Why do we need another imaging test for a wrist fracture

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Q: Can you explain something to me? My mother broke her wrist and when I took her to the hospital they did X-rays but also a CT scan. Once they knew the break was a simple fracture without separation of the bones (seen with the X-ray) why the need for another expensive imaging test?

A: There are some potential complications with wrist fractures that can cause serious problems later. This is true even with nondisplaced fractures. One of those complications is a rupture of the extensor pollicis longus (EPL tendon). This tendon helps move both the tip of the thumb and the wrist, so damage to it can impair function of the hand.

There are reports of how often this tendon rupture occurs after radial wrist fractures. Up to five per cent of patients with a radial wrist fracture later develop an EPL tendon rupture. X-rays can be used to look at the angle and height of the radial bone as well as the alignment of the wrist joint

But X-rays do not show much if anything about the soft tissues around the break. And that's where CT scans come into play. When the force that breaks a bone is not enough to rip or tear the soft tissues around the bone, complications like the tendon rupture can occur later. This is because the tendon is held tightly against the bone. The fracture results in swelling, bleeding into the area, and the formation of a bone callus as healing takes place.

All of these events decrease the space around the tendon and put pressure on the tendon. The EPL tendon in particular doesn't have a very good blood supply to its own tendon sheath (outer protective covering). Anything that disrupts this area can reduce blood flow and nutrition causing avascular necrosis. Avascular necrosis means death of the tissue due to loss of blood. The end result is rupture of the tendon.

More advanced imaging studies like CT scans help identify other problems that are either developing or already present. The surgeon treating your mother may have had an inkling that something else was going on -- either from the type of injury or from the clinical presentation.

You can always ask for an explanation for a procedure (either before it is done or even afterwards). Preventing complications and/or treating them early on is possible with the information CT scans provide. And that could prevent a lot of suffering for some patients with unknown soft tissue damage.

Reference: Karen M. Roth, MD, et al. Incidence of Extensor Pollicis Longus Tendon Rupture After Nondisplaced Distal Radius Fractures. In The Journal of Hand Surgery. May 2012. Vol. 37A. No. 5. Pp. 942-947.

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