Splinting for the non‐operative management of developmental dysplasia of the hip (DDH) in children under six months of age
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To determine the role of splinting and the optimal treatment strategy for the non‐operative management of DDH in children under six months of age. To identify if there are particular subgroups of patients for whom the optimal management strategy may differ.
Background
Description of the condition
Developmental dysplasia of the hip (DDH) is a common paediatric condition, with a variable incidence that appears to be based on ethnicity (Loder 2011). Within the UK, USA, and Australia, the incidence is approximately 10 per 1000 live births, with 1 in 1000 hips being dislocated at birth (Storer 2006). Amongst Native Americans, however, the incidence may be more than 10 times higher, and amongst African people it is believed to be extremely rare (Loder 2011). In the UK, abnormalities of the hip are screened for as part of the Newborn and Infant Physical Examination (NIPE) programme (UK National Screening Programme 2013). A Cochrane systematic review has assessed screening for DDH (Shorter 2013). DDH encompasses a spectrum of abnormalities, which range from delayed physiological development of the hip, through to acetabular deficiency, subluxation, and dislocation of the hip. It is more common in females, babies in the breech position in the third trimester, firstborn children, oligohydramnios (not enough amniotic fluid during pregnancy), and in those with a family history of the condition (Storer 2006).
The management strategy for DDH depends on the child's age and the severity of the disease. In children under six months of age the usual strategy, once abnormalities are identified, is to apply an abduction splint, such as a Pavlik harness (Mubarak 2003), and monitor the disease progression with serial ultrasound scans (Cooper 2014). If this is successful, no further intervention is required. If the child fails to respond to splinting, then they are managed with surgery to gently reduce (relocate) the hip, which may be achieved closed (i.e. without surgical incisions) or may necessitate a formal surgical approach to achieve reduction of the hip. There is no consensus on the length of time splinting should be pursued before reverting to surgical intervention, but reports of treatment length vary from 11 weeks to 28 weeks (Tomlinson 2016).
The paediatric hip undergoes a variety of changes in normal physiological development. Indeed, evidence has suggested that some hips that are abnormal in newborns may become normal without any intervention at all (Barlow 1962; Gardiner 1990; Shipman 2006). Therefore, there is a balance between undertreating and overtreating this condition. This is especially important because therapy with splints risks localised blood supply damage known as avascular necrosis (AVN) and femoral nerve palsy (Murnaghan 2010; Pollet 2010). The risk of AVN using a splint is in the region of 1% (Cashman 2002; Eidelman 2003), although some reports may be as high as 11% (Suzuki 2000). Furthermore, treating newborns in splints can cause considerable upset to new parents and can interfere with the bond between mothers and their new baby (Gardner 2005). Parents are also concerned about the use of splints interfering with ‘tummy time’ as ‘tummy time’ can affect both fine and gross motor skills.
Decisions regarding the treatment of DDH are typically made based on the ultrasonographic appearance of the hips. The most commonly used classification system is based on a static ultrasound image (Graf 2006; see Table 1). Other types of ultrasound assessment are also used, such as the dynamic assessment popularised by Harcke 1984; however, these techniques are typically combined with a static ultrasound assessment.
