Hip Displacement in Cerebral Palsy: Difference between revisions

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== Introduction  ==
== Introduction  ==
 
[[File:Cp child sit balance.jpg|thumb]]
Hip displacement is very common in children with [[Cerebral Palsy Introduction|cerebral palsy]] (CP) and the incidence has been reported to be 35%<ref name="Soo">Soo B, Howard J, Boyd R, et al. Hip displacement in cerebral palsy. J Bone Joint Surg Am. 2006;88(1):121-129</ref><ref name="Novak">Novak I, Hines M, Goldsmith S, Barclay R. Clinical prognostic messages from a systematic review on cerebral palsy. Pediatrics. 2012;130(5):e1285-e1312.</ref>. It is directly related to the child’s [[Gross Motor Function Classification System - Expanded and Revised (GMFCS-ER)|Gross Motor Function Classification Scale]] (GMFCS) level with a reported incidence of between 68-90% for children in GMFCS Level IV and V<ref name="Soo" /><ref name="Terjesen">Terjesen T. The natural history of hip development in cerebral palsy. Dev Med Child Neurol. 2012;54(10):951-957.</ref>. Progressive hip displacement can cause severe pain. In a recent study examining hip health at skeletal maturity in 98 young adults with CP, hip pain was reported in 72% of participants and pain frequency and severity increased with worsening hip morphology<ref name="Wawrzuta">Wawrzuta J, Willoughby K, Molesworth C, et al. Hip health at skeletal maturity: A population-based study of young adults with cerebral palsy. Dev Med Child Neurol. 2016.</ref>. It can also lead to difficulties with positioning, sitting, standing and walking and negatively impact quality of life<ref name="Hägglund">Hägglund G, Andersson S, Düppe H, Lauge Pedersen H, Nordmark E, Westbom L. Prevention of dislocation of the hip in children with cerebral palsy. the first ten years of a population-based prevention programme. J Bone Joint Surg Br. 2005;87(1):95-101.</ref><ref name="Robb">Robb JE, Hägglund G. Hip surveillance and management of the displaced hip in cerebral palsy. J Child Orthop. 2013;7(5):407-413.</ref><ref name="Shore">Shore B, Spence D, Graham H. The role for hip surveillance in children with cerebral palsy. Curr Rev Musculoskelet Med. 2012;5(2):126-134.</ref><br>  
Hip displacement is very common in children with [[Cerebral Palsy Introduction|cerebral palsy]] (CP) and the incidence has been reported to be 35%<ref name="Soo">Soo B, Howard J, Boyd R, et al. [https://journals.lww.com/jbjsjournal/abstract/2006/01000/hip_displacement_in_cerebral_palsy.15.aspx Hip displacement in cerebral palsy.] J Bone Joint Surg Am. 2006;88(1):121-129</ref><ref name="Novak">Novak I, Hines M, Goldsmith S, Barclay R. [https://publications.aap.org/pediatrics/article-abstract/130/5/e1285/32499 Clinical prognostic messages from a systematic review on cerebral palsy.] Pediatrics. 2012;130(5):e1285-e1312.</ref>. It is directly related to the child’s [[Gross Motor Function Classification System - Expanded and Revised (GMFCS-ER)|Gross Motor Function Classification Scale]] (GMFCS) level with a reported incidence of between 68-90% for children in GMFCS Level IV and V<ref name="Soo" /><ref name="Terjesen">Terjesen T. [https://onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8749.2012.04385.x The natural history of hip development in cerebral palsy.] Dev Med Child Neurol. 2012;54(10):951-957.</ref>. Progressive hip displacement can cause severe pain. In a recent study examining hip health at skeletal maturity in 98 young adults with CP, hip pain was reported in 72% of participants and pain frequency and severity increased with worsening hip morphology<ref name="Wawrzuta">Wawrzuta J, Willoughby K, Molesworth C, et al. [https://onlinelibrary.wiley.com/doi/full/10.1111/dmcn.13171 Hip health at skeletal maturity: A population-based study of young adults with cerebral palsy.] Dev Med Child Neurol. 2016.</ref>. It can also lead to difficulties with positioning, sitting, standing and walking and negatively impact quality of life.<ref name="Hägglund">Hägglund G, Andersson S, Düppe H, Lauge Pedersen H, Nordmark E, Westbom L. [https://boneandjoint.org.uk/article/10.1302/0301-620x.87b1.15146 Prevention of dislocation of the hip in children with cerebral palsy. the first ten years of a population-based prevention programme.] J Bone Joint Surg Br. 2005;87(1):95-101.</ref><ref name="Robb">Robb JE, Hägglund G. [https://journals.sagepub.com/doi/full/10.1007/s11832-013-0515-6 Hip surveillance and management of the displaced hip in cerebral palsy.] J Child Orthop. 2013;7(5):407-413.</ref><ref name="Shore">Shore B, Spence D, Graham H. [https://link.springer.com/article/10.1007/s12178-012-9120-4 The role for hip surveillance in children with cerebral palsy.] Curr Rev Musculoskelet Med. 2012;5(2):126-134.</ref>  


