Cortical desmoids, also known as cortical avulsive injuries, Bufkin lesion or distal cortical femoral defects/irregularities, are a benign self-limiting entity that are common incidental findings. This is a classic "do not touch" lesion, and should not be confused with an aggressive cortical/periosteal process (e.g. osteosarcoma).
Cortical desmoid is a misnomer as this lesion does not histologically correlate to true desmoid tumors with more recent literature (c. 2020) referring these to distal cortical femoral irregularities.
It typically presents in adolescents (10-15 years of age). There may be a male predilection.
Patients are usually asymptomatic, and it is discovered incidentally. Occasionally pain may be present.
Cortical desmoids are classically seen at the posteromedial aspect of the distal femur. They can be bilateral in approximately one-third of cases .
Typically shows a saucer-shaped radiolucent cortical irregularity involving the posteromedial aspect of the distal femoral metaphysis at the attachment of the adductor magnus tendon. The lesion lacks an outer margin.
Defines anatomy much better and is seen as a cortically based lesion in the expected location (i.e. posteromedial distal femoral metaphysis) :
- T1: low signal
- T2: high signal and surrounding low signal rim representing sclerosis may be present
- T1 C+ (Gd): most show enhancement
On bone scan, there is an abnormal increase in activity because of the chronic stress/traumatic origin of this lesion.
Imaging differential considerations include:
- cortical desmoid is one of the skeletal “don’t touch” lesions