Children`s Orthopaedics

Osteonecrosis of femoral head in growing child
Unknown etiology
Males more common (4:1)
Age between 4 - 7 years old
Bilateral in 10 % of cases
Variable outcome
Higher risk in

• Caucasian
• Positive family history
• Coagulopathy / Thrombopilia

Blood supply to femoral head

Birth to 4 years old
Mainly from transepiphyseal artery crossing the physis especially early phase of this age group.
Supply from retinacular artery which starts to develop later

4 - 7 years old
Solely from retinacular artery via posterior ascending branch of medial circumflex femoral artery.
Other name for retinacular artery are capsular and lateral epiphyseal arteries
Transepiphyseal artery fades away and no longer penetrates the physis to supply femoral epiphysis
Artery from ligamentous teres just starts to develop at end of this age group
Insult during this age group has been postulated as theory for disturbance of blood supply to femoral head ( retinacular artery ) leading to AVN. But the real pathogenesis is still unknown.

More than 7 years old
Artery from ligamentous teres
Retinacular artery

Adolescent
Retinacular artery
Metaphyseal artery from metaphysis to epiphysis since growth plate already fused
Ligamentum teres artery

History

Limp

• Can be painless or mildly painful limp

Pain

• Activity related
• From hip or referred pain from knee / thigh
• Rare as acute painful onset
• Trivial injury / trauma

Examination

Limp
Limited hip motion - abduction, internal rotation and extension
Hip goes into abduction in passive flexion of the hip
Lesser extent of limb length discrepency if any
Muscle atrophy if any

Clinical “at risk” sign

• Female
• Older age
• Obesity
• Bilateral
• Stiffness

Imaging Classification

Radiographic Stages ( Waldenstorm`s )

Severity - During fragmentation phase

• Catterall
• Salter-Thompson
• Herring lateral pillar

Outcome

• Mose
• Stulberg

Imaging classification addressing stages

Radiographic Stages ( Waldenstorm`s )

Initial ( Sclerotic )

• 6-12 months
• Pathology - ischaemia / necrosis
• Widening joint space due to cartilage keeps growing ( nutrient from synovial fluid ) whereas subchondral bone necrosis ( subchondral sclerosis )

Fragmentation

• 12-24 months
• Pathology - revascularization
• Radiolucency & radiodensity ( mottling )
• Lucency due to revascularization, bone resorbsion and osteoclast activity removing the necrotic bone which earlier looks radiodense
• Critical phase
• Soft head, need to keep within acetabulum for natural moulding in order to maintain its sphericity. If uncontained the soft head will be extruded, collapse and loss its sphericity leading to early OA of head and acetabulum

Reossification(6-24 months) / healed(24-48 months) / remodelling(skeletal maturity)

• Head becomes hard
• Residual deformity of head according to the shape at end of fragmentation phase
• Normal density returns
• New bone is formed
• Overgrowth often produces coxa magna ( unpreventable )

Waldenstorm`s sign
A linear fracture is visible in the subchondral region of the femoral head, usually best seen in the frog lateral view

Imaging classification addressing severity

Catterall ( based on extent of head involvement at fragmentation phase)

Catterall I

• 0 - 25 % head involvement
• Involvement - anterior epiphysis
• (therefore seen only on the frog lateral film)

Catterall II

• 25 - 50 % head involvement
• Anterior & central segment - fragmentation ( sequestrum )
• Lateral part / rim is intact ( protects the central involved area )
• Junction - clear
• Metaphyseal reaction present - anterior
• Subchondral fracture - anterior

Catterall III

• 50 - 75 % head involvement
• Anterior segment involved. Lateral head - also fragmented
• Only the medial portion is spared.
• Loss of lateral part / support worsens the prognosis
• Junction - sclerotic
• Metaphyseal reaction present - anterior & lateral

Catterall IV

• > 75 % head involvement. The entire head is involved

In Catterall, its prognostic value is limited in early stages

Radiographic Catterall`s “head at risk of collapse” sign

• Gage`s sign ( V shape lucency at lateral epiphysis )
• Horizontal growth plate - implies a growth arrest phenomenon and deformity
• Lateral calcification ( lateral to the epiphysis - implies loss of lateral support )
• Lateral subluxation - implies loss of lateral support
• Metaphyseal rarefaction

Salter and Thompson

Salter and Thompson recognized that Catterall’s first two groups and second two groups were distinct and therefore proposed a two part classification.

