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Sports Medicine

MRI to detect a loose body in ankle

07/10/2006

Question:

During a soccer match , my son had an ankle injury. An Xray was ordered.

Xray report: Soft tissue swelling over the lateral malleolus and anterior ankle is noted. A small 3 mm calcific density is seen projected over the medial ankle joint seen only on the frontal view. The exact location is uncrtain but is suspected to be within the ankle joint and is supicious for a fracture fragment. The donor site may be in the distal tibial articular surface medially where there is a very faint cortical irregularity.

Our GP referrred to a sports doctor who ordered an MRI. MRI report:

  • Small impaction fracture involving the medial talus at the head/neck junction. Concomitant contusional injury anterior tibial plafond and medial malleolus Small bone fragment measuring 3mm is present within the fracture involving the talar neck/head
  • Small undisplaced intra-articular fracture posterior aspect tibial plafond
  • Complete disruption anterior talofibular and calcaneofibular ligaments
  • Injury tibiofibular ligament with mild high ankle sprain but no evidence of mal-alignment
  • Contusion injury/tear deep portion deltoid ligament with mild contusional of superficial fibres

    My sports doctor then referred us to an orthopadic surgeon. The orthopaedic surgeon looked at both the xray films and MRI report and said that he wanted my son to have a CT scan to rule out a loose body as shown by the intial xray.

    I am confused. Hasn't the MRI shown that the bone fragment is within the fracture? He told us that the CT scan will show up the position of the bone fragment better. He wants my son to have the CT scan in 2 weeks time., It will be 4 weeks since his injury

    Can you please explain the benefit of doing the CT scan when we have the MRI. Is there any other reason?

    I am so grateful there is someone else I can ask. Thank you so much. I am looking forward to hearing from you. I do not want my son to have an unnecessary CT scan

  • Answer:

    The MRI scan has provided excellent additional information about your son's ankle injury.  A CT scan would actually provide even more detailed information regarding the extent of bony/skeletal injury, compared to the MRI scan.  MRI, however, is better at imaging ligaments, muscles, cartilage, and other "soft tissues."

    If your son's orthopedist feels the additional information from a CT scan will influence decision-making regarding treatment (surgery vs. no surgery), then a CT scan of your son's ankle would be worthwhile.  Tests are usually performed only when results may change treatment.

    For more information:

    Go to the Sports Medicine health topic, where you can:

    Response by:

    Brian L Bowyer, MD Brian L Bowyer, MD
    Clinical Associate Professor
    Physical Medicine & Rehabilitation
    College of Medicine
    The Ohio State University