Clinical diagnosis
Case 185
【Progress】
After she got knee MRI, she returned to the local clinic with the report which said distal femoral cortical irregularity.
【Discussion】
Distal femoral cortical irregularity (DFCI) is termed lately, it was previously referred as cortical desmoid and cortical avulsive irregularity (1). The word of desmoid is inappropriate because its histological findings are not related to desmoid tumor. DFCI appears at medial dorsal metaphysis of femur above medial condyle. This region corresponds to attachment of adductor magnus muscle or medial head of gastro-cremius muscle. It is considered the repetitive muscle retraction of these muscles causes stress to the develop stage of bone growth, leading to DFCI (2, 3).
DFCI appears in childhood and teens: the higher incidence in younger teens than late teens (2). It presents predominantly in male and bilaterally in one third of cases. It resembles to cortical defect (non-ossifying fibroma) of tibia in a point where it appears in a bone development stage. DFCI disappears naturally with advancement of age.
DFCI is known as a “don’t touch lesion” because the histological findings are fibro-osseous non-tumor proliferation which cannot differentiate from fibroma, osteosarcoma and aggressive fibromatosis (2, 3). It resembles to cortical defect (non-ossifying fibroma) of tibia in a point of “don’t touch lesion” where it appears in a bone development stage.
Femur radiograph, CT and MRI are useful for diagnosis of DFCI. MRI shows a lesion with low to intermediate signal intensity with on T1WI and high signal intensity on T2WI depending on the volume of fibrous and/or osseous component. DFCI lesion is specific for having low intensity rim as low as bone cortex, implying the tear of femur cortex.
In our case, she suffered from slight pain of right knee and MRI showed a lesion having rim with low signal intensity at the metaphysis of distal femur cortex, indicating compatible image of DFCI.
【Summary】
We present an eight-year-old girl for right knee pain. MRI showed a lesion having rim with low signal intensity at the metaphysis of distal femur cortex, indicating compatible image of DFCI. It is borne in mind that DFCI present in young teens at dorsal medial side of distal femur corresponded to attachment of femoral adduct magnus muscle and/or medial head of gastrocremius. It probably occurs due to repetitive stimuli of these muscles in development stage of femur. DFCI is a “don’t touch lesion” because the histological findings cannot differentiate from fibroma, osteosarcoma and aggressive fibromatosis. It resembles to cortical defect (non-ossifying fibroma) of tibia in a point of “don’t touch lesion”
【References】
1.Bufkin, WJ . The avulsive cortical irregularity. Am J Roentgenol 1971 Jul;112(3):487-489.
2.Muramatsu K, et al. Distal Femoral Cortical Irregularity in children. Acta Orthop Belg. 2015;81(3):392-7.
3.Verdonk PC, et al. Distal femoral cortical irregularity in a 13-year old boy. A case report. Acta Orthop Belg. 2003;69(4):377-81.
2020.3.25