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|
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.