DEVELOPMENTAL DYSPLASIA OF THE HIP
INTRODUCTION
Developmental Dysplasia of the Hip (DDH), describes a spectrum of anatomic abnormalities of the hip in infants and young children. It encompasses abnormal development of the femoral head and acetabulum, and mechanical instability of the hip joint (Mulpuri et al., 2014). These abnormalities may be congenital or develop during the weeks and months following birth (Rhodes & Clarke, 2014).
According to the International Hip Dysplasia Institute (2018b), 1 in 10 infants are born with hip instability, 1 in 100 infants are treated for hip dysplasia and 1 in 500 infants are born with completely dislocated hips.
DDH may vary from mild to severe. The acetabulum may be shallow, and the structures that support the head of femur within the acetabulum may be lax. This may cause the femoral head to be unstable (Australian Physiotherapy Association (APA), 2019a). In more severe cases, the femoral head may lose contact with the acetabulum causing subluxation or dislocation (APA, 2019a).
One or both hips of an infant may be affected by the condition (Royal Children’s Hospital, 2018b). Whilst DDH is not painful in infants and young children, untreated DDH may result in abnormal gait, decreased strength, and increased rate of degenerative hip and knee joint diseases during adolescence and adulthood (Kotlarsky, Harber, Bialik, & Eidelman, 2015).
Physiotherapists play a major role in identifying DDH and determining the best course of treatment / management to facilitate optimal functional outcomes (APA, 2019a).
For More Information on Developmental Dysplasia of the Hip
Figure 32. Types of DDH (International Hip Dysplasia Institute, 2018b)
CLINICALLY RELEVANT ANATOMY
The hip is a ball and socket joint composed of the femoral head and acetabulum. The hip joint is normally held tightly in place by the surrounding ligaments and joint capsule (International Hip Dysplasia Institute, 2018e).
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The head of femur and acetabulum are largely cartilaginous in newborn infants (Noordin, Umer, Hafeez, & Nawaz, 2010). Newborns often have physiologic laxity of the hip and immaturity of the acetabulum during the first few weeks of life (Rosenfeld, Phillips, & Torchia, 2019). In most cases, the laxity resolves and the acetabulum proceeds to develop normally, thus creating a strong and stable hip joint (Rosenfeld et al., 2019). For infants with DDH, the hip does not develop as expected (Royal Children’s Hospital, 2011).
Figure 33. Hip Joint Anatomy
(International Hip Dysplasia Institute, 2018c).
Figure 34. Development of Femoral Head
(Royal Children’s Hospital, 2017a).
AETIOLOGY
The hormone, Relaxin is released into the mother’s blood stream during pregnancy. The role of this hormone is to relax the pelvic ligaments to prepare the birth canal for parturition (Rhodes & Clarke, 2014). Some of the Relaxin hormone may enter the foetuses’ blood stream. This may directly influence the foetuses’ connective tissue metabolism, and subsequently cause laxity within the ligaments supporting the femoral head within the acetabulum (Rhodes & Clarke, 2014).
Positioning of the baby in utero may also cause increased pressure on the hip joints and/or stretching of the ligaments (International Hip Dysplasia Institute, 2018d). Similarly, postnatal mechanical forces associated with tight swaddling or wrapping cause the infant’s hips to rest in a position of adduction and internal rotation. This position increases the risk of the femoral head to becoming unstable and/or dislocating (International Hip Dysplasia Institute, 2018d).