| Graf | Sonographic hip type | Bony roof | Ossific rim | Cartilage rim | Alpha angle |
| Ia | Mature | Good | Sharp | Long and narrow, extends far over femoral head | > 60 |
| Ib | Mature | Good | Usually blunt | Short and broad, but covers femoral head | > 60 |
| IIa | Physiological delay in ossification > 3 months (physiological immature but stable hips) | Deficient | Rounded | Covers femoral head | 50 to 59 |
| IIb | Physiological delay in ossification > 3 months (inherently stable) | Deficient | Rounded | Covers femoral head | 50 to 59 |
| IIc | On point of dislocation (unstable, requires immediate treatment) | Deficient | Rounded or flat | Covers femoral head | 43 to 49 |
| IId | On point of dislocation | Severley deficient | Rounded or flat | Compressed | 43 to 49 |
| IIIa | Dislocated (subluxation) | Poor | Flat | Displaced upwards and echo poor | < 43 |
| IIIb | Dislocated (subluxation) | Poor | Flat | Displaced upwards and more reflective than femoral head | < 43 |
| IV | Dislocated (complete) | Poor | Flat | Interposed | < 43 |
1. Karnik 2007
Patients with an alpha angle above 60 degrees are considered normal, and are classified as a Graf I hip (Graf 2006). Patients with an alpha angle from 50 to 59 degrees and under the age of three months are classified as Graf IIa (Karnik 2007); they are usually managed with ultrasound follow‐up alone to ensure resolution. Children with a persistent alpha angle from 50 to 59 degrees and older than three months are classified as Graf IIb. In the UK, children with Graf IIb hips who are under the age of six months are frequently managed with a splint, in conjunction with ultrasound follow‐up. Graf IIb hips constitute the most common reason to use a splint in the treatment of DDH; however, debate exists as to whether treating Graf IIb hips has any bearing on the outcome, with many centres ceasing to use splints for this reason. Those with more severe dysplasia (Graf III hips) or those that are dislocated (Graf IV hips) routinely receive treatment in the form of an abduction splint, but it is unclear when this should commence, which splint is best, or the extent to which splints offer additional benefit over natural history alone (Tomlinson 2016).
Therefore, it is important to establish the best practice for the non‐surgical management of children with DDH under six months old, and identify the extent to which the intervention with a splint alters the prognosis of disease.
Description of the intervention
A variety of splints are used to abduct and flex the hips into the desired position.
The most commonly used splint is the Pavlik harness. This splint promotes a dynamic reduction; that is, children are free to move their legs within the range permitted by the splint. This is thought to provide a more gentle reduction than other splints that fix the legs in a predefined position, thereby potentially lowering the risk of complications. Pavlik harnesses are also readily adjustable to the size of the infant and are more convenient to store (pack flat) than fixed abduction splints.
Fixed abduction splints (e.g. Von Rosen splint) are less commonly used, with greater concerns about complications and less convenience. These splints fix the legs of the child in flexion and abduction using a hard plastic splint. One study reported excellent results with the Von Rosen splint but the quality of evidence was limited (Heikkilä 1988). Other static splints include the Denis Browne bar (which splints the hips in abduction and flexion), the Rhino brace, and the Tübingen hip flexion splint (Ottobock splint).
The Frejka pillow is a further alternative, which is described as a non‐static splinting technique. This is widely used in Norway. The pillow is a further form of abduction splint; that is, a simple foam‐rubber pillow that is strapped to the child to flex and abduct the legs. The legs are fixed in abduction though not rigidly fixed. The argument for the use of this splint is that it is easy to use, needing less specialist supervision than other splints (Hinderaker 1992), which is better suited to the very disperse populations (i.e. Norway). However, there are concerns about high complications and treatment failures.
All splints are applied by an individual with specialist knowledge of the use of these devices, which is typically a children’s orthopaedic surgeon, an extended scope practitioner (physiotherapist or nurse with specialist training), or an orthotist. The splint is worn for a period of time defined by local policy, which will depend upon the appearance of the hip; typically this is between six and 16 weeks. Throughout the period of splinting, ultrasound scans are performed at regular intervals (typically between one and three weeks, depending upon the practitioner and type of splint used) to monitor progression. At the end of treatment, some centres immediately discontinue the use of the splint, whilst other centres 'wean' the splint and often advise treatment at night‐time only for a period of time. Children are then monitored according to local policy, for a time period between three years and 16 years.
There is no national or international consensus of type of splint, duration of splinting, weaning versus complete cessation, and long‐term follow‐up.
How the intervention might work
The interventions seek to direct the femoral head (ball) into the acetabulum (socket), thereby promoting the development of the joint. In infants, both femoral head and acetabulum are malleable and will readily undergo plastic deformation. With both the acetabulum and femoral head appropriately aligned, plastic deformation will ensue, to enable both head and socket to form the appropriate shape. For hips that have not sufficiently developed in utero, splints position the hips in flexion and abduction to achieve the optimal position for hip development. Splints can be either dynamic splints (i.e. Pavlik splint), whereby the child is free to move his or her legs within the range permitted by the splint, or fixed (i.e. Von Rosen splint), whereby the child’s legs are fixed in position to achieve the optimal position.
