What are dislocated or shallow hips?
Dislocated or shallow hips occur when the ball and socket at the end of the thighbone do not fit together. The medical term is ‘developmental dysplasia of the hip' (DDH). Shallow hips occur in 10 out of 1000 newborn babies, though dislocated hips are rarer, occurring in 1 in every 1000 newborns. Hips can be ‘dislocated’, unstable (i.e. easily fall out of the socket during examination) or ‘stable’ (i.e. located in the joint throughout examination).
How are these hips treated?
Shallow and dislocated hips are commonly treated with hip splints. Splints control the movement of the legs to guide the hips into the socket, allowing the hip to improve naturally. Splints can either fix the legs in position, called ‘static splints’, or allow the legs some freedom to move, called ‘dynamic splints’. Occasionally, clinicians may recommend the use of double nappies (double diapers), which are bulky, and gently push the legs apart to act as a type of splint.
What did we want to find out?
We wanted to know how successful splinting was, and if there were any groups of babies for whom the best treatment may differ. We focused on the development of the socket, the need for further surgery, and any complications up to two years after treatment. We were also interested in factors that parents told us were important, such as the ability to breastfeed and the bond between the parent and baby.
What did we do?
We searched for studies that investigated splinting for shallow and dislocated hips amongst babies under six months of age. We were interested in studies that compared the success of one type of splint to another splint, or a splint compared to no treatment. We included studies that assigned babies into different treatment groups using a process called randomization and studies that did not assign babies at random. In the studies that did not use randomization, babies were usually allocated to the different groups based on the choice of the clinician. Whilst studies without randomization contributed to the discussion, our conclusions are based largely on the results of the studies that used randomization.
We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and study size.
What did we find?
We found six studies that used randomization and included 576 babies and 16 studies that did not use randomization and included 8237 babies.
Five studies had non-commercial funding, three studies stated that there was no funding and 14 studies did not state the funding source.
Main results
Comparing immediate dynamic splinting to delayed dynamic or no splinting
Four studies compared dynamic splinting at first diagnosis with a strategy of waiting up to 12 weeks after diagnosis before starting treatment. Two studies looked at stable shallow hips, one at unstable shallow hips and one at a combination of both. None of the studies considered dislocated hips.
Amongst hips that were not dislocated, two studies showed no clear evidence of a difference in the development of the socket at one year by delaying the initial treatment. Furthermore, two studies of stable hips showed that the development of the socket was no different at two years by delaying the initial treatment. No studies reported results at five years after treatment.
Delaying the start of treatment did not increase the number of complications or the rates of later surgery in three studies. One study identified two babies who required surgery in the dynamic splinting group.
Two studies looked at an important complication called 'avascular necrosis', where the blood supply to the hip is damaged. No hips were affected by this in either study.
Comparing immediate static splinting to delayed static splinting or no splinting
No randomized studies compared these treatments.
Comparing double nappies to single nappies
One study compared double nappies with single nappies but did not report any outcomes of interest.
Comparing dynamic to static splinting
One study reported no occurrences of avascular necrosis with either treatment.
Comparing immediate removal of splint at the end of treatment to gradual removal (weaning)
No randomized studies compared these treatments.
Overall summary
Only 576 babies have been involved in randomized studies to find the best treatments in DDH. Amongst stable hips, there was no clear evidence to support treatment with splints at any time point. For unstable hips, a delay in treatment of up to six weeks had similar results at one year, with fewer hips requiring treatment.
Results from studies without randomization supported the findings from the studies with randomization, without offering any additional clarity.
What are the limitations of the evidence?
We were not confident in the evidence because we found only a few studies, which were small, with few babies randomly placed into treatment groups. In addition, studies were done in different types of babies and not all studies provided data about everything we wanted to know.
How up to date is the evidence?
The evidence is up to date to November 2021.
There is a paucity of RCT evidence for splinting for the non-operative management of DDH: we included only six RCTs with 576 babies. Moreover, there was considerable heterogeneity between the studies, precluding meta-analysis. We judged the RCT evidence for all primary outcomes as being of very low certainty, meaning we are very uncertain about the true effects.
Results from individual studies provide limited evidence of intervention effects on different severities of DDH. Amongst stable dysplastic hips, there was no evidence to suggest that treatment at any stage expedited the development of the acetabulum. For dislocatable hips, a delay in treatment onset to six weeks does not appear to result in any evidence of a difference in the development of the acetabulum at one year or increased risk of surgery. However, delayed splinting may reduce the number of babies requiring treatment with a harness.
