Paeds Hip (Complete)

Question 1

What are the risk factors for the development of DDH?

[Clinical Pediatrics 2015, Vol. 54(10) 921–928][Lovell and Winter]

Answer 1

1. Female
2. Feet first (breech)
3. First born
4. Family history
5. Oligohydramnios
6. Swaddling
7. Caucasian

Question 2

What hip is most commonly affected in DDH?

[Orthobullets]

Answer 2

Left hip (60%)

Question 3

What are the examination findings in DDH?

[Miller’s, 6th ed.]

Answer 3

1. Dislocated – Ortolani positive (early), Galleazzi sign
2. Dislocatable – Barlow positive
3. Subluxable – Barlow suggestive
4. Other – asymmetric gluteal fold, decreased hip abduction (>3 months), wide perineum (bilateral dislocated hips)

Question 4

What are the potential obstructions to obtaining a concentric reduction in DDH?

[Miller’s, 6th ed.]

Answer 4

• Iliopsoas tendon (creates hourglass capsule)
• Adductor tendon (limits abduction)
• Inverted labrum
• Contracted inferomedial capsule
• Transverse acetabular ligament
• Pulvinar
• Ligamentum teres
• Limbus (ridge of cartilage tissue that divides the acetabulum into a true and a false acetabulum)

Question 5

When do you choose hip ultrasound over radiographs?

Answer 5

1. Ultrasound prior to femoral head ossification (<6months)
2. Radiographs following femoral head ossification (>6months)

Question 6

Describe the ultrasound features to assess for when evaluating DDH?

Answer 6

1. Lines drawn parallel to the iliac wing, roof of acetabulum, labrum
2. Alpha angle

• Formed between line parallel to ilium and acetabular roof
• Normal = >60

3. Beta angle

• Formed between line parallel to ilium and labrum
• .Normal = <55

4. Femoral head should be bisected by line parallel to ilium

• Morin index = percentage of the head covered by the acetabulum (below the ilium line)
  
  • Calculated as the width of the femoral head below the line divided by the width of the femoral head
  • Normal = >50%
  • Borderline = 46-50%
  • Abnormal = <46%

Question 7

Describe the radiographic features of DDH

Answer 7

1. Delayed ossification of femoral head (small)
2. Hilgenreiner’s line = horizontal line through the right and left triradiate cartilage
   * Normal femoral head should be below line
3. Perkins line = line perpendicular to Hilgenreiner’s line passing through point at the lateral acetabular roof
   * Normal femoral head lies medial to line
4. Shenton’s line = line along the inferior femoral neck and inferior superior pubic ramus
   * Normal = smooth and unbroken
5. Acetabular index = line parallel to the acetabular roof forms angle with Hilgenreiner’s line

• Normal = <25 after 6 months of age
• (24 at 24)

Question 8

Describe the application of the Pavlik harness

Answer 8

1. Hip flexion 100+/-10 degrees
   * Controlled by anterior strap – in line with anterior axillary line
2. Hip abduction in the safe zone (between maximum abduction which places head at risk of AVN and adduction point where hip dislocates/subluxes)

• Controlled by the posterior strap – at level of scapula
• Straps should not force abduction, rather should prevent adduction beyond neutral

3. Chest halter strap at nipple level

Question 9

What are the complications associated with Pavlik harness use?

[Lovell and Winter]

Answer 9

1. Transient femoral nerve palsy (excessive flexion)
2. Femoral head AVN (excessive abduction)
   * Due to compression of the posterosuperior retinacular branch of the medial femoral circumflex artery
3. Brachial plexus neuropathy (compression by shoulder straps)
4. Pavlik harness disease

• Persistent pavlik harness use despite unsuccessful reduction resulting in pathologic changes – damage to femoral head, acetabular cartilage
• “Prolonged positioning of the dislocated hip in flexion and abduction that potentiates dysplasia, particularly of the posterolateral acetabulum, and increases the difficulty of obtaining a stable closed reduction.” [Jones et al. J Pediatr Orthop. 2018 Jul; 38(6): 297–304.]

5. Skin breakdown (groin and popliteal fossa)
6. Inferior dislocation (excessive flexion)

Question 10

What are contraindications to Pavlik Harness use?

[World J Orthop. 2013 Apr 18; 4(2): 32–41]

Answer 10

1. Major muscle imbalance (eg. myelomeningocele – L2 to L4 functional level)
2. Major stiffness (eg. arthrogryposis)
3. Ligamentous laxity (eg. Ehlers-Danlos syndrome)

Question 11

What is the recommended DDH treatment for patients <6 months and >6 months?