== Causes / Risk factors  ==
== Causes / Risk factors  ==


Muscular imbalance around the hip has been proposed as one possible cause of the lateral displacement. Yildiz et al (2014) suggest that hyperactivity of the hip flexors and adductors are contributing factors<ref name="Yildiz">Yildiz C, Demirkale I. Hip problems in cerebral palsy: Screening, diagnosis and treatment. Curr Opin Pediatr. 2014;26(1):85-92.</ref>. In addition the combination of femoral neck-shaft angle and femoral anteversion contributes to the risk of hip displacement<ref name="Shore" />. A clear relationship between GMFCS level and hip displacement has been established. Children with greater functional loss (GMFCS levels IV and V) are at a highest risk<ref name="Soo" /><ref name="Terjesen" /><ref name="Hägglund2">Hägglund G. Characteristics of children with hip displacement in cerebral palsy. BMC musculoskeletal disorders. 2007;8:101-101.</ref><ref name="Wynter">Wynter M, Gibson N, Willoughby K, et al. Australian hip surveillance guidelines for children with cerebral palsy: 5-year review. Dev Med Child Neurol. 2015;57(9):808-820.</ref>. Age is also a factor. Hagglund et al (2007) reported that the most common age of displacement in their population was 3-4 years and some were as young as 2 years9. Progression of hip displacement has also been reported after puberty and progression and dislocation has occurred after skeletal maturity, the latter happening in the presence of scoliosis and pelvic obliquity<ref name="Wynter" />. It appears that topography and movement disorder are poor predictors of hip subluxation<ref name="Wynter" />.<br>
Muscular imbalance around the hip has been proposed as one possible cause of the lateral displacement. Yildiz et al (2014) suggest that hyperactivity of the hip flexors and adductors are contributing factors<ref name="Yildiz">Yildiz C, Demirkale I. [https://journals.lww.com/co-pediatrics/abstract/2014/02000/hip_problems_in_cerebral_palsy__screening,.14.aspx Hip problems in cerebral palsy: Screening, diagnosis and treatment.] Curr Opin Pediatr. 2014;26(1):85-92.</ref>. In addition the combination of femoral neck-shaft angle and femoral anteversion contributes to the risk of hip displacement<ref name="Shore" />. A clear relationship between GMFCS level and hip displacement has been established. Children with greater functional loss (GMFCS levels IV and V) are at a highest risk<ref name="Soo" /><ref name="Terjesen" /><ref name="Hägglund2">Hägglund G. [https://link.springer.com/article/10.1186/1471-2474-8-101 Characteristics of children with hip displacement in cerebral palsy.] BMC musculoskeletal disorders. 2007;8:101-101.</ref><ref name="Wynter">Wynter M, Gibson N, Willoughby K, et al. [https://onlinelibrary.wiley.com/doi/abs/10.1111/dmcn.12754 Australian hip surveillance guidelines for children with cerebral palsy: 5-year review.] Dev Med Child Neurol. 2015;57(9):808-820.</ref>. Age is also a factor. Hagglund et al (2007) reported that the most common age of displacement in their population was 3-4 years and some were as young as 2 years9. Progression of hip displacement has also been reported after puberty and progression and dislocation has occurred after skeletal maturity, the latter happening in the presence of scoliosis and pelvic obliquity<ref name="Wynter" />. It appears that topography and movement disorder are poor predictors of hip subluxation<ref name="Wynter" />.  