Why it is important to do this review
There is considerable variation in the non‐operative management of DDH (Tomlinson 2016). Treatment varies by country, institution, and even surgeon. Non‐operative management is not without complication. Therefore, it is important to determine an optimal strategy that achieves the greatest successes (i.e. avoids subsequent operative interventions), whilst minimising complications related to splinting (which includes AVN and femoral nerve palsy). It is also important to identify whether there are particular subgroups for whom the optimal management strategy may differ.
Objectives
To determine the role of splinting and the optimal treatment strategy for the non‐operative management of DDH in children under six months of age. To identify if there are particular subgroups of patients for whom the optimal management strategy may differ.
Methods
Criteria for considering studies for this review
Types of studies
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Randomised controlled trials (RCTs), quasi‐RCTs, and cluster‐RCTs.
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Prospective and retrospective non‐randomised controlled studies and cohort studies. We will consider non‐randomised trials for inclusion, as we expect that the number of randomised trials in this population will be limited.
Types of participants
Children with all severities of DDH who are under six months of age.
If studies include children over six months of age, we will contact the study authors to obtain data on children under six months of age.
We will exclude children with neurodevelopmental problems or neuromuscular syndromes.
Types of interventions
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Dynamic splinting (i.e. Pavlik harness, Frejka pillow).
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Static splinting (e.g. Von Rosen, Denis Browne bar, Rhino brace, Tübingen hip flexion splint (Ottobock splint)).
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Double nappies.
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No treatment or delayed treatment.
We will make the following comparisons.
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Dynamic splinting versus delayed or none.
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Static splinting versus delayed or none.
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Double nappies versus delayed or none.
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Dynamic versus static.
Types of outcome measures
Primary outcomes
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Measurement of acetabular index at years 1, 2, and 5, as determined by radiographs (angle).
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Need for operative intervention (dichotomous):
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to achieve reduction; and
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to address dysplasia.
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Complications (dichotomous):
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AVN (there are several grading systems, most commonly "total" AVN (Salter 1969), and "partial" AVN (Gage 1972));
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femoral nerve palsy;
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other nerve palsies; and
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pressure areas on skin.
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We will use the primary outcomes to populate the ʽSummary of findings' table.
Secondary outcomes
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Health economic assessment (including financial impact on the family), as reported in the included studies.
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Bonding between parents and child (including obstacles to breastfeeding, problems with winding and bathing baby), as reported in the included studies.
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Motor skill development, as reported in the included studies. Motor skills is an outcome that parents are concerned about, as ʽtummy time’ affects both fine and gross motor skills, and the use of splints interferes with ʽtummy time':
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fine motor skill development; and
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gross motor skill development.
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Search methods for identification of studies
Electronic searches
We will search the following electronic databases and trials registers.
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Central Register of Controlled Trials (CENTRAL; current issue) in the Cochrane Library, which includes the Cochrane Developmental, Psychosocial and Learning Problems Group's Specialised Register.
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MEDLINE Ovid (1946 onwards).
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MEDLINE In‐Process and Other Non‐Indexed Citations Ovid (current issue).
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MEDLINE Epub Ahead of Print Ovid (current issue).
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Embase Ovid (1974 onwards).
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CINAHL Plus EBSCOhost (Cumulative Index to Nursing and Allied Health Literature; 1937 onwards).
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PEDro (Physiotherapy Evidence Database; www.pedro.org.au).
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Science Citation Index ‐ Expanded Web of Science (SCI‐EXPANDED; 1970 onwards).
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Conference Proceedings Citation Index ‐ Science Web of Science (CPCI‐S; 1990 onwards).
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Cochrane Database of Systematic Reviews (CDSR; current issue), part of the Cochrane Library.
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Database of Abstracts of Reviews of Effects (DARE; current issue), part of the Cochrane Library.
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Networked Digital Library of Theses and Dissertations (NDLTD; search.ndltd.org/index.php).
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ClinicalTrials.gov (clinicaltrials.gov).
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World Health Organization International Clinical Trials Registry Platform (WHO ICTRP; www.who.int/ictrp/en).