[Lovell and Winter]

Answer 11

1.Neonate – 6 months

• First line = Pavlik Harness
  
  • 95% resolution of hip instability in Ortolani positive hips maintained in Pavlik for 6 weeks
  • >50% failure rate if used in patients > 6 months
  • Harness applied with followup in one week to confirm reduction (confirmation by clinical exam and US both acceptable) followed by weekly followup to adjust straps and confirm reduction
  • Duration of treatment variable
    
    • Minimum 6 weeks of full time use (23 hours a day)
    • Usually followed by period of weaning
    • One algorithm treats until hip normal by US (Graf classification type I) [J Child Orthop. 2018 Aug 1; 12(4): 308–316.]
  • If not reduced after 2 weeks – discontinue use and consider closed/open reduction at 4-6 months

2. 6 months – 4 years
   * First line = Closed reduction +/- adductor tenotomy
   
   • Closed reduction performed in OR
     
     • Reduction achieved with flexion, abduction, longitudinal traction, slight posterior pressure to GT
     • Arthrogram used to assess quality of reduction (medial dye pool <5mm or <16% of the width of the femoral head indicates concentric reduction)
     • Adductor tenotomy can be performed to widen the “safe zone”
       
       • Consider if narrow “safe zone” of less than 40°
     • Hip spica cast applied with 100° flexion and abduction in the “safe zone” (<55°) with molding posterior to GT
       
       • 100° of flexion and 40–50° of abduction referred to as the “human position” of the hip
     • Reduction is confirmed with CT (or MRI)
     • Spica cast use for 3 months
       
       • Cast change at 6 weeks – assess reduction, stability and hygiene purposes
       • Followed by abduction brace fulltime for 4 weeks
       • Followed by nighttime brace for 4 weeks
       • Second line = open reduction
   • Indicated in cases of failed closed reduction
   • Technique:
     
     • Smith-Peterson approach with modified “bikini” incision, adductor tenotomy, psoas recession, T capsulotomy, remove blocks toreduction, capsulorrhaphy (lateral leaf brought medial)
     • Ligamentum teres is guide to true acetabulum
     • Possible femoral shortening osteotomy if > age 3 or under tension after reduction
     • Possible acetabular procedure if >18 months
     • Spica cast is used for approximately 6 weeks with immobilization in about 30 degrees of abduction, 30 degrees of flexion, and 30 degrees of internal rotation

Question 12

What are advantages and disadvantages of medial vs. anterior approach for open reduction?

[Orthobullets]

Answer 12

1. Medial

• Advantages
  
  • Can be done at <12months
  • Directly addresses inferomedial blocks to reduction, less blood loss
• Disadvantages
  
  • Cannot perform capsulorrhaphy or bony work, risk of AVN
  • Note – Ludloff described interval between adductor longus and pectineus

2. Anterior

• Advantages
  
  • Performed at >12 months
  • Less AVN risk
  • Can perform capsulorrhaphy or bony work

Question 13

What is the technique for administration of contrast dye to the hip for arthrogram?

Answer 13

Needle directed medial to lateral 45° to the thigh and 45° to the horizon aiming towards the ASIS

• Inject 1:1 ratio of saline:contrast

Question 14

Recommended interventions of DDH based on age?

[JAAOS 2016;24:615-624]

Answer 14

• <6 months = Pavlik harness
• 6-12 months = closed reduction and spica casting
  
  • Closed reduction, possible adductor tenotomy, hip arthrogram, spica casting, CT/MRI
• 12-18 months = open reduction
  • Open reduction, adductor tenotomy/psoas recession, capsulorrhaphy, spica casting, CT/MRI
• 18 months – 3 years = open reduction and pelvic OR femoral osteotomy
• >3 years = open reduction and pelvic + femoral osteotomy
• Open reduction, adductor tenotomy/psoas recession, pelvic osteotomy, femoral shortening and derotation osteotomy, capsulorrhaphy, spica casting, CT/MRI

Question 15

What is the role of femoral osteotomy in DDH?

[JAAOS 2016;24:615-624]

Answer 15

1. Shortening of the femur reduces contact pressure on the femoral head thereby reducing the risk of osteonecrosis
2. Derotation of the femur reduces the excessive anteversion
3. Technique

• Performed through a lateral approach
• Subtrochanteric osteotomy just below level of LT
• Amount of shortening is determined by amount of overlap after femoral head reduced in the acetabulum
• Amount of derotation is determined by matching the opposite limb

Question 16

What is the role of the pelvic osteotomy?