== Diagnostic Procedures  ==
== Diagnostic Procedures  ==
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=== Hip surveillance  ===
=== Hip surveillance  ===


[[The_Role_of_Hip_Surveillance_in_Cerebral_Palsy|Hip surveillance]] programmes have been established in many countries in order to identify and monitor those children at risk for hip displacement. There have been reports of a significantly decreased incidence of hip dislocation as a result of these programmes<ref name="Wynter" />. Two that are cited frequently are The Cerebral Palsy Follow-Up Programme (CPUP)<ref name="Hägglund2" /> which was established in Sweden in 1994 and is currently being used in all or parts of Denmark, Iceland, Norway and Scotland and the revised Australian Hip Surveillance Guidelines for Children with Cerebral Palsy<ref name="Wynter" />.While hip surveillance identifies those children with progressive displacement it does not dictate the type or timing of intervention<ref name="Wynter" />.<br>
[[The_Role_of_Hip_Surveillance_in_Cerebral_Palsy|Hip surveillance]] programmes have been established in many countries in order to identify and monitor those children at risk for hip displacement. There have been reports of a significantly decreased incidence of hip dislocation as a result of these programmes<ref name="Wynter" />. Two that are cited frequently are The Cerebral Palsy Follow-Up Programme (CPUP)<ref name="Hägglund2" /> which was established in Sweden in 1994 and is currently being used in all or parts of Denmark, Iceland, Norway and Scotland and the revised Australian Hip Surveillance Guidelines for Children with Cerebral Palsy<ref name="Wynter" />.While hip surveillance identifies those children with progressive displacement it does not dictate the type or timing of intervention<ref name="Wynter" />.  


=== Radiological examination  ===
=== Radiological examination  ===


Diagnosis is by x-ray as a clinical examination alone in insufficient to evaluate hip displacement<ref name="Shore" />. Reimer’s migration percentage (MP) is the most common measure used to examine the amount of lateral displacement of the femoral head<ref name="Reimers">Reimers J. The stability of the hip in children. A radiological study of the results of muscle surgery in cerebral palsy. Acta Orthop Scand Suppl. 1980;184:1-100.</ref>. Hips presenting with MP &gt;30% are considered to be displaced and hips with an MP &gt; 90%-100% are dislocated<ref name="Hägglund" /> . Progression of the MP greater than 7% per year is considered to be worrying<ref name="Shore" />.<br>
Diagnosis is by x-ray as a clinical examination alone in insufficient to evaluate hip displacement<ref name="Shore" />. Reimer’s migration percentage (MP) is the most common measure used to examine the amount of lateral displacement of the femoral head<ref name="Reimers">Reimers J. [https://www.tandfonline.com/doi/pdf/10.3109/ort.1980.51.suppl-184.01 The stability of the hip in children. A radiological study of the results of muscle surgery in cerebral palsy.] Acta Orthop Scand Suppl. 1980;184:1-100.</ref>. Hips presenting with MP &gt;30% are considered to be displaced and hips with an MP &gt; 90%-100% are dislocated<ref name="Hägglund" /> . Progression of the MP greater than 7% per year is considered to be worrying<ref name="Shore" />.  


=== Clinical examination  ===
=== Clinical examination  ===


The clinical examination is often the responsibility of the physiotherapist. It can include but is not limited to <br>• assignment of GMFCS and FMS (Functional Mobility Scale) levels<br>• assessment of <br>
The clinical examination is often the responsibility of the physiotherapist. It can include but is not limited to <br>• assignment of GMFCS and FMS (Functional Mobility Scale) levels<br>• assessment of


*Sitting, standing and walking abilities  
*Sitting, standing and walking abilities  
Line 28: Line 28:
*Passive range of motion (PROM): Thomas test, hip abduction (in extension and flexion); hip internal and external rotation, popliteal angle (single and bilateral), Ely’s test, knee extension, dorsiflexion (knee extended and flexed)  
*Passive range of motion (PROM): Thomas test, hip abduction (in extension and flexion); hip internal and external rotation, popliteal angle (single and bilateral), Ely’s test, knee extension, dorsiflexion (knee extended and flexed)  
*Spine ([[Scoliosis|scoliosis]])  
*Spine ([[Scoliosis|scoliosis]])  
*Leg length discrepancy<br>
*Leg length discrepancy


== Outcome Measures  ==
== Outcome Measures  ==
Line 38: Line 38:
[[Ely's test|Ely's test]]<br>  
[[Ely's test|Ely's test]]<br>  


The CPUP programme has evaluation forms for physiotherapists and occupational therapists that can be down loaded from the website. www.CPUP.se<br>  
The [https://cpup.se/in-english/ CPUP programme] has evaluation forms for physiotherapists and occupational therapists that can be down loaded from the website.<br>  


== Management / Interventions  ==
== Management / Interventions  ==
Line 44: Line 44:
=== Non-operative    ===
=== Non-operative    ===


