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Cortical desmoid

Dr David Dang et al.

Cortical desmoids, also known as cortical avulsive injuries, are a benign self limiting entity. This is a classic 'don't touch' lesion, and should not be confused with an agressive cortical/periosteal process (e.g. osteosarcoma). 

Epidemiology

It typically presents in adolescents (10-15 years of age). There may be a male predilection. 

Clinical presentation

Patients are usually asymptomatic and it is discovered incidentally. Occasionally pain may be present.

Pathology

It is related to repetitive stress at the attachment of the adductor magnus aponeurosis at the medial posterior aspect of the distal femoral metaphysis.

Location

It is seen at the posterior aspect of the distal femur. Can be bilateral in approximately one-third of cases.

Radiographic features

Plain film

Typically shows a saucer-shaped radiolucent cortical irregularity involving posteromedial aspect of the distal femoral metaphysis at the attachment of the adductor magnus tendon. The lesion lacks an outer margin.

MRI

Defines anatomy much better and is seen as a cortically based lesion in the expected location (i.e. posteromedial distal femoral metaphysis) 3,4:

  • T1: low signal
  • T2: high signal and surrounding low signal rim may be present
  • T1 C+ (Gd):  most show enhancement
Nuclear medicine

On bone scan there is an abnormal increase in activity because of the chronic stress/traumatic origin of this lesion.

Differential diagnosis

Imaging differential considerations include

Practical points

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