Background

 

 

Definition

 

Progressive collapsing foot deformity

 

Acquired flat foot deformity / planovalgus foot secondary to tibialis posterior dysfunction

 

Epidemiology

 

F > 40

 

Associations - hypertension / diabetes / obesity 

 

Anatomy Tibialis Posterior

 

Origin	Insertion	Nerve supply	Action
Posterior tibia, fibula and inter-osseous membrane   Acute angle around medial malleolus - flexor retinaculum holds tendon in groove  - relative hypo-vascular zone 1-2cm distal to medial malleolus	Navicular tuberosity Plantar cuneiforms 2,3,4 metatarsals Sustentaculum tali	Tibial nerve (L4/5, S1)	Plantar flexor ankle joint Inverts subtalar joint Adducts foot Maintains longitudinal arch   Single heel raise - locks the midtarsal joints - allows T Achilles to perform heel raise

 

Pathology

 

Avascular zone 

- behind medial malleolus

- area of incomplete mesotenon which provides blood supply

 

Tendon changes

- paratendinitis - fluid in sheath + synovial proliferation

- tendinosis - tendon degeneration with enlargement and longitudinal splits

- elongation of tendon

- rupture

 

 

Deformity

 

Acquired planovalgus

- medial arch collapse

- subtalar joint everts / valgus heel

- foot abducts at TNJ

- Achilles tendon acts as evertor when heel in valgus

- calcaneus impinges on fibular causing lateral ankle joint pain

- attenuation of TNJ capsule, spring ligament and deltoid ligament

 

Johnson Classification

Stage 1	Stage 2	Stage 3	Stage 4
T posterior tendonitis	T posterior elongation / attenuation / rupture	Fixed deformity subtalar joint	Varus angulation talus in ankle joint
Able to single heel raise	Unable to single heel raise Correctable subtalar joint	Non correctable valgus
	IIA: As above IIB: Forefoot abduction	+/- subtalar OA	+/- ankle joint OA

 

History

 

Deformity

Medial pain

Lateral pain due to fibular impingement

Difficulty with shoe wear

 

Examination

 

 

Stage 1 

- normal arch with tenderness tibialis posterior tendon

 

Stage 2

- planovalgus foot - flattened medial arch + valgus heel

- flexible subtalar joint - good ROM, moves into varus with heel raise

- weak tibialis posterior power - foot inverted and in equinus

 

 

X-ray

 

Lateral weight bearing

 

Early - reduced talo-metatarsal angle / Meary's angle

Late - subtalar joint OA

 

AP weight bearing foot

 

Talonavicular uncovering > 40% - forefoot abduction / stage IIB

 

AP weight bearing of ankle

 

Early - calcaneus under lateral malleolus

Late - valgus tilt of talus with ankle joint osteoarthritis

 

MRI 

 

Tendonitis - fluid around tendon

Tendinopathy - tendon thickening

Tears

 

Tibialis posterior tendonitis

 

Tibialis posterior tendinopathy

 

Tear tibialis posterior with 10 cm gap