osteochondral lesions of talar dome

definition

· fracture of talar bone through articular cartilage into subchondral bone

· due to force transmitted from distal tibia

· osteochondritis dessicans is chronic, nonunion stage of osteochondral lesion

epidemiology

· account for 1% of talar fractures

· OCD of talus accounts for 4% of all OCD

· occur in 6.5 per 100 ankle sprains

· average age is 25 yrs

· male predominance

· usually located

· anterolateral

· posteromedial

aetiology

· due to inversion injuries

· lateral fractures with dorsiflexed ankle

· medial fractures wih plantarflexed ankle

· stage 2 lesion associated with

· lateral ligament injury in lateral fractures

· deltoid ligament injury in medial fractures

pathology

· originate as acute intra-articular fractures

· bony fragment may

· revascularise and unite

· undergo osteonecrosis and not unite

· overlying cartilage may degenerate

· cyst may develop under fragment

classification

· of Berndt and Hardy

· stage 1

· small area of compression in subchondral bone

· stage 2

· partially attached osteochondral fragment

· stage 3

· detached but undisplaced fragment

· stage 4

· detached displaced fragment

clinical

Presentation

· lateral ankle sprain from inversion injury

· chronic symptoms after ankle sprain settles

· activity-related pain, stiffness and swelling

· crepitus, instability and locking

· symptoms of lateral ligament injury

· instability

· pain with inversion

· recurrent sprains

Findings

· tenderness in anteromedial or anterolateral corner of ankle joint

· pain with dorsiflexion and eversion

· decreased ROM, esp. dorsiflexion

· effusion

· ligament laxity

radiology

Plain x-ray

· lesion visible in 70-100%

· findings

· wafer of bone (acute)

· sclerotic line around margin of crater (recent)

· ill-defined lucencies (old)

· further imaging if lesion suspected

· bone scan if clinically suspected

· CT scan (or tomograms) if suspicious lesion on x-ray

Tomograms

· give additional information in 50%

Bone scan

· useful screening test

· 100% specific

· 80% sensitive

CT scan

· fine-cuts delineate lesion clearly

MRI

· determine stability of fragment

· stable lesion has intact overlying cartilage

· unstable lesion has fluid at fragment-crater interface

treatment

Guidelines

Stage 1

· asymptomatic

· no treatment

· symptomatic

· restricted activity

Stage 2

· asymptomatic

· no treatment

· symptomatic

· short leg cast for 6 weeks

· successful in 90%

Stage 3

· asymptomatic

· no treatment

· symptomatic

· controversial

· surgery probably indicated

Stage 4

· surgery

Surgery

Approach

· open or arthroscopic

· lateral lesion approached through anterolateral approach

· larger lesion may need fibular osteotomy

· medial lesion approached through anteromedial approach

· larger lesion may need medial malleolar osteotomy

Technique

· excision of smaller fragments

· excision of necrotic sequestrum

· abrasion of crater

· drilling of subchondral bone

· internal fixation of larger fragments

· with absorbable pegs or Herbert screws

Prognosis

· osteoarthritis develops in 25%

· in 75% of stage 3 and 4

· surgical intervention decreases rate of progression