No RCTs compared static splinting with delayed or no splinting, staged weaning versus immediate removal or double nappies versus delayed or no splinting.
There were few operative interventions or complications amongst the RCTs and the non-randomised studies. There's no apparent signal to indicate a higher frequency of either outcome in either intervention group.
Given the frequency of this disease, and the fact that many countries undertake mandatory DDH screening, there is a clear need to develop an evidence-based pathway for treatment. Particular uncertainties requiring future research are the effectiveness of splinting amongst stable dysplastic hips, the optimal timing for the onset of splinting, the optimal type of splint to use and the need for 'weaning of splints'. Only once a robust pathway for treatment is established, can we properly assess the cost-effectiveness of screening interventions for DDH.
Developmental dysplasia of the hip (DDH) describes the abnormal development of a hip in childhood, ranging from complete dislocation of the hip joint to subtle immaturity of a hip that is enlocated and stable within the socket. DDH occurs in around 10 per 1000 live births, though only one per 1000 are completely dislocated. There is variation in treatment pathways for DDH, which differs between hospitals and even between clinicians within the same hospital. The variation is related to the severity of dysplasia that is believed to require treatment, and the techniques used to treat dysplasia.
To determine the effectiveness of splinting and the optimal treatment strategy for the non-operative management of DDH in babies under six months of age.
We searched CENTRAL, MEDLINE, Embase, seven other electronic databases, and two trials registers up to November 2021. We also checked reference lists, contacted study authors, and handsearched relevant meetings abstracts.
Randomised controlled trials (RCTs), including quasi-RCTs, as well as non-RCTs and cohort studies conducted after 1980 were included. Participants were babies with all severities of DDH who were under six months of age. Interventions included dynamic splints (e.g. Pavlik harness), static splints (e.g Fixed abduction brace) or double nappies (diapers), compared to no splinting or delayed splinting.
Two review authors independently selected studies, extracted data and performed risk of bias and GRADE assessments. The primary outcomes were: measurement of acetabular index at years one, two and five, as determined by radiographs (angle): the need for operative intervention to achieve reduction and to address dysplasia; and complications. We also investigated other outcomes highlighted by parents as important, including the bond between parent and child and the ability of mothers to breastfeed.
We included six RCTs or quasi-RCTs (576 babies). These were supported by 16 non-RCTs (8237 babies). Five studies had non-commercial funding, three studies stated 'no funding' and 14 studies did not state funding source. The RCTs were generally at unclear risk of bias, although we judged three RCTs to be at high risk of bias for incomplete outcome data. The non-RCTs were of moderate and critical risk of bias. We did not undertake meta-analysis due to methodological and clinical differences between studies; instead, we have summarised the results narratively.
Dynamic splinting versus delayed or no splinting
Four RCTs and nine non-RCTs compared immediate dynamic splinting and delayed dynamic splinting or no splinting. Of the RCTs, two considered stable hips and one considered unstable (dislocatable) hips and one jointly considered unstable and stable hips. No studies considered only dislocated hips.
Two RCTs (265 babies, very low-certainty evidence) reported acetabular index at one year amongst stable or dislocatable hips. Both studies found there may be no evidence of a difference in splinting stable hips at first diagnosis compared to a strategy of active surveillance: one reported a mean difference (MD) of 0.10 (95% confidence interval (CI) −0.74 to 0.94), and the other an MD of 0.20 (95% CI −1.65 to 2.05). Two RCTs of stable hips (181 babies, very low-certainty evidence) reported there may be no evidence of a difference between groups for acetabular index at two years: one study reported an MD of −1.90 (95% CI −4.76 to 0.96), and another study reported an MD of −0.10 (95% CI −1.93 to 1.73), but did not take into account hips from the same child. No study reported data at five years.
Four RCTs (434 babies, very low-certainty evidence) reported the need for surgical intervention. Three studies reported that no surgical interventions occurred. In the remaining study, two babies in the dynamic splinting group developed instability and were subsequently treated surgically. This study did not explicitly state if this treatment was to achieve concentric reduction or address residual dysplasia.
Three RCTs (390 babies, very low-certainty evidence) reported no complications (avascular necrosis and femoral nerve palsy).
Dynamic splinting versus static splinting
One RCT and five non-RCTs compared dynamic versus static splinting. The RCT (118 hips) reported no occurrences of avascular necrosis (very low-certainty evidence) and did not report radiological outcomes or need for operative intervention.
One quasi-RCT compared double nappies versus delayed or no splinting but reported no outcomes of interest.
Other comparisons
No RCTs compared static splinting versus delayed or no splinting or staged weaning versus immediate removal.