[JAAOS 2016;24:615-624]

Answer 16

Improves the stability of the open reduction, improves the coverage of the femoral head

• Type of osteotomy is based largely on surgeon preference

Question 17

What are 4 radiographic markers used as the child grows to ensure that the reduction of DDH hip was successful?

[JAAOS 2016;24:615-624]

Answer 17

1. Improvement in the acetabular index
2. Sharp (not rounded) lateral border of the acetabulum
3. Narrow teardrop
4. Intact Shenton line

Question 18

What radiographic criteria can help diagnosis of osteonecrosis after DDH reduction?

[JAAOS 2016;24:615-624]

Answer 18

1. Failure of femoral head to ossify (or failure of an already present ossific nucleus to grow) within 1 year of reduction
2. Broadening of the femoral neck
3. Increased density of the femoral head (followed by fragmentation)
4. Residual deformity after ossification is complete

Question 19

What is the classification of osteonecrosis following treatment of DDH?

[JAAOS 2016;24:615-624]

Answer 19

Kalamchi and MacEwan

• Type I - alteration in the ossific nucleus
• Type II - lateral physeal damage
• Type III - central physeal damage
• Type IV - total damage to the head and physis

Question 20

What are the risk factors for SCFE?

[Lovell and Winter][J Am Acad Orthop Surg 2006;14:666-679]

Answer 20

1. Obesity (~50% are above the 95th percentile for weight)
2. Boys
3. Pacific Islanders
4. African american
5. Endocrinopathy (hypothyroidism, panhypopituitarism, growth hormone abnormalities, hypogonadism)
6. Radiation to the proximal femur
7. Renal osteodystrophy

Question 21

What is the average age of diagnosis for SCFE?

[J Am Acad Orthop Surg 2006;14:666-679]

Answer 21

1. 13.5 for boys
2. 12 for girls

Question 22

What classification systems are used to describe SCFE?

[J Am Acad Orthop Surg 2006;14:666-679]

Answer 22

1. Temporal classification

• Pre-slip
  
  • Symptoms, no radiographic evidence of slip (may have physis widening/irregularity)
• Acute slip
  
  • <3 weeks of symptoms
• Chronic slip
  
  • >3 weeks of symptoms
  • Most common type (85%)
• Acute-on-chronic slip
  2. Loder classification
• Stable – patient can walk and bear weight, with or without crutches
  
  • Nearly 0% incidence of osteonecrosis
• Unstable – patient unable to walk even with crutches
  
  • Up to 50% incidence of osteonecrosis
    
    • 10-60% (30%)

Question 23

How can you quantify the degree of slip in SCFE?

[J Am Acad Orthop Surg 2006;14:666-679]

Answer 23

1. Displacement in relation to the width of the metaphysis

• <33% = mild
• 33-50% = moderate
• >50% = severe

2. Southwick angle

• Epiphyseal-shaft angle is measured on the frog-leg lateral
• Degree of slip is calculated by subtracting the epiphyseal-shaft angle on the uninvolved side from that on the side with SCFE
  
  • <30 degree = mild
  • 30-50 degree = moderate
  • >50 degree = severe
• If both hips are involved 12° is considered normal

Question 24

What are the radiographic features of SCFE?

Answer 24

1. Widening and irregularity of the physis
2. Metaphyseal blanch sign of Steel
   * Radiographic double density created by the posteriorly displaced epiphysis overlapping the medial metaphysis
3. Kleins line – epiphysis is flush with or below the line (AP view)

Question 25

Describe the technique for single screw fixation in SCFE

[J Am Acad Orthop Surg 2006;14:666-679]

Answer 25

1. Patient placed supine on fracture table with involved extremity in traction
2. Triangulate with fluoro to confirm skin start point

• On AP and lateral use a wire placed on the skin so that it projects over the centre of the epiphysis and perpendicular to the physis
• Draw a line on the skin parallel to these lines, the point where they intersect a stab incision is made

3. Advance the guidewire free hand through the incision and fascia down to start point on the anterior femoral neck
4. Advance the wire with drill so that the wire is in the centre of the epiphysis and perpendicular to the physis on both the AP and lateral views
5. Measure the screw length with depth gauge
6. Ream over the wire
7. Advance a 7.3mm cannulated screw over the wire such that 4-5 threads engage the epiphysis and the tip is no closer than 5mm within subchondral bone
   * If <5 threads across physis, 41% progress >10°
   * If 5 threads across physis, no progression
8. Confirm screw does not penetrate joint with the “near-far” technique by taking hip from max internal to external rotation
   * Screw tip should move closer to subchondral bone (approach), then move away (withdraw)
   * True position of screw is found at moment approach changes to withdraw
9. Consider pinning contralateral hip based on risk factors

Question 26

Prophylactic pinning of the contralateral hip in a patient with unilateral SCFE should be done on an individual patient basis. What factors should be considered when deciding to prophylactically pin?