RISK FACTORS
According to Mulpuri et al’s (2014) clinical practice guidelines, risk factors that have been associated with a higher probability of DDH include:
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Breech position in utero
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Family history of DDH / hip instability
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Female gender
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First born
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Multiple pregnancies (Eg. twins or triplets)
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Large birth weight (> 4000g)
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Prematurity
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Swaddling practices
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Intrauterine crowding
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Torticollis, Plagiocephaly and foot deformities (Eg. Talipes Equinovarus)
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Limited hip abduction range of motion
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Neurological disorders (Eg. Cerebral Palsy and Spina Bifida)
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Oligohydramnios (ie. decreased amniotic fluid inside the uterus)
CLINICAL PRESENTATION
The clinical features of DDH depend upon the age of the child and the severity of the abnormality (Rosenfeld et al., 2019). According to Noordin et al. (2010), infants with DDH typically present with the following signs:
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Hip instability or stiffness
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One leg appearing shorter than the other
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Uneven positioning of the legs (Eg. external rotation of one leg)
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Uneven thigh or buttock creases
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Limited hip abduction range of motion
OBJECTIVE ASSESSMENT
Physical examination is vital in the initial identification of DDH. The following is a general overview of the procedure used to examine an infant’s hips. Please note that the reliability of physical examination changes as the child grows, therefore examination techniques vary depending on the age of the child (Northern Child Health Network, 2011).
BIRTH TO 3 MONTHS OF AGE
Figure 34. Barlow Test (Williams, 2018)
BARLOW TEST
The Barlow provocative test detects an unstable and/or dislocatable hip during examination (Williams, 2018).
Test Administration
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To perform the Barlow test on an infant (Williams, 2018):
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Place the infant supine on a firm flat surface, unclothed below the waist
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Ensure the infant’s buttocks are flat against the surface
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Place the practitioner’s hand over the infant’s anterior knee, with the thumb on medial thigh and fingers on lateral thigh
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Flex the infant’s hip and knee to 90°
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Ensure the practitioner’s second and third digits are palpating the grater trochanter of the ipsilateral leg
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Gradually and gently adduct the infant’s hip and apply a gentle posterior pressure through the line of the femur
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Feel for a ‘clunk’ and degree of posterior translation
Test Interpretation
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The Barlow test is considered to be positive if the gentle posterior force causes a palpable ‘clunk’ as the femoral head exits the posterior acetabulum (Williams, 2018).
For More Information on the Barlow Test
ORTOLANI TEST
The Ortolani provocative test is an examination method that identifies a dislocated hip that may be reduced into the acetabulum (Williams, 2018). It is crucial that the Ortolani test is always performed after the Barlow test in case hip has been dislocated and requires relocation.
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Test Administration
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To perform the Ortolani test on an infant (Williams, 2018):
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Place the infant supine on a firm flat surface, unclothed below the waist
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Ensure the infant’s buttocks are flat against the surface
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Place the practitioner’s hand over the infant’s anterior knee, with the thumb on medial thigh and fingers on lateral thigh
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Flex the infant’s hip and knee to 90°
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Ensure the practitioner’s second and third digit are palpating the greater trochanter of the ipsilateral leg
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Gradually and gently abduct the infant’s hip whilst applying a gentle traction and anterior pressure through the greater trochanter
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Feel for a ‘clunk’ (ie. relocation of femoral head)
Test Interpretation
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The Ortolani test is considered to be positive if a ‘clunk’ is felt as the dislocated femoral head reduces into the acetabulum (Williams, 2018).
For More Information on the Ortolani Test
Figure 35. Ortolani Test (Williams, 2018)
OLDER INFANTS (> 3 MONTHS OF AGE)
After 3 months of age the Barlow and Ortolani tests may be unreliable, therefore additional means of examination, used in combination with the Barlow and Ortolani tests are necessary (Royal Children’s Hospital, 2018c).
COMBINED HIP ABDUCTION RANGE OF MOTION
Limited hip abduction is the most sensitive sign associated with DDH in the older infant (Williams, 2018).
Test Administration
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To assess an infant’s combined hip abduction range of motion (Williams, 2018):
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Place the infant supine on a firm flat surface, unclothed below the waist
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Ensure the infant’s buttocks are flat against the surface
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Flex the infant’s hips and knees to 90°
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Gradually and gently abduct the infant’s hips
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Observe the infant’s combined hip abduction range of motion and symmetry
Note: This manoeuvre may need to be repeated a number of times to ensure an accurate result is obtained.
