Paediatrics


 

Hip surveillance for children with cerebral palsy

Fabian Norman-Taylor
Consultant Orthopaedic Surgeon The London Clinic



Cerebral palsy is common. It affects 2-3 children per 1000 live births throughout Europe and a similar number elsewhere. It is the commonest cause of physical disability in childhood and is associated with numerous co-morbidities, one of which is the painful dislocation of one or both hips. Dislocation occurs gradually as the child grows. The term “displacement” has been adopted by most centres to describe this process, as it avoids the need for terms such as dislocation, subluxation and migration, although all have their uses. Displacement can be measured on AP pelvic radiographs using Reimer’s Migration Percentage (or Reimer’s Migration Index – RMI). This is the percentage of the femoral ossific nucleus that lies outside the bony acetabulum. It is a well-established index and its measurement has been described in detail in the literature and in text books; before the radiograph is taken the knees should face forward and the lumbar lordosis should be eliminated. A hip is “displaced” if the index is equal to or greater than 33%.

Cerebral palsy causes a spectrum of physical disability, and the most severely affected children are at greatest risk of hip displacement. The Gross Motor Function Classification System (GMFCS) is the most widely used system for identifying the severity of physical disability, and it classifies children into groups I to V. Group I children are the least affected. Almost 90% of children in Group V and 70% of children in Group IV will develop hip displacement. It is still not known how many of these children have pain or how many have pain as adults, because the natural history in most cohorts is confounded by treatment such as surgery. The accepted figure is about 50%; in other words 50% of displaced hips become painful.

Historically most children referred to an orthopaedic surgeon with hip displacement would already have pain, many with advanced joint deformity and osteoarthritis. Surgery in this situation is less likely to be successful. The concept of preventative surgery has therefore evolved. This relies on early referral, preferably before the onset of pain. Early referral requires early detection, in this case by a programme of surveillance. In my own practice, an audit in 2003 revealed that 75% of children referred with a hip problem already had pain. Since the re-introduction of hip surveillance this figure is now 20%. Some centres using hip surveillance have virtually eliminated surgery for the dislocated and/or painful hip.

Surveillance is in principle quite simple. Physical examination cannot exclude hip displacement. Therefore the recommendation is that all children with cerebral palsy and GMFCS II to V should have an annual x-ray of the pelvis in accordance with Reimer’s method from the age of 3 years. If (and for many children when) the index reaches 40%, surgery should be performed to restore stability to the hip. Notwithstanding the errors that occur when measuring RMI, a simple guide is to refer the child to a children’s orthopaedic surgeon if the index is greater than 30% for either hip, or if it increases by more than 7% between x-rays.

There has been some discussion about postural management, tone management and ambulation in terms of the prevention and treatment of hip displacement. None has proved effective. Walking for example, does not prevent hip displacement; instead, those children who can walk are at less risk of hip displacement because the severity of their overall disability is less. Similarly, children who can tolerate postural management are likely to be at less risk of hip displacement anyway. The management of severe dystonia, for example by deep brain stimulation, may well have a role in the control of hip displacement but it is not yet proven.

Botulinum toxin injections have proved highly effective in managing chronic hip pain, both before and after surgery, and have become the mainstay of non-surgical pain management. They are not useful in the prevention of hip displacement however.



There has also been much discussion about what surgery is appropriate. It has become clear that muscle releases alone are not effective in preventing hip displacement, except perhaps in more ambulant children, i.e. GMFCS II and III. Current evidence supports femoral osteotomy, combined with muscle releases, as the only effective prophylaxis and/or treatment of hip displacement. If there is any windsweep (pelvic obliquity due to hip asymmetry) both femurs should have the osteotomy; soft tissue releases are then performed to restore balance. Unilateral surgery has a higher recurrence rate. If there is acetabular dysplasia, this should be addressed with an acetabuloplasty, using bone taken from the femur at the time of femoral osteotomy. This sort of surgery can be repeated if continued surveillance detects further displacement.

Surveillance aims to prevent any child from needing surgery for a dislocated (fully displaced) or painful hip. Although surgery for the painful and/or dislocated hip is usually successful, it is a much greater undertaking for the child and the family, often preceded by months or even years of pain. Unsuccessful surgery can then be a source of great disappointment and even anguish, as further surgery is contemplated and the child continues with chronic pain management. Cohort studies of adults who have had hip surgery in childhood will reflect the difficulties of managing painful dislocated hips in the past; adults will often still have pain, and their carers will attribute it to their surgery, not the underlying femoral and acetabular deformities and secondary osteoarthritis. Surgery was (and still is) often too little and too late, as a result of an ill-advised assumption that children with cerebral palsy should not be subjected to major surgery, inexperience with major hip reconstruction techniques or a lack of paediatric back-up to support such undertakings. The longer the surgery is postponed for these reasons, the more important these reasons become. The reputation of orthopaedic surgery for children with cerebral palsy has therefore been adversely affected by historical experience.

Early surgery is less “major”, requires less expertise and requires less back-up. Current evidence and expert consensus support the early use of surgery for children with hip displacement of >40% by means of femoral osteotomy as described above.

There is no doubt however that children with cerebral palsy should only undergo surgery in a paediatric facility with on-site paediatric HDU or PICU, and should be under the care of a paediatrician or a paediatric team. With careful multidisciplinary preparation, it is thus possible to operate safely on children with profound physical disability. The professions involved include physiotherapists, occupational therapists, anaesthetists, speech and language therapists, dieticians and a range of paediatric specialists such as neurologists, haematologists, cardiologists and respiratory physicians. The school, social services and of course the family/carers are all involved as well from an early stage in order to make the child’s stay in hospital as brief and as safe as possible.

Hip surveillance for children with cerebral palsy is the first step to achieving pain-free hips, balanced posture, better seating, easier dressing and better personal hygiene. It requires leadership from community paediatricians and physiotherapists, backed up by a repeated educational programme, and supported by ready access to x-ray facilities and radiological reporting. In order to be effective, the surveillance programme then requires the support of a paediatric hospital capable of undertaking the necessary surgery safely and in a timely fashion. This has proved achievable and sustainable in relatively small and stable communities, but may be somewhat harder in major conurbations.

A simple start would be for all clinicians responsible for any child with cerebral palsy, regardless of their clinical opinion, to order a pelvic x-ray and ask the radiologist to work out Reimer’s percentage (RMI). Modern digital imaging makes measurement quite easy, and there are also programmes such as Orthoview that will do it for you. It should also be straight forward to ensure that the results are acted upon and to ensure that another request is made 12 months later so that surveillance can continue.

Summary

• Cerebral palsy is common.
• The GMFCS is a useful system for determining the severity of cerebral palsy.
• Hip displacement in children with severe cerebral palsy is almost universal.
• Reimer’s Migration Percentage can measure hip displacement on a simple AP radiograph of the pelvis.
• Early femoral osteotomy is the only treatment known to prevent hip displacement.
• A surveillance programme of annual pelvic x-rays for all children with cerebral palsy is effective in the early detection of hip displacement, and therefore the prevention of advanced painful hip deformity.

Further reading

• Scrutton D and Baird G. Surveillance measures of the hips of children with bilateral cerebral palsy Arch Dis Child 1997;76:381-384v
• Soo et al. Hip Displacement in Cerebral Palsy. The Journal of Bone & Joint Surgery. 2006; 88:121-129
• CanChild - GMFCS - Expanded and Revised (2007) www.canchild.ca/en/ measures/gmfcs_expanded_revised.asp

 

 Date of upload: 26th Jul 2012

 

                                  
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