Tibialis posterior tendon rupture

epidemiology

· common in women > 40

· may be associated with

· recurrent trauma

· rheumatoid arthritis

pathophysiology

Function

· PT inverts hindfoot

· locks midtarsal joints

· allows triceps surae to act at MT heads for plantar flexion

· with loss of PT, triceps surae acts across TN jt

· leads to giving way of longitudinal arch

Tendon changes

· starts with varying combination of

1. peritendinitis

· synovial fluid in sheath

· synovial proliferation

2. tendon degeneration

· tendon enlarged

· longitudinal splits develop

· becomes yellowish

· next stage is elongation of tendon

· finally rupture occurs

Deformity

· loss of function of TP leads to aquired flat foot

· initial deformity is collapse of medial longitudinal arch

clinical stages

Tests

Single heel raise

· face wall and use hands for balance

· ask patient to rise up on ball of good foot

· then on bad foot

· normal sequence is

· TP inverts and locks midfoot

· triceps surae pulls up calcaneus

· abnormal sequence

· if moderate, lack of inversion and incomplete heel raise

· if severe, unable to heel raise

Too many toes sign

· observation from behind

· both legs in same posture

· more toes seen laterally on affected foot

· due to hindfoot eversion and resultant forefoot abduction

Stage 1

· tendon length normal

Symptoms

· aching along medial aspect of foot

· exacerbated by physical activity

Signs

· swelling along tendon

· fullness inferior to medial malleolus

· tenderness along tendon

· from medial malleolus to navicular

· manual testing of PT power is normal

· single heel raise usually causes pain but otherwise normal

X-rays

· normal

Stage 2

· tendon elongated

· hindfoot everts and forefoot abducts

· hindfoot mobile

Symptoms

· pain more severe and continuous

· interferes with activities

Signs

· swelling and tenderness over tendon

· decreased medial arch

· positive too many toes sign

· single heel raise

· incomplete or impossible

X-rays

· AP

· abducted forefoot

· navicular subluxed laterally

· long axis between talus and calcaneus increased

· lateral

· sagging at TN joint

· divergence of long axis of talus and calcaneus

Stage 3

· tendon disrupted

· hindfoot deformed and stiff

Symptoms

· tendon less painful

· pain over sinus tarsi

· from impingement of talus

Signs

· significant deformity

· hindfoot in valgus

· forefoot abducted

· pes planus

· positive too many toes sign

· single heel raise

· loss of heel inversion

X-ray

· more marked changes

· degenerative changes in subtalar and midtarsal joints

· sclerosis in midsuperior talus from impingement

treatment

Stage 1

Nonoperative

· NSAIDs

· arch supports

Operative

· decompression of PT tendon

· tendon sheath opened from musculotendinous junction to insertion

· 1 cm pulley left just posterior to medial malleolus

· synovectomy and debridement

· tendon debulked if very large

· short leg cast for 3 weeks

Stage 2

· transfer of FDL to substitute for PT

· FDL detached distally

· reinserted into underside of navicular through drillhole

· should be pulled tight with ankle in equinus and forefoot in varus

· no need to attach proximal PT to FDL

· no functional loss in toe from loss of FDL

Stage 3

· arthrodesis of subtalar joint

· morsellised bone graft from ASIS inserted into subtalar joint

· joint fixed with Steinmann pin