Test Interpretation
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Normal hip abduction range of motion in infants is ~70° - 90°. Therefore, the combined hip abduction range is usually around ~140° - 180° with both hips achieving symmetrical range of motion. Decreased hip abduction range of motion and asymmetrical hip abduction range are red flags for DDH (Northern Child Health Network, 2011).
Figure 36. Combined Hip Abduction
(Chandler & Brady, 2016)
HIP / GLUTEAL CREASES
Asymmetrical skin folds alone do not constitute a diagnosis of DDH; however, this information may be used in combination with other physical signs during assessment (International Hip Dysplasia Institute, 2018a).
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Test Administration
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To examine an infant’s hip and thigh creases (Williams, 2018):
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Place the infant supine on a firm flat surface, unclothed below the waist
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Ensure the infant’s buttocks are flat against the surface
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Observe the number and symmetry of creases on the infant’s thighs
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Place the infant in prone
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Observe the number and symmetry of creases on the infant’s thighs and gluteal region
Test Interpretation
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Increased depth and increased number of posterior gluteal creases, particularly if proximal, are more indicative of DDH (International Hip Dysplasia Institute, 2018a).
Figure 37. Thigh and Gluteal Creases (International Hip Dysplasia Institute, 2018a)
GALEAZZI TEST
When an infant’s hip dislocation has been present for several months, the hips gradually lose range of motion and one leg generally appears shorter than the other as the hip has migrated upward (International Hip Dysplasia Institute, 2018a).​
Test Administration
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To perform the Galeazzi test on an infant (Williams, 2018):
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Place the infant supine on a firm flat surface, unclothed below the waist
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Ensure the infant’s buttocks are flat against the surface
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Flex the infant’s hips to 90°
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Place the infant’s legs in neutral adduction/abduction with knees in flexion
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Observe the vertical level of the infant’s knees
Figure 38. Galeazzi Sign (Kumari, 2018)
Test Interpretation
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The Galeazzi Test is considered to be positive if a limb-length discrepancy exists. The knee on the ipsilateral side to the affected hip will be lower than the knee on the unaffected side (Williams, 2018).
OBJECTIVE ASSESSMENT MEASURES FOR ALL INFANTS
DEVELOPMENTAL MILESTONE SCREENING
For more information on developmental milestone screening
HEAD AND NECK SCREENING
For more information on head and neck screening
SPINE AND TRUNK SCREENING
Routine screening of the spine increases the likelihood of spinal abnormalities being detected early. Screening involves examining the alignment of the spine and identifying any hairy patches and a natal cleft. If a curvature of the infant’s spine is present, this may be indicative of early onset scoliosis (Ridderbusch et al., 2018). Furthermore, if hairy patches or a natal cleft are present, this may be indicative of Spina Bifida (David, 2016).
FOOT SCREENING
Routine screening of the feet will increase the likelihood of foot abnormalities including Positional Talipes and Metatarsus Adductus being detected early. Positional Talipes refers to the foot resting in a position of adduction and supination (Royal Children’s Hospital, 2010b). Metatarsus Adductus refers to adduction of the forefoot with normal hindfoot alignment (Royal Children’s Hospital, 2010a). Both are thought to be related to the position of the foetus inside the mother’s uterus and may affect one or both feet (Royal Children’s Hospital, 2010b; Royal Children’s Hospital, 2010a).
TREATMENT OPTIONS
PREVENTATIVE MEASURES
SAFE SWADDLING PROCEDURES
Swaddling is commonly used to promote improved sleep patterns and calm an infant. When in the uterus, infants’ legs are in the foetal position (ie. hip and knee flexion). Improper swaddling positions, including those that tightly bind the infant’s hips and knees together in a position of extension and adduction, place increased stress upon the fragile structures of the hip joint (American Academy of Orthopaedic Surgeons, 2018). As such, the infant’s hips are more likely to become unstable, subluxate or dislocate with prolonged, tight swaddling (American Academy of Orthopaedic Surgeons, 2018).