We will search MEDLINE using the search strategy in Appendix 1. This strategy will be adapted for the other databases listed above. We will not restrict the search by date, publication status, study type, or language. We will seek translations if necessary.
Searching other resources
We will search the reference lists of included studies and any relevant reviews identified by the electronic searches (see Electronic searches). We will also contact study authors to ask if they know of any other studies, including those that are ongoing and unpublished, and will handsearch Orthopaedic Proceedings, which is a source of abstracts from major international orthopaedic meetings (bjjprocs.boneandjoint.org.uk).
Data collection and analysis
Selection of studies
Two review authors (one clinical expert and one methodologist, e.g. KD or JK and AN or DP) will independently screen the titles and abstracts of studies identified by the search strategy for eligibility (see Criteria for considering studies for this review). They will then independently assess the full texts of potentially eligible studies. We will resolve any differences by discussion or by consulting a third review author. We will list all studies excluded after full‐text assessment and their reasons for exclusion in a ʽCharacteristics of excluded studies' table. We will illustrate the study selection process in a PRISMA flow diagram (Moher 2009).
Data extraction and management
Two review authors (one clinical expert and one methodologist, e.g. KD or JK and AN or DP) will independently extract data onto a prepiloted data extraction form (Appendix 2), which we will manage in Microsoft Excel and refine accordingly. We will resolve any disagreements through discussion or by consulting a third review author.
Assessment of risk of bias in included studies
Two review authors (one clinical expert and one methodologist, e.g. KD or JK and AN or DP) will independently assess RCTs and quasi‐RCTs for risk of bias, using Cochrane's ʽRisk of bias' tool, which is described in further detail in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We will resolve disagreements through discussion or by consulting a third review author. The seven domains to be assessed are: sequence generation, allocation sequence concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and other potential threats to validity. Review authors will assign a judgement of either unclear, low, or high risk of bias (Appendix 3), along with a justification for this decision in the ʽRisk of bias' tables.
If we identify any cluster‐RCTs, we will also consider (i) recruitment bias; (ii) baseline imbalance; (iii) loss of clusters; (iv) incorrect analysis; and (v) comparability with individually randomised trials.
Due to our expectation that most studies we will identify will be observational in nature, we will assess the risk of bias for non‐randomised studies using the recently developed ROBINS‐I (Risk Of Bias In Non‐randomised Studies ‐ of Interventions) tool (Sterne 2016); for two outcomes of interest (need for surgical open reduction and acetabular index at one year) in each study, we will perform a separate 'Risk of bias' assessment. This tool considers seven domains of bias: two domains of bias pre‐intervention (bias due to confounding and bias in selection of participants into the study), one domain of bias at intervention (bias in the classification of interventions), and four domains of bias postintervention (bias due to departures from intended interventions, bias due to missing data, bias in measurement of outcomes, and bias in selection of the reported result). Central to implementing ROBINS‐I is the consideration of confounding factors and cointerventions that have the potential to lead to bias.
Important confounders of interest in this Cochrane Review include the following.
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Age of child at intervention (i.e. harness commencement).
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Proportion of females.
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Ethnicity of the participants (or if not stated, the country in which the study was conducted).
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Clinical assessment of the hip. Dislocated hip (reducible or not reducible), clinically unstable hip (i.e. dislocatable), or clinically stable hip.
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Ultrasound assessment of the hip. Acetabular dysplasia assessed using the alpha angle according to Graf classification of hip: I (normal), IIa or IIb (centred hip, 50 to 60 degrees of dysplasia), IIc (centred hip 43 to 50 degrees of dysplasia), III (de‐centred hip), and IV (dislocated hip).
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Indication for ultrasound screening (i.e. breech presentation in third trimester, family history of DDH, lower than normal levels of amniotic fluid, ʽclick' on clinical screening (abnormal clinical examination producing ʽclick' sound on hip movements), unequal skin creases).
