Answer for CoW 16 July 2017
Findings
Exuberant soft tissue ossification noted in both iliac regions, abutting iliac bones
Discussion
Heterotopic ossification (HO) refers to the presence of bone in soft tissue where bone normally does not exist. The acquired form of HO most frequently is seen with either musculoskeletal trauma, spinal cord injury, burns or traumatic brain injury injury. Modified classification for HO (Della Valle) has 3 grades : grade A: absence of HO (may be ≥1 island of bone of <1 cm in length grade B: presence of ≥1 islands of bone of at least 1 cm in length and bone spurs from the pelvis or femur. 1 cm distance between opposing surfaces of bone grade C: bone spurs arising from the pelvis or femur with <1 cm between opposing surfaces or apparent bone ankylosis The important distinction in reporting the presence of HO is therefore the presence of a space of more or less than 1 cm between opposing surfaces of bone. Clinical presentation : The most common presentation with with pain around the site of HO. Associated features can include fever, soft tissue swelling, and poor mobility of the affected joint. Radiographic features Plain radiograph Early stage : typical finding is a soft tissue mass without calcific change these can often be missed since radiographs are typically done for vague symptoms of pain Mineralisation: can occur within 10 days after the causative insult calcification usually starts peripherally, though cases associated with fibrodysplasia ossificans progressiva can calcify from the central zone out to the periphery lesions can also be poorly organised without a recognisable mineralisation pattern Maturation: mature cortical bone is formed if no treatment is used for the evolving heterotopic ossification CT: early stage low-attenuation soft tissue mass with indistinct surrounding soft tissue planes it may show contrast enhancement mineralisation zonal mineralisation pattern as described previously a central fatty marrow component can occasionally be seen maturation mature cortical bone at the periphery MRI: early stage soft tissue mass with heterogenous high T2 signal lesion may manifest simply as enlargment of an involved muscle surrounding ill defined high T2 signal representing oedema enhancement of the soft tissue lesion and surrounding oedematous tissue mineralisation this is seen as peripheral low T1 signal in the zonal pattern described high T1 signal centrally representing fatty marrow change maturation low T1 signal peripherally in keeping with cortical bone persisting T2 signal components within the lesion delayed low signal on STIR with little residual oedema
Exuberant soft tissue ossification noted in both iliac regions, abutting iliac bones
Discussion
Heterotopic ossification (HO) refers to the presence of bone in soft tissue where bone normally does not exist. The acquired form of HO most frequently is seen with either musculoskeletal trauma, spinal cord injury, burns or traumatic brain injury injury. Modified classification for HO (Della Valle) has 3 grades : grade A: absence of HO (may be ≥1 island of bone of <1 cm in length grade B: presence of ≥1 islands of bone of at least 1 cm in length and bone spurs from the pelvis or femur. 1 cm distance between opposing surfaces of bone grade C: bone spurs arising from the pelvis or femur with <1 cm between opposing surfaces or apparent bone ankylosis The important distinction in reporting the presence of HO is therefore the presence of a space of more or less than 1 cm between opposing surfaces of bone. Clinical presentation : The most common presentation with with pain around the site of HO. Associated features can include fever, soft tissue swelling, and poor mobility of the affected joint. Radiographic features Plain radiograph Early stage : typical finding is a soft tissue mass without calcific change these can often be missed since radiographs are typically done for vague symptoms of pain Mineralisation: can occur within 10 days after the causative insult calcification usually starts peripherally, though cases associated with fibrodysplasia ossificans progressiva can calcify from the central zone out to the periphery lesions can also be poorly organised without a recognisable mineralisation pattern Maturation: mature cortical bone is formed if no treatment is used for the evolving heterotopic ossification CT: early stage low-attenuation soft tissue mass with indistinct surrounding soft tissue planes it may show contrast enhancement mineralisation zonal mineralisation pattern as described previously a central fatty marrow component can occasionally be seen maturation mature cortical bone at the periphery MRI: early stage soft tissue mass with heterogenous high T2 signal lesion may manifest simply as enlargment of an involved muscle surrounding ill defined high T2 signal representing oedema enhancement of the soft tissue lesion and surrounding oedematous tissue mineralisation this is seen as peripheral low T1 signal in the zonal pattern described high T1 signal centrally representing fatty marrow change maturation low T1 signal peripherally in keeping with cortical bone persisting T2 signal components within the lesion delayed low signal on STIR with little residual oedema
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!