To optimise positioning of the infant’s hip when swaddled, it is imperative that parents are provided detailed education and advice regarding proper swaddling methods. According to the American Academy of Orthopaedic Surgeons (2018), an infant’s hips should be positioned in slight flexion and abduction when swaddled. The infant’s knees should also be maintained in slight flexion. It is recommended that the infant’s hips are allowed to move freely and forced or sustained passive hip extension and adduction are avoided to promote optimal hip development.
Moreover, swaddling should be snug around the infant's chest with enough space so that the caregiver's hand can fit between the blanket and the baby's chest. If the swaddle becomes loose, it may result in head covering or strangulation. A swaddled infant should always be placed on his or her back to reduce the risk of Sudden Infant Death Syndrome (SIDS). When an infant exhibits signs of attempting to roll, swaddling should no longer be used as a swaddled infant in the prone position is at high risk for SIDS and suffocation (American Academy of Orthopaedic Surgeons, 2018).
The following method may be used to safely swaddle an infant (International Hip Dysplasia Institute, 2018f):
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Using a square cloth, fold back one corner creating a straight edge
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Place the infant on the cloth, so that the top of the fabric is at shoulder level
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Bring the right arm down and wrap the cloth over the arm and chest
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Tuck the cloth under the left side of the infant
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Bring the left arm down and wrap the cloth over the arm and chest
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Tuck the cloth under the right side of the infant
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The weight of the infant will hold the cloth firmly in place
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Twist or fold the bottom end of the cloth and tuck behind the infant ensuring that both legs are slightly flexed and abducted
Figure 39. Safe Swaddling
(Royal Children’s Hospital, 2010c)
BABY WEARING
Proper infant hip positioning while baby wearing is essential as the period of time for baby wearing is usually longer than transport. When proper hip position is maintained while baby wearing, there may be substantial benefits for natural hip development (International Hip Dysplasia Institute, 2018c).
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The Spread Squat Position, also known as the M-Position or Jockey Position is recommended as the infant’s thighs are spread around the parent’s torso. Each hip is maintained in approximately 40° - 55° of abduction and 90° - 110° flexion. This position ensures the femoral head presses evenly into the centre of the acetabulum. Muscle action of the infant further presses the femoral head into the acetabulum as the infant moves and clings onto the parent. The combination of the hip positioning and muscle activity are beneficial for healthy hip joint development (International Hip Dysplasia Institute, 2018c).
Figure 40. Baby Wearing (International hip dysplasia Institute, 2018b)
BABY CARRIERS AND CAR SEATS
Some types of baby carriers, prams and car seats may interfere with healthy hip positioning. These devices may inadvertently place the hips in a position of extension and adduction, especially when used for an extended period of time. Any device that restrains a baby’s legs in an unhealthy position should be considered a potential risk for abnormal hip development (International Hip Dysplasia Institute, 2018b).
Therefore, it is important that parents are advised to adjust the size of their carriers and devices according to their infant’s size. All devices should allow the infant to move their legs freely into flexion and abduction as described in the Spread Squat Position above. Parents are advised to research the general safety and risks of any device they wish to purchase (International Hip Dysplasia Institute, 2018b).
Figure 41. Car Seat Position (International hip dysplasia Institute, 2018b)
TREATMENTS
Treatment varies depending on the child’s age and the severity of the condition. According to Charlton, Schoo and Walters (2017), early detection and treatment of DDH is paramount as the acetabulum is able to best remodel within the first 6 weeks of life. Commencing treatment within this period increases the likelihood of the hip becoming stable and well-formed as an enlocated femoral head stimulates the acetabulum to develop appropriately (Charlton et al., 2017).
BRACES
The first line of treatment for infants under 6 months of age, is bracing. Braces are designed to hold the infant in a “frog-leg” position (ie. hip flexion, abduction and external rotation). This position facilitates contact between the femoral head and acetabulum and subsequently causes the acetabulum to deepen. Furthermore, ligaments and muscles supporting the hip are strengthened in this position. The combination of the aforementioned allows the hip joint to become more stable with growth (Royal Children’s Hospital, 2018b). The two most common braces used include the Pavlik Harness and the Denis Browne Bar.