We will add to the above list any further confounders we identify following assessment of the included studies, if appropriate, and specify these confounders as post hoc. We do not anticipate that there will be any important cointerventions to consider. Each of the seven domains of bias contain signalling questions to facilitate judgements of risk of bias. The full signalling question and response framework for each outcome is provided in Sterne 2016. Following completion of the signalling questions, we will seek a ʽRisk of bias' judgement for each domain and obtain an overall ʽRisk of bias' judgement for each outcome and result being assessed. Overall risk of bias has four categories ranging from low risk of bias (the study is at low risk of bias across all domains) to critical risk of bias (the study is at critical risk of bias in at least one domain). If there is insufficient information to assess the risk of bias in one or more key domains, but there is no indication that there is any critical or serious risk of bias in any of the other domains, then we will designate the overall classification as 'no information'.
Measures of treatment effect
Dichotomous outcome data
We will summarise data from dichotomous outcomes (e.g. need for operative intervention, femoral nerve palsy, AVN) using the risk ratio (RR) and 95% confidence intervals (CIs).
AVN is measured using a grading system and therefore is categorical. If this is reported as categorical data within a trial, we will use a clinical rating of two and above to define AVN, thereby dichotomising the data. There are many different rating systems for AVN, which are difficult to amalgamate. In all rating systems type‐I AVN is mild AVN that is clinically unimportant, as it completely heals without long‐term consequence. We therefore plan to dichotomise the outcome to the presence or absence of clinically important AVN. If we are unable to compute an effect size, we will provide a narrative description of the results.
Continuous outcome data
For continuous outcomes (e.g. bonding between parents and child, measurement of acetabular index, fine and gross motor skills) measured on the same scale, we will compute the mean difference (MD) and 95% CIs; if different measures are reported, we will compute the standardised mean difference (SMD) and 95% CIs. If we are unable to compute an effect size, we will provide a narrative description of the results.
For measurement of acetabular index, less than 30 degrees is considered normal in children aged over six months, and less than 25 degrees for children aged 24 months. Under six months of age, an alpha angle of the hip on ultrasound scan above 60 degrees is considered normal.
Health economic assessment
We will provide a narrative description of the results of the health economic assessment.
Unit of analysis issues
Cluster‐RCTs
If we include cluster‐RCTs in which the trial authors have not accounted for the cluster in their analyses, we will reduce the size of each trial to its effective sample size by diving the original sample size by the design effect (by using the average cluster size and the intracluster correlation coefficient (ICC)). If the ICC value is unavailable, we will impute it from a similar study, if possible. We will then include the data in the latest version of Review Manager 5 (RevMan 5) (Review Manager 2014), using the generic inverse variance method.
Cross‐over RCTs
We will exclude cross‐over trials. These are not appropriate as DHH is not a chronic condition.
Multiple groups
If a study includes more than two similar intervention groups, we will combine them and compare them with the control arm, creating a single pair‐wise comparison. If a study includes more than two dissimilar intervention groups, we will include these arms in the review separately, and halve the control group to ensure there is no double counting of participants.
Dealing with missing data
We will contact the authors of the included studies for missing data. For transparency, if we do not receive a reply, we will note this in the ʽCharacteristics of included studies' tables. If we can not obtain missing statistics (i.e. standard deviations), or calculate them from data reported in the trial report, then we will attempt to impute them for similar studies. We will not attempt imputation on missing participant data as we expect most studies to be non‐randomised studies.
Assessment of heterogeneity
We will assess clinical and methodological aspects of the included studies to determine whether there is clinical or methodological heterogeneity.
We will assess statistical heterogeneity visually by looking at the forest plots. We will calculate the Chi² test and will use a P value of less than (<) 0.10 to determine statistical significance due to the low power of the test. We will also calculate the I² statistic and 95% CIs, which describe the percentage of the variability in effect estimates that is due to heterogeneity rather than sampling error (chance) (Higgins 2003). We will use the thresholds below for interpretation.
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0% to 40%: might not be important.
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30% to 60%: may represent moderate heterogeneity.
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50% to 90%: may represent substantial heterogeneity.
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75% to 100%: considerable heterogeneity.
Assessment of reporting biases
If we include 10 or more studies in the review, we will construct a funnel plot to assess for publication bias. However, it should be noted that asymmetry in the funnel plot can be caused by other reasons, such as heterogeneity. We will also use Egger's test to formally assess funnel plot asymmetry (Egger 1997).
