Definition
Developmental dysplasia of the hip
- the femoral head does not have the normal relationship with the acetabulum
- child with subluxable, reducible or irreducible hip
- may not be present at birth (hence not called CDH)
Instability
- ability to dislocate or reduce femoral head into or out of acetabulum
Dislocated
- complete loss of contact
Irreducible
- unable to be reduced
Subluxation
- partial contact
Dysplasia
- an abnormal acetabulum
- it is both shallower than normal & its inclination is more vertical than normal
Epidemiology
Incidence
- DDH = 2: 1000 (requiring treatment)
- instability 10 : 1000
Influenced by
- presence of screening
- age of baby at examination
- experience of examiner
Factors
- females 7x
- first-born
- L > R (L 2/3 of cases / LOA lie)
Bilateral 20%
Associations
Congenital Torticollis - 20%
Metatarsus Adductus - 2%
Screening
Nursery screening has decreased incidence of late dislocation
- decrease of 85% in incidence of walking CDH
- increase of early instability
Aetiology
1. Ligamentous laxity
Different in sexes
- maternal hormones
- female baby have increased response to relaxin
Familial hyperlaxity in males
- usually familial hyperlaxity with collagen alteration
2. Positional
A. Breech position
- important risk factor
- 25% of DDH were breech
- normally 2.5% of births
Female breech
- 1 :35 = dislocated hips
- 1:15 = unstable hips
B. Oligohydramnios
C. Twins
D. Firstborn - ? small uterus
E. Increased L>R
- usually LOA (vertex) position
- adduction left hip against mother's spine
E. Post-natal
- decreased where babies carried astride waist (Eskimos and Africans)
- increased where babies strapped to cradle board (Indians)
3. Genetic
Nature of genetic predisposition unclear
- may be related to familial ligamentous laxity
- increased in Indians and Lapps
- decreased in Chinese and Africans
If child has DDH
- 5% of siblings DDH
- 1% of brothers
- 10% of sisters
Parent
- 12 % for child
4. Teratologic Dislocation
Associated with other malformations
- irreducible at birth
- Arthrogryposis
- Larsen's
Pathology
Newborn
- hip is spontaneously dislocating & reducing
- minimal anatomical changes
- lax joint capsule
- shallow acetabulum
- flattening of posterosuperior labrum
Dislocated
Acetabular Dysplasia
- muscle action encourages proximal and lateral migration of head
- acetabulum and head rely on each other for development
- unreduced acetabulum becomes vertical and shallow
- becomes more anteverted
Femoral head
- dislocates upwards & backwards
- head becomes more globular & less spherical
- neck becomes more anteverted
Capsule
- enlarges & narrows at isthmus
- where iliopsoas crosses
- Zona Orbicularis
Ligamentum teres
- longer & thicker
Pulvinar
- fills with thickened fat pad
Transverse ligament
- pulled superiorly and blocks inferior socket
Labrum
- may invert
Subluxation
Space between head & medial wall of acetabulum widens
Dysplasia of acetabulum develops
- vertical
- shallow
- increased anteversion
NHx
50% of unstable hips resolve without treatment
Subluxation
- acetabular dysplasia
- always leads to early OA
Dislocation
- long term follow up
- 60% significant pain & disability
- 40% no pain but abnormal gait
- increased incidence of pain & OA with well-developed false acetabulum
History
Suspected in Neonate
- female
- firstborn / breech / twins
- FHx of DDH / ligamentous laxity
- metatarsus adductus / torticollis / calcaneovalgus
Infant
- difficulty with nappies due to limited abduction
- shortening of thigh
Child
- delay in walking or running
- limp
- increased lumbar lordosis
- unilateral toe walking
- intoeing
DDx
PFFD
Septic dislocation
SUFE
Coxa vara
Trauma
Neurological - CP, Spina bifida
Screening
All neonates within 48 / 24
- treatment begun ASAP
- ultrasound "At risk" population
Beware
- CTEV / torticollis
- breech
- FHx
Examination Neonate
Thigh folds
Reduced abduction
- dislocated
Ortolani Test
- hip is out, tests reduces hip
- thumb on adductor tubercle & ring finger on GT
- place in 90° flexion
- abduct both hips & lift GT forward
- clunk of reduction felt
Barlow Provocation Test
- push hip back out
- one hand holds pelvis
- adduction to 10o while axial pushing thigh backward
- dislocates in this position over post lip / feel clunk of dislocation
- may feel sliding of subluxable hip
- very deficient lip may give false negative with no clunk
Hip may be
- stable
- subluxable
- dislocatable
- dislocated (reducible / not reducible)
Clicks
- not significant
- innocent clicks secondary to ligamentum teres / iliopsoas / iliotibial band
Examination Infant
Unilateral
- decreased abduction (< 60° suspicious, < 45° definite)
- apparently short femur - Galleazi's
- extra thigh folds
Bilateral
- more difficult
- symmetrical decrease of Abduction
Signs shortening above the GT
Klisic's line
- line from ASIS to GT
