Radiographs of eighteen patients who had had a diagnosis of
metal-induced synovitis subsequent to a knee-replacement arthroplasty were
retrospectively reviewed. The presence of a dense line outlining a portion
of the capsule or articular surface of the knee joint (the so-called
metal-line sign) was noted in association with wear in eleven patients. In
the nine patients who had a positive sign and also had specimens available
for histological examination, there was dense deposition of metal
particles, whereas in the six patients who did not have a metal-line sign
and had specimens available for histological examination, five had only a
slight amount of metal in the synovial tissue and one, a moderate amount.
The presence of the metal-line sign was associated with metal-induced
synovitis in eleven of the eighteen patients. The sign should be useful in
helping to make this diagnosis preoperatively in many patients.