[J Bone Joint Surg Br 2012;94-B:596–602] [J Bone Joint Surg Am. 2013;95:146-50]

Answer 26

1. Obesity
2. Endocrinopathy (hypothyroidism, GH treatment, etc.)
3. Young age of first SCFE (<9y)
   * Skeletally immature/open triradiate cartilage
4. Children with adiposogenital dystrophy (low GnRH, hypogonadism, increased caloric intake/obesity)
5. Unable to comply with close clinical and radiologic observation due to geographic or social reasons
6. High posterior sloping angle (>14°)

Question 27

What is the resulting deformity of the proximal femur after in situ pinning?

[JAAOS 2011;19:667-677]

Answer 27

1. Sagittal plane = posterior displacement of epiphysis on metaphysis
2. Coronal plane = displacement of epiphysis into varus
3. Axial plane = external rotation of the femur on the epiphysis

Question 28

What is the management of resulting FAI after SCFE in the adult?

[JAAOS 2011;19:667-677]

Answer 28

1. Slip angle <15 (southwick angle)
   * Arthroscopic femoral neck osteochondroplasty
2. Slip angle 15-30
   * Limited open anterior arthrotomy and femoral neck osteochondroplasty
3. Slip angle 30-45
   * Surgical hip dislocation and femoral neck osteochondroplasty
4. Slip angle >30

• Flexion intertrochanteric osteotomy
  
  • Achieves flexion, valgus and IR
  • Modified Imhauser technique
    • Lateral approach to the proximal femur
    • Chisel for blade plate is inserted into the femoral neck at the appropriate flexion angle
    • Transverse osteotomy is made just proximal to the LT
    • Blade plate is inserted and stabilized with a screw in the proximal fragment
    • The distal fragment is internally rotated the desired amount and flexed to reduce to the plate
      5. Slip angle >60
• Combined flexion intertrochanteric osteotomy and surgical hip dislocation (possibly staged)

Question 29

What is the epidemiology of LCP?

[JAAOS 2010;18:676-686]

Answer 29

1. Age = 5-8
2. Males (5:1)
3. Bilateral 10-15%
4. Delayed bone age compared to chronological age

Question 30

What are the risk factors for LCP?

Answer 30

• Males
• Family history
• Delayed bone age
• Low birth weight
• Second hand smoke
• Low socioeconomic status

Question 31

What is the differential diagnosis of LCP?

Answer 31

1. Other causes of AVN

• Sickle cell disease
• Other hemoglobinopathies (eg. thalassaemia)
• Chronic myelogenous leukemia
• Steroids
• Traumatic hip dislocation
• Treatment of DDH
• Septic arthritis

2. Epiphyseal dysplasias
   * MED, SED, mucopolysaccharidoses, hypothyroidism
3. Other syndromes
   * Osteochondromoatosis, metachondromatosis, Schwartz-Jampel syndrome, others

Question 32

What is the radiographic classification of LCP based on stages of progression?

[JAAOS 2010;18:676-686]

Answer 32

Waldenstrom

• Initial
• Fragmentation
• Reossification
• Healed (residual)

Question 33

What is the classification system that describes shape of the femoral head and joint congruity at skeletal maturity in LCP?

[JAAOS 2010;18:676-686]

Answer 33

1. Stulberg

• Class I - Normal hip joint
  
  • Good outcomes
• Class II - Spherical head with enlargement, short neck or steep acetabulum
  
  • Good outcomes
• Class III - Nonspherical head (ovoid, mushroom-shaped, umbrella-shaped)
  
  • Poor outcomes, FAI and instability
• Class IV - Flat head, flat acetabulum
  
  • Poor outcomes, very early OA/FAI
• Class V - Flat head with incongruent hip joint
  
  • Poor outcomes, very early OA/FAI

2. Three types of congruency are described:

• Spherical congruency (classes I and II)
• Aspherical congruency (classes III and IV)
• Aspherical incongruency (class V)

3. Note: increasing class # correlates with onset of osteoarthritis

Question 34

What is the Catterall classification of LCP?

