Radio-opaque marker of a surgical sponge appearing as an intra-articular foreign body after total hip arthroplasty

We report a 73-year-old female patient who underwent total hip arthroplasty for osteoarthritis of the right hip. An anteroposterior radiograph obtained 1 week after surgery showed an intra-articular striated foreign body. This was subsequently removed and found to be a radio-opaque marker of a surgical sponge that had been used during the operation. The patient made an uneventful recovery. In recent years, cases of retained surgical sponge after surgery have been reported occasionally. Counting surgical sponges and using sponges with radio-opaque markers are methods for preventing them from being accidentally left in situ. However, to our knowledge, there has been no report of retention of a surgical sponge radio-opaque marker at the operation site, appearing as a foreign body on an X-ray film.