Physiotherapists have proposed and examined standing programmes for children at risk of hip displacement. Pountney et al (2009) investigated the effectiveness of early postural management programmes in 39 children with CP<ref name="Pountney">Pountney T, Mandy A, Green E, Gard P. Hip subluxation and dislocation in cerebral palsy - a prospective study on the effectiveness of postural management programmes. Physiother Res Int. 2009;14(2):116-127.</ref>. The programme included a standing support (in addition to sitting and lying supports) and children were monitored from 18-60 months using x-rays. They found that those children who used the equipment at the recommended frequency had significantly less chance of both hips being subluxed than those using the equipment at minimal levels. It is difficult to tease out the relative contribution of the standing programme to these results. Martinsson et al (2011) examined the effect of one-year, one and a half hour/day straddled weight-bearing on MP in 14 children with CP who were non ambulatory<ref name="Martinsson">Martinsson C, Himmelmann K. Effect of weight-bearing in abduction and extension on hip stability in children with cerebral palsy. Pediatr Phys Ther. 2011;23(2):150-157.</ref>. They reported a reduction of MP and preservation of PROM compared to controls. However they cautioned that because the number of children in the study was small further studies would be required to confirm the results. A more recent study examined a standing programme in 26 children with CP, GMFCS level III. Half the children stood in an individually fabricated standing frame with hips in 60 degrees of abduction for 70-90 minutes/day. The programme started when the child was 12-14 months and continued until 5 years of age. They report that the MP of those who stood remained stable at 5 years (13-23%) versus controls (12-47%). A recent randomized controlled trial examined the use of Botulinum toxin A combined with bracing in 90 children with CP and concluded that it was not effective in preventing hip displacement<ref name="Graham">Graham HK, Boyd R, Carlin J, et al. Does botulinum toxin a combined with bracing prevent hip displacement in children with cerebral palsy and "hips at risk"? A randomized, controlled trial. J Bone Joint Surg Am. 2008;90(1):23-33.</ref>.<br>


<u>lying support</u><br>[[Image:Lying support CP.jpg|left|250x200px]]<br>
Physiotherapists have proposed and examined standing programmes for children at risk of hip displacement. Pountney et al (2009) investigated the effectiveness of early postural management programmes in 39 children with CP<ref name="Pountney">Pountney T, Mandy A, Green E, Gard P. [https://onlinelibrary.wiley.com/doi/abs/10.1002/pri.434 Hip subluxation and dislocation in cerebral palsy - a prospective study on the effectiveness of postural management programmes.] Physiother Res Int. 2009;14(2):116-127.</ref>. The programme included a standing support (in addition to sitting and lying supports) and children were monitored from 18-60 months using x-rays. They found that those children who used the equipment at the recommended frequency had significantly less chance of both hips being subluxed than those using the equipment at minimal levels. It is difficult to tease out the relative contribution of the standing programme to these results. Martinsson et al (2011) examined the effect of one-year, one and a half hour/day straddled weight-bearing on MP in 14 children with CP who were non ambulatory<ref name="Martinsson">Martinsson C, Himmelmann K. [https://journals.lww.com/pedpt/FullText/2011/23020/Effect_of_Weight_Bearing_in_Abduction_and.6.aspx Effect of weight-bearing in abduction and extension on hip stability in children with cerebral palsy.] Pediatr Phys Ther. 2011;23(2):150-157.</ref>. They reported a reduction of MP and preservation of PROM compared to controls. However they cautioned that because the number of children in the study was small further studies would be required to confirm the results. A more recent study examined a standing programme in 26 children with CP, GMFCS level III. Half the children stood in an individually fabricated standing frame with hips in 60 degrees of abduction for 70-90 minutes/day. The programme started when the child was 12-14 months and continued until 5 years of age. They report that the MP of those who stood remained stable at 5 years (13-23%) versus controls (12-47%). A recent randomized controlled trial examined the use of Botulinum toxin A combined with bracing in 90 children with CP and concluded that it was not effective in preventing hip displacement<ref name="Graham">Graham HK, Boyd R, Carlin J, et al. [https://journals.lww.com/jbjsjournal/abstract/2008/01000/does_botulinum_toxin_a_combined_with_bracing.5.aspx Does botulinum toxin a combined with bracing prevent hip displacement in children with cerebral palsy and "hips at risk"? A randomized, controlled trial.] J Bone Joint Surg Am. 2008;90(1):23-33.</ref>.<br>
[[File:Lying_support_CP.jpg|250x250px]]


<br>
'''Lying support'''
 