- should point to umbilicus
- points horizontally in DDH
Nelaton's line
- line from ischial tuberosity to ASIS
- thigh adducted & flexed
- normally GT caudad to it
- in DDH GT cephalad to it
Examination Child
Unilateral
- limp
- abductor lurch / trendelenberg gait
- short-leg component
- decreased ROM / mild FFD / decreased abduction
- full rotation
Bilateral
- increased lumbar lordosis
- waddling gait / bilateral trendelenberg gait
- bilateral decrease ROM
X-ray
Timing
- AP after 6/12
- when SFE ossified
- obturator foramina should be symmetrical / no rotation
Quadrants
Hilgenreiner's Line
- horizontal through triradiate cartilages
Perkin's Line
- vertical through lateral edge of bony acetabulum
4 quadrants
- ossific nucleus usually lies in inferior / medial quadrant
Findings
1. Delayed development of ossific nucleus / smaller
2. Ossific nucleus in upper / outer quadrant
3. Disruption Shenton's Line
- curved line along inferior neck
- inferior border superior ramus
4. Head to Teardrop Distance
- lateral tear drop to medial ossification centre
- use metaphyseal edge if no SFE
- wide medial joint space compared with normal side
5. Acetabular Index
- angle between Hilgenreiner's & acetabular lines
- 30° at birth to 20° at 2 years
- Normal < 30°
- DDH > 35°
6. Centre - Edge Angle
- angle between Perkin's & CE line
- measure of coverage of femoral head
- Normal 30°
- DDH < 20° Protrusio >40°
Von Rosen's view
Technique
AP pelvis with legs abducted 45° & IR 20°
- lines along femoral shafts should pass through centre acetabulum & intersect at sacrum
- DDH line not through acetabulum & intersects to side of sacrum
Indication
Use in late presentation
- if femoral head reduces with von rosen then suitable for pelvic osteotomy only
- if head appears to articulate on edge of acetabulum may have false acetabulum
- then must do open reduction, femoral osteotomy & pelvic osteotomy
Ultrasound
Background
Best imaging before 4 - 6 months when pelvis cartilaginous
- very accurate
- static & dynamic images
- coronal view most important
No role in general screening as is too sensitive
- many hips with alpha angles 50 - 60o will resolve
Alpha Angle
- between ilium & bony roof acetabulum
- normal > 60°
Beta Angle
- between ilium & cartilage roof / labrum
- normal < 60o
Dynamic stress
- is the head reducible
- perform Ortolani's under ultrasound
Graaf's Classification
| Type | Alpha | Beta | ||
| 1 | > 60 | < 60 | Normal | |
| 2A | 50 - 59 | Immaturity < 3/12 | ||
| 2B | 50 - 59 | Delayed Ossification > 3/12 | ||
| 2C | 43 - 49 | < 77 | ||
| 2D | 43 - 49 | >77 | Labrum everted | |
| 3 | < 43 | >77 | Dislocated | |
| 4 | <43 | >77 | Dislocated & Labrum interposed |
Arthrography
Normal hip shows projection of labrum
Abnormal hip shows
- widened medial joint space / medial pooling
- blunting / infolding of labrum superiorly
- enlargement of ligamentum teres
- neolimbus bulge in acetabular cartilage
- hourglass constriction of capsule
Useful in evaluating reduction intra-operatively
MRI / CT
Indication
- assess post operative hip reduction when child in spica
Management Algorithm
0 - 6 months
Attempt closed reduction
- Pavlik harness
- von Rosen splint
6 - 18 months
Closed reduction
- adductor tenotomy / hip spica
Open reduction
- medial approach
- Smith Petersen approach
After age of 1 consider adding
- acetabular osteotomy to address acetabular dysplasia
- FDRO if required to obtain reduction
18 - 3 years
Dislocated hip
- open reduction + acetabular osteotomy
- femoral osteotomy if difficulty reducing hip
Acetabular dysplasia
- hip reduced but large acetabular index
- > 30o and not improving with time
- acetabuloplasty
> 3 years
Dislocated hip
- open reduction
- acetabular osteotomy to correct acetabular index
- hip will be difficult to reduce so need to shorten femur / FDRO
Complications Management
AVN
Aetiology
Result of treatment
- doesn't occur in untreated DDH
1. Excessive abduction / splint / traction
2. Forceful closed reduction
3. Vascular damage at open reduction
Reduced by
Adductor tenotomy
Femoral osteotomy
Avoid medial reduction
X-ray Classification
Kalamachi and McEwan 1980
1. Nucleus only
- temporary irregular fragmentation of SFE
- head will subsequently be normal
2. Lateral Physis
- early lateral premature fusion
- femoral head will tilt into valgus
- lateral portion of femoral neck short
3. Central physis involved
- femoral neck will be short / coxa breva
- coxa vara secondary to due to GT growth
4. Whole physis involved
- femoral neck will be short & in valgus
- GT overgrowth
Outcome
Coxa breva / Coxa valga / Coxa vara
Relative overgrowth of GT
LLD
Trendelenberg gait
Management
1. Trochanteric Physiodesis
- to reduce overgrowth
- if <7
2. Trochanteric transfer
- if trochanter has reached level of femoral head
- transferred distally & laterally