Salter & Thompson Group A: Less than 1/2 head involved.
Salter & Thompson Group B: More than 1/2 head involved.

Again the main difference between these two groups is the integrity of the lateral pillar.

(Herring) Lateral Pillar

Based specifically on the integrity of the lateral pillar. Determined from AP film only, at the beginning of the fragmentation phase.

Group A

• Normal height of the lateral 1/3 of the head is maintained
• Fragmentation occurs in the central segment of the head.

Group B

• More than 50% of the original lateral pillar height is maintained
• There may be some lateral extrusion of the head.

Group C

• Less than 50% of the original lateral pillar height is maintained
• The lateral pillar is lower than the central segment early on

Imaging classification addressing outcome

Mose Classification

Using concentric circle technique
Compare and classify the final outcome in Perthes at the end of growth
The final shape of the head may be compared to a perfect circle using the Mose template and both AP and lateral images.

Good outcome

• Aspherical head contour is within 1 mm of a given circle on both views

Fair outcome

• Aspherical head contour is 1 - 2 mm

Poor outcome

• Aspherical head contour is > 2 mm

Given that a congruous but aspherical head can perform well suggests that the Mose criteria are too strict and impractical.

Stulberg Classification

Management

1. Symptomatic treatment.
2. Non operative “containment” of the head within the acetabulum.
3. Surgical containment” procedures.

Symptomatic treatments

Pain - occurs at initial fragmentation phase
Joint stiffness ( reduced range of motion ) due to synovitis
Muscle spasm

Rest
NSAID reduces synovitis
Gentle traction

• relieves muscle spasm and pain
• help to return a reasonable abduction range.

Short term crutch use is indicated
Prolonged non weight bearing in bed or on crutches is no longer supported.

Nonoperative containment

• Encourages spherical remodelling during the reossification and subsequent phases
• Abduction encourages the head to travel beneath the lateral acetabular rim.
• Abduction is restricted in hips with moderate to severe disease and therefore abduction traction and adductor tenotomy may regain some movement.
• A Petri abduction cast may be placed under general anaesthesia and will hold the position. It allows ambulation and thus maintains motion in the hip.
• Bracing is continued until new bone formation is seen ( reossification phase).

Surgical containment

Femoral subtrochanteric varus osteotomy

• Encourage the head to sit deeper in the acetabulum.
• It should optimally be done before the reossification phase when “biological plasticity” is greater.
• Extension and derotation may be added.
• Trendelenberg gait may worsen following varus osteotomy.

A pelvic osteotomy,

• Such as that of Salter
• Increases antero lateral coverage of the head.
• The hip should have a good range of motion before the procedure and have minimal deformity.
• After age 6 years.
• Adductor and iliopsoas releases are necessary.
• Stiffness following early Salter’s osteotomy .
• Shelf osteotomies have been used in the past. Salvage procedure in subluxated head in older age. Head has potential to reform sphericity following shelf osteotomy even after fragmentation phase.
• Cheilectomy , or excision of the extruded lateral head segment has a poor reputation.

Valgus femoral osteotomy

Performed in a flattened head with hinge abduction if the hip is congruous in adduction.

Greater trochanteric overgrowth be addressed in Perthes

The trochanteric overgrowth can be dramatic
Trendelenberg gait does not always occur. If it does occur, and is significant, then trochanteric advancement may improve the gait.
An alternative is to perform a trochanteric arrest at an earlier date

Who is to be treated and what are the treatment options in Perthes disease

< 6 years old

• Prognosis is good for the majority.
• Bed rest, traction, pain relieving anti-inflammatory medication and rest.
• No evidence that abduction splints or surgical intervention is warranted in the majority of these younger patients.

6 - 8 years and Herring lateral pillar classification B

• Containment  of the head within the acetabulum seems to be warranted.
• This may be done by abduction bracing, femoral varus osteotomy or a pelvic osteotomy.

6 and 8 and are in lateral pillar group C

• The result of intervention are equivocal.
• Children presenting with Perthes disease at age 9 or older often have lateral pillar B or C and a poor prognosis.
• The trend is towards early containment of these hips although stiffness can be a problem following early pelvic (Salter’s) osteotomy.

This entry was posted on Saturday, December 22nd, 2007 at 1:53 pm and is filed under Perthes. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.