<br>
 
<br>
 
<br>
 
<br>
 
<br>
 
<br>


=== Operative  ===
=== Operative  ===


Preventative surgery is indicated when MP&gt;40%, or an increase in MP&gt;10% over the past year and hip abduction &lt;30°. Reconstructive surgery is indicated when MP&gt;50%. Salvage surgery is indicated for those with painful and degenerative dislocated hips.<ref name="Shore" /><br>  
Preventative surgery is indicated when MP&gt;40%, or an increase in MP&gt;10% over the past year and hip abduction &lt;30°. Reconstructive surgery is indicated when MP&gt;50%. Salvage surgery is indicated for those with painful and degenerative dislocated hips<ref name="Shore" />.<br>  


== References  ==
== References  ==
<br>
<references />
<references />
[[Category:Paediatrics]]
[[Category:Paediatrics]]
[[Category:Cerebral Palsy]]
[[Category:Cerebral Palsy]]
[[Category:Paediatrics - Conditions]]
[[Category:Paediatrics - Conditions]]

Latest revision as of 15:16, 31 October 2023

Introduction[edit | edit source]

Cp child sit balance.jpg

Hip displacement is very common in children with cerebral palsy (CP) and the incidence has been reported to be 35%[1][2]. It is directly related to the child’s Gross Motor Function Classification Scale (GMFCS) level with a reported incidence of between 68-90% for children in GMFCS Level IV and V[1][3]. Progressive hip displacement can cause severe pain. In a recent study examining hip health at skeletal maturity in 98 young adults with CP, hip pain was reported in 72% of participants and pain frequency and severity increased with worsening hip morphology[4]. It can also lead to difficulties with positioning, sitting, standing and walking and negatively impact quality of life.[5][6][7]

Causes / Risk factors[edit | edit source]

Muscular imbalance around the hip has been proposed as one possible cause of the lateral displacement. Yildiz et al (2014) suggest that hyperactivity of the hip flexors and adductors are contributing factors[8]. In addition the combination of femoral neck-shaft angle and femoral anteversion contributes to the risk of hip displacement[7]. A clear relationship between GMFCS level and hip displacement has been established. Children with greater functional loss (GMFCS levels IV and V) are at a highest risk[1][3][9][10]. Age is also a factor. Hagglund et al (2007) reported that the most common age of displacement in their population was 3-4 years and some were as young as 2 years9. Progression of hip displacement has also been reported after puberty and progression and dislocation has occurred after skeletal maturity, the latter happening in the presence of scoliosis and pelvic obliquity[10]. It appears that topography and movement disorder are poor predictors of hip subluxation[10].

Diagnostic Procedures[edit | edit source]

Hip surveillance[edit | edit source]

Hip surveillance programmes have been established in many countries in order to identify and monitor those children at risk for hip displacement. There have been reports of a significantly decreased incidence of hip dislocation as a result of these programmes[10]. Two that are cited frequently are The Cerebral Palsy Follow-Up Programme (CPUP)[9] which was established in Sweden in 1994 and is currently being used in all or parts of Denmark, Iceland, Norway and Scotland and the revised Australian Hip Surveillance Guidelines for Children with Cerebral Palsy[10].While hip surveillance identifies those children with progressive displacement it does not dictate the type or timing of intervention[10].

Radiological examination[edit | edit source]

Diagnosis is by x-ray as a clinical examination alone in insufficient to evaluate hip displacement[7]. Reimer’s migration percentage (MP) is the most common measure used to examine the amount of lateral displacement of the femoral head[11]. Hips presenting with MP >30% are considered to be displaced and hips with an MP > 90%-100% are dislocated[5] . Progression of the MP greater than 7% per year is considered to be worrying[7].

Clinical examination[edit | edit source]

The clinical examination is often the responsibility of the physiotherapist. It can include but is not limited to
• assignment of GMFCS and FMS (Functional Mobility Scale) levels
• assessment of

  • Sitting, standing and walking abilities
  • Bed mobility
  • Pain
  • Spasticity (Modified Ashworth Scale/ Modified Tardieu Scale)
  • Passive range of motion (PROM): Thomas test, hip abduction (in extension and flexion); hip internal and external rotation, popliteal angle (single and bilateral), Ely’s test, knee extension, dorsiflexion (knee extended and flexed)
  • Spine (scoliosis)
  • Leg length discrepancy

Outcome Measures[edit | edit source]

Gross Motor Function Classification Scale

Thomas test

Ely's test

The CPUP programme has evaluation forms for physiotherapists and occupational therapists that can be down loaded from the website.