In addition, we will complete an Outcome Reporting Bias in Trials (ORBIT) matrix to help with the assessment of selective outcome reporting (Kirkham 2010).
Data synthesis
We will analyse different study designs separately (RCTs, quasi‐RCTs, retrospective and prospective non‐randomised studies). We will use a fixed‐effect analysis unless there is substantial heterogeneity (i.e. I² statistic value of greater than (>) 50%); in which case, we will use a random‐effects analysis as a sensitivity analysis (see Sensitivity analysis) and report both results (we will also report the Tau² value). We will use the inverse variance method. If there is considerable heterogeneity (i.e. I² statistic value > 75%), we will not conduct a meta‐analysis, but will provide a narrative description of the results.
We will assess the comparisons below.
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Splint versus no treatment or delayed treatment.
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Double nappies versus no treatment or delayed treatment.
Subgroup analysis and investigation of heterogeneity
If sufficient studies are available, we will consider conducting the subgroup analyses listed below.
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Age (birth to three months, three months to six months). The splint is thought to work better in younger infants.
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Sex (boys, girls). DDH is more common in girls.
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Type of splint (Pavlik harness or Frejka pillow; Von Rosen splint, Denis Browne bar, Rhino brace, Tübingen hip flexion splint (Ottobock splint)).
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Clinical assessment of the hip (dislocated hip (reducible or not reducible), clinically unstable hip (i.e. dislocatable), or clinically stable hip).
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Static ultrasound assessment of the hip. Acetabular dysplasia assessed using the alpha angle according to Graf classification of hip: I (normal), IIa or IIb (centred hip, 50 to 60 degrees of dysplasia), IIc (centred hip 43 to 50 degrees of dysplasia), III (de‐centred hip), and IV (dislocated hip).
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Dynamic ultrasound assessment of the hip (normal or abnormal (subluxed or dislocated) based on the assessment criteria used).
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Type of dysplasia (unilateral or bilateral disease). This is important because bilateral dislocations are harder to treat and there is a higher failure rate, which is thought to be because neither of the hips form a stable base for the treatment.
Sensitivity analysis
We will conduct sensitivity analyses for our primary outcomes from RCTs and quasi‐RCTs only (Primary outcomes). We will assess the impact on our results of excluding quasi‐RCTs and studies at unclear or high risk of bias. We will also conduct a sensitivity analysis using a random‐effects model when there is substantial heterogeneity.
GRADE
Two review authors (one clinical expert and one methodologist, e.g. KD or JK and AN or DP) will independently assess the quality of the evidence using the GRADE approach by considering the risk of bias, directness of evidence, heterogeneity, precision of effect estimates, and risk of publication bias. We will resolve disagreements through discussion with a third review author. We will use the GRADEpro Guideline Development Tool (GDT), GRADEpro GDT 2015, to create a ʽSummary of findings' table for our primary outcomes (see Primary outcomes) for each comparison.
| Graf | Sonographic hip type | Bony roof | Ossific rim | Cartilage rim | Alpha angle |
| Ia | Mature | Good | Sharp | Long and narrow, extends far over femoral head | > 60 |
| Ib | Mature | Good | Usually blunt | Short and broad, but covers femoral head | > 60 |
| IIa | Physiological delay in ossification > 3 months (physiological immature but stable hips) | Deficient | Rounded | Covers femoral head | 50 to 59 |
| IIb | Physiological delay in ossification > 3 months (inherently stable) | Deficient | Rounded | Covers femoral head | 50 to 59 |
| IIc | On point of dislocation (unstable, requires immediate treatment) | Deficient | Rounded or flat | Covers femoral head | 43 to 49 |
| IId | On point of dislocation | Severley deficient | Rounded or flat | Compressed | 43 to 49 |
| IIIa | Dislocated (subluxation) | Poor | Flat | Displaced upwards and echo poor | < 43 |
| IIIb | Dislocated (subluxation) | Poor | Flat | Displaced upwards and more reflective than femoral head | < 43 |
| IV | Dislocated (complete) | Poor | Flat | Interposed | < 43 |
| 1. Karnik 2007 | |||||
