Background

 

 

Definition

 

Avascular necrosis of the immature femoral capital epiphysis 

- self limiting 

- goes through defined stages over 2-5 years

- can cause femoral head deformity and lead to osteoarthritis

 

 

Epidemiology

 

1/10,000 in Caucasians

- age 4 - 8 

- male 4 x females

 

Bilateral - between 8 - 24%

 

Etiology

 

Lateral epiphyseal artery occlusion

 

Theories of cause

Genetic	Vascular	Coagulation disorder	Environmental
Unclear if this is true in twin studies   Likely enviromental	Increased intra-articular pressure   Increased intra-osseous pressure	Factor C / S deficiencies	Lower socioeconomic   Short stature / low birth weight   Malnutrition   Parental smoking smoking

 

Transient synovitis

 

Xinling et al J Orthop Surg Res 2024

- systematic review of prevalence of Perthes in transient synovitis

- overall prevalence Perthes 3%

- recurrent transient synovitis: prevalence Perthes 36%

 

Pathology

 

Physis

- loses height

- increases width

- focal lateral collapse under acetabular margin

 

Coxa magna and partial subluxed head

 

Coxa breva 

- physeal growth arrest

- prominent greater trochanter

 

Classification

 

Waldenstrom - natural history / chronological

Herring / Catterall - prognosis / treatment based upon extent of head involvement 

Stuhlberg - long term outcome based upon residual femoral head deformity

 

Waldenstrom classification

 

Stage I	Stage II	Stage III	Stage IV
Necrosis	Fragmentation	Reossification	Remodelling
Dense flattened epiphysis	Resorption of necrotic bone	New bone formation	Head larger / neck shorter
6 - 12 months	12 months	2 - 3 years	Until skeletal maturity

 

Herring lateral pillar classification

 

AP xray when disease in fragmentation

- divide femoral head into 3 pillars

- lateral (25%) / medial (25%) / central (50%)

- classification based upon lateral pillar involvement

- lateral pillar involvement leads to subluxation and deformity 

- added group B/C: 50% involvement

 

Group A	Group B	Group C
No lateral pillar involvement	> 50% lateral pillar intact	< 50% lateral pillar intact

 

Catterall classification

 

Based upon extent of involvement of femoral head

- Grade I:    < 25%

- Grade II:   < 50%

- Grade III:  < 75%

- Grade IV:   Entire femoral head

 

Stuhlberg classification

 

Estimate long term prognosis of the hip based upon final joint morphology

- increasing deformity

- increasing risk of developing early osteoarthritis

- modified into 3 groups

 

Group A	Group B	Group C
Class I / II	Class III	Class III/IV
Round femoral head	Ovoid femoral head	Flat femoral head
Low risk OA	Moderate risk OA	High risk OA

 

Larson et al JBJS Am 2012

- 58 hips followed for 20 years

- incidence OA: spherical hips 22%, ovoid hips 61%, flat hips 62% 

 

Huhnstock et al BJJ 2021

- 88 hips followed for 21 years

- incidence OA: spherical hips 3%, ovoid hips 15%, flat hips 54% 

 

Prognosis

 

Poor prognostic factors

- age > 8 at age of diagnosis

- females do worse / less time for femoral head remodel

- lateral pillar collapse / Herring C

- extent of head involvement / Catterall

- lateral extrusion of femoral head

- poor range of motion

 

Herring et al JBJS Am 2004

- 345 Perthes hips

- worse outcomes age onset > 8 / females / Herring group C

 

Clinical

 

Hip / knee pain

Short stature

Antalgic / Trendelenberg gait

Decreased ROM

 

Xray

 

Lateral pillar involvement guides management

 

No lateral pillar involvement versus significant lateral pillar involvement

 

Containment - if the head is not contained within acetabulum, guides management

 

Contained versus uncontained hip

 

 Hinge abduction

 

Abducted hip does not obtain full coverage of femoral cartilage / full containment

- hinging on portion of femoral head

- varising femoral osteotomy will worsen symptoms

 

 

Intra-operative arthrogram

 

Findings 

- hinge abduction / rose thorn appearance

- medial pooling

 

Hinge abduction with rose thorn appearance

 

Hinge abduction with rose thorn appearance

 

MRI

 

Uses

- early diagnosis of Perthes / MRA

- assess containment / amount of cartilaginous head outside of acetabulum

 

Central Perthes on MRI

 

Early presentation of Perthes with contained hip

 

Uncontained left hip with Perthes

 

 CT

 

 

Differential diagnosis

 

AVN

MED / SED

Hypothyroidism

 

Multiple epithelial dysplasia

- bilateral and symmetrical

- acetabular involvement

- no metaphyseal cysts

- other joint involvement

- consider skeletal survey in those with bilateral "perthes"

 

Multiple epithelial dysplasia with bilateral symmetrical involvement of both hips