Management / Interventions[edit | edit source]

Non-operative[edit | edit source]

Physiotherapists have proposed and examined standing programmes for children at risk of hip displacement. Pountney et al (2009) investigated the effectiveness of early postural management programmes in 39 children with CP[12]. The programme included a standing support (in addition to sitting and lying supports) and children were monitored from 18-60 months using x-rays. They found that those children who used the equipment at the recommended frequency had significantly less chance of both hips being subluxed than those using the equipment at minimal levels. It is difficult to tease out the relative contribution of the standing programme to these results. Martinsson et al (2011) examined the effect of one-year, one and a half hour/day straddled weight-bearing on MP in 14 children with CP who were non ambulatory[13]. They reported a reduction of MP and preservation of PROM compared to controls. However they cautioned that because the number of children in the study was small further studies would be required to confirm the results. A more recent study examined a standing programme in 26 children with CP, GMFCS level III. Half the children stood in an individually fabricated standing frame with hips in 60 degrees of abduction for 70-90 minutes/day. The programme started when the child was 12-14 months and continued until 5 years of age. They report that the MP of those who stood remained stable at 5 years (13-23%) versus controls (12-47%). A recent randomized controlled trial examined the use of Botulinum toxin A combined with bracing in 90 children with CP and concluded that it was not effective in preventing hip displacement[14].
Lying support CP.jpg

Lying support

Operative[edit | edit source]

Preventative surgery is indicated when MP>40%, or an increase in MP>10% over the past year and hip abduction <30°. Reconstructive surgery is indicated when MP>50%. Salvage surgery is indicated for those with painful and degenerative dislocated hips[7].

References[edit | edit source]

  1. 1.0 1.1 1.2 Soo B, Howard J, Boyd R, et al. Hip displacement in cerebral palsy. J Bone Joint Surg Am. 2006;88(1):121-129
  2. Novak I, Hines M, Goldsmith S, Barclay R. Clinical prognostic messages from a systematic review on cerebral palsy. Pediatrics. 2012;130(5):e1285-e1312.
  3. 3.0 3.1 Terjesen T. The natural history of hip development in cerebral palsy. Dev Med Child Neurol. 2012;54(10):951-957.
  4. Wawrzuta J, Willoughby K, Molesworth C, et al. Hip health at skeletal maturity: A population-based study of young adults with cerebral palsy. Dev Med Child Neurol. 2016.
  5. 5.0 5.1 Hägglund G, Andersson S, Düppe H, Lauge Pedersen H, Nordmark E, Westbom L. Prevention of dislocation of the hip in children with cerebral palsy. the first ten years of a population-based prevention programme. J Bone Joint Surg Br. 2005;87(1):95-101.
  6. Robb JE, Hägglund G. Hip surveillance and management of the displaced hip in cerebral palsy. J Child Orthop. 2013;7(5):407-413.
  7. 7.0 7.1 7.2 7.3 7.4 Shore B, Spence D, Graham H. The role for hip surveillance in children with cerebral palsy. Curr Rev Musculoskelet Med. 2012;5(2):126-134.
  8. Yildiz C, Demirkale I. Hip problems in cerebral palsy: Screening, diagnosis and treatment. Curr Opin Pediatr. 2014;26(1):85-92.
  9. 9.0 9.1 Hägglund G. Characteristics of children with hip displacement in cerebral palsy. BMC musculoskeletal disorders. 2007;8:101-101.
  10. 10.0 10.1 10.2 10.3 10.4 10.5 Wynter M, Gibson N, Willoughby K, et al. Australian hip surveillance guidelines for children with cerebral palsy: 5-year review. Dev Med Child Neurol. 2015;57(9):808-820.
  11. Reimers J. The stability of the hip in children. A radiological study of the results of muscle surgery in cerebral palsy. Acta Orthop Scand Suppl. 1980;184:1-100.
  12. Pountney T, Mandy A, Green E, Gard P. Hip subluxation and dislocation in cerebral palsy - a prospective study on the effectiveness of postural management programmes. Physiother Res Int. 2009;14(2):116-127.
  13. Martinsson C, Himmelmann K. Effect of weight-bearing in abduction and extension on hip stability in children with cerebral palsy. Pediatr Phys Ther. 2011;23(2):150-157.
  14. Graham HK, Boyd R, Carlin J, et al. Does botulinum toxin a combined with bracing prevent hip displacement in children with cerebral palsy and "hips at risk"? A randomized, controlled trial. J Bone Joint Surg Am. 2008;90(1):23-33.