The Pavlik Harness has straps that are fastened around the infant’s legs and held up by the shoulder and chest straps (Royal Children’s Hospital, 2018d). The Denis Browne Bar has cuffs that go around to the upper thigh and are attached to a posterior bar (Royal Children’s Hospital, 2018a).
Whilst undergoing brace treatment, the infant will be seen regularly by their doctor to monitor their progress and check the brace. Hip ultrasounds performed every 4 to 6 weeks are used to monitor hip development until the infant is 6 months old. For infants older than 6 months, x-ray is used (Ömeroglu, 2018). Most infants will wear the brace for approximately 12 weeks; however, this will vary depending on how the infant responds to treatment. Older infants or those with more severe DDH may need to wear the brace for longer as the time taken to remodel the bones is greater (Ömeroglu, 2018).
The brace is usually worn 23-24 hours per day, until the hip appears stable on ultrasound or x-ray. The infant is then weaned off the brace over 6 weeks (Wahlen & Zambelli, 2015). A rare complication of brace treatment is avascular necrosis of the femoral head. It is important that the infant visit the doctor for follow up after brace treatment has concluded (Wahlen & Zambelli, 2015).
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For More Information on the Denis Browne Bar
Figure 42. Pavlik Harness and Denis Browne Bar
(Royal Children’s Hospital, 2018d; Royal Children’s Hospital, 2018a)
CLOSED REDUCTION
For infants between the ages of 6 and 24 months and for those in which bracing was unsuccessful, a closed reduction procedure may be performed. This procedure involves a surgeon physically manipulating the femoral head to relocate it within the acetabulum whilst the infant is under general anaesthesia (Royal Children’s Hospital, 2018b).
A hip spica (ie. a plaster cast that covers the infant’s body from waist to knee) will be fitted following the procedure. The hip spica will ensure the hip remains in the newly aligned position whilst the joint heals and encourages proper formation of the joint as the child grows (Royal Children’s Hospital, 2018b).
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OPEN REDUCTION
Occasionally when bracing and closed reduction are unsuccessful, or if DDH was diagnosed later than 6 months of age, an infant may require open reduction surgery (Royal Children’s Hospital, 2018b). This surgery involves an incision and the removal of any tissue(s) that prevent the femoral head to relocate into the acetabulum. The femoral head is then realigned in the acetabulum and the surrounding ligaments are tightened (Royal Children’s Hospital, 2018b).
A hip spica (ie. a plaster cast that covers the infant’s body from hip to knee) will be fitted following the procedure. The hip spica will ensure the hip remains in the newly aligned position whilst the joint heals and encourages proper formation of the joint as the child grows (Royal Children’s Hospital, 2018b).
OSTEOTOMY
Occasionally when DDH is diagnosed late, additional surgery to the pelvis or femur is necessary to stabilise the hip joint (Royal Children’s Hospital, 2018b).
RECOMMENDED REFERRALS
All infants with suspected DDH must be referred to the Royal Children’s Hospital Orthopaedic outpatient department for further assessment and monitoring (Victoria State Government, 2019).
Early referrals to an infant’s General Practitioner and Paediatrician should also be made to arrange the necessary imaging investigations for DDH. According to Mulpuri et al’s (2014) clinical practice guidelines, infants presenting with risk factors for DDH (ie. breech presentation, family history / history of clinical instability) should undergo routine radiological evaluation despite normal physical assessment findings.
Ultrasound and x-ray imaging may be used to confirm the clinical signs of DDH and assist in monitoring response to treatment (Victorian Agency for Health Information, 2019). Infants less than 6 months of age with suspected DDH should be referred for a hip ultrasound. As the femoral head is largely cartilaginous prior to 6 months of age, it will not be visible on x-ray. For infants with suspected DDH over 6 months of age, a hip x-ray is recommended as their femoral head has begun to ossify and will be visible on x-ray (Victorian Agency for Health Information, 2019).