 11 children with progressive hip displacement had late reconstructive surgery when symptoms first started. There was strong evidence of a relationship between GMFCS and both progressive hip displacement (χ(2) =17.78; p=0.001) and final Melbourne Cerebral Palsy Hip Classification Scale grade (odds ratio 12.5; p=0.012; 95% confidence interval 1.7-90.4). There was also evidence of those children who pursued CAM requiring more complex surgery than the group who had surgery when recommended (odds ratio 2.5; p=0.002; 95% confidence interval 1.4-4.5). INTERPRETATION: CAM therapy did not appear to influence the progression of hip displacement in children with cerebral palsy. Most children required major reconstructive surgery or salvage surgery despite pursuing CAM.

The impact of botulinum toxin A and abduction bracing on long-term hip development in children with cerebral palsy.

AIM: To study the long-term impact of 3 years of botulinum toxin A (BoNT-A) injections and abduction bracing on hip development in children with bilateral spastic cerebral palsy (CP). We wanted to know if early treatment improved hip development and reduced the need for surgery. METHOD: A long-term review of hip morphology and surgery requirements in children who participated in a multicentre, randomized controlled trial. The trial investigated short-term effects of BoNT-A injections combined with an abduction brace, compared with usual care, on hip displacement in children with bilateral spastic CP. RESULTS: Forty-six children with bilateral spastic CP (31 males, 15 females; 10 with diplegia, 36 with quadriplegia; mean age at enrolment of 3 y 2 mo, mean age at most recent clinical review 13 y 11 mo [range 10 y 6 mo-16 y 8 mo]; three children in Gross Motor Function Classification System level II, 11 in level III, 20 in level IV, 12 in level V) were followed for a mean of 10 years 10 months from recruitment to the trial. Mean migration percentage was 15.9% in the BoNT-A group and 15.2% in the comparison group (t = 0.26, p = 0.79). Eighty-nine percent of hips in the treatment group and 91% hips in the comparison group had satisfactory development, using a valid scale (Mann-Whitney U test = 867.50, z = -1.59, p = 0.11). Forty children had preventive surgery (21 treatment group, 19 comparison group) and 18 children had reconstructive surgery (10 treatment, 8 comparison). INTERPRETATION: In children with bilateral spastic CP, early treatment with BoNT-A and hip abduction bracing does not reduce the need for surgery or improve hip development at skeletal maturity.

Efficacy of partial body weight-supported treadmill training compared with overground walking practice for children with cerebral palsy: a randomized controlled trial.

OBJECTIVE: To evaluate the efficacy of 9 weeks of twice-weekly partial body weight-supported treadmill training (PBWSTT) for children with cerebral palsy (CP) and moderate to severe walking difficulty compared with overground walking. DESIGN: Randomized controlled trial. SETTING: Metropolitan Specialist School for children with moderate to severe physical and/or intellectual disabilities. PARTICIPANTS: Thirty-four children classified level III or IV by the Gross Motor Function Classification System were recruited and randomly allocated to experimental or control groups. Of these, 26 (15 girls, 11 boys; mean age 10 y, 10 mo +/- 3 y, 11 mo [range, 5-18 y]) completed training and testing. INTERVENTIONS: Both groups completed 9 weeks of twice-weekly walking training. The experimental group completed PBWSTT, and the control group completed overground walking practice. MAIN OUTCOME MEASURES: Ten-meter walk test (self-selected walking speed), 10-minute walk (walking endurance), School Function Assessment. RESULTS: The overground walking group showed a trend for an increase in the distance walked over 10 minutes (F=3.004, P=.097). There was no statistically significant difference in self-selected walking speed over 10 meters or in walking function in the school environment as measured by the School Function Assessment. CONCLUSIONS: PBWSTT is safe and feasible to implement in a special school setting; however, it may be no more effective than overground walking for improving walking speed and endurance for children with CP. Continued emphasis on progressive reduction of body weight support along with adding concurrent overground walking practice to a treadmill training protocol may increase the intensity of training and assist with carryover of improvements to overground walking. Treadmill training programs that include concurrent overground walking as an additional key feature of the training protocol need to be rigorously evaluated for children with CP.

A systematic review of the effectiveness of treadmill training for children with cerebral palsy.

PURPOSE: The development of efficient and independent walking is an important therapeutic goal for many children with cerebral palsy (CP). Consequently, there has been growing interest in determining the effects of treadmill training programs for these children. METHOD: A systematic review of the literature was conducted to evaluate the effectiveness of treadmill training for children with CP. Relevant trials were identified by searching electronic databases and by citation tracking. RESULTS: Of 125 papers initially identified, five met the criteria for review. Results showed that treadmill training is safe and feasible for children with CP across a wide range of ages and functional abilities. Children with more severely affected walking ability significantly increased their walking speed (d = 1.48, 95% CI: 0.49-2.40) and gross motor performance (d = 1.5, 95% CI: 0.50-2.50) after training. However, the results also suggested that treadmill speed and length of training sessions might need to be set to specifically match desired intervention goals such as increasing walking speed or endurance. CONCLUSIONS: The review suggests that treadmill training is safe and feasible for children with CP and indicates that there may be some positive benefits in walking speed over short distances and in general gross motor skills. The provision of PBWS may be particularly beneficial for children with more severe walking disability (GMFCS III and IV). Further research is necessary before it can be concluded that treadmill training is beneficial for children with CP.

Season of birth bias in eating disorders--fact or fiction?

OBJECTIVE: A season of birth (SoB) bias is said to be present if the SoB pattern for a particular group varies from the pattern within the normal population. Significant biases have been found for several disorders including eating disorders (EDs). This article critically reviews the existing literature on SoB in ED in order to inform future hypothesis-based research. METHOD: A literature search identified 12 papers investigating SoB in ED. RESULTS: Despite methodological differences, the studies consistently show a SoB bias for anorexia nervosa (AN) in the spring months, in both the northern and southern Hemispheres. This is especially strong for early-onset and restrictive subtype of AN. CONCLUSION: These findings suggest that SoB is a risk factor for AN. However, none of the studies have been methodologically satisfactory. Future research needs to overcome numerous methodological challenges and to explore specific hypotheses to explain this bias.