blount’s disease

definition

· localised varus deformity due to disordered growth of the proximal medial tibial epiphysis

· 2 forms

· infantile form (onset age 1 to 3.5 yrs)

· adolescent form (onset after age 6 yrs)

Infantile tibia vara

epidemiology

· rare

· unusual in Australia

· more common in blacks and Scandinavians

· increased incidence if

· female

· early walking

· obese

· affected family

aetiology

· unknown

Constitutional factors

· no consistent inheritance pattern

Disturbed biomechanics

· most likely due to abnormal compression on medial side of proximal tibial physis

· causes retardation of growth

pathology

· disordered endochondral ossification

· dense islands of hypertrophied chondrocytes

· acellular areas of dense fibrocartilage in resting zone

· abnormal groups of capillaries

clinical

Presentation

· usually presents at age 14-36 mths

· bowing noticed after commence walking

Findings

· genu varum

· internal tibial torsion

· usually bilateral and symmetrical

radiology

· localised deformity at proximal tibia

· metaphyseal-diaphyseal angle

· line drawn perpendicular to axis of tibia and line drawn through medial and lateral beaks of metaphysis

· angle between them usually > 11^o

· medial metaphyseal lesion

· medial physeal slope

· line through medial physis and line through lateral physis

· significant if > 60^o

· tomograms help define physeal bar

Assessment of genu varum

· milestones

· height and weight percentiles

· knee ROM

· measurement of genu varum and tibial torsion

· ligamentous laxity

· radiographs if

· severe genu varum

· deformity rapidly worsening

· height < 25th %ile

· marked asymmetry

classification

· radiological classification by Lagenskiold

Stage I

· irreguar metaphyseal ossification

· medial metaphyseal beaking

Stage II

· cartilage filled depression in metaphyseal beak

· medial epiphyseal wedging

Stage III

· ossification in infero-medial corner of epiphysis

Stage IV

· epiphyseal ossification extends to fill metaphyseal depression

Stage V

· so called "double epiphyseal plate"

· radiological appearance of severe postero-medial depression

Stage VI

· medial physeal closure

differential diagnosis

· physiological varus

· symmetrical involvement

· normal growth plate

· medial bowing of proximal tibia and distal femur

· metaphyseal-diaphyseal angle < 11^o

· hypophosphataemic rickets

· short stature

· widened physes

· low serum phosphorus

· dysplasias

· metaphyseal chondrodysplasia

· focal fibrocartilagenous dysplasia

natural history

· progresses to severe degenerative joint disease by early adulthood

treatment

· depends on

· age of child

· stage of disease

Nonoperative

· indications

· age < 3 yrs

· in form of KAFO

· single medial upright

· free ankle

· no knee hing

· cuff around knee to pull knee into valgus

· aim at full-time bracing

· successful > 50%

Operative

Indications

· age > 3 yrs

· failure of bracing

Osteotomy

· technique

· performed distal to tibial tubercle

· osteotomy of fibula performed

· osteotomy of tibia performed

· desired valgus and external rotation achieved

· held with wires or screws

· plaster

· type of osteotomy varies

· closing wedge

· opening/closing wedge

· dome

· oblique rotation

· aim for an overcorrection of 10^o

Other procedures

· progression after osteotomy more likely if

· massive obesity

· Langenskiold III +

· medial physeal slope > 60^o

· age > 5 yrs

· should add supplementary procedures

Physeal bridge resection

· excise bar where

· tomograms demonstrates a bridge

· bridge < 50^o of width of physis

· insert fat in defect

Lateral hemiepiphyseodesis

· where riks factors present but no physeal bar

Complications

· comparment syndrome

· recurrence of varus

· leg length discrepancy

Adolescent tibia vara

epidemiology

· 3-5 times less common than infantile variety

· males more commonly affected

· more common in blacks

aetiology

· some consider it due to trauma or infection

· others consider it similar to infantile variety

pathology

· similar to the infantile type

clinical

· pain and tenderness over medial aspect of knee

· usually unilateral

radiology

· middle portion of medial physis is narrowed and remainder widened

· sclerosis on either side of the isthmus

· beaking not seen

· wedging only mild or moderate

treatment

High tibial osteotomy

· indications

· mild deformity

· nonprogressive deformity

· older patient

· no physeal bridgin

· surgery delayed until after skeletal maturity

Physeal bridge resection

· recommended if patient has significant remaining growth