[AAOS comprehensive review, 2014]

Answer 34

Based on the extent of head involvement during fragmentation stage

• Group I - anterior head involvement (25%)
• Group II - anterior and central head involvement (50%)
• Group III - only a small part of the epiphysis is not involved (usually posteromedial) (75%)
• Group IV - total head involvement (100%)

Note: poor interobserver reliability

Question 35

What are the Catterall head at risk signs?

[JAAOS 2010;18:676-686]

Answer 35

1. Lateral subluxation
2. Lateral calcification
3. Diffuse metaphyseal reaction (i.e. metaphyseal cysts)
4. Horizontal growth plate
5. Gage sign
   * V-shaped radiolucency in the lateral portion of the epiphysis and/or adjacent metaphysis

NOTE – indicate a more severe disease course

Question 36

What is the lateral pillar (Herring) classification of LCP?

[JAAOS 2010;18:676-686]

Answer 36

Based on the height of the lateral 15-30% of the femoral epiphysis (aka. Lateral pillar) during fragmentation phase

• Group A - no loss of height
• Group B - <50% loss of height
• B/C Border
  
  • B/C 1 - lateral pillar is narrow (2-3mm wide)
  • B/C 2 - poorly ossified
  • B/C 3 - exactly 50% height loss without central depression
• Group C - >50% loss of height

Note: better interobserver reliability compared to Catterall and is prognostic

Question 37

What is the Salter-Thompson classification of LCP?

Answer 37

Based on radiographic crescent sign in fragmentation stage

• Class A – crescent involves <1/2 femoral head involved
• Class B – crescent involves >1/2 femoral head involved

Note: Allows for early classificaiton

Question 38

What are the prognostic indicators of outcome in patients with LCP disease?

[JAAOS 2010;18:676-686] )

Answer 38

1. Extent of femoral head deformity and loss of hip joint congruity at maturity (Stulberg classification)
2. Age at onset
   * >8y do worse, <6y do best
3. Extent of subchondral fracture (Salter-Thompson classification)
4. Extent of head involvement at the fragmentation stage (Catterall classification)
5. Two or more Catterall head-at-risk signs (lateral subluxation, lateral calcification, diffuse metaphyseal reaction, horizontal growth plate, Gage sign)
6. Lateral pillar height at the fragmentation stage (lateral pillar classification)
7. Premature physeal closure

Question 39

What is extrusion of the femoral head in LCP?

[JAAOS 2018;26:526-536]

Answer 39

1. Lateral extrusion of the femoral head results from synovitis and articular hypertrophy
2. Results in abnormal contact with acetabular rim and predisposes to femoral head deformation
3. Defined as the percentage of the femoral ossific nucleus that lies outside the bony acetabulum (extrusion = A/Bx100)

Question 40

What imaging can be done to assess for hinge abduction in context of LCP?

[JAAOS 2018;26:526-536]

Answer 40

1. Dynamic hip arthrogram

• What 3 findings on hip arthrogram indicate hip abduction as determined from hip adduction to abduction?
  
  • The extruded lateral portion of the head contacts the acetabulum and does not move under the lateral acetabulum with further abduction
  • The center of rotation moves from the epiphysis (or center physis) to the lateral acetabulum
  • The medial dye pool increases in size
    
    2. Alternative – dynamic radiography
• Defined as widening of the medial joint space >2mm and decreased superolateral joint space with hip abduction

Question 41

What are the goals of treatment in LCP?

Answer 41

Containment of the femoral head in the acetabulum with the aim to achieve a spherical femoral head and congruent joint ultimately to minimize risk of OA

Question 42

What is the recommended treatment of LCP based on patients age and severity of femoral head involvement (defined by lateral pillar classification)?

[JAAOS 2010;18:676-686]

Answer 42

1. Age <6

• Nonsurgical
• Activity modification and PT
• Abduction bracing/casting (i.e. Petrie cast)

2. Age 6-8

• Evidence is not clear
• Primary treatment is non-surgical
  • ROM and XR check q3 months in fragmentation stage
• If hip abduction <30°or lateral subluxation on XR:
  
  • Do arthrogram for hinge abduction
    
    • If concentric motion:
      
      • ​Brace/tenotomy to maintain motion
      • If losing motion, do VDRO
    • If hinge abduction:
      
      • Do shelf acetabuloplasty

3. Age 8-11
   * Primary treatment is surgical containment

• Treat early (before significant femoral head deformity)
  
  • Lateral Pillar B and B/C have greatest benefit
• VDRO
• Pelvic osteotomy
  
  • Salter/triple/shelf
• Can do staged if irritable hip
  
  • Adductor tenotomy/casting x 6 weeks, then VDRO

4. Age > 11
   * Poor prognosis
   * Effectiveness of surgery unclear

Question 43

What nonsurgical options are available for LCP?

