Pes planus

Flexible flat foot

definition

· no good definition

· medial longitudinal arch of foot in weight-bearing is in contact with ground or closer to ground than ‘normal’

epidemiology

· common condition

· almost always bilateral

· strong familial and racial tendency

aetiology

Physiological

· at birth, foot is in calcaneovalgus and there is no medial arch

· when child begins to walk, feet everted and externally rotated

· foot has large medial fat pat

· arch begins to develop in 2nd and 3rd year to variable degree

· thus flatfeet are

· usual in infants

· common in children

· within normal range for adults

Compensatory

· due to another anatomical variation

Genu valgum

· physiological knock-knees most pronounced at age 3-4

· leads to apparent flatfoot

Out-toeing

· external rotation of foot causes body weight to fall anteromedial to ankle

· result is valgus of heel and flatfoot

Tight tendo Achilles

· lack of dorsiflexion compensated by external rotation and pronation of forefoot and eversion of heel

Joint laxity

· seen in idiopathic joint hypermobility

· also seen with conditions associated with hypermobility

· Marfan’s syndrome

· Ehlers-Danlos syndrome

clinical features

History

· almost always asymptomatic

· may cause aching midfoot (foot strain)

· incidence of pain may be no more than in general population

Examination

· on weightbearing, combination of

· flattening of longitudinal arch

· pronation of forefoot

· valgus of heel

· flexible flatfoot confirmed by

· foot appears normal when suspended

· recreation of longitudinal arch and correction of heel valgus to varus on standing on toes

· recreation of longitudinal arch by passive dorsiflexion of hallux (Jack’s test)

· mobile or hypermobile subtalar joint

· weightbearing callus on lateral longitudinal arch

differential diagnosis

Painful flatfoot

· osteochondral fracture of subtalar joint

· inflammatory subtalar arthritis

· tibialis posterior tendinitis

Stiff flatfoot

· congenital vertical talus

· tarsal coalition

Neurological flatfoot

· esp. cerebral palsy

· contracture of Achilles tendon

Accessory navicular

· flatfoot from secondary tibialis posterior dysfunction

treatment

· usually resolves by age 5 or 6

· 15-20% of adults have some degree of asymptomatic flexible flatfoot

· no treatment needed unless symptomatic

· orthoses and shoe modifications have no effect on outcome

Symptomatic

Nonoperative

· most surgeons disagree with treatment as does not affect natural history

· may try insoles to

· relieve pain

· allay parental anxiety

· improve life of footwear

· in form of custom moulded insole

Operative

· indication

· disabling pain not responsive to nonoperative measures

· in form of

· medial displacement sliding calcaneal osteotomy

· limited subtalar or triple arthrodesis