Avulsion fracture of the anterior superior iliac spine: misdiagnosis of a bone tumour

Abstract

Avulsion fractures of the anterior superior iliac spine are rare. This injury is usually seen in adolescents, as an avulsion fracture of the apophyses, a result of sudden vigorous contraction or repetitive contraction of the sartorius and tensor fasciae latae muscles. Treatment for this injury is usually conservative; however, surgical management has been reported in those with significant displacement. We present a 14 year old male patient who was referred to our unit for biopsy of a possible pathological fracture of his right ilium. The authors feel it is essential to understand the importance of ruling out a bone tumour, if the possibility has been raised, before managing a suspected fracture. If there is any doubt, the case should be referred to an appropriate sarcoma unit for review prior to any intervention.

Fig. 1

Axial T1-weighted image. Note the sharp anterior superior iliac spine fracture line (long white arrow) with retracted sartorius tendon margin (short white arrow). Also note that the signal intensity of haematoma is slightly hyperintense (as compared to skeletal muscle, indicated by the chevron mark), which is suggestive of a haemorrhagic product rather than a tumour mass

Fig. 2

Coronal T1-weighted image. Note the slightly hyperintense haematoma (short white arrow). Signal is compared to skeletal muscle (long white arrow)

Fig. 3

Axial T1 fat-saturated pre-gadolinium image. Note that the surrounding haematoma shows a bright signal indicating haemorrhagic components (short white arrow)

Fig. 4

Axial post-intravenous gadolinium T1 fat-saturated image. The haematoma also shows diffuse solid enhancement (short white arrow). There is, however, no enhancement in bone (long white arrow). Bone tumours with surrounding mass usually show marrow infiltration indicated by low T1 and bright T2 signals in bone that enhance with gadolinium

Fig. 5

Axial proton density images obtained 3 months after the first scan indicate that the avulsion fracture shows signs of healing. The surrounding haematoma is smaller. Bone marrow signal is also normal

Fig. 6

Fat-saturated images obtained 3 months after the first scan show signs of fracture healing