[JAAOS 2010;18:676-686]

Answer 43

1. Nonoperative containment

• Petrie casting
• A-frame brace (abduction orthosis)
• NOTE: rarely used now given results of operative containment [Lovell and Winter]

2. Protected WB
3. Physiotherapy

Question 44

What salvage options are available for a LCP hip that is not containable or a hip with hinge abduction?

Answer 44

1. Chiari or shelf acetabuloplasty
2. Valgus femoral osteotomy

Question 45

What are the general classes of pelvic osteotomies?

[JAAOS 2016;24:615-624]

Answer 45

1. Redirectional (volume stable)

• Salter
  
  • Cuts both columns (requires internal fixation)
  • Improves anterior and lateral coverage
  • Rotates through pubic symphysis
  • Correction = 15° of lateral coverage, 25° of anterior coverage
• Triple
  
  • Same as Salter but adds superior and inferior pubic rami osteotomies
  • No hinge, acetabulum free to rotate
• Ganz (PAO)
  
  • Posterior column intact

2. Reshaping (volume reducing)

• Dega
  
  • No internal fixation required
  • Improves lateral coverage
  • Rotates through the triradiate cartilage
• Pemberton
  
  • No internal fixation required
  • Improves anterior coverage
  • Rotates through the triradiate

3. Salvage

• Shelf
• Chiari
  
  • Medial displacement osteotomy
  • Hinges on the pubic symphysis

Question 46

What are the genetic mutations associated with MED?

[J Am Acad Orthop Surg 2015;23:164-172]

Answer 46

1.75% are autosomal dominant mutations in:

• 66% COMP (collagen oligomeric matrix protein)
• 24% matrillin-3 (MATN3)
• 10% collagen IX (COL9A)

Question 47

What are the clinical features of MED?

[J Am Acad Orthop Surg 2015;23:164-172]

Answer 47

1. Childhood presentation
2. Early fatigue with walking/playing
3. Limited motion
4. Limp
5. Periarticular hip, knee, shoulder pain
6. Contractures hip, knee, shoulder
7. Brachydactyly
8. Mild short stature, normal trunk height

Question 48

What are the radiographic features of MED?

[J Am Acad Orthop Surg 2015;23:164-172]

Answer 48

1. Bilateral symmetric involvement
2. Hip

• Loss of height, irregular, underdeveloped femoral epiphysis
• Short, wide, varus femoral neck
• Acetabular irregularities

3. Knee

• Genu valgum
• Double layered patella (anterior/posterior) - pathognomonic

4. Hands
   * a. Brachydactyly
5. Spine
   * Endplate irregularities or Schmorl nodes

Question 49

When MED is suspected what radiograph(s) need to be ordered?

[J Am Acad Orthop Surg 2015;23:164-172]

Answer 49

Skeletal survey

Question 50

What is the importance of genetic testing in MED?

Answer 50

1. Accurate diagnosis

2 .Family planning (educate on pattern of inheritance and chance offspring will be affected)

Note – should be offered to all patients

Question 51

What is the differential diagnosis for MED?

[J Am Acad Orthop Surg 2015;23:164-172]

Answer 51

1. LCP

• MED is bilateral, symmetric – LCP is rarely bilateral (13%)
• MED can involve joints other than the hips (importance of skeletal survey)
• MED is usually associated with acetabular changes – initially acetabulum are normal in LCP
• MED does not have metaphyseal cysts

2. Spondyloephiphyseal dysplasia

• SED has vertebral body abnormalities and significant scoliosis – MED has minimal or no spine involvement
• Mutation in COL2A1
• Spine manifestations [Orthobullets]
  
  • Atlantoaxial instability, odontoid hypoplasia or os odontodium, kyphoscoliosis, increased lumbar lordosis, platyspondyly (flattened VB)

3. Congenital hypothyroidism
4. Mucopolysaccharidoses
5. Pseudoachondroplasia
6